%0 Journal Article %T Chemogenetics defines receptor-mediated functions of short chain free fatty acids %J - %D 2019 %R https://doi.org/10.1038/s41589-019-0270-1 %X Differentiating actions of short chain fatty acids (SCFAs) at free fatty acid receptor 2 (FFA2) from other free fatty acid-responsive receptors and from non-receptor-mediated effects has been challenging. Using a novel chemogenetic and knock-in strategy, whereby an engineered variant of FFA2 (FFA2-DREADD) that is unresponsive to natural SCFAs but is instead activated by sorbic acid replaced the wild-type receptor, we determined that activation of FFA2 in differentiated adipocytes and colonic crypt enteroendocrine cells of mouse accounts fully for SCFA-regulated lipolysis and release of the incretin glucagon-like peptide-1 (GLP-1), respectively. In vivo studies confirmed the specific role of FFA2 in GLP-1 release and also demonstrated a direct role for FFA2 in accelerating gut transit. Thereby, we establish the general principle that such a chemogenetic knock-in strategy can successfully define novel G-protein-coupled receptor (GPCR) biology and provide both target validation and establish therapeutic potential of a ¡®hard to target¡¯ GPCR %U https://www.nature.com/articles/s41589-019-0270-1