The Experts below are selected from a list of 11202 Experts worldwide ranked by ideXlab platform
Vivek Malhotra - One of the best experts on this subject based on the ideXlab platform.
-
sphingolipid metabolic flow controls phosphoinositide turnover at the Trans Golgi Network
bioRxiv, 2016Co-Authors: Serena Capasso, Lucia Sticco, Riccardo Rizzo, Marinella Pirozzi, Domenico Russo, Nina A Dathan, Felix Campelo, Josse Van Galen, Angelika Hausser, Vivek MalhotraAbstract:Sphingolipids are membrane lipids, which are globally required for eukaryotic life. Sphingolipid composition varies among endomembranes with pre- and post-Golgi compartments being poor and rich in sphingolipids, respectively. Thanks to this different sphingolipid content, pre- and post-Golgi membranes serve different cellular functions. Nevertheless, how subcellular sphingolipid levels are maintained in spite of trafficking and metabolic fluxes is only partially understood. Here we describe a homeostatic control circuit that controls sphingolipid levels at the Trans Golgi Network. Specifically, we show that sphingomyelin production at the Trans Golgi Network triggers a signalling reaction leading to PtdIns(4)P dephosphorylation. Since PtdIns(4)P is required for cholesterol, and sphingolipid Transport to the Trans Golgi Network, PtdIns(4)P consumption leads to the interruption of this Transport in response to excessive sphingomyelin production. Based on this evidence we envisage a model where this homeostatic circuit maintains the sphingolipid composition of Trans Golgi Network and thus of post-Golgi compartments constant, against instant fluctuations in the sphingolipid biosynthetic flow.
-
sphingomyelin homeostasis is required to form functional enzymatic domains at the Trans Golgi Network
Journal of Cell Biology, 2014Co-Authors: Josse Van Galen, Felix Campelo, Emma Martinezalonso, Margherita Scarpa, Jose A Martinezmenarguez, Vivek MalhotraAbstract:Do lipids such as sphingomyelin (SM) that are known to assemble into specific membrane domains play a role in the organization and function of Transmembrane proteins? In this paper, we show that disruption of SM homeostasis at the Trans-Golgi Network (TGN) by treatment of HeLa cells with d-ceramide-C6, which was converted together with phosphatidylcholine to short-chain SM and diacylglycerol by SM synthase, led to the segregation of Golgi-resident proteins from each other. We found that TGN46, which cycles between the TGN and the plasma membrane, was not sialylated by a sialylTransferase at the TGN and that this enzyme and its substrate TGN46 could not physically interact with each other. Our results suggest that SM organizes Transmembrane proteins into functional enzymatic domains at the TGN.
-
kinesin 5 eg5 is important for Transport of carts from the Trans Golgi Network to the cell surface
Journal of Cell Biology, 2013Co-Authors: Josse Van Galen, Yuichi Wakana, Julien Villeneuve, David Cruzgarcia, Mitsuo Tagaya, Vivek MalhotraAbstract:Here we report that the kinesin-5 motor Klp61F, which is known for its role in bipolar spindle formation in mitosis, is required for protein Transport from the Golgi complex to the cell surface in Drosophila S2 cells. Disrupting the function of its mammalian orthologue, Eg5, in HeLa cells inhibited secretion of a protein called pancreatic adenocarcinoma up-regulated factor (PAUF) but, surprisingly, not the trafficking of vesicular stomatitis virus G protein (VSV-G) to the cell surface. We have previously reported that PAUF is Transported from the Trans-Golgi Network (TGN) to the cell surface in specific carriers called CARTS that exclude VSV-G. Inhibition of Eg5 function did not affect the biogenesis of CARTS; however, their migration was delayed and they accumulated near the Golgi complex. Altogether, our findings reveal a surprising new role of Eg5 in nonmitotic cells in the facilitation of the Transport of specific carriers, CARTS, from the TGN to the cell surface.
-
recruitment of arfaptins to the Trans Golgi Network by pi 4 p and their involvement in cargo export
The EMBO Journal, 2013Co-Authors: David Cruzgarcia, Thomas Seufferlein, Vivek Malhotra, Margherita Scarpa, Julien Villeneuve, Maria Ortegabellido, Marko Jovic, Marc Porzner, Tamas BallaAbstract:The BAR (Bin/Amphiphysin/Rvs) domain proteins arfaptin1 and arfaptin2 are localized to the Trans-Golgi Network (TGN) and, by virtue of their ability to sense and/or generate membrane curvature, could play an important role in the biogenesis of Transport carriers. We report that arfaptins contain an amphipathic helix (AH) preceding the BAR domain, which is essential for their binding to phosphatidylinositol 4-phosphate (PI(4)P)-containing liposomes and the TGN of mammalian cells. The binding of arfaptin1, but not arfaptin2, to PI(4)P is regulated by protein kinase D (PKD) mediated phosphorylation at Ser100 within the AH. We also found that only arfaptin1 is required for the PKD-dependent trafficking of chromogranin A by the regulated secretory pathway. Altogether, these findings reveal the importance of PI(4)P and PKD in the recruitment of arfaptins at the TGN and their requirement in the events leading to the biogenesis of secretory storage granules.
-
cab45 is required for ca2 dependent secretory cargo sorting at the Trans Golgi Network
Journal of Cell Biology, 2012Co-Authors: Julia Von Blume, Christine Kienzle, Annemarie Alleaume, Amado Carrerassureda, Miguel A Valverde, Vivek MalhotraAbstract:Ca(2+) import into the lumen of the Trans-Golgi Network (TGN) by the secretory pathway calcium ATPase1 (SPCA1) is required for the sorting of secretory cargo. How is Ca(2+) retained in the lumen of the Golgi, and what is its role in cargo sorting? We show here that a soluble, lumenal Golgi resident protein, Cab45, is required for SPCA1-dependent Ca(2+) import into the TGN; it binds secretory cargo in a Ca(2+)-dependent reaction and is required for its sorting at the TGN.
Julia Von Blume - One of the best experts on this subject based on the ideXlab platform.
-
lipid dependent coupling of secretory cargo sorting and trafficking at the Trans Golgi Network
FEBS Letters, 2019Co-Authors: Julia Von Blume, Angelika HausserAbstract:In eukaryotic cells, the Trans-Golgi Network (TGN) serves as a platform for secretory cargo sorting and trafficking. In recent years, it has become evident that a complex Network of lipid-lipid and lipid-protein interactions contributes to these key functions. This review addresses the role of lipids at the TGN with a particular emphasis on sphingolipids and diacylglycerol. We further highlight how these lipids couple secretory cargo sorting and trafficking for spatiotemporal coordination of protein Transport to the plasma membrane.
-
activity of the spca1 calcium pump couples sphingomyelin synthesis to sorting of secretory proteins in the Trans Golgi Network
Developmental Cell, 2018Co-Authors: Yongqiang Deng, Christopher G Burd, Birgit Blank, Mehrshad Pakdel, Emma L Sundberg, Julia Von BlumeAbstract:Summary How the principal functions of the Golgi apparatus—protein processing, lipid synthesis, and sorting of macromolecules—are integrated to constitute cargo-specific trafficking pathways originating from the Trans-Golgi Network (TGN) is unknown. Here, we show that the activity of the Golgi localized SPCA1 calcium pump couples sorting and export of secreted proteins to synthesis of new lipid in the TGN membrane. A secreted Ca2+-binding protein, Cab45, constitutes the core component of a Ca2+-dependent, oligomerization-driven sorting mechanism whereby secreted proteins bound to Cab45 are packaged into a TGN-derived vesicular carrier whose membrane is enriched in sphingomyelin, a lipid implicated in TGN-to-cell surface Transport. SPCA1 activity is controlled by the sphingomyelin content of the TGN membrane, such that local sphingomyelin synthesis promotes Ca2+ flux into the lumen of the TGN, which drives secretory protein sorting and export, thereby establishing a protein- and lipid-specific secretion pathway.
-
cab45 unraveling key features of a novel secretory cargo sorter at the Trans Golgi Network
European Journal of Cell Biology, 2017Co-Authors: Birgit Blank, Julia Von BlumeAbstract:The accurate and efficient delivery of proteins to specific domains of the plasma membrane or to the extracellular space is critical for the ordered function of surface receptors and proteins such as insulin, collagens, antibodies, extracellular proteases. The Trans-Golgi Network is responsible for sorting proteins onto specific carriers for Transport to their final destination. The role of the mannose-6-phosphate receptor in the sorting of hydrolases destined for lysosomes has been studied extensively, but the sorting mechanisms for secreted proteins remains poorly understood. We recently described a novel process that links the cytoplasmic actin cytoskeleton to the membrane-anchored Ca2+ ATPase SPCA1 and the lumenal Ca2+-binding protein Cab45, which mediates sorting of a subset of secretory proteins at the TGN. In response to Ca2+ influx, Cab45 forms oligomers, enabling it to bind a variety of specific cargo molecules. Thus, we suggest that this represents a novel way to export cargo molecules without the need for a bona fide Transmembrane cargo receptor. This review focuses on Cab45's molecular function and highlights its possible role in disease.
-
Secretory cargo sorting at the Trans-Golgi Network
Trends in Cell Biology, 2014Co-Authors: Christine Kienzle, Julia Von BlumeAbstract:Sorting of proteins for secretion from cells is crucial for normal physiology and the regulation of key cellular events. Although the sorting of lysosomal hydrolases at the Trans-Golgi Network (TGN) for delivery to pre-lysosomes is well characterized, the corresponding mechanism by which secreted proteins are sorted for plasma-membrane delivery remains poorly understood. Recent discoveries have revealed a novel sorting mechanism that requires the linkage between the cytoplasmic actin cytoskeleton to the membrane-anchored Ca2+ATPase, SPCA1 (secretory pathway calcium ATPase 1), and the luminal 45kDa Ca2+-binding protein, Cab45, for successful sorting of a subset of proteins at the TGN. We review progress in understanding these processes.
-
cab45 is required for ca2 dependent secretory cargo sorting at the Trans Golgi Network
Journal of Cell Biology, 2012Co-Authors: Julia Von Blume, Christine Kienzle, Annemarie Alleaume, Amado Carrerassureda, Miguel A Valverde, Vivek MalhotraAbstract:Ca(2+) import into the lumen of the Trans-Golgi Network (TGN) by the secretory pathway calcium ATPase1 (SPCA1) is required for the sorting of secretory cargo. How is Ca(2+) retained in the lumen of the Golgi, and what is its role in cargo sorting? We show here that a soluble, lumenal Golgi resident protein, Cab45, is required for SPCA1-dependent Ca(2+) import into the TGN; it binds secretory cargo in a Ca(2+)-dependent reaction and is required for its sorting at the TGN.
Kai Simons - One of the best experts on this subject based on the ideXlab platform.
-
lipid dependent protein sorting at the Trans Golgi Network
Biochimica et Biophysica Acta, 2012Co-Authors: Michal A Surma, Christian Klose, Kai SimonsAbstract:In eukaryotic cells, the Trans-Golgi Network serves as a sorting station for post-Golgi traffic. In addition to coat- and adaptor-mediated mechanisms, studies in mammalian epithelial cells and yeast have provided evidence for lipid-dependent protein sorting as a major delivery mechanism for cargo sorting to the cell surface. The mechanism for lipid-mediated sorting is the generation of raft platforms of sphingolipids, sterols and specific sets of cargo proteins by phase segregation in the TGN. Here, we review the evidence for such lipid-raft-based sorting at the TGN, as well as their involvement in the formation of TGN-to-PM Transport carriers. This article is part of a Special Issue entitled Lipids and Vesicular Transport.
-
dual color visualization of Trans Golgi Network to plasma membrane traffic along microtubules in living cells
Journal of Cell Science, 1999Co-Authors: Derek Toomre, Patrick Keller, Jamie White, Jeanchristophe Olivo, Kai SimonsAbstract:The mechanisms and carriers responsible for exocytic protein trafficking between the Trans-Golgi Network (TGN) and the plasma membrane remain unclear. To investigate the dynamics of TGN-to-plasma membrane traffic and role of the cytoskeleton in these processes we Transfected cells with a GFP-fusion protein, vesicular stomatitis virus G protein tagged with GFP (VSVG3-GFP). After using temperature shifts to block VSVG3-GFP in the endoplasmic reticulum and subsequently accumulate it in the TGN, dynamics of TGN-to-plasma membrane Transport were visualized in real time by confocal and video microscopy. Both small vesicles ( 1.5 microm long) are used as Transport containers (TCs). These TCs rapidly moved out of the Golgi along curvilinear paths with average speeds of approximately 0.7 micrometer/second. Automatic computer tracking objectively determined the dynamics of different carriers. Fission and fusion of TCs were observed, suggesting that these late exocytic processes are highly interactive. To directly determine the role of microtubules in post-Golgi traffic, rhodamine-tubulin was microinjected and both labeled cargo and microtubules were simultaneously visualized in living cells. These studies demonstrated that exocytic cargo moves along microtubule tracks and reveals that carriers are capable of switching between tracks.
-
protein and lipid sorting from the Trans Golgi Network to the plasma membrane in polarized cells
Seminars in Cell & Developmental Biology, 1998Co-Authors: Elina Ikonen, Kai SimonsAbstract:The targeting of proteins and lipids to the cell surface domains of polarized cells is not a simple bulk flow process but requires sorting into distinct apical and basolateral pathways from the Trans-Golgi Network. Here, we describe the sorting determinants in the cargo molecules, the cellular sorting machineries responsible for the hierarchical read-out of the signals, and the mechanisms of cargo delivery. Furthermore, we discuss the implications of these findings for protein-lipid interactions in other cellular machineries.
-
caveolae and sorting in the Trans Golgi Network of epithelial cells
The EMBO Journal, 1993Co-Authors: Paul Dupree, Robert G Parton, Graca Raposo, Teymuras V Kurzchalia, Kai SimonsAbstract:The specific characteristics of cellular membranes are a consequence not only of their protein constituents, but also of their lipid composition. It is obvious that the behavior of a membrane protein is dependent upon its lipid environment. The interplay between proteins and lipids during membrane trafficking is, however, an area of research that has been largely neglected. Interest in the glycolipid-dependent sorting of proteins in membranes is an exception, and has provided a paradigm that demonstrates the importance of these interactions. This phenomenon was first proposed during studies of protein and lipid sorting in simple epithelial cells. The apical and basolateral plasma membrane domains of these cells have not only distinct protein compositions, but the various lipid classes vary in their distribution as well (van Meer and Simons 1988; Simons and van Meer 1988). In particular, the apical plasma membrane is enriched in certain glycolipids. This polarity is in part generated in the Trans- Golgi Network (TGN), where the proteins and lipids destined for the individual plasma membrane domains are sorted into distinct vesicle carriers (Griffiths and Simons 1986; Wandinger-Ness et al. 1990).
Juan S Bonifacino - One of the best experts on this subject based on the ideXlab platform.
-
ap 4 mediates export of atg9a from the Trans Golgi Network to promote autophagosome formation
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Rafael Mattera, Sang Yoon Park, Raffaella De Pace, Carlos M Guardia, Juan S BonifacinoAbstract:AP-4 is a member of the heterotetrameric adaptor protein (AP) complex family involved in protein sorting in the endomembrane system of eukaryotic cells. Interest in AP-4 has recently risen with the discovery that mutations in any of its four subunits cause a form of hereditary spastic paraplegia (HSP) with intellectual disability. The critical sorting events mediated by AP-4 and the pathogenesis of AP-4 deficiency, however, remain poorly understood. Here we report the identification of ATG9A, the only multispanning membrane component of the core autophagy machinery, as a specific AP-4 cargo. AP-4 promotes signal-mediated export of ATG9A from the Trans-Golgi Network to the peripheral cytoplasm, contributing to lipidation of the autophagy protein LC3B and maturation of preautophagosomal structures. These findings implicate AP-4 as a regulator of autophagy and altered autophagy as a possible defect in AP-4–deficient HSP.
-
formation of tubulovesicular carriers from endosomes and their fusion to the Trans Golgi Network
International Review of Cell and Molecular Biology, 2015Co-Authors: Aitor Hierro, David C Gershlick, Adriana L Rojas, Juan S BonifacinoAbstract:Endosomes undergo extensive spatiotemporal rearrangements as proteins and lipids flux through them in a series of fusion and fission events. These controlled changes enable the concentration of cargo for eventual degradation while ensuring the proper recycling of other components. A growing body of studies has now defined multiple recycling pathways from endosomes to the Trans-Golgi Network (TGN) which differ in their molecular machineries. The recycling process requires specific sets of lipids, coats, adaptors, and accessory proteins that coordinate cargo selection with membrane deformation and its association with the cytoskeleton. Specific tethering factors and SNARE (SNAP (Soluble NSF Attachment Protein) Receptor) complexes are then required for the docking and fusion with the acceptor membrane. Herein, we summarize some of the current knowledge of the machineries that govern the retrograde Transport from endosomes to the TGN.
-
Transport according to garp receiving retrograde cargo at the Trans Golgi Network
Trends in Cell Biology, 2011Co-Authors: Juan S Bonifacino, Aitor HierroAbstract:Tethering factors are large protein complexes that capture Transport vesicles and enable their fusion with acceptor organelles at different stages of the endomembrane system. Recent studies have shed new light on the structure and function of a heterotetrameric tethering factor named Golgi-associated retrograde protein (GARP), which promotes fusion of endosome-derived, retrograde Transport carriers to the Trans -Golgi Network (TGN). X-ray crystallography of the Vps53 and Vps54 subunits of GARP has revealed that this complex is structurally related to other tethering factors such as the exocyst, the conserved oligomeric Golgi (COG) and Dsl1 (dependence on SLY1–20) complexes, indicating that they all might work by a similar mechanism. Loss of GARP function compromises the growth, fertility and/or viability of the defective organisms, emphasizing the essential nature of GARP-mediated retrograde Transport.
-
retrograde Transport from endosomes to the Trans Golgi Network
Nature Reviews Molecular Cell Biology, 2006Co-Authors: Juan S Bonifacino, Raul RojasAbstract:A subset of intracellular Transmembrane proteins such as acid-hydrolase receptors, processing peptidases and SNAREs, as well as extracellular protein toxins such as Shiga toxin and ricin, undergoes 'retrograde' Transport from endosomes to the Trans-Golgi Network. Here, we discuss recent studies that have begun to unravel the molecular machinery that is involved in this process. We also propose a central role for a 'tubular endosomal Network' in sorting to recycling pathways that lead not only to the Trans-Golgi Network but also to different plasma-membrane domains and to specialized storage vesicles.
-
morphology and dynamics of clathrin gga1 coated carriers budding from the Trans Golgi Network
Molecular Biology of the Cell, 2003Co-Authors: Rosa Puertollano, Evan Eisenberg, Lois E Greene, Nicole N Van Der Wel, P J M Peters, Juan S BonifacinoAbstract:Sorting of Transmembrane proteins and their ligands at various compartments of the endocytic and secretory pathways is mediated by selective incorporation into clathrin-coated intermediates. Previous morphological and biochemical studies have shown that these clathrin-coated intermediates consist of spherical vesicles with a diameter of 60 –100 nm. Herein, we report the use of fluorescent imaging of live cells to demonstrate the existence of a different type of Transport intermediate containing associated clathrin coats. Clathrin and the adaptors GGA1 and adaptor protein-1, labeled with different spectral variants of the green fluorescent protein, are shown to colocalize to the Trans-Golgi Network and to a population of vesicles and tubules budding from it. These intermediates are highly pleiomorphic and move toward the peripheral cytoplasm for distances of up to 10 m with average speeds of 1 m/s. The labeled clathrin and GGA1 cycle on and off membranes with half-times of 10 –20 s, independently of vesicle budding. Our observations indicate the existence of a novel type of Trans-Golgi Network-derived carriers containing associated clathrin, GGA1 and adaptor protein-1 that are larger than conventional clathrin-coated vesicles, and that undergo long-range Translocation in the cytoplasm before losing their coats.
Suzanne R Pfeffer - One of the best experts on this subject based on the ideXlab platform.
-
Transport vesicle tethering at the Trans Golgi Network coiled coil proteins in action
Frontiers in Cell and Developmental Biology, 2016Co-Authors: Pak Yan Cheung, Suzanne R PfefferAbstract:The Golgi complex is decorated with so-called Golgin proteins that share a common feature: a large proportion of their amino acid sequences are predicted to form coiled-coil structures. The possible presence of extensive coiled coils implies that these proteins are highly elongated molecules that can extend a significant distance from the Golgi surface. This property would help them to capture or trap inbound Transport vesicles and to tether Golgi mini-stacks together. This review will summarize our current understanding of coiled coil tethers that are needed for the receipt of Transport vesicles at the Trans Golgi Network (TGN). How do long tethering proteins actually catch vesicles? Golgi-associated, coiled coil tethers contain numerous binding sites for small GTPases, SNARE proteins, and vesicle coat proteins. How are these interactions coordinated and are any or all of them important for the tethering process? Progress toward understanding these questions and remaining, unresolved mysteries will be discussed.
-
a novel assay reveals a role for soluble n ethylmaleimide sensitive fusion attachment protein in mannose 6 phosphate receptor Transport from endosomes to the Trans Golgi Network
Journal of Biological Chemistry, 1997Co-Authors: Christian Itin, Carmen Rancano, Yoshiaki Nakajima, Suzanne R PfefferAbstract:Abstract Soluble N-ethylmaleimide-sensitive fusion protein (NSF) attachment protein (α-SNAP) is a soluble protein that enables the NSF ATPase to associate with membranes and facilitate membrane trafficking events. Although NSF and α-SNAP have been shown to be required for many membrane Transport processes, their role in the Transport of mannose 6-phosphate receptors from endosomes to the Trans Golgi Network was not established. We present here a novel in vitro assay that monitors the Transport of cation-dependent mannose 6-phosphate receptors between endosomes and the Trans Golgi Network. The assay relies on the Trans Golgi Network localization of tyrosine sulfoTransferase and monitors Transport of mannose 6-phosphate receptors engineered to contain a consensus sequence for modification by this enzyme. Using this new assay we show that α-SNAP strongly stimulates Transport in reactions containing limiting amounts of cytosol. Together with α-SNAP, NSF can increase the extent of Transport. These data show that α-SNAP, a soluble component of the SNAP receptor machinery, facilitates Transport from endosomes to the Trans Golgi Network.
-
rab9 functions in Transport between late endosomes and the Trans Golgi Network
The EMBO Journal, 1993Co-Authors: D Lombardi, Yukiko Goda, Thierry Soldati, M A Riederer, Marino Zerial, Suzanne R PfefferAbstract:Rab proteins represent a large family of ras-like GTPases that regulate distinct vesicular Transport events at the level of membrane targeting and/or fusion. We report here the primary sequence, subcellular localization and functional activity of a new member of the rab protein family, rab9. The majority of rab9 appears to be located on the surface of late endosomes. Rab9, purified from Escherichia coli strains expressing this protein, could be prenylated in vitro in the presence of cytosolic proteins and geranylgeranyl diphosphate. In vitro-prenylated rab9 protein, but not C-terminally truncated rab9, stimulated the Transport of mannose 6-phosphate receptors from late endosomes to the Trans Golgi Network in a cell-free system that reconstitutes this Transport step. Rab7, a related rab protein that is also localized to late endosomes, was inactive in the in vitro Transport assay, despite its efficient prenylation and capacity to bind and hydrolyze GTP. These results strongly suggest that rab9 functions in the Transport of mannose 6-phosphate receptors between late endosomes and the Trans Golgi Network. Moreover, our results confirm the observation that a given organelle may bear multiple rab proteins with different biological functions.
