Regulation of Na+/H+ exchanger 1 allosteric balance by its localization in cholesterol- and caveolin-rich membrane microdomains.
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.
Tekpli
Xavier
X
INSERM U620, Equipe Labellisée Ligue contre Le Cancer, Rennes Cedex, France.
Huc
Laurence
L
Lacroix
Jérôme
J
Rissel
Mary
M
Poët
Mallorie
M
Noël
Josette
J
Dimanche-Boitrel
Marie-Thérèse
MT
Counillon
Laurent
L
Lagadic-Gossmann
Dominique
D
D000494:Allosteric Regulation; D000818:Animals; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D022461:Caveolins / Q000378:metabolism*; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D002789:Cholesterol Oxidase / Q000378:metabolism; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005677:G(M1) Ganglioside / Q000378:metabolism; D006801:Humans; D006859:Hydrogen / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D021962:Membrane Microdomains / Q000737:chemistry / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D012964:Sodium / Q000378:metabolism; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D047392:beta-Cyclodextrins / Q000378:metabolism
D027682:Cation Transport Proteins; D022461:Caveolins; D036341:Intercellular Signaling Peptides and Proteins; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D005677:G(M1) Ganglioside; D006859:Hydrogen; D002784:Cholesterol; D012964:Sodium; D002789:Cholesterol Oxidase; D048049:Extracellular Signal-Regulated MAP Kinases