ahmed EL MARJOU - Academia.edu (original) (raw)

Papers by ahmed EL MARJOU

Cancer immunology research, Nov 30, 2023

Frontiers in Immunology, Feb 2, 2023

Introduction: Spondylarthritis (SpA) development in HLA-B27/human b2microglobulin transgenic rat ... more Introduction: Spondylarthritis (SpA) development in HLA-B27/human b2microglobulin transgenic rat (B27-rat) is correlated with altered conventional dendritic cell (cDC) function that promotes an inflammatory pattern of CD4+T cells, including a biased expansion of pro-inflammatory Th 17 population and imbalance of regulatory T cells cytokine profile. Transcriptomic analysis revealed that cDCs from B27-rats under express IL-27, an anti-inflammatory cytokine which induces the differentiation of IL-10 + regulatory T cells and inhibits Th 17 cells. Methods: Here, we first investigated whether in vitro addition of exogenous IL-27 could reverse the inflammatory pattern observed in CD4 + T cells. Next, we performed preclinical assay using IL-27 to investigate whether in vivo treatment could prevent SpA development in B27-rats. Results: in vitro addition of IL-27 to cocultures of cDCs and CD4 + T cell subsets from B27-rats reduced IL-17 and enhanced IL-10 production by T cells. Likewise, IL-27 inhibited the production of IL-17 by CD4 + T cells from SpA Frontiers in Immunology frontiersin.org 01

KIF20A is a critical kinesin for cell division and a promising anti-cancer drug target. The mecha... more KIF20A is a critical kinesin for cell division and a promising anti-cancer drug target. The mechanisms underlying its cellular roles remain elusive. Interestingly, unusual coupling between the nucleotide- and microtubule-binding sites of this kinesin-6 has been reported but little is known about how its divergent sequence leads to atypical motility properties. We present here the first high-resolution structure of its motor domain that delineates the highly unusual structural features of this motor, including a long L6 insertion that integrates into the core of the motor domain and that drastically affects allostery and ATPase activity. Together with the high-resolution cryo-EM microtubule-bound KIF20A structure that reveal the microtubule-binding interface, we dissect the peculiarities of the KIF20A sequence that work to favor fast dissociation of ADP, particularly in contrast to other kinesins. Structural and functional insights from the KIF20A pre-power stroke conformation thus h...

Angewandte Chemie International Edition

Angewandte Chemie

Interferons (IFN) are cytokines which, upon binding to cell surface receptors, trigger a series o... more Interferons (IFN) are cytokines which, upon binding to cell surface receptors, trigger a series of downstream biochemical events including Janus Kinase (JAK) activation, phosphorylation of Signal Transducer and Activator of Transcription protein (STAT), translocation of pSTAT to the nucleus and transcriptional activation. Dysregulated IFN signalling has been linked to cancer progression and auto-immune diseases. Here, we report the serendipitous discovery of a small molecule that blocks IFNγ activation of JAK-STAT signalling. Further lead optimisation gave rise to a potent and more selective analogue that exerts its activity by a mechanism consistent with direct IFNγ targeting in vitro, which reduces bleeding in model of haemorrhagic colitis in vivo. This first-in-class small molecule also inhibits type I and III IFN-induced STAT phosphorylation in vitro. Our work provides the basis for the development of pan-IFN inhibitory drugs.

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JNCI: Journal of the National Cancer Institute, 2020

Background Uveal melanoma (UM) arises from malignant transformation of melanocytes in the uveal t... more Background Uveal melanoma (UM) arises from malignant transformation of melanocytes in the uveal tract of the eye. This rare tumor has a poor outcome with frequent chemo-resistant liver metastases. BAP1 is the only known predisposing gene for UM. UMs are generally characterized by low tumor mutation burden, but some UMs display a high level of CpG>TpG mutations associated with MBD4 inactivation. Here, we explored the incidence of germline MBD4 variants in a consecutive series of 1093 primary UM case patients and a series of 192 UM tumors with monosomy 3 (M3). Methods We performed MBD4 targeted sequencing on pooled germline (n = 1093) and tumor (n = 192) DNA samples of UM patients. MBD4 variants (n = 28) were validated by Sanger sequencing. We performed whole-exome sequencing on available tumor samples harboring MBD4 variants (n = 9). Variants of unknown pathogenicity were further functionally assessed. Results We identified 8 deleterious MBD4 mutations in the consecutive UM series...

Science, 2019

Commensals rule the MAITrix Mucosal-associated invariant T (MAIT) cells play an important role in... more Commensals rule the MAITrix Mucosal-associated invariant T (MAIT) cells play an important role in mucosal homeostasis. MAIT cells recognize microbial small molecules presented by the major histocompatibility complex class Ib molecule MR1. MAIT cells are absent in germ-free mice, and the mechanisms by which microbiota control MAIT cell development are unknown (see the Perspective by Oh and Unutmaz). Legoux et al. show that, in mice, development of MAIT cells within the thymus is governed by the bacterial product 5-(2-oxopropylideneamino)-6- d -ribitylaminouracil, which rapidly traffics from the mucosa to the thymus, where it is captured by MR1 and presented to developing MAIT cells. Constantinides et al. report that MAIT cell induction only occurs during a limited, early-life window and requires exposure to defined microbes that produce riboflavin derivatives. Continual interactions between MAIT cells and commensals in the skin modulates tissue repair functions. Together, these paper...

SummaryThe BRCA2 tumor suppressor protein is involved in the maintenance of genome integrity thro... more SummaryThe BRCA2 tumor suppressor protein is involved in the maintenance of genome integrity through its role in homologous recombination. In mitosis, BRCA2 is phosphorylated by Polo-like kinase 1 (PLK1). Here we describe how this phosphorylation contributes to the control of mitosis. We identified two highly conserved phosphorylation sites at S193 and T207 of BRCA2. Phosphorylated-T207 is a bona fide docking site for PLK1 as illustrated by the crystal structure of the BRCA2 peptide bound to PLK1 Polo-box domain. We found that BRCA2 bound to PLK1 forms a complex with the phosphatase PP2A and phosphorylated-BUBR1. Reducing BRCA2 binding to PLK1, as observed in BRCA2 breast cancer variants S206C and T207A, alters the tetrameric complex resulting in misaligned chromosomes, faulty chromosome segregation and aneuploidy. We thus reveal a direct role of BRCA2 in the alignment of chromosomes, distinct from its DNA repair function, with important consequences on chromosome stability. These f...

eLife, 2018

The two Ral GTPases, RalA and RalB, have crucial roles downstream Ras oncoproteins in human cance... more The two Ral GTPases, RalA and RalB, have crucial roles downstream Ras oncoproteins in human cancers; in particular, RalB is involved in invasion and metastasis. However, therapies targeting Ral signalling are not available yet. By a novel optogenetic approach, we found that light-controlled activation of Ral at plasma-membrane promotes the recruitment of the Wave Regulatory Complex (WRC) via its effector exocyst, with consequent induction of protrusions and invasion. We show that active Ras signals to RalB via two RalGEFs (Guanine nucleotide Exchange Factors), RGL1 and RGL2, to foster invasiveness; RalB contribution appears to be more important than that of MAPK and PI3K pathways. Moreover, on the clinical side, we uncovered a potential role of RalB in human breast cancers by determining that RalB expression at protein level increases in a manner consistent with progression toward metastasis. This work highlights the Ras-RGL1/2-RalB-exocyst-WRC axis as appealing target for novel ant...

Http Www Theses Fr, 2001

Les anomalies structurales et fonctionnelles de plusieurs recepteurs a activite tyrosine kinase s... more Les anomalies structurales et fonctionnelles de plusieurs recepteurs a activite tyrosine kinase sont associees a plusieurs cancers chez l’homme. Les etudes conjointes sur les biopsies de tumeurs humaines, sur les lignees cellulaires derivees de ces tumeurs et sur les modeles animaux developpant ces cancers sont d'une importance capitale. Elles permettent de comprendre les mecanismes moleculaires qui sont a la base des deregulations contribuant a l'apparition des cancers. Lors de mon projet de these, j'ai utilise le modele murin de cancer de la vessie chimioinduit. Le traitement par le BBN des souris B6D2F2 et C57BL/6 induit des tumeurs infiltrantes tres proches des tumeurs de la vessie humaines. J'ai mis en evidence une activation du recepteura l'EGFR dans les tumeurs de la vessie. Ces tumeurs coex priment l'ARNm de l'EGFR, et plusieurs de ses ligands (TGFα, HB-EGF, AR , BTC) suggerant l'activation de boucles autocrines. Plusieurs arguments sont en faveur de cette hypothese. 1) Les lignees derivees de ces carcinomes sont capables de proliferer dans un milieu sans serum. 2) Le traitement de ces lignees par un inhibiteur de l'activite tyrosine kinase de l'EGFR et par des anticorps diriges contre le domaine extracellulaire de ce recepteur inhibent la phosphorylation de ce recepteur et la proliferation cellulaire. 3) Le milieu conditionne de ces cellules contient des facteurs capables de stimuler la proliferation de la lignee NBTII dependante de l'activite de l'EGFR. Comme les souris sauvages, les souris dont les genes TGFα ont ete invalides (souris KO-TGFα) traitees par le BBN developpent des tumeurs de la vessie. Ces resultats suggerent que le TGFα n'est pas implique dans la progression tumorale du cancer de la vessie. L'analyse de l'urothelium des souris sauvages et KO TGFα traitees pendant un temps court par le BBN montre que l'expression de plusieurs autres ligands de l'EGFR est induite tres precocement. Ces expressions s'accompagnent egalement de perturbations dans l'expression de certains regulateurs du cycle cellulaire comme la cycline Dl et la p27Kip1. L'ensemble des resultats de ce travail confirme l'importance de l'expression de l'EGFR observee dans les tumeurs humaines. L'activite de ce recepteur est probablement impliquee dans les stades precoces de la progression tumorale du cancer de la vessie. Dans le deuxieme volet de ma these, j'ai contribue a l'etude du role du FGFR2 IIIb dans les tumeurs de la vessie. Ce recepteur serait un frein a la progression tumorale. En effet d'une part, la perte de ce recepteur est associee a des tumeurs de mauvais pronostic. D'autre part, son introduction dans des lignees cellulaires de la vessie n'exprimant pas ce recepteur reduit leur proliferation in vitro et leur tumorigenicite chez les souris "nude". L'activation de certains recepteurs comme l'EGFR et la perte d'autres recepteurs comme FGFR2 IIIb contribuent a l'emergence et a la progression des tumeurs de la vessie.

Archives of biochemistry and biophysics, Jan 17, 2015

Cadherin-mediated adhesion plays a crucial role in multicellular organisms. Dysfunction within th... more Cadherin-mediated adhesion plays a crucial role in multicellular organisms. Dysfunction within this adhesion system has major consequences in many pathologies, including cancer invasion and metastasis. However, mechanisms controlling cadherin recognition and adhesive strengthening are only partially understood. Here, we investigated the homophilic interactions and mechanical stability of the extracellular (EC) domains of E-cadherin and cadherin 7 using atomic force microscopy and magnetic tweezers. Besides exhibiting stronger interactions, E-cadherin also showed more efficient force-induced self-strengthening of interactions than cadherin 7. In addition, the distributions of the unbinding forces for both cadherins partially overlap with those of the unfolding forces, indicating that partial unfolding/deformation of the cadherin EC domains may take place during their homophilic interactions. These conformational changes may be involved in cadherins physiology function and contribute ...

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Methods in Enzymology, 2001

ABSTRACT This chapter discusses the expression, purification, and biochemical properties of Ypt/R... more ABSTRACT This chapter discusses the expression, purification, and biochemical properties of Ypt/Rab guanosine-5'-triphosphate (GTP)ase-activating proteins of Gyp family. It is suggested that the production of C-terminally His6- tagged versions is the method of choice for large-scale preparations of Ypt/Rab GTPase-activating proteins (GAPs). For quantitative GAP assays and kinetic analyses, GTPases loaded with unlabeled GTP were used and GTP-GDP ratios were followed by high performance liquid chromatography (HPLC) analysis. Km and kcat values of the Gyp7p-Ypt7p interaction can be obtained by classical Michaelis-Menten kinetics. Under single turnover conditions, Ypt7p-GTP can be considered the substrate and Ypt7p-GDP the product of the reaction. Because the intrinsic rate of GTP hydrolysis is negligible compared to the GAP-activated rate, Gyp7p is regarded as an enzyme despite the fact that the catalytic center of the reaction is present on Ypt7p. To determine initial rates (V) of the GAP-catalyzed GTP hydrolysis at different Ypt7p-GTP concentrations, quantitative GAP assays are performed.

The Journal of biological chemistry, Jan 26, 2002

Post-translational modifications of GTPases from the Ras superfamily enable them to associate wit... more Post-translational modifications of GTPases from the Ras superfamily enable them to associate with membrane compartments where they exert their biological activities. However, no protein acting like Rho and Rab dissociation inhibitor (GDI) that regulate the membrane association of Rho and Rab GTPases has been described for Ras and closely related proteins. We report here that the delta subunit of retinal rod phosphodiesterase (PDEdelta) is able to interact with prenylated Ras and Rap proteins, and to solubilize them from membranes, independently of their nucleotide-bound (GDP or GTP) state. We show that PDEdelta exhibits striking structural similarities with RhoGDI, namely conservation of the Ig-like fold and presence of a series of hydrophobic residues which could act as in RhoGDI to sequester the prenyl group of its target proteins, thereby providing structural support for the biochemical activity of PDEdelta. We observe that the overexpression of PDEdelta interferes with Ras traf...

Experimental nephrology

Altered nitrogen metabolism is a feature of chronic renal failure (CRF). The present study examin... more Altered nitrogen metabolism is a feature of chronic renal failure (CRF). The present study examined changes in renal expression of mRNA for enzymes involved in ornithine and polyamine metabolism, i.e. ornithine aminotransferase (OAT), ornithine decarboxylase (ODC), and S-adenosylmethionine synthetase (S-ADMase), during the early phase of renal insufficiency in rats after 5/6 nephrectomy (Nx). Involvement of androgens, the most potent stimulators of renal ODC, in these changes, was also evaluated inasmuch as testoseronemia is known to be significantly decreased in male uremic subjects. The abundance of mRNA was evaluated by quantitative Northern analysis of total RNA extracted from the remnant kidney of male or female Nx rats. The level mRNA for ODC was depressed by 76, 83, and 79%, that for OAT by 60, 76 and 63%, and that for S-ADMase by 37, 58 and 30%, at, respectively, 2, 7 and 35 days after Nx, in both male and female rats. ODC but not OAT enzyme activity was decreased. The expre...

Laboratory Investigation, 2003

Members of the epidermal growth factor (EGF) family and their receptors are involved in many cell... more Members of the epidermal growth factor (EGF) family and their receptors are involved in many cellular processes, including proliferation, migration, and differentiation. We have previously reported that these growth factors are expressed and have specific regulatory functions in an organ-like culture model of normal human urothelial cells. Here, we used this model to investigate the involvement of EGF receptor (EGFR) in human urothelial regeneration. Three 4-mm-diameter damaged areas were made in confluent normal human urothelial cell cultures with a biopsy punch. Regeneration was measured, on fixed stained cultures, with an image analyzer, at 4, 24, and 48 hours after injury. Cell proliferation was assessed by 5-bromo-2-deoxyuridine incorporation. To identify EGF family factors potentially involved in the healing process, we studied the effect of these factors on damaged confluent cultures and the level of expression of mRNAs extracted from these cultures. EGFR inhibition of the proliferation and migration of urothelial cells was tested with (1) a specific tyrosine kinase inhibitor (AG1478) and (2) a blocking anti-EGFR antibody (LA22). Exogenously added amphiregulin, EGF, transforming growth factor-␣ and heparin-binding EGF (HB-EGF) stimulated urothelial regeneration. The damaged areas were repaired by regrowth within 48 hours. Both AG1478 and LA22 inhibited the repair (by 50% and 30%, respectively), as well as proliferation and migration. This regeneration was accompanied by increased HB-EGF mRNA expression in cultures of cells from four of six subjects, but no corresponding change in EGFR protein level was observed. These results indicate that the EGFR signaling pathway is involved in urothelial regeneration. Our data support an autocrine role of HB-EGF in this process and suggest that the EGFR pathway is a potential therapeutic target for modulating urothelial cell proliferation.

Journal of Biotechnology, 2012

The tobacco etch virus (TEV) protease is a useful tool for the removal of fusion tags from recomb... more The tobacco etch virus (TEV) protease is a useful tool for the removal of fusion tags from recombinant proteins. The difficulty in obtaining this enzyme led us to look for an optimal method for its use. In this work, we produced both the wild-type and the S219V mutant TEV proteases fused to the Streptag II affinity sequence (Streptag II-TEV WT , and Streptag II-TEV S219V , respectively). The two enzymes were affinity immobilized on a streptavidin-agarose matrix and compared to their respective free forms. Both immobilized Streptag II-TEV WT and Streptag II-TEV S219V were active on the 74-kDa Streptag II substrate with a retained activity of 83.5% and 81%, respectively compared to their free corresponding forms. The slight enzyme activity decrease caused by the immobilization was balanced by the enhanced stability and the successful repetitive use of the proteolytic columns. Thus, the wild-type and the mutant immobilized proteases were used, during a period of 18 months, for nine batch reactions with retention of 38% and 51% of their initial activities, respectively. The present results demonstrate that immobilized TEV protease on streptavidin-agarose is an attractive and efficient tool for fusion protein cleavage, especially when the target protein is fused to a streptagged fusion partner. Using this strategy, the total process can be shortened by performing the cleavage and the recovery of the purified target protein in one step.

Journal of Biological Chemistry, 2004

We recently have identified a new cytoplasmic linker protein (CLIP), CLIPR-59, which is involved ... more We recently have identified a new cytoplasmic linker protein (CLIP), CLIPR-59, which is involved in the regulation of early endosome/trans-Golgi network dynamics. In contrast with CLIP-170, CLIPR-59 is not localized to microtubules at steady state but is associated with the trans-Golgi network and the plasma membrane. Here we show that the last 30 amino acids (C30) are sufficient for membrane targeting and that two cysteines in the C30 domain are palmitoylated. We demonstrate that CLIPR-59 is associated with lipid rafts via its C-terminal palmitoylated domain. In vitro experiments suggest that CLIPR-59 and its microtubule-binding domain alone have a better affinity for unpolymerized tubulin or small oligomers than for microtubules. In contrast with the CLIP-170 microtubule-binding domain, the CLIPR-59 microtubule-binding domain diminishes microtubule regrowth after nocodazole washout in vivo, showing that this domain can prevent microtubule polymerization. In contrast with the role of linker between membranes and microtubules that was proposed for CLIP function, CLIPR-59 thus may have an "anti-CLIP" function by preventing microtubule-raft interactions.

Immunity, 2013

HIV-2 is less pathogenic for humans than HIV-1 and might provide partial cross-protection from HI... more HIV-2 is less pathogenic for humans than HIV-1 and might provide partial cross-protection from HIV-1induced pathology. Although both viruses replicate in the T cells of infected patients, only HIV-2 replicates efficiently in dendritic cells (DCs) and activates innate immune pathways. How HIV is sensed in DC is unknown. Capsid-mutated HIV-2 revealed that sensing by the host requires viral cDNA synthesis, but not nuclear entry or genome integration. The HIV-1 capsid prevented viral cDNA sensing up to integration, allowing the virus to escape innate recognition. In contrast, DCs sensed capsid-mutated HIV-1 and enhanced stimulation of T cells in the absence of productive infection. Finally, we found that DC sensing of HIV-1 and HIV-2 required the DNA sensor cGAS. Thus, the HIV capsid is a determinant of innate sensing of the viral cDNA by cGAS in dendritic cells. This pathway might potentially be harnessed to develop effective vaccines against HIV-1.

Biology of Reproduction, 2011

Oocyte maturation (OM) in teleosts is under precise hormonal control by progestins and estrogens.... more Oocyte maturation (OM) in teleosts is under precise hormonal control by progestins and estrogens. We show here that estrogens activate an epidermal growth factor receptor (Egfr) signaling pathway in fully grown, denuded zebrafish (Danio rerio) oocytes through the G protein-coupled estrogen receptor (Gper; also known as GPR30) to maintain oocyte meiotic arrest in a germinal vesicle breakdown (GVBD) bioassay. A GPER-specific antagonist, G-15, increased spontaneous OM, indicating that the inhibitory estrogen actions on OM are mediated through Gper. Estradiol-17beta-bovine serum albumin, which cannot enter oocytes, decreased GVBD, whereas treatment with actinomycin D did not block estrogen's inhibitory effects, suggesting that estrogens act at the cell surface via a nongenomic mechanism to prevent OM. The intracellular tyrosine kinase (Src) inhibitor, PP2, blocked estrogen inhibition of OM. Expression of egfr mRNA and Egfr protein were detected in denuded zebrafish oocytes. The matrix metalloproteinase (MMP) inhibitor, ilomastat, which prevents the release of heparin-bound epidermal growth factor, increased spontaneous OM, whereas the MMP activator, interleukin-1alpha, decreased spontaneous OM. Moreover, inhibitors of EGFR (ErbB1) and extracellular-related kinase 1 and 2 (Erk1/2; official symbol Mapk3/1) increased spontaneous OM. In addition, estradiol-17beta and the GPER agonist, G-1, increased phosphorylation of Erk, and this was abrogated by simultaneous treatment with the EGFR inhibitor. Taken together, these results suggest that estrogens act through Gper to maintain meiotic arrest via an Src kinase-dependent G-protein betagamma subunit signaling pathway involving transactivation of egfr and phosphorylation of Mapk3/1. To our knowledge, this is the first evidence that EGFR signaling in vertebrate oocytes can prevent meiotic progression.