Stabilization of Kv1.5 channel protein by bepridil through its action as a chemical chaperone

• Published in: European journal of pharmacology 2012-12, Vol.696 (1-3), p.28-34
• Main Authors: Suzuki, Sayuri, Kurata, Yasutaka, Li, Peili, Notsu, Tomomi, Hasegawa, Akira, Ikeda, Nobuhito, Kato, Masaru, Miake, Junichiro, Sakata, Shinji, Shiota, Goshi, Yoshida, Akio, Ninomiya, Haruaki, Higaki, Katsumi, Yamamoto, Kazuhiro, Shirayoshi, Yasuaki, Hisatome, Ichiro
• Format: Article
• Language: English
• Subjects: 4-Aminopyridine - pharmacology; Animals; Bepridil; Bepridil - pharmacology; Cercopithecus aethiops; Chemical chaperone; COS Cells; Endoplasmic Reticulum - drug effects; Endoplasmic Reticulum - metabolism; Golgi Apparatus - drug effects; Golgi Apparatus - metabolism; Kv1.5 channel; Kv1.5 Potassium Channel - metabolism; Membrane Transport Modulators - pharmacology; Potassium Channel Blockers - pharmacology; Protein stability; Rats
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/j.ejphar.2012.09.025

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 0.3–30μM 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 1μM 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.