Doctorant (M/F)

Job Description

Thesis Subject

Structural and Functional Study of the Glycoprotein of the Borna Disease Virus.

The Bornaviridae belong to the order Mononegavirales (enveloped, negative-sense, single-stranded RNA viruses). Borna disease virus (BDV-1), the most extensively studied member of this family, is a neurotropic virus responsible for persistent infections in many vertebrates, including rodents, horses, and potentially humans. This virus possesses a single envelope glycoprotein on its surface, called glycoprotein G (GP), which plays a central role in viral entry. GP is the primary determinant of BDV-1's cellular and tissue tropism. GP performs two key functions during viral entry into the host cell: recognition of and binding to the cellular receptor, and membrane fusion.

Indeed, infection is initiated by GP recognizing and binding to a cellular receptor, which leads to the internalization of the virion via endocytosis. Following internalization, acidification of the endosomal compartment triggers a conformational change in GP, shifting it from a pre-fusion state to a post-fusion state. This conformational transition allows the viral membrane to fuse with the endosomal membrane, resulting in the release of the viral genome into the cytoplasm, followed by its transport to the nucleus to continue the viral cycle.

GP is a type I glycoprotein synthesized in the endoplasmic reticulum and processed in the Golgi apparatus. Despite its central role in infection, the three-dimensional structure of GP remains unknown to date, unlike those of several other Mononegavirales.
Furthermore, it has not yet been established whether, as with other enveloped viruses, the receptor-binding and membrane-fusion functions of GP can be dissociated.

This thesis project therefore aims to characterize the BDV-1 GP glycoprotein both functionally and structurally.
More specifically, the goal is to determine the structure of GP in different conformations (pre- and post-fusion) using cryo-electron microscopy (cryo-EM) and/or X-ray crystallography. Key residues for GP function will then be identified, and mutant glycoproteins will be functionally characterized using cellular assays (cell-to-cell fusion and virus pseudotyping assays).
Next, GP's ability to bind to various proposed cellular receptors will be tested, and the structure of the GP/receptor complex will be studied by cryo-EM and/or X-ray crystallography. Structural analysis will identify key residues involved in receptor recognition, which will then be functionally tested.

Overall, this project will provide new insights into the molecular mechanisms of Bornavirus entry. It also draws on the team's recognized expertise in determining the structures of class III viral glycoproteins, particularly those of Rhabdoviruses. The structural data obtained through this work will not only help elucidate the molecular mechanisms of Bornavirus entry but will also shed new light on the structural and functional evolution of class III glycoproteins.

This project employs approaches from biochemistry, structural biology, and cell biology: The glycoproteins will be expressed in insect cells. The purified glycoproteins will then be characterized (MALS, mass photometry, electron microscopy, etc.). All of these techniques are available through the institute's platforms. The various receptors will be expressed (in bacteria, insect cells, and HEK cells) and purified according to established protocols. The structure of the various complexes and glycoproteins will be determined by X-ray crystallography or cryo-electron microscopy. The infectivity of pseudotyped viruses expressing the various glycoproteins (mutated or unmutated) will be assessed by flow cytometry.

Your Work Environment

The student will work at the Institute of Integrative Cell Biology (I2BC) on the CNRS campus in Gif-sur-Yvette. The I2BC is a joint research unit (UMR 9198) of the CNRS, the CEA, and Paris-Saclay University, comprising nearly 650 people. The unit has recently moved into new facilities and offers a rich and dynamic scientific environment with 60 research teams spread across 5 scientific departments and 15 technology platforms.
The RHABDOVIRUS team, into which the candidate will be integrated, consists of two CNRS research directors, one university professor, two research engineers, and two postdoctoral researchers. The team focuses on the study of rhabdoviruses such as VSV and the rabies virus, examining their entry mechanisms (which will be the Ph.D. student's research topic), their interactions with the innate immune system, and the formation of viral replication factories.

Constraints and risks

In addition to scientific tasks, the candidate must also take into account the following aspects of the position: working with pathogens in an L2 environment, and adhering to safety protocols and good laboratory practices when handling pathogens.
Travel outside the laboratory for data collection may be required, including visits to synchrotrons and facilities housing electron microscopes (Saclay and Grenoble).

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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