Document Detail


Basolateral chloride loading by the anion exchanger type 2: role in fluid secretion by the human airway epithelial cell line Calu-3.
MedLine Citation:
PMID:  22802585     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Anion exchanger type 2 (AE2 or SLC4A2) is an electroneutral Cl(-)/HCO(3)(-) 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-circuit current (I(sc)). We have studied the role of AE2 in Cl(-) and fluid secretion by the airway epithelial cell line Calu-3. After confirming expression of its mRNA and protein, a knock-down cell line called AE2-KD was generated by lentivirus-mediated RNA interference in which AE2 mRNA and protein levels were reduced 90%. Suppressing AE2 increased the expression of the cystic fibrosis transmembrane conductance regulator (CFTR) by ∼70% without affecting the levels of NKCC1 (Na(+)-K(+)-2Cl(-) cotransporter) or NBCe1 (Na(+)-nHCO(3)(-) cotransporter). cAMP agonists stimulated fluid secretion by parental Calu-3 and scrambled shRNA cells >6.5-fold. In AE2-KD cells this response was reduced by ∼70%, and the secreted fluid exhibited elevated pH and [HCO(3)(-)] as compared with the control lines. Unstimulated equivalent short-circuit current (I(eq)) was elevated in AE2-KD cells, but the incremental response to forskolin was unaffected. The modest bumetanide-induced reductions in both I(eq) and fluid secretion were more pronounced in AE2-KD cells. Basolateral Cl(-)/HCO(3)(-) exchange measured by basolateral pH-stat in cells with permeabilized apical membranes was abolished in AE2-KD monolayers, and the intracellular alkalinization resulting from basolateral Cl(-) removal was reduced by ∼80% in AE2-KD cells. These results identify AE2 as a major pathway for basolateral Cl(-) loading during cAMP-stimulated secretion of Cl(-) and fluid by Calu-3 cells, and help explain the large bumetanide-insensitive component of fluid secretion reported previously in airway submucosal glands and some other epithelia.
Authors:
Junwei Huang; Jiajie Shan; Dusik Kim; Jie Liao; Alexandra Evagelidis; Seth L Alper; John W Hanrahan
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2012-07-16
Journal Detail:
Title:  The Journal of physiology     Volume:  590     ISSN:  1469-7793     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-02     Completed Date:  2013-03-25     Revised Date:  2013-11-06    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  5299-316     Citation Subset:  IM    
Affiliation:
Department of Physiology, McGill University, Montr´eal, QC, Canada.
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MeSH Terms
Descriptor/Qualifier:
Anion Transport Proteins / physiology*
Antiporters / physiology*
Bicarbonates / metabolism
Bumetanide / pharmacology
Cell Line
Chlorides / metabolism
Cyclic AMP / metabolism
Cystic Fibrosis Transmembrane Conductance Regulator / metabolism
Epithelial Cells / metabolism*
Gene Knockdown Techniques
Humans
Intracellular Fluid / secretion*
Ion Transport
RNA, Small Interfering / genetics
Respiratory System / cytology,  metabolism
Sodium Potassium Chloride Symporter Inhibitors / pharmacology
Grant Support
ID/Acronym/Agency:
DK43495/DK/NIDDK NIH HHS; HL077765/HL/NHLBI NIH HHS; //Canadian Institutes of Health Research
Chemical
Reg. No./Substance:
0/AE2 anion exchanger; 0/Anion Transport Proteins; 0/Antiporters; 0/Bicarbonates; 0/CFTR protein, human; 0/Chlorides; 0/RNA, Small Interfering; 0/Sodium Potassium Chloride Symporter Inhibitors; 126880-72-6/Cystic Fibrosis Transmembrane Conductance Regulator; 28395-03-1/Bumetanide; 60-92-4/Cyclic AMP
Comments/Corrections

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