Activation by phorbol esters of protein kinase C in MCF-7 human breast cancer cells |
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Authors: | M Issandou F Bayard J M Darbon |
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Affiliation: | Inserm U 168, Department of Endocrinology, Chu Rangueil, Université Paul Sabotier, 31054 Toulouse Cedex, France |
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Abstract: | Exposure of MCF-7 human breast cancer cells to the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) leads to the inhibition of cell proliferation. We investigate here the short-term effects of TPA on subcellular distribution of protein kinase C, and on protein phosphorylation in cultured MCF-7 cells. We report a rapid and dramatic decrease in cytosolic protein kinase C activity after TPA treatment. Only 30% of the enzymatic activity lost in the cytosol was recovered in the particulate fraction. These data suggest that subcellular translocation of protein kinase C is accompanied by a rapid down-regulation of the enzyme (70%). Furthermore, TPA and other protein kinase C activators rapidly induce the phosphorylation of a 28 kDa protein in intact MCF-7 cells. Phorbol esters devoid of tumor-promoting activity are ineffective both for inducing these early biochemical events and for inhibiting cell proliferation. |
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Keywords: | Protein kinase C Phorbol ester Diacylglycerol Protein phosphorylation |
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