THE PROTEIN-KINASE-C, CALCIUM-INDEPENDENT AND CALCIUM-DEPENDENT KINASE-ACTIVITIES OF GLIAL-CELLS IN PRIMARY CULTURE AND SUBCULTURE

The activity of calcium-independent, calcium-dependent and calcium + p hospholipid-dependent (protein kinase C) kinases in cytosol fractions from rat brain glial cells in primary culture and from subcultured ast rocytes and in oligodendrocyte-type 2 astrocyte lineage glia has been measured with histone Type IIIS as substrate. Accurate measurement of protein kinase C activity was achieved only after chromatography of gl ial cytosols on DE-52 anion exchange columns to remove an endogenous i nhibitor, identified tentatively as a phosphatase possibly of the prot ein phosphatase 2A class. The specific activity of protein kinase C in glial cell cytosol increased from 7.5 +/- 0.8 to 37.9 +/- 0.9 nmol P- 32 incorporated/mg protein/10 min within creasing culture age. Protein kinase C activity in glial cytosol was significantly higher when prim ary cultures were grown in a defined medium lacking serum. Astrocyte-c onditioned medium and phorbol esters caused a rapid translocation of g lial cell protein kinase C activity from cytosol to membrane compartme nts. Myelin basic protein and protamine have been compared with histon e as substrates for measurement of calcium-independent, calcium-depend ent and calcium + phospholipid-dependent kinase activities in glial cy tosol.