{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,26]],"date-time":"2026-09-26T07:01:03Z","timestamp":1790406063465,"version":"4.1.0"},"reference-count":65,"publisher":"Wiley","issue":"21","license":[{"start":{"date-parts":[[2012,10,1]],"date-time":"2012-10-01T00:00:00Z","timestamp":1349049600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["The Journal of Physiology"],"published-print":{"date-parts":[[2012,11]]},"abstract":"<jats:title>Key points<\/jats:title><jats:p><jats:list list-type=\"explicit-label\">\n<jats:list-item><jats:p>The companion paper provided evidence for basolateral anion exchange during cAMP stimulation of chloride and fluid secretion by Calu\u20103 monolayers; however, the molecular basis of this transport was not identified.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>To test the role of AE2, an anion exchanger expressed at the basolateral membrane of Calu\u20103 and many other epithelial cells, we used lentivirus\u2010mediated RNA interference to generate a stable Calu\u20103 AE2 knock\u2010down cell line and characterized its fluid and anion transport properties.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>AE2 knock\u2010down suppressed fluid secretion and increased the fraction of cAMP\u2010stimulated anion secretion that was sensitive to bumetanide inhibition.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>Basolateral Cl<jats:sup>\u2212<\/jats:sup>\/HCO<jats:sub>3<\/jats:sub><jats:sup>\u2212<\/jats:sup> exchange was nearly abolished in AE2 knock\u2010down cells.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>We conclude that AE2 is active during forskolin\u2010stimulated fluid secretion and mediates chloride uptake and bicarbonate recycling at the basolateral membrane.<\/jats:p><\/jats:list-item>\n<\/jats:list><\/jats:p><jats:p><jats:bold>Abstract\u2002<\/jats:bold> Anion exchanger type 2 (AE2 or SLC4A2) is an electroneutral Cl<jats:sup>\u2212<\/jats:sup>\/HCO<jats:sub>3<\/jats:sub><jats:sup>\u2212<\/jats:sup> exchanger expressed at the basolateral membrane of many epithelia. It is thought to participate in fluid secretion by airway epithelia. However, the role of AE2 in fluid secretion remains uncertain, due to the lack of specific pharmacological inhibitors, and because it is electrically silent and therefore does not contribute directly to short\u2010circuit current (<jats:italic>I<\/jats:italic><jats:sub>sc<\/jats:sub>). We have studied the role of AE2 in Cl<jats:sup>\u2212<\/jats:sup> and fluid secretion by the airway epithelial cell line Calu\u20103. After confirming expression of its mRNA and protein, a knock\u2010down cell line called AE2\u2010KD was generated by lentivirus\u2010mediated RNA interference in which AE2 mRNA and protein levels were reduced \u226590%. Suppressing AE2 increased the expression of the cystic fibrosis transmembrane conductance regulator (CFTR) by \u223c70% without affecting the levels of NKCC1 (Na<jats:sup>+<\/jats:sup>\u2013K<jats:sup>+<\/jats:sup>\u20132Cl<jats:sup>\u2212<\/jats:sup> cotransporter) or NBCe1 (Na<jats:sup>+<\/jats:sup>\u2013nHCO<jats:sub>3<\/jats:sub><jats:sup>\u2212<\/jats:sup> cotransporter). cAMP agonists stimulated fluid secretion by parental Calu\u20103 and scrambled shRNA cells &gt;6.5\u2010fold. In AE2\u2010KD cells this response was reduced by \u223c70%, and the secreted fluid exhibited elevated pH and [HCO<jats:sub>3<\/jats:sub><jats:sup>\u2212<\/jats:sup>] as compared with the control lines. Unstimulated equivalent short\u2010circuit current (<jats:italic>I<\/jats:italic><jats:sub>eq<\/jats:sub>) was elevated in AE2\u2010KD cells, but the incremental response to forskolin was unaffected. The modest bumetanide\u2010induced reductions in both <jats:italic>I<\/jats:italic><jats:sub>eq<\/jats:sub> and fluid secretion were more pronounced in AE2\u2010KD cells. Basolateral Cl<jats:sup>\u2212<\/jats:sup>\/HCO<jats:sub>3<\/jats:sub><jats:sup>\u2212<\/jats:sup> exchange measured by basolateral pH\u2010stat in cells with permeabilized apical membranes was abolished in AE2\u2010KD monolayers, and the intracellular alkalinization resulting from basolateral Cl<jats:sup>\u2212<\/jats:sup> removal was reduced by \u223c80% in AE2\u2010KD cells. These results identify AE2 as a major pathway for basolateral Cl<jats:sup>\u2212<\/jats:sup> loading during cAMP\u2010stimulated secretion of Cl<jats:sup>\u2212<\/jats:sup> and fluid by Calu\u20103 cells, and help explain the large bumetanide\u2010insensitive component of fluid secretion reported previously in airway submucosal glands and some other epithelia.<\/jats:p>","DOI":"10.1113\/jphysiol.2012.236919","type":"journal-article","created":{"date-parts":[[2012,7,17]],"date-time":"2012-07-17T13:09:10Z","timestamp":1342530550000},"page":"5299-5316","source":"Crossref","is-referenced-by-count":26,"title":["Basolateral chloride loading by the anion exchanger type 2: role in fluid secretion by the human airway epithelial cell line 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