EFFECTS OF H2O2 ON PROTEIN-TYROSINE-PHOSPHATASE ACTIVITY IN HER14 CELLS

Oxidative stress has been implicated in protein phosphorylation and de phosphorylation in cells. In our current studies, H2O2 was shown to re versibly inhibit protein tyrosine phosphatase (PTPase) activity in HER 14 cells. H2O2 (150mM) resulted in 40% inhibition of PTPase activity b y 15 min and recovery from inhibition was nearly complete by 60 min. H 2O2-induced inhibition or recovery of PTPase activity was not affected by cycloheximide, a protein synthesis inhibitor. L-Buthionine-[S,R]-s ulfoximine (BSO), an inhibitor of glutathione synthesis, had no effect on H2O2-induced inhibition of PTPase activity but retarded the recove ry of activity. Epidermal growth factor (EGF) and EGTA, a Ca2+ chelato r, did not influence H2O2-induced inhibition or recovery of PTPase act ivity. These results suggest that at least 40% of fibroblast PTPase ac tivity can be regulated by cellular redox activity.