Regulation of Na+/H+ exchanger 1 allosteric balance by its localization in cholesterol- and caveolin-rich membrane microdomains.

Xavier Tekpli (1, 2) , Laurence Huc (2, 3) , Jérôme Lacroix (4, 5) , Mary Rissel (1, 2) , Mallorie Poët (5, 6) , Josette Noël (7) , Marie-Thérèse Dimanche-Boitrel (1, 2) , Laurent Counillon (6) , Dominique Lagadic-Gossmann (1)

1 SeRAIC - Signalisation et Réponses aux Agents Infectieux et Chimiques
2 Détoxication et réparation tissulaire
3 Experimental Medicine and Toxicology
4 Transport ionique aspects normaux et pathologiques
5 PCMSI - Physiologie cellulaire et moléculaire des systèmes intégrés
6 IPMC - Institut de pharmacologie moléculaire et cellulaire
7 Département de Physiologie

The Na+/H+ exchanger 1, which plays an essential role in intracellular pH regulation in most tissues, is also known to be a key actor in both proliferative and apoptotic processes. Its activation by H+ is best described by the Monod-Wyman-Changeux model: the dimeric NHE-1 oscillates between a low and a high affinity conformation, the balance between the two forms being defined by the allosteric constant L(0). In this study, influence of cholesterol- and caveolin-rich microdomains on NHE-1 activity was examined by using cholesterol depleting agents, including methyl-beta-cyclodextrin (MBCD). These agents activated NHE-1 by modulating its L(0) parameter, which was reverted by cholesterol repletion. This activation was associated with NHE-1 relocation outside microdomains, and was distinct from NHE-1 mitogenic and hormonal stimulation; indeed MBCD and serum treatments were additive, and serum alone did not change NHE-1 localization. Besides, MBCD activated a serum-insensitive, constitutively active mutated NHE-1 ((625)KDKEEEIRK(635) into KNKQQQIRK). Finally, the membrane-dependent NHE-1 regulation occurred independently of Mitogen Activated Protein Kinases, especially Extracellular Regulated Kinase activation, although this kinase was activated by MBCD. In conclusion, localization of NHE-1 in membrane cholesterol- and caveolin-rich microdomains constitutes a novel physiological negative regulator of NHE-1 activity.

Domaines: Biologie cellulaire

Xavier Tekpli, Laurence Huc, Jérôme Lacroix, Mary Rissel, Mallorie Poët, et al.. Regulation of Na+/H+ exchanger 1 allosteric balance by its localization in cholesterol- and caveolin-rich membrane microdomains.. Journal of Cellular Physiology, 2008, 216 (1), pp.207-20. ⟨10.1002/jcp.21395⟩. ⟨hal-00696172⟩