1. University of California, San Diego, Skaggs School of Pharmacy, PSB Lab 3186, 9500 Gilman Drive MC0749, La Jolla, CA 92093-0749, USA
2. The Scripps Research Institute, Cell Biology Department, 10550 N Torrey Pines Road, La Jolla, CA 92037, USA
3. Present address: Kyowa Hakko Kirin California, La Jolla, CA, USA
4. University of California, San Diego, Skaggs School of Pharmacy, PSB Lab 3186, 9500 Gilman Drive MC0749, La Jolla, CA 92093-0749, USA.