Inhibition of Epidermal Growth Factor Receptor Biosynthesis Caused by the src Oncogene Product, pp60^v-src

Abstract

We have previously shown that an intracellular mechanism down regulates epidermal growth factor (EGF) receptor levels in rodent fibroblasts transformed by the src oncogene (W. J. Wasilenko, L. K. Shawver, and M. J. Weber, J. Cell. Physiol. 131:450-457, 1987). We now report that this down regulation is due to an inhibition of EGF receptor biosynthesis. With Rat-1 (R1) cells infected with a temperature-sensitive src mutant, we found that ¹²⁵I-labeled EGF binding to cells began to decrease soon after the activation of pp60^v-src by shift down to the permissive temperature for transformation. This effect of src on EGF receptors was reversible. Pulse-chase studies with [³⁵S]methionine-labeled cells revealed that the tyrosine protein kinase activity of pp60^v-src had little if any effect on EGF receptor degradation rate. By contrast, the expression of pp60^v-src caused a large reduction in the apparent rate of EGF receptor biosynthesis. Northern (RNA) blot analysis demonstrated that pp60^v-src also caused marked reductions in the steady-state level of EGF receptor mRNA. These data indicate that one way the expression of the src oncogene can affect the machinery of growth control is by affecting the expression of specific genes for growth factor receptors.