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Int Immunopharmacol. 2015 Nov;29(1):143-7. doi: 10.1016/j.intimp.2015.06.005. Epub 2015 Jun 20.

Cholinergic chemosensory cells of the thymic medulla express the bitter receptor Tas2r131.

Author information

1
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.
2
Department of Molecular Genetics, German Institute of Human Nutrition, Potsdam Rehbruecke, Nuthetal, Germany.
3
Walter-Straub-Institute for Pharmacology and Toxicology, Ludwig-Maximilian-University, Munich, Germany.
4
Department of Pharmacology and Toxicology, University of Saarland School of Medicine, Homburg, Germany.
5
Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, German Center for Lung Research, Giessen, Germany.

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.

KEYWORDS:

Bitter; Chemosensory; Non-neuronal acetylcholine; Taste; Thymus

PMID:
26102274
DOI:
10.1016/j.intimp.2015.06.005
[Indexed for MEDLINE]

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