A PI3K gamma mimetic peptide triggers CFTR gating, bronchodilation, and reduced inflammation in obstructive airway diseases

Cyclic adenosine 3',5'-monophosphate (cAMP)-elevating agents, such as beta(2)-adrenergic receptor (beta(2)-AR) agonists and phosphodiesterase (PDE) inhibitors, remain a mainstay in the treatment of obstructive respiratory diseases, conditions characterized by airway constriction, inflammation, and mucus hypersecretion. However, their clinical use is limited by unwanted side effects because of unrestricted cAMP elevation in the airways and in distant organs. Here, we identified the A-kinase anchoring protein phosphoinositide 3-kinase gamma (PI3K gamma) as a critical regulator of a discrete cAMP signaling microdomain activated by beta(2)-ARs in airway structural and inflammatory cells. Displacement of the PI3K gamma-anchored pool of protein kinase A (PKA) by an inhaled, cell-permeable, PI3K gamma mimetic peptide (PI3K gamma MP) inhibited a pool of subcortical PDE4B and PDE4D and safely increased cAMP in the lungs, leading to airway smooth muscle relaxation and reduced neutrophil infiltration in a murine model of asthma. In human bronchial epithelial cells, PI3K gamma MP induced unexpected cAMP and PKA elevations restricted to the vicinity of the cystic fibrosis transmembrane conductance regulator (CFTR), the ion channel controlling mucus hydration that is mutated in cystic fibrosis (CF). PI3K gamma MP promoted the phosphorylation of wild-type CFTR on serine-737, triggering channel gating, and rescued the function of F508del-CFTR, the most prevalent CF mutant, by enhancing the effects of existing CFTR modulators. These results unveil PI3K. as the regulator of a beta(2)-AR/cAMP microdomain central to smooth muscle contraction, immune cell activation, and epithelial fluid secretion in the airways, suggesting the use of a PI3K gamma MP for compartment-restricted, therapeutic cAMP elevation in chronic obstructive respiratory diseases.