scholarly journals The Arf GAP SMAP2 is necessary for organized vesicle budding from the trans-Golgi network and subsequent acrosome formation in spermiogenesis

2013 ◽  
Vol 24 (17) ◽  
pp. 2633-2644 ◽  
Author(s):  
Tomo Funaki ◽  
Shunsuke Kon ◽  
Kenji Tanabe ◽  
Waka Natsume ◽  
Sayaka Sato ◽  
...  
Keyword(s):  
Membrane Vesicles ◽  
Round Spermatid ◽  
Snare Complex ◽  
Coated Vesicle ◽  
Vesicle Budding ◽  
Trans Golgi Network ◽  
Protein Receptor ◽  
Acrosome Formation ◽  
Golgi Network ◽  
Coated Membrane

The trans-Golgi network (TGN) functions as a hub organelle in the exocytosis of clathrin-coated membrane vesicles, and SMAP2 is an Arf GTPase-activating protein that binds to both clathrin and the clathrin assembly protein (CALM). In the present study, SMAP2 is detected on the TGN in the pachytene spermatocyte to the round spermatid stages of spermatogenesis. Gene targeting reveals that SMAP2-deficient male mice are healthy and survive to adulthood but are infertile and exhibit globozoospermia. In SMAP2-deficient spermatids, the diameter of proacrosomal vesicles budding from TGN increases, TGN structures are distorted, acrosome formation is severely impaired, and reorganization of the nucleus does not proceed properly. CALM functions to regulate vesicle sizes, and this study shows that CALM is not recruited to the TGN in the absence of SMAP2. Furthermore, syntaxin2, a component of the soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) complex, is not properly concentrated at the site of acrosome formation. Thus this study reveals a link between SMAP2 and CALM/syntaxin2 in clathrin-coated vesicle formation from the TGN and subsequent acrosome formation. SMAP2-deficient mice provide a model for globozoospermia in humans.

scholarly journals Syntaxin 16’s Newly Deciphered Roles in Autophagy

Cells ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 1655 ◽  
Author(s):  
Bor Luen Tang
Keyword(s):  
Membrane Trafficking ◽  
Functional Redundancy ◽  
Transport Processes ◽  
Snare Complex ◽  
Dual Roles ◽  
Trans Golgi Network ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Golgi Network

Syntaxin 16, a Qa-SNARE (soluble N-ethylmaleimide-sensitive factor activating protein receptor), is involved in a number of membrane-trafficking activities, particularly transport processes at the trans-Golgi network (TGN). Recent works have now implicated syntaxin 16 in the autophagy process. In fact, syntaxin 16 appears to have dual roles, firstly in facilitating the transport of ATG9a-containing vesicles to growing autophagosomes, and secondly in autolysosome formation. The former involves a putative SNARE complex between syntaxin 16, VAMP7 and SNAP-47. The latter occurs via syntaxin 16’s recruitment by Atg8/LC3/GABARAP family proteins to autophagosomes and endo-lysosomes, where syntaxin 16 may act in a manner that bears functional redundancy with the canonical autophagosome Qa-SNARE syntaxin 17. Here, I discuss these recent findings and speculate on the mechanistic aspects of syntaxin 16’s newly found role in autophagy.

scholarly journals A new role for RINT-1 in SNARE complex assembly at the trans-Golgi network in coordination with the COG complex

2013 ◽  
Vol 24 (18) ◽  
pp. 2907-2917 ◽  
Author(s):  
Kohei Arasaki ◽  
Daichi Takagi ◽  
Akiko Furuno ◽  
Miwa Sohda ◽  
Yoshio Misumi ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Trafficking ◽  
Retrograde Transport ◽  
Snare Complex ◽  
Initial Contact ◽  
Complex Assembly ◽  
Trans Golgi Network ◽  
Cog Complex ◽  
Protein Receptor ◽  
Golgi Network

Docking and fusion of transport vesicles/carriers with the target membrane involve a tethering factor–mediated initial contact followed by soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE)–catalyzed membrane fusion. The multisubunit tethering CATCHR family complexes (Dsl1, COG, exocyst, and GARP complexes) share very low sequence homology among subunits despite likely evolving from a common ancestor and participate in fundamentally different membrane trafficking pathways. Yeast Tip20, as a subunit of the Dsl1 complex, has been implicated in retrograde transport from the Golgi apparatus to the endoplasmic reticulum. Our previous study showed that RINT-1, the mammalian counterpart of yeast Tip20, mediates the association of ZW10 (mammalian Dsl1) with endoplasmic reticulum–localized SNARE proteins. In the present study, we show that RINT-1 is also required for endosome-to–trans-Golgi network trafficking. RINT-1 uncomplexed with ZW10 interacts with the COG complex, another member of the CATCHR family complex, and regulates SNARE complex assembly at the trans-Golgi network. This additional role for RINT-1 may in part reflect adaptation to the demand for more diverse transport routes from endosomes to the trans-Golgi network in mammals compared with those in a unicellular organism, yeast. The present findings highlight a new role of RINT-1 in coordination with the COG complex.

scholarly journals P4-ATPase Requirement for AP-1/Clathrin Function in Protein Transport from the trans-Golgi Network and Early Endosomes

2008 ◽  
Vol 19 (8) ◽  
pp. 3526-3535 ◽  
Author(s):  
Ke Liu ◽  
Kavitha Surendhran ◽  
Steven F. Nothwehr ◽  
Todd R. Graham
Keyword(s):  
Protein Transport ◽  
Early Endosome ◽  
Coated Vesicle ◽  
Transport Pathways ◽  
Vesicle Budding ◽  
Trans Golgi Network ◽  
Conditional Allele ◽  
Early Endosomes ◽  
Clathrin Adaptor ◽  
Golgi Network

Drs2p is a resident type 4 P-type ATPase (P4-ATPase) and potential phospholipid translocase of the trans-Golgi network (TGN) where it has been implicated in clathrin function. However, precise protein transport pathways requiring Drs2p and how it contributes to clathrin-coated vesicle budding remain unclear. Here we show a functional codependence between Drs2p and the AP-1 clathrin adaptor in protein sorting at the TGN and early endosomes of Saccharomyces cerevisiae. Genetic criteria indicate that Drs2p and AP-1 operate in the same pathway and that AP-1 requires Drs2p for function. In addition, we show that loss of AP-1 markedly increases Drs2p trafficking to the plasma membrane, but does not perturb retrieval of Drs2p from the early endosome back to the TGN. Thus AP-1 is required at the TGN to sort Drs2p out of the exocytic pathway, presumably for delivery to the early endosome. Moreover, a conditional allele that inactivates Drs2p phospholipid translocase (flippase) activity disrupts its own transport in this AP-1 pathway. Drs2p physically interacts with AP-1; however, AP-1 and clathrin are both recruited normally to the TGN in drs2Δ cells. These results imply that Drs2p acts independently of coat recruitment to facilitate AP-1/clathrin-coated vesicle budding from the TGN.

scholarly journals The Tlg SNARE complex is required for TGN homotypic fusion

2001 ◽  
Vol 155 (6) ◽  
pp. 969-978 ◽  
Author(s):  
Jason H. Brickner ◽  
Jennifer M. Blanchette ◽  
György Sipos ◽  
Robert S. Fuller
Keyword(s):  
Membrane Fusion ◽  
Fusion Reaction ◽  
Snare Complex ◽  
Snare Proteins ◽  
Attachment Protein ◽  
Trans Golgi Network ◽  
Rab Protein ◽  
Protein Receptor ◽  
Golgi Network ◽  
Antibody Inhibition

Using a new assay for membrane fusion between late Golgi/endosomal compartments, we have reconstituted a rapid, robust homotypic fusion reaction between membranes containing Kex2p and Ste13p, two enzymes resident in the yeast trans-Golgi network (TGN). Fusion was temperature, ATP, and cytosol dependent. It was inhibited by dilution, Ca+2 chelation, N-ethylmaleimide, and detergent. Coimmunoisolation confirmed that the reaction resulted in cointegration of the two enzymes into the same bilayer. Antibody inhibition experiments coupled with antigen competition indicated a requirement for soluble NSF attachment protein receptor (SNARE) proteins Tlg1p, Tlg2p, and Vti1p in this reaction. Membrane fusion also required the rab protein Vps21p. Vps21p was sufficient if present on either the Kex2p or Ste13p membranes alone, indicative of an inherent symmetry in the reaction. These results identify roles for a Tlg SNARE complex composed of Tlg1p, Tlg2p, Vti1p, and the rab Vps21p in this previously uncharacterized homotypic TGN fusion reaction.

scholarly journals Actin dynamics coupled to clathrin-coated vesicle formation at the trans-Golgi network

2004 ◽  
Vol 165 (6) ◽  
pp. 781-788 ◽  
Author(s):  
Sebastien Carreno ◽  
Åsa E. Engqvist-Goldstein ◽  
Claire X. Zhang ◽  
Kent L. McDonald ◽  
David G. Drubin
Keyword(s):  
Time Lapse ◽  
Actin Dynamics ◽  
Coated Vesicle ◽  
Cell Cortex ◽  
Actin Assembly ◽  
Trans Golgi Network ◽  
Lysosome Biogenesis ◽  
Diverse Species ◽  
Golgi Network ◽  
Golgi Organization

In diverse species, actin assembly facilitates clathrin-coated vesicle (CCV) formation during endocytosis. This role might be an adaptation specific to the unique environment at the cell cortex, or it might be fundamental, facilitating CCV formation on different membranes. Proteins of the Sla2p/Hip1R family bind to actin and clathrin at endocytic sites in yeast and mammals. We hypothesized that Hip1R might also coordinate actin assembly with clathrin budding at the trans-Golgi network (TGN). Using deconvolution and time-lapse microscopy, we showed that Hip1R is present on CCVs emerging from the TGN. These vesicles contain the mannose 6-phosphate receptor involved in targeting proteins to the lysosome, and the actin nucleating Arp2/3 complex. Silencing of Hip1R expression by RNAi resulted in disruption of Golgi organization and accumulation of F-actin structures associated with CCVs on the TGN. Hip1R silencing and actin poisons slowed cathepsin D exit from the TGN. These studies establish roles for Hip1R and actin in CCV budding from the TGN for lysosome biogenesis.

scholarly journals Adaptor and Clathrin Exchange at the Plasma Membrane andtrans-Golgi Network

2003 ◽  
Vol 14 (2) ◽  
pp. 516-528 ◽  
Author(s):  
Xufeng Wu ◽  
Xiaohong Zhao ◽  
Rosa Puertollano ◽  
Juan S. Bonifacino ◽  
Evan Eisenberg ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Fluorescence Recovery After Photobleaching ◽  
Fluorescence Recovery ◽  
Coated Vesicle ◽  
Coated Pits ◽  
Trans Golgi Network ◽  
Rapid Exchange ◽  
Dynamic Structures ◽  
Golgi Network ◽  
Network Exchange

We previously demonstrated, using fluorescence recovery after photobleaching, that clathrin in clathrin-coated pits at the plasma membrane exchanges with free clathrin in the cytosol, suggesting that clathrin-coated pits are dynamic structures. We now investigated whether clathrin at the trans-Golgi network as well as the clathrin adaptors AP2 and AP1 in clathrin-coated pits at the plasma membrane and trans-Golgi network, respectively, also exchange with free proteins in the cytosol. We found that when the budding of clathrin-coated vesicle is blocked without significantly affecting the structure of clathrin-coated pits, both clathrin and AP2 at the plasma membrane and clathrin and AP1 at thetrans-Golgi network exchange rapidly with free proteins in the cytosol. In contrast, when budding of clathrin-coated vesicles was blocked at the plasma membrane or trans-Golgi network by hypertonic sucrose or K+ depletion, conditions that markedly affect the structure of clathrin-coated pits, clathrin exchange was blocked but AP2 at the plasma membrane and both AP1 and the GGA1 adaptor at the trans-Golgi network continue to rapidly exchange. We conclude that clathrin-coated pits are dynamic structures with rapid exchange of both clathrin and adaptors and that adaptors are able to exchange independently of clathrin when clathrin exchange is blocked.

scholarly journals SNARE complexes of different composition jointly mediate membrane fusion in Arabidopsis cytokinesis

2013 ◽  
Vol 24 (10) ◽  
pp. 1593-1601 ◽  
Author(s):  
Farid El Kasmi ◽  
Cornelia Krause ◽  
Ulrike Hiller ◽  
York-Dieter Stierhof ◽  
Ulrike Mayer ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Membrane Vesicles ◽  
Snare Complex ◽  
The Other ◽  
Division Plane ◽  
Daughter Cells ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Membrane Type ◽  
Cell Division Plane

Membrane fusion is mediated by soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) complexes. Although membrane fusion is required for separating daughter cells in eukaryotic cytokinesis, the SNARE complexes involved are not known. In plants, membrane vesicles targeted to the cell division plane fuse with one another to form the partitioning membrane, progressing from the center to the periphery of the cell. In Arabidopsis, the cytokinesis-specific Qa-SNARE KNOLLE interacts with two other Q-SNAREs, SNAP33 and novel plant-specific SNARE 11 (NPSN11), whose roles in cytokinesis are not clear. Here we show by coimmunoprecipitation that KNOLLE forms two SNARE complexes that differ in composition. One complex is modeled on the trimeric plasma membrane type of SNARE complex and includes, in addition to KNOLLE, the promiscuous Qb,c-SNARE SNAP33 and the R-SNARE vesicle-associated membrane protein (VAMP) 721,722, also involved in innate immunity. In contrast, the other KNOLLE-containing complex is tetrameric and includes Qb-SNARE NPSN11, Qc-SNARE SYP71, and VAMP721,722. Elimination of only one or the other type of KNOLLE complex by mutation, including the double mutant npsn11 syp71, causes a mild or no cytokinesis defect. In contrast, the two double mutants snap33 npsn11 and snap33 syp71 eliminate both types of KNOLLE complexes and display knolle-like cytokinesis defects. Thus the two distinct types of KNOLLE complexes appear to jointly mediate membrane fusion in Arabidopsis cytokinesis.

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