The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Asa B Gustafsson - One of the best experts on this subject based on the ideXlab platform.
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BNIP3L nix and fundc1 mediated mitophagy is required for mitochondrial network remodeling during cardiac progenitor cell differentiation
Autophagy, 2019Co-Authors: Mark A. Lampert, Amabel M Orogo, Babette C Hammerling, Rita H. Najor, Leonardo J. Leon, Bingyan J. Wang, Taeyong Kim, Mark A. Sussman, Asa B GustafssonAbstract:Cell-based therapies represent a very promising strategy to repair and regenerate the injured heart to prevent progression to heart failure. To date, these therapies have had limited success due to a lack of survival and retention of the infused cells. Therefore, it is important to increase our understanding of the biology of these cells and utilize this information to enhance their survival and function in the injured heart. Mitochondria are critical for progenitor cell function and survival. Here, we demonstrate the importance of mitochondrial autophagy, or mitophagy, in the differentiation process in adult cardiac progenitor cells (CPCs). We found that mitophagy was rapidly induced upon initiation of differentiation in CPCs. We also found that mitophagy was mediated by mitophagy receptors, rather than the PINK1-PRKN/PARKIN pathway. Mitophagy mediated by BNIP3L/NIX and FUNDC1 was not involved in regulating progenitor cell fate determination, mitochondrial biogenesis, or reprogramming. Instead, mitophagy facilitated the CPCs to undergo proper mitochondrial network reorganization during differentiation. Abrogating BNIP3L- and FUNDC1-mediated mitophagy during differentiation led to sustained mitochondrial fission and formation of donut-shaped impaired mitochondria. It also resulted in increased susceptibility to cell death and failure to survive the infarcted heart. Finally, aging is associated with accumulation of mitochondrial DNA (mtDNA) damage in cells and we found that acquiring mtDNA mutations selectively disrupted the differentiation-activated mitophagy program in CPCs. These findings demonstrate the importance of BNIP3L- and FUNDC1-mediated mitophagy as a critical regulator of mitochondrial network formation during differentiation, as well as the consequences of accumulating mtDNA mutations. Abbreviations: Baf: bafilomycin A1; BCL2L13: BCL2 like 13; BNIP3: BCL2 interacting protein 3; BNIP3L: BCL2 interacting protein 3 like; CPCs: cardiac progenitor cells; DM: differentiation media; DNM1L: dynamin 1 like; EPCs: endothelial progenitor cells; FCCP: carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone; FUNDC1: FUN14 domain containing 1; HSCs: hematopoietic stem cells; MAP1LC3B/LC3: microtubule-associated protein 1 light chain 3 beta; MFN1/2: mitofusin 1/2; MSCs: mesenchymal stem cells; mtDNA: mitochondrial DNA; OXPHOS: oxidative phosphorylation; PPARGC1A: PPARG coactivator 1 alpha; PHB2: prohibitin 2; POLG: DNA polymerase gamma, catalytic subunit; SQSTM1: sequestosome 1; TEM: transmission electron microscopy; TMRM: tetramethylrhodamine methyl ester.
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BNIP3L/NIX and FUNDC1-mediated mitophagy is required for mitochondrial network remodeling during cardiac progenitor cell differentiation
2019Co-Authors: Mark A. Lampert, Amabel M Orogo, Babette C Hammerling, Rita H. Najor, Leonardo J. Leon, Bingyan J. Wang, Taeyong Kim, Mark A. Sussman, Asa B GustafssonAbstract:Cell-based therapies represent a very promising strategy to repair and regenerate the injured heart to prevent progression to heart failure. To date, these therapies have had limited success due to a lack of survival and retention of the infused cells. Therefore, it is important to increase our understanding of the biology of these cells and utilize this information to enhance their survival and function in the injured heart. Mitochondria are critical for progenitor cell function and survival. Here, we demonstrate the importance of mitochondrial autophagy, or mitophagy, in the differentiation process in adult cardiac progenitor cells (CPCs). We found that mitophagy was rapidly induced upon initiation of differentiation in CPCs. We also found that mitophagy was mediated by mitophagy receptors, rather than the PINK1-PRKN/PARKIN pathway. Mitophagy mediated by BNIP3L/NIX and FUNDC1 was not involved in regulating progenitor cell fate determination, mitochondrial biogenesis, or reprogramming. Instead, mitophagy facilitated the CPCs to undergo proper mitochondrial network reorganization during differentiation. Abrogating BNIP3L- and FUNDC1-mediated mitophagy during differentiation led to sustained mitochondrial fission and formation of donut-shaped impaired mitochondria. It also resulted in increased susceptibility to cell death and failure to survive the infarcted heart. Finally, aging is associated with accumulation of mitochondrial DNA (mtDNA) damage in cells and we found that acquiring mtDNA mutations selectively disrupted the differentiation-activated mitophagy program in CPCs. These findings demonstrate the importance of BNIP3L- and FUNDC1-mediated mitophagy as a critical regulator of mitochondrial network formation during differentiation, as well as the consequences of accumulating mtDNA mutations. Abbreviations: Baf: bafilomycin A1; BCL2L13: BCL2 like 13; BNIP3: BCL2 interacting protein 3; BNIP3L: BCL2 interacting protein 3 like; CPCs: cardiac progenitor cells; DM: differentiation media; DNM1L: dynamin 1 like; EPCs: endothelial progenitor cells; FCCP: carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone; FUNDC1: FUN14 domain containing 1; HSCs: hematopoietic stem cells; MAP1LC3B/LC3: microtubule-associated protein 1 light chain 3 beta; MFN1/2: mitofusin 1/2; MSCs: mesenchymal stem cells; mtDNA: mitochondrial DNA; OXPHOS: oxidative phosphorylation; PPARGC1A: PPARG coactivator 1 alpha; PHB2: prohibitin 2; POLG: DNA polymerase gamma, catalytic subunit; SQSTM1: sequestosome 1; TEM: transmission electron microscopy; TMRM: tetramethylrhodamine methyl ester
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Abstract 174: The BH3-Only Protein BNIP3 Induces Mitochondrial Clearance via Multiple Pathways
Circulation Research, 2015Co-Authors: Eileen R Gonzalez, Dieter A. Kubli, Rita A. Hanna, Babette C Hammerling, Asa B GustafssonAbstract:Autophagy plays an important role in cellular quality control and is responsible for removing protein aggregates and dysfunctional organelles. BNIP3 is an atypical BH3-only protein which is known to cause mitochondrial dysfunction and cell death in the myocardium. Interestingly, BNIP3 can also protect against cell death by promoting removal of dysfunctional mitochondria via autophagy (mitophagy). We have previously reported that BNIP3 is a potent inducer of mitophagy in cardiac myocytes and that BNIP3 contains an LC3 Interacting Region (LIR) that binds to LC3 on the autophagosome, tethering the mitochondrion to the autophagosome for engulfment. However, the molecular mechanism(s) underlying BNIP3-mediated mitophagy are still unclear. In this study, we discovered that BNIP3 can mediate mitochondrial clearance in cells even in the absence of a functional autophagy pathway. We found that overexpression of BNIP3 led to significant clearance of mitochondria in both wild type (WT) and autophagy deficient Atg5-/- MEFs. BNIP3 caused an increase in LC3II levels in WT MEFs, indicating increased formation of autophagosomes. In contrast, LC3II was undetectable in Atg5-/- MEFs. Furthermore, we found that BNIP3-mediated clearance in WT and Atg5-/- MEFs did not require the presence of Parkin, an E3 ubiquitin ligase which plays a critical role in clearing dysfunctional mitochondria in cells. Also, overexpression of Parkin did not enhance BNIP3-mediated mitochondrial clearance. When investigating activation of alternative cellular degradation pathways, we found that BNIP3 induced activation of the endosomal-lysosomal pathway in both WT and Atg5-/- MEFs. Mutating the LC3 binding site in BNIP3 did not interfere with the activation of the endosomal pathway and clearance of mitochondria in Atg5-/- MEFs. Thus, these findings suggest that BNIP3 can promote clearance of mitochondria via multiple pathways in cells. The role of autophagy in removing mitochondria is already well established and we are currently exploring the roles of the endosomal and alternative autophagy pathways in BNIP3-mediated mitochondrial clearance in myocytes.
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microtubule associated protein 1 light chain 3 lc3 interacts with bnip3 protein to selectively remove endoplasmic reticulum and mitochondria via autophagy
Journal of Biological Chemistry, 2012Co-Authors: Rita A. Hanna, Melissa N Quinsay, Amabel M Orogo, Kayla Giang, Shivaji Rikka, Asa B GustafssonAbstract:Autophagy plays an important role in cellular quality control and is responsible for removing protein aggregates and dysfunctional organelles. Bnip3 is an atypical BH3-only protein that is known to cause mitochondrial dysfunction and cell death. Interestingly, Bnip3 can also protect against cell death by inducing mitochondrial autophagy. The mechanism for this process, however, remains poorly understood. Bnip3 contains a C-terminal transmembrane domain that is essential for homodimerization and proapoptotic function. In this study, we show that homodimerization of Bnip3 is also a requirement for induction of autophagy. Several Bnip3 mutants that do not interfere with its mitochondrial localization but disrupt homodimerization failed to induce autophagy in cells. In addition, we discovered that endogenous Bnip3 is localized to both mitochondria and the endoplasmic reticulum (ER). To investigate the effects of Bnip3 at mitochondria or the ER on autophagy, Bnip3 was targeted specifically to each organelle by substituting the Bnip3 transmembrane domain with that of Acta or cytochrome b5. We found that Bnip3 enhanced autophagy in cells from both sites. We also discovered that Bnip3 induced removal of both ER (ERphagy) and mitochondria (mitophagy) via autophagy. The clearance of these organelles was mediated in part via binding of Bnip3 to LC3 on the autophagosome. Although ablation of the Bnip3-LC3 interaction by mutating the LC3 binding site did not impair the prodeath activity of Bnip3, it significantly reduced both mitophagy and ERphagy. Our data indicate that Bnip3 regulates the apoptotic balance as an autophagy receptor that induces removal of both mitochondria and ER.
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mitochondrial autophagy by bnip3 involves drp1 mediated mitochondrial fission and recruitment of parkin in cardiac myocytes
American Journal of Physiology-heart and Circulatory Physiology, 2011Co-Authors: Rita A. Hanna, Asa B GustafssonAbstract:The Bcl2/adenovirus E1B 19-kDa interacting protein 3 (Bnip3) is an atypical BH3-only protein that is associated with mitochondrial dysfunction and cell death. Bnip3 is also a potent inducer of mitochondrial autophagy, and in this study we have investigated the mechanisms by which Bnip3 induces autophagy in cardiac myocytes. We found that Bnip3 induced mitochondrial translocation of dynamin-related protein 1 (Drp1), a protein involved in mitochondrial fission in adult myocytes. Drp1-mediated mitochondrial fission correlated with increased autophagy, and inhibition of Drp1 reduced Bnip3-mediated autophagy. Overexpression of Drp1K38E, a dominant negative of Drp1, or mitofusin 1 prevented mitochondrial fission and autophagy by Bnip3. Also, inhibition of mitochondrial fission or autophagy resulted in increased death of myocytes overexpressing Bnip3. Moreover, Bnip3 promoted translocation of the E3 ubiquitin ligase Parkin to mitochondria, which was prevented in the presence of a Drp1 inhibitor. Interestingly, induction of autophagy by Bnip3 was reduced in Parkin-deficient myocytes. Thus our data suggest that induction of autophagy in response to Bnip3 is a protective response activated by the cell that involves Drp1-mediated mitochondrial fission and recruitment of Parkin.
Lorrie A Kirshenbaum - One of the best experts on this subject based on the ideXlab platform.
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bnip3 mediates doxorubicin induced cardiac myocyte necrosis and mortality through changes in mitochondrial signaling
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Rimpy Dhingra, Victoria Margulets, Gerald W. Dorn, Subir Roy K Chowdhury, James A Thliveris, Davinder S Jassal, Paul Fernyhough, Lorrie A KirshenbaumAbstract:Doxorubicin (DOX) is widely used for treating human cancers, but can induce heart failure through an undefined mechanism. Herein we describe a previously unidentified signaling pathway that couples DOX-induced mitochondrial respiratory chain defects and necrotic cell death to the BH3-only protein Bcl-2-like 19kDa-interacting protein 3 (Bnip3). Cellular defects, including vacuolization and disrupted mitochondria, were observed in DOX-treated mice hearts. This coincided with mitochondrial localization of Bnip3, increased reactive oxygen species production, loss of mitochondrial membrane potential, mitochondrial permeability transition pore opening, and necrosis. Interestingly, a 3.1-fold decrease in maximal mitochondrial respiration was observed in cardiac mitochondria of mice treated with DOX. In vehicle-treated control cells undergoing normal respiration, the respiratory chain complex IV subunit 1 (COX1) was tightly bound to uncoupling protein 3 (UCP3), but this complex was disrupted in cells treated with DOX. Mitochondrial dysfunction induced by DOX was accompanied by contractile failure and necrotic cell death. Conversely, shRNA directed against Bnip3 or a mutant of Bnip3 defective for mitochondrial targeting abrogated DOX-induced loss of COX1-UCP3 complexes and respiratory chain defects. Finally, Bnip3−/− mice treated with DOX displayed relatively normal mitochondrial morphology, respiration, and mortality rates comparable to those of saline-treated WT mice, supporting the idea that Bnip3 underlies the cardiotoxic effects of DOX. These findings reveal a new signaling pathway in which DOX-induced mitochondrial respiratory chain defects and necrotic cell death are mutually dependent on and obligatorily linked to Bnip3 gene activation. Interventions that antagonize Bnip3 may prove beneficial in preventing mitochondrial injury and heart failure in cancer patients undergoing chemotherapy.
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a novel hypoxia inducible spliced variant of mitochondrial death gene bnip3 promotes survival of ventricular myocytes
Circulation Research, 2011Co-Authors: Hongying Gang, Natalia Yurkova, Rimpy Dhingra, Floribeth Aguilar, Yan Hai, Joseph W Gordon, Yaron Aviv, Aaron J Marshall, Etienne Leygue, Lorrie A KirshenbaumAbstract:Rationale:Alternative splicing provides a versatile mechanism by which cells generate proteins with different or even antagonistic properties. Previously, we established hypoxia-inducible death factor Bnip3 as a critical component of the intrinsic death pathway. Objective:To investigate alternative splicing of Bnip3 pre-mRNA in postnatal ventricular myocytes during hypoxia. Methods and Results:We identify a novel previously unrecognized spliced variant of Bnip3 (Bnip3Δex3) generated by alternative splicing of exon3 exclusively in cardiac myocytes subjected to hypoxia. Sequencing of Bnip3Δex3 revealed a frame shift mutation that terminated transcription up-stream of exon5 and exon6 ablating translation of the BH3-like domain and critical carboxyl-terminal transmembrane domain crucial for mitochondrial localization and cell death. Notably, although the 26-kDa Bnip3 protein (Bnip3FL) encoded by full-length mRNA was localized to mitochondria and provoked cell death, the 8.2-kDa Bnip3Δex3 protein encoded by th...
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antagonism of e2f 1 regulated bnip3 transcription by nf κb is essential for basal cell survival
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: James Shaw, Natalia Yurkova, Danielle Weidman, Tong Zhang, Hongying Gang, Floribeth Aguilar, Carly Scramstad, Harvey Weisman, Lorrie A KirshenbaumAbstract:The transcription factor E2F-1 drives proliferation and death, but the mechanisms that differentially regulate these divergent actions are poorly understood. The hypoxia-inducible death factor Bnip3 is an E2F-1 target gene and integral component of the intrinsic mitochondrial death pathway. The mechanisms that govern Bnip3 gene activity remain cryptic. Herein we show that the transcription factor NF-κB provides a molecular switch that determines whether E2F-1 signals proliferation or death under physiological conditions. We show under basal nonapoptotic conditions that NF-κB constitutively occupies and transcriptionally silences Bnip3 gene transcription by competing with E2F-1 for Bnip3 promoter binding. Conversely, in the absence of NF-κB, or during hypoxia when NF-κB abundance is reduced, basal Bnip3 gene transcription is activated by the unrestricted binding of E2F-1 to the Bnip3 promoter. Genetic knock-down of E2F-1 or retinoblastoma gene product over-expression in cardiac and human pancreatic cancer cells deficient for NF-κB signaling abrogated basal and hypoxia-inducible Bnip3 transcription. The survival kinase PI3K/Akt inhibited Bnip3 expression levels in cells in a manner dependent upon NF-κB activation. Hence, by way of example, we show that the transcriptional inhibition of E2F-1-dependent Bnip3 expression by NF-κB highlights a survival pathway that overrides the E2F-1 tumor suppressor program. Our data may explain more fundamentally how cells, by selectively inhibiting E2F-1-dependent death gene transcription, avert apoptosis down-stream of the retinoblastoma/E2F-1 cell cycle pathway.
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cardiac reanimation targeting cardiomyocyte death by bnip3 and nix BNIP3L
Oncogene, 2008Co-Authors: G W Dorn, Lorrie A KirshenbaumAbstract:Programmed cardiac myocyte death contributes to pathological ventricular remodeling and the progression of myocardial infarction or pressure overload hypertrophy to dilated cardiomyopathy. Recent work has identified importance of stress-mediated transcriptional induction of BNIP3 (BCL2 and 19-kDa interacting protein-3) and NIX/BNIP3L in cardiac remodeling. Here, the regulatory mechanisms for these two factors in the heart and their effects on programmed cardiomyocyte death are reviewed, with a focus on information derived from studies using mouse models of cardiac BNIP3 and NIX/BNIP3L overexpression and gene ablation.
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the cell cycle factor e2f 1 activates bnip3 and the intrinsic death pathway in ventricular myocytes
Circulation Research, 2008Co-Authors: Natalia Yurkova, James Shaw, Karen Blackie, Danielle Weidman, Ravi Jayas, Bryan Flynn, Lorrie A KirshenbaumAbstract:The cell cycle factor E2F-1 is known to regulate a variety of cellular processes including apoptosis. Previously we showed that disruption of Rb-E2F-1 complexes provoked apoptosis of postmitotic adult and neonatal ventricular myocytes; however, the underlying mechanism was undetermined. In this report, we show that E2F-1 provokes cell death of ventricular myocytes through a mechanism that directly impinges on the intrinsic death pathway. Furthermore, we show mechanistically that the hypoxia-inducible death factor Bnip3 is a direct transcriptional target of E2F-1 that is necessary and sufficient for E2F-1-induced cell death. Expression of E2F-1 resulted in a 4.9-fold increase (P<0.001) in nucleosomal DNA fragmentation and cell death by Hoechst 33258 dye and vital staining. E2F-1 provoked mitochondrial perturbations that were consistent with permeability transition pore opening. As determined by quantitative real-time PCR analysis, a 6.2-fold increase (P<0.001) in endogenous Bnip3 gene transcription was observed in cells expressing wild-type E2F-1 but not in cells expressing a mutation of E2F-1 defective for DNA binding. Rb, the principle regulator of cellular E2F-1 activity, was proteolytically cleaved and inactivated in ventricular myocytes during hypoxia. Consistent with the proteolytic cleavage of Rb, chromatin immunoprecipitation analysis revealed increased binding of E2F-1 to the Bnip3 promoter during hypoxia, a finding concordant with the induction of Bnip3 gene transcription. The Bnip3 homolog Nix/BNIP3L was unaffected in ventricular myocytes by either E2F-1 or hypoxia. Genetic knockdown of E2F-1 or expression of a caspase-resistant form of Rb suppressed basal and hypoxia-inducible Bnip3 gene transcription. Loss-of-function mutations of Bnip3 defective for mitochondrial membrane insertion or small interference RNA directed against Bnip3 suppressed cell death signals elicited by E2F-1. To our knowledge, the data provide the first direct evidence that activation of the intrinsic mitochondrial death pathway by E2F-1 is mutually dependent on and obligatorily linked to the transcriptional activation of Bnip3.
Nathalie M Mazure - One of the best experts on this subject based on the ideXlab platform.
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hypoxia induced autophagy cell death or cell survival
Current Opinion in Cell Biology, 2010Co-Authors: Nathalie M Mazure, Jacques PouyssegurAbstract:Hypoxia (approximately 3-0.1% oxygen) is capable of rapidly inducing, via the hypoxia-inducible factor (HIF-1), a cell survival response engaging autophagy. This process is mediated by the atypical BH3-only proteins the Bcl-2/E1B 19kDa-interacting protein 3 (BNIP3/BNIP3L (NIX)) that are induced by HIF-1. These mitochondrial associated BNIP proteins also mediate mitophagy, a metabolic adaptation for survival that is able to control reactive oxygen species (ROS) production and DNA damage. In contrast, severe hypoxic conditions or anoxia (<0.1% oxygen), where the latter is often confused with physiological hypoxia, are capable of inducing a HIF-independent autophagic response, generated via an extreme nutritional stress response implicating the AMPK-mTOR and unfolded protein response (UPR) pathways. The autophagic cell death that is often observed in these extreme stress conditions should be seen as the outcome of failed adaptation.
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Atypical BH3-domains of BNIP3 and BNIP3L lead to autophagy in hypoxia.
Autophagy, 2009Co-Authors: Nathalie M Mazure, Jacques PouyssegurAbstract:Normal and tumor cells subjected to a hypoxic microenvironment show evidence of autophagy. We hypothesize that cells will sense hypoxia as a warning signal to upcoming drastic microenvironmental conditions and that autophagy, acting as a survival mechanism, will provide time for cells to adapt. This work demonstrates for the first time that the atypical BH3-domain of BNIP3 and BNIP3L, two HIF-target genes, can compete with Beclin 1-Bcl-2 and Beclin 1-Bcl-X(L) complexes, releasing Beclin 1 from the complex and then enhancing autophagy. We thus revealed a new role for BH3-only proteins in the cellular response to hypoxia.
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hypoxia induced autophagy is mediated through hypoxia inducible factor induction of bnip3 and BNIP3L via their bh3 domains
Molecular and Cellular Biology, 2009Co-Authors: Gregory Bellot, R Garciamedina, Pierre Gounon, Johanna Chiche, Daniele Roux, Jacques Pouyssegur, Nathalie M MazureAbstract:While hypoxia-inducible factor (HIF) is a major actor in the cell survival response to hypoxia, HIF also is associated with cell death. Several studies implicate the HIF-induced putative BH3-only proapoptotic genes bnip3 and BNIP3L in hypoxia-mediated cell death. We, like others, do not support this assertion. Here, we clearly demonstrate that the hypoxic microenvironment contributes to survival rather than cell death by inducing autophagy. The ablation of Beclin1, a major actor of autophagy, enhances cell death under hypoxic conditions. In addition, the ablation of BNIP3 and/or BNIP3L triggers cell death, and BNIP3 and BNIP3L are crucial for hypoxia-induced autophagy. First, while the small interfering RNA-mediated ablation of either BNIP3 or BNIP3L has little effect on autophagy, the combined silencing of these two HIF targets suppresses hypoxia-mediated autophagy. Second, the ectopic expression of both BNIP3 and BNIP3L in normoxia activates autophagy. Third, 20-mer BH3 peptides of BNIP3 or BNIP3L are sufficient in initiating autophagy in normoxia. Herein, we propose a model in which the atypical BH3 domains of hypoxia-induced BNIP3/BNIP3L have been designed to induce autophagy by disrupting the Bcl-2-Beclin1 complex without inducing cell death. Hypoxia-induced autophagy via BNIP3 and BNIP3L is clearly a survival mechanism that promotes tumor progression.
Jacques Pouyssegur - One of the best experts on this subject based on the ideXlab platform.
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hypoxia induced autophagy cell death or cell survival
Current Opinion in Cell Biology, 2010Co-Authors: Nathalie M Mazure, Jacques PouyssegurAbstract:Hypoxia (approximately 3-0.1% oxygen) is capable of rapidly inducing, via the hypoxia-inducible factor (HIF-1), a cell survival response engaging autophagy. This process is mediated by the atypical BH3-only proteins the Bcl-2/E1B 19kDa-interacting protein 3 (BNIP3/BNIP3L (NIX)) that are induced by HIF-1. These mitochondrial associated BNIP proteins also mediate mitophagy, a metabolic adaptation for survival that is able to control reactive oxygen species (ROS) production and DNA damage. In contrast, severe hypoxic conditions or anoxia (<0.1% oxygen), where the latter is often confused with physiological hypoxia, are capable of inducing a HIF-independent autophagic response, generated via an extreme nutritional stress response implicating the AMPK-mTOR and unfolded protein response (UPR) pathways. The autophagic cell death that is often observed in these extreme stress conditions should be seen as the outcome of failed adaptation.
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Atypical BH3-domains of BNIP3 and BNIP3L lead to autophagy in hypoxia.
Autophagy, 2009Co-Authors: Nathalie M Mazure, Jacques PouyssegurAbstract:Normal and tumor cells subjected to a hypoxic microenvironment show evidence of autophagy. We hypothesize that cells will sense hypoxia as a warning signal to upcoming drastic microenvironmental conditions and that autophagy, acting as a survival mechanism, will provide time for cells to adapt. This work demonstrates for the first time that the atypical BH3-domain of BNIP3 and BNIP3L, two HIF-target genes, can compete with Beclin 1-Bcl-2 and Beclin 1-Bcl-X(L) complexes, releasing Beclin 1 from the complex and then enhancing autophagy. We thus revealed a new role for BH3-only proteins in the cellular response to hypoxia.
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hypoxia induced autophagy is mediated through hypoxia inducible factor induction of bnip3 and BNIP3L via their bh3 domains
Molecular and Cellular Biology, 2009Co-Authors: Gregory Bellot, R Garciamedina, Pierre Gounon, Johanna Chiche, Daniele Roux, Jacques Pouyssegur, Nathalie M MazureAbstract:While hypoxia-inducible factor (HIF) is a major actor in the cell survival response to hypoxia, HIF also is associated with cell death. Several studies implicate the HIF-induced putative BH3-only proapoptotic genes bnip3 and BNIP3L in hypoxia-mediated cell death. We, like others, do not support this assertion. Here, we clearly demonstrate that the hypoxic microenvironment contributes to survival rather than cell death by inducing autophagy. The ablation of Beclin1, a major actor of autophagy, enhances cell death under hypoxic conditions. In addition, the ablation of BNIP3 and/or BNIP3L triggers cell death, and BNIP3 and BNIP3L are crucial for hypoxia-induced autophagy. First, while the small interfering RNA-mediated ablation of either BNIP3 or BNIP3L has little effect on autophagy, the combined silencing of these two HIF targets suppresses hypoxia-mediated autophagy. Second, the ectopic expression of both BNIP3 and BNIP3L in normoxia activates autophagy. Third, 20-mer BH3 peptides of BNIP3 or BNIP3L are sufficient in initiating autophagy in normoxia. Herein, we propose a model in which the atypical BH3 domains of hypoxia-induced BNIP3/BNIP3L have been designed to induce autophagy by disrupting the Bcl-2-Beclin1 complex without inducing cell death. Hypoxia-induced autophagy via BNIP3 and BNIP3L is clearly a survival mechanism that promotes tumor progression.
Adrian L Harris - One of the best experts on this subject based on the ideXlab platform.
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The role of the hypoxia-inducible BH3-only proteins BNIP3 and BNIP3L in cancer.
Cancer metastasis reviews, 2007Co-Authors: Howard R Mellor, Adrian L HarrisAbstract:In this review, we summarize current knowledge of the biological functions of the atypical BH3-only proteins BNIP3 and BNIP3L, focusing on the role of these proteins in cancer. Hypoxia increases the expression of BNIP3 through the transcription factor HIF-1, but despite a considerable number of investigations, it has proven difficult to establish a clear role for BNIP3 in the cellular hypoxic response. BNIP3 can induce a form of cell death that shows features of both necrosis and apoptosis, but unusually for a BH3-only protein, death occurs independently of the BH3 domain and is critically dependent on a C-terminal transmembrane domain, which also localizes the protein to the mitochondria. BNIP3 expression does not always result in cell death, suggesting that additional factors may suppress BNIP3 or cooperate with it to induce death. BNIP3 is highly expressed in some tumors, including those of the breast, lung and cervix. However, in colorectal and pancreatic cancers BNIP3 is frequently epigenetically silenced, possibly reflecting different functions for BNIP3 in different tissues. Recent reports have shown that BNIP3 can induce autophagy and there is some evidence to suggest this may represent an emerging role for BH3-only proteins in general. However, the mechanism through which BNIP3 induces autophagy and the cellular consequences of this are yet to be established.
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bnip3 as a progression marker in primary human breast cancer opposing functions in in situ versus invasive cancer
Clinical Cancer Research, 2007Co-Authors: E Y Tan, Helen Turley, Adrian L Harris, Leticia Campo, Cheng Han, Francesco Pezzella, Kevin C Gatter, Stephen B FoxAbstract:Purpose: BNIP3 is involved in cell death and cell survival via autophagy. Its perinecrotic localization within ductal carcinoma in situ (DCIS) suggests an involvement in neoplastic cellular adaptation to low oxygen tension. This study has investigated the role of BNIP3 in normal and neoplastic breast. Experimental Design: Whole sections from 11 normal breast and microarrayed tissue cores from 81 DCIS and 251 invasive carcinomas were stained for BNIP3 and hypoxia-inducible factor-1α. The pattern and level of BNIP3 expression were correlated with clinicopathologic variables and hypoxia-inducible factor-1α. Results: BNIP3 expression was significantly up-regulated in the cytoplasm of DCIS and invasive carcinoma compared with normal breast ( P = 0.0005 and P P = 0.04), low tumor grade ( P = 0.005), and estrogen receptor positivity ( P = 0.008) in invasive tumors. Nuclear BNIP3 expression was also associated with a longer disease-free survival among low-grade and estrogen receptor–positive tumors. ( P = 0.03 and 0.04, respectively). Conversely, nuclear BNIP3 expression in DCIS was associated with a 3-fold increase in recurrence and a shorter disease-free survival ( P = 0.03). Conclusions: Up-regulation of BNIP3 expression in DCIS and invasive carcinoma suggests a significant role in breast tumor progression. Its association with good survival outcome in invasive carcinoma but with an increased risk of recurrence and shorter disease-free survival in DCIS may suggest a pivotal switch from a cell death to survival function during the transition from preinvasive to invasive breast cancer.
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selective silencing of the hypoxia inducible factor 1 target gene bnip3 by histone deacetylation and methylation in colorectal cancer
Oncogene, 2007Co-Authors: A L Bacon, Stephen B Fox, Helen Turley, Adrian L HarrisAbstract:Hypoxia, via the hypoxia-inducible factors 1 and 2 (HIF-1 and HIF-2), upregulates many genes involved in cell survival. However, proapoptotic pathways are also induced. BCL-2/adenovirus E1B-19 kDa-interacting protein 3 (BNIP3) represents a paradigm of a cell death protein that is hypoxically upregulated via HIF-1 in most cancers. We found that in contrast to many other cell types, 6/8 colorectal cancer (CRC) cell lines show little hypoxic induction of BNIP3 despite an intact HIF signalling system. Colorectal tumour tissue also loses BNIP3 expression relative to matched normal samples. Downregulation of hypoxic BNIP3 in CRC cells was independent of the expression of other BCL-2 family members, or BNIP3L. That BNIP3 plays a functional role in hypoxic survival in CRC cells was demonstrated by the fact that CRC cell lines that do not upregulate BNIP3 or have been treated with BNIP3 RNA interference were insensitive to hypoxia-induced cell death. Promoter methylation and histone deacetylation were shown to silence BNIP3 in these CRC cell lines. Of significance, hypoxic induction of BNIP3 was restored in 4/6 cell lines by trichostatin-A treatment alone. These data suggest that BNIP3 plays an important role in hypoxic cell death and epigenetic mechanisms selectively silence its expression in CRC.