title: Pacemaking by HCN channels requires interaction with phosphoinositides.
abstract: Hyperpolarization-activated, cyclic-nucleotide-gated (HCN) channels mediate the depolarizing cation current (termed I(h) or I(f)) that initiates spontaneous rhythmic activity in heart and brain. This function critically depends on the reliable opening of HCN channels in the subthreshold voltage-range. Here we show that activation of HCN channels at physiologically relevant voltages requires interaction with phosphoinositides such as phosphatidylinositol-4,5-bisphosphate (PIP(2)). PIP(2) acts as a ligand that allosterically opens HCN channels by shifting voltage-dependent channel activation approximately 20 mV toward depolarized potentials. Allosteric gating by PIP(2) occurs in all HCN subtypes and is independent of the action of cyclic nucleotides. In CNS neurons and cardiomyocytes, enzymatic degradation of phospholipids results in reduced channel activation and slowing of the spontaneous firing rate. These results demonstrate that gating by phospholipids is essential for the pacemaking activity of HCN channels in cardiac and neuronal rhythmogenesis.
authors.affiliation: Institute of Physiology, University of Freiburg, Hermann-Herder-Strasse 7, 79104 Freiburg, Germany.
authors.forename: Gerd
authors.initials: G
authors.lastname: Zolles
authors.forename: Nikolaj
authors.initials: N
authors.lastname: Klöcker
authors.forename: Daniela
authors.initials: D
authors.lastname: Wenzel
authors.forename: Jutta
authors.initials: J
authors.lastname: Weisser-Thomas
authors.forename: Bernd K
authors.initials: BK
authors.lastname: Fleischmann
authors.forename: Jochen
authors.initials: J
authors.lastname: Roeper
authors.forename: Bernd
authors.initials: B
authors.lastname: Fakler
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000166:cytology; D054815:Cyclic Nucleotide-Gated Cation Channels; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D004622:Embryo, Mammalian; D004625:Embryo, Nonmammalian; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation / Q000502:physiology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009865:Oocytes; D018408:Patch-Clamp Techniques / Q000379:methods; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000502:physiology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D015221:Potassium Channels; D011743:Pyrimidines / Q000494:pharmacology; D000077191:Wortmannin; D014981:Xenopus
chemical_list: D000730:Androstadienes; D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D010726:Phosphodiesterase Inhibitors; D015221:Potassium Channels; D011743:Pyrimidines; C082246:ICI D2788; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000077191:Wortmannin