The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Jennifer Lippincottschwartz - One of the best experts on this subject based on the ideXlab platform.
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er membranes exhibit phase behavior at sites of Organelle contact
Proceedings of the National Academy of Sciences of the United States of America, 2020Co-Authors: Christopher L King, Prabuddha Sengupta, Jennifer LippincottschwartzAbstract: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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applying systems level spectral imaging and analysis to reveal the Organelle interactome
Nature, 2017Co-Authors: Alex M. Valm, Sarah S Cohen, Wesley R Legant, Justin Melunis, Uri Hershberg, Eric Wait, Andrew R Cohen, Michael W Davidson, Eric Betzig, Jennifer LippincottschwartzAbstract:Using confocal and lattice light sheet microscopy, the authors perform systems-level analysis of the Organelle interactome in live cells, allowing them to visualize the frequency and locality of up to five-way interactions between different Organelles. Various cell components, or Organelles, make contacts that are not mediated by trafficking vesicles, and which result in changes to their physical behaviour, biochemical composition and functionality. Imaging is a powerful tool for studying inter-Organelle contact sites, but work by Jennifer Lippincott-Schwartz and colleagues take such analysis to a new level. Using confocal and lattice light sheet microscopy, as well as a multispectral image acquisition and analysis method, they perform systems-level analysis of the Organelle interactome in live cells. The approach allows them to visualize the frequency and locality of up to five-way interactions among six different Organelles (endoplasmic reticulum, Golgi, lysosome, peroxisome, mitochondria and lipid droplet), providing unexpected insights into the dynamics of these interactions. The method could prove a useful tool for further analysis of non-vesicular communication within the cell. The organization of the eukaryotic cell into discrete membrane-bound Organelles allows for the separation of incompatible biochemical processes, but the activities of these Organelles must be coordinated. For example, lipid metabolism is distributed between the endoplasmic reticulum for lipid synthesis, lipid droplets for storage and transport, mitochondria and peroxisomes for β-oxidation, and lysosomes for lipid hydrolysis and recycling1,2,3,4,5. It is increasingly recognized that Organelle contacts have a vital role in diverse cellular functions5,6,7,8. However, the spatial and temporal organization of Organelles within the cell remains poorly characterized, as fluorescence imaging approaches are limited in the number of different labels that can be distinguished in a single image9. Here we present a systems-level analysis of the Organelle interactome using a multispectral image acquisition method that overcomes the challenge of spectral overlap in the fluorescent protein palette. We used confocal and lattice light sheet10 instrumentation and an imaging informatics pipeline of five steps to achieve mapping of Organelle numbers, volumes, speeds, positions and dynamic inter-Organelle contacts in live cells from a monkey fibroblast cell line. We describe the frequency and locality of two-, three-, four- and five-way interactions among six different membrane-bound Organelles (endoplasmic reticulum, Golgi, lysosome, peroxisome, mitochondria and lipid droplet) and show how these relationships change over time. We demonstrate that each Organelle has a characteristic distribution and dispersion pattern in three-dimensional space and that there is a reproducible pattern of contacts among the six Organelles, that is affected by microtubule and cell nutrient status. These live-cell confocal and lattice light sheet spectral imaging approaches are applicable to any cell system expressing multiple fluorescent probes, whether in normal conditions or when cells are exposed to disturbances such as drugs, pathogens or stress. This methodology thus offers a powerful descriptive tool and can be used to develop hypotheses about cellular organization and dynamics.
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brefeldin a insights into the control of membrane traffic and Organelle structure
Journal of Cell Biology, 1992Co-Authors: Richard D Klausner, Julie G Donaldson, Jennifer LippincottschwartzAbstract:THE definition of cellular Organelles has evolved over the last hundred years largely driven by morphologic observations, but more recently has been supplemented and complemented by functional and biochemical studies (Palade, 1975) . Thus, Organelles are now identified both by their morphology and by the set ofcomponents that comprise them . Determining how Organelle identity is established and maintained and how newly synthesized protein and membrane are sorted to different Organelles are the central issues of organellogenesis . Essential to the many cellular functions that take place within the central vacuolar system (which consists ofthe ER, Golgi apparatus, secretory vesicles, endosomes, and lysosomes) is membrane traffic which mediates the exchange of components between different Organelles . There are two critical characteristics of membrane traffic . First, only certain sets ofOrganelles exchange membrane and the patterns of this exchange define what are called membrane pathways . Second, multiple pathways intersect at specific points within the central vacuolar system . For specific components to "choose" the correct pathway at such points of crossing, mechanisms exist to impose choices on specific molecules . This process is called sorting . The characteristicsofeachOrganelle within the central vacuolar system are likely to be intimately tied to the properties ofmembrane traffic . An imbalance in the magnitude ofmembrane input into and egress from an Organelle would have profound effects on the size ofthat compartment . In addition, failures in sorting or aberrations in targeting pathways would be expected to profoundly affect the identity of individual Organelles . Recently, the relationship between the control of membrane traffic and the maintenance of Organelle structure has been investigated with the use ofa remarkable drug, brefeldin A (BFA).' In this review we will summarize recent findings with BFA and propose some speculative models concerning the mechanism and regulation ofmembrane traffic within the central vacuolar system .
Chris Hawes - One of the best experts on this subject based on the ideXlab platform.
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Organelle biogenesis and positioning in plants.
Biochemical Society Transactions, 2010Co-Authors: David E. Evans, Chris HawesAbstract: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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Truncated myosin XI tail fusions inhibit peroxisome, Golgi, and mitochondrial movement in tobacco leaf epidermal cells: A genetic tool for the next generation
Journal of Experimental Botany, 2008Co-Authors: Imogen A. Sparkes, Nicholas A. Teanby, Chris HawesAbstract:Although Organelle movement in higher plants is predominantly actin-based, potential roles for the 17 predicted Arabidopsis myosins in motility are only just emerging. It is shown here that two Arabidopsis myosins from class XI, XIE, and XIK, are involved in Golgi, peroxisome, and mitochondrial movement. Expression of dominant negative forms of the myosin lacking the actin binding domain at the amino terminus perturb Organelle motility, but do not completely inhibit movement. Latrunculin B, an actin destabilizing drug, inhibits Organelle movement to a greater extent compared to the effects of AtXIE-T/XIK-T expression. Amino terminal YFP fusions to XIE-T and XIK-T are dispersed throughout the cytosol and do not completely decorate the Organelles whose motility they affect. XIE-T and XIK-T do not affect the global actin architecture, but their movement and location is actin-dependent. The potential role of these truncated myosins as genetically encoded inhibitors of Organelle movement is discussed.
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mapping the arabidopsis Organelle proteome
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Tom Dunkley, Julian L Griffin, Svenja Hester, Ian Shadforth, John Runions, Thilo Weimar, Sally L Hanton, Conrad Bessant, Federica Brandizzi, Chris HawesAbstract:A challenging task in the study of the secretory pathway is the identification and localization of new proteins to increase our understanding of the functions of different Organelles. Previous proteomic studies of the endomembrane system have been hindered by contaminating proteins, making it impossible to assign proteins to Organelles. Here we have used the localization of Organelle proteins by the isotope tagging technique in conjunction with isotope tags for relative and absolute quantitation and 2D liquid chromatography for the simultaneous assignment of proteins to multiple subcellular compartments. With this approach, the density gradient distributions of 689 proteins from Arabidopsis thaliana were determined, enabling confident and simultaneous localization of 527 proteins to the endoplasmic reticulum, Golgi apparatus, vacuolar membrane, plasma membrane, or mitochondria and plastids. This parallel analysis of endomembrane components has enabled protein steady-state distributions to be determined. Consequently, genuine Organelle residents have been distinguished from contaminating proteins and proteins in transit through the secretory pathway.
Yoshimi Tsuchiya - One of the best experts on this subject based on the ideXlab platform.
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characteristics in sliding motions of small Organelles in a nitella internodal cell
Journal of the Physical Society of Japan, 1995Co-Authors: Go Uchida, Tomomi Nemoto, Yoshimi TsuchiyaAbstract:Steady velocities of small Organelles smoothly moving on chloroplasts in a Nitella internodal cell have been investigated at various temperatures. It has been found that variance in the velocities of the Organelles changes in proportion to their average velocity, which has been first elucidated from the temperature dependence of the Organelle's velocity. This result suggests that the generation process of the force due to the actin-myosin is a Poisson like stochastic one. Thus, we have discussed a stochastic model for the motion of the Organelle with many myosin-like molecules and estimated the force to be 4.2×10 -12 N.
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stochastic behavior of Organelle motion in nitella internodal cells
Biochemical and Biophysical Research Communications, 1995Co-Authors: T Nemoto, Go Uchida, Atsuko Takamatsu, Yoshimi TsuchiyaAbstract:Abstract The stochastic behavior of Organelles during the recovery process of protoplasmic streaming is investigated in Nitella internodal cells at a nanometer space resolution. The motions of Organelles in the components parallel and perpendicular to the alignment of actin filaments in the cell are analysed from the traces of displacement of 860 Organelles in 1/30s (=video rate). The analysis of those traces shows that the generation of motive forces to the Organelle follows the Poisson process. Therefore, we have been able to estimate the step size corresponding to the single force generation as ∼100 nm.
Randeep Rakwal - One of the best experts on this subject based on the ideXlab platform.
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Plant Organelle proteomics: Collaborating for optimal cell function
Mass Spectrometry Reviews, 2011Co-Authors: Ganesh Kumar Agrawal, Pascale Jolivet, Geneviève Ephritikhine, Niranjan Chakraborty, Michel Jaquinod, John H Doonan, J. Bourguignon, Thierry Chardot, Myriam Ferro, Norbert Rolland, Konstantinos G Alexiou, Randeep RakwalAbstract:Organelle proteomics describes the study of proteins present in Organelle at a particular instance during the whole period of their life cycle in a cell. Organelles are specialized membrane bound structures within a cell that function by interacting with cytosolic and luminal soluble proteins making the protein composition of each Organelle dynamic. Depending on organism, the total number of Organelles within a cell varies, indicating their evolution with respect to protein number and function. For example, one of the striking differences between plant and animal cells is the plastids in plants. Organelles have their own proteins, and few Organelles like mitochondria and chloroplast have their own genome to synthesize proteins for specific function and also require nuclear-encoded proteins. Enormous work has been performed on animal Organelle proteomics. However, plant Organelle proteomics has seen limited work mainly due to: (i) inter-plant and inter-tissue complexity, (ii) difficulties in isolation of subcellular compartments, and (iii) their enrichment and purity. Despite these concerns, the field of Organelle proteomics is growing in plants, such as Arabidopsis, rice and maize. The available data are beginning to help better understand Organelles and their distinct and/or overlapping functions in different plant tissues, organs or cell types, and more importantly, how protein components of Organelles behave during development and with surrounding environments. Studies on Organelles have provided a few good reviews, but none of them are comprehensive. Here, we present a comprehensive review on plant Organelle proteomics starting from the significance of Organelle in cells, to Organelle isolation, to protein identification and to biology and beyond. To put together such a systematic, in-depth review and to translate acquired knowledge in a proper and adequate form, we join minds to provide discussion and viewpoints on the collaborative nature of Organelles in cell, their proper function and evolution. -� 2010 Wiley Periodicals, Inc., Mass Spec Rev 30:772–853, 2011
Lukas C Kapitein - One of the best experts on this subject based on the ideXlab platform.
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optogenetic control of Organelle transport and positioning
Nature, 2015Co-Authors: Petra Van Bergeijk, Max Adrian, Casper C Hoogenraad, Lukas C KapiteinAbstract:An optogenetic strategy allowing light-mediated recruitment of distinct cytoskeletal motor proteins to specific Organelles is established; this technique enabled rapid and reversible activation or inhibition of the transport of Organelles such as peroxisomes, recycling endosomes and mitochondria with high spatiotemporal accuracy, and the approach was also applied to primary neurons to demonstrate optical control of axonal growth by recycling endosome repositioning. How does the position of Organelles within a cell influence cellular functions? In the absence of strategies to control intracellular Organelle positioning with spatiotemporal precision, it has been difficult to answer this question. Lukas Kapitein and colleagues have developed an optogenetic strategy, based on light-mediated recruitment of distinct cytoskeletal motor proteins to their specific cargo Organelles that allows such cellular manipulations. Using the new technique it is possible to rapidly and reversibly activate or inhibit the transport of specific Organelles and demonstrate local modulation of Organelle distributions — including peroxisomes, recycling endosomes and mitochondria — with high spatiotemporal accuracy. The authors demonstrate local modulation of Organelle distributions for peroxisomes, recycling endosomes and mitochondria. They also applied this approach in primary neurons to establish optical control of axon outgrowth. Proper positioning of Organelles by cytoskeleton-based motor proteins underlies cellular events such as signalling, polarization and growth1,2,3,4,5,6,7,8. For many Organelles, however, the precise connection between position and function has remained unclear, because strategies to control intracellular Organelle positioning with spatiotemporal precision are lacking. Here we establish optical control of intracellular transport by using light-sensitive heterodimerization to recruit specific cytoskeletal motor proteins (kinesin, dynein or myosin) to selected cargoes. We demonstrate that the motility of peroxisomes, recycling endosomes and mitochondria can be locally and repeatedly induced or stopped, allowing rapid Organelle repositioning. We applied this approach in primary rat hippocampal neurons to test how local positioning of recycling endosomes contributes to axon outgrowth and found that dynein-driven removal of endosomes from axonal growth cones reversibly suppressed axon growth, whereas kinesin-driven endosome enrichment enhanced growth. Our strategy for optogenetic control of Organelle positioning will be widely applicable to explore site-specific Organelle functions in different model systems.
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Optogenetic control of Organelle transport and positioning
Nature, 2015Co-Authors: Petra Van Bergeijk, Max Adrian, Casper C Hoogenraad, Lukas C KapiteinAbstract:Proper positioning of Organelles by cytoskeleton-based motor proteins underlies cellular events such as signalling, polarization and growth. For many Organelles, however, the precise connection between position and function has remained unclear, because strategies to control intracellular Organelle positioning with spatiotemporal precision are lacking. Here we establish optical control of intracellular transport by using light-sensitive heterodimerization to recruit specific cytoskeletal motor proteins (kinesin, dynein or myosin) to selected cargoes. We demonstrate that the motility of peroxisomes, recycling endosomes and mitochondria can be locally and repeatedly induced or stopped, allowing rapid Organelle repositioning. We applied this approach in primary rat hippocampal neurons to test how local positioning of recycling endosomes contributes to axon outgrowth and found that dynein-driven removal of endosomes from axonal growth cones reversibly suppressed axon growth, whereas kinesin-driven endosome enrichment enhanced growth. Our strategy for optogenetic control of Organelle positioning will be widely applicable to explore site-specific Organelle functions in different model systems.
