The nicotinic alpha subunit MARA1 is necessary for cholinergic evoked calcium transients in Manduca neurons

The functional contribution of cloned subunits to insect nicotinic acetylch oline (ACh) receptors has been difficult to determine using heterologous ex pression. Instead, in this study we explore the subunit composition of natu rally expressed functional receptors in an insect using RNA interference. T he nicotinic alpha subunit, Manduca ACh Receptor Alpha 1 (MARA1) can be det ected in neuronal cultures isolated from the ventral nerve cord of fifth in star larvae of Manduca sexta by in situ hybridization. It's presence correl ates with large ACh induced, nicotinic Ca2+ responses. The expression of MA RA1 is downregulated by treatment with dsRNA which significantly reduced bo th the number of responding cells and the amplitude of remaining Ca2+ respo nses. These results suggest that MARA1 is part of a nicotinic receptor func tionally coupled to Ca2+ entry. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.