PP2C PHOSPHATASE-ACTIVITY IS COUPLED TO CAMP-MEDIATED PATHWAY IN RAT PAROTID ACINAR-CELLS

A 26 kDa particulate protein is phosphorylated during stimulation of a mylase secretion by a beta-adrenergic agonist in the rat parotid gland . Previous study has shown that PP2C phosphatase is involved in dephos phorylation of this 26 kDa protein [Yokoyama, N. et al. (1994) Biochem . Biophys. Res. Commun. 200, 497-503]. In this study, immunotransblot analysis using anti-PP2C phosphatase antibody showed that PP2C phospha tase was found prominently in the cytosolic fractions and less in secr etory granule membranes. When cells were stimulated by isoproterenol, cytosolic PP2C phosphatase activity increased to 145 % at 5 min and re turned to basal level at 30 min. Forskolin increased PP2C phosphatase activity. H89 inhibited increase of PP2C phosphatase activity followin g beta-adrenergic stimulation. These results suggest that PP2C phospha tase activity is regulated by cAMP-mediated signaling following beta-a drenergic stimulation and participates in dephosphorylation of this 26 kDa protein.