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1
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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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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Voeltz, Gia K., and Francis A. Barr. "Cell organelles." Current Opinion in Cell Biology 25, no. 4 (August 2013): 403–5. http://dx.doi.org/10.1016/j.ceb.2013.06.001.
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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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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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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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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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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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Lu, Sha, Zhiqi Dai, Yunxi Cui, and De-Ming Kong. "Recent Development of Advanced Fluorescent Molecular Probes for Organelle-Targeted Cell Imaging." Biosensors 13, no. 3 (March 8, 2023): 360. http://dx.doi.org/10.3390/bios13030360.
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Fluorescent molecular probes are very powerful tools that have been generally applied in cell imaging in the research fields of biology, pathology, pharmacology, biochemistry, and medical science. In the last couple of decades, numerous molecular probes endowed with high specificity to particular organelles have been designed to illustrate intracellular images in more detail at the subcellular level. Nowadays, the development of cell biology has enabled the investigation process to go deeply into cells, even at the molecular level. Therefore, probes that can sketch a particular organelle’s location while responding to certain parameters to evaluate intracellular bioprocesses are under urgent demand. It is significant to understand the basic ideas of organelle properties, as well as the vital substances related to each unique organelle, for the design of probes with high specificity and efficiency. In this review, we summarize representative multifunctional fluorescent molecular probes developed in the last decade. We focus on probes that can specially target nuclei, mitochondria, endoplasmic reticulums, and lysosomes. In each section, we first briefly introduce the significance and properties of different organelles. We then discuss how probes are designed to make them highly organelle-specific. Finally, we also consider how probes are constructed to endow them with additional functions to recognize particular physical/chemical signals of targeted organelles. Moreover, a perspective on the challenges in future applications of highly specific molecular probes in cell imaging is also proposed. We hope that this review can provide researchers with additional conceptual information about developing probes for cell imaging, assisting scientists interested in molecular biology, cell biology, and biochemistry to accelerate their scientific studies.
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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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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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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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Kachar, B., P. C. Bridgman, and T. S. Reese. "Dynamic shape changes of cytoplasmic organelles translocating along microtubules." Journal of Cell Biology 105, no. 3 (September 1, 1987): 1267–71. http://dx.doi.org/10.1083/jcb.105.3.1267.
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Transient shape changes of organelles translocating along microtubules are directly visualized in thinly spread cytoplasmic processes of the marine foraminifer. Allogromia laticollaris, by a combination of high-resolution video-enhanced microscopy and fast-freezing electron microscopy. The interacting side of the organelle flattens upon binding to a microtubule, as if to maximize contact with it. Organelles typically assume a teardrop shape while moving, as if they were dragged through a viscous medium. Associated microtubules bend around attachments of the teardrop-shaped organelles, suggesting that they too are acted on by the forces deforming the organelles. An 18-nm gap between the organelles and the microtubules is periodically bridged by 10-nm-thick cross-bridge structures that may be responsible for the binding and motive forces deforming organelles and microtubules.
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Laan, Sebastiaan N. J., Richard J. Dirven, Petra E. Bürgisser, Jeroen Eikenboom, and Ruben Bierings. "Automated segmentation and quantitative analysis of organelle morphology, localization and content using CellProfiler." PLOS ONE 18, no. 6 (June 14, 2023): e0278009. http://dx.doi.org/10.1371/journal.pone.0278009.
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One of the most used and versatile methods to study number, dimensions, content and localization of secretory organelles is confocal microscopy analysis. However, considerable heterogeneity exists in the number, size and shape of secretory organelles that can be present in the cell. One thus needs to analyze large numbers of organelles for valid quantification. Properly evaluating these parameters requires an automated, unbiased method to process and quantitatively analyze microscopy data. Here, we describe two pipelines, run by CellProfiler software, called OrganelleProfiler and OrganelleContentProfiler. These pipelines were used on confocal images of endothelial colony forming cells (ECFCs), which contain unique secretory organelles called Weibel-Palade bodies (WPBs), and on early endosomes in ECFCs and human embryonic kidney 293T (HEK293T) cells. Results show that the pipelines can quantify the cell count, size, organelle count, organelle size, shape, relation to cells and nuclei, and distance to these objects in both endothelial and HEK293T cells. Additionally, the pipelines were used to measure the reduction in WPB size after disruption of the Golgi and to quantify the perinuclear clustering of WPBs after triggering of cAMP-mediated signaling pathways in ECFCs. Furthermore, the pipeline is able to quantify secondary signals located in or on the organelle or in the cytoplasm, such as the small WPB GTPase Rab27A. Cell profiler measurements were checked for validity using Fiji. To conclude, these pipelines provide a powerful, high-processing quantitative tool for the characterization of multiple cell and organelle types. These pipelines are freely available and easily editable for use on different cell types or organelles.
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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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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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Bridgman, P. C. "Myosin VA Movements in Normal and Dilute-Lethal Axons Provide Support for a Dual Filament Motor Complex." Journal of Cell Biology 146, no. 5 (September 6, 1999): 1045–60. http://dx.doi.org/10.1083/jcb.146.5.1045.
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To investigate the role that myosin Va plays in axonal transport of organelles, myosin Va–associated organelle movements were monitored in living neurons using microinjected fluorescently labeled antibodies to myosin Va or expression of a green fluorescent protein–myosin Va tail construct. Myosin Va–associated organelles made rapid bi-directional movements in both normal and dilute-lethal (myosin Va null) neurites. In normal neurons, depolymerization of microtubules by nocodazole slowed, but did not stop movement. In contrast, depolymerization of microtubules in dilute-lethal neurons stopped movement. Myosin Va or synaptic vesicle protein 2 (SV2), which partially colocalizes with myosin Va on organelles, did not accumulate in dilute-lethal neuronal cell bodies because of an anterograde bias associated with organelle transport. However, SV2 showed peripheral accumulations in axon regions of dilute-lethal neurons rich in tyrosinated tubulin. This suggests that myosin Va–associated organelles become stranded in regions rich in dynamic microtubule endings. Consistent with these observations, presynaptic terminals of cerebellar granule cells in dilute-lethal mice showed increased cross-sectional area, and had greater numbers of both synaptic and larger SV2 positive vesicles. Together, these results indicate that myosin Va binds to organelles that are transported in axons along microtubules. This is consistent with both actin- and microtubule-based motors being present on these organelles. Although myosin V activity is not necessary for long-range transport in axons, myosin Va activity is necessary for local movement or processing of organelles in regions, such as presynaptic terminals that lack microtubules.
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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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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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YENER, Yeşim, Mustafa YILMAZ, Burak KIRAS, and Mert ŞEN. "Preservice science teachers’ cognitive structures regarding the cell and its organelles." Acta Didactica Napocensia 17, no. 1 (September 7, 2024): 178–97. http://dx.doi.org/10.24193/adn.17.1.14.
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Learning the cell, one of the basic subjects of science education, by preservice teachers in a comprehensive way is important for making sense of its vital activities and teaching the subject in a meaningful way in the future. The study aimed to determine preservice science teachers' cognitive structures related to the cell and its organelles before and after the Biology course. The study group consists of 32 preservice science teachers. The single-group interrupted time series design was adopted in the study. Data were collected through the word association test. As a result of the data analysis, it was determined that some organelles could not be associated with other organelles, there was no knowledge about the peroxisome organelle before the intervention. It was observed that more comprehensive and interrelated cognitive structures were formed after the intervention and the peroxisome organelle was also added to this structure.
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Busch, Nils, Andreas Rausch, and Thomas Schanze. "Estimation of accuracy loss by training a deep-learning-based cell organelle recognition software using full dataset and a reduced dataset containing only subviral particle distribution information." Current Directions in Biomedical Engineering 7, no. 2 (October 1, 2021): 183–86. http://dx.doi.org/10.1515/cdbme-2021-2047.
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Abstract In collaboration with the Institute of Virology, Philipps University, Marburg, a deep-learning-based method that recognizes and classifies cell organelles based on the distribution of subviral particles in fluorescence microscopy images of virus-infected cells has been further developed. In this work a method to recognize cell organelles by means of partial image information is extended. The focus is on investigating loss of accuracy by only providing information about subviral particles and not all cell organelles to an adopted Mask-R convolutional neural network. Our results show that the subviral particle distribution holds information about the cell morphology, thus making it possible to use it for cell organelle-labelling.
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Nishida, Keiji, Fumi Yagisawa, Haruko Kuroiwa, Toshiyuki Nagata, and Tsuneyoshi Kuroiwa. "Cell Cycle-regulated, Microtubule-independent Organelle Division in Cyanidioschyzon merolae." Molecular Biology of the Cell 16, no. 5 (May 2005): 2493–502. http://dx.doi.org/10.1091/mbc.e05-01-0068.
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Mitochondrial and chloroplast division controls the number and morphology of organelles, but how cells regulate organelle division remains to be clarified. Here, we show that each step of mitochondrial and chloroplast division is closely associated with the cell cycle in Cyanidioschyzon merolae. Electron microscopy revealed direct associations between the spindle pole bodies and mitochondria, suggesting that mitochondrial distribution is physically coupled with mitosis. Interconnected organelles were fractionated under microtubule-stabilizing condition. Immunoblotting analysis revealed that the protein levels required for organelle division increased before microtubule changes upon cell division, indicating that regulation of protein expression for organelle division is distinct from that of cytokinesis. At the mitochondrial division site, dynamin stuck to one of the divided mitochondria and was spatially associated with the tip of a microtubule stretching from the other one. Inhibition of microtubule organization, proteasome activity or DNA synthesis, respectively, induced arrested cells with divided but shrunk mitochondria, with divided and segregated mitochondria, or with incomplete mitochondrial division restrained at the final severance, and repetitive chloroplast division. The results indicated that mitochondrial morphology and segregation but not division depend on microtubules and implied that the division processes of the two organelles are regulated at distinct checkpoints.
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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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Serrano-Puebla, Ana, and Patricia Boya. "Lysosomal membrane permeabilization as a cell death mechanism in cancer cells." Biochemical Society Transactions 46, no. 2 (February 22, 2018): 207–15. http://dx.doi.org/10.1042/bst20170130.
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Lysosomes are acidic organelles that contain hydrolytic enzymes that mediate the intracellular degradation of macromolecules. Damage of these organelles often results in lysosomal membrane permeabilization (LMP) and the release into the cytoplasm of the soluble lysosomal contents, which include proteolytic enzymes of the cathepsin family. This, in turn, activates several intracellular cascades that promote a type of regulated cell death, called lysosome-dependent cell death (LDCD). LDCD can be inhibited by pharmacological or genetic blockade of cathepsin activity, or by protecting the lysosomal membrane, thereby stabilizing the organelle. Lysosomal alterations are common in cancer cells and may increase the sensitivity of these cells to agents that promote LMP. In this review, we summarize recent findings supporting the use of LDCD as a means of killing cancer cells.
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Luzio, J. P., B. A. Rous, N. A. Bright, P. R. Pryor, B. M. Mullock, and R. C. Piper. "Lysosome-endosome fusion and lysosome biogenesis." Journal of Cell Science 113, no. 9 (May 1, 2000): 1515–24. http://dx.doi.org/10.1242/jcs.113.9.1515.
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Recent data both from cell-free experiments and from cultured cells have shown that lysosomes can fuse directly with late endosomes to form a hybrid organelle. This has a led to a hypothesis that dense core lysosomes are in essence storage granules for acid hydrolases and that, when the former fuse with late endosomes, a hybrid organelle for digestion of endocytosed macromolecules is created. Lysosomes are then re-formed from hybrid organelles by a process involving condensation of contents. In this Commentary we review the evidence for formation of the hybrid organelles and discuss the current status of our understanding of the mechanisms of fusion and lysosome re-formation. We also review lysosome biosynthesis, showing how recent studies of lysosome-like organelles including the yeast vacuole, Drosophila eye pigment granules and mammalian secretory lysosomes have identified novel proteins involved in this process.
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Coale, Tyler H., Valentina Loconte, Kendra A. Turk-Kubo, Bieke Vanslembrouck, Wing Kwan Esther Mak, Shunyan Cheung, Axel Ekman, et al. "Nitrogen-fixing organelle in a marine alga." Science 384, no. 6692 (April 12, 2024): 217–22. http://dx.doi.org/10.1126/science.adk1075.
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Symbiotic interactions were key to the evolution of chloroplast and mitochondria organelles, which mediate carbon and energy metabolism in eukaryotes. Biological nitrogen fixation, the reduction of abundant atmospheric nitrogen gas (N 2 ) to biologically available ammonia, is a key metabolic process performed exclusively by prokaryotes. Candidatus Atelocyanobacterium thalassa, or UCYN-A, is a metabolically streamlined N 2 -fixing cyanobacterium previously reported to be an endosymbiont of a marine unicellular alga. Here we show that UCYN-A has been tightly integrated into algal cell architecture and organellar division and that it imports proteins encoded by the algal genome. These are characteristics of organelles and show that UCYN-A has evolved beyond endosymbiosis and functions as an early evolutionary stage N 2 -fixing organelle, or “nitroplast.”
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Yakışan, Mehmet. "THE ALTERNATIVE CONCEPTIONS OF PRE-SERVICE TEACHERS CONCERNING THE STATUS OF ORGANELLES DURING CELL DIVISION." Journal of Baltic Science Education 12, no. 6 (December 15, 2013): 813–28. http://dx.doi.org/10.33225/jbse/13.12.813.
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The aim of this study was to identify pre-service teachers' alternative conceptions concerning the status of organelles during cell division. A total of 212 pre-service teachers participated in the study. Data were collected by asking open-ended questions of all pre-service teachers, and semi-structured interviews were conducted with 12 participants. Data were analyzed by coding data segments within 11 categories. Categories were tabulated and interpreted by including sample data sections about the codes. The results indicated that there were some students who explained that no organelle dissolved or disappeared and no change occurred in any organelles during cell division besides pre-service teachers who said that all organelles dissolved and disappeared during cell division. In addition, a few pre-service teachers thought that while some organelles dissolved and disappeared, others did not. It was understood that those pre-service teachers were confused about which structures and organelles disappeared and which ones continued their existence, and they had various alternative conceptions. Moreover, pre-service teachers had alternative conceptions regarding the status of organelles particularly about structures such as chromosome, centrosome, DNA, and RNA. Key words: alternative conceptions, cell division, organelles, pre-service teachers.
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Richardson, Jennifer L., Ramesh A. Shivdasani, Chad Boers, John H. Hartwig, and Joseph E. Italiano. "Mechanisms of organelle transport and capture along proplatelets during platelet production." Blood 106, no. 13 (December 15, 2005): 4066–75. http://dx.doi.org/10.1182/blood-2005-06-2206.
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Megakaryocytes generate platelets by remodeling their cytoplasm into long proplatelet extensions, which serve as assembly lines for platelet production. Platelet packaging and release concludes at the tips of each proplatelet. Essential in this process is the distribution of organelles and platelet-specific granules into the nascent platelets. To investigate the mechanism of delivery of organelles into putative platelets, the distribution and dynamics of organelles/granules was monitored. Individual organelles are sent from the cell body to the proplatelets where they move bidirectionally until they are captured at proplatelet ends. Movement occurs at approximately 0.2 μm/min, but pauses and changes in direction are frequent. At any given time, approximately 30% of organelles/granules are in motion. Actin poisons do not diminish organelle motion, and vesicular structures are intimately associated with the microtubules. Therefore, movement appears to involve microtubule-based forces. Bidirectional organelle movement is conveyed by the bipolar organization of microtubules within the proplatelet, as kinesin-coated beads move bidirectionally on the microtubule arrays of permeabilized proplatelets. Movement of organelles along proplatelets involves 2 mechanisms: organelles travel along microtubules, and the linked microtubules move relative to each other. These studies demonstrate that the components that form platelets are delivered to and assembled de novo along proplatelets.
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Ferrari, Giorgio, Andrew M. Knight, Colin Watts, and Jean Pieters. "Distinct Intracellular Compartments Involved in Invariant Chain Degradation and Antigenic Peptide Loading of Major Histocompatibility Complex (MHC) Class II Molecules." Journal of Cell Biology 139, no. 6 (December 15, 1997): 1433–46. http://dx.doi.org/10.1083/jcb.139.6.1433.
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Major histocompatibility complex (MHC) class II molecules are transported to intracellular MHC class II compartments via a transient association with the invariant chain (Ii). After removal of the invariant chain, peptides can be loaded onto class II molecules, a process catalyzed by human leukocyte antigen-DM (HLA-DM) molecules. Here we show that MHC class II compartments consist of two physically and functionally distinct organelles. Newly synthesized MHC class II/Ii complexes were targeted to endocytic organelles lacking HLA-DM molecules, where Ii degradation occurred. From these organelles, class II molecules were transported to a distinct organelle containing HLA-DM, in which peptides were loaded onto class II molecules. This latter organelle was not directly accessible via fluid phase endocytosis, suggesting that it is not part of the endosomal pathway. Uptake via antigen-specific membrane immunoglobulin resulted however in small amounts of antigen in the HLA-DM positive organelles. From this peptide-loading compartment, class II–peptide complexes were transported to the plasma membrane, in part after transit through endocytic organelles. The existence of two separate compartments, one involved in Ii removal and the other functioning in HLA-DM–dependent peptide loading of class II molecules, may contribute to the efficiency of antigen presentation by the selective recruitment of peptide-receptive MHC class II molecules and HLA-DM to the same subcellular location.
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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.
Full textAbstract:
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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Hollenbeck, P. J., and D. Bray. "Rapidly transported organelles containing membrane and cytoskeletal components: their relation to axonal growth." Journal of Cell Biology 105, no. 6 (December 1, 1987): 2827–35. http://dx.doi.org/10.1083/jcb.105.6.2827.
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We have examined the movements, composition, and cellular origin of phase-dense varicosities in cultures of chick sympathetic and sensory neurons. These organelles are variable in diameter (typically between 0.2 and 2 microns) and undergo saltatory movements both towards and away from the neuronal cell body. Their mean velocities vary inversely with the size of the organelle and are greater in the retrograde than the anterograde direction. Organelles stain with the lipophilic dye 1, 1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine and with antibodies to cytoskeletal components. In cultures double-stained with antibodies to alpha-tubulin and 70-kD neurofilament protein (NF-L), approximately 40% of the organelles stain for tubulin, 30% stain for NF-L, 10% stain for both tubulin and NF-L, and 40% show no staining with either antibody. The association of cytoskeletal proteins with the organelles shows that these proteins are able to move by a form of rapid axonal transport. Under most culture conditions the predominant direction of movement is towards the cell body, suggesting that the organelles are produced at or near the growth cone. Retrograde movements continue in culture medium lacking protein or high molecular mass components and increase under conditions in which the advance of the growth cone is arrested. There is a fourfold increase in the number of organelles moving retrogradely in neurites that encounter a substratum-associated barrier to elongation; retrograde movements increase similarly in cultures exposed to cytochalasin at levels known to block growth cone advance. No previously described organelle shows behavior coordinated with axonal growth in this way. We propose that the organelles contain membrane and cytoskeletal components that have been delivered to the growth cone, by slow or fast anterograde transport, in excess of the amounts required to synthesize more axon. In view of their rapid mobility and variable contents, we suggest that they be called "neuronal parcels."
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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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Prinz, William A. "Bridging the gap: Membrane contact sites in signaling, metabolism, and organelle dynamics." Journal of Cell Biology 205, no. 6 (June 23, 2014): 759–69. http://dx.doi.org/10.1083/jcb.201401126.
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Regions of close apposition between two organelles, often referred to as membrane contact sites (MCSs), mostly form between the endoplasmic reticulum and a second organelle, although contacts between mitochondria and other organelles have also begun to be characterized. Although these contact sites have been noted since cells first began to be visualized with electron microscopy, the functions of most of these domains long remained unclear. The last few years have witnessed a dramatic increase in our understanding of MCSs, revealing the critical roles they play in intracellular signaling, metabolism, the trafficking of metabolites, and organelle inheritance, division, and transport.
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Banfield, David K., and Will Prinz. "Editorial overview: Cell organelles." Current Opinion in Cell Biology 29 (August 2014): v—vi. http://dx.doi.org/10.1016/j.ceb.2014.07.001.
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Rabouille, Catherine, and Bruno Antonny. "Editorial overview: Cell organelles." Current Opinion in Cell Biology 47 (August 2017): iv—vi. http://dx.doi.org/10.1016/j.ceb.2017.07.001.
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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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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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Langford, G. M., S. A. Kuznetsov, D. Johnson, D. L. Cohen, and D. G. Weiss. "Movement of axoplasmic organelles on actin filaments assembled on acrosomal processes: evidence for a barbed-end-directed organelle motor." Journal of Cell Science 107, no. 8 (August 1, 1994): 2291–98. http://dx.doi.org/10.1242/jcs.107.8.2291.
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The directionality of the actin-dependent motors on squid axoplasmic organelles was determined using actin filaments assembled on the barbed ends of acrosomal processes. Acrosomal processes were isolated from Limulus polyphemus sperm and incubated in monomeric actin under conditions that promoted barbed end assembly only. Newly assembled actin was stabilized and stained with rhodamine-phalloidin and the presence of filaments at the barbed ends of the acrosomal processes was verified by fluorescence microscopy and negative contrast electron microscopy. Axoplasmic organelles that dissociated from extruded axoplasm were observed by video microscopy to move along the newly assembled actin filaments at an average velocity of 1.1 +/- 0.3 microns/second. All organelles moved in the direction away from the acrosomal fragment and towards the tip of the actin filaments. Therefore, the actin-dependent organelle motor on axoplasmic organelles is a barbed-end-directed motor like other myosins analyzed. These findings support the conclusions that axoplasmic organelles are driven by a myosin-like motor along actin filaments and that these filaments as well as microtubules function in fast axonal transport.
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Kjeken, Rune, Morten Egeberg, Anja Habermann, Mark Kuehnel, Pascale Peyron, Matthias Floetenmeyer, Paul Walther, et al. "Fusion between Phagosomes, Early and Late Endosomes: A Role for Actin in Fusion between Late, but Not Early Endocytic Organelles." Molecular Biology of the Cell 15, no. 1 (January 2004): 345–58. http://dx.doi.org/10.1091/mbc.e03-05-0334.
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Actin is implicated in membrane fusion, but the precise mechanisms remain unclear. We showed earlier that membrane organelles catalyze the de novo assembly of F-actin that then facilitates the fusion between latex bead phagosomes and a mixture of early and late endocytic organelles. Here, we correlated the polymerization and organization of F-actin with phagosome and endocytic organelle fusion processes in vitro by using biochemistry and light and electron microscopy. When membrane organelles and cytosol were incubated at 37°C with ATP, cytosolic actin polymerized rapidly and became organized into bundles and networks adjacent to membrane organelles. By 30-min incubation, a gel-like state was formed with little further polymerization of actin thereafter. Also during this time, the bulk of in vitro fusion events occurred between phagosomes/endocytic organelles. The fusion between latex bead phagosomes and late endocytic organelles, or between late endocytic organelles themselves was facilitated by actin, but we failed to detect any effect of perturbing F-actin polymerization on early endosome fusion. Consistent with this, late endosomes, like phagosomes, could nucleate F-actin, whereas early endosomes could not. We propose that actin assembled by phagosomes or late endocytic organelles can provide tracks for fusion-partner organelles to move vectorially toward them, via membrane-bound myosins, to facilitate fusion.
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Bridgman, P. C., B. Kachar, and T. S. Reese. "The structure of cytoplasm in directly frozen cultured cells. II. Cytoplasmic domains associated with organelle movements." Journal of Cell Biology 102, no. 4 (April 1, 1986): 1510–21. http://dx.doi.org/10.1083/jcb.102.4.1510.
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The relationship between organelle movement and cytoplasmic structure in cultured fibroblasts or epithelial cells was studied using video-enhanced differential interference contrast microscopy and electron microscopy of directly frozen whole mounts. Two functional cytoplasmic domains are characterized by these techniques. A central domain rich in microtubules is associated with directed as well as Brownian movements of organelles, while a surrounding domain rich in f-actin supports directed but often intermittent organelle movements more distally along small but distinct individual microtubule tracks. Differences in the organization of the cytoplasm near microtubules may explain why organelle movements are typically continuous in central regions but usually intermittent along the small tracks through the periphery. The central type of cytoplasm has a looser cytoskeletal meshwork than the peripheral cytoplasm which might, therefore, interfere less frequently with organelles moving along microtubules there.
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He, Rongrong, Yinzi Li, Mark A. Bernards, and Aiming Wang. "Manipulation of the Cellular Membrane-Cytoskeleton Network for RNA Virus Replication and Movement in Plants." Viruses 15, no. 3 (March 14, 2023): 744. http://dx.doi.org/10.3390/v15030744.
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Viruses infect all cellular life forms and cause various diseases and significant economic losses worldwide. The majority of viruses are positive-sense RNA viruses. A common feature of infection by diverse RNA viruses is to induce the formation of altered membrane structures in infected host cells. Indeed, upon entry into host cells, plant-infecting RNA viruses target preferred organelles of the cellular endomembrane system and remodel organellar membranes to form organelle-like structures for virus genome replication, termed as the viral replication organelle (VRO) or the viral replication complex (VRC). Different viruses may recruit different host factors for membrane modifications. These membrane-enclosed virus-induced replication factories provide an optimum, protective microenvironment to concentrate viral and host components for robust viral replication. Although different viruses prefer specific organelles to build VROs, at least some of them have the ability to exploit alternative organellar membranes for replication. Besides being responsible for viral replication, VROs of some viruses can be mobile to reach plasmodesmata (PD) via the endomembrane system, as well as the cytoskeleton machinery. Viral movement protein (MP) and/or MP-associated viral movement complexes also exploit the endomembrane-cytoskeleton network for trafficking to PD where progeny viruses pass through the cell-wall barrier to enter neighboring cells.
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Cohen, Sarah, Alex M. Valm, and Jennifer Lippincott-Schwartz. "Interacting organelles." Current Opinion in Cell Biology 53 (August 2018): 84–91. http://dx.doi.org/10.1016/j.ceb.2018.06.003.
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Grant, Carly R., Juan Wan, and Arash Komeili. "Organelle Formation in Bacteria and Archaea." Annual Review of Cell and Developmental Biology 34, no. 1 (October 6, 2018): 217–38. http://dx.doi.org/10.1146/annurev-cellbio-100616-060908.
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Uncovering the mechanisms that underlie the biogenesis and maintenance of eukaryotic organelles is a vibrant and essential area of biological research. In comparison, little attention has been paid to the process of compartmentalization in bacteria and archaea. This lack of attention is in part due to the common misconception that organelles are a unique evolutionary invention of the “complex” eukaryotic cell and are absent from the “primitive” bacterial and archaeal cells. Comparisons across the tree of life are further complicated by the nebulous criteria used to designate subcellular structures as organelles. Here, with the aid of a unified definition of a membrane-bounded organelle, we present some of the recent findings in the study of lipid-bounded organelles in bacteria and archaea.
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Habermann, A., T. A. Schroer, G. Griffiths, and J. K. Burkhardt. "Immunolocalization of cytoplasmic dynein and dynactin subunits in cultured macrophages: enrichment on early endocytic organelles." Journal of Cell Science 114, no. 1 (January 1, 2001): 229–40. http://dx.doi.org/10.1242/jcs.114.1.229.
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Cytoplasmic dyneins and their cofactor, dynactin, work together to mediate the movement of numerous cargo organelles toward the minus-ends of microtubules. In many cases, there is compelling evidence that dynactin functions in part to attach dyneins to cargo organelles, but this may not always be the case. We have localized three dynactin subunits (Arp1, p62 and p150(Glued)) and two subunits of conventional cytoplasmic dynein (dynein intermediate chain and dynein heavy chain 1) in murine macrophages using immunogold labeling of thawed cryosections. Using stereological techniques, we have quantified the relative distributions of each of these subunits on specific membrane organelles to generate a comprehensive analysis of the distribution of these proteins in a single cell type. Our results show that each of the subunits tested exhibits the same distribution with respect to different membrane organelles, with highest levels present on early endosomes, and lower levels present on later endocytic organelles, the mitochondrial outer membrane, the plasma membrane and vesicles in the Golgi region. An additional pool of punctate dynactin labeling was detected in the cell periphery, in the absence of dynein labeling. Even when examined closely, membrane organelles could not be detected in association with these dynactin-positive sites; however, double labeling with anti-tubulin antibody revealed that at least some of these sites represent the ends of microtubules. The similarities among the labeling profiles with respect to membrane organelles suggest that dynein and dynactin bind to membrane organelles as an obligate unit. In contrast, our results show that dynactin can associate with microtubule ends in the absence of dynein, perhaps providing sites for subsequent organelle and dynein association to form a functional motility complex.
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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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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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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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Navarro-Espíndola, Raful, Fernando Suaste-Olmos, and Leonardo Peraza-Reyes. "Dynamic Regulation of Peroxisomes and Mitochondria during Fungal Development." Journal of Fungi 6, no. 4 (November 20, 2020): 302. http://dx.doi.org/10.3390/jof6040302.
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Peroxisomes and mitochondria are organelles that perform major functions in the cell and whose activity is very closely associated. In fungi, the function of these organelles is critical for many developmental processes. Recent studies have disclosed that, additionally, fungal development comprises a dynamic regulation of the activity of these organelles, which involves a developmental regulation of organelle assembly, as well as a dynamic modulation of the abundance, distribution, and morphology of these organelles. Furthermore, for many of these processes, the dynamics of peroxisomes and mitochondria are governed by common factors. Notably, intense research has revealed that the process that drives the division of mitochondria and peroxisomes contributes to several developmental processes—including the formation of asexual spores, the differentiation of infective structures by pathogenic fungi, and sexual development—and that these processes rely on selective removal of these organelles via autophagy. Furthermore, evidence has been obtained suggesting a coordinated regulation of organelle assembly and dynamics during development and supporting the existence of regulatory systems controlling fungal development in response to mitochondrial activity. Gathered information underscores an important role for mitochondrial and peroxisome dynamics in fungal development and suggests that this process involves the concerted activity of these organelles.