The Polarity of Lipid-Exposed Residues Contributes to the Functional Differences between Torpedo and Muscle-Type Nicotinic Receptors

The Polarity of Lipid-Exposed Residues Contributes to the Functional Differences between Torpedo... A comparison between the Torpedo and muscle-type acetylcholine receptors (AChRs) reveals differences in several lipid-exposed amino acids, particularly in the polarity of those residues. The goal of this study was to characterize the role of eight lipid-exposed residues in the functional differences between the Torpedo and muscle-type AChRs. To this end, residues αS287, αC412, βY441, γM299, γS460, δM293, δS297 and δN305 in the Torpedo AChR were replaced with those found in the muscle-type receptor. Mutant receptor expression was measured in Xenopus oocytes using [125I]-α-bungarotoxin, and AChR ion channel function was evaluated using the two-electrode voltage clamp. Eight mutant combinations resulted in an increase (1.5- to 5.2-fold) in AChR expression. Four mutant combinations produced a significant 46% decrease in the ACh 50% inhibitory concentration (EC50), while three mutant combinations resulted in 1.7- to 2-fold increases in ACh EC50. Finally, seven mutant combinations resulted in a decrease in normalized, ACh-induced currents. Our results suggest that these residues, although remote from the ion channel pore, (1) contribute to ion channel gating, (2) may affect trafficking of AChR into specialized membrane domains and (3) account for the functional differences between Torpedo and muscle-type AChR. These findings emphasize the importance of the lipid-protein interface in the functional differences between the Torpedo and muscle-type AChRs. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

The Polarity of Lipid-Exposed Residues Contributes to the Functional Differences between Torpedo and Muscle-Type Nicotinic Receptors

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Publisher
Springer-Verlag
Copyright
Copyright © 2007 by Springer Science+Business Media, LLC
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-006-0051-0
Publisher site
See Article on Publisher Site

Abstract

A comparison between the Torpedo and muscle-type acetylcholine receptors (AChRs) reveals differences in several lipid-exposed amino acids, particularly in the polarity of those residues. The goal of this study was to characterize the role of eight lipid-exposed residues in the functional differences between the Torpedo and muscle-type AChRs. To this end, residues αS287, αC412, βY441, γM299, γS460, δM293, δS297 and δN305 in the Torpedo AChR were replaced with those found in the muscle-type receptor. Mutant receptor expression was measured in Xenopus oocytes using [125I]-α-bungarotoxin, and AChR ion channel function was evaluated using the two-electrode voltage clamp. Eight mutant combinations resulted in an increase (1.5- to 5.2-fold) in AChR expression. Four mutant combinations produced a significant 46% decrease in the ACh 50% inhibitory concentration (EC50), while three mutant combinations resulted in 1.7- to 2-fold increases in ACh EC50. Finally, seven mutant combinations resulted in a decrease in normalized, ACh-induced currents. Our results suggest that these residues, although remote from the ion channel pore, (1) contribute to ion channel gating, (2) may affect trafficking of AChR into specialized membrane domains and (3) account for the functional differences between Torpedo and muscle-type AChR. These findings emphasize the importance of the lipid-protein interface in the functional differences between the Torpedo and muscle-type AChRs.

Journal

The Journal of Membrane BiologySpringer Journals

Published: May 25, 2007

References

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