Role of the C-terminal part of the extracellular domain of the alpha-ENaC in activation by sulfonylurea glibenclamide.
The epithelial sodium channel (ENaC) is regulated by hormones and by other intracellular or extracellular factors. It is activated by the sulfonylurea drug glibenclamide. The activator effect of glibenclamide is fast and reversible and was observed in Xenopus oocytes coexpressing the alpha subunit from human, Xenopus, or guinea pig (but not rat) with betagamma-rat ENaC subunits. The mechanism of this effect is not yet well understood. We hypothesize that the extracellular loop of ENaC plays a major role in this activation. Mutants and chimeras of alpha subunits harboring different parts of the rat and guinea pig alpha-subunit extracellular loops were generated and coexpressed with betagamma-rat subunits in Xenopus oocytes. The effect of glibenclamide on ENaC activity was measured using two-electrode voltage-clamp technique. The alpha-rat ENaC chimera containing the C-terminal part of the extracellular loop of the alpha-guinea pig ENaC was significantly stimulated by glibenclamide (1.26-fold), whereas the rat-alpha combination was not activated by this sulfonylurea. Mutagenesis of specific residues on the rat alpha subunit did not generate channels sensitive to glibenclamide, suggesting that the overall structure of the extracellular loop is required for activation of the channel by this drug. These results support the hypothesis of the existence of a role played by the last 100 amino acids of the extracellular loop and confirm that the ENaC behaves as a ligand-gated channel similar to several other members of the ENaC/degenerin family.
Renauld
Stephane
S
Département de Physiologie et de Biophysique, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, QC, Canada.
Chraibi
Ahmed
A
D000584:Amiloride / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D004594:Electrophysiology; D062708:Epithelial Sodium Channel Agonists; D053503:Epithelial Sodium Channels / Q000737:chemistry* / Q000235:genetics; D005905:Glyburide / Q000494:pharmacology*; D006168:Guinea Pigs; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000235:genetics; D051381:Rats; D017386:Sequence Homology, Amino Acid; D026941:Sodium Channel Blockers / Q000494:pharmacology; D014981:Xenopus
D062708:Epithelial Sodium Channel Agonists; D053503:Epithelial Sodium Channels; D007004:Hypoglycemic Agents; D026941:Sodium Channel Blockers; D000584:Amiloride; D005905:Glyburide
Curr Opin Nephrol Hypertens. 2007 Sep;16(5):444-50
17693760
Nature. 2007 Sep 20;449(7160):316-23
17882215
EMBO J. 1998 Jan 15;17(2):344-52
9430626
Physiol Rev. 1997 Apr;77(2):359-96
9114818
Nat Genet. 1996 Mar;12(3):325-8
8589728
J Membr Biol. 2001 Sep 1;183(1):15-23
11547348
J Biol Chem. 1997 Aug 22;272(34):21075-83
9261110
Pflugers Arch. 2001 Aug;442(5):752-61
11512032
Nature. 1993 Feb 4;361(6411):467-70
8381523
J Gen Physiol. 1997 Jun;109(6):681-92
9222895
J Am Soc Nephrol. 2008 Oct;19(10):1845-54
18753254
J Gen Physiol. 1998 Jan;111(1):127-38
9417140
Nephron Physiol. 2004;96(2):p37-41
14988660
IUBMB Life. 2008 Sep;60(9):620-8
18459164
J Biol Chem. 1998 Jan 9;273(2):681-4
9422716
Am J Physiol Gastrointest Liver Physiol. 2000 May;278(5):G718-24
10801264
Am J Physiol Renal Physiol. 2003 Dec;285(6):F1279-90
12928313
J Biol Chem. 2003 Sep 26;278(39):37073-82
12871941
J Biol Chem. 2008 May 2;283(18):11981-94
18326490
J Gen Physiol. 2007 Jul;130(1):55-70
17562820
Cell Physiol Biochem. 2008;22(1-4):101-8
18769036
J Biol Chem. 2004 Oct 22;279(43):44483-9
15308635
Proc Am Thorac Soc. 2004;1(1):4-9
16113404
Curr Opin Nephrol Hypertens. 1994 Sep;3(5):487-96
7804746
Am J Physiol Lung Cell Mol Physiol. 2006 Dec;291(6):L1207-19
16891388
Mol Biosyst. 2009 Feb;5(2):123-7
19156256
Pflugers Arch. 2000 Mar;439(5):579-87
10764218
J Am Soc Nephrol. 2002 Mar;13(3):588-594
11856761
J Pharmacol Exp Ther. 1999 Jul;290(1):341-7
10381797
J Biol Chem. 2006 Sep 8;281(36):26159-69
16844684
J Gen Physiol. 1997 Jan;109(1):15-26
8997662
Nature. 1994 Feb 3;367(6462):463-7
8107805
Physiol Rev. 2002 Jul;82(3):735-67
12087134
Nature. 1997 Oct 9;389(6651):607-10
9335501
Biochim Biophys Acta. 2003 Jan 31;1609(2):170-6
12543378