Functional roles of amino acids of nicotinic receptors are conserved between C. elegans and human

BERGÉ IGNACIO; HERNANDO GUILLERMINA; ANDREOCCI EMANUEL; ROCCAMO ANA MARÍA; BOUZAT CECILIA

Congreso; XLIII Reunión Anual SAB 2014; 2014

Mutations in ion channels may lead to genetic disorders named aschannelopathies. Congenital myasthenic syndromes (CMS) arechannelopathies produced by mutations in the muscle nicotinicreceptor (AChR). Our goal is to generate models of these humanneuromuscular disorders to be used for drug screening anddevelopment of therapeutic strategies. To this end, we use thefree-living nematode C. elegans, whose muscle AChR (L-AChR) isessential for neuromuscular transmission and locomotion. Wegenerated gain-of-function mutant L-AChRs by exchanginghydrophobic residues at 9' position of M2 segment, which havebeen shown to form the gate of the ion channel in vertebrates, byhydrophilic residues in two essential subunits of the L-AChR.Single-channel recordings from muscle cells of the mutanttransgenic worms show a dramatic increase (11- to 14-fold) of theopen duration of mutant L-AChR with respect to wild-type.Macroscopic currents elicited by ACh show a decrease in thedesensitization rate. These functional changes are similar to thoseobserved in vertebrate AChRs carrying the equivalent mutations,thus revealing a high degree of conservation of functional roles ofAChR amino acids. Generation and analysis of a mutant straincarrying in the L-AChR a gain-of-function mutation (T12´M2P) thatin human leads to a severe slow-channel CMS reveals that thefunctional changes in the worm mimic those of the patients. Theseresults open doors for establishing C. elegans models for humanmyasthenic syndromes.