title: Structural basis for the mutual antagonism of cAMP and TRIP8b in regulating HCN channel function.
abstract: cAMP signaling in the brain mediates several higher order neural processes. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels directly bind cAMP through their cytoplasmic cyclic nucleotide binding domain (CNBD), thus playing a unique role in brain function. Neuronal HCN channels are also regulated by tetratricopeptide repeat-containing Rab8b interacting protein (TRIP8b), an auxiliary subunit that antagonizes the effects of cAMP by interacting with the channel CNBD. To unravel the molecular mechanisms underlying the dual regulation of HCN channel activity by cAMP/TRIP8b, we determined the NMR solution structure of the HCN2 channel CNBD in the cAMP-free form and mapped on it the TRIP8b interaction site. We reconstruct here the full conformational changes induced by cAMP binding to the HCN channel CNBD. Our results show that TRIP8b does not compete with cAMP for the same binding region; rather, it exerts its inhibitory action through an allosteric mechanism, preventing the cAMP-induced conformational changes in the HCN channel CNBD.
authors.affiliation: Department of Biosciences, University of Milan, 20133 Milan, Italy;
authors.forename: Andrea
authors.initials: A
authors.lastname: Saponaro
authors.affiliation: Rede de Química e Tecnologia/Centro de Química Fina e Biotecnologia (REQUIMTE/CQFB), Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal;
authors.forename: Sofia R
authors.initials: SR
authors.lastname: Pauleta
authors.affiliation: Centro Risonanze Magnetiche (CERM) and Departement of Chemistry, University of Florence, 50019 Sesto Fiorentino, Italy;
authors.forename: Francesca
authors.initials: F
authors.lastname: Cantini
authors.affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, 2780-157 Oeiras, Portugal;
authors.forename: Manolis
authors.initials: M
authors.lastname: Matzapetakis
authors.affiliation: School of Engineering and Science, Molecular Life Sciences Research Center, Jacobs University Bremen, DE-28759 Bremen, Germany;
authors.forename: Christian
authors.initials: C
authors.lastname: Hammann
authors.affiliation: Department of Biosciences, University of Milan, 20133 Milan, Italy;
authors.forename: Chiara
authors.initials: C
authors.lastname: Donadoni
authors.affiliation: Department of Neuroscience, Columbia University, New York, NY 10032; and.
authors.forename: Lei
authors.initials: L
authors.lastname: Hu
authors.affiliation: Membrane Biophysics, Technical University of Darmstadt, 64287 Darmstadt, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Thiel
authors.affiliation: Centro Risonanze Magnetiche (CERM) and Departement of Chemistry, University of Florence, 50019 Sesto Fiorentino, Italy;
authors.forename: Lucia
authors.initials: L
authors.lastname: Banci
authors.affiliation: Department of Neuroscience, Columbia University, New York, NY 10032; and.
authors.forename: Bina
authors.initials: B
authors.lastname: Santoro
authors.affiliation: Department of Biosciences, University of Milan, 20133 Milan, Italy; anna.moroni@unimi.it.
authors.forename: Anna
authors.initials: A
authors.lastname: Moroni
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D000242:Cyclic AMP / Q000737:chemistry* / Q000378:metabolism; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000737:chemistry / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / Q000737:chemistry* / Q000378:metabolism; D015640:Ion Channel Gating; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D015221:Potassium Channels / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000378:metabolism
chemical_list: D054815:Cyclic Nucleotide-Gated Cation Channels; C578710:HCN2 protein, human; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; C529762:PEX5L protein, human; D015221:Potassium Channels; D018160:Receptors, Cytoplasmic and Nuclear; D000242:Cyclic AMP