Elucidating the Role of Subcellular GPCR Nanoswitches in Signaling Specificity

forthcoming

G protein-coupled receptors (GPCRs) relay extracellular information across the cell membrane to mediate most physiological cell functions. Many cell-surface GPCRs stimulate the production of cyclic adenosine monophosphate (cAMP), a diffusible second messenger, to elicit receptor-specific, long-range cell functions. However, given the mobility of second messengers, this canonical model fails to explain receptor-specific functions across multiple GPCRs that signal via cAMP. This application proposes that GPCRs, in dramatic contrast to the second messenger concept, form highly-localized, nanometer-size cAMP signaling units at various subcellular locations, i.e. subcellular GPCR nanoswitches. At these locations, GPCR nanoswitches tightly control cAMP signaling at the nanometer scale in a receptor- and location-specific manner. These nanoswitches enable cells to retain the spatial-ID of every cAMP molecule and, thus, allow precise, spatially encoded, and receptor-specific cell functions even in the presence of multiple co-activated receptors. The combination of cutting-edge technologies such as genetically encoded Foerster resonance energy transfer (FRET)-based biosensors, fluorescence-lifetime imaging microscopy (FLIM)-FRET multiplexing, and advanced proximity proteomics, will enable mapping the architecture and dynamics of these subcellular GPCR nanoswitches at nanometer scales. This proposal will then explore how endogenous GPCR nanoswitches control insulin secretion from pancreatic beta-cells in response to endogenous incretins as well as licensed obesity drugs. This will establish the physiological relevance of subcellular GPCR nanoswitches. If successful, this proposal has the potential to revolutionize our understanding of cell signaling and to fundamentally transform GPCR drug discovery, offering opportunities for the development of location-specific drugs with reduced side effects that precisely modulate individual subcellular GPCR nanoswitches