title: Trafficking and gating of hyperpolarization-activated cyclic nucleotide-gated channels are regulated by interaction with tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b) and cyclic AMP at distinct sites.
abstract: Ion channel trafficking and gating are often influenced by interactions with auxiliary subunits. Tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b) is an auxiliary subunit for neuronal hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. TRIP8b interacts directly with two distinct sites of HCN channel pore-forming subunits to control channel trafficking and gating. Here we use mutagenesis combined with electrophysiological studies to define and distinguish the functional importance of the HCN/TRIP8b interaction sites. Interaction with the last three amino acids of the HCN1 C terminus governed the effect of TRIP8b on channel trafficking, whereas TRIP8b interaction with the HCN1 cyclic nucleotide binding domain (CNBD) affected trafficking and gating. Biochemical studies revealed that direct interaction between TRIP8b and the HCN1 CNBD was disrupted by cAMP and that TRIP8b binding to the CNBD required an arginine residue also necessary for cAMP binding. In accord, increasing cAMP levels in cells antagonized the up-regulation of HCN1 channels mediated by a TRIP8b construct binding the CNBD exclusively. These data illustrate the distinct roles of the two TRIP8b-HCN interaction domains and suggest that TRIP8b and cAMP may directly compete for binding the HCN CNBD to control HCN channel gating, kinetics, and trafficking.
authors.affiliation: Davee Department of Neurology and Clinical Neurosciences, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA.
authors.forename: Ye
authors.initials: Y
authors.lastname: Han
authors.forename: Yoav
authors.initials: Y
authors.lastname: Noam
authors.forename: Alan S
authors.initials: AS
authors.lastname: Lewis
authors.forename: Johnie J
authors.initials: JJ
authors.lastname: Gallagher
authors.forename: Wytse J
authors.initials: WJ
authors.lastname: Wadman
authors.forename: Tallie Z
authors.initials: TZ
authors.lastname: Baram
authors.forename: Dane M
authors.initials: DM
authors.lastname: Chetkovich
mesh_terms: D000818:Animals; D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism*; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D015640:Ion Channel Gating / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D000074401:Peroxins; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D015854:Up-Regulation / Q000502:physiology
chemical_list: D054815:Cyclic Nucleotide-Gated Cation Channels; C578665:HCN1 protein, human; C578666:Hcn1 protein, mouse; C578667:Hcn1 protein, rat; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D008565:Membrane Proteins; D000074401:Peroxins; C501732:Pex5l protein, mouse; C523657:Pex5l protein, rat; D015221:Potassium Channels; D000242:Cyclic AMP