Protein kinase C activity of the human myeloma cell line, RPMI 8226, was studied after prepurification on DEAE-cellulose. The total protein kinase activity, eluted at 0.12 M NaCl, was 493 81187-S/asset/equation/feb2001457939081187s-math-si1.gif?v=1&s=8bef760a5bbf299b5dd24f99c66d843edbf9c34f)
cells, but 38% was associated with membranes. The lipid dependence of cytosolic and membrane activities was only 52% and 21%, respectively. This activity increased with time, to as much as 200% for the membrane fraction after 7 days, whereas lipid dependence and the PDBu binding properties were lost. This modified activity was not due to the extinction of a copurifying endogenous inhibitor nor to classical PKC proteolysis. TPA-treatment of these eels is accompanied by a rapid, selective and complete loss of lipid-dependent activity of the cytosol, thus benefiting co-migrating lipid independent activity, with no membrane fraction recovery or PKM formation.
