title: Enhanced mast cell activation in mice deficient in the A2b adenosine receptor.
abstract: Antigen-mediated cross-linking of IgE bound to mast cells via the high affinity receptor for IgE triggers a signaling cascade that results in the release of intracellular calcium stores, followed by an influx of extracellular calcium. The collective increase in intracellular calcium is critical to the release of the granular contents of the mast cell, which include the mediators of acute anaphylaxis. We show that the sensitivity of the mast cell to antigen-mediated degranulation through this pathway can be dramatically influenced by the A2b adenosine receptor. Loss of this Gs-coupled receptor on mouse bone marrow-derived mast cells results in decreased basal levels of cyclic AMP and an excessive influx of extracellular calcium through store-operated calcium channels following antigen activation. Mice lacking the A2b receptor display increased sensitivity to IgE-mediated anaphylaxis. Collectively, these findings show that the A2b adenosine receptor functions as a critical regulator of signaling pathways within the mast cell, which act in concert to limit the magnitude of mast cell responsiveness when antigen is encountered.
authors.affiliation: Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Xiaoyang
authors.initials: X
authors.lastname: Hua
authors.forename: Martina
authors.initials: M
authors.lastname: Kovarova
authors.forename: Kelly D
authors.initials: KD
authors.lastname: Chason
authors.forename: MyTrang
authors.initials: M
authors.lastname: Nguyen
authors.forename: Beverly H
authors.initials: BH
authors.lastname: Koller
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Tilley
mesh_terms: D000707:Anaphylaxis / Q000276:immunology / Q000378:metabolism; D000818:Animals; D000941:Antigens / Q000008:administration & dosage; D003994:Bucladesine / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D015550:Cell Degranulation / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D066298:In Vitro Techniques; D015850:Interleukin-6 / Q000096:biosynthesis; D008407:Mast Cells / Q000187:drug effects / Q000276:immunology* / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D043704:Receptor, Adenosine A2B / Q000172:deficiency* / Q000235:genetics; D017455:Receptors, IgE / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000941:Antigens; D015850:Interleukin-6; D043704:Receptor, Adenosine A2B; D017455:Receptors, IgE; D003994:Bucladesine; D000242:Cyclic AMP