Differential regulation of proline-rich tyrosine kinase 2/cell adhesion kinase beta (PYK2/CAKbeta) and pp125(FAK) by glutamate and depolarization in rat hippocampus

The mechanisms by which stimuli that raise cytosolic free Ca2+ concentrations in neurons can increase protein tyrosine phosphorylation are not known. Using rat hippocampal slices and cortical synaptosomes, we have examined the regulation of two highly related cytoplasmic tyrosine kinases, pp125 focal adhesion kinase (pp125(FAK)) and proline-rich tyrosine kinase 2/cell adhesion kinase beta (PYK2/CAKbeta). Membrane depolarization increased tyrosine phosphorylation of PYK2/CAKbeta and pp125(FAK). These effects were blocked by EGTA or by protein kinase C inhibitors (RO31-8220; GF109203X) and mimicked by ionomycin or phorbol 12-myristate 13-acetate, in the case of pp125(FAK), or their combination in the case of PYK2/CAKbeta. Glutamate and specific agonists of ionotropic (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate and N-methyl-D-aspartate) or metabotropic (trans-1-aminocyclopentane-1,3, -dicarboxylate) glutamate receptors stimulated the phosphorylation of pp125(FAK), but not of PYK2/CAKbeta. Glutamate effects were prevented by GF109203X. Thus, in hippocampal slices, tyrosine phosphorylation of pp125(FAK) and PYK2/CAKbeta are regulated differentially by pathways involving Ca2+ and protein kinase C. pp125(FAK) and PYK2/CAKbeta may provide specific links between neuronal activity, increases in cytosolic Ca2+ and protein tyrosine phosphorylation, which may be important for neuronal survival, and synaptic plasticity.