CHARACTERIZATION OF GAMMA-SUBUNITS AND DELTA-SUBUNITS OF CA2+ CALMODULIN-DEPENDENT PROTEIN-KINASE II IN RAT GASTRIC-MUCOSAL CELL-POPULATIONS/

We searched for the occurrence of a Ca2+/calmodulin-dependent protein kinase in rat gastric cell types as a likely member in the chain of ga strin- and muscarinic-receptor-mediated signal transmission. A Ca2+- a nd calmodulin-dependent phosphorylation of major 50, 60 and 100 kDa su bstrates was observed in parietal cell cytosol and a major 60 and 61 k Da protein doublet was found to bind I-125-calmodulin in I-125-calmodu lin-gel overlays. A specific substrate of the multifunctional Ca2+/cal modulin-dependent protein kinase II, autocamtide II, was phosphorylate d in a calmodulin-dependent manner. The specific inhibitor of this enz yme, KN-62, antagonized protein kinase activity. RNA extracted from ga stric mucosal cells was shown to contain sequences of the gamma- and d elta- but not alpha- and beta-subunits of the calmodulin-dependent kin ase II, and mRNA of both subtypes was demonstrated in highly purified parietal, chief and mucous cells. A calmodulin-dependent kinase II com posed of gamma- and delta subunits is a likely mediator of Ca2+-depend ent signal transmission in these populations of gastric cells.