title: Defective adenosine-stimulated cAMP production in cystic fibrosis airway epithelia: a novel role for CFTR in cell signaling.
abstract: Adenosine (ADO) is an extracellular signaling molecule that is an important regulator of innate lung defense. On binding ADO, the A2B receptor (A2BR) stimulates cAMP production to activate the CFTR Cl(-) channel, increase ciliary beating, and initiate cytokine secretion. We tested the hypothesis that CFTR served as a positive regulator of the A2BRs. We found that A2BR and CFTR coimmunoprecipitated. They also underwent ADO-dependent Förster resonance energy transfer (FRET), which increased from 5% in the absence of agonist to 18% with 100 μM ADO (EC₅₀ 1.7 μM), suggesting that they dynamically associate in the plasma membrane. In contrast, despite colocalization, no FRET was observed between CFTR and GAP43. The interaction between A2BR and CFTR had some specificity: A2BR-stimulated but not forskolin-stimulated cAMP production was ~50% greater in the presence of CFTR, due to a CFTR-dependent increase in plasma membrane A2BR levels. These CFTR-dependent increases in A2BR levels and cAMP production resulted in significantly enhanced ciliary beating and increased cytokine secretion in normal compared to cystic fibrosis airway epithelia. Thus, we hypothesize that CFTR regulates A2BR levels in the plasma membrane to modulate cell signaling and to enhance selective components of the innate lung defense system.
authors.affiliation: Cystic Fibrosis/Pulmonary Research and Treatment Center, The University of North Carolina, Chapel Hill, NC 27599-7248, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Watson
authors.forename: Erin N
authors.initials: EN
authors.lastname: Worthington
authors.forename: Lucy A
authors.initials: LA
authors.lastname: Clunes
authors.forename: Julia E
authors.initials: JE
authors.lastname: Rasmussen
authors.forename: Lisa
authors.initials: L
authors.lastname: Jones
authors.forename: Robert
authors.initials: R
authors.lastname: Tarran
mesh_terms: D000241:Adenosine / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002450:Cell Communication; D002478:Cells, Cultured; D002923:Cilia / Q000502:physiology; D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism*; D003550:Cystic Fibrosis / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism; D043704:Receptor, Adenosine A2B / Q000378:metabolism; D020545:Respiratory Mucosa / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: C505032:CFTR protein, human; D016209:Interleukin-8; D043704:Receptor, Adenosine A2B; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000242:Cyclic AMP; D000241:Adenosine