title: Hyperpolarization-activated, cyclic nucleotide-gated HCN2 cation channel forms a protein assembly with multiple neuronal scaffold proteins in distinct modes of protein-protein interaction.
abstract: Hyperpolarization-activated cation currents, termed Ih, are non-uniformly distributed along dendritic arbors with current density increasing with increasing distance from the soma. The non-uniform distribution of Ih currents contributes to normalization of location-dependent variability in temporal integration of synaptic input, but the molecular basis for the graded HCN distribution remains to be investigated. The hyperpolarization-activated, cyclic nucleotide-gated cation channels (HCNs) underlie Ih currents and consist of four members (HCN1-HCN4) of the gene family in mammals. In this investigation, we report that HCN2 forms a protein assembly with tamalin, S-SCAM and Mint2 scaffold proteins, using several different approaches including immunoprecipitation of rat brain and heterologously expressing cell extracts and glutathione S-transferase pull-down assays. The PDZ domain of tamalin interacts with HCN2 at both the PDZ-binding motif and the internal carboxy-terminal tail of HCN2, whereas binding of the PDZ domain of S-SCAM occurs at the cyclic nucleotide-binding domain (CNBD) and the CNBD-downstream sequence of the carboxy-terminal tail of HCN2. A protein assembly between HCN2 and Mint2 is formed by the interaction of the munc18-interacting domain of Mint2 with the CNBD-downstream sequence of HCN2. The results demonstrate that HCN2 forms a protein complex with multiple neuronal scaffold proteins in distinct modes of protein-protein interaction.
authors.affiliation: Department of Biological Sciences, Faculty of Medicine, and Department of Molecular and System Biology, Graduate School of Biostudies, Kyoto University, Yoshida Konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan.
authors.forename: Kouji
authors.initials: K
authors.lastname: Kimura
authors.forename: Jun
authors.initials: J
authors.lastname: Kitano
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Nakajima
authors.forename: Shigetada
authors.initials: S
authors.lastname: Nakanishi
mesh_terms: D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism; D018076:DNA, Complementary; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D047468:Immunoprecipitation; D015640:Ion Channel Gating; D007473:Ion Channels / Q000378:metabolism / Q000502:physiology*; D009124:Muscle Proteins / Q000378:metabolism / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D015221:Potassium Channels; D011233:Precipitin Tests; D051381:Rats; D020798:Two-Hybrid System Techniques
chemical_list: D018076:DNA, Complementary; C578712:Hcn2 protein, rat; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D015221:Potassium Channels