Protein kinase Calpha is implicated in cholecystokinin-induced activation of 70-kd S6 kinase in AR42J cells.

OBJECTIVES:We showed previously that cholecystokinin (CCK)-induced 70-kd S6 kinase activation is partly mediated by protein kinase C in pancreatic acinar AR42J cells. Here, we examined which isoform of is involved in this process. METHODS:AR42J cells were infected with adenovirus vectors carrying the kinase-deficient alpha, delta, and epsilon isoforms of the dominant-negative form of the 85-kd regulatory subunit of phosphatidylinositol (PI) 3-kinase, and the dominant-negative form of Sos. CCK-induced p70 S6 kinase activation was determined in AR42J cells infected with these adenovirus vectors. RESULTS:CCK-induced p70 S6 kinase activity was significantly reduced in cells overexpressing the dominant-negative p85 subunit of PI 3-kinase but not in cells overexpressing dominant-negative Sos or beta-galactosidase. CCK-induced p70 S6 kinase activity was inhibited in parallel with the expression levels of kinase-deficient whereas it was unaffected by the expression of kinase-deficient or is implicated in CCK-induced activation of p70 S6 kinase in AR42J cells.

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