251
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Li Y, Tsun A, Gao Z, Han Z, Gao Y, Li Z, Lin F, Wang Y, Wei G, Yao Z, Li B. 60-kDa Tat-interactive protein (TIP60) positively regulates Th-inducing POK (ThPOK)-mediated repression of eomesodermin in human CD4+ T cells. J Biol Chem 2013; 288:15537-46. [PMID: 23609452 DOI: 10.1074/jbc.m112.430207] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The abundant expression of IFNγ in Th-inducing POK (ThPOK)-deficient CD4(+) T cells requires the activation of Eomesodermin (Eomes); however, the underlying mechanism of this phenomenon remains unclear. Here we report that ThPOK binds directly to the promoter region of the Eomes gene to repress its expression in CD4(+) T cells. We identified the histone acetyltransferase TIP60 as a co-repressor of ThPOK-target genes, where ectopically expressed TIP60 increased ThPOK protein stability by promoting its acetylation at its Lys(360) residue to then augment the transcriptional repression of Eomes. Moreover, knockdown of endogenous TIP60 abolished the stabilization of ThPOK in CD4(+) T cells, which led to the transcriptional activation of Eomes and increased production of IFNγ. Our results reveal a novel pathway by which TIP60 and ThPOK synergistically suppresses Eomes function and IFNγ production, which could contribute to the regulation of inflammation.
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Affiliation(s)
- Yangyang Li
- Key Laboratory of Molecular Virology and Immunology, Unit of Molecular Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 411 Hefei Road, Shanghai 200025, China
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252
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Zhou J, Freeman TA, Ahmad F, Shang X, Mangano E, Gao E, Farber J, Wang Y, Ma XL, Woodgett J, Vagnozzi RJ, Lal H, Force T. GSK-3α is a central regulator of age-related pathologies in mice. J Clin Invest 2013; 123:1821-32. [PMID: 23549082 DOI: 10.1172/jci64398] [Citation(s) in RCA: 125] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Accepted: 01/24/2013] [Indexed: 12/12/2022] Open
Abstract
Aging is regulated by conserved signaling pathways. The glycogen synthase kinase-3 (GSK-3) family of serine/threonine kinases regulates several of these pathways, but the role of GSK-3 in aging is unknown. Herein, we demonstrate premature death and acceleration of age-related pathologies in the Gsk3a global KO mouse. KO mice developed cardiac hypertrophy and contractile dysfunction as well as sarcomere disruption and striking sarcopenia in cardiac and skeletal muscle, a classical finding in aging. We also observed severe vacuolar degeneration of myofibers and large tubular aggregates in skeletal muscle, consistent with impaired clearance of insoluble cellular debris. Other organ systems, including gut, liver, and the skeletal system, also demonstrated age-related pathologies. Mechanistically, we found marked activation of mTORC1 and associated suppression of autophagy markers in KO mice. Loss of GSK-3α, either by pharmacologic inhibition or Gsk3a gene deletion, suppressed autophagy in fibroblasts. mTOR inhibition rescued this effect and reversed the established pathologies in the striated muscle of the KO mouse. Thus, GSK-3α is a critical regulator of mTORC1, autophagy, and aging. In its absence, aging/senescence is accelerated in multiple tissues. Strategies to maintain GSK-3α activity and/or inhibit mTOR in the elderly could retard the appearance of age-related pathologies.
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Affiliation(s)
- Jibin Zhou
- Center for Translational Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
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253
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Guan JL, Simon AK, Prescott M, Menendez JA, Liu F, Wang F, Wang C, Wolvetang E, Vazquez-Martin A, Zhang J. Autophagy in stem cells. Autophagy 2013; 9:830-49. [PMID: 23486312 DOI: 10.4161/auto.24132] [Citation(s) in RCA: 221] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Autophagy is a highly conserved cellular process by which cytoplasmic components are sequestered in autophagosomes and delivered to lysosomes for degradation. As a major intracellular degradation and recycling pathway, autophagy is crucial for maintaining cellular homeostasis as well as remodeling during normal development, and dysfunctions in autophagy have been associated with a variety of pathologies including cancer, inflammatory bowel disease and neurodegenerative disease. Stem cells are unique in their ability to self-renew and differentiate into various cells in the body, which are important in development, tissue renewal and a range of disease processes. Therefore, it is predicted that autophagy would be crucial for the quality control mechanisms and maintenance of cellular homeostasis in various stem cells given their relatively long life in the organisms. In contrast to the extensive body of knowledge available for somatic cells, the role of autophagy in the maintenance and function of stem cells is only beginning to be revealed as a result of recent studies. Here we provide a comprehensive review of the current understanding of the mechanisms and regulation of autophagy in embryonic stem cells, several tissue stem cells (particularly hematopoietic stem cells), as well as a number of cancer stem cells. We discuss how recent studies of different knockout mice models have defined the roles of various autophagy genes and related pathways in the regulation of the maintenance, expansion and differentiation of various stem cells. We also highlight the many unanswered questions that will help to drive further research at the intersection of autophagy and stem cell biology in the near future.
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Affiliation(s)
- Jun-Lin Guan
- Division of Molecular Medicine, Department of Internal Medicine and Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA.
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254
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Bánréti A, Sass M, Graba Y. The emerging role of acetylation in the regulation of autophagy. Autophagy 2013; 9:819-29. [PMID: 23466676 DOI: 10.4161/auto.23908] [Citation(s) in RCA: 143] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Autophagy is an evolutionarily conserved catabolic process through which different components of the cells are sequestered into double-membrane cytosolic vesicles called autophagosomes, and fated to degradation through fusion with lysosomes. Autophagy plays a major function in many physiological processes including response to different stress factors, energy homeostasis, elimination of cellular organelles and tissue remodeling during development. Consequently, autophagy is strictly controlled and post-translational modifications such as phosphorylation and ubiquitination have long been associated with autophagy regulation. In contrast, the importance of acetylation in autophagy control has only emerged in the last few years. In this review, we summarize how previously identified histone acetylases and deacetylases modify key autophagic effector proteins, and discuss how this has an impact on physiological and pathological cellular processes.
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Affiliation(s)
- Agnes Bánréti
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary.
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255
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McAlpine F, Williamson LE, Tooze SA, Chan EY. Regulation of nutrient-sensitive autophagy by uncoordinated 51-like kinases 1 and 2. Autophagy 2013; 9:361-73. [PMID: 23291478 PMCID: PMC3590256 DOI: 10.4161/auto.23066] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Macroautophagy, commonly referred to as autophagy, is a protein degradation pathway that occurs constitutively in cells, but can also be induced by stressors such as nutrient starvation or protein aggregation. Autophagy has been implicated in multiple disease mechanisms including neurodegeneration and cancer, with both tumor suppressive and oncogenic roles. Uncoordinated 51-like kinase 1 (ULK1) is a critical autophagy protein near the apex of the hierarchal regulatory pathway that receives signals from the master nutrient sensors MTOR and AMP-activated protein kinase (AMPK). In mammals, ULK1 has a close homolog, ULK2, although their functional distinctions have been unclear. Here, we show that ULK1 and ULK2 both function to support autophagy activation following nutrient starvation. Increased autophagy following amino acid or glucose starvation was disrupted only upon combined loss of ULK1 and ULK2 in mouse embryonic fibroblasts. Generation of PtdIns3P and recruitment of WIPI2 or ZFYVE1/DFCP1 to the phagophore following amino acid starvation was blocked by combined Ulk1/2 double knockout. Autophagy activation following glucose starvation did not involve recruitment of either WIPI1 or WIPI2 to forming autophagosomes. Consistent with a PtdIns3P-independent mechanism, glucose-dependent autophagy was resistant to wortmannin. Our findings support functional redundancy between ULK1 and ULK2 for nutrient-dependent activation of autophagy and furthermore highlight the differential pathways that respond to amino acid and glucose deprivation.
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Affiliation(s)
- Fiona McAlpine
- London Research Institute; Cancer Research UK; Secretory Pathways Laboratory; London, UK
| | - Leon E. Williamson
- Strathclyde Institute of Pharmacy and Biomedical Sciences; RICAS Group; University of Strathclyde; Glasgow, Scotland
| | - Sharon A. Tooze
- London Research Institute; Cancer Research UK; Secretory Pathways Laboratory; London, UK
| | - Edmond Y.W. Chan
- Strathclyde Institute of Pharmacy and Biomedical Sciences; RICAS Group; University of Strathclyde; Glasgow, Scotland
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256
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Functions of BCL-X L at the Interface between Cell Death and Metabolism. Int J Cell Biol 2013; 2013:705294. [PMID: 23533418 PMCID: PMC3603586 DOI: 10.1155/2013/705294] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 01/09/2013] [Accepted: 01/23/2013] [Indexed: 02/07/2023] Open
Abstract
The BCL-2 homolog BCL-XL, one of the two protein products of BCL2L1, has originally been characterized for its prominent prosurvival functions. Similar to BCL-2, BCL-XL binds to its multidomain proapoptotic counterparts BAX and BAK, hence preventing the formation of lethal pores in the mitochondrial outer membrane, as well as to multiple BH3-only proteins, thus interrupting apical proapoptotic signals. In addition, BCL-XL has been suggested to exert cytoprotective functions by sequestering a cytosolic pool of the pro-apoptotic transcription factor p53 and by binding to the voltage-dependent anion channel 1 (VDAC1), thereby inhibiting the so-called mitochondrial permeability transition (MPT). Thus, BCL-XL appears to play a prominent role in the regulation of multiple distinct types of cell death, including apoptosis and regulated necrosis. More recently, great attention has been given to the cell death-unrelated functions of BCL-2-like proteins. In particular, BCL-XL has been shown to modulate a number of pathophysiological processes, including-but not limited to-mitochondrial ATP synthesis, protein acetylation, autophagy and mitosis. In this short review article, we will discuss the functions of BCL-XL at the interface between cell death and metabolism.
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257
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Wong PM, Puente C, Ganley IG, Jiang X. The ULK1 complex: sensing nutrient signals for autophagy activation. Autophagy 2013; 9:124-37. [PMID: 23295650 PMCID: PMC3552878 DOI: 10.4161/auto.23323] [Citation(s) in RCA: 368] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The Atg1/ULK1 complex plays a central role in starvation-induced autophagy, integrating signals from upstream sensors such as MTOR and AMPK and transducing them to the downstream autophagy pathway. Much progress has been made in the last few years in understanding the mechanisms by which the complex is regulated through protein-protein interactions and post-translational modifications, providing insights into how the cell modulates autophagy, particularly in response to nutrient status. However, how the ULK1 complex transduces upstream signals to the downstream central autophagy pathway is still unclear. Although the protein kinase activity of ULK1 is required for its autophagic function, its protein substrate(s) responsible for autophagy activation has not been identified. Furthermore, examples of potential ULK1-independent autophagy have emerged, indicating that under certain specific contexts, the ULK1 complex might be dispensable for autophagy activation. This raises the question of how the autophagic machinery is activated independent of the ULK1 complex and what are the biological functions of such noncanonical autophagy pathways.
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Affiliation(s)
- Pui-Mun Wong
- Cell Biology Program; Memorial Sloan-Kettering Cancer Center; New York, NY USA
| | - Cindy Puente
- Cell Biology Program; Memorial Sloan-Kettering Cancer Center; New York, NY USA
| | - Ian G. Ganley
- MRC Protein Phosphorylation Unit; University of Dundee; Dundee, Scotland UK
| | - Xuejun Jiang
- Cell Biology Program; Memorial Sloan-Kettering Cancer Center; New York, NY USA
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258
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Abstract
RVB1/RVB2 (RuvBL1/RuvBL2 or pontin/reptin) are enigmatic AAA(+) ATPase proteins that are present in multiple cellular complexes. Although they have been implicated in many cellular functions, the exact molecular function of RVB proteins in the various complexes is not clear. TIP60 complex (TIP60.com) is a tumor suppressor chromatin-remodeling complex containing RVB proteins. RVBs are required for the lysine acetyltransferase activity of TIP60.com but not for that of the pure recombinant TIP60 polypeptide. Here we describe two molecular functions of RVBs in TIP60.com. First, RVBs negate the repression of catalytic activity of TIP60 by another protein in TIP60.com, p400. RVBs competitively displace the SNF2 domain of p400 from the TIP60 polypeptide. In addition RVBs are also required for heat stability of TIP60.com by a p400-independent pathway. RVB1 and RVB2 are redundant with each other for these functions and do not require their ATPase activities. Thus, RVB proteins act as molecular adaptors that can substitute for one another to facilitate the optimal assembly, heat stability, and function of the TIP60 complex.
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259
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Mleczak A, Millar S, Tooze SA, Olson MF, Chan EYW. Regulation of autophagosome formation by Rho kinase. Cell Signal 2013; 25:1-11. [PMID: 22975682 DOI: 10.1016/j.cellsig.2012.09.010] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Accepted: 09/04/2012] [Indexed: 01/22/2023]
Abstract
Macroautophagy, commonly referred to as autophagy, is a protein degradation pathway that functions at a constitutive level in cells, which may become further activated by stressors such as nutrient starvation or protein aggregation. Autophagy has multiple beneficial roles for maintaining normal cellular homeostasis and these roles are related to the implications of autophagy in disease mechanisms including neurodegeneration and cancer. We previously searched for novel autophagy regulators and identified Rho-kinase 1 (ROCK1) as a candidate. Here, we show that activated ROCK1 inhibits autophagy in human embryonic kidney 293 cells. Conversely, ROCK inhibitory compounds enhanced the autophagy response to amino acid starvation or rapamycin treatment. Inhibition of ROCK during the starvation period led to a more rapid response with the production of larger early autophagosomes that matured into enlarged late degradative autolysosomes. Despite the production of enlarged LC3-positive early autophagosomes, membrane precursors containing WD-repeat protein interacting with phosphoinositides 1 (WIPI1) and mammalian Atg9 were not affected by ROCK inhibition, suggesting that phagophore elongation had been unusually extended. However, the enlarged autophagosomes were enriched in ULK1 which was essential to allow progression of autophagy flux. Our results demonstrate a novel role for ROCK in the control of autophagosome size and degradative capacity.
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260
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Mihaylova MM, Shaw RJ. Metabolic reprogramming by class I and II histone deacetylases. Trends Endocrinol Metab 2013; 24:48-57. [PMID: 23062770 PMCID: PMC3532556 DOI: 10.1016/j.tem.2012.09.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 09/04/2012] [Accepted: 09/06/2012] [Indexed: 12/25/2022]
Abstract
Accumulating evidence suggests that protein acetylation plays a major regulatory role in many facets of transcriptional control of metabolism. The enzymes that catalyze the addition and removal of acetyl moieties are the histone acetyl transferases (HATs) and histone deacetylases (HDACs), respectively. Several recent studies have uncovered novel mechanisms and contexts in which different HDACs play crucial roles in metabolic control. Understanding the role of class I and II HDACs in different metabolic programs during development, as well as in the physiology and pathology of the adult organism, will lead to novel therapeutics for metabolic disease. Here, we review the current understanding of how class I and class II HDACs contribute to metabolic control.
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261
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Affiliation(s)
- Shun Kageyama
- Protein Metabolism Project, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo, Japan
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262
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Stabilization of p21 (Cip1/WAF1) following Tip60-dependent acetylation is required for p21-mediated DNA damage response. Cell Death Differ 2012; 20:620-9. [PMID: 23238566 DOI: 10.1038/cdd.2012.159] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The molecular mechanisms controlling post-translational modifications of p21 have been pursued assiduously in recent years. Here, utilizing mass-spectrometry analysis and site-specific acetyl-p21 antibody, two lysine residues of p21, located at amino-acid sites 161 and 163, were identified as Tip60-mediated acetylation targets for the first time. Detection of adriamycin-induced p21 acetylation, which disappeared after Tip60 depletion with concomitant destabilization of p21 and disruption of G1 arrest, suggested that Tip60-mediated p21 acetylation is necessary for DNA damage-induced cell-cycle regulation. The ability of 2KQ, a mimetic of acetylated p21, to induce cell-cycle arrest and senescence was significantly enhanced in p21 null MEFs compared with those of cells expressing wild-type p21. Together, these observations demonstrate that Tip60-mediated p21 acetylation is a novel and essential regulatory process required for p21-dependent DNA damage-induced cell-cycle arrest.
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263
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Hilscher M, Hernandez-Gea V, Friedman SL. Autophagy and mesenchymal cell fibrogenesis. Biochim Biophys Acta Mol Basis Dis 2012; 1831:972-8. [PMID: 23142802 DOI: 10.1016/j.bbadis.2012.11.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 10/29/2012] [Accepted: 11/02/2012] [Indexed: 02/06/2023]
Abstract
Autophagy is a catabolic pathway essential for cellular energy homeostasis that involves the self-degradation of intracellular components in lysosomes. This process has been implicated in the pathophysiology of many human disorders, including infection, cancer, and fibrosis. Autophagy is also recognized as a mediator of survival and proliferation, and multiple pathways induce autophagy under conditions of cellular stress, including nutrient and energy depletion. High autophagic activity has been detected in fibrogenic cells from several tissues; however the role of autophagy in fibrogenesis and mesenchymal cells varies greatly in different tissues and settings, with contributions uncovered to energy metabolism and collagen turnover by fibrogenic cells. Because several chemical modulators of autophagy have already been identified, autophagy regulation constitutes a potential target for antifibrotic therapy. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.
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Affiliation(s)
- Moira Hilscher
- Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY, USA
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264
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Chondrogianni N, Petropoulos I, Grimm S, Georgila K, Catalgol B, Friguet B, Grune T, Gonos ES. Protein damage, repair and proteolysis. Mol Aspects Med 2012; 35:1-71. [PMID: 23107776 DOI: 10.1016/j.mam.2012.09.001] [Citation(s) in RCA: 160] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 09/26/2012] [Indexed: 01/10/2023]
Abstract
Proteins are continuously affected by various intrinsic and extrinsic factors. Damaged proteins influence several intracellular pathways and result in different disorders and diseases. Aggregation of damaged proteins depends on the balance between their generation and their reversal or elimination by protein repair systems and degradation, respectively. With regard to protein repair, only few repair mechanisms have been evidenced including the reduction of methionine sulfoxide residues by the methionine sulfoxide reductases, the conversion of isoaspartyl residues to L-aspartate by L-isoaspartate methyl transferase and deglycation by phosphorylation of protein-bound fructosamine by fructosamine-3-kinase. Protein degradation is orchestrated by two major proteolytic systems, namely the lysosome and the proteasome. Alteration of the function for both systems has been involved in all aspects of cellular metabolic networks linked to either normal or pathological processes. Given the importance of protein repair and degradation, great effort has recently been made regarding the modulation of these systems in various physiological conditions such as aging, as well as in diseases. Genetic modulation has produced promising results in the area of protein repair enzymes but there are not yet any identified potent inhibitors, and, to our knowledge, only one activating compound has been reported so far. In contrast, different drugs as well as natural compounds that interfere with proteolysis have been identified and/or developed resulting in homeostatic maintenance and/or the delay of disease progression.
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Affiliation(s)
- Niki Chondrogianni
- Institute of Biology, Medicinal Chemistry and Biotechnology, National Helenic Research Foundation, 48 Vas. Constantinou Ave., 116 35 Athens, Greece.
| | - Isabelle Petropoulos
- Laboratoire de Biologie Cellulaire du Vieillissement, UR4-UPMC, IFR 83, Université Pierre et Marie Curie-Paris 6, 4 Place Jussieu, 75005 Paris, France
| | - Stefanie Grimm
- Department of Nutritional Toxicology, Institute of Nutrition, Friedrich-Schiller University, Dornburger Straße 24, 07743 Jena, Germany
| | - Konstantina Georgila
- Institute of Biology, Medicinal Chemistry and Biotechnology, National Helenic Research Foundation, 48 Vas. Constantinou Ave., 116 35 Athens, Greece
| | - Betul Catalgol
- Department of Biochemistry, Faculty of Medicine, Genetic and Metabolic Diseases Research Center (GEMHAM), Marmara University, Haydarpasa, Istanbul, Turkey
| | - Bertrand Friguet
- Laboratoire de Biologie Cellulaire du Vieillissement, UR4-UPMC, IFR 83, Université Pierre et Marie Curie-Paris 6, 4 Place Jussieu, 75005 Paris, France
| | - Tilman Grune
- Department of Nutritional Toxicology, Institute of Nutrition, Friedrich-Schiller University, Dornburger Straße 24, 07743 Jena, Germany
| | - Efstathios S Gonos
- Institute of Biology, Medicinal Chemistry and Biotechnology, National Helenic Research Foundation, 48 Vas. Constantinou Ave., 116 35 Athens, Greece.
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265
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Phosphorylation of Atg5 by the Gadd45β-MEKK4-p38 pathway inhibits autophagy. Cell Death Differ 2012; 20:321-32. [PMID: 23059785 DOI: 10.1038/cdd.2012.129] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Autophagy is a lysosomal degradation pathway important for cellular homeostasis, mammalian development, cancer and immunity. Many molecular components of autophagy have been identified, but little is known about regulatory mechanisms controlling their effector functions. Here, we show that, in contrast to other p38 MAP kinase activators, the growth arrest and DNA damage 45 beta (Gadd45β)-MAPK/ERK kinase kinase 4 (MEKK4) pathway specifically directs p38 to autophagosomes. This process results in an accumulation of autophagosomes through p38-mediated inhibition of lysosome fusion. Conversely, autophagic flux is increased in p38-deficient fibroblasts and Gadd45β-deficient cells. We further identified the underlying mechanism and demonstrate that phosphorylation of the autophagy regulator autophagy-related (Atg)5 at threonine 75 through p38 is responsible for inhibition of starvation-induced autophagy. Thus, we show for the first time that Atg5 activity is controlled by phosphorylation and, moreover, that the spatial regulation of p38 by Gadd45β/MEKK4 negatively regulates the autophagic process.
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266
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Leidal AM, Pringle ES, McCormick C. Evasion of oncogene-induced senescence by gammaherpesviruses. Curr Opin Virol 2012; 2:748-54. [PMID: 23064053 DOI: 10.1016/j.coviro.2012.09.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Revised: 09/17/2012] [Accepted: 09/20/2012] [Indexed: 12/15/2022]
Abstract
A common feature of herpesvirus infection is activation of DNA damage responses (DDRs) that are essential for efficient lytic replication. Latent infection with Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) also elicit DDRs via the action of latent viral oncoproteins that deregulate cell proliferation and initiate a host anti-proliferative defense known as oncogene-induced senescence (OIS). These viruses encode auxiliary latent proteins that undermine OIS to allow the ongoing proliferation of infected cells despite robust DDR signaling. Persistent DDRs have also been linked to the aberrant secretion of pathogenetically important inflammatory mediators from infected cells. The accumulating evidence indicates that herpesviruses have evolved ways to co-opt DDR signaling to manage both latent and lytic phases of infection, and that DDR subversion may contribute to herpesvirus-associated disease states.
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Affiliation(s)
- Andrew M Leidal
- Department of Microbiology and Immunology, Dalhousie University, 5850 College Street, PO Box 15000, Halifax, NS, Canada B3H 4R2
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267
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Macroautophagy deficiency mediates age-dependent neurodegeneration through a phospho-tau pathway. Mol Neurodegener 2012; 7:48. [PMID: 22998728 PMCID: PMC3544596 DOI: 10.1186/1750-1326-7-48] [Citation(s) in RCA: 127] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 09/05/2012] [Indexed: 11/10/2022] Open
Abstract
Background Macroautophagy is an evolutionarily conserved mechanism for bulk intracellular degradation of proteins and organelles. Pathological studies have implicated macroautophagy defects in human neurodegenerative disorders of aging including Alzheimer’s disease and tauopathies. Neuronal deficiency of macroautophagy throughout mouse embryonic development results in neurodevelopmental defects and early postnatal mortality. However, the role of macroautophagy in mature CNS neurons, and the relationship with human disease neuropathology, remains unclear. Here we describe mice deficient in an essential macroautophagy component, Atg7, specifically within postnatal CNS neurons. Results Postnatal forebrain-specific Atg7 conditional knockout (cKO) mice displayed age-dependent neurodegeneration and ubiquitin- and p62-positive inclusions. Phosphorylated tau was significantly accumulated in Atg7 cKO brains, but neurofibrillary tangles that typify end-stage human tauopathy were not apparent. A major tau kinase, glycogen synthase kinase 3β (GSK3β), was also accumulated in Atg7 cKO brains. Chronic pharmacological inhibition of tau phosphorylation, or genetic deletion of tau, significantly rescued Atg7-deficiency-mediated neurodegeneration, but did not suppress inclusion formation. Conclusions These data elucidate a role for macroautophagy in the long-term survival and physiological function of adult CNS neurons. Neurodegeneration in the context of macroautophagy deficiency is mediated through a phospho-tau pathway.
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268
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Liu SY, Chen CL, Yang TT, Huang WC, Hsieh CY, Shen WJ, Tsai TT, Shieh CC, Lin CF. Albumin prevents reactive oxygen species-induced mitochondrial damage, autophagy, and apoptosis during serum starvation. Apoptosis 2012; 17:1156-69. [DOI: 10.1007/s10495-012-0758-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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269
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Affiliation(s)
- Lindsey D Mayo
- Herman B Wells Center for Pediatric Research, Indiana University School of Medicine; Indianapolis, IN, USA.
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270
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Autophagy and apoptosis act as partners to induce germ cell death after heat stress in mice. PLoS One 2012; 7:e41412. [PMID: 22848486 PMCID: PMC3405141 DOI: 10.1371/journal.pone.0041412] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2012] [Accepted: 06/22/2012] [Indexed: 12/02/2022] Open
Abstract
Testicular heating suppresses spermatogenesis which is marked by germ cell loss via apoptotic pathways. Recently, it is reported that autophagy also can be induced by heat treatment in somatic cells. In this study, the status of autophagy in germ cells after heat treatment, as well as the partnership between autophagy and apoptosis in these cells was investigated. The results demonstrated that besides initiating apoptotic pathways, heat also induced autophagic pathways in germ cells. Exposure of germ cells to hyperthermia resulted in several specific features of the autophagic process, including autophagosome formation and the conversion of LC3-I to LC3-II. Furthermore, the ubiquitin-like protein conjugation system was implicated as being likely responsible for heat-induced autophagy in germ cells since all genes involving this system were found to be expressed in the testes. In addition, the upstream protein in this system, Atg7 (Autophagy-related gene 7), was found to be expressed in all types of spermatogenic cells, and its expression level was positively correlated with the level of autophagy in germ cells. As a result, Atg7 was selected as the investigative target to further analyze the role of autophagy in heat-induced germ cell death. It was shown that down expression of Atg7 protein resulted in the notable decrease in the level of autophagy in heat-treated germ cells, and this down-regulation of autophagy caused by Atg7 knockdown further reduced the apoptotic rate of germ cells. These results suggest that autophagy plays a positive role in the process of germ cell apoptosis after heat treatment. In conclusion, this study demonstrates that heat triggers autophagy and apoptosis in germ cells. These two mechanisms might act as partners, not antagonist, to induce cell death and lead to eventual destruction of spermatogenesis.
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271
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Banerji V, Gibson SB. Targeting metabolism and autophagy in the context of haematologic malignancies. Int J Cell Biol 2012; 2012:595976. [PMID: 22829831 PMCID: PMC3399452 DOI: 10.1155/2012/595976] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 05/28/2012] [Indexed: 12/19/2022] Open
Abstract
Autophagy is a cellular process that maintains the homeostasis of the normal cell. It not only allows for cell survival in times of metabolic stress with nutrient recycling but also is able to lead to cell death when required. During malignant transformation the cell is able to proliferate and survive. This is due to altered cell metabolism and the presence of altered genetic changes that maintain the cell survival. Metabolism was considered an innocent bystander that was a consequence of the increased nutrient requirement for the survival and proliferation of haematological malignancies. The interdependency of metabolism and cellular mechanisms such as autophagy are becoming more evident and important. This interdependence contributes to increased cancer progression and drug resistance. In this paper we aim to discuss autophagy, how it pertains to metabolism in the context of hematologic malignancies, and the implications for therapy.
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Affiliation(s)
- Versha Banerji
- Manitoba Institute of Cell Biology, 675 McDermot Avenue, Winnipeg, MB, Canada R3E 0V9
- Department of Internal Medicine, Faculty of Medicine, University of Manitoba, 770 Bannatyne Avenue, Winnipeg, MB, Canada R3T 2N2
- CancerCare Manitoba, Section of Haematology/Oncology, 675 McDermot Avenue, Winnipeg, MB, Canada R3E 0V9
| | - Spencer B. Gibson
- Manitoba Institute of Cell Biology, 675 McDermot Avenue, Winnipeg, MB, Canada R3E 0V9
- CancerCare Manitoba, Section of Haematology/Oncology, 675 McDermot Avenue, Winnipeg, MB, Canada R3E 0V9
- Biochemistry and Medical Genetics, Faculty of Medicine, University of Manitoba, 745 Bannatyne Avenue, Winnipeg, MB, Canada R3E 0J9
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272
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Abstract
Macroautophagy is an evolutionarily conserved homeostatic process that mediates the degradation of long-lived cytoplasmic components in eukaryotes, which allows cells to survive stresses such as inflammation, hypoxia, and deprivation of nutrients or growth factors. At least 30 members of the Atg (autophagy-related) protein family orchestrate this degradative process. Additional complexity resides in the signaling networks controlling the autophagic process, which include various posttranslational modifications of key components. Evidence is accumulating that protein acetylation represents an evolutionarily conserved mechanism tightly regulating macroautophagy.
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Affiliation(s)
- Ahmed Hamaï
- INSERM U984, University Paris-Sud 11, 92296 Châtenay-Malabry, France
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273
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Unlu S, Tang S, Wang EN, Martinez I, Tang D, Bianchi ME, Zeh HJ, Lotze MT. Damage associated molecular pattern molecule-induced microRNAs (DAMPmiRs) in human peripheral blood mononuclear cells. PLoS One 2012; 7:e38899. [PMID: 22745684 PMCID: PMC3382181 DOI: 10.1371/journal.pone.0038899] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Accepted: 05/14/2012] [Indexed: 12/11/2022] Open
Abstract
Endogenous damage associated molecular pattern molecules (DAMPs) released from necrotic, damaged or stressed cells are associated with an inflammatory response. Whether the microRNA (miR) expression signature of this response is different from that of a pathogen associated molecular pattern (PAMP)-stimulated inflammatory response is unknown. We report here that miR-34c and miR-214 are significantly expressed in fresh human peripheral blood mononuclear cells (PBMCs) exposed to DAMP-containing freeze-thaw lysates, or to conditioned media from serum-starved and glucose-deprived cells (p<6×10−4 and p<3.7×10−3), respectively. Interestingly, only miR-34c expression was differentially expressed in PBMCs exposed to freeze-thaw lysates or conditioned media from wildtype High Mobility Group B1 (HMGB1+/+) mouse embryonic fibroblast (MEF) cells, when compared to cultures exposed to lysates or conditioned media from HMGB1−/− MEFs. miR-155 expression in these cultures was negligible, but was significantly expressed in PBMCs stimulated with Lipopolysaccahride (LPS) or most other Toll-like receptor (TLR) ligands, making it the prototypic “PAMPmiR”. Exposure to a damaged human colorectal carcinoma cell line lysate (HCT116) similarly resulted in increased miR-34c and miR-214 levels. When PBMCs were pre-transfected with anti-miR-34c and then exposed to lysate, expression levels of IKKγ mRNA, a putative target of miR-34c, increased, while protein levels of IKKγ in cultures transfected with a pre-miR-34c were abrogated. Levels of miR-34c expression (as well as pro-inflammatory cytokines, IL-1β and TNFα) decreased when PBMC cultures were briefly pre-incubated with the K+ channel (inflammasome) inhibitor, glybenclamide, suggesting that inflammasome activation is upstream of miR-34c expression in response to DAMPs. Our findings demonstrate that a specific microRNA expression signature is associated with the inflammatory response to damaged/injured cells and carries implications for many acute and chronic inflammatory disorders.
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Affiliation(s)
- Sebnem Unlu
- Department of Surgery, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- * E-mail: (SU); or (MTL)
| | - Siuwah Tang
- Department of Surgery, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - E. na Wang
- Infectious Disease and Immunogenetics Laboratory, Department of Transfusion Medicine, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Ivan Martinez
- Department of Genetics, School of Medicine, Yale University, New Haven, Connecticut, United States of America
| | - Daolin Tang
- Department of Surgery, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Marco E. Bianchi
- Department of Molecular Biology and Functional Genomics, San Raffaele University and Scientific Institute, Milano, Italy
| | - Herbert J. Zeh
- Department of Surgery, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Michael T. Lotze
- Department of Surgery, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- * E-mail: (SU); or (MTL)
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