title: The tetramerization domain potentiates Kv4 channel function by suppressing closed-state inactivation.
abstract: A-type Kv4 potassium channels undergo a conformational change toward a nonconductive state at negative membrane potentials, a dynamic process known as pre-open closed states or closed-state inactivation (CSI). CSI causes inhibition of channel activity without the prerequisite of channel opening, thus providing a dynamic regulation of neuronal excitability, dendritic signal integration, and synaptic plasticity at resting. However, the structural determinants underlying Kv4 CSI remain largely unknown. We recently showed that the auxiliary KChIP4a subunit contains an N-terminal Kv4 inhibitory domain (KID) that directly interacts with Kv4.3 channels to enhance CSI. In this study, we utilized the KChIP4a KID to probe key structural elements underlying Kv4 CSI. Using fluorescence resonance energy transfer two-hybrid mapping and bimolecular fluorescence complementation-based screening combined with electrophysiology, we identified the intracellular tetramerization (T1) domain that functions to suppress CSI and serves as a receptor for the binding of KID. Disrupting the Kv4.3 T1-T1 interaction interface by mutating C110A within the C3H1 motif of T1 domain facilitated CSI and ablated the KID-mediated enhancement of CSI. Furthermore, replacing the Kv4.3 T1 domain with the T1 domain from Kv1.4 (without the C3H1 motif) or Kv2.1 (with the C3H1 motif) resulted in channels functioning with enhanced or suppressed CSI, respectively. Taken together, our findings reveal a novel (to our knowledge) role of the T1 domain in suppressing Kv4 CSI, and that KChIP4a KID directly interacts with the T1 domain to facilitate Kv4.3 CSI, thus leading to inhibition of channel function.
authors.affiliation: Department of Molecular and Cellular Pharmacology, State Key Laboratory of Natural and Biomimetic Drugs, Peking University School of Pharmaceutical Sciences, Beijing, China.
authors.forename: Yi-Quan
authors.initials: YQ
authors.lastname: Tang
authors.affiliation: Department of Molecular and Cellular Pharmacology, State Key Laboratory of Natural and Biomimetic Drugs, Peking University School of Pharmaceutical Sciences, Beijing, China.
authors.forename: Jing-Heng
authors.initials: JH
authors.lastname: Zhou
authors.affiliation: Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, California.
authors.forename: Fan
authors.initials: F
authors.lastname: Yang
authors.affiliation: Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, California.
authors.forename: Jie
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Department of Molecular and Cellular Pharmacology, State Key Laboratory of Natural and Biomimetic Drugs, Peking University School of Pharmaceutical Sciences, Beijing, China; PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing, China. Electronic address: wangkw@hsc.pku.edu.cn.
authors.forename: KeWei
authors.initials: K
authors.lastname: Wang
mesh_terms: D000818:Animals; D019921:Biotinylation; D015153:Blotting, Western; D031541:Fluorescence Resonance Energy Transfer; D057809:HEK293 Cells; D006801:Humans; D051605:Kv Channel-Interacting Proteins / Q000235:genetics / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D018613:Microscopy, Confocal; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D011109:Polymethacrylic Acids; D000644:Quaternary Ammonium Compounds; D051672:Shal Potassium Channels / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014982:Xenopus laevis
chemical_list: D051605:Kv Channel-Interacting Proteins; D011109:Polymethacrylic Acids; D000644:Quaternary Ammonium Compounds; D051672:Shal Potassium Channels; C569264:poly-omega-methacryloyloxyundecyltrimethylammonium bromide