Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Free fatty acids (FFAs) play important physiological roles in many tissues as an energy source and as signaling molecules in various cellular processes. Elevated levels of circulating FFAs are associated with obesity, dyslipidemia, and diabetes. Here we show that GPR84, a previously orphan G protein-coupled receptor, functions as a receptor for medium-chain FFAs with carbon chain lengths of 9-14. Medium-chain FFAs elicit calcium mobilization, inhibit 3',5'-cyclic AMP production, and stimulate [35S]guanosine 5'-O-(3-thiotriphosphate) binding in a GPR84-dependent manner. The activation of GPR84 by medium-chain FFAs couples primarily to a pertussis toxin-sensitive G(i/o) pathway. In addition, we show that GPR84 is selectively expressed in leukocytes and markedly induced in monocytes/macrophages upon activation by lipopolysaccharide. Furthermore, we demonstrate that medium-chain FFAs amplify lipopolysaccharide-stimulated production of the proinflammatory cytokine interleukin-12 p40 through GPR84. Our results indicate a role for GPR84 in directly linking fatty acid metabolism to immunological regulation.
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PMID:Medium-chain fatty acids as ligands for orphan G protein-coupled receptor GPR84. 1696 19

GPR84 was identified as a receptor for medium-chain fatty acids with carbon chain lengths of 9-14. It has previously been reported that lipopolysaccharide (LPS) induces significantly up-regulation of zebrafish gpr84, and zebrafish gpr84 overexpression markedly increased the LPS-stimulated production of the cytokine IL-12. Here we expanded on these studies to further investigate the roles of zebrafish Gpr84 in immune reaction. Flow cytometric assay was used to assess the effects of zebrafish Gpr84 on the phagocytosis of bacteria by macrophages. It was found that overexpression of zebrafish gpr84 significantly increased both the phagocytic ability (PA) and phagocytic index (PI) values of the macrophages engulfing the bacteria, suggesting that zebrafish Gpr84 was able to promote the phagocytosis of bacteria by the macrophages. The data proves the direct effect of Gpr84 in immune reaction.
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PMID:Zebrafish fatty acids receptor Gpr84 enhances macrophage phagocytosis. 3041 94

Many members of the G protein-coupled receptor family, including examples with clear therapeutic potential, remain poorly characterised. This often reflects limited availability of suitable tool ligands with which to interrogate receptor function. In the case of GPR84, currently a target for the treatment of idiopathic pulmonary fibrosis, recent times have seen the description of novel orthosteric and allosteric agonists. Using 2-(hexylthiol)pyrimidine-4,6 diol (2-HTP) and di(5,7-difluoro-1H-indole-3-yl)methane (PSB-16671) as exemplars of each class, in cell lines transfected to express either human or mouse GPR84, both ligands acted as effective on-target activators and with high co-operativity in their interactions. This was also the case in lipopolysaccharide-activated model human and mouse immune cell lines. However in mouse bone-marrow-derived neutrophils, where expression of GPR84 is particularly high, the capacity of PSB-16671 but not of 2-HTP to promote G protein activation was predominantly off-target because it was not blocked by an antagonist of GPR84 and was preserved in neutrophils isolated from GPR84 deficient mice. These results illustrate the challenges of attempting to study and define functions of poorly characterised receptors using ligands that have been developed via medicinal chemistry programmes, but where assessed activity has been limited largely to the initially identified target.
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PMID:On-target and off-target effects of novel orthosteric and allosteric activators of GPR84. 3075 5