ClC-2Cl(-) channels in human lung epithelia: activation by arachidonic acid, amidation, and acid- activated omeprazole

ClC-2 Cl- channels represent a potential target for therapy in cystic fibro sis. Key questions regarding the feasibility of using ClC-2 as a therapeuti c target are addressed in the present studies, including whether the channe ls are present in human lung epithelia and whether activators of the channe l can be identified. Two new mechanisms of activation of human recombinant ClC-2 Cl- channels expressed in HEK-293 cells were identified: amidation wi th glycine methyl ester catalyzed by 1-ethyl-3(3-dimethylaminopropyl) carbo diimide (EDC) and treatment with acid-activated omeprazole. ClC-2 mRNA was detected by RT-PCR. Channel function was assessed by measuring Cl- currents by patch clamp in the presence of a cAMP-dependent protein kinase (PKA) in hibitor, myristoylated protein kinase inhibitor, to prevent PKA-activated C l- currents. Calu-3, A549, and BEAS-2B cell lines derived from different hu man lung epithelia contained ClC-2 mRNA, and Cl- currents were increased by amidation, acid-activated omeprazole, and arachidonic acid. Similar result s were obtained with buccal cells from healthy individuals and cystic fibro sis patients. The ClC-2 Cl- channel is thus a potential target for therapy in cystic fibrosis.