1986•Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)Requires access
Epidermal growth factor (EGE) reduces the phosphorylation of a 50KD protein in A431 cells
Richard Selinfreund, Perry Lin, Walker Wharton
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Abstract
Previous reports have shown that EGF induces the phosphorylation of the EGF receptor. In the present study the authors report the EGF sensitive reduction of the phosphorylation of a 50KD protein in solubilized A431 membranes. Membranes were prepared from A431 cell using a technique previously reported. Phosphorylation as determined by PAGE and autoradiography demonstrated an EGF sensitive phosphorylation of the EGF receptor at 170 and 150KD. A 50KD protein was phosphorylated in the absence of EGF. The presence of EGF decreased the phosphorylation of a 50KD protein. Prephosphorylation of the 50KD protein and the addition of EGF for increasing periods of time demonstrated no change in the phosphorylation level. These data suggest: (1) EGF reduces the phosphorylation of a 50KD protein. (2) The addition of EGF for increasing time periods with no change in the 50KD phosphorylation level might indicate that EGF is inhibiting a kinase rather than stimulating a phosphatase.