scholarly journals AtVPS45 Complex Formation at thetrans-Golgi Network

2000 ◽  
Vol 11 (7) ◽  
pp. 2251-2265 ◽  
Author(s):  
Diane C. Bassham ◽  
Anton A. Sanderfoot ◽  
Valentina Kovaleva ◽  
Haiyan Zheng ◽  
Natasha V. Raikhel
Keyword(s):  
Secretory Pathway ◽  
Gene Families ◽  
Immunogold Electron Microscopy ◽  
Fusion Reactions ◽  
Attachment Protein ◽  
Sensitive Factor ◽  
Protein Receptors ◽  
Target Membrane ◽  
Functional Complexity ◽  
Golgi Network

The Sec1p family of proteins are thought to be involved in the regulation of vesicle fusion reactions through interaction with t-SNAREs (target soluble N-ethylmaleimide–sensitive factor attachment protein receptors) at the target membrane. AtVPS45 is a member of this family from Arabidopsis thaliana that we now demonstrate to be present on the trans-Golgi network (TGN), where it colocalizes with the vacuolar cargo receptor AtELP. Unlike yeast Vps45p, AtVPS45 does not interact with, or colocalize with, the prevacuolar t-SNARE AtPEP12. Instead, AtVPS45 interacts with two t-SNAREs, AtTLG2a and AtTLG2b, that show similarity to the yeast t-SNARE Tlg2p. AtTLG2a and -b each colocalize with AtVPS45 at the TGN; however, AtTLG2a is in a different region of the TGN than AtTLG2b by immunogold electron microscopy. Therefore, we propose that complexes containing AtVPS45 and either AtTLG2a or -b define functional subdomains of the TGN and may be required for different trafficking events. Among other Arabidopsis SNAREs, AtVPS45 antibodies preferentially coprecipitate AtVTI1b over the closely related isoform AtVTI1a, implying that AtVTI1a and AtVTI1b also have distinct functions within the cell. These data point to a functional complexity within the plant secretory pathway, where proteins encoded by gene families have specialized functions, rather than functional redundancy.

scholarly journals GLUT4 Recycles via a trans-Golgi Network (TGN) Subdomain Enriched in Syntaxins 6 and 16 But Not TGN38: Involvement of an Acidic Targeting Motif

2003 ◽  
Vol 14 (3) ◽  
pp. 973-986 ◽  
Author(s):  
Annette M. Shewan ◽  
Ellen M. van Dam ◽  
Sally Martin ◽  
Tang Bor Luen ◽  
Wanjin Hong ◽  
...  
Keyword(s):  
Cell Surface ◽  
Glucose Transporter ◽  
Adipocyte Differentiation ◽  
Attachment Protein ◽  
Trans Golgi Network ◽  
Sensitive Factor ◽  
Protein Receptors ◽  
Glucose Transporter Glut4 ◽  
Golgi Network ◽  
Endosomal System

Insulin stimulates glucose transport in fat and muscle cells by triggering exocytosis of the glucose transporter GLUT4. To define the intracellular trafficking of GLUT4, we have studied the internalization of an epitope-tagged version of GLUT4 from the cell surface. GLUT4 rapidly traversed the endosomal system en route to a perinuclear location. This perinuclear GLUT4 compartment did not colocalize with endosomal markers (endosomal antigen 1 protein, transferrin) or TGN38, but showed significant overlap with the TGN target (t)-solubleN-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) Syntaxins 6 and 16. These results were confirmed by vesicle immunoisolation. Consistent with a role for Syntaxins 6 and 16 in GLUT4 trafficking we found that their expression was up-regulated significantly during adipocyte differentiation and insulin stimulated their movement to the cell surface. GLUT4 trafficking between endosomes and trans-Golgi network was regulated via an acidic targeting motif in the carboxy terminus of GLUT4, because a mutant lacking this motif was retained in endosomes. We conclude that GLUT4 is rapidly transported from the cell surface to a subdomain of thetrans-Golgi network that is enriched in the t-SNAREs Syntaxins 6 and 16 and that an acidic targeting motif in the C-terminal tail of GLUT4 plays an important role in this process.

scholarly journals Munc18a clusters SNARE-bearing liposomes prior to trans-SNARE zippering

2017 ◽  
Vol 474 (19) ◽  
pp. 3339-3354 ◽  
Author(s):  
Matthew Grant Arnold ◽  
Pratikshya Adhikari ◽  
Baobin Kang ◽  
Hao Xu (徐昊)
Keyword(s):  
Snare Complex ◽  
Binary Interaction ◽  
Fusion Reactions ◽  
Sm Proteins ◽  
Attachment Protein ◽  
Direct Role ◽  
Vesicle Docking ◽  
Sensitive Factor ◽  
Protein Receptors ◽  
Snare Complex Formation

Sec1–Munc18 (SM) proteins co-operate with SNAREs {SNAP [soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein] receptors} to mediate membrane fusion in eukaryotic cells. Studies of Munc18a/Munc18-1/Stxbp1 in neurotransmission suggest that SM proteins accelerate fusion kinetics primarily by activating the partially zippered trans-SNARE complex. However, accumulating evidence has argued for additional roles for SM proteins in earlier steps in the fusion cascade. Here, we investigate the function of Munc18a in reconstituted exocytic reactions mediated by neuronal and non-neuronal SNAREs. We show that Munc18a plays a direct role in promoting proteoliposome clustering, underlying vesicle docking during exocytosis. In the three different fusion reactions examined, Munc18a-dependent clustering requires an intact N-terminal peptide (N-peptide) motif in syntaxin that mediates the binary interaction between syntaxin and Munc18a. Importantly, clustering is preserved under inhibitory conditions that abolish both trans-SNARE complex formation and lipid mixing, indicating that Munc18a promotes membrane clustering in a step that is independent of trans-SNARE zippering and activation.

scholarly journals Yeast vacuolar HOPS, regulated by its kinase, exploits affinities for acidic lipids and Rab:GTP for membrane binding and to catalyze tethering and fusion

2015 ◽  
Vol 26 (2) ◽  
pp. 305-315 ◽  
Author(s):  
Amy Orr ◽  
William Wickner ◽  
Scott F. Rusin ◽  
Arminja N. Kettenbach ◽  
Michael Zick
Keyword(s):  
Protein Sorting ◽  
Rab Gtpase ◽  
Attachment Protein ◽  
Functional Relationships ◽  
Sensitive Factor ◽  
Protein Receptors ◽  
Membrane Tethering ◽  
Rab Effector ◽  
Supporting Membrane ◽  
Acidic Lipids

Fusion of yeast vacuoles requires the Rab GTPase Ypt7p, four SNAREs (soluble N-ethylmaleimide–sensitive factor attachment protein receptors), the SNARE disassembly chaperones Sec17p/Sec18p, vacuolar lipids, and the Rab-effector complex HOPS (homotypic fusion and vacuole protein sorting). Two HOPS subunits have direct affinity for Ypt7p. Although vacuolar fusion has been reconstituted with purified components, the functional relationships between individual lipids and Ypt7p:GTP have remained unclear. We now report that acidic lipids function with Ypt7p as coreceptors for HOPS, supporting membrane tethering and fusion. After phosphorylation by the vacuolar kinase Yck3p, phospho-HOPS needs both Ypt7p:GTP and acidic lipids to support fusion.

scholarly journals Organelle tethering, pore formation and SNARE compensation in the late endocytic pathway

2021 ◽  
Author(s):  
Luther J. Davis ◽  
Nicholas A. Bright ◽  
James R. Edgar ◽  
Michael D.J. Parkinson ◽  
Lena Wartosch ◽  
...  
Keyword(s):  
Pore Formation ◽  
Endocytic Pathway ◽  
Multivesicular Bodies ◽  
Lysosomal Hydrolases ◽  
Attachment Protein ◽  
Body Protein ◽  
Protein Carrier ◽  
Sensitive Factor ◽  
Protein Receptors ◽  
Pore Expansion

To provide insights into the kiss-and-run and full fusion events resulting in endocytic delivery to lysosomes, we investigated conditions causing increased tethering and pore formation between late endocytic organelles in HeLa cells. Knockout of the SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) VAMP7 and VAMP8 showed, by electron microscopy, the accumulation of tethered LAMP (lysosome associated membrane protein)-carrier vesicles around multivesicular bodies, as well as the appearance of ‘hourglass’ profiles of late endocytic organelles attached by filamentous tethers, but did not prevent endocytic delivery to lysosomal hydrolases. Subsequent depletion of the SNARE YKT6 reduced this delivery, consistent with it compensating for the absence of VAMP7 and VAMP8. We also investigated filamentous tethering between multivesicular bodies and enlarged endolysosomes following depletion of CHMP6 (charged multi-vesicular body protein 6) and provide the first evidence that pore formation commences at the edge of tether arrays, with pore expansion required for full membrane fusion.

Roles of the cytoplasmic and transmembrane domains of syntaxins in intracellular localization and trafficking

2001 ◽  
Vol 114 (17) ◽  
pp. 3115-3124 ◽  
Author(s):  
Kazuo Kasai ◽  
Kimio Akagawa
Keyword(s):  
Plasma Membrane ◽  
Transmembrane Domain ◽  
Intracellular Localization ◽  
Transmembrane Domains ◽  
Cytoplasmic Domains ◽  
Immunofluorescence Analysis ◽  
Attachment Protein ◽  
Transport Pathways ◽  
Sensitive Factor ◽  
Protein Receptors

Syntaxins are target-soluble N-ethylmaleimide-sensitive factor-attachment protein receptors (t-SNAREs) involved in docking and fusion of vesicles in exocytosis and endocytosis. Many syntaxin isoforms have been isolated, and each one displays a distinct intracellular localization pattern. However, the signals that drive the specific intracellular localization of syntaxins are poorly understood. In this study, we used indirect immunofluorescence analysis to examine the localization of syntaxin chimeras, each containing a syntaxin transmembrane domain fused to a cytoplasmic domain derived from a different syntaxin. We show that the cytoplasmic domains of syntaxins 5, 6, 7 and 8 have important effects on intracellular localization. We also demonstrate that the transmembrane domain of syntaxin 5 is sufficient to localize the chimera to the compartment expected for wild-type syntaxin 5. Additionally, we find that syntaxins 6, 7 and 8, but not syntaxin 5, are present at the plasma membrane, and that these syntaxins cycle through the plasma membrane by virtue of their cytoplasmic domains. Finally, we find that di-leucine-based motifs in the cytoplasmic domains of syntaxins 7 and 8 are necessary for their intracellular localization and trafficking via distinct transport pathways. Combined, these results suggest that both the cytoplasmic and the transmembrane domains play important roles in intracellular localization and trafficking of syntaxins.

scholarly journals Alterations in platelet secretion differentially affect thrombosis and hemostasis

2018 ◽  
Vol 2 (17) ◽  
pp. 2187-2198 ◽  
Author(s):  
Smita Joshi ◽  
Meenakshi Banerjee ◽  
Jinchao Zhang ◽  
Akhil Kesaraju ◽  
Irina D. Pokrovskaya ◽  
...  
Keyword(s):  
Attachment Protein ◽  
Granule Exocytosis ◽  
Key Points ◽  
Sensitive Factor ◽  
Protein Receptors ◽  
Granule Secretion ◽  
Platelet Secretion

Key Points VAMP isoforms regulate the kinetics and extent of platelet granule exocytosis. Manipulating platelet sensitive factor attachment protein receptors alters granule secretion, which affects the hemostatic balance.

scholarly journals The R-SNARE Endobrevin/VAMP-8 Mediates Homotypic Fusion of Early Endosomes and Late Endosomes

2000 ◽  
Vol 11 (10) ◽  
pp. 3289-3298 ◽  
Author(s):  
Wolfram Antonin ◽  
Claudia Holroyd ◽  
Ritva Tikkanen ◽  
Stefan Höning ◽  
Reinhard Jahn
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Subcellular Fractionation ◽  
Immunogold Electron Microscopy ◽  
Fusion Reactions ◽  
Coated Pits ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Golgi Network

Endobrevin/VAMP-8 is an R-SNARE localized to endosomes, but it is unknown in which intracellular fusion step it operates. Using subcellular fractionation and quantitative immunogold electron microscopy, we found that endobrevin/VAMP-8 is present on all membranes known to communicate with early endosomes, including the plasma membrane, clathrin-coated pits, late endosomes, and membranes of thetrans-Golgi network. Affinity-purified antibodies that block the ability of endobrevin/VAMP-8 to form SNARE core complexes potently inhibit homotypic fusion of both early and late endosomes in vitro. Fab fragments were as active as intact immunoglobulin Gs. Recombinant endobrevin/VAMP-8 inhibited both fusion reactions with similar potency. We conclude that endobrevin/VAMP-8 operates as an R-SNARE in the homotypic fusion of early and late endosomes.

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