Biology subjects

Fouillen, A.

Publications and source records attributed to Fouillen, A..

6 recordsLinked to original sources

bioRxiv2026

Distinct atypical chemokine receptor 1 determinants underlie bacterial toxins recognition and pore formation

Atypical chemokine receptor 1 (ACKR1) is one of the most promiscuous receptors in the human chemokine system, engaging structurally diverse chemokines through a conformationally flexible N-terminal tail. This same interface is exploited by pathogens, including Plasmodium vivax and Staphylococcus aureus (SA), via a compact sulfotyrosine code. Among pathogenic proteins recognizing ACKR1, the SA leukocidin pair HlgAB is a notable exception. HlgAB-mediated pore formation is only weakly competed by chemokines, the Duffy binding protein, or antibodies targeting the receptor's N-terminus, leaving open how HlgAB engage ACKR1. Combining structural biology approaches with cell-based assays, we show that HlgA and HlgB engage ACKR1 sulfated N-terminus with distinct affinities and site hierarchies, with a single higher-affinity site for sulfated tyrosine 41 present in HlgA but absent in HlgB. Unexpectedly, this N-terminal engagement is dispensable for pore formation; productive lysis instead requires a separate interaction between the toxins and ACKR1 extracellular vestibule. These results define a two-step recognition mechanism, toxin capture by the sulfotyrosine N-terminus followed by vestibule-dependent pore formation, and extend the view that ACKR1 promiscuity arises from distributed, ligand-specific use of multiple receptor surfaces rather than a single adaptable interface.

biochemistry↗

bioRxiv2025

Deltaviruses spread through a viral Trojan Horse

Hepatitis D-like viral satellites, known as deltaviruses, have been recently discovered in a wide range of animals. These viruses are thought to expropriate glycoproteins from helper viruses to form infectious particles. Here, we challenge this paradigm and demonstrate that deltaviruses are packaged within helper virus particles, using them as viral Trojan Horses for cell entry. By leveraging orthogonal electronic and photonic super-resolution microscopy, we visualize deltaviruses enclosed within virions from rhabdo-, herpes-, and arenavirus families. We show that this conserved hitchhiking mechanism ensures concomitant deltavirus-helper virus spread, which advantages the dissemination of deltaviruses, broadens their host range and expands their tropism. Our findings reveal a previously unrecognized mode of viral transmission, providing a framework to investigate overlooked deltavirus infections outside of the human liver.

microbiology↗

bioRxiv2024

Inactive structures of the vasopressin V2 receptor reveal distinct antagonist binding modes for Tolvaptan and Mambaquaretin toxin

AbstractAntagonists of the arginine-vasopressin (AVP) V2 receptor (V2R) are key therapeutic compounds to treat hyponatremia or polycystic kidney diseases. Compounds such as Tolvaptan (TVP) and Conivaptan are marketed drugs but their mechanisms of inhibition are not known. In addition, TVP presents unwanted side effects such as serious liver injury. Conivaptan also targets AVP V1a receptor subtype and thus is not selective to V2R. To develop novel molecules with less side effects and better selectivity, rational drug design based on experimental three-dimensional G protein-coupled receptor (GPCR) structures is a powerful and successful avenue. The lack of antagonist-bound V2R structures has however impaired this strategy for this GPCR. To fill this gap of knowledge, we solved here the cryo-electron microscopy structures of the vasopressin V2R in complex with two selective antagonists, the nonpeptide TVP and the green mamba snake Mambaquaretin toxin (MQ1). Both ligands, known to be competitive, bind into the orthosteric AVP binding site but with substantial differences. The small molecule binds deeper than MQ1, and directly contacts the toggle switch residue W2846.48 in the transmembrane domain 6 (TM6), whereas the peptide Kunitz- fold toxin presents more extensive contacts with the receptor through additional interactions with extracellular and transmembrane residues. As anticipated from the pharmacological properties of TVP and MQ1, both structures represent inactive conformations of the V2R. Their comparison with those of the active AVP-bound V2R reveals the molecular mechanisms modulating receptor activity. Finally, the structure of the V2R bound to a mini-protein such as MQ1 opens a new pharmacology era in the field of water homeostasis and renal diseases.

pharmacology and toxicology↗

bioRxiv2023

Conformational diversity in class C GPCR positive allosteric modulation

The metabotropic glutamate receptors (mGlus) are class C G protein coupled receptors (GPCR) that form obligate dimers activated by the major excitatory neurotransmitter L-glutamate1,2. The architecture of mGlu receptor comprises an extracellular Venus-Fly Trap domain (VFT) connected to a transmembrane domain (7TM) through a Cysteine-Rich Domain (CRD). The binding of L-glutamate in the VFTs and subsequent conformational change results in the signal being transmitted to the 7TM inducing G-protein binding and activation 3-6. The mGlu receptors signal transduction can be allosterically potentiated by positive allosteric modulators (PAMs) binding to the 7TMs, which are of therapeutic interest in various neurological disorders7-9. Here, we report the cryoEM structures of metabotropic glutamate receptor 5 (mGlu5) purified with three chemically and pharmacologically distinct PAMs. We find that PAMs modulate the receptor equilibrium through their different binding modes, revealing how their interactions in the 7TMs impact the mGlu5 receptor conformational landscape and function. In addition, we identified a PAM-free but agonist-bound intermediate state that is stabilised by interactions mediated by intracellular loop 2. The activation of mGlu5 receptor is a multi-step sequential process in which the binding of the PAMs in the 7TM modulates the equilibrium towards the active state.

biochemistry↗

bioRxiv2023

Biased activation of the vasopressin V2 receptor probed by NMR, paramagnetic ligands, and molecular dynamics simulations

G protein-coupled receptors (GPCRs) control critical intercellular communications by responding to extracellular stimuli and undertaking conformational changes to convey signals to intracellular effectors. We combined NMR, molecular pharmacology, and molecular dynamics (MD) simulations to study the conformational diversity of the vasopressin V2 GPCR subtype (V2R) bound to different types of ligands: the antagonist tolvaptan, the endogenous unbiased agonist arginine-vasopressin, and MCF14, a Gs-protein biased agonist. We developed a double-labeling NMR scheme to study the conformational dynamics: V2R was subjected to lysine 13CH3 methylation, whereas the agonists were tagged with a paramagnetic probe. Paramagnetic relaxation enhancements were used to validate the ligand binding poses in the MD simulations. We found that the bias for the Gs protein over the {beta}-arrestin pathway involves interactions between the conserved NPxxY motif in the transmembrane helix (TM) 7 and a central hydrophobic patch in TM3, which constrains TM7 and likely inhibits {beta}-arrestin signaling. A similar mechanism was observed for the pathogenic mutation, I1303.43N, which constitutively activates the Gs protein without concomitant {beta}-arrestin recruitment. This mechanism resembles to opioid receptors findings indicating common patterns in class A GPCRs.

biophysics↗

bioRxiv2022

Structure of the vasopressin hormone-V2 receptor-β-arrestin1 ternary complex

Arrestins interact with G protein-coupled receptors (GPCRs) to stop G protein activation and to initiate key signaling pathways. Recent structural studies shed light on the molecular mechanisms involved in GPCR-arrestin coupling, but whether this process is conserved among GPCRs is poorly understood. Here, we report the cryo-electron microscopy active structure of the wild-type arginine-vasopressin V2 receptor (V2R) in complex with {beta}-arrestin1. It reveals an atypical position of {beta}-arrestin1 compared to previously described GPCR-arrestin assemblies, associated with an original V2R/{beta}-arrestin1 interface involving all receptor intracellular loops. Phosphorylated sites of the V2R C-terminus are clearly identified and interact extensively with the {beta}-arrestin1 N-lobe, in agreement with structural data obtained with chimeric or synthetic systems. Overall, these findings highlight a striking structural variability among GPCR-arrestin signaling complexes.

biochemistry↗