H-7, a protein kinase C inhibitor, inhibits phorbol ester-caused ornithine decarboxylase induction but fails to inhibit phorbol ester-caused suppression of epidermal growth factor binding in primary cultured mouse epidermal cells.
12-O-tetradecanoylphorbol-13-acetate (TPA) induced ornithine decarboxylase (ODC) and suppressed 125I-epidermal growth factor (EGF) binding in primary cultured mouse epidermal cells. TPA (30 nM)-caused ODC induction was almost completely blocked by 30 microM H-7 [1-(5-isoquinolinylsulfonyl)-2-methylpiperazine], a well known protein kinase C inhibitor, but the same concentration of H-7 failed to restore the 125I-EGF binding suppressed by TPA (10 nM). On the other hand, sphingosine, another protein kinase C inhibitor, blocked not only TPA-caused ODC induction but also TPA-caused suppression of 125I-EGF binding. Concentration-response curves of sphingosine for these two TPA-caused cellular responses were almost identical. 1,2-Diacylglycerols such as 1,2-dioctanoylglycerol (30-300 microM) and 1-oleoyl-2-acetylglycerol (OAG) (30-300 microM) mimicked TPA actions. Similar to the case of TPA, suppression of 125I-EGF binding by OAG was barely inhibited by H-7, whereas sphingosine was more effective in inhibiting the OAG-caused suppression of 125I-EGF binding than was H-7. In TPA (50 nM)-pretreated epidermal cells, TPA (10 nM) failed to suppress 125I-EGF binding. H-7 (30 microM) did not affect TPA (30 nM)-caused translocation of protein kinase C. These results clearly demonstrate the differential inhibition by H-7 of the TPA-caused cellular responses and indicate that TPA-caused suppression of 125I-EGF binding to epidermal cells is mediated through protein kinase C function, which is barely inhibited by H-7.
Nakadate
T
T
Department of Pharmacology, School of Medicine, Keio University, Tokyo, Japan.
Yamamoto
S
S
Aizu
E
E
Nishikawa
K
K
Kato
R
R
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000818:Animals; D002478:Cells, Cultured; D004790:Enzyme Induction / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000378:metabolism*; D004817:Epidermis / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology*; D051379:Mice; D009955:Ornithine Decarboxylase / Q000096:biosynthesis*; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D013110:Sphingosine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D007546:Isoquinolines; D010879:Piperazines; D004815:Epidermal Growth Factor; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D009955:Ornithine Decarboxylase; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate