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International audience; The proteins of the Bcl-2 family are important regulators of apoptosis, or programmed cell death. These proteins regulate this fundamental biological process via the formation of heterodimers involving both pro- and anti-apoptotic family members. Disruption of the balance between anti- and pro-apoptotic Bcl-2 proteins is the cause of numerous pathologies. Bcl-xl, an anti-apoptotic protein of this family, is known to form heterodimers with multiple pro-apoptotic proteins, such as Bad, Bim, Bak, and Bid. To elucidate the molecular basis of this recognition process, we used molecular dynamics simulations coupled with the Molecular Mechanics/Poisson-Boltzmann Surface Area approach to identify the amino acids that make significant energetic contributions to the binding free energy of four complexes formed between Bcl-xl and pro-apoptotic Bcl-2 homology 3 peptides. A fifth protein-peptide complex composed of another anti-apoptotic protein, Bcl-w, in complex with the peptide from Bim was also studied. The results identified amino acids of both the anti-apoptotic proteins as well as the Bcl-2 homology 3 (BH3) domains of the pro-apoptotic proteins that make strong, recurrent interactions in the protein complexes. The calculations show that the two anti-apoptotic proteins, Bcl-xl and Bcl-w, share a similar recognition mechanism. Our results provide insight into the molecular basis for the promiscuous nature of this molecular recognition process by members of the Bcl-2 protein family. These amino acids could be targeted in the design of new mimetics that serve as scaffolds for new antitumoral molecules.

International audience; One of the major challenges in human therapy is to develop delivery systems that are convenient and effective for tackling problems in disease treatments. In the past 20 years, liposomes have represented promising pharmaceutical carriers for drug delivery. Due to their biophysical properties, liposomes can deliver and specifically target a large set of bioactive molecules, they can protect molecules from degradation, and their composition is easily modifiable. The use of recombinant proteoliposomes containing therapeutic membrane proteins is a recently developed technology that allows biologically active proteins to penetrate across the plasma membrane of eukaryotic cells. One of the bottlenecks in this powerful delivery system lies in the production of functional therapeutic membrane proteins mainly due to their biophysical characteristics. Membrane proteins represent about 30% of the total proteins from an organism, and play a central role in drug discovery as potential pharmaceutical targets. This chapter describes the methodology for the production of bioactive proteoliposomes containing therapeutic, proapoptotic membrane proteins synthesized with an optimized cell-free expression system. We will examine (1) the design of the expression vectors and the liposome compositions compatible with the cell-free expression system; (2) the production of membrane proteins using a cell-free expression system in combination with liposomes, to obtain in a one-step reaction functional therapeutic proteoliposomes; (3) proteoliposome purification for further use in the treatment of cancer cells; and (4) the methodology for detecting apoptosis in cells after treatment. Furthermore, this system can be easily adapted for producing "difficult to express proteins" compared with the classical overexpression (bacterial or eukaryotic) systems.

International audience; Myocardial ischemia-reperfusion injury is a major cause of morbidity and mortality in developed countries. To date, the only treatment of complete ischemia is to restore blood flow; thus the search for new cardioprotective approaches is absolutely necessary to reduce the mortality associated with myocardial ischemia. Ischemia has long been considered to result in necrotic tissue damage but the reduction in oxygen supply can also lead to apoptosis. Therefore, in the last few years, mitochondria have become the subject of growing interest in myocardial ischemia-reperfusion since they are strongly involved in the regulation of the apoptotic process. Indeed, during ischemia-reperfusion, pathological signals converge in the mitochondria to induce permeabilization of the mitochondrial membrane. Two classes of mechanisms, which are not mutually exclusive, emerged to explain mitochondrial membrane permeabilization. The first occurs via a non-specific channel known as the mitochondrial permeability transition pore (mPTP) in the inner and the outer membranes causing disruption of the impermeability of the inner membrane, and ultimately complete inhibition of mitochondrial function. The second mechanism, involving only the outer membrane, induces the release of cell death effectors. Thus, drugs able to block or to limit mitochondrial membrane permeabilization may be cytoprotective during ischemia-reperfusion. The objective of this review is to examine the pharmacological strategies capable of inhibiting mitochondrial membrane permeabilization induced by myocardial ischemia-reperfusion.

International audience; Myocardial ischemia-reperfusion injury is a major cause of morbidity and mortality in developed countries. To date, the only treatment of complete ischemia is to restore blood flow; thus the search for new cardioprotective approaches is absolutely necessary to reduce the mortality associated with myocardial ischemia. Ischemia has long been considered to result in necrotic tissue damage but the reduction in oxygen supply can also lead to apoptosis. Therefore, in the last few years, mitochondria have become the subject of growing interest in myocardial ischemia-reperfusion since they are strongly involved in the regulation of the apoptotic process. Indeed, during ischemia-reperfusion, pathological signals converge in the mitochondria to induce permeabilization of the mitochondrial membrane. Two classes of mechanisms, which are not mutually exclusive, emerged to explain mitochondrial membrane permeabilization. The first occurs via a non-specific channel known as the mitochondrial permeability transition pore (mPTP) in the inner and the outer membranes causing disruption of the impermeability of the inner membrane, and ultimately complete inhibition of mitochondrial function. The second mechanism, involving only the outer membrane, induces the release of cell death effectors. Thus, drugs able to block or to limit mitochondrial membrane permeabilization may be cytoprotective during ischemia-reperfusion. The objective of this review is to examine the pharmacological strategies capable of inhibiting mitochondrial membrane permeabilization induced by myocardial ischemia-reperfusion.

This commentary is addressed at the paper by Dr Jie and his co-workers in the current issue of Leukemia (‘Differential involvement of Bax and Bak in TRAIL-mediated apoptosis of leukemic T cells’). In this paper, the authors show the preferential use of Bax over Bak for the induction of mitochondrial apoptotic events in leukemic cell exposed to TRAIL 1. These findings are consistent with previous studies involving Bax in TRAIL-mediated apoptosis in the colon carcinoma cell line HCT116 2–4. The redundant function of Bak and Bax was initially demonstrated in lymphocytes subjected to various apoptotic stimuli 5–8. Hence, simultaneous Bax and Bak gene inactivation results in a profound effect on the control of lymphocyte survival upon growth factor or glucose deprivation 9. Whereas, Bak inactivation, alone, appears to have no effect, Bax inactivation, however, slightly affected lymphocyte survival 9. These data could therefore suggest that Bax and Bak may not be so redundant after all. Accordingly, the use of Jurkat clones deficient for both Bak and Bax by Jie and collaborators, revealed that Bax and Bak could exhibit differential functions, at least in the studied cell type system, as only Bax re-expression could restore caspase-3 processing and sensitization to TRAIL-induced cell death 1. Loss of function mutations of Bax are often found both in colon carcinomas 10 and in leukemias 11,12. Therefore, since both death domain containing receptors and chemotherapeutic agents may require Bax for the triggering of the apoptotic process 2,13, this information may be important for future cancer therapeutic approaches using TRAIL or TRAIL receptor agonists either alone or in combination with chemotherapeutic agents.