Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are key modulators of neuronal activity by providing the depolarizing cation current I(h) involved in rhythmogenesis, dendritic integration, and synaptic transmission. These tasks critically depend on the availability of HCN channels, which is dynamically regulated by intracellular cAMP; the range of this regulation, however, largely differs among neurons in the mammalian brain. Using affinity purification and high-resolution mass spectrometry, we identify the PEX5R/Trip8b protein as the beta subunit of HCN channels in the mammalian brain. Coassembly of PEX5R/Trip8b affects HCN channel gating in a subtype-dependent and mode-specific way: activation of HCN2 and HCN4 by cAMP is largely impaired, while gating by phosphoinositides and basal voltage-dependence remain unaffected. De novo expression of PEX5R/Trip8b in cardiomyocytes abolishes beta-adrenergic stimulation of HCN channels. These results demonstrate that PEX5R/Trip8b is an intrinsic auxiliary subunit of brain HCN channels and establish HCN-PEX5R/Trip8b coassembly as a mechanism to control the channels' responsiveness to cyclic nucleotide signaling.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adrenergic beta-1 Receptor Antagonists
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Animals
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Brain / ultrastructure
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Cyclic AMP / pharmacology*
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Cyclic Nucleotide-Gated Cation Channels / genetics
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Cyclic Nucleotide-Gated Cation Channels / metabolism*
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Embryo, Mammalian
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Enzyme Inhibitors / pharmacology
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Gene Expression Regulation / drug effects*
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Gene Expression Regulation / genetics
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Green Fluorescent Proteins / genetics
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Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels
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Ion Channel Gating / drug effects*
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Ion Channel Gating / genetics
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Isoproterenol / pharmacology
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Mass Spectrometry / methods
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Membrane Potentials / drug effects*
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Membrane Potentials / genetics
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Microinjections / methods
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Myocytes, Cardiac / drug effects
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Myocytes, Cardiac / metabolism
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Oocytes
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Patch-Clamp Techniques / methods
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Peroxins
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Potassium Channels / genetics
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Potassium Channels / metabolism*
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Protein Multimerization / physiology
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Protein Subunits / genetics
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Protein Subunits / metabolism
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Rats
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Receptors, Adrenergic, beta-1 / metabolism*
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Synaptosomes / drug effects
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Synaptosomes / metabolism
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Transduction, Genetic / methods
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Xenopus
Substances
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Adrenergic beta-1 Receptor Antagonists
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Cyclic Nucleotide-Gated Cation Channels
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Enzyme Inhibitors
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Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels
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Membrane Proteins
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Peroxins
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Pex5l protein, mouse
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Potassium Channels
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Protein Subunits
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Receptors, Adrenergic, beta-1
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Green Fluorescent Proteins
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Cyclic AMP
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Isoproterenol