Cyclic dinucleotides bind the C-linker of HCN4 to control channel cAMP responsiveness

  • Nat Chem Biol. 2014 Jun;10(6):457-62. doi: 10.1038/nchembio.1521.
Marco Lolicato  1 ,  Annalisa Bucchi  1 ,  Cristina Arrigoni  2 ,  Stefano Zucca  2 ,  Marco Nardini  2 ,  Indra Schroeder  3 ,  Katie Simmons  4 ,  Marco Aquila  2 ,  Dario DiFrancesco  2 ,  Martino Bolognesi  5 ,  Frank Schwede  6 ,  Dmitry Kashin  6 ,  Colin W G Fishwick  4 ,  A Peter Johnson  4 ,  Gerhard Thiel  3 ,  Anna Moroni  5
Affiliations
  • 1. 1] Department of Biosciences, University of Milan, Milan, Italy. [2].
  • 2. Department of Biosciences, University of Milan, Milan, Italy.
  • 3. Department of Biology, Technische Universität Darmstadt, Darmstadt, Germany.
  • 4. School of Chemistry, University of Leeds, Leeds, UK.
  • 5. 1] Department of Biosciences, University of Milan, Milan, Italy. [2] Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Milan, Italy.
  • 6. BIOLOG Life Science Institute, Forschungslabor und Biochemica-Vertrieb GmbH D-28199, Bremen, Germany.
PMID: 24776929 DOI: 10.1038/nchembio.1521
Abstract

cAMP mediates autonomic regulation of heart rate by means of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which underlie the pacemaker current If. cAMP binding to the C-terminal cyclic nucleotide binding domain enhances HCN open probability through a conformational change that reaches the pore via the C-linker. Using structural and functional analysis, we identified a binding pocket in the C-linker of HCN4. Cyclic dinucleotides, an emerging class of second messengers in mammals, bind the C-linker pocket (CLP) and antagonize cAMP regulation of the channel. Accordingly, cyclic dinucleotides prevent cAMP regulation of If in sinoatrial node myocytes, reducing heart rate by 30%. Occupancy of the CLP hence constitutes an efficient mechanism to hinder β-adrenergic stimulation on If. Our results highlight the regulative role of the C-linker and identify a potential drug target in HCN4. Furthermore, these data extend the signaling scope of cyclic dinucleotides in mammals beyond their first reported role in innate immune system.

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