title: Class I odorant receptors, TAS1R and TAS2R taste receptors, are markers for subpopulations of circulating leukocytes.
abstract: Our cellular immune system has to cope constantly with foodborne substances that enter the bloodstream postprandially. Here, they may activate leukocytes via specific but yet mostly unknown receptors. Ectopic RNA expression out of gene families of chemosensory receptors, i.e., the ∼400 ORs, ∼25 TAS2R bitter-taste receptors, and the TAS1R umami- and sweet-taste receptor dimers by which we typically detect foodborne substances, has been reported in a variety of peripheral tissues unrelated to olfaction or taste. In the present study, we have now discovered, by gene-specific RT-PCR experiments, the mRNA expression of most of the Class I ORs (TAS1R) and TAS2R in 5 different types of blood leukocytes. Surprisingly, we did not detect Class II OR mRNA. By RT-qPCR, we show the mRNA expression of human chemosensory receptors and their cow orthologs in PMN, thus suggesting an evolutionary concept. By immunocytochemistry, we demonstrate that some olfactory and taste receptors are expressed, on average, in 40-60% of PMN and T or B cells and largely coexpress in the same subpopulation of PMN. The mRNA expression and the size of subpopulations expressing certain chemosensory receptors varied largely among individual blood samples, suggesting a regulated expression of olfactory and taste receptors in these cells. Moreover, we show mRNA expression of their downstream signaling molecules and demonstrate that PTX abolishes saccharin- or 2-PEA-induced PMN chemotactic migration, indicating a role for Gi-type proteins. In summary, our data suggest "chemosensory"-type subpopulations of circulating leukocytes.
authors.affiliation: *Deutsche Forschungsanstalt für Lebensmittelchemie Leibniz Institute, Freising, Germany; and Technische Universität München, Lehrstuhl für Physiologie-Wissenschaftszentrum Weihenstephan, Freising, Germany.
authors.forename: Agne
authors.initials: A
authors.lastname: Malki
authors.affiliation: *Deutsche Forschungsanstalt für Lebensmittelchemie Leibniz Institute, Freising, Germany; and Technische Universität München, Lehrstuhl für Physiologie-Wissenschaftszentrum Weihenstephan, Freising, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Fiedler
authors.affiliation: *Deutsche Forschungsanstalt für Lebensmittelchemie Leibniz Institute, Freising, Germany; and Technische Universität München, Lehrstuhl für Physiologie-Wissenschaftszentrum Weihenstephan, Freising, Germany.
authors.forename: Kristina
authors.initials: K
authors.lastname: Fricke
authors.affiliation: *Deutsche Forschungsanstalt für Lebensmittelchemie Leibniz Institute, Freising, Germany; and Technische Universität München, Lehrstuhl für Physiologie-Wissenschaftszentrum Weihenstephan, Freising, Germany.
authors.forename: Ines
authors.initials: I
authors.lastname: Ballweg
authors.affiliation: *Deutsche Forschungsanstalt für Lebensmittelchemie Leibniz Institute, Freising, Germany; and Technische Universität München, Lehrstuhl für Physiologie-Wissenschaftszentrum Weihenstephan, Freising, Germany.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Pfaffl
authors.affiliation: *Deutsche Forschungsanstalt für Lebensmittelchemie Leibniz Institute, Freising, Germany; and Technische Universität München, Lehrstuhl für Physiologie-Wissenschaftszentrum Weihenstephan, Freising, Germany dietmar.krautwurst@lrz.tum.de.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Krautwurst
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D002417:Cattle; D002465:Cell Movement / Q000187:drug effects; D002633:Chemotaxis / Q000187:drug effects; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D007150:Immunohistochemistry; D007962:Leukocytes / Q000166:cytology* / Q000378:metabolism*; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D012439:Saccharin / Q000494:pharmacology; D012903:Smell / Q000187:drug effects; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D015293:Transducin / Q000378:metabolism; D000098706:Taste Receptors, Type 2
chemical_list: D015415:Biomarkers; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; C431926:taste receptors, type 1; D000098706:Taste Receptors, Type 2; C075192:gustducin; D015293:Transducin; D012439:Saccharin
keywords: blood leukocytes; chemosensory GPCR; lactisole; olfactory; saccharin; siRNA