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Mutation Linked to Autosomal Dominant Nocturnal Frontal Lobe Epilepsy Reduces Low-Sensitivity α4β2, and Increases α5α4β2, Nicotinic Receptor Surface Expression

Nichols, Weston A. and Henderson, Brandon J. and Marotta, Christopher B. and Yu, Caroline Y. and Richards, Chris and Dougherty, Dennis A. and Lester, Henry A. and Cohen, Bruce N. (2016) Mutation Linked to Autosomal Dominant Nocturnal Frontal Lobe Epilepsy Reduces Low-Sensitivity α4β2, and Increases α5α4β2, Nicotinic Receptor Surface Expression. PLoS ONE, 11 (6). Art. No. e0158032. ISSN 1932-6203. PMCID PMC4918917. doi:10.1371/journal.pone.0158032. https://resolver.caltech.edu/CaltechAUTHORS:20160706-102113506

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Abstract

A number of mutations in α4β2-containing (α4β2*) nicotinic acetylcholine (ACh) receptors (nAChRs) are linked to autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE), including one in the β2 subunit called β2V287L. Two α4β2* subtypes with different subunit stoichiometries and ACh sensitivities co-exist in the brain, a high-sensitivity subtype with (α4)2(β2)3 subunit stoichiometry and a low-sensitivity subtype with (α4)3(β2)2 stoichiometry. The α5 nicotinic subunit also co-assembles with α4β2 to form a high-sensitivity α5α4β2 nAChR. Previous studies suggest that the β2V287L mutation suppresses low-sensitivity α4β2* nAChR expression in a knock-in mouse model and also that α5 co-expression improves the surface expression of ADNFLE mutant nAChRs in a cell line. To test these hypotheses further, we expressed mutant and wild-type (WT) nAChRs in oocytes and mammalian cell lines, and measured the effects of the β2V287L mutation on surface receptor expression and the ACh response using electrophysiology, a voltage-sensitive fluorescent dye, and superecliptic pHluorin (SEP). The β2V287L mutation reduced the EC_(50) values of high- and low-sensitivity α4β2 nAChRs expressed in Xenopus oocytes for ACh by a similar factor and suppressed low-sensitivity α4β2 expression. In contrast, it did not affect the EC50 of α5α4β2 nAChRs for ACh. Measurements of the ACh responses of WT and mutant nAChRs expressed in mammalian cell lines using a voltage-sensitive fluorescent dye and whole-cell patch-clamping confirm the oocyte data. They also show that, despite reducing the maximum response, β2V287L increased the α4β2 response to a sub-saturating ACh concentration (1 μM). Finally, imaging SEP-tagged α5, α4, β2, and β2V287L subunits showed that β2V287L reduced total α4β2 nAChR surface expression, increased the number of β2 subunits per α4β2 receptor, and increased surface α5α4β2 nAChR expression. Thus, the β2V287L mutation alters the subunit composition and sensitivity of α4β2 nAChRs, and increases α5α4β2 surface expression.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1371/journal.pone.0158032DOIArticle
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4918917/PubMed CentralArticle
ORCID:
AuthorORCID
Henderson, Brandon J.0000-0003-0381-028X
Dougherty, Dennis A.0000-0003-1464-2461
Lester, Henry A.0000-0002-5470-5255
Additional Information:© 2016 Nichols et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Received: February 22, 2016; Accepted: June 9, 2016; Published: June 23, 2016. This research was supported by grants to D.A.D. (NS034407), H.A.L. (DA017279), B.J.H. (DA033721), and C.R. (DA030877) from the National Institutes of Health (http://www.nih.gov/) and to C.Y.Y. from the Rose Hills foundation (http://rosehillsfoundation.org/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors acknowledge the assistance of Timothy F. Miles (Division of Biology & Biological Engineering, California Institute of Technology, Pasadena, CA) in making the TIRF measurements. Author Contributions: Conceived and designed the experiments: WAN BJH CBM HAL BNC. Performed the experiments: WAN BJH CBM CYY. Analyzed the data: WAN BJH CBM CYY BNC. Contributed reagents/materials/analysis tools: CR. Wrote the paper: WAN BJH CBM DAD HAL BNC. Data Availability: All relevant data are within the paper. The authors have declared that no competing interests exist.
Funders:
Funding AgencyGrant Number
NIHNS034407
NIHDA017279
NIHDA033721
NIHDA030877
Rose Hills FoundationUNSPECIFIED
Issue or Number:6
PubMed Central ID:PMC4918917
DOI:10.1371/journal.pone.0158032
Record Number:CaltechAUTHORS:20160706-102113506
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20160706-102113506
Official Citation:Nichols WA, Henderson BJ, Marotta CB, Yu CY, Richards C, Dougherty DA, et al. (2016) Mutation Linked to Autosomal Dominant Nocturnal Frontal Lobe Epilepsy Reduces Low-Sensitivity α4β2, and Increases α5α4β2, Nicotinic Receptor Surface Expression. PLoS ONE 11(6): e0158032. doi:10.1371/journal.pone.0158032
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:68854
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:06 Jul 2016 21:31
Last Modified:11 Nov 2021 04:05

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