Cyclic AMP-dependent protein kinase stimulates the formation of polyphosphoinositides in the plasma membranes of different blood cells.
Plasma membrane preparations from lymphocytes, platelets and red cells were phosphorylated in the presence of [gamma-32 P]ATP. The dissociated catalytic subunit of cyclic AMP-dependent protein kinase increased the 32P-labelling of proteins and polyphosphoinositides in lymphocyte, platelet and in some red cell membranes. In the majority of red cell membrane preparations the 32P-labelling of proteins and polyphosphoinositides seemed to be stimulated by the catalytic subunit of the endogenous protein kinase, since the phosphorylation was not increased by the addition of the catalytic subunit but it was decreased by the heat-stable inhibitor protein of the protein kinase. Different sets of 32P-labelled proteins were shown by SDS-gel electrophoresis in the membranes of the 3 cell types. A 24000-Mr protein was the only one which was phosphorylated by the catalytic subunit in each membrane.