Differentiative action of K252a on protein kinase C and a calcium-unresponsive, phorbol ester/phospholipid-activated protein kinase.
The Triton X-100 extract of the particulate fraction of porcine spleen contains a protein kinase which can be activated by phospholipid and the phorbol ester TPA but does not respond to phospholipid and calcium. The partially purified kinase has a molecular weight of 76 kDa (p76-kinase) and hence is somewhat smaller than the similarly behaving p82-kinase from mouse epidermis and spleen. The p76-kinase shows strong autophosphorylation. The protein kinase inhibitor K252a clearly differentiates between the Ca2+-unresponsive p76-kinase and Ca2+-responsive PKC. At concentrations of up to 5 x 10(-7)M it fails to suppress p76-kinase-catalyzed autophosphorylation and histone phosphorylation, but it inhibits PKC-catalyzed phosphorylation up to 50%. The IC50 values of K252a regarding PKC and the p76-kinase differ by two orders of magnitude. At low concentrations, K252a appears to slightly activate further TPA-activated p76-kinase. It is not able, however, to replace TPA and to stimulate the p76-kinase in the presence of phospholipid alone.
Gschwendt
M
M
Deutsches Krebsforschungszentrum (German Cancer Research Center), Institut für Biochemie, Heidelberg, F.R.G.
Leibersperger
H
H
Marks
F
F
D000818:Animals; D001921:Brain / Q000201:enzymology; D002227:Carbazoles / Q000494:pharmacology*; D004789:Enzyme Activation; D006657:Histones; D026121:Indole Alkaloids; D007700:Kinetics; D051379:Mice; D010743:Phospholipids / Q000494:pharmacology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism; D013154:Spleen / Q000201:enzymology; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D002227:Carbazoles; D006657:Histones; D026121:Indole Alkaloids; D010743:Phospholipids; D047428:Protein Kinase Inhibitors; C049985:staurosporine aglycone; D011494:Protein Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate