Fibroblast growth factor receptor 2 (FGFR2) in brain neurons and retinal pigment epithelial cells act via stimulation of neuroendocrine L-type channels (Ca(v)1,3)

In contrast to the fibroblast growth factor receptor 1 (FGFR1), little is k nown about intracellular signaling of FGFR2, The signaling cascade of FGFR2 was studied using the perforated patch configuration of the patch-clamp te chnique in cultured rat retinal pigment epithelial (RPE) cells that express both FGFR1 and FGFR2, Interaction of signaling proteins was studied using immunoprecipitation techniques with membrane proteins from RPE cells and fr eshly isolated rat brain, When Ba2+ currents through L-type channels were s tudied, extracellular application of bFGF (10 ng/ml) led to a shift of the steady-state activation to more negative values. In 50% of cells, an additi onal increase in maximal current amplitude was observed, This effect was bl ocked by the tyrosine kinase inhibitor lavendustin A (10(-5) M) but was not influenced by the FGFR1 blocker SU5402 (2x10(-5) M) or by the blocker for src-kinase herbimycin A (10(-5) M). Immunoprecipitation of FGFR2 led to cop recipitation of alpha 1D Ca2+ channel subunits and precipitation of alpha 1 D subunits led to coprecipitation of FGFR2, Immunoprecipitation of FGFR1 di d not result in the coprecipitation with alpha 1D Ca2+ channel subunits, Th e coprecipitation results were comparable when using brain tissue and RPE c ells. The alpha 1D subunit-specific band were stained with antiphosphotyros ine antibodies, We conclude that FGFR2 acts via a different signaling casca de than FGFR1, This cascade involves an src-kinase-independent, close funct ional interaction of FGFR2 and the alpha subunit of neuroendocrine L-type c hannels.