Biology subjects

Audebert, S.

Publications and source records attributed to Audebert, S..

29 records · Page 2Linked to original sources

bioRxiv2020

A novel Golgi-associated Vangl2 translational variant required for PCP regulation in vertebrates

First described in Drosophila melanogaster, planar cell polarity (PCP) is a developmental process essential for embryogenesis and development of polarized structures in Metazoans. This signaling pathway involves a set of evolutionarily conserved genes encoding transmembrane (Vangl, Frizzled, Celsr) and cytoplasmic (Prickle, Dishevelled) molecules. Vangl2 is of major importance in embryonic development as illustrated by its pivotal role during neural tube closure in human, mouse, Xenopus and zebrafish embryos. The regulated and poorly understood traffic of Vangl2 to the plasma membrane is a key event for its function in development. Here we report on the molecular and functional characterization of a novel 569-amino acid N-terminally extended Vangl2 isoform, Vangl2-Long, that arises from an alternative non-AUG translation initiation site, lying 144 base pair upstream of the conventional start codon. While missing in Vangl1 paralogs and in all invertebrates, including Drosophila melanogaster, this N-terminal extension is conserved in all vertebrate Vangl2 sequences and confers a subcellular localization in the Golgi apparatus, probably as a result of an extended retention time in this organelle. Vangl2-Long belongs to a multimeric complex with Vangl1 and Vangl2 and we show that its down-regulation leads to severe PCP-related phenotypes in Xenopus embryos, including shorter body axis and neural tube closure defects. Altogether, our study unveils a novel level of complexity in Vangl2 expression, trafficking and function.

cell biology↗

bioRxiv2020

E-cadherin: Unexpected actor of invadopodia formation in pancreatic cancer

Graphical abstract BackgroundThe appearance of hybrid epithelial-mesenchymal (E/M) cells expressing E-cadherin is favourable for the establishment of pro-invasive function. However, the molecular mechanism and potential roles of E-cadherin in cancer cell invasion stay unexplored. MethodsWe used models of E/M hybrid cell lines, tissues sections and patient-derived xenografts from a multi-center clinical trial. E-cadherin involvement in invadopodia formation was assessed using a gelatin-FITC degradation assay. Mechanistic studies were performed by using proteomic analysis, siRNA strategy and proximity ligation assay. ResultsWe showed that E-cadherin is a critical component of invadopodia. This unexpected localization results from a synergistic trafficking of E-cadherin and MT1-MMP through Rab vesicle-dependent pathway. Modulation of E-cadherin expression or activation impacted invadopodia formation. Moreover, colocalization of E-cadherin and Actin in [-]ring structures|| as precursor of invadopodia reveals that E-cadherin is required for invadopodia structuration. ConclusionE-cadherin, initially localized in the adherens junctions could be recycled to nascent invadopodia where it will interact with several components such as Arp2/3, Cortactin or MT1-MMP. The trans-adhesive properties of E-cadherin are therefore essential for structuring invadopodia. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=152 SRC="FIGDIR/small/332783v2_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@13b08e8org.highwire.dtl.DTLVardef@c5d19eorg.highwire.dtl.DTLVardef@14511cforg.highwire.dtl.DTLVardef@19436eb_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2020

Self-organized Toll-8/Cirl GPCR asymmetry drives planar polarized cell contractility

During development, interfaces between cells with distinct genetic identities elicit signals to organize local cell behaviors driving tissue morphogenesis. The Drosophila embryonic axis extension requires planar polarized enrichment of Myosin-II powering oriented cell intercalations. Myosin-II levels are quantitatively controlled by G protein-coupled receptor (GPCR) signaling whereas Myosin-II polarity requires patterned expression of several Toll receptors. How Toll receptors polarizes Myosin-II, and how this involves GPCRs, remain unknown. Here we report that differential expression of a single Toll receptor, Toll-8, polarizes Myosin-II via a novel binding partner, the adhesion GPCR Cirl/Latrophilin. Asymmetric expression of Cirl is sufficient to enrich Myosin-II and Cirl localization is asymmetric at Toll-8 expression boundaries. Exploring the process dynamically, we reveal that Toll-8 and Cirl exhibit mutually dependent planar polarity in response to quantitative differences in Toll-8 expression between neighboring cells. Collectively, we propose that a novel cell surface protein complex Toll-8/Cirl self-organizes to generate local asymmetric interfaces essential for planar polarization of contractile interfaces.

developmental biology↗

bioRxiv2020

Biophysical forces rewire cell metabolism to guide microtubule-dependent cell mechanics

Mechanical signals regulate cell shape and influence cell metabolism and behavior. Cells withstand external forces by adjusting the stiffness of its cytoskeleton. Microtubules (MTs) act as compression-bearing elements in response to mechanical cues. Therefore, MT dynamics affect cell mechanics. Yet, how mechanical loads control MT dynamics to adjust cell mechanics to its locally constrained environment has remained unclear. Here, we show that mechanical forces rewire glutamine metabolism to promote MT glutamylation and force cell mechanics, thereby modulating mechanodependent cell functions. Pharmacologic inhibition of glutamine metabolism decreased MT glutamylation and affected their mechanical stabilization. Similarly, depletion of the tubulin glutamylase TTLL4 or overexpression of tubulin mutants lacking glutamylation site(s) increased MT dynamics, cell compliance and contractility, and thereby impacted cell spreading, proliferation and migration. Together our results indicate that mechanical cues sustain cell mechanics through glutaminolysis-dependent MT glutamylation, linking cell metabolism to MT dynamics and cell mechanics. Furthermore, our results decipher part of the enigmatic tubulin code that coordinates the fine tunable properties of MT mechanics, allowing cells to adjust the stiffness of their cytoskeleton to the mechanical loads of their environment.

cell biology↗

bioRxiv2019

A proximity-labeling proteomic approach to investigate invadopodia molecular landscape in breast cancer cells

Metastatic progression is the leading cause of mortality in breast cancer. Invasive tumor cells develop invadopodia to travel through basement membranes and the interstitial matrix. Substantial efforts have been made to characterize invadopodia molecular composition. However, their full molecular identity is still missing due to the difficulty in isolating them. To fill this gap, we developed a non-hypothesis driven proteomic approach based on the BioID proximity biotinylation technology, using the invadopodia-specific protein Tks5 fused to the promiscuous biotin ligase BirA* as bait. In invasive breast cancer cells, Tks5 fusion concentrated to invadopodia and selectively biotinylated invadopodia components, in contrast to a fusion which lacked the membrane-targeting PX domain (Tks5{beta}). Biotinylated proteins were isolated by affinity capture and identified by mass spectrometry. We identified known invadopodia components, revealing the pertinence of our strategy. Furthermore, we observed that Tks5 newly identified close neighbors belonged to a biologically relevant network centered on actin cytoskeleton organization. Analysis of Tks5{beta} interactome demonstrated that some partners bound Tks5 before its recruitment to invadopodia. Thus, the present strategy allowed us to identify novel Tks5 partners that were not identified by traditional approaches and could help get a more comprehensive picture of invadopodia molecular landscape.

cancer biology↗

bioRxiv2019

iASPP contributes to cortex rigidity, astral microtubule capture and mitotic spindle positioning

The microtubule plus-end binding protein EB1 is the core of a complex protein network which regulates microtubule dynamics during important biological processes such as cell motility and mitosis. We found that iASPP, an inhibitor of p53 and predicted regulatory subunit of the PP1 phosphatase, associates with EB1 at microtubule plus-ends via a SxIP motif. iASPP silencing or mutation of the SxIP motif led to defective microtubule capture at the leading edge of migrating cells, and at the cortex of mitotic cells leading to abnormal positioning of the mitotic spindle. These effects were recapitulated by the knockdown of Myosin-Ic (Myo1c), identified as a novel partner of iASPP. Moreover, iASPP or Myo1c knockdown cells failed to round up during mitosis because of defective cortical rigidity. We propose that iASPP, together with EB1 and Myo1c, contributes to mitotic cell cortex rigidity, allowing astral microtubule capture and appropriate positioning of the mitotic spindle.

cell biology↗

bioRxiv2019

Targeting DDR1 and DDR2 overcomes matrix-mediated melanoma cell adaptation to BRAF-targeted therapy

Resistance to BRAF and MEK inhibitors in BRAFV600E mutant melanomas remains a major obstacle that limits patient benefit. Microenvironment components including the extracellular matrix (ECM) can support tumor cell adaptation and tolerance to targeted therapies, however the underlying mechanisms remain poorly understood. Here, we investigated the process of matrix-mediated drug resistance (MM-DR) in response to BRAF inhibition in melanoma. We demonstrate that physical and structural cues from fibroblast-derived ECM abrogate anti-proliferative responses to BRAF/MEK inhibition. MM-DR is mediated by the drug-induced clustering of DDR1 and DDR2, two tyrosine kinase collagen receptors. Genetic depletion and pharmacological inhibition of DDR1 and DDR2 overcome ECM-mediated resistance to BRAF inhibition. In melanoma xenografts, targeting DDRs by Imatinib enhances BRAF inhibitor efficacy, counteracts drug-induced collagen remodeling and delays tumor relapse. Mechanistically, DDR-mediated MM-DR fosters a targetable pro-survival NIK/IKK/NF-{kappa}B2 pathway. Our study reveals a novel role of collagen-rich matrix and DDRs in tumor cell adaptation and therapy resistance, thus providing important insights into environment-mediated drug resistance and a pre-clinical rationale for targeting DDR1/2 signaling in combination with BRAF-targeted therapy in melanoma.

cancer biology↗

bioRxiv2019

UFMylation of MRE11 is essential for telomere length and hematopoietic stem cell survival

Genetic studies using knockout mouse models provide strong evidence for the essential role of the ubiquitin-like protein UFM1 for hematopoiesis, especially erythroid development, yet its biological roles in this process are largely unknown. Here we have identified a UFL1-dependent UFMylation of the MRE11 nuclease on the K281 and K282 residues. We show that Hela cells lacking the specific UFM1 E3 ligase display severe telomere shortening. We further demonstrate either by deleting UFM1 or by mutating MRE11 UFMylation sites that preventing MRE11 UFMylation impacts its interaction with the telomere protein TRF2. However, the MRE11 function in double-strand-break repair remains intact. We validate these results in vivo by showing that Zebrafish knockouts for the genes ufl1 and ufm1 have shorter telomeres in hematopoietic cells. Here we present UFMylation has a new mechanisms of regulation for telomere length maintenance with a role in hematopoiesis. Key pointsModification of MRE11 by UFM1 regulates telomere maintenance and cell death in HSCs Scientific categoryUFMylation, telomere maintenance, hematopoietic stem cell survival.

molecular biology↗

bioRxiv2019

CRB2 controls primary ciliogenesis in association with PAR6α, HOOK2 and RAB8A

Ciliogenesis is an essential process in animal development and physiology and when affected, the origin of severe pathologies called ciliopathies. CRB2 has been recently implicated when mutated in several pathologies such as retina degeneration and a ciliopathy-like syndrome. Here, we have investigated the role of CRB2 in primary ciliogenesis and showed that CRB2 depletion blocks the formation of the ciliary vesicle after activation of the mother centriole, indicating a defect in either transport or anchoring of the ciliary vesicle. CRB2 is accumulated in intracellular vesicles in the vicinity of the centrosome and we showed here that CRB2 forms a complex made of HOOK2 and PAR6, two proteins important for primary ciliogenesis or centrosome integrity. In addition, CRB2 interacts with RAB8A which over-expression rescued CRB2 knockdown. All together, these findings indicate that CRB2 regulates a membrane transport step essential for the formation of the ciliary vesicle.

cell biology↗

bioRxiv2019

Integrative proteomic and phosphoproteomic profiling of prostate cell lines

BackgroundProstate cancer is a major public health issue, mainly because patients relapse after androgen deprivation therapy. Proteomic strategies, aiming to reflect the functional activity of cells, are nowadays among the leading approaches to tackle the challenges not only of better diagnosis, but also of unraveling mechanistic details related to disease etiology and progression.\n\nMethodsWe conducted here a large SILAC-based Mass Spectrometry experiment to map the proteomes and phosphoproteomes of four widely used prostate cell lines, namely PNT1A, LNCaP, DU145 and PC3, representative of different cancerous and hormonal status.\n\nResultsWe identified more than 3000 proteins and phosphosites, from which we quantified more than 1000 proteins and 500 phosphosites after stringent filtering. Extensive exploration of this proteomics and phosphoproteomics dataset allowed characterizing housekeeping as well as cell-line specific proteins, phosphosites and functional features of each cell line. In addition, by comparing the sensitive and resistant cell lines, we identified protein and phosphosites differentially expressed in the resistance context. Further data integration in a molecular network highlighted the differentially expressed pathways, in particular migration and invasion, RNA splicing, DNA damage repair response and transcription regulation.\n\nConclusionsOverall, this study proposes a valuable resource toward the characterization of proteome and phosphoproteome of four widely used prostate cell lines and reveals candidates to be involved in prostate cancer progression for further experimental validation.

bioinformatics↗

bioRxiv2018

ECT2 associated to PRICKLE1 are poor-prognosis markers in triple-negative breast cancer

BackgroundTriple-negative breast cancers are poor-prognosis tumors characterized by absence of molecular signature and are chemotherapy is still the only systemic treatment. Currently, research focus to identify biomarkers that may be usable for prognosis and/or for treatment, notably among the proteins involved in cell migration and metastatic capacity.\n\nMethodsWe used proteomic approach to identify protein complexes associated to PRICKLE1 and the mRNA expression level of the corresponding genes in a retrospective series of 8,982 clinically annotated patients with invasive primary breast cancer were assessed. Then, we characterize molecularly the interaction between PRICKLE1 and the guanine nucleotide exchange factor ECT2. Finally, experiments in Xenopus have been carrying out to determine their evolutionary conserved interaction.\n\nResultsWe have identified a network of proteins interacting with the prometastatic scaffold protein PRICKLE1 that includes several small G-protein regulators involved in cell migration and metastasis. Combined analysis expression of PRICKLE1 and small G-protein regulators expression has a strong prognostic value in TNBC. We show that PRICKLE1 controls the activity of ECT2 on RAC1 signaling, a pathway required for cancer cell dissemination.\n\nConclusionsThis work supports the idea that promigratory proteins, which are overexpressed in cancerous epithelium, are suitable pharmaceutical targets.

cancer biology↗