Mutation causing congenital myasthenia reveals acetylcholine receptor β/δ subunit interaction essential for assembly

Polly A. Quiram, Kinji Ohno, Margherita Milone, Marc C. Patterson, Ned J. Pruitt, Joan M. Brengman, Steven M. Sine, Andrew G. Engel

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Abstract

We describe a severe postsynaptic congenital myasthenic syndrome with marked endplate acetylcholine receptor (AChR) deficiency caused by 2 heteroallelic mutations in the β subunit gene. One mutation causes skipping of exon 8,truncating the β subunit before its M1 transmembrane domain, and abolishing surface expression of pentameric AChR. The other mutation, a 3- codon deletion (β426delEQE) in the long cytoplasmic loop between the M3 and M4 domains, curtails but does not abolish expression. By coexpressing β426delEQE with combinations of wild-type subunits in 293 HEK cells, we demonstrate that β426delEQE impairs AChR assembly by disrupting a specific interaction between β and δ subunits. Studies with related deletion and missense mutants indicate that secondary structure in this region of the β subunit is crucial for interaction with the δ subunit. The findings imply that the mutated residues are positioned at the interface between β and δ subunits and demonstrate contribution of this local region of the long cytoplasmic loop to AChR assembly.

Original languageEnglish (US)
Pages (from-to)1403-1410
Number of pages8
JournalJournal of Clinical Investigation
Volume104
Issue number10
DOIs
Publication statusPublished - Nov 1999
Externally publishedYes

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ASJC Scopus subject areas

  • Medicine(all)

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