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Journal articles on the topic 'Organell'
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1
Wagner, Nicolai, Milena Stephan, Doris Höglinger, and André Nadler. "Der Click‐Cage: Organell‐spezifische Photoaktivierung von Lipid‐Botenstoffen." Angewandte Chemie 130, no. 40 (September 3, 2018): 13523–27. http://dx.doi.org/10.1002/ange.201807497.
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Oborník, Miroslav. "Organellar Evolution: A Path from Benefit to Dependence." Microorganisms 10, no. 1 (January 7, 2022): 122. http://dx.doi.org/10.3390/microorganisms10010122.
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Eukaryotic organelles supposedly evolved from their bacterial ancestors because of their benefits to host cells. However, organelles are quite often retained, even when the beneficial metabolic pathway is lost, due to something other than the original beneficial function. The organellar function essential for cell survival is, in the end, the result of organellar evolution, particularly losses of redundant metabolic pathways present in both the host and endosymbiont, followed by a gradual distribution of metabolic functions between the organelle and host. Such biological division of metabolic labor leads to mutual dependence of the endosymbiont and host. Changing environmental conditions, such as the gradual shift of an organism from aerobic to anaerobic conditions or light to dark, can make the original benefit useless. Therefore, it can be challenging to deduce the original beneficial function, if there is any, underlying organellar acquisition. However, it is also possible that the organelle is retained because it simply resists being eliminated or digested untill it becomes indispensable.
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Mallo, Natalia, Justin Fellows, Carla Johnson, and Lilach Sheiner. "Protein Import into the Endosymbiotic Organelles of Apicomplexan Parasites." Genes 9, no. 8 (August 14, 2018): 412. http://dx.doi.org/10.3390/genes9080412.
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: The organelles of endosymbiotic origin, plastids, and mitochondria, evolved through the serial acquisition of endosymbionts by a host cell. These events were accompanied by gene transfer from the symbionts to the host, resulting in most of the organellar proteins being encoded in the cell nuclear genome and trafficked into the organelle via a series of translocation complexes. Much of what is known about organelle protein translocation mechanisms is based on studies performed in common model organisms; e.g., yeast and humans or Arabidopsis. However, studies performed in divergent organisms are gradually accumulating. These studies provide insights into universally conserved traits, while discovering traits that are specific to organisms or clades. Apicomplexan parasites feature two organelles of endosymbiotic origin: a secondary plastid named the apicoplast and a mitochondrion. In the context of the diseases caused by apicomplexan parasites, the essential roles and divergent features of both organelles make them prime targets for drug discovery. This potential and the amenability of the apicomplexan Toxoplasma gondii to genetic manipulation motivated research about the mechanisms controlling both organelles’ biogenesis. Here we provide an overview of what is known about apicomplexan organelle protein import. We focus on work done mainly in T. gondii and provide a comparison to model organisms.
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Evans, David E., and Chris Hawes. "Organelle Biogenesis and Positioning in Plants." Biochemical Society Transactions 38, no. 3 (May 24, 2010): 729–32. http://dx.doi.org/10.1042/bst0380729.
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The biogenesis and positioning of organelles involves complex interacting processes and precise control. Progress in our understanding is being made rapidly as advances in analysing the nuclear and organellar genome and proteome combine with developments in live-cell microscopy and manipulation at the subcellular level. This paper introduces the collected papers resulting from Organelle Biogenesis and Positioning in Plants, the 2009 Biochemical Society Annual Symposium. Including papers on the nuclear envelope and all major organelles, it considers current knowledge and progress towards unifying themes that will elucidate the mechanisms by which cells generate the correct complement of organelles and adapt and change it in response to environmental and developmental signals.
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Costello, Rona, David M. Emms, and Steven Kelly. "Gene Duplication Accelerates the Pace of Protein Gain and Loss from Plant Organelles." Molecular Biology and Evolution 37, no. 4 (November 21, 2019): 969–81. http://dx.doi.org/10.1093/molbev/msz275.
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Abstract Organelle biogenesis and function is dependent on the concerted action of both organellar-encoded (if present) and nuclear-encoded proteins. Differences between homologous organelles across the Plant Kingdom arise, in part, as a result of differences in the cohort of nuclear-encoded proteins that are targeted to them. However, neither the rate at which differences in protein targeting accumulate nor the evolutionary consequences of these changes are known. Using phylogenomic approaches coupled to ancestral state estimation, we show that the plant organellar proteome has diversified in proportion with molecular sequence evolution such that the proteomes of plant chloroplasts and mitochondria lose or gain on average 3.6 proteins per million years. We further demonstrate that changes in organellar protein targeting are associated with an increase in the rate of molecular sequence evolution and that such changes predominantly occur in genes with regulatory rather than metabolic functions. Finally, we show that gain and loss of protein target signals occurs at a higher rate following gene duplication, revealing that gene and genome duplication are a key facilitator of plant organelle evolution.
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Okamoto, Koji. "Organellophagy: Eliminating cellular building blocks via selective autophagy." Journal of Cell Biology 205, no. 4 (May 26, 2014): 435–45. http://dx.doi.org/10.1083/jcb.201402054.
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Maintenance of organellar quality and quantity is critical for cellular homeostasis and adaptation to variable environments. Emerging evidence demonstrates that this kind of control is achieved by selective elimination of organelles via autophagy, termed organellophagy. Organellophagy consists of three key steps: induction, cargo tagging, and sequestration, which involve signaling pathways, organellar landmark molecules, and core autophagy-related proteins, respectively. In addition, posttranslational modifications such as phosphorylation and ubiquitination play important roles in recruiting and tailoring the autophagy machinery to each organelle. The basic principles underlying organellophagy are conserved from yeast to mammals, highlighting its biological relevance in eukaryotic cells.
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Haggie, Peter M., and A. S. Verkman. "Defective organellar acidification as a cause of cystic fibrosis lung disease: reexamination of a recurring hypothesis." American Journal of Physiology-Lung Cellular and Molecular Physiology 296, no. 6 (June 2009): L859—L867. http://dx.doi.org/10.1152/ajplung.00018.2009.
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The cellular mechanisms by which loss-of-function mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel produce cystic fibrosis (CF) lung disease remain uncertain. Defective organellar function has been proposed as an important determinant in the pathogenesis of CF lung disease. According to one hypothesis, reduced CFTR chloride conductance in organelles in CF impairs their acidification by preventing chloride entry into the organelle lumen, which is needed to balance the positive charge produced by proton entry. According to a different hypothesis, CFTR mutation hyperacidifies organelles by an indirect mechanism involving unregulated sodium efflux through epithelial sodium channels. There are reports of defective Golgi, endosomal and lysosomal acidification in CF epithelial cells, defective phagolysosomal acidification in CF alveolar macrophages, and organellar hyperacidification in CF respiratory epithelial cells. The common theme relating too high or low organellar pH to cellular dysfunction and CF pathogenesis is impaired functioning of organellar enzymes, such as those involved in ceramide metabolism and protein processing in epithelial cells and antimicrobial activity in alveolar macrophages. We review here the evidence for defective organellar acidification in CF. Significant technical and conceptual concerns are discussed regarding the validity of data showing too high/low organellar pH in CF cells, and rigorous measurements of organellar pH in CF cells are reviewed that fail to support defective organellar acidification in CF. Indeed, there is an expanding body of evidence supporting the involvement of non-CFTR chloride channels in organellar acidification. We conclude that biologically significant involvement of CFTR in organellar acidification is unlikely.
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Hume, Alistair N., and Miguel C. Seabra. "Melanosomes on the move: a model to understand organelle dynamics." Biochemical Society Transactions 39, no. 5 (September 21, 2011): 1191–96. http://dx.doi.org/10.1042/bst0391191.
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Advances in live-cell microscopy have revealed the extraordinarily dynamic nature of intracellular organelles. Moreover, movement appears to be critical in establishing and maintaining intracellular organization and organellar and cellular function. Motility is regulated by the activity of organelle-associated motor proteins, kinesins, dyneins and myosins, which move cargo along polar MT (microtubule) and actin tracks. However, in most instances, the motors that move specific organelles remain mysterious. Over recent years, pigment granules, or melanosomes, within pigment cells have provided an excellent model for understanding the molecular mechanisms by which motor proteins associate with and move intracellular organelles. In the present paper, we discuss recent discoveries that shed light on the mechanisms of melanosome transport and highlight future prospects for the use of pigment cells in unravelling general molecular mechanisms of intracellular transport.
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Wang, Yan, Jennifer Selinski, Chunli Mao, Yanqiao Zhu, Oliver Berkowitz, and James Whelan. "Linking mitochondrial and chloroplast retrograde signalling in plants." Philosophical Transactions of the Royal Society B: Biological Sciences 375, no. 1801 (May 4, 2020): 20190410. http://dx.doi.org/10.1098/rstb.2019.0410.
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Retrograde signalling refers to the regulation of nuclear gene expression in response to functional changes in organelles. In plants, the two energy-converting organelles, mitochondria and chloroplasts, are tightly coordinated to balance their activities. Although our understanding of components involved in retrograde signalling has greatly increased in the last decade, studies on the regulation of the two organelle signalling pathways have been largely independent. Thus, the mechanism of how mitochondrial and chloroplastic retrograde signals are integrated is largely unknown. Here, we summarize recent findings on the function of mitochondrial signalling components and their links to chloroplast retrograde responses. From this, a picture emerges showing that the major regulators are integrators of both organellar retrograde signalling pathways. This article is part of the theme issue ‘Retrograde signalling from endosymbiotic organelles’.
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Robles, Pedro, and Víctor Quesada. "Transcriptional and Post-transcriptional Regulation of Organellar Gene Expression (OGE) and Its Roles in Plant Salt Tolerance." International Journal of Molecular Sciences 20, no. 5 (February 28, 2019): 1056. http://dx.doi.org/10.3390/ijms20051056.
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Given their endosymbiotic origin, chloroplasts and mitochondria genomes harbor only between 100 and 200 genes that encode the proteins involved in organellar gene expression (OGE), photosynthesis, and the electron transport chain. However, as the activity of these organelles also needs a few thousand proteins encoded by the nuclear genome, a close coordination of the gene expression between the nucleus and organelles must exist. In line with this, OGE regulation is crucial for plant growth and development, and is achieved mainly through post-transcriptional mechanisms performed by nuclear genes. In this way, the nucleus controls the activity of organelles and these, in turn, transmit information about their functional state to the nucleus by modulating nuclear expression according to the organelles’ physiological requirements. This adjusts organelle function to plant physiological, developmental, or growth demands. Therefore, OGE must appropriately respond to both the endogenous signals and exogenous environmental cues that can jeopardize plant survival. As sessile organisms, plants have to respond to adverse conditions to acclimate and adapt to them. Salinity is a major abiotic stress that negatively affects plant development and growth, disrupts chloroplast and mitochondria function, and leads to reduced yields. Information on the effects that the disturbance of the OGE function has on plant tolerance to salinity is still quite fragmented. Nonetheless, many plant mutants which display altered responses to salinity have been characterized in recent years, and interestingly, several are affected in nuclear genes encoding organelle-localized proteins that regulate the expression of organelle genes. These results strongly support a link between OGE and plant salt tolerance, likely through retrograde signaling. Our review analyzes recent findings on the OGE functions required by plants to respond and tolerate salinity, and highlights the fundamental role that chloroplast and mitochondrion homeostasis plays in plant adaptation to salt stress.
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Mastud, Pragati, and Swati Patankar. "An ambiguous N-terminus drives the dual targeting of an antioxidant protein Thioredoxin peroxidase (TgTPx1/2) to endosymbiotic organelles in Toxoplasma gondii." PeerJ 7 (July 18, 2019): e7215. http://dx.doi.org/10.7717/peerj.7215.
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Toxoplasma gondii harbors two endosymbiotic organelles: a relict plastid, the apicoplast, and a mitochondrion. The parasite expresses an antioxidant protein, thioredoxin peroxidase 1/2 (TgTPx1/2), that is dually targeted to these organelles. Nuclear-encoded proteins such as TgTPx1/2 are trafficked to the apicoplast via a secretory route through the endoplasmic reticulum (ER) and to the mitochondrion via a non-secretory pathway comprising of translocon uptake. Given the two distinct trafficking pathways for localization to the two organelles, the signals in TgTPx1/2 for this dual targeting are open areas of investigation. Here we show that the signals for apicoplast and mitochondrial trafficking lie in the N-terminal 50 amino acids of the protein and are overlapping. Interestingly, mutational analysis of the overlapping stretch shows that despite this overlap, the signals for individual organellar uptake can be easily separated. Further, deletions in the N-terminus also reveal a 10 amino acid stretch that is responsible for targeting the protein from punctate structures surrounding the apicoplast into the organelle itself. Collectively, results presented in this report suggest that an ambiguous signal sequence for organellar uptake combined with a hierarchy of recognition by the protein trafficking machinery drives the dual targeting of TgTPx1/2.
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Barriere, Herve, Miklos Bagdany, Florian Bossard, Tsukasa Okiyoneda, Gabriella Wojewodka, Dieter Gruenert, Danuta Radzioch, and Gergely L. Lukacs. "Revisiting the Role of Cystic Fibrosis Transmembrane Conductance Regulator and Counterion Permeability in the pH Regulation of Endocytic Organelles." Molecular Biology of the Cell 20, no. 13 (July 2009): 3125–41. http://dx.doi.org/10.1091/mbc.e09-01-0061.
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Organellar acidification by the electrogenic vacuolar proton-ATPase is coupled to anion uptake and cation efflux to preserve electroneutrality. The defective organellar pH regulation, caused by impaired counterion conductance of the mutant cystic fibrosis transmembrane conductance regulator (CFTR), remains highly controversial in epithelia and macrophages. Restricting the pH-sensitive probe to CFTR-containing vesicles, the counterion and proton permeability, and the luminal pH of endosomes were measured in various cells, including genetically matched CF and non-CF human respiratory epithelia, as well as cftr+/+and cftr−/−mouse alveolar macrophages. Passive proton and relative counterion permeabilities, determinants of endosomal, lysosomal, and phagosomal pH-regulation, were probed with FITC-conjugated transferrin, dextran, and Pseudomonas aeruginosa, respectively. Although CFTR function could be documented in recycling endosomes and immature phagosomes, neither channel activation nor inhibition influenced the pH in any of these organelles. CFTR heterologous overexpression also failed to alter endocytic organellar pH. We propose that the relatively large CFTR-independent counterion and small passive proton permeability ensure efficient shunting of the proton-ATPase–generated membrane potential. These results have implications in the regulation of organelle acidification in general and demonstrate that perturbations of the endolysosomal organelles pH homeostasis cannot be linked to the etiology of the CF lung disease.
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Liu, Fangfang, Seng Kah Ng, Yanfen Lu, Wilson Low, Julian Lai, and Gregory Jedd. "Making two organelles from one: Woronin body biogenesis by peroxisomal protein sorting." Journal of Cell Biology 180, no. 2 (January 28, 2008): 325–39. http://dx.doi.org/10.1083/jcb.200705049.
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Woronin bodies (WBs) are dense-core organelles that are found exclusively in filamentous fungi and that seal the septal pore in response to wounding. These organelles consist of a membrane-bound protein matrix comprised of the HEX protein and, although they form from peroxisomes, their biogenesis is poorly understood. In Neurospora crassa, we identify Woronin sorting complex (WSC), a PMP22/MPV17-related membrane protein with dual functions in WB biogenesis. WSC localizes to large peroxisome membranes where it self-assembles into detergent-resistant oligomers that envelop HEX assemblies, producing asymmetrical nascent WBs. In a reaction requiring WSC, these structures are delivered to the cell cortex, which permits partitioning of the nascent WB and WB inheritance. Our findings suggest that WSC and HEX collaborate and control distinct aspects of WB biogenesis and that cortical association depends on WSC, which in turn depends on HEX. This dependency helps order events across the organellar membrane, permitting the peroxisome to produce a second organelle with a distinct composition and intracellular distribution.
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Smith, R. S., and W. S. Kendal. "The recovery of organelle transport and microtubule integrity in myelinated axons that are frozen and thawed." Canadian Journal of Physiology and Pharmacology 63, no. 4 (April 1, 1985): 292–97. http://dx.doi.org/10.1139/y85-053.
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Myelinated axons of Xenopus laevis were rapidly frozen in liquid nitrogen and thawed in a potassium glutamate based medium. Organelles within isolated, thawed axons were visualized by light microscopy. After thawing, organelles were stationary for about 5 min. Following this quiescent period, organelles exhibited a low frequency oscillation in the longitudinal direction of the axon; some of the organelles then began to move in either the anterograde or retrograde directions. Electron microscopic examination of axonal cross sections showed that few microtubules were present immediately after thawing, but the numbers of microtubules recovered to approximately normal levels with a time course closely resembling that of the recovery of organelle transport. The effects of colchicine and taxol on the recovery of organelle transport and the microtubule content of axons was consistent with the hypothesis that the recovery in microtubule numbers was related to the recovery of organelle transport. Vanadate ions inhibited the recovery of organelle transport at concentrations known to inhibit dynein ATPase.
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Ouellet, Jimmy, and Yves Barral. "Organelle segregation during mitosis: Lessons from asymmetrically dividing cells." Journal of Cell Biology 196, no. 3 (February 6, 2012): 305–13. http://dx.doi.org/10.1083/jcb.201102078.
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Studies on cell division traditionally focus on the mechanisms of chromosome segregation and cytokinesis, yet we know comparatively little about how organelles segregate. Analysis of organelle partitioning in asymmetrically dividing cells has provided insights into the mechanisms through which cells control organelle distribution. Interestingly, these studies have revealed that segregation mechanisms frequently link organelle distribution to organelle growth and formation. Furthermore, in many cases, cells use organelles, such as the endoplasmic reticulum and P granules, as vectors for the segregation of information. Together, these emerging data suggest that the coordination between organelle growth, division, and segregation plays an important role in the control of cell fate inheritance, cellular aging, and rejuvenation, i.e., the resetting of age in immortal lineages.
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Hertle, Alexander P., Benedikt Haberl, and Ralph Bock. "Horizontal genome transfer by cell-to-cell travel of whole organelles." Science Advances 7, no. 1 (January 2021): eabd8215. http://dx.doi.org/10.1126/sciadv.abd8215.
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Recent work has revealed that both plants and animals transfer genomes between cells. In plants, horizontal transfer of entire plastid, mitochondrial, or nuclear genomes between species generates new combinations of nuclear and organellar genomes, or produces novel species that are allopolyploid. The mechanisms of genome transfer between cells are unknown. Here, we used grafting to identify the mechanisms involved in plastid genome transfer from plant to plant. We show that during proliferation of wound-induced callus, plastids dedifferentiate into small, highly motile, amoeboid organelles. Simultaneously, new intercellular connections emerge by localized cell wall disintegration, forming connective pores through which amoeboid plastids move into neighboring cells. Our work uncovers a pathway of organelle movement from cell to cell and provides a mechanistic framework for horizontal genome transfer.
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Eubel, Holger. "Von Organen und Organellen: Proteomanalysen in Pflanzen." BIOspektrum 18, no. 6 (October 2012): 603–6. http://dx.doi.org/10.1007/s12268-012-0236-2.
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Chesser, Ronald K. "Heteroplasmy and Organelle Gene Dynamics." Genetics 150, no. 3 (November 1, 1998): 1309–27. http://dx.doi.org/10.1093/genetics/150.3.1309.
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Abstract This study assesses factors that influence the rates of change of organelle gene diversity and the maintenance of heteroplasmy. Losses of organelle gene diversity within individuals via vegetative segregation during ontogeny are paramount to resultant spatial and temporal patterns. Steady-state losses of organelle variation from the zygote to the gametes are determined by the effective number of organelles, which will be approximately equal to the number of intracellular organelles if random segregation prevails. Both rapid increases in organelle number after zygote formation and reductions at germ lines will reduce variation within individuals. Terminal reductions in organelles must be to very low copy numbers (<5) for substantial losses in variation to occur rapidly. Nonrandom clonal expansion and vegetative segregation during gametogenesis may be effective in reducing genetic variation in gametes. If organelles are uniparentally inherited, the asymptotic expectations for effective numbers of gametes and spatial differentiation will be identical for homoplasmic and heteroplasmic conditions. The rate of attainment of asymptote for heteroplasmic organelles, however, is governed by the rate of loss of variation during ontogeny. With sex-biased dispersal, the effective number of gametes is maximized when the proportional contributions of the sex having the higher dispersal rate are low.
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Kumar, Vaishali, and Shuvadeep Maity. "ER Stress-Sensor Proteins and ER-Mitochondrial Crosstalk—Signaling Beyond (ER) Stress Response." Biomolecules 11, no. 2 (January 28, 2021): 173. http://dx.doi.org/10.3390/biom11020173.
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Recent studies undoubtedly show the importance of inter organellar connections to maintain cellular homeostasis. In normal physiological conditions or in the presence of cellular and environmental stress, each organelle responds alone or in coordination to maintain cellular function. The Endoplasmic reticulum (ER) and mitochondria are two important organelles with very specialized structural and functional properties. These two organelles are physically connected through very specialized proteins in the region called the mitochondria-associated ER membrane (MAM). The molecular foundation of this relationship is complex and involves not only ion homeostasis through the shuttling of calcium but also many structural and apoptotic proteins. IRE1alpha and PERK are known for their canonical function as an ER stress sensor controlling unfolded protein response during ER stress. The presence of these transmembrane proteins at the MAM indicates its potential involvement in other biological functions beyond ER stress signaling. Many recent studies have now focused on the non-canonical function of these sensors. In this review, we will focus on ER mitochondrial interdependence with special emphasis on the non-canonical role of ER stress sensors beyond ER stress.
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Powell, Martha J., and Will H. Blackwell. "Searching for homologous ultrastructural characters in zoosporic fungi." Canadian Journal of Botany 73, S1 (December 31, 1995): 693–700. http://dx.doi.org/10.1139/b95-312.
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One aim of ultrastructural studies of motile cells of Oomycetes and Chytridiomycetes, two groups of organisms recognized to have evolved along distinct lineages, has been to compile data bases of characters for reconstruction of phylogenetic hypotheses. Because little is known about the ontogeny, composition, and function of many structures that might be useful, assuming homology owing to similarity in ultrastructural form is problematic. In this paper we explore approaches to elucidating homologies between single membrane bounded organelles in zoospores. We use K-bodies of Oomycete zoospores as an example of an organelle for which ontogenic studies have revealed that certain morphological forms are analogous to other forms. Results of these studies demonstrate that as a morphological character K-body structure can be valuable among subgroups of Oomycetes, but convergence in structure makes it unreliable as a comparative character across the class. Although comparative morphology as an avenue to understanding phylogeny is sometimes challenged, this approach can provide valuable insights into processes involved in organellar evolution. Key words: Chytridiomycetes, Oomycetes, organelles, systematics, ultrastructure, zoospores.
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Morley, Stewart A., Niaz Ahmad, and Brent L. Nielsen. "Plant Organelle Genome Replication." Plants 8, no. 10 (September 21, 2019): 358. http://dx.doi.org/10.3390/plants8100358.
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Mitochondria and chloroplasts perform essential functions in respiration, ATP production, and photosynthesis, and both organelles contain genomes that encode only some of the proteins that are required for these functions. The proteins and mechanisms for organelle DNA replication are very similar to bacterial or phage systems. The minimal replisome may consist of DNA polymerase, a primase/helicase, and a single-stranded DNA binding protein (SSB), similar to that found in bacteriophage T7. In Arabidopsis, there are two genes for organellar DNA polymerases and multiple potential genes for SSB, but there is only one known primase/helicase protein to date. Genome copy number varies widely between type and age of plant tissues. Replication mechanisms are only poorly understood at present, and may involve multiple processes, including recombination-dependent replication (RDR) in plant mitochondria and perhaps also in chloroplasts. There are still important questions remaining as to how the genomes are maintained in new organelles, and how genome copy number is determined. This review summarizes our current understanding of these processes.
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Li, Angdi, Shuning Zhang, Valentina Loconte, Yan Liu, Axel Ekman, Garth J. Thompson, Andrej Sali, et al. "An intensity-based post-processing tool for 3D instance segmentation of organelles in soft X-ray tomograms." PLOS ONE 17, no. 9 (September 1, 2022): e0269887. http://dx.doi.org/10.1371/journal.pone.0269887.
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Investigating the 3D structures and rearrangements of organelles within a single cell is critical for better characterizing cellular function. Imaging approaches such as soft X-ray tomography have been widely applied to reveal a complex subcellular organization involving multiple inter-organelle interactions. However, 3D segmentation of organelle instances has been challenging despite its importance in organelle characterization. Here we propose an intensity-based post-processing tool to identify and separate organelle instances. Our tool separates sphere-like (insulin vesicle) and columnar-shaped organelle instances (mitochondrion) based on the intensity of raw tomograms, semantic segmentation masks, and organelle morphology. We validate our tool using synthetic tomograms of organelles and experimental tomograms of pancreatic β-cells to separate insulin vesicle and mitochondria instances. As compared to the commonly used connected regions labeling, watershed, and watershed + Gaussian filter methods, our tool results in improved accuracy in identifying organelles in the synthetic tomograms and an improved description of organelle structures in β-cell tomograms. In addition, under different experimental treatment conditions, significant changes in volumes and intensities of both insulin vesicle and mitochondrion are observed in our instance results, revealing their potential roles in maintaining normal β-cell function. Our tool is expected to be applicable for improving the instance segmentation of other images obtained from different cell types using multiple imaging modalities.
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Klemm, Robin W. "Getting in Touch Is an Important Step: Control of Metabolism at Organelle Contact Sites." Contact 4 (January 2021): 251525642199370. http://dx.doi.org/10.1177/2515256421993708.
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Metabolic pathways are often spread over several organelles and need to be functionally integrated by controlled organelle communication. Physical organelle contact-sites have emerged as critical hubs in the regulation of cellular metabolism, but the molecular understanding of mechanisms that mediate formation or regulation of organelle interfaces was until recently relatively limited. Mitochondria are central organelles in anabolic and catabolic pathways and therefore interact with a number of other cellular compartments including the endoplasmic reticulum (ER) and lipid droplets (LDs). An interesting set of recent work has shed new light on the molecular basis forming these contact sites. This brief overview describes the discovery of unanticipated functions of contact sites between the ER, mitochondria and LDs in de novo synthesis of storage lipids of brown and white adipocytes. Interestingly, the factors involved in mediating the interaction between these organelles are subject to unexpected modes of regulation through newly uncovered Phospho-FFAT motifs. These results suggest dynamic regulation of contact sites between organelles and indicate that spatial organization of organelles within the cell contributes to the control of metabolism.
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Ci, Yali, and Lei Shi. "Compartmentalized replication organelle of flavivirus at the ER and the factors involved." Cellular and Molecular Life Sciences 78, no. 11 (April 12, 2021): 4939–54. http://dx.doi.org/10.1007/s00018-021-03834-6.
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AbstractFlaviviruses are positive-sense single-stranded RNA viruses that pose a considerable threat to human health. Flaviviruses replicate in compartmentalized replication organelles derived from the host endoplasmic reticulum (ER). The characteristic architecture of flavivirus replication organelles includes invaginated vesicle packets and convoluted membrane structures. Multiple factors, including both viral proteins and host factors, contribute to the biogenesis of the flavivirus replication organelle. Several viral nonstructural (NS) proteins with membrane activity induce ER rearrangement to build replication compartments, and other NS proteins constitute the replication complexes (RC) in the compartments. Host protein and lipid factors facilitate the formation of replication organelles. The lipid membrane, proteins and viral RNA together form the functional compartmentalized replication organelle, in which the flaviviruses efficiently synthesize viral RNA. Here, we reviewed recent advances in understanding the structure and biogenesis of flavivirus replication organelles, and we further discuss the function of virus NS proteins and related host factors as well as their roles in building the replication organelle.
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Brill, Julie A., and Jared Rutter. "Quality control and organelle trafficking: ensuring functional organelles and cells." Molecular Biology of the Cell 28, no. 6 (March 15, 2017): 701–2. http://dx.doi.org/10.1091/mbc.e16-11-0798.
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Smith, Richard S., and David S. Forman. "Organelle dynamics in lobster zxons: anterograde and retrograde particulate organelles." Brain Research 446, no. 1 (April 1988): 26–36. http://dx.doi.org/10.1016/0006-8993(88)91293-0.
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Ren, Shanhui, Chan Ding, and Yingjie Sun. "Morphology Remodeling and Selective Autophagy of Intracellular Organelles during Viral Infections." International Journal of Molecular Sciences 21, no. 10 (May 23, 2020): 3689. http://dx.doi.org/10.3390/ijms21103689.
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Viruses have evolved different strategies to hijack subcellular organelles during their life cycle to produce robust infectious progeny. Successful viral reproduction requires the precise assembly of progeny virions from viral genomes, structural proteins, and membrane components. Such spatial and temporal separation of assembly reactions depends on accurate coordination among intracellular compartmentalization in multiple organelles. Here, we overview the rearrangement and morphology remodeling of virus-triggered intracellular organelles. Focus is given to the quality control of intracellular organelles, the hijacking of the modified organelle membranes by viruses, morphology remodeling for viral replication, and degradation of intracellular organelles by virus-triggered selective autophagy. Understanding the functional reprogram and morphological remodeling in the virus-organelle interplay can provide new insights into the development of broad-spectrum antiviral strategies.
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Mai, Zhiming, Sudip Ghosh, Marta Frisardi, Ben Rosenthal, Rick Rogers, and John Samuelson. "Hsp60 Is Targeted to a Cryptic Mitochondrion-Derived Organelle (“Crypton”) in the Microaerophilic Protozoan Parasite Entamoeba histolytica." Molecular and Cellular Biology 19, no. 3 (March 1, 1999): 2198–205. http://dx.doi.org/10.1128/mcb.19.3.2198.
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ABSTRACT Entamoeba histolytica is a microaerophilic protozoan parasite in which neither mitochondria nor mitochondrion-derived organelles have been previously observed. Recently, a segment of anE. histolytica gene was identified that encoded a protein similar to the mitochondrial 60-kDa heat shock protein (Hsp60 or chaperonin 60), which refolds nuclear-encoded proteins after passage through organellar membranes. The possible function and localization of the amebic Hsp60 were explored here. Like Hsp60 of mitochondria, amebic Hsp60 RNA and protein were both strongly induced by incubating parasites at 42°C. 5′ and 3′ rapid amplifications of cDNA ends were used to obtain the entire E. histolytica hsp60 coding region, which predicted a 536-amino-acid Hsp60. The E. histolytica hsp60 gene protected from heat shockEscherichia coli groEL mutants, demonstrating the chaperonin function of the amebic Hsp60. The E. histolyticaHsp60, which lacked characteristic carboxy-terminal Gly-Met repeats, had a 21-amino-acid amino-terminal, organelle-targeting presequence that was cleaved in vivo. This presequence was necessary to target Hsp60 to one (and occasionally two or three) short, cylindrical organelle(s). In contrast, amebic alcohol dehydrogenase 1 and ferredoxin, which are bacteria-like enzymes, were diffusely distributed throughout the cytosol. We suggest that the Hsp60-associated, mitochondrion-derived organelle identified here be named “crypton,” as its structure was previously hidden and its function is still cryptic.
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Pelham, R. J., J. J. Lin, and Y. L. Wang. "A high molecular mass non-muscle tropomyosin isoform stimulates retrograde organelle transport." Journal of Cell Science 109, no. 5 (May 1, 1996): 981–89. http://dx.doi.org/10.1242/jcs.109.5.981.
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Although non-muscle tropomyosins (TM) have been implicated in various cellular functions, such as stabilization of actin filaments and possibly regulation of organelle transport, their physiological role is still poorly understood. We have probed the role of a high molecular mass isoform of human fibroblast TM, hTM3, in regulating organelle transport by microinjecting an excess amount of bacterially-expressed protein into normal rat kidney (NRK) epithelial cells. The microinjection induced the dramatic retrograde translocation of organelles into the perinuclear area. Microinjection of hTM5, a low molecular mass isoform had no effect on organelle distribution. Fluorescent staining indicated that hTM3 injection stimulated the retrograde movement of both mitochondria and lysosomes. Moreover, both myosin I and cytoplasmic dynein were found to redistribute with the translocated organelles to the perinuclear area, indicating that these organelles were able to move along both microtubules and actin filaments. The involvement of microtubules was further suggested by the partial inhibition of hTM3-induced organelle movement by the microtubule-depolymerizing drug nocodazole. Our results, along with previous genetic and antibody microinjection studies, suggest that hTM3 may be involved in the regulation of organelle transport.
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Marshall, Wallace F. "Scaling of Subcellular Structures." Annual Review of Cell and Developmental Biology 36, no. 1 (October 6, 2020): 219–36. http://dx.doi.org/10.1146/annurev-cellbio-020520-113246.
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As cells grow, the size and number of their internal organelles increase in order to keep up with increased metabolic requirements. Abnormal size of organelles is a hallmark of cancer and an important aspect of diagnosis in cytopathology. Most organelles vary in either size or number, or both, as a function of cell size, but the mechanisms that create this variation remain unclear. In some cases, organelle size appears to scale with cell size through processes of relative growth, but in others the size may be set by either active measurement systems or genetic programs that instruct organelle biosynthetic activities to create organelles of a size appropriate to a given cell type.
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Walsh, J. B. "Intracellular selection, conversion bias, and the expected substitution rate of organelle genes." Genetics 130, no. 4 (April 1, 1992): 939–46. http://dx.doi.org/10.1093/genetics/130.4.939.
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Abstract A key step in the substitution of a new organelle mutant throughout a population is the generation of germ-line cells homoplasmic for that mutant. Given that each cell typically contains multiple copies of organelles, each of which in turn contains multiple copies of the organelle genome, processes akin to drift and selection in a population are responsible for producing homoplasmic cells. This paper examines the expected substitution rate of new mutants by obtaining the probability that a new mutant is fixed throughout a cell, allowing for arbitrary rates of genome turnover within an organelle and organelle turnover within the cell, as well as (possibly biased) gene conversion and genetic differences in genome and/or organelle replication rates. Analysis is based on a variation of Moran's model for drift in a haploid population. One interesting result is that if the rate of unbiased conversion is sufficiently strong, it creates enough intracellular drift to overcome even strong differences in the replication rates of wild-type and mutant genomes. Thus, organelles with very high conversion rates are more resistant to intracellular selection based on differences in genome replication and/or degradation rates. It is found that the amount of genetic exchange between organelles within the cell greatly influences the probability of fixation. In the absence of exchange, biased gene conversion and/or differences in genome replication rates do not influence the probability of fixation beyond the initial fixation within a single organelle. With exchange, both these processes influence the probability of fixation throughout the entire cell. Generally speaking, exchange between organelles accentuates the effects of directional intracellular forces.(ABSTRACT TRUNCATED AT 250 WORDS)
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Esch, Nicholas, Seokwon Jo, Mackenzie Moore, and Emilyn U. Alejandro. "Nutrient Sensor mTOR and OGT: Orchestrators of Organelle Homeostasis in Pancreatic β-Cells." Journal of Diabetes Research 2020 (December 15, 2020): 1–24. http://dx.doi.org/10.1155/2020/8872639.
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The purpose of this review is to integrate the role of nutrient-sensing pathways into β-cell organelle dysfunction prompted by nutrient excess during type 2 diabetes (T2D). T2D encompasses chronic hyperglycemia, hyperlipidemia, and inflammation, which each contribute to β-cell failure. These factors can disrupt the function of critical β-cell organelles, namely, the ER, mitochondria, lysosomes, and autophagosomes. Dysfunctional organelles cause defects in insulin synthesis and secretion and activate apoptotic pathways if homeostasis is not restored. In this review, we will focus on mTORC1 and OGT, two major anabolic nutrient sensors with important roles in β-cell physiology. Though acute stimulation of these sensors frequently improves β-cell function and promotes adaptation to cell stress, chronic and sustained activity disturbs organelle homeostasis. mTORC1 and OGT regulate organelle function by influencing the expression and activities of key proteins, enzymes, and transcription factors, as well as by modulating autophagy to influence clearance of defective organelles. In addition, mTORC1 and OGT activity influence islet inflammation during T2D, which can further disrupt organelle and β-cell function. Therapies for T2D that fine-tune the activity of these nutrient sensors have yet to be developed, but the important role of mTORC1 and OGT in organelle homeostasis makes them promising targets to improve β-cell function and survival.
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FOSTER, LEONARD J. "MASS SPECTROMETRY OUTGROWS SIMPLE BIOCHEMISTRY: NEW APPROACHES TO ORGANELLE PROTEOMICS." Biophysical Reviews and Letters 01, no. 02 (April 2006): 209–21. http://dx.doi.org/10.1142/s1793048006000057.
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Organelles are subcellular compartments or structures that typically carry out a defined set of functions within the cell. The functions of many organelles are known or predicted, but without knowing all the components of any recognized organelle it is difficult to fully understand them. Mass spectrometry-based proteomics now allows for routine identification of several hundreds or thousands of proteins in very complex samples; for cell biologists, organelles represent perhaps the most interesting class of cellular components to apply this new technology to. However, in order to analyze the proteome of an organelle it first must be purified, and the limitations in purifying any biological sample to homogeneity quickly become apparent to the vigilant mass spectrometrist. At the end of an organelle proteomic investigation, investigators are left with a long list of proteins whose location needs to be verified by an orthogonal method, a daunting prospect; or, they must accept an unknown and possibly very high level of incorrect localizations. Some of these caveats can be partially overcome by incorporating quantitative aspects into organelle proteomic studies. This review discusses some alternative approaches to organelle proteomics where questions of specificity and/or functional relevance are addressed by incorporating a quantitative dimension into the experiment.
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Steinberg, G., and M. Schliwa. "Organelle movements in the wild type and wall-less fz;sg;os-1 mutants of Neurospora crassa are mediated by cytoplasmic microtubules." Journal of Cell Science 106, no. 2 (October 1, 1993): 555–64. http://dx.doi.org/10.1242/jcs.106.2.555.
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The cellular basis of organelle transport in filamentous fungi is still unresolved. Here we have studied the intracellular movement of mitochondria and other organelles in the fungus Neurospora crassa. Four different model systems were employed: hyphae, protoplasts, a cell wallless mutant, and experimentally generated small, flattened cell fragments of the mutant cells. Organelle movements were visualized by DIC optics and computer-enhanced video microscopy. In all cell models the transport of organelles was vectorial and saltatory in nature. The mean velocities for mitochondria, particles and nuclei were 1.4, 2.0, and 0.9 microns/s, respectively. Treatment with 10 microM nocodazole for 30 minutes caused a complete disappearance of microtubules and reversibly blocked directed transport of virtually all organelles, whereas cytochalasin D up to 20 microM was without effect. Correlative video and immunofluorescence microscopy of small fragments of wall-less mutant cells revealed a clear match between microtubule distribution and the tracks of moving organelles. We conclude that organelle movement in the filamentous fungus Neurospora crassa is a microtubule-dependent process.
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Schnapp, B. J., T. S. Reese, and R. Bechtold. "Kinesin is bound with high affinity to squid axon organelles that move to the plus-end of microtubules." Journal of Cell Biology 119, no. 2 (October 15, 1992): 389–99. http://dx.doi.org/10.1083/jcb.119.2.389.
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This paper addresses the question of whether microtubule-directed transport of vesicular organelles depends on the presence of a pool of cytosolic factors, including soluble motor proteins and accessory factors. Earlier studies with squid axon organelles (Schroer et al., 1988) suggested that the presence of cytosol induces a > 20-fold increase in the number of organelles moving per unit time on microtubules in vitro. These earlier studies, however, did not consider that cytosol might nonspecifically increase the numbers of moving organelles, i.e., by blocking adsorption of organelles to the coverglass. Here we report that treatment of the coverglass with casein, in the absence of cytosol, blocks adsorption of organelles to the coverglass and results in vigorous movement of vesicular organelles in the complete absence of soluble proteins. This technical improvement makes it possible, for the first time, to perform quantitative studies of organelle movement in the absence of cytosol. These new studies show that organelle movement activity (numbers of moving organelles/min/micron microtubule) of unextracted organelles is not increased by cytosol. Unextracted organelles move in single directions, approximately two thirds toward the plus-end and one third toward the minus-end of microtubules. Extraction of organelles with 600 mM KI completely inhibits minus-end, but not plus-end directed organelle movement. Upon addition of cytosol, minus-end directed movement of KI organelles is restored, while plus--end directed movement is unaffected. Biochemical studies indicate that KI-extracted organelles attach to microtubules in the presence of AMP-PNP and copurify with tightly bound kinesin. The bound kinesin is not extracted from organelles by 1 M KI, 1 M NaCl or carbonate (pH 11.3). These results suggest that kinesin is irreversibly bound to organelles that move to the plus-end of microtubules and that the presence of soluble kinesin and accessory factors is not required for movement of plus-end organelles in squid axons.
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Fan, Jiangbo, Qiang Li, Lin Chen, Jinglei Du, Wenqiang Xue, Shiping Yu, Xiuqin Su, and Yongzhen Yang. "Research Progress in the Synthesis of Targeting Organelle Carbon Dots and Their Applications in Cancer Diagnosis and Treatment." Journal of Biomedical Nanotechnology 17, no. 10 (October 1, 2021): 1891–916. http://dx.doi.org/10.1166/jbn.2021.3167.
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With increasing knowledge about diseases at the histological, cytological to sub-organelle level, targeting organelle therapy has gradually been envisioned as an approach to overcome the shortcomings of poor specificity and multiple toxic side effects on tissues and cell-level treatments using the currently available therapy. Organelle carbon dots (CDs) are a class of functionalized CDs that can target organelles. CDs can be prepared by a “synchronous in situ synthesis method” and “asynchronous modification method.” The superior optical properties and good biocompatibility of CDs can be preserved, and they can be used as targeting particles to carry drugs into cells while reducing leakage during transport. Given the excellent organelle fluorescence imaging properties, targeting organelle CDs can be used to monitor the physiological metabolism of organelles and progression of human diseases, which will provide advanced understanding and accurate diagnosis and targeted treatment of cancers. This study reviews the methods used for preparation of targeting organelle CDs, mechanisms of accurate diagnosis and targeted treatment of cancer, as well as their application in the area of cancer diagnosis and treatment research. Finally, the current difficulties and prospects for targeting organelle CDs are prospected.
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Heywood-Waddington, D., T. J. Peters, and I. A. Sutherland. "The dynamics of phase partition. A study of parameters affecting rat liver organelle partitioning in aqueous two-polymer phase systems." Biochemical Journal 235, no. 1 (April 1, 1986): 245–49. http://dx.doi.org/10.1042/bj2350245.
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Separation of subcellular organelles by two-phase partition is thought to reflect differential partition of the organelles between the two phases or between one of the phases and the interface. Studies by Fisher and colleagues [Fisher & Walter (1984) Biochim. Biophys. Acta 801, 106-110] suggest that cell separation by phase partition is a dynamic process in which the partition changes with time. This is mainly due to association of the cells with sedimenting droplets of one phase in the bulk of the other. Rat liver organelle partition was studied to determine whether the same dynamic behaviour is observed. Partition was clearly time-dependent during 24 h at unit gravity, and was also affected by altering the volume ratio of the two phases and the duration of phase mixing. These results indicate that, as with cells, the partition of organelles between phases is a dynamic process, and is consistent with the demonstration that organelles adhere to the phase droplet surfaces. Optimization of the volume ratio between phases may lead to significant processing economies. Organelle sedimentation in the upper phase was significantly faster than in the isoosmotic sucrose. Theoretical modelling of apparent organelle sizes indicates that aggregation occurs in the poly(ethylene glycol)-rich upper phase. This phenomenon is likely to limit the use of this technique in organelle separations unless means can be found to decrease aggregation.
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Morgan, Anthony J., Lianne C. Davis, Siegfried K. T. Y. Wagner, Alexander M. Lewis, John Parrington, Grant C. Churchill, and Antony Galione. "Bidirectional Ca2+ signaling occurs between the endoplasmic reticulum and acidic organelles." Journal of Cell Biology 200, no. 6 (March 11, 2013): 789–805. http://dx.doi.org/10.1083/jcb.201204078.
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The endoplasmic reticulum (ER) and acidic organelles (endo-lysosomes) act as separate Ca2+ stores that release Ca2+ in response to the second messengers IP3 and cADPR (ER) or NAADP (acidic organelles). Typically, trigger Ca2+ released from acidic organelles by NAADP subsequently recruits IP3 or ryanodine receptors on the ER, an anterograde signal important for amplification and Ca2+ oscillations/waves. We therefore investigated whether the ER can signal back to acidic organelles, using organelle pH as a reporter of NAADP action. We show that Ca2+ released from the ER can activate the NAADP pathway in two ways: first, by stimulating Ca2+-dependent NAADP synthesis; second, by activating NAADP-regulated channels. Moreover, the differential effects of EGTA and BAPTA (slow and fast Ca2+ chelators, respectively) suggest that the acidic organelles are preferentially activated by local microdomains of high Ca2+ at junctions between the ER and acidic organelles. Bidirectional organelle communication may have wider implications for endo-lysosomal function as well as the generation of Ca2+ oscillations and waves.
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Gimple, O., and A. Schön. "In Vitro and in Vivo Processing of Cyanelle tmRNA by RNase P." Biological Chemistry 382, no. 10 (October 15, 2001): 1421–29. http://dx.doi.org/10.1515/bc.2001.175.
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Abstract Ribonuclease P, the ubiquitous endonuclease required for generating mature tRNA 5 ends, is a ribonucleoprotein in most organisms and organelles, with the exception of mitochondria and chloroplasts of multicellular organisms. The cyanelle of the primitive alga Cyanophora paradoxa is the only photosynthetic organelle where the ribonucleoprotein nature of this enzyme has been functionally proven. tmRNA is another highly structured RNA: it can be aminoacylated with alanine, which is then incorporated into a tag peptide encoded on the same RNA molecule. This dualfunction RNA has been found in bacteria, and its gene is also present in mitochondria and plastids from primitive organisms. Since nothing is known about the expression of this RNA in organelles, we have performed processing studies and determined the promoter of cyanelle pretmRNA. This RNA is transcribed as a precursor molecule in vivo. Synthetic transcripts of cyanelle pretmRNA, including or lacking the mature 3 CCAend, are efficiently and correctly processed in vitro by bacterial RNase P ribo and holoenzymes and by the homologous cyanelle RNase P. In addition to these experimental data, we propose a novel secondary structure model for this organellar tmRNA, which renders it more similar to its bacterial counterpart.
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TANAKA, Arowu, Fumi KANO, and Masayuki MURATA. "Organelle Inheritance-Cell Cycle Dependent Dynamics of Organelles in Mammalian Cells." Seibutsu Butsuri 42, no. 3 (2002): 116–21. http://dx.doi.org/10.2142/biophys.42.116.
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van der Bliek, Alexander, and Xinnan Wang. "Organelles and spatial organization of the cell: organelle homeostasis and turnover." Molecular Biology of the Cell 27, no. 6 (March 15, 2016): 873–74. http://dx.doi.org/10.1091/mbc.e15-11-0761.
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Schuldiner, Maya, and Wei Guo. "Editorial overview: Cell organelles: Organelle communication: new means and new views." Current Opinion in Cell Biology 35 (August 2015): v—vi. http://dx.doi.org/10.1016/j.ceb.2015.07.008.
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Chen, Xian-Ming, Steven P. O'Hara, Bing Q. Huang, Jeremy B. Nelson, Jim Jung-Ching Lin, Guan Zhu, Honorine D. Ward, and Nicholas F. LaRusso. "Apical Organelle Discharge by Cryptosporidium parvum Is Temperature, Cytoskeleton, and Intracellular Calcium Dependent and Required for Host Cell Invasion." Infection and Immunity 72, no. 12 (December 2004): 6806–16. http://dx.doi.org/10.1128/iai.72.12.6806-6816.2004.
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ABSTRACT The apical organelles in apicomplexan parasites are characteristic secretory vesicles containing complex mixtures of molecules. While apical organelle discharge has been demonstrated to be involved in the cellular invasion of some apicomplexan parasites, including Toxoplasma gondii and Plasmodium spp., the mechanisms of apical organelle discharge by Cryptosporidium parvum sporozoites and its role in host cell invasion are unclear. Here we show that the discharge of C. parvum apical organelles occurs in a temperature-dependent fashion. The inhibition of parasite actin and tubulin polymerization by cytochalasin D and colchicines, respectively, inhibited parasite apical organelle discharge. Chelation of the parasite's intracellular calcium also inhibited apical organelle discharge, and this process was partially reversed by raising the intracellular calcium concentration by use of the ionophore A23187. The inhibition of parasite cytoskeleton polymerization by cytochalasin D and colchicine and the depletion of intracellular calcium also decreased the gliding motility of C. parvum sporozoites. Importantly, the inhibition of apical organelle discharge by C. parvum sporozoites blocked parasite invasion of, but not attachment to, host cells (i.e., cultured human cholangiocytes). Moreover, the translocation of a parasite protein, CP2, to the host cell membrane at the region of the host cell-parasite interface was detected; an antibody to CP2 decreased the C. parvum invasion of cholangiocytes. These data demonstrate that the discharge of C. parvum sporozoite apical organelle contents occurs and that it is temperature, intracellular calcium, and cytoskeleton dependent and required for host cell invasion, confirming that apical organelles play a central role in C. parvum entry into host cells.
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Bearer, E. L., J. A. DeGiorgis, R. A. Bodner, A. W. Kao, and T. S. Reese. "Evidence for myosin motors on organelles in squid axoplasm." Proceedings of the National Academy of Sciences 90, no. 23 (December 1, 1993): 11252–56. http://dx.doi.org/10.1073/pnas.90.23.11252.
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Squid axoplasm has proved a rich source for the identification of motors involved in organelle transport. Recently, squid axoplasmic organelles have been shown to move on invisible tracks that are sensitive to cytochalasin, suggesting that these tracks are actin filaments. Here, an assay is described that permits observation of organelles moving on unipolar actin bundles. This assay is used to demonstrate that axoplasmic organelles move on actin filaments in the barbed-end direction, suggesting the presence of a myosin motor on axoplasmic organelles. Indeed, axoplasm contains actin-dependent ATPase activity, and a pan-myosin antibody recognized at least four bands in Western blots of axoplasm. An approximately 235-kDa band copurified in sucrose gradients with KI-extracted axoplasmic organelles, and the myosin antibody stained the organelle surfaces by immunogold electron microscopy. The myosin is present on the surface of at least some axoplasmic organelles and thus may be involved in their transport through the axoplasm, their movement through the cortical actin in the synapse, or some other aspect of axonal function.
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Mano, S., T. Miwa, S. i. Nishikawa, T. Mimura, and M. Nishimura. "The plant organelles database (PODB): a collection of visualized plant organelles and protocols for plant organelle research." Nucleic Acids Research 36, Database (December 23, 2007): D929—D937. http://dx.doi.org/10.1093/nar/gkm789.
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Mendoza, Hector, Michael H. Perlin, and Jan Schirawski. "Mitochondrial Inheritance in Phytopathogenic Fungi—Everything Is Known, or Is It?" International Journal of Molecular Sciences 21, no. 11 (May 29, 2020): 3883. http://dx.doi.org/10.3390/ijms21113883.
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Mitochondria are important organelles in eukaryotes that provide energy for cellular processes. Their function is highly conserved and depends on the expression of nuclear encoded genes and genes encoded in the organellar genome. Mitochondrial DNA replication is independent of the replication control of nuclear DNA and as such, mitochondria may behave as selfish elements, so they need to be controlled, maintained and reliably inherited to progeny. Phytopathogenic fungi meet with special environmental challenges within the plant host that might depend on and influence mitochondrial functions and services. We find that this topic is basically unexplored in the literature, so this review largely depends on work published in other systems. In trying to answer elemental questions on mitochondrial functioning, we aim to introduce the aspect of mitochondrial functions and services to the study of plant-microbe-interactions and stimulate phytopathologists to consider research on this important organelle in their future projects.
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Seefried, L., R. Ebert, S. Müller-Deubert, B. Klotz, M. Kober, A. Liedert, A. Ignatius, and F. Jakob. "Mechanotransduktion im Alter und bei Osteoporose." Osteologie 19, no. 03 (2010): 232–39. http://dx.doi.org/10.1055/s-0037-1619947.
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ZusammenfassungKnochen wird permanent an die alltäglichen mechanischen Kräfte adaptiert, um für die natürlichen Gegebenheiten eine optimale Frakturresistenz zu gewährleisten. Osteoporose ist eine Erkrankung, bei der unter Alltagsbedingungen Fragilitätsfrakturen entstehen. Ursache dafür sind strukturelle und qualitative Defizite und eine Verminderung der Knochenmasse. Es handelt sich somit um eine Dysadaptation des Organs, verursacht entweder durch ungenügenden Krafteintrag oder durch eine Störung der Mechanosensitivität der Osteoblasten und Osteozyten. Kraft durch Dehnung, Kompression oder Flüssigkeits-Scher-Stress wird über Adhäsionsmoleküle, Rezeptoren, Kanäle und über das Zytoskelett auf die Zelle übertragen. Die Umwandlung in biologische Signale geschieht durch Signaltransduktionskaskaden bis hin zur Genregulation im Zellkern. Neben den membranständigen molekularen Strukturen werden auch subzelluläre Organell-Strukturen wie z.B. das primäre Zilium als Übermittler mechanischer Signale diskutiert. Bei Osteoporose sind häufig Signalwege gestört, die mit der Mechanotransduktion zusammenhängen, was man an den Hauptrisikofaktoren der Osteoporose ablesen kann. Östrogene wirken als Mechanosensitizer, so dass nach der Menopause die Gefahr der Dysadaptation steigt. Zelluläre Alterung ist mit Störungen der Mechanotransduktion verknüpft, wie am Beispiel von Laminopathien gezeigt werden konnte, präklinischen und klinischen Modellerkrankungen für vorzeitiges Altern. Die als Haupt-Risikogene für den genetischen Hintergrund der Osteoporose identifizierten Kandidaten sind fast sämtlich molekular in die Regulation der Mechanotransduktion eingebunden. Es gibt präklinische und klinische Evidenz dafür, dass z.B. die anabole Therapie mit Parathormon/Teriparatid nur unter Einwirkung mechanischer Kräfte wirklich wirksam ist. Ein überwältigender Hinweis für das Vorliegen fundamentaler Störungen der Regulation der Mechanosensitivität bei der Osteoporose ist die Tatsache, dass meistens der Gewinn von Knochenmasse durch die verfügbaren therapeutischen Prinzipien nicht wirklich nachhaltig ist. Antiresorptive und anabole Prinzipien der Therapie der Knochenmasse sind bereits auf dem Markt, weitere sind in der Entwicklung. Ein Medikament, das die Mechanosensitivität des Knochens beeinflusst, wäre das ideale Werkzeug, um per se anabol zu wirken und/oder den Therapieerfolg mit anderen Medikamenten zu erhalten. Die Forschung hierüber ist daher von hoher klinischer Relevanz.
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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.
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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.
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Friedman, Jonathan R. "Mitochondria from the Outside in: The Relationship Between Inter-Organelle Crosstalk and Mitochondrial Internal Organization." Contact 5 (January 2022): 251525642211332. http://dx.doi.org/10.1177/25152564221133267.
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A fundamental role of membrane-bound organelles is the compartmentalization and organization of cellular processes. Mitochondria perform an immense number of metabolic chemical reactions and to efficiently regulate these, the organelle organizes its inner membrane into distinct morphological domains, including its characteristic cristae membranes. In recent years, a structural feature of increasing apparent importance is the inter-connection between the mitochondrial exterior and other organelles at membrane contact sites (MCSs). Mitochondria form MCSs with almost every other organelle in the cell, including the endoplasmic reticulum, lipid droplets, and lysosomes, to coordinate global cellular metabolism with mitochondrial metabolism. However, these MCSs not only facilitate the transport of metabolites between organelles, but also directly impinge on the physical shape and functional organization inside mitochondria. In this review, we highlight recent advances in our understanding of how physical connections between other organelles and mitochondria both directly and indirectly influence the internal architecture of mitochondria.
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Inagi, Reiko. "The Implication of Organelle Cross Talk in AKI." Nephron 144, no. 12 (2020): 634–37. http://dx.doi.org/10.1159/000508639.
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Organelle stress, such as mitochondrial or endoplasmic reticulum damage, plays a crucial role in the pathogenesis of acute kidney injury (AKI). Further, persistent organelle stress, which causes metabolic abnormality followed by inflammation and fibrosis, is an important mediator of AKI-to-CKD transition. Organelle stress closely links to the derangement of organelle cross talk. Organelles intricately interact with each other under the physiological conditions to maintain their function each other and subsequent cell fate. Organelle stress and their cross talk are now a focus of intensive researches in the field of AKI as they are in the field of CKD.