Reversal of HCN channel voltage dependence via bridging of the S4-S5 linker and Post-S6.
Voltage-gated ion channels possess charged domains that move in response to changes in transmembrane voltage. How this movement is transduced into gating of the channel pore is largely unknown. Here we show directly that two functionally important regions of the spHCN1 pacemaker channel, the S4-S5 linker and the C-linker, come into close proximity during gating. Cross-linking these regions with high-affinity metal bridges or disulfide bridges dramatically alters channel gating in the absence of cAMP; after modification the polarity of voltage dependence is reversed. Instead of being closed at positive voltage and activating with hyperpolarization, modified channels are closed at negative voltage and activate with depolarization. Mechanistically, this reversal of voltage dependence occurs as a result of selectively eliminating channel deactivation, while retaining an existing inactivation process. Bridging also alters channel activation by cAMP, showing that interaction of these two regions can also affect the efficacy of physiological ligands.
Prole
David L
DL
Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
Yellen
Gary
G
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D054815:Cyclic Nucleotide-Gated Cation Channels; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D006801:Humans; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D015640:Ion Channel Gating / Q000502:physiology*; D007473:Ion Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D008564:Membrane Potentials; D008954:Models, Biological; D008969:Molecular Sequence Data; D017354:Point Mutation; D015221:Potassium Channels; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000502:physiology; D012617:Sea Urchins / Q000378:metabolism
D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D015221:Potassium Channels; D021122:Protein Subunits; D000242:Cyclic AMP; D003545:Cysteine