Activation of protein kinase C by a tumor-promoting phorbol ester in pancreatic islets |
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Authors: | C J Hubinont L Best A Sener W J Malaisse |
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Institution: | Laboratory of Experimental Medicine, Brussels Free University, Brussels 1000, Belgium |
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Abstract: | Rat pancreatic islet homogenates display protein kinase C activity. This phospholipid-dependent and calcium-sensitive enzyme is activated by diacylglycerol or the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). In the presence of TPA, the Ka for Ca2+ is close to 5 microM. TPA does not affect phosphoinositide turnover but stimulates 32P]- and 3H]choline-labelling of phosphatidylcholine in intact islets. Exogenous phospholipase C stimulates insulin release, in a sustained and glucose-independent fashion. The secretory response to phospholipase C persists in media deprived of CaCl2. It is proposed that protein kinase C participates in the coupling of stimulus recognition to insulin release evoked by TPA, phospholipase C and, possibly, those secretatogues causing phosphoinositide breakdown in pancreatic islets. |
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Keywords: | Protein kinase C Phospholipase C |
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