1. University of Kentucky, Department of Physiology, Lexington, Kentucky 40536 1 ;
2. Center for Basic Research in Digestive Diseases, Department of Biochemistry and Molecular Biology, and Department of Molecular Neuroscience, Mayo Clinic and Foundation, Rochester, Minnesota 55905 2 ;
3. Department of Pharmacology, Yale University School of Medicine, Boyer Center for Molecular Medicine, New Haven, Connecticut 06536 3 ;
4. Department of Molecular Pharmacology and The Albert Einstein Cancer Center, 4 and
5. Department of Cell Biology, 5 Albert Einstein College of Medicine, Bronx, New York 10461; and
6. Department of Neurosciences, The Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 441956