An optimized fluorescent biosensor for monitoring long-chain fatty acyl-CoAs metabolism in vivo.

Long-chain fatty acyl-CoAs (LCACoAs) are intermediates in lipid metabolism that exert a wide range of cellular functions. However, our knowledge about the subcellular distribution and regulatory impacts of LCACoAs is limited by a lack of methods for detecting LCACoAs in living cells and tissues. Here, we report our development of LACSerHR, a genetically encoded fluorescent biosensor that enables precise measurement of subtle fluctuations in the levels of endogenous LCACoAs in vivo. LACSerHR significantly improve the fluorescent brightness and analyte affinity, in vitro and in vivo testing showcased LACSerHR's large dynamic range. We demonstrate LACSerHR's capacity for real-time evaluation of LCACoA levels in specific subcellular compartments, for example in response to disruption of ACSL enzyme function in HEK293T cells. Moreover, we show the application of LACSerHR for sensitive measurement of elevated LCACoA levels in the livers of mouse models for two common metabolic diseases (NAFLD and type 2 diabetes). Thus, our LACSerHR sensor is a powerful, broadly applicable tool for studying LCACoAs metabolism and disease.