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1
Naftalin, R. J. "Chloride transport coupling in biological membranes and epithelia." FEBS Letters 196, no. 1 (February 3, 1986): 182–83. http://dx.doi.org/10.1016/0014-5793(86)80240-x.
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Cabantchik, Z. I., and R. Greger. "Chemical probes for anion transporters of mammalian cell membranes." American Journal of Physiology-Cell Physiology 262, no. 4 (April 1, 1992): C803—C827. http://dx.doi.org/10.1152/ajpcell.1992.262.4.c803.
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Mammalian cell membranes harbor several types of chloride channels, chloride-cation symporters/cotransporters, and several classes of anion exchangers/antiporters. These transport systems subserve different cellular or organismic functions, depending on the nature of the cell, the spatial organization of transporters, and their functional interplay. Chemical probing has played a central role in the structural and functional delineation of the various anion transport systems. The design of specific probes or their selection from existing sources coupled with their judicious application to the most appropriate biological system had led to the identification of specific anion transporters and to the elucidation of the underlying molecular transport mechanism. In many instances, chemical probing has remained the major or exclusive analytical tool for the functional definition or identification of a given transport system, particularly for discerning among the various anion transporters which operate in highly heterogeneous cell membrane systems. This work critically reviews the present state of the chemical armamentarium available for the most common anion transporters found in mammalian cell membranes. It encompasses the description of the most useful or commonly used probes in terms of their chemical, biochemical, physiological, and pharmacological properties. The review deals primarily with what chemical probes tell about anion transporters and, most importantly, with the limitations inherent in the use of probes in transport studies.
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Gałczyńska, Katarzyna, Jarosław Rachuna, Karol Ciepluch, Magdalena Kowalska, Sławomir Wąsik, Tadeusz Kosztołowicz, Katarzyna D. Lewandowska, Jacek Semaniak, Krystyna Kurdziel, and Michał Arabski. "Experimental and Theoretical Analysis of Metal Complex Diffusion through Cell Monolayer." Entropy 23, no. 3 (March 17, 2021): 360. http://dx.doi.org/10.3390/e23030360.
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The study of drugs diffusion through different biological membranes constitutes an essential step in the development of new pharmaceuticals. In this study, the method based on the monolayer cell culture of CHO-K1 cells has been developed in order to emulate the epithelial cells barrier in permeability studies by laser interferometry. Laser interferometry was employed for the experimental analysis of nickel(II) and cobalt(II) complexes with 1-allylimidazole or their chlorides’ diffusion through eukaryotic cell monolayers. The amount (mol) of nickel(II) and cobalt(II) chlorides transported through the monolayer was greater than that of metals complexed with 1-allylimidazole by 4.34-fold and 1.45-fold, respectively, after 60 min. Thus, laser interferometry can be used for the quantitative analysis of the transport of compounds through eukaryotic cell monolayers, and the resulting parameters can be used to formulate a mathematical description of this process.
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Verkman, A. S. "Development and biological applications of chloride-sensitive fluorescent indicators." American Journal of Physiology-Cell Physiology 259, no. 3 (September 1, 1990): C375—C388. http://dx.doi.org/10.1152/ajpcell.1990.259.3.c375.
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Chloride movement across cell plasma and internal membranes, is of central importance for regulation of cell volume and pH, vectorial salt movement in epithelia, and, probably, intracellular traffic. Quinolinium-based chloride-sensitive fluorescent indicators provide a new approach to study chloride transport mechanisms and regulation that is complementary to 36Cl tracer methods, intracellular microelectrodes, and patch clamp. Indicator fluorescence is quenched by chloride by a collisional mechanism with Stern-Volmer constants of up to 220 M-1. Fluorescence is quenched selectively by chloride in physiological systems and responds to changes in chloride concentration in under 1 ms. The indicators are nontoxic and can be loaded into living cells for continuous measurement of intracellular chloride concentration by single-cell fluorescence microscopy. In this review, the structure-activity relationships for chloride-sensitive fluorescent indicators are described. Methodology for measurement of chloride transport in isolated vesicle and liposome systems and in intact cells is evaluated critically by use of examples from epithelial cell physiology. Future directions for synthesis of tailored chloride-sensitive indicators and new applications of indicators for studies of transport regulation and intracellular ion gradients are proposed.
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Fahlke, Christoph. "Ion permeation and selectivity in ClC-type chloride channels." American Journal of Physiology-Renal Physiology 280, no. 5 (May 1, 2001): F748—F757. http://dx.doi.org/10.1152/ajprenal.2001.280.5.f748.
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Voltage-gated anion channels are present in almost every living cell and have many physiological functions. Recently, a novel gene family encoding voltage-gated chloride channels, the ClC family, was identified. The knowledge of primary amino acid sequences has allowed for the study of these anion channels in heterologous expression systems and made possible the combination of site-directed mutagenesis and high-resolution electrophysiological measurements as a means of gaining insights into the molecular basis of channel function. This review focuses on one particular aspect of chloride channel function, the selective transport of anions through biological membranes. I will describe recent experiments using a combination of cellular electrophysiology, molecular genetics, and recombinant DNA technology to study the molecular basis of ion permeation and selection in ClC-type chloride channels. These novel tools have provided new insights into basic mechanisms underlying the function of these biologically important channels.
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El-Etri, M., and J. Cuppoletti. "Metalloporphyrin chloride ionophores: induction of increased anion permeability in lung epithelial cells." American Journal of Physiology-Lung Cellular and Molecular Physiology 270, no. 3 (March 1, 1996): L386—L392. http://dx.doi.org/10.1152/ajplung.1996.270.3.l386.
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5,10,15,20-Tetraphenyl-21H,23H-porphine manganese (III) chloride [TPPMn(III)] is a positively charged lipophilic anion carrier that is widely used as a Cl- sensor. TPPMn(III) increased anion permeability of cultured mouse lung epithelial (MLE) cells as measured by short-circuit current (ISC) to a level similar to that induced by forskolin analogues. Anion permeability was also studied in cultured human lung epithelial (A549) cells by measurement of the rates of change of fluorescence of the anion sensitive fluorescent dye, 6-methoxy-N-(3-sulfopropyl)quinolinium (SPQ). In these studies, cells were incubated with SPQ in SO2-4- medium, washed free of extracellular SPQ, and then perfused with medium containing anions that are known to quench SPQ fluorescence. The effect of TPPMn(III) on anion transport was then determined either microscopically in single cell studies or using cell monolayers mounted in a front face fluorimeter. TPPMn(III) in the range from 1 to 100 micrograms/ml induced a dose-dependent increase in Br- transport. The half-maximal quenching effect was estimated to be approximate 5 micrograms/ml. TPPMn(III) increased the rates of fluorescence quench of anions by up to fourfold. TPPMn(III) was without effect on -Ca2+-i level in A549 cells as measured with fura 2-AM. This indicates that TPPMn(III) effects were not mediated through effects on Ca+2 -activated Cl- channels, or by compromise of energy metabolism or membrane integrity of the cells. This study suggests that TPPMn(III) and, by extension, other lipophilic Mn(III) or Co(III) derivatives wherein the selectivity of lipophilicity is altered, could increase the anion permeability of biological membranes, and suggests a new approach for treatment of diseases such as cystic fibrosis, where transport of Cl- is defective.
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Jentsch, Thomas J., and Michael Pusch. "CLC Chloride Channels and Transporters: Structure, Function, Physiology, and Disease." Physiological Reviews 98, no. 3 (July 1, 2018): 1493–590. http://dx.doi.org/10.1152/physrev.00047.2017.
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CLC anion transporters are found in all phyla and form a gene family of eight members in mammals. Two CLC proteins, each of which completely contains an ion translocation parthway, assemble to homo- or heteromeric dimers that sometimes require accessory β-subunits for function. CLC proteins come in two flavors: anion channels and anion/proton exchangers. Structures of these two CLC protein classes are surprisingly similar. Extensive structure-function analysis identified residues involved in ion permeation, anion-proton coupling and gating and led to attractive biophysical models. In mammals, ClC-1, -2, -Ka/-Kb are plasma membrane Cl−channels, whereas ClC-3 through ClC-7 are 2Cl−/H+-exchangers in endolysosomal membranes. Biological roles of CLCs were mostly studied in mammals, but also in plants and model organisms like yeast and Caenorhabditis elegans. CLC Cl−channels have roles in the control of electrical excitability, extra- and intracellular ion homeostasis, and transepithelial transport, whereas anion/proton exchangers influence vesicular ion composition and impinge on endocytosis and lysosomal function. The surprisingly diverse roles of CLCs are highlighted by human and mouse disorders elicited by mutations in their genes. These pathologies include neurodegeneration, leukodystrophy, mental retardation, deafness, blindness, myotonia, hyperaldosteronism, renal salt loss, proteinuria, kidney stones, male infertility, and osteopetrosis. In this review, emphasis is laid on biophysical structure-function analysis and on the cell biological and organismal roles of mammalian CLCs and their role in disease.
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Su, Xianbin, Ruihong Li, Ka-Fai Kong, and Jimmy S. H. Tsang. "Transport of haloacids across biological membranes." Biochimica et Biophysica Acta (BBA) - Biomembranes 1858, no. 12 (December 2016): 3061–70. http://dx.doi.org/10.1016/j.bbamem.2016.09.017.
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Fuliński, A. "Noise-stimulated active transport in biological cell membranes." Physics Letters A 193, no. 3 (October 1994): 267–73. http://dx.doi.org/10.1016/0375-9601(94)90595-9.
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McPherson, M. A., D. K. Shori, and R. L. Dormer. "Defective regulation of apical membrane chloride transport and exocytosis in cystic fibrosis." Bioscience Reports 8, no. 1 (February 1, 1988): 27–33. http://dx.doi.org/10.1007/bf01128969.
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A biochemical link is proposed between recent observations on defective regulation of Cl− transport in CF respiratory epithelial cells and studies showing altered biological activity of calmodulin in exocrine glands from CF patients. A consensus is emerging that defective β-adrenergic secretory responsiveness in CF cells is caused by a defect in a regulator protein at a site distal to cyclic AMP formation. Our results indicate that this protein might be a specific calmodulin acceptor protein which modifies the activity of calmodulin in epithelial cells. Alteration in Ca2+/calmodulin dependent regulation of Cl− transport and protein secretion could explain (i) alterations in Ca2+ homeostasis seen in CF, (ii) defective β-adrenergic responses of CF cells, and (iii) the observed inability of cyclic AMP (acting via its specific protein kinase, A-kinase) to open apical membrane Cl− channels in CF epithelial cells. Most of the physiological abnormalities of CF including elevated sweat electrolytes and hyperviscous mucus can be explained on this basis.
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Videv, Pavel, Nikola Mladenov, Tonya Andreeva, Kirilka Mladenova, Veselina Moskova-Doumanova, Georgi Nikolaev, Svetla Petrova, and Jordan Doumanov. "Condensing Effect of Cholesterol on hBest1/POPC and hBest1/SM Langmuir Monolayers." Membranes 11, no. 1 (January 13, 2021): 52. http://dx.doi.org/10.3390/membranes11010052.
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Human bestrophin-1 protein (hBest1) is a transmembrane channel associated with the calcium-dependent transport of chloride ions in the retinal pigment epithelium as well as with the transport of glutamate and GABA in nerve cells. Interactions between hBest1, sphingomyelins, phosphatidylcholines and cholesterol are crucial for hBest1 association with cell membrane domains and its biological functions. As cholesterol plays a key role in the formation of lipid rafts, motional ordering of lipids and modeling/remodeling of the lateral membrane structure, we examined the effect of different cholesterol concentrations on the surface tension of hBest1/POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and hBest1/SM Langmuir monolayers in the presence/absence of Ca2+ ions using surface pressure measurements and Brewster angle microscopy studies. Here, we report that cholesterol: (1) has negligible condensing effect on pure hBest1 monolayers detected mainly in the presence of Ca2+ ions, and; (2) induces a condensing effect on composite hBest1/POPC and hBest1/SM monolayers. These results offer evidence for the significance of intermolecular protein–lipid interactions for the conformational dynamics of hBest1 and its biological functions as multimeric ion channel.
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Anderson, M. P., D. N. Sheppard, H. A. Berger, and M. J. Welsh. "Chloride channels in the apical membrane of normal and cystic fibrosis airway and intestinal epithelia." American Journal of Physiology-Lung Cellular and Molecular Physiology 263, no. 1 (July 1, 1992): L1—L14. http://dx.doi.org/10.1152/ajplung.1992.263.1.l1.
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Cl- channels located in the apical membrane of secretory epithelia play a key role in epithelial fluid and electrolyte transport. Dysfunction of one of these channels, cystic fibrosis transmembrane conductance regulator (CFTR), causes the genetic disease cystic fibrosis (CF). We review here the properties and regulation of the different types of Cl- channels that have been reported in airway and intestinal epithelia. We begin by describing the properties of the CFTR Cl- channel and then use those properties as a point of reference. We focused particularly on the evidence that localizes specific types of Cl- channel to the apical membrane. With that background, we assess the biological function of various Cl- channels in airway and intestinal epithelia.
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Inesi, Giuseppe. "The mutual binding exclusion mechanism in active transport across biological membranes." Cell Biophysics 11, no. 1 (December 1987): 269–77. http://dx.doi.org/10.1007/bf02797124.
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Xu, Ziyang, Lijuan Gao, Pengyu Chen, and Li-Tang Yan. "Diffusive transport of nanoscale objects through cell membranes: a computational perspective." Soft Matter 16, no. 16 (2020): 3869–81. http://dx.doi.org/10.1039/c9sm02338k.
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Clarifying the diffusion dynamics of nanoscale objects with cell membrane is critical for revealing fundamental physics in biological systems. This perspective highlights the advances in computational and theoretical aspects of this emerging field.
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Stauber, Tobias. "The volume-regulated anion channel is formed by LRRC8 heteromers – molecular identification and roles in membrane transport and physiology." Biological Chemistry 396, no. 9-10 (September 1, 2015): 975–90. http://dx.doi.org/10.1515/hsz-2015-0127.
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Abstract Cellular volume regulation is fundamental for numerous physiological processes. The volume-regulated anion channel, VRAC, plays a crucial role in regulatory volume decrease. This channel, which is ubiquitously expressed in vertebrates, has been vastly characterized by electrophysiological means. It opens upon cell swelling and conducts chloride and arguably organic osmolytes. VRAC has been proposed to be critically involved in various cellular and organismal functions, including cell proliferation and migration, apoptosis, transepithelial transport, swelling-induced exocytosis and intercellular communication. It may also play a role in pathological states like cancer and ischemia. Despite many efforts, the molecular identity of VRAC had remained elusive for decades, until the recent discovery of heteromers of LRRC8A with other LRRC8 family members as an essential VRAC component. This identification marks a starting point for studies on the structure-function relation, for molecular biological investigations of its cell biology and for re-evaluating the physiological roles of VRAC. This review recapitulates the identification of LRRC8 heteromers as VRAC components, depicts the similarities between LRRC8 proteins and pannexins, and discussed whether VRAC conducts larger osmolytes. Furthermore, proposed physiological functions of VRAC and the present knowledge about the physiological significance of LRRC8 proteins are summarized and collated.
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Palivan, Cornelia G., Roland Goers, Adrian Najer, Xiaoyan Zhang, Anja Car, and Wolfgang Meier. "Bioinspired polymer vesicles and membranes for biological and medical applications." Chemical Society Reviews 45, no. 2 (2016): 377–411. http://dx.doi.org/10.1039/c5cs00569h.
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Biological membranes play an essential role in living organisms by providing stable and functional compartments, supporting signalling and selective transport. Combining synthetic polymer membranes with biological molecules promises to be an effective strategy to mimic the functions of cell membranes and apply them in artificial systems.
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Chattopadhyay, Madhurima, Hanna Orlikowska, Emilia Krok, and Lukasz Piatkowski. "Sensing Hydration of Biomimetic Cell Membranes." Biosensors 11, no. 7 (July 16, 2021): 241. http://dx.doi.org/10.3390/bios11070241.
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Biological membranes play a vital role in cell functioning, providing structural integrity, controlling signal transduction, and controlling the transport of various chemical species. Owing to the complex nature of biomembranes, the self-assembly of lipids in aqueous media has been utilized to develop model systems mimicking the lipid bilayer structure, paving the way to elucidate the mechanisms underlying various biological processes, as well as to develop a number of biomedical and technical applications. The hydration properties of lipid bilayers are crucial for their activity in various cellular processes. Of particular interest is the local membrane dehydration, which occurs in membrane fusion events, including neurotransmission, fertilization, and viral entry. The lack of universal technique to evaluate the local hydration state of the membrane components hampers understanding of the molecular-level mechanisms of these processes. Here, we present a new approach to quantify the hydration state of lipid bilayers. It takes advantage of the change in the lateral diffusion of lipids that depends on the number of water molecules hydrating them. Using fluorescence recovery after photobleaching technique, we applied this approach to planar single and multicomponent supported lipid bilayers. The method enables the determination of the hydration level of a biomimetic membrane down to a few water molecules per lipid.
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Gaididei, Yuri B. "Ion-conformational interaction and charge transport through channels of biological membranes." Journal of Biological Physics 19, no. 1 (1993): 19–38. http://dx.doi.org/10.1007/bf00700128.
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Haslberger, A., C. Romanin, and R. Koerber. "Membrane potential modulates release of tumor necrosis factor in lipopolysaccharide-stimulated mouse macrophages." Molecular Biology of the Cell 3, no. 4 (April 1992): 451–60. http://dx.doi.org/10.1091/mbc.3.4.451.
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Lipopolysaccharide (LPS)-mediated synthesis of macrophage gene products such as tumor necrosis factor (TNF) is controlled by different signaling pathways. We investigated intracellular free Ca2+ (Ca2+ic) and the membrane potential as early cellular responses to LPS and their role in the synthesis and release of TNF. In peritoneal macrophages and in the RAW 269 mouse macrophage cell line, LPS and its biologically active moiety lipid A stimulated TNF synthesis but exerted no significant effects on these early cellular responses using Fura-2/Indo-1 to measure Ca2+ic and bis-oxonol, as well as the patch-clamp technique to monitor membrane potential. In contrast, the platelet-activating factor transiently induced both an increase in Ca2+ic and cell membrane depolarization but no significant TNF release. Increased extracellular K+ concentrations or K(+)-channel blockers, such as quinine, tetraethylammonium, or barium chloride, inhibited the LPS-stimulated release of TNF alpha, as well as the accumulation of cell-associated TNF alpha as found by enzyme-linked immunosorbent assay analysis, but did not inhibit TNF alpha mRNA accumulation. Concentrations of quinine (greater than 125 microM) or of enhanced extracellular K+ (25-85 mM) required to inhibit TNF production both significantly depolarized macrophages. These results indicate a lack of ion transport activities as early cellular responses of macrophages to LPS but suggest an important regulatory role of the membrane potential on the posttranscriptional synthesis and release of TNF in macrophages.
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De Rouffignac, C. "Multihormonal regulation of nephron epithelia: achieved through combinational mode?" American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 269, no. 4 (October 1, 1995): R739—R748. http://dx.doi.org/10.1152/ajpregu.1995.269.4.r739.
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The kidney is the main organ regulating composition of body fluids. A considerable number of hormones control the activity of renal cells to maintain hydromineral equilibrium. It becomes more and more difficult to interpret this multihormonal control in terms of regulatory processes. To illustrate this complexity, the hormonal regulation of electrolyte transport in the nephron thick ascending limb is taken as an example. This nephron segment is largely responsible for two kidney functions: the urinary-concentrating ability (by its capacity to deliver hypertonic sodium chloride into the medullary interstitium) and regulation of magnesium excretion into final urine. Six hormones are presently identified as acting on the transport of both sodium chloride and magnesium ions in this nephron segment. Therefore, the pertinent question is how the thick ascending limb and, hence, the kidney, is capable of regulating water balance independently from magnesium balance. It is proposed that the hormones act in combination: circulating levels of the individual hormones acting on these cells may determine the configuration of the paracellular and transcellular transport pathways of the epithelium either in the “sodium” or “magnesium” mode. The configuration would depend on the distribution and activity of the receptor at the surface of the basolateral membrane in contact with the circulating hormones. This distribution along with stimulation of respective signal transduction pathways would lead to the final biological effects. It is already known that the distribution of cell receptors may vary according to factors such as age, nutritional variability, hormonal status, degree of desensitization of the receptors, etc. The modulation of hormonal responses would depend therefore on the degree of coupling of hormone-receptor complexes to different intracellular transduction pathways and on the resulting negative and/or positive interactions between these pathways.
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Van Kerkhove, Emmy, Valérie Pennemans, and Quirine Swennen. "Cadmium and transport of ions and substances across cell membranes and epithelia." BioMetals 23, no. 5 (June 27, 2010): 823–55. http://dx.doi.org/10.1007/s10534-010-9357-6.
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Stephenson, Keith. "Sec-dependent protein translocation across biological membranes: evolutionary conservation of an essential protein transport pathway (Review)." Molecular Membrane Biology 22, no. 1-2 (January 2005): 17–28. http://dx.doi.org/10.1080/09687860500063308.
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Jobin, Marie-Lise, Lydie Vamparys, Romain Deniau, Axelle Grélard, Cameron Mackereth, Patrick Fuchs, and Isabel Alves. "Biophysical Insight on the Membrane Insertion of an Arginine-Rich Cell-Penetrating Peptide." International Journal of Molecular Sciences 20, no. 18 (September 9, 2019): 4441. http://dx.doi.org/10.3390/ijms20184441.
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Cell-penetrating peptides (CPPs) are short peptides that can translocate and transport cargoes into the intracellular milieu by crossing biological membranes. The mode of interaction and internalization of cell-penetrating peptides has long been controversial. While their interaction with anionic membranes is quite well understood, the insertion and behavior of CPPs in zwitterionic membranes, a major lipid component of eukaryotic cell membranes, is poorly studied. Herein, we investigated the membrane insertion of RW16 into zwitterionic membranes, a versatile CPP that also presents antibacterial and antitumor activities. Using complementary approaches, including NMR spectroscopy, fluorescence spectroscopy, circular dichroism, and molecular dynamic simulations, we determined the high-resolution structure of RW16 and measured its membrane insertion and orientation properties into zwitterionic membranes. Altogether, these results contribute to explaining the versatile properties of this peptide toward zwitterionic lipids.
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Guziewicz, Megan, Toni Vitullo, Bethany Simmons, and Rebecca Eustance Kohn. "Analyzing Defects in the Caenorhabditis elegans Nervous System Using Organismal and Cell Biological Approaches." Cell Biology Education 1, no. 1 (March 2002): 18–25. http://dx.doi.org/10.1187/cbe.01-08-0001.
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The goal of this laboratory exercise is to increase student understanding of the impact of nervous system function at both the organismal and cellular levels. This inquiry-based exercise is designed for an undergraduate course examining principles of cell biology. After observing the movement of Caenorhabditis elegans with defects in their nervous system, students examine the structure of the nervous system to categorize the type of defect. They distinguish between defects in synaptic vesicle transport and defects in synaptic vesicle fusion with membranes. The synaptic vesicles are tagged with green fluorescent protein (GFP), simplifying cellular analysis. The expected outcome of this experiment is that students will better understand the concepts of vesicle transport, neurotransmitter release, GFP, and the relation between the nervous system and behavior.
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Alper, Mark. "The Biological Membrane." MRS Bulletin 17, no. 11 (November 1992): 53–55. http://dx.doi.org/10.1557/s0883769400046674.
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All living cells, and many of the structures within these cells (mitochondria, nuclei, chloroplasts) are surrounded by biological membranes which serve to separate the cell contents from the surrounding environment. The biological membrane is an extraordinary material. It controls the highly selective transport of molecules into and out of the cell. It senses the environment outside the cell and transmits information about it to the intracellular machinery. It reports information about the cell to the outside world—its identity and its state of function. It transports electrons, converts sunlight to chemical and electrical energy, pumps small molecules against a concentration gradient, and uses that gradient as a source of energy. The membrane is a generally robust structure, and one that can be modified in a controlled manner, making it adaptable for use in nonbiological applications. It has served as a model for sensors and detectors, for surface modification agents, for drug delivery systems, and for information storage and delivery, as well as other optoelectronic functions.
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Gavin, C. E., K. K. Gunter, and T. E. Gunter. "Mn2+ transport across biological membranes may be monitored spectroscopically using the Ca2+ indicator dye antipyrylazo III." Analytical Biochemistry 192, no. 1 (January 1991): 44–48. http://dx.doi.org/10.1016/0003-2697(91)90180-2.
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Vocke, Kerstin, Kristin Dauner, Anne Hahn, Anne Ulbrich, Jana Broecker, Sandro Keller, Stephan Frings, and Frank Möhrlen. "Calmodulin-dependent activation and inactivation of anoctamin calcium-gated chloride channels." Journal of General Physiology 142, no. 4 (September 30, 2013): 381–404. http://dx.doi.org/10.1085/jgp.201311015.
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Calcium-dependent chloride channels serve critical functions in diverse biological systems. Driven by cellular calcium signals, the channels codetermine excitatory processes and promote solute transport. The anoctamin (ANO) family of membrane proteins encodes three calcium-activated chloride channels, named ANO 1 (also TMEM16A), ANO 2 (also TMEM16B), and ANO 6 (also TMEM16F). Here we examined how ANO 1 and ANO 2 interact with Ca2+/calmodulin using nonstationary current analysis during channel activation. We identified a putative calmodulin-binding domain in the N-terminal region of the channel proteins that is involved in channel activation. Binding studies with peptides indicated that this domain, a regulatory calmodulin-binding motif (RCBM), provides two distinct modes of interaction with Ca2+/calmodulin, one at submicromolar Ca2+ concentrations and one in the micromolar Ca2+ range. Functional, structural, and pharmacological data support the concept that calmodulin serves as a calcium sensor that is stably associated with the RCBM domain and regulates the activation of ANO 1 and ANO 2 channels. Moreover, the predominant splice variant of ANO 2 in the brain exhibits Ca2+/calmodulin-dependent inactivation, a loss of channel activity within 30 s. This property may curtail ANO 2 activity during persistent Ca2+ signals in neurons. Mutagenesis data indicated that the RCBM domain is also involved in ANO 2 inactivation, and that inactivation is suppressed in the retinal ANO 2 splice variant. These results advance the understanding of Ca2+ regulation in anoctamin Cl− channels and its significance for the physiological function that anoctamin channels subserve in neurons and other cell types.
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Hume, Joseph R., Dayue Duan, Mei Lin Collier, Jun Yamazaki, and Burton Horowitz. "Anion Transport in Heart." Physiological Reviews 80, no. 1 (January 1, 2000): 31–81. http://dx.doi.org/10.1152/physrev.2000.80.1.31.
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Anion transport proteins in mammalian cells participate in a wide variety of cell and intracellular organelle functions, including regulation of electrical activity, pH, volume, and the transport of osmolites and metabolites, and may even play a role in the control of immunological responses, cell migration, cell proliferation, and differentiation. Although significant progress over the past decade has been achieved in understanding electrogenic and electroneutral anion transport proteins in sarcolemmal and intracellular membranes, information on the molecular nature and physiological significance of many of these proteins, especially in the heart, is incomplete. Functional and molecular studies presently suggest that four primary types of sarcolemmal anion channels are expressed in cardiac cells: channels regulated by protein kinase A (PKA), protein kinase C, and purinergic receptors ( I Cl.PKA); channels regulated by changes in cell volume ( I Cl.vol); channels activated by intracellular Ca2+ ( I Cl.Ca); and inwardly rectifying anion channels ( I Cl.ir). In most animal species, I Cl.PKA is due to expression of a cardiac isoform of the epithelial cystic fibrosis transmembrane conductance regulator Cl− channel. New molecular candidates responsible for I Cl.vol, I Cl.Ca, and I Cl.ir(ClC-3, CLCA1, and ClC-2, respectively) have recently been identified and are presently being evaluated. Two isoforms of the band 3 anion exchange protein, originally characterized in erythrocytes, are responsible for Cl−/HCO3 − exchange, and at least two members of a large vertebrate family of electroneutral cotransporters (ENCC1 and ENCC3) are responsible for Na+-dependent Cl− cotransport in heart. A 223-amino acid protein in the outer mitochondrial membrane of most eukaryotic cells comprises a voltage-dependent anion channel. The molecular entities responsible for other types of electroneutral anion exchange or Cl− conductances in intracellular membranes of the sarcoplasmic reticulum or nucleus are unknown. Evidence of cardiac expression of up to five additional members of the ClC gene family suggest a rich new variety of molecular candidates that may underlie existing or novel Cl− channel subtypes in sarcolemmal and intracellular membranes. The application of modern molecular biological and genetic approaches to the study of anion transport proteins during the next decade holds exciting promise for eventually revealing the actual physiological, pathophysiological, and clinical significance of these unique transport processes in cardiac and other mammalian cells.
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Jay, Anthony G., Jeffrey R. Simard, Nasi Huang, and James A. Hamilton. "SSO and other putative inhibitors of FA transport across membranes by CD36 disrupt intracellular metabolism, but do not affect FA translocation." Journal of Lipid Research 61, no. 5 (February 26, 2020): 790–807. http://dx.doi.org/10.1194/jlr.ra120000648.
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Membrane-bound proteins have been proposed to mediate the transport of long-chain FA (LCFA) transport through the plasma membrane (PM). These proposals are based largely on reports that PM transport of LCFAs can be blocked by a number of enzymes and purported inhibitors of LCFA transport. Here, using the ratiometric pH indicator (2′,7′-bis-(2-carboxyethyl)-5-(and-6-)-carboxyfluorescein and acrylodated intestinal FA-binding protein-based dual fluorescence assays, we investigated the effects of nine inhibitors of the putative FA transporter protein CD36 on the binding and transmembrane movement of LCFAs. We particularly focused on sulfosuccinimidyl oleate (SSO), reported to be a competitive inhibitor of CD36-mediated LCFA transport. Using these assays in adipocytes and inhibitor-treated protein-free lipid vesicles, we demonstrate that rapid LCFA transport across model and biological membranes remains unchanged in the presence of these purported inhibitors. We have previously shown in live cells that CD36 does not accelerate the transport of unesterified LCFAs across the PM. Our present experiments indicated disruption of LCFA metabolism inside the cell within minutes upon treatment with many of the “inhibitors” previously assumed to inhibit LCFA transport across the PM. Furthermore, using confocal microscopy and a specific anti-SSO antibody, we found that numerous intracellular and PM-bound proteins are SSO-modified in addition to CD36. Our results support the hypothesis that LCFAs diffuse rapidly across biological membranes and do not require an active protein transporter for their transmembrane movement.
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Jennings, Michael L., and Jian Cui. "Chloride Homeostasis in Saccharomyces cerevisiae: High Affinity Influx, V-ATPase-dependent Sequestration, and Identification of a Candidate Cl− Sensor." Journal of General Physiology 131, no. 4 (March 31, 2008): 379–91. http://dx.doi.org/10.1085/jgp.200709905.
Full textAbstract:
Chloride homeostasis in Saccharomyces cerevisiae has been characterized with the goal of identifying new Cl− transport and regulatory pathways. Steady-state cellular Cl− contents (∼0.2 mEq/liter cell water) differ by less than threefold in yeast grown in media containing 0.003–5 mM Cl−. Therefore, yeast have a potent mechanism for maintaining constant cellular Cl− over a wide range of extracellular Cl−. The cell water:medium [Cl−] ratio is >20 in media containing 0.01 mM Cl− and results in part from sequestration of Cl− in organelles, as shown by the effect of deleting genes involved in vacuolar acidification. Organellar sequestration cannot account entirely for the Cl− accumulation, however, because the cell water:medium [Cl−] ratio in low Cl− medium is ∼10 at extracellular pH 4.0 even in vma1 yeast, which lack the vacuolar H+-ATPase. Cellular Cl− accumulation is ATP dependent in both wild type and vma1 strains. The initial 36Cl− influx is a saturable function of extracellular [36Cl−] with K1/2 of 0.02 mM at pH 4.0 and >0.2 mM at pH 7, indicating the presence of a high affinity Cl− transporter in the plasma membrane. The transporter can exchange 36Cl− for either Cl− or Br− far more rapidly than SO4=, phosphate, formate, HCO3−, or NO3−. High affinity Cl− influx is not affected by deletion of any of several genes for possible Cl− transporters. The high affinity Cl− transporter is activated over a period of ∼45 min after shifting cells from high-Cl− to low-Cl− media. Deletion of ORF YHL008c (formate-nitrite transporter family) strongly reduces the rate of activation of the flux. Therefore, Yhl008cp may be part of a Cl−-sensing mechanism that activates the high affinity transporter in a low Cl− medium. This is the first example of a biological system that can regulate cellular Cl− at concentrations far below 1 mM.
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Alonso, Miguel A., and Jaime Millán. "The role of lipid rafts in signalling and membrane trafficking in T lymphocytes." Journal of Cell Science 114, no. 22 (November 15, 2001): 3957–65. http://dx.doi.org/10.1242/jcs.114.22.3957.
Full textAbstract:
Combinatorial association of different lipid species generates microheterogeneity in biological membranes. The association of glycosphingolipids with cholesterol forms membrane microdomains – lipid rafts – that are involved in specialised pathways of protein/lipid transport and signalling. Lipid rafts are normally dispersed in cellular membranes and appear to require specialised machinery to reorganise them to operate. Caveolin-1 and MAL are members of two different protein families involved in reorganisation of lipid rafts for signalling and/or intracellular transport in epithelial cells. T cell activation induces a rapid compartmentalisation of signalling machinery into reorganised rafts that are used as platforms for the assembly of the signalling complex. Costimulatory molecules participate in this process by providing signals that mobilise raft lipids and proteins, and remodel the cytoskeleton to the contact site. As in epithelial cells, rafts are used also as vesicular carriers for membrane trafficking in T lymphocytes. Furthermore, there are potential similarities between the specialised protein machinery underlying raft-mediated processes in T lymphocytes and polarised epithelial cells.
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López-Marqués, Rosa L., Pontus Gourdon, Thomas Günther Pomorski, and Michael Palmgren. "The transport mechanism of P4 ATPase lipid flippases." Biochemical Journal 477, no. 19 (October 12, 2020): 3769–90. http://dx.doi.org/10.1042/bcj20200249.
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P4 ATPase lipid flippases are ATP-driven transporters that translocate specific lipids from the exoplasmic to the cytosolic leaflet of biological membranes, thus establishing a lipid gradient between the two leaflets that is essential for many cellular processes. While substrate specificity, subcellular and tissue-specific expression, and physiological functions have been assigned to a number of these transporters in several organisms, the mechanism of lipid transport has been a topic of intense debate in the field. The recent publication of a series of structural models based on X-ray crystallography and cryo-EM studies has provided the first glimpse into how P4 ATPases have adapted the transport mechanism used by the cation-pumping family members to accommodate a substrate that is at least an order of magnitude larger than cations.
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Bisha, Ina, and Alessandra Magistrato. "The molecular mechanism of secondary sodium symporters elucidated through the lens of the computational microscope." RSC Advances 6, no. 12 (2016): 9522–40. http://dx.doi.org/10.1039/c5ra22131e.
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Transport of molecules across cellular membranes is a key biological process for normal cell function. In this review we describe current state-of-the-art knowledge on molecular mechanism of secondary active transporters obtained by molecular simulations studies.
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Lapointe, Jean-Yves, Marilène P. Gagnon, Dominique G. Gagnon, and Pierre Bissonnette. "Controversy regarding the secondary active water transport hypothesis." Biochemistry and Cell Biology 80, no. 5 (October 1, 2002): 525–33. http://dx.doi.org/10.1139/o02-150.
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Historically, water transport across biological membranes has always been considered a passive process, i.e., the net water transport is proportional to the gradients of hydrostatic and osmotic pressure. More recently, this dogma was challenged by the suggestion that secondary active transporters such as the Na/glucose cotransporter (SGLT1) could perform secondary active water transport with a fixed stoichiometry. In the case of SGLT1, the stoichiometry would consist of one glucose molecule to two Na+ ions to 220400 water molecules. In the present minireview, we summarize and criticize the evidence supporting and opposing this water cotransport hypothesis. Published and unpublished observations from our own laboratory are also presented in support of the idea that transport-dependent osmotic gradients begin to build up immediately after cotransport commences and are fully responsible for the cell swelling observed.Key words: Xenopus oocyte, intracellular diffusion, water cotransport, SGLT1.
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Subczynski, W. K., and A. Wisniewska. "Physical properties of lipid bilayer membranes: relevance to membrane biological functions." Acta Biochimica Polonica 47, no. 3 (September 30, 2000): 613–25. http://dx.doi.org/10.18388/abp.2000_3983.
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Over the last 25 years one of us (WKS) has been investigating physical properties of lipid bilayer membranes. In 1991 a group led by WKS was organized into the Laboratory of Structure and Dynamics of Biological Membranes, the effective member of which is AW. Using mainly the electron paramagnetic resonance (EPR) spin-labeling method, we obtained unexpected results, which are significant for the better understanding of the functioning of biological membranes. We have developed a new pulse EPR spin-labeling method for the detection of membrane domains and evaluation of lipid exchange rates. This review will be focused on our main results which can be summarized as follows: (1) Unsaturation of alkyl chains greatly reduces the ordering and rigidifying effects of cholesterol although the unsaturation alone gives only minor fluidizing effects, as observed by order and reorientational motion, and rather significant rigidifying effects, as observed by translational motion of probe molecules; (2) Fluid-phase model membranes and cell plasma membranes are not barriers to oxygen and nitric oxide transport; (3) Polar carotenoids can regulate membrane fluidity in a way similar to cholesterol; (4) Formation of effective hydrophobic barriers to the permeation of small polar molecules across membranes requires alkyl chain unsaturation and/or the presence of cholesterol; (5) Fluid-phase micro-immiscibility takes place in cis-unsaturated phosphatidylcholine-cholesterol membranes and induces the formation of cholesterol-rich domains; (6) In membranes containing high concentrations of transmembrane proteins a new lipid domain is formed, with lipids trapped within aggregates of proteins, in which the lipid dynamics is diminished to the level of gel-phase.
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Kim, John, Sidney V. Scott, Michael N. Oda, and Daniel J. Klionsky. "Transport of a Large Oligomeric Protein by the Cytoplasm to Vacuole Protein Targeting Pathway." Journal of Cell Biology 137, no. 3 (May 5, 1997): 609–18. http://dx.doi.org/10.1083/jcb.137.3.609.
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Aminopeptidase I (API) is transported into the yeast vacuole by the cytoplasm to vacuole targeting (Cvt) pathway. Genetic evidence suggests that autophagy, a major degradative pathway in eukaryotes, and the Cvt pathway share largely the same cellular machinery. To understand the mechanism of the Cvt import process, we examined the native state of API. Dodecameric assembly of precursor API in the cytoplasm and membrane binding were rapid events, whereas subsequent vacuolar import appeared to be rate limiting. A unique temperature-sensitive API-targeting mutant allowed us to kinetically monitor its oligomeric state during translocation. Our findings indicate that API is maintained as a dodecamer throughout its import and will be useful to study the posttranslational movement of folded proteins across biological membranes.
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Vermaas, Josh V., Richard A. Dixon, Fang Chen, Shawn D. Mansfield, Wout Boerjan, John Ralph, Michael F. Crowley, and Gregg T. Beckham. "Passive membrane transport of lignin-related compounds." Proceedings of the National Academy of Sciences 116, no. 46 (October 28, 2019): 23117–23. http://dx.doi.org/10.1073/pnas.1904643116.
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Lignin is an abundant aromatic polymer found in plant secondary cell walls. In recent years, lignin has attracted renewed interest as a feedstock for bio-based chemicals via catalytic and biological approaches and has emerged as a target for genetic engineering to improve lignocellulose digestibility by altering its composition. In lignin biosynthesis and microbial conversion, small phenolic lignin precursors or degradation products cross membrane bilayers through an unidentified translocation mechanism prior to incorporation into lignin polymers (synthesis) or catabolism (bioconversion), with both passive and transporter-assisted mechanisms postulated. To test the passive permeation potential of these phenolics, we performed molecular dynamics simulations for 69 monomeric and dimeric lignin-related phenolics with 3 model membranes to determine the membrane partitioning and permeability coefficients for each compound. The results support an accessible passive permeation mechanism for most compounds, including monolignols, dimeric phenolics, and the flavonoid, tricin. Computed lignin partition coefficients are consistent with concentration enrichment near lipid carbonyl groups, and permeability coefficients are sufficient to keep pace with cellular metabolism. Interactions between methoxy and hydroxy groups are found to reduce membrane partitioning and improve permeability. Only carboxylate-modified or glycosylated lignin phenolics are predicted to require transporters for membrane translocation. Overall, the results suggest that most lignin-related compounds can passively traverse plant and microbial membranes on timescales commensurate with required biological activities, with any potential transport regulation mechanism in lignin synthesis, catabolism, or bioconversion requiring compound functionalization.
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Richter, Silke, Ute Lindenstrauss, Christian Lücke, Richard Bayliss, and Thomas Brüser. "Functional Tat Transport of Unstructured, Small, Hydrophilic Proteins." Journal of Biological Chemistry 282, no. 46 (September 11, 2007): 33257–64. http://dx.doi.org/10.1074/jbc.m703303200.
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The twin-arginine translocation (Tat) system is a protein translocation system that is adapted to the translocation of folded proteins across biological membranes. An understanding of the folding requirements for Tat substrates is of fundamental importance for the elucidation of the transport mechanism. We now demonstrate for the first time Tat transport for fully unstructured proteins, using signal sequence fusions to naturally unfolded FG repeats from the yeast Nsp1p nuclear pore protein. The transport of unfolded proteins becomes less efficient with increasing size, consistent with only a single interaction between the system and the substrate. Strikingly, the introduction of six residues from the hydrophobic core of a globular protein completely blocked translocation. Physiological data suggest that hydrophobic surface patches abort transport at a late stage, most likely by membrane interactions during transport. This study thus explains the observed restriction of the Tat system to folded globular proteins on a molecular level.
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Poccia, Dominic, and Banafshé Larijani. "Phosphatidylinositol metabolism and membrane fusion." Biochemical Journal 418, no. 2 (February 11, 2009): 233–46. http://dx.doi.org/10.1042/bj20082105.
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Membrane fusion underlies many cellular events, including secretion, exocytosis, endocytosis, organelle reconstitution, transport from endoplasmic reticulum to Golgi and nuclear envelope formation. A large number of investigations into membrane fusion indicate various roles for individual members of the phosphoinositide class of membrane lipids. We first review the phosphoinositides as membrane recognition sites and their regulatory functions in membrane fusion. We then consider how modulation of phosphoinositides and their products may affect the structure and dynamics of natural membranes facilitating fusion. These diverse roles underscore the importance of these phospholipids in the fusion of biological membranes.
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Falguières, Thomas, Frédéric Mallard, Carole Baron, Daniel Hanau, Clifford Lingwood, Bruno Goud, Jean Salamero, and Ludger Johannes. "Targeting of Shiga Toxin B-Subunit to Retrograde Transport Route in Association with Detergent-resistant Membranes." Molecular Biology of the Cell 12, no. 8 (August 2001): 2453–68. http://dx.doi.org/10.1091/mbc.12.8.2453.
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In HeLa cells, Shiga toxin B-subunit is transported from the plasma membrane to the endoplasmic reticulum, via early endosomes and the Golgi apparatus, circumventing the late endocytic pathway. We describe here that in cells derived from human monocytes, i.e., macrophages and dendritic cells, the B-subunit was internalized in a receptor-dependent manner, but retrograde transport to the biosynthetic/secretory pathway did not occur and part of the internalized protein was degraded in lysosomes. These differences correlated with the observation that the B-subunit associated with Triton X-100-resistant membranes in HeLa cells, but not in monocyte-derived cells, suggesting that retrograde targeting to the biosynthetic/secretory pathway required association with specialized microdomains of biological membranes. In agreement with this hypothesis we found that in HeLa cells, the B-subunit resisted extraction by Triton X-100 until its arrival in the target compartments of the retrograde pathway, i.e., the Golgi apparatus and the endoplasmic reticulum. Furthermore, destabilization of Triton X-100-resistant membranes by cholesterol extraction potently inhibited B-subunit transport from early endosomes to thetrans-Golgi network, whereas under the same conditions, recycling of transferrin was not affected. Our data thus provide first evidence for a role of lipid asymmetry in membrane sorting at the interface between early endosomes and the trans-Golgi network.
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Casey, Joseph R. "Why bicarbonate?This paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Membrane Proteins in Health and Disease." Biochemistry and Cell Biology 84, no. 6 (December 2006): 930–39. http://dx.doi.org/10.1139/o06-184.
Full textAbstract:
Bicarbonate is a simple single carbon molecule that plays surprisingly important roles in diverse biological processes. Among these are photosynthesis, the Krebs cycle, whole-body and cellular pH regulation, and volume regulation. Since bicarbonate is charged it is not permeable to lipid bilayers. Mammalian membranes thus contain bicarbonate transport proteins to facilitate the specific transmembrane movement of HCO3–. This review provides a wide-ranging view of the biochemistry of bicarbonate and its membrane transporters, revealing what makes the study of bicarbonate transport such a rewarding activity.
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Quazi, Faraz, and Robert S. Molday. "Lipid transport by mammalian ABC proteins." Essays in Biochemistry 50 (September 7, 2011): 265–90. http://dx.doi.org/10.1042/bse0500265.
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ABC (ATP-binding cassette) proteins actively transport a wide variety of substrates, including peptides, amino acids, sugars, metals, drugs, vitamins and lipids, across extracellular and intracellular membranes. Of the 49 hum an ABC proteins, a significant number are known to mediate the extrusion of lipids from membranes or the flipping of membrane lipids across the bilayer to generate and maintain membrane lipid asymmetry. Typical lipid substrates include phospholipids, sterols, sphingolipids, bile acids and related lipid conjugates. Members of the ABCA subfamily of ABC transporters and other ABC proteins such as ABCB4, ABCG1 and ABCG5/8 implicated in lipid transport play important roles in diverse biological processes such as cell signalling, membrane lipid asymmetry, removal of potentially toxic compounds and metabolites, and apoptosis. The importance of these ABC lipid transporters in cell physiology is evident from the finding that mutations in the genes encoding many of these proteins are responsible for severe inherited diseases. For example, mutations in ABCA1 cause Tangier disease associated with defective efflux of cholesterol and phosphatidylcholine from the plasma membrane to the lipid acceptor protein apoA1 (apolipoprotein AI), mutations in ABCA3 cause neonatal surfactant deficiency associated with a loss in secretion of the lipid pulmonary surfactants from lungs of newborns, mutations in ABCA4 cause Stargardt macular degeneration, a retinal degenerative disease linked to the reduced clearance of retinoid compounds from photoreceptor cells, mutations in ABCA12 cause harlequin and lamellar ichthyosis, skin diseases associated with defective lipid trafficking in keratinocytes, and mutations in ABCB4 and ABCG5/ABCG8 are responsible for progressive intrafamilial hepatic disease and sitosterolaemia associated with defective phospholipid and sterol transport respectively. This chapter highlights the involvement of various mammalian ABC transporters in lipid transport in the context of their role in cell signalling, cellular homoeostasis, apoptosis and inherited disorders.
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Ruiz-Colón, Eduardo, and David Suleiman. "Normalized Selectivity and Separation Efficiency of Phosphonated Graphene Oxide and Sulfonated Poly(styrene-isobutylene-styrene) Composite Membranes." MRS Advances 4, no. 3-4 (November 29, 2018): 231–40. http://dx.doi.org/10.1557/adv.2018.620.
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ABSTRACTPhosphonated graphene oxide (pGO) has been incorporated to sulfonated poly(styrene-isobutylene-styrene) (SO3H SIBS) to prepare polymer nanocomposite membranes (PNMs) for direct methanol fuel cell (DMFC) and chemical and biological protective clothing (CBPC) applications. The performance of the membranes was evaluated per SIBS sulfonation level (i.e. 38, 61, and 90 mole %), filler type (i.e. GO and pGO) and filler loading (i.e. 0.1, 0.5 and 1.0 wt.%). The transport properties (i.e. proton conductivity and methanol and vapor permeability) were determined to assess the performance of the PNMs per each application. The ionic interactions between the phosphonic and sulfonic groups (i.e. PO3H2 and SO3H, respectively) altered the pathways of SO3H SIBS, influencing the transport of permeants through the membranes. SIBS 61 pGO 0.1 presented the highest separation efficiency and a DMFC performance comparable to the state-of-the-art Nafion®, indicating that this membrane could potentially be implemented as protective fabric as well as functioning for fuel cell applications.
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Dubyak, George R. "Ion homeostasis, channels, and transporters: an update on cellular mechanisms." Advances in Physiology Education 28, no. 4 (December 2004): 143–54. http://dx.doi.org/10.1152/advan.00046.2004.
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The steady-state maintenance of highly asymmetric concentrations of the major inorganic cations and anions is a major function of both plasma membranes and the membranes of intracellular organelles. Homeostatic regulation of these ionic gradients is critical for most functions. Due to their charge, the movements of ions across biological membranes necessarily involves facilitation by intrinsic membrane transport proteins. The functional characterization and categorization of membrane transport proteins was a major focus of cell physiological research from the 1950s through the 1980s. On the basis of these functional analyses, ion transport proteins were broadly divided into two classes: channels and carrier-type transporters (which include exchangers, cotransporters, and ATP-driven ion pumps). Beginning in the mid-1980s, these functional analyses of ion transport and homeostasis were complemented by the cloning of genes encoding many ion channels and transporter proteins. Comparison of the predicted primary amino acid sequences and structures of functionally similar ion transport proteins facilitated their grouping within families and superfamilies of structurally related membrane proteins. Postgenomics research in ion transport biology increasingly involves two powerful approaches. One involves elucidation of the molecular structures, at the atomic level in some cases, of model ion transport proteins. The second uses the tools of cell biology to explore the cell-specific function or subcellular localization of ion transport proteins. This review will describe how these approaches have provided new, and sometimes surprising, insights regarding four major questions in current ion transporter research. 1) What are the fundamental differences between ion channels and ion transporters? 2) How does the interaction of an ion transport protein with so-called adapter proteins affect its subcellular localization or regulation by various intracellular signal transduction pathways? 3) How does the specific lipid composition of the local membrane microenvironment modulate the function of an ion transport protein? 4) How can the basic functional properties of a ubiquitously expressed ion transport protein vary depending on the cell type in which it is expressed?
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Müller, Peter, Andreas Herrmann, Ingolf Bernhardt, and Roland Glaser. "Influence of the intracellular and extracellular cation concentration on monovalent cation efflux of resealed human erythrocyte ghosts." Bioscience Reports 5, no. 5 (May 1, 1985): 425–32. http://dx.doi.org/10.1007/bf01116560.
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Tracer efflux measurements (86Rb+ and2NaNa+) were performed on resealed human erythrocyte ghosts at different intra- and extracellular NaCI concentrations. Using a modified Goldman equation the observed alterations of the rate constants could be explained by taking into account the transmembrane and surface potentials, at constant permeability coefficient. These results emphasize the importance of membrane surface potentials in triggering ion transport across biological membranes.
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Mescia, Luciano, Michele Alessandro Chiapperino, Pietro Bia, Claudio Maria Lamacchia, Johan Gielis, and Diego Caratelli. "Design of Electroporation Process in Irregularly Shaped Multicellular Systems." Electronics 8, no. 1 (January 1, 2019): 37. http://dx.doi.org/10.3390/electronics8010037.
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Electroporation technique is widely used in biotechnology and medicine for the transport of various molecules through the membranes of biological cells. Different mathematical models of electroporation have been proposed in the literature to study pore formation in plasma and nuclear membranes. These studies are mainly based on models using a single isolated cell with a canonical shape. In this work, a space–time (x,y,t) multiphysics model based on quasi-static Maxwell’s equations and nonlinear Smoluchowski’s equation has been developed to investigate the electroporation phenomenon induced by pulsed electric field in multicellular systems having irregularly shape. The dielectric dispersion of the cell compartments such as nuclear and plasmatic membranes, cytoplasm, nucleoplasm and external medium have been incorporated into the numerical algorithm, too. Moreover, the irregular cell shapes have been modeled by using the Gielis transformations.
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Wöhlert, David, Werner Kühlbrandt, and Özkan Yildiz. "Structure and function of an Antiporter." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1046. http://dx.doi.org/10.1107/s2053273314089530.
Full textAbstract:
Membrane proteins are essential to transport molecules across biological membranes. This gateway task makes them important drug targets. About 60% of all approved drugs target membrane proteins. Transport of ions across membranes is essential for every cell to maintain physiological salt concentrations and to keep pH homeostasis. In the past years X-Ray structures of various secondary transporters have provided insight into the mechanisms of membrane transport. However, difficulties in expression, purification and crystallization of membrane proteins still restrict the number of available structures. For well-characterized secondary transporters such as LeuT (1), BetP (2) and Ca2+/H+-exchangers (3) crystal structures in different conformations and substrate binding states have been obtained. However, for many important classes of transport proteins, detailed structures are urgently needed to understand their mechanism of action and to guide drug development. We report crystal structures of 2 homologues of a new secondary transporter in different states, with or without substrate bound. These structures shed light on the transport mechanism of this important class of membrane transport proteins.
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REIGADA, RAMON, JORDI GÓMEZ, JAVIER BUCETA, KATJA LINDENBERG, and FRANCESC SAGUÉS. "PATTERN FORMATION IN NONEQUILIBRIUM LIPID MEMBRANES: FROM MEMBRANE UNDULATIONS TO LIPID RAFTS." Biophysical Reviews and Letters 05, no. 01 (March 2010): 1–34. http://dx.doi.org/10.1142/s179304801000110x.
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Lipid membranes, particularly under nonequilibrium conditions, have recently been investigated ever more vigorously because of their relevance in the biological context. We survey our recent approaches to the theoretical study of lipid bilayers that are perturbed in different ways. Self-organization phenomena involving curvature and/or composition spatiotemporal organization are investigated in membrane systems subjected to externally induced chemical reactions, transversal mass transport and insertion of proteins. The outcomes of these studies are expected to be applicable to different curvature and lateral organization phenomena in synthetic lipid bilayers and also in plasmatic cell membranes.
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Darley, Es, Jasleen Kaur Daljit Singh, Natalie A. Surace, Shelley F. J. Wickham, and Matthew A. B. Baker. "The Fusion of Lipid and DNA Nanotechnology." Genes 10, no. 12 (December 3, 2019): 1001. http://dx.doi.org/10.3390/genes10121001.
Full textAbstract:
Lipid membranes form the boundary of many biological compartments, including organelles and cells. Consisting of two leaflets of amphipathic molecules, the bilayer membrane forms an impermeable barrier to ions and small molecules. Controlled transport of molecules across lipid membranes is a fundamental biological process that is facilitated by a diverse range of membrane proteins, including ion-channels and pores. However, biological membranes and their associated proteins are challenging to experimentally characterize. These challenges have motivated recent advances in nanotechnology towards building and manipulating synthetic lipid systems. Liposomes—aqueous droplets enclosed by a bilayer membrane—can be synthesised in vitro and used as a synthetic model for the cell membrane. In DNA nanotechnology, DNA is used as programmable building material for self-assembling biocompatible nanostructures. DNA nanostructures can be functionalised with hydrophobic chemical modifications, which bind to or bridge lipid membranes. Here, we review approaches that combine techniques from lipid and DNA nanotechnology to engineer the topography, permeability, and surface interactions of membranes, and to direct the fusion and formation of liposomes. These approaches have been used to study the properties of membrane proteins, to build biosensors, and as a pathway towards assembling synthetic multicellular systems.
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Garland, Peter B. "Chemiosmotic systems in medicine." Bioscience Reports 11, no. 6 (December 1, 1991): 445–75. http://dx.doi.org/10.1007/bf01130215.
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The concept of chemiosmotic systems arises from the pioneering work of Peter Mitchell on two fronts. One is concerned with the mechanisms by which molecules are transported across membranes which are generally barriers to such transport. These mechanisms are inevitably molecular, and are now yielding their secrets to a combination of structural protein chemistry and molecular biology. The other front is more physiological, and explores the functional relationships between metabolism and transport. Nevertheless, the two fronts form a continuum of mutally related structure and function. Chemiosmotic systems provide a hierarchy of complexity, starting from say a uniporter reconstituted in a chemically defined bilayer, and proceeding to greater complexity in mitochondria, chloroplasts, eukaryotic and prokaryotic cell membranes, and multicellular systems. Their relationship to medicine is profound, because they provide many opportunities for therapeutic intervention. In this paper I present an overview of chemiosmotic systems at different levels of complexity, both molecular and biological, of their involvements in pathology, and of possible pharmacological treatment or prevention of disease.