A2 adenosine receptors regulate CFTR through PKA and PLA2

We investigated adenosine (Ado) activation of the cystic fibrosis transmembrane conductance regulator (CFTR) in vitro and in vivo. A(2B) Ado receptors were identified in Calu-3, IB-3-1, COS-7, and primary human airway cells. Ado elevated cAMP in Calu-3, IB-3-1, and COS-7 cells and activated protein kinase A-dependent halide efflux in Calu-3 cells. Ado promoted arachidonic acid release from Calu-3 cells, and phospholipase A(2) (PLA(2)) inhibition blocked Ado-activated halide efflux in Calu-3 and COS-7 cells expressing CFTR. Forskolin- and beta (2)-adrenergic receptor-stimulated efflux were not affected by the same treatment. Cytoplasmic PLA(2) (cPLA(2)) was identified in Calu-3, IB-3-1, and COS-7 cells, but cPLA(2) inhibition did not affect Ado-stimulated cAMP concentrations. In cftr(+) and cftr(-/-) mice, Ado stimulated nasal Cl- secretion that was CFTR dependent and sensitive to A(2) receptor and PLA(2) blockade. In COS-7 cells transiently expressing Delta F508 CFTR, Ado activated halide efflux. Ado also activated G551D CFTR-dependent halide efflux when combined with arachidonic acid and phosphodiesterase inhibition. In conclusion, PLA(2) and protein kinase A both contribute to A(2) receptor activation of CFTR, and components of this signaling pathway can augment wild-type and mutant CFTR activity.