Cellular localization and stimulation-associated distribution dynamics of syntaxin-1 and syntaxin-3 in gastric parietal cells.
Syntaxins are differentially localized in polarized cells and play an important role in vesicle trafficking and membrane fusion. These soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins are believed to be involved in tubulovesicle trafficking and membrane fusion during the secretory cycle of the gastric parietal cell. We examined the cellular localization and distribution of syntaxin-1 and syntaxin-3 in rabbit parietal cells. Fractionation of gastric epithelial cell membranes showed that syntaxin-1 was more abundant in a fraction enriched in apical plasma membranes, whereas syntaxin-3 was found predominantly in the H,K-ATPase-rich tubulovesicle fraction. We also examined the cellular localization of syntaxins in cultured parietal cells. Parietal cells were infected with CFP-syntaxin-1 and CFP-syntaxin-3 adenoviral constructs. Fluorescence microscopy of live and fixed cells demonstrated that syntaxin-1 was primarily on the apical membrane vacuoles of infected cells, but there was also the expression of syntaxin-1 in a subadjacent cytoplasmic compartment. In resting, non-secreting parietal cells, syntaxin-3 was distributed throughout the cytoplasmic compartment; after stimulation, syntaxin-3 translocated to the apical membrane vacuoles, there co-localizing with H,K-ATPase, syntaxin-1 and F-actin. The differential location of these syntaxin isoforms in gastric parietal cells suggests that these proteins may be critical for maintaining membrane compartment identity and that they may play important, but somewhat different, roles in the membrane recruitment processes associated with secretory activation.
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
Serhan
S
Karvar
Lixin
L
Zhu
James
J
Crothers
Waylan
W
Wong
Mustafa
M
Turkoz
John G
JG
Forte
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000199:Actins / Q000378:metabolism; D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D000954:Antigens, Surface / Q000235:genetics / Q000378:metabolism*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D049452:Green Fluorescent Proteins / Q000235:genetics; D017506:H(+)-K(+)-Exchanging ATPase / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010295:Parietal Cells, Gastric / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D011401:Promoter Regions, Genetic; D050765:Qa-SNARE Proteins; D011817:Rabbits; D050600:SNARE Proteins; D050827:Syntaxin 1; D014162:Transfection; D033921:Vesicular Transport Proteins / Q000378:metabolism*
D000199:Actins; D000954:Antigens, Surface; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins; D006632:Histamine; D017506:H(+)-K(+)-Exchanging ATPase; D015056:1-Methyl-3-isobutylxanthine