The exchange of nerve growth factor receptor/Trk and epidermal growth factor receptor (EGFR) phospholipase C gamma (PLC gamma) binding sites resulted in the transfer of their distinct affinities for this Src homology 2 domain-containing protein. Relative to wild-type EGFR, the PLC gamma affinity increase of the EGFR switch mutant EGFR.X enhanced its inositol trisphosphate (IP3) and calcium signals and resulted in a more sustained mitogen-activated protein (MAP) kinase activation and accelerated receptor dephosphorylation. In parallel, EGFR.X exhibited a significantly decreased mitogenic and transforming potential in NIH 3T3 cells. Conversely, the transfer of the EGFR PLC gamma binding site into the Trk cytoplasmic domain context impaired the IP3/calcium signal and attenuated the MAP kinase activation and receptor dephosphorylation, but resulted in an enhancement of the ETR.X exchange mutant mitogenic and oncogenic capacity. Our findings establish the significance of PLC gamma affinity for signal definition, the role of this receptor tyrosine kinase substrate as a negative feedback regulator and the importance of this regulatory function for mitogenesis and its disturbance in oncogenic aberrations.