Intracellular trafficking of Gag and Env proteins and their interactions modulate pseudotyping of retroviruses
Virginie Sandrin1, Delphine Muriaux, Jean-Luc Darlix
1Laboratoire de Vectorologie Rétrovirale et Thérapie Génique, INSERM U412, IFR128 BioSciences Lyon-Gerland, Ecole Normal Supérieure de Lyon, France.
Abstract:
Glycoproteins derived from most retroviruses and from several families of enveloped viruses can form infectious pseudotypes with murine leukemia virus (MLV) and lentiviral core particles, like the MLV envelope glycoproteins (Env) that are incorporated on either virus type. However, coexpression of a given glycoprotein with heterologous core proteins does not always give rise to highly infectious viral particles, and restrictions on pseudotype formation have been reported. To understand the mechanisms that control the recruitment of viral surface glycoproteins on lentiviral and retroviral cores, we exploited the fact that the feline endogenous retrovirus RD114 glycoprotein does not efficiently pseudotype lentiviral cores derived from simian immunodeficiency virus, whereas it is readily incorporated onto MLV particles. Our results indicate that recruitment of glycoproteins by the MLV and lentiviral core proteins occurs in intracellular compartments and not at the cell surface. We found that Env and core protein colocalization in intracytoplasmic vesicles is required for pseudotype formation. By investigating MLV/RD114 Env chimeras, we show that signals in the cytoplasmic tail of either glycoprotein differentially influenced their intracellular localization; that of MLV allows endosomal localization and hence recruitment by both lentiviral and MLV cores. Furthermore, we found that upon membrane binding, MLV core proteins could relocalize Env glycoproteins in late endosomes and allow their incorporation on viral particles. Thus, intracellular colocalization, as well as interactions between Env and core proteins, may influence the recruitment of the glycoprotein onto viral particles and generate infectious pseudotyped viruses.
Insights
Viral glycoproteins and core proteins must colocalize in intracellular vesicles for infectious pseudotyped virus formation. Specific protein interactions and localization signals dictate glycoprotein recruitment onto retroviral and lentiviral cores.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Enveloped viruses, including retroviruses like murine leukemia virus (MLV) and lentiviruses, utilize viral envelope glycoproteins (Env) for cell entry.
- Pseudotyping, the incorporation of heterologous glycoproteins onto viral cores, is a common method to study viral entry mechanisms.
- However, restrictions exist in pseudotype formation, suggesting complex interactions between viral glycoproteins and core proteins.
Purpose of the Study:
- To elucidate the mechanisms controlling the recruitment of viral surface glycoproteins onto lentiviral and retroviral cores.
- To investigate the role of intracellular localization and protein interactions in pseudotyped virus assembly.
Main Methods:
- Utilized feline endogenous retrovirus RD114 glycoprotein and simian immunodeficiency virus (SIV)-derived lentiviral cores, alongside MLV cores and glycoproteins.
- Generated and analyzed MLV/RD114 Env chimeras to identify functional domains.
- Investigated Env and core protein colocalization within intracellular compartments using microscopy and biochemical assays.
Main Results:
- Glycoprotein recruitment onto MLV and lentiviral cores occurs in intracellular compartments, not at the cell surface.
- Colocalization of Env and core proteins within intracytoplasmic vesicles is essential for pseudotype formation.
- Cytoplasmic tail signals of glycoproteins differentially regulate intracellular localization; MLV Env's signal promotes endosomal localization for recruitment by both MLV and lentiviral cores.
- MLV core proteins can relocalize Env glycoproteins in late endosomes upon membrane binding, facilitating incorporation.
Conclusions:
- Intracellular colocalization of viral glycoproteins and core proteins is a critical determinant of pseudotyped virus assembly.
- Specific interactions between Env and core proteins, influenced by cytoplasmic tail domains, govern glycoprotein recruitment and the generation of infectious pseudotyped viruses.
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