The Experts below are selected from a list of 31680 Experts worldwide ranked by ideXlab platform

Gerald W Dorn - One of the best experts on this subject based on the ideXlab platform.

  • a nucleus targeted alternately spliced Nix bnip3l protein isoform modifies nuclear factor κb nfκb mediated cardiac transcription
    Journal of Biological Chemistry, 2013
    Co-Authors: Yun Chen, Scot J Matkovich, Keith F Decker, Dali Zheng, Gerald W Dorn
    Abstract:

    Abstract Several Bcl2 family proteins are expressed both as mitochondrial-targeted full-length and as cytosolic truncated alternately spliced isoforms. Recombinantly expressed shorter Bcl2 family isoforms can heterotypically bind to and prevent mitochondrial localization of their full-length analogs, thus suppressing their activity by sequestration. This “sponge” role requires 1:1 expression stoichiometry; absent this an alternate role is suggested. Here, RNA sequencing revealed coordinate regulation of BH3-only protein Nix/Bnip3L (Nix) and its alternately spliced soluble form (sNix) in hearts, but relative sNix/Nix expression of ∼1:10. Accordingly, we examined other putative functions of sNix. Although Nix expressed in H9c2 rat myoblasts localized to mitochondria, sNix showed variable cytoplasmic and nuclear distribution. Tumor necrosis factor α (TNFα) induced rapid and complete sNix nucleoplasmic translocation concomitant with nuclear translocation of the p65/RelA subunit of NFκB. sNix co-localized and co-precipitated with p65/RelA after TNFα stimulation; TNFα-induced sNix nuclear translocation did not occur in p65/RelA null murine embryonic fibroblasts. ChIP sequencing of TNFα-stimulated H9c2 cells revealed sNix suppression of p65/RelA binding to a subset of weaker DNA binding sites, accounting for its ability to alter gene expression in cultured cells and in vivo mouse hearts. These findings reveal TNFα-stimulated cytoplasmic-nuclear shuttling of the alternately spliced non-mitochondrial Nix isoform and uncover a role for sNix as a modulator of TNFα/NFκB-stimulated cardiac gene expression. Transcriptional co-regulation of sNix and Nix, combined with sNix posttranslational regulation by TNFα, comprises a previously unknown mechanism for molecular cross-talk between extrinsic death receptor and intrinsic mitochondrial apoptosis pathways.

  • loss of Nix in pdx1 deficient mice prevents apoptotic and necrotic β cell death and diabetes
    Journal of Clinical Investigation, 2010
    Co-Authors: Kei Fujimoto, Gerald W Dorn, Eric L Ford, Hung Tran, Burton M Wice, Seth D Crosby, Kenneth S Polonsky
    Abstract:

    Mutations in pancreatic duodenal homeobox (PDX1) are linked to human type 2 diabetes and maturity-onset diabetes of the young type 4. Consistent with this, Pdx1-haploinsufficient mice develop diabetes. Both apoptosis and necrosis of β cells are mechanistically implicated in diabetes in these mice, but a molecular link between Pdx1 and these 2 forms of cell death has not been defined. In this study, we introduced an shRNA into mouse insulinoma MIN6 cells to deplete Pdx1 and found that expression of proapoptotic genes, including NIP3-like protein X (Nix), was increased. Forced Nix expression in MIN6 and pancreatic islet β cells induced programmed cell death by simultaneously activating apoptotic and mitochondrial permeability transition–dependent necrotic pathways. Preventing Nix upregulation during Pdx1 suppression abrogated apoptotic and necrotic β cell death in vitro. In Pdx1-haploinsufficient mice, Nix ablation normalized pancreatic islet architecture, β cell mass, and insulin secretion and eliminated reactive hyperglycemia after glucose challenge. These results establish Nix as a critical mediator of β cell apoptosis and programmed necrosis in Pdx1-deficient diabetes.

  • dual autonomous mitochondrial cell death pathways are activated by Nix bnip3l and induce cardiomyopathy
    Proceedings of the National Academy of Sciences of the United States of America, 2010
    Co-Authors: Yun Chen, William Lewis, Abhinav Diwan, Emily H Cheng, Scot J Matkovich, Gerald W Dorn
    Abstract:

    Dysregulation of programmed cell death due to abnormal expression of Bcl-2 proteins is implicated in cancer, neurodegenerative diseases, and heart failure. Among Bcl-2 family members, BNip proteins uniquely stimulate cell death with features of both apoptosis and necrosis. Localization of these factors to mitochondria and endoplasmic reticulum (ER) provides additional complexity. Previously, we observed regulation of intracellular calcium stores by reticular Nix. Here, we report effects of Nix targeting to mitochondria or ER on cell death pathways and heart failure progression. Nix-deficient fibroblasts expressing mitochondrial-directed or ER-directed Nix mutants exhibited similar cytochrome c release, caspase activation, annexin V and TUNEL labeling, and cell death. ER-Nix cells, but not mitochondrial-Nix cells, showed dissipation of mitochondrial inner membrane potential, Δψm, and were protected from cell death by cyclosporine A or ppif ablation, implicating the mitochondrial permeability transition pore (MPTP). ER-Nix cells were not protected from death by caspase inhibition or combined ablation of Bax and Bak. Combined inhibition of caspases and the MPTP fully protected against Nix-mediated cell death. To determine the role of the dual pathways in heart failure, mice conditionally overexpressing Nix or Nix mutants in hearts were created. Cardiomyocte death caused by mitochondrial- and ER-directed Nix was equivalent, but ppif ablation fully protected only ER-Nix. Thus, Nix stimulates dual autonomous death pathways, determined by its subcellular localization. Mitochondrial Nix activates Bax/Bak- and caspase-dependent apoptosis, whereas ER-Nix activates Bax/Bak-independent, MPTP-dependent necrosis. Complete protection against programmed cell death mediated by Nix and related factors can be achieved by simultaneous inhibition of both pathways.

  • Dual autonomous mitochondrial cell death pathways are activated by Nix/BNip3L and induce cardiomyopathy
    Proceedings of the National Academy of Sciences of the United States of America, 2010
    Co-Authors: Yun Chen, William Lewis, Abhinav Diwan, Emily H Cheng, Scot J Matkovich, Gerald W Dorn
    Abstract:

    Dysregulation of programmed cell death due to abnormal expression of Bcl-2 proteins is implicated in cancer, neurodegenerative diseases, and heart failure. Among Bcl-2 family members, BNip proteins uniquely stimulate cell death with features of both apoptosis and necrosis. Localization of these factors to mitochondria and endoplasmic reticulum (ER) provides additional complexity. Previously, we observed regulation of intracellular calcium stores by reticular Nix. Here, we report effects of Nix targeting to mitochondria or ER on cell death pathways and heart failure progression. Nix-deficient fibroblasts expressing mitochondrial-directed or ER-directed Nix mutants exhibited similar cytochrome c release, caspase activation, annexin V and TUNEL labeling, and cell death. ER-Nix cells, but not mitochondrial-Nix cells, showed dissipation of mitochondrial inner membrane potential, Δψm, and were protected from cell death by cyclosporine A or ppif ablation, implicating the mitochondrial permeability transition pore (MPTP). ER-Nix cells were not protected from death by caspase inhibition or combined ablation of Bax and Bak. Combined inhibition of caspases and the MPTP fully protected against Nix-mediated cell death. To determine the role of the dual pathways in heart failure, mice conditionally overexpressing Nix or Nix mutants in hearts were created. Cardiomyocte death caused by mitochondrial- and ER-directed Nix was equivalent, but ppif ablation fully protected only ER-Nix. Thus, Nix stimulates dual autonomous death pathways, determined by its subcellular localization. Mitochondrial Nix activates Bax/Bak- and caspase-dependent apoptosis, whereas ER-Nix activates Bax/Bak-independent, MPTP-dependent necrosis. Complete protection against programmed cell death mediated by Nix and related factors can be achieved by simultaneous inhibition of both pathways.

  • endoplasmic reticulum mitochondria crosstalk in Nix mediated murine cell death
    Journal of Clinical Investigation, 2008
    Co-Authors: Abhinav Diwan, Scot J Matkovich, Qunying Yuan, Wen Zhao, Atsuko Yatani, Joan Heller Brown, Jeffery D Molkentin, Evangelia G Kranias, Gerald W Dorn
    Abstract:

    : Transcriptional upregulation of the proapoptotic BCL2 family protein Nix limits red blood cell formation and can cause heart failure by inducing cell death, but the requisite molecular events are poorly defined. Here, we show complementary mechanisms for Nix-mediated cell death involving direct and ER/sarcoplasmic reticulum-mediated (ER/SR-mediated) mitochondria disruption. Endogenous cardiac Nix and recombinant Nix localize both to the mitochondria and to the ER/SR. In genetic mouse models, cardiomyocyte ER/SR calcium stores are proportional to the level of expressed Nix. Whereas Nix ablation was protective in a mouse model of apoptotic cardiomyopathy, genetic correction of the decreased SR calcium content of Nix-null mice restored sensitivity to cell death and reestablished cardiomyopathy. Nix mutants specific to ER/SR or mitochondria activated caspases and were equally lethal, but only ER/SR-Nix caused loss of the mitochondrial membrane potential. These results establish a new function for Nix as an integrator of transcriptional and calcium-mediated signals for programmed cell death.

Abhinav Diwan - One of the best experts on this subject based on the ideXlab platform.

  • dual autonomous mitochondrial cell death pathways are activated by Nix bnip3l and induce cardiomyopathy
    Proceedings of the National Academy of Sciences of the United States of America, 2010
    Co-Authors: Yun Chen, William Lewis, Abhinav Diwan, Emily H Cheng, Scot J Matkovich, Gerald W Dorn
    Abstract:

    Dysregulation of programmed cell death due to abnormal expression of Bcl-2 proteins is implicated in cancer, neurodegenerative diseases, and heart failure. Among Bcl-2 family members, BNip proteins uniquely stimulate cell death with features of both apoptosis and necrosis. Localization of these factors to mitochondria and endoplasmic reticulum (ER) provides additional complexity. Previously, we observed regulation of intracellular calcium stores by reticular Nix. Here, we report effects of Nix targeting to mitochondria or ER on cell death pathways and heart failure progression. Nix-deficient fibroblasts expressing mitochondrial-directed or ER-directed Nix mutants exhibited similar cytochrome c release, caspase activation, annexin V and TUNEL labeling, and cell death. ER-Nix cells, but not mitochondrial-Nix cells, showed dissipation of mitochondrial inner membrane potential, Δψm, and were protected from cell death by cyclosporine A or ppif ablation, implicating the mitochondrial permeability transition pore (MPTP). ER-Nix cells were not protected from death by caspase inhibition or combined ablation of Bax and Bak. Combined inhibition of caspases and the MPTP fully protected against Nix-mediated cell death. To determine the role of the dual pathways in heart failure, mice conditionally overexpressing Nix or Nix mutants in hearts were created. Cardiomyocte death caused by mitochondrial- and ER-directed Nix was equivalent, but ppif ablation fully protected only ER-Nix. Thus, Nix stimulates dual autonomous death pathways, determined by its subcellular localization. Mitochondrial Nix activates Bax/Bak- and caspase-dependent apoptosis, whereas ER-Nix activates Bax/Bak-independent, MPTP-dependent necrosis. Complete protection against programmed cell death mediated by Nix and related factors can be achieved by simultaneous inhibition of both pathways.

  • Dual autonomous mitochondrial cell death pathways are activated by Nix/BNip3L and induce cardiomyopathy
    Proceedings of the National Academy of Sciences of the United States of America, 2010
    Co-Authors: Yun Chen, William Lewis, Abhinav Diwan, Emily H Cheng, Scot J Matkovich, Gerald W Dorn
    Abstract:

    Dysregulation of programmed cell death due to abnormal expression of Bcl-2 proteins is implicated in cancer, neurodegenerative diseases, and heart failure. Among Bcl-2 family members, BNip proteins uniquely stimulate cell death with features of both apoptosis and necrosis. Localization of these factors to mitochondria and endoplasmic reticulum (ER) provides additional complexity. Previously, we observed regulation of intracellular calcium stores by reticular Nix. Here, we report effects of Nix targeting to mitochondria or ER on cell death pathways and heart failure progression. Nix-deficient fibroblasts expressing mitochondrial-directed or ER-directed Nix mutants exhibited similar cytochrome c release, caspase activation, annexin V and TUNEL labeling, and cell death. ER-Nix cells, but not mitochondrial-Nix cells, showed dissipation of mitochondrial inner membrane potential, Δψm, and were protected from cell death by cyclosporine A or ppif ablation, implicating the mitochondrial permeability transition pore (MPTP). ER-Nix cells were not protected from death by caspase inhibition or combined ablation of Bax and Bak. Combined inhibition of caspases and the MPTP fully protected against Nix-mediated cell death. To determine the role of the dual pathways in heart failure, mice conditionally overexpressing Nix or Nix mutants in hearts were created. Cardiomyocte death caused by mitochondrial- and ER-directed Nix was equivalent, but ppif ablation fully protected only ER-Nix. Thus, Nix stimulates dual autonomous death pathways, determined by its subcellular localization. Mitochondrial Nix activates Bax/Bak- and caspase-dependent apoptosis, whereas ER-Nix activates Bax/Bak-independent, MPTP-dependent necrosis. Complete protection against programmed cell death mediated by Nix and related factors can be achieved by simultaneous inhibition of both pathways.

  • endoplasmic reticulum mitochondria crosstalk in Nix mediated murine cell death
    Journal of Clinical Investigation, 2008
    Co-Authors: Abhinav Diwan, Scot J Matkovich, Qunying Yuan, Wen Zhao, Atsuko Yatani, Joan Heller Brown, Jeffery D Molkentin, Evangelia G Kranias, Gerald W Dorn
    Abstract:

    : Transcriptional upregulation of the proapoptotic BCL2 family protein Nix limits red blood cell formation and can cause heart failure by inducing cell death, but the requisite molecular events are poorly defined. Here, we show complementary mechanisms for Nix-mediated cell death involving direct and ER/sarcoplasmic reticulum-mediated (ER/SR-mediated) mitochondria disruption. Endogenous cardiac Nix and recombinant Nix localize both to the mitochondria and to the ER/SR. In genetic mouse models, cardiomyocyte ER/SR calcium stores are proportional to the level of expressed Nix. Whereas Nix ablation was protective in a mouse model of apoptotic cardiomyopathy, genetic correction of the decreased SR calcium content of Nix-null mice restored sensitivity to cell death and reestablished cardiomyopathy. Nix mutants specific to ER/SR or mitochondria activated caspases and were equally lethal, but only ER/SR-Nix caused loss of the mitochondrial membrane potential. These results establish a new function for Nix as an integrator of transcriptional and calcium-mediated signals for programmed cell death.

  • Endoplasmic reticulum–mitochondria crosstalk in Nix-mediated murine cell death
    Journal of Clinical Investigation, 2008
    Co-Authors: Abhinav Diwan, Scot J Matkovich, Qunying Yuan, Wen Zhao, Atsuko Yatani, Joan Heller Brown, Jeffery D Molkentin, Evangelia G Kranias, Gerald W Dorn
    Abstract:

    : Transcriptional upregulation of the proapoptotic BCL2 family protein Nix limits red blood cell formation and can cause heart failure by inducing cell death, but the requisite molecular events are poorly defined. Here, we show complementary mechanisms for Nix-mediated cell death involving direct and ER/sarcoplasmic reticulum-mediated (ER/SR-mediated) mitochondria disruption. Endogenous cardiac Nix and recombinant Nix localize both to the mitochondria and to the ER/SR. In genetic mouse models, cardiomyocyte ER/SR calcium stores are proportional to the level of expressed Nix. Whereas Nix ablation was protective in a mouse model of apoptotic cardiomyopathy, genetic correction of the decreased SR calcium content of Nix-null mice restored sensitivity to cell death and reestablished cardiomyopathy. Nix mutants specific to ER/SR or mitochondria activated caspases and were equally lethal, but only ER/SR-Nix caused loss of the mitochondrial membrane potential. These results establish a new function for Nix as an integrator of transcriptional and calcium-mediated signals for programmed cell death.

  • Targeting erythroblast-specific apoptosis in experimental anemia
    Apoptosis, 2008
    Co-Authors: Abhinav Diwan, Andrew G. Koesters, Theodosia A. Kalfa, Devan Capella, Hartmut Geiger, Gerald W Dorn
    Abstract:

    Erythrocyte production is regulated by balancing precursor cell apoptosis and survival signaling. Previously, we found that BH3-only proapoptotic factor, Nix, opposed erythroblast-survival signaling by erythropoietin-induced Bcl-xl during normal erythrocyte formation. Since erythropoietin treatment of human anemia has limitations, we explored the therapeutic potential of abrogating Nix -mediated erythroblast apoptosis to enhance erythrocyte production. Nix gene ablation blunted the phenylhydrazine-induced fall in blood count, enhanced hematocrit recovery, and reduced erythroblast apoptosis, despite lower endogenous erythropoietin levels. Similar to erythropoietin, Nix ablation increased early splenic erythroblasts and circulating reticulocytes, while maintaining a pool of mature erythroblasts as erythropoietic reserve. Erythrocytes in Nix -deficient mice showed morphological abnormalities, suggesting that apoptosis during erythropoiesis not only controls red blood cell number, but also serves a “triage” function, preferentially eliminating abnormal erythrocytes. These results support the concept of targeting erythroblast apoptosis to maximize erythrocyte production in acute anemia, which may be of value in erythropoietin resistance.

Ji Zhang - One of the best experts on this subject based on the ideXlab platform.

  • role of bnip3 and Nix in cell death autophagy and mitophagy
    Cell Death & Differentiation, 2009
    Co-Authors: Ji Zhang
    Abstract:

    BNIP3 and Nix are proteins related to the BH3-only family, which induce both cell death and autophagy. Consistent with their ability to induce cell death, BNIP3 and Nix are implicated in the pathogenesis of cancer and heart disease. In tumor cells, BNIP3 and Nix are regulated by hypoxia, and the deregulation of BNIP3 or Nix expression is associated with tumor growth. In heart muscle, BNIP3 and Nix are regulated by hypoxia and Gαq-dependent signaling, respectively, and their expression is associated with decreased myocardial function. Apart from their role in cell death, BNIP3 and Nix are also implicated in the induction of autophagy. In erythroid cells, Nix is required for a specialized type of autophagy that targets mitochondria for elimination (mitophagy). Similarly, BNIP3 regulates mitophagy in response to hypoxia. In this review, we will discuss possible mechanisms by which BNIP3 and Nix induce cell death and mitophagy. We will also consider the potential relationship between cell death pathways and autophagy in development and homeostasis.

  • Nix induces mitochondrial autophagy in reticulocytes
    Autophagy, 2008
    Co-Authors: Ji Zhang
    Abstract:

    The controlled elimination of defective mitochondria is necessaryfor the health of long-lived post-mitotic cells, like cardiomyocytesand neurons. Mitochondrial elimination also occurs during thecourse of normal development, in lens epithelial and erythroidcells. Strikingly, at the final stage of erythroid cell maturation,newly formed erythrocytes, also known as reticulocytes, eliminatetheir entire cohort of mitochondria. We have employed thismodel to investigate the mechanism of programmed mitochondrialclearance. Nix (BNIP3L) is a Bcl-2-related protein that is upregulatedduring terminal erythroid differentiation.1,2 Nix-deficientreticulocytes have a significant defect of mitochondrial clearance.Consistent with the ability of Nix to cause mitochondrial depolarization, 3,4 we show that mitochondria are depolarized in wildtype but not Nix deficient reticulocytes. Nix does not functionthrough established proapoptotic pathways, nor does it mediate theinduction of autophagy in erythroid cells. Rather, Nix is re...

  • Nix is required for programmed mitochondrial clearance during reticulocyte maturation
    Proceedings of the National Academy of Sciences of the United States of America, 2007
    Co-Authors: Rachel L Schweers, Ji Zhang, Mindy S Randall, Melanie R Loyd, Weimin Li, Frank C Dorsey, Mondira Kundu, Joseph T Opferman, John L Cleveland, Jeffery L Miller
    Abstract:

    The regulated clearance of mitochondria is a well recognized but poorly understood aspect of cellular homeostasis, and defects in this process have been linked to aging, degenerative diseases, and cancer. Mitochondria are recycled through an autophagy-related process, and reticulocytes, which completely eliminate their mitochondria during maturation, provide a physiological model to study this phenomenon. Here, we show that mitochondrial clearance in reticulocytes requires the BCL2-related protein Nix (BNIP3L). Mitochondrial clearance does not require BAX, BAK, BCL-XL, BIM, or PUMA, indicating that Nix does not function through established proapoptotic pathways. Similarly, Nix is not required for the induction of autophagy during terminal erythroid differentiation. Nix is required for the selective elimination of mitochondria, however, because mitochondrial clearance, in the absence of Nix, is arrested at the stage of mitochondrial incorporation into autophagosomes and autophagosome maturation. These results yield insight into the mechanism of mitochondrial clearance in higher eukaryotes. Furthermore, they show a BAX- and BAK-independent role for a BCL2-related protein in development.

Gang Chen - One of the best experts on this subject based on the ideXlab platform.

  • Nix Plays a Neuroprotective Role in Early Brain Injury After Experimental Subarachnoid Hemorrhage in Rats
    Frontiers in Neuroscience, 2020
    Co-Authors: Juyi Zhang, Guiqiang Yuan, Tianyu Liang, Xiang Li, Haiying Li, Haitao Shen, Zhong Wang, Gang Chen
    Abstract:

    : Nix is located in the outer membrane of mitochondria, mediates mitochondrial fission and implicated in many neurological diseases. However, the association between Nix and subarachnoid hemorrhage (SAH) has not previously been reported. Therefore, the present study was designed to evaluate the expression of Nix and its role in early brain injury (EBI) after SAH. Adult male Sprague-Dawley (SD) rats were randomly assigned to various time points for investigation after SAH. A rat model of SAH was induced by injecting 0.3 ml of autologous non-heparinized arterial blood into the prechiasmatic cistern. The expression of Nix was investigated by Western blot and immunohistochemistry. Next, Nix-specific overexpression plasmids and small interfering RNAs (siRNAs) were separately administered. Western blot, neurological scoring, Morris water maze, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining and fluoro-jade B (FJB) staining were performed to evaluate the role of Nix in EBI following SAH. We found that Nix was expressed in neurons and its expression level in the SAH groups was higher than that in the Sham group, which peaked at 24 h after SAH. Overexpression of Nix following SAH significantly decreased the expression of translocase of outer mitochondrial membrane 20 (TOMM20, a marker of mitochondria), ameliorated neurological/cognitive deficits induced by SAH, and reduced the total number of apoptotic/neurodegenerative cells, whereas siRNA knockdown of Nix yielded opposite effects. Taken together, our findings demonstrated that the expression of Nix is increased in neurons after experimental SAH in rats, and may play a neuroprotective role in EBI following SAH.

  • potential roles of Nix bnip3l pathway in rat traumatic brain injury
    Cell Transplantation, 2019
    Co-Authors: Haibo Ni, Feng Jiang, Di Li, Gang Chen
    Abstract:

    : Nix/BNIP3L is known as a proapoptotic protein that is also related to mitophagy. Previous reports have shown that Nix could be involved in neuronal apoptosis after intracerebral hemorrhage, but it also plays a protective role in mitophagy in ischemic brain injury. How Nix works in traumatic brain injury (TBI) is unclear. Thus, this study was designed to observe the expression of Nix and perform a preliminary exploration of the possible effects of Nix in a rat TBI model. The results showed that Nix expression decreased after damage, and colocalized with neuronal cells in cortical areas. Moreover, when we induced upregulation of Nix, autophagy was increased, while neuronal apoptosis and brain water content decreased along with neurological deficits. These findings remind us that Nix probably plays a neuroprotective role in TBI through autophagy and apoptosis pathways.

  • Potential Roles of Nix/BNIP3L Pathway in Rat Traumatic Brain Injury.
    Cell Transplantation, 2019
    Co-Authors: Jialing Ma, Haibo Ni, Feng Jiang, Di Li, Gang Chen
    Abstract:

    : Nix/BNIP3L is known as a proapoptotic protein that is also related to mitophagy. Previous reports have shown that Nix could be involved in neuronal apoptosis after intracerebral hemorrhage, but it also plays a protective role in mitophagy in ischemic brain injury. How Nix works in traumatic brain injury (TBI) is unclear. Thus, this study was designed to observe the expression of Nix and perform a preliminary exploration of the possible effects of Nix in a rat TBI model. The results showed that Nix expression decreased after damage, and colocalized with neuronal cells in cortical areas. Moreover, when we induced upregulation of Nix, autophagy was increased, while neuronal apoptosis and brain water content decreased along with neurological deficits. These findings remind us that Nix probably plays a neuroprotective role in TBI through autophagy and apoptosis pathways.

John Sharkey - One of the best experts on this subject based on the ideXlab platform.

  • differential profile of Nix upregulation and translocation during hypoxia ischaemia in vivo versus in vitro
    Journal of Cerebral Blood Flow and Metabolism, 2005
    Co-Authors: Juilee A Birsearchbold, Lorraine E Kerr, Paul A Jones, James Mcculloch, John Sharkey
    Abstract:

    Nix, a hypoxia-sensitive member of the Bcl-2 family, is upregulated at the mRNA level during hypoxia through induction of a hypoxia-inducible factor-1 (HIF-1) response element in its promoter sequence. However, the mechanism(s) regulating Nix protein activation remain unclear. The present studies examine Nix protein expression and subcellular distribution in response to hypoxic stimuli in vivo and in culture and to two disparate apoptotic stimuli in vitro. Upregulation and translocation of Nix (by day 5) in hypoxic/serum-deprived CHO-K1 cells, was preceded by Bax activation (by day 4) and caspase-3 processing (by day 2), suggesting that initiation of cell death in vitro is a Nix-independent event. In contrast, an early Nix response (upregulation and translocation to the mitochondria) was observed after 6 h of middle cerebral artery occlusion in the rat. Nix translocation was observed in the ipsilateral cortex and striatum before other histological (infarct development, neuronal loss, apoptotic body formation) or biochemical (Bax activation or caspase-3 cleavage) markers of damage were detected. While fundamental differences between hypoxia/ischaemia in culture and in vivo likely explain the different temporal profiles of Nix, Bax, and caspase-3 activation observed, these studies show that like Bax, mitochondrial accumulation is a common event during Nix activation. These are the first studies to show upregulation and translocation of Nix in the ischaemic brain and suggest Nix to be a novel therapeutic target in ischaemic research. Moreover, Nix upregulation in staurosporine-treated SH-SY5Y cells and dexamethasone-treated A1.1 cells supports a more generalized role for Nix in apoptotic cell death.

  • Differential profile of Nix upregulation and translocation during hypoxia/ischaemia in vivo versus in vitro.
    Journal of Cerebral Blood Flow and Metabolism, 2005
    Co-Authors: Jui-lee A Birse-archbold, Lorraine E Kerr, Paul A Jones, James Mcculloch, John Sharkey
    Abstract:

    Nix, a hypoxia-sensitive member of the Bcl-2 family, is upregulated at the mRNA level during hypoxia through induction of a hypoxia-inducible factor-1 (HIF-1) response element in its promoter sequence. However, the mechanism(s) regulating Nix protein activation remain unclear. The present studies examine Nix protein expression and subcellular distribution in response to hypoxic stimuli in vivo and in culture and to two disparate apoptotic stimuli in vitro. Upregulation and translocation of Nix (by day 5) in hypoxic/serum-deprived CHO-K1 cells, was preceded by Bax activation (by day 4) and caspase-3 processing (by day 2), suggesting that initiation of cell death in vitro is a Nix-independent event. In contrast, an early Nix response (upregulation and translocation to the mitochondria) was observed after 6 h of middle cerebral artery occlusion in the rat. Nix translocation was observed in the ipsilateral cortex and striatum before other histological (infarct development, neuronal loss, apoptotic body formation) or biochemical (Bax activation or caspase-3 cleavage) markers of damage were detected. While fundamental differences between hypoxia/ischaemia in culture and in vivo likely explain the different temporal profiles of Nix, Bax, and caspase-3 activation observed, these studies show that like Bax, mitochondrial accumulation is a common event during Nix activation. These are the first studies to show upregulation and translocation of Nix in the ischaemic brain and suggest Nix to be a novel therapeutic target in ischaemic research. Moreover, Nix upregulation in staurosporine-treated SH-SY5Y cells and dexamethasone-treated A1.1 cells supports a more generalized role for Nix in apoptotic cell death.