title: Functional role of a putative carbonic anhydrase II-binding domain in the electrogenic Na+ -HCO₃- cotransporter NBCe1 expressed in Xenopus oocytes.
abstract: The electrogenic Na+ -HCO₃⁻ cotransporter NBCe1 plays essential roles in the regulation of systemic and/or local pH. Homozygous inactivating mutations in NBCe1 cause proximal renal tubular acidosis associated with ocular abnormalities. We recently showed that defective membrane expression of NBCe1, caused by several mutations such as Delta65bp (S982NfsX4), is also associated with familial migraine. The Delta65bp mutant is quite unique in that it lacks a putative carbonic anhydrase (CA) II-binding domain but still shows an apparently normal transport activity in Xenopus oocytes. In this addendum, we show that the co-expression of CAII together with the wild-type NBCe1 or the Delta65bp mutant does not enhance the NBCe1 activities in oocytes. Moreover, a carbonic anhydrase inhibitor acetazolamide fails to inhibit the wild-type or the Delta65bp activities co-expressed with CAII. These results indicate that a bicarbonate transport metabolon proposed for the interaction between CAII and NBCe1 does not work at least in Xenopus oocytes.
authors.affiliation: Department of Internal Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Hideomi
authors.initials: H
authors.lastname: Yamada
authors.forename: Shoko
authors.initials: S
authors.lastname: Horita
authors.forename: Masashi
authors.initials: M
authors.lastname: Suzuki
authors.forename: Toshiro
authors.initials: T
authors.lastname: Fujita
authors.forename: George
authors.initials: G
authors.lastname: Seki
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology; D000141:Acidosis, Renal Tubular / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000838:Anions; D001639:Bicarbonates / Q000737:chemistry; D024402:Carbonic Anhydrase II / Q000737:chemistry*; D004594:Electrophysiology / Q000379:methods; D006801:Humans; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D051381:Rats; D027982:Sodium-Bicarbonate Symporters / Q000378:metabolism*; D029867:Xenopus Proteins / Q000378:metabolism*; D014982:Xenopus laevis / Q000378:metabolism*
chemical_list: D000838:Anions; D001639:Bicarbonates; C522009:SLC4A4 protein, Xenopus; D027982:Sodium-Bicarbonate Symporters; D029867:Xenopus Proteins; D024402:Carbonic Anhydrase II; D000086:Acetazolamide