title: CRACM/Orai ion channel expression and function in human lung mast cells.
abstract: BACKGROUND
  Influx of extracellular Ca(2+) into human lung mast cells (HLMCs) is essential for the FcεRI-dependent release of preformed granule-derived mediators and newly synthesized autacoids and cytokines. However, the identity of the ion channels underlying this Ca(2+) influx is unknown. The recently discovered members of the CRACM/Orai ion channel family that carries the Ca(2+) release-activated Ca(2+) current are candidates.
  
  
  OBJECTIVE
  To investigate the expression and function of CRACM channels in HLMCs.
  
  
  METHODS
  CRACM mRNA, protein, and functional expression were examined in purified HLMCs and isolated human bronchus.
  
  
  RESULTS
  CRACM1, -2, and -3 mRNA transcripts and CRACM1 and -2 proteins were detectable in HLMCs. A CRACM-like current was detected following FcεRI-dependent HLMC activation and also in HLMCs dialyzed with 30 μM inositol triphosphate. The Ca(2+)-selective current obtained under both conditions was blocked by 10 μM La(3+) and Gd(3+), known blockers of CRACM channels, and 2 distinct and specific CRACM-channel blockers-GSK-7975A and Synta-66. Both blockers reduced FcεRI-dependent Ca(2+) influx, and 3 μM GSK-7975A and Synta-66 reduced the release of histamine, leukotriene C(4), and cytokines (IL-5/-8/-13 and TNFα) by up to 50%. Synta-66 also inhibited allergen-dependent bronchial smooth muscle contraction in ex vivo tissue.
  
  
  CONCLUSIONS
  The presence of CRACM channels, a CRACM-like current, and functional inhibition of HLMC Ca(2+) influx, mediator release, and allergen-induced bronchial smooth muscle contraction by CRACM-channel blockers supports a role for CRACM channels in FcεRI-dependent HLMC secretion. CRACM channels are therefore a potential therapeutic target in the treatment of asthma and related allergic diseases.
authors.affiliation: Department of Infection, Immunity and Inflammation, Institute for Lung Health, University of Leicester, Leicester, United Kingdom.
authors.forename: Ian
authors.initials: I
authors.lastname: Ashmole
authors.forename: S Mark
authors.initials: SM
authors.lastname: Duffy
authors.forename: Mark L
authors.initials: ML
authors.lastname: Leyland
authors.forename: Valerie S
authors.initials: VS
authors.lastname: Morrison
authors.forename: Malcolm
authors.initials: M
authors.lastname: Begg
authors.forename: Peter
authors.initials: P
authors.lastname: Bradding
mesh_terms: D000485:Allergens / Q000276:immunology; D001980:Bronchi / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000378:metabolism / Q000494:pharmacology; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism; D008168:Lung / Q000166:cytology / Q000378:metabolism*; D008407:Mast Cells / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D000485:Allergens; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D012333:RNA, Messenger; D007073:Immunoglobulin E; D002118:Calcium