title: The pH-sensing receptor OGR1 improves barrier function of epithelial cells and inhibits migration in an acidic environment.
abstract: The pH-sensing receptor ovarian cancer G protein-coupled receptor 1 (OGR1; GPR68) is expressed in the gut. Inflammatory bowel disease is typically associated with a decrease in local pH, which may lead to altered epithelial barrier function and subsequent gastrointestinal repair involving epithelial cell adhesion and migration. As the mechanisms underlying the response to pH changes are not well understood, we have investigated OGR1-mediated, pH-dependent signaling pathways in intestinal epithelial cells. Caco-2 cells stably overexpressing OGR1 were created and validated as tools to study OGR1 signaling. Barrier function, migration, and proliferation were measured using electric cell-substrate impedance-sensing technology. Localization of the tight junction proteins zonula occludens protein 1 and occludin and the rearrangement of cytoskeletal actin were examined by confocal microscopy. Paracellular permeability and protein and gene expression analysis using DNA microarrays were performed on filter-grown Caco-2 monolayers. We report that an acidic pH shift from pH 7.8 to 6.6 improved barrier function and stimulated reorganization of filamentous actin with prominent basal stress fiber formation. Cell migration and proliferation during in vitro wound healing were inhibited. Gene expression analysis revealed significant upregulation of genes related to cytoskeleton remodeling, cell adhesion, and growth factor signaling. We conclude that acidic extracellular pH can have a signaling function and impact the physiology of intestinal epithelial cells. The deconstruction of OGR1-dependent signaling may aid our understanding of mucosal inflammation mechanisms.
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland; Novartis Institutes for Biomedical Research, Basel, Switzerland;
authors.forename: Cheryl
authors.initials: C
authors.lastname: de Vallière
authors.affiliation: Novartis Institutes for Biomedical Research, Basel, Switzerland;
authors.forename: Solange
authors.initials: S
authors.lastname: Vidal
authors.affiliation: Novartis Institutes for Biomedical Research, Basel, Switzerland;
authors.forename: Ieuan
authors.initials: I
authors.lastname: Clay
authors.affiliation: Novartis Institutes for Biomedical Research, Basel, Switzerland;
authors.forename: Giorgia
authors.initials: G
authors.lastname: Jurisic
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland;
authors.forename: Irina
authors.initials: I
authors.lastname: Tcymbarevich
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland;
authors.forename: Silvia
authors.initials: S
authors.lastname: Lang
authors.affiliation: Novartis Institutes for Biomedical Research, Basel, Switzerland;
authors.forename: Marie-Gabrielle
authors.initials: MG
authors.lastname: Ludwig
authors.affiliation: Functional Genomics Center, University of Zurich, Zurich, Switzerland;
authors.forename: Michal
authors.initials: M
authors.lastname: Okoniewski
authors.affiliation: Department of Clinical Pharmacology and Toxicology, University Hospital Zurich, Zurich, Switzerland;
authors.forename: Jyrki J
authors.initials: JJ
authors.lastname: Eloranta
authors.affiliation: Department of Clinical Pharmacology and Toxicology, University Hospital Zurich, Zurich, Switzerland;
authors.forename: Gerd A
authors.initials: GA
authors.lastname: Kullak-Ublick
authors.affiliation: Institute of Physiology, University of Zurich, Zurich, Switzerland; and Zurich Center for Integrative Human Physiology, Zurich, Switzerland.
authors.forename: Carsten A
authors.identifier: http://orcid.org/0000-0002-9874-8898
authors.initials: CA
authors.lastname: Wagner
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland; Zurich Center for Integrative Human Physiology, Zurich, Switzerland.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Rogler
authors.affiliation: Novartis Institutes for Biomedical Research, Basel, Switzerland; klaus.seuwen@novartis.com.
authors.forename: Klaus
authors.initials: K
authors.lastname: Seuwen
mesh_terms: D000143:Acids; D000199:Actins / Q000378:metabolism; D018938:Caco-2 Cells; D002118:Calcium / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology*; D017097:Electric Impedance; D004847:Epithelial Cells / Q000502:physiology*; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology; D010766:Phosphorylation; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D014945:Wound Healing / Q000235:genetics
chemical_list: D000143:Acids; D000199:Actins; C486281:GPR68 protein, human; D007295:Inositol Phosphates; D043562:Receptors, G-Protein-Coupled; D002118:Calcium
keywords: F-actin; IBD; acidic pH; electrical impedance; inflammation; intestinal epithelial cells; tight junctions