Biology subjects

Audebert, S.

Publications and source records attributed to Audebert, S..

At least 19 recordsLinked to original sources

bioRxiv2026

A quantitative interactome map reveals affinity tailored hijacking of human cellular functions by resident and pathogenic bacteria

Bacteria employ molecular mimicry to hijack host cellular functions for their own benefit. Despite the wealth of data mapping human-bacteria interactions, a comprehensive view of how these networks are fine-tuned remains elusive. In particular, there have been no large-scale screenings measuring human-bacterial protein-protein binding affinities to explore their role in functional and pathological outcomes. Here, we report the largest quantitative interactome to date between the family of human PDZ domains and C-terminal PDZ-binding motifs (PBMs) in effectors from pathogenic and resident gut bacteria. We show that bacteria tailor effector sequences to bind PDZ domains with similar or higher binding affinities than human PBMs to hijack their associated cellular functions. For a subset of the dataset, we validate PDZ-PBM interactions with the corresponding full-length proteins and show that for pathogenic E. coli effector NleA, its C-terminal PBM is necessary for interactions with proteins involved in intracellular transport and membrane organization, probably impacting the host glycocalyx to favor infection. Finally, we show that motifs overlapping with effector PBMs target interaction modules other than PDZ domains, adding an additional layer of complexity to the host-microbe molecular dialogue.

systems biology↗

bioRxiv2026

The atypical cadherin CELSR2 regulates distinct epithelial-mesenchymal states and oxidative phosphorylation in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is characterized by marked intratumoral heterogeneity, which contributes to metastatic dissemination, therapeutic resistance, and poor clinical outcome. Epithelial-mesenchymal plasticity is a major contributor to this heterogeneity. Identifying the molecular regulators governing epithelial-mesenchymal plasticity is therefore essential to understanding how distinct tumor cell populations arise and fuel TNBC progression. Here, we identify the adhesion G protein-coupled receptor CELSR2 as an independent poor-prognosis marker and regulator of epithelial-mesenchymal plasticity in TNBC. Spatial transcriptomic analyses revealed segregation of CELSR2high tumor cells within the epithelial tumor core and CELSR2low tumor cells at the invasive front. In line with the latter observation, CELSR2 expression decreases during EMT and its loss promotes acquisition of a hybrid epithelial-mesenchymal state. CELSR2high tumor cells display a CREB-associated oxidative phosphorylation (OXPHOS) program and promote cell proliferation and primary tumor growth. Conversely, CELSR2low cells display features of a more migratory phenotype. Collectively, our findings identify CELSR2 as a previously unknown regulator of epithelial-mesenchymal plasticity and reveal that heterogeneous CELSR2 expression shapes spatially and functionally distinct tumor cell populations, thereby contributing to intratumoral heterogeneity in TNBC.

cancer biology↗

bioRxiv2026

Circulating colorectal tumor cells remodel their surfaceome to increase their viability and metastatic potential in the bloodstream

Circulating tumor cells (CTCs) are the potential seeds of distant metastases; however, little is known about how they survive in the bloodstream. Using a large cohort of colorectal cancer (CRC) patients, we found that the pseudokinase receptor PTK7 is highly expressed in primary tumors and metastatic lesions. Consistent with previous reports, high PTK7 expression is associated with reduced disease-free survival and increased metastatic dissemination. Surprisingly, PTK7 is absent from most CTCs and undergoes a cell-autonomous ONtumor/OFFCTC/ONmetastasis switch that can be recapitulated in a xenografted mouse model, in in vitro systems, and a fluidic platform. PTK7-negative cancer cells exhibit increased expression of YAP1-driven genes, senescence-like features, and enhanced resistance to hemodynamic stress following loss of cell-cell and cell-matrix adhesion. This adaptive phenotype depends on metalloproteases, notably ADAM17, whose cleavage activity remodels the CTCs surfaceome. Functionally, the PTK7 OFFCTC state confers enhanced metastatic potential in vivo, and can be pharmacologically suppressed using metalloprotease inhibitors. Collectively, our findings identify a reversible, cell-autonomous, protease-driven surfaceome remodeling program that enables metastatic adaptation during hematogenous dissemination. Highlights / statement of significanceBy investigating potential markers for circulating colorectal tumor cells with strong metastatic potential, we describe a reversible and cell-autonomous remodeling of the circulating tumor cell surfaceome in patients that confers resistance to anoikis and stress induced by entry into the bloodstream. One Sentence SummaryThe dynamic regulation of PTK7 serves as a surrogate marker for tumor cell plasticity, aggressiveness, survival in the bloodstream, and efficiency in forming metastases. Trial registrationCTC colon Cohort: registered on https://ClinicalTrials.gov identifier NCT03256084; date of registration 2017-07-17 B-Org cohort: registered on https://ClinicalTrials.gov NCT05384184; date of registration 2019-06-06 Ethics statement for animal experimentsStudies on animals were conducted in accordance with the current ethical standards of the European Community (Directive 2010/63/EU), the Ethics Committee for Animal Experimentation (CEEA#14) and the French Ministry of Higher Education and Research, which approved and authorized the entire procedure described in this paper (project number APAFIS #35294).

cancer biology↗

bioRxiv2026

Cardiolipin constrains lipid unsaturation during anaerobic adaptation in Escherichia coli

Membrane lipids play a crucial role in cellular adaptation; though their specific functions in bacterial adaptation to oxygen limitation are not yet fully elucidated. Cardiolipin (CL), a signature phospholipid in energy-transducing membranes and a key organizer of mitochondrial respiration, has an unclear role in bacterial anaerobic physiology. Here, genetics, quantitative lipidomics and proteomics, enzymology, and fluorescence imaging were combined to explore how CL facilitates hypoxia adaptation in Escherichia coli. ClsA emerged as the predominant CL synthase under anaerobic conditions, and CL deficiency selectively impaired nitrate-dependent growth, while fermentation and fumarate respiration remained largely unaffected. CL depletion triggered extensive lipidome rewiring during the aerobic-to-anaerobic transition, including increased levels of phosphatidylglycerol, phosphatidic acid, and diacylglycerol, along with a broad enrichment of more unsaturated lipid species. In parallel, proteome remodeling linked CL loss to reduced abundance of proteins involved in anoxic respiration and nitrosative stress management, alongside the induction of membrane stress responses. Interestingly, CL deficiency did not markedly affect cell morphology, nor the spatial distribution or stability of respiratory complexes. This suggests a specialized role in optimizing membrane protein function rather than providing generic structural support. Wild-type lipidome profiling further showed that anaerobiosis induces a shift of lipid species toward higher unsaturation, with only modest class-level changes. Collectively, these results connect lipid remodeling to functional outcomes in vivo, offering mechanistic insights into how bacteria adapt their membranes to maintain energy conservation in fluctuating environments.

microbiology↗

bioRxiv2026

PSMD14 drives melanoma cell survival and MAPK inhibitor resistance through histone H2A deubiquitination

Melanoma progression and resistance to targeted therapies remain major clinical challenges, driven in part by the remarkable phenotypic plasticity of melanoma cells. Identifying molecular mechanisms that couple tumor survival to adaptative drug responses is therefore essential. Here, we identify PSMD14, a proteasome-associated deubiquitinase, as an essential regulator of melanoma plasticity, growth, survival, and therapeutic resistance with strong prognostic significance in metastatic disease. An unbiased siRNA screen targeting the human deubiquitinase family revealed PSMD14 (proteasome 26S subunit, non-ATPase 14) as a top regulator of melanoma cell proliferation. Integrative analyses of DepMap, TCGA, and patient-derived datasets revealed that PSMD14 is frequently upregulated in melanoma, enriched in metastatic lesions, and significantly associated with poor patient outcome. Functional and pharmacological studies demonstrated that genetic depletion or inhibition of PSMD14 suppresses proliferation, clonogenic and long-term growth, and viability of melanoma cells across BRAF-, NRAS-, and NF1-driven genotypes, while inducing DNA damage and apoptosis. Consistently, PSMD14 inhibition markedly reduced tumor growth in Nras and Braf syngeneic mouse models. Mechanistically, we uncover a non-proteolytic role for PSMD14 as an epigenetic regulator of chromatin state. Proteomic and biochemical analyses identified histone H2A as a direct interactor and substrate of PSMD14. PSMD14 deubiquitinates H2A at lysine 119 independently of the proteasome, antagonizing the Polycomb E3 ligase RING1B. Loss of PSMD14 allows the increment of H2AK119 ubiquitination, transcriptional repression of pro-survival genes, including MCL1 and BCL2, and apoptotic cell death, effects rescued by RING1B depletion. Importantly, we demonstrate that the PSMD14-H2A axis governs melanoma adaptation to MAPK pathway inhibition. PSMD14 expression and H2AK119 ubiquitination dynamically correlate with therapeutic response, drug-tolerant persistence, and acquired resistance. Targeting PSMD14 genetically or pharmacologically enhances the efficacy of BRAF and MEK inhibitors, suppresses the emergence of drug-tolerant persister cells, and prevents tumor relapse in vivo. Together, this findings establish PSMD14 as a chromatin-rewiring enzyme that links proteostasis to epigenetic control of melanoma plasticity and therapy resistance, highlighting PSMD14 as a promising biomarker and therapeutic target in aggressive and drug-resistant melanoma.

cancer biology↗

bioRxiv2026

ADAM10 tailors extracellular vesicles for content transfer rather than signaling by contact

Etxtracellular vesicles (EVs) support cell-to-cell communication, both in physiological and pathological contexts and emerge as new biomarkers and potential therapeutics. Yet, despite EVs holding huge promises, our understanding of core mechanisms governing EV signaling remains significantly underdeveloped. Our previous work indicated that syndecans and their cytosolic adaptor syntenin control the biogenesis of a major subset of small EVs (sEVs). Here we show that syndecans control the accumulation of ADAM10 into sEVs. ADAM10 promotes the formation of sEVs enriched in cleaved receptors (reducing sEV corona), supports the sorting of proteins with intracellular functions, and tailors sEVs for the delivery of their internal content, e.g. syntenin, into the cytosol of recipient cells. Conversely, inhibition of ADAM10 favors the production of sEVs bearing full-length, signaling-competent receptors/ligands and enhances contact-dependent signaling. These findings uncover a protease-regulated switch that tailors sEV composition and signaling modality, providing important new mechanistic insights into the core molecular pathways supporting EV-mediated communication.

cell biology↗

bioRxiv2025

Non-canonical TERT function mitigates adipose tissue inflammation in obesity by modulating stem cell-macrophage communication and macrophage states

Background and aimsObesity drives adipose tissue (AT) expansion and chronic inflammation, leading to metabolic dysfunction through adipocyte hypertrophy, impaired ASPC differentiation, immune infiltration, and fibrosis. Stromal vascular remodeling prominently features expansion of Gdf15- and Trem2-expressing lipid-associated macrophages (LAMs), which respond to adipocyte stress and act as lipid scavengers to buffer excess lipids released by adipocytes. Here, we examined macrophage reprogramming in p21+/Tert and p21+/TertCi mice, which express active TERT or its catalytically inactive TERTCi mutant from the endogenous Cdkn1a promoter. ResultsFollowing HFD exposure, conditional expression of TERT or TERTCi resulted in a pronounced downregulation of p21 in macrophage subsets, accompanied by a reduction in AT inflammation. Notably, TERT and TERTCi expression reshaped the adipose-tissue macrophage (ATM) landscape depleting Trem2+ and Gdf15+ LAMs while preserving resident macrophages. This shift was accompanied by marked suppression of the Trem2 transcriptional program and down-regulation of PPAR-{gamma} and NR1H3 in LAMs and by impaired ASPC-LAM signaling pathways that normally drive LAM recruitment and activation. Proteomic profiling further showed that p21+/Tert ASPCs secreted markedly higher levels of proteins associated with non-conventional secretion, while extracellular matrix-associated factors and cytokines/chemokines including key mediators of ASPC-LAM communication such as Ccl2, C3, and Csf1 were substantially reduced. However, only p21+/Tert mice, and not p21+/TertCi mice, exhibited significant metabolic improvements, indicating that macrophage remodeling alone is insufficient to restore systemic metabolic function. Consistent with this, enhanced ASPC expansion and differentiation, supporting improved adipose-tissue remodeling, was observed exclusively in p21+/Tert obese mice. ConclusionsTERT remodels adipose tissue immunity independently of its enzymatic activity, and TERT-driven reprogramming of the ASPC secretome may emerge as a promising strategy to combat obesity-related metabolic dysfunction. HighlightsO_LIConditional expression of TERT or catalytically inactive TERTCi results in the depletion Trem2+ and Gdf15+ LAMs while preserving resident macrophages C_LIO_LITERT and TERTCi expression impairs ASPC-adipocyte/LAM communication pathways that normally drive LAM recruitment and activation. C_LIO_LIIn vitro, TERT conditional expression in ASPCs promotes non-conventional protein secretion and reduces the secretion of key mediators of ASPC-LAM communication C_LIO_LIOnly p21+/Tert mice, and not p21+/TertCi mice, exhibited enhanced ASPC expansion, improved adipose-tissue remodeling, and systemic metabolic benefits, demonstrating that macrophage remodeling alone is insufficient to restore metabolic function. C_LI

physiology↗

bioRxiv2025

TTLL6-mediated Polyglutamylation of PurA Maintains Colonic Crypt Integrity

The tubulin tyrosine ligase-like (TTLL) family comprises enzymes catalyzing posttranslational modifications of tubulin, including glutamylation and glycylation. We previously described a critical role for the monoglycylase TTLL3 in colon. Here, we identified TTLL6 as the predominant polyglutamylase in the colon, specifically expressed in epithelial cells of distal and transverse segments. TTLL6 expression decreases during CRC progression, correlating with poor patient prognosis. Deletion of Ttll6 in mice resulted in elongated colonic crypts, expansion of stem and transit-amplifying compartments, and increased numbers of differentiated epithelial cells. Moreover, Ttll6-deficient mice showed an elevated susceptibility to chemically induced colon carcinogenesis. Notably, we identified the nucleic acid-binding protein PurA as a novel TTLL6 substrate with both proteins mutually required for nuclear localization. Consistently, both nuclear polyglutamylation and PurA were present in the bottom compartment of control colons, but reduced in Ttll6-deficient colons. These findings reveal a TTLL6-PurA axis being critical in maintaining colonic homeostasis.

cell biology↗

bioRxiv2025

Identification of AB8939, a novel synthetic microtubule destabilizer and ALDH inhibitor that overcomes multidrug resistance in tumor cells as a drug candidate for the treatment of refractory acute myeloid leukemia

We identified AB8939, a novel small synthetic molecule that exhibits strong and broad antiproliferative activity against a panel of various cancer cell types with IC50 values in the nanomolar range. In vitro investigations showed that AB8939 is a novel microtubule-targeting agent that interacts with the colchicine-binding site of tubulin. AB8939 disrupts the microtubule network, leading to mitotic arrest in G2/M phase and subsequent apoptosis. Importantly, AB8939 overcomes drug resistance mechanisms, including overexpression of efflux transporters such as P-glycoprotein (P-gp) and aberrant expression of {beta}3-tubulin. AB8939 displays high cytotoxicity against blasts from AML patients, including blasts resistant to cytarabine (Ara-C). In vivo, AB8939 shows strong antitumor activity in MOLM-14, an Ara-C-resistant AML model, as evidenced by tumor growth inhibition and substantial increase in mouse survival. Further experiments performed on an AML PDX TG-AML-36 model demonstrated that AB8939 efficiently kills leukemic stem cells (CD34+/CD38-). Reverse proteomic experiments revealed that AB8939 inhibits ALDH1 and ALDH2, enzymes often overexpressed in tumors and tumor stem cells, thereby favoring tumor progression and relapse. AB8939 is a novel dual-targeting drug that acts on both tubulin and ALDH enzymes, with potential activity against various cancer types, especially refractory AML with complex karyotypes such as those displaying MECOM rearrangement and AML with mutations associated with poor prognosis, such as ASXL1 and TP53.

cell biology↗

bioRxiv2025

Systematic yeast two-hybrid screening identifies novel functions for SET1C/COMPASS

Set1 is the catalytic subunit of SET1C or COMPASS, which methylates histone H3K4 and serves as a scaffold for the association of seven tightly bound polypeptides. We have employed yeast two-hybrid screenings to determine the interactome of Set1 and each subunit, providing a unique resource for exploring known and novel roles of the complex. Our screenings identified a multitude of potential interactors involved in chromatin regulation, DNA replication, meiotic breaks, and Ty transposition, processes previously associated with SET1C. Consistent with Set1 being an RNA-binding protein, the screens link SET1C to multiple aspects of RNA biogenesis, including pre-mRNA splicing and polyadenylation. The results reveal that several importins are candidate interactors of Set1, along with RGG motif-containing proteins, providing insights into the mechanisms by which Set1 moves between cytoplasmic and nuclear compartments. We further reveal that reconstituted SET1C interacts with the AT hook domain of the chromatin remodeler Snf2 and methylates multiple arginines within this domain. In vivo, we report that the ARTSTRGR AT-hook motif is methylated in a Set1-dependent manner revealing new interplay between lysine and arginine methylation.

molecular biology↗

bioRxiv2025

Deciphering the dynamic proteome of multiciliated cells

Multiciliated cells (MCCs) are essential for generating directional fluid flow across specialized epithelia in various vertebrate organs. MCC differentiation involves a unique, tightly regulated program characterized by massive centriole amplification, independently of DNA replication. Although much is known about the transcriptional control of MCC development, insights into proteome dynamics have been limited due to the lack of suitable models. In this study, we report the generation of a stable inducible MCC line, derived from Xenopus laevis A6 kidney epithelial cells. Upon induction of the MCC master regulator Multicilin (MCI), most A6-MCI cells synchronously differentiate into mature MCCs in 48 hours. Using this novel resource, custom antibodies and super-resolution imaging, we characterized Xenopus deuterosomes, the platforms that allow massive centriole synthesis in vertebrate MCCs. We performed a detailed proteomic profiling throughout MCC differentiation, and uncovered previously uncharacterized regulators. Notably, we highlight a critical role for CDK7 in MCC differentiation in both Xenopus and human systems. Our work provides a valuable resource for mechanistic studies of MCC biology and opens avenues to identify novel therapeutic targets for motile ciliopathies.

cell biology↗

bioRxiv2024

USP9X is a mechanosensitive deubiquitinase that controls tumor cell invasiveness and drug response through YAP stabilization

Post-translational modification by ubiquitin is crucial for protein turnover. Deubiquitinases (DUBs) remove ubiquitin chains from target proteins to prevent their degradation by the proteasome, thus acting as gatekeepers of protein homeostasis alongside the ubiquitin-proteasome system (UPS). Tumor cells exhibit remarkable plasticity, enabling them to adapt to anticancer treatments and the conditions of the tumor microenvironment, including mechanical cues from the extracellular matrix (ECM). However, the role of DUBs in mechanotransduction remains unexplored. To identify DUBs involved in cancer cell mechanosignaling, we used melanoma cells grown on collagen matrices with varying stiffnesses and an activity-based ubiquitin probe to profile DUB activities. Our approach, combined with quantitative proteomics, revealed that ubiquitin-specific protease 9X (USP9X) is sensitive to ECM stiffness through discoidin domain receptors (DDR)/actomyosin signaling pathway. In silico analysis further indicated that the mechanosensor YAP is part of the USP9X interactome, and USP9X expression correlates with the YAP transcriptional signature in melanoma. We hypothesized that mechanical signals regulate YAP levels through USP9X DUB activity. Consistently, low collagen stiffness reduced YAP expression, and siRNA-mediated depletion or pharmacological inhibition of USP9X decreased YAP protein expression in tumor cells. Conversely, knockdown of the ubiquitin E3 ligase {beta}TrCP increased YAP protein levels. Affinity purification of polyubiquitinated proteins using Tandem Ubiquitin Binding Entities (TUBEs) showed that combined USP9X and proteasome inhibition increased YAP poly-ubiquitination, revealing that USP9X deubiquitinates YAP to prevent its proteasomal degradation. Targeting USP9X impaired stiffness-mediated responses, including YAP nuclear translocation and transcriptional activity, cell migration and invasion, and drug resistance. An experimental metastasis assay showed that stable knockdown of USP9X impaired melanoma cell lung colonization. Finally, targeting USP9X in a syngeneic BRAF-mutant melanoma model counteracted targeted therapy-induced ECM remodeling, enhanced treatment efficacy, and delayed tumor relapse. Our findings reveal a novel role of USP9X in cancer cell mechanobiology and drug resistance through stiffness-dependent stabilization of the oncoprotein YAP, proposing USP9X as a targetable "mechano-DUB" in cancer.

cancer biology↗

bioRxiv2023

Downregulation of stromal syntenin sustains AML development

The crosstalk between cancer and stromal cells plays a critical role in tumor progression. Syntenin is a small scaffold protein involved in the regulation of intercellular communication that is emerging as a target for cancer therapy. Here, we show that certain aggressive forms of acute myeloid leukemia (AML) reduce the expression of syntenin in bone marrow stromal cells (BMSC), stromal syntenin deficiency, in turn, generating a pro-tumoral microenvironment. From serial transplantations in mice and co-culture experiments, we conclude that syntenin-deficient BMSC stimulate AML aggressiveness by promoting AML cell survival and protein synthesis. This pro-tumoral activity is supported by increased expression of endoglin, a classical marker of BMSC, which in trans stimulates AML translational activity. In short, our study reveals a vicious signaling loop potentially at the heart of AML-stroma crosstalk and unsuspected tumor-suppressive effects of syntenin that need to be considered during systemic targeting of syntenin in cancer therapy.

cancer biology↗

bioRxiv2022

Integrative study of mitochondrial dysfunction in skeletal muscle during pancreatic cancer cachexia

AimsPancreatic Ductal AdenoCarcinoma (PDAC), the most common pancreatic cancer, is a deadly cancer, often diagnosed late and resistant to current therapies. PDAC patients are frequently affected by cachexia characterized by muscle mass and strength loss (sarcopenia) contributing to patient frailty and poor therapeutic response. The objective of this work was to investigate the mechanisms underlying mitochondrial remodeling in the cachectic skeletal muscle, through an integrative study combining functional, morphological and omics-based evaluation of gastrocnemius muscle from genetically-engineered mice developing autochthonous pancreatic tumor and cachexia (KIC GEMM). ResultsKIC cachectic PDAC mice exhibit severe sarcopenia with loss of muscle mass and strength associated with reduced muscle fibers size and induction of protein degradation processes. Mitochondria in PDAC atrophied muscles show reduced respiratory capacities and structural alterations, associated with deregulation of oxidative phosphorylation and mitochondrial dynamics pathways. Beyond the metabolic pathways known to be altered in sarcopenic muscle (carbohydrates, proteins, and redox), lipid and nucleic acid metabolisms are also affected. While the number of mitochondria per cell is not altered, mitochondrial mass is decreased by a factor of 2 and the mitochondrial DNA by a factor of 3, suggesting a defect in mitochondrial genome homeostasis. InnovationMuscle atrophy is associated with strong mitochondrial metabolic defects that are not limited to carbohydrate, protein and redox metabolism, but concern also lipid and nucleic acid metabolism. ConclusionThis work provides a framework to guide towards the most relevant targets in the clinic to limit PDAC-induced cachexia, in particular mitochondrial fatty acid metabolism.

cancer biology↗

bioRxiv2021

SLX4 dampens MutSα-dependent mismatch repair

The tumour suppressor SLX4 plays multiple roles in the maintenance of genome stability, acting as a scaffold for structure-specific endonucleases and other DNA repair proteins. It directly interacts with the mismatch repair (MMR) protein MSH2 but the significance of this interaction remained unknown until recent findings showing that MutS{beta} (MSH2-MSH3) stimulates in vitro the SLX4-dependent Holliday junction resolvase activity. Here, we characterize the mode of interaction between SLX4 and MSH2, which relies on an MSH2-interacting peptide (SHIP box) that drives interaction of SLX4 with both MutS{beta} and MutS (MSH2-MSH6). While we show that this MSH2 binding domain is dispensable for the well-established role of SLX4 in interstrand crosslink repair, we find that it mediates inhibition of MutS-dependent MMR by SLX4, unravelling an unanticipated function of SLX4.

molecular biology↗

bioRxiv2021

The serine/threonine kinase MINK1 directly regulates the function of promigratory proteins

Upregulation of the developmental Wnt/planar cell polarity pathway is observed in many cancers and is associated with cancer development at early and late stages. We recently showed that PRICKLE1 and VANGL2, two core Wnt/PCP components, are overexpressed in triple negative breast cancer and associated with poor prognosis. PRICKLE1 is a cytoplasmic protein phosphorylated by the poorly described serine/threonine kinase MINK1 which triggers its localization at the plasma membrane, a key step for its function. Knockdown experiments have demonstrated that MINK1 and PRICKLE1 contribute to TNBC cell motility and spreading in vitro and in vivo. However, the identity of MINK1 substrates and the role of MINK1 enzymatic activity in this process have not yet been addressed issues. We carried out a phosphoproteomic strategy and identified novel MINK1 substrates including LL5{beta}. LL5{beta} is a membrane scaffold molecule that anchors microtubules at the cell cortex through its association with the plus-end MT proteins CLASPs to trigger focal adhesion disassembly. LL5{beta} is a prominent member of the MINK1-PRICKLE1 protein complex and is directly phosphorylated by MINK1 that promotes its interaction with CLASP. Using a kinase inhibitor, we demonstrate that the enzymatic activity of MINK1 is involved in the protein complex assembly and localization, and cell migration. Analysis of gene expression data show that the concomitant up-regulation of PRICKLE1 and LL5{beta} mRNA levels encoding MINK1 substrates is associated with a poor metastasis-free survival for TNBC patients. Altogether, our results suggest that MINK1 may represent a potential target in TNBC.

cell biology↗

bioRxiv2021

Insights into animal septins using recombinant human septin octamers with distinct SEPT9 isoforms

Septin GTP-binding proteins contribute essential biological functions that range from the establishment of cell polarity to animal tissue morphogenesis. Human septins in cells form hetero-octameric septin complexes containing the ubiquitously expressed SEPT9. Despite the established role of SEPT9 in mammalian development and human pathophysiology, biochemical and biophysical studies have relied on monomeric SEPT9 thus not recapitulating its native assembly into hetero-octameric complexes. We established a protocol that enabled the first-time isolation of recombinant human septin octamers containing distinct SEPT9 isoforms. A combination of biochemical and biophysical assays confirmed the octameric nature of the isolated complexes in solution. Reconstitution studies showed that octamers with either a long or a short SEPT9 isoform form filament assemblies, and can directly bind and cross-link actin filaments, raising the possibility that septin-decorated actin structures in cells reflect direct actin-septin interactions. Recombinant SEPT9-containing octamers will make it possible to design cell-free assays to dissect the complex interactions of septins with cell membranes and the actin/microtubule cytoskeleton. SummaryHuman septins in cells form hetero-octameric complexes containing the ubiquitously expressed SEPT9. Iv et al. describe the first-time isolation of recombinant human septin octamers with distinct SEPT9 isoforms. Reconstitution studies show that octamers with either a long or a short SEPT9 isoform form higher-order filament assemblies and directly bind and cross-link actin filaments.

cell biology↗

bioRxiv2020

PLD2-phosphatidic acid recruit ESCRT-I to late endosomes for exosome biogenesis.

It is important to understand the biogenesis of exosomes, extracellular vesicles of endosomal origin controlling cell-to-cell communication. We previously reported that Phospholipase D2 (PLD2) supports late endosome (LE) budding and the biogenesis of syntenin-dependent exosomes. Here, we reveal that PLD2 has a broader generic effect on exosome production. Combining gain- and loss-of-function experiments, proteomics, microscopy and lipid-binding studies with reconstituted liposomes mimicking LE, we show that: (i) PLD2 activity controls the recruitment of MVB12B to LE and the exosomal secretion of ESCRT-I; (ii) loss-of-MVB12B phenocopies loss-of-PLD2, similarly affecting LE budding, the number of exosomes released and exosome loading with cargo; (iii) MVB12B MABP domain directly interacts with phosphatidic acid, the product of PLD2. We therefore propose that PLD2 and phosphatidic acid support ESCRT-I recruitment to LE for the formation of exosomes. This work highlights a major unsuspected piece of the molecular framework supporting LE and exosome biogenesis.

cell biology↗