Decreased expression of Slc26a4 (Pendrin) and Slc26a7 in the kidneys of carbonic anhydrase II-deficient mice.
OBJECTIVE
Intercalated cells (ICs) of the kidney collecting duct are rich in carbonic anhydrase II (CAII), which facilitates proton and bicarbonate transport. Bicarbonate secretion is mediated via Pendrin (Slc26a4), which is expressed on the apical membrane of B-ICs and nonA-nonB ICs in the cortical collecting ducts (CCD). Bicarbonate absorption is mediated via anion exchanger 1 (AE1-Slc4a1) in the CCD and via AE1 and possibly Slc26a7 in the OMCD. Both exchangers are expressed on the basolateral membrane of A-ICs. The aim of this study was to examine the expression of pendrin, Slc26a7, and AE1 in the kidneys of CAII-deficient (CAR2-null) mice.


METHODS
For the expression studies, we used real-time RT-PCR, Northern hybridization, immunolabeling, and immunoblotting.


RESULTS
Pendrin mRNA expression was reduced 63% along with decreased pendrin immunolabeling in the cortex of CAR2-null mice present predominantly in nonA-nonB ICs. Slc26a7 mRNA expression was decreases by 73% and Slc26a7 immunolabeling, present in A-ICs, severely reduced in the outer medulla of CAR2-null mice. AE1 mRNA expression was decreased to a similar degree (62%) along with reduced AE1 immunolabeling. The expression of aquaporin 2 (AQP2) water channel, exclusively present in principal cells of the collecting duct, was comparable in the wild type and CAR2-null mice.


CONCLUSIONS
CAII deficiency results in a significant decrease in the gene and protein expression of bicarbonate transport proteins from Slc26 gene family - Slc26a4 (pendrin) and Slc26a7. These results emphasize the critical role of CAII for the maintenance of the intercalated cell phenotype.
Sun
Xuming
X
Department of Medicine, University of Cincinnati, Cincinnati, OH 45267-0585, USA.
Soleimani
Manoocher
M
Petrovic
Snezana
S
D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000235:genetics / Q000378:metabolism; D027321:Anion Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D051399:Aquaporin 2 / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D024402:Carbonic Anhydrase II / Q000172:deficiency*; D027963:Chloride-Bicarbonate Antiporters / Q000235:genetics* / Q000378:metabolism*; D003720:Densitometry; D005786:Gene Expression Regulation; D007668:Kidney / Q000166:cytology / Q000201:enzymology*; D051379:Mice; D006180:Proton-Translocating ATPases / Q000378:metabolism; D000076988:Sulfate Transporters
D001457:Anion Exchange Protein 1, Erythrocyte; D027321:Anion Transport Proteins; D051399:Aquaporin 2; D027963:Chloride-Bicarbonate Antiporters; C494849:Slc26a4 protein, mouse; C486743:Slc26a7 protein, mouse; C523515:Slc4a1 protein, mouse; D000076988:Sulfate Transporters; D006180:Proton-Translocating ATPases; D024402:Carbonic Anhydrase II