Assembly and function of levamisole receptors. C. elegans levamisole sensitive AChR channels in the muscle membrane are formed by five subunits (UNC-38, blue; UNC-29, purple; UNC-63, yellow; LEV-1, green; and LEV-8, red) with normal function being supported by OIG-1, NRA-1, NRA-2, NRA-4, SOC-1, TAX-6, TPA-1, LEV-9 and LEV-10 proteins. Once the levamisole AChR channel opens, calcium enters and its signal is amplified by the ryanodine receptor (UNC-68); the increased calcium then initiates contraction, requiring the proteins UNC-22 and LEV-11. The expression of the levamisole receptor subunits requires RNAs encoding the five subunits together with three C. elegans ancillary proteins involved in AChR assembly (RIC-3), folding (UNC-74) and trafficking (UNC-50) [24, 27, 45]. MicroRNA (miR-1) is also known to regulate and modulate the expression of subunit RNA. Abbreviations: ER, endoplasmic reticulum; SR sarcoplasmic reticulum.