Molecular cloning and functional expression of a sodium bicarbonate cotransporter from guinea-pig parotid glands.
We recently found that the concentration of HCO3- in guinea-pig saliva is very similar to that of human saliva; however, the entity that regulates HCO3- transport has not yet been fully characterized. In order to investigate the mechanism of HCO3- transport, we identified, cloned, and characterized a sodium bicarbonate (Na(+)/HCO3- cotransporter found in guinea-pig parotid glands (gpNBC1). The gpNBC1 gene encodes a 1079-amino acid protein that has 95% and 96% homology with human and mouse parotid NBC1, respectively. Oocytes expressing gpNBC1 were exposed to HCO3- or Na(+)-free solutions, which resulted in a marked change in membrane potentials (V(m)), suggesting that gpNBC1 is electrogenic. Likewise, a gpNBC1-mediated pH recovery was observed in gpNBC1 transfected human hepatoma cells; however, in the presence of 4, 4-diisothiocyanostilbene-2,2-disulfonic acid, a specific NBC1 inhibitor, such changes in V(m) and pH(i) were not observed. Together, the data show that the cloned guinea-pig gene is a functional, as well as sequence homologue of human NBC1.
Koo
Na-Youn
NY
Department of Physiology and Dental Research Institute, School of Dentistry, Seoul National University, Seoul 110-749, Republic of Korea.
Li
Jingchao
J
Hwang
Sung Min
SM
Choi
Se-Young
SY
Lee
Sung Joong
SJ
Oh
Seog-Bae
SB
Kim
Joong-Soo
JS
Lee
Jong Heun
JH
Park
Kyungpyo
K
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D003001:Cloning, Molecular; D006168:Guinea Pigs; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology*; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism*; D010306:Parotid Gland / Q000378:metabolism*; D027982:Sodium-Bicarbonate Symporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
D027982:Sodium-Bicarbonate Symporters