Positive modulation of a Cys-loop acetylcholine receptor by an auxiliary transmembrane subunit

Abstract

Auxiliary subunits regulate the trafficking, localization or gating kinetics of voltage- and ligand-gated ion channels by associating tightly and specifically with pore-forming subunits. However, no auxiliary subunits have been identified for members of the Cys-loop receptor superfamily. Here we identify MOLO-1, a positive regulator of levamisole-sensitive acetylcholine receptors (L-AChRs) at the Caenorhabditis elegans neuromuscular junction. MOLO-1 is a one-pass transmembrane protein that contains a single extracellular globular domain-the TPM domain, found in bacteria, plants and invertebrates, including nonvertebrate chordates. Loss of MOLO-1 impairs locomotion and renders worms resistant to the anthelmintic drug levamisole. In molo-1 mutants, L-AChR-dependent synaptic transmission is reduced by half, while the number and localization of receptors at synapses remain unchanged. In a heterologous expression system, MOLO-1 physically interacts with L-AChRs and directly enhances channel gating without affecting unitary conductance. The identification of MOLO-1 expands the mechanisms for generating functional and pharmacological diversity in the Cys-loop superfamily.

Biosynthesis of ionotropic acetylcholine receptors requires the evolutionarily conserved ER membrane complex

“…To identify new components involved in AChR metabolism, we used Mos1-mediated insertional mutagenesis to generate mutants resistant to the cholinergic agonist levamisole (42). A strain carrying the mutant allele kr150 was isolated based on its ability to adapt to overnight exposure to 0.6 mM levamisole.…”

“…Such mutants completely paralyze on high levamisole concentration within a few hours but subsequently adapt within 12-16 h and recover motility in contrast to WT worms (41,42). Here, we identify and characterize in vivo the ER membrane protein complex-6 (emc-6) gene.…”

C. elegans Punctin Clusters GABAA Receptors via Neuroligin Binding and UNC-40/DCC Recruitment

“…Quantification of synaptic GABA A R, NLG-1-RFP, or UNC-40-RFP was achieved as described previously (Boulin et al, 2012;Pinan-Lucarré et al, 2014). For the quantification of AChR fluorescence (kr208[unc-29-RFP]) in living worms, young adult animals were mounted on 2% agarose pads, immobilized using 0.1 M sodium azide (Sigma) in M9 buffer and pictures of dorsal cords were acquired as described previously (Pinan-Lucarré et al, 2014).…”

Advances in the pharmacology of lGICs auxiliary subunits

“…On the other hand, Amyloid Precursor Protein (APP) infusion increases NMDAR evoked currents [87] and together with its related proteins, amyloid precursor-like proteins 1 and 2 (APLP1 & APLP2), enhance surface NMDA receptors expression in vitro [88].…”