title: cAMP Modulation of the cytoplasmic domain in the HCN2 channel investigated by molecular simulations.
abstract: The hyperpolarization-activated cyclic nucleotide-modulated (HCN) cation channels are opened by membrane hyperpolarization, while their activation is modulated by the binding of cyclic adenosine monophosphate (cAMP) in the cytoplasm. Here we investigate the molecular basis of cAMP channel modulation by performing molecular dynamics simulations of a segment comprising the C-linker and the cyclic nucleotide binding domain (CNBD) in the presence and absence of cAMP, based on the available crystal structure of HCN2 from mouse. In presence of cAMP, the protein undergoes an oscillation of the quaternary structure on the order of 10 ns, not observed in the apoprotein. In contrast, the absence of ligand causes conformational rearrangements within the CNBDs, driving these domains to a more flexible state, similar to that described in CNBDs of other proteins. This increased flexibility causes a rather disordered movement of the CNBDs, resulting in an inhibitory effect on the channel. We propose that the cAMP-triggered large-scale oscillation plays an important role for the channel's function, being coupled to a motion of the C-linker which, in turn, modulates the gating of the channel.
authors.affiliation: Scuola Internazionale Superiore di Studi Avanzati and Istituto Nazionale per la Fisica della Materia, Democritos Modeling Center for Research in Atomic Simulation, Trieste, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Berrera
authors.forename: Sergio
authors.initials: S
authors.lastname: Pantano
authors.forename: Paolo
authors.initials: P
authors.lastname: Carloni
mesh_terms: D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000737:chemistry; D003198:Computer Simulation; D000242:Cyclic AMP / Q000737:chemistry*; D003593:Cytoplasm / Q000737:chemistry*; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D015640:Ion Channel Gating; D007473:Ion Channels / Q000737:chemistry*; D051379:Mice; D008956:Models, Chemical; D008958:Models, Molecular; D009038:Motion; D015221:Potassium Channels; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: C578711:Hcn2 protein, mouse; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D015221:Potassium Channels; D000242:Cyclic AMP