The HCN gene family: molecular basis of the hyperpolarization-activated pacemaker channels.
The molecular basis of the hyperpolarization-activated cation channels that underlie the anomalous rectifying current variously termed Ih, Iq, or I(f) is discussed. On the basis of the expression patterns and biophysical properties of the newly cloned HCN ion channels, an initial attempt at defining the identity and subunit composition of channels underlying native Ih is undertaken. By comparing the sequences of HCN channels to other members of the K channel superfamily, we discuss how channel opening may be coupled to membrane hyperpolarization and to direct binding of cyclic nucleotide. Finally, we consider some of the questions in cardiovascular physiology and neurobiology that can be addressed as a result of the demonstration that Ih is encoded by the HCN gene family.
Santoro
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B
Center for Neurobiology and Behavior, Columbio University, New York, New York 10032, USA.
Tibbs
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GR
D000200:Action Potentials / Q000187:drug effects; D000595:Amino Acid Sequence; D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D054815:Cyclic Nucleotide-Gated Cation Channels; D004837:Epinephrine / Q000494:pharmacology; D006321:Heart / Q000502:physiology; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels / Q000145:classification / Q000235:genetics*; D008969:Molecular Sequence Data; D009712:Nucleotides, Cyclic / Q000378:metabolism; D015221:Potassium Channels; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D009712:Nucleotides, Cyclic; D015221:Potassium Channels; D004837:Epinephrine