Increased expression of pp60c-src protein-tyrosine kinase during peripheral nerve regeneration

Since little is known about the intracellular changes that take place in response to Schwann cell-neuron interactions that occur during neurite outgrowth and myelination, we investigated the expression of a protein-tyrosine kinase, pp60c-src, during peripheral nerve regeneration through a silicone tube. Segments of regenerated nerve, extracted at various times following nerve-transection, showed an induction of in vitro c-src kinase activity as measured by autophosphorylation of immunoprecipitated pp60c-src. This activity occurred at 7 days following nerve transection coincident with the onset of neurite outgrowth in vivo. This kinase activity, which peaked out between 21 and 35 days and decreased thereafter, appeared to be associated with axonal growth and myelination, but not mitogenesis in the tube. Analysis of c-src proteins levels by Western blot showed a similar expression profile as that of the kinase activity. Qualitatively, the expression of an immunoreactive c-src band, migrating slightly slower than pp60, was detected in extracts of regenerating nerve segments as well as in the corresponding L4 and L5 dorsal root ganglia. This protein may be the CNS neuronal-specific form (pp60+) of the c-src protein. In situ hybridi...Continue Reading