A Caltech Library Service

5-HT₃ Receptor MX Helix Contributes to Receptor Function

Mocatta, James and Mesoy, Susanne M. and Dougherty, Dennis A. and Lummis, Sarah C. R. (2022) 5-HT₃ Receptor MX Helix Contributes to Receptor Function. ACS Chemical Neuroscience, 13 (15). pp. 2338-2345. ISSN 1948-7193. PMCID PMC9354082. doi:10.1021/acschemneuro.2c00339.

[img] PDF - Published Version
Creative Commons Attribution.


Use this Persistent URL to link to this item:


5-HT₃ receptors are members of the family of pentameric ligand-gated ion channels. Each subunit has an extracellular, transmembrane, and intracellular domain. Only part of the intracellular domain structure has been solved, revealing it contains two α-helical segments; one, the MA helix, is an extension of M4, while the other, the MX helix, is formed from residues located close to the end of M3. This MX helix is in distinct locations in open and closed receptor structures, suggesting it may play a role in function. Here, we explore this hypothesis using functional responses of Ala-substituted mutant receptors expressed in HEK293 cells. The data show altering many of the MX residues results in a small decrease in EC50 (up to 5-fold), although in one (H232A) this is increased. Radiolabeled ligand binding on selected mutants showed no change in binding affinity, indicating an effect on gating and not binding. In addition, five mutations (P316A, V317A, P318A, D319A, and H323A) initially resulted in nonfunctional receptors, but the function could be rescued by coexpression with a chaperone protein, suggesting a likely role in assembly or folding. Examination of previously obtained MD simulation data shows that the extent of MX encompassed by membrane lipids differs considerably in the open and closed structures, suggesting that lipid–protein interactions in this region could have a major effect on channel opening propensity. We conclude that the MX helix can modulate the function of the receptor and propose that its interactions with membrane lipids play a major role in this.

Item Type:Article
Related URLs:
URLURL TypeDescription CentralArticle
Mesoy, Susanne M.0000-0001-7497-9985
Dougherty, Dennis A.0000-0003-1464-2461
Lummis, Sarah C. R.0000-0001-9410-9805
Additional Information:© 2022 The Authors. Published by American Chemical Society. Attribution 4.0 International (CC BY 4.0). Received 10 June 2022. Accepted 6 July 2022. Published online 22 July 2022. S.M. was supported by an AstraZeneca studentship. S.C.R.L. was supported by the MRC (MR/L021676/1). Author Contributions. Participated in research design: S.C.R.L. Conducted experiments and data analysis: J.M., S.M., and S.C.R.L. Designed and provided reagents: D.A.D. The authors declare no competing financial interest.
Funding AgencyGrant Number
Medical Research Council (UK)MR/L021676/1
Subject Keywords:Cys-loop receptor, binding site, mutagenesis, noncanonical amino acid, nonsense suppression
Issue or Number:15
PubMed Central ID:PMC9354082
Record Number:CaltechAUTHORS:20220725-414654000
Persistent URL:
Official Citation:5-HT3 Receptor MX Helix Contributes to Receptor Function. James Mocatta, Susanne M. Mesoy, Dennis A. Dougherty, and Sarah C. R. Lummis. ACS Chemical Neuroscience 2022 13 (15), 2338-2345; DOI: 10.1021/acschemneuro.2c00339
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115811
Deposited By: George Porter
Deposited On:27 Jul 2022 15:11
Last Modified:17 Aug 2022 17:13

Repository Staff Only: item control page