Abstract

The N-terminal domain (NTD) of alpha-amino-3-hydroxy-5-methylisoxazolepropionate (AMPA) and kainate glutamate receptors plays an important role in controlling subtype specific receptor assembly. To identify NTD subdomains involved in this process we generated AMPA glutamate receptor 3 (GluR3) mutants having intra-NTD substitutions with the corresponding regions of the kainate receptor GluR6 and tested their ability to form functional heteromers with wild-type subunits. The chimeric design was based on the homology of the NTD to the NTD of the metabotropic GluR1, shown to form two globular lobes and to assemble in dimers. Accordingly, the NTD was divided into four regions, termed here N1-N4, of which N1 and N3 correspond to the regions forming lobe-1 and N2 and N4 to those forming lobe-2. Substituting N1 or N3 impaired functional heteromerization but allowed protein-protein interactions. Conversely, exchanging N2 or N4 preserved functional heteromerization, although it significantly decreased homomeric activity, indicating a role in subunit folding. Moreover, a deletion in GluR3 corresponding to the hotfoot mouse mutation of the glutamate receptor delta2, covering part of N2, N3, and N4, impaired both homomeric and heteromeric oligomerization, thus explaining the null-like mouse phenotype. Finally, computer modeling suggested that the dimer interface, largely formed by N1, is highly hydrophobic in GluR3, whereas in GluR6 it contains electrostatic interactions, hence offering an explanation for the subtype assembly specificity conferred by this region. N3, however, is positioned perpendicular to the dimer interface and therefore may be involved in secondary interactions between dimers in the assembled tetrameric receptor.

Highlights

  • Glutamate, the major excitatory neurotransmitter, activates two receptor families: metabotropic glutamate receptors,1 which are coupled to G-proteins, and ionotropic

  • Our data fit a model in which iGluRs assemble as dimer-of-dimers in a two-step basic process: 1) two monomers associate at their Nterminal domain (NTD) to form dimers; and 2) two dimers undergo a secondary dimerization at the glutamate-binding domains and at the membrane domains to form the tetramer, which is stabilized by secondary NTD interactions

  • glutamate receptor 3 (GluR3)/GluR6 Intra-NTD Chimeric Design—Applying the approach taken in our previous study [8] we further investigated the contribution of the NTD to subtype-specific assembly by generating chimeras containing AMPA(GluR3) and kainate(GluR6) substitutions confined to the NTD and tested their ability to assemble with wild-type subunits

Read more

Summary

Introduction

The major excitatory neurotransmitter, activates two receptor families: metabotropic glutamate receptors (mGluRs),1 which are coupled to G-proteins, and ionotropic. To identify NTD subdomains involved in this process we generated AMPA glutamate receptor 3 (GluR3) mutants having intra-NTD substitutions with the corresponding regions of the kainate receptor GluR6 and tested their ability to form functional heteromers with wild-type subunits.

Results
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call