Beyond the mutations: spatiotemporal regulation of CFTR by cAMP and calcium signaling in epithelial physiology and cystic fibrosis

Cystic fibrosis (CF) is a life-shortening monogenic disease caused by mutations in the CFTR gene, but the functional expression of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl^-/HCO₃^- channel is determined by more than its genetic sequence. Beyond the well-known folding defect of the common F508del mutation, CFTR activity is dynamically modulated by a network of intracellular signaling pathways that control the channel's gating, trafficking to, and retention at the apical membrane. Foremost is the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway, which drives CFTR opening via phosphorylation of its regulatory (R) domain and coordination by scaffolding proteins (e.g., A-kinase anchoring proteins (AKAPs) and Na⁺/H⁺ exchanger regulatory factor 1 (NHERF1)). Equally important, Ca²⁺-dependent signaling cascades provide complementary fine-tuning: Ca²⁺-bound calmodulin can directly bind and increase the CFTR open probability, Ca²⁺-activated kinases such as Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and the tyrosine kinase Pyk2 (with Src) can phosphorylate CFTR through noncanonical routes, and signaling intermediates such as IP₃ receptor binding protein released with IP₃(IRBIT) connect Ca²⁺ release to CFTR activation. These cAMP- and Ca²⁺-driven pathways intersect in specialized subcellular nanodomains, enabling precise spatiotemporal regulation of CFTR function. Clinically, although new CFTR modulator drugs have greatly improved outcomes, their effectiveness is limited by mutation-specific responses and incomplete restoration of channel activity. Understanding how cAMP-Ca²⁺ crosstalk governs CFTR in context can reveal novel therapeutic strategies targeting the channel's regulatory microenvironment. This review highlights how compartmentalized cAMP and Ca²⁺ signals orchestrate CFTR function and discusses emerging approaches to harness this insight for better therapies across CF-affected organs.