The glucagon-like peptide-1 receptor (GLP1R) is a broadly expressed target of
peptide hormones with essential roles in energy and glucose homeostasis, as well
as of the blockbuster weight-loss drugs semaglutide and liraglutide. Despite its
large clinical relevance, tools to investigate the precise activation dynamics
of this receptor with high spatiotemporal resolution are limited. Here, we
introduce a novel genetically encoded sensor based on the engineering of a
circularly permuted green fluorescent protein into the human GLP1R, named
GLPLight1. We demonstrate that fluorescence signal from GLPLight1 accurately
reports the expected receptor conformational activation in response to
pharmacological ligands with high sensitivity (max ΔF/F0=528%) and
temporal resolution (τON= 4.7 s). We further demonstrated that
GLPLight1 shows comparable responses to glucagon-like peptide-1 (GLP-1)
derivatives as observed for the native receptor. Using GLPLight1, we established
an all-optical assay to characterize a novel photocaged GLP-1 derivative
(photo-GLP1) and to demonstrate optical control of GLP1R activation. Thus, the
new all-optical toolkit introduced here enhances our ability to study GLP1R
activation with high spatiotemporal resolution.