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Patients with idiopathic pulmonary fibrosis show a strongly upregulated expression of chemokine CXCL14, whose target is still unknown. Screening of CXCL14 in a panel of human G protein-coupled receptors (GPCRs) revealed its potent and selective activation of the orphan MAS-related GPCR X2 (MRGPRX2). This receptor is expressed on mast cells and − like CXCL14 − upregulated in bronchial inflammation. CXCL14 induces robust activation of MRGPRX2 and its putative mouse ortholog MRGPRB2 in G protein-dependent and β-arrestin recruitment assays that is blocked by a selective MRGPRX2/B2 antagonist. Truncation combined with mutagenesis and computational studies identified the pharmacophoric sequence of CXCL14 and its presumed interaction with the receptor. Intriguingly, C-terminal domain sequences of CXCL14 consisting of 4 to 11 amino acids display similar or increased potency and efficacy compared to the full CXCL14 sequence (77 amino acids). These results provide a rational basis for the future development of potential idiopathic pulmonary fibrosis therapies. This study reveals that the proinflammatory chemokine CXCL14 activates MAS-related G protein-coupled receptor MRGPRX2; these results provide a rational basis for the future development of idiopathic pulmonary fibrosis therapies. [ABSTRACT FROM AUTHOR]

G protein-coupled receptors (GPCRs) transfer extracellular signals across cell membranes by activating intracellular heterotrimeric G proteins. Several studies suggested G proteins as novel drug targets for the treatment of complex diseases, e.g., asthma and cancer. Recently, we developed specific radiotracers, [³H]PSB-15900-FR and [³H]PSB-16254-YM, for the Gαq family of G proteins by tritiation of the macrocyclic natural products FR900359 (FR) and YM-254890 (YM). In the present study, we utilized these potent radioligands to perform autoradiography studies in tissues of healthy mice, mouse models of disease, and human tissues. Specific binding was high, while non-specific binding was extraordinarily low, giving nearly identical results for both radioligands. High expression levels of Gαq proteins were detected in healthy mouse organs showing the following rank order of potency: kidney > liver > brain > pancreas > lung > spleen, while expression in the heart was low. Organ sub-structures, e.g., of mouse brain and lung, were clearly distinguishable. Whereas an acute asthma model in mice did not result in altered Gαq protein expressions as compared to control animals, a cutaneous melanoma model displayed significantly increased expression in comparison to healthy skin. These results suggest the future development of Gαq-protein-binding radio-tracers as novel diagnostics. [ABSTRACT FROM AUTHOR]