G protein-coupled receptors (GPCRs) mediate the actions of a wide variety of hormones and neurotransmittersto control functions in all mammalian cells. As such, GPCRs are major targets of therapeutics. IndividualGPCRs directly couple to distinct complements of heterotrimeric G protein ? and ?? subunits that drivedownstream signaling pathways to shape the cellular responses that determine GPCR efficacy. Both G? andG?? subunits interact directly with effectors to produce cellular responses. Our laboratory has focused largelyon G?? subunit signaling and has identified a series of small molecules that bind to G?? to ?bias? signalingpathways downstream of GPCRs. These inhibitors have been applied extensively to dissect G?? functions inbiology, and to validate G?? as a viable therapeutic target. Most recently we have identified a small moleculethat activates G?? subunit signaling without activating G protein ? subunits. We have applied this tool to studysignaling 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 moleculesfunction at a molecular level, and explore the mechanistic role for G?i in chemoattractant receptor signaling inthe following specific aims.
Aim 1. Determination of the mechanisms of action of 12155 and M119/gallein on Gprotein 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?iactivation in chemoattractant-dependent directional cell migration. We believe that these studies will reveal anew molecular target and cellular function for G?i in regulation of integrin function that will have wideimplications for chemoattractant/chemokine receptor and integrin regulation.
G protein coupled receptors (GPCRs) are a major class of transmembrane receptors responsible forrecognition of a large class of diverse ligands. Here we propose investigation of selective small moleculeinhibitors and activators of G protein ?? subunits identified in our laboratory which could be used to inhibitmultiple GPCRs and modify actions of existing GPCR directed pharmaceuticals. Results of theseexperiments will help to validate this alternate approach to modification of signaling pathways downstreamof GPCRs that could ultimately lead to development of novel therapeutics.
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