New Fairlie Group paper: Europium-Labeled Synthetic C3a Protein as a Novel Fluorescent Probe for Human Complement C3a Receptor

Europium-Labeled Synthetic C3a Protein as a Novel Fluorescent Probe for Human Complement C3a Receptor

Dantas de Araujo A, Wu C, Wu KC, Reid RC, Durek T, Lim J, Fairlie DP.

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Measuring ligand affinity for a G protein-coupled receptor is often a crucial step in drug discovery. It has been traditionally determined by binding putative new ligands in competition with native ligand labeled with a radioisotope of finite lifetime. Competing instead with a lanthanide-based fluorescent ligand is more attractive due to greater longevity, stability, and safety. Here, we have chemically synthesized the 77 residue human C3a protein and conjugated its N-terminus to europium diethylenetriaminepentaacetate to produce a novel fluorescent protein (Eu–DTPA–hC3a). Time-resolved fluorescence analysis has demonstrated that Eu–DTPA–hC3a binds selectively to its cognate G protein-coupled receptor C3aR with full agonist activity and similar potency and selectivity as native C3a in inducing calcium mobilization and phosphorylation of extracellular signal-regulated kinases in HEK293 cells that stably expressed C3aR. Time-resolved fluorescence analysis for saturation and competitive binding gave a dissociation constant (Kd) of 8.7 ± 1.4 nM for Eu–DTPA–hC3a and binding affinities for hC3a (pKi of 8.6 ± 0.2 and Ki of 2.5 nM) and C3aR ligands TR16 (pKi of 6.8 ± 0.1 and Ki of 138 nM), BR103 (pKi of 6.7 ± 0.1 and Ki of 185 nM), BR111 (pKi of 6.3 ± 0.2 and Ki of 544 nM) and SB290157 (pKi of 6.3 ± 0.1 and Ki of 517 nM) via displacement of Eu–DTPA–hC3a from hC3aR. The macromolecular conjugate Eu–DTPA–hC3a is a novel nonradioactive probe suitable for studying ligand–C3aR interactions with potential value in accelerating drug development for human C3aR in physiology and disease.

Bioconjug Chem. 2017, In Press.

May 31. doi: 10.1021/acs.bioconjchem.7b00132. 

http://fairlie.imb.uq.edu.au/index.php

New Fairlie Group Paper: Quinazolinone derivatives as inhibitors of homologous recombinase RAD51.

Quinazolinone derivatives as inhibitors of homologous recombinase RAD51.

Ward A, Dong L, Harris JM, Khanna KK, Al-Ejeh F, Fairlie DP, Wiegmans AP, Liu L.

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Bioorg Med Chem Lett. 2017, In Press.

May 15. pii: S0960-894X(17)30520-6. doi: 10.1016/j.bmcl.2017.05.039.

Abstract

RAD51 is a vital component of the homologous recombination DNA repair pathway and is overexpressed in drug-resistant cancers, including aggressive triple negative breast cancer (TNBC). A proposed strategy for improving therapeutic outcomes for patients is through small molecule inhibition of RAD51, thereby sensitizing tumor cells to DNA damaging irradiation and/or chemotherapy. Here we report structure-activity relationships for a library of quinazolinone derivatives. A novel RAD51 inhibitor (17) displays up to 15-fold enhanced inhibition of cell growth in a panel of TNBC cell lines compared to compound B02, and approximately 2-fold increased inhibition of irradiation-induced RAD51 foci formation. Additionally, compound 17 significantly inhibits TNBC cell sensitivity to DNA damage, implying a potentially targeted therapy for cancer treatment.

New review from the Fairlie Group out now in Chemical Reviews. Orally absorbed cyclic peptides.

Orally Absorbed Cyclic Peptides

Nielsen DS, Shepherd NE, Xu W, Lucke AJ, Stoermer MJ and Fairlie DP.

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Chem. Rev., In Press
Publication Date (Web): May 25, 2017

Peptides and proteins are important mediators of biological processes, and modulating protein-target interactions is an attractive way to develop new drugs. Unfortunately proteins and peptides are usually only deliverable intravenously, due to their generally poor absorption, or rapid degradation when take orally.

Due to their high specificity however, increasing efforts are being made to modify peptides to increase their oral absorption and consequently, their utility. One approach used by nature and synthetic chemists alike is to increase the stability of peptidic drug candidates by cyclisation.

In this review we survey 125 cyclic peptides and analyse how cyclisation and other modifications affects the flexibility and other molecular properties such as the rule-of-five (RO5) rubric, more commonly associated with small molecule drugs.

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Xray crystal structure of cyclosporine A, Dotted lines indicate internal hydrogen bonds. (Loosli 1985).

 

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Xray crystal structure of cyclic hexaleucine , a small bioavailable cyclic peptide. (Hill 2014)

This work was supported by grants from the National Health and Medical Research Council and the Australian Research Council

 

Orally absorbed cyclic peptides. Daniel S. Nielsen, Nicholas E. Shepherd, Weijun Xu, Andrew J. Lucke, Martin J. Stoermer,* and David P. Fairlie* Chem. Rev., 2017, Article ASAP. Copyright (2017) American Chemical Society. DOI: 10.1021/acs.chemrev.6b00838. TOC graphic reprinted with permission.

The conformation of cyclosporin a in the crystal and in solution.Loosli, H.-R.; Kessler, H.; Oschkinat, H.; Weber, H.-P.; Petcher, T.J.; Widmer, A. Peptide conformations. Part 31†. Helv. Chim. Acta 1985, 68, 682-704. DOI: 10.1002/hlca.19850680319

Cyclic Penta- and Hexa- Leucine Peptides Without N-Methylation Are Orally Absorbed. Timothy A Hill , Rink-Jan J Lohman , Huy Ngoc Hoang , Daniel S Nielsen , Conor CG Scully, Woan Mei Kok , Ligong Liu , Andrew J Lucke , Martin J Stoermer , Christina I Schroeder , Stephanie Chaousis , Barbara Colless , Paul Vincent Bernhardt , David J. Edmonds , David A. Griffith , Charles J. Rotter , Roger B. Ruggeri , David A. Price , Spiros Liras , David J Craik , and David P. Fairlie, ACS Med. Chem. Lett., 2014, 5, 1148-1151. Copyright (2014) American Chemical Society. DOI: 10.1021/ml5002823. TOC graphic reprinted with permission.

http://fairlie.imb.uq.edu.au/index.php

New Paper: Drugs and drug-like molecules can modulate the function of mucosal-associated invariant T cells.

Drugs and drug-like molecules can modulate the function of mucosal-associated invariant T cells.
Keller AN, Eckle SB, Xu W, Liu L, Hughes VA, Mak JY, Meehan BS, Pediongco T, Birkinshaw RW, Chen Z, Wang H, D’Souza C, Kjer-Nielsen L, Gherardin NA, Godfrey DI, Kostenko L, Corbett AJ, Purcell AW, Fairlie DP*, McCluskey J*, Rossjohn J*.
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Nature Immunology 2017, 18, 402-411.

The major-histocompatibility-complex-(MHC)-class-I-related molecule MR1 can present activating and non-activating vitamin-B-based ligands to mucosal-associated invariant T cells (MAIT cells). Whether MR1 binds other ligands is unknown. Here we identified a range of small organic molecules, drugs, drug metabolites and drug-like molecules, including salicylates and diclofenac, as MR1-binding ligands. Some of these ligands inhibited MAIT cells ex vivo and in vivo, while others, including diclofenac metabolites, were agonists. Crystal structures of a T cell antigen receptor (TCR) from a MAIT cell in complex with MR1 bound to the non-stimulatory and stimulatory compounds showed distinct ligand orientations and contacts within MR1, which highlighted the versatility of the MR1 binding pocket. The findings demonstrated that MR1 was able to capture chemically diverse structures, spanning mono- and bicyclic compounds, that either inhibited or activated MAIT cells. This indicated that drugs and drug-like molecules can modulate MAIT cell function in mammals.

 

http://fairlie.imb.uq.edu.au/index.php

Tracking the Chemical Footprints of Bacteria

9 March, 2017

We all know that green leafy vegetables, seafood, meat, dairy, cereals and even mushrooms, almonds and vegemite are all healthy for us. One essential ingredient in them is vitamin B2 (riboflavin) that enriches our immune system. But did you know that bacteria in our bodies also make this vitamin?

Scientists at the Universities of Queensland, Melbourne and Monash recently learned that when bacteria produce this vitamin, they leave behind a trail of chemical footprints that are invisible under microscopes and vanish in minutes. Two chemists at the University of Queensland’s Institute for Molecular Bioscience, Dr Jeff Mak and Dr Ligong Liu, have now made these chemicals in a testube.

Dr Mak said “Certain white blood cells in our immune system act like sniffer dogs in finding these footprints and chasing after bacteria to destroy them”. Dr Liu said “Our immune cells can find just a few molecules in a trillion (1,000,000,000,000) of these chemical footprints”. “By learning how to make these trace chemicals from bacteria, scientists around the world now have new tools to find even traces of infection in our body and new clues to fight disease”, added team leader Professor David Fairlie.

The work published this week in Nature Communications was supported by the ARC Centre of Excellence in Advanced Molecular Imaging and the National Health and Medical Research Council of Australia.

Drugs and Drug-Like Molecules Activate or Inhibit T cells

7 February, 2017

PhD student Weijun Xu from The University of Queensland’s Institute for Molecular Bioscience used computer modelling to predict chemical structures, drugs and drug-like molecules that activate or inhibit T cells called MAIT cells. Such small compounds included salicylates, non-steroidal anti-inflammatory drugs like diclofenac, and drug metabolites. Researchers from University of Queensland, Monash University and University of Melbourne are a step closer to understanding immune sensitivities to well-known, and commonly prescribed, medications (Nature Immunology 2017, doi: 10.1038/ni.3679 [Epub ahead of print]).