Epstein-Barr virus latent membrane protein-1 (LMP-1) and lytic LMP-1 localization in plasma membrane-derived extracellular vesicles and intracellular virions.
Epstein-Barr virus (EBV) is a human herpesvirus associated with a number of malignancies. EBV establishes a latent infection in human B cells in vitro, and infected lymphoblastoid cells proliferate indefinitely as a result of virus activation of cellular signalling pathways. Latently infected cells express a viral oncoprotein called the latent membrane protein-1 (LMP-1). LMP-1 signals both proliferative and survival signals to the infected B cell. The switch from latency to lytic replication is associated with upregulation of an N-terminally truncated LMP-1, called lytic LMP-1 (lyLMP-1). To understand better the relationship between LMP-1 protein function and the virus life cycle, LMP-1 and lyLMP-1 were precisely localized in infected B cells. Immunoelectron microscopy of latently infected cells revealed LMP-1 localized in discrete patches in the plasma membrane. Unexpectedly, immunogold-labelled LMP-1 was found in vesicles budding from the plasma membrane into the extracellular space and in small membrane vesicles accumulating in conditioned medium from infected cells. LyLMP-1 immunolabelling was observed only in B95-8 cells harbouring detectable intracellular virus particles and was abundant in the nuclear membrane early, and in the plasma membrane late, following lytic cycle induction. LyLMP-1 immunoreactivity was also observed at sites of virus budding and associated with intracellular virions, suggesting that lyLMP-1 might be incorporated into cytoplasmic virions when budding through the nuclear membrane.
Vazirabadi
Golnar
G
Department of Molecular, Cellular and Developmental Biology, University of Colorado, Campus Box 347, Boulder, CO 80309, USA.
Geiger
Timothy R
TR
Department of Molecular, Cellular and Developmental Biology, University of Colorado, Campus Box 347, Boulder, CO 80309, USA.
Coffin Iii
William F
WF
Department of Molecular, Cellular and Developmental Biology, University of Colorado, Campus Box 347, Boulder, CO 80309, USA.
Martin
Jennifer M
JM
Department of Molecular, Cellular and Developmental Biology, University of Colorado, Campus Box 347, Boulder, CO 80309, USA.
D001402:B-Lymphocytes / Q000821:virology; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D004854:Herpesvirus 4, Human / Q000502:physiology*; D006801:Humans; D016253:Microscopy, Immunoelectron; D014763:Viral Matrix Proteins / Q000378:metabolism*; D014771:Virion / Q000378:metabolism*; D014775:Virus Activation; D017735:Virus Latency; D014779:Virus Replication
C037662:EBV-associated membrane antigen, Epstein-Barr virus; D014763:Viral Matrix Proteins