Cholesterol is an essential constituent of eukaryotes membranes and its derivate metabolites also serve as a signaling molecule that is crucial for growth, development and differentiation. Dysregulation of cholesterol metabolism is strongly associated with the development of cardiovascular disorders and neurodegeneration. Caenorhabditis elegans is especially suited to genetically study organismal orchestration of cholesterol metabolism. This worm requires exogenous cholesterol to survive and perturbations in cholesterol trafficking result in an early development larval arrest. Thus, tight regulation of cholesterol storage and distribution within the organism is critical. We have recently demonstrated that the endocannabinoid 2-arachidonoylglycerol (2-AG) plays a key role in C. elegans modulating sterol mobilization (Galles et al, Sci Rep. 2018; 6398). However, the mechanism by which 2-AG controls cholesterol trafficking in C. elegans is not known. Recent reports have shown that C. elegans has two cannabinoid-like receptors named NPR-19 and NPR 32, which are involved in nociception and regenerative axon navigation, respectively (Oakes et al, J. Neurosci. 2017; 2859, Pastuhov et al, Genes Cells. 2016; 696). Here we show that neither NPR-19 or NPR-32 are involved in 2-AG-mediated cholesterol trafficking. Furthermore, we found that the insulin-IGF1(IIS) signalling pathway is essential for the 2-AG suppression of larval arrest induced by cholesterol depletion. Studying the linkage between IIS and 2-AG we found two C. elegans single mutants,
ocr-2 and
osm-9, were insensitive to the 2-AG-mediated mobilization cholesterol in sterol-depleted worms. OCRs and OSM-9 proteins belong to C. elegans Transient Receptor Potential Vanilloid (TRPV) subfamily channels (Colbert et al, J. Neurosci. 1997; 8259). TRPV channels were previously reported as a sort of cannabinoid receptors in mammals (Ahluwalia et al, Eur J. Neurosci. 2003; 2611). Thus, we propose that OCR-2 and OSM-9 are endocannabinoid receptors in C. elegans, defining a novel signalling pathway mediated by 2-AG that modulates sterol metabolism in C. elegans.