DIFFERENTIAL CA2-FACTOR AND NERVE GROWTH-FACTOR RECEPTORS( SIGNALING INDUCED BY ACTIVATION OF THE EPIDERMAL GROWTH)

Stimulation by epidermal growth factor (EGF) of NIH3T3 cells overexpre ssing the EGF receptor (EGFR) results in a release of Ca2+ from intern al stores, Ca2+ release is followed by an influx of extracellular calc ium which can be recorded by the influx of the calcium surrogate Mn2+, Both Ca2+ release and Mn2+/Ca2+ influx are inhibited by expression of the dominant negative Asn(17)-Ras mutant and abrogated by microinject ed neutralizing anti-aas antibody Y13-259, whereas microinjection of t he anti-Ras antibody Y13-238 which does not interact with the effector binding domain of pas is without any effect on the EGF-induced Ca2+ t ransient, Neither Asn(17)-Ha-Ras nor the Y13-259 antibody interferes w ith the thapsigargin-induced Mn2+/Ca2+ influx. The nerve growth factor receptor (Trk)-mediated Ca2+ transient was found to be unaffected by the dominant negative Ras mutant or microinjected neutralizing anti-Ra s antibodies, Substitution of the phospholipase C gamma 1 (PLC gamma 1 ) binding site of the EGFR by the PLC gamma binding domain of Trk rend ers the EGFR-induced Ca2+ influx insensitive to the expression of Asn( 17)-Ha-Ras, whereas the Ca2+ signal induced by Trk carrying the PLC bi nding site of EGFR is Ras-dependent and abrogated by the dominant nega tive Ras mutant. It is concluded that the Ca2+ transient induced by th e activated EGFR, not, however, the Ca2+ transient elicited by the act ivated NGFR/Trk, is a Ras-mediated phenomenon and that the role of Ras in regulating EGFR-induced Ca2+ influx depends on the structure of th e PLC gamma binding domain.