Biology subjects

Ancelin, A.

Publications and source records attributed to Ancelin, A..

4 recordsLinked to original sources

bioRxiv2025

Dengue virus harnesses mosquito Syntenin to load and secrete viral RNA into salivary exosomes

Viruses exploit extracellular vesicles (EVs) to transfer infection-enhancing viral RNAs. However, mechanisms underlying viral RNA loading remain elusive. We leveraged our previous discovery that dengue virus secretes transmission-enhancing subgenomic flaviviral RNA (sfRNA) into mosquito salivary EVs to investigate viral RNA loading mechanism. We demonstrate that sfRNA alone promotes the secretion of sfRNA-containing EVs marked by the mosquito EV biogenesis protein AeSyntenin, by applying microscopy and viral genetic editing in in vitro and in vivo models. SfRNA via its stem loop structures interacts intracellularly with mosquito AeSyntenin and this interaction is selectively maintained within EVs as shown by complementary RNA-affinity chromatography and RNA immunoprecipitation, and AI-based prediction. Finally, we used systemic and salivary gland-specific protein depletion to establish a functional role for mosquito AeSyntenin in exosome production and salivary secretion of sfRNA. We propose that sfRNA binds AeSyntenin to drive its selective packaging and release into exosomes, elucidating a mechanism for viral RNA incorporation into EVs. Significance statementViruses hijack extracellular vesicles (EVs) to enhance viral dissemination, but the mechanisms enabling selective viral RNA packaging into EVs remain unclear. Specifically, dengue virus transmission by mosquitoes relies on EV-based delivery of an immune-inhibitory subgenomic flaviviral RNA (sfRNA). Here, we uncover how dengue virus sfRNA is actively sorted into EVs from mosquito saliva. We show that sfRNA alone induces its secretion via EVs. We discover that sfRNA directly interacts with AeSyntenin intracellularly, and that this interaction persists in secreted EVs. Functional depletion studies reveal AeSyntenins role in salivary EV formation and sfRNA secretion. These findings establish a novel paradigm by which viral RNAs exploit vector EV pathways for dissemination.

microbiology↗

bioRxiv2024

Structure of the turnip yellows virus particles. How is the readthrough domain exposed on the capsid surface?

Turnip yellows virus (TuYV) is a plant virus infecting important crops such as oilseed rape. TuYV is phloem-restricted and transmitted by aphids. The capsid contains two subunit types: the major capsid protein (CP) and a minor component (RTP*) which arises from the C-terminal cleavage of a readthrough product (RTP). RTP* contains the CP sequence fused with a structured domain, denoted NRTD, which is a key determinant of virus transmission. Though both CP and RTP* are involved in virus movement and aphid transmission, how RTP* is incorporated into the capsid is poorly understood. We present here the structural characterisation, by immunogold labelling and 3D cryo-EM, of the wild-type TuYV and a mutant whose capsid contains the CP only. We show that incorporation of RTP* does not impair the capsid structure, and the NRTD does not adopt well-defined positions at the capsid surface. The number of incorporated RTP*s suggests a random insertion.

microbiology↗

bioRxiv2022

Cryo-EM structure of the agonist-bound Hsp90-XAP2-AHR complex

SummaryLiving organisms have developed protein sensors helping them to adapt to their environment1. The aryl hydrocarbon receptor (AHR) is an emblematic member of this class of proteins, and a ligand-dependent transcription factor that mediates a broad spectrum of (patho)physiological processes in response to numerous substances including pollutants, natural products and metabolites2. However, in the absence of high-resolution structural data, a molecular understanding of how AHR is activated by such diverse compounds is lacking. Here we present a 2.85 [A] cryo-electron microscopy structure of the cytosolic complex comprising AHR bound to the ligand indirubin, the chaperone Hsp90 and the co-chaperone XAP2. The structure reveals a closed Hsp90 dimer with AHR threaded through its lumen. XAP2 directly interacts with Hsp90 and the AHR ligand-binding domain, thereby acting as a brace stabilizing the entire complex. Importantly, we provide the first experimental visualization of the AHR PAS-B domain bound to a ligand, revealing a unique organization of the ligand-binding pocket and the structural determinants of ligand-binding specificity and promiscuity of the receptor. By providing unprecedented structural details of the molecular initiating event leading to AHR activation, our study rationalizes prior biochemical data and provides a framework for future mechanistic studies and structure-guided drug design.

biochemistry↗

bioRxiv2020

Structure of the antidiuretic hormone vasopressin receptor signalling complex.

Arginine-vasopressin (AVP) is a neurohypophysial peptide known as the antidiuretic hormone. It forms an active signalling complex with the V2 receptor (V2R) and the Gs protein, promoting a cAMP/PKA-dependent aquaporin insertion in apical membranes of principal cells of the renal collecting ducts and ultimately, water reabsorption. Molecular mechanisms underlying activation of this critical G protein-coupled receptor (GPCR) signalling system are still unknown. To fill this gap of knowledge, we report here the structure of the AVP-V2R-Gs complex using cryo-electron microscopy (cryo-EM). Single-particle analysis revealed the presence of three different states. The two best maps were combined with computational and NMR spectroscopy constraints to reconstruct two structures of the ternary complex. These structures differ in AVP and Gs binding modes and could thus represent distinct complex conformations along the signalling activation pathway. Importantly, as compared to those of other class A GPCR-Gs complexes, the structures revealed an original receptor-Gs interface in which the Gs subunit penetrates deeper into the active V2R, notably forming an ionic bond between its free C-terminal carboxylic function and the side chain of R137 in the V2R. Interestingly, the structures help to explain how V2R R137H or R137L/C variants can lead to two severe genetic diseases with opposite clinical outcomes, cNDI or NSIAD respectively. Our study thus provides important structural insights into the function of this clinically relevant GPCR signalling complex.

biochemistry↗