ENRICHMENT OF RAB11, A SMALL GTP-BINDING PROTEIN, IN GASTRIC PARIETAL-CELLS

Parietal cell secretion of acid requires the coordinated fusion of H+- K+-adenosinetriphosphatase (ATPase)-containing tubulovesicles with a s ecretory canalicular target membrane. We have previously reported the pres ence of rab2 on parietal cell tubulovesicles (L. H. Tang, S. A. S toch, I. M. Modlin, and J. R. Goldenring. Biochen. J. 285: 715-719, 19 92). Since 60% of the small GTP-binding protein sequences obtained fro m parietal cells were >95% homologous with human rab11 (J. R. Goldenri ng, K. R. Shen, H. D. Vaughan, and I. M. Modlin. J. Biol. Chem. 268: 1 8419-18422, 1993), we sought to study rab11 in gastric parietal cells. A complete rab11 sequence was obtained, and the deduced amino acid se quence of rabbit rab11 was identical to that for human. Rab11 mRNA was present throughout the gastrointestinal mucosa. mRNA for both rab11 a nd rab2 were enriched in isolated parietal cells compared with chief c ells. A polyclonal antiserum against rab11 labeled a single 25-kDa ban d in isolated parietal cells. Immunostaining of rat fundic tissue demo nstrated prominent staining of parietal cells. Rab11 staining cosegreg ated with alpha-H+-K+-ATPase staining in enriched preparations of rabb it parietal cell tubulovesicles. These results suggest that rab11 is e nriched in parietal cells and is associated with intracellular tubulov esicles.