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Minimal molecular determinants of isoform-specific differences in efficacy in the HCN channel family

Hyperpolarization-activated, cyclic nucleotide–gated (HCN) channels generate rhythmic activity in the heart and brain. Isoform-specific functional differences reflect the specializations required for the various roles that they play. Despite a high sequence and structural similarity, HCN isoforms di...

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Autores principales: Alvarez-Baron, Claudia P., Klenchin, Vadim A., Chanda, Baron
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Rockefeller University Press 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6080897/
https://www.ncbi.nlm.nih.gov/pubmed/29980633
http://dx.doi.org/10.1085/jgp.201812031
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author Alvarez-Baron, Claudia P.
Klenchin, Vadim A.
Chanda, Baron
author_facet Alvarez-Baron, Claudia P.
Klenchin, Vadim A.
Chanda, Baron
author_sort Alvarez-Baron, Claudia P.
collection PubMed
description Hyperpolarization-activated, cyclic nucleotide–gated (HCN) channels generate rhythmic activity in the heart and brain. Isoform-specific functional differences reflect the specializations required for the various roles that they play. Despite a high sequence and structural similarity, HCN isoforms differ greatly in their response to cyclic nucleotides. Cyclic AMP (cAMP) enhances the activity of HCN2 and HCN4 isoforms by shifting the voltage dependence of activation to more depolarized potentials, whereas HCN1 and HCN3 isoforms are practically insensitive to this ligand. Here, to determine the molecular basis for increased cAMP efficacy in HCN2 channels, we progressively mutate residues in the C-linker and cyclic nucleotide–binding domain (CNBD) of the mouse HCN2 to their equivalents in HCN1. We identify two clusters of mutations that determine the differences in voltage-dependent activation between these two isoforms. One maps to the C-linker region, whereas the other is in proximity to the cAMP-binding site in the CNBD. A mutant channel containing just five mutations (M485I, G497D, S514T, V562A, and S563G) switches cAMP sensitivity of full-length HCN2 to that of HCN1 channels. These findings, combined with a detailed analysis of various allosteric models for voltage- and ligand-dependent gating, indicate that these residues alter the ability of the C-linker to transduce signals from the CNBD to the pore gates of the HCN channel.
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spelling pubmed-60808972019-02-06 Minimal molecular determinants of isoform-specific differences in efficacy in the HCN channel family Alvarez-Baron, Claudia P. Klenchin, Vadim A. Chanda, Baron J Gen Physiol Research Articles Hyperpolarization-activated, cyclic nucleotide–gated (HCN) channels generate rhythmic activity in the heart and brain. Isoform-specific functional differences reflect the specializations required for the various roles that they play. Despite a high sequence and structural similarity, HCN isoforms differ greatly in their response to cyclic nucleotides. Cyclic AMP (cAMP) enhances the activity of HCN2 and HCN4 isoforms by shifting the voltage dependence of activation to more depolarized potentials, whereas HCN1 and HCN3 isoforms are practically insensitive to this ligand. Here, to determine the molecular basis for increased cAMP efficacy in HCN2 channels, we progressively mutate residues in the C-linker and cyclic nucleotide–binding domain (CNBD) of the mouse HCN2 to their equivalents in HCN1. We identify two clusters of mutations that determine the differences in voltage-dependent activation between these two isoforms. One maps to the C-linker region, whereas the other is in proximity to the cAMP-binding site in the CNBD. A mutant channel containing just five mutations (M485I, G497D, S514T, V562A, and S563G) switches cAMP sensitivity of full-length HCN2 to that of HCN1 channels. These findings, combined with a detailed analysis of various allosteric models for voltage- and ligand-dependent gating, indicate that these residues alter the ability of the C-linker to transduce signals from the CNBD to the pore gates of the HCN channel. Rockefeller University Press 2018-08-06 /pmc/articles/PMC6080897/ /pubmed/29980633 http://dx.doi.org/10.1085/jgp.201812031 Text en © 2018 Alvarez-Baron et al. http://www.rupress.org/terms/https://creativecommons.org/licenses/by-nc-sa/4.0/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 4.0 International license, as described at https://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Research Articles
Alvarez-Baron, Claudia P.
Klenchin, Vadim A.
Chanda, Baron
Minimal molecular determinants of isoform-specific differences in efficacy in the HCN channel family
title Minimal molecular determinants of isoform-specific differences in efficacy in the HCN channel family
title_full Minimal molecular determinants of isoform-specific differences in efficacy in the HCN channel family
title_fullStr Minimal molecular determinants of isoform-specific differences in efficacy in the HCN channel family
title_full_unstemmed Minimal molecular determinants of isoform-specific differences in efficacy in the HCN channel family
title_short Minimal molecular determinants of isoform-specific differences in efficacy in the HCN channel family
title_sort minimal molecular determinants of isoform-specific differences in efficacy in the hcn channel family
topic Research Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6080897/
https://www.ncbi.nlm.nih.gov/pubmed/29980633
http://dx.doi.org/10.1085/jgp.201812031
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