| Extracellular signal regulated kinase 8 ( Erk 8 ) is a large MAP kinase whose activity is controlled by serum and the c Src non receptor tyrosine kinase . ^^^ Extracellular signal regulated kinase 8 ( Erk 8 ) is a large MAP kinase whose activity is controlled by serum and the c Src non receptor tyrosine kinase . ^^^ By using RET / PTC3 molecules mutated in specific tyrosine autophosphorylation sites , we characterized Tyr ( 981 ) , a known binding site for c Src , as a major determinant of RET / PTC3 induced Erk 8 activation , although , surprisingly , the underlying mechanism did not strictly depend on the activity of Src . ^^^ |