Functional Coupling of TRPM2 and NMDARs exacerbates excitotoxicity in ischemic brain injury

<jats:title>SUMMARY</jats:title><jats:p>Excitotoxicity caused by NMDA receptors (NMDARs) is a major cause of neuronal death in ischemic stroke. However, past efforts of directly targeting NMDARs have unfortunately failed in clinical ischemic stroke trials. Here we reveal an unexpected mechanism underlying NMDARs-mediated neurotoxicity, which leads to identification of a novel target and development of an effective therapeutic peptide for ischemic stroke. We show that NMDAR’s excitotoxicity upon ischemic insults is mediated by physical and functional coupling to TRPM2. The physical interaction of TRPM2 with NMDARs results in markedly increase in the surface expression of NMDARs, leading to enhanced NMDAR function and increased neuronal death. We identified a specific NMDAR-interacting domain on TRPM2, and developed a cell-permeable peptide to uncouple TRPM2-NMDARs. The disrupting-peptide protects neurons against ischemic injury <jats:italic>in vitro</jats:italic> and protects mice against ischemic stroke <jats:italic>in vivo</jats:italic>. These findings provide an unconventional strategy to eliminate excitotoxic neuronal death without directly targeting NMDARs.</jats:p><jats:sec><jats:title>HIGHLIGHTS</jats:title><jats:list list-type="bullet"><jats:list-item><jats:p>TRPM2 physically and functionally interacts with NMDARs</jats:p></jats:list-item><jats:list-item><jats:p>Interaction of TRPM2 with NMDARs exacerbates NMDAR’s extrasynaptic excitotoxicity by increasing NMDAR’s surface expression during ischemic injury</jats:p></jats:list-item><jats:list-item><jats:p>TRPM2 recruits PKCγ to the interacting complexes to increase NMDAR’s surface expression</jats:p></jats:list-item><jats:list-item><jats:p>Uncoupling the interaction between TRPM2 and NMDARs with a disrupting peptide (TAT-EE<jats:sub>3</jats:sub>) protects neurons against ischemic stroke <jats:italic>in vitro</jats:italic> and <jats:italic>in vivo</jats:italic></jats:p></jats:list-item></jats:list></jats:sec><jats:sec><jats:title>GRAPHIC ABSTRACT</jats:title><jats:fig id="ufig1" position="float" orientation="portrait" fig-type="figure"><jats:graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="454247v1_ufig1" position="float" orientation="portrait" /></jats:fig><jats:p>TRPM2 excerbates NMDAR’s excitotoxicity by physically and functionally interacting with NMDARs. The disrupting pipette TAT-EE<jats:sub>3</jats:sub> protects neurons against ischemic injury <jats:italic>in vitro</jats:italic> and <jats:italic>in vivo</jats:italic>.</jats:p></jats:sec>