RESUMO
Candid#1 (Cd1) is an attenuated vaccine strain of Junin virus, the causative agent of Argentine hemorrhagic fever. Although several substitutions are present in Cd1, their importance for attenuation has not been established. We functionally characterized the substitutions present in the Cd1 glycoprotein (GP) and identified F427I in the transmembrane domain of the GP2 subunit as reducing infectivity in a reconstituted viral system. We further showed that this phenotype derives from the destabilization of the GP metastable conformation. Lastly, we identified an increased dependence of Cd1 GP on human transferrin receptor type 1 (hTfR-1) for entry, which may affect the tropism of the attenuated strain in vivo.
Assuntos
Antígenos CD/metabolismo , Vírus Junin/patogenicidade , Glicoproteínas de Membrana/metabolismo , Receptores da Transferrina/metabolismo , Receptores Virais/metabolismo , Proteínas do Envelope Viral/metabolismo , Fatores de Virulência/metabolismo , Internalização do Vírus , Substituição de Aminoácidos , Animais , Linhagem Celular , Humanos , Vírus Junin/genética , Glicoproteínas de Membrana/química , Glicoproteínas de Membrana/genética , Conformação Proteica , Vacinas Atenuadas/genética , Proteínas do Envelope Viral/química , Proteínas do Envelope Viral/genética , Vacinas Virais/genética , Fatores de Virulência/química , Fatores de Virulência/genéticaRESUMO
Clade B of the New World arenaviruses contains both pathogenic and nonpathogenic members, whose surface glycoproteins (GPs) are characterized by different abilities to use the human transferrin receptor type 1 (hTfR1) protein as a receptor. Using closely related pairs of pathogenic and nonpathogenic viruses, we investigated the determinants of the GP1 subunit that confer these different characteristics. We identified a central region (residues 85 to 221) in the Guanarito virus GP1 that was sufficient to interact with hTfR1, with residues 159 to 221 being essential. The recently solved structure of part of the Machupo virus GP1 suggests an explanation for these requirements.
Assuntos
Arenavirus do Novo Mundo/fisiologia , Arenavirus do Novo Mundo/patogenicidade , Proteínas Recombinantes de Fusão , Proteínas do Envelope Viral , Sequência de Aminoácidos , Animais , Arenavirus do Novo Mundo/classificação , Arenavirus do Novo Mundo/genética , Células CHO , Linhagem Celular , Cricetinae , Cricetulus , Glicoproteínas/química , Glicoproteínas/genética , Glicoproteínas/metabolismo , Humanos , Modelos Moleculares , Dados de Sequência Molecular , Receptores da Transferrina/metabolismo , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Proteínas do Envelope Viral/química , Proteínas do Envelope Viral/genética , Proteínas do Envelope Viral/metabolismoRESUMO
BACKGROUND: The gibbon ape leukemia virus (GaLV) Env protein mediates entry into a wide range of human cells and is frequently used to pseudotype retroviral vectors. However, an incompatibility exists between GaLV Env and lentiviral vectors that results in decreased steady-state levels of the mature GaLV Env in cells and prevents its incorporation into lentiviral vector particles. RESULTS: We identified the HIV-1 Vpu protein as the major cause of the depletion in GaLV Env levels that occurs when lentiviral vector components are present. This activity of Vpu targeted the mature (cleaved) form of the GaLV Env that exists within or beyond the trans-Golgi. The activity required two conserved phospho-serines in the cytoplasmic tail of Vpu that are known to recruit beta TrCP, a substrate adaptor for an SCF E3 ubiquitin ligase complex, and could be blocked by mutation of lysine 618 in the GaLV Env tail. Moreover, the Vpu-mediated decrease of GaLV Env levels was inhibited by the lysosomal inhibitor, bafilomycin A1. Interestingly, this activity of Vpu was only observed in the presence of other lentiviral vector components. CONCLUSIONS: Similar to the mechanism whereby Vpu targets BST-2/tetherin for degradation, these findings implicate beta-TrCP-mediated ubiquitination and the endo-lysosomal pathway in the degradation of the GaLV Env by lentiviral vector components. Possibly, the cytoplasmic tail of the GaLV Env contains features that mimic bona fide targets of Vpu, important to HIV-1 replication. Furthermore, the lack of effect of Vpu on GaLV Env in the absence of other HIV-1 proteins, suggests that a more complex interaction may exist between Vpu and its target proteins, with the additional involvement of one or more component(s) of the HIV-1 replication machinery.
Assuntos
Produtos do Gene env/antagonistas & inibidores , Produtos do Gene env/genética , HIV-1/genética , Proteínas do Vírus da Imunodeficiência Humana/genética , Proteínas do Vírus da Imunodeficiência Humana/metabolismo , Vírus da Leucemia do Macaco Gibão/genética , Mapeamento de Interação de Proteínas , Proteínas Virais Reguladoras e Acessórias/genética , Proteínas Virais Reguladoras e Acessórias/metabolismo , Linhagem Celular , Humanos , Proteínas Contendo Repetições de beta-Transducina/metabolismoRESUMO
BACKGROUND: In the absence of the Vpu protein, newly formed HIV-1 particles can remain attached to the surface of human cells due to the action of an interferon-inducible cellular restriction factor, BST-2/tetherin. Tetherin also restricts the release of other enveloped viral particles and is counteracted by a several viral anti-tetherin factors including the HIV-2 Env, SIV Nef and KSHV K5 proteins. RESULTS: We observed that a fraction of tetherin is located at the surface of restricting cells, and that co-expression of both HIV-1 Vpu and HIV-2 Env reduced this population. In addition, Vpu, but not the HIV-2 Env, reduced total cellular levels of tetherin. An additional effect observed for both Vpu and the HIV-2 Env was to redirect tetherin to an intracellular perinuclear compartment that overlapped with markers for the TGN (trans-Golgi network). Sequestration of tetherin in this compartment was independent of tetherin's normal endocytosis trafficking pathway. CONCLUSIONS: Both HIV-1 Vpu and HIV-2 Env redirect tetherin away from the cell surface and sequester the protein in a perinuclear compartment, which likely blocks the action of this cellular restriction factor. Vpu also promotes the degradation of tetherin, suggesting that it uses more than one mechanism to counteract tetherin restriction.