Interaction of the tyrosine kinase Pyk2 with the N-methyl-D-aspartate receptor complex

The protein tyrosine kinase Pyk2/CAKβ is a key activator of Src, a kinase that among other things upregulates the activity of NMDA-type glutamate receptors. Both kinases have recently been implicated in the induction of long-term potentiation (LTP). Because localization of protein kinases next to their substrate is often crucial for effective regulation, we have investigated how Pyk2 is anchored at the postsynaptic density. Synapse-associated proteins (SAPs), including PSD-95/SAP90 and SAP102, are involved in clustering synaptic glutamate receptors and serve as scaffolding proteins to recruit signaling molecules involved in regulating protein-protein interactions at the post-synapse. Immunoprecipitation studies from rat brain extracts and HEK cell lysates indicate that the interaction between Pyk2 and the NMDA receptor is meditated by PSD-95 and SAP102. These proteins colocalize with Pyk2 at postsynaptic dendritic spines in the cerebral cortex.; We have identified the interacting domains by GST fusion-protein pull-down assays from HEK 293 cell transiently expressing Pyk2 or SAP family members. These results indicate that the C-terminal region of Pyk2 binds to the SH3 domains of the PSD-95, SAP102, and CHAPSYN-110, but not SAP97. However, the structural conformation of the SAPS at the synapse is not well understood. The intramolecular interaction between the SH3 and guanylate kinase (GK) domains of SAP family members suggests that access to the different domains of the SAPs may be regulated for certain binding partners. We are currently investigating the regulation of Pyk2 association with these SAPs and whether other PSD-95 interacting proteins influence Pyk2 access or binding.