Selectivity of protein kinase inhibitors in human intact platelets.
The specificity of commonly used protein kinase inhibitors has been evaluated in the intact human platelet. Protein kinase C (PKC) and cyclic AMP-dependent protein kinase (PKA) were activated selectively by treating platelets with phorbol dibutyrate (PDBu) or prostacyclin (PGl2). PKC activity was quantitated by measuring PDBu-specific phosphorylation of a 47,000 molecular weight protein, and PKA activity monitored by measuring prostacyclin-dependent phosphorylation of a 22,000 molecular weight protein. Staurosporine and 1-(5-isoquinolinylsulphonyl)-2-methyl-piperazine (H-7) were found to be non-specific inhibitors in the intact platelet, consistent with their effects on the isolated enzymes. Tamoxifen inhibited PKC activity (IC50 = 80 microM) but increased PKA-dependent protein phosphorylation. These results support the use of human platelets for measuring the specificity of protein kinase inhibitors and indicate that tamoxifen might have value for experimental purposes as a relatively selective PKC inhibitor.
Spacey
G D
GD
Wellcome Research Laboratories, Beckenham, Kent, U.K.
Bonser
R W
RW
Randall
R W
RW
Garland
L G
LG
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000470:Alkaloids / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects* / Q000201:enzymology; D002352:Carrier Proteins / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D007546:Isoquinolines / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000097:blood; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000097:blood; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D019311:Staurosporine; D013629:Tamoxifen / Q000494:pharmacology
D000470:Alkaloids; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D007546:Isoquinolines; D010879:Piperazines; D047428:Protein Kinase Inhibitors; C015482:protein kinase modulator; D013629:Tamoxifen; D015240:Phorbol 12,13-Dibutyrate; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011494:Protein Kinases; D011493:Protein Kinase C; D019311:Staurosporine