G protein-coupled receptors (GPCRs) are historically the most successful family of drug targets. In recent times it has become clear that the pharmacology of these receptors is far more complex than ...previously imagined. Understanding of the pharmacological regulation of GPCRs now extends beyond simple competitive agonism or antagonism by ligands interacting with the orthosteric binding site of the receptor to incorporate concepts of allosteric agonism, allosteric modulation, signaling bias, constitutive activity, and inverse agonism. Herein, we consider how evolving concepts of GPCR pharmacology have shaped understanding of the complex pharmacology of receptors that recognize and are activated by nonesterified or “free” fatty acids (FFAs). The FFA family of receptors is a recently deorphanized set of GPCRs, the members of which are now receiving substantial interest as novel targets for the treatment of metabolic and inflammatory diseases. Further understanding of the complex pharmacology of these receptors will be critical to unlocking their ultimate therapeutic potential.
The purpose of this study was to compare the penetration of 808 and 980 nm laser light through bovine tissue samples 18-95 mm thick.
Low-level laser therapy (LLLT) is frequently used to treat ...musculoskeletal pathologies. Some of the therapeutic targets are several centimeters deep.
Laser light at 808 and 980 nm (1 W/cm(2)) was projected through bovine tissue samples ranging in thickness from 18 to 95 mm. Power density measurements were taken for each wavelength at the various depths.
For 808 nm, 1 mW/cm(2) was achieved at 3.4 cm, but for 980 nm, 1 mW/cm(2) was achieved at only 2.2 cm depth of tissue.
It was determined that 808 nm of light penetrates as much as 54% deeper than 980 nm light in bovine tissue.
GPR120 is a receptor of unsaturated long-chain fatty acids reported to mediate GLP-1 secretion, insulin sensitization, anti-inflammatory, and anti-obesity effects and is therefore emerging as a new ...potential target for treatment of type 2 diabetes and metabolic diseases. Further investigation is however hindered by the lack of suitable receptor modulators. Screening of FFA1 ligands provided a lead with moderate activity on GPR120 and moderate selectivity over FFA1. Optimization led to the discovery of the first potent and selective GPR120 agonist.
TUG-891 3-(4-((4-fluoro-4'-methyl-1,1'-biphenyl-2-yl)methoxy)phenyl)propanoic acid was recently described as a potent and selective agonist for the long chain free fatty acid (LCFA) receptor 4 (FFA4; ...previously G protein-coupled receptor 120, or GPR120). Herein, we have used TUG-891 to further define the function of FFA4 and used this compound in proof of principle studies to indicate the therapeutic potential of this receptor. TUG-891 displayed similar signaling properties to the LCFA α-linolenic acid at human FFA4 across various assay end points, including stimulation of Ca²⁺ mobilization, β-arrestin-1 and β-arrestin-2 recruitment, and extracellular signal-regulated kinase phosphorylation. Activation of human FFA4 by TUG-891 also resulted in rapid phosphorylation and internalization of the receptor. While these latter events were associated with desensitization of the FFA4 signaling response, removal of TUG-891 allowed both rapid recycling of FFA4 back to the cell surface and resensitization of the FFA4 Ca²⁺ signaling response. TUG-891 was also a potent agonist of mouse FFA4, but it showed only limited selectivity over mouse FFA1, complicating its use in vivo in this species. Pharmacologic dissection of responses to TUG-891 in model murine cell systems indicated that activation of FFA4 was able to mimic many potentially beneficial therapeutic properties previously reported for LCFAs, including stimulating glucagon-like peptide-1 secretion from enteroendocrine cells, enhancing glucose uptake in 3T3-L1 adipocytes, and inhibiting release of proinflammatory mediators from RAW264.7 macrophages, which suggests promise for FFA4 as a therapeutic target for type 2 diabetes and obesity. Together, these results demonstrate both potential but also significant challenges that still need to be overcome to therapeutically target FFA4.
FFA4/GPR120: Pharmacology and Therapeutic Opportunities Milligan, Graeme; Alvarez-Curto, Elisa; Hudson, Brian D. ...
Trends in pharmacological sciences (Regular ed.),
September 2017, 2017-09-00, 20170901, Letnik:
38, Številka:
9
Journal Article
Recenzirano
Odprti dostop
Free Fatty Acid receptor 4 (FFA4), also known as GPR120, is a G-protein-coupled receptor (GPCR) responsive to long-chain fatty acids that is attracting considerable attention as a potential novel ...therapeutic target for the treatment of type 2 diabetes mellitus (T2DM). Although no clinical studies have yet been initiated to assess efficacy in this indication, a significant number of primary publications and patents have highlighted the ability of agonists with potency at FFA4 to improve glucose disposition and enhance insulin sensitivity in animal models. However, the distribution pattern of the receptor suggests that targeting FFA4 may also be useful in other conditions, ranging from cancer to lung function. Here, we discuss and contextualise the basis for these ideas and the results to support these conclusions.
Substantial focus on the therapeutic potential of FFA4/GPR120 is currently directed towards type 2 diabetes.
Progress in the identification and characterisation of FFA4/GPR120 agonist ligands is apparent in both the primary scientific and patent literatures.
In models of glucose handling, FFA4/GPR120 agonists appear highly effective.
Recent indications provide support for consideration of FFA4/GPR120 ligands in areas of cancer treatment.
High levels of expression of FFA4/GPR120 in the lung suggest utility in analysis of the potential therapeutic roles of FFA4/GPR120 ligands in both acute and chronic airway inflammatory conditions.
The succinate receptor (SUCNR1) has emerged as a potential target for the treatment of various metabolic and inflammatory diseases, including hypertension, inflammatory bowel disease, and rheumatoid ...arthritis. While several ligands for this receptor have been reported, species differences in pharmacology between human and rodent orthologs have limited the validation of SUCNR1’s therapeutic potential. Here, we describe the development of the first potent fluorescent tool compounds for SUCNR1 and use these to define key differences in ligand binding to human and mouse SUCNR1. Starting from known agonist scaffolds, we developed a potent agonist tracer, TUG-2384 (22), with affinity for both human and mouse SUCNR1. In addition, we developed a novel antagonist tracer, TUG-2465 (46), which displayed high affinity for human SUCNR1. Using 46 we demonstrate that three humanizing mutations on mouse SUCNR1, N181.31E, K2697.32N, and G84EL1W, are sufficient to restore high-affinity binding of SUCNR1 antagonists to the mouse receptor ortholog.
Metabolic disorders including obesity, diabetes and non-alcoholic steatohepatitis are a group of conditions characterised by chronic low-grade inflammation of metabolic tissues. There is now a ...growing appreciation that various metabolites released from adipose tissue serve as key signalling mediators, influencing this interaction with inflammation. G protein-coupled receptors (GPCRs) are the largest family of signal transduction proteins and most historically successful drug targets. The signalling pathways for several key adipose metabolites are mediated through GPCRs expressed both on the adipocytes themselves and on infiltrating macrophages. These include three main groups of GPCRs: the FFA4 receptor, which is activated by long chain free fatty acids; the HCA
and HCA
receptors, activated by hydroxy carboxylic acids; and the succinate receptor. Understanding the roles these metabolites and their receptors play in metabolic-immune interactions is critical to establishing how these GPCRs may be exploited for the treatment of metabolic disorders.
The long-chain fatty acid receptor FFA4 (previously GPR120) is receiving substantial interest as a novel target for the treatment of metabolic and inflammatory disease. This study examines for the ...first time the detailed mode of binding of both long-chain fatty acid and synthetic agonist ligands at FFA4 by integrating molecular modeling, receptor mutagenesis, and ligand structure-activity relationship approaches in an iterative format. In doing so, residues required for binding of fatty acid and synthetic agonists to FFA4 have been identified. This has allowed for the refinement of a well validated model of the mode of ligand-FFA4 interaction that will be invaluable in the identification of novel ligands and the future development of this receptor as a therapeutic target. The model reliably predicted the effects of substituent variations on agonist potency, and it was also able to predict the qualitative effect of binding site mutations in the majority of cases.
Background: FFA4 is a receptor for long-chain fatty acids and is considered a novel target for metabolic diseases.
Results: Combinations of molecular modeling, receptor mutagenesis, and ligand structure-activity relationships defined the binding pocket.
Conclusion: Fatty acid and synthetic agonists share an overlapping binding site.
Significance: The validated homology model will assist the search for novel ligands.
Free fatty acid receptors 2 and 3 (FFA2 and FFA3) are G protein-coupled receptors for short chain free fatty acids (SCFAs). They respond to the same set of endogenous ligands but with distinct ...rank-order of potency such that acetate (C2) has been described as FFA2-selective, whereas propionate (C3) is non-selective. Although C2 was confirmed to be selective for human FFA2 over FFA3, this ligand was not selective between the mouse orthologs. Moreover, although C3 was indeed not selective between the human orthologs, it displayed clear selectivity for mouse FFA3 over mouse FFA2. This altered selectivity to C2 and C3 resulted from broad differences in SCFAs potency at the mouse orthologs. In studies to define the molecular basis for these observations, marked variation in ligand-independent constitutive activity was identified using a 35SGTPγS assay. The orthologs with higher potency for the SCFAs, human FFA2 and mouse FFA3, displayed high constitutive activity in this assay, whereas the orthologs with lower potency for the agonist ligands, mouse FFA2 and human FFA3, did not. Sequence alignments of the second extracellular loop identified single negatively charged residues in FFA2 and FFA3 not conserved between species and predicted to form ionic lock interactions with arginine residues within the FFA2 or FFA3 agonist binding pocket to regulate constitutive activity and SCFA potency. Reciprocal mutation of these residues between species orthologs resulted in the induction (or repression) of constitutive activity and in most cases also yielded corresponding changes in SCFA potency.
Background: Differences in ligand potency and selectivity are observed between human and mouse FFA2 and FFA3 orthologs.
Results: Potency differences result from differential constitutive activity between species.
Conclusion: An “ionic lock” between extracellular loop 2 and the ligand binding pocket regulates constitutive activity.
Significance: Understanding species differences in FFA2 and FFA3 function is critical to future studies with these receptors.
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