pp59fyn and pp62c-yes are enriched in SH-SY5Y neuroblastoma growth cones but do not associate to the 38 kDa protein which complexes with pp60c src and pp60c-srcN.

The tyrosine-specific kinases pp60c-src and pp60c-srcN (pp60src) are slightly enriched and activated in growth cones isolated from neuronally differentiating SH-SY5Y neuroblastoma cells. In the growth cones the two src isoforms are associated with a 38 kDa protein. In this report, we have compared the subcellular distribution of pp59fyn and pp62c-yes with that of pp60src in differentiating SH-SY5Y cells. Like pp60src, the other two tyrosine kinases were slightly enriched and activated in the growth cones as compared to the levels in the cell bodies. The kinase activities were 3- to 4-times higher in growth cones than in cell bodies. However, only pp60src formed a complex with the 38 kDa protein while immunoprecipitation of pp59fyn brought down an additional protein of 90 kDa. This may suggest that these related tyrosine kinases have different substrates and in part mediate different cellular responses in the growth cones of differentiating SH-SY5Y cells.