Title: Structural Basis of G-protein selectivity in GPCRs using Multiscale Dynamics Upon binding to agonists G protein-coupled receptors (GPCRs) mediate multiple signaling pathways by coupling to intracellular transducer proteins such as G proteins and/or ?-arrestins. Certain agonists exhibit selectivity in their efficacy to specific G-protein signaling pathways. Such selective ligands provide precise therapeutic benefits with fewer side effects as drugs compared to GPCR-targeted drugs in the market. There are very few G-protein selective GPCR agonists known to date, because designing G-protein selective agonists is a daunting experimental challenge. Additionally, there is a serious lack of understanding of structural information on how GPCRs modulate their functional selectivity for their cognate G-protein in cells. There are several contributing factors to how an agonist- GPCR pair shows selectivity to specific G-protein. These factors include, nature of conformational ensembles of the agonist-GPCR-G-protein complexes, and several cellular factors. Delineating the contribution from the structural ensemble of the agonist-GPCR-G-protein complexes has been sparse due to huge experimental challenges in crystallography and NMR of these complexes. We propose to combine two state-of-the-art dynamics techniques, such as ensemble based multi-resolution molecular dynamics method tightly integrated in an iterative fashion with scalable genetically coded FRET sensor biophysical measurements in live cells, to probe the structural basis of G-protein selectivity. The scalability of these two techniques is a huge advantage to probe the functional selectivity of several agonist-GPCR pairings. We propose to use the combination of these two techniques to (a) identify the structural determinants in the agonist-GPCR complex that contribute significantly to G-protein selectivity in nine different agonist-GPCR pairs. (b) We also propose to delineate the structural determinants that contribute to functional selectivity when the GPCR is bound to a partial agonist as opposed to a full agonist, and when the agonist-GPCR is also bound to an allosteric modulator. The outcome of the proposed work will enable structure based design of selective agonists for class A GPCRs, and also provide an understanding of the biological process of how GPCRs recognize their cognate G-proteins in live cells.
Understanding the mechanisms of how G-protein coupled receptors (GPCRs) couple selectively to their cognate G-proteins is the holy grail of functional selectivity in GPCRs. The proposed interdisciplinary research will develop computational methods concurrent with experiments to provide insight into the dynamics and structural basis of how class A GPCRs recognize their cognate G-proteins. The combination of computational methods and experiments will provide an understanding of how agonists with varied efficacies affect the functional selectivity and pave way to designing ligands with functional selectivity for GPCRs for treatment of hypertension, diabetes and cancer.
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