Cysteine residues of SNAP-25 are required for SNARE disassembly and exocytosis, but not for membrane targeting

2001 ◽  
Vol 357 (3) ◽  
pp. 625-634 ◽  
Author(s):  
Philip WASHBOURNE ◽  
Victor CANSINO ◽  
James R. MATHEWS ◽  
Margaret GRAHAM ◽  
Robert D. BURGOYNE ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Lipid Bilayers ◽  
Transmembrane Domain ◽  
Snare Complex ◽  
Cysteine Residues ◽  
Cell Secretion ◽  
Transport Pathway ◽  
Syntaxin 1A ◽  
Golgi Transport ◽  
Membrane Target

The release of neurotransmitter at a synapse occurs via the regulated fusion of synaptic vesicles with the plasma membrane. The fusion of the two lipid bilayers is mediated by a protein complex that includes the plasma membrane target soluble N-ethylmaleimide-sensitive fusion protein (NSF) attachment protein (SNAP) receptors (t-SNAREs), syntaxin 1A and synaptosome-associated protein of 25kDa (SNAP-25), and the vesicle SNARE (v-SNARE), vesicle-associated membrane protein (VAMP). Whereas syntaxin 1A and VAMP are tethered to the membrane by a C-terminal transmembrane domain, SNAP-25 has been suggested to be anchored to the membrane via four palmitoylated cysteine residues. We demonstrate that the cysteine residues of SNAP-25 are not required for membrane localization when syntaxin 1A is present. Analysis of the 7S and 20S complexes formed by mutants that lack cysteine residues demonstrates that the cysteines are required for efficient SNARE complex dissociation. Furthermore, these mutants are unable to support exocytosis, as demonstrated by a PC12 cell secretion assay. We hypothesize that syntaxin 1A serves to direct newly synthesized SNAP-25 through the Golgi transport pathway to the axons and synapses, and that palmitoylation of cysteine residues is not required for targeting, but to optimize interactions required for SNARE complex dissociation.

scholarly journals Novel isoform of syntaxin 1 is expressed in mammalian cells

1997 ◽  
Vol 321 (1) ◽  
pp. 151-156 ◽  
Author(s):  
Mittur N. JAGADISH ◽  
Judy T. TELLAM ◽  
S. Lance MACAULAY ◽  
Keith H. GOUGH ◽  
David E. JAMES ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Amino Acid ◽  
Cdna Clone ◽  
Mammalian Cells ◽  
Transmembrane Domain ◽  
Terminal Region ◽  
Receptor Protein ◽  
Fat Cell ◽  
Syntaxin 1A ◽  
Truncated Protein

Syntaxin 1A has been identified previously as a neural-cell-specific, membrane-anchored receptor protein required for docking and fusion of synaptic vesicles with the presynaptic plasma membrane. Syntaxin 1A consists of 288 amino acid residues including a 265-residue N-terminal region exposed to the cytoplasm and a C-terminal hydrophobic stretch of 23 residues believed to anchor syntaxin to the plasma membrane. Using a human fat-cell library we have isolated a novel cDNA clone of syntaxin 1A containing an insert of 91 bp in codon 226. This insert and subsequent frame shift generated a cDNA that codes for a truncated protein of 260 residues without the C-terminal transmembrane domain characteristic of the syntaxin family. Analysis of the deduced amino acid sequence of the new cDNA clone, termed syntaxin 1C, showed that it was identical for the first 226 residues with the previously described neural syntaxin 1A, and diverged thereafter. The truncated protein lacked the botulinum neurotoxin C cleavage site (Lys253-Ala254), a feature of the syntaxin 1A protein, because of the novel C-terminal domain of 34 residues. The new C-terminal region contained a single cysteine residue and was moderately rich in proline, with three repeats of a PXP motif. The insert occurred within the region encoding the coiled-coil motifs required for interactions with synaptobrevin, α-SNAP (SNAP being soluble N-ethylmaleimide-sensitive factor attachment protein) and n-Sec1/Munc-18 (n-Sec1 being the rat brain homologue of yeast Sec1p and Munc-18 the mammalian homologue of Caenorhabditis elegans unc-18, but five residues outside the domain previously mapped as being required for binding SNAP-25. Interaction studies in vitro suggested that unlike syntaxin 1A, which binds to both Munc-18a and -18b, syntaxin 1C binds only to Munc-18b. The new isoform syntaxin 1C, which might be generated by alternative splicing of the syntaxin 1 gene, was expressed in several human tissues, including brain. Immunoprecipitation and immunoblotting with the monoclonal antibody HPC-1 and a polyclonal antibody raised against a peptide corresponding to the unique C-terminal 35 residues of syntaxin 1C failed to detect syntaxin 1C at the protein level in extracts of muscle, fat or brain.

scholarly journals The Polybasic Juxtamembrane Region of Sso1p Is Required for SNARE Function In Vivo

2005 ◽  
Vol 4 (12) ◽  
pp. 2017-2028 ◽  
Author(s):  
Jeffrey S. Van Komen ◽  
Xiaoyang Bai ◽  
Travis L. Rodkey ◽  
Johanna Schaub ◽  
James A. McNew
Keyword(s):  
Plasma Membrane ◽  
Membrane Fusion ◽  
Transmembrane Domain ◽  
Transmembrane Helix ◽  
Specific Interaction ◽  
Coiled Coil ◽  
Snare Complex ◽  
Juxtamembrane Region

ABSTRACT Exocytosis in Saccharomyces cerevisiae requires the specific interaction between the plasma membrane t-SNARE complex (Sso1/2p;Sec9p)and a vesicular v-SNARE (Snc1/2p). While SNARE proteins drive membrane fusion, many aspects of SNARE assembly and regulation are ill defined. Plasma membrane syntaxin homologs (including Sso1p) contain a highly charged juxtamembrane region between the transmembrane helix and the“ SNARE domain” or core complex domain. We examined this region in vitro and in vivo by targeted sequence modification, including insertions and replacements. These modified Sso1 proteins were expressed as the sole copy of Sso in S. cerevisiae and examined for viability. We found that mutant Sso1 proteins with insertions or duplications show limited function, whereas replacement of as few as three amino acids preceding the transmembrane domain resulted in a nonfunctional SNARE in vivo. Viability is also maintained when two proline residues are inserted in the juxtamembrane of Sso1p, suggesting that helical continuity between the transmembrane domain and the core coiled-coil domain is not absolutely required. Analysis of these mutations in vitro utilizing a reconstituted fusion assay illustrates that the mutant Sso1 proteins are only moderately impaired in fusion. These results suggest that the sequence of the juxtamembrane region of Sso1p is vital for function in vivo, independent of the ability of these proteins to direct membrane fusion.

scholarly journals MT1-MMP recruits the ER-Golgi SNARE Bet1 for efficient MT1-MMP transport to the plasma membrane

2019 ◽  
Vol 218 (10) ◽  
pp. 3355-3371 ◽  
Author(s):  
Takuya Miyagawa ◽  
Kana Hasegawa ◽  
Yoko Aoki ◽  
Takuya Watanabe ◽  
Yuka Otagiri ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Intracellular Transport ◽  
Early Stage ◽  
Snare Complex ◽  
Invasion And Metastasis ◽  
Golgi Transport ◽  
Syntaxin 4 ◽  
Membrane Type

Metastasis is a major cause of cancer-related death. Membrane type 1–matrix metalloproteinase (MT1-MMP) is a critical protease for local invasion and metastasis. MT1-MMP is synthesized in the endoplasmic reticulum (ER) and transported in vesicles to invadopodia, specialized subdomains of the plasma membrane, through secretory and endocytic recycling pathways. The molecular mechanism underlying intracellular transport of MT1-MMP has been extensively studied, but is not fully understood. We show that MT1-MMP diverts the SNARE Bet1 from its function in ER-Golgi transport, to promote MT1-MMP trafficking to the cell surface, likely to invadopodia. In invasive cells, Bet1 is localized in MT1-MMP–positive endosomes in addition to the Golgi apparatus, and forms a novel SNARE complex with syntaxin 4 and endosomal SNAREs. MT1-MMP may also use Bet1 for its export from raft-like structures in the ER. Our results suggest the recruitment of Bet1 at an early stage after MT1-MMP expression promotes the exit of MT1-MMP from the ER and its efficient transport to invadopodia.

scholarly journals Geranylgeranylated Snares Are Dominant Inhibitors of Membrane Fusion

2000 ◽  
Vol 151 (2) ◽  
pp. 453-466 ◽  
Author(s):  
Eric Grote ◽  
Misuzu Baba ◽  
Yoshinori Ohsumi ◽  
Peter J. Novick
Keyword(s):  
Plasma Membrane ◽  
Transmembrane Domain ◽  
Secretory Vesicle ◽  
Snare Complex ◽  
Snare Proteins ◽  
Wild Type ◽  
Protein Receptor ◽  
High Level ◽  
Order Complexes ◽  
Mutant Cells

Exocytosis in yeast requires the assembly of the secretory vesicle soluble N-ethylmaleimide–sensitive factor attachment protein receptor (v-SNARE) Sncp and the plasma membrane t-SNAREs Ssop and Sec9p into a SNARE complex. High-level expression of mutant Snc1 or Sso2 proteins that have a COOH-terminal geranylgeranylation signal instead of a transmembrane domain inhibits exocytosis at a stage after vesicle docking. The mutant SNARE proteins are membrane associated, correctly targeted, assemble into SNARE complexes, and do not interfere with the incorporation of wild-type SNARE proteins into complexes. Mutant SNARE complexes recruit GFP-Sec1p to sites of exocytosis and can be disassembled by the Sec18p ATPase. Heterotrimeric SNARE complexes assembled from both wild-type and mutant SNAREs are present in heterogeneous higher-order complexes containing Sec1p that sediment at greater than 20S. Based on a structural analogy between geranylgeranylated SNAREs and the GPI-HA mutant influenza virus fusion protein, we propose that the mutant SNAREs are fusion proteins unable to catalyze fusion of the distal leaflets of the secretory vesicle and plasma membrane. In support of this model, the inverted cone–shaped lipid lysophosphatidylcholine rescues secretion from SNARE mutant cells.

scholarly journals Contribution of the Cytoplasmic Determinants of Vpu to the Expansion of Virus-Containing Compartments in HIV-1-Infected Macrophages

2019 ◽  
Vol 93 (11) ◽  
Author(s):  
Olivier Leymarie ◽  
Leslie Lepont ◽  
Margaux Versapuech ◽  
Delphine Judith ◽  
Sophie Abelanet ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Viral Particle ◽  
Transmembrane Domain ◽  
Immune Surveillance ◽  
Restriction Factor ◽  
Viral Particles ◽  
Protein Functions ◽  
Specific Accumulation ◽  
Model Cell ◽  
Hiv 1

ABSTRACTHIV-1 infection of macrophages leads to the sequestration of newly formed viruses in intracellular plasma membrane-connected structures termed virus-containing compartments (VCCs), where virions remain infectious and hidden from immune surveillance. The cellular restriction factor bone marrow stromal cell antigen 2 (BST2), which prevents HIV-1 dissemination by tethering budding viral particles at the plasma membrane, can be found in VCCs. The HIV-1 accessory protein Vpu counteracts the restriction factor BST2 by downregulating its expression and removing it from viral budding sites. Numerous studies described these Vpu countermeasures in CD4+T cells or model cell lines, but the interplay between Vpu and BST2 in VCC formation and HIV-1 production in macrophages is less explored. Here, we show that Vpu expression in HIV-1-infected macrophages enhances viral release. This effect is related to Vpu’s ability to circumvent BST2 antiviral activity. We show that in absence of Vpu, BST2 is enriched in VCCs and colocalizes with capsid p24, whereas Vpu expression significantly reduces the presence of BST2 in these compartments. Furthermore, our data reveal that BST2 is dispensable for the formation of VCCs and that Vpu expression impacts the volume of these compartments. This Vpu activity partly depends on BST2 expression and requires the integrity of the Vpu transmembrane domain, the dileucine-like motif E59XXXLV64and phosphoserines 52 and 56 of Vpu. Altogether, these results highlight that Vpu controls the volume of VCCs and promotes HIV-1 release from infected macrophages.IMPORTANCEHIV-1 infection of macrophages leads to the sequestration of newly formed viruses in virus-containing compartments (VCCs), where virions remain infectious and hidden from immune surveillance. The restriction factor BST2, which prevents HIV-1 dissemination by tethering budding viral particles, can be found in VCCs. The HIV-1 Vpu protein counteracts BST2. This study explores the interplay between Vpu and BST2 in the viral protein functions on HIV-1 release and viral particle sequestration in VCCs in macrophages. The results show that Vpu controls the volume of VCCs and favors viral particle release. These Vpu functions partly depend on Vpu’s ability to antagonize BST2. This study highlights that the transmembrane domain of Vpu and two motifs of the Vpu cytoplasmic domain are required for these functions. These motifs were notably involved in the control of the volume of VCCs by Vpu but were dispensable for the prevention of the specific accumulation of BST2 in these structures.

scholarly journals Visualization of the exocyst complex dynamics at the plasma membrane of Arabidopsis thaliana

2013 ◽  
Vol 24 (4) ◽  
pp. 510-520 ◽  
Author(s):  
Matyáš Fendrych ◽  
Lukáš Synek ◽  
Tamara Pečenková ◽  
Edita Janková Drdová ◽  
Juraj Sekereš ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Fluorescent Protein ◽  
Complex Dynamics ◽  
Active Regions ◽  
Snare Complex ◽  
Epifluorescence Microscopy ◽  
Rab Gtpases ◽  
Exocyst Complex ◽  
Protein Receptor ◽  
Outer Domain

The exocyst complex, an effector of Rho and Rab GTPases, is believed to function as an exocytotic vesicle tether at the plasma membrane before soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) complex formation. Exocyst subunits localize to secretory-active regions of the plasma membrane, exemplified by the outer domain of Arabidopsis root epidermal cells. Using variable-angle epifluorescence microscopy, we visualized the dynamics of exocyst subunits at this domain. The subunits colocalized in defined foci at the plasma membrane, distinct from endocytic sites. Exocyst foci were independent of cytoskeleton, although prolonged actin disruption led to changes in exocyst localization. Exocyst foci partially overlapped with vesicles visualized by VAMP721 v-SNARE, but the majority of the foci represent sites without vesicles, as indicated by electron microscopy and drug treatments, supporting the concept of the exocyst functioning as a dynamic particle. We observed a decrease of SEC6–green fluorescent protein foci in an exo70A1 exocyst mutant. Finally, we documented decreased VAMP721 trafficking to the plasma membrane in exo70A1 and exo84b mutants. Our data support the concept that the exocyst-complex subunits dynamically dock and undock at the plasma membrane to create sites primed for vesicle tethering.

Identification of a di-leucine motif within the C terminus domain of the Menkes disease protein that mediates endocytosis from the plasma membrane

1999 ◽  
Vol 112 (11) ◽  
pp. 1721-1732 ◽  
Author(s):  
M.J. Francis ◽  
E.E. Jones ◽  
E.R. Levy ◽  
R.L. Martin ◽  
S. Ponnambalam ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Golgi Apparatus ◽  
Transmembrane Domain ◽  
Menkes Disease ◽  
Cytoplasmic Domain ◽  
Endocytic Pathway ◽  
Site Directed Mutagenesis ◽  
Trans Golgi Network ◽  
C Terminus ◽  
Golgi Network

The protein encoded by the Menkes disease gene (MNK) is localised to the Golgi apparatus and cycles between the trans-Golgi network and the plasma membrane in cultured cells on addition and removal of copper to the growth medium. This suggests that MNK protein contains active signals that are involved in the retention of the protein to the trans-Golgi network and retrieval of the protein from the plasma membrane. Previous studies have identified a signal involved in Golgi retention within transmembrane domain 3 of MNK. To identify a motif sufficient for retrieval of MNK from the plasma membrane, we analysed the cytoplasmic domain, downstream of transmembrane domain 7 and 8. Chimeric constructs containing this cytoplasmic domain fused to the reporter molecule CD8 localised the retrieval signal(s) to 62 amino acids at the C terminus. Further studies were performed on putative internalisation motifs, using site-directed mutagenesis, protein expression, chemical treatment and immunofluorescence. We observed that a di-leucine motif (L1487L1488) was essential for rapid internalisation of chimeric CD8 proteins and the full-length Menkes cDNA from the plasma membrane. We suggest that this motif mediates the retrieval of MNK from the plasma membrane into the endocytic pathway, via the recycling endosomes, but is not sufficient on its own to return the protein to the Golgi apparatus. These studies provide a basis with which to identify other motifs important in the sorting and delivery of MNK from the plasma membrane to the Golgi apparatus.

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