ERYTHROCYTE THIOL STATUS REGULATES BAND-3 PHOSPHOTYROSINE LEVEL VIA OXIDATION REDUCTION OF BAND 3-ASSOCIATED PHOSPHOTYROSINE PHOSPHATASE/

Oxidative stress-induced tyrosine phosphorylation has been ascribed to activation of phosphotyrosine kinase or to inhibition of phosphotyros ine phosphatase (PTP), We have previously identified a PTP associated with band 3 in the human erythrocyte membrane, a PTP that is normally highly active and prevents the appearance of band 3 phosphotyrosine. H ere we show that treatment of erythrocytes with the thiol-oxidizing ag ent diamide leads to the formation of PTP disulfides (PTP-band 3 mixed disulfides) and inhibition of dephosphorylation, allowing the accumul ation of band 3 phosphotyrosine, Upon reduction of the disulfides, the band 3 phosphotyrosine is dephosphorylated, Erythrocyte thiol alkylat ion by N-ethylmaleimide results in irreversible PTP inhibition and irr eversible phosphorylation, The results are consistent with the notion that alterations in cellular thiol status affect the cell phosphotyros ine status and that oxidative stress-induced tyrosine phosphorylation involves inhibition of PTP. (C) 1997 Federation of European Biochemica l Societies.