Okadaic acid, sphingosine, and phorbol ester reversibly modulate heat induction on protein kinase FA/GSK-3 alpha in A431 cells.
Exposure of A431 cells to a rapid and sudden increase from 37 degrees C to 46 degrees C for 30 min could induce an increase in protein level and cellular activity of protein (kinase FA/GSK-3 alpha) up to approximately 200% of control level. However, when cells were first treated with 500 nM tumor promoter phorbol ester TPA at 37 degrees C for 30 min to activate cellular protein kinase C (PKC) or with 400 nM okadaic acid at 37 degrees C for 30 min to inhibit cellular protein phosphatases followed by heat shock at 46 degrees C for another 30 min, the heat induction on kinase FA/GSK-3 alpha was found to be completed blocked. In sharp contrast, when cells were first treated with 1 microM TPA at 37 degrees C for 24 h or with 5 microM sphingosine at 37 degrees C for 30 min to down-regulate cellular PKC, the heat induction on kinase FA/GSK-3 alpha was found to be reversely promoted up to approximately 250% of control level, demonstrating that kinase FA/GSK-3 alpha may not represent a constitutively active/mitogen-inactivated protein kinase as previously conceived. Taken together, the results provide initial evidence that TPA/sphingosine and okadaic acid could reversibly modulate the heat induction on kinase FA/GSK-3 alpha in A431 cells, suggesting that phosphorylation/dephosphorylation mechanisms are involved in the regulation of the heat-shock induction of kinase FA/GSK-3 alpha, representing a new mode of signal transduction for the regulation of this multisubstrate protein kinase and a new mode of signaling pathway modulating the heat-induction process.
Yang
S D
SD
Institute of Biomedical Sciences, National Tsing Hua University, Hsinchu, Taiwan, R.O.C.
Chang
H C
HC
Lee
S C
SC
D000595:Amino Acid Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000096:biosynthesis*; D002273:Carcinogens / Q000494:pharmacology*; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004988:Ethers, Cyclic / Q000494:pharmacology*; D038362:Glycogen Synthase Kinase 3; D006358:Hot Temperature; D006801:Humans; D008969:Molecular Sequence Data; D019319:Okadaic Acid; D015398:Signal Transduction / Q000187:drug effects; D013110:Sphingosine / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D002273:Carcinogens; D004791:Enzyme Inhibitors; D004988:Ethers, Cyclic; D019319:Okadaic Acid; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate