Journal
PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY
Volume 469, Issue 9, Pages 1073-1091Publisher
SPRINGER HEIDELBERG
DOI: 10.1007/s00424-017-1981-3
Keywords
CK2; SLC4A2; Anion transport; HCO3-; Airway epithelia
Categories
Funding
- overseas studentship - Higher Committee for Education Development (HCED), Iraq
- MRC
- Cystic Fibrosis Trust [SRC003]
- Medical Research Foundation [MRF-091-0001-RG-GARNE]
- Wellcome Trust
- Italian Cystic Fibrosis Research Foundation (FFC) [7/2014]
- Open d'Italia di Golf
- MRC [MR/M008797/1, G0800419] Funding Source: UKRI
- Cystic Fibrosis Trust [SRC003] Funding Source: researchfish
- Medical Research Council [G0800419, MR/M008797/1] Funding Source: researchfish
- Medical Research Foundation [MRF-091-0001-RG-GARNE] Funding Source: researchfish
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Transepithelial bicarbonate secretion by human airway submucosal glands and surface epithelial cells is crucial to maintain the pH-sensitive innate defence mechanisms of the lung. cAMP agonists stimulate HCO3 (-) secretion via coordinated increases in basolateral HCO3 (-) influx and accumulation, as well as CFTR-dependent HCO3 (-) efflux at the luminal membrane of airway epithelial cells. Here, we investigated the regulation of a basolateral located, DIDS-sensitive, Cl-/HCO3 (-) exchanger, anion exchanger 2 (AE2; SLC4A2) which is postulated to act as an acid loader, and therefore potential regulator of HCO3 (-) secretion, in human airway epithelial cells. Using intracellular pH measurements performed on Calu-3 cells, we demonstrate that the activity of the basolateral Cl-/HCO3 (-) exchanger was significantly downregulated by cAMP agonists, via a PKA-independent mechanism and also required Ca2+ and calmodulin under resting conditions. AE2 contains potential phosphorylation sites by a calmodulin substrate, protein kinase CK2, and we demonstrated that AE2 activity was reduced in the presence of CK2 inhibition. Moreover, CK2 inhibition abolished the activity of AE2 in primary human nasal epithelia. Studies performed on mouse AE2 transfected into HEK-293T cells confirmed almost identical Ca2+/calmodulin and CK2 regulation to that observed in Calu-3 and primary human nasal cells. Furthermore, mouse AE2 activity was reduced by genetic knockout of CK2, an effect which was rescued by exogenous CK2 expression. Together, these findings are the first to demonstrate that CK2 is a key regulator of Cl--dependent HCO3 (-) export at the serosal membrane of human airway epithelial cells.
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