Investigation of congenital myasthenia reveals functional asymmetry of invariant acetylcholine receptor (AChR) cys-loop aspartates

Xin Ming Shen, Joan Brengman, David Neubauer, Steven M Sine, Andrew G Engel

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

We identify two heteroallelic mutations in the acetylcholine receptor δ-subunit from a patient with severe myasthenic symptoms since birth: a novel δD140N mutation in the signature Cys-loop and a mutation in intron 7 of the δ-subunit gene that disrupts splicing of exon 8. The mutated Asp residue, which determines the disease phenotype, is conserved in all eukaryotic members of the Cys-loop receptor superfamily. Studies of the mutant acetylcholine receptor expressed in HEK 293 cells reveal that δD140N attenuates cell surface expression and apparent channel gating, predicting a reduced magnitude and an accelerated decay of the synaptic response, thus reducing the safety margin for neuromuscular transmission. Substituting Asn for Asp at equivalent positions in the α-, β-, and ϵ-subunits also suppresses apparent channel gating, but the suppression is much greater in the α-subunit. Mutant cycle analysis applied to single and pairwise mutations reveals that αAsp-138 is energetically coupled to αArg-209 in the neighboring pre-M1 domain. Our findings suggest that the conserved αAsp-138 and αArg-209 contribute to a principal pathway that functionally links the ligand binding and pore domains.

Original languageEnglish (US)
Pages (from-to)3291-3301
Number of pages11
JournalJournal of Biological Chemistry
Volume291
Issue number7
DOIs
StatePublished - Feb 12 2016

    Fingerprint

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Cite this