Institut de recherche biomédicale
     

    Research projects

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    Endothelial cell response to infection by Neisseria meningitidis

    Our team studies the intricate interactions of Neisseria meningitidis (meningococcus) with human peripheral and brain vasculatures, two interactions at the heart of meningococcal pathogenesis (necrotic purpura and meningitis) (1, 2). We are deciphering how N. meningitidis manipulates the endothelial cell response to establish intimate interactions and induce dysfunctions, rupture and breaching of the endothelial barriers (3, 4). We recently identified key host and bacterial factors involved in such interactions (5-7) (Patent WO 2014/016152 A1). In addition, we have identified compounds that target type IV pili reduce vascular colonization by meningococci and prevent subsequent vascular dysfunctions, intravascular coagulation and overwhelming inflammation (8) (Patents WO/2017/121755; WO/2018/083314).

    Taking advantage of an 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.

     

    The Blood Brain Barrier

    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 (9, 10) [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 (11). Taking advantage of this host-pathogen interaction which constitutes a unique tool to study the mechanisms of ErbB2 activation, we identified novel proteins promoting the allosteric inhibition of the ligand-independent activation of ErbB2 (Patent WO/2011/036211), and which is repressed in HER2+ breast cancers (PCT/EP2018/079213). Based on this interaction, we set up a high throughput screening method (Patent FR 14 52246) and identified novel molecules with potent anti-HER2 activity that mimic the suppressor activity (Patent WO/2017/121755). These molecules, able to cross the blood-brain barrier, inhibit both the progression of human breast cancer overexpressing HER2 and brain tumor progression.

    Now, we aim at elucidating the mechanisms regulating the gene expression of the allosteric inhibitor in HER2+ breast cancers with a focus on the role of miRNAs, key regulators of gene expression often deregulated in cancers. We identified key miRNAs representing good diagnosis and prognosis biomarkers for HER2+ breast cancers (Patent PCT/EP2018/079215) and showed that their inhibition can efficiently repress HER2 activation/expression in breast cancer tumors (Patent PCT/EP2018/079212). These approaches represent innovative complementary strategies for HER2+ breast cancer therapies.

     

     References

    1. M. Coureuil, S. Bourdoulous, S. Marullo, X. Nassif, Invasive meningococcal disease: a disease of the endothelial cells. Trends Mol Med 20, 571-578 (2014).
    2. M. Coureuil, H. Lecuyer, S. Bourdoulous, X. Nassif, A journey into the brain: insight into how bacterial pathogens cross blood-brain barriers. Nat Rev Microbiol 15, 149-159 (2017).
    3. E. Lemichez, M. Lecuit, X. Nassif, S. Bourdoulous, Breaking the wall: targeting of the endothelium by pathogenic bacteria. Nat Rev Microbiol 8, 93-104 (2010).
    4. M. Coureuil et al., Pathogenesis of meningococcemia. Cold Spring Harb Perspect Med 3,  (2013).
    5. M. Coureuil et al., Meningococcus Hijacks a beta2-adrenoceptor/beta-Arrestin pathway to cross brain microvasculature endothelium. Cell 143, 1149-1160 (2010).
    6. S. C. Bernard et al., Pathogenic Neisseria meningitidis utilizes CD147 for vascular colonization. Nat Med 20, 725-731 (2014).
    7. N. Maissa et al., Strength of Neisseria meningitidis binding to endothelial cells requires highly-ordered CD147/beta2-adrenoceptor clusters assembled by alpha-actinin-4. Nat Commun 8, 15764 (2017).
    8. K. Denis et al.,  Targeting Type IV pili as an antivirulence strategy against invasive meningococcal disease. Nat Microbiol, 6, 972-984 (2019).
    9. B. B. Weksler et al., Blood-brain barrier-specific properties of a human adult brain endothelial cell line. FASEB J 19, 1872-1874 (2005).
    10. B. Weksler, I. A. Romero, P. O. Couraud, The hCMEC/D3 cell line as a model of the human blood brain barrier. Fluids Barriers CNS 10, 16 (2013).
    11. I. Hoffmann, E. Eugene, X. Nassif, P. O. Couraud, S. Bourdoulous, Activation of ErbB2 receptor tyrosine kinase supports invasion of endothelial cells by Neisseria meningitidis. J Cell Biol 155, 133-143 (2001).