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The MA Helix Is Important for Receptor Assembly and Function in the α4β2 nACh Receptor.

Published version
Peer-reviewed

Repository DOI


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Authors

Fricska, Dorottya I 
Lummis, Sarah CR 

Abstract

Pentameric ligand-gated ion channels (pLGICs) are expressed throughout the central and peripheral nervous systems of vertebrates and modulate many aspects of human health and disease. Recent structural and computational data indicate that cation-selective pLGICs contain a long helical extension (MA) of one of the transmembrane helices. The MA helix has been shown to affect both the membrane expression of, and ion conductance levels through, these pLGICs. Here we probe the functional effects of 68 mutations in the MA region of the α4β2 nicotinic acetylcholine receptor (nAChR), using a voltage-sensitive membrane dye and radioligand binding to measure receptor function and expression/assembly. We found seven alanine mutations in a stretch of the MA helix that prevent correct receptor folding and/or assembly, as evidenced by the lack of both function and ligand binding. A further two alanine mutations resulted in receptors that were capable of binding ligand but showed no functional response, and we propose that, in these mutants, ligand binding is insufficient to trigger channel opening. The data clarify the effect of the MA helix, and as the effects of some of our mutations in the α4β2 nAChR differ from the effects of equivalent mutations in other cation-selective pLGICs, we suggest that residues in the MA helix may play subtly different roles in different receptors.

Description

Peer reviewed: True


Publication status: Published


Funder: AstraZeneca

Keywords

Cys-loop receptor, acetylcholine receptor, intracellular domain, neurotransmitter receptor, pentameric ligand-gated ion channel

Journal Title

Membranes (Basel)

Conference Name

Journal ISSN

2077-0375
2077-0375

Volume Title

13

Publisher

MDPI AG
Sponsorship
Medical Research Council (MR/L021676/1)