CDKL5 controls postsynaptic localization of GluN2B-containing NMDA receptors in the hippocampus and regulates seizure susceptibility

Neurobiol Dis. 2017 Oct;106:158-170. doi: 10.1016/j.nbd.2017.07.002. Epub 2017 Jul 6.

Abstract

Mutations in the Cyclin-dependent kinase-like 5 (CDKL5) gene cause severe neurodevelopmental disorders accompanied by intractable epilepsies, i.e. West syndrome or atypical Rett syndrome. Here we report generation of the Cdkl5 knockout mouse and show that CDKL5 controls postsynaptic localization of GluN2B-containing N-methyl-d-aspartate (NMDA) receptors in the hippocampus and regulates seizure susceptibility. Cdkl5 -/Y mice showed normal sensitivity to kainic acid; however, they displayed significant hyperexcitability to NMDA. In concordance with this result, electrophysiological analysis in the hippocampal CA1 region disclosed an increased ratio of NMDA/α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated excitatory postsynaptic currents (EPSCs) and a significantly larger decay time constant of NMDA receptor-mediated EPSCs (NMDA-EPSCs) as well as a stronger inhibition of the NMDA-EPSCs by the GluN2B-selective antagonist ifenprodil in Cdkl5 -/Y mice. Subcellular fractionation of the hippocampus from Cdkl5 -/Y mice revealed a significant increase of GluN2B and SAP102 in the PSD (postsynaptic density)-1T fraction, without changes in the S1 (post-nuclear) fraction or mRNA transcripts, indicating an intracellular distribution shift of these proteins to the PSD. Immunoelectron microscopic analysis of the hippocampal CA1 region further confirmed postsynaptic overaccumulation of GluN2B and SAP102 in Cdkl5 -/Y mice. Furthermore, ifenprodil abrogated the NMDA-induced hyperexcitability in Cdkl5 -/Y mice, suggesting that upregulation of GluN2B accounts for the enhanced seizure susceptibility. These data indicate that CDKL5 plays an important role in controlling postsynaptic localization of the GluN2B-SAP102 complex in the hippocampus and thereby regulates seizure susceptibility, and that aberrant NMDA receptor-mediated synaptic transmission underlies the pathological mechanisms of the CDKL5 loss-of-function.

Keywords: CDKL5; Developmental disorders; Epilepsy; Excitatory synapses; GluN2B; Hippocampus; Ifenprodil; NMDA receptors; SAP102.

MeSH terms

  • Animals
  • Disease Models, Animal
  • Disease Susceptibility / metabolism
  • Excitatory Amino Acid Antagonists / pharmacology
  • Guanylate Kinases / metabolism
  • Hippocampus / drug effects
  • Hippocampus / metabolism*
  • Hippocampus / pathology
  • Kainic Acid
  • Membrane Proteins / metabolism
  • Mice, Inbred C57BL
  • Mice, Knockout
  • N-Methylaspartate
  • Piperidines / pharmacology
  • Post-Synaptic Density / drug effects
  • Post-Synaptic Density / metabolism*
  • Post-Synaptic Density / pathology
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA, Messenger / metabolism
  • Receptors, N-Methyl-D-Aspartate / antagonists & inhibitors
  • Receptors, N-Methyl-D-Aspartate / metabolism*
  • Seizures / metabolism*
  • Seizures / pathology
  • Tissue Culture Techniques

Substances

  • Excitatory Amino Acid Antagonists
  • Membrane Proteins
  • NR2B NMDA receptor
  • Piperidines
  • RNA, Messenger
  • Receptors, N-Methyl-D-Aspartate
  • N-Methylaspartate
  • Protein-Serine-Threonine Kinases
  • CDKL5 protein, mouse
  • Dlgh3 protein, mouse
  • Guanylate Kinases
  • ifenprodil
  • Kainic Acid