GEM-IL: A highly responsive fluorescent lactate indicator

Lactate metabolism has been shown to have increasingly important implications in cellular functions as well as in the development and pathophysiology of disease. The various roles as a signaling molecule and metabolite have led to interest in establishing a new method to detect lactate changes in live cells. Here we report our development of a genetically encoded metabolic indicator specifically for probing lactate (GEM-IL) based on superfolder fluorescent proteins and mutagenesis. With improvements in its design, specificity, and sensitivity, GEM-IL allows new applications compared with the previous lactate indicators, Laconic and Green Lindoblum. We demonstrate the functionality of GEM-IL to detect differences in lactate changes in human oncogenic neural progenitor cells and mouse primary ventricular myocytes. The development and application of GEM-IL show promise for enhancing our understanding of lactate dynamics and roles. [Display omitted] •Development of a genetically encoded metabolic indicator for lactate (GEM-IL)•Mutagenesis and fluorophore alteration improve responsivity and specificity to lactate•In vivo model generation, validation, and application of GEM-IL•GEM-IL shows improved sensitivity over currently available lactate indicators The ability to detect and monitor changes in lactate at the cellular level is essential for understanding various physiological systems. Current methods have limited sensitivity and low intracellular expression, and there are no genetically encoded in vivo models available. To address these issues and monitor changes in lactate, we have developed, optimized, and characterized a genetically encoded metabolic indicator for lactate (GEM-IL). This tool is a reliable method for studying metabolic activity as demonstrated in vitro and in situ. In addition, we have developed an in vivo murine model for this indicator for further applications in metabolism study. Bekdash et al. report the development of a genetically encoded metabolic indicator for probing lactate (GEM-IL) based on superfolder fluorescent proteins and mutagenesis. With improvements in the design, specificity, and sensitivity, the authors demonstrate GEM-IL's usefulness and functionality compared with previous lactate indicators, Laconic and Green Lindoblum.