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Investigation of the Bcl-2 multimerisation process: structural and functional implications. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:850-7. [PMID: 21320534 DOI: 10.1016/j.bbamcr.2011.02.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Revised: 01/15/2011] [Accepted: 02/07/2011] [Indexed: 11/22/2022]
Abstract
Bcl-2 plays a prominent role in regulating the function of mitochondria during respiration and in determining the threshold of apoptotic sensitivity. Despite its relevance, the mechanism through which these processes are achieved is still unknown. Using surface plasmon resonance technology to monitor Bcl-2 multimerisation we discovered that a simple dimeric model does not fit with experimental data. A molecular model of the experimentally observed Bcl-2 homomeric complex has been developed. Accordingly, using a panel of mutants we identified in the loop a critical region for the process of Bcl-2 multimerisation. Our results indicate that the Bcl-2 loop posttranscriptional changes can modulate its ability to make homo and hetero-complexes, ultimately leading to functional modulation, suggesting an intriguing relationship between the ability of Bcl-2 to form multimeric complexes and its multi-functional role as a membrane channel. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.
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52
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Pore-forming activity of BAD is regulated by specific phosphorylation and structural transitions of the C-terminal part. Biochim Biophys Acta Gen Subj 2011; 1810:162-9. [DOI: 10.1016/j.bbagen.2010.11.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Revised: 09/26/2010] [Accepted: 11/09/2010] [Indexed: 01/01/2023]
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53
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Zhou F, Yang Y, Xing D. Bcl-2 and Bcl-xL play important roles in the crosstalk between autophagy and apoptosis. FEBS J 2010; 278:403-13. [PMID: 21182587 DOI: 10.1111/j.1742-4658.2010.07965.x] [Citation(s) in RCA: 315] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Autophagy and apoptosis play important roles in the development, cellular homeostasis and, especially, oncogenesis of mammals. They may be triggered by common upstream signals, resulting in combined autophagy and apoptosis. In other instances, they may be mutually exclusive. Recent studies have suggested possible molecular mechanisms for crosstalk between autophagy and apoptosis. Bcl-2 and Bcl-xL, the well-characterized apoptosis guards, appear to be important factors in autophagy, inhibiting Beclin 1-mediated autophagy by binding to Beclin 1. In addition, Beclin 1, Bcl-2 and Bcl-xL can cooperate with Atg5 or Ca(2+) to regulate both autophagy and apoptosis. Thus, Bcl-2 and Bcl-xL represent a molecular link between autophagy and apoptosis. Here, we discuss the possible roles of Bcl-2 and Bcl-xL in apoptosis and autophagy, and the crosstalk between them.
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Affiliation(s)
- Feifan Zhou
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou, China
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54
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Hockenbery DM. Targeting mitochondria for cancer therapy. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2010; 51:476-489. [PMID: 20213841 DOI: 10.1002/em.20552] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Several recent insights into the roles of mitochondria in cancer have renewed efforts to develop nongenotoxic therapies targeting mitochondrial proteins and functions. Mitochondria are central hubs for intrinsic apoptotic pathways that are activated by cellular stress and injury, and as a consequence, cancers often have defects in these pathways. Bcl-2, the first identified regulator of apoptotic cell deaths, was discovered as an oncogene in human cancers. BCL-2 inhibits mitochondrial pathways of apoptosis through local effects at mitochondrial and endoplasmic reticulum membranes. Increased expression of BCL-2 and the related antiapoptotic proteins BCL-X(L), MCL-1, and BCL-W occurs in significant subsets of common cancer types (Table I) and is generally correlated with poor response. Although incomplete, the emerging understanding of BCL-2 functions through structural, biochemical, and organelle physiology studies has provided paths for targeting BCL-2 with small molecules. Cancer cells also exhibit metabolic differences with their normal cell counterparts, including aerobic glycolysis, known as the Warburg effect, mitochondrial membrane hyperpolarization, and unusual dependence on nutrient substrates such as glucose and glutamine. This knowledge has prompted reexamination of the potential cancer selectivity of previously identified mitochondriotoxic compounds, including approved drugs for other indications, and screening programs to identify new compounds with mitochondrial activities.
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Peixoto PM, Ryu SY, Kinnally KW. Mitochondrial ion channels as therapeutic targets. FEBS Lett 2010; 584:2142-52. [PMID: 20178788 PMCID: PMC2872129 DOI: 10.1016/j.febslet.2010.02.046] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Revised: 02/12/2010] [Accepted: 02/16/2010] [Indexed: 12/31/2022]
Abstract
The study of mitochondrial ion channels changed our perception of these double-wrapped organelles from being just the power house of a cell to the guardian of a cell's fate. Mitochondria communicate with the cell through these special channels. Most of the time, the message is encoded by ion flow across the mitochondrial outer and inner membranes. Potassium, sodium, calcium, protons, nucleotides, and proteins traverse the mitochondrial membranes in an exquisitely regulated manner to control a myriad of processes, from respiration and mitochondrial morphology to cell proliferation and cell death. This review is an update on both well established and putative mitochondrial channels regarding their composition, function, regulation, and therapeutic potential.
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Affiliation(s)
| | - Shin-Young Ryu
- New York University College of Dentistry, New York, NY, 10002
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56
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Pedrini S, Sau D, Guareschi S, Bogush M, Brown RH, Naniche N, Kia A, Trotti D, Pasinelli P. ALS-linked mutant SOD1 damages mitochondria by promoting conformational changes in Bcl-2. Hum Mol Genet 2010; 19:2974-86. [PMID: 20460269 PMCID: PMC2901139 DOI: 10.1093/hmg/ddq202] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
In mutant superoxide dismutase (SOD1)-linked amyotrophic lateral sclerosis (ALS), accumulation of misfolded mutant SOD1 in spinal cord mitochondria is thought to cause mitochondrial dysfunction. Whether mutant SOD1 is toxic per se or whether it damages the mitochondria through interactions with other mitochondrial proteins is not known. We previously identified Bcl-2 as an interacting partner of mutant SOD1 specifically in spinal cord, but not in liver, mitochondria of SOD1 mice and patients. We now show that mutant SOD1 toxicity relies on this interaction. Mutant SOD1 induces mitochondrial morphological changes and compromises mitochondrial membrane integrity leading to release of Cytochrome C only in the presence of Bcl-2. In cells, mouse and human spinal cord with SOD1 mutations, the binding to mutant SOD1 triggers a conformational change in Bcl-2 that results in the uncovering of its toxic BH3 domain and conversion of Bcl-2 into a toxic protein. Bcl-2 carrying a mutagenized, non-toxic BH3 domain fails to support mutant SOD1 mitochondrial toxicity. The identification of Bcl-2 as a specific target and active partner in mutant SOD1 mitochondrial toxicity suggests new therapeutic strategies to inhibit the formation of the toxic mutant SOD1/Bcl-2 complex and to prevent mitochondrial damage in ALS.
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Affiliation(s)
- Steve Pedrini
- Frances and Joseph Weinberg Unit for ALS Research, Farber Institute for Neurosciences, Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107, USA
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57
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Intracellular Ca2+ storage in health and disease: a dynamic equilibrium. Cell Calcium 2010; 47:297-314. [PMID: 20189643 DOI: 10.1016/j.ceca.2010.02.001] [Citation(s) in RCA: 147] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Revised: 01/31/2010] [Accepted: 02/01/2010] [Indexed: 12/17/2022]
Abstract
Homeostatic control of the endoplasmic reticulum (ER) both as the site for protein handling (synthesis, folding, trafficking, disaggregation and degradation) and as a Ca2+ store is of crucial importance for correct functioning of the cell. Disturbance of the homeostatic control mechanisms leads to a vast array of severe pathologies. The Ca2+ content of the ER is a dynamic equilibrium between active uptake via Ca2+ pumps and Ca2+ release by a number of highly regulated Ca2+-release channels. Regulation of the Ca2+-release channels is very complex and several mechanisms are still poorly understood or controversial. There is increasing evidence that a number of unrelated proteins, either by themselves or in association with other Ca2+ channels, can provide additional Ca2+-leak pathways. The ER is a dynamic organelle and changes in its size and components have been described, either as a result of (de)differentiation processes affecting the secretory capacity of cells, or as a result of adaptation mechanisms to diverse stress conditions such as the unfolded protein response and autophagy. In this review we want to give an overview of the current knowledge of the (short-term) regulatory mechanisms that affect Ca2+-release and Ca2+-leak pathways and of the (long-term) adaptations in ER size and capacity. Understanding of the consequences of these mechanisms for cellular Ca2+ signaling could provide a huge therapeutic potential.
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58
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Guillemin Y, Lopez J, Gimenez D, Fuertes G, Valero JG, Blum L, Gonzalo P, Salgado J, Girard-Egrot A, Aouacheria A. Active fragments from pro- and antiapoptotic BCL-2 proteins have distinct membrane behavior reflecting their functional divergence. PLoS One 2010; 5:e9066. [PMID: 20140092 PMCID: PMC2816717 DOI: 10.1371/journal.pone.0009066] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Accepted: 01/17/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The BCL-2 family of proteins includes pro- and antiapoptotic members acting by controlling the permeabilization of mitochondria. Although the association of these proteins with the outer mitochondrial membrane is crucial for their function, little is known about the characteristics of this interaction. METHODOLOGY/PRINCIPAL FINDINGS Here, we followed a reductionist approach to clarify to what extent membrane-active regions of homologous BCL-2 family proteins contribute to their functional divergence. Using isolated mitochondria as well as model lipid Langmuir monolayers coupled with Brewster Angle Microscopy, we explored systematically and comparatively the membrane activity and membrane-peptide interactions of fragments derived from the central helical hairpin of BAX, BCL-xL and BID. The results show a connection between the differing abilities of the assayed peptide fragments to contact, insert, destabilize and porate membranes and the activity of their cognate proteins in programmed cell death. CONCLUSION/SIGNIFICANCE BCL-2 family-derived pore-forming helices thus represent structurally analogous, but functionally dissimilar membrane domains.
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Affiliation(s)
- Yannis Guillemin
- Institut de Biologie et Chimie des Protéines (IBCP), CNRS UMR5086, University of Lyon, Lyon, France
| | - Jonathan Lopez
- Institut de Biologie et Chimie des Protéines (IBCP), CNRS UMR5086, University of Lyon, Lyon, France
| | - Diana Gimenez
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, Paterna, Valencia, España
| | - Gustavo Fuertes
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, Paterna, Valencia, España
| | - Juan Garcia Valero
- Institut de Biologie et Chimie des Protéines (IBCP), CNRS UMR5086, University of Lyon, Lyon, France
| | - Loïc Blum
- Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICBMS), CNRS UMR5246, University of Lyon, Villeurbanne, France
| | - Philippe Gonzalo
- Institut de Biologie et Chimie des Protéines (IBCP), CNRS UMR5086, University of Lyon, Lyon, France
| | - Jesùs Salgado
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, Paterna, Valencia, España
- Departamento de Bioquímica y Biología Molecular, Universidad de Valencia, Burjassot, Valencia, España
| | - Agnès Girard-Egrot
- Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICBMS), CNRS UMR5246, University of Lyon, Villeurbanne, France
| | - Abdel Aouacheria
- Institut de Biologie et Chimie des Protéines (IBCP), CNRS UMR5086, University of Lyon, Lyon, France
- * E-mail:
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Oligomerization of membrane-bound Bcl-2 is involved in its pore formation induced by tBid. Apoptosis 2010; 14:1145-53. [PMID: 19701793 DOI: 10.1007/s10495-009-0389-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Both pro-apoptotic Bax and anti-apoptotic Bcl-2 are structurally homologous to the pore-forming domain of bacterial toxins. Bax proteins oligomerize in the mitochondrial outer membranes forming pores that release cytochrome c from the mitochondrial intermembrane space. Bcl-2 proteins also form pores that, however, are much smaller than the Bax pore. It is unknown whether Bcl-2 forms monomeric or oligomeric pores. Here, we characterized the Bcl-2 pore formation in liposomes using biophysical and biochemical techniques. The results show that the Bcl-2 pore enlarges as the concentration of Bcl-2 increases, suggesting that the pore is formed by Bcl-2 oligomers. As expected from oligomerization-mediated pore-formation, the small pores are formed earlier than the large ones. Bcl-2 oligomers form pores faster than the monomer, indicating that the oligomerization constitutes an intermediate step of the pore formation. A Bcl-2 mutant with higher affinity for oligomerization forms pores faster than wild type Bcl-2. Bcl-2 oligomers were detected in the liposomal membranes under conditions that Bcl-2 forms pores, and the extent of oligomerization was positively correlated with the pore-forming activity. Therefore, Bcl-2 oligomerizes in membranes forming pores, but the extent of oligomerization and the size of the resulting pores are much smaller than that of Bax, supporting the model that Bcl-2 is a defective Bax.
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60
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The Interplay between BCL-2 Family Proteins and Mitochondrial Morphology in the Regulation of Apoptosis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 687:97-114. [DOI: 10.1007/978-1-4419-6706-0_6] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
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61
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Structure assembly of Bcl-x(L) through alpha5-alpha5 and alpha6-alpha6 interhelix interactions in lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:2389-95. [PMID: 19761754 DOI: 10.1016/j.bbamem.2009.09.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Revised: 08/18/2009] [Accepted: 09/06/2009] [Indexed: 11/21/2022]
Abstract
Lipid bilayer membrane is the main site where Bcl-x(L) executes its anti-apoptotic function. Here we used site-directed mutagenesis and cysteine-directed cross-linking to trap the structure of Bcl-x(L) upon membrane insertion. Cys151 on alpha5-helix and Asn185 on alpha6-helix of two neighboring Bcl-x(L) are found in close positions, respectively. The FRET based binding assay indicated that the BH3-peptide binding pocket in Bcl-x(L) is disrupted after its membrane insertion. Co-immunoprecipitation experiments showed that the membrane-bound Bcl-x(L) sequestered tBid by direct interaction at physiological pH. If Bcl-x(L) behaves similarly at low pH as it does at physiological pH, the membrane-bound Bcl-x(L) should bind to tBid through protein regions other than the BH3 domain of tBid and the hydrophobic pocket of Bcl-x(L). Previously, a crystallography study demonstrated that Bcl-x(L) formed homodimers through domain swapping in water, where Cys151 and Asn185 of two monomeric subunits are far apart from each other and the BH3-peptide binding pocket is intact. Our results indicated that Bcl-x(L) dimer trapped by cross-linking in lipids is distinct from the domain swapped dimer, suggesting that Bcl-x(L) transits through a structural change from the water-soluble state to the membrane-bound state and there are multiple possibilities for structural reorganization of Bcl-x(L) protein.
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62
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Polzien L, Baljuls A, Rennefahrt UEE, Fischer A, Schmitz W, Zahedi RP, Sickmann A, Metz R, Albert S, Benz R, Hekman M, Rapp UR. Identification of novel in vivo phosphorylation sites of the human proapoptotic protein BAD: pore-forming activity of BAD is regulated by phosphorylation. J Biol Chem 2009; 284:28004-28020. [PMID: 19667065 DOI: 10.1074/jbc.m109.010702] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
BAD is a proapoptotic member of the Bcl-2 protein family that is regulated by phosphorylation in response to survival factors. Although much attention has been devoted to the identification of phosphorylation sites in murine BAD, little data are available with respect to phosphorylation of human BAD protein. Using mass spectrometry, we identified here besides the established phosphorylation sites at serines 75, 99, and 118 several novel in vivo phosphorylation sites within human BAD (serines 25, 32/34, 97, and 124). Furthermore, we investigated the quantitative contribution of BAD targeting kinases in phosphorylating serine residues 75, 99, and 118. Our results indicate that RAF kinases represent, besides protein kinase A, PAK, and Akt/protein kinase B, in vivo BAD-phosphorylating kinases. RAF-induced phosphorylation of BAD was reduced to control levels using the RAF inhibitor BAY 43-9006. This phosphorylation was not prevented by MEK inhibitors. Consistently, expression of constitutively active RAF suppressed apoptosis induced by BAD and the inhibition of colony formation caused by BAD could be prevented by RAF. In addition, using the surface plasmon resonance technique, we analyzed the direct consequences of BAD phosphorylation by RAF with respect to association with 14-3-3 and Bcl-2/Bcl-X(L) proteins. Phosphorylation of BAD by active RAF promotes 14-3-3 protein association, in which the phosphoserine 99 represented the major binding site. Finally, we show here that BAD forms channels in planar bilayer membranes in vitro. This pore-forming capacity was dependent on phosphorylation status and interaction with 14-3-3 proteins. Collectively, our findings provide new insights into the regulation of BAD function by phosphorylation.
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Affiliation(s)
- Lisa Polzien
- Institute for Medical Radiation and Cell Research, University of Wuerzburg, 97078 Wuerzburg
| | - Angela Baljuls
- Institute for Medical Radiation and Cell Research, University of Wuerzburg, 97078 Wuerzburg
| | - Ulrike E E Rennefahrt
- Institute for Medical Radiation and Cell Research, University of Wuerzburg, 97078 Wuerzburg
| | - Andreas Fischer
- Institute for Medical Radiation and Cell Research, University of Wuerzburg, 97078 Wuerzburg
| | - Werner Schmitz
- Institute of Physiological Chemistry, University of Wuerzburg, 97078 Wuerzburg
| | - Rene P Zahedi
- Institute for Analytical Sciences, Department of Bioanalytics, 44139 Dortmund
| | - Albert Sickmann
- Institute for Analytical Sciences, Department of Bioanalytics, 44139 Dortmund; Medical Proteome Center, Ruhr University of Bochum, 44801 Bochum, Germany
| | - Renate Metz
- Institute for Medical Radiation and Cell Research, University of Wuerzburg, 97078 Wuerzburg
| | - Stefan Albert
- Julius-von-Sachs Institute for Biosciences, University of Wuerzburg, 97078 Wuerzburg
| | - Roland Benz
- Institute of Biotechnology, University of Wuerzburg, 97078 Wuerzburg
| | - Mirko Hekman
- Institute for Medical Radiation and Cell Research, University of Wuerzburg, 97078 Wuerzburg
| | - Ulf R Rapp
- Institute for Medical Radiation and Cell Research, University of Wuerzburg, 97078 Wuerzburg.
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Peng J, Lapolla SM, Zhang Z, Lin J. The Bax BH3 peptide H2-H3 promotes apoptosis by inhibiting Bcl-2's pore-forming and anti-Bax activities in the membrane. SHENG WU YI XUE GONG CHENG XUE ZA ZHI = JOURNAL OF BIOMEDICAL ENGINEERING = SHENGWU YIXUE GONGCHENGXUE ZAZHI 2009; 26:829-835. [PMID: 19813621 PMCID: PMC2844869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Pore-formation and protein-protein interactions are considered to play critical roles in the regulation of apoptosis by Bcl-2 family proteins. During the initiation of apoptosis, the anti-apoptotic Bcl-2 and the pro-apoptotic Bax form different pores to regulate the permeability of mitochondrial outer membrane, playing their opposite functions. Overexpression of Bcl-2 has been found in various cancer cells, therefore it is gaining widespread interest to discover small molecules to compromise Bcl-2 function for anti-cancer treatment. Since Bax binds to Bcl-2's hydrophobic groove via its BH3 domain (composed of helices 2 and 3), by which their functions are inhibited each other, the H2-H3 peptide that contains the functional BH3 domain of Bax has been considered as a potential Bcl-2 antagonist. We recently reported that Bax peptide H2-H3 promotes cell death by inducing Bax-mediated cytochrome c release and by antagonizing Bcl-2's inhibitory effect on Bax. However, the mechanism of how H2-H3 inhibits the anti-apoptotic activity of Bcl-2 remains poorly understood. To address this question, we reconstituted the Bcl-2 or Bax pore-forming process in vitro. We found that H2-H3 inhibited Bcl-2's pore formation and neutralized Bcl-2's inhibitory effect on Bax pore formation in the membrane, whereas the mutant H2-H3 peptide that does not induce apoptosis in cells was shown to have no effect on Bcl-2's activities. Thus, inhibiting Bcl-2's pore-forming and anti-Bax activities in the membrane is strongly correlated with H2-H3's pro-apoptosis function in cells.
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Affiliation(s)
- Jun Peng
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Boulevard, Oklahoma City, OK 73190, USA.
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Szegezdi E, MacDonald DC, Ní Chonghaile T, Gupta S, Samali A. Bcl-2 family on guard at the ER. Am J Physiol Cell Physiol 2009; 296:C941-53. [DOI: 10.1152/ajpcell.00612.2008] [Citation(s) in RCA: 199] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The endoplasmic reticulum (ER) is the main site for protein folding, lipid biosynthesis, and calcium storage in the cell. Disturbances of these critical cellular functions lead to ER stress. The ER responds to disturbances in its homeostasis by launching an adaptive signal transduction pathway, known as the unfolded protein response (UPR). The UPR strives to maintain ER function during stress; however, if the stress is not resolved, apoptotic responses are activated that involve cross talk between the ER and mitochondria. In addition, ER stress is also known to induce autophagy to counteract XBP-1-mediated ER expansion and assist in the degradation of unfolded proteins. One family of proteins involved in the regulation of apoptosis is that of B-cell lymphoma protein 2 (Bcl-2). Complex interactions among the three subgroups within the Bcl-2 family [the antiapoptotic, the multidomain proapoptotic, and the Bcl-2 homology domain 3 (BH3)-only members] control the signaling events of apoptosis upstream of mitochondrial outer membrane permeabilization. These proteins were found to have diverse subcellular locations to aid in the response to varied intrinsic and extrinsic stimuli. Of recent interest is the presence of the Bcl-2 family at the ER. Here, we review the involvement of proteins from each of the three Bcl-2 family subgroups in the maintenance of ER homeostasis and their participation in ER stress signal transduction pathways.
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65
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Cantrel C, Zachowski A, Geny B. Over-expression of the Anti-apoptotic Protein Bcl-2 Affects Membrane Lipid Composition in HL-60 Cells. Lipids 2009; 44:499-509. [DOI: 10.1007/s11745-009-3292-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Accepted: 02/12/2009] [Indexed: 11/29/2022]
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66
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Abstract
The mitochondrial pathway to apoptosis is a major pathway of physiological cell death in vertebrates. The mitochondrial cell death pathway commences when apoptogenic molecules present between the outer and inner mitochondrial membranes are released into the cytosol by mitochondrial outer membrane permeabilization (MOMP). BCL-2 family members are the sentinels of MOMP in the mitochondrial apoptotic pathway; the pro-apoptotic B cell lymphoma (BCL)-2 proteins, BCL-2 associated x protein and BCL-2 antagonist killer 1 induce MOMP whereas the anti-apoptotic BCL-2 proteins, BCL-2, BCL-xl and myeloid cell leukaemia 1 prevent MOMP from occurring. The release of pro-apoptotic factors such as cytochrome c from mitochondria leads to formation of a multimeric complex known as the apoptosome and initiates caspase activation cascades. These pathways are important for normal cellular homeostasis and play key roles in the pathogenesis of many diseases. In this review, we will provide a brief overview of the mitochondrial death pathway and focus on a selection of diseases whose pathogenesis involves the mitochondrial death pathway and we will examine the various pharmacological approaches that target this pathway.
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67
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Peng J, Lapolla SM, Zhang Z, Lin J. The cytosolic domain of Bcl-2 forms small pores in model mitochondrial outer membrane after acidic pH-induced membrane association. SHENG WU YI XUE GONG CHENG XUE ZA ZHI = JOURNAL OF BIOMEDICAL ENGINEERING = SHENGWU YIXUE GONGCHENGXUE ZAZHI 2009; 26:130-137. [PMID: 19334571 PMCID: PMC2844873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The permeability of mitochondrial outer membrane (MOM) is regulated by the proteins of the Bcl-2 family via their interactions at the membrane. While pro-apoptotic Bax protein promotes MOM permeabilization (MOMP) releasing cytochrome c after activation by BH3-only protein, anti-apoptotic Bcl-2 protein protects MOM. However both Bax and Bcl-2 can form pores in model membranes. Unlike Bax pore that has been extensively studied and reported to be directly linked to MOMP, Bcl-2 pore is much less known; thus we investigated the pore-forming property of recombinant Bcl-2 lacking the C-terminal transmembrane sequence (Bcl-2deltaTM) in liposomal membranes of MOM lipids. We found that: (1) Bcl-2 formed pores at acidic pH that induced the association of Bcl-2 with liposome; (2) Bcl-2 pore size was dependent on Bcl-2 concentration, suggesting that oligomerization is involved in Bcl-2 pore formation; (3) Unlike Bax pore that could release large molecules up to 2 mega-Da, Bcl-2 pore was smaller and could only release the molecules of a few kilo-Da. Therefore, Bcl-2 and Bax may form different size pores in MOM, and while the large pore formed by Bax may release cytochrome c during apoptosis, the small pore formed by Bcl-2 may maintain the normal MOM permeability.
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Affiliation(s)
- Jun Peng
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Boulevard, Oklahoma City, OK 73190, USA.
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68
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Feng Y, Zhang L, Hu T, Shen X, Ding J, Chen K, Jiang H, Liu D. A conserved hydrophobic core at Bcl-xL mediates its structural stability and binding affinity with BH3-domain peptide of pro-apoptotic protein. Arch Biochem Biophys 2009; 484:46-54. [PMID: 19161970 DOI: 10.1016/j.abb.2009.01.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2008] [Revised: 01/02/2009] [Accepted: 01/05/2009] [Indexed: 10/21/2022]
Abstract
Bcl-2 family proteins regulate apoptosis through their homo- and heterodimerization. By protein sequence analysis and structural comparison, we have identified a conserved hydrophobic core at the BH1 and BH2 domains of Bcl-2 family proteins. The hydrophobic core is stabilized by hydrophobic interactions among the residues of Trp137, Ile140, Trp181, Ile182, Trp188 and Phe191 in Bcl-x(L). Destabilization of the hydrophobic core can promote the protein unfolding and pore formation in synthetic lipid vesicles. Interestingly, though the hydrophobic core does not participate in binding with BH3 domain of pro-apoptotic proteins, disruption of the hydrophobic core can reduce the affinity of Bcl-x(L) with BH3-domain peptide by changing the conformation of Bcl-x(L) C-terminal residues that are involved in the peptide interaction. The BH3-domain peptide binding affinity and pore forming propensity of Bcl-x(L) were correlated to its death-repressor activity, which provides new information to help study the regulatory mechanism of anti-apoptotic proteins. Meanwhile, as the tryptophans are conserved in the hydrophobic core, in vitro binding assay based on FRET of "Trp-->AEDANS" can be devised to screen for new modulators targeting anti-apoptotic proteins as well as "multi-BH domains" pro-apoptotic proteins.
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Affiliation(s)
- Yu Feng
- Department of Molecular Pharmacology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu-Chong-Zhi Road, Shanghai 201203, China
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69
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Apoptosis induction by Bcl-2 proteins independent of the BH3 domain. Biochem Pharmacol 2008; 76:1612-9. [DOI: 10.1016/j.bcp.2008.08.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2008] [Revised: 08/08/2008] [Accepted: 08/13/2008] [Indexed: 02/02/2023]
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70
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Heazell AEP, Crocker IP. Live and let die - regulation of villous trophoblast apoptosis in normal and abnormal pregnancies. Placenta 2008; 29:772-83. [PMID: 18706691 DOI: 10.1016/j.placenta.2008.07.003] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Revised: 06/30/2008] [Accepted: 07/03/2008] [Indexed: 01/16/2023]
Abstract
Since 1995 the number of publications investigating apoptosis in villous trophoblast has increased exponentially. This scientific interest is in part due to observations that this specialised form of cell death is increased in pregnancy complications such as pre-eclampsia and intra-uterine growth restriction. In addition, apoptosis is described in normal villous trophoblast and elements of the apoptotic machinery are involved in the fusion between cytotrophoblast and the overlying multinucleate syncytiotrophoblast. The increase in descriptions of apoptotic cell death in villous trophoblast has been accompanied by investigations of regulators of apoptosis. It is anticipated that understanding the regulation of apoptosis in villous trophoblast may provide new insights into placental pathologies. This review describes current knowledge regarding the expression and function of these regulators in villous trophoblast, both in normal and complicated pregnancies.
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Affiliation(s)
- A E P Heazell
- Maternal and Fetal Health Research Group, St Mary's Hospital, Manchester M13 0JH, UK.
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71
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Rimessi A, Giorgi C, Pinton P, Rizzuto R. The versatility of mitochondrial calcium signals: from stimulation of cell metabolism to induction of cell death. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:808-16. [PMID: 18573473 DOI: 10.1016/j.bbabio.2008.05.449] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Revised: 05/22/2008] [Accepted: 05/23/2008] [Indexed: 10/21/2022]
Abstract
Both the contribution of mitochondria to intracellular calcium (Ca(2+)) signalling and the role of mitochondrial Ca(2+) uptake in shaping the cytoplasmic response and controlling mitochondrial function are areas of intense investigation. These studies rely on the appropriate use of emerging techniques coupled with judicious data interpretation to a large extent. The development of targeted probes based on the molecular engineering of luminescent proteins has allowed the specific measurement of Ca(2+) concentration ([Ca(2+)]) and adenosine trisphosphate concentration ([ATP]) in intracellular organelles or cytoplasmic subdomains. This approach has given novel information on different aspects of mitochondrial homeostasis.
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Affiliation(s)
- Alessandro Rimessi
- Department of Experimental and Diagnostic Medicine, Section of General Pathology, Interdisciplinary Center for the Study of Inflammation and Emilia Romagna Laboratory BioPharmaNet, University of Ferrara, Ferrara, Italy
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72
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The pleiotropic effects of heterologous Bax expression in yeast. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:1449-65. [DOI: 10.1016/j.bbamcr.2007.12.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Revised: 12/14/2007] [Accepted: 12/30/2007] [Indexed: 12/27/2022]
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73
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Lin H, Zhang X, Cheng G, Tang HF, Zhang W, Zhen HN, Cheng JX, Liu BL, Cao WD, Dong WP, Wang P. Apoptosis induced by ardipusilloside III through BAD dephosphorylation and cleavage in human glioblastoma U251MG cells. Apoptosis 2008; 13:247-57. [PMID: 18181022 DOI: 10.1007/s10495-007-0170-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ardipusilloside III is a saponin newly isolated from Ardisia pusilla A.DC. Since saponins have exhibited broad anti-cancer and pro-apoptotic activity, we investigated the ability of ardipusilloside III to induce apoptosis in human glioblastoma U251MG cells, as well as the involvement of apoptotic signaling pathways. Ardipusilloside III markedly suppressed proliferation of U251MG cells in a time- and dose-dependent manner (P < 0.05, IC50 = 8.2 microg/ml), but did not affect the growth of primary cultures of human astrocytes. Ardipusilloside III-treated U251MG cells underwent typical apoptotic changes. Exposure to a low dose of ardipusilloside III provoked G2/M-phase cell cycle arrest, which preceded apoptosis characterized by the appearance of cells with sub-G1 DNA content. However, a higher dose of ardipusilloside III induced apoptosis without first causing cell cycle arrest. In addition, ardipusilloside III exposure resulted in time-dependent BAD dephosphorylation and cleavage as well as activation of caspase-8 and caspase-3. Therefore, both the intrinsic pathway of apoptosis, mediated by BAD dephosphorylation and cleavage, and the extrinisic pathway of apoptosis, mediated by caspase-8 and caspase-3 activation, were involved in ardipusilloside III-induced apoptosis. These data suggest that ardipusilloside III is a reliable candidate for chemotherapeutic treatment of human glioblastomas, and should be investigated further.
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Affiliation(s)
- Hong Lin
- Department of Neurosurgery, Xijing Institute of Clinical Neuroscience, Xijing Hospital, Fourth Military Medical University, No127 Changle Western Road, Xi'an 710032, PR China
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74
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Abstract
BCL-2 was the first antideath gene discovered, a milestone that effectively launched a new era in cell death research. Since its discovery more than 2 decades ago, multiple members of the human Bcl-2 family of apoptosis-regulating proteins have been identified, including 6 antiapoptotic proteins, 3 structurally similar proapoptotic proteins, and several structurally diverse proapoptotic interacting proteins that operate as upstream agonists or antagonists. Bcl-2-family proteins regulate all major types of cell death, including apoptosis, necrosis, and autophagy. As such, they operate as nodal points at the convergence of multiple pathways with broad relevance to biology and medicine. Bcl-2 derives its name from its original discovery in the context of B-cell lymphomas, where chromosomal translocations commonly activate the BCL-2 protooncogene, endowing B cells with a selective survival advantage that promotes their neoplastic expansion. The concept that defective programmed cell death contributes to malignancy was established by studies of Bcl-2, representing a major step forward in current understanding of tumorigenesis. Experimental therapies targeting Bcl-2 family mRNAs or proteins are currently in clinical testing, raising hopes that a new class of anticancer drugs may be near.
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75
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High-yield expression and purification of soluble forms of the anti-apoptotic Bcl-x(L) and Bcl-2 as TolAIII-fusion proteins. Protein Expr Purif 2008; 60:214-20. [PMID: 18522870 DOI: 10.1016/j.pep.2008.04.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 03/26/2008] [Accepted: 04/15/2008] [Indexed: 11/23/2022]
Abstract
A method is presented to produce large amounts of Bcl-2 and Bcl-x(L), two anti-apoptotic proteins of considerable biomedical interest. Expression constructs were prepared in which the Escherichia coli protein TolAIII, known to promote over expression of soluble product, was added to the N-terminus of Bcl-2 or Bcl-x(L) proteins, which had their C-terminal hydrophobic anchors deleted. Here the expression of these TolAIII-fusion constructs, followed by a two-step metal-affinity based purification protocol is described. The method delivers at least 20 and 10mg of more than 90% pure TolAIII-Bcl-x(L)DeltaC and TolAIII-Bcl-2(2)DeltaC proteins, respectively, per liter of E. coli cell culture. The proteins are released by proteolysis with thrombin providing > 12 mg of Bcl-x(L)DeltaC or > 6 mg of Bcl-2(2)DeltaC per liter of E. coli cell culture with a purity of more than 95%. Whereas Bcl-x(L)DeltaC is soluble both before and after TolAIII removal, Triton X-100 can significantly increase the extraction of TolAIII- Bcl-2(2)DeltaC from the bacterial cells and its subsequent solubility. Far-UV CD spectroscopy demonstrated that they both have an alpha-helical structure. Fluorescence spectroscopy was used to quantitatively analyze the binding of the respiratory inhibitor antimycin A to recombinant Bcl-2 and Bcl-x(L) proteins as well as the displacement of this ligand from the hydrophobic pocket with BH3 Bad-derived peptide. Purified Bcl-x(L)DeltaC and Bcl-2(2)DeltaC both protect isolated mitochondria from Bax-induced release of cytochrome c. The ensemble of data shows that the expressed proteins are correctly folded and functional. Therefore, the TolAIII-fusion system provides a convenient tool for functional characterization and structural studies of anti-apoptotic proteins.
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76
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Cao X, Bennett RL, May WS. c-Myc and caspase-2 are involved in activating Bax during cytotoxic drug-induced apoptosis. J Biol Chem 2008; 283:14490-6. [PMID: 18375382 DOI: 10.1074/jbc.m801107200] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of Bax following diverse cytotoxic stress has been shown to be an essential gateway to mitochondrial dysfunction and activation of the intrinsic apoptotic pathway characterized by cytochrome c release with caspase-9/-3 activation. Interestingly, c-Myc has been reported to promote apoptosis by destabilizing mitochondrial integrity in a Bax-dependent manner. Stress-induced activation of caspase-2 may also induce permeabilization of mitochondria with activation of the intrinsic death pathway. To test whether c-Myc and caspase-2 cooperate to activate Bax and thereby mediate intrinsic apoptosis, small interfering RNA was used to efficiently knock down the expression of c-Myc, caspase-2, and Apaf-1, an activating component in the apoptosome, in two human cancer cell lines, lung adenocarcinoma A-549 and osteosarcoma U2-OS cells. Under conditions when the expression of endogenous c-Myc, caspase-2, or Apaf-1 is reduced 80-90%, cisplatin (or etoposide)-induced apoptosis is significantly decreased. Biochemical studies reveal that the expression of c-Myc and caspase-2 is crucial for cytochrome c release from mitochondria during cytotoxic stress and that Apaf-1 is only required following cytochrome c release to activate caspases-9/-3. Although knockdown of c-Myc or caspase-2 does not affect Bax expression, caspase-2 is important for cytosolic Bax to integrate into the outer mitochondrial membrane, and c-Myc is critical for oligomerization of Bax once integrated into the membrane.
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Affiliation(s)
- Xuefang Cao
- University of Florida Shands Cancer Center and Department of Medicine, University of Florida College of Medicine, Gainesville, FL 32610, USA
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77
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Danial NN. BCL-2 family proteins: critical checkpoints of apoptotic cell death. Clin Cancer Res 2008; 13:7254-63. [PMID: 18094405 DOI: 10.1158/1078-0432.ccr-07-1598] [Citation(s) in RCA: 283] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Apoptosis is a morphologically distinct form of programmed cell death essential for normal development and tissue homeostasis. Aberrant regulation of this pathway is linked to multiple human diseases, including cancer, autoimmunity, neurodegenerative disorders, and diabetes. The BCL-2 family of proteins constitutes a critical control point in apoptosis residing immediately upstream of irreversible cellular damage, where family members control the release of apoptogenic factors from mitochondria. The cardinal member of this family, BCL-2, was originally discovered as the defining oncogene in follicular lymphomas, located at one reciprocal breakpoint of the t(14;18) (q32;q21) chromosomal translocation. Since this original discovery, remarkable efforts marshaled by many investigators around the world have advanced our knowledge of the basic biology, molecular mechanisms, and therapeutic targets in the apoptotic pathway. This review highlights findings from many laboratories that have helped uncover some of the critical control points in apoptosis. The emerging picture is that of an intricate cellular machinery orchestrated by tightly regulated molecular interactions and conformational changes within BCL-2 family proteins that ultimately govern the cellular commitment to apoptotic death.
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Affiliation(s)
- Nika N Danial
- Department of Pathology, Harvard Medical School and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
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78
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Xu C, Xu W, Palmer AE, Reed JC. BI-1 regulates endoplasmic reticulum Ca2+ homeostasis downstream of Bcl-2 family proteins. J Biol Chem 2008; 283:11477-84. [PMID: 18299329 DOI: 10.1074/jbc.m708385200] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
BI-1 (Bax inhibitor-1) is an evolutionarily conserved multitransmembrane protein that resides in the endoplasmic reticulum (ER) and that has documented cytoprotective functions in both animals and plants. Recent studies indicate that BI-1 shares in common with Bcl-2/Bax family proteins the ability to regulate the amounts of Ca(2+) that can be released from the ER by agents, such as the ER-Ca(2+)-ATPase (SERCA) inhibitor thapsigargin (TG). Using an ER-targeted, Ca(2+) indicator (cameleon), with characteristics optimized for measuring ER Ca(2+) ([Ca(2+)](er)), we studied the effects of BI-1 on [Ca(2+)](er) in resting and TG-treated cells. Similar to cells overexpressing antiapoptotic Bcl-2 or Bcl-X(L), overexpression of BI-1 resulted in lower resting [Ca(2+)](er), with concomitantly less Ca(2+) released into the cytosol upon stimulation by TG and with a higher rate of Ca(2+) leakage from the ER. Co-expression of SERCA restored levels of [Ca(2+)](er) to normal, showing opposing actions of the ER-Ca(2+)ATPase and BI-1 on ER Ca(2+) homeostasis. Conversely, cells with deficient BI-1 have increased [Ca(2+)](er), and release more Ca(2+) into the cytosol when challenged with TG. In BI-1-deficient cells, Bcl-X(L) fails to reduce [Ca(2+)](er), indicating that BI-1 functions downstream of Bcl-X(L). In bax(-/-)bak(-/-) double knock-out cells, both BI-1 and Bcl-X(L) retained their ability to reduce [Ca(2+)](er), suggesting that BI-1 and Bcl-X(L) operate downstream of or parallel to Bax/Bak. The findings reveal a hierarchy of functional interactions of BI-1 with Bcl-2/Bax family proteins in regulating ER Ca(2+) homeostasis.
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Affiliation(s)
- Chunyan Xu
- Program on Apoptosis and Cell Death Research, Burnham Institute for Medical Research, La Jolla, California 92037, USA
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79
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Susini L, Besse S, Duflaut D, Lespagnol A, Beekman C, Fiucci G, Atkinson AR, Busso D, Poussin P, Marine JC, Martinou JC, Cavarelli J, Moras D, Amson R, Telerman A. TCTP protects from apoptotic cell death by antagonizing bax function. Cell Death Differ 2008; 15:1211-20. [PMID: 18274553 DOI: 10.1038/cdd.2008.18] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Translationally controlled tumor protein (TCTP) is a potential target for cancer therapy. It functions as a growth regulating protein implicated in the TSC1-TSC2 -mTOR pathway or a guanine nucleotide dissociation inhibitor for the elongation factors EF1A and EF1Bbeta. Accumulating evidence indicates that TCTP also functions as an antiapoptotic protein, through a hitherto unknown mechanism. In keeping with this, we show here that loss of tctp expression in mice leads to increased spontaneous apoptosis during embryogenesis and causes lethality between E6.5 and E9.5. To gain further mechanistic insights into this apoptotic function, we solved and refined the crystal structure of human TCTP at 2.0 A resolution. We found a structural similarity between the H2-H3 helices of TCTP and the H5-H6 helices of Bax, which have been previously implicated in regulating the mitochondrial membrane permeability during apoptosis. By site-directed mutagenesis we establish the relevance of the H2-H3 helices in TCTP's antiapoptotic function. Finally, we show that TCTP antagonizes apoptosis by inserting into the mitochondrial membrane and inhibiting Bax dimerization. Together, these data therefore further confirm the antiapoptotic role of TCTP in vivo and provide new mechanistic insights into this key function of TCTP.
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Affiliation(s)
- L Susini
- Molecular Engines Laboratories, 20 rue Bouvier, Paris, France
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80
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Rasola A, Bernardi P. The mitochondrial permeability transition pore and its involvement in cell death and in disease pathogenesis. Apoptosis 2008; 12:815-33. [PMID: 17294078 DOI: 10.1007/s10495-007-0723-y] [Citation(s) in RCA: 385] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Current research on the mitochondrial permeability transition pore (PTP) and its role in cell death faces a paradox. Initially considered as an in vitro artifact of little pathophysiological relevance, in recent years the PTP has received considerable attention as a potential mechanism for the execution of cell death. The recent successful use of PTP desensitizers in several disease paradigms leaves little doubt about its relevance in pathophysiology; and emerging findings that link the PTP to key cellular signalling pathways are increasing the interest on the pore as a pharmacological target. Yet, recent genetic data have challenged popular views on the molecular nature of the PTP, and called into question many early conclusions about its structure. Here we review basic concepts about PTP structure, function and regulation within the framework of intracellular death signalling, and its role in disease pathogenesis.
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Affiliation(s)
- Andrea Rasola
- CNR Institute of Neuroscience and Department of Biomedical Sciences, University of Padova, Viale Giuseppe Colombo 3, I-35121 Padua, Italy.
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81
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Miyaji EN, Menck CFM. Human BCL-2 Expression Delays Ultraviolet-Induced Apoptosis in Marsupial Cells. Photochem Photobiol 2008. [DOI: 10.1111/j.1751-1097.1998.tb02535.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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82
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Chalah A, Khosravi-Far R. The Mitochondrial Death Pathway. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 615:25-45. [DOI: 10.1007/978-1-4020-6554-5_3] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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83
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Rusznák Z, Bakondi G, Kosztka L, Pocsai K, Dienes B, Fodor J, Telek A, Gönczi M, Szűcs G, Csernoch L. Mitochondrial expression of the two-pore domain TASK-3 channels in malignantly transformed and non-malignant human cells. Virchows Arch 2007; 452:415-26. [DOI: 10.1007/s00428-007-0545-x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Revised: 10/20/2007] [Accepted: 10/31/2007] [Indexed: 11/30/2022]
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84
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Torrecillas A, Martínez-Senac MM, Ausili A, Corbalán-García S, Gómez-Fernández JC. Interaction of the C-terminal domain of Bcl-2 family proteins with model membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2931-9. [PMID: 17905195 DOI: 10.1016/j.bbamem.2007.08.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2007] [Revised: 07/23/2007] [Accepted: 08/13/2007] [Indexed: 11/19/2022]
Abstract
Bcl-2 family proteins are involved in the cell homeostasis by regulating programmed cell death. Some of these proteins promote apoptosis, while others inhibit the same process. The C-terminal hydrophobic domain of some of these proteins is predicted to be involved in anchoring them to a variety of cell membranes, such as mitochondrial, endoplasmic reticulum and nuclear membranes. We have used five synthetic peptides imitating the C-terminal domain from both anti-apoptotic (Bcl-2) and pro-apoptotic members (Bak, Bax, and two mutants of this last protein) of this family to study their interaction with model membranes. Some differences were detected in the interaction with these peptides. The addition of all the peptides to large unilamellar vesicles destabilized them and released encapsulated carboxyfluorescein to different degrees, so that fluidity and the increase in negative curvature favoured the extent in the release of carboxyfluorescein. Bcl-2-C and Bax-C peptides produced the highest release levels in most cases, while BaxS184K-C was the least efficient in this respect. These results indicate that these C-terminal domains are able to insert themselves in the membranes, each in a different way that is probably related with their different way which can be related to their differing locations within the cell and their different roles in regulating apoptosis.
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Affiliation(s)
- Alejandro Torrecillas
- Departamento de Bioquímica y Biología Molecular (A), Facultad de Veterinaria, Universidad de Murcia, Apartado de Correos 4021, E-30080, Murcia, Spain
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85
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Grant JR, Moise AR, Jefferies WA. Identification of a novel immunosubversion mechanism mediated by a virologue of the B-lymphocyte receptor TACI. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2007; 14:907-17. [PMID: 17538121 PMCID: PMC1951057 DOI: 10.1128/cvi.00058-07] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
TACI (transmembrane activator and calcium modulator and cyclophilin ligand [CAML] interactor) is a part of a novel network of ligands and receptors involved in B-cell survival and isotype switching. The TACI protein mediates its effects through CAML, an endoplasmic reticulum (ER)-localized protein that controls Ca(2+) efflux. The adenovirus E3-6.7K protein prevents inflammatory responses and also confers resistance from a variety of apoptotic stimuli and maintains ER Ca(2+) homeostasis; however, the mechanism of action is unknown. Here, we provide evidence that E3-6.7K shares sequence homology with TACI and inhibits apoptosis and ER Ca(2+) efflux through an interaction with CAML, a Ca(2+)-modulating protein. We demonstrate a direct interaction between E3-6.7K and CAML and reveal that the two proteins colocalize in an ER-like compartment. Furthermore, the interaction between the two proteins is localized to the N-terminal domain of CAML and to a 22-amino-acid region near the C terminus of E3-6.7K termed the CAML-binding domain (CBD). Mutational analysis of the CBD showed that an interaction with CAML is required for E3-6.7K to inhibit thapsigargin-induced apoptosis and ER Ca(2+) efflux. E3-6.7K appears to be the first virologue of TACI to be identified. It targets CAML in a novel immunosubversive mechanism to alter ER Ca(2+) homeostasis, which consequently inhibits inflammation and protects infected cells from apoptosis.
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Affiliation(s)
- Jason R Grant
- The Michael Smith Laboratories, The Biomedical Research Centre, Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada.
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86
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Aisenbrey C, Sudheendra US, Ridley H, Bertani P, Marquette A, Nedelkina S, Lakey JH, Bechinger B. Helix orientations in membrane-associated Bcl-XL determined by 15N-solid-state NMR spectroscopy. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2007; 37:71-80. [PMID: 17492281 DOI: 10.1007/s00249-007-0165-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Revised: 03/22/2007] [Accepted: 03/31/2007] [Indexed: 11/24/2022]
Abstract
Controlled cell death is fundamental to tissue hemostasis and apoptosis malfunctions can lead to a wide range of diseases. Bcl-x(L) is an anti-apoptotic protein the function of which is linked to its reversible interaction with mitochondrial outer membranes. Its interfacial and intermittent bilayer association makes prediction of its bound structure difficult without using methods able to extract data from dynamic systems. Here we investigate Bcl-x(L) associated with oriented lipid bilayers at physiological pH using solid-state NMR spectroscopy. The data are consistent with a C-terminal transmembrane anchoring sequence and an average alignment of the remaining helices, i.e. including helices 5 and 6, approximately parallel to the membrane surface. Data from several biophysical approaches confirm that after removal of the C-terminus from Bcl-x(L) its membrane interactions are weak. In the presence of membranes Bcl-x(L) can still interact with a Bak BH3 domain peptide suggesting a model where the hydrophobic C-terminus of the protein unfolds and inserts into the membrane. During this conformational change the Bcl-x(L) hydrophobic binding pocket becomes accessible for protein-protein interactions whilst the structure of the N-terminal region remains intact.
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Affiliation(s)
- Christopher Aisenbrey
- Institut de Chimie de Strasbourg, Université Louis Pasteur/CNRS LC3-UMR 7177, 4 rue Blaise Pascal, 67070 Strasbourg, France
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87
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Usuda J, Azizuddin K, Chiu SM, Oleinick NL. Association Between the Photodynamic Loss of Bcl-2 and the Sensitivity to Apoptosis Caused by Phthalocyanine Photodynamic Therapy¶. Photochem Photobiol 2007. [DOI: 10.1562/0031-8655(2003)0780001abtplo2.0.co2] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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88
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Abstract
In work spanning more than a century, mitochondria have been recognized for their multifunctional roles in metabolism, energy transduction, ion transport, inheritance, signaling, and cell death. Foremost among these tasks is the continuous production of ATP through oxidative phosphorylation, which requires a large electrochemical driving force for protons across the mitochondrial inner membrane. This process requires a membrane with relatively low permeability to ions to minimize energy dissipation. However, a wealth of evidence now indicates that both selective and nonselective ion channels are present in the mitochondrial inner membrane, along with several known channels on the outer membrane. Some of these channels are active under physiological conditions, and others may be activated under pathophysiological conditions to act as the major determinants of cell life and death. This review summarizes research on mitochondrial ion channels and efforts to identify their molecular correlates. Except in a few cases, our understanding of the structure of mitochondrial ion channels is limited, indicating the need for focused discovery in this area.
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Affiliation(s)
- Brian O'Rourke
- Institute of Molecular Cardiobiology, Division of Cardiology, Department of Medicine, The Johns Hopkins University, Baltimore, Maryland 21205, USA.
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89
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Vanhollebeke B, Truc P, Poelvoorde P, Pays A, Joshi PP, Katti R, Jannin JG, Pays E. Human Trypanosoma evansi infection linked to a lack of apolipoprotein L-I. N Engl J Med 2006; 355:2752-6. [PMID: 17192540 DOI: 10.1056/nejmoa063265] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Humans have innate immunity against Trypanosoma brucei brucei that is known to involve apolipoprotein L-I (APOL1). Recently, a case of T. evansi infection in a human was identified in India. We investigated whether the APOL1 pathway was involved in this occurrence. The serum of the infected patient was found to have no trypanolytic activity, and the finding was linked to the lack of APOL1, which was due to frameshift mutations in both APOL1 alleles. Trypanolytic activity was restored by the addition of recombinant APOL1. The lack of APOL1 explained the patient's infection with T. evansi.
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Affiliation(s)
- Benoit Vanhollebeke
- Laboratory of Molecular Parasitology, Institut de Biologie et de Médecine Moléculaires, Université Libre de Bruxelles, Gosselies, Belgium
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90
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Abstract
Apoptosis has been recognized as a central component in the pathogenesis of atherosclerosis, in addition to the other human pathologies such as cancer and diabetes. The pathophysiology of atherosclerosis is complex, involving both apoptosis and proliferation at different phases of its progression. Oxidative modification of lipids and inflammation differentially regulate the apoptotic and proliferative responses of vascular cells during progression of the atherosclerotic lesion. Bcl-2 proteins act as the major regulators of extrinsic and intrinsic apoptosis signalling pathways and more recently it has become evident that they mediate the apoptotic response of vascular cells in response to oxidation and inflammation either in a provocative or an inhibitory mode of action. Here we address Bcl-2 proteins as major therapeutic targets for the treatment of atherosclerosis and underscore the need for the novel preventive and therapeutic interventions against atherosclerosis, which should be designed in the light of molecular mechanisms regulating apoptosis of vascular cells in atherosclerotic lesions.
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Affiliation(s)
- Ozgur Kutuk
- Biological Sciences and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, 34956 Orhanli, Tuzla, Istanbul, Turkey
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91
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Antignani A, Youle RJ. How do Bax and Bak lead to permeabilization of the outer mitochondrial membrane? Curr Opin Cell Biol 2006; 18:685-9. [PMID: 17046225 DOI: 10.1016/j.ceb.2006.10.004] [Citation(s) in RCA: 214] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Accepted: 10/02/2006] [Indexed: 11/23/2022]
Abstract
Bcl-2 family members, like the structurally similar translocation domain of diphtheria toxin, can form ion-selective channels and larger-diameter pores in artificial lipid bilayers. Recent studies show how Bcl-2 family members change topology in membranes during apoptosis and that these different states may either promote or inhibit apoptosis. Binding of BH3-only proteins alters the subcellular localization and/or membrane topology and probably affects the channel formation of Bcl-2, Bcl-xL and Bcl-w. However, it remains unclear how the pore-forming activity functions in cells to regulate mitochondrial membrane permeabilization and cell death. Bcl-2 family members in flies and worms regulate apoptosis by mechanisms seemingly unrelated to membrane permeabilization, leaving a unifying model for the biochemical activity of this protein family unknown. Work linking Bcl-2 family members to mitochondrial morphogenesis in worms and mammals suggests some common functions of Bcl-2 family proteins may exist.
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Affiliation(s)
- Antonella Antignani
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive MSC 3704, Bethesda, MD 20892, USA
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92
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Peng J, Tan C, Roberts GJ, Nikolaeva O, Zhang Z, Lapolla SM, Primorac S, Andrews DW, Lin J. tBid elicits a conformational alteration in membrane-bound Bcl-2 such that it inhibits Bax pore formation. J Biol Chem 2006; 281:35802-11. [PMID: 17005564 PMCID: PMC2825177 DOI: 10.1074/jbc.m608303200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
During initiation of apoptosis, Bcl-2 family proteins regulate the permeability of mitochondrial outer membrane. BH3-only protein, tBid, activates pro-apoptotic Bax to release cytochrome c from mitochondria. tBid also activates anti-apoptotic Bcl-2 in the mitochondrial outer membrane, changing it from a single-spanning to a multispanning conformation that binds the active Bax and inhibits cytochrome c release. However, it is not known whether other mitochondrial proteins are required to elicit the tBid-induced Bcl-2 conformational alteration. To define the minimal components that are required for the functionally important Bcl-2 conformational alteration, we reconstituted the reaction using purified proteins and liposomes. We found that purified tBid was sufficient to induce a conformational alteration in the liposome-tethered, but not cytosolic Bcl-2, resulting in a multispanning form that is similar to the one found in the mitochondrial outer membrane of drug-treated cells. Mutations that abolished tBid/Bcl-2 interaction also abolished the conformational alteration, demonstrating that a direct tBid/Bcl-2 interaction at the membrane is both required and sufficient to elicit the conformational alteration. Furthermore, active Bax also elicited the Bcl-2 conformational alteration. Bcl-2 mutants that displayed increased or decreased activity in the conformational alteration assay showed corresponding activities in inhibiting pore formation by Bax in vitro and in preventing apoptosis in vivo. Thus, there is a strong correlation between the direct interaction of membrane-bound Bcl-2 and tBid with activation of Bcl-2 in vitro and in vivo.
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Affiliation(s)
- Jun Peng
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Boulevard, Oklahoma City, OK 73190
| | - Chibing Tan
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Boulevard, Oklahoma City, OK 73190
| | - G. Jane Roberts
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1200 Main Street West, Hamilton, Ontario L8N 3Z5, Canada
| | - Olga Nikolaeva
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Boulevard, Oklahoma City, OK 73190
| | - Zhi Zhang
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Boulevard, Oklahoma City, OK 73190
| | - Suzanne M. Lapolla
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Boulevard, Oklahoma City, OK 73190
| | - Steve Primorac
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1200 Main Street West, Hamilton, Ontario L8N 3Z5, Canada
| | - David W. Andrews
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1200 Main Street West, Hamilton, Ontario L8N 3Z5, Canada
| | - Jialing Lin
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Boulevard, Oklahoma City, OK 73190
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93
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Er E, Oliver L, Cartron PF, Juin P, Manon S, Vallette FM. Mitochondria as the target of the pro-apoptotic protein Bax. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:1301-11. [PMID: 16836974 DOI: 10.1016/j.bbabio.2006.05.032] [Citation(s) in RCA: 191] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2006] [Revised: 04/20/2006] [Accepted: 05/23/2006] [Indexed: 11/21/2022]
Abstract
During apoptosis, engagement of the mitochondrial pathway involves the permeabilization of the outer mitochondrial membrane (OMM), which leads to the release of cytochrome c and other apoptogenic proteins such as Smac/DIABLO, AIF, EndoG, Omi/HtraA2 and DDP/TIMM8a. OMM permeabilization depends on activation, translocation and oligomerization of multidomain Bcl-2 family proteins such as Bax or Bak. Factors involved in Bax conformational change and the function(s) of the distinct domains controlling the addressing and the insertion of Bax into mitochondria are described in this review. We also discuss our current knowledge on Bax oligomerization and on the molecular mechanisms underlying the different models accounting for OMM permeabilization during apoptosis.
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Affiliation(s)
- Emine Er
- UMR 601 INSERM, Université de Nantes, 9 Quai Moncousu F-44035 Nantes, Cedex 01 France
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94
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Butterfield DA, Abdul HM, Opii W, Newman SF, Joshi G, Ansari MA, Sultana R. REVIEW: Pin1 in Alzheimer's disease. J Neurochem 2006; 98:1697-706. [PMID: 16945100 DOI: 10.1111/j.1471-4159.2006.03995.x] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Proteolytic processing and phosphorylation of amyloid precursor protein (APP), and hyperphosphorylation of tau protein, have been shown to be increased in Alzheimer's disease (AD) brains, leading to increased production of beta-amyloid (Abeta) peptides and neurofibrillary tangles, respectively. These observations suggest that phosphorylation events are critical to the understanding of the pathogenesis and treatment of this devastating disease. Pin-1, one of the peptidyl-prolyl isomerases (PPIase), catalyzes the isomerization of the peptide bond between pSer/Thr-Pro in proteins, thereby regulating their biological functions which include protein assembly, folding, intracellular transport, intracellular signaling, transcription, cell cycle progression and apoptosis. A number of previous studies have shown that Pin1 is co-localized with phosphorylated tau in AD brain, and shows an inverse relationship to the expression of tau. Pin1 protects neurons under in vitro conditions. Moreover, recent studies demonstrate that APP is a target for Pin1 and thus, in Abeta production. Furthermore, Pin1 was found to be oxidatively modified and to have reduced activity in the hippocampus in mild cognitive impairment (MCI) and AD. Because of the diverse functions of Pin1, and the discovery that this protein is one of the oxidized proteins common to both MCI and AD brain, the question arises as to whether Pin1 is one of the driving forces for the initiation or progression of AD pathogenesis, finally leading to neurodegeneration and neuronal apoptosis. In the present review, we discuss the role of Pin1 with respect to Alzheimer's disease.
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95
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Abstract
The protein BAX of the Bcl-2-family is felt to be one of the two Bcl-2-family proteins that directly participate in the mitochondrial cytochrome c-translocating pore. We have studied the kinetics, stoichiometry and size of the pore formed by BAX in planar lipid bilayers and synthetic liposomes. Our data indicate that a cytochrome c-competent pore can be formed by in-membrane association of BAX monomers.
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Affiliation(s)
- P H Schlesinger
- Department of Physiology and Cell Biology, Washington University School of Medicine, St. Louis, MO 63110, USA
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96
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Abstract
The discovery of B-cell lymphoma-2 (BCL-2) over 20 years ago revealed a new paradigm in cancer biology: the development and persistence of cancer can be driven by molecular roadblocks along the natural pathway to cell death. The subsequent identification of an expansive family of BCL-2 proteins provoked an intensive investigation of the interplay among these critical regulators of cell death. What emerged was a compelling tale of guardians and executioners, each participating in a molecular choreography that dictates cell fate. Ten years into the BCL-2 era, structural details defined how certain BCL-2 family proteins interact, and molecular targeting of the BCL-2 family has since become a pharmacological quest. Although many facets of BCL-2 family death signaling remain a mechanistic mystery, small molecules and peptides that effectively target BCL-2 are eliminating the roadblock to cell death, raising hopes for a medical breakthrough in cancer and other diseases of deregulated apoptosis.
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Affiliation(s)
- L D Walensky
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
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97
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Gaggelli E, Kozlowski H, Valensin D, Valensin G. Copper Homeostasis and Neurodegenerative Disorders (Alzheimer's, Prion, and Parkinson's Diseases and Amyotrophic Lateral Sclerosis). Chem Rev 2006; 106:1995-2044. [PMID: 16771441 DOI: 10.1021/cr040410w] [Citation(s) in RCA: 1236] [Impact Index Per Article: 68.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Elena Gaggelli
- Department of Chemistry, University of Siena, Via Aldo Moro 2, Siena 53100, Italy
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98
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Pinton P, Rizzuto R. Bcl-2 and Ca2+ homeostasis in the endoplasmic reticulum. Cell Death Differ 2006; 13:1409-18. [PMID: 16729032 DOI: 10.1038/sj.cdd.4401960] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Recent data have revealed an unexpected role of Bcl-2 in modulating the steady-state levels and agonist-dependent fluxes of Ca(2+) ions. Direct monitoring of endoplasmic reticulum (ER) Ca(2+) concentration with recombinant probes reveals a lower state of filling in Bcl-2-overexpressing cells and a higher leak rate from the organelle. The broader set of indirect data using cytosolic probes reveals a more complex scenario, as in many cases no difference was detected in the Ca(2+) content of the intracellular pools. At the same time, Ca(2+) signals have been shown to affect important checkpoints of the apoptotic process, such as mitochondria, thus tuning the sensitivity of cells to various challenges. In this contribution, we will review (i) the data on the effect of Bcl-2 on [Ca(2+)](er), (ii) the functional significance of the Ca(2+)-signalling alteration and (iii) the current insight into the possible mechanisms of this effect.
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Affiliation(s)
- P Pinton
- Department of Experimental and Diagnostic Medicine, Section of General Pathology, ER-GenTech laboratory and Interdisciplinary Center for the Study of Inflammation (ICSI), University of Ferrara, Italy
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99
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Thomadaki H, Scorilas A. BCL2 family of apoptosis-related genes: functions and clinical implications in cancer. Crit Rev Clin Lab Sci 2006; 43:1-67. [PMID: 16531274 DOI: 10.1080/10408360500295626] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
One of the most effective ways to combat different types of cancer is through early diagnosis and administration of effective treatment, followed by efficient monitoring that will allow physicians to detect relapsing disease and treat it at the earliest possible time. Apoptosis, a normal physiological form of cell death, is critically involved in the regulation of cellular homeostasis. Dysregulation of programmed cell death mechanisms plays an important role in the pathogenesis and progression of cancer as well as in the responses of tumours to therapeutic interventions. Many members of the BCL2 (B-cell CLL/lymphoma 2; Bcl-2) family of apoptosis-related genes have been found to be differentially expressed in various malignancies, and some are useful prognostic cancer biomarkers. We have recently cloned a new member of this family, BCL2L12, which was found to be differentially expressed in many tumours. Most of the BCL2 family genes have been found to play a central regulatory role in apoptosis induction. Results have made it clear that a number of coordinating alterations in the BCL2 family of genes must occur to inhibit apoptosis and provoke carcinogenesis in a wide variety of cancers. However, more research is required to increase our understanding of the extent to which and the mechanisms by which they are involved in cancer development, providing the basis for earlier and more accurate cancer diagnosis, prognosis and therapeutic intervention that targets the apoptosis pathways. In the present review, we describe current knowledge of the function and molecular characteristics of a series of classic but also newly discovered genes of the BCL2 family as well as their implications in cancer development, prognosis and treatment.
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Affiliation(s)
- Hellinida Thomadaki
- Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Athens, Panepistimiopolis, 15701 Athens, Greece
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100
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Nilsson C, Johansson U, Johansson AC, Kågedal K, Ollinger K. Cytosolic acidification and lysosomal alkalinization during TNF-α induced apoptosis in U937 cells. Apoptosis 2006; 11:1149-59. [PMID: 16699952 DOI: 10.1007/s10495-006-7108-5] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Apoptosis is often associated with acidification of the cytosol and since loss of lysosomal proton gradient and release of lysosomal content are early events during apoptosis, we investigated if the lysosomal compartment could contribute to cytosolic acidification. After exposure of U937 cells to tumor necrosis factor-alpha, three populations; healthy, pre-apoptotic, and apoptotic cells, were identified by flow cytometry. These populations were investigated regarding intra-cellular pH and apoptosis-associated events. There was a drop in cytosolic pH from 7.2 +/- 0.1 in healthy cells to 6.8 +/- 0.1 in pre-apoptotic, caspase-negative cells. In apoptotic, caspase-positive cells, the pH was further decreased to 5.7 +/- 0.04. The cytosolic acidification was not affected by addition of specific inhibitors towards caspases or the mitochondrial F(0)F(1)-ATPase. In parallel to the cytosolic acidification, a rise in lysosomal pH from 4.3 +/- 0.3, in the healthy population, to 4.8 +/- 0.3 and 5.5 +/- 0.3 in the pre-apoptotic- and apoptotic populations, respectively, was detected. In addition, lysosomal membrane permeability increased as detected as release of cathepsin D from lysosomes to the cytosol in pre-apoptotic and apoptotic cells. We, thus, suggest that lysosomal proton release is the cause of the cytosolic acidification of U937 cells exposed to TNF-alpha.
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Affiliation(s)
- Cathrine Nilsson
- Division of Experimental Pathology, Faculty of Health Sciences, Linköping University, S-581 85 Linköping, Sweden.
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