Biology subjects

Gelin, M.

Publications and source records attributed to Gelin, M..

10 recordsLinked to original sources

bioRxiv2025

The Magnaporthe oryzae MAX effector AVR-Pia binds a novel group of rice HMA domain-containing proteins

Phytopathogenic fungi secrete effector proteins to promote virulence. MAX (Magnaporthe Avrs and ToxB-like) effectors form a sequence-diverse family sharing a conserved protein structure. AVR-Pia, a MAX effector from the rice blast fungus Magnaporthe oryzae, is recognised by the paired rice nucleotide-binding leucine-rich repeat immune receptors OsRGA4/OsRGA5 through direct binding to an integrated heavy metal-associated (HMA) domain in OsRGA5. Here, we identify previously unknown host targets of AVR-Pia: four HMA domain-containing rice proteins, belonging to the HMA Isoprenylated Plant Proteins (HIPPs) and HMA Plant Proteins (HPPs). AVR-Pia interacted with all four proteins, both in vitro and in planta, and bound their HMA domains with varying affinities. The crystal structure of AVR-Pia in complex with the HMA domain of OsHPP09 revealed the molecular details of the binding interface. Structure-guided mutagenesis of OsHPP09 identified a single point mutation which prevents AVR-Pia binding, providing a foundation for targeted engineering of HMA domains to evade effector binding.

plant biology↗

bioRxiv2025

Intratumoral Heterogeneity of Vimentin Modulates Nuclear Mechanotransduction, DNA Damage Response and Cancer Cell Survival

Vimentin, a major intermediate filament protein, is essential for maintaining cellular integrity and regulating cytoskeletal dynamics. Its upregulation is a hallmark of epithelial-to-mesenchymal transition (EMT), a process that enhances cancer cell migration, invasion, and metastatic potential. However, single-cell transcriptomic analyses of glioblastoma, the most common and aggressive primary brain tumor, reveal that vimentin expression exhibits significant intratumoral heterogeneity, reflecting diverse cellular subpopulations that may contribute to tumor plasticity, therapy resistance, and disease progression. Here, we show that the absence of vimentin alters nuclear mechanotransduction in response to compression, leading to chromatin remodelling and profound changes in gene expression in cancer cells. Remarkably, we demonstrate that external compressive forces, akin to vimentin deficiency, disrupt DNA damage response pathways. This impairment compromises DNA damage sensing and repair, bypassing DNA damage checkpoints and apoptosis. Consequently, vimentin-negative tumor cells exhibit increased survival in response to physical stress and DNA damage, potentially driving radioresistance and further amplifying intratumoral heterogeneity.

cancer biology↗

bioRxiv2025

Identification of CaVβ1 isoforms required for neuromuscular junction formation and maintenance

Voltage-gated Ca{superscript 2} channels (VGCCs) are regulated by four CaV{beta} subunits (CaV{beta}1-CaV{beta}4), each showing specific expression patterns in excitable cells. While primarily known for regulating VGCC function, CaV{beta} proteins also have channel-independent roles, including gene expression modulation. Among these, CaV{beta}1 is expressed in skeletal muscle as multiple isoforms. The adult isoform, CaV{beta}1D, localizes at the triad and modulates CaV1 activity during Excitation-Contraction Coupling (ECC). In this study, we investigated the lesser-known embryonic/perinatal CaV{beta}1 isoforms and their roles in neuromuscular junction (NMJ) formation, maturation, and maintenance. We found that CaV{beta}1 isoform expression is developmentally regulated through differential promoter activation. Specifically, CaV{beta}1A is expressed in embryonic muscle and reactivated in denervated adult muscle, alongside the known CaV{beta}1E isoform. Nerve injury in adult muscle triggers a shift in promoter usage, resulting in re-expression of embryonic/perinatal Cacnb1A and Cacnb1E transcripts. Functional analyses using aneural agrin-induced AChR clustering on primary myotubes demonstrated that these isoforms contribute to NMJ formation. Additionally, their expression during early postnatal development is essential for NMJ maturation and long-term maintenance. These findings reveal previously unrecognized roles of CaV{beta}1 isoforms beyond VGCC regulation, highlighting their significance in neuromuscular system development and homeostasis.

physiology↗

bioRxiv2025

Structural and molecular basis of resistance to aminoglycoside antibiotics by APH(3')-IIb from Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the six bacteria of greatest concern identified by the WHO for its resistance to antibiotics. In the case of aminoglycosides, used in combination with other antibiotics in the treatment of severe infections, resistance is mainly due to modification of the antibiotic by bacterial enzymes. In this study, we have functionally and structurally characterized one such enzyme from P. aeruginosa, aminoglycoside 3-O-phosphotransferase IIb, APH(3)-IIb. The results will provide a better understanding of this resistance mechanism and enable us to envisage solutions for blocking it and restoring the efficacy of aminoglycosides.

biochemistry↗

bioRxiv2024

Centrosome positioning independently of microtubule-based forces

The regulation of centrosome position is central to the establishment of polarized cell functions. This process is thought to rely on the generation of mechanical forces along microtubules, the balance of which determines centrosome position. By studying these forces in adherent cells in culture, we found that neither pushing nor pulling forces propagate along microtubules to the centrosome. Inhibiting dyneins or disassembling microtubules did not disrupt the maintenance of the centrosome at the center of the cell. In contrast, the actomyosin contractile network appears to be responsible for the generation of a centripetal flow that drives the centrosome towards the center of the cell independently of the microtubules. Furthermore, we found that centering of the centrosome depends more on the reorganization of cell shape around the centrosome than on an effective centrosome displacement throughout the cytoplasm. Interestingly, despite their lack of mechanical role, microtubules appear to direct this remodeling of cell shape. This revised view of centrosome positioning offers a new perspective for understanding the establishment of cell polarity.

cell biology↗

bioRxiv2023

Deletion of FAT1 in hybrid EMT cells stimulates the migration of neighboring non-mutant cells through secretion of extracellular vesicles

Cells in hybrid state of the epithelial-to-mesenchymal transition (EMT) have been shown to be responsible for tumor cell metastasis. However, the precise mechanisms underlying the morphological changes and acquisition of invasive phenotypes in hybrid EMT cells are still unknown. Here, we introduced the deletion of a proto-cadherin and well described oncogene, FAT1, in skin carcinoma cells to generate a hybrid state of EMT. Surprisingly, the FAT1 knock-out (KO) cells were less motile than the parental non-mutated cell line they were derived from. However, we observed that FAT1 KO cells secrete specific factors in the form of extra-cellular vesicles into their microenvironment, which promote the migration of surrounding non-mutant cells. When stimulated with these extracellular vesicles, groups of non-mutated parental cells collectively migrated faster and formed finger-like instabilities at the migrating front. Furthermore, we found that the actomyosin contractility of FAT1 KO cells in hybrid EMT states was much lower than the parental cells. It appeared that the factors secreted by FAT1 KO cells relaxed the traction forces in recipient cells. This force release likely fostered the scattering and migration of non-mutated cells surrounding FAT1 mutant cells. Thus, we characterized a non-autonomous promotion of cell invasiveness in the cancer cells surrounding FAT1-deficient cells. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=181 SRC="FIGDIR/small/556588v1_ufig1.gif" ALT="Figure 1"> View larger version (61K): org.highwire.dtl.DTLVardef@104063eorg.highwire.dtl.DTLVardef@135f9fforg.highwire.dtl.DTLVardef@b0052eorg.highwire.dtl.DTLVardef@243864_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure:C_FLOATNO Schematic showing how FAT1 deletion stimulates the migration of neighboring non mutant cells. FAT1 KO cells secrete extracellular vesicles that carry factors that promote migration of non-mutant control cells, possibly through relaxation of traction forces in the recipient cells. C_FIG

cell biology↗

bioRxiv2023

Specific heterotypic interaction promotes asymmetric division of human hematopoietic stem and progenitor cells

Hematopoietic Stem and Progenitor Cells (HSPCs) give rise to all cell types of the hematopoietic system through various processes including asymmetric divisions. However, the contribution of stromal cells of the hematopoietic niches in the control of HSPC asymmetric divisions remains unknown. Using polyacrylamide microwells as minimalist niches, we show that heterotypic interaction with osteoblast promotes asymmetric division of human HSPC. Upon interaction, HSPCs polarize in interphase with centrosome, the Golgi apparatus and lysosomes positioned close to the site of contact. Subsequently during mitosis, HSPCs orient their spindle perpendicular to the plane of contact. This division gives rise to siblings with unequal amounts of lysosomes and differentiation markers such as CD34. Such asymmetric inheritance generates heterogeneity in the progeny, which is likely to be a key contributor to the plasticity of the early steps of hematopoiesis.

cell biology↗

bioRxiv2023

wTSA-CRAFT : an open-access web server for rapid analysis of thermal shift assay experiments

The automated data processing provided by the TSA-CRAFT tool enables now to reach high throughput speed analysis of thermal shift assays. While the software is powerful and freely available, it still requires installation process and command line efforts that could be discouraging. To simplify the procedure, we decided to make it available and easy to use by implementing it with a graphical interface via a web server, enabling a cross-platform usage from any web browsers. We developed a web server embedded version of the TSA-CRAFT tool, enabling a user-friendly graphical interface for formatting and submission of the input file and visualization of the selected thermal denaturation profiles. We describe a typical case study of buffer condition optimization of the biologically relevant APH(3)-IIb bacterial protein in a 96 deep-well thermal shift analysis screening. wTSA-CRAFT is freely accessible for non-commercial usage at https://bioserv.cbs.cnrs.fr/TSA_CRAFT.

bioinformatics↗

bioRxiv2023

Microtubules under mechanical pressure can breach dense actin networks

The crosstalk between actin network and microtubules is key to the establishment of cell polarity. It ensures that the asymmetry of actin architec ture along cell periphery directs the organization of microtubules in cell interior. In particular, the way the two networks are physically inter-twined regulates the spatial organization and the distribution of forces in the microtubule network. While their biochemical crosstalk is getting uncovered, their mechanical crosstalk is still poorly understood. Here we designed an in vitro reconstitution assay to study the physical interaction between dynamic microtubules with various structures made of actin fil aments. We found that microtubules can align and move by their polymerization force along linear bundles of actin filaments. But they cannot enter dense and branched actin meshworks, such as those found in the lamellipodium along cell periphery. However, when microtubules are immobilized, by their crosslinking with actin structures or others means, the force of polymerization builds up pressure in the microtubules that is sufficient to allow them to breach and penetrate these dense actin meshworks. This mechanism may explain the final progression of microtubules up to cell periphery through the denser parts of the actin network.

biophysics↗

bioRxiv2021

Kinesin-6 Klp9 orchestrates spindle elongation by regulating microtubule sliding and growth

Mitotic spindle function depends on the precise regulation of microtubule dynamics and microtubule sliding. Throughout mitosis, both processes have to be orchestrated to establish and maintain spindle stability. We show that during anaphase B spindle elongation in S. pombe, the sliding motor Klp9 (kinesin-6) also promotes microtubule growth in vivo. In vitro, Klp9 can enhance and dampen microtubule growth, depending on the tubulin concentration. This indicates that the motor is able to promote and block tubulin subunit incorporation into the microtubule lattice in order to set a well-defined microtubule growth velocity. Moreover, Klp9 recruitment to spindle microtubules is dependent on its dephosphorylation mediated by XMAP215/Dis1, a microtubule polymerase, to link the regulation of spindle length and spindle elongation velocity. Collectively, we unravel the mechanism of anaphase B, from Klp9 recruitment to the motors dual-function in regulating microtubule sliding and microtubule growth, allowing an inherent coordination of both processes.

cell biology↗