Details

Autor(en) / Beteiligte

• Kao, Liyo
• Azimov, Rustam
• Shao, Xuesi M
• Abuladze, Natalia
• Newman, Debra
• Zhekova, Hristina
• Noskov, Sergei
• Pushkin, Alexander
• Kurtz, Ira

Titel

SLC4A11 function: evidence for H+(OH-) and NH3-H+ transport

Ist Teil von

• American Journal of Physiology: Cell Physiology, 2020-02, Vol.318 (2), p.C392-C405

Ort / Verlag

Bethesda, MD: American Physiological Society

Erscheinungsjahr

2020

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Whether SLC4A11 transports ammonia and its potential mode of ammonia transport ( NH 4 + , NH 3 , or NH 3 -2H + transport have been proposed) are controversial. In the absence of ammonia, whether SLC4A11 mediates significant conductive H + (OH − ) transport is also controversial. The present study was performed to determine the mechanism of human SLC4A11 ammonia transport and whether the transporter mediates conductive H + (OH − ) transport in the absence of ammonia. We quantitated H + flux by monitoring changes in intracellular pH (pH i ) and measured whole cell currents in patch-clamp studies of HEK293 cells expressing the transporter in the absence and presence of NH 4 Cl. Our results demonstrate that SLC4A11 mediated conductive H + (OH − ) transport that was stimulated by raising the extracellular pH (pH e ). Ammonia-induced HEK293 whole cell currents were also stimulated by an increase in pH e . In studies using increasing NH 4 Cl concentrations with equal NH 4 + extracellular and intracellular concentrations, the shift in the reversal potential ( E rev ) due to the addition of ammonia was compatible with NH 3 -H + transport competing with H + (OH − ) rather than NH 3 -nH + ( n ≥ 2) transport. The increase in equivalent H + (OH − ) flux observed in the presence of a transcellular H + gradient was also compatible with SLC4A11-mediated NH 3 -H + flux. The NH 3 versus E rev data fit a theoretical model suggesting that NH 3 -H + and H + (OH − ) competitively interact with the transporter. Studies of mutant SLC4A11 constructs in the putative SLC4A11 ion coordination site showed that both H + (OH − ) transport and ammonia-induced whole cell currents were blocked suggesting that the H + (OH − ) and NH 3 -H + transport processes share common features involving the SLC4A11 transport mechanism.