Biology subjects

Bremaud, E.

Publications and source records attributed to Bremaud, E..

4 recordsLinked to original sources

bioRxiv2026

SARS-CoV-2 spike protein-associated sialoglycoconjugates induce nanoscale filipodia to facilitate micro-size platelet clotting

COVID-19 disease is associated with thrombosis, but the pathogenic mechanism remains unclear. Here, we investigate how SARS-CoV-2 spike protein causes platelet activation and aggregation. Our three-dimensional ultrastructural analyses showed that invaginated platelet structures, open canalicular system (OCS), expanded upon activation, trapping viral particles in the process. Binding with platelet OCS concealed SAR-CoV-2 spike-coated particles from virion detection in platelet-depleted blood plasma. Both SARS-CoV-2 spike coated-particles and recombinant spikes specifically induced platelet aggregation with nanoscale filipodia extensions, with the terminal sialic acids of the SARS-CoV-2 spike protein-associated sialoglycoconjugates being the key determinant in platelet activation. Our work illustrates that virus-associated sialic acids, not proteins, are functionally responsible for SARS-CoV-2 induced thrombotic events, providing a mechanistic insight on how glycosylation contributes to disease severity in COVID-19. This study lays the foundation for the development of glycan-modified vaccines with reduced risks of thrombosis.

molecular biology↗

bioRxiv2026

Calcium-phosphate bridge is a novel phosphorylation switch that stabilises protein-complexes during HIV assembly

Calcium (Ca2+) and phosphate (PO43-) are fundamental-element and -chemical group in biology. Specifically, the chemistry of both Ca2+ signalling and phosphorylation switch are independent mechanisms regulating a broad spectrum of biological processes. It is, however, not appreciated that a normal function of phospho-mimic amino acids (aspartate/glutamate) is to interact with Ca2+ at the atomic level. Here, we leveraged HIV-Ca2+ biology in primary cells to describe an unknown layer of regulatory processes via Ca2+-phosphate (PO43-) bridge to support protein complex formation. We identified novel HIV phosphorylation sites overlapping Ca2+ binding domains through phospho-proteomics. Integrating primary cells, molecular virology, structural biology, biophysical and ultrastructural analyses, we presented multiple examples of Ca2+-PO43- bridges that support HIV assembly and function. These include Ca2+-PO43- bridges: (i) stabilising Pr55Gag-Pr160GagPol complex for virus function; (ii) mediating p6Pol dimerization to support virion maturation; and (iii) modulating viral complex formation to package both viral enzymatic- and cellular-proteins. As the convergent enrichment of these signatured calcium-phosphorylation domains occurs across a wide range of viral and cellular proteins, we propose Ca2+-PO43- bridge to be a general principle for Ca2+-coordinated phosphorylation switch to regulate biological processes.

cell biology↗

bioRxiv2022

HIV-1 diverts actin debranching mechanismsfor particle assembly and release in CD4 Tlymphocytes.

Enveloped viruses assemble and bud from the host cell membranes. Possible roles of cortical actin in these processes have often been a source of controversy. Here, we assessed the involvement of the Arp2/3 mediated branched actin in HIV-1 assembly at the membrane of infected CD4 T lymphocytes. Our results show that actin debranching not only increases HIV-1 release but also the number of individual HIV-1 assembly clusters present at the cell plasma membrane unravelling new mechanisms. Indeed, we showed that, in infected T lymphocytes, HIV-1 Gag prefers areas deficient in F-actin for assembly. In vitro, we could reproduce and quantify this mechanism using model systems. Finally, we found that the actin debranching factor, Arpin, an Arp2/3 inhibitor, is recruited by Gag at the cell membrane to promote virus assembly. Altogether, our data show that HIV-1 favors local actin debranching for assembly and release by subverting the host factor Arpin.

microbiology↗

bioRxiv2022

Quantification of membrane binding and diffusion using Fluorescence Correlation Spectroscopy diffusion laws

Many transient processes in cells arise from the binding of cytosolic proteins to membranes. Quantifying this membrane binding and its associated diffusion in the living cell is therefore of primary importance. Dynamic photonic microscopies, e.g. single/multiple particle tracking, fluorescence recovery after photobleaching and fluorescence correlation spectroscopy (FCS) enable noninvasive measurement of molecular mobility in living cells and their plasma membranes. However, FCS with a single beam waist is of limited applicability with complex, non Brownian, motions. Recently, the development of FCS diffusion laws methods has given access to the characterization of these complex motions, although none of them is applicable to the membrane binding case at the moment. In this study, we combined computer simulations and FCS experiments to propose an FCS diffusion law for membrane binding. First, we generated computer simulations of spot-variation FCS (svFCS) measurements for a membrane binding process combined to 2D and 3D diffusion at the membrane and in the bulk/cytosol, respectively. Then, using these simulations as a learning set, we derived an empirical diffusion law with three free parameters: the apparent binding constant KDapp, the diffusion coefficient on the membrane D2D and the diffusion coefficient in the bulk/cytosol, D3D. Finally, we monitored, using svFCS, the dynamics of retroviral Gag proteins and associated mutants during their binding to supported lipid bilayers of different lipid composition or at plasma membranes of living cells and we quantified KDapp and D2D in these conditions using our empirical diffusion law. Based on these experiments and numerical simulations, we conclude that this new approach enables correct estimation of membrane partitioning and membrane diffusion properties (KDapp and D2D) for peripheral membrane molecules.

biophysics↗