Brain-derived neurotrophic factor stimulates interactions of Shp2 with phosphatidylinositol 3-kinase and Grb2 in cultured cerebral cortical neurons

Shp2, a protein tyrosine phosphatase possessing SH2 domains, is utilized in the intracellular signaling of various growth factors. Shp2 is highly expr essed in the CNS. Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, which also shows high levels of expression in the CNS , exerts neurotrophic and neuromodulatory effects in CNS neurons. We examin ed how BDNF utilizes Shp2 in its signaling pathway in cultured cerebral cor tical neurons. We found that BDNF stimulated coprecipitation of several tyr osine-phosphorylated proteins with anti-Shp2 antibody and that Grb2 and pho sphatidylinositol 3-kinase (PI3-K) were coprecipitated with anti-Shp2 antib ody in response to BDNF. In addition, both anti-Grb2 and anti-PI3-K antibod ies coprecipitated Shp2 in response to BDNF. The BDNF-stimulated coprecipit ation of the tyrosine-phosphorylated proteins, Grb2, and PI3-K with anti-Sh p2 antibody was completely inhibited by K252a, an inhibitor of TrkB recepto r tyrosine kinase. This BDNF-stimulated Shp2 signaling was markedly sustain ed as well as BDNF-induced phosphorylation of TrkB and mitogen-activated pr otein kinases. In PC12 cells stably expressing TrkB, both BDNF and nerve gr owth factor stimulated Shp2 signaling similarly to that by BDNF in cultured cortical neurons. These results indicated that Shp2 shows crosstalk with v arious signaling molecules including Grb2 and PI3-K in BDNF-induced signali ng and that Shp2 may be involved in the regulation of various actions of BD NF in CNS neurons.