Peptide EphB2/CTF2 generated by the gamma-secretase processing of EphB2 receptor promotes tyrosine phosphorylation and cell surface localization of N-methyl-D-aspartate receptors.

Presenilin 1, a protein involved in the development of familial Alzheimer disease, is an important functional component of the gamma-secretase complex that processes many cell surface receptors including the EphB2 tyrosine kinase receptors (Litterst, C., Georgakopoulos, A., Shioi, J., Ghersi, E., Wisniewski, T., Wang, R., Ludwig, A., and Robakis, N. K. (2007) J. Biol. Chem. 282, 16155-16163). Recent evidence reveals that cytosolic peptides produced by the combined metalloproteinase/gamma-secretase processing of cell surface proteins function in signal transduction and protein phosphorylation. Here we show that peptide EphB2/CTF2 released to the cytosol by the gamma-secretase processing of EphB2 receptor, has tyrosine kinase activity, and directly phosphorylates the N-methyl-d-aspartate receptor (NMDAR) subunits in both cell lines and primary neuronal cultures. This phosphorylation occurs in the absence of Src kinases and is resistant to Src inhibitors revealing a novel pathway of NMDAR tyrosine phosphorylation independent of Src activity. EphB2/CTF2, but not a kinase-deficient mutant of EphB2/CTF2, promotes the cell surface expression of NMDAR. Because NMDAR plays central roles in synaptic plasticity and function, our results provide a potential link between the gamma-secretase function of presenilin 1 and learning and memory.