Expression of Na+/H+ exchanger isoforms in normal human nasal epithelial cells and functional activity of Na+/H+ exchanger 1 in intracellular pH regulation.
CONCLUSIONS
Both the mRNA and protein of NHE1, -2 and -3 were expressed in NHNE cells. NHE1 is a major NHE isoform which is expressed in the basolateral membranes of NHNE cells.


OBJECTIVE
Na+/H+ exchangers are ubiquitous plasma membrane transport proteins implicated in the maintenance of intracellular pH. The aim of this study was to examine the expression of Na+/H+ exchangers as a function of the differentiation of normal human nasal epithelial (NHNE) cells. In addition, we investigated the functional activity of the Na+/H+ exchanger 1 (NHE1) in basolateral membranes.


METHODS
Cultured passage-2 NHNE cells were used. RNA and histological samples were collected on the day of confluence and on the 7th, 14th and 28th days after confluence in order to determine the effects of time. Cell lysates were collected on the day of confluence to investigate the presence of the proteins. Reverse transcriptase polymerase chain reaction and Western blotting were performed to investigate the presence of mRNA and protein, respectively. The functional activity of NHE1 was examined using 3-methylsulfonyl-4-piperidinobenzoyl guanidine methanesulfonate (HOE694), an NHE1-specific inhibitor, on the day of confluence.


RESULTS
The NHE1 mRNA expression level did not change as a function of differentiation. However, the NHE2 mRNA expression levels increased on the 7th, 14th and 28th days after confluence. The NHE3 mRNA expression levels increased on the 14th and 28th days after confluence. Western blot analysis confirmed the expression of NHE1 (91 kDa), NHE2 (90 kDa) and NHE3 (93 kDa). In addition, HOE694 inhibited basolateral NHE activity by 68% at 1 microM and by 85% at 5 microM in the NHNE cells.
Shin
Ji-Hyun
JH
Brain Korea 21 Project for Medical Sciences, Yonsei University College of Medicine, Seodaemun-gu, Seoul, South Korea.
Namkung
Wan
W
Kim
Chang-Hoon
CH
Choi
Jae Young
JY
Yoo
Jong-Bum
JB
Lee
Kyung-Dong
KD
Lee
Jeung-Gweon
JG
Lee
Min Goo
MG
Yoon
Joo-Heon
JH
D015153:Blotting, Western; D027682:Cation Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002454:Cell Differentiation; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000737:chemistry*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009297:Nasal Mucosa / Q000166:cytology*; D020033:Protein Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013450:Sulfones / Q000494:pharmacology
D027682:Cation Transport Proteins; D006146:Guanidines; D008565:Membrane Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D013450:Sulfones; C074107:3-methylsulfonyl-4-piperidinobenzoyl guanidine