title: Regulated expression of pH sensing G Protein-coupled receptor-68 identified through chemical biology defines a new drug target for ischemic heart disease.
abstract: Chemical biology promises discovery of new and unexpected mechanistic pathways, protein functions and disease targets. Here, we probed the mechanism-of-action and protein targets of 3,5-disubstituted isoxazoles (Isx), cardiomyogenic small molecules that target Notch-activated epicardium-derived cells (NECs) in vivo and promote functional recovery after myocardial infarction (MI). Mechanistic studies in NECs led to an Isx-activated G(q) protein-coupled receptor (G(q)PCR) hypothesis tested in a cell-based functional target screen for GPCRs regulated by Isx. This screen identified one agonist hit, the extracellular proton/pH-sensing GPCR GPR68, confirmed through genetic gain- and loss-of-function. Overlooked until now, GPR68 expression and localization were highly regulated in early post-natal and adult post-infarct mouse heart, where GPR68-expressing cells accumulated subepicardially. Remarkably, GPR68-expressing cardiomyocytes established a proton-sensing cellular "buffer zone" surrounding the MI. Isx pharmacologically regulated gene expression (mRNAs and miRs) in this GPR68-enriched border zone, driving cardiomyogenic and pro-survival transcriptional programs in vivo. In conclusion, we tracked a (micromolar) bioactive small molecule's mechanism-of-action to a candidate target protein, GPR68, and validated this target as a previously unrecognized regulator of myocardial cellular responses to tissue acidosis, setting the stage for future (nanomolar) target-based drug lead discovery.
authors.affiliation: Departments of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Jamie L
authors.initials: JL
authors.lastname: Russell
authors.forename: Sean C
authors.initials: SC
authors.lastname: Goetsch
authors.forename: Hector R
authors.initials: HR
authors.lastname: Aguilar
authors.forename: Helen
authors.initials: H
authors.lastname: Coe
authors.forename: Xiang
authors.initials: X
authors.lastname: Luo
authors.forename: Ning
authors.initials: N
authors.lastname: Liu
authors.forename: Eva
authors.initials: E
authors.lastname: van Rooij
authors.forename: Doug E
authors.initials: DE
authors.lastname: Frantz
authors.forename: Jay W
authors.initials: JW
authors.lastname: Schneider
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D007555:Isoxazoles / Q000737:chemistry* / Q000494:pharmacology*; D051379:Mice; D009203:Myocardial Infarction / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010496:Pericardium / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D043562:Receptors, G-Protein-Coupled / Q000235:genetics*; D051880:Receptors, Notch / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects*
chemical_list: C486281:GPR68 protein, human; D007555:Isoxazoles; D043562:Receptors, G-Protein-Coupled; D051880:Receptors, Notch; D002118:Calcium