title: Kv4.2 and accessory dipeptidyl peptidase-like protein 10 (DPP10) subunit preferentially form a 4:2 (Kv4.2:DPP10) channel complex.
abstract: Kv4 is a member of the voltage-gated K(+) channel family and forms a complex with various accessory subunits. Dipeptidyl aminopeptidase-like protein (DPP) is one of the auxiliary subunits for the Kv4 channel. Although DPP has been well characterized and is known to increase the current amplitude and accelerate the inactivation and recovery from inactivation of Kv4 current, it remains to be determined how many DPPs bind to one Kv4 channel. To examine whether the expression level of DPP changes the biophysical properties of Kv4, we expressed Kv4.2 and DPP10 in different ratios in Xenopus oocytes and analyzed the currents under two-electrode voltage clamp. The current amplitude and the speed of recovery from inactivation of Kv4.2 changed depending on the co-expression level of DPP10. This raised the possibility that the stoichiometry of the Kv4.2-DPP10 complex is variable and affects the biophysical properties of Kv4.2. We next determined the stoichiometry of DPP10 alone by subunit counting using single-molecule imaging. Approximately 70% of the DPP10 formed dimers in the plasma membrane, and the rest existed as monomers in the absence of Kv4.2. We next determined the stoichiometry of the Kv4.2-DPP10 complex; Kv4.2-mCherry and mEGFP-DPP10 were co-expressed in different ratios and the stoichiometries of Kv4.2-DPP10 complexes were evaluated by the subunit counting method. The stoichiometry of the Kv4.2-DPP10 complex was variable depending on the relative expression level of each subunit, with a preference for 4:2 stoichiometry. This preference may come from the bulky dimeric structure of the extracellular domain of DPP10.
authors.affiliation: From the Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan and the Department of Physiological Sciences, Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0155, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kitazawa
authors.affiliation: From the Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan and the Department of Physiological Sciences, Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0155, Japan ykubo@nips.ac.jp.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kubo
authors.affiliation: From the Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan and the Department of Physiological Sciences, Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0155, Japan knakajo@art.osaka-med.ac.jp.
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakajo
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051672:Shal Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D046912:Multiprotein Complexes; D051672:Shal Potassium Channels; C476879:DPP10 protein, human; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases
keywords: dipeptidyl aminopeptidase-like protein (DPP); electrophysiology; fluorescence; imaging; potassium channel; protein complex; single-molecule imaging; stoichiometry; voltage-gated potassium channel (Kv)