Neuropharmacology

Biography

Biography: Martin Horak

Abstract

Glutamate is the principal excitatory neurotransmitter in the mammalian Central Nervous System (CNS). The primary ionotropic glutamate receptor subtypes are the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) and N-methyl-D-aspartate receptors (NMDARs), which are present at the postsynaptic membrane of most excitatory synapses in the mammalian CNS. Our research is focused primarily on NMDARs. Nearly every protein that enters the endoplasmic reticulum lumen becomes N-glycosylated, including NMDARs; the glycans are then trimmed and replaced by more complex and variable glycan structures in the Golgi apparatus. However, the identity of the N-glycans that are present on the NMDARs and their role during the early trafficking and functioning of NMDARs have not yet been investigated in detail. Using biochemistry, confocal and electron microscopy, and electrophysiology in conjunction with a lentivirus-based molecular replacement strategy, we found that NMDARs are released from the ER only when two asparagine residues in the GluN1 subunit (N203 and N368) are N-glycosylated. Interestingly, other N-glycosylation sites in the GluN1, GluN2A, and GluN2B subunits do not play a critical role in the trafficking of NMDARs. Furthermore, we found that removing N-glycans from native NMDARs alters the receptor affinity for glutamate. We also revealed 21 lectins that can immunoprecipitate native NMDARs and AMPARs; moreover, two lectins are specific only for NMDARs. Finally, we showed that several lectins alter the functional properties of native NMDARs. Together, our findings suggest that NMDARs contain a specific composition of glycans that can be targeted in the development of novel pharmacological interventions.