Inverse Relationship Between Membrane Lipid Fluidity and Activity of Na+/H+ Exchangers, NHE1 and NHE3, in Transfected Fibroblasts |
| |
Authors: | C Bookstein MW Musch PK Dudeja RL McSwine Y Xie TA Brasitus MC Rao EB Chang |
| |
Institution: | (1) Division of Gastroenterology, Department of Medicine, mc 6084, University of Chicago, 5841 S. Maryland Ave., Chicago, IL 60637, USA, US;(2) Department of Physiology, University of Illinois at Chicago School of Medicine, 812 E. Wolcott, Chicago, IL 60612, USA, US;(3) Research and Development Service, VA West Side Medical Center, 820 S. Damen Ave., Chicago, IL 60612, USA, US |
| |
Abstract: | This report presents a study of the effects of the membrane fluidizer, benzyl alcohol, on NHE isoforms 1 and 3. Using transfectants
of an NHE-deficient fibroblast, we analyzed each isoform separately. An increase in membrane fluidity resulted in a decrease
of ≈50% in the specific activities of both NHE1 and NHE3. Only V
max was affected; K
Na was unchanged. This effect was specific, as Na+, K+, ATPase activity was slightly stimulated. Inhibition of NHE1 and NHE3 was reversible and de novo protein synthesis was not required to restore NHE activity after washout of fluidizer. Inhibition kinetics of NHE1 by amiloride,
5-(N,N-dimethyl)amiloride (DMA), 5-(N-hexamethyl)amiloride (HMA) and 5-(N-ethyl-N-isopropyl)amiloride (EIPA) were largely
unchanged. Half-maximal inhibition of NHE3 was also reached at approximately the same concentrations of amiloride and analogues
in control and benzyl alcohol treated, suggesting that the amiloride binding site was unaffected. Inhibition of vesicular
transport by incubation at 4°C augmented the benzyl alcohol inhibition of NHE activity, suggesting that the fluidizer effect
does not solely involve vesicle trafficking. In summary, our data demonstrate that the physical state of membrane lipids (fluidity)
influences Na+/H+ exchange and may represent a physiological regulatory mechanism of NHE1 and NHE3 activity.
Received: 23 January 1997/Revised: 1 August 1997 |
| |
Keywords: | : Ion transport — Na+/H+ exchange — NHE — Membrane fluidity — Benzyl alcohol |
本文献已被 SpringerLink 等数据库收录! |
|