NMDA Receptor Autoantibodies in Autoimmune Encephalitis Cause a Subunit-Specific Nanoscale Redistribution of NMDA Receptors

Abstract

Summary: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a severe neuropsychiatric disorder mediated by autoantibodies against the GluN1 subunit of the NMDAR. Patients’ antibodies cause cross-linking and internalization of NMDAR, but the synaptic events leading to depletion of NMDAR are poorly understood. Using super-resolution microscopy, we studied the effects of the autoantibodies on the nanoscale distribution of NMDAR in cultured neurons. Our findings show that, under control conditions, NMDARs form nanosized objects and patients’ antibodies increase the clustering of synaptic and extrasynaptic receptors inside the nano-objects. This clustering is subunit specific and predominantly affects GluN2B-NMDARs. Following internalization, the remaining surface NMDARs return to control clustering levels but are preferentially retained at the synapse. Monte Carlo simulations using a model in which antibodies induce NMDAR cross-linking and disruption of interactions with other proteins recapitulated these results. Finally, activation of EphB2 receptor partially antagonized the antibody-mediated disorganization of the nanoscale surface distribution of NMDARs. : Ladépêche et al. visualize NMDAR nano-organization in a model of NMDAR encephalitis. NMDARs organize in nano-objects, which show a time-dependent and subunit-specific change in their size and content upon patients’ antibody treatment. EphB2 receptor activation, which stabilizes NMDAR-protein interactions, partially antagonizes the alteration of NMDAR nano-organization caused by patients’ antibodies. Keywords: NMDAR encephalitis, antibody, autoimmune, pathogenic mechanism, STORM, super-resolution microscopy, synaptic proteins, GluN2 subunits