Activation and desensitization of C. elegans muscle Levamvisole-sensitive Nicotinic receptors

HERNANDO, G.; RAYES, D.; BOUZAT, C.

Huerta Grande, Cordoba, Arg.

Congreso; Second Join Meeting of the Argentine Society for Neurosciences and the Argentine Workshop in Neurosciences.; 2010

the Argentine Society for Neurosciences and the Argentine Workshop in Neurosciences.

The  levamisole-sensitive  nicotinic  acetylcholine  receptor  (L-AChR)  is  a  pentameric protein involved in neuromuscular transmission in C. elegans. These receptors appear to be  composed  of  three  essential  (UNC-63, UNC-38,  and UNC-29)  and  two  accessory subunits  (LEV-1  and  LEV-8).  We  explored  the  contribution  of  the  α-type  LEV-8 subunit  to  the  kinetics  of  activation  and  desensitization  of L-AChRs  from C.  elegans muscle cultured cells. Single-channel  activity  of  L-AChRs  can  be  detected  from  LEV-8  null mutant  strain, confirming  that LEV-8  is  not  an  essential  subunit. Channel  conductance  is  similar  to that of wild-type L-AChRs (~36 pS). In contrast, in the null mutant the duration of the slowest  open  component  is  about  3-fold  more  prolonged.  In  addition,  a  dramatic difference between recordings from LEV-8 null mutant and wild-type muscle cells is a time-dependent  reduction  in  the  frequency  of  opening  events,  suggesting  enhanced desensitization. ACh-elicited macroscopic currents show that the decay time constant is ~4-fold  reduced  in  the mutant  compared  to wild-type L-AChRs,  therefore  confirming faster desensitization. ). Thus, the properties of L-AChRs-mediated responses in muscle cells  can  be  substantially  changed  whether  or  not  accessory  LEV-8  subunit  is incorporated into the receptor.