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Galea C.A.,Monash Institute of Pharmaceutical Sciences
Cellular and molecular life sciences : CMLS | Year: 2014

MMP23 is a member of the matrix metalloprotease family of zinc- and calcium-dependent endopeptidases, which are involved in a wide variety of cellular functions. Its catalytic domain displays a high degree of structural homology with those of other metalloproteases, but its atypical domain architecture suggests that it may possess unique functional properties. The N-terminal MMP23 pro-domain contains a type-II transmembrane domain that anchors the protein to the plasma membrane and lacks the cysteine-switch motif that is required to maintain other MMPs in a latent state during passage to the cell surface. Instead of the C-terminal hemopexin domain common to other MMPs, MMP23 contains a small toxin-like domain (TxD) and an immunoglobulin-like cell adhesion molecule (IgCAM) domain. The MMP23 pro-domain can trap Kv1.3 but not closely-related Kv1.2 channels in the endoplasmic reticulum, preventing their passage to the cell surface, while the TxD can bind to the channel pore and block the passage of potassium ions. The MMP23 C-terminal IgCAM domain displays some similarity to Ig-like C2-type domains found in IgCAMs of the immunoglobulin superfamily, which are known to mediate protein-protein and protein-lipid interactions. MMP23 and Kv1.3 are co-expressed in a variety of tissues and together are implicated in diseases including cancer and inflammatory disorders. Further studies are required to elucidate the mechanism of action of this unique member of the MMP family.


Christopoulos A.,Monash Institute of Pharmaceutical Sciences
Molecular Pharmacology | Year: 2014

It is now widely accepted that G protein-coupled receptors (GPCRs) are highly dynamic proteins that adopt multiple active states linked to distinct functional outcomes. Furthermore, these states can be differentially stabilized not only by orthosteric ligands but also by allosteric ligands acting at spatially distinct binding sites. The key pharmacologic characteristics of GPCR allostery include improved selectivity due to either greater sequence divergence between receptor subtypes and/or subtype-selective cooperativity, a ceiling level to the effect, probe dependence (whereby the magnitude and direction of the allosteric effect change with the nature of the interacting ligands), and the potential for biased signaling. Recent chemical biology developments are beginning to demonstrate how the incorporation of analytical pharmacology and operational modeling into the experimental workflow can enrich structure-activity studies of allostery and bias, and have also led to the discovery of a new class of hybrid orthosteric/ allosteric (bitopic) molecules. The potential for endogenous allosteric modulators to play a role in physiology and disease remains to be fully appreciated but will likely represent an important area for future studies. Finally, breakthroughs in structural and computational biology are beginning to unravel the mechanistic basis of GPCR allosteric modulation at the molecular level. Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics.


Canals M.,Monash Institute of Pharmaceutical Sciences | Sexton P.M.,Monash Institute of Pharmaceutical Sciences | Christopoulos A.,Monash Institute of Pharmaceutical Sciences
Trends in Biochemical Sciences | Year: 2011

G protein-coupled receptors (GPCRs) constitute the largest family of receptors in the genome and are the targets for at least 30% of current medicines. In recent years, there has been a dramatic increase in the discovery of allosteric modulators of GPCR activity and a growing appreciation of the diverse modes by which GPCRs can be regulated by both orthosteric and allosteric ligands. Interestingly, some of the contemporary views of GPCR function reflect characteristics that are shared by prototypical allosteric proteins, as encompassed in the classic Monod-Wyman-Changeux (MWC) model initially proposed for enzymes and subsequently extended to other protein families. In this review, we revisit the MWC model in the context of emerging structural, functional and operational data on GPCR allostery. © 2011 Elsevier Ltd.


Langmead C.J.,Monash Institute of Pharmaceutical Sciences | Christopoulos A.,Monash Institute of Pharmaceutical Sciences
Current Opinion in Cell Biology | Year: 2014

Traditionally, optimizing lead molecule interactions with the orthosteric site has been viewed as the best means for attaining selectivity at G protein-coupled receptors (GPCRs), but GPCRs possess spatially distinct allosteric sites that can also modulate receptor activity. Allosteric sites offer a greater potential for receptor subtype selectivity, the ability to fine-tune physiological responses, and the ability to engender signal pathway bias. The detection and quantification of allosteric drug candidates remain an ongoing challenge, but the development of novel analytical approaches for quantifying allostery is enriching structure-activity and structure-function studies of the phenomenon. Very recent breakthroughs in both structural and computational biology of GPCRs are also beginning to unravel the mechanistic basis of allosteric modulation at the molecular level. © 2013 Elsevier Ltd.


Canals M.,Monash Institute of Pharmaceutical Sciences
Molecular Pharmacology | Year: 2015

This Commentary focuses on two articles in the October 2015 issue of Molecular Pharmacology that investigate the role of μ-opioid receptor phosphorylation in receptor agonist binding and desensitization. The work of Birdsong et al. and Yousuf et al. clearly highlights the complexity that researchers face when trying to assess the signaling and regulatory consequences of G protein-coupled receptor phosphorylation. Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.


Irving H.R.,Monash Institute of Pharmaceutical Sciences
Plant signaling & behavior | Year: 2012

Guanylate cyclase (GC) catalyzes the formation of cGMP and it is only recently that such enzymes have been characterized in plants. One family of plant GCs contains the GC catalytic center encapsulated within the intracellular kinase domain of leucine rich repeat receptor like kinases such as the phytosulfokine and brassinosteroid receptors. In vitro studies show that both the kinase and GC domain have catalytic activity indicating that these kinase-GCs are examples of moonlighting proteins with dual catalytic function. The natural ligands for both receptors increase intracellular cGMP levels in isolated mesophyll protoplast assays suggesting that the GC activity is functionally relevant. cGMP production may have an autoregulatory role on receptor kinase activity and / or contribute to downstream cell expansion responses. We postulate that the receptors are members of a novel class of receptor kinases that contain functional moonlighting GC domains essential for complex signaling roles.


Le T.,CSIRO | Epa V.C.,CSIRO | Burden F.R.,CSIRO | Winkler D.A.,CSIRO | Winkler D.A.,Monash Institute of Pharmaceutical Sciences
Chemical Reviews | Year: 2012

A study was conducted to demonstrate the most commonly used predictive quantitative structure-property relationship (QSPR) modeling methods and their applications to materials design. QSPR methods were based on the hypothesis that changes in molecular structure were reflected in changes in observed macroscopic properties of materials. QSPR modeling was a supervised learning method that extracted the complex relationships between the microscopic structure and properties of materials and their macroscopic properties. The key requirement for QSPR modeling was a reliable data set of molecules or materials whose microscopic structures and properties were well-defined along with their measured macroscopic properties of interest. The reliability of the experimental property chosen to be modeled was important, as it was one of the factors that determined the stability and predictivity of models.


Velkov T.,Monash Institute of Pharmaceutical Sciences
PPAR Research | Year: 2013

Fatty acid binding proteins (FABPs) act as intracellular shuttles for fatty acids as well as lipophilic xenobiotics to the nucleus, where these ligands are released to a group of nuclear receptors called the peroxisome proliferator activated receptors (PPARs). PPAR mediated gene activation is ultimately involved in maintenance of cellular homeostasis through the transcriptional regulation of metabolic enzymes and transporters that target the activating ligand. Here we show that liver- (L-) FABP displays a high binding affinity for PPAR subtype selective drugs. NMR chemical shift perturbation mapping and proteolytic protection experiments show that the binding of the PPAR subtype selective drugs produces conformational changes that stabilize the portal region of L-FABP. NMR chemical shift perturbation studies also revealed that L-FABP can form a complex with the PPAR ligand binding domain (LBD) of PPARα. This protein-protein interaction may represent a mechanism for facilitating the activation of PPAR transcriptional activity via the direct channeling of ligands between the binding pocket of L-FABP and the PPARαLBD. The role of L-FABP in the delivery of ligands directly to PPARα via this channeling mechanism has important implications for regulatory pathways that mediate xenobiotic responses and host protection in tissues such as the small intestine and the liver where L-FABP is highly expressed. © 2013 Tony Velkov.


Bunnett N.W.,Monash Institute of Pharmaceutical Sciences
Journal of Physiology | Year: 2014

In addition to their role in the digestion and absorption of dietary fats, bile acids (BAs) are tightly regulated signalling molecules. Their levels in the intestinal lumen, circulation and tissues fluctuate after feeding and fasting, and as a result of certain diseases and therapies. BAs regulate many cell types in the gut wall and beyond by activating nuclear and plasma membrane receptors. Of these, the G protein-coupled receptor TGR5 has emerged as a key mediator of the non-genomic actions of BAs. TGR5 is a cell-surface receptor that couples to Gαs, formation of cAMP, activation of protein kinase A and extracellular signal-regulated kinases, and inhibition of inflammatory signalling pathways. TGR5 has been implicated in mediating the actions of BAs on secretion of glucagon-like peptide 1 and glucose homeostasis, gastrointestinal motility and transit, electrolyte and fluid transport in the colon, bile formation and secretion, sensory transduction and inflammation. TGR5 agonists have been developed as treatments for metabolic, inflammatory and digestive disorders, and emerging evidence suggests that TGR5 mutations are associated with inflammatory diseases. Thus, TGR5 plays an important role in the normal processes of digestion and is a new therapeutic target for important digestive diseases. © 2014 The Physiological Society.


News Article | February 15, 2017
Site: phys.org

Multi-drug resistance in bacteria has been identified as a major worldwide public health concern by the World Health Organization.  Multi-drug resistant bacteria are responsible for approximately 700,000 deaths per year, a figure which the WHO says could reach 10 million by the year 2050. EptA causes multi-drug resistance by masking bacteria against both the human immune system and important classes of antibiotics. A very similar variant of EptA called MCR-1 was discovered in 2015 causing resistance to colistin, a last resort antibiotic for bacteria untreatable by other means. Alarmingly, MCR-1 is not limited to a single type of bacteria, but is able to spread between different species of bacteria increasing its harmfullness significantly. Lead scientist in the study, Professor of Structural Biology Alice Vrielink from UWA's School of Molecular Sciences, said the researchers used a technique called X-ray crystallography to map three-dimensional shape of EptA. "The function of a protein molecule is directly related to it's three-dimensional shape," Professor Vrielink said. "This new knowledge of the shape and unique structure of EptA (and MCR-1) will help scientists develop an effective treatment to prevent antibiotic resistance of these super bugs, a huge step forward for global health." Work towards identifying potential new therapuetic molecules targeting EptA and MCR-1 is already underway through joint efforts by researchers at the UWA School of Molecular Sciences, the Marshall Center for Infectious Disease and the Monash Institute of Pharmaceutical Sciences. The research is funded by National Health and Medical Research Council of Australia and included collaborations from several universities and organisations around the globe. The research has been published in the journal Proceedings of the National Academy of Sciences (PNAS). Explore further: Antibiotics can still kill drug-resistant bacteria if they 'push' hard enough into bacterial cells More information: Anandhi Anandan et al. Structure of a lipid A phosphoethanolamine transferase suggests how conformational changes govern substrate binding, Proceedings of the National Academy of Sciences (2017). DOI: 10.1073/pnas.1612927114

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