The Formation of the cAMP/PKA-dependent Annexin 2-S100A10 Complex with CFTR Regulates CFTR Channel Function

Cystic fibrosis results from mutations in the cystic fibrosis conductance regulator protein (CFTR), a cAMP/PKA and ATP-regulated Cl channel. CFTR is increasingly recognized as a component of multi-protein complexes and although several inhibitory proteins to CFTR have been identified, protein complexes that stimulate CFTR function remain less well characterised. We report that annexin 2 (anx 2)-S100A10 forms a functional cAMP/PKA/calcineurin (CaN)-dependent complex with CFTR. Cell stimulation with FSK/IBMX significantly increases the amount of anx 2-S100A10 that reciprocally coimmunoprecipitates with cell surface CFTR and CaN A. Pre-inhibition with PKA or CaN inhibitors attenuates the interaction. Furthermore, we find that the acetylated peptide (STVHEILCKLSLEG, Ac1-14), but not the non-acetylated equivalent N1-14, corresponding to the S100A10 binding site on anx 2, disrupts the anx 2-S100A10/CFTR complex. Analysis of DIDS and CFTRinh172-sensitive currents, taken as indication of the outwardly rectifying Cl channels (ORCC) and CFTR-mediated currents, respectively, showed that Ac1-14, but not N1-14, inhibits both the cAMP/PKA-dependent ORCC and CFTR activities. CaN inhibitors (cypermethrin, cyclosporin A) discriminated between ORCC/CFTR by inhibiting the CFTRinh172-, but not the DIDS, sensitive currents, by more than 70%. Furthermore, peptide Ac1-14 inhibited acetylcholine-induced short-circuit current measured across a sheet of intact intestinal biopsy. Our data suggests that the anx 2-S100A10/CFTR complex is important for CFTR function across epithelia.