Evidence for involvement of the protein kinase C pathway in the activation of p37v-mos protein kinase.
Protein kinases are known to undergo phosphorylation to regulate their activity. To determine whether the protein kinase activity of p37v-mos was similarly regulated, we investigated the influence of two well known protein kinases, namely protein kinase C and protein kinase A, on the activity of p37v-mos in vivo. NIH3T3 cells chronically transformed with Moloney murine sarcoma virus 124 were treated with high concentrations (200-400 nM) of phorbol 12-myristate 13-acetate (PMA) for 24-48 h, concentrations known to result in the total loss of protein kinase C by causing its translocation from the cytosol to cell membranes where it is downregulated. PMA treatment caused a drastic decrease in the protein kinase activity of p37v-mos without affecting its steady state level. Similar results were obtained with p85gag-mos expressed in ts110 Mo-MuSV transformed NRK cells. Control treatment with an inactive analogue of PMA, 4-alpha phorbol 12,13-didecanoate, had no effect on the p37v-mos protein kinase activity. Treatment of cells with a direct chemical inhibitor of protein kinase C, H-7 (1-(5-isoquinoline sulfonyl)-2-methylpiperazine dihydrochloride), approximately halved p37v-mos kinase activity, although the drug did not inhibit p37v-mos kinase activity directly in vitro. In contrast to the PMA effect, in vivo activation of protein kinase A by 8-(4-chlorophenylthio)-adenosine 3',5' cyclic monophosphate did not affect p37v-mos protein kinase activity levels. These findings indicate that the protein kinase C pathway but not the protein kinase A pathway modulates v-mos protein kinase activity.
al-Bagdadi
F
F
Department of Molecular Pathology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
Singh
B
B
Arlinghaus
R B
RB
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D015536:Down-Regulation; D004789:Enzyme Activation; D015683:Gene Products, gag / Q000032:analysis; D007546:Isoquinolines / Q000494:pharmacology; D017232:Oncogene Proteins v-mos; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology*; D011494:Protein Kinases / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000032:analysis* / Q000502:physiology; D015682:Retroviridae Proteins, Oncogenic / Q000032:analysis* / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology
D015683:Gene Products, gag; D007546:Isoquinolines; D017232:Oncogene Proteins v-mos; D010879:Piperazines; D015682:Retroviridae Proteins, Oncogenic; D013873:Thionucleotides; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000242:Cyclic AMP; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate