µ-Calpain Conversion of Antiapoptotic Bfl-1 (BCL2A1) into a Prodeath Factor Reveals Two Distinct alpha-Helices Inducing Mitochondria-Mediated Apoptosis

Anti-apoptotic Bfl-1 and pro-apoptotic Bax, two members of the Bcl-2 family sharing a similar structural fold, are classically viewed as antagonist regulators of apoptosis. However, both proteins were reported to be death inducers following cleavage by the cysteine protease µ-calpain. Here we demonstrate that calpain-mediated cleavage of full-length Bfl-1 induces the release of C-terminal membrane active α-helices that are responsible for its conversion into a pro-apoptotic factor. A careful comparison of the different membrane-active regions present in the Bfl-1 truncated fragments with homologous domains of Bax show that helix α5, but not α6, of Bfl-1 induces cell death and cytochrome c release from purified mitochondria through a Bax/Bak-dependent mechanism. In contrast, both helices α5 and α6 of Bax permeabilize mitochondria regardless of the presence of Bax or Bak. Moreover, we provide evidence that the α9 helix of Bfl-1 promotes cytochrome c release and apoptosis through a unique membrane-destabilizing action whereas Bax-α9 does not display such activities. Hence, despite a common 3D-structure, C-terminal toxic domains present on Bfl-1 and Bax function in a dissimilar manner to permeabilize mitochondria and induce apoptosis. These findings provide insights for designing therapeutic approaches that could exploit the cleavage of endogenous Bcl-2 family proteins or the use of Bfl-1/Bax-derived peptides to promote tumor cell clearance

Synthesis and biological activities of polyquinoline derivatives: new Bcl-2 family protein modulators.

International audienceThe synthesis of quinoline derivatives, designed to interact with Bcl-xL, and to inhibit its interaction with pro-apoptotic partners, is described and their biological effects investigated. We showed that 5 out of 28 synthetized compounds restored cell death of 3T3 cells overexpressing Bcl-xL following serum starvation. Active compounds were further characterized for their binding capacity to the anti-apoptotic member of the Bcl-2 family, Bcl-xL as well as Bcl-2, Bfl-1 and Mcl-1, and for their pro-apoptotic activities toward lymphoid tumor cells and peripheral blood mononuclear cells. Altogether our results indicate that dimeric, rather than trimeric quinoline derivatives, represent a new attractive class of BH3 mimetics for cancer therapy

Synthesis and biological activities of new di- and trimeric quinoline derivatives

International audienceThe synthesis of non-peptidic helix mimetics based on a trimeric quinoline scaffold is described. The ability of these new compounds, as well as their synthetic dimeric intermediates, to bind to various members of the Bcl-2 protein anti-apoptotic group is also evaluated. The most interesting derivative of this new series (compound A) inhibited Bcl-xL/Bak, Bcl-xL/Bax and Bcl-xL/Bid interactions with IC50 values around 25 μM

NOD1 Cooperates with TLR2 to Enhance T Cell Receptor-Mediated Activation in CD8 T Cells

<div><p>Pattern recognition receptors (PRR), like Toll-like receptors (TLR) and NOD-like receptors (NLR), are involved in the detection of microbial infections and tissue damage by cells of the innate immune system. Recently, we and others have demonstrated that TLR2 can additionally function as a costimulatory receptor on CD8 T cells. Here, we establish that the intracytosolic receptor NOD1 is expressed and functional in CD8 T cells. We show that C12-iEDAP, a synthetic ligand for NOD1, has a direct impact on both murine and human CD8 T cells, increasing proliferation and effector functions of cells activated via their T cell receptor (TCR). This effect is dependent on the adaptor molecule RIP2 and is associated with an increased activation of the NF-κB, JNK and p38 signaling pathways. Furthermore, we demonstrate that NOD1 stimulation can cooperate with TLR2 engagement on CD8 T cells to enhance TCR-mediated activation. Altogether our results indicate that NOD1 might function as an alternative costimulatory receptor in CD8 T cells. Our study provides new insights into the function of NLR in T cells and extends to NOD1 the recent concept that PRR stimulation can directly control T cell functions.</p> </div

NOD1 cooperates with TLR2 to enhance TCR-mediated activation in human CD8 T cells.

<p>Flow cytometry assessment of the (A) proliferation (the percentage of proliferating cells is indicated), (B) CD25 expression (the mean fluorescence intensity of CD8 T cells is indicated) and (C) cell numbers of CFSE stained human CD8 T cells activated for 72 h with anti-CD3 in the absence or presence of C12, Pam, or both C12 and Pam. Results are representative of 3 independent experiments. CD8 T cell numbers are the mean cell number ± SD of triplicates.</p

NOD1 cooperates with TLR2 to enhance TCR-mediated CD8 T cell activation.

<p>(A–C) Flow cytometry assessment of the proliferation (the percentage of proliferating cells is indicated within the histograms) (A), cell numbers (B) and CD25 expression (the mean fluorescence intensity of CD8 T cells is indicated within the histograms) (C) of CFSE stained murine CD8 T cells cultured for 48 h with anti-CD3, in the absence or presence of C12, Pam, or both C12 and Pam. (D–F) Determination of IL-2 (D), IFN-γ (E) and TNF-α (F) concentrations in the supernatants of CD8 T cells cultured for 48 h with anti-CD3, in the absence or presence of C12, Pam, or both C12 and Pam. (G) Determination by western blotting of IκBα, β-actin, Phospho-ERK (P-ERK), total ERK, Phospho-JNK (P-JNK), total JNK, Phospho-p38 (P-p38) and total p38 protein levels in F5 CD8 lymphoblasts cultured for 30 minutes in medium alone or with 1 nM of NP68, in the absence or presence of C12, Pam, or both C12 and Pam. (B) Cell number values are the mean fold increases of anti-CD3 stimulated CD8 T cell numbers in the different conditions, in comparison to the control condition anti-CD3 alone, ± SD from 4 independent experiments (** = p<0.01; Student <i>t</i> test). The other results are representative of 4 (A and C) or 3 (D, E, F and G) independent experiments.</p

NOD1 ligand directly increases TCR-activated CD8 T cell proliferation and effector functions.

<p>(A) Flow cytometry assessment of the proliferation of CFSE stained murine CD8 T cells cultured for 72 h with or without anti-CD3 antibody, in the absence or presence of a dose range of C12, anti-CD28 or TLR2 ligand Pam. The percentage of proliferating cells is indicated within the histograms. The column graph represents the mean fold increase of anti-CD3 stimulated CD8 T cell proliferation in the different conditions, in comparison to the control condition anti-CD3 alone, ± SD from 5 independent experiments. (B–E) Flow cytometry assessment of CD69 (B) expression by CD8 T cell after 20 h of culture and of CD25 (C), CD44 (D) and CD62L (E) expression after 48 h of culture in medium containing or not anti-CD3 antibody, in the absence (solid grey) or presence of C12, anti-CD28 or Pam (black lines). The column graphs represent the mean fold increase of anti-CD3 stimulated CD8 T cell expression level of the different activation markers in the different conditions, in comparison to the control condition anti-CD3 alone, ± SD from 3 independent experiments. (F–H) Determination of IL-2, IFN-γ and TNF-α concentrations in CD8 T cells supernatants following 48 h of activation with anti-CD3, in the absence or presence of C12, anti-CD28 or Pam. Results are the mean concentrations of cytokines determined ± SD from 3 independent experiments. (I) Flow cytometry assessment of the surface expression of CD107a by CD8 T cells activated for 72 h with anti-CD3 in the absence or presence of C12, anti-CD28 or Pam, and restimulated for 4 h with anti-CD3. The column graph represents the mean fold increase of CD8 T cell surface expression level of CD107a in the different conditions, in comparison to the control condition anti-CD3 alone, ± SD from 3 independent experiments. (* = p<0.05 and ** = p<0.01; Student <i>t</i> test).</p

C12 effect on activated CD8 T cells is NOD1- and RIP2- dependent, and is associated with activation of the NF-κB, JNK and p38 signaling pathways.

<p>(A–B) Flow cytometry assessment of the proliferation of CFSE stained WT, NOD1^−/−, RIP2^−/−, MyD88^−/− and TRIF^−/− CD8 T cells activated for 72 h with anti-CD3, in the absence or presence of C12 or Pam. (A) The percentage of proliferating cells is indicated within the histograms. (B) The column graph represents the mean fold increase of anti-CD3 stimulated CD8 T cell proliferation in the different conditions, in comparison to the control condition anti-CD3 alone, ± SD from 3 independent experiments. (C) Determination by western blotting of IκBα, β-actin, Phospho-ERK (P-ERK), total ERK, Phospho-JNK (P-JNK), total JNK, Phospho-p38 (P-p38) and total p38 protein levels in F5 CD8 lymphoblasts cultured for 30 minutes in medium alone or with 1 nM of their specific antigenic peptide, NP68, in the absence or presence of C12, anti-CD28 or Pam. Results are representative of 3 independent experiments.</p

NOD1 is expressed by CD8 T cells.

<p>NLR mRNA expression assessed by quantitative RT-PCR in murine CD8 T cells (black bars), macrophages (white bars) and splenocytes (grey bars) (nd: not detected). Results are the mean expression of NLR relative to HPRT ± SD of 3 independent experiments.</p

TLR9 transcriptional regulation in response to double-stranded DNA viruses

International audienceThe stimulation of TLRs by pathogen-derived molecules leads to the production of proinflammatory cytokines. Because uncontrolled inflammation can be life threatening, TLR regulation is important; however, few studies have identified the signaling pathways that contribute to the modulation of TLR expression. In this study, we examined the relationship between activation and the transcriptional regulation of TLR9. We demonstrate that infection of primary human epithelial cells, B cells, and plasmacytoid dendritic cells with dsDNA viruses induces a regulatory temporary negative-feedback loop that blocks TLR9 transcription and function. TLR9 transcriptional downregulation was dependent on TLR9 signaling and was not induced by TLR5 or other NF-\kappaB activators, such as TNF-α. Engagement of the TLR9 receptor induced the recruitment of a suppressive complex, consisting of NF-\kappaBp65 and HDAC3, to an NF-\kappaB cis element on the TLR9 promoter. Knockdown of HDAC3 blocked the transient suppression in which TLR9 function was restored. These results provide a framework for understanding the complex pathways involved in transcriptional regulation of TLR9, immune induction, and inflammation against viruses