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Mouat MA, Coleman JLJ, Smith NJ. GPCRs in context: sexual dimorphism in the cardiovascular system. Br J Pharmacol 2018; 175:4047-4059. [PMID: 29451687 DOI: 10.1111/bph.14160] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 01/31/2018] [Accepted: 02/09/2018] [Indexed: 12/31/2022] Open
Abstract
Cardiovascular disease (CVD) remains the largest cause of mortality worldwide, and there is a clear gender gap in disease occurrence, with men being predisposed to earlier onset of CVD, including atherosclerosis and hypertension, relative to women. Oestrogen may be a driving factor for female-specific cardioprotection, though androgens and sex chromosomes are also likely to contribute to sexual dimorphism in the cardiovascular system (CVS). Many GPCR-mediated processes are involved in cardiovascular homeostasis, and some exhibit clear sex divergence. Here, we focus on the G protein-coupled oestrogen receptor, endothelin receptors ETA and ETB and the eicosanoid G protein-coupled receptors (GPCRs), discussing the evidence and potential mechanisms leading to gender dimorphic responses in the vasculature. The use of animal models and pharmacological tools has been essential to understanding the role of these receptors in the CVS and will be key to further delineating their sex-specific effects. Ultimately, this may illuminate wider sex differences in cardiovascular pathology and physiology. LINKED ARTICLES This article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.21/issuetoc.
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Wirasinha RC, Vijayan D, Smith NJ, Parnell GP, Swarbrick A, Brink R, King C, Stewart G, Booth DR, Batten M. GPR65 inhibits experimental autoimmune encephalomyelitis through CD4+
T cell independent mechanisms that include effects on iNKT cells. Immunol Cell Biol 2017; 96:128-136. [DOI: 10.1111/imcb.1031] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 11/14/2017] [Accepted: 11/15/2017] [Indexed: 12/18/2022]
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Abstract
Acute trauma can lead to life-long changes in susceptibility to psychiatric disease, such as post-traumatic stress disorder (PTSD). Rats given free access to a concentrated glucose solution for 24 h beginning immediately after trauma failed to show stress-related pathology in the learned helplessness model of PTSD and comorbid major depression. We assessed effective dosing and temporal constraints of the glucose intervention in three experiments. We exposed 120 male Sprague-Dawley rats to 100, 1 mA, 3-15 s, inescapable and unpredictable electric tail shocks (over a 110-min period) or simple restraint in the learned helplessness procedure. Rats in each stress condition had access to a 40% glucose solution or water. We measured fluid consumption under 18-h free access conditions, or limited access (1, 3, 6, 18 h) beginning immediately after trauma, or 3-h access with delayed availability of the glucose solution (0, 1, 3, 6 h). We hypothesized that longer and earlier access following acute stress would improve shuttle-escape performance. Rats exposed to traumatic shock and given 18-h access to glucose failed to show exaggerated fearfulness and showed normal reactivity to foot shock during testing as compared to their water-treated counterparts. At least 3 h of immediate post-stress access to glucose were necessary to see these improvements in test performance. Moreover, delaying access to glucose for more than 3 h post-trauma yielded no beneficial effects. These data clearly identify limits on the post-stress glucose intervention. In conclusion, glucose should be administered almost immediately and at the highest dose after trauma.
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Coleman JLJ, Ngo T, Smith NJ. The G protein-coupled receptor N-terminus and receptor signalling: N-tering a new era. Cell Signal 2017; 33:1-9. [PMID: 28188824 DOI: 10.1016/j.cellsig.2017.02.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 02/06/2017] [Indexed: 01/22/2023]
Abstract
G protein-coupled receptors (GPCRs) are a vast family of membrane-traversing proteins, essential to the ability of eukaryotic life to detect, and mount an intracellular response to, a diverse range of extracellular stimuli. GPCRs have evolved with archetypal features including an extracellular N-terminus and intracellular C-terminus that flank a transmembrane structure of seven sequential helices joined by intracellular and extracellular loops. These structural domains contribute to the ability of a GPCR to be correctly synthesised and inserted into the cell membrane, to interact with its cognate ligand(s) and to couple with signal-transducing heterotrimeric G proteins, allowing the activated receptor to selectively modulate a number of signalling cascades. Whilst well known for its importance in receptor translation and trafficking, the GPCR N-terminus is underexplored as a participant in receptor signalling. This review aims to discuss and integrate recent advances in knowledge of the vital roles of the GPCR N-terminus in receptor signalling.
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Ngo T, Kufareva I, Coleman JL, Graham RM, Abagyan R, Smith NJ. Identifying ligands at orphan GPCRs: current status using structure-based approaches. Br J Pharmacol 2016; 173:2934-51. [PMID: 26837045 PMCID: PMC5341249 DOI: 10.1111/bph.13452] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 11/18/2015] [Accepted: 01/29/2016] [Indexed: 12/26/2022] Open
Abstract
GPCRs are the most successful pharmaceutical targets in history. Nevertheless, the pharmacology of many GPCRs remains inaccessible as their endogenous or exogenous modulators have not been discovered. Tools that explore the physiological functions and pharmacological potential of these 'orphan' GPCRs, whether they are endogenous and/or surrogate ligands, are therefore of paramount importance. Rates of receptor deorphanization determined by traditional reverse pharmacology methods have slowed, indicating a need for the development of more sophisticated and efficient ligand screening approaches. Here, we discuss the use of structure-based ligand discovery approaches to identify small molecule modulators for exploring the function of orphan GPCRs. These studies have been buoyed by the growing number of GPCR crystal structures solved in the past decade, providing a broad range of template structures for homology modelling of orphans. This review discusses the methods used to establish the appropriate signalling assays to test orphan receptor activity and provides current examples of structure-based methods used to identify ligands of orphan GPCRs. Linked Articles This article is part of a themed section on Molecular Pharmacology of G Protein-Coupled Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.20/issuetoc.
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Coleman JLJ, Ngo T, Schmidt J, Mrad N, Liew CK, Jones NM, Graham RM, Smith NJ. Metalloprotease cleavage of the N terminus of the orphan G protein-coupled receptor GPR37L1 reduces its constitutive activity. Sci Signal 2016; 9:ra36. [PMID: 27072655 DOI: 10.1126/scisignal.aad1089] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Little is known about the pharmacology or physiology of GPR37L1, a G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptor that is abundant in the cerebellum. Mice deficient in this receptor exhibit precocious cerebellar development and hypertension. We showed that GPR37L1 coupled to the G protein Gα(s) when heterologously expressed in cultured cells in the absence of any added ligand, whereas a mutant receptor that lacked the amino terminus was inactive. Conversely, inhibition of ADAMs (a disintegrin and metalloproteases) enhanced receptor activity, indicating that the presence of the amino terminus is necessary for GPR37L1 signaling. Metalloprotease-dependent processing of GPR37L1 was evident in rodent cerebellum, where we detected predominantly the cleaved, inactive form. However, comparison of the accumulation of cAMP (adenosine 3',5'-monophosphate) in response to phosphodiesterase inhibition in cerebellar slice preparations from wild-type and GPR37L1-null mice showed that some constitutive signaling remained in the wild-type mice. In reporter assays of Gα(s) or Gα(i) signaling, the synthetic, prosaposin-derived peptide prosaptide (TX14A) did not increase GPR37L1 activity. Our data indicate that GPR37L1 may be a constitutively active receptor, or perhaps its ligand is present under the conditions that we used for analysis, and that the activity of this receptor is instead controlled by signals that regulate metalloprotease activity in the tissue.
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McNamara JW, Li A, Smith NJ, Lal S, Graham RM, Kooiker KB, van Dijk SJ, Remedios CGD, Harris SP, Cooke R. Ablation of cardiac myosin binding protein-C disrupts the super-relaxed state of myosin in murine cardiomyocytes. J Mol Cell Cardiol 2016; 94:65-71. [PMID: 27021517 DOI: 10.1016/j.yjmcc.2016.03.009] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 03/17/2016] [Accepted: 03/19/2016] [Indexed: 11/24/2022]
Abstract
Cardiac myosin binding protein-C (cMyBP-C) is a structural and regulatory component of cardiac thick filaments. It is observed in electron micrographs as seven to nine transverse stripes in the central portion of each half of the A band. Its C-terminus binds tightly to the myosin rod and contributes to thick filament structure, while the N-terminus can bind both myosin S2 and actin, influencing their structure and function. Mutations in the MYBPC3 gene (encoding cMyBP-C) are commonly associated with hypertrophic cardiomyopathy (HCM). In cardiac cells there exists a population of myosin heads in the super-relaxed (SRX) state, which are bound to the thick filament core with a highly inhibited ATPase activity. This report examines the role cMyBP-C plays in regulating the population of the SRX state of cardiac myosin by using an assay that measures single ATP turnover of myosin. We report a significant decrease in the proportion of myosin heads in the SRX state in homozygous cMyBP-C knockout mice, however heterozygous cMyBP-C knockout mice do not significantly differ from the wild type. A smaller, non-significant decrease is observed when thoracic aortic constriction is used to induce cardiac hypertrophy in mutation negative mice. These results support the proposal that cMyBP-C stabilises the thick filament and that the loss of cMyBP-C results in an untethering of myosin heads. This results in an increased myosin ATP turnover, further consolidating the relationship between thick filament structure and the myosin ATPase.
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Soetanto R, Hynes CJ, Patel HR, Humphreys DT, Evers M, Duan G, Parker BJ, Archer SK, Clancy JL, Graham RM, Beilharz TH, Smith NJ, Preiss T. Role of miRNAs and alternative mRNA 3'-end cleavage and polyadenylation of their mRNA targets in cardiomyocyte hypertrophy. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2016; 1859:744-56. [PMID: 27032571 DOI: 10.1016/j.bbagrm.2016.03.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Revised: 02/25/2016] [Accepted: 03/20/2016] [Indexed: 12/19/2022]
Abstract
miRNAs play critical roles in heart disease. In addition to differential miRNA expression, miRNA-mediated control is also affected by variable miRNA processing or alternative 3'-end cleavage and polyadenylation (APA) of their mRNA targets. To what extent these phenomena play a role in the heart remains unclear. We sought to explore miRNA processing and mRNA APA in cardiomyocytes, and whether these change during cardiac hypertrophy. Thoracic aortic constriction (TAC) was performed to induce hypertrophy in C57BL/6J mice. RNA extracted from cardiomyocytes of sham-treated, pre-hypertrophic (2 days post-TAC), and hypertrophic (7 days post-TAC) mice was subjected to small RNA- and poly(A)-test sequencing (PAT-Seq). Differential expression analysis matched expectations; nevertheless we identified ~400 mRNAs and hundreds of noncoding RNA loci as altered with hypertrophy for the first time. Although multiple processing variants were observed for many miRNAs, there was little change in their relative proportions during hypertrophy. PAT-Seq mapped ~48,000 mRNA 3'-ends, identifying novel 3' untranslated regions (3'UTRs) for over 7000 genes. Importantly, hypertrophy was associated with marked changes in APA with a net shift from distal to more proximal mRNA 3'-ends, which is predicted to decrease overall miRNA repression strength. We independently validated several examples of 3'UTR proportion change and showed that alternative 3'UTRs associate with differences in mRNA translation. Our work suggests that APA contributes to altered gene expression with the development of cardiomyocyte hypertrophy and provides a rich resource for a systems-level understanding of miRNA-mediated regulation in physiological and pathological states of the heart.
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Grundmann M, Tikhonova IG, Hudson BD, Smith NJ, Mohr K, Ulven T, Milligan G, Kenakin T, Kostenis E. A Molecular Mechanism for Sequential Activation of a G Protein-Coupled Receptor. Cell Chem Biol 2016; 23:392-403. [PMID: 26991104 DOI: 10.1016/j.chembiol.2016.02.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 02/11/2016] [Accepted: 02/22/2016] [Indexed: 01/05/2023]
Abstract
Ligands targeting G protein-coupled receptors (GPCRs) are currently classified as either orthosteric, allosteric, or dualsteric/bitopic. Here, we introduce a new pharmacological concept for GPCR functional modulation: sequential receptor activation. A hallmark feature of this is a stepwise ligand binding mode with transient activation of a first receptor site followed by sustained activation of a second topographically distinct site. We identify 4-CMTB (2-(4-chlorophenyl)-3-methyl-N-(thiazol-2-yl)butanamide), previously classified as a pure allosteric agonist of the free fatty acid receptor 2, as the first sequential activator and corroborate its two-step activation in living cells by tracking integrated responses with innovative label-free biosensors that visualize multiple signaling inputs in real time. We validate this unique pharmacology with traditional cellular readouts, including mutational and pharmacological perturbations along with computational methods, and propose a kinetic model applicable to the analysis of sequential receptor activation. We envision this form of dynamic agonism as a common principle of nature to spatiotemporally encode cellular information.
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Smith NJ. Drug Discovery Opportunities at the Endothelin B Receptor-Related Orphan G Protein-Coupled Receptors, GPR37 and GPR37L1. Front Pharmacol 2015; 6:275. [PMID: 26635605 PMCID: PMC4648071 DOI: 10.3389/fphar.2015.00275] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 10/30/2015] [Indexed: 01/01/2023] Open
Abstract
Orphan G protein-coupled receptors (GPCRs) represent a largely untapped resource for the treatment of a variety of diseases, despite sophisticated advances in drug discovery. Two promising orphan GPCRs are the endothelin B receptor-like proteins, GPR37 [ET(B)R-LP, Pael-R] and GPR37L1 [ET(B)R-LP-2]. Originally identified through searches for homologs of endothelin and bombesin receptors, neither GPR37 nor GPR37L1 were found to bind endothelins or related peptides. Instead, GPR37 was proposed to be activated by head activator (HA) and both GPR37 and GPR37L1 have been linked to the neuropeptides prosaposin and prosaptide, although these pairings are yet to be universally acknowledged. Both orphan GPCRs are widely expressed in the brain, where GPR37 has received the most attention for its link to Parkinson’s disease and parkinsonism, while GPR37L1 deletion leads to precocious cerebellar development and hypertension. In this review, the existing pharmacology and physiology of GPR37 and GPR37L1 is discussed and the potential therapeutic benefits of targeting these receptors are explored.
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Coote KJ, Paisley D, Czarnecki S, Tweed M, Watson H, Young A, Sugar R, Vyas M, Smith NJ, Baettig U, Groot-Kormelink PJ, Gosling M, Lock R, Ethell B, Williams G, Schumacher A, Harris J, Abraham WM, Sabater J, Poll CT, Faller T, Collingwood SP, Danahay H. NVP-QBE170: an inhaled blocker of the epithelial sodium channel with a reduced potential to induce hyperkalaemia. Br J Pharmacol 2015; 172:2814-26. [PMID: 25573195 DOI: 10.1111/bph.13075] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 12/23/2014] [Accepted: 12/23/2014] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND AND PURPOSE Inhaled amiloride, a blocker of the epithelial sodium channel (ENaC), enhances mucociliary clearance (MCC) in cystic fibrosis (CF) patients. However, the dose of amiloride is limited by the mechanism-based side effect of hyperkalaemia resulting from renal ENaC blockade. Inhaled ENaC blockers with a reduced potential to induce hyperkalaemia provide a therapeutic strategy to improve mucosal hydration and MCC in the lungs of CF patients. The present study describes the preclinical profile of a novel ENaC blocker, NVP-QBE170, designed for inhaled delivery, with a reduced potential to induce hyperkalaemia. EXPERIMENTAL APPROACH The in vitro potency and duration of action of NVP-QBE170 were compared with amiloride and a newer ENaC blocker, P552-02, in primary human bronchial epithelial cells (HBECs) by short-circuit current. In vivo efficacy and safety were assessed in guinea pig (tracheal potential difference/hyperkalaemia), rat (hyperkalaemia) and sheep (MCC). KEY RESULTS In vitro, NVP-QBE170 potently inhibited ENaC function in HBEC and showed a longer duration of action to comparator molecules. In vivo, intratracheal (i.t.) instillation of NVP-QBE170 attenuated ENaC activity in the guinea pig airways with greater potency and duration of action than that of amiloride without inducing hyperkalaemia in either guinea pig or rat. Dry powder inhalation of NVP-QBE170 by conscious sheep increased MCC and was better than inhaled hypertonic saline in terms of efficacy and duration of action. CONCLUSIONS AND IMPLICATIONS NVP-QBE170 highlights the potential for inhaled ENaC blockers to exhibit efficacy in the airways with a reduced risk of hyperkalaemia, relative to existing compounds.
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Coleman JLJ, Brennan K, Ngo T, Balaji P, Graham RM, Smith NJ. Rapid Knockout and Reporter Mouse Line Generation and Breeding Colony Establishment Using EUCOMM Conditional-Ready Embryonic Stem Cells: A Case Study. Front Endocrinol (Lausanne) 2015; 6:105. [PMID: 26175717 PMCID: PMC4485191 DOI: 10.3389/fendo.2015.00105] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 06/15/2015] [Indexed: 12/18/2022] Open
Abstract
As little as a decade ago, generation of a single knockout mouse line was an expensive and time-consuming undertaking available to relatively few researchers. The International Knockout Mouse Consortium, established in 2007, has revolutionized the use of such models by creating an open-access repository of embryonic stem (ES) cells that, through sequential breeding with first FLP1 recombinase and then Cre recombinase transgenic mice, facilitates germline global or conditional deletion of almost every gene in the mouse genome. In this Case Study, we describe our experience using the repository to create mouse lines for a variety of experimental purposes. Specifically, we discuss the process of obtaining germline transmission of two European Conditional Mouse Mutagenesis Program (EUCOMM) "knockout-first" gene targeted constructs and the advantages and pitfalls of using this system. We then outline our breeding strategy and the outcomes of our efforts to generate global and conditional knockouts and reporter mice for the genes of interest. Line maintenance, removal of recombinase transgenes, and cryopreservation are also considered. Our approach led to the generation of heterozygous knockout mice within 6 months of commencing breeding to the founder mice. By describing our experiences with the EUCOMM ES cells and subsequent breeding steps, we hope to assist other researchers with the application of this valuable approach to generating versatile knockout mouse lines.
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Yu ZY, Tan JC, McMahon AC, Iismaa SE, Xiao XH, Kesteven SH, Reichelt ME, Mohl MC, Smith NJ, Fatkin D, Allen D, Head SI, Graham RM, Feneley MP. RhoA/ROCK signaling and pleiotropic α1A-adrenergic receptor regulation of cardiac contractility. PLoS One 2014; 9:e99024. [PMID: 24919197 PMCID: PMC4053326 DOI: 10.1371/journal.pone.0099024] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 05/09/2014] [Indexed: 11/18/2022] Open
Abstract
Aims To determine the mechanisms by which the α1A-adrenergic receptor (AR) regulates cardiac contractility. Background We reported previously that transgenic mice with cardiac-restricted α1A-AR overexpression (α1A-TG) exhibit enhanced contractility but not hypertrophy, despite evidence implicating this Gαq/11-coupled receptor in hypertrophy. Methods Contractility, calcium (Ca2+) kinetics and sensitivity, and contractile proteins were examined in cardiomyocytes, isolated hearts and skinned fibers from α1A-TG mice (170-fold overexpression) and their non-TG littermates (NTL) before and after α1A-AR agonist stimulation and blockade, angiotensin II (AngII), and Rho kinase (ROCK) inhibition. Results Hypercontractility without hypertrophy with α1A-AR overexpression is shown to result from increased intracellular Ca2+ release in response to agonist, augmenting the systolic amplitude of the intracellular Ca2+ concentration [Ca2+]i transient without changing resting [Ca2+]i. In the absence of agonist, however, α1A-AR overexpression reduced contractility despite unchanged [Ca2+]i. This hypocontractility is not due to heterologous desensitization: the contractile response to AngII, acting via its Gαq/11-coupled receptor, was unaltered. Rather, the hypocontractility is a pleiotropic signaling effect of the α1A-AR in the absence of agonist, inhibiting RhoA/ROCK activity, resulting in hypophosphorylation of both myosin phosphatase targeting subunit 1 (MYPT1) and cardiac myosin light chain 2 (cMLC2), reducing the Ca2+ sensitivity of the contractile machinery: all these effects were rapidly reversed by selective α1A-AR blockade. Critically, ROCK inhibition in normal hearts of NTLs without α1A-AR overexpression caused hypophosphorylation of both MYPT1 and cMLC2, and rapidly reduced basal contractility. Conclusions We report for the first time pleiotropic α1A-AR signaling and the physiological role of RhoA/ROCK signaling in maintaining contractility in the normal heart.
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Smith NJ, Sheldrick RC, Perrin EC. An Abbreviated Screening Instrument for Autism Spectrum Disorders. Infant Ment Health J 2012. [DOI: 10.1002/imhj.21356] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Currie AC, Evans J, Smith NJ, Brown G, Abulafi AM, Swift RI. The impact of the two-week wait referral pathway on rectal cancer survival. Colorectal Dis 2012; 14:848-53. [PMID: 21920010 DOI: 10.1111/j.1463-1318.2011.02829.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
AIM The aim of this study was to compare the outcome of patients with rectal cancer referred through the two-week wait (TWW) system with those identified by routine referral pathways (non-TWW). METHOD A prospective study was carried out of 125 consecutive patients diagnosed with rectal cancer between January 2000 and December 2005 (6 years) in one district general hospital. Data were recorded prospectively in a local clinicopathological registry. The patients were divided into two groups: group 1 (TWW) and group 2 (routine referral pathway). RESULTS Fifty-two (41%) of the 125 patients were diagnosed through the TWW (group 1). There was no significant difference in patient demographics, including baseline tumour characteristics, between the two groups. There was no difference in preoperative or postoperative T stage between the two groups (P = 0.63). There was no significant difference in circumferential margin positivity (five of 52 in group 1 vs four of 73 in group 2; P = 0.52) or local recurrence rates (P = 0.37). The 5-year all-cause mortality was 49% for group 1 and 52% for group 2 (P = 0.3). The overall disease-free survival was similar in the two groups (1521 days for group 1 vs 1591 days for group 1, P = 0.29). CONCLUSION Referral under the TWW strategy does not translate into improved survival in rectal cancer.
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Smith NJ. Low affinity GPCRs for metabolic intermediates: challenges for pharmacologists. Front Endocrinol (Lausanne) 2012; 3:1. [PMID: 22649402 PMCID: PMC3355937 DOI: 10.3389/fendo.2012.00001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Accepted: 01/03/2012] [Indexed: 12/22/2022] Open
Abstract
The discovery that a number of metabolites and metabolic intermediates can act through G protein-coupled receptors has attracted great interest in the field and has led to new therapeutic targets for diseases such as hypertension, type 2 diabetes, inflammation, and metabolic syndrome. However, the low apparent affinity of these ligands for their cognate receptors poses a number of challenges for pharmacologists interested in investigating receptor structure, function or physiology. Furthermore, the endogenous ligands matched to their receptors have other, well established metabolic roles and thus selectivity is difficult to achieve. This review discusses some of the issues researchers face when working with these receptors and highlights the ways in which a number of these obstacles have been overcome.
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Smith NJ, Chan HW, Qian H, Bourne AM, Hannan KM, Warner FJ, Ritchie RH, Pearson RB, Hannan RD, Thomas WG. Determination of the Exact Molecular Requirements for Type 1 Angiotensin Receptor Epidermal Growth Factor Receptor Transactivation and Cardiomyocyte Hypertrophy. Hypertension 2011; 57:973-80. [DOI: 10.1161/hypertensionaha.110.166710] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Smith NJ, Ward RJ, Stoddart LA, Hudson BD, Kostenis E, Ulven T, Morris JC, Tränkle C, Tikhonova IG, Adams DR, Milligan G. Extracellular loop 2 of the free fatty acid receptor 2 mediates allosterism of a phenylacetamide ago-allosteric modulator. Mol Pharmacol 2011; 80:163-73. [PMID: 21498659 DOI: 10.1124/mol.110.070789] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Allosteric agonists are powerful tools for exploring the pharmacology of closely related G protein-coupled receptors that have nonselective endogenous ligands, such as the short chain fatty acids at free fatty acid receptors 2 and 3 (FFA2/GPR43 and FFA3/GPR41, respectively). We explored the molecular mechanisms mediating the activity of 4-chloro-α-(1-methylethyl)-N-2-thiazolylbenzeneacetamide (4-CMTB), a recently described phenylacetamide allosteric agonist and allosteric modulator of endogenous ligand function at human FFA2, by combining our previous knowledge of the orthosteric binding site with targeted examination of 4-CMTB structure-activity relationships and mutagenesis and chimeric receptor generation. Here we show that 4-CMTB is a selective agonist for FFA2 that binds to a site distinct from the orthosteric site of the receptor. Ligand structure-activity relationship studies indicated that the N-thiazolyl amide is likely to provide hydrogen bond donor/acceptor interactions with the receptor. Substitution at Leu(173) or the exchange of the entire extracellular loop 2 of FFA2 with that of FFA3 was sufficient to reduce or ablate, respectively, allosteric communication between the endogenous and allosteric agonists. Thus, we conclude that extracellular loop 2 of human FFA2 is required for transduction of cooperative signaling between the orthosteric and an as-yet-undefined allosteric binding site of the FFA2 receptor that is occupied by 4-CMTB.
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Smith NJ, Milligan G. Allostery at G protein-coupled receptor homo- and heteromers: uncharted pharmacological landscapes. Pharmacol Rev 2011; 62:701-25. [PMID: 21079041 DOI: 10.1124/pr.110.002667] [Citation(s) in RCA: 211] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
For many years seven transmembrane domain G protein-coupled receptors (GPCRs) were thought to exist and function exclusively as monomeric units. However, evidence both from native cells and heterologous expression systems has demonstrated that GPCRs can both traffic and signal within higher-order complexes. As for other protein-protein interactions, conformational changes in one polypeptide, including those resulting from binding of pharmacological ligands, have the capacity to alter the conformation and therefore the response of the interacting protein(s), a process known as allosterism. For GPCRs, allosterism across homo- or heteromers, whether dimers or higher-order oligomers, represents an additional topographical landscape that must now be considered pharmacologically. Such effects may offer the opportunity for novel therapeutic approaches. Allosterism at GPCR heteromers is particularly exciting in that it offers additional scope to provide receptor subtype selectivity and tissue specificity as well as fine-tuning of receptor signal strength. Herein, we introduce the concept of allosterism at both GPCR homomers and heteromers and discuss the various questions that must be addressed before significant advances can be made in drug discovery at these GPCR complexes.
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Tikhonova IG, Smith NJ, Ward RJ, Stoddart LA, Hudson BD, Kostenis E, Ulven T, Morris JC, Adams D, Milligan G. Probing Allosteric Binding Site Mapping in the Free Fatty Acid 2 receptor. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Smith NJ, Bennett KA, Milligan G. When simple agonism is not enough: emerging modalities of GPCR ligands. Mol Cell Endocrinol 2011; 331:241-7. [PMID: 20654693 DOI: 10.1016/j.mce.2010.07.009] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Revised: 06/15/2010] [Accepted: 07/13/2010] [Indexed: 01/03/2023]
Abstract
Recent advances in G protein-coupled receptors have challenged traditional definitions of agonism, antagonism, affinity and efficacy. The discovery of agonist functional selectivity and receptor allosterism has meant researchers have an expanded canvas for designing and discovering novel drugs. Here we describe modes of agonism emerging from the discovery of functional selectivity and allosterism. We discuss the concept of ago-allosterism, where ligands can initiate signaling by themselves and influence the actions of another ligand at the same receptor. We introduce the concept of dualsteric ligands that consist of distinct elements which bind to each of the orthosteric and an allosteric domain on a single receptor to enhance subtype selectivity. Finally, the concept that efficacy should be defined by the activity of an endogenous ligand will be challenged by the discovery that some ligands act as 'super-agonists' in specific pathways or at certain receptor mutations.
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Schmidt J, Smith NJ, Christiansen E, Tikhonova IG, Grundmann M, Hudson BD, Ward RJ, Drewke C, Milligan G, Kostenis E, Ulven T. Selective orthosteric free fatty acid receptor 2 (FFA2) agonists: identification of the structural and chemical requirements for selective activation of FFA2 versus FFA3. J Biol Chem 2011; 286:10628-40. [PMID: 21220428 PMCID: PMC3060514 DOI: 10.1074/jbc.m110.210872] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Free fatty acid receptor 2 (FFA2; GPR43) is a G protein-coupled seven-transmembrane receptor for short-chain fatty acids (SCFAs) that is implicated in inflammatory and metabolic disorders. The SCFA propionate has close to optimal ligand efficiency for FFA2 and can hence be considered as highly potent given its size. Propionate, however, does not discriminate between FFA2 and the closely related receptor FFA3 (GPR41). To identify FFA2-selective ligands and understand the molecular basis for FFA2 selectivity, a targeted library of small carboxylic acids was examined using holistic, label-free dynamic mass redistribution technology for primary screening and the receptor-proximal G protein [35S]guanosine 5′-(3-O-thio)triphosphate activation, inositol phosphate, and cAMP accumulation assays for hit confirmation. Structure-activity relationship analysis allowed formulation of a general rule to predict selectivity for small carboxylic acids at the orthosteric binding site where ligands with substituted sp3-hybridized α-carbons preferentially activate FFA3, whereas ligands with sp2- or sp-hybridized α-carbons prefer FFA2. The orthosteric binding mode was verified by site-directed mutagenesis: replacement of orthosteric site arginine residues by alanine in FFA2 prevented ligand binding, and molecular modeling predicted the detailed mode of binding. Based on this, selective mutation of three residues to their non-conserved counterparts in FFA3 was sufficient to transfer FFA3 selectivity to FFA2. Thus, selective activation of FFA2 via the orthosteric site is achievable with rather small ligands, a finding with significant implications for the rational design of therapeutic compounds selectively targeting the SCFA receptors.
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Hudson B, Smith NJ, Milligan G. Experimental Challenges to Targeting Poorly Characterized GPCRs: Uncovering the Therapeutic Potential for Free Fatty Acid Receptors. PHARMACOLOGY OF G PROTEIN COUPLED RECEPTORS 2011; 62:175-218. [DOI: 10.1016/b978-0-12-385952-5.00006-3] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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Flores-Muñoz M, Smith NJ, Haggerty C, Milligan G, Nicklin SA. Angiotensin1-9 antagonises pro-hypertrophic signalling in cardiomyocytes via the angiotensin type 2 receptor. J Physiol 2010; 589:939-51. [PMID: 21173078 DOI: 10.1113/jphysiol.2010.203075] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The renin–angiotensin system (RAS) regulates blood pressure mainly via the actions of angiotensin (Ang)II, generated via angiotensin converting enzyme (ACE). The ACE homologue ACE2 metabolises AngII to Ang1-7, decreasing AngII and increasing Ang1-7, which counteracts AngII activity via the Mas receptor. However, ACE2 also converts AngI to Ang1-9, a poorly characterised peptide which can be further converted to Ang1-7 via ACE. Ang1-9 stimulates bradykinin release in endothelium and has antihypertrophic actions in the heart, attributed to its being a competitive inhibitor of ACE, leading to decreased AngII, rather than increased Ang1-7. To date no direct receptor-mediated effects of Ang1-9 have been described. To further understand the role of Ang1-9 in RAS function we assessed its action in cardiomyocyte hypertrophy in rat neonatal H9c2 and primary adult rabbit left ventricular cardiomyocytes, compared to Ang1-7. Cardiomyocyte hypertrophy was stimulated with AngII or vasopressin, significantly increasing cell size by approximately 1.2-fold (P < 0.05) as well as stimulating expression of the hypertrophy gene markers atrial natriuretic peptide, brain natriuretic peptide, β-myosin heavy chain and myosin light chain (2- to 5-fold, P < 0.05). Both Ang1-9 and Ang1-7 were able to block hypertrophy induced by either agonist (control, 186.4 μm; AngII, 232.8 μm; AngII+Ang1-7, 198.3 μm; AngII+Ang1-9, 195.9 μm; P < 0.05). The effects of Ang1-9 were not inhibited by captopril, supporting previous evidence that Ang1-9 acts independently of Ang1-7. Next, we investigated receptor signalling via angiotensin type 1 and type 2 receptors (AT1R, AT2R) and Mas. The AT1R antagonist losartan blocked AngII-induced, but not vasopressin-induced, hypertrophy. Losartan did not block the antihypertrophic effects of Ang1-9, or Ang1-7 on vasopressin-stimulated cardiomyocytes. The Mas antagonist A779 efficiently blocked the antihypertrophic effects of Ang1-7, without affecting Ang1-9. Furthermore, Ang1-7 activity was also inhibited in the presence of the bradykinin type 2 receptor antagonist HOE140, without affecting Ang1-9. Moreover, we observed that the AT2R antagonist PD123,319 abolished the antihypertrophic effects of Ang1-9, without affecting Ang1-7, suggesting Ang1-9 signals via the AT2R. Radioligand binding assays demonstrated that Ang1-9 was able to bind the AT2R (pKi = 6.28 ± 0.1). In summary, we ascribe a direct biological role for Ang1-9 acting via the AT2R. This has implications for RAS function and identifying new therapeutic targets in cardiovascular disease.
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Schröder R, Janssen N, Schmidt J, Kebig A, Merten N, Hennen S, Müller A, Blättermann S, Mohr-Andrä M, Zahn S, Wenzel J, Smith NJ, Gomeza J, Drewke C, Milligan G, Mohr K, Kostenis E. Deconvolution of complex G protein-coupled receptor signaling in live cells using dynamic mass redistribution measurements. Nat Biotechnol 2010; 28:943-9. [PMID: 20711173 DOI: 10.1038/nbt.1671] [Citation(s) in RCA: 221] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Label-free biosensor technology based on dynamic mass redistribution (DMR) of cellular constituents promises to translate GPCR signaling into complex optical 'fingerprints' in real time in living cells. Here we present a strategy to map cellular mechanisms that define label-free responses, and we compare DMR technology with traditional second-messenger assays that are currently the state of the art in GPCR drug discovery. The holistic nature of DMR measurements enabled us to (i) probe GPCR functionality along all four G-protein signaling pathways, something presently beyond reach of most other assay platforms; (ii) dissect complex GPCR signaling patterns even in primary human cells with unprecedented accuracy; (iii) define heterotrimeric G proteins as triggers for the complex optical fingerprints; and (iv) disclose previously undetected features of GPCR behavior. Our results suggest that DMR technology will have a substantial impact on systems biology and systems pharmacology as well as for the discovery of drugs with novel mechanisms.
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