Selective Targeting of G Protein beta gamma Subunits with Small Molecules

摘要

Abstract G protein-coupled receptors (GPCRs) mediate the actions of a wide variety of hormones and neurotransmitters to control functions in all mammalian cells. As such, GPCRs are major targets of therapeutics. Individual GPCRs directly couple to distinct complements of heterotrimeric G protein  and  subunits that drive downstream signaling pathways to shape the cellular responses that determine GPCR efficacy. Both G and G subunits interact directly with effectors to produce cellular responses. Our laboratory has focused largely on G subunit signaling and has identified a series of small molecules that bind to G to “bias” signaling pathways downstream of GPCRs. These inhibitors have been applied extensively to dissect G functions in biology, and to validate G as a viable therapeutic target. Most recently we have identified a small molecule that activates G subunit signaling without activating G protein  subunits. We have applied this tool to study signaling in immune cells to reveal exciting and previously unappreciated roles for Gi in chemokine- chemoattractant receptor signaling. In this proposal we will examine in detail how G activating molecules function at a molecular level, and explore the mechanistic role for Gi in chemoattractant receptor signaling in the following specific aims. Aim 1. Determination of the mechanisms of action of 12155 and M119/gallein on G protein subunit interactions and GPCR coupling. Aim 2. Determining the mechanism(s) for GiGTP- dependent regulation of cell migration and adhesion. Aim 3. Analysis of spatiotemporal regulation of Gi activation in chemoattractant-dependent directional cell migration. We believe that these studies will reveal a new molecular target and cellular function for Gi in regulation of integrin function that will have wide implications for chemoattractant/chemokine receptor and integrin regulation.