REGULATION OF GROWTH IN A NEOPLASTIC B-CELL LINE BY TRANSFECTED SUBUNITS OF 3',5'-CYCLIC ADENOSINE MONOPHOSPHATE-DEPENDENT PROTEIN-KINASE

cAMP inhibits the proliferation of both normal peripheral blood B and T lymphocytes as well as the proliferation of a human neoplastic B pre cursor cell line (Reh). To positively show that this is mediated via t he the catalytic subunit, C alpha, of cAMP-dependent protein kinase, s tably transfected Reh cell lines overexpressing C alpha were establish ed. This was achived by transfection with a construct confering hygrom y cin resistance together with a zinc-inducible expression of C alpha from the human metallothionine promoter. C alpha transfected clones we re shown to confer a 2- to 2.5-fold zinc-dependent increase in C alpha messenger RNA, immunoreactive C, and phosphotransferase activity. The growth rate of clones transfected with C alpha was retarded, and a zi nc-dependent inhibition of cell proliferation was demonstrated in the presence of a small trigger dose of forskolin. In contrast, overexpres sion of the regulatory subunit Ia had no effect on cAMP-dependent inhi bition of cell proliferation. Furthermore, expression of mutant regula tory subunit I alpha(AB) which renders cAMP-dependent protein kinase u nresponsive to cAMP, clearly protected against the inhibitory effect o f cAMP. These data provides evidence that activation of the C subunit (C alpha) of cAMP-dependent protein kinase mediates the inhibitory act ion of cAMP on cell proliferation in Reh cells.