Abstract
The endocannabinoid, N-arachidonoylethanolamine (anandamide; AEA) is known to interact with voltage-gated K+ (Kv) channels in a cannabinoid receptor-independent manner. AEA modulates the functional properties of Kv channels, converting channels with slowly inactivating current into apparent fast inactivation. In this study, we characterize the mechanism of action and binding site for AEA on Kv1.5 channels expressed on HEK-293 cells using the patch-clamp techniques. AEA exhibited high-potency block (IC50 ≈ 200 nM) from the cytoplasmic membrane surface, consistent with open-channel block. Alanine-scanning mutagenesis revealed that AEA interacts with two crucial β-branching amino acids, Val505 and Ile508 within the S6 domain. Both residues face toward the central cavity and constitute a motif that forms a hydrophobic ring around the ion conduction pathway. This hydrophobic ring motif may be a critical determinant of cannabinoid receptor-independent AEA modulation in other K+ channel families.
Footnotes
This work was supported by the Consejo Nacional de Ciencia y Tecnología, México [Grant CONACyT-054577] and the Nora Eccles Treadwell Foundation.
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.109.063008.
-
ABBREVIATIONS:
- AEA
- N-arachidonoylethanolamine
- Kv
- voltage-gated potassium channel
- TEA
- tetraethylammonium
- HEK
- human embryonic kidney
- WT
- wild type
- K4BAPTA
- 1,2-bis (2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid, tetrapotassium salt
- S9947
- 2′-(benzyloxycarbonylaminomethyl)biphenyl-2-carboxylic acid 2-(2-pyridyl)ethylamide
- S0100176
- N-benzyl-N-pyridin-3-ylmethyl-2-(toluene-4-sulfonylamino)-benzamide hydrochloride
- AVE0118
- 2′-{[2-(4-methoxy-phenyl)-acetylamino]-methyl}-biphenyl-2-carboxylic acid (2-pyridin-3-yl-ethyl)-amide
- ICAGEN-4
- N-[3-(4-ethyl-benzene-sulfonylamino)-2-hydroxy-indan-5-yl]-3-methoxy-benzamide
- MSD-D
- 2-(4-methoxy-phenyl)-5-methyl-3-oxo-6-p-tolylsulfanyl-2,3-dihydro-pyridazine-4-carbonitrile.
- Received December 7, 2009.
- Accepted January 28, 2010.
- Copyright © 2010 The American Society for Pharmacology and Experimental Therapeutics
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|