Non-specific stimulatory effects of mastoparan on pancreatic islet nucleoside diphosphokinase activity: dissociation from insulin secretion.
We examined whether mastoparan (MAS)-induced insulin secretion might involve the activation of nucleoside diphosphokinase (NDP kinase), which catalyzes the conversion of GDP to GTP, a known permissive factor for insulin secretion. MAS and MAS 7 (which activate GTP-binding proteins), but not MAS 17 (an inactive analog), stimulated insulin secretion from normal rat islets. In contrast to their specific effects on insulin secretion, MAS, MAS 7 and MAS 17 each stimulated formation of the phosphoenzyme-intermediate of NDP kinase, as well as its catalytic activity. These effects were mimicked by several cationic drugs. Thus, caution is indicated in using MAS to study cellular regulation, since some of its effects appear to be non-specific, and may be due, in part, to its amphiphilic, cationic nature.
Department of Medicine, University of Wisconsin School of Medicine, Madison 53792.
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Kowluru
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Seavey
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Rabaglia
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Metz
D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D036341:Intercellular Signaling Peptides and Proteins; D007515:Islets of Langerhans / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D009701:Nucleoside-Diphosphate Kinase / Q000378:metabolism*; D010455:Peptides; D051381:Rats; D017207:Rats, Sprague-Dawley; D014862:Wasp Venoms / Q000494:pharmacology*
D007328:Insulin; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D014862:Wasp Venoms; C037500:mastoparan; D009701:Nucleoside-Diphosphate Kinase