title: Inhibition of protein tyrosine phosphatase activity in HER14 cells by melittin and Ca2+ ionophore A23187.
abstract: We investigated the effect of melittin and Ca2+ ionophore A23187 on protein tyrosine phosphatase activity in HER14 cells (NIH-3T3 cells transfected with human epidermal growth factor 'EGF' receptor). Cell fractions were used to measure protein tyrosine phosphatase activity in vitro using 32P-labeled poly(Glu/Tyr) (4:1) peptide as a substrate. Treatment of HER14 cells with melittin or with A23187, inhibited protein tyrosine phosphatase activity in the cell sonicate and homogenate, as well as in cytosolic and particulate fractions of these cells. The inhibitory effect of both drugs was prevented by preincubating cells with EGTA (ethyleneglycolbis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid). The cyclooxygenase inhibitor indomethacin enhanced the inhibitory effect of A23187, but not that of melittin. Addition of arachidonic acid to the cells partially prevented the inhibition of protein tyrosine phosphatase activity by melittin or A23187. Preexposure of cells to EGF enhanced the inhibitory effect of melittin--but not that of A23187. Addition of CaCl2, or MgCl2 to the cell homogenate inhibited protein tyrosine phosphatase activity. These results show that protein tyrosine phosphatase activity in HER14 cells is inhibited by melittin and Ca2+ ionophore A23187 through a Ca(2+)-dependent mechanism, and is regulated by arachidonic acid metabolism and EGF receptor activation.
authors.affiliation: Department of Pharmacology, New York University Medical Center, NY 10016.
authors.forename: M
authors.initials: M
authors.lastname: Errasfa
authors.forename: A
authors.initials: A
authors.lastname: Stern
mesh_terms: D016475:3T3 Cells; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology*; D002122:Calcium Chloride / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D015636:Magnesium Chloride / Q000494:pharmacology; D008555:Melitten / Q000494:pharmacology*; D051379:Mice; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D015636:Magnesium Chloride; D008555:Melitten; D016718:Arachidonic Acid; D000001:Calcimycin; D004533:Egtazic Acid; D004815:Epidermal Growth Factor; D017027:Protein Tyrosine Phosphatases; D002122:Calcium Chloride; D007213:Indomethacin