SOS1 is the guanine nucleotide exchange factor (GEF) for RAS. SOS1, recruited by GRB2 bound to p-SHC1:p-EGFRvIII mutant, is assumed to activate RAS nucleotide exchange from the inactive form (bound to GDP) to an active form (bound to GTP). Although this reaction has not been shown to occur directly for EGFRvIII cancer mutant, activation of RAF/MAP kinase cascade has been demonstrated in cells expressing EGFRvIII (Montgomery et al. 1995).
Stahl, WL, Montgomery, RB, Moscatello, DK, Cooper, JA, Wong, AJ
guanyl-nucleotide exchange factor activity of p-5Y-EGFRvIII:p-Y349,Y350-SHC1:GRB2:SOS1 [plasma membrane]
Gain of function of p-5Y-EGFRvIII:p-Y349,Y350-SHC1:GRB2:SOS1 [plasma membrane]
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