1. University of Texas Southwestern Medical Center in Dallas, Department of Cell Biology, Associate Professor (2007-present). 2. University of Texas Southwestern Medical Center in Dallas, Department of Cell Biology, Assistant Professor (2005-2007). 3. University of Miami School of Medicine, Department of Molecular and Cellular Pharmacology, Assistant Professor (2001-2005). Member of the Sylvester Cancer Center at University of Miami School of Medicine. (2005-present) Adjunct Faculty in the Department of Molecular and Cellular Pharmacology. 4. Howard Hughes Medical Institute, Laboratory of Cell Biology, The Rockefeller University, New York, N.Y., Post-Doctoral Associate (1996-2001). 5. New York University Medical Center, New York, N.Y., Department of Pathology, Graduate Student (Ph.D.) (1991 - 1996). 6. Cornell University Medical College, New York, N.Y., Department of Physiology, Visiting Fellow (1988-1990). 7. Paulista School of Medicine, Sao Paulo, S.P., Brazil, Department of Biochemistry, Graduate Student (M.S.), (1985-1988). 8. University of Sao Paulo, Brazil, Biochemistry Laboratory, University Hospital, Staff Member (1984-1985).