1. Department of Medicine
2. Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
3. Division of Biology, University of California, San Diego, 9500 Gilman Dr., La Jolla, California 92093
4. San Diego Veterans Affairs Healthcare System, 3350 La Jolla Village Dr., San Diego, California 92121