A dominant role of the juxtamembrane region of the TrkA nerve growth factor receptor during neuronal cell differentiation

All receptor tyrosine kinases share a common intracellular signaling machinery, including ras activation, whereas cellular responses vary from mitogenesis to cell differentiation. To investigate the structural basis for receptor tyrosine kinase action for nerve growth factor, the juxtamembrane region of TrkA was transferred to a corresponding region of the epidermal growth factor (EGF) receptor. The resulting chimeric receptor contains an additional She site, Tyr(490), in the juxtamembrane region. In transfected PC12 cell lines, neuronal differentiation was observed with EGF treatment, as evidenced by increased neurite extension. The action of the chimeric receptor was correlated with prolonged activation of MAP kinases and a 3-4-fold increase in phosphatidylinositol 3-kinase activity. The effect of the juxtamembrane chimera was dependent upon the She site at Tyr(490), because expression of a chimeric receptor containing a Y490F mutation resulted in a complete loss of neuritogenesis by EGF treatment. These findings indicate that the juxtamembrane region of the TrkA receptor serves as a key functional domain that can confer a dominant effect upon neuronal differentiation.