title: Cholinergic chemosensory cells of the thymic medulla express the bitter receptor Tas2r131.
abstract: The thymus is the site of T cell maturation which includes positive selection in the cortex and negative selection in the medulla. Acetylcholine is locally produced in the thymus and cholinergic signaling influences the T cell development. We recently described a distinct subset of medullary epithelial cells in the murine thymus which express the acetylcholine-synthesizing enzyme choline acetyltransferase (ChAT) and components of the canonical taste transduction cascade, i.e. transient receptor potential melastatin-like subtype 5 channel (TRPM5), phospholipase Cβ(2), and Gα-gustducin. Such a chemical phenotype is characteristic for chemosensory cells of mucosal surfaces which utilize bitter receptors for detection of potentially hazardous compounds and cholinergic signaling to initiate avoidance reflexes. We here demonstrate mRNA expression of bitter receptors Tas2r105, Tas2r108, and Tas2r131 in the murine thymus. Using a Tas2r131-tauGFP reporter mouse we localized the expression of this receptor to cholinergic cells expressing the downstream elements of the taste transduction pathway. These cells are distinct from the medullary thymic epithelial cells which promiscuously express tissue-restricted self-antigens during the process of negative selection, since double-labeling immunofluorescence showed no colocalization of autoimmune regulator (AIRE), the key mediator of negative selection, and TRPM5. These data demonstrate the presence of bitter taste-sensing signaling in cholinergic epithelial cells in the thymic medulla and opens a discussion as to what is the physiological role of this pathway.
authors.affiliation: Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, German Center for Lung Research, Giessen, Germany. Electronic address: aichurek.soultanova@anatomie.med.uni-giessen.de.
authors.forename: Aichurek
authors.initials: A
authors.lastname: Soultanova
authors.affiliation: Department of Molecular Genetics, German Institute of Human Nutrition, Potsdam Rehbruecke, Nuthetal, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Voigt
authors.affiliation: Walter-Straub-Institute for Pharmacology and Toxicology, Ludwig-Maximilian-University, Munich, Germany.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Chubanov
authors.affiliation: Walter-Straub-Institute for Pharmacology and Toxicology, Ludwig-Maximilian-University, Munich, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gudermann
authors.affiliation: Department of Molecular Genetics, German Institute of Human Nutrition, Potsdam Rehbruecke, Nuthetal, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Meyerhof
authors.affiliation: Department of Pharmacology and Toxicology, University of Saarland School of Medicine, Homburg, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Boehm
authors.affiliation: Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, German Center for Lung Research, Giessen, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kummer
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002628:Chemoreceptor Cells / Q000502:physiology*; D004847:Epithelial Cells; D005786:Gene Expression Regulation / Q000502:physiology; D049452:Green Fluorescent Proteins; D051379:Mice; D008822:Mice, Transgenic; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013649:Taste; D013950:Thymus Gland / Q000166:cytology*
chemical_list: D043562:Receptors, G-Protein-Coupled; C578844:Tas2r131 protein, mouse; D049452:Green Fluorescent Proteins; D000109:Acetylcholine
keywords: Bitter; Chemosensory; Non-neuronal acetylcholine; Taste; Thymus