Common determinants of single channel conductance within the large cytoplasmic loop of 5-hydroxytryptamine type 3 and alpha4beta2 nicotinic acetylcholine receptors.

Hales, Tim G. and Dunlop, James I. and Deeb, Tarek Z. and Carland, Jane E. and Kelley, Stephen P. and Lambert, Jeremy J. and Peters, John A. (2006) Common determinants of single channel conductance within the large cytoplasmic loop of 5-hydroxytryptamine type 3 and alpha4beta2 nicotinic acetylcholine receptors. Journal of Biological Chemistry, 281 . pp. 8062-8071. ISSN 0021-9258. (Full text available)

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http://dx.doi.org/10.1074/jbc.M513222200

Abstract

Homomeric 5-hydroxytryptamine type 3A receptors (5-HT3ARs) have a single channel conductance (γ) below the resolution of single channel recording (966 ± 75 fS, estimated by variance analysis). By contrast, heteromeric 5-HT3A/B and nicotinic acetylcholine receptors (nAChRs) have picosiemen range γ values. In this study, single channel recordings revealed that replacement of cytoplasmic membrane-associated (MA) helix arginine 432 (-4′), 436 (0′), and 440 (4′) residues by 5-HT3B (-4′Gln, 0′Asp, and 4′Ala) residues increases γ to 36.5 ± 1.0 pS. The 0′ residue makes the most substantial contribution to γ of the 5-HT3AR. Replacement of 0′Arg by aspartate, glutamate (α7 nAChR subunit MA 0′), or glutamine (β2 subunit MA 0′) increases γ to the resolvable range (>6 pS). By contrast, replacement of 0′Arg by phenylalanine (α4 subunit MA 0′) reduced γ to 416 ± 107 fS. In reciprocal experiments with α4β2 nAChRs (γ = 31.3 ± 0.8 pS), replacement of MA 0′ residues by arginine in α4β2(Q443R) and α4(F588R)β2 reduced γ slightly. By contrast, the γ of double mutant α4(F588R)β2(Q443R) was halved. The MA -4′ and 4′ residues also influenced γ of 5-HT3ARs. Replacement of nAChR α4 or β2 MA 4′ residues by arginine made current density negligible. By contrast, replacement of both -4′ residues by arginine produced functional nAChRs with substantially reduced γ (11.4 ± 0.5 pS). Homology models of the 5-HT3A and α4β2 nAChRs against Torpedo nAChR revealed MA -4′, 0′, and 4′ residues within five intracellular portals. This locus may be a common determinant of ion conduction throughout the Cys loop receptor family.

Item Type: Article
Subjects: Q Science > QP Physiology (Living systems)
R Medicine > RM Therapeutics. Pharmacology
Q Science > QC Physics
Divisions: Faculties > Science Technology and Medical Studies > Medway School of Pharmacy
Depositing User: Stephen Kelley
Date Deposited: 29 Jun 2011 17:04
Last Modified: 29 Apr 2014 08:17
Resource URI: http://kar.kent.ac.uk/id/eprint/11373 (The current URI for this page, for reference purposes)
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