Integrins regulate NMDA receptor-mediated synaptic currents

Synapses contain high concentrations of integrins, adhesion receptors known to influence the operation of neighboring transmembrane proteins. Evidence that integrins are important for consolidation of long-term potentiation suggests that these adhesion proteins may modulate activities of synaptic glutamate receptors. The present study provides a first test of the possibility that integrins modulate synaptic N-methyl-D-aspartate (NMDA)-type glutamate receptor activities. Excitatory postsynaptic currents (EPSCs) were recorded with whole cell clamp from hippocampal slices in which AMPA-type glutamate receptors and GABA(A) receptors were pharmacologically blocked. Microperfusion of the peptide integrin ligand gly-arg-gly-asp-ser-pro (GRGDSP) caused an approximately twofold increase in the amplitude and duration of NMDA receptor-gated synaptic currents. Control peptides had no effect. Paired-pulse facilitation was unchanged, indicating that the ligand did not modify neurotransmitter release probabilities. Infusion of the Src kinase antagonist PP2 but not the control drug 4-amino-7-phenylpyrazolo[3,4-d] pyrimidine eliminated the enhancing effect of GRGDSP. Integrins regulate Src kinases that are known to phosphorylate NMDA receptors. It is concluded that integrins act through this route to exert potent modulatory effects on the operation of NMDA receptors.