Research

Metabolic control of Inflammation and Immunity

Metabolic changes in cells that participate in inflammation, such as activated macrophages and T- helper 17 cells, include a shift towards enhanced glucose uptake, glycolysis, and increased activity of the pentose phosphate pathway. Nuclear receptors, PPAR, ROR, and LXRs are involved in this inflammation process and as such we are developing inverse agonists or agonists of those nuclear receptors. Compounds of interest are evaluated pharmacology in rodent models of arthritis, the CIA mouse (collagen induced arthritis); and a model of obesity and diabetes, the DIO mouse (Diet induced obesity). Anti-inflammatory cells, such as M2 macrophages, regulatory T cells and quiescent memory T cells have lower glycolytic rates and higher levels of oxidative metabolism. Recently we published the efficacy of a novel PPARγ antagonist (SR1664) and a potent and selective inverse agonist of RORγ (SR2211). We are now studying their effects on enhancing anti-inflammatory cells in DIO and CIA models.

Structural and Chemical Biology of Enzymes and Receptors

P.R. Griffin, S.A. Busby, M. J. Chalmers, R. Garcia-Ordonez, M. Istrate, N. Kumar, R. Landgraf, S. Novick, B. Pascal, G. West, S. Willis, (former members of the lab: D. Policastro, C. Griffin, E. Tracy, J. Zhang, X. Zhang, S. Dai, S. Prasad).

 

Our group combines chemical and cell biology with structural biology to study mechanism and structure-function of enzymes and receptors; particularly kinases, G-protein coupled receptors (GPCRs) and nuclear receptors (NRs). During the past few years we have focused on developing hydrogen/deuterium exchange (HDX) technology for probing the mechanism of activation of ligands that modulate nuclear receptors. We have used HDX, chemical libraries and cell-based assays to better understand ligand activation, DNA and co-receptor/co-factor interaction with VDR, PPARG, PR, MR, ERalpha, ERbeta, ERRG, TR, CAR, RXR and LXR.  We have applied HDX and chemical approaches to the study of the orphan nuclear receptors LRH-1 and RORA (in collaboration with the labs of Thomas Burris, Bill Roush, Ted Kamenecka, and Mike Cameron) which have been implicated in cancer, metabolic and immune disorders.  Our lab activities are past of a Center Driven initiative of the Scripps Research Institute Molecular Screening Center (SRIMSC) and is being applied to several chemical probe development projects. As part of the SRIMSC initiative e have developed novel screening platforms to facilitate the discovery of potent and selective nuclear receptor modulators. Finally, we have a HDX collaboration with the Stevens’ laboratory, TSRI CA, to study the dynamics of GPCRs upon ligand interaction.

Mechanistic studies of ligand activation of VDR/RXR full length heterodimer complex

Here we are applying HDX towards the characterization of ligand activation of the vitamin D receptor (VDR) in complex with its co-receptor retinoid X receptor alpha (RXRa). This project is driving further development of our HDX platform to facilitate the analysis of large transcriptional complexes. We have successfully probed the dynamics of the functional domains of both VDR and RXR within this complex as a function of both ligand and DNA interaction. Our data clearly demonstrates the role of DNA interaction in the functional state of the VDR/RXR heterodimer complex by directly controlling dynamics of surfaces of the receptor complex that interact with co-activators.  A manuscripts is in press at Structure and another has been submitted describing various aspects of VDR/ligand interactions as well as VDR/RXR interaction with DNA and cofactors.

Probing GPCRs by HDX

GPCRs are an important family of trans-membrane signaling proteins and are therapeutic targets in many disorders. The characterization of the structure and dynamics of these receptors present a considerable analytical challenge due to the hydrophobic nature of their transmembrane domains.  The Stevens’ lab recently solved the structure of the beta-2 adrenergic receptor at 2.4 Å resolution and in collaboration with their lab we have initiated studies to probe beta-2 adrenergic receptor-ligand interactions.

Read our recent article on HDX characterization of beta-2 adrenergic receptor which is available on-line at http://pubs.acs.org/doi/pdf/10.1021/ac902484p

Structural and Chemical Biology of the orphan nuclear receptor LRH-1

Our laboratory has taken a multi-pronged approach to understanding the biology of the orphan nuclear receptor LRH-1 (liver receptor homolog-1). Modulation of LRH-1 activity has been implicated in breast cancer, cholesterol homeostasis, and in intestinal inflammation. We have developed several HTS ready assays to facilitate screening for small molecules that positively modulate (agonize) or negatively modulate (inverse agonize) the activity of the receptor. More importantly, we have developed several functional assays to better understand the potential utility of small molecule modulators of LRH-1 for treatment of breast cancer and metabolic disorders.

Novel modulators of RORa

Using a unique human nuclear receptor library we have discovered novel modulators of RORa. In collaboration with William Roush and the SRIMSC, we have generated structure-activity-relationships around this molecule in an effort to improve potency and selectivity. HDX is being employed to guide SAR studies in this project. In addition, we have developed several cell-based assays to examine the effects of these molecules in biological pathways controlled by RORa; such as the control of adipogenesis and it role in insulin sensitization.

Read our recent articles in Molecular Pharmacology, JBC, and ACS Chemical Biology on synthetic and natural ligands for the RORs.