1. Department of Cell Biology, Biomedical Research Center, Room 264, 975 N.E. 10th Street, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, Department of Biochemistry and Department of Neurology and Neuroscience, Weill Medical College of Cornell University, 1330 York Avenue, New York, New York 10021, and Burke Medical Research Institute, 785 Mamaroneck Avenue, White Plains, New York 10605