title: Receptor-promoted exocytosis of airway epithelial mucin granules containing a spectrum of adenine nucleotides.
abstract: Purinergic regulation of airway innate defence activities is in part achieved by the release of nucleotides from epithelial cells. However, the mechanisms of airway epithelial nucleotide release are poorly understood. We have previously demonstrated that ATP is released from ionomycin-stimulated airway epithelial goblet cells coordinately with mucin exocytosis, suggesting that ATP is released as a co-cargo molecule from mucin-containing granules. We now demonstrate that protease-activated-receptor (PAR) agonists also stimulate the simultaneous release of mucins and ATP from airway epithelial cells. PAR-mediated mucin and ATP release were dependent on intracellular Ca(2+) and actin cytoskeleton reorganization since BAPTA AM, cytochalasin D, and inhibitors of Rho and myosin light chain kinases blocked both responses. To test the hypothesis that ATP is co-released with mucin from mucin granules, we measured the nucleotide composition of isolated mucin granules purified based on their MUC5AC and VAMP-8 content by density gradients. Mucin granules contained ATP, but the levels of ADP and AMP within granules exceeded by nearly 10-fold that of ATP. Consistent with this finding, apical secretions from PAR-stimulated cells contained relatively high levels of ADP/AMP, which could not be accounted for solely based on ATP release and hydrolysis. Thus, mucin granules contribute to ATP release and also are a source of extracellular ADP and AMP. Direct release of ADP/AMP from mucin granules is likely to provide a major source of airway surface adenosine to signal in a paracrine faction ciliated cell A(2b) receptors to activate ion/water secretion and appropriately hydrate goblet cell-released mucins.
authors.affiliation: Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina at Chapel Hill, 4029A Thurston Bowles Building, Chapel Hill, NC 27599-7248, USA. silvia_kreda@med.unc.edu
authors.forename: Silvia M
authors.initials: SM
authors.lastname: Kreda
authors.forename: Lucia
authors.initials: L
authors.lastname: Seminario-Vidal
authors.forename: Catharina A
authors.initials: CA
authors.lastname: van Heusden
authors.forename: Wanda
authors.initials: W
authors.lastname: O'Neal
authors.forename: Lisa
authors.initials: L
authors.lastname: Jones
authors.forename: Richard C
authors.initials: RC
authors.lastname: Boucher
authors.forename: Eduardo R
authors.initials: ER
authors.lastname: Lazarowski
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000227:Adenine Nucleotides / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects; D020397:Goblet Cells / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D055271:Mucin 5AC / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D050683:R-SNARE Proteins / Q000378:metabolism; D044462:Receptors, Proteinase-Activated / Q000819:agonists / Q000378:metabolism*; D020545:Respiratory Mucosa / Q000187:drug effects / Q000378:metabolism*; D022142:Secretory Vesicles / Q000187:drug effects / Q000378:metabolism*; D013917:Thrombin / Q000494:pharmacology; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000227:Adenine Nucleotides; D002614:Chelating Agents; C524678:MUC5AC protein, human; D055271:Mucin 5AC; D010455:Peptides; D047428:Protein Kinase Inhibitors; D050683:R-SNARE Proteins; D044462:Receptors, Proteinase-Activated; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D054460:rho-Associated Kinases; D009219:Myosin-Light-Chain Kinase; D013917:Thrombin; D002118:Calcium