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Regulation of Na/H excharger activity

Na/H 放电活性的调节

基本信息

批准号：
04670520
负责人：
TAKAICHI Kenmei
金额：
$ 1.34万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04670520/
关键词：
Na H exchanger NHE NHE-1 NHE-3 Amiloride Epithelium Isoform Targeting アイソクォ-ム

项目摘要

Several isoforms exist in Na/H exchangers (NHE) . It is generally believed that NHE-3, which is resistant to amiloride inhibition, is located in the apical membrane and NHE-1, which is sensitive to amiloride inhibition, is located in the basolateral membrane in the epithelial cells. We characterized NHE activity and its modulation in the cultured renal epithelial cells (OK cells and LLC-PK1 cells) .We identified NHE activity in the basolateral membrane in addition to well known NHE activity in the apical membrane in OK cells. Since NHE in the both membranes is resistant to amiloride and its maximum activity is inhibited by parathyroid hormone, NHE in the both membranes seems to be NHE-3. Thus, NHE-3 can be expressed not only in the apical membrane but also in the basolateral membrane in OK cells. The affinity for cytosolic [H^+] of NHE in the basolateral membrane is different from that in the apical membrane. Thus, the character of NHE-3 may vary depending on the side where NHE-3 is located. Since OK cells transfected with human NHE-1 cDNA expressed NHE-1 activity only in the basolateral membrane, NHE-1 may have intrinsic signal to target itself to the basolateral membrane in the epithelial cells.NHE activity in the apical membrane of LLC-PK1 cells is more sensitive to amiloride than typical NHE-3. To clarify whether NHE-1 activity might be expressed in the apical membrane as well as in the basolateral membrane, we examined the effects of NHE-1 antisense oligonucleotide. Since transfection with antisense oligonucleotide inhibited only basolateral NHE activity in LLC-PK1 cells, NHE in the only basolateral membrane is encoded by NHE-1 mRNA.

Na/H交换物（NHE）中存在多种同工异构体。一般认为，对阿米洛利抑制有抗性的NHE-3位于顶端膜，而对阿米洛利抑制敏感的NHE-1位于上皮细胞的基底外膜。我们在培养的肾上皮细胞（OK细胞和LLC-PK1细胞）中表征了NHE活性及其调控。我们在OK细胞的基底外侧膜中发现了NHE活性，在顶端膜中也发现了NHE活性。由于两膜中的NHE对阿米洛利具有抗性，且其最大活性被甲状旁腺激素抑制，因此两膜中的NHE似乎是NHE-3。因此，在OK细胞中，NHE-3不仅可以在顶膜中表达，也可以在基底膜中表达。NHE在基底膜和顶膜中对胞质[H^+]的亲和力不同。因此，NHE-3的性质可能因NHE-3所处的位置而异。由于转染人NHE-1 cDNA的OK细胞仅在基底外膜表达NHE-1活性，因此NHE-1可能在上皮细胞中具有靶向基底外膜的内在信号。与典型的NHE-3相比，lc - pk1细胞顶膜的NHE活性对阿米洛利更为敏感。为了阐明NHE-1活性是否可能在根尖膜和基底膜中表达，我们检测了NHE-1反义寡核苷酸的作用。由于转染反义寡核苷酸仅能抑制lc - pk1细胞基底外侧NHE活性，因此只有基底外侧膜上的NHE是由NHE-1 mRNA编码的。