INVOLVEMENT OF TYPE 2C PHOSPHATASE IN THE DEPHOSPHORYLATION OF 26 KDAPHOSPHOPROTEIN IN RAT PAROTID ACINAR-CELLS

Posphorylation of three particulate proteins with molecular masses of 34, 26, and 22 kDa was stimulated in the presence of cyclic AMP / 3-is obutyl-1-methylxanthine in saponin-permeabilized rat parotid acinar ce lls. When the particulate fraction isolated from the cells labeled wit h gamma-P-32ATP was incubated at 30 degrees C, dephosphorylation of the 26 kDa phosphoprotein occurred in the presence of Mg2+ or Mn2+. Ok adaic acid had no effect on the Mg2+-dependent dephosphorylation of th e 26 kDa phosphoprotein. Addition of the recombinant type 2C phosphata se, Mg2+-dependent and okadaic acid-insensitive phosphatase, caused a remarkable dephosphorylation of the 26 kDa phosphoprotein. These obser vations strongly suggest type 2C phosphatase is involved in the dephos phorylation of the 26 kDa phosphoprotein. (C) 1994 Academic Press, Inc .