| Tyrosine phosphorylation of phospholipase Cgamma ( PLCgamma ) , tyrosine phosphatase SHP 2 , Crk , and extracellular regulated kinases 1 and 2 ( Erk1 / 2 ) was registered in response to VEGF A treatment of the PAE / VEGFR 1 cells . ^^^ However , these two mutant VEGFR 1 failed to mediate increased mitogenesis and were unable to stimulate increased tyrosine phosphorylation of SHP 2 , Crk , and Erk1 / 2 , indicating that the mutations lead to a perturbation in VEGF A induced signal transduction . . ^^^ |