551
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Janku F, McConkey DJ, Hong DS, Kurzrock R. Autophagy as a target for anticancer therapy. Nat Rev Clin Oncol 2011; 8:528-39. [PMID: 21587219 DOI: 10.1038/nrclinonc.2011.71] [Citation(s) in RCA: 650] [Impact Index Per Article: 46.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Autophagy is an important homeostatic cellular recycling mechanism responsible for degrading unnecessary or dysfunctional cellular organelles and proteins in all living cells. Autophagy is particularly active during metabolic stress. In the cancer cell it fulfils a dual role, having tumor-promoting and tumor-suppressing properties. Functional autophagy prevents necrosis and inflammation, which can lead to genetic instability. On the other hand, autophagy might be important for tumor progression by providing energy through its recycling mechanism during unfavorable metabolic circumstances. A central checkpoint that negatively regulates autophagy is mTOR, and anticancer drugs inhibiting the PI3K/Akt/mTOR axis putatively stimulate autophagy. However, whether autophagy contributes to the antitumor effect of these drugs or to drug resistance is largely unknown. The antimalarial drugs chloroquine and hydroxychloroquine inhibit autophagy, leading to increased cytotoxicity in combination with several anticancer drugs in preclinical models. The therapeutic clinical roles of autophagy induction and inhibition remain to be defined. To improve our understanding of autophagy in human cancers new methods for measuring autophagy in clinical samples need to be developed. This Review delineates the possible role of autophagy as a novel target for anticancer therapy.
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Affiliation(s)
- Filip Janku
- Department of Investigational Cancer Therapeutics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
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552
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Isaacs AM, Johannsen P, Holm I, Nielsen JE, FReJA consortium. Frontotemporal dementia caused by CHMP2B mutations. Curr Alzheimer Res 2011; 8:246-51. [PMID: 21222599 PMCID: PMC3182073 DOI: 10.2174/156720511795563764] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 11/28/2010] [Accepted: 11/30/2010] [Indexed: 01/13/2023]
Abstract
CHMP2B mutations are a rare cause of autosomal dominant frontotemporal dementia (FTD). The best studied example is frontotemporal dementia linked to chromosome 3 (FTD-3) which occurs in a large Danish family, with a further CHMP2B mutation identified in an unrelated Belgian familial FTD patient. These mutations lead to C-terminal truncations of the CHMP2B protein and we will review recent advances in our understanding of the molecular effects of these mutant truncated proteins on vesicular fusion events within the endosome-lysosome and autophagy degradation pathways. We will also review the clinical features of FTD caused by CHMP2B truncation mutations as well as new brain imaging and neuropathological findings. Finally, we collate the current data on CHMP2B missense mutations, which have been reported in FTD and motor neuron disease.
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Affiliation(s)
- A M Isaacs
- Department of Neurodegenerative Disease, VCL Institute of Neurology, Queen Square, London, UK.
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553
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Abstract
Innate immune activation is initiated by recognition of pathogen associated molecular patterns (PAMPs). Delivery of PAMPs to their respective receptors, regulation of receptor activity, and effector functions downstream from these receptors, which constitute part of the initiated innate immune control, are in part mediated via macroautophagy, an evolutionary conserved pathway for cytoplasmic constituent degradation in lysosomes. In this review these facets of the recently unveiled involvement of macroautophagy in innate immunity will be summarized, and aspects that need additional investigations will be high-lighted. The improved understanding of the capabilities of macroautophagy for immunity suggests that this pathway should be harnessed in immunotherapies against infectious diseases.
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Affiliation(s)
- Christian Münz
- Viral Immunobiology, Institute of Experimental Immunology, University of Zürich Zürich, Switzerland
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554
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Ding WX, Manley S, Ni HM. The emerging role of autophagy in alcoholic liver disease. Exp Biol Med (Maywood) 2011; 236:546-56. [PMID: 21478210 DOI: 10.1258/ebm.2011.010360] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Autophagy is a highly conserved intracellular catabolic pathway that degrades cellular long-lived proteins and organelles. Autophagy is normally activated in response to nutrient deprivation and other stresses as a cell survival mechanism. Accumulating evidence indicates that autophagy plays a critical role in liver pathophysiology, in addition to maintaining hepatic energy and nutrient balance. Alcohol consumption causes hepatic metabolic changes, oxidative stress, accumulation of lipid droplets and damaged mitochondria; all of these can be regulated by autophagy. This review summarizes the recent findings about the role and mechanisms of autophagy in alcoholic liver disease (ALD), and the possible intervention for treating ALD by modulating autophagy.
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Affiliation(s)
- Wen-Xing Ding
- Department of Pharmacology, Toxicology and Therapeutics, The University of Kansas Medical Center, Kansas City, 66160, USA.
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555
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Higashi S, Moore DJ, Minegishi M, Kasanuki K, Fujishiro H, Kabuta T, Togo T, Katsuse O, Uchikado H, Furukawa Y, Hino H, Kosaka K, Sato K, Arai H, Wada K, Iseki E. Localization of MAP1-LC3 in vulnerable neurons and Lewy bodies in brains of patients with dementia with Lewy bodies. J Neuropathol Exp Neurol 2011; 70:264-80. [PMID: 21412173 DOI: 10.1097/nen.0b013e318211c86a] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
There is emerging evidence implicating a role for the autophagy-lysosome pathway in the pathogenesis of Lewy body disease. We investigated potential neuropathologic and biochemical alterations of autophagy-lysosome pathway-related proteins in the brains of patients with dementia with Lewy bodies (DLB), Alzheimer disease (AD), and control subjects using antibodies against Ras-related protein Rab-7B (Rab7B), lysosomal-associated membrane protein 2 (LAMP2), and microtubule-associated protein 1A/1B light chain 3 (LC3). In DLB, but not in control brains, there were large Rab7B-immunoreactive endosomal granules. LC3 immunoreactivity was increased in vulnerable areas of DLB brains relative to that in control brains; computerized cell counting analysis revealed that LC3 levels were greater in the entorhinal cortex and amygdala of DLB brains than in controls. Rab7B levels were increased, and LAMP2 levels were decreased in the entorhinal cortex of DLB brains. In contrast, only a decrease in LAMP2 levels versus controls was found in AD brains. LC3 widely colocalized with several types of Lewy pathology; LAMP2 localized to the periphery or outside of brainstem-type Lewy bodies; Rab7B did not colocalize with Lewy pathology. Immunoblot analysis demonstrated specific accumulation of the autophagosomal LC3-II isoform in detergent-insoluble fractions from DLB brains. These results support apotential role for the autophagy-lysosome pathway in the pathogenesis of DLB.
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Affiliation(s)
- Shinji Higashi
- PET/CT Dementia Research Center, Juntendo Tokyo Koto Geriatric Medical Center, Juntendo University School of Medicine, Shinsuna, Koto-ku, Tokyo, Japan.
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556
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Fujitani Y, Uchida T, Komiya K, Abe H, Kawamori R, Watada H. Roles of autophagy in pancreatic β-cell function and type 2 diabetes. Diabetol Int 2011. [DOI: 10.1007/s13340-011-0020-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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557
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Katona I, Zhang X, Bai Y, Shy ME, Guo J, Yan Q, Hatfield J, Kupsky WJ, Li J. Distinct pathogenic processes between Fig4-deficient motor and sensory neurons. Eur J Neurosci 2011; 33:1401-10. [DOI: 10.1111/j.1460-9568.2011.07651.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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558
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Abstract
Autophagy (macroautophagy) is a dynamic process for degradation of cytosolic components. Autophagy has intracellular anti-viral and anti-bacterial functions, and plays a role in the initiation of innate and adaptive immune system responses to viral and bacterial infections. Some viruses encode virulence factors for blocking autophagy, whereas others utilize some autophagy components for their intracellular growth or cellular budding. The "core" autophagy-related (Atg) complexes in mammals are ULK1 protein kinase, Atg9-WIPI-1 and Vps34-beclin1 class III PI3-kinase complexes, and the Atg12 and LC3 conjugation systems. In addition, PI(3)-binding proteins, PI3-phosphatases, and Rab proteins contribute to autophagy. The autophagy process consists of continuous dynamic membrane formation and fusion. In this review, the relationships between these Atg complexes and each process are described. Finally, the critical points for monitoring autophagy, including the use of GFP-LC3 and GFP-Atg5, are discussed.
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Affiliation(s)
- Isei Tanida
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Toyama, Shinjyuku, Tokyo, Japan.
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559
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Palmisano R, Golfi P, Heimann P, Shaw C, Troakes C, Schmitt-John T, Bartsch JW. Endosomal accumulation of APP in wobbler motor neurons reflects impaired vesicle trafficking: implications for human motor neuron disease. BMC Neurosci 2011; 12:24. [PMID: 21385376 PMCID: PMC3058068 DOI: 10.1186/1471-2202-12-24] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 03/07/2011] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND The cause of sporadic amyotrophic lateral sclerosis (ALS) is largely unknown but hypotheses about disease mechanisms include oxidative stress, defective axonal transport, mitochondrial dysfunction and disrupted RNA processing. Whereas familial ALS is well represented by transgenic mutant SOD1 mouse models, the mouse mutant wobbler (WR) develops progressive motor neuron degeneration due to a point mutation in the Vps54 gene, and provides an animal model for sporadic ALS. VPS54 protein as a component of a protein complex is involved in vesicular Golgi trafficking; impaired vesicle trafficking might also be mechanistic in the pathogenesis of human ALS. RESULTS In motor neurons of homozygous symptomatic WR mice, a massive number of endosomal vesicles significantly enlarged (up to 3 μm in diameter) were subjected to ultrastructural analysis and immunohistochemistry for the endosome-specific small GTPase protein Rab7 and for amyloid precursor protein (APP). Enlarged vesicles were neither detected in heterozygous WR nor in transgenic SOD1(G93A) mice; in WR motor neurons, numerous APP/Rab7-positive vesicles were observed which were mostly LC3-negative, suggesting they are not autophagosomes. CONCLUSIONS We conclude that endosomal APP/Rab7 staining reflects impaired vesicle trafficking in WR mouse motor neurons. Based on these findings human ALS tissues were analysed for APP in enlarged vesicles and were detected in spinal cord motor neurons in six out of fourteen sporadic ALS cases. These enlarged vesicles were not detected in any of the familial ALS cases. Thus our study provides the first evidence for wobbler-like aetiologies in human ALS and suggests that the genes encoding proteins involved in vesicle trafficking should be screened for pathogenic mutations.
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Affiliation(s)
- Ralf Palmisano
- King's College London, Pharmaceutical Science Research Division, 150 Stamford Street, London SE1 9NH, UK
| | - Panagiota Golfi
- King's College London, Pharmaceutical Science Research Division, 150 Stamford Street, London SE1 9NH, UK
| | - Peter Heimann
- Department of Cell Biology, Bielefeld University, 33501 Bielefeld, Germany
| | - Christopher Shaw
- Kings College London, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK
| | - Claire Troakes
- Kings College London, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK
| | | | - Jörg W Bartsch
- King's College London, Pharmaceutical Science Research Division, 150 Stamford Street, London SE1 9NH, UK
- Department of Neurosurgery, University of Marburg, Baldingerstrasse, 35033 Marburg, Germany
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560
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Amaravadi RK, Lippincott-Schwartz J, Yin XM, Weiss WA, Takebe N, Timmer W, DiPaola RS, Lotze MT, White E. Principles and current strategies for targeting autophagy for cancer treatment. Clin Cancer Res 2011; 17:654-66. [PMID: 21325294 PMCID: PMC3075808 DOI: 10.1158/1078-0432.ccr-10-2634] [Citation(s) in RCA: 715] [Impact Index Per Article: 51.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Autophagy is an evolutionarily conserved, intracellular self-defense mechanism in which organelles and proteins are sequestered into autophagic vesicles that are subsequently degraded through fusion with lysosomes. Cells, thereby, prevent the toxic accumulation of damaged or unnecessary components, but also recycle these components to sustain metabolic homoeostasis. Heightened autophagy is a mechanism of resistance for cancer cells faced with metabolic and therapeutic stress, revealing opportunities for exploitation as a therapeutic target in cancer. We summarize recent developments in the field of autophagy and cancer and build upon the results presented at the Cancer Therapy Evaluation Program (CTEP) Early Drug Development meeting in March 2010. Herein, we describe our current understanding of the core components of the autophagy machinery and the functional relevance of autophagy within the tumor microenvironment, and we outline how this knowledge has informed preclinical investigations combining the autophagy inhibitor hydroxychloroquine (HCQ) with chemotherapy, targeted therapy, and immunotherapy. Finally, we describe ongoing clinical trials involving HCQ as a first generation autophagy inhibitor, as well as strategies for the development of novel, more potent, and specific inhibitors of autophagy.
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Affiliation(s)
- Ravi K Amaravadi
- Abramson Cancer Center and Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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561
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Sphingolipid storage affects autophagic metabolism of the amyloid precursor protein and promotes Abeta generation. J Neurosci 2011; 31:1837-49. [PMID: 21289194 PMCID: PMC6623751 DOI: 10.1523/jneurosci.2954-10.2011] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Deposition of amyloid β peptides (Aβs) in extracellular amyloid plaques within the human brain is a hallmark of Alzheimer's disease (AD). Aβ derives from proteolytic processing of the amyloid precursor protein (APP) by β- and γ-secretases. The initial cleavage by β-secretase results in shedding of the APP ectodomain and generation of APP C-terminal fragments (APP-CTFs), which can then be further processed within the transmembrane domain by γ-secretase, resulting in release of Aβ. Here, we demonstrate that accumulation of sphingolipids (SLs), as occurs in lysosomal lipid storage disorders (LSDs), decreases the lysosome-dependent degradation of APP-CTFs and stimulates γ-secretase activity. Together, this results in increased generation of both intracellular and secreted Aβ. Notably, primary fibroblasts from patients with different SL storage diseases show strong accumulation of potentially amyloidogenic APP-CTFs. By using biochemical, cell biological, and genetic approaches, we demonstrate that SL accumulation affects autophagic flux and impairs the clearance of APP-CTFs. Thus, accumulation of SLs might not only underlie the pathogenesis of LSDs, but also trigger increased generation of Aβ and contribute to neurodegeneration in sporadic AD.
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562
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Schneede A, Schmidt CK, Hölttä-Vuori M, Heeren J, Willenborg M, Blanz J, Domanskyy M, Breiden B, Brodesser S, Landgrebe J, Sandhoff K, Ikonen E, Saftig P, Eskelinen EL. Role for LAMP-2 in endosomal cholesterol transport. J Cell Mol Med 2011; 15:280-95. [PMID: 19929948 PMCID: PMC3822795 DOI: 10.1111/j.1582-4934.2009.00973.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Accepted: 11/09/2009] [Indexed: 01/24/2023] Open
Abstract
The mechanisms of endosomal and lysosomal cholesterol traffic are still poorly understood. We showed previously that unesterified cholesterol accumulates in the late endosomes and lysosomes of fibroblasts deficient in both lysosome associated membrane protein-2 (LAMP-2) and LAMP-1, two abundant membrane proteins of late endosomes and lysosomes. In this study we show that in cells deficient in both LAMP-1 and LAMP-2 (LAMP(-/-)), low-density lipoprotein (LDL) receptor levels and LDL uptake are increased as compared to wild-type cells. However, there is a defect in esterification of both endogenous and LDL cholesterol. These results suggest that LAMP(-/-) cells have a defect in cholesterol transport to the site of esterification in the endoplasmic reticulum, likely due to defective export of cholesterol out of late endosomes or lysosomes. We also show that cholesterol accumulates in LAMP-2 deficient liver and that overexpression of LAMP-2 retards the lysosomal cholesterol accumulation induced by U18666A. These results point to a critical role for LAMP-2 in endosomal/lysosomal cholesterol export. Moreover, the late endosomal/lysosomal cholesterol accumulation in LAMP(-/-) cells was diminished by overexpression of any of the three isoforms of LAMP-2, but not by LAMP-1. The LAMP-2 luminal domain, the membrane-proximal half in particular, was necessary and sufficient for the rescue effect. Taken together, our results suggest that LAMP-2, its luminal domain in particular, plays a critical role in endosomal cholesterol transport and that this is distinct from the chaperone-mediated autophagy function of LAMP-2.
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Affiliation(s)
| | | | | | - Jörg Heeren
- Department of Biochemistry and Molecular Biology II: Molecular Cell Biology, University Medical Center Hamburg-EppendorfHamburg, Germany
| | | | - Judith Blanz
- Institute of Biochemistry, University of KielKiel, Germany
| | - Mykola Domanskyy
- Department of Biological and Environmental Sciences, Division of Biochemistry, University of HelsinkiHelsinki, Finland
| | - Bernadette Breiden
- LIMES, Membrane Biology and Lipid Biochemistry Unit, c/o Kekulé-Institute for Organic Chemistry and BiochemistryBonn, Germany
| | - Susanne Brodesser
- LIMES, Membrane Biology and Lipid Biochemistry Unit, c/o Kekulé-Institute for Organic Chemistry and BiochemistryBonn, Germany
| | - Jobst Landgrebe
- Georg-August University Göttingen, Department of BiochemistryGöttingen, Germany
| | - Konrad Sandhoff
- LIMES, Membrane Biology and Lipid Biochemistry Unit, c/o Kekulé-Institute for Organic Chemistry and BiochemistryBonn, Germany
| | - Elina Ikonen
- Institute of Biomedicine/Anatomy, University of HelsinkiHelsinki, Finland
| | - Paul Saftig
- Institute of Biochemistry, University of KielKiel, Germany
| | - Eeva-Liisa Eskelinen
- Department of Biological and Environmental Sciences, Division of Biochemistry, University of HelsinkiHelsinki, Finland
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563
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Manjithaya R, Subramani S. Autophagy: a broad role in unconventional protein secretion? Trends Cell Biol 2011; 21:67-73. [PMID: 20961762 PMCID: PMC3025270 DOI: 10.1016/j.tcb.2010.09.009] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2010] [Revised: 09/15/2010] [Accepted: 09/22/2010] [Indexed: 01/06/2023]
Abstract
Autophagy, a cellular 'self-eating' process in eukaryotic cells, exists in both a basal and in an activated state that is induced in response to starvation. Basal and induced autophagy are associated with the packaging of cellular components, including damaged and/or redundant organelles, into double-membrane vesicles called autophagosomes, followed by autophagosome fusion with lysosomes, in which their contents are degraded and recycled. Recent results highlight a novel role for autophagy that does not involve lysosomal degradation of autophagosomal contents, but instead involves their redirection towards the extracellular delivery of an unconventionally secreted protein. Here, we discuss these findings, evaluate the strength of evidence, consider their implications for the field of protein trafficking, and suggest the next steps required to probe this interesting pathway.
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Affiliation(s)
- Ravi Manjithaya
- Section of Molecular Biology, University of California, San Diego, La Jolla, CA 92093-0322, USA
| | - Suresh Subramani
- Section of Molecular Biology, University of California, San Diego, La Jolla, CA 92093-0322, USA
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564
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Chang JW, Choi H, Cotman SL, Jung YK. Lithium rescues the impaired autophagy process in CbCln3(Δex7/8/Δex7/8) cerebellar cells and reduces neuronal vulnerability to cell death via IMPase inhibition. J Neurochem 2011; 116:659-68. [PMID: 21175620 PMCID: PMC4517618 DOI: 10.1111/j.1471-4159.2010.07158.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Juvenile neuronal ceroid lipofuscinosis (Batten disease) is a neurodegenerative disorder caused by mutation in CLN3. Defective autophagy and concomitant accumulation of autofluorescence enriched with mitochondrial ATP synthase subunit c were previously discovered in Cln3 mutant knock-in mice. In this study, we show that treatment with lithium reduces numbers of LC3-positive autophagosomes and accumulation of LC3-II in Cln3 mutant knock-in cerebellar cells (CbCln3(Δex7/8/Δex7/8) ). Lithium, an inhibitor of GSK3 and IMPase, reduces the accumulation of mitochondrial ATP synthase subunit c and autofluorescence in CbCln3(Δex7/8/Δex7/8) cells, and mitigates the abnormal subcellular distribution of acidic vesicles in the cells. L690,330, an IMPase inhibitor, is as effective as lithium in restoring autophagy in CbCln3(Δex7/8/Δex7/8) cells. Moreover, lithium or down-regulation of IMPase expression protects CbCln3(Δex7/8/Δex7/8) cells from cell death induced by amino acid deprivation. These results suggest that lithium overcomes the autophagic defect in CbCln3(Δex7/8/Δex7/8) cerebellar cells probably through IMPase, thereby reducing their vulnerability to cell death.
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Affiliation(s)
- Jae-Woong Chang
- Creative Research Initiative (CRI)-Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 599 Gwanak-ro, Seoul 151-747, Korea
| | - Hyunwoo Choi
- Creative Research Initiative (CRI)-Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 599 Gwanak-ro, Seoul 151-747, Korea
| | - Susan L. Cotman
- Molecular Neurogenetics Unit and Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Yong-Keun Jung
- Creative Research Initiative (CRI)-Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 599 Gwanak-ro, Seoul 151-747, Korea
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565
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Bains M, Zaegel V, Mize-Berge J, Heidenreich KA. IGF-I stimulates Rab7-RILP interaction during neuronal autophagy. Neurosci Lett 2011; 488:112-7. [PMID: 20849920 PMCID: PMC3027408 DOI: 10.1016/j.neulet.2010.09.018] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 08/12/2010] [Accepted: 09/03/2010] [Indexed: 11/19/2022]
Abstract
Restoration of autophagy represents a potential therapeutic target for neurodegenerative disorders, but factors that regulate autophagic flux are largely unknown. When deprived of trophic factors, cultured Purkinje neurons die by an autophagy associated cell death mechanism. The accumulation of autophagic vesicles and cell death of Purkinje neurons is inhibited by insulin-like growth factor, by a mechanism that enhances autophagic vesicle turnover. In this report, we identify Rab7 as an IGF-I regulated target during neuronal autophagy. Purkinje neurons transfected with EGFP-Rab7-WT and constitutively active EGFP-Rab7-Q67L contained few RFP-LC3 positive autophagosomes and little co-localization with GFP-Rab7 under control conditions. Upon induction of autophagy, RFP-LC3 positive autophagosomes increased and co-localized with GFP-Rab7. Conversely, expression of the dominant negative mutant EGFP-Rab7-T22N increased the accumulation of autophagosomes under control conditions, which accumulated even further during trophic factor withdrawal. There was no vesicular co-localization between Rab7-T22N and RFP-LC3 under control or trophic factor withdrawal conditions. During prolonged trophic factor withdrawal, a condition that leads to the accumulation of autophagic vesicles and cell death, Rab7 activity decreased significantly. IGF-I, added at the time of trophic factor withdrawal, prevented the deactivation of Rab7 and increased the interaction of Rab7 with its interacting protein (RILP), restoring autophagic flux. These results provide a novel mechanism by which IGF-I regulates autophagic flux during neuronal stress.
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Affiliation(s)
- Mona Bains
- Department of Pharmacology, University of Colorado Denver, Aurora, CO, USA
| | - Vincent Zaegel
- Department of Pharmacology, University of Colorado Denver, Aurora, CO, USA
| | - Janna Mize-Berge
- Department of Pharmacology, University of Colorado Denver, Aurora, CO, USA
| | - Kim A. Heidenreich
- Department of Pharmacology, University of Colorado Denver, Aurora, CO, USA
- Denver Veterans Affairs Medical Center, Denver, Colorado, USA
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566
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Taylor GS, Mautner J, Münz C. Autophagy in herpesvirus immune control and immune escape. HERPESVIRIDAE 2011; 2:2. [PMID: 21429245 PMCID: PMC3063195 DOI: 10.1186/2042-4280-2-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 01/05/2011] [Indexed: 01/06/2023]
Abstract
Autophagy delivers cytoplasmic constituents for lysosomal degradation, and thereby facilitates pathogen degradation and pathogen fragment loading onto MHC molecules for antigen presentation to T cells. Herpesviruses have been used to demonstrate these novel functions of autophagy, which previously has been primarily appreciated for its pro-survival role during starvation. In this review, we summarize recent findings how macroautophagy restricts herpesvirus infections directly, how macroautophagy and chaperone mediated autophagy contribute to herpesviral antigen presentation on MHC molecules, and which mechanisms herpesviruses have developed to interfere with these pathways. These studies suggest that herpesviruses significantly modulate autophagy to escape from its functions in innate and adaptive immunity.
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Affiliation(s)
- Graham S Taylor
- School of Cancer Sciences and Medical Research Council Centre for Immune Regulation, University of Birmingham, Birmingham, UK.
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567
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Claerhout S, Lorenzi PL, Weinstein JN, Mills GB. MODULATION OF AUTOPHAGY AND ITS POTENTIAL FOR CANCER THERAPY. DRUG FUTURE 2011; 36:10.1358/dof.2011.036.12.1711892. [PMID: 25419038 PMCID: PMC4239665 DOI: 10.1358/dof.2011.036.12.1711892] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Autophagy is a process in which cellular contents are captured in specialized, membrane-bounded vesicles and delivered to lysosomes for final degradation. Most studies support an inherent connection between autophagy and survival, but increasing evidence also suggests an association between autophagy and cell death. The therapeutic potential of targeting the autophagy pathway in cancer seems clear, but specific strategies for achieving successful eradication of cancer cells are less obvious. Recent developments in the fields of autophagy and programmed cell death, nevertheless, have shed light on therapeutic strategies with significant potential. In this review, we provide an overview of the autophagy process, pathways that modulate autophagy, and promising autophagy-based therapeutic strategies for cancer.
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Affiliation(s)
- Sofie Claerhout
- Department of Systems Biology, The University of Texas M.D. Anderson Cancer Center, Houston, TX
| | - Philip L. Lorenzi
- Department of Bioinformatics and Computational Biology, The University of Texas M.D. Anderson Cancer Center, Houston, TX
| | - John N. Weinstein
- Department of Bioinformatics and Computational Biology, The University of Texas M.D. Anderson Cancer Center, Houston, TX
| | - Gordon B. Mills
- Department of Systems Biology, The University of Texas M.D. Anderson Cancer Center, Houston, TX
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568
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Hidvegi T, Mukherjee A, Ewing M, Kemp C, Perlmutter DH. The Role of Autophagy in Alpha-1-Antitrypsin Deficiency. Methods Enzymol 2011; 499:33-54. [DOI: 10.1016/b978-0-12-386471-0.00003-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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569
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Abstract
Autophagy is a major catabolic pathway in eukaryotes, which is required for the lysosomal/vacuolar degradation of cytoplasmic proteins and organelles. Interest in the autophagy pathway has recently gained momentum largely owing to identification of multiple autophagy-related genes and recognition of its involvement in various physiological conditions. Here we review current knowledge of the molecular mechanisms regulating autophagy in mammals and yeast, specifically the biogenesis of autophagosomes and the selectivity of their cargo recruitment. We discuss the different steps of autophagy, from the signal transduction events that regulate it to the completion of this pathway by fusion with the lysosome/vacuole. We also review research on the origin of the autophagic membrane, the molecular mechanism of autophagosome formation, and the roles of two ubiquitin-like protein families and other structural elements that are essential for this process. Finally, we discuss the various modes of autophagy and highlight their functional relevance for selective degradation of specific cargos.
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Affiliation(s)
- Hilla Weidberg
- Department of Biological Chemistry, The Weizmann Institute of Science, 76100 Rehovot, Israel
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570
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Ke PY, Chen SSL. Activation of the unfolded protein response and autophagy after hepatitis C virus infection suppresses innate antiviral immunity in vitro. J Clin Invest 2011; 121:37-56. [PMID: 21135505 PMCID: PMC3007134 DOI: 10.1172/jci41474] [Citation(s) in RCA: 277] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Accepted: 10/06/2010] [Indexed: 12/11/2022] Open
Abstract
Autophagy, a process for catabolizing cytoplasmic components, has been implicated in the modulation of interactions between RNA viruses and their host. However, the mechanism underlying the functional role of autophagy in the viral life cycle still remains unclear. Hepatitis C virus (HCV) is a single-stranded, positive-sense, membrane-enveloped RNA virus that can cause chronic liver disease. Here we report that HCV induces the unfolded protein response (UPR), which in turn activates the autophagic pathway to promote HCV RNA replication in human hepatoma cells. Further analysis revealed that the entire autophagic process through to complete autolysosome maturation was required to promote HCV RNA replication and that it did so by suppressing innate antiviral immunity. Gene silencing or activation of the UPR-autophagy pathway activated or repressed, respectively, IFN-β activation mediated by an HCV-derived pathogen-associated molecular pattern (PAMP). Similar results were achieved with a PAMP derived from Dengue virus (DEV), indicating that HCV and DEV may both exploit the UPR-autophagy pathway to escape the innate immune response. Taken together, these results not only define the physiological significance of HCV-induced autophagy, but also shed light on the knowledge of host cellular responses upon HCV infection as well as on exploration of therapeutic targets for controlling HCV infection.
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Affiliation(s)
- Po-Yuan Ke
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
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571
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Duivenvoorde LPM, van Schothorst EM, Bunschoten A, Keijer J. Dietary restriction of mice on a high-fat diet induces substrate efficiency and improves metabolic health. J Mol Endocrinol 2011; 47:81-97. [PMID: 21610007 DOI: 10.1530/jme-11-0001] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
High energy intake and, specifically, high dietary fat intake challenge the mammalian metabolism and correlate with many metabolic disorders such as obesity and diabetes. However, dietary restriction (DR) is known to prevent the development of metabolic disorders. The current western diets are highly enriched in fat, and it is as yet unclear whether DR on a certain high-fat (HF) diet elicits similar beneficial effects on health. In this research, we report that HF-DR improves metabolic health of mice compared with mice receiving the same diet on an ad libitum basis (HF-AL). Already after five weeks of restriction, the serum levels of cholesterol and leptin were significantly decreased in HF-DR mice, whereas their glucose sensitivity and serum adiponectin levels were increased. The body weight and measured serum parameters remained stable in the following 7 weeks of restriction, implying metabolic adaptation. To understand the molecular events associated with this adaptation, we analyzed gene expression in white adipose tissue (WAT) with whole genome microarrays. HF-DR strongly influenced gene expression in WAT; in total, 8643 genes were differentially expressed between both groups of mice, with a major role for genes involved in lipid metabolism and mitochondrial functioning. This was confirmed by quantitative real-time reverse transcription-PCR and substantiated by increase in mitochondrial density in WAT of HF-DR mice. These results provide new insights in the metabolic flexibility of dietary restricted animals and suggest the development of substrate efficiency.
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Affiliation(s)
- Loes P M Duivenvoorde
- Department of Human and Animal Physiology, Wageningen University, Marijkeweg 40, 6709 GP Wageningen, PO Box 338, 6700 AH Wageningen, The Netherlands
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572
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Lin F, Ren XD, Pan Z, Macri L, Zong WX, Tonnesen MG, Rafailovich M, Bar-Sagi D, Clark RA. Fibronectin growth factor-binding domains are required for fibroblast survival. J Invest Dermatol 2011; 131:84-98. [PMID: 20811396 PMCID: PMC3139177 DOI: 10.1038/jid.2010.253] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Fibronectin (FN) is required for embryogenesis, morphogenesis, and wound repair, and its Arg-Gly-Asp-containing central cell-binding domain (CCBD) is essential for mesenchymal cell survival and growth. Here, we demonstrate that FN contains three growth factor-binding domains (FN-GFBDs) that bind platelet-derived growth factor-BB (PDGF-BB), a potent fibroblast survival and mitogenic factor. These sites bind PDGF-BB with dissociation constants of 10-100 nM. FN-null cells cultured on recombinant CCBD (FNIII(8-11)) without a FN-GFBD demonstrated minimal metabolism and underwent autophagy at 24 hours, followed by apoptosis at 72 hours, even in the presence of PDGF-BB. In contrast, FN-null cells plated on FNIII(8-11) contiguous with FN-GFBD survived without, and proliferated with, PDGF-BB. FN-null cell survival on FNIII(8-11) and noncontiguous arrays of FN-GFBDs required these domains to be adsorbed on the same surface, suggesting the existence of a mesenchymal cell-extracellular matrix synapse. Thus, fibroblast survival required GF stimulation in the presence of a FN-GFBD, as well as adhesion to FN through the CCBD. The findings that fibroblast survival is dependent on FN-GFBD underscore the critical importance of pericellular matrix for cell survival and have significant implications for cutaneous wound healing and regeneration.
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Affiliation(s)
- Fubao Lin
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York, USA
| | - Xiang-Dong Ren
- Department of Dermatology, Stony Brook University, Stony Brook, New York, USA
| | - Zhi Pan
- Department of Materials Science, Stony Brook University, Stony Brook, New York, USA
| | - Lauren Macri
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York, USA
| | - Wei-Xing Zong
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, USA
| | - Marcia G. Tonnesen
- Department of Dermatology, Stony Brook University, Stony Brook, New York, USA
- Dermatology Division, Northport VAMC, Northport, New York, USA
| | - Miriam Rafailovich
- Department of Materials Science, Stony Brook University, Stony Brook, New York, USA
| | - Dafna Bar-Sagi
- Department of Biochemistry, New York University, New York, New York, USA
| | - Richard A.F. Clark
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York, USA
- Department of Dermatology, Stony Brook University, Stony Brook, New York, USA
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573
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Hamacher-Brady A, Stein HA, Turschner S, Toegel I, Mora R, Jennewein N, Efferth T, Eils R, Brady NR. Artesunate activates mitochondrial apoptosis in breast cancer cells via iron-catalyzed lysosomal reactive oxygen species production. J Biol Chem 2010; 286:6587-601. [PMID: 21149439 DOI: 10.1074/jbc.m110.210047] [Citation(s) in RCA: 175] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The antimalarial agent artesunate (ART) activates programmed cell death (PCD) in cancer cells in a manner dependent on the presence of iron and the generation of reactive oxygen species. In malaria parasites, ART cytotoxicity originates from interactions with heme-derived iron within the food vacuole. The analogous digestive compartment of mammalian cells, the lysosome, similarly contains high levels of redox-active iron and in response to specific stimuli can initiate mitochondrial apoptosis. We thus investigated the role of lysosomes in ART-induced PCD and determined that in MCF-7 breast cancer cells ART activates lysosome-dependent mitochondrial outer membrane permeabilization. ART impacted endolysosomal and autophagosomal compartments, inhibiting autophagosome turnover and causing perinuclear clustering of autophagosomes, early and late endosomes, and lysosomes. Lysosomal iron chelation blocked all measured parameters of ART-induced PCD, whereas lysosomal iron loading enhanced death, thus identifying lysosomal iron as the lethal source of reactive oxygen species upstream of mitochondrial outer membrane permeabilization. Moreover, lysosomal inhibitors chloroquine and bafilomycin A1 reduced ART-activated PCD, evidencing a requirement for lysosomal function during PCD signaling. ART killing did not involve activation of the BH3-only protein, Bid, yet ART enhanced TNF-mediated Bid cleavage. We additionally demonstrated the lysosomal PCD pathway in T47D and MDA-MB-231 breast cancer cells. Importantly, non-tumorigenic MCF-10A cells resisted ART-induced PCD. Together, our data suggest that ART triggers PCD via engagement of distinct, interconnected PCD pathways, with hierarchical signaling from lysosomes to mitochondria, suggesting a potential clinical use of ART for targeting lysosomes in cancer treatment.
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Affiliation(s)
- Anne Hamacher-Brady
- Division of Theoretical Bioinformatics, Applied Systems Biology Group, German Cancer Research Center, 69120 Heidelberg, Germany
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574
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Hariharan N, Maejima Y, Nakae J, Paik J, DePinho RA, Sadoshima J. Deacetylation of FoxO by Sirt1 Plays an Essential Role in Mediating Starvation-Induced Autophagy in Cardiac Myocytes. Circ Res 2010; 107:1470-82. [PMID: 20947830 PMCID: PMC3011986 DOI: 10.1161/circresaha.110.227371] [Citation(s) in RCA: 558] [Impact Index Per Article: 37.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 10/01/2010] [Indexed: 12/21/2022]
Abstract
RATIONALE autophagy, a bulk degradation process of cytosolic proteins and organelles, is protective during nutrient starvation in cardiomyocytes (CMs). However, the underlying signaling mechanism mediating autophagy is not well understood. OBJECTIVE we investigated the role of FoxOs and its posttranslational modification in mediating starvation-induced autophagy. METHODS AND RESULTS glucose deprivation (GD) increased autophagic flux in cultured CMs, as evidenced by increased mRFP-GFP-LC3 puncta and decreases in p62, which was accompanied by upregulation of Sirt1 and FoxO1. Overexpression of either Sirt1 or FoxO1 was sufficient for inducing autophagic flux, whereas both Sirt1 and FoxO1 were required for GD-induced autophagy. GD increased deacetylation of FoxO1, and Sirt1 was required for GD-induced deacetylation of FoxO1. Overexpression of FoxO1(3A/LXXAA), which cannot interact with Sirt1, or p300, a histone acetylase, increased acetylation of FoxO1 and inhibited GD-induced autophagy. FoxO1 increased expression of Rab7, a small GTP-binding protein that mediates late autophagosome-lysosome fusion, which was both necessary and sufficient for mediating FoxO1-induced increases in autophagic flux. Although cardiac function was maintained in control mice after 48 hours of food starvation, it was significantly deteriorated in mice with cardiac-specific overexpression of FoxO1(3A/LXXAA), those with cardiac-specific homozygous deletion of FoxO1 (c-FoxO1(-/-)), and beclin1(+/-) mice, in which autophagy is significantly inhibited. CONCLUSIONS these results suggest that Sirt1-mediated deacetylation of FoxO1 and upregulation of Rab7 play an important role in mediating starvation-induced increases in autophagic flux, which in turn plays an essential role in maintaining left ventricular function during starvation.
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Affiliation(s)
- Nirmala Hariharan
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ, USA
| | - Yasuhiro Maejima
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ, USA
| | - Jun Nakae
- Frontier Medicine on Metabolic Syndrome, Division of Endocrinology, Metabolism and Nephrology, Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Jihye Paik
- Belfer Institute for Applied Cancer Science, Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - Ronald A DePinho
- Belfer Institute for Applied Cancer Science, Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - Junichi Sadoshima
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ, USA
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575
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Kim HJ, Lee S, Jung JU. When autophagy meets viruses: a double-edged sword with functions in defense and offense. Semin Immunopathol 2010; 32:323-41. [PMID: 20865416 PMCID: PMC3169181 DOI: 10.1007/s00281-010-0226-8] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Accepted: 08/29/2010] [Indexed: 10/19/2022]
Abstract
Autophagy is a ubiquitous catabolic process that ensures organism's well-being by sequestering a wide array of undesired intracellular constituents into double-membrane vesicles termed autophagosomes for lysosomal degradation. Interest in autophagy research has recently gained momentum as it is increasingly being recognized to play fundamental roles in diverse aspects of human pathophysiology including virus infection and its subsequent complications. This review discusses recent advances in autophagy studies with respect to virus infection and pathogenesis. A growing body of evidence suggests that the autophagy pathway and/or autophagy genes play pleiotropic functions in the host's intrinsic, innate, and adaptive immune response against viruses. However, some viruses have evolved to encode virulence factors that evade or counteract the execution of autophagy. Furthermore, certain viruses are equipped to enhance autophagy or exploit the autophagy machinery for their replication and pathogenesis. A comprehensive understanding of the roles of autophagy pathway and autophagy genes during viral infection may enable the discovery of novel antiviral drug targets.
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Affiliation(s)
- Hee Jin Kim
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
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576
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Li B, Castano AP, Hudson TE, Nowlin BT, Lin SL, Bonventre JV, Swanson KD, Duffield JS. The melanoma‐associated transmembrane glycoprotein Gpnmb controls trafficking of cellular debris for degradation and is essential for tissue repair. FASEB J 2010. [DOI: 10.1096/fj.10.154757] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Bing Li
- Laboratory of Inflammation Research Boston Massachusetts USA
- Renal DivisionBrigham and Women's Hospital and Harvard Medical School Boston Massachusetts USA
- Department of Nephrology2nd Affiliated Hospital of Harbin Medical University Harbin China
| | - Ana P. Castano
- Laboratory of Inflammation Research Boston Massachusetts USA
- Renal DivisionBrigham and Women's Hospital and Harvard Medical School Boston Massachusetts USA
| | - Thomas E. Hudson
- Laboratory of Inflammation Research Boston Massachusetts USA
- Renal DivisionBrigham and Women's Hospital and Harvard Medical School Boston Massachusetts USA
| | - Brian T. Nowlin
- Laboratory of Inflammation Research Boston Massachusetts USA
- Renal DivisionBrigham and Women's Hospital and Harvard Medical School Boston Massachusetts USA
| | - Shuei-Liong Lin
- Laboratory of Inflammation Research Boston Massachusetts USA
- Renal DivisionBrigham and Women's Hospital and Harvard Medical School Boston Massachusetts USA
| | - Joseph V. Bonventre
- Renal DivisionBrigham and Women's Hospital and Harvard Medical School Boston Massachusetts USA
| | - Kenneth D. Swanson
- Department of Nephrology2nd Affiliated Hospital of Harbin Medical University Harbin China
- Division of Signal TransductionBeth Israel Deaconess Medical Center Boston Massachusetts USA
| | - Jeremy S. Duffield
- Laboratory of Inflammation Research Boston Massachusetts USA
- Renal DivisionBrigham and Women's Hospital and Harvard Medical School Boston Massachusetts USA
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577
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Metcalf D, Isaacs AM. The role of ESCRT proteins in fusion events involving lysosomes, endosomes and autophagosomes. Biochem Soc Trans 2010; 38:1469-73. [PMID: 21118109 DOI: 10.1042/bst0381469] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
ESCRT (endosomal sorting complex required for transport) proteins were originally identified for their role in delivering endocytosed proteins to the intraluminal vesicles of late-endosomal structures termed multivesicular bodies. Multivesicular bodies then fuse with lysosomes, leading to degradation of the internalized proteins. Four ESCRT complexes interact to concentrate cargo on the endosomal membrane, induce membrane curvature to form an intraluminal bud and finally pinch off the bud through a membrane-scission event to produce the intraluminal vesicle. Recent work suggests that ESCRT proteins are also required downstream of these events to enable fusion of multivesicular bodies with lysosomes. Autophagy is a related pathway required for the degradation of organelles, long-lived proteins and protein aggregates which also converges on lysosomes. The proteins or organelle to be degraded are encapsulated by an autophagosome that fuses either directly with a lysosome or with an endosome to form an amphisome, which then fuses with a lysosome. A common machinery is beginning to emerge that regulates fusion events in the multivesicular body and autophagy pathways, and we focus in the present paper on the role of ESCRT proteins. These fusion events have been implicated in diseases including frontotemporal dementia, Alzheimer's disease, lysosomal storage disorders, myopathies and bacterial pathogen invasion, and therefore further examination of the mechanisms involved may lead to new insight into disease pathogenesis and treatments.
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Affiliation(s)
- Daniel Metcalf
- Department of Neurodegenerative Disease, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
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578
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Abstract
Two major proteolysis systems, the ubiquitin-proteasome system, and the autophagy-lysosome system, contribute to degradation of various types of protein and/or protein aggregates. In general, the autophagy-lysosome system is involved in bulk intracellular degradation of proteins and organelles, while the ubiquitin-proteasome system is selective. During autophagy, a cytosolic form of LC3 (LC3-I) is conjugated to phosphatidylethanolamine to form LC3-phosphatidylethanolamine conjugate (LC3-II), which is recruited to autophagosomal membranes, and LC3-II is degraded by lysosomal hydrolases after the fusion of autophagosomes with lysosomes. Therefore, lysosomal turnover of LC3-II reflects starvation-induced autophagic activity, and detection of LC3 by immunoblotting or immunofluorescence has become a reliable method for monitoring autophagy. When autophagy is impaired, the level of p62/SQSTM1, a ubiquitin- and LC3-binding protein, is increased in addition to the accumulation of ubiquitinated proteins. Here, we describe basic protocols to analyze endogenous LC3-II, p62, and autophagy-related proteins by immunoblotting, immunofluorescence, and electron microscopy.
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579
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Abstract
The paper reviews the rapidly expanding pool of information on cellular and molecular mechanisms of autophagy, including autophagy types, macroautophagy induction, formation of autophagosomes and cross-talk between autophagy and apoptosis. Special attention is given to generation of reactive oxygen species (ROS) in various cellular compartments of cells under stress conditions inducing autophagy. The roles of hydrogen peroxide and superoxide in autophagy are analysed based on the recent experimental work. The relation between ROS and life span prolongation is briefly discussed, with the final conclusion that the paradox of dual role of ROS in life and death may be solved to a considerable extent due to research on autophagy.
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Affiliation(s)
- Irena Szumiel
- Center of Radiobiology and Biological Dosimetry, Institute of Nuclear Chemistry and Technology, Warsaw, Poland.
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580
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Tabata K, Matsunaga K, Sakane A, Sasaki T, Noda T, Yoshimori T. Rubicon and PLEKHM1 negatively regulate the endocytic/autophagic pathway via a novel Rab7-binding domain. Mol Biol Cell 2010; 21:4162-72. [PMID: 20943950 PMCID: PMC2993745 DOI: 10.1091/mbc.e10-06-0495] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Rubicon, a subunit of the Beclin 1-PI3-kinase complex and its homologue, PLEKHM1, negatively regulate endocytic pathway through the interaction with Rab7. Synchronous association with the Beclin 1–PI3-kinase complex and Rab7 is necessary for the function of Rubicon, but not PLEKHM1. The endocytic and autophagic pathways are involved in the membrane trafficking of exogenous and endogenous materials to lysosomes. However, the mechanisms that regulate these pathways are largely unknown. We previously reported that Rubicon, a Beclin 1–binding protein, negatively regulates both the autophagic and endocytic pathways by unidentified mechanisms. In this study, we performed database searches to identify potential Rubicon homologues that share the common C-terminal domain, termed the RH domain. One of them, PLEKHM1, the causative gene of osteopetrosis, also suppresses endocytic transport but not autophagosome maturation. Rubicon and PLEKHM1 specifically and directly interact with Rab7 via their RH domain, and this interaction is critical for their function. Furthermore, we show that Rubicon but not PLEKHM1 uniquely regulates membrane trafficking via simultaneously binding both Rab7 and PI3-kinase.
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Affiliation(s)
- Keisuke Tabata
- Department of Genetics, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
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581
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Cogli L, Progida C, Lecci R, Bramato R, Krüttgen A, Bucci C. CMT2B-associated Rab7 mutants inhibit neurite outgrowth. Acta Neuropathol 2010; 120:491-501. [PMID: 20464402 DOI: 10.1007/s00401-010-0696-8] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 05/04/2010] [Accepted: 05/05/2010] [Indexed: 12/11/2022]
Abstract
Charco-Marie-Tooth type 2B (CMT2B) neuropathy is a rare autosomal-dominant axonal disorder characterized by distal weakness, muscle atrophy, and prominent sensory loss often complicated by foot ulcerations. CMT2B is associated with mutations of the Rab7 protein, a small GTPase controlling late endocytic traffic. Currently, it is still unknown how these mutations cause the neuropathy. Indeed, CMT2B selectively affects neuronal processes, despite the ubiquitous expression of Rab7. Therefore, this study focused on whether these disorder-associated mutations exert an effect on neurite outgrowth. We observed a marked inhibition of neurite outgrowth upon expression of all the CMT2B-associated mutants in the PC12 and Neuro2A cell lines. Thus, our data strongly support previous genetic data which proposed that these Rab7 mutations are indeed causally related to CMT2B. Inhibition of neurite outgrowth by these CMT2B-associated Rab7 mutants was confirmed biochemically by impaired up-regulation of growth-associated protein 43 (GAP43) in PC12 cells and of the nuclear neuronal differentiation marker NeuN in Neuro2A cells. Expression of a constitutively active Rab7 mutant had a similar effect to the expression of the CMT2B-associated Rab7 mutants. The active behavior of these CMT2B-associated mutants is in line with their previously demonstrated increased GTP loading, thus confirming that active Rab7 mutants are responsible for CMT2B. Our findings provide an explanation for the ability of CMT2B-associated Rab7 mutants to override the activity of wild-type Rab7 in heterozygous patients. Thus, our data suggest that lowering the activity of Rab7 in neurons could be a targeted therapy for CMT2B.
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Affiliation(s)
- Laura Cogli
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, 73100 Lecce, Italy
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582
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Tong J, Yan X, Yu L. The late stage of autophagy: cellular events and molecular regulation. Protein Cell 2010; 1:907-15. [PMID: 21204017 PMCID: PMC4875124 DOI: 10.1007/s13238-010-0121-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Accepted: 10/18/2010] [Indexed: 12/28/2022] Open
Abstract
Autophagy is an intracellular degradation system that delivers cytoplasmic contents to the lysosome for degradation. It is a "self-eating" process and plays a "house-cleaner" role in cells. The complex process consists of several sequential steps-induction, autophagosome formation, fusion of lysosome and autophagosome, degradation, efflux transportation of degradation products, and autophagic lysosome reformation. In this review, the cellular and molecular regulations of late stage of autophagy, including cellular events after fusion step, are summarized.
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Affiliation(s)
- Jingjing Tong
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Science, Tsinghua University, Beijing, 100084 China
- College of Animal Sciences and Technology, Huazhong Agricultural University, Wuhan, 430070 China
| | - Xianghua Yan
- College of Animal Sciences and Technology, Huazhong Agricultural University, Wuhan, 430070 China
| | - Li Yu
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Science, Tsinghua University, Beijing, 100084 China
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583
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Ravikumar B, Sarkar S, Davies JE, Futter M, Garcia-Arencibia M, Green-Thompson ZW, Jimenez-Sanchez M, Korolchuk VI, Lichtenberg M, Luo S, Massey DCO, Menzies FM, Moreau K, Narayanan U, Renna M, Siddiqi FH, Underwood BR, Winslow AR, Rubinsztein DC. Regulation of mammalian autophagy in physiology and pathophysiology. Physiol Rev 2010; 90:1383-435. [PMID: 20959619 DOI: 10.1152/physrev.00030.2009] [Citation(s) in RCA: 1367] [Impact Index Per Article: 91.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
(Macro)autophagy is a bulk degradation process that mediates the clearance of long-lived proteins and organelles. Autophagy is initiated by double-membraned structures, which engulf portions of cytoplasm. The resulting autophagosomes ultimately fuse with lysosomes, where their contents are degraded. Although the term autophagy was first used in 1963, the field has witnessed dramatic growth in the last 5 years, partly as a consequence of the discovery of key components of its cellular machinery. In this review we focus on mammalian autophagy, and we give an overview of the understanding of its machinery and the signaling cascades that regulate it. As recent studies have also shown that autophagy is critical in a range of normal human physiological processes, and defective autophagy is associated with diverse diseases, including neurodegeneration, lysosomal storage diseases, cancers, and Crohn's disease, we discuss the roles of autophagy in health and disease, while trying to critically evaluate if the coincidence between autophagy and these conditions is causal or an epiphenomenon. Finally, we consider the possibility of autophagy upregulation as a therapeutic approach for various conditions.
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Affiliation(s)
- Brinda Ravikumar
- Department of Medical Genetics, University of Cambridge, Cambridge Institute for Medical Research, Addenbrooke’s Hospital, Cambridge, United Kingdom
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584
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Kwon SI, Cho HJ, Jung JH, Yoshimoto K, Shirasu K, Park OK. The Rab GTPase RabG3b functions in autophagy and contributes to tracheary element differentiation in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 64:151-64. [PMID: 20659276 DOI: 10.1111/j.1365-313x.2010.04315.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The tracheary elements (TEs) of the xylem serve as the water-conducting vessels of the plant vascular system. To achieve this, TEs undergo secondary cell wall thickening and cell death, during which the cell contents are completely removed. Cell death of TEs is a typical example of developmental programmed cell death that has been suggested to be autophagic. However, little evidence of autophagy in TE differentiation has been provided. The present study demonstrates that the small GTP binding protein RabG3b plays a role in TE differentiation through its function in autophagy. Differentiating wild type TE cells were found to undergo autophagy in an Arabidopsis culture system. Both autophagy and TE formation were significantly stimulated by overexpression of a constitutively active mutant (RabG3bCA), and were inhibited in transgenic plants overexpressing a dominant negative mutant (RabG3bDN) or RabG3b RNAi (RabG3bRNAi), a brassinosteroid insensitive mutant bri1-301, and an autophagy mutant atg5-1. Taken together, our results suggest that autophagy occurs during TE differentiation, and that RabG3b, as a component of autophagy, regulates TE differentiation.
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Affiliation(s)
- Soon Il Kwon
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea RIKEN Plant Science Center, Yokohama 230-0045, Japan
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585
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Wang T, Ming Z, Xiaochun W, Hong W. Rab7: role of its protein interaction cascades in endo-lysosomal traffic. Cell Signal 2010; 23:516-21. [PMID: 20851765 DOI: 10.1016/j.cellsig.2010.09.012] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2010] [Accepted: 09/06/2010] [Indexed: 12/23/2022]
Abstract
Protein-protein interaction cascades are crucial for cellular signaling pathways and cell morphogenesis. Membrane traffic along the secretory and endocytic pathways is similarly governed by regulated protein-protein interactions of diverse machineries, which are inter-regulated, assembled and disassembled sequentially to drive membrane budding, vesicle transport, membrane fission and fusion. Rab7, the key regulator in endo-lysosomal trafficking investigated extensively in the past decades, is emerging to govern early-to-late endosomal maturation, microtubule minus-end as well as plus-end directed endosomal migration and positioning, and endosome-lysosome transport through different protein-protein interaction cascades. We summarize here the key protein interaction cascades of Rab7 by focusing on endo-lysosomal trafficking regulated by its interaction with HOPs, RILP, ORP1L, FYCO1 and Mon1/Sand1-CCZ1 complex.
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Affiliation(s)
- Tuanlao Wang
- Institute for Biomedical Research, Xiamen University, Xiamen, Fujian, China 361005
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586
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Li B, Castano AP, Hudson TE, Nowlin BT, Lin SL, Bonventre JV, Swanson KD, Duffield JS. The melanoma-associated transmembrane glycoprotein Gpnmb controls trafficking of cellular debris for degradation and is essential for tissue repair. FASEB J 2010; 24:4767-81. [PMID: 20709912 DOI: 10.1096/fj.10-154757] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Kidney damage due to injury rarely resolves completely, and there are currently no therapies capable of promoting repair. In addition to understanding mechanisms by which tissues are damaged, illuminating mechanisms of repair and regeneration is also of great importance. Here we show that the melanoma-associated, transmembrane glycoprotein, Gpnmb, is up-regulated 15-fold following ischemic damage in kidney tissue and by more than 10-fold in macrophages and 3-fold in surviving epithelial cells. Gpnmb-expressing macrophages and epithelial cells were found to contain apoptotic bodies at 3 times the rate of nonexpressing cells. Either mutation of Gpnmb or ablation of inflammatory macrophages prevents normal repair of the kidney. Significantly, the kidneys from postischemic Gpnmb mutant mice exhibited a 5-fold increase in apoptotic cellular debris compared to wild-type mice. These mice also experienced an 85% increase in mortality following bilateral ischemic kidney. Finally, we demonstrate that Gpnmb is a phagocytic protein that is necessary for recruitment of the autophagy protein LC3 to the phagosome where these proteins are colocalized and for lysosomal fusion with the phagosome and hence bulk degradation of their content. Therefore, Gpnmb is a novel prorepair gene that is necessary for crosstalk between the macroautophagic degradation pathway and phagocytosis.
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Affiliation(s)
- Bing Li
- Laboratory of Inflammation Research, Brigham and Womens Hospital and Harvard Medical School, Boston, MA 02115, USA
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587
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Sakurai A, Maruyama F, Funao J, Nozawa T, Aikawa C, Okahashi N, Shintani S, Hamada S, Ooshima T, Nakagawa I. Specific behavior of intracellular Streptococcus pyogenes that has undergone autophagic degradation is associated with bacterial streptolysin O and host small G proteins Rab5 and Rab7. J Biol Chem 2010; 285:22666-75. [PMID: 20472552 PMCID: PMC2903418 DOI: 10.1074/jbc.m109.100131] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Streptococcus pyogenes (group A streptococcus (GAS)) is a pathogen that invades non-phagocytic host cells, and causes a variety of acute infections such as pharyngitis. Our group previously reported that intracellular GAS is effectively degraded by the host-cell autophagic machinery, and that a cholesterol-dependent cytolysin, streptolysin O (SLO), is associated with bacterial escape from endosomes in epithelial cells. However, the details of both the intracellular behavior of GAS and the process leading to its autophagic degradation remain unknown. In this study, we found that two host small G proteins, Rab5 and Rab7, were associated with the pathway of autophagosome formation and the fate of intracellular GAS. Rab5 was involved in bacterial invasion and endosome fusion. Rab7 was clearly multifunctional, with roles in bacterial invasion, endosome maturation, and autophagosome formation. In addition, this study showed that the bacterial cytolysin SLO supported the escape of GAS into the cytoplasm from endosomes, and surprisingly, a SLO-deficient mutant of GAS was viable longer than the wild-type strain although it failed to escape the endosomes. This intracellular behavior of GAS is unique and distinct from that of other types of bacterial invaders. Our results provide a new picture of GAS infection and host-cell responses in epithelial cells.
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Affiliation(s)
- Atsuo Sakurai
- From the Department of Pediatric Dentistry, Tokyo Dental College, 1-2-2 Masago, Mihama-Ku, Chiba 261-8502, Japan
- the Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan
- the Oral Health Science Center, hrc7, Tokyo Dental College, Mihama-ku, Chiba 261-8502, Japan
| | - Fumito Maruyama
- the Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8501, Japan
| | - Junko Funao
- the Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan
| | - Takashi Nozawa
- the Section of Bacterial Pathogenesis, Tokyo Medical and Dental University Graduate School of Medical and Dental Sciences, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
- the Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8562, Japan
| | - Chihiro Aikawa
- the Section of Bacterial Pathogenesis, Tokyo Medical and Dental University Graduate School of Medical and Dental Sciences, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
- the Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8562, Japan
| | - Nobuo Okahashi
- the Department of Oral Frontier Biology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita-Osaka 565-0871, Japan, and
| | - Seikou Shintani
- From the Department of Pediatric Dentistry, Tokyo Dental College, 1-2-2 Masago, Mihama-Ku, Chiba 261-8502, Japan
- the Oral Health Science Center, hrc7, Tokyo Dental College, Mihama-ku, Chiba 261-8502, Japan
| | - Shigeyuki Hamada
- the Department of Medical Sciences, Research Collaboration Center on Emerging and Reemerging Infections (RCC-ERI) 6F, Ministry of Public Health, Tiwanon Road, Muang Nonthaburi 11000, Thailand
| | - Takashi Ooshima
- the Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan
- To whom correspondence should be addressed. Fax: 81-6-6879-2965; E-mail:
| | - Ichiro Nakagawa
- the Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8562, Japan
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588
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Yu L, McPhee CK, Zheng L, Mardones GA, Rong Y, Peng J, Mi N, Zhao Y, Liu Z, Wan F, Hailey DW, Oorschot V, Klumperman J, Baehrecke EH, Lenardo MJ. Termination of autophagy and reformation of lysosomes regulated by mTOR. Nature 2010; 465:942-6. [PMID: 20526321 PMCID: PMC2920749 DOI: 10.1038/nature09076] [Citation(s) in RCA: 1212] [Impact Index Per Article: 80.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Accepted: 04/01/2010] [Indexed: 12/16/2022]
Abstract
Autophagy is an evolutionarily conserved process by which cytoplasmic proteins and organelles are catabolized. During starvation, the protein TOR (target of rapamycin), a nutrient-responsive kinase, is inhibited, and this induces autophagy. In autophagy, double-membrane autophagosomes envelop and sequester intracellular components and then fuse with lysosomes to form autolysosomes, which degrade their contents to regenerate nutrients. Current models of autophagy terminate with the degradation of the autophagosome cargo in autolysosomes, but the regulation of autophagy in response to nutrients and the subsequent fate of the autolysosome are poorly understood. Here we show that mTOR signalling in rat kidney cells is inhibited during initiation of autophagy, but reactivated by prolonged starvation. Reactivation of mTOR is autophagy-dependent and requires the degradation of autolysosomal products. Increased mTOR activity attenuates autophagy and generates proto-lysosomal tubules and vesicles that extrude from autolysosomes and ultimately mature into functional lysosomes, thereby restoring the full complement of lysosomes in the cell-a process we identify in multiple animal species. Thus, an evolutionarily conserved cycle in autophagy governs nutrient sensing and lysosome homeostasis during starvation.
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Affiliation(s)
- Li Yu
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
- School of Life Science, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Beijing China
| | - Christina K. McPhee
- Department of Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Lixin Zheng
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Gonzalo A. Mardones
- Cell Biology and Metabolism Program, National Institute of Child Health & Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Yueguang Rong
- School of Life Science, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Beijing China
| | - Junya Peng
- School of Life Science, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Beijing China
| | - Na Mi
- School of Life Science, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Beijing China
| | - Ying Zhao
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center,38 Xueyuan Road, Beijing 100191, China
| | - Zhihua Liu
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Fengyi Wan
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Dale W. Hailey
- Cell Biology and Metabolism Program, National Institute of Child Health & Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Viola Oorschot
- Department of Cell Biology, University Medical Center Utrecht, 3584CX Utrecht, The Netherlands
| | - Judith Klumperman
- Department of Cell Biology, University Medical Center Utrecht, 3584CX Utrecht, The Netherlands
| | - Eric H. Baehrecke
- Department of Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Michael J. Lenardo
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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589
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Mehrpour M, Esclatine A, Beau I, Codogno P. Overview of macroautophagy regulation in mammalian cells. Cell Res 2010; 20:748-62. [DOI: 10.1038/cr.2010.82] [Citation(s) in RCA: 382] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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590
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Abstract
Autophagy is a cellular process for the disposal of damaged organelles or denatured proteins through a lysosomal degradation pathway. By reducing endogenous macromolecules to their basic components (i.e., amino acids, lipids), autophagy serves a homeostatic function by ensuring cell survival during starvation. Increased autophagy can be found in dying cells, although the relationships between autophagy and programmed cell death remain unclear. To date, few studies have examined the regulation and functional significance of autophagy in human lung disease. The lung, a complex organ that functions primarily in gas exchange, consists of diverse cell types (i.e., endothelial, epithelial, mesenchymal, inflammatory). In lung cells, autophagy may represent a general inducible adaptive response to injury resulting from exposure to stress agents, including hypoxia, oxidants, inflammation, ischemia-reperfusion, endoplasmic reticulum stress, pharmaceuticals, or inhaled xenobiotics (i.e., air pollution, cigarette smoke). In recent studies, we have observed increased autophagy in mouse lungs subjected to chronic cigarette smoke exposure, and in pulmonary epithelial cells exposed to cigarette smoke extract. Knockdown of autophagic proteins inhibited apoptosis in response to cigarette smoke exposure in vitro, suggesting that increased autophagy was associated with epithelial cell death. We have also observed increased morphological and biochemical markers of autophagy in human lung specimens from patients with chronic obstructive pulmonary disease (COPD). We hypothesize that increased autophagy contributes to COPD pathogenesis by promoting epithelial cell death. Further research will examine whether autophagy plays a homeostatic or maladaptive role in COPD and other human lung diseases.
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591
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Abstract
Autophagy, or "self eating," refers to a regulated cellular process for the lysosomal-dependent turnover of organelles and proteins. During starvation or nutrient deficiency, autophagy promotes survival through the replenishment of metabolic precursors derived from the degradation of endogenous cellular components. Autophagy represents a general homeostatic and inducible adaptive response to environmental stress, including endoplasmic reticulum stress, hypoxia, oxidative stress, and exposure to pharmaceuticals and xenobiotics. Whereas elevated autophagy can be observed in dying cells, the functional relationships between autophagy and programmed cell death pathways remain incompletely understood. Preclinical studies have identified autophagy as a process that can be activated during vascular disorders, including ischemia-reperfusion injury of the heart and other organs, cardiomyopathy, myocardial injury, and atherosclerosis. The functional significance of autophagy in human cardiovascular disease pathogenesis remains incompletely understood, and potentially involves both adaptive and maladaptive outcomes, depending on model system. Although relatively few studies have been performed in the lung, our recent studies also implicate a role for autophagy in chronic lung disease. Manipulation of the signaling pathways that regulate autophagy could potentially provide a novel therapeutic strategy in the prevention or treatment of human disease.
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592
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Progida C, Cogli L, Piro F, De Luca A, Bakke O, Bucci C. Rab7b controls trafficking from endosomes to the TGN. J Cell Sci 2010; 123:1480-91. [PMID: 20375062 DOI: 10.1242/jcs.051474] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2025] Open
Abstract
Rab7b is a recently identified member of the Rab GTPase protein family and has high similarity to Rab7. It has been reported that Rab7b is lysosome associated, that it is involved in monocytic differentiation and that it promotes lysosomal degradation of TLR4 and TLR9. Here we investigated further the localization and function of this GTPase. We found that wild-type Rab7b is lysosome associated whereas an activated, GTP-bound form of Rab7b localizes to the Golgi apparatus. In contrast to Rab7, Rab7b is not involved in EGF and EGFR degradation. Depletion of Rab7b or expression of Rab7b T22N, a Rab7b dominant-negative mutant, impairs cathepsin-D maturation and causes increased secretion of hexosaminidase. Moreover, expression of Rab7b T22N or depletion of Rab7b alters TGN46 distribution, cation-independent mannose-6-phosphate receptor (CI-MPR) trafficking, and causes an increase in the levels of the late endosomal markers CI-MPR and cathepsin D. Vesicular stomatitis virus G protein (VSV-G) trafficking, by contrast, is normal in Rab7b-depleted or Rab7b-T22N-expressing cells. In addition, depletion of Rab7b prevents cholera toxin B-subunit from reaching the Golgi. Altogether, these data indicate that Rab7b is required for normal lysosome function, and, in particular, that it is an essential factor for retrograde transport from endosomes to the trans-Golgi network (TGN).
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Affiliation(s)
- Cinzia Progida
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni, 73100 Lecce, Italy
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593
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Glick D, Barth S, Macleod KF. Autophagy: cellular and molecular mechanisms. J Pathol 2010; 221:3-12. [PMID: 20225336 PMCID: PMC2990190 DOI: 10.1002/path.2697] [Citation(s) in RCA: 2746] [Impact Index Per Article: 183.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Accepted: 01/26/2010] [Indexed: 12/12/2022]
Abstract
Autophagy is a self-degradative process that is important for balancing sources of energy at critical times in development and in response to nutrient stress. Autophagy also plays a housekeeping role in removing misfolded or aggregated proteins, clearing damaged organelles, such as mitochondria, endoplasmic reticulum and peroxisomes, as well as eliminating intracellular pathogens. Thus, autophagy is generally thought of as a survival mechanism, although its deregulation has been linked to non-apoptotic cell death. Autophagy can be either non-selective or selective in the removal of specific organelles, ribosomes and protein aggregates, although the mechanisms regulating aspects of selective autophagy are not fully worked out. In addition to elimination of intracellular aggregates and damaged organelles, autophagy promotes cellular senescence and cell surface antigen presentation, protects against genome instability and prevents necrosis, giving it a key role in preventing diseases such as cancer, neurodegeneration, cardiomyopathy, diabetes, liver disease, autoimmune diseases and infections. This review summarizes the most up-to-date findings on how autophagy is executed and regulated at the molecular level and how its disruption can lead to disease.
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Affiliation(s)
- Danielle Glick
- Ben May Department for Cancer Research, Gordon Center for Integrative Sciences, University of Chicago, IL, USA
- Committee on Cancer Biology, Gordon Center for Integrative Sciences, University of Chicago, IL, USA
| | - Sandra Barth
- Ben May Department for Cancer Research, Gordon Center for Integrative Sciences, University of Chicago, IL, USA
| | - Kay F. Macleod
- Ben May Department for Cancer Research, Gordon Center for Integrative Sciences, University of Chicago, IL, USA
- Committee on Cancer Biology, Gordon Center for Integrative Sciences, University of Chicago, IL, USA
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594
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Fighting disease by selective autophagy of aggregate-prone proteins. FEBS Lett 2010; 584:2635-45. [DOI: 10.1016/j.febslet.2010.04.041] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Revised: 04/09/2010] [Accepted: 04/15/2010] [Indexed: 12/12/2022]
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595
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Abstract
The autophagic/lysosomal system includes a variety of vesicular compartments that undergo dynamic fusion events. However, the characteristics and factors modulating these interactions remain, for the most part, unknown. To gain insights on the properties that govern lysosomal fusion events, we have established an in vitro fusion assay using different lysosomal/autophagic compartments isolated from mouse liver. We have found that autophagosome/lysosome fusion is a temperature-dependent process (fusion increment of 0.2+/-0.01%/degrees C), which requires ATP (1-3 mM), GTP (1-2 mM), Ca(2+) (0.2-2 mM), and an acidic lysosomal pH (pH 5.2). Furthermore, changes in membrane lipid composition, induced either in vitro, by treatment with 25 mM methyl-beta-cyclodextrin, or in vivo, by subjecting animals to a high-fat-diet challenge (60% kcal in fat) reduce autophagosome/lysosome fusion up to 70% of that observed in untreated fractions or from animals under a normal regular diet. These findings reveal a novel role for lipids in autophagic fusion and provide a mechanism for the reduced macroautophagic rates observed during exposure to a chronic lipid challenge. Changes in the intracellular lipid content (i.e., metabolic disorders) may thus have pronounced effects on the fusion step of macroautophagy and affect the overall activity of this intracellular proteolytic pathway.
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Affiliation(s)
- Hiroshi Koga
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
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596
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Peralta ER, Martin BC, Edinger AL. Differential effects of TBC1D15 and mammalian Vps39 on Rab7 activation state, lysosomal morphology, and growth factor dependence. J Biol Chem 2010; 285:16814-21. [PMID: 20363736 DOI: 10.1074/jbc.m110.111633] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The small GTPase Rab7 promotes fusion events between late endosomes and lysosomes. Rab7 activity is regulated by extrinsic signals, most likely via effects on its guanine nucleotide exchange factor (GEF) or GTPase-activating protein (GAP). Based on their homology to the yeast proteins that regulate the Ypt7 GTP binding state, TBC1D15, and mammalian Vps39 (mVps39) have been suggested to function as the Rab7 GAP and GEF, respectively. We developed an effector pull-down assay to test this model. TBC1D15 functioned as a Rab7 GAP in cells, reducing Rab7 binding to its effector protein RILP, fragmenting the lysosome, and conferring resistance to growth factor withdrawal-induced cell death. In a cellular context, TBC1D15 GAP activity was selective for Rab7. TBC1D15 overexpression did not inhibit transferrin internalization or recycling, Rab7-independent processes that require Rab4, Rab5, and Rab11 activation. TBC1D15 was thus renamed Rab7-GAP. Contrary to expectations for a Rab7 GEF, mVps39 induced lysosomal clustering without increasing Rab7 GTP binding. Moreover, a dominant-negative mVps39 mutant fragmented the lysosome and promoted growth factor independence without decreasing Rab7-GTP levels. These findings suggest that a protein other than mVps39 serves as the Rab7 GEF. In summary, although only TBC1D15/Rab7-GAP altered Rab7-GTP levels, both Rab7-GAP and mVps39 regulate lysosomal morphology and play a role in maintaining growth factor dependence.
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Affiliation(s)
- Eigen R Peralta
- Department of Developmental and Cell Biology, University of California, Irvine, California 92697-2300, USA
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597
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The Beclin 1-VPS34 complex--at the crossroads of autophagy and beyond. Trends Cell Biol 2010; 20:355-62. [PMID: 20356743 DOI: 10.1016/j.tcb.2010.03.002] [Citation(s) in RCA: 639] [Impact Index Per Article: 42.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 03/05/2010] [Accepted: 03/10/2010] [Indexed: 02/06/2023]
Abstract
An increasing body of research on autophagy provides overwhelming evidence for its connection to diverse biological functions and human diseases. Beclin 1, the first mammalian autophagy protein to be described, appears to act as a nexus point between autophagy, endosomal, and perhaps also cell death pathways. Beclin 1 performs these roles as part of a core complex that contains vacuolar sorting protein 34 (VPS34), a class III phosphatidylinositol-3 kinase. The precise mechanism of Beclin 1-mediated regulation of these cellular functions is unclear, but substantial progress has recently been made in identifying new players and their functions in Beclin 1-VSP34 complexes. Here we review emerging studies that are beginning to unveil the physiological functions of Beclin 1-VPS34 in the central control of autophagic activity and other trafficking events through the formation of distinct Beclin 1-VPS34 protein complexes.
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598
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Pankiv S, Alemu EA, Brech A, Bruun JA, Lamark T, Overvatn A, Bjørkøy G, Johansen T. FYCO1 is a Rab7 effector that binds to LC3 and PI3P to mediate microtubule plus end-directed vesicle transport. ACTA ACUST UNITED AC 2010; 188:253-69. [PMID: 20100911 PMCID: PMC2812517 DOI: 10.1083/jcb.200907015] [Citation(s) in RCA: 506] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
FYCO1 recognition of LC3 on autophagosomes facilitates microtubule-mediated cytosolic transport of this degradative organelle. Autophagy is the main eukaryotic degradation pathway for long-lived proteins, protein aggregates, and cytosolic organelles. Although the protein machinery involved in the biogenesis of autophagic vesicles is well described, very little is known about the mechanism of cytosolic transport of autophagosomes. In this study, we have identified an adaptor protein complex, formed by the two autophagic membrane-associated proteins LC3 and Rab7 and the novel FYVE and coiled-coil (CC) domain–containing protein FYCO1, that promotes microtubule (MT) plus end–directed transport of autophagic vesicles. We have characterized the LC3-, Rab7-, and phosphatidylinositol-3-phosphate–binding domains in FYCO1 and mapped part of the CC region essential for MT plus end–directed transport. We also propose a mechanism for selective autophagosomal membrane recruitment of FYCO1.
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Affiliation(s)
- Serhiy Pankiv
- Molecular Cancer Research Group, Institute of Medical Biology, University of Tromsø, 9037 Tromsø, Norway
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599
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Tresse E, Salomons FA, Vesa J, Bott LC, Kimonis V, Yao TP, Dantuma NP, Taylor JP. VCP/p97 is essential for maturation of ubiquitin-containing autophagosomes and this function is impaired by mutations that cause IBMPFD. Autophagy 2010; 6:217-27. [PMID: 20104022 DOI: 10.4161/auto.6.2.11014] [Citation(s) in RCA: 365] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
VCP (VCP/p97) is a ubiquitously expressed member of the AAA(+)-ATPase family of chaperone-like proteins that regulates numerous cellular processes including chromatin decondensation, homotypic membrane fusion and ubiquitin-dependent protein degradation by the proteasome. Mutations in VCP cause a multisystem degenerative disease consisting of inclusion body myopathy, Paget disease of bone, and frontotemporal dementia (IBMPFD). Here we show that VCP is essential for autophagosome maturation. We generated cells stably expressing dual-tagged LC3 (mCherry-EGFP-LC3) which permit monitoring of autophagosome maturation. We determined that VCP deficiency by RNAi-mediated knockdown or overexpression of dominant-negative VCP results in significant accumulation of immature autophagic vesicles, some of which are abnormally large, acidified and exhibit cathepsin B activity. Furthermore, expression of disease-associated VCP mutants (R155H and A232E) also causes this autophagy defect. VCP was found to be essential to autophagosome maturation under basal conditions and in cells challenged by proteasome inhibition, but not in cells challenged by starvation, suggesting that VCP might be selectively required for autophagic degradation of ubiquitinated substrates. Indeed, a high percentage of the accumulated autophagic vesicles contain ubiquitin-positive contents, a feature that is not observed in autophagic vesicles that accumulate following starvation or treatment with Bafilomycin A. Finally, we show accumulation of numerous, large LAMP-1 and LAMP-2-positive vacuoles and accumulation of LC3-II in myoblasts derived from patients with IBMPFD. We conclude that VCP is essential for maturation of ubiquitin-containing autophagosomes and that defect in this function may contribute to IBMPFD pathogenesis.
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Affiliation(s)
- Emilie Tresse
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, USA
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600
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Abstract
Macroautophagy is a vacuolar degradation pathway that terminates in the lysosomal compartment. Macroautophagy is a multistep process involving: (1) signaling events that occur upstream of the molecular machinery of autophagy; (2) molecular machinery involved in the formation of the autophagosome, the initial multimembrane-bound compartment formed in the autophagic pathway; and (3) maturation of autophagosomes, which acquire acidic and degradative capacities. In this chapter we summarize what is known about the regulation of the different steps involved in autophagy, and we also discuss how macroautophagy can be manipulated using drugs or genetic approaches that affect macroautophagy signaling, and the subsequent formation and maturation of the autophagosomes. Modulating autophagy offers a promising new therapeutic approach to human diseases that involve macroautophagy.
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Affiliation(s)
- Audrey Esclatine
- INSERM U756, Université Paris-Sud 11, Faculté de Pharmacie, 5 rue Jean-Baptiste Clément, 92290 Châtenay-Malabry, France
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