Jean Paul Briand

Cellular uptake of functionalized carbon nanotubes is independent of functional group and cell type

The development of nanomaterials for biomedical and biotechnological applications is an area of research that holds great promise and intense interest1, and carbon-based nanostructures in particular, such as carbon nanotubes (CNTs), are attracting an increasing level of attention2,3. One of the key advantages that CNTs offer is the possibility of effectively crossing biological barriers, which would allow their use in the delivery of therapeutically active molecules. Our laboratories have been investigating the use of CNTs in biomedical applications, and in particular as nanovectors for therapeutic agent delivery4,5,6,7,8. The interaction between cells and CNTs is a critical issue that will determine any future biological application of such structures. Here we show that various types of functionalized carbon nanotubes (f-CNTs) exhibit a capacity to be taken up by a wide range of cells and can intracellularly traffic through different cellular barriers.

Suppression of Tumor Growth and Angiogenesis by a Specific Antagonist of the Cell-Surface Expressed Nucleolin

Background Emerging evidences suggest that nucleolin expressed on the cell surface is implicated in growth of tumor cells and angiogenesis. Nucleolin is one of the major proteins of the nucleolus, but it is also expressed on the cell surface where is serves as a binding protein for variety of ligands implicated in cell proliferation, differentiation, adhesion, mitogenesis and angiogenesis. Methodology/Principal Findings By using a specific antagonist that binds the C-terminal tail of nucleolin, the HB-19 pseudopeptide, here we show that the growth of tumor cells and angiogenesis are suppressed in various in vitro and in vivo experimental models. HB-19 inhibited colony formation in soft agar of tumor cell lines, impaired migration of endothelial cells and formation of capillary-like structures in collagen gel, and reduced blood vessel branching in the chick embryo chorioallantoic membrane. In athymic nude mice, HB-19 treatment markedly suppressed the progression of established human breast tumor cell xenografts in nude mice, and in some cases eliminated measurable tumors while displaying no toxicity to normal tissue. This potent antitumoral effect is attributed to the direct inhibitory action of HB-19 on both tumor and endothelial cells by blocking and down regulating surface nucleolin, but without any apparent effect on nucleolar nucleolin. Conclusion/Significance Our results illustrate the dual inhibitory action of HB-19 on the tumor development and the neovascularization process, thus validating the cell-surface expressed nucleolin as a strategic target for an effective cancer drug. Consequently, the HB-19 pseudopeptide provides a unique candidate to consider for innovative cancer therapy.

A novel receptor – ligand pathway for entry of Francisella tularensis in monocyte-like THP-1 cells: interaction between surface nucleolin and bacterial elongation factor Tu

BackgroundFrancisella tularensis, the causative agent of tularemia, is one of the most infectious human bacterial pathogens. It is phagocytosed by immune cells, such as monocytes and macrophages. The precise mechanisms that initiate bacterial uptake have not yet been elucidated. Participation of C3, CR3, class A scavenger receptors and mannose receptor in bacterial uptake have been already reported. However, contribution of an additional, as-yet-unidentified receptor for F. tularensis internalization has been suggested.ResultsWe show here that cell-surface expressed nucleolin is a receptor for Francisella tularensis Live Vaccine Strain (LVS) and promotes LVS binding and infection of human monocyte-like THP-1 cells. The HB-19 pseudopeptide that binds specifically carboxy-terminal RGG domain of nucleolin inhibits LVS binding and infection of monocyte-like THP-1 cells. In a pull-down assay, elongation factor Tu (EF-Tu), a GTP-binding protein involved in protein translation, usually found in cytoplasm, was recovered among LVS bacterial membrane proteins bound on RGG domain of nucleolin. A specific polyclonal murine antibody was raised against recombinant LVS EF-Tu. By fluorescence and electron microscopy experiments, we found that a fraction of EF-Tu could be detected at the bacterial surface. Anti-EF-Tu antibodies reduced LVS binding to monocyte-like THP-1 cells and impaired infection, even in absence of complement and complement receptors. Interaction between EF-Tu and nucleolin was illustrated by two different pull-down assays using recombinant EF-Tu proteins and either RGG domain of nucleolin or cell solubilized nucleolin.DiscussionAltogether, our results demonstrate that the interaction between surface nucleolin and its bacterial ligand EF-Tu plays an important role in Francisella tularensis adhesion and entry process and may therefore facilitate invasion of host tissues. Since phagosomal escape and intra-cytosolic multiplication of LVS in infected monocytes are very similar to those of human pathogenic F. tularensis ssp tularensis, the mechanism of entry into monocyte-like THP-1 cells, involving interaction between EF-Tu and nucleolin, might be similar in the two subspecies. Thus, the use of either nucleolin-specific pseudopeptide HB-19 or recombinant EF-Tu could provide attractive therapeutic approaches for modulating F. tularensis infection.

Deimination of linker histones links neutrophil extracellular trap release with autoantibodies in systemic autoimmunity

Autoantibodies to nuclear antigens arise in human autoimmune diseases, but a unifying pathogenetic mechanism remains elusive. Recently we reported that exposure of neutrophils to inflammatory conditions induces the citrullination of core histones by peptidylarginine deiminase 4 (PAD4) and that patients with autoimmune disorders produce autoantibodies that recognize such citrullinated histones. Here we identify histone H1 as an additional substrate of PAD4, localize H1 within neutrophil extracellular traps, and detect autoantibodies to citrullinated H1 in 6% of sera from patients with systemic lupus erythematosus and Sjögrens syndrome. No preference for deiminated H1 was observed in healthy control sera and sera from patients with scleroderma or rheumatoid arthritis. We map binding to the winged helix of H1 and determine that citrulline 53 represents a key determinant of the autoantibody epitope. In addition, we quantitate RNA for H1 histone subtypes in mature human neutrophils and identify citrulline residues by liquid chromatography and tandem mass spectrometry. Our results indicate that deimination of linker histones generates new autoantibody epitopes with enhanced potential for stimulating autoreactive human B cells.—Dwivedi, N., Neeli, I., Schall, N., Wan, H., Desiderio, D. M., Csernok, E., Thompson, P. R., Dali, H., Briand, J.‐P., Muller, S., Radic, M. Deimination of linker histones links neutrophil extracellular trap release with autoantibodies in systemic autoimmunity. FASEB J. 28, 2840–2851 (2014). www.fasebj.org

Modulation of deregulated chaperone-mediated autophagy by a phosphopeptide.

The P140 peptide, a 21-mer linear peptide (sequence 131–151) generated from the spliceosomal SNRNP70/U1–70K protein, contains a phosphoserine residue at position 140. It significantly ameliorates clinical manifestations in autoimmune patients with systemic lupus erythematosus and enhances survival in MRL/lpr lupus-prone mice. Previous studies showed that after P140 treatment, there is an accumulation of autophagy markers sequestosome 1/p62 and MAP1LC3-II in MRL/lpr B cells, consistent with a downregulation of autophagic flux. We now identify chaperone-mediated autophagy (CMA) as a target of P140 and demonstrate that its inhibitory effect on CMA is likely tied to its ability to alter the composition of HSPA8/HSC70 heterocomplexes. As in the case of HSPA8, expression of the limiting CMA component LAMP2A, which is increased in MRL/lpr B cells, is downregulated after P140 treatment. We also show that P140, but not the unphosphorylated peptide, uses the clathrin-dependent endo-lysosomal pathway to enter into MRL/lpr B lymphocytes and accumulates in the lysosomal lumen where it may directly hamper lysosomal HSPA8 chaperoning functions, and also destabilize LAMP2A in lysosomes as a result of its effect on HSP90AA1. This dual effect may interfere with the endogenous autoantigen processing and loading to major histocompatibility complex class II molecules and as a consequence, lead to lower activation of autoreactive T cells. These results shed light on mechanisms by which P140 can modulate lupus disease and exert its tolerogenic activity in patients. The unique selective inhibitory effect of the P140 peptide on CMA may be harnessed in other pathological conditions in which reduction of CMA activity would be desired.

Structure-Based Design of Short Peptide Ligands Binding onto the E. coli Processivity Ring

The multimeric DNA sliding clamps confer high processivity to replicative DNA polymerases and are also binding platforms for various enzymes involved in DNA metabolism. These enzymes interact with the clamp through a small peptide that binds into a hydrophobic pocket which is a potential target for the development of new antibacterial compounds. Starting from a generic heptapeptide, we used a structure-based strategy to improve the design of new peptide ligands. Chemical modifications at specific residues result in a dramatic increase of the interaction as measured by SPR and ITC. The affinity of our best hits was improved by 2 orders of magnitude as compared to the natural ligand, reaching 10(-8) M range. The molecular basis of the interactions was analyzed by solving the co-crystal structures of the most relevant peptides bound to the clamp and reveals how chemical modifications establish new contacts and contributes to an increased affinity of the ligand.

A flavivirus protein M-derived peptide directly permeabilizes mitochondrial membranes, triggers cell death and reduces human tumor growth in nude mice

Dengue viruses belong to the Flavivirus family and are responsible for hemorrhagic fever in Human. Dengue virus infection triggers apoptosis especially through the expression of the small membrane (M) protein. Using isolated mitochondria, we found that synthetic peptides containing the C-terminus part of the M ectodomain caused apoptosis-related mitochondrial membrane permeabilization (MMP) events. These events include matrix swelling and the dissipation of the mitochondrial transmembrane potential (ΔΨm). Protein M Flavivirus sequence alignments and helical wheel projections reveal a conserved distribution of charged residues. Moreover, when combined to the cell penetrating HIV-1 Tat peptide transduction domain (Tat-PTD), this sequence triggers a caspase-dependent cell death associated with ΔΨm loss and cytochrome c release. Mutational approaches coupled to functional screening on isolated mitochondria resulted in the selection of a protein M derived sequence containing nine residues with potent MMP-inducing properties on isolated mitochondria. A chimeric peptide composed of a Tat-PTD linked to the 9-mer entity triggers MMP and cell death. Finally, local administration of this chimeric peptide induces growth inhibition of xenograft prostate PC3 tumors in immuno-compromised mice, and significantly enhances animal survival. Together, these findings support the notion of using viral genomes as valuable sources to discover mitochondria-targeted sequences that may lead to the development of new anticancer compounds.

The P9 peptide sidechain specificity of I-Ad

The murine MHC class II variant I-Ad confers susceptibility to herpes simplex virus (HSV)-induced keratitis and relative protection against type 1 diabetes mellitus. The association to these autoimmune diseases appears to be largely determined by the peptide sidechain specificity of the P9 pocket, which we therefore have analyzed in detail. Assessment of T-cell responses and I-Ad binding capacity of position 446-substituted analogs of an IgG2a allotype b (IgG2a(b)) heavy chain peptide demonstrates that engagement of the P9 pocket is crucial for effective peptide presentation. Sidechain size rather than charge decides the capacity to engage the P9 pocket. Thus, small, uncharged sidechains are accepted, whereas acidic and aromatic amino acids as well as lysine and arginine are disfavored. The specificity of the P9 pocket of I-Ad (serine beta57) is distinct from that of the diabetes-associated I-Ag7 (aspartic acid beta57), supporting the contention that the polymorphism at residue beta57 influences diabetes susceptibility via P9-specific effects on the repertoires of self peptides presented to T cells. Furthermore, the data rationalize the susceptibility to HSV-induced keratitis conferred by the a and the protection conferred by the b allotypes of the IgG2a heavy chain. Keratitogenic T cells, which cross-react with the viral UL6 protein and a corneal antigen, are silenced in IgG2a(b) mice because of antigenic mimicry with gamma2a(b) 435-451. Our finding that the lysine P9 residue of the corresponding gamma2a(a) allopeptide precludes high-affinity binding to I-Ad indicates that the susceptibility of IgG2a(a) mice reflects inefficient thymic presentation of autologous IgG2a and thus failure to purge the T-cell repertoire of the pathogenic clones.