Sexton Laboratory

Understanding GPCR structure and function

Prof. Patrick M Sexton
Theme Leader, Drug Discovery Biology
NHMRC Principal Research Fellow
Email: patrick.sexton@monash.edu
Project areas | Key publications | Collaborations | Lab members | Funding

Project areas

Research focus

Laboratory overview
Laboratory overview: From a molecular understanding of receptor structure and ligand interaction to fine control of physiological response and disease treatment.

Understanding the behaviour and quantification of allosteric drug action, and ligand-directed stimulus bias, are key areas at the forefront of GPCR research as these are considered critical to future successful drug discovery and development. My laboratory studies these novel paradigms of GPCR function  across  all levels of investigation; from elucidating receptor structure, by combination of x-ray crystallography, biophysical characterisation and 3D molecular modelling, through to examination of drug behaviour in whole animal models of physiology and disease.

My laboratory has a particular focus on Family B GPCRs that regulate the function of key peptide hormones involved in major diseases including metabolic disease (diabetes, obesity, osteoporosis), cardiovascular disease and diseases of the central nervous system. Much of the work in the laboratory is  co-run  with Dr Denise Wootten.

The structural basis of receptor function

molecular model of GLP1molecular model of GLP1
Left: molecular model of the transmembrane domain of the GLP1 receptor  illustrating  key amino acids involved in pathway bias (green), packing and global activation (blue), ligand-induced conformational bias (red) or othosteric versus allosteric effects. Right: molecular dynamics simulation of allosteric drug docking to the M2 muscarinic ACh receptor, video  avialable  through Nature website.

Understanding receptor structure, how ligand bind, and the dynamic changes that lead to selective engagement of signaling and regulatory partners is critical to drug design and effective control of disease.

We use a range of approaches to understand receptor function that include protein mutagenesis, use of biophysical techniques to examine receptor dynamics and x-ray crytallography to generate high resolution structural data of stable conformations.

This work is combined with 3D protein modelling to understand drug and natural ligand docking and how specific receptor residues contribute to signalling or regulatory bias.

Chemical biology and drug design

Ligands of GLP1
Distinct ligands of the GLP1 receptor cause differential activation of signaling pathways (signaling bias). The WEB of bias plot illustrates the efficacy of each of the ligands relative to GLP1 (set at  1);  note the logarithmic scale.

We are currently seeking to understand the link between chemistry and the selective control of receptor function.

There are two main areas of focus; ligand-directed signal bias and allosteric regulation of receptor function.

We aim to develop SAR for ligands around parameters that describe selective signaling and allosteric co-operativity.

Cellular signalling and regulation

Both endogenous (and exogenous) peptide ligands and small molecule allosteric compounds can differentially modulate cellular function both in signal generation and signal termination (biased signaling). We are characterising ligands across a wide range of cellular endpoints (second messenger assay,  receptor  trafficking and regulation, cell proliferation and apoptosis, gene regulation, etc) in both recombinant and native cellular expression systems. These insights on how biased ligands control cellular function can then be used to link to understanding of systems physiology and targeted drug discovery  and  development.

Animal models of physiology and disease

molecular model of GLP1
Allosteric potentiation of oxyntomodulin-mediated insulin secretion by the allosteric GLP1 receptor modulator BETP in Sprague-Dawley rats.

Translation of key mechanistic findings on ligand-mediated signal bias and allosteric regulation of receptor function requires understanding of these paradigms in model systems of physiology and disease.

For the GLP1 receptor we are examining wild-type and transgenic mice to understand the impact on insulin secretion, glucose homeostasis, islet integrity, gastric emptying and neuronal activation.

Model mouse systems include GLP1R knockouts, tagged human receptor knock-ins, modified GLP1Rs that are biased for either G protein-signaling or arrestin signaling and mice with receptors with impaired dimerisation

In work with other receptors we are looking at the effects of allosteric and biased ligands on CNS function including models of locomotion, anxiety, learning and memory and sensory gating.

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Key publications

Research papers

Dror RO, Green HF, Valant C, Borhani DW, Pan AC, Arlow DH, Valcourt JR, Canals M, Lane JR, Rahmani R, Baell JB, Sexton PM, Christopoulos A, Shaw DE. Structural basis for modulation of a GPCR by allosteric drugs. Nature (in press, July 2013).

Kruse AC, Ring AM, Manglik A, Hu J, Hu K, Eitel K, Hübner H, Pardon E, Valant C, Sexton PM, Christopoulos A, Felder CC, Gmeiner P, Steyaert J, Weis WI, Garcia KC, Jü Wess J, Kobilka BK. Activation and allosteric modulation of a muscarinic acetylcholine receptor. Nature (in press, September 2013).

Wootten D, Simms J, Miller LJ, Christopoulos, A and Sexton PM. Polar transmembrane interactions drive formation of ligand-specific and signal pathway-biased Family B GPCR conformations. Proc Natl Acad Sci USA 110: 5211-5216, 2013.

Harikumar KG, Wootten D, Pinon DI, Koole C, Ball AM, Furness SGB, Graham B, Dong M, Christopoulos A, Miller LJ, Sexton PM. Glucagon-like peptide-1 receptor dimerisation differentially regulates agonist signalling but does not affect small molecule allostery. Proc Natl Acad Sci USA 109: 18607-18612, 2012.

Wootten D, Savage EE, Valant C, May LT, Sloop KW, Ficorilli J, Showalter AD, Willard FS, Christopoulos A, Sexton PM. Allosteric modulation of endogenous metabolites as an avenue for drug discovery. Mol Pharmacol 82:281-290, 2012.

Wootten D, Savage EE, Willard FS, Bueno AB, Sloop KW, Christopoulos A, Sexton PM. Differential activation and modulation of the glucagon-like peptide-1 receptor by small molecule ligands. Mol Pharmacol 83:822-834, 2013.

Wootten D, Savage EE, Valant C, May LT, Sloop KW, Ficorilli J, Showalter AD, Willard FS, Christopoulos A, Sexton PM. Allosteric modulation of endogenous metabolites as an avenue for drug discovery. Mol Pharmacol 82:281-290, 2012.

Koole C, Wootten D, Simms J, Miller LJ, Christopoulos A, Sexton PM. The second extracellular loop of the human glucagon-like peptide-1 receptor (GLP-1R) has a critical role in GLP-1 peptide binding and receptor activation. J Biol Chem 287:3642-3648, 2012.

Koole C, Wootten D, Simms J, Savage EE, Miller LJ, Christopoulos A, Sexton PM. The second extracellular loop of the human glucagon-like peptide-1 receptor (GLP-1R) differentially regulates orthosteric but not allosteric agonist binding and function. J Biol Chem 287:3659-3673, 2012.

Koole C, Wootten D, Simms J, Valant C, Miller LJ, Christopoulos A, Sexton PM. Polymorphism and ligand dependent changes in human glucagon-like peptide-1 receptor (GLP-1R) function: allosteric rescue of loss of function mutation. Mol Pharmacol 80: 486-497, 2011.

Reviews

Wootten D, Christopoulos A, Sexton PM. Emerging paradigms in GPCR allostery: implications for drug discovery. Nature Rev Drug Discov 12:630-644, 2013.

Sexton PM, Wootten D. Structural biology: meet the B family. Nature 499:417-418, 2013.

Koole C, Savage EE, Christopoulos A, Miller LJ, Sexton PM, Wootten D. Signal bias, allosterism and polymorphic variation at the GLP-1R: Implications for drug discovery. Mol Endocrinol 27:1234-1244, 2013.

Lane JR, Sexton PM, Christopoulos A. Bridging the gap: Bitopic ligands of G protein-coupled receptors. Trends Pharmacol Sci 34:59-66, 2013.

Valant C, Lane JR, Sexton PM, Christopoulos A. The best of both worlds? Biotopic orthosteric/allosteric ligands of G protein-coupled receptors. Ann Rev Pharmacol Toxicol 52:153-78, 2012.

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Collaborations

Understanding GPCR allostery and signal bias

GPCR drug discovery

Structural basis of GPCR function

  • Prof. Arthur Christopoulos, Drug Discovery Biology, MIPS
  • Prof. Larry Miller, Mayo Clinic, USA
  • Prof. Brian Kobilka, Stanford University, USA
  • Prof. Ruben Abagyan, Univ. California, San Diego, USA
  • Dr Ron Dror, DE Shaw Research, USA
  • Dr Celine Valant, Drug Discovery Biology, MIPS
  • Dr Rob Lane, Drug Discovery Biology, MIPS

Modulation of glucagon-like peptide 1 receptor signaling, regulation and physiology to treat metabolic disease

Targeting adenosine receptors to treat ischemia/reperfusion

Modulation of muscarnic acetylcholine receptor signaling, regulation and physiology to treat neuropsychitric disease

Allosteric control of calcium receptor function

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Lab members

Dr Denise Wooten
Co-lab head

Dr Sebastian Furness
Research fellow

Dr Lynn Liang
Research Officer

Dr Caroline Hick
Research officer

Dr Carl White
Research officer

Dr Shannen Lau
Research officer

Dr David Thal
Research officer

Mr George Christopoulos
Research assistant

Emilia Savage
Student

Kavita Pabreia
Student

Thomas Coudrat
Student

Emma Dal Maso
Student

Bhumika Aurora
Student

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Funding

  • NHMRC Principal Research Fellowship (2009 – 2013; 2014 – 2018)
  • NHMRC Program Grant (2009 – 2013): Understanding G protein-coupled receptors (GPCRs): accellerating discovery from concept to clinic.
  • NHMRC Program Grant (2014 – 2018): The Janus Faces of G Protein-Coupled Receptors: Implications for Disease Mechanisms and Opportunities.
  • NHMRC Project Grant (2011 – 2013): Molecular characterisation of the glucagon-like peptide 1 receptor.
  • NHMRC Project Grant (2014 – 2016): Understanding the structural basis for Family B G protein-coupled receptor function.
  • ARC Linkage Grant (2012 – 2015): Subtypes selectivity and functional bias of receptor positive allosteric modulators for understanding models of pulmonary disease.
  • Alchemia/Audeo Discovery (2010-2015): GPCR drug discovery.
  • Servier (2012-2016): GPCR drug discovery.
  • Eli Lilly (2013-2014): Development of transgenic mice expressing biased GLP1 receptors.

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