title: Cloning and functional characterization of novel variants and tissue-specific expression of alternative amino and carboxyl termini of products of slc4a10.
abstract: Previous studies have shown that the electroneutral Na(+)/HCO(3) (-) cotransporter NBCn2 (SLC4A10) is predominantly expressed in the central nervous system (CNS). The physiological and pathological significances of NBCn2 have been well recognized. However, little is known about the tissue specificity of expression of different NBCn2 variants. Moreover, little is known about the expression of NBCn2 proteins in systems other than CNS. Here, we identified a set of novel Slc4a10 variants differing from the originally described ones by containing a distinct 5' untranslated region encoding a new extreme amino-terminus (Nt). Electrophysiology measurements showed that both NBCn2 variants with alternative Nt contain typical electroneutral Na(+)-coupled HCO(3) (-) transport activity in Xenopus oocytes. Luciferase reporter assay showed that Slc4a10 contains two alternative promoters responsible for expression of the two types of NBCn2 with distinct extreme Nt. Western blotting showed that NBCn2 proteins with the original Nt are primarily expressed in CNS, whereas those with the novel Nt are predominantly expressed in the kidney and to a lesser extent in the small intestine. Due to alternative splicing, the known NBCn2 variants contain two types of carboxyl-termini (CT) differing in the optional inclusion of a PDZ-binding motif. cDNA cloning showed that virtually all NBCn2 variants expressed in epithelial tissues contain, but the vast majority of those from the neural tissues lack the PDZ-binding motif. We conclude that alternative transcription and splicing of Slc4a10 products are regulated in a tissue-specific manner. Our findings provide critical insights that will greatly influence the study of the physiology of NBCn2.
authors: Department of Biophysics and Molecular Physiology, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science & Technology School of Life Science & Technology, Wuhan, Hubei, China.
authors: Ying
authors: Y
authors: Liu
authors: Deng-Ke
authors: DK
authors: Wang
authors: De-Zhi
authors: DZ
authors: Jiang
authors: Xue
authors: X
authors: Qin
authors: Zhang-Dong
authors: ZD
authors: Xie
authors: Qing K
authors: QK
authors: Wang
authors: Mugen
authors: M
authors: Liu
authors: Li-Ming
authors: LM
authors: Chen
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D027963:Chloride-Bicarbonate Antiporters / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005786:Gene Expression Regulation; D023061:Gene Order; D051379:Mice; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000235:genetics*; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms; D051381:Rats; D016415:Sequence Alignment; D027982:Sodium-Bicarbonate Symporters / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D027963:Chloride-Bicarbonate Antiporters; D018076:DNA, Complementary; D020033:Protein Isoforms; C526208:Slc4a10 protein, mouse; D027982:Sodium-Bicarbonate Symporters