Intradomain Interactions in an NMDA Receptor Fragment Mediate N-Glycan Processing and Conformational Sampling

Abstract

Summary The structural and functional roles of highly conserved asparagine-linked (N)-glycans on the extracellular ligand-binding domain (LBD) of the N-methyl-D-aspartate receptors (NMDAR) are poorly understood. We applied solution- and computation-based methods that identified N-glycan mediated intradomain and interglycan interactions. NMR spectra of the GluN1 LBD showed clear signals corresponding to each of the three N-glycans and indicated the reducing end of glycans at N440 and N771 potentially contacted nearby amino acids. Molecular dynamics simulations identified contacts between nearby amino acids and the N440 and N771-glycans that were consistent with the NMR spectra. The distal portions of the N771-glycan also contacted the core residues of the nearby N471 glycan. This result was consistent with MS data indicating the limited N471-glycan core fucosylation and reduced branch processing of the N771-glycan could be explained by interglycan contacts. We discuss a potential role for the GluN1 LBD N-glycans in interdomain contacts formed in NMDA receptors.

Structural and Functional Insights into GluK3-kainate Receptor Desensitization and Recovery

“…Further, iGluRs including GluK3, are extensively N-glycosylated which likely imparts an additional level of regulation of their functions. These glycans have been reported to affect the trafficking, gating properties 16–18 and assembly of iGluRs 19–24 . They likely affect receptor functions by interactions with other synaptic proteins or by mediating inter- and intra-domain interactions in iGluRs 19 affecting receptor functionality 20 .…”

Distinct Cell Surface Expression Patterns of N-Glycosylation Site Mutants of AMPA-Type Glutamate Receptor under the Homo-Oligomeric Expression Conditions

“…The role of N-glycans of GluN1, an NMDA-type glutamate receptor subunit, has been extensively investigated using nuclear magnetic resonance and molecular dynamics analyses. N-glycans on the ligand-binding region of GluN1 have been shown to directly interact with nearby peptides and N-glycans, maintaining its structure and regulating its glycin-binding ability [28,29]. Moreover, since AMPARs are tetrameric ion channels, stoichiometry studies are needed to determine how many and which N-glycans of the four subunits are necessary to maintain AMPAR function.…”

Glycan-Protein Interactions Determine Kinetics ofN-Glycan Remodeling

“…Inverse distances of glycan residues to vicinal hexoses and amino acids (with hydrogen bond donating/accepting side chains) were chosen as features for the MSMs, as described before [13,14]. Each glycan was individually analyzed using a site-specific choice of considered neighboring glycans and protein surface residues for the (inverse) distance calculations (table EV1).…”

“…It is however the single high-mannose type UMOD glycan that mediates encapsulation and aggregation of uropathogens by UMOD filaments via interactions with mannoside-specific pilus lectins from the pathogens [12]. In addition, the rise of computational glycobiology allowed the simulation of glycan-protein interactions [13,14] and indicated that these interactions could reduce the accessibility of the glycan to glycan-processing enzymes [15]. Consequently, glycan-protein interactions are considered a major determinant of N-glycan microheterogeneity [15,16].…”