title: Stabilization of Kv1.5 channel protein by bepridil through its action as a chemical chaperone.
abstract: While bepridil has been reported to alter the stability of ion channel proteins, the precise mechanism of action remains unclear. We examined the effect of bepridil on the stability of Kv1.5 channel proteins expressed in COS7 cells. Bepridil at 0.3-30 μM increased the protein level of Kv1.5 channels in a concentration-dependent manner. Chase experiments showed that bepridil delayed the degradation process of Kv1.5 channel proteins in the same manner as a proteasomal inhibitor, MG132, did. Bepridil increased the immunofluorescent signal of Kv1.5 channel proteins in the endoplasmic reticulum (ER) and Golgi apparatus and on the cell surface. The cell fraction experiment also showed bepridil-induced increases in Kv1.5 in the ER, Golgi apparatus, and the cell membrane. Bepridil at a lower concentration of 1 μM had no effect on the proteasome activity in vitro. A blocker of the ultrarapid delayed-rectifier K(+) channel current, 4-aminopyridine (4AP), abolished bepridil-induced increases in Kv1.5. Kv1.5-medicated membrane currents measured as 4AP-sensitive currents were increased by bepridil. Taken together, we conclude that bepridil stabilizes Kv1.5 proteins at the ER through an action as a chemical chaperone, thereby increasing the density of Kv1.5 channels in the cell membrane.
authors.affiliation: Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Institute of Regenerative Medicine and Biofunction, Tottori University Graduate School of Medical Science, Yonago 683-8503, Japan.
authors.forename: Sayuri
authors.initials: S
authors.lastname: Suzuki
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Kurata
authors.forename: Peili
authors.initials: P
authors.lastname: Li
authors.forename: Tomomi
authors.initials: T
authors.lastname: Notsu
authors.forename: Akira
authors.initials: A
authors.lastname: Hasegawa
authors.forename: Nobuhito
authors.initials: N
authors.lastname: Ikeda
authors.forename: Masaru
authors.initials: M
authors.lastname: Kato
authors.forename: Junichiro
authors.initials: J
authors.lastname: Miake
authors.forename: Shinji
authors.initials: S
authors.lastname: Sakata
authors.forename: Goshi
authors.initials: G
authors.lastname: Shiota
authors.forename: Akio
authors.initials: A
authors.lastname: Yoshida
authors.forename: Haruaki
authors.initials: H
authors.lastname: Ninomiya
authors.forename: Katsumi
authors.initials: K
authors.lastname: Higaki
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Shirayoshi
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hisatome
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D015764:Bepridil / Q000494:pharmacology*; D019556:COS Cells; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism; D051666:Kv1.5 Potassium Channel / Q000378:metabolism*; D049990:Membrane Transport Modulators / Q000494:pharmacology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D051381:Rats
chemical_list: D051666:Kv1.5 Potassium Channel; D049990:Membrane Transport Modulators; D026902:Potassium Channel Blockers; D015764:Bepridil; D015761:4-Aminopyridine