Amyloid precursor protein activates phosphotyrosine signaling pathway

Amyloid precursor protein (APP) is known to have neurotrophic effects but little information is available on the signaling pathways activated by APP. Since neurotrophic factors activate tyrosine phosphorylation signaling pathway in general, we investigated whether or not APP activates tyrosine phosphorylation pathway. Alpha-secretase derived APP (sAPP alpha) increased the number of neurites per cell and enhanced tyrosine phosphorylation levels on distinct 125 and 200 kDa protein bands. The APP3 19-335 17-mer peptide, which has been reported to be responsible for the neurotrophic effect of sAPP alpha [Jin, L.-W., Ninomiya, H., Roch, J.-M., Schubert, D., Masliah, E., Otero, D.A.C. and Saitoh, T., J. Neurosci., 14 (1994) 5461-5470], increased neurite extension as well as tyrosine phosphorylation on 125 and 200 kDa proteins in a similar manner to sAPP alpha. Both effects were blocked by an antagonist peptide to 17-mer ERMSQ (APP329-333). These results indicate that the 17-mer domain of APP induces tyrosine phosphorylation on distinct proteins under the condition that induces neurite extension.