| Summary: | 碩士 === 國立清華大學 === 生命科學系 === 88 === Cardiotoxins from Naja nigricollis snake venom, toxin gamma (Tg), exhibits general cytotoxicity. Recently, cardiotoxins have been shown to bind different glycosaminoglycans (GAGs) with different affinity. (Vyas, K. A., et. al. (1998) Biochemistry 37, 4527-4534) Here we ask whether the presence of heparan sulfate on the plasma membrane of target cells is potent for the cytotoxicity of Tg. The wild type Chinese hamster ovary cell (CHO-K1) and two of its mutants defective in the synthesis of either heparan sulfate (pgsD-677) or of all proteoglycans (pgsA-745) were used as target cells. Comparison of mutant cell lines revealed a lower sensitivity towards Tg. Wild type CHO-K1 treated with p-nitrophenyl-O-b-D-xylopyranoside, inhibition of GAGs biosynthesis, appeard to depress susceptibility to toxin. Furthermore, treatment with heparan sulfate lyase resulted in a reduction of cytotoxic effect in wild type cells. Finally, incubation of wild type cells in the presence of sodium chlorate, inhibitor of GAGs sulfation, also showed lower cytotoxicity responsible for Tg. Taken together, these results indicated that cell surface with sulfated heparin sulfate is important for Tg to exert its cytotoxic action.
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