Defective formation of PKA/CnA-dependent annexin 2-S100A10/CFTR complex in Delta F508 cystic fibrosis cells

Cystic fibrosis (CF) is characterised by impaired epithelial ion transport and is caused by mutations in the cystic fibrosis conductance regulator protein (CFTR), a cAMP/PKA and ATP-regulated chloride channel. We recently demonstrated a cAMP/PKA/calcineurin (CnA)-driven association between annexin 2 (anx 2), its cognate partner -S100A10 and cell surface CFTR. The complex is required for CFTR and outwardly rectifying chloride channel function in epithelia. Since the cAMP/PKA-induced Cl- current is absent in CF epithelia, we hypothesized that the anx 2-S100A10/CFTR complex may be defective in CFBE41o cells expressing the commonest F508del-CFTR (Delta F-CFTR) mutation. Here, we demonstrate that, despite the presence of cell surface Delta F-CFTR, cAMP/PKA fails to induce anx 2-S100A10/CFTR complex formation in CFBE41o- cells homozygous for F508del-CFTR. Mechanistically, PKA-dependent serine phosphorylation of CnA, CnA-anx 2 complex formation and CnA-dependent depbosphorylation of anx 2 are all defective in CFBE41o- cells. Immumohistochemical analysis confirms an abnormal cellular distribution of anx 2 in human and CIF mouse epithelia.

Thus, we demonstrate that cAMP/PKA/CnA signaling pathway is defective in CF cells and suggest that loss of anx 2-S100A10/CFTR complex formation may contribute to defective cAMP/PKA-dependent CFTR channel function. (C) 2008 Elsevier Inc. All rights reserved.