Biology subjects

Clavel, M.

Publications and source records attributed to Clavel, M..

11 recordsLinked to original sources

bioRxiv2025

Preclinical characterization of AT-03, a novel Serum Amyloid P fusion protein that demonstrates pan-amyloid binding and removal

The systemic amyloidoses are progressive disorders caused by extracellular deposition of insoluble amyloid fibrils leading to organ dysfunction that often proves fatal. New therapeutics aiming at removing deposited amyloid are urgently needed to improve patient outcomes. MethodsWe developped AT-03 (originally called SAP-scFc), a fusion protein consisting of serum amyloid P-component, which binds all types of amyloid, linked to a single chain human IgG1 Fc domain. AT-03 binding to diverse types of amyloid and phagocytic activity were assessed both in vitro and in vivo. Therapeutic efficacy was evaluated in an AA mouse model. ResultsAT-03 bound with high potency to AL and ATTR human amyloid extracts. In murine models, intravenously administered AT-03 bound to AA, AL and AApoA2 amyloid, including in the heart. Ex vivo AT-03 opsonization induced phagocytosis of human AL extract by activated human THP-1 macrophages and enhanced in vivo phagocytosis in mice. A single intravenous injection of SAP-scFc induced a significant reduction of splenic amyloid in a murine model of AA amyloidosis. ConclusionsAT-03 binds many amyloid types and can promote macrophage-mediated phagocytosis of the deposits. Thus, AT-03 is a promising novel therapeutic agent for the removal of systemic amyloid.

pathology↗

bioRxiv2025

Ancestral P-body proteins rewired for autophagic recyclingin the early land plant Marchantia polymorpha

Processing bodies (P-bodies) are conserved ribonucleoprotein (RNP) granules central to RNA metabolism across eukaryotes. Although the mechanisms underlying their assembly are well understood, the pathways governing their selective turnover remain unclear. Here, we identify the conserved decapping proteins EDC4 and DCP1 as a selective autophagy receptor pair responsible for P-body turnover in the early land plant Marchantia polymorpha. MpEDC4 engages ATG8 via a canonical AIM motif, while MpDCP1 contains a previously unrecognized reverse AIM within its intrinsically disordered region. Mutations disrupting these motifs impair autophagic degradation of P-bodies, demonstrating a cooperative receptor mechanism. Notably, this autophagic function is lineage-specific, as orthologs in Arabidopsis and humans lack ATG8-binding capacity. Strikingly, heterologous expression of MpEDC4 in human cells promotes degradation of -synuclein, a protein strongly linked to Parkinsons disease etiology. Our findings thus uncover an evolutionary innovation that links RNA metabolism to selective autophagy and opens avenues for cross-kingdom engineering of targeted protein degradation pathways.

plant biology↗

bioRxiv2024

Cross-species interactome analysis uncovers a conserved selective autophagy mechanism for protein quality control in plants

Selective autophagy is a fundamental protein quality control pathway that safeguards proteostasis by degrading damaged or surplus cellular components, particularly under stress. This process is orchestrated by selective autophagy receptors (SARs) that direct specific cargo for degradation. While significant strides have been made in understanding the molecular framework of selective autophagy, the diversity of SAR repertoires across species remain largely unexplored. Through a comparative interactome analysis across five model organisms, we identified a suite of conserved and lineage-specific SAR candidates. Among these, we validated CESAR as a conserved SAR critical for proteostasis under heat stress. CESAR specifically facilitates the degradation of hydrophobic, ubiquitinated protein aggregates and is indispensable for heat stress tolerance. Our study offers a rich resource for SAR discovery and positions CESAR as a pivotal regulator of proteostasis, with broad implications for improving stress resilience in plants.

plant biology↗

bioRxiv2024

Electrostatic changes enabled the diversification of an exocyst subunit via protein complex escape

The evolution of cellular complexity hinges on the capacity of multimeric protein complexes to diversify without compromising their ancestral functions. A central question is how individual subunits within these complexes can evolve novel functions while maintaining the integrity of the original assembly. Here, we explore this question by tracing the evolutionary trajectory of the plant exocyst, an octameric complex essential for exocytosis in eukaryotes. Remarkably, the Exo70 subunit underwent dramatic expansion and functional divergence in plants. We demonstrate that electrostatic alterations in the N-terminal region of the Exo70 subunit precipitated its dissociation from the exocyst complex. This release mitigated paralog interference, thereby facilitating the subunits extensive functional co-option. Our findings reveal a nuanced mechanism by which a protein subunit, ancestrally constrained within a multimeric complex, can escape those constraints and evolve novel functions, shedding light on the molecular underpinnings of cellular innovation. One-Sentence SummaryEvolutionary diversification of an exocyst subunit is driven by electrostatic shifts that dissociates it from the ancestral complex.

evolutionary biology↗

bioRxiv2024

Metabolic enzymes moonlight as selective autophagy receptors to protect plants against viral-induced cellular damage

AbstractRNA viruses co-opt the host endomembrane system and organelles to build replication complexes for infection. How the host responds to these membrane perturbations is poorly understood. Here, we explore the autophagic response of Arabidopsis thaliana to three viruses that hijack different cellular compartments. Autophagy is significantly induced within systemically infected tissues, its disruption rendering plants highly sensitive to infection. Contrary to being an antiviral defense mechanism as previously suggested, quantitative analyses of the viral loads established autophagy as a tolerance pathway. Further analysis of one of these viruses, the Turnip Crinkle Virus (TCV) that hijack mitochondria, showed that despite perturbing mitochondrial integrity, TCV does not trigger a typical mitophagy response. Instead, TCV and Turnip yellow mosaic virus (TYMV) infection activates a distinct selective autophagy mechanism, where oligomeric metabolic enzymes moonlight as selective autophagy receptors and degrade key executors of defense and cell death such as EDS1. Altogether, our study reveals an autophagy-regulated metabolic rheostat that gauges cellular integrity during viral infection and degrades cell death executors to avoid catastrophic amplification of immune signaling.

plant biology↗

bioRxiv2024

ATG8ylation of vacuolar membrane protects plants against cell wall damage

Vacuoles are essential for cellular metabolism, growth, and the maintenance of internal turgor pressure. They sequester lytic enzymes, ions, and secondary metabolites that, if leaked into the cytosol, could lead to cell death. Despite their pivotal roles, quality control pathways that safeguard vacuolar integrity remained elusive in plants. Here, we discovered a conserved vacuolar quality control (VQC) pathway that is activated upon cell wall damage in a turgor pressure dependent manner. Cell wall perturbations induce a distinct modification - ATG8ylation - on the vacuolar membrane (tonoplast) that is regulated by the V-ATPase and ATG8 conjugation machinery. Genetic disruption of tonoplast ATG8ylation impairs vacuolar integrity, leading to cell death. Together, our findings reveal a homeostatic pathway that preserves vacuolar integrity upon cell wall damage.

plant biology↗

bioRxiv2023

A RabGAP-Rab GTPase pair regulates plant autophagy and immunity

Plants rely on autophagy and membrane trafficking to tolerate stress, combat infections, and maintain cellular homeostasis. However, the molecular interplay between autophagy and membrane trafficking is poorly understood. Using an AI-assisted approach, we identified Rab3GAP-like (Rab3GAPL) as an important membrane trafficking node that controls plant autophagy negatively. Rab3GAPL suppresses autophagy by binding to ATG8, the core autophagy adaptor, and deactivating Rab8a, a small GTPase essential for autophagosome formation and defense-related secretion. Rab3GAPL from Nicotiana benthamiana, but not its mutated form deficient in ATG8 binding, reduced autophagic flux in N. benthamiana and Arabidopsis. Furthermore, Rab3GAPL-knockout mutants of the liverwort Marchantia polymorpha exhibited enhanced autophagic flux under both normal and heat stress conditions, suggesting that Rab3GAPLs negative regulatory role in autophagy is conserved in land plants. Beyond autophagy regulation, Rab3GAPL modulates focal immunity against the oomycete pathogen Phytophthora infestans by preventing defense-related secretion. Altogether, our results suggest that Rab3GAPL acts as a molecular rheostat to coordinate autophagic flux and defense-related secretion by restraining Rab8a-mediated trafficking. This unprecedented interplay between a RabGAP-Rab pair and ATG8 sheds new light on the intricate membrane transport mechanisms underlying plant autophagy and immunity.

plant biology↗

bioRxiv2022

Plant autophagosomes mature into amphisomes prior to their delivery to the central vacuole

Autophagosomes are double-membraned vesicles that traffic harmful or unwanted cellular macromolecules to the vacuole for recycling. Although autophagosome biogenesis has been extensively studied, mechanisms of autophagosome maturation, i.e., delivery and fusion with the vacuole, remain largely unknown in plants. Here, we have identified an autophagy adaptor, CFS1, that directly interacts with the autophagosome marker ATG8 and localizes on both membranes of the autophagosome. Autophagosomes form normally in Arabidopsis thaliana cfs1 mutants, but their delivery to the vacuole is disrupted. CFS1s function is evolutionarily conserved in plants as it also localizes to the autophagosomes and plays a role in autophagic flux in the liverwort Marchantia polymorpha. CFS1 regulates autophagic flux by connecting autophagosomes with the ESCRT-I component VPS23, leading to the formation of amphisomes. Disrupting the VPS23-CFS1 interaction affects autophagic flux and renders plants sensitive to starvation stress. Altogether, our results reveal a deeply conserved mechanism of vacuolar delivery in plants that is mediated by amphisomes.

plant biology↗

bioRxiv2021

The Arabidopsis F-box protein FBW2 degrades AGO1 to avoid spurious loading of illegitimate small RNA

RNA silencing is a conserved mechanism in eukaryotes and is involved in development, heterochromatin maintenance and defense against viruses. In plants, ARGONAUTE1 (AGO1) protein plays a central role in both microRNA (miRNA) and small interfering RNA (siRNA)-directed silencing and its expression is regulated at multiple levels. Here, we report that the F-box protein FBW2 targets proteolysis of AGO1 by a CDC48-mediated mechanism. We found that FBW2 assembles an SCF complex that recognizes the MID-PIWI domain of AGO1 and requires its C-terminal domain containing a GW motif for AGO1 turnover. We showed that FBW2 prefers the unloaded and some mutated forms of AGO1 protein. While FBW2 loss of function does not lead to strong growth or developmental defects, it significantly increases RNA silencing activity. Interestingly, under conditions in which small RNA production or accumulation is affected, the failure to degrade AGO1 in fbw2 mutants becomes more deleterious for the plant. Hence, the non-degradable AGO1 protein assembles high molecular weight complexes and binds illegitimate small RNA leading to the cleavage of new target genes that belong to stress responses and cellular metabolic processes. Therefore, the control of AGO1 homeostasis by ubiquitin ligases plays an important role in quality control to avoid off-target cleavage.

cell biology↗

bioRxiv2021

Molecular features of RNA silencing against phloem-restricted polerovirus TuYV enable amplification of silencing signal from host transcripts

In plants and some animal lineages, RNA silencing is an efficient and adaptable defense mechanism against viruses. To counter it, viruses encode suppressor proteins that interfere with RNA silencing. Phloem-restricted viruses are spreading at an alarming rate and cause substantial reduction of crop yield, but how they interact with their hosts at the molecular level is still insufficiently understood. Here, we investigate the antiviral response against phloem-restricted turnip yellows virus (TuYV) in the model plant Arabidopsis thaliana. Using a combination of genetics, deep sequencing, and mechanical vasculature enrichment, we show that the main axis of silencing active against TuYV involves 22-nt vsiRNA production by DCL2, and their preferential loading into AGO1. Unexpectedly, and despite the viral encoded VSR P0 previously shown to mediate degradation of AGO proteins, vascular AGO1 undergoes specific post-translational stabilization during TuYV infection. We also identify vascular novel secondary siRNA produced from conserved plant transcripts and initiated by DCL2-processed AGO1-loaded vsiRNA, supporting a viral strategy to modulate host response. Collectively, our work uncovers the complexity of antiviral RNA silencing against phloem-restricted TuYV and prompts a re-assessment of the role of its suppressor of silencing P0 during genuine infection.

plant biology↗

bioRxiv2020

A cross-kingdom conserved ER-phagy receptor maintains endoplasmic reticulum homeostasis during stress

Eukaryotes have evolved various quality control mechanisms to promote proteostasis in the ER. Selective removal of certain ER domains via autophagy (termed as ER-phagy) has emerged as a major quality control mechanism. However, the degree to which ER-phagy is employed by other branches of ER-quality control remains largely elusive. Here, we identify a cytosolic protein, C53, that is specifically recruited to autophagosomes during ER-stress, in both plant and mammalian cells. C53 interacts with ATG8 via a distinct binding epitope, featuring a shuffled ATG8 interacting motif (sAIM). C53 senses proteotoxic stress in the ER lumen by forming a tripartite receptor complex with the ER-associated ufmylation ligase UFL1 and its membrane adaptor DDRGK1. The C53/UFL1/DDRGK1 receptor complex is activated by stalled ribosomes and induces the degradation of internal or passenger proteins in the ER. Consistently, the C53 receptor complex and ufmylation mutants are highly susceptible to ER stress. Thus, C53 forms an ancient quality control pathway that bridges selective autophagy with ribosome-associated quality control at the ER.

cell biology↗