VDAC2 and the BCL-2 family of proteins.
Ontology highlight
ABSTRACT:
SUBMITTER: Yuan Z
PROVIDER: S-EPMC8786305 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The network of protein-protein interactions among the BCL-2 protein family plays a critical role in regulating cellular commitment to mitochondrial apoptosis. Anti-apoptotic BCL-2 proteins are considered promising targets for drug discovery and exciting clinical progress has stimulated intense investigations in the broader family. Here, we discuss recent developments in small molecules targeting anti-apoptotic proteins and alternative approaches to targeting BCL-2 family interactions. These studies advance our understanding of the role of BCL-2 family proteins in physiology and disease, providing unique tools for dissecting these functions. The BCL-2 family of proteins is a prime example of targeting protein-protein interactions and further chemical biology approaches will increase opportunities for novel targeted therapies in cancer, autoimmune and aging-associated diseases.
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Project description:Early in mitochondria-mediated apoptosis, the mitochondrial outer membrane becomes permeable to proteins that, when released into the cytosol, initiate the execution phase of apoptosis. Proteins in the Bcl-2 family regulate this permeabilization, but the molecular composition of the mitochondrial outer membrane pore is under debate. We reported previously that at physiologically relevant levels, ceramides form stable channels in mitochondrial outer membranes capable of passing the largest proteins known to exit mitochondria during apoptosis (Siskind, L. J., Kolesnick, R. N., and Colombini, M. (2006) Mitochondrion 6, 118-125). Here we show that Bcl-2 proteins are not required for ceramide to form protein-permeable channels in mitochondrial outer membranes. However, both recombinant human Bcl-x(L) and CED-9, the Caenorhabditis elegans Bcl-2 homologue, disassemble ceramide channels in the mitochondrial outer membranes of isolated mitochondria from rat liver and yeast. Importantly, Bcl-x L and CED-9 disassemble ceramide channels in the defined system of solvent-free planar phospholipid membranes. Thus, ceramide channel disassembly likely results from direct interaction with these anti-apoptotic proteins. Mutants of Bcl-x L act on ceramide channels as expected from their ability to be anti-apoptotic. Thus, ceramide channels may be one mechanism for releasing pro-apoptotic proteins from mitochondria during the induction phase of apoptosis.
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Project description:Guided by a combination of nuclear magnetic resonance binding assays and computational docking studies, we synthesized a library of 5,5' substituted Apogossypol derivatives as potent Bcl-XL antagonists. Each compound was subsequently tested for its ability to inhibit Bcl-XL in an in vitro fluorescence polarization competition assay and exert single-agent proapoptotic activity in human cancer cell lines. The most potent compound BI79D10 binds to Bcl-XL, Bcl-2, and Mcl-1 with IC50 values of 190, 360, and 520 nmol/L, respectively, and potently inhibits cell growth in the H460 human lung cancer cell line with an EC50 value of 680 nmol/L, expressing high levels of Bcl-2. BI79D10 also effectively induces apoptosis of the RS11846 human lymphoma cell line in a dose-dependent manner and shows little cytotoxicity against bax-/-bak-/- mouse embryonic fibroblast cells, in which antiapoptotic Bcl-2 family proteins lack a cytoprotective phenotype, implying that BI79D10 has little off-target effects. BI79D10 displays in vivo efficacy in transgenic mice, in which Bcl-2 is overexpressed in splenic B cells. Together with its improved plasma and microsomal stability relative to Apogossypol, BI79D10 represents a lead compound for the development of novel apoptosis-based therapies for cancer.
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Project description:Malignant melanoma is one of the most difficult cancers to treat due to its resistance to chemotherapy. Despite recent successes with BRAF inhibitors and immune checkpoint inhibitors, many patients do not respond or become resistant to these drugs. Hence, alternative treatments are still required. Due to the importance of the BCL-2-regulated apoptosis pathway in cancer development and drug resistance, it is of interest to establish which proteins are most important for melanoma cell survival, though the outcomes of previous studies have been conflicting. To conclusively address this question, we tested a panel of established and early passage patient-derived cell lines against several BH3-mimetic drugs designed to target individual or subsets of pro-survival BCL-2 proteins, alone and in combination, in both 2D and 3D cell cultures. None of the drugs demonstrated significant activity as single agents, though combinations targeting MCL-1 plus BCL-XL, and to a lesser extent BCL-2, showed considerable synergistic killing activity that was elicited via both BAX and BAK. Genetic deletion of BFL-1 in cell lines that express it at relatively high levels only had minor impact on BH3-mimetic drug sensitivity, suggesting it is not a critical pro-survival protein in melanoma. Combinations of MCL-1 inhibitors with BRAF inhibitors also caused only minimal additional melanoma cell killing over each drug alone, whilst combinations with the proteasome inhibitor bortezomib was more effective in multiple cell lines. Our data show for the first time that therapies targeting specific combinations of BCL-2 pro-survival proteins, namely MCL-1 plus BCL-XL and MCL-1 plus BCL-2, could have significant benefit for the treatment of melanoma.
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Project description:BCL2DB (http://bcl2db.ibcp.fr) is a database designed to integrate data on BCL-2 family members and BH3-only proteins. These proteins control the mitochondrial apoptotic pathway and probably many other cellular processes as well. This large protein group is formed by a family of pro-apoptotic and anti-apoptotic homologs that have phylogenetic relationships with BCL-2, and by a collection of evolutionarily and structurally unrelated proteins characterized by the presence of a region of local sequence similarity with BCL-2, termed the BH3 motif. BCL2DB is monthly built, thanks to an automated procedure relying on a set of homemade profile HMMs computed from seed reference sequences representative of the various BCL-2 homologs and BH3-only proteins. The BCL2DB entries integrate data from the Ensembl, Ensembl Genomes, European Nucleotide Archive and Protein Data Bank databases and are enriched with specific information like protein classification into orthology groups and distribution of BH motifs along the sequences. The Web interface allows for easy browsing of the site and fast access to data, as well as sequence analysis with generic and specific tools. BCL2DB provides a helpful and powerful tool to both 'BCL-2-ologists' and researchers working in the various fields of physiopathology. Database URL: http://bcl2db.ibcp.fr.
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Project description:Bcl-2 family proteins are recognized as major regulators of the mitochondrial pathway of apoptosis. They control the mitochondrial outer membrane permeabilization (MOMP) by directly localizing to this organelle. Further investigations demonstrated that Bcl-2 related proteins are also found in other intracellular compartments such as the endoplasmic reticulum, the Golgi apparatus, the nucleus and the peroxisomes. At the level of these organelles, Bcl-2 family proteins not only regulate MOMP in a remote fashion but also participate in major cellular processes including calcium homeostasis, cell cycle control and cell migration. With the advances of live cell imaging techniques and the generation of fluorescent recombinant proteins, it became clear that the distribution of Bcl-2 proteins inside the cell is a dynamic process which is profoundly affected by changes in the cellular microenvironment. Here, we describe the current knowledge related to the subcellular distribution of the Bcl-2 family of proteins and further emphasize on the emerging concept that this highly dynamic process is critical for cell fate determination.
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Project description:The natural product gambogic acid (GA) has been reported to have cytotoxic activity against tumor cells in culture and was identified as an active compound in a cell-based high-throughput screening assay for activators of caspases, proteases involved in apoptosis. Using the antiapoptotic Bcl-2 family protein, Bfl-1, as a target for screening of a library of natural products, we identified GA as a competitive inhibitor that displaced BH3 peptides from Bfl-1 in a fluorescence polarization assay. Analysis of competition for BH3 peptide binding revealed that GA inhibits all six human Bcl-2 family proteins to various extents, with Mcl-1 and Bcl-B the most potently inhibited [concentrations required for 50% inhibition (IC(50)), < 1 micromol/L]. Competition for BH3 peptide binding was also confirmed using a time-resolved fluorescence resonance energy transfer assay. GA functionally inhibited the antiapoptotic Bcl-2 family proteins as shown by experiments using isolated mitochondria in which recombinant purified Bcl-2 family proteins suppress SMAC release in vitro, showing that GA neutralizes their suppressive effects on mitochondria in a concentration-dependent manner. GA killed tumor cell lines via an apoptotic mechanism, whereas analogues of GA with greatly reduced potency at BH3 peptide displacement showed little or no cytotoxic activity. However, GA retained cytotoxic activity against bax-/-bak-/- cells in which antiapoptotic Bcl-2 family proteins lack a cytoprotective phenotype, implying that GA also has additional targets that contribute to its cytotoxic mechanism. Altogether, the findings suggest that suppression of antiapoptotic Bcl-2 family proteins may be among the cytotoxic mechanisms by which GA kills tumor cells.
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Project description:Permeabilization of the outer mitochondrial membrane that leads to the release of cytochrome c and several other apoptogenic proteins from mitochondria into cytosol represents a commitment point of apoptotic pathway in mammalian cells. This crucial event is governed by proteins of the Bcl-2 family. Molecular mechanisms, by which Bcl-2 family proteins permeabilize mitochondrial membrane, remain under dispute. Although yeast does not have apparent homologues of these proteins, when mammalian members of Bcl-2 family are expressed in yeast, they retain their activity, making yeast an attractive model system, in which to study their action. This review focuses on using yeast expressing mammalian proteins of the Bcl-2 family as a tool to investigate mechanisms, by which these proteins permeabilize mitochondrial membranes, mechanisms, by which pro- and antiapoptotic members of this family interact, and involvement of other cellular components in the regulation of programmed cell death by Bcl-2 family proteins.
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Project description:The BCL-2 family proteins are key regulators of programmed cell death or apoptosis, and represent important targets for the development of anticancer drugs. Because their functions are intimately connected with intracellular membranes, it is important to perform structural and activity studies in precisely characterized samples that include phospholipids and capture the features of the native physiological environment as closely as possible. NMR studies and activity assays based on lipid bilayer nanodiscs are ideally suited for this purpose: they enable the conformations and interactions of these proteins to be probed at atomic resolution in their membrane-associated states. Here we describe detailed protocols for generating the protein components and the reconstituted nanodisc samples suitable for NMR studies and functional assays. The protocols focus on the BCL-2 family protein BCL-XL, a dominant inhibitor of programmed cell death and a major anticancer drug target. The protocols are relatively straightforward. Provided care is taken to ensure protein integrity and sample homogeneity, BCL-XL can be readily reconstituted in nanodiscs, with its hydrophobic C-terminal tail anchored through the nanodisc lipid bilayer, and its folded N-terminal head and ligand binding pocket exposed to the aqueous solution. We anticipate that BCL-2 samples prepared with these protocols will advance structural and mechanistic studies for this important protein family.
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