tailieunhanh - Báo cáo Y học: The mechanism of nitrogen monoxide (NO)-mediated iron mobilization from cells NO intercepts iron before incorporation into ferritin and indirectly mobilizes iron from ferritin in a glutathione-dependent manner

Nitrogen monoxide (NO) is a cytotoxic effector molecule produced by macrophages that results in Fe mobilization from tumour target cells which inhibits DNA synthesis and mitochondrial respiration. It is well known that NO has a high affinity for Fe, and we showed that NO-mediated Fe mobilization is markedly potentiated by glutathione (GSH) generated by the hexose monophosphate shunt [Watts, . & Richardson, . (2001) J. Biol. Chem. 276, 4724–4732]. We hypothesized that GSH completes the coordination shell of an NO–Fe complex that is released from the cell. In this report we have extended our studies to further characterize the mechanism. | Eur. J. Biochem. 269 3383-3392 2002 FEBS 2002 doi The mechanism of nitrogen monoxide NO -mediated iron mobilization from cells NO intercepts iron before incorporation into ferritin and indirectly mobilizes iron from ferritin in a glutathione-dependent manner Ralph N. Watts and Des R. Richardson The Iron Metabolism and Chelation Group The Heart Research Institute Camperdown Sydney New South Wales Australia Nitrogen monoxide NO is a cytotoxic effector molecule produced by macrophages that results in Fe mobilization from tumour target cells which inhibits DNA synthesis and mitochondrial respiration. It is well known that NO has a high affinity for Fe and we showed that NO-mediated Fe mobilization is markedly potentiated by glutathione GSH generated by the hexose monophosphate shunt Watts . Richardson . 2001 J. Bull. Chem. 276 4724-4732 . We hypothesized that GSH completes the coordination shell of an NO-Fe complex that is released from the cell. In this report we have extended our studies to further characterize the mechanism of NO-mediated Fe mobilization. Native PAGE 59Fe-autoradiography shows that NO decreased ferritin-59Fe levels in cells prelabelled with 59Fe transferrin. In prelabelled cells ferritin-59Fe levels increased when cells were reincubated with control media between 30 and 240 min. In contrast when cells were reincubated with NO ferritin-59Fe levels decreased 10-fold compared with control cells after a 240-min reincubation. However NO could not remove Fe from ferritin in cell lysates. Our data suggest that NO intercepts 59Fe on route to ferritin and indirectly facilitates removal of 59Fe from the protein. Studies using the GSH-depleting agent L-buthionine- S R -sulphoximine indicated that the reduction in ferritin-59Fe levels via NO was GSH-dependent. Competition experiments with NO and permeable chelators demonstrated that both bind a similar Fe pool. We suggest that NO requires cellular metabolism in .

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