Ligand-specific conformational change of the G-protein-coupled receptor ALX/FPR2 determines proresolving functional responses (original) (raw)
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Heterologously expressed formyl peptide receptor 2 (FPR2/ALX) does not respond to lipoxin A4
Biochemical Pharmacology, 2013
Lipoxin A 4 (LXA 4) has been described as an anti-inflammatory mediator, which exerts its effects through the formyl peptide receptor FPR2, also known as ALX. However, there has been a controversy whether or not cells expressing FPR2/ALX, such as neutrophils, respond to LXA 4. We, therefore, systematically examined the ability of the human and murine forms of the receptor to respond to LXA 4. We show that both receptor orthologues responded to the FPR2/ALX peptide agonist WKYMVM when expressed heterologously. In contrast, LXA 4 from different sources neither increased [Ca 2+ ] i and extracellularsignal-regulated kinase (ERK) phosphorylation, nor did it induce a decrease in cAMP levels or a translocation of b-arrestin. Also, several LXA 4 analogs were found to be unable to signal through FPR2/ ALX. We conclude that FPR2/ALX is not activated by LXA 4 and that the molecular mechanism by which LXA 4 functions still needs to be identified.
Journal of Biological Chemistry, 2012
Background: FPR2/ALX is activated by many ligands, including annexin A1 (AnxA1), which activates resolution circuits in inflammation. Results: Cells transfected with FPR2/ALX and clones with domains swapped with FPR1 afforded identification of N-terminal and extracellular loop II domains as transducers of AnxA1 signaling. Conclusion: We identified AnxA1 distinct domains of FPR2/ALX and unveiled potential specific signaling. Significance: FPR2/ALX domain identification permits development of anti-inflammatory AnxA1 mimetics.
What Formyl Peptide Receptors, if Any, Are Triggered by Compound 43 and Lipoxin A4?
Scandinavian Journal of Immunology, 2011
In this study, we determined receptor preferences for compound 43, a nitrosylated pyrazolone derivative, and the eicosanoid lipoxin A 4 (LXA 4), potent antiinflammatory mediators in many experimental in vivo models. Their effects have been suggested to be mediated through binding to formyl peptide receptor (FPR)2 [earlier known as formyl peptide receptor-like 1 or the lipoxin A 4 receptor (ALXR)], one of the two members of the FPR family expressed in neutrophils. Compound 43 activates all neutrophil functions investigated, whereas LXA 4 induces a unique inhibiting pathway suggested to involve barrestin binding as an early signalling step, but not a transient rise in intracellular Ca 2+. We show that compound 43 can activate not only FPR2 but also FPR1, the other neutrophil receptor in the FPR family, and FPR1 is actually the preferred receptor in human neutrophils and possibly also in the murine equivalent. LXA 4 analogues from two commercial sources were used, and neither of these induced any translocation of b-arrestin as measured in an enzyme fragment complementation assay. The conclusions drawn from these experiments are that neither compound 43 nor LXA 4 works as FPR2 agonists in neutrophils, findings of importance for a proper interpretation of results obtained with these compounds as regulators of inflammation.
Journal of Leukocyte Biology, 2008
Neutrophils have a central role in innate immunity, and their programmed cell death and removal are critical to the optimal expression as well as to efficient resolution of inflammation. Human neutrophils express the pleiotropic receptor formyl peptide receptor-like 1/lipoxin A4 (LXA(4)) receptor that binds a variety of ligands, including the acute-phase reactant serum amyloid A (SAA), the anti-inflammatory lipids LXA(4) and aspirin-triggered 15-epi-LXA(4) (ATL), and the glucocorticoid-inducible protein annexin 1. In addition to regulation of neutrophil activation and recruitment, these ligands have a profound influence on neutrophil survival and apoptosis with contrasting actions, mediating aggravation or resolution of the inflammatory response. Thus, annexin 1 accelerates, whereas SAA rescues human neutrophils from constitutive apoptosis by preventing mitochondrial dysfunction and subsequent activation of caspase-3. Furthermore, ATL overcomes the antiapoptosis signal from SAA and redirects neutrophils to caspase-mediated cell death. We review recent developments about the molecular basis of these actions and suggest a novel mechanism by which aspirin promotes resolution of acute inflammation and tissue injury.
2010
The human formyl-peptide receptor (FPR)-2 is a G protein-coupled receptor that transduces signals from lipoxin A 4 , annexin A1, and serum amyloid A (SAA) to regulate inflammation. In this study, we report the creation of a novel mouse colony in which the murine FprL1 FPR2 homologue, Fpr2, has been deleted and describe its use to explore the biology of this receptor. Deletion of murine fpr2 was verified by Southern blot analysis and PCR, and the functional absence of the G protein-coupled receptor was confirmed by radioligand binding assays. In vitro, Fpr2 2/2 macrophages had a diminished response to formyl-Met-Leu-Phe itself and did not respond to SAA-induced chemotaxis. ERK phosphorylation triggered by SAA was unchanged, but that induced by the annexin A1derived peptide Ac2-26 or other Fpr2 ligands, such as W-peptide and compound 43, was attenuated markedly. In vivo, the antimigratory properties of compound 43, lipoxin A 4 , annexin A1, and dexamethasone were reduced notably in Fpr2 2/2 mice compared with those in wild-type littermates. In contrast, SAA stimulated neutrophil recruitment, but the promigratory effect was lost following Fpr2 deletion. Inflammation was more marked in Fpr2 2/2 mice, with a pronounced increase in cell adherence and emigration in the mesenteric microcirculation after an ischemia-reperfusion insult and an augmented acute response to carrageenan-induced paw edema, compared with that in wild-type controls. Finally, Fpr2 2/2 mice exhibited higher sensitivity to arthrogenic serum and were completely unable to resolve this chronic pathology. We conclude that Fpr2 is an anti-inflammatory receptor that serves varied regulatory functions during the host defense response. These data support the development of Fpr2 agonists as novel anti-inflammatory therapeutics.
Insights into the Activation Mechanism of the ALX/FPR2 Receptor
Journal of Physical Chemistry Letters, 2020
The formyl peptide receptor 2 (ALX/FPR2), a G-protein-coupled receptor (GPCR), plays an important role in host defense and inflammation. This receptor can be driven as pro-or anti-inflammatory depending on its agonist, such as N-formyl-Met-Leu-Phe-Lys (fMLFK) and resolvin D1 (RvD1) or its aspirin-triggered 17 (R)-epimer, AT-RvD1, respectively. However, the activation mechanism of ALX/FPR2 by pro-and anti-inflammatory agonists remains unclear. In this work, on the basis of molecular dynamics simulations, we evaluated a model of the ALX/ FPR2 receptor activation process using two agonists, fMLFK and AT-RvD1, with opposite effects. The simulations by both fMLFK and AT-RvD1 induced the ALX/FPR2 activation through a set of receptor-core residues, in particular, R205, Q258, and W254. In addition, the activation was dependent on the disruption of electrostatic interactions in the cytoplasmic region of the receptor. We also found that in the AT-RvD1 simulations, the position of the H8 helix was similar to that of the same helix in other class-A GPCRs coupled to arrestin. Thus our results shed light on the mechanism of activation of the ALX/FPR2 receptor by pro-inflammatory and pro-resolution agonists.
Journal of Pharmacology and Experimental Therapeutics, 2009
Activation of the formyl-peptide receptor-like (FPRL) 1 pathway has recently gained high recognition for its significance in therapy of inflammatory diseases. Agonism at FPRL1 affords a beneficial effect in animal models of acute inflammatory conditions, as well as in chronic inflammatory diseases. TIPMFVPESTSKLQKFTSWFM-amide (CGEN-855A) is a novel 21-amino acid peptide agonist for FPRL1 and also activates FPRL2. CGEN-855A was discovered using a computational platform designed to predict novel G protein-coupled receptor peptide agonists cleaved from secreted proteins by convertase proteolysis. In vivo, CGEN-855A displays anti-inflammatory activity manifested as 50% inhibition of polymorphonuclear neutrophil (PMN) recruitment to inflamed air pouch and provides protection against ischemia-reperfusion-mediated injury to the myocardium in both murine and rat models (36 and 25% reduction in infarct size, respectively). Both these activities are accompanied by inhibition of PMN recruitment to the injured organ. The secretion of inflammatory cytokines, including interleukin (IL)-6, IL-1beta, and tumor necrosis factor-alpha, was not affected upon incubation of human peripheral blood mononuclear cells with CGEN-855A, whereas IL-8 secretion was elevated up to 2-fold upon treatment with the highest CGEN-855A dose only. Collectively, these new data support a potential role for CGEN-855A in the treatment of reperfusion-mediated injury and in other acute and chronic inflammatory conditions.
Anti-inflammatory circuitry: Lipoxin, aspirin-triggered lipoxins and their receptor ALX
Prostaglandins, Leukotrienes and Essential Fatty Acids, 2005
Endogenous chemical mediators or autacoids play key roles in controlling inflammation and its programmed resolution. Among them, it is known that lipoxins (LX) and aspirin-triggered LX (ATL) evoke bioactions in a range of physiologic and pathophysiologic processes and serve as endogenous lipid/chemical mediators that stop neutrophilic infiltration and initiate resolution. LXA 4 , ATL and their metabolic stable analogs elicit cellular responses and regulate PMN in vivo via interacting with their specific receptor, namely ALX. ALX is the first cloned and identified lipoxygenase-derived eicosanoid receptor with cell typespecific signaling pathways. Also, ALX could regulate PMN by interacting with each class of ligands (lipid vs. peptide) within specific phases of an inflammatory response. Together LX, ATL and ALX may provide new opportunities to design ''resolutiontargeted'' therapies with high degree of precision in controlling inflammation. In this chapter, we give an overview and update of the current actions for LX and ATL, the identification of ALX and their novel anti-inflammatory and pro-resolving signals. r