Down-regulation of protein kinase C activity preferentially attenuates high K(+)-stimulated tyrosine hydroxylase activity in adrenal chromaffin cells cultured with insulin-like growth factor-I.
The purpose of this study was to determine whether the loss of protein kinase C (PKC) from adrenal chromaffin cells affected the enhancement of high K(+)- and forskolin-stimulated tyrosine hydroxylase (tyrosine 3-monooxygenase, EC 1.14.16.2) activity observed in cells treated with insulin-like growth factor-I (IGF-I). Forskolin-stimulated tyrosine hydroxylase activation was not affected by down-regulation of PKC. High K(+)-stimulated tyrosine hydroxylase activity decreased substantially after treating the cells for approximately 18 h with active, but not inactive, phorbol ester (300 nM). After down-regulation of PKC, high K(+)-stimulated tyrosine hydroxylase activity in cells cultured with IGF-I decreased by 61 +/- 5% (n = 14) compared to 36 +/- 8% (n = 14) in cells cultured without IGF-I. These data suggest that PKC is required for the enhancement of high K(+)-stimulated tyrosine hydroxylase activity observed with IGF-I treatment.
Dahmer
M K
MK
Department of Biochemistry, University of Tennessee, Memphis 38163, USA.
D000818:Animals; D002417:Cattle; D002838:Chromaffin System / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D011188:Potassium / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D011493:Protein Kinase C / Q000096:biosynthesis*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
D007334:Insulin-Like Growth Factor I; D014446:Tyrosine 3-Monooxygenase; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D011188:Potassium