Journal articles: 'Membrane contact site'

1

Westermann, Benedikt. "The mitochondria–plasma membrane contact site." Current Opinion in Cell Biology 35 (August 2015): 1–6. http://dx.doi.org/10.1016/j.ceb.2015.03.001.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Bean, Björn D. M., Samantha K. Dziurdzik, Kathleen L. Kolehmainen, Claire M. S. Fowler, Waldan K. Kwong, Leslie I. Grad, Michael Davey, Cayetana Schluter, and Elizabeth Conibear. "Competitive organelle-specific adaptors recruit Vps13 to membrane contact sites." Journal of Cell Biology 217, no. 10 (July 17, 2018): 3593–607. http://dx.doi.org/10.1083/jcb.201804111.

Full text

Abstract:

The regulated expansion of membrane contact sites, which mediate the nonvesicular exchange of lipids between organelles, requires the recruitment of additional contact site proteins. Yeast Vps13 dynamically localizes to membrane contacts that connect the ER, mitochondria, endosomes, and vacuoles and is recruited to the prospore membrane in meiosis, but its targeting mechanism is unclear. In this study, we identify the sorting nexin Ypt35 as a novel adaptor that recruits Vps13 to endosomal and vacuolar membranes. We characterize an interaction motif in the Ypt35 N terminus and identify related motifs in the prospore membrane adaptor Spo71 and the mitochondrial membrane protein Mcp1. We find that Mcp1 is a mitochondrial adaptor for Vps13, and the Vps13–Mcp1 interaction, but not Ypt35, is required when ER-mitochondria contacts are lost. All three adaptors compete for binding to a conserved six-repeat region of Vps13 implicated in human disease. Our results support a competition-based model for regulating Vps13 localization at cellular membranes.

APA, Harvard, Vancouver, ISO, and other styles

3

Gipson, Preeti, Yoshiyuki Fukuda, Radostin Danev, Ying Lai, Dong-Hua Chen, Wolfgang Baumeister, and Axel T. Brunger. "Morphologies of synaptic protein membrane fusion interfaces." Proceedings of the National Academy of Sciences 114, no. 34 (July 24, 2017): 9110–15. http://dx.doi.org/10.1073/pnas.1708492114.

Full text

Abstract:

Neurotransmitter release is orchestrated by synaptic proteins, such as SNAREs, synaptotagmin, and complexin, but the molecular mechanisms remain unclear. We visualized functionally active synaptic proteins reconstituted into proteoliposomes and their interactions in a native membrane environment by electron cryotomography with a Volta phase plate for improved resolvability. The images revealed individual synaptic proteins and synaptic protein complex densities at prefusion contact sites between membranes. We observed distinct morphologies of individual synaptic proteins and their complexes. The minimal system, consisting of neuronal SNAREs and synaptotagmin-1, produced point and long-contact prefusion states. Morphologies and populations of these states changed as the regulatory factors complexin and Munc13 were added. Complexin increased the membrane separation, along with a higher propensity of point contacts. Further inclusion of the priming factor Munc13 exclusively restricted prefusion states to point contacts, all of which efficiently fused upon Ca2+ triggering. We conclude that synaptic proteins have evolved to limit possible contact site assemblies and morphologies to those that promote fast Ca2+-triggered release.

APA, Harvard, Vancouver, ISO, and other styles

4

Pfanner, Nikolaus, Martin van der Laan, Paolo Amati, Roderick A. Capaldi, Amy A. Caudy, Agnieszka Chacinska, Manjula Darshi, et al. "Uniform nomenclature for the mitochondrial contact site and cristae organizing system." Journal of Cell Biology 204, no. 7 (March 31, 2014): 1083–86. http://dx.doi.org/10.1083/jcb.201401006.

Full text

Abstract:

The mitochondrial inner membrane contains a large protein complex that functions in inner membrane organization and formation of membrane contact sites. The complex was variably named the mitochondrial contact site complex, mitochondrial inner membrane organizing system, mitochondrial organizing structure, or Mitofilin/Fcj1 complex. To facilitate future studies, we propose to unify the nomenclature and term the complex “mitochondrial contact site and cristae organizing system” and its subunits Mic10 to Mic60.

APA, Harvard, Vancouver, ISO, and other styles

5

Mannella, C. A., K. F. Buttle, K. A. O‘Farrell, A. Leith, and M. Marko. "Structure of contact sites between the outer and inner mitochondrial membranes investigated by HVEM tomography." Proceedings, annual meeting, Electron Microscopy Society of America 54 (August 11, 1996): 966–67. http://dx.doi.org/10.1017/s0424820100167299.

Full text

Abstract:

Early transmission electron microscopy of plastic-embedded, thin-sectioned mitochondria indicated that there are numerous junctions between the outer and inner membranes of this organelle. More recent studies have suggested that the mitochondrial membrane contacts may be the site of protein complexes engaged in specialized functions, e.g., import of mitochondrial precursor proteins, adenine nucleotide channeling, and even intermembrane signalling. It has been suggested that the intermembrane contacts may be sites of membrane fusion involving non-bilayer lipid domains in the two membranes. However, despite growing interest in the nature and function of intramitochondrial contact sites, little is known about their structure.We are using electron microscopic tomography with the Albany HVEM to determine the internal organization of mitochondria. We have reconstructed a 0.6-μm section through an isolated, plasticembedded rat-liver mitochondrion by combining 123 projections collected by tilting (+/- 70°) around two perpendicular tilt axes. The resulting 3-D image has confirmed the basic inner-membrane organization inferred from lower-resolution reconstructions obtained from single-axis tomography.

APA, Harvard, Vancouver, ISO, and other styles

6

Rinnerthaler, G., B. Geiger, and J. V. Small. "Contact formation during fibroblast locomotion: involvement of membrane ruffles and microtubules." Journal of Cell Biology 106, no. 3 (March 1, 1988): 747–60. http://dx.doi.org/10.1083/jcb.106.3.747.

Full text

Abstract:

We have correlated the motility of the leading edge of fibroblasts, monitored by phase-contrast cinematography, with the relative distributions of several cytoskeletal elements (vinculin, tubulin, and actin) as well as with the contact patterns determined by interference reflection microscopy. This analysis has revealed the involvement of both ruffles and microspikes, as well as microtubules in the initiation of focal contact formation. Nascent vinculin sites within the leading edge or at its base, taken as primordial cell-substrate contacts, were invariably colocalized with sites that showed a history of transient, prolonged, or cyclic ruffling activity. Extended microspike structures, often preceded the formation of ruffles. Immunofluorescent labeling indicated that some of these primordial contacts were in close apposition to the ends of microtubules that penetrated into the leading edge. By fluorescence and electron microscopy short bundles of actin filaments found at the base of the leading edge were identified as presumptive, primordial contacts. It is concluded that ruffles and microspikes, either independently or in combination, initiate and mark the sites for future contact. Plaque proteins then accumulate (within 10-30 s) at the contract site and, beneath ruffles, induce localized bundling of actin filaments. We propose that all primordial contacts support traction for leading edge protrusion but that only some persist long enough to nucleate stress fiber assembly. Microtubules are postulated as the elements that select, stabilize, and potentiate the formation of these latter, long-lived contacts.

APA, Harvard, Vancouver, ISO, and other styles

7

Quon, Evan, Aleksa Nenadic, Mohammad F. Zaman, Jesper Johansen, and Christopher T. Beh. "ER-PM membrane contact site regulation by yeast ORPs and membrane stress pathways." PLOS Genetics 18, no. 3 (March 3, 2022): e1010106. http://dx.doi.org/10.1371/journal.pgen.1010106.

Full text

Abstract:

In yeast, at least seven proteins (Ice2p, Ist2p, Scs2/22p, Tcb1-Tcb3p) affect cortical endoplasmic reticulum (ER) tethering and contact with the plasma membrane (PM). In Δ-super-tether (Δ-s-tether) cells that lack these tethers, cortical ER-PM association is all but gone. Yeast OSBP homologue (Osh) proteins are also implicated in membrane contact site (MCS) assembly, perhaps as subunits for multicomponent tethers, though their function at MCSs involves intermembrane lipid transfer. Paradoxically, when analyzed by fluorescence and electron microscopy, the elimination of the OSH gene family does not reduce cortical ER-PM association but dramatically increases it. In response to the inactivation of all Osh proteins, the yeast E-Syt (extended-synaptotagmin) homologue Tcb3p is post-transcriptionally upregulated thereby generating additional Tcb3p-dependent ER-PM MCSs for recruiting more cortical ER to the PM. Although the elimination of OSH genes and the deletion of ER-PM tether genes have divergent effects on cortical ER-PM association, both elicit the Environmental Stress Response (ESR). Through comparisons of transcriptomic profiles of cells lacking OSH genes or ER-PM tethers, changes in ESR expression are partially manifested through the induction of the HOG (high-osmolarity glycerol) PM stress pathway or the ER-specific UPR (unfolded protein response) pathway, respectively. Defects in either UPR or HOG pathways also increase ER-PM MCSs, and expression of extra “artificial ER-PM membrane staples” rescues growth of UPR mutants challenged with lethal ER stress. Transcriptome analysis of OSH and Δ-s-tether mutants also revealed dysregulation of inositol-dependent phospholipid gene expression, and the combined lethality of osh4Δ and Δ-s-tether mutations is suppressed by overexpression of the phosphatidic acid biosynthetic gene, DGK1. These findings establish that the Tcb3p tether is induced by ER and PM stresses and ER-PM MCSs augment responses to membrane stresses, which are integrated through the broader ESR pathway.

APA, Harvard, Vancouver, ISO, and other styles

8

Balla, Tamas, Yeun Ju Kim, Alejandro Alvarez-Prats, and Joshua Pemberton. "Lipid Dynamics at Contact Sites Between the Endoplasmic Reticulum and Other Organelles." Annual Review of Cell and Developmental Biology 35, no. 1 (October 6, 2019): 85–109. http://dx.doi.org/10.1146/annurev-cellbio-100818-125251.

Full text

Abstract:

Phospholipids are synthesized primarily within the endoplasmic reticulum and are subsequently distributed to various subcellular membranes to maintain the unique lipid composition of specific organelles. As a result, in most cases, the steady-state localization of membrane phospholipids does not match their site of synthesis. This raises the question of how diverse lipid species reach their final membrane destinations and what molecular processes provide the energy to maintain the lipid gradients that exist between various membrane compartments. Recent studies have highlighted the role of inositol phospholipids in the nonvesicular transport of lipids at membrane contact sites. This review attempts to summarize our current understanding of these complex lipid dynamics and highlights their implications for defining future research directions.

APA, Harvard, Vancouver, ISO, and other styles

9

Rassow, J., B. Guiard, U. Wienhues, V. Herzog, F. U. Hartl, and W. Neupert. "Translocation arrest by reversible folding of a precursor protein imported into mitochondria. A means to quantitate translocation contact sites." Journal of Cell Biology 109, no. 4 (October 1, 1989): 1421–28. http://dx.doi.org/10.1083/jcb.109.4.1421.

Full text

Abstract:

Passage of precursor proteins through translocation contact sites of mitochondria was investigated by studying the import of a fusion protein consisting of the NH2-terminal 167 amino acids of yeast cytochrome b2 precursor and the complete mouse dihydrofolate reductase. Isolated mitochondria of Neurospora crassa readily imported the fusion protein. In the presence of methotrexate import was halted and a stable intermediate spanning both mitochondrial membranes at translocation contact sites accumulated. The complete dihydrofolate reductase moiety in this intermediate was external to the outer membrane, and the 136 amino acid residues of the cytochrome b2 moiety remaining after cleavage by the matrix processing peptidase spanned both outer and inner membranes. Removal of methotrexate led to import of the intermediate retained at the contact site into the matrix. Thus unfolding at the surface of the outer mitochondrial membrane is a prerequisite for passage through translocation contact sites. The membrane-spanning intermediate was used to estimate the number of translocation sites. Saturation was reached at 70 pmol intermediate per milligram of mitochondrial protein. This amount of translocation intermediates was calculated to occupy approximately 1% of the total surface of the outer membrane. The morphometrically determined area of close contact between outer and inner membranes corresponded to approximately 7% of the total outer membrane surface. Accumulation of the intermediate inhibited the import of other precursor proteins suggesting that different precursor proteins are using common translocation contact sites. We conclude that the machinery for protein translocation into mitochondria is present at contact sites in limited number.

APA, Harvard, Vancouver, ISO, and other styles

10

Bohnert, Maria, and Maya Schuldiner. "Stepping outside the comfort zone of membrane contact site research." Nature Reviews Molecular Cell Biology 19, no. 8 (May 15, 2018): 483–84. http://dx.doi.org/10.1038/s41580-018-0022-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Kvam, E., and D. S. Goldfarb. "Nucleus–vacuole junctions in yeast: anatomy of a membrane contact site." Biochemical Society Transactions 34, no. 3 (May 22, 2006): 340–42. http://dx.doi.org/10.1042/bst0340340.

Full text

Abstract:

NV junctions (nucleus–vacuole junctions) in Saccharomyces cerevisiae are MCSs (membrane contact sites) formed through specific interactions between Vac8p on the vacuole membrane and Nvj1p in the outer nuclear membrane, which is continuous with the perinuclear ER (endoplasmic reticulum). NV junctions mediate a unique autophagic process that degrades portions of the yeast nucleus through a process called ‘piecemeal microautophagy of the nucleus’ (PMN). Our studies suggest that the lipid composition of NV junctions plays an important role in the biogenesis of PMN structures. NV junctions represent a unique model system for studying the biology of ER MCSs, as well as the molecular mechanism of selective microautophagy.

APA, Harvard, Vancouver, ISO, and other styles

12

Anishkin, Andriy, Kiran Kumar Adepu, Dipendra Bhandari, Sean H. Adams, and Sree V. Chintapalli. "Computational Analysis Reveals Unique Binding Patterns of Oxygenated and Deoxygenated Myoglobin to the Outer Mitochondrial Membrane." Biomolecules 13, no. 7 (July 17, 2023): 1138. http://dx.doi.org/10.3390/biom13071138.

Full text

Abstract:

Myoglobin (Mb) interaction with the outer mitochondrial membrane (OMM) promotes oxygen (O2) release. However, comprehensive molecular details on specific contact regions of the OMM with oxygenated (oxy-) and deoxygenated (deoxy-)Mb are missing. We used molecular dynamics (MD) simulations to explore the interaction of oxy- and deoxy-Mb with the membrane lipids of the OMM in two lipid compositions: (a) a typical whole membrane on average, and (b) specifically the cardiolipin-enriched cristae region (contact site). Unrestrained relaxations showed that on average, both the oxy- and deoxy-Mb established more stable contacts with the lipids typical of the cristae contact site, then with those of the average OMM. However, in steered detachment simulations, deoxy-Mb clung more tightly to the average OMM, and oxy-Mb strongly preferred the contact sites of the OMM. The MD simulation analysis further indicated that a non-specific binding, mediated by local electrostatic interactions, existed between charged or polar groups of Mb and the membrane, for stable interaction. To the best of our knowledge, this is the first computational study providing the molecular details of the direct Mb–mitochondria interaction that assisted in distinguishing the preferred localization of oxy- and deoxy-Mb on the OMM. Our findings support the existing experimental evidence on Mb–mitochondrial association and shed more insights on Mb-mediated O2 transport for cellular bioenergetics.

APA, Harvard, Vancouver, ISO, and other styles

13

Singh, Neha Pratap, Christian Vannier, and Thierry Galli. "SNAP iN, SNAP oUT—SNAREs at ER-PM Contact Sites." Contact 3 (January 2020): 251525642097958. http://dx.doi.org/10.1177/2515256420979586.

Full text

Abstract:

Inter-organelle communication is essential for the exchange of cellular content in eukaryotes, particularly at membrane contact sites between the endoplasmic reticulum (ER) and the plasma membrane (PM). Accomplishing this critical task requires close positioning of the involved membranes via tether proteins and associated complexes. One such complex involves the SNAREs Sec22b and Syntaxin 1. Discovered to be interacting at the ER-PM membrane contact site (MCS), Sec22b-Stx1 forms a unique non-fusogenic bridge tethering the two membranes. Contrarily, SNAP25 was shown to be absent from the Sec22b-Stx1 complexes. Two recent studies focused on this interplay of SNARES and Lipid transfer proteins at MCSs. The Longin domain of Sec22b appeared to be the reason behind SNAP25’s exclusion from Sec22b-Stx1 assembly, and inclusion of E-Syts. It was also shown that yeast Sec9p and mammalian SNAP25 regulate ER-PM contact sites via their interaction with LTP OSBP-homologous proteins (ORP/OSH). In this following short review, we will take a closer look at the protein complexes involving SNAREs at MCSs and potential regulation by the Longin domain of Sec22b.

APA, Harvard, Vancouver, ISO, and other styles

14

King, Christopher, Prabuddha Sengupta, Arnold Y. Seo, and Jennifer Lippincott-Schwartz. "ER membranes exhibit phase behavior at sites of organelle contact." Proceedings of the National Academy of Sciences 117, no. 13 (March 16, 2020): 7225–35. http://dx.doi.org/10.1073/pnas.1910854117.

Full text

Abstract:

The endoplasmic reticulum (ER) is the site of synthesis of secretory and membrane proteins and contacts every organelle of the cell, exchanging lipids and metabolites in a highly regulated manner. How the ER spatially segregates its numerous and diverse functions, including positioning nanoscopic contact sites with other organelles, is unclear. We demonstrate that hypotonic swelling of cells converts the ER and other membrane-bound organelles into micrometer-scale large intracellular vesicles (LICVs) that retain luminal protein content and maintain contact sites with each other through localized organelle tethers. Upon cooling, ER-derived LICVs phase-partition into microscopic domains having different lipid-ordering characteristics, which is reversible upon warming. Ordered ER lipid domains mark contact sites with ER and mitochondria, lipid droplets, endosomes, or plasma membrane, whereas disordered ER lipid domains mark contact sites with lysosomes or peroxisomes. Tethering proteins concentrate at ER–organelle contact sites, allowing time-dependent behavior of lipids and proteins to be studied at these sites. These findings demonstrate that LICVs provide a useful model system for studying the phase behavior and interactive properties of organelles in intact cells.

APA, Harvard, Vancouver, ISO, and other styles

15

Dunn, Tyler W., and Wayne S. Sossin. "Excitatory postsynaptic calcium transients at Aplysia sensory–motor neuron synapses allow for quantal examination of synaptic strength over multiple days in culture." Learning & Memory 28, no. 9 (August 16, 2021): 277–90. http://dx.doi.org/10.1101/lm.052639.120.

Full text

Abstract:

A more thorough description of the changes in synaptic strength underlying synaptic plasticity may be achieved with quantal resolution measurements at individual synaptic sites. Here, we demonstrate that by using a membrane targeted genetic calcium sensor, we can measure quantal synaptic events at the individual synaptic sites of Aplysia sensory neuron to motor neuron synaptic connections. These results show that synaptic strength is not evenly distributed between all contacts in these cultures, but dominated by multiquantal sites of synaptic contact, likely clusters of individual synaptic sites. Surprisingly, most synaptic contacts were not found opposite presynaptic varicosities, but instead at areas of pre- and postsynaptic contact with no visible thickening of membranes. The release probability, quantal size, and quantal content can be measured over days at individual synaptic contacts using this technique. Homosynaptic depression was accompanied by a reduction in release site probability, with no evidence of individual synaptic site silencing over the course of depression. This technique shows promise in being able to address outstanding questions in this system, including determining the synaptic changes that maintain long-term alterations in synaptic strength that underlie memory.

APA, Harvard, Vancouver, ISO, and other styles

16

SHIAO, Young-Ji, Bénédicte BALCERZAK, and Jean E. VANCE. "A mitochondrial membrane protein is required for translocation of phosphatidylserine from mitochondria-associated membranes to mitochondria." Biochemical Journal 331, no. 1 (April 1, 1998): 217–23. http://dx.doi.org/10.1042/bj3310217.

Full text

Abstract:

The mechanism of import of phosphatidylserine (PtdSer) into mitochondria was investigated using a reconstituted system of isolated organelles in vitroin which PtdSer was translocated from donor membranes to mitochondria and was decarboxylated therein. Neither phosphatidylcholine nor phosphatidylethanolamine (PtdEtn) was translocated under the same conditions. Transfer of PtdSer from its site of synthesis on the endoplasmic reticulum and mitochondria-associated membranes [J. E. Vance (1990) J. Biol. Chem. 265, 7248–7256] to its site of decarboxylation on mitochondrial inner membranes is predicted to be mediated by membrane contact. A mitochondrial membrane protein appears to be involved in the translocation event since proteolysis of proteins exposed on the mitochondrial surface potently inhibited PtdSer transfer, whereas proteolysis of surface proteins of mitochondria-associated membranes did not impair the transfer. The nature of the membranes that donate PtdSer to mitochondria in vitrois not crucial since PtdSer of mitochondria-associated membranes, endoplasmic reticulum and microsomes was decarboxylated to PtdEtn with approximately equal efficiency. The translocation of PtdSer to mitochondria was stimulated by magnesium and calcium ions and was inhibited by incubation of mitochondria with sulphydryl group-modifying reagents. Reconstitution of PtdSer translocation/decarboxylation using digitonin-solubilized mitochondria and PtdSer-donor membranes suggested that the putative PtdSer-translocation protein is primarily localized to contract sites between mitochondrial inner and outer membranes. These studies provide evidence for the involvement of a mitochondrial membrane protein in the import of newly-synthesized PtdSer into mitochondria.

APA, Harvard, Vancouver, ISO, and other styles

17

Axmann, Markus, Birgit Plochberger, Mario Mikula, Florian Weber, Witta Monika Strobl, and Herbert Stangl. "Plasma Membrane Lipids: An Important Binding Site for All Lipoprotein Classes." Membranes 11, no. 11 (November 17, 2021): 882. http://dx.doi.org/10.3390/membranes11110882.

Full text

Abstract:

Cholesterol is one of the main constituents of plasma membranes; thus, its supply is of utmost importance. This review covers the known mechanisms of cholesterol transfer from circulating lipoprotein particles to the plasma membrane, and vice versa. To achieve homeostasis, the human body utilizes cellular de novo synthesis and extracellular transport particles for supply of cholesterol and other lipids via the blood stream. These lipoprotein particles can be classified according to their density: chylomicrons, very low, low, and high-density lipoprotein (VLDL, LDL, and HDL, respectively). They deliver and receive their lipid loads, most importantly cholesterol, to and from cells by several redundant routes. Defects in one of these pathways (e.g., due to mutations in receptors) usually are not immediately fatal. Several redundant pathways, at least temporarily, compensate for the loss of one or more of them, but the defects trigger systemic diseases, such as atherosclerosis later on. Recently, intracellular membrane–membrane contact sites were shown to be involved in intracellular cholesterol transfer and the plasma membrane itself has been proposed to act as a binding site for lipoprotein-mediated cargo unloading.

APA, Harvard, Vancouver, ISO, and other styles

18

Olmo, Valerie N., and Eric Grote. "Prm1 Targeting to Contact Sites Enhances Fusion during Mating in Saccharomyces cerevisiae." Eukaryotic Cell 9, no. 10 (August 20, 2010): 1538–48. http://dx.doi.org/10.1128/ec.00116-10.

Full text

Abstract:

ABSTRACT Prm1 is a pheromone-regulated membrane glycoprotein involved in the plasma membrane fusion event of Saccharomyces cerevisiae mating. Although this function suggests that Prm1 should act at contact sites in pairs of mating yeast cells where plasma membrane fusion occurs, only a small percentage of the total Prm1 was actually detected on the plasma membrane. We therefore investigated the intracellular transport of Prm1 and how this transport contributes to cell fusion. Two Prm1 chimeras that were sorted away from the contact site had reduced fusion activity, indicating that Prm1 indeed functions at contact sites. However, most Prm1 is located in endosomes and other cytoplasmic organelles and is targeted to vacuoles for degradation. Mutations in a putative endocytosis signal in a cytoplasmic loop partially stabilized the Prm1 protein and caused it to accumulate on the plasma membrane, but this endocytosis mutant actually had reduced mating activity. When Prm1 was expressed from a galactose-regulated promoter and its synthesis was repressed at the start of mating, vanishingly small amounts of Prm1 protein remained at the time when the plasma membranes came into contact. Nevertheless, this stable pool of Prm1 was retained at polarized sites on the plasma membrane and was sufficient to promote plasma membrane fusion. Thus, the amount of Prm1 expressed in mating yeast is far in excess of the amount required to facilitate fusion.

APA, Harvard, Vancouver, ISO, and other styles

19

Georgatos, S. D., D. C. Weaver, and V. T. Marchesi. "Site specificity in vimentin-membrane interactions: intermediate filament subunits associate with the plasma membrane via their head domains." Journal of Cell Biology 100, no. 6 (June 1, 1985): 1962–67. http://dx.doi.org/10.1083/jcb.100.6.1962.

Full text

Abstract:

Fragments of vimentin, generated by chemical or enzymatic cleavages, were analyzed for their capacity to bind to human inverted erythrocyte membrane vesicles. Only peptides comprising the amino-terminal head domain of vimentin molecules were competent in associating with the membranes. In vitro studies also demonstrated that isolated ankyrin (the major vimentin acceptor site on the membrane) binds to an oligomeric species of vimentin and prevents the formation of characteristic 10-nm filaments. These data, taken together with the observation that the NH2-terminal end of vimentin is implicated in the polymerization process (Traub, P., and C. Vorgias, J. Cell Sci., 1983, 63:43-67), imply that intermediate filaments may contact the membrane in an end-on fashion, using the exposed head domains of their terminal subunits.

APA, Harvard, Vancouver, ISO, and other styles

20

Sachelaru, Ilie, Narcis Adrian Petriman, Renuka Kudva, Patrick Kuhn, Thomas Welte, Bettina Knapp, Friedel Drepper, Bettina Warscheid, and Hans-Georg Koch. "YidC Occupies the Lateral Gate of the SecYEG Translocon and Is Sequentially Displaced by a Nascent Membrane Protein." Journal of Biological Chemistry 288, no. 23 (April 22, 2013): 16295–307. http://dx.doi.org/10.1074/jbc.m112.446583.

Full text

Abstract:

Most membrane proteins are co-translationally inserted into the lipid bilayer via the universally conserved SecY complex and they access the lipid phase presumably via a lateral gate in SecY. In bacteria, the lipid transfer of membrane proteins from the SecY channel is assisted by the SecY-associated protein YidC, but details on the SecY-YidC interaction are unknown. By employing an in vivo and in vitro site-directed cross-linking approach, we have mapped the SecY-YidC interface and found YidC in contact with all four transmembrane domains of the lateral gate. This interaction did not require the SecDFYajC complex and was not influenced by SecA binding to SecY. In contrast, ribosomes dissociated the YidC contacts to lateral gate helices 2b and 8. The major contact between YidC and the lateral gate was lost in the presence of ribosome nascent chains and new SecY-YidC contacts appeared. These data demonstrate that the SecY-YidC interaction is influenced by nascent-membrane-induced lateral gate movements.

APA, Harvard, Vancouver, ISO, and other styles

21

Vissers, MC, WA Day, and CC Winterbourn. "Neutrophils adherent to a nonphagocytosable surface (glomerular basement membrane) produce oxidants only at the site of attachment." Blood 66, no. 1 (July 1, 1985): 161–66. http://dx.doi.org/10.1182/blood.v66.1.161.161.

Full text

Abstract:

Abstract Adherence of neutrophils to glomerular basement membrane containing immunoglobulin G aggregates was accompanied by a marked increase in oxygen uptake (eightfold). Very little of the O2 consumed was recovered as superoxide, measured by cytochrome c reduction, or as H2O2, measured with horseradish peroxidase and scopoletin. When neutrophils were incubated with the basement membrane preparation in the presence of cerium chloride to detect H2O2, electron micrographs showed cerium perhydroxide deposits in the contact area between the cells and the basement membrane, but not on the remainder of the cell surface. The results imply that superoxide is produced only where the plasma membrane is in contact with the basement membrane matrix, and that it mostly breaks down to H2O2 or undergoes other reactions at this site. The longer lifetime of H2O2 compared with that of superoxide allows some of the H2O2 produced to be detected in the medium. The results also suggest that the area of contact between the neutrophil and surfaces such as basement membrane is inaccessible to proteins in the medium, eg, cytochrome c. Circulating scavengers such as superoxide dismutase or catalase, or proteolytic inhibitors, may therefore be unable to control events occurring at this site.

APA, Harvard, Vancouver, ISO, and other styles

22

Vissers, MC, WA Day, and CC Winterbourn. "Neutrophils adherent to a nonphagocytosable surface (glomerular basement membrane) produce oxidants only at the site of attachment." Blood 66, no. 1 (July 1, 1985): 161–66. http://dx.doi.org/10.1182/blood.v66.1.161.bloodjournal661161.

Full text

Abstract:

Adherence of neutrophils to glomerular basement membrane containing immunoglobulin G aggregates was accompanied by a marked increase in oxygen uptake (eightfold). Very little of the O2 consumed was recovered as superoxide, measured by cytochrome c reduction, or as H2O2, measured with horseradish peroxidase and scopoletin. When neutrophils were incubated with the basement membrane preparation in the presence of cerium chloride to detect H2O2, electron micrographs showed cerium perhydroxide deposits in the contact area between the cells and the basement membrane, but not on the remainder of the cell surface. The results imply that superoxide is produced only where the plasma membrane is in contact with the basement membrane matrix, and that it mostly breaks down to H2O2 or undergoes other reactions at this site. The longer lifetime of H2O2 compared with that of superoxide allows some of the H2O2 produced to be detected in the medium. The results also suggest that the area of contact between the neutrophil and surfaces such as basement membrane is inaccessible to proteins in the medium, eg, cytochrome c. Circulating scavengers such as superoxide dismutase or catalase, or proteolytic inhibitors, may therefore be unable to control events occurring at this site.

APA, Harvard, Vancouver, ISO, and other styles

23

Yadav, Shweta, Shamshad Cockcroft, and Padinjat Raghu. "The Drosophila photoreceptor as a model system for studying signalling at membrane contact sites." Biochemical Society Transactions 44, no. 2 (April 11, 2016): 447–51. http://dx.doi.org/10.1042/bst20150256.

Full text

Abstract:

Several recent studies have demonstrated the existence of membrane contact sites (MCS) between intracellular organelles in eukaryotic cells. Recent exciting studies have also demonstrated the existence of biomolecular interactions at these contact sites in mediating changes in the membrane composition of the cellular compartments. However, the role of such contact sites in regulating organelle function and physiological processes remains less clear. In this review we discuss the existence of a contact site between the plasma membrane (PM) and the endoplasmic reticulum (ER) in Drosophila photoreceptors. Further, we discuss the role of specific proteins present at this location in regulating phospholipid turnover and its impact in regulating a physiological process, namely phototransduction.

APA, Harvard, Vancouver, ISO, and other styles

24

Hayes, Matthew J., Anne-C. Zakrzewski, Timothy P. Levine, and Maximilian J. Telford. "Nucleus–Plasma Membrane Contact Sites Are Formed During Spermiogenesis in the Acoel Symsagittifera roscoffensis." Contact 3 (January 2020): 251525642092635. http://dx.doi.org/10.1177/2515256420926354.

Full text

Abstract:

Symsagittifera roscoffensis is a small marine worm found in the intertidal zone of sandy beaches around the European shores of the Atlantic. S. roscoffensis is a member of the Acoelomorpha, a group of flatworms formerly classified with the Platyhelminthes, but now recognized as Xenacoelomorpha, a separate phylum of disputed affinity. We have used electron microscopy to examine the process of spermiogenesis (the final stage of spermatogenesis) in S. roscoffensis, by which spermatids form highly elongated spermatozoa. Their nuclei are long and thread-like, running most of the cell’s length, and during the process, a pair of flagella are fully incorporated into the cell body. Two previously undescribed interorganelle contact sites form at different stages of spermiogenesis. Strikingly, there is an extensive nucleus–plasma membrane contact site. Golgi-derived granules containing electron-dense filaments line up along the spermatid plasma membrane, undergo a conformational change, and donate material that forms a perinuclear layer that cements this contact site. We also show in spermatids at an earlier stage that the same granules are associated with microtubules, presumably for traffic along the elongating cell. We identify a second spermiogenesis-specific contact site where sheaths engulfing each internalizing flagellum contact the nuclear envelope.

APA, Harvard, Vancouver, ISO, and other styles

25

McCulloh, D. H., and E. L. Chambers. "Fusion of membranes during fertilization. Increases of the sea urchin egg's membrane capacitance and membrane conductance at the site of contact with the sperm." Journal of General Physiology 99, no. 2 (February 1, 1992): 137–75. http://dx.doi.org/10.1085/jgp.99.2.137.

Full text

Abstract:

The early events of fertilization that precede and cause activation of an egg have not been fully elucidated. The earliest electrophysiological change in the sea urchin egg is a sperm-evoked increase of the egg's membrane conductance. The resulting depolarization facilitates entry of the fertilizing sperm and precludes the entry of supernumerary sperm. The sequence of the increase in the egg's membrane conductance, gamete membrane fusion, egg activation, and sperm entry, including causal relationships between these events, are not known. This study reports the use of whole egg voltage clamp and loose patch clamp to monitor simultaneously changes of membrane conductance and capacitance at the site of sperm-egg contact. Measurements were made during sperm-egg interactions where sperm entry readily proceeded or was precluded by maintaining the egg's membrane potential either at large, negative values or at positive values. Whenever the sperm evoked an increase of the egg's membrane conductance, that increase initiated abruptly, was localized to the site of sperm attachment, and was accompanied by a simultaneous abrupt increase of the membrane capacitance. This increase of capacitance indicated the establishment of electrical continuity between gametes (possibly fusion of the gametes' plasma membranes). If sperm entry was blocked by large negative membrane potentials, the capacitance cut off rapidly and simultaneously with a decrease of the membrane conductance, indicating that electrical continuity between gametes was disrupted. When sperm entry was precluded by positive membrane potentials, neither conductance nor capacitance increased, indicating that sperm entry was halted before the fusion of membranes. A second, smooth increase of capacitance was associated with the exocytosis of cortical granules near the sperm in eggs that were activated. Electrical continuity between the gametes always preceded activation of the egg, but transient electrical continuity between the gametes alone was not always sufficient to induce activation.

APA, Harvard, Vancouver, ISO, and other styles

26

Schulz, Timothy A., Mal-Gi Choi, Sumana Raychaudhuri, Jason A. Mears, Rodolfo Ghirlando, Jenny E. Hinshaw, and William A. Prinz. "Lipid-regulated sterol transfer between closely apposed membranes by oxysterol-binding protein homologues." Journal of Cell Biology 187, no. 6 (December 14, 2009): 889–903. http://dx.doi.org/10.1083/jcb.200905007.

Full text

Abstract:

Sterols are transferred between cellular membranes by vesicular and poorly understood nonvesicular pathways. Oxysterol-binding protein–related proteins (ORPs) have been implicated in sterol sensing and nonvesicular transport. In this study, we show that yeast ORPs use a novel mechanism that allows regulated sterol transfer between closely apposed membranes, such as organelle contact sites. We find that the core lipid-binding domain found in all ORPs can simultaneously bind two membranes. Using Osh4p/Kes1p as a representative ORP, we show that ORPs have at least two membrane-binding surfaces; one near the mouth of the sterol-binding pocket and a distal site that can bind a second membrane. The distal site is required for the protein to function in cells and, remarkably, regulates the rate at which Osh4p extracts and delivers sterols in a phosphoinositide-dependent manner. Together, these findings suggest a new model of how ORPs could sense and regulate the lipid composition of adjacent membranes.

APA, Harvard, Vancouver, ISO, and other styles

27

Anari, Zahra, Arijit Sengupta, and Sumith Wickramasinghe. "Surface Oxidation of Ethylenechlorotrifluoroethylene (ECTFE) Membrane for the Treatment of Real Produced Water by Membrane Distillation." International Journal of Environmental Research and Public Health 15, no. 8 (July 24, 2018): 1561. http://dx.doi.org/10.3390/ijerph15081561.

Full text

Abstract:

Modification of ethyleneechlorotrifluoroethylene (ECTFE) membranes by simple surface oxidation was reported in the present investigation in order to induce thin hydrophilic layer on hydrophobic membrane surface for the treatment of real produced water (PW). FTIR spectra indicates the appearance of hydrophilic functional groups (–OH and –COOH) on the membrane surface due to modification, while water contact angle, zeta potential measurement, EDX, XPS analysis confirmed the presence of O functionalized hydrophilic groups on the surface. The effect of modification temperature and the time of surface oxidation on the performance of the resulting membranes were studied systematically, which revealed that induction of optimized hydrophilicity can successfully reduce the organic fouling. However, too much hydrophilic surface induces polar/electrostatic interaction resulting salt deposition on membrane surface. A simple on site cleaning procedure was demonstrated to be successful for the treatment PW for at least three consecutive cycles of membrane distillation (MD).

APA, Harvard, Vancouver, ISO, and other styles

28

Murley, Andrew, Reta D. Sarsam, Alexandre Toulmay, Justin Yamada, William A. Prinz, and Jodi Nunnari. "Ltc1 is an ER-localized sterol transporter and a component of ER–mitochondria and ER–vacuole contacts." Journal of Cell Biology 209, no. 4 (May 18, 2015): 539–48. http://dx.doi.org/10.1083/jcb.201502033.

Full text

Abstract:

Organelle contact sites perform fundamental functions in cells, including lipid and ion homeostasis, membrane dynamics, and signaling. Using a forward proteomics approach in yeast, we identified new ER–mitochondria and ER–vacuole contacts specified by an uncharacterized protein, Ylr072w. Ylr072w is a conserved protein with GRAM and VASt domains that selectively transports sterols and is thus termed Ltc1, for Lipid transfer at contact site 1. Ltc1 localized to ER–mitochondria and ER–vacuole contacts via the mitochondrial import receptors Tom70/71 and the vacuolar protein Vac8, respectively. At mitochondria, Ltc1 was required for cell viability in the absence of Mdm34, a subunit of the ER–mitochondria encounter structure. At vacuoles, Ltc1 was required for sterol-enriched membrane domain formation in response to stress. Increasing the proportion of Ltc1 at vacuoles was sufficient to induce sterol-enriched vacuolar domains without stress. Thus, our data support a model in which Ltc1 is a sterol-dependent regulator of organelle and cellular homeostasis via its dual localization to ER–mitochondria and ER–vacuole contact sites.

APA, Harvard, Vancouver, ISO, and other styles

29

Selitrennik, Michael, and Sima Lev. "The role of phosphatidylinositol-transfer proteins at membrane contact sites." Biochemical Society Transactions 44, no. 2 (April 11, 2016): 419–24. http://dx.doi.org/10.1042/bst20150182.

Full text

Abstract:

Phosphatidylinositol-transfer proteins (PITPs) have been initially identified as soluble factors that accelerate the monomeric exchange of either phosphatidylinositol (PI) or phosphatidylcholine (PC) between membrane bilayers in vitro. They are highly conserved in eukaryotes and have been implicated in different cellular processes, including vesicular trafficking, signal transduction, and lipid metabolism. Recent studies suggest that PITPs function at membrane contact sites (MCSs) to facilitate the transport of PI from its synthesis site at the endoplasmic reticulum (ER) to various membrane compartments. In this review, we describe the underlying mechanism of PITPs targeting to MCSs, discuss their cellular roles and potential mode of action.

APA, Harvard, Vancouver, ISO, and other styles

30

FRASER, Fiona, and A. Victor ZAMMIT. "Enrichment of carnitine palmitoyltransferases I and II in the contact sites of rat liver mitochondria." Biochemical Journal 329, no. 2 (January 15, 1998): 225–29. http://dx.doi.org/10.1042/bj3290225.

Full text

Abstract:

The submitochondrial distribution of the overt and latent carnitine palmitoyltransferases (CPT I and II respectively) of rat liver mitochondria were studied. Separation of outer and inner membranes, as well as of a fraction of intermediate density consisting of contact sites between the two membranes, was achieved, as judged by the distribution of marker enzymes. Both CPT I and CPT II were found to be enriched within the contact- site fraction of mitochondria. These data show that the two carnitine acyltransferases are distributed non-uniformly within their respective membranes, and that subpopulations of the two enzymes occur in close proximity within the mitochondrial membrane structure, while retaining their different accessibilities to cytosolic and matrix pools of metabolites. As the number of contact sites is known to vary with changes in the energy status of mitochondria, the possibility that such changes may acutely affect the proportion of CPT I within the distinctive lipid environment of the contact sites, and thus its overall kinetic characteristics, is discussed.

APA, Harvard, Vancouver, ISO, and other styles

31

McCloskey, M. A., and M. M. Poo. "Contact-induced redistribution of specific membrane components: local accumulation and development of adhesion." Journal of Cell Biology 102, no. 6 (June 1, 1986): 2185–96. http://dx.doi.org/10.1083/jcb.102.6.2185.

Full text

Abstract:

We have used a model system to explore the importance of long-range lateral diffusion of membrane proteins in specific membrane-membrane adhesion. Single, cell-size phospholipid vesicles containing a dinitrophenyl (DNP)-lipid hapten were maneuvered into contact with rat basophilic leukemia (RBL) cells carrying fluorescent anti-DNP IgE in their cell-surface Fc epsilon receptors. Upon cell-vesicle contact the antibody molecules underwent a marked lateral redistribution, accumulating at the site of contact and becoming significantly depleted from noncontacting membrane. As assayed with a micropipette suction method, there was a time-dependent increase in the strength of cell-vesicle adhesion. This development of adhesion paralleled the kinetics of accumulation of the adhesion-mediating antibody molecules at the zone of membrane-membrane contact. Both adhesion and redistribution were absolutely dependent upon a specific interaction of the IgE with the hapten: No redistribution occurred when vesicles lacking the DNP hapten were pushed against IgE-armed RBL cells, and on cells bearing a 1:1 mixture of nonimmune rat IgE and anti-DNP mouse IgE, only the latter underwent redistribution. Vesicles containing DNP-lipids bound to RBL cells carrying anti-DNP IgE but not to cells carrying nonimmune rat IgE. Measurable nonspecific binding did not develop even after 15 min of pushing DNP-bearing vesicles against RBL cells sensitized with nonimmune IgE. Neither redistribution nor adhesion was blocked by metabolic poisons such as NaN3 and NaF. Both redistribution and adhesion occurred in plasma membrane blebs previously shown to lack cytoskeletal filaments. The above observations are consistent with contact-induced redistribution of the IgE being a result of passive diffusion-mediated trapping rather than active cellular responses. Thus, long-range diffusion of specific proteins can in some cases contribute to the formation of stable adhesion between membranes.

APA, Harvard, Vancouver, ISO, and other styles

32

Jin, Hui, J. Michael McCaffery, and Eric Grote. "Ergosterol promotes pheromone signaling and plasma membrane fusion in mating yeast." Journal of Cell Biology 180, no. 4 (February 25, 2008): 813–26. http://dx.doi.org/10.1083/jcb.200705076.

Full text

Abstract:

Ergosterol depletion independently inhibits two aspects of yeast mating: pheromone signaling and plasma membrane fusion. In signaling, ergosterol participates in the recruitment of Ste5 to a polarized site on the plasma membrane. Ergosterol is thought to form microdomains within the membrane by interacting with the long acyl chains of sphingolipids. We find that although sphingolipid-free ergosterol is concentrated at sites of cell–cell contact, transmission of the pheromone signal at contact sites depends on a balanced ratio of ergosterol to sphingolipids. If a mating pair forms between ergosterol-depleted cells despite the attenuated pheromone response, the subsequent process of membrane fusion is retarded. Prm1 also participates in membrane fusion. However, ergosterol and Prm1 have independent functions and only prm1 mutant mating pairs are susceptible to contact-dependent lysis. In contrast to signaling, plasma membrane fusion is relatively insensitive to sphingolipid depletion. Thus, the sphingolipid-free pool of ergosterol promotes plasma membrane fusion.

APA, Harvard, Vancouver, ISO, and other styles

33

Sytnyk, Vladimir, Iryna Leshchyns'ka, Markus Delling, Galina Dityateva, Alexander Dityatev, and Melitta Schachner. "Neural cell adhesion molecule promotes accumulation of TGN organelles at sites of neuron-to-neuron contacts." Journal of Cell Biology 159, no. 4 (November 18, 2002): 649–61. http://dx.doi.org/10.1083/jcb.200205098.

Full text

Abstract:

Transformation of a contact between axon and dendrite into a synapse is accompanied by accumulation of the synaptic machinery at this site, being delivered in intracellular organelles mainly of TGN origin. Here, we report that in cultured hippocampal neurons, TGN organelles are linked via spectrin to clusters of the neural cell adhesion molecule (NCAM) in the plasma membrane. These complexes are translocated along neurites and trapped at sites of initial neurite-to-neurite contacts within several minutes after initial contact formation. The accumulation of TGN organelles at contacts with NCAM-deficient neurons is reduced when compared with wild-type cells, suggesting that NCAM mediates the anchoring of intracellular organelles in nascent synapses.

APA, Harvard, Vancouver, ISO, and other styles

34

Lin, Wenwu, Zhike Feng, K. Reddisiva Prasanth, Yuyan Liu, and Peter D. Nagy. "Dynamic interplay between the co-opted Fis1 mitochondrial fission protein and membrane contact site proteins in supporting tombusvirus replication." PLOS Pathogens 17, no. 3 (March 16, 2021): e1009423. http://dx.doi.org/10.1371/journal.ppat.1009423.

Full text

Abstract:

Plus-stranded RNA viruses have limited coding capacity and have to co-opt numerous pro-viral host factors to support their replication. Many of the co-opted host factors support the biogenesis of the viral replication compartments and the formation of viral replicase complexes on subverted subcellular membrane surfaces. Tomato bushy stunt virus (TBSV) exploits peroxisomal membranes, whereas the closely-related carnation Italian ringspot virus (CIRV) hijacks the outer membranes of mitochondria. How these organellar membranes can be recruited into pro-viral roles is not completely understood. Here, we show that the highly conserved Fis1 mitochondrial fission protein is co-opted by both TBSV and CIRV via direct interactions with the p33/p36 replication proteins. Deletion ofFIS1in yeast or knockdown of the homologous Fis1 in plants inhibits tombusvirus replication. Instead of the canonical function in mitochondrial fission and peroxisome division, the tethering function of Fis1 is exploited by tombusviruses to facilitate the subversion of membrane contact site (MCS) proteins and peroxisomal/mitochondrial membranes for the biogenesis of the replication compartment. We propose that the dynamic interactions of Fis1 with MCS proteins, such as the ER resident VAP tethering proteins, Sac1 PI4P phosphatase and the cytosolic OSBP-like oxysterol-binding proteins, promote the formation and facilitate the stabilization of virus-induced vMCSs, which enrich sterols within the replication compartment. We show that this novel function of Fis1 is exploited by tombusviruses to build nuclease-insensitive viral replication compartment.

APA, Harvard, Vancouver, ISO, and other styles

35

Schuldiner, Maya, and Einat Zalckvar. "Incredibly close—A newly identified peroxisome–ER contact site in humans." Journal of Cell Biology 216, no. 2 (January 20, 2017): 287–89. http://dx.doi.org/10.1083/jcb.201701072.

Full text

Abstract:

Peroxisomes are tiny organelles that control important and diverse metabolic processes via their interplay with other organelles, including the endoplasmic reticulum (ER). In this issue, Costello et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201607055) and Hua et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201608128) identify a peroxisome–ER contact site in human cells held together by a tethering complex of VAPA/B (vesicle-associated membrane protein–associated proteins A/B) and ACBD5 (acyl Co-A binding protein 5).

APA, Harvard, Vancouver, ISO, and other styles

36

Chan, P. Y., M. B. Lawrence, M. L. Dustin, L. M. Ferguson, D. E. Golan, and T. A. Springer. "Influence of receptor lateral mobility on adhesion strengthening between membranes containing LFA-3 and CD2." Journal of Cell Biology 115, no. 1 (October 1, 1991): 245–55. http://dx.doi.org/10.1083/jcb.115.1.245.

Full text

Abstract:

We have used an in vitro model system of glass-supported planar membranes to study the effects of lateral mobility of membrane-bound receptors on cell adhesion. Egg phosphatidylcholine (PC) bilayers were reconstituted with two anchorage isoforms of the adhesion molecule lymphocyte function-associated antigen 3 (LFA-3). The diffusion coefficient of glycosyl phosphatidylinositol (GPI)-anchored LFA-3 approached that of phospholipids in the bilayers, whereas the transmembrane (TM)-anchored isoform of LFA-3 was immobile. Both static and laminar flow assays were used to quantify the strength of adherence to the lipid bilayers of the T lymphoma cell line Jurkat that expresses the counter-receptor CD2. Cell adhesion was dependent on LFA-3 density and was more efficient on membranes containing the GPI isoform than the TM isoform. Kinetic measurements demonstrated an influence of contact time on the strength of adhesion to the GPI isoform at lower site densities (25-50 sites/microns2), showing that the mobility of LFA-3 is important in adhesion strengthening. At higher site densities (1,500 sites/microns2) and longer contact times (20 min), Jurkat cell binding to the TM and GPI isoforms of LFA-3 showed equivalent adhesion strengths, although adhesion strength of the GPI isoform developed twofold more rapidly than the TM isoform. Reduction of CD2 mobility on Jurkat cells at 5 degrees C greatly decreased the rate of adhesion strengthening with the TM isoform of LFA-3, resulting in a 30-fold difference between the two LFA-3 isoforms. Our results demonstrate that the ability of a membrane receptor and its membrane-bound counter-receptor to diffuse laterally enhances cell adhesion both by allowing accumulation of ligands in the cell contact area and by increasing the rate of receptor-ligand bond formation.

APA, Harvard, Vancouver, ISO, and other styles

37

Mahen, Robert. "cNap1 bridges centriole contact sites to maintain centrosome cohesion." PLOS Biology 20, no. 10 (October 25, 2022): e3001854. http://dx.doi.org/10.1371/journal.pbio.3001854.

Full text

Abstract:

Centrioles are non-membrane-bound organelles that participate in fundamental cellular processes through their ability to form physical contacts with other structures. During interphase, two mature centrioles can associate to form a single centrosome—a phenomenon known as centrosome cohesion. Centrosome cohesion is important for processes such as cell migration, and yet how it is maintained is unclear. Current models indicate that pericentriolar fibres termed rootlets, also known as the centrosome linker, entangle to maintain centriole proximity. Here, I uncover a centriole–centriole contact site and mechanism of centrosome cohesion based on coalescence of the proximal centriole component cNap1. Using live-cell imaging of endogenously tagged cNap1, I show that proximal centrioles form dynamic contacts in response to physical force from the cytoskeleton. Expansion microscopy reveals that cNap1 bridges between these contact sites, physically linking proximal centrioles on the nanoscale. Fluorescence correlation spectroscopy (FCS)-calibrated imaging shows that cNap1 accumulates at nearly micromolar concentrations on proximal centrioles, corresponding to a few hundred protein copy numbers. When ectopically tethered to organelles such as lysosomes, cNap1 forms viscous and cohesive assemblies that promote organelle spatial proximity. These results suggest a mechanism of centrosome cohesion by cNap1 at the proximal centriole and illustrate how a non-membrane-bound organelle forms organelle contact sites.

APA, Harvard, Vancouver, ISO, and other styles

38

Taskinen, Juuso H., Hanna Ruhanen, Silke Matysik, Reijo Käkelä, and Vesa M. Olkkonen. "Systemwide effects of ER-intracellular membrane contact site disturbance in primary endothelial cells." Journal of Steroid Biochemistry and Molecular Biology 232 (September 2023): 106349. http://dx.doi.org/10.1016/j.jsbmb.2023.106349.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Hoffmann, Juliane J., and Thomas Becker. "Crosstalk between Mitochondrial Protein Import and Lipids." International Journal of Molecular Sciences 23, no. 9 (May 9, 2022): 5274. http://dx.doi.org/10.3390/ijms23095274.

Full text

Abstract:

Mitochondria import about 1000 precursor proteins from the cytosol. The translocase of the outer membrane (TOM complex) forms the major entry site for precursor proteins. Subsequently, membrane-bound protein translocases sort the precursor proteins into the outer and inner membrane, the intermembrane space, and the matrix. The phospholipid composition of mitochondrial membranes is critical for protein import. Structural and biochemical data revealed that phospholipids affect the stability and activity of mitochondrial protein translocases. Integration of proteins into the target membrane involves rearrangement of phospholipids and distortion of the lipid bilayer. Phospholipids are present in the interface between subunits of protein translocases and affect the dynamic coupling of partner proteins. Phospholipids are required for full activity of the respiratory chain to generate membrane potential, which in turn drives protein import across and into the inner membrane. Finally, outer membrane protein translocases are closely linked to organellar contact sites that mediate lipid trafficking. Altogether, intensive crosstalk between mitochondrial protein import and lipid biogenesis controls mitochondrial biogenesis.

APA, Harvard, Vancouver, ISO, and other styles

40

Tarasenko, Daryna, Mariam Barbot, Daniel C. Jans, Benjamin Kroppen, Boguslawa Sadowski, Gudrun Heim, Wiebke Möbius, Stefan Jakobs, and Michael Meinecke. "The MICOS component Mic60 displays a conserved membrane-bending activity that is necessary for normal cristae morphology." Journal of Cell Biology 216, no. 4 (March 2, 2017): 889–99. http://dx.doi.org/10.1083/jcb.201609046.

Full text

Abstract:

The inner membrane (IM) of mitochondria displays an intricate, highly folded architecture and can be divided into two domains: the inner boundary membrane adjacent to the outer membrane and invaginations toward the matrix, called cristae. Both domains are connected by narrow, tubular membrane segments called cristae junctions (CJs). The formation and maintenance of CJs is of vital importance for the organization of the mitochondrial IM and for mitochondrial and cellular physiology. The multisubunit mitochondrial contact site and cristae organizing system (MICOS) was found to be a major factor in CJ formation. In this study, we show that the MICOS core component Mic60 actively bends membranes and, when inserted into prokaryotic membranes, induces the formation of cristae-like plasma membrane invaginations. The intermembrane space domain of Mic60 has a lipid-binding capacity and induces membrane curvature even in the absence of the transmembrane helix. Mic60 homologues from α-proteobacteria display the same membrane deforming activity and are able to partially overcome the deletion of Mic60 in eukaryotic cells. Our results show that membrane bending by Mic60 is an ancient mechanism, important for cristae formation, and had already evolved before α-proteobacteria developed into mitochondria.

APA, Harvard, Vancouver, ISO, and other styles

41

Mothes, Walther, Berit Jungnickel, Josef Brunner, and Tom A. Rapoport. "Signal Sequence Recognition in Cotranslational Translocation by Protein Components of the Endoplasmic Reticulum Membrane." Journal of Cell Biology 142, no. 2 (July 27, 1998): 355–64. http://dx.doi.org/10.1083/jcb.142.2.355.

Full text

Abstract:

We have investigated the role of membrane proteins and lipids during early phases of the cotranslational insertion of secretory proteins into the translocation channel of the endoplasmic reticulum (ER) membrane. We demonstrate that all steps, including the one during which signal sequence recognition occurs, can be reproduced with purified translocation components in detergent solution, in the absence of bulk lipids or a bilayer. Photocross-linking experiments with native membranes show that upon complete insertion into the channel signal sequences are both precisely positioned with respect to the protein components of the channel and contact lipids. Together, these results indicate that signal sequences are bound to a specific binding site at the interface between the channel and the surrounding lipids, and are recognized ultimately by protein–protein interactions. Our data also suggest that at least some signal sequences reach the binding site by transfer through the interior of the channel.

APA, Harvard, Vancouver, ISO, and other styles

42

Johnson, Ben, Ashley N. Leek, Laura Solé, Emily E. Maverick, Tim P. Levine, and Michael M. Tamkun. "Kv2 potassium channels form endoplasmic reticulum/plasma membrane junctions via interaction with VAPA and VAPB." Proceedings of the National Academy of Sciences 115, no. 31 (June 25, 2018): E7331—E7340. http://dx.doi.org/10.1073/pnas.1805757115.

Full text

Abstract:

Kv2.1 exhibits two distinct forms of localization patterns on the neuronal plasma membrane: One population is freely diffusive and regulates electrical activity via voltage-dependent K+ conductance while a second one localizes to micrometer-sized clusters that contain densely packed, but nonconducting, channels. We have previously established that these clusters represent endoplasmic reticulum/plasma membrane (ER/PM) junctions that function as membrane trafficking hubs and that Kv2.1 plays a structural role in forming these membrane contact sites in both primary neuronal cultures and transfected HEK cells. Clustering and the formation of ER/PM contacts are regulated by phosphorylation within the channel C terminus, offering cells fast, dynamic control over the physical relationship between the cortical ER and PM. The present study addresses the mechanisms by which Kv2.1 and the related Kv2.2 channel interact with the ER membrane. Using proximity-based biotinylation techniques in transfected HEK cells we identified ER VAMP-associated proteins (VAPs) as potential Kv2.1 interactors. Confirmation that Kv2.1 and -2.2 bind VAPA and VAPB employed colocalization/redistribution, siRNA knockdown, and Förster resonance energy transfer (FRET)-based assays. CD4 chimeras containing sequence from the Kv2.1 C terminus were used to identify a noncanonical VAP-binding motif. VAPs were first identified as proteins required for neurotransmitter release in Aplysia and are now known to be abundant scaffolding proteins involved in membrane contact site formation throughout the ER. The VAP interactome includes AKAPs, kinases, membrane trafficking machinery, and proteins regulating nonvesicular lipid transport from the ER to the PM. Therefore, the Kv2-induced VAP concentration at ER/PM contact sites is predicted to have wide-ranging effects on neuronal cell biology.

APA, Harvard, Vancouver, ISO, and other styles

43

Lee, Jaeyong, Svetla G. Taneva, Bryan W. Holland, D. Peter Tieleman, and Rosemary B. Cornell. "Structural Basis for Autoinhibition of CTP:Phosphocholine Cytidylyltransferase (CCT), the Regulatory Enzyme in Phosphatidylcholine Synthesis, by Its Membrane-binding Amphipathic Helix." Journal of Biological Chemistry 289, no. 3 (November 25, 2013): 1742–55. http://dx.doi.org/10.1074/jbc.m113.526970.

Full text

Abstract:

CTP:phosphocholine cytidylyltransferase (CCT) interconverts between an inactive soluble and active membrane-bound form in response to changes in membrane lipid composition. Activation involves disruption of an inhibitory interaction between the αE helices at the base of the active site and an autoinhibitory (AI) segment in the regulatory M domain and membrane insertion of the M domain as an amphipathic helix. We show that in the CCT soluble form the AI segment functions to suppress kcat and elevate the Km for CTP. The crystal structure of a CCT dimer composed of the catalytic and AI segments reveals an AI-αE interaction as a cluster of four amphipathic helices (two αE and two AI helices) at the base of the active sites. This interaction corroborates mutagenesis implicating multiple hydrophobic residues within the AI segment that contribute to its silencing function. The AI-αE interaction directs the turn at the C-terminal end of the AI helix into backbone-to-backbone contact with a loop (L2) at the opening to the active site, which houses the key catalytic residue, lysine 122. Molecular dynamics simulations suggest that lysine 122 side-chain orientations are constrained by contacts with the AI helix-turn, which could obstruct its engagement with substrates. This work deciphers how the CCT regulatory amphipathic helix functions as a silencing device.

APA, Harvard, Vancouver, ISO, and other styles

44

Welte, Thomas, Renuka Kudva, Patrick Kuhn, Lukas Sturm, David Braig, Matthias Müller, Bettina Warscheid, Friedel Drepper, and Hans-Georg Koch. "Promiscuous targeting of polytopic membrane proteins to SecYEG or YidC by the Escherichia coli signal recognition particle." Molecular Biology of the Cell 23, no. 3 (February 2012): 464–79. http://dx.doi.org/10.1091/mbc.e11-07-0590.

Full text

Abstract:

Protein insertion into the bacterial inner membrane is facilitated by SecYEG or YidC. Although SecYEG most likely constitutes the major integration site, small membrane proteins have been shown to integrate via YidC. We show that YidC can also integrate multispanning membrane proteins such as mannitol permease or TatC, which had been considered to be exclusively integrated by SecYEG. Only SecA-dependent multispanning membrane proteins strictly require SecYEG for integration, which suggests that SecA can only interact with the SecYEG translocon, but not with the YidC insertase. Targeting of multispanning membrane proteins to YidC is mediated by signal recognition particle (SRP), and we show by site-directed cross-linking that the C-terminus of YidC is in contact with SRP, the SRP receptor, and ribosomal proteins. These findings indicate that SRP recognizes membrane proteins independent of the downstream integration site and that many membrane proteins can probably use either SecYEG or YidC for integration. Because protein synthesis is much slower than protein transport, the use of YidC as an additional integration site for multispanning membrane proteins may prevent a situation in which the majority of SecYEG complexes are occupied by translating ribosomes during cotranslational insertion, impeding the translocation of secretory proteins.

APA, Harvard, Vancouver, ISO, and other styles

45

Aaltonen, Mari J., Jonathan R. Friedman, Christof Osman, Bénédicte Salin, Jean-Paul di Rago, Jodi Nunnari, Thomas Langer, and Takashi Tatsuta. "MICOS and phospholipid transfer by Ups2–Mdm35 organize membrane lipid synthesis in mitochondria." Journal of Cell Biology 213, no. 5 (May 30, 2016): 525–34. http://dx.doi.org/10.1083/jcb.201602007.

Full text

Abstract:

Mitochondria exert critical functions in cellular lipid metabolism and promote the synthesis of major constituents of cellular membranes, such as phosphatidylethanolamine (PE) and phosphatidylcholine. Here, we demonstrate that the phosphatidylserine decarboxylase Psd1, located in the inner mitochondrial membrane, promotes mitochondrial PE synthesis via two pathways. First, Ups2–Mdm35 complexes (SLMO2–TRIAP1 in humans) serve as phosphatidylserine (PS)-specific lipid transfer proteins in the mitochondrial intermembrane space, allowing formation of PE by Psd1 in the inner membrane. Second, Psd1 decarboxylates PS in the outer membrane in trans, independently of PS transfer by Ups2–Mdm35. This latter pathway requires close apposition between both mitochondrial membranes and the mitochondrial contact site and cristae organizing system (MICOS). In MICOS-deficient cells, limiting PS transfer by Ups2–Mdm35 and reducing mitochondrial PE accumulation preserves mitochondrial respiration and cristae formation. These results link mitochondrial PE metabolism to MICOS, combining functions in protein and lipid homeostasis to preserve mitochondrial structure and function.

APA, Harvard, Vancouver, ISO, and other styles

46

Murphy, CR. "THE PLASMA MEMBRANE TRANSFORMATION: A KEY CONCEPT IN UTERINE RECEPTIVITY." Reproductive Medicine Review 9, no. 3 (October 2001): 197–208. http://dx.doi.org/10.1017/s0962279901000321.

Full text

Abstract:

The first site of contact between maternal and fetal tissue at the beginning of blastocyst attachment and implantation is the plasma membrane of uterine epithelial cells. Indeed, as has been noted often, regardless of the mode of placentation which ultimately occurs, contact between this plasma membrane and that of the trophoblast is a common beginning to implantation in most species studied so far, which now range from viviparous lizards to human beings. The similarities in these early events of uterine receptivity and placentation go further than mere contact between opposing surfaces however. A considerable body of evidence indicates that the behaviour of the plasma membrane of uterine epithelial cells during early pregnancy has many common aspects across species including humans. This review pays special attention to events in the human uterus and the epithelial cells in particular, but examines them within the wider context of uterine receptivity for implantation across species.

APA, Harvard, Vancouver, ISO, and other styles

47

Kumakiri, Izumi, Yusuke Maruo, Ryotaro Kishibe, Masayuki Murata, Tomoyuki Kosaka, and Mamoru Yamada. "Application of Zeolite Membranes to Dehydrate a Bio-Ethanol Solution Produced by High-Temperature Fermentation." Fuels 2, no. 4 (December 3, 2021): 533–45. http://dx.doi.org/10.3390/fuels2040031.

Full text

Abstract:

The combination of high-temperature fermentation and membrane separation has the potential to realize a simple on-site process to produce concentrated bioethanol. The performance of dehydration membranes in separating bioethanol was investigated in this study. Three types of zeolite membranes, LTA, MFI, and MOR, were synthesized. Their dehydration ability was compared using a bioethanol solution produced by high-temperature fermentation followed by vacuum distillation. The LTA zeolite membranes deformed and became amorphous while treating the distillate. On the contrary, no significant changes were observed in the MFI and MOR zeolite membranes analyzed by X-ray diffraction after treating the distillate. However, the flux declined when the membranes were in contact with the distillate (pH = 3.8). Neutralizing the distillate to pH 6.6 with sodium hydroxide did not prevent the flux decline. Even though flux decreased by about 20–30%, the MOR membrane showed quite high water-selectivity, with a water concentration of over 99.9% in the permeate, suggesting the feasibility of its application to concentrate bioethanol.

APA, Harvard, Vancouver, ISO, and other styles

48

Pawlik, Grzegorz, Mike F. Renne, Matthijs A. Kol, and Anton I. P. M. de Kroon. "The topology of the ER-resident phospholipid methyltransferase Opi3 of Saccharomyces cerevisiae is consistent with in trans catalysis." Journal of Biological Chemistry 295, no. 8 (January 13, 2020): 2473–82. http://dx.doi.org/10.1074/jbc.ra119.011102.

Full text

Abstract:

Phospholipid N-methyltransferases (PLMTs) synthesize phosphatidylcholine by methylating phosphatidylethanolamine using S-adenosylmethionine as a methyl donor. Eukaryotic PLMTs are integral membrane enzymes located in the endoplasmic reticulum (ER). Recently Opi3, a PLMT of the yeast Saccharomyces cerevisiae was proposed to perform in trans catalysis, i.e. while localized in the ER, Opi3 would methylate lipid substrates located in the plasma membrane at membrane contact sites. Here, we tested whether the Opi3 active site is located at the cytosolic side of the ER membrane, which is a prerequisite for in trans catalysis. The membrane topology of Opi3 (and its human counterpart, phosphatidylethanolamine N-methyltransferase, expressed in yeast) was addressed by topology prediction algorithms and by the substituted cysteine accessibility method. The results of these analyses indicated that Opi3 (as well as phosphatidylethanolamine N-methyltransferase) has an N-out C-in topology and contains four transmembrane domains, with the fourth forming a re-entrant loop. On the basis of the sequence conservation between the C-terminal half of Opi3 and isoprenyl cysteine carboxyl methyltransferases with a solved crystal structure, we identified amino acids critical for Opi3 activity by site-directed mutagenesis. Modeling of the structure of the C-terminal part of Opi3 was consistent with the topology obtained by the substituted cysteine accessibility method and revealed that the active site faces the cytosol. In conclusion, the location of the Opi3 active site identified here is consistent with the proposed mechanism of in trans catalysis, as well as with conventional catalysis in cis.

APA, Harvard, Vancouver, ISO, and other styles

49

Won, Jongdae, Yuri Choi, Yaejin Yun, and Hyung Ho Lee. "Biochemical Characterization of the Num1-Mdm36 Complex at the Mitochondria-Plasma Membrane Contact Site." Molecules and Cells 44, no. 4 (April 30, 2021): 207–13. http://dx.doi.org/10.14348/molcells.2021.0016.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

Pfaller, R., H. F. Steger, J. Rassow, N. Pfanner, and W. Neupert. "Import pathways of precursor proteins into mitochondria: multiple receptor sites are followed by a common membrane insertion site." Journal of Cell Biology 107, no. 6 (December 1, 1988): 2483–90. http://dx.doi.org/10.1083/jcb.107.6.2483.

Full text

Abstract:

The precursor of porin, a mitochondrial outer membrane protein, competes for the import of precursors destined for the three other mitochondrial compartments, including the Fe/S protein of the bc1-complex (intermembrane space), the ADP/ATP carrier (inner membrane), subunit 9 of the F0-ATPase (inner membrane), and subunit beta of the F1-ATPase (matrix). Competition occurs at the level of a common site at which precursors are inserted into the outer membrane. Protease-sensitive binding sites, which act before the common insertion site, appear to be responsible for the specificity and selectivity of mitochondrial protein uptake. We suggest that distinct receptor proteins on the mitochondrial surface specifically recognize precursor proteins and transfer them to a general insertion protein component (GIP) in the outer membrane. Beyond GIP, the import pathways diverge, either to the outer membrane or to translocation contact-sites, and then subsequently to the other mitochondrial compartments.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Membrane contact site'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles