INHIBITION OF EPIDERMAL GROWTH FACTOR-DEPENDENT PROTEIN-TYROSINE PHOSPHORYLATION BY PHORBOL-MYRISTATE ACETATE IS MEDIATED BY PROTEIN-TYROSINE-PHOSPHATASE ACTIVITY
M. Errasfa et A. Stern, INHIBITION OF EPIDERMAL GROWTH FACTOR-DEPENDENT PROTEIN-TYROSINE PHOSPHORYLATION BY PHORBOL-MYRISTATE ACETATE IS MEDIATED BY PROTEIN-TYROSINE-PHOSPHATASE ACTIVITY, FEBS letters, 339(1-2), 1994, pp. 7-10
Incubation of HER14 cells with phorbol myristate acetate (PMA) decreas
es epidermal growth factor (EGF)-dependent protein tyrosine phosphoryl
ation, except for a 40-kDa MAP kinase II-like protein, whose tyrosine
phosphorylation is further enhanced. The inhibitory effect of PMA on E
GF-dependent protein tyrosine phosphorylation is reversed if cells are
pre-incubated with a combination of Na-3,VO4, and NaF, two known inhi
bitors of protein tyrosine phosphatase activity. Protein tyrosine phos
phatase activity of cell homogenate was measured on immunopurified EGF
receptor, and was found to be enhanced in PMA-treated cells. These da
ta suggest that the inhibitory effect of PMA on EGF-dependent protein
tyrosine phosphorylation in HER14 cells may be mediated by protein tyr
osine phosphatase activity.