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Fatty acid modulation and polyamine block of GluK2 kainate receptors analyzed by scanning mutagenesis

RNA editing of kainate receptor subunits at the Q/R site determines their susceptibility to inhibition by cis-unsaturated fatty acids as well as block by cytoplasmic polyamines. Channels comprised of unedited (Q) subunits are strongly blocked by polyamines, but insensitive to fatty acids, such as ar...

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Autores principales: Wilding, Timothy J., Chen, Kevin, Huettner, James E.
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 2010
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2931155/
https://www.ncbi.nlm.nih.gov/pubmed/20805577
http://dx.doi.org/10.1085/jgp.201010442
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author Wilding, Timothy J.
Chen, Kevin
Huettner, James E.
author_facet Wilding, Timothy J.
Chen, Kevin
Huettner, James E.
author_sort Wilding, Timothy J.
collection PubMed
description RNA editing of kainate receptor subunits at the Q/R site determines their susceptibility to inhibition by cis-unsaturated fatty acids as well as block by cytoplasmic polyamines. Channels comprised of unedited (Q) subunits are strongly blocked by polyamines, but insensitive to fatty acids, such as arachidonic acid (AA) and docosahexaenoic acid (DHA), whereas homomeric edited (R) channels resist polyamine block but are inhibited by AA and DHA. In the present study, we have analyzed fatty acid modulation of whole-cell currents mediated by homomeric recombinant GluK2 (formerly GluR6) channels with individual residues in the pore-loop, M1 and M3 transmembrane helices replaced by scanning mutagenesis. Our results define three abutting surfaces along the M1, M2, and M3 helices where gain-of-function substitutions render GluK2(Q) channels susceptible to fatty acid inhibition. In addition, we identify four locations in the M3 helix (F611, L614, S618, and T621) at the level of the central cavity where Arg substitution increases relative permeability to chloride and eliminates polyamine block. Remarkably, for two of these positions, L614R and S618R, exposure to fatty acids reduces the apparent chloride permeability and potentiates whole-cell currents ∼5 and 2.5-fold, respectively. Together, our results suggest that AA and DHA alter the orientation of M3 in the open state, depending on contacts at the interface between M1, M2, and M3. Moreover, our results demonstrate the importance of side chains within the central cavity in determining ionic selectivity and block by cytoplasmic polyamines despite the inverted orientation of GluK2 as compared with potassium channels and other pore-loop family members.
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spelling pubmed-29311552011-03-01 Fatty acid modulation and polyamine block of GluK2 kainate receptors analyzed by scanning mutagenesis Wilding, Timothy J. Chen, Kevin Huettner, James E. J Gen Physiol Article RNA editing of kainate receptor subunits at the Q/R site determines their susceptibility to inhibition by cis-unsaturated fatty acids as well as block by cytoplasmic polyamines. Channels comprised of unedited (Q) subunits are strongly blocked by polyamines, but insensitive to fatty acids, such as arachidonic acid (AA) and docosahexaenoic acid (DHA), whereas homomeric edited (R) channels resist polyamine block but are inhibited by AA and DHA. In the present study, we have analyzed fatty acid modulation of whole-cell currents mediated by homomeric recombinant GluK2 (formerly GluR6) channels with individual residues in the pore-loop, M1 and M3 transmembrane helices replaced by scanning mutagenesis. Our results define three abutting surfaces along the M1, M2, and M3 helices where gain-of-function substitutions render GluK2(Q) channels susceptible to fatty acid inhibition. In addition, we identify four locations in the M3 helix (F611, L614, S618, and T621) at the level of the central cavity where Arg substitution increases relative permeability to chloride and eliminates polyamine block. Remarkably, for two of these positions, L614R and S618R, exposure to fatty acids reduces the apparent chloride permeability and potentiates whole-cell currents ∼5 and 2.5-fold, respectively. Together, our results suggest that AA and DHA alter the orientation of M3 in the open state, depending on contacts at the interface between M1, M2, and M3. Moreover, our results demonstrate the importance of side chains within the central cavity in determining ionic selectivity and block by cytoplasmic polyamines despite the inverted orientation of GluK2 as compared with potassium channels and other pore-loop family members. The Rockefeller University Press 2010-09 /pmc/articles/PMC2931155/ /pubmed/20805577 http://dx.doi.org/10.1085/jgp.201010442 Text en © 2010 Wilding et al. This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).
spellingShingle Article
Wilding, Timothy J.
Chen, Kevin
Huettner, James E.
Fatty acid modulation and polyamine block of GluK2 kainate receptors analyzed by scanning mutagenesis
title Fatty acid modulation and polyamine block of GluK2 kainate receptors analyzed by scanning mutagenesis
title_full Fatty acid modulation and polyamine block of GluK2 kainate receptors analyzed by scanning mutagenesis
title_fullStr Fatty acid modulation and polyamine block of GluK2 kainate receptors analyzed by scanning mutagenesis
title_full_unstemmed Fatty acid modulation and polyamine block of GluK2 kainate receptors analyzed by scanning mutagenesis
title_short Fatty acid modulation and polyamine block of GluK2 kainate receptors analyzed by scanning mutagenesis
title_sort fatty acid modulation and polyamine block of gluk2 kainate receptors analyzed by scanning mutagenesis
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2931155/
https://www.ncbi.nlm.nih.gov/pubmed/20805577
http://dx.doi.org/10.1085/jgp.201010442
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