Premium
NBCe1‐A Is Not The Only NBCe1 (SLC4A4) Isoform Expressed in the Mouse Kidney
Author(s) -
Verlander Jill W.,
Chen Chao,
Lee HyunWook,
Osis Gunars,
Fang Lijuan,
Chen AnPing,
Holmes Heather L,
Romero Michael F.,
Weiner I. David
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.857.5
Subject(s) - splice , gene isoform , reabsorption , kidney , convoluted tubule , microbiology and biotechnology , endocrinology , medicine , biology , alternative splicing , distal convoluted tubule , chemistry , gene , biochemistry
The A‐splice variant of Na + ‐dependent, electrogenic bicarbonate transporter‐1 (SLC4A4, NBCe1‐A) is generally believed to be the only SLC4A4 isoform expressed in the mammalian proximal tubule, and to have critical roles in filtered bicarbonate reabsorption, proximal tubule ammonia metabolism and proximal tubule organic anion metabolism. The purpose of the current study was to examine expression of other splice variants in the mouse kidney. We used recently generated mice with TALEN‐generated deletion of A and D NBCe1 splice‐variants, but with intact expression of the B, C and E isoforms. RT‐PCR using primers specific to the B, C and E isoforms showed mRNA of non‐A,D splice variants was expressed in the kidney of mice with intact NBCe1‐A expression and with NBCe1‐A‐specific deletion. We then used an antibody that recognizes portions of NBCe1 present in all splice isoforms and examined immunolabel in the kidney of NBCe1‐A‐deletion mice. There was basolateral immunolabel in the proximal convoluted tubule in the cortex, and lesser intensity basolateral immunolabel in the proximal tubule straight tubule in both the cortex and outer medulla. Specificity of this antibody was demonstrated by identifying that mice with deletion of all splice variants had no detectable immunolabel. An antibody specific to the A‐splice variant showed basolateral immunolabel throughout the entire proximal tubule of mice with intact NBCe1‐A expression, but no detectable immunolabel in mice with NBCe1‐A‐specific deletion. Thus, an NBCe1 splice variant other than NBCe1‐A appears to be expressed in the mouse proximal tubule. In acid‐loaded NBCe1‐A‐deletion mice, immunolabel observed using the pan‐specific anti‐NBCe1 antibody showed increased immunolabel in the proximal straight tubule, particularly in the outer medulla. These studies show that splice variants of NBCe1 other than NBCe1‐A/D are present in the mouse kidney and that their expression appears to be increased with acid‐loading. We conclude that these splice variants may have important roles in proximal tubule filtered bicarbonate reabsorption, ammonia metabolism and organic anion metabolism. Support or Funding Information The studies were supported by funds from the NIH (R01–DK045788 to IDW, R01‐DK107798 to IDW and JWV, and R01‐EY017732 to MFR) and the Department of Veterans Affairs (1I01BX000818 to IDW).