1. Torrey Pines Institute for Molecular Studies, 3550 General Atomics Court, San Diego, California 92121
2. Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan
3. Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-85, Japan