title: Interrelationship between cytoplasmic retroviral Gag concentration and Gag-membrane association.
abstract: The early events in the retrovirus assembly pathway, particularly the timing and nature of Gag translocation from the site of protein translation to the inner leaflet of the plasma membrane, are poorly understood. We have investigated the interrelationship between cytoplasmic Gag concentration and plasma membrane association using complementary live-cell biophysical fluorescence techniques in real time with both human T-cell leukemia virus type 1 (HTLV-1) and human immunodeficiency virus type 1 (HIV-1) Gag proteins. In particular, dual-color, z-scan fluorescence fluctuation spectroscopy in conjunction with total internal reflection fluorescence and conventional, epi-illumination imaging were utilized. Our results demonstrate that HTLV-1 Gag is capable of membrane targeting and particle assembly at low (i.e., nanomolar) cytoplasmic concentrations and that there is a critical threshold concentration (approaching micromolar) prior to the observation of HIV-1 Gag associated with the plasma membrane. These observations imply fundamental differences between HIV-1 and HTLV-1 Gag trafficking and membrane association.
authors: Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA; Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA; School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA.
authors: Keir H
authors: KH
authors: Fogarty
authors: Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA; Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
authors: Serkan
authors: S
authors: Berk
authors: Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA; Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA.
authors: Iwen F
authors: IF
authors: Grigsby
authors: Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA; School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA.
authors: Yan
authors: Y
authors: Chen
authors: Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA; Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA; Department of Microbiology, University of Minnesota, Minneapolis, MN 55455, USA. Electronic address: mansky@umn.edu.
authors: Louis M
authors: LM
authors: Mansky
authors: Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA; School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA; Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA. Electronic address: mueller@physics.umn.edu.
authors: Joachim D
authors: JD
authors: Mueller
mesh_terms: D002462:Cell Membrane / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D015683:Gene Products, gag / Q000378:metabolism*; D015368:Human T-lymphotropic virus 1 / Q000378:metabolism; D012190:Retroviridae / Q000378:metabolism*; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000378:metabolism*
chemical_list: D015683:Gene Products, gag; D054301:gag Gene Products, Human Immunodeficiency Virus
keywords: assembly; fluorescence; membrane; oligomerization; retrovirus