EXPRESSION AND HERBIMYCIN A-SENSITIVE LOCALIZATION OF PP125FAK IN RETINAL GROWTH CONES

PROPER elongation of Xenopus retinal ganglion cell (RGC) axons in the optic tract during development requires intact functioning of beta(1) integrin and tyrosine kinase (TK) activity. The cytoplasmic TK pp125FA K can directly associate with and become activated by beta(1) integrin in cultured fibroblasts. Here we demonstrate the presence of pp125FAK in the developing retina and in cultured retinal neurites, growth con es and filopodia. We show that pp125FAK immunoprecipitated from neural tissue is phosphorylated, and we compare the pattern of FAK and phosp hotyrosine immunolabeling. Finally, we show that the localization of p p125FAK in filopodia depends upon TK activity sensitive to the TK inhi bitor herbimycin A. These results indicate a role for pp125FAK in sign aling the growth of retinal axons.