Association of Signaling Proteins with a Nonmitogenic Heterodimeric Complex Composed of Epidermal Growth Factor Receptor and Kinase-Inactive p185 c- neu "

The functional consequences of heterodimer formation between the epidermal growth factor receptor (EGFr) and the p185^{c-ncu e"} receptor tyrosine kinase include increased mitogenic and transformation potencies. To determine the possible alteration of signal transduction pathways resulting from this heteromeric complex, the capacity of several signaling proteins to associate with the heterodimeric receptors has been assayed. The in vivo interaction with the EGF1/pl^{-neu "c"} heterodimer of several signal transduction proteins, including phospholipasγ1C-yl (γ1C-yl), the p85 subunit of phosphotidylinositol 3-kinase, the ras GTPase activating protein, SHC, NCK, p72RAF, and the tyrosine phosphatase SHPTP2, was measured by coimmunoprecipitation. The binding of these signaling proteins to a complex composed of EGFr and a kinase-inactive form 1f pl81 (pl85K757M) was not impaired, even though the mitogenic and transformation activity of this complex had been abrogated. In addition, the EGF-induced phosphorylation of GAP, p85, and γ1C-yl did not correlate with the dominant-negative action 1f pl85K757M on EGFr function. Thus, substrate association and phosphorylation do not correlate stringently with the mitogenic and transforming activity of this receptor complex, suggesting additional pathways or mechanisms vital to EG1r/p- ^{neu c""e"} heterodimeric signaling.