Differential expression of Rab3 isoforms during differentiation of pancreatic acinar cell line AR42J.

Evidence is accumulating that low molecular weight GTPases of the Rab3 subfamily regulate exocytosis in secretory cells. The different isoforms of Rab3 (Rab3AD) probably have opposite roles in secretory processes. In the present study we have investigated differentiation-dependent expression of Rab3 isoforms in the pancreatic acinar carcinoma cell line AR42J. The data show that AR42J cells express all four different isoforms of Rab3. Dexamethasone treatment, which increases the number of secretory granules and secretagogue-induced exocytosis several-fold, was accompanied by down-regulation of Rab3A, Rab3C, and Rab3D mRNA, whereas Rab3B mRNA and Rab3 protein were found up-regulated at the mRNA and protein level, suggesting that Rab3B might be involved in the secretory function of AR42J cells.