Abstract
We previously demonstrated that RhoA is expressed in rat pancreatic acini and is implicated in the mediation of pancreatic enzyme secretion. In the present study, we aimed to evaluate 1) RhoA and cell to cell adherence protein (E-cadherin and β-catenin) expression in response to cholecystokinin octapeptide ( CCK-8 ), carbamylcholine ( CCh ), or 12-O-tetra-decanoylphorbol 13-acetate ( TPA ), and 2) the interaction between RhoA, E-cadherin and β-catenin in rat pancreatic acini. Isolated pancreatic acini were prepared by collagenase digestion of Sprague-Dawley rat pancreas. Western blotting and immunoprecipitation were performed on extracts of the isolated acinar cells. Increased expression of RhoA, E-cadherin and β-caten in was found 1 to 3 min after treatment with CCK-8 (10-11 to 10-8 M), CCh (10-7 to 10-4 M), or the protein kinase C activator, 12-O-tetradecanoylphorbol 13-acetate (TPA) (10-8 to 10-6 M), and these levels were sustained for up to 30 min. Preloading of pancreatic acini with intracellular Ca2+ chelator, 1, 2-bis (2-aminopenoxy) ethane-N, N, N, N'-tetraacetic acid-AM (BAPTA-AM) at 10-4 M for 10 min abolished the enhancement of RhoA and E-cadherin expression following CCK-8 (10-8 M) stimulation. Immunoprecipitates of β-catenin also contained E-cadherin and RhoA, and the amount of immunocomplex formation increased after CCK-8 and CCh stimulation. The results of our study suggest that β-catenin associates with RhoA and E-cadherin and that these proteins are involved in signaling pathways evoked by CCK-8 and Cch, probably via the action of protein kinase C.
