1. Laboratory of Single-Molecule Cell Biology, Tohoku University Graduate School of Life Sciences, 6-3 Aoba, Aramaki-Aza, Aoba-ku, Sendai, Miyagi 980-8578, Japan.
2. Department of Pharmacology, Kyoto University Faculty of Medicine, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.