ISSN:
1432-1424
Keywords:
Key words: Na+ sensor — Inward rectifier K+ channel — ROMK — Na+/H+ antiporter
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract. To examine the extracellular Na+ sensitivity of a renal inwardly rectifying K+ channel, we performed electrophysiological experiments on Xenopus oocytes or a human kidney cell line, HEK293, in which we had expressed the cloned renal K+ channel, ROMK1 (Kir1.1). When extracellular Na+ was removed, the whole-cell ROMK1 currents were markedly suppressed in both the oocytes and HEK293 cells. Single-channel ROMK1 activities recorded in the cell-attached patch on the oocyte were not affected by removal of Na+ from the pipette solution. However, macro-patch ROMK1 currents recorded on the oocyte were significantly suppressed by Na+ removal from the bath solution. A blocker of Na+/H+ antiporters, amiloride, largely inhibited the Na+ removal-induced suppression of whole-cell ROMK1 currents in the oocytes. The pH-insensitive K80M mutant of ROMK1 was much less sensitive to Na+ removal. Na+ removal was found to induce a significant decrease in intracellular pH in the oocytes using H+-selective microelectrodes. Coexpression of ROMK1 with NHE3, which is a Na+/H+ antiporter isoform of the kidney apical membrane, conferred increased sensitivity of ROMK1 channels to extracellular Na+ in both the oocytes and HEK293 cells. Thus, it is concluded that the ROMK1 channel is regulated indirectly by extracellular Na+, and that the interaction between NHE transporter and ROMK1 channel appears to be involved in the mechanism of Na+ sensitivity of ROMK1 channel via regulating intracellular pH.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002329900584
