title: Localization and function of soluble N-ethylmaleimide-sensitive factor attachment protein-25 and vesicle-associated membrane protein-2 in functioning gastric parietal cells.
abstract: The soluble N-ethylmaleimide-sensitive factor attachment protein of 25 kDa (SNAP-25) plays an important role in vesicle trafficking. Together with vesicle-associated membrane protein-2 (VAMP-2) and syntaxin, SNAP-25 forms a ternary complex implicated in docking and fusion of secretory vesicles with the plasma membrane during exocytosis. These so-called SNARE proteins are believed to regulate tubulovesicle trafficking and fusion during the secretory cycle of the gastric parietal cell. Here we examined the cellular localization and functional importance of SNAP-25 in parietal cell cultures. Adenoviral constructs were used to express SNAP-25 tagged with cyan fluorescent protein, VAMP-2 tagged with yellow fluorescent protein, and SNAP-25 in which the C-terminal 25 amino acids were deleted (SNAP-25 Delta181-206). Membrane fractionation experiments and fluorescent imaging showed that SNAP-25 is localized to the apical plasma membrane. The expression of the mutant SNAP-25 Delta181-226 inhibited the acid secretory response of parietal cells. Also, SNAP Delta181-226 bound poorly in vitro with recombinant syntaxin-1 compared with wild type SNAP-25, indicating that pairing between syntaxin-1 and SNAP-25 is required for parietal cell activation. Dual expression of SNAP-25 tagged with cyan fluorescent protein and VAMP-2 tagged with yellow fluorescent protein revealed a dynamic change in distribution associated with acid secretion. In resting cells, SNAP-25 is at the apical plasma membrane and VAMP-2 is associated with cytoplasmic H,K-ATPase-rich tubulovesicles. After stimulation, the two proteins co-localize on the apical plasma membrane. These data demonstrate the functional significance of SNAP-25 as a SNARE protein in the parietal cell and show the dynamic stimulation-associated redistribution of VAMP-2 from H,K-ATPase-rich tubulovesicles to co-localize with SNAP-25 on the apical plasma membrane.
authors.affiliation: Department of Molecular & Cell Biology, University of California, Berkeley, CA 94720, USA.
authors.forename: Serhan
authors.initials: S
authors.lastname: Karvar
authors.forename: Xuebiao
authors.initials: X
authors.lastname: Yao
authors.forename: James M
authors.initials: JM
authors.lastname: Crothers
authors.forename: Yuechueng
authors.initials: Y
authors.lastname: Liu
authors.forename: John G
authors.initials: JG
authors.lastname: Forte
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005033:Ethylmaleimide / Q000494:pharmacology*; D017353:Gene Deletion; D049452:Green Fluorescent Proteins; D006168:Guinea Pigs; D017506:H(+)-K(+)-Exchanging ATPase / Q000737:chemistry; D008164:Luminescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D008856:Microscopy, Fluorescence; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000502:physiology*; D010295:Parietal Cells, Gastric / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D050683:R-SNARE Proteins; D011817:Rabbits; D051381:Rats; D050600:SNARE Proteins; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; D013997:Time Factors; D033921:Vesicular Transport Proteins
chemical_list: D008164:Luminescent Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050683:R-SNARE Proteins; D050600:SNARE Proteins; C494210:Snap25 protein, rat; C494213:Stx1a protein, rat; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins; D017506:H(+)-K(+)-Exchanging ATPase; D005033:Ethylmaleimide