ASSOCIATION OF SYNTAXIN-3 AND VESICLE-ASSOCIATED MEMBRANE-PROTEIN (VAMP) WITH H+ K+-ATPASE-CONTAINING TUBULOVESICLES IN GASTRIC PARIETAL-CELLS/

H+/K+-ATPase is the proton pump in the gastric parietal cell that is r esponsible for gastric acid secretion. Stimulation of acid secretion i s associated with a reorganization of the parietal cells resulting in the incorporation of H+/K+-ATPase from a cytoplasmic membrane pool, th e tubulovesicle compartment, into the apical canalicular membrane. To better characterize the role of membrane trafficking events in the mor phological and physiological changes associated with acid secretion fr om parietal cells, we have characterized the expression and localizati on of soluble N-ethylmaleimide-sensitive factor attachment protein rec eptors (SNAREs) in these cells. Each of the six different SNARE protei ns examined [syntaxins 1 through 4 of 25-kDa synaptosome-associated pr otein, and vesicle-associated membrane protein] were found to be expre ssed in parietal cells. Furthermore, two of these SNAREs, vesicle-asso ciated membrane protein and syntaxin 3, were associated with H+/K+-ATP ase-containing tubulovesicles while the remainder were excluded from t his compartment. The expression of syntaxin 1 and synaptosome-associat ed protein of 25 kDa in parietal cells, two SNAREs previously thought to be restricted to neuroendocrine tissues, suggests that parietal cel ls may utilize membrane trafficking machinery that is similar to that utilized for regulated exocytosis in neurons. Furthermore, the localiz ation of syntaxin 3, a putative target membrane SNARE, to the tubulove sicle compartment indicates that syntaxin 3 may have an alternative fu nction. These observations support a role for intracellular membrane t rafficking events in the regulated recruitment of H+/K+-ATPase to the plasma membrane after parietal cell stimulation.