Hypofunction of the N-methyl D-aspartate subtype of glutamate receptor (NMDAR) is hypothesized to be a mechanism underlying cognitive dysfunction in individuals with schizophrenia. For the schizophrenia-linked genes NRG1 and ERBB4, NMDAR hypofunction is thus considered a key detrimental consequence of the excessive NRG1-ErbB4 signaling found in people with schizophrenia. However, we show here that neuregulin 1ÎČ-ErbB4 (NRG1ÎČ-ErbB4) signaling does not cause general hypofunction of NMDARs. Rather, we find that, in the hippocampus and prefrontal cortex, NRG1ÎČ-ErbB4 signaling suppresses the enhancement of synaptic NMDAR currents by the nonreceptor tyrosine kinase Src. NRG1ÎČ-ErbB4 signaling prevented induction of long-term potentiation at hippocampal Schaffer collateral-CA1 synapses and suppressed Src-dependent enhancement of NMDAR responses during theta-burst stimulation. Moreover, NRG1ÎČ-ErbB4 signaling prevented theta burst-induced phosphorylation of GluN2B by inhibiting Src kinase activity. We propose that NRG1-ErbB4 signaling participates in cognitive dysfunction in schizophrenia by aberrantly suppressing Src-mediated enhancement of synaptic NMDAR function.Correspondence should be addressed to M.W.S. (mike.salter@utoronto.ca). 5 These authors contributed equally to this work.Note: Supplementary information is available on the Nature Medicine website.
AUTHOR CONTRIBUTIONSG.M.P. designed the project, conducted the hippocampal experiments, analyzed the data and wrote the manuscript. L.V.K. and D.N. carried out and analyzed biochemical experiments. E.K.L. oversaw and analyzed the prefrontal cortex experiments. N.M.G. carried out and analyzed the prefrontal cortex experiments. K.T.Y. maintained, housed and provided ErbB4 knockout mice. All authors participated in revising the manuscript and agreed to the final version. M.W.S. conceived the study, analyzed data, supervised the overall project and wrote the manuscript.
COMPETING FINANCIAL INTERESTSThe authors declare no competing financial interests.Reprints and permissions information is available online at http://npg.nature.com/reprintsandpermissions/. Nat Med. Author manuscript; available in PMC 2012 January 23.
CIHR Author Manuscript
CIHR Author Manuscript
CIHR Author ManuscriptThe NMDAR, a major excitatory ligand-gated ion channel in the central nervous system and a principal mediator of synaptic plasticity, is a multiprotein complex whose core is a heterotetramer comprising two obligate GluN1 subunits and two GluN2(A-D) subunits 1,2 . Proteins associated with the core NMDAR have key roles in trafficking, stability, subunit composition and function of NMDARs 3 . A key process regulating NMDAR activity is phosphorylation by NMDAR-associated kinases. Certain NMDAR-dependent functions, such as ventilation and locomotion, may be independent of NMDAR phosphorylation 4 , whereas phosphorylation-induced upregulation of NMDARs is critical for synaptic plasticity [5][6][7] .A prominent hypothesis for the pathophysiology of schizophrenia is that core symptoms such as...