Na/H exchange activities in NHE1-transfected OK-cells: cell polarity and regulation.
The human fibroblast, "amiloride-sensitive" Na/H exchanger (NHE1) was transfected into opossum kidney cells (OK cells) (OK/NHE1 cells). Northern blot analysis confirmed that the NHE1 message is expressed in OK/NHE1 cells. In immunoblot analysis, an anti-human NHE1 antibody labelled a membrane protein only present in OK/NHE1 cells. In contrast to the parental cell line containing only an apically located, "amiloride-resistant" Na/H exchange activity, OK/NHE1 cells contain apically and basolaterally located Na/H exchange activities, the apical activity being "amiloride resistant" and the basolateral being "amiloride sensitive". Parathyroid hormone (PTH) inhibited apical transport activity (OK and OK/NHE1 cells) but had no effect on basolateral transport activity (OK/NHE1 cells). Pharmacological activation of protein kinase A (forskolin) decreased both apical and basolateral Na/H exchange activity. Incubation with phorbol ester (exogenous activation of protein kinase C) reduced apical Na/H exchange activity (OK and OK/NHE1 cells) but had only a moderate, inhibitory effect on basolateral Na/H exchange activity (OK/NHE1 cells). These results indicate that transfection of OK cells with human fibroblast NHE1 cDNA encoding an "amiloride-sensitive" form of the Na/H exchanger results in expression of basolaterally located "NHE1-related" transport activity. Regulatory control of intracellular Na/H exchange activities (apically versus basolaterally located) and intercellular Na/H exchange activities (NHE1-related) differs. This may relate to cell-specific properties as well as to exchanger-specific properties.
Helmle-Kolb
C
C
University of Zürich, Institute of Physiology, Switzerland.
Counillon
L
L
Roux
D
D
Pouysségur
J
J
Mrkic
B
B
Murer
H
H
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D015152:Blotting, Northern; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007668:Kidney; D009893:Opossums; D010281:Parathyroid Hormone / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
D010281:Parathyroid Hormone; D012333:RNA, Messenger; D017923:Sodium-Hydrogen Exchangers; D005576:Colforsin; D000584:Amiloride; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate