Title : Role of
Site-Specific N-Glycans Expressed on
GluA2 in the Regulation of Cell Surface Expression of AMPA-Type Glutamate Receptors
Abstract :
- The AMPA-type glutamate receptor ( AMPAR ), which is a tetrameric complex composed of four subunits ( GluA1-4) with several combinations, mediates the majority of rapid excitatory synaptic transmissions in the nervous system
- Cell surface expression levels of AMPAR modulate synaptic plasticity, which is considered one of the molecular bases for learning and memory formation
- To date, a unique trisaccharide (HSO3-3GlcAβ1-3Galβ1-4GlcNAc), human natural killer-1 (HNK-1) carbohydrate, was found expressed specifically on N-linked glycans of GluA2 and regulated the cell surface expression of AMPAR and the spine maturation process
- However, evidence that the HNK-1 epitope on N-glycans of GluA2 directly affects these phenomena is lacking
- Moreover, it is thought that other N-glycans on GluA2 also have potential roles in the regulation of AMPAR functions
- In the present study, using a series of mutants lacking potential N-glycosylation sites ( N256, N370, N406, and N413 ) within GluA2 , we demonstrated that the mutant lacking the N-glycan at N370 strongly suppressed the intracellular trafficking of GluA2 from the endoplasmic reticulum (ER) in HEK293 cells
- Cell surface expression of GluA1 , which is a major subunit of AMPAR in neurons, was also suppressed by co-expression of the GluA2 N370S mutant
- The N370S mutant and wild-type GluA2 were co-immunoprecipitated with GluA1 , suggesting that N370S was properly associated with GluA1
- Moreover, we found that N413 was the main potential site of the HNK-1 epitope that promoted the interaction of GluA2 with N-cadherin , resulting in enhanced cell surface expression of GluA2
- The HNK-1 epitope on N-glycan at the N413 of GluA2 was also involved in the cell surface expression of GluA1
- Thus, our data suggested that site-specific N-glycans on GluA2 regulate the intracellular trafficking and cell surface expression of AMPAR