Institut de recherche biomédicale
     

    Research projects

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    Endothelial cell response to infection by Neisseria meningitidis

    A wide range of pathogens directly targets peripheral and brain endothelia. Among those, Neisseria meningitidis is potentially one of the most harmful [1-3]. Our team is deciphering how N. meningitidis manipulates the endothelial cell response to establish intimate interactions and induce dysfunctions, rupture and breaching of the endothelial barriers [4-10]. We recently identified key host and bacterial factors involved in such interactions [11-13].  We are currently dissecting the intricate interplay between two identified host receptors and meningococcal type IV pili. Furthermore, taking advantage of a novel in vivo model of meningococcal infection, we aim at deciphering the molecular and cellular events leading to vascular dysfunction, thrombosis, organ failure and immune escape by these bacterial pathogens.

     

    Leukocyte interaction with endothelial cells

    To reach inflammation sites, leukocytes must adhere to the vascular wall and cross the endothelial barrier, a series of events that involves a network of adhesion molecules with overlapping functions in capture, rolling, and firm adhesion of leukocytes, along with the formation of endothelial docking structures that stabilize adherent leukocytes. We identified JAM-L, a novel leukocyte adhesion molecule strengthening the integrin-dependent adhesion of leukocytes to endothelial cells, adding a novel twist to this adhesion cascade [14, 15]. We also showed that vascular infection by N. meningitidis interferes with the formation of leukocyte/endothelium docking structures, therefore hampering the host inflammatory response [16]. We are now further dissecting why and how the infection by pathogenic N. meningitidis is poorly controlled by the innate immune responses.

     

    The Blood Brain Barrie

    The Blood-brain barrier (BBB) is a complex biological system ensuring the proper function of the brain. As a result of its restricted permeability, only 2% of therapeutic compounds in clinical use get access to the brain, limiting dramatically the development of pharmacotherapies and immunotherapies for most neurological disorders.  Our team has engineered a unique human brain endothelial cell line (hCMEC/D3) that phenocopies the normal human BBB, as judged for low permeability, polarized secretion and transport, architectural organization, and protein expression providing a highly valuable tool for drug design and brain targeting [17, 18] [Patent WO/2006/056879, now distributed in more than 300 laboratories worldwide and under license with several pharmaceutical companies].

    We are now further improving the in vitro set up by growing hCMEC/D3 under laminar flow to increase adherens and tight junction maturation and barrier tightness.

    Taking advantage of this in vitro model, we aim at elucidating the intricate network of interactions and molecular strategies selected by Neisseria meningitidis to colonize human brain vasculature and get access to the brain with a minimal loss of BBB integrity. Our ultimate objective is to identify mimicking drug delivery strategies for a successful treatment of CNS diseases.

     

    Inhibition of the tyrosine kinase receptor ErbB2/HER2: from bacterial meningitis to human cancers

    Among the ErbB family of tyrosine kinase receptors, ErbB2/HER2 displays unique properties. This orphan receptor exists in a ligand-independent, activated configuration that promotes cell transformation when overexpressed. Intriguingly, this structure does not lead readily to ErbB2 activation. We previously showed that infection of endothelial cells by N. meningitidis induces the selective recruitment and tyrosine phosphorylation of ErbB2 [18]. Taking advantage of this host-pathogen interaction which constitutes a unique tool to study the mechanisms of ErbB2 activation, we identified a novel tumor suppressor gene promoting the allosteric inhibition of the ligand-independent activation of ErbB2. Based on this interaction, we set up a high throughput screening method and identified novel molecules with potent anti-HER2 activity that mimic the suppressor activity. These patented compounds now provide an original and robust starting point for the design of attractive molecules for therapeutic interventions on human cancers overexpressing HER2, with clinical, financial and beneficial aspects. Now, we aim at elucidating the regulatory mechanisms of the tumor suppressor gene expression in HER2-positive cancers.


    Conclusion

    Our projects aim at deciphering molecular mechanisms driving infection, inflammation and cancer. Our results illustrate how pathogens and leukocytes establish intimate interactions with endothelial cells and highlight novel aspects of endothelial dysfunctions. Furthermore, our work at the interface of bacterial infection and oncogenic transformation paved the way to novel unexpected translational applications.

    1. Coureuil M, Join-Lambert O, Lecuyer H, Bourdoulous S, Marullo S, Nassif X. Mechanism of meningeal invasion by Neisseria meningitidis. Virulence. 2012;3(2):164-72.
    2. Lemichez E, Lecuit M, Nassif X, Bourdoulous S. Breaking the wall: targeting of the endothelium by pathogenic bacteria. Nat Rev Microbiol. 2010;8(2):93-104.
    3. Coureuil M, Join-Lambert O, Lecuyer H, Bourdoulous S, Marullo S, Nassif X. Pathogenesis of meningococcemia. Cold Spring Harb Perspect Med. 2013;3(6).
    4. Nassif X, Bourdoulous S, Eugene E, Couraud PO. How do extracellular pathogens cross the blood-brain barrier? Trends Microbiol. 2002;10(5):227-32.
    5. Corbett A, Exley R, Bourdoulous S, Tang CM. Interactions between Neisseria meningitidis and human cells that promote colonisation and disease. Expert Rev Mol Med. 2004;6(14):1-14.
    6. Join-Lambert O, Morand PC, Carbonnelle E, Coureuil M, Bille E, Bourdoulous S, et al. Mechanisms of meningeal invasion by a bacterial extracellular pathogen, the example of Neisseria meningitidis. Prog Neurobiol. 2010;91(2):130-9.
    7. Eugene E, Hoffmann I, Pujol C, Couraud PO, Bourdoulous S, Nassif X. Microvilli-like structures are associated with the internalization of virulent capsulated Neisseria meningitidis into vascular endothelial cells. J Cell Sci. 2002;115(Pt 6):1231-41.
    8. Lambotin M, Hoffmann I, Laran-chich M, Nassif X, Couraud PO, Bourdoulous S. Invasion of endothelial cells by Neisseria meningitidis requires cortactin recruitment by a PI3-Kinase/Rac1 signalling pathway triggered by the lipo-oligosaccharide. J Cell Sci.    2005;118(Pt16):3805-16.
    9. Coureuil M, Mikaty G, Miller F, Lecuyer H, Bernard C, Bourdoulous S, et al. Meningococcal type IV pili recruit the polarity complex to cross the brain endothelium. Science. 2009;325(5936):83-7.
    10. Carbonnelle E, Hill DJ, Morand P, Griffiths NJ, Bourdoulous S, Murillo I, et al. Meningococcal interactions with the host. Vaccine. 2009;27 Suppl 2:B78-89.
    11. Coureuil M, Lecuyer H, Scott MG, Boularan C, Enslen H, Soyer M, et al. Meningococcus Hijacks a beta2-adrenoceptor/beta-Arrestin pathway to cross brain microvasculature endothelium. Cell. 2010;143(7):1149-60.
    12. Coureuil M, Bourdoulous S, Marullo S, Nassif X. Invasive meningococcal disease: a disease of the endothelial cells. Trends Mol Med. 2014;20(10):571-8.
    13. Bernard SC, Simpson N, Join-Lambert O, Federici C, Laran-Chich MP, Maissa N, et al. Pathogenic Neisseria meningitidis utilizes CD147 for vascular colonization. Nat Med. 2014;20(7):725-31.
    14. Moog-Lutz C, Cave-Riant F, Guibal FC, Breau MA, Di Gioia Y, Couraud PO, et al. JAML, a novel protein with characteristics of a junctional adhesion molecule, is induced during differentiation of myeloid leukemia cells. Blood. 2003;102(9):3371-8.
    15. Luissint AC, Lutz PG, Calderwood DA, Couraud PO, Bourdoulous S. JAM-L-mediated leukocyte adhesion to endothelial cells is regulated in cis by alpha4beta1 integrin activation. J Cell Biol. 2008;183(6):1159-73.
    16. Doulet N, Donnadieu E, Laran-Chich MP, Niedergang F, Nassif X, Couraud PO, et al. Neisseria meningitidis infection of human endothelial cells interferes with leukocyte transmigration by preventing the formation of endothelial docking structures. J Cell Biol. 2006;173(4):627-37. 
    17. Weksler BB, Subileau EA, Perriere N, Charneau P, Holloway K, Leveque M, et al. Blood-brain barrier-specific properties of a human adult brain endothelial cell line. Faseb J. 2005;19(13):1872-4. 
    18. Weksler B, Romero IA, Couraud PO. The hCMEC/D3 cell line as a model of the human blood brain barrier. Fluids Barriers CNS. 2013;10(1):16.
    19. Hoffmann I, Eugene E, Nassif X, Couraud PO, Bourdoulous S. Activation of ErbB2 receptor tyrosine kinase supports invasion of endothelial cells by Neisseria meningitidis. J Cell Biol. 2001;155(1):133-43.