A Cys-loop mutation in the Caenorhabditis elegans nicotinic receptor subunit UNC-63 impairs but does not abolish channel function

ANDREW K. JONES; DIEGO RAYES; ADAM AL-DIWANI; THOMAS P. R. MAYNARD; RACHEL JONES; GUILLERMINA HERNANDO; STEVEN D. BUCKINGHAM; CECILIA BOUZAT; DAVID B. SATTELLE

JOURNAL OF BIOLOGICAL CHEMISTRY

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Lugar: Bethesda, Maryland; Año: 2011 vol. 286 p. 2550 - 2558

0021-9258

The nematode Caenorhabditis elegansis an established model organism for studying neurobiology. UNC-63 is a C. elegans nicotinic acetylcholine receptor (nAChR)-subunit. It is an essential component of the levamisole-sensitive muscle nAChR (L-nAChR) and therefore plays an important role in cholinergic transmission at the nematode neuromuscular junction. Here, we show that worms with the unc-63(x26) allele, with its C151Y mutation disrupting the Cys-loop, have deficient muscle function reflected by impaired swimming (thrashing). Single-channel recordings from cultured muscle cells from the mutant strain showed a 100-fold reduced fre-quency of opening events and shorter channel openings of L-nAChRs compared with those of wild-type worms. Anti-UNC-63 antibody staining in both cultured adult muscle and embryonic cells showed that L-nAChRs were expressed at sim-ilar levels in the mutant and wild-type cells, suggesting that the functional changes in the receptor, rather than changes in ex-pression, are the predominant effect of the mutation. The ki-netic changes mimic those reported in patients with fast-chan-nel congenital myasthenic syndromes. We show that pyridostigmine bromide and 3,4-diaminopyridine, which are drugs used to treat fast-channel congenital myasthenic syn-dromes, partially rescued the motility defect seen in unc-63(x26). The C. elegans unc-63(x26) mutant may therefore of-fer a useful model to assist in the development of therapies for syndromes produced by altered function of human nAChRs.