n2STAR SEMINAR
*********************************
Speaker: Prof. J. Joshua Ziarek, Indiana University
Title: Ligands selectively tune the local and global motions of G protein-coupled receptors (GPCRs)
Date: Thursday, May 4, 2023
Time: 7 PM, ISTANBUL
Place: Zoom Webinar
Abstract:
The neurotensin receptor 1 (NTS1) is a G protein-coupled receptor (GPCR) with promise as a drug target for the treatment of pain, schizophrenia, obesity, addiction, and various cancers. A detailed picture of the NTS1 structural landscape has been established by X-ray crystallography and cryo-EM and yet, the molecular determinants for the diverse pharmacology of GPCRs remain poorly defined. These static structures can be thought of as describing the enthalpic contributions to binding and activity. Nuclear magnetic resonance (NMR) studies of very fast methyl sidechain dynamics can report on entropically-driven mechanisms; yet, technical challenges have largely limited the application of NMR to the super-microsecond motional regimes of GPCRs. We employed NMR and density functional theory (DFT) to probe global sub-microsecond motions of 13Cε-methionine residues. Using this approach, known as methionine chemical shift-based global order parameters, we establish that the NTS1 solution ensemble includes substates with lifetimes on several discrete timescales. The longest-lived metastable states reflect those captured in agonist- and inverse agonist-bound crystal structures separated by large energy barriers. Individual methionine residues sense the rapid concerted motions superimposed within these long-lived states. The degree of these fast, global dynamics correlates with ligand pharmacology suggesting a role for conformational entropy in GPCR ligand discrimination. Together, our work demonstrates the importance of kinetic information to a complete picture of the GPCR activation landscape.
Short Bio:
My fascination with the GPCR superfamily began with my graduate training in Prof. Brian Volkman’s lab at the Medical College of Wisconsin (MCW). My thesis combined NMR with conventional biochemical and biophysical methods to rationally-design therapeutic leads targeting chemokines and their receptor. We developed novel protein-therapies, resulting in three patents, and tested them in myocardial infarction/reperfusion injury, melanoma, and colorectal cancer animal models. After earning a Ph.D. in Biochemistry, I was awarded a one-year MCW Cancer Center Postdoctoral Fellowship before continuing my training in Prof. Gerhard Wagner’s group at Harvard Medical School where I was awarded an NIH Ruth L. Kirschstein National Research Service Award (NRSA) Postdoctoral Fellowship followed by a prestigious NIH K99/R00 Pathway to Independence Award. My postdoctoral research led to the developing and implementation of state-of-the-art NMR pulse sequences for the structural and dynamic characterization of large, challenging proteins. Since joining the faculty at Indiana University, we’ve worked to decipher the molecular mechanisms of GPCR allostery to lay the foundation for rational drug discovery related to substance use disorders.