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Voyer, J.

Publications and source records attributed to Voyer, J..

3 recordsLinked to original sources
bioRxiv2023

Antibody-mediated cell entry of SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters host cells by first engaging its cellular receptor angiotensin converting enzyme 2 (ACE2) to induce conformational changes in the virus-encoded spike protein and fusion between the viral and target cell membranes. We report here that certain monoclonal neutralizing antibodies against distinct epitopic regions of the receptor-binding domain of the spike can replace ACE2 to serve as a receptor and efficiently support membrane fusion and viral infectivity. These receptor-like antibodies can function in the form of a complex of their soluble immunoglobulin G with Fc-gamma receptor I, a chimera of their antigen-binding fragment with the transmembrane domain of ACE2 or a membrane-bound B cell receptor, indicating that ACE2 and its specific interactions with the spike protein are dispensable for SARS-CoV-2 entry. These results suggest that antibody responses against SARS-CoV-2 may expand the viral tropism to otherwise nonpermissive cell types; they have important implications for viral transmission and pathogenesis.

microbiology↗
bioRxiv2022

Cryo-EM structure of SARS-CoV-2 postfusion spike in membrane

Entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into host cells depends on refolding of the virus-encoded spike protein from a prefusion conformation, metastable after cleavage, to a lower energy, stable postfusion conformation. This transition overcomes kinetic barriers for fusion of viral and target cell membranes. We report here a cryo-EM structure of the intact postfusion spike in a lipid bilayer that represents single-membrane product of the fusion reaction. The structure provides structural definition of the functionally critical membraneinteracting segments, including the fusion peptide and transmembrane anchor. The internal fusion peptide forms a hairpin-like wedge that spans almost the entire lipid bilayer and the transmembrane segment wraps around the fusion peptide at the last stage of membrane fusion. These results advance our understanding of the spike protein in a membrane environment and may guide development of intervention strategies.

biochemistry↗
bioRxiv2022

Epstein-Barr virus latency programs dynamically sensitize B-cells to ferroptosis

Epstein-Barr virus (EBV) causes 200,000 cancers annually. Upon B-cell infection, EBV induces lipid metabolism to support B-cell proliferation. Yet, little is known about how latent EBV infection, or human B-cell stimulation more generally, alter sensitivity to ferroptosis, a non-apoptotic form of programmed cell death driven by iron-dependent lipid peroxidation and membrane damage. To gain insights, we analyzed lipid reactive oxygen species (ROS) levels and ferroptosis vulnerability in primary human CD19+ B-cells infected by EBV or stimulated by key B-cell receptors. Prior to the first mitosis, EBV-infected cells were exquisitely sensitive to blockade of glutathione biosynthesis, a phenomenon not observed with B-cell receptor stimulation. Subsequently, EBV-mediated Burkitt-like hyper-proliferation generated elevated levels of lipid ROS, which necessitated SLC7A11-mediated cystine import and glutathione peroxidase 4 (GPX4) activity to prevent ferroptosis. By comparison, B-cells were sensitized to ferroptosis induction by combinatorial CD40-ligand and interleukin-4 stimulation or anti-B-cell receptor and Toll-like receptor 9 stimulation upon GPX4 inhibition, but not with SLC7A11 blockade. EBV transforming B-cells became progressively resistant to ferroptosis induction upon switching to the latency III program and lymphoblastoid physiology. Similarly, latency I Burkitt cells were particularly vulnerable to blockade of SLC7A11 or GPX4 or cystine withdrawal, while latency III Burkitt and lymphoblastoid cells were comparatively resistant. The selenocysteine biosynthesis kinase PSTK was newly implicated as a cellular target for ferroptosis induction including in Burkitt cells, likely due to roles in GPX4 biosynthesis. These results highlight ferroptosis as an intriguing therapeutic target for the prevention or treatment of particular EBV-driven B-cell malignancies. SignificanceEBV contributes to B-cell Burkitt and post-transplant lymphoproliferative disease (PTLD). EBV transforming programs activate lipid metabolism to convert B-cells into immortalized lymphoblastoid cell lines (LCL), a PTLD model. We found that stages of EBV transformation generate lipid reactive oxygen species (ROS) byproducts to varying degrees, and that a Burkitt-like phase of B-cell outgrowth is dependent on lipid ROS detoxification by glutathione peroxidase 4 and its cofactor glutathione. Perturbation of this redox defense in early stages of B-cell transformation or in Burkitt cells triggered ferroptosis, a programmed cell death pathway. LCLs were less dependent on this defense, a distinction tied to EBV latency programs. This highlights ferroptosis induction as a novel therapeutic approach for prevention or treatment of EBV+ lymphomas.

microbiology↗