151
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Nikoletopoulou V, Papandreou ME, Tavernarakis N. Autophagy in the physiology and pathology of the central nervous system. Cell Death Differ 2014; 22:398-407. [PMID: 25526091 PMCID: PMC4326580 DOI: 10.1038/cdd.2014.204] [Citation(s) in RCA: 150] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 11/06/2014] [Accepted: 11/07/2014] [Indexed: 02/07/2023] Open
Abstract
Neurons are highly specialized postmitotic cells that depend on dynamic cellular processes for their proper function.These include among others, neuronal growth and maturation, axonal migration, synapse formation and elimination, all requiring continuous protein synthesis and degradation. Therefore quality-control processes in neurons are directly linked to their physiology. Autophagy is a tightly regulated cellular degradation pathway by which defective or superfluouscytosolic proteins, organelles and other cellular constituents are sequestered in autophagosomes and delivered to lysosomes for degradation. Here we present emerging evidence indicating that constitutive autophagic fluxin neurons has essential roles in key neuronal processes under physiological conditions.Moreover, we discuss how perturbations of the autophagic pathway may underlie diverse pathological phenotypes in neurons associated with neurodevelopmental and neurodegenerative diseases.
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Affiliation(s)
- V Nikoletopoulou
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete 71110, Greece
| | - M-E Papandreou
- 1] Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete 71110, Greece [2] Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Crete 71110, Greece
| | - N Tavernarakis
- 1] Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Crete 71110, Greece [2] Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Crete 71110, Greece
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152
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The role of protein clearance mechanisms in organismal ageing and age-related diseases. Nat Commun 2014; 5:5659. [DOI: 10.1038/ncomms6659] [Citation(s) in RCA: 442] [Impact Index Per Article: 44.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 10/24/2014] [Indexed: 12/27/2022] Open
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153
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Piekarski A, Khaldi S, Greene E, Lassiter K, Mason JG, Anthony N, Bottje W, Dridi S. Tissue distribution, gender- and genotype-dependent expression of autophagy-related genes in avian species. PLoS One 2014; 9:e112449. [PMID: 25386921 PMCID: PMC4227737 DOI: 10.1371/journal.pone.0112449] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 10/07/2014] [Indexed: 12/29/2022] Open
Abstract
As a result of the genetic selection of broiler (meat-type breeders) chickens for enhanced growth rate and lower feed conversion ratio, it has become necessary to restrict feed intake. When broilers are fed ad libitum, they would become obese and suffer from several health-related problems. A vital adaptation to starvation is autophagy, a self-eating mechanism for recycling cellular constituents. The autophagy pathway has witnessed dramatic growth in the last few years and extensively studied in yeast and mammals however, there is a paucity of information in avian (non-mammalian) species. Here we characterized several genes involved in autophagosome initiation and elongation in Red Jungle fowl (Gallus gallus) and Japanese quail (coturnix coturnix Japonica). Both complexes are ubiquitously expressed in chicken and quail tissues (liver, leg and breast muscle, brain, gizzard, intestine, heart, lung, kidney, adipose tissue, ovary and testis). Alignment analysis showed high similarity (50.7 to 91.5%) between chicken autophagy-related genes and their mammalian orthologs. Phylogenetic analysis demonstrated that the evolutionary relationship between autophagy genes is consistent with the consensus view of vertebrate evolution. Interestingly, the expression of autophagy-related genes is tissue- and gender- dependent. Furthermore, using two experimental male quail lines divergently selected over 40 generations for low (resistant, R) or high (sensitive, S) stress response, we found that the expression of most studied genes are higher in R compared to S line. Together our results indicate that the autophagy pathway is a key molecular signature exhibited gender specific differences and likely plays an important role in response to stress in avian species.
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Affiliation(s)
- Alissa Piekarski
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, Arkansas, United States of America
| | - Stephanie Khaldi
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, Arkansas, United States of America
| | - Elizabeth Greene
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, Arkansas, United States of America
| | - Kentu Lassiter
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, Arkansas, United States of America
| | - James G. Mason
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, Arkansas, United States of America
| | - Nicholas Anthony
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, Arkansas, United States of America
| | - Walter Bottje
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, Arkansas, United States of America
| | - Sami Dridi
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, Arkansas, United States of America
- * E-mail:
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154
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Alves S, Cormier-Dequaire F, Marinello M, Marais T, Muriel MP, Beaumatin F, Charbonnier-Beaupel F, Tahiri K, Seilhean D, El Hachimi K, Ruberg M, Stevanin G, Barkats M, den Dunnen W, Priault M, Brice A, Durr A, Corvol JC, Sittler A. The autophagy/lysosome pathway is impaired in SCA7 patients and SCA7 knock-in mice. Acta Neuropathol 2014; 128:705-22. [PMID: 24859968 DOI: 10.1007/s00401-014-1289-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 04/18/2014] [Accepted: 04/26/2014] [Indexed: 01/11/2023]
Abstract
There is still no treatment for polyglutamine disorders, but clearance of mutant proteins might represent a potential therapeutic strategy. Autophagy, the major pathway for organelle and protein turnover, has been implicated in these diseases. To determine whether the autophagy/lysosome system contributes to the pathogenesis of spinocerebellar ataxia type 7 (SCA7), caused by expansion of a polyglutamine tract in the ataxin-7 protein, we looked for biochemical, histological and transcriptomic abnormalities in components of the autophagy/lysosome pathway in a knock-in mouse model of the disease, postmortem brain and peripheral blood mononuclear cells (PBMC) from patients. In the mouse model, mutant ataxin-7 accumulated in inclusions immunoreactive for the autophagy-associated proteins mTOR, beclin-1, p62 and ubiquitin. Atypical accumulations of the autophagosome/lysosome markers LC3, LAMP-1, LAMP2 and cathepsin-D were also found in the cerebellum of the SCA7 knock-in mice. In patients, abnormal accumulations of autophagy markers were detected in the cerebellum and cerebral cortex of patients, but not in the striatum that is spared in SCA7, suggesting that autophagy might be impaired by the selective accumulation of mutant ataxin-7. In vitro studies demonstrated that the autophagic flux was impaired in cells overexpressing full-length mutant ataxin-7. Interestingly, the expression of the early autophagy-associated gene ATG12 was increased in PBMC from SCA7 patients in correlation with disease severity. These results provide evidence that the autophagy/lysosome pathway is impaired in neurons undergoing degeneration in SCA7. Autophagy/lysosome-associated molecules might, therefore, be useful markers for monitoring the effects of potential therapeutic approaches using modulators of autophagy in SCA7 and other autophagy/lysosome-associated neurodegenerative disorders.
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155
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Ching JK, Ju JS, Pittman SK, Margeta M, Weihl CC. Increased autophagy accelerates colchicine-induced muscle toxicity. Autophagy 2014; 9:2115-25. [DOI: 10.4161/auto.26150] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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156
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Parveen Z, Bibi Z, Bibi N, Neesen J, Rashid S. Disruption of murine Tcte3-3 induces tissue specific apoptosis via co-expression of Anxa5 and Pebp1. Comput Biol Chem 2014; 53PB:214-225. [PMID: 25462330 DOI: 10.1016/j.compbiolchem.2014.10.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 10/12/2014] [Accepted: 10/21/2014] [Indexed: 01/07/2023]
Abstract
Programmed cell death or apoptosis plays a vital physiological role in the development and homeostasis. Any discrepancy in apoptosis may trigger testicular and neurodegenerative diseases, ischemic damage, autoimmune disorders and many types of cancer. Tcte3 (T-complex testis expressed 3) is an accessory component of axonemal and cytoplasmic dynein which expresses predominantly in meiotic and postmeiotic germ cells. It plays an essential role during spermatogenesis; however, to explore its diverse and complex functioning in male germ cell apoptosis, requires further prosecution. Here, 2D-gel electrophoresis, mass spectrometry and qRT-PCR analyses were performed to elucidate the differential expression of genes, in both wild-type and homozygous Tcte3-3 mice. We observed an increased expression of Tcte3 in homozygotes as compared to wild-type testes. Perpetually, an increased expression of Anxa5 and Pebp1, while a lower expression of Rsph1 was detected in Tcte3-3-/- mice. We propose that over-expression of Pebp1 and Anxa5 in Tcte3-3-/- testes might be due to increased apoptosis. To evaluate this possibility, testes specific microarray data set extracted from NCBI gene ontology omnibus (GEO) was used to cluster the possible co-expression partners of Tcte3. Further functional coherence of compiled candidate genes was monitored computationally by studying the common TFBS overlapped at the regulatory regions. Differential expression of Tcte3-3 and its involvement in apoptosis may provide a basis for the investigation of transcriptional specificities of other Tcte3 paralogs (Tcte3-1 and Tcte3-2). A complete understanding of controlling factors which have implications in regulating tissue-specific Tcte3 expression would provide additional insights into the gene control events. The collective knowledge may prove useful for the development of novel therapeutic regimen and would open new avenues in defining selective roles of Tcte3 in germ cell development.
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Affiliation(s)
- Zahida Parveen
- National Center for Bioinformatics, Quaid-i-Azam University, Islamabad, Pakistan
| | - Zohra Bibi
- National Center for Bioinformatics, Quaid-i-Azam University, Islamabad, Pakistan
| | - Nousheen Bibi
- National Center for Bioinformatics, Quaid-i-Azam University, Islamabad, Pakistan
| | - Juergen Neesen
- Institute of Medical Genetics, Medical University of Vienna, Austria
| | - Sajid Rashid
- National Center for Bioinformatics, Quaid-i-Azam University, Islamabad, Pakistan.
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157
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Martin DDO, Ladha S, Ehrnhoefer DE, Hayden MR. Autophagy in Huntington disease and huntingtin in autophagy. Trends Neurosci 2014; 38:26-35. [PMID: 25282404 DOI: 10.1016/j.tins.2014.09.003] [Citation(s) in RCA: 225] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 09/08/2014] [Accepted: 09/09/2014] [Indexed: 01/20/2023]
Abstract
Autophagy is an important biological process that is essential for the removal of damaged organelles and toxic or aggregated proteins by delivering them to the lysosome for degradation. Consequently, autophagy has become a primary target for the treatment of neurodegenerative diseases that involve aggregating proteins. In Huntington disease (HD), an expansion of the polyglutamine (polyQ) tract in the N-terminus of the huntingtin (HTT) protein leads to protein aggregation. However, HD is unique among the neurodegenerative proteinopathies in that autophagy is not only dysfunctional but wild type (wt) HTT also appears to play several roles in regulating the dynamics of autophagy. Herein, we attempt to integrate the recently described novel roles of wtHTT and altered autophagy in HD.
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Affiliation(s)
- Dale D O Martin
- Centre for Molecular Medicine and Therapeutics (CMMT), Department of Medical Genetics, Child and Family Research Institute, University of British Columbia, Vancouver, BC, Canada.
| | - Safia Ladha
- Centre for Molecular Medicine and Therapeutics (CMMT), Department of Medical Genetics, Child and Family Research Institute, University of British Columbia, Vancouver, BC, Canada
| | - Dagmar E Ehrnhoefer
- Centre for Molecular Medicine and Therapeutics (CMMT), Department of Medical Genetics, Child and Family Research Institute, University of British Columbia, Vancouver, BC, Canada
| | - Michael R Hayden
- Centre for Molecular Medicine and Therapeutics (CMMT), Department of Medical Genetics, Child and Family Research Institute, University of British Columbia, Vancouver, BC, Canada.
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158
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Börlin CS, Lang V, Hamacher-Brady A, Brady NR. Agent-based modeling of autophagy reveals emergent regulatory behavior of spatio-temporal autophagy dynamics. Cell Commun Signal 2014; 12:56. [PMID: 25214434 PMCID: PMC4172826 DOI: 10.1186/s12964-014-0056-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 08/31/2014] [Indexed: 01/07/2023] Open
Abstract
Background Autophagy is a vesicle-mediated pathway for lysosomal degradation, essential under basal and stressed conditions. Various cellular components, including specific proteins, protein aggregates, organelles and intracellular pathogens, are targets for autophagic degradation. Thereby, autophagy controls numerous vital physiological and pathophysiological functions, including cell signaling, differentiation, turnover of cellular components and pathogen defense. Moreover, autophagy enables the cell to recycle cellular components to metabolic substrates, thereby permitting prolonged survival under low nutrient conditions. Due to the multi-faceted roles for autophagy in maintaining cellular and organismal homeostasis and responding to diverse stresses, malfunction of autophagy contributes to both chronic and acute pathologies. Results We applied a systems biology approach to improve the understanding of this complex cellular process of autophagy. All autophagy pathway vesicle activities, i.e. creation, movement, fusion and degradation, are highly dynamic, temporally and spatially, and under various forms of regulation. We therefore developed an agent-based model (ABM) to represent individual components of the autophagy pathway, subcellular vesicle dynamics and metabolic feedback with the cellular environment, thereby providing a framework to investigate spatio-temporal aspects of autophagy regulation and dynamic behavior. The rules defining our ABM were derived from literature and from high-resolution images of autophagy markers under basal and activated conditions. Key model parameters were fit with an iterative method using a genetic algorithm and a predefined fitness function. From this approach, we found that accurate prediction of spatio-temporal behavior required increasing model complexity by implementing functional integration of autophagy with the cellular nutrient state. The resulting model is able to reproduce short-term autophagic flux measurements (up to 3 hours) under basal and activated autophagy conditions, and to measure the degree of cell-to-cell variability. Moreover, we experimentally confirmed two model predictions, namely (i) peri-nuclear concentration of autophagosomes and (ii) inhibitory lysosomal feedback on mTOR signaling. Conclusion Agent-based modeling represents a novel approach to investigate autophagy dynamics, function and dysfunction with high biological realism. Our model accurately recapitulates short-term behavior and cell-to-cell variability under basal and activated conditions of autophagy. Further, this approach also allows investigation of long-term behaviors emerging from biologically-relevant alterations to vesicle trafficking and metabolic state. Electronic supplementary material The online version of this article (doi:10.1186/s12964-014-0056-8) contains supplementary material, which is available to authorized users.
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159
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Proteomic analysis of the action of the Mycobacterium ulcerans toxin mycolactone: targeting host cells cytoskeleton and collagen. PLoS Negl Trop Dis 2014; 8:e3066. [PMID: 25101965 PMCID: PMC4125307 DOI: 10.1371/journal.pntd.0003066] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 06/20/2014] [Indexed: 12/21/2022] Open
Abstract
Buruli ulcer (BU) is a neglected tropical disease caused by Mycobacterium ulcerans. The tissue damage characteristic of BU lesions is known to be driven by the secretion of the potent lipidic exotoxin mycolactone. However, the molecular action of mycolactone on host cell biology mediating cytopathogenesis is not fully understood. Here we applied two-dimensional electrophoresis (2-DE) to identify the mechanisms of mycolactone's cellular action in the L929 mouse fibroblast proteome. This revealed 20 changed spots corresponding to 18 proteins which were clustered mainly into cytoskeleton-related proteins (Dync1i2, Cfl1, Crmp2, Actg1, Stmn1) and collagen biosynthesis enzymes (Plod1, Plod3, P4ha1). In line with cytoskeleton conformational disarrangements that are observed by immunofluorescence, we found several regulators and constituents of both actin- and tubulin-cytoskeleton affected upon exposure to the toxin, providing a novel molecular basis for the effect of mycolactone. Consistent with these cytoskeleton-related alterations, accumulation of autophagosomes as well as an increased protein ubiquitination were observed in mycolactone-treated cells. In vivo analyses in a BU mouse model revealed mycolactone-dependent structural changes in collagen upon infection with M. ulcerans, associated with the reduction of dermal collagen content, which is in line with our proteomic finding of mycolactone-induced down-regulation of several collagen biosynthesis enzymes. Our results unveil the mechanisms of mycolactone-induced molecular cytopathogenesis on exposed host cells, with the toxin compromising cell structure and homeostasis by inducing cytoskeleton alterations, as well as disrupting tissue structure, by impairing the extracellular matrix biosynthesis. Buruli Ulcer (BU) is a neglected tropical disease caused by Mycobacterium ulcerans infection. It has been recognized for many years that BU pathogenesis is mediated by the potent exotoxin mycolactone; however, the molecular action of this toxin on the host cell biology that drives its pathogenesis is not fully understood. Here we present a proteomic-based study that explores the molecular action of mycolactone on host cells biology. Our results provide further molecular evidence for the cytoskeleton-disarrangement induced by mycolactone, and unveil its impact on cytoskeleton-dependent cellular functions. Moreover, we extend the field of action of this toxin to the biosynthesis of collagen, implicating mycolactone on the decrease of dermal collagen found on BU lesions. Given the dependence of M. ulcerans virulence on its toxin, these findings on mycolactone's molecular action on host cells and tissues are of major importance for the understanding of BU pathogenesis.
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160
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Fu MM, Nirschl JJ, Holzbaur ELF. LC3 binding to the scaffolding protein JIP1 regulates processive dynein-driven transport of autophagosomes. Dev Cell 2014; 29:577-590. [PMID: 24914561 DOI: 10.1016/j.devcel.2014.04.015] [Citation(s) in RCA: 153] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 03/04/2014] [Accepted: 04/14/2014] [Indexed: 12/14/2022]
Abstract
Autophagy is essential for maintaining cellular homeostasis in neurons, where autophagosomes undergo robust unidirectional retrograde transport along axons. We find that the motor scaffolding protein JIP1 binds directly to the autophagosome adaptor LC3 via a conserved LIR motif. This interaction is required for the initial exit of autophagosomes from the distal axon, for sustained retrograde transport along the midaxon, and for autophagosomal maturation in the proximal axon. JIP1 binds directly to the dynein activator dynactin but also binds to and activates kinesin-1 in a phosphorylation-dependent manner. Following JIP1 depletion, phosphodeficient JIP1-S421A rescues retrograde transport, while phosphomimetic JIP1-S421D aberrantly activates anterograde transport. During normal autophagosome transport, residue S421 of JIP1 may be maintained in a dephosphorylated state by autophagosome-associated MKP1 phosphatase. Moreover, binding of LC3 to JIP1 competitively disrupts JIP1-mediated activation of kinesin. Thus, dual mechanisms prevent aberrant activation of kinesin to ensure robust retrograde transport of autophagosomes along the axon.
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Affiliation(s)
- Meng-Meng Fu
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Jeffrey J Nirschl
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Erika L F Holzbaur
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
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161
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Calderilla-Barbosa L, Seibenhener ML, Du Y, Diaz-Meco MT, Moscat J, Yan J, Wooten MW, Wooten MC. Interaction of SQSTM1 with the motor protein dynein--SQSTM1 is required for normal dynein function and trafficking. J Cell Sci 2014; 127:4052-63. [PMID: 25015291 DOI: 10.1242/jcs.152363] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The dynein motor protein complex is required for retrograde transport of vesicular cargo and for transport of aggregated proteins along microtubules for processing and degradation at perinuclear aggresomes. Disruption of this process leads to dysfunctional endosome accumulation and increased protein aggregation in the cell cytoplasm, both pathological features of neurodegenerative diseases. However, the exact mechanism of dynein functionality in these pathways is still being elucidated. Here, we show that the scaffolding protein SQSTM1 directly interacts with dynein through a previously unidentified dynein-binding site. This interaction is independent of HDAC6, a known interacting protein of both SQSTM1 and dynein. However, knockdown of HDAC6 increases the interaction of SQSTM1 with dynein, indicating a possible competitive interaction. Using different dynein cargoes, we show that SQSTM1 is required for proper dynein motility and trafficking along microtubules. Based on our results, we propose a new model of competitive interaction between SQSTM1 and HDAC6 with dynein. In this model, SQSTM1 would not only affect the association of polyubiquitylated protein aggregates and endosomes with dynein, but would also be required for normal dynein function.
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Affiliation(s)
- Luis Calderilla-Barbosa
- Department of Biological Sciences, 331 Funchess Hall, Auburn University, Auburn, AL 36849, USA
| | - M Lamar Seibenhener
- Department of Biological Sciences, 331 Funchess Hall, Auburn University, Auburn, AL 36849, USA
| | - Yifeng Du
- Department of Biological Sciences, 331 Funchess Hall, Auburn University, Auburn, AL 36849, USA
| | - Maria-Theresa Diaz-Meco
- 10901 North Torrey Pines Road, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Jorge Moscat
- 10901 North Torrey Pines Road, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Jin Yan
- Graduate Center for Toxicology, Markey Cancer Center, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Marie W Wooten
- Department of Biological Sciences, 331 Funchess Hall, Auburn University, Auburn, AL 36849, USA
| | - Michael C Wooten
- Department of Biological Sciences, 331 Funchess Hall, Auburn University, Auburn, AL 36849, USA
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162
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Autophagy as a Possible Underlying Mechanism of Nanomaterial Toxicity. NANOMATERIALS 2014; 4:548-582. [PMID: 28344236 PMCID: PMC5304698 DOI: 10.3390/nano4030548] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 05/23/2014] [Accepted: 06/23/2014] [Indexed: 12/27/2022]
Abstract
The rapid development of nanotechnologies is raising safety concerns because of the potential effects of engineered nanomaterials on human health, particularly at the respiratory level. Since the last decades, many in vivo studies have been interested in the pulmonary effects of different classes of nanomaterials. It has been shown that some of them can induce toxic effects, essentially depending on their physico-chemical characteristics, but other studies did not identify such effects. Inflammation and oxidative stress are currently the two main mechanisms described to explain the observed toxicity. However, the exact underlying mechanism(s) still remain(s) unknown and autophagy could represent an interesting candidate. Autophagy is a physiological process in which cytoplasmic components are digested via a lysosomal pathway. It has been shown that autophagy is involved in the pathogenesis and the progression of human diseases, and is able to modulate the oxidative stress and pro-inflammatory responses. A growing amount of literature suggests that a link between nanomaterial toxicity and autophagy impairment could exist. In this review, we will first summarize what is known about the respiratory effects of nanomaterials and we will then discuss the possible involvement of autophagy in this toxicity. This review should help understand why autophagy impairment could be taken as a promising candidate to fully understand nanomaterials toxicity.
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163
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Yan J. Interplay between HDAC6 and its interacting partners: essential roles in the aggresome-autophagy pathway and neurodegenerative diseases. DNA Cell Biol 2014; 33:567-80. [PMID: 24932665 DOI: 10.1089/dna.2013.2300] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Cytoplasmic localization and possession of two deacetylase domains and a ubiquitin-binding domain make histone deacetylase 6 (HDAC6) a unique histone deacetylase. HDAC6 interacts with a number of proteins in the cytoplasm. Some of these proteins can be deacetylated by HDAC6 deacetylase activity. Others can affect HDAC6 functions by modulating its catalytic activity or ubiquitin-binding capability. Over the last decade, HDAC6 has been shown to play important roles in the aggresome-autophagy pathway, which selectively targets on protein aggregates or damaged organelles for their accumulation and clearance in cells. HDAC6-interacting partners are integral components in this pathway with regard to their regulatory roles through interaction with HDAC6. The aggresome-autophagy pathway appears to be an attractive therapeutic target for the treatment of neurodegenerative diseases as accumulation of protein aggregates are hallmarks in these diseases. In the current review, I discuss the molecular details of how HDAC6 and its interacting partners regulate each individual step in the aggresome-autophagy pathway and also provide perspectives of how HDAC6 can be targeted in treating neurodegenerative diseases.
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Affiliation(s)
- Jin Yan
- Department of Biological Sciences, Auburn University , Auburn, Alabama
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164
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Xu M, Li XX, Chen Y, Pitzer AL, Zhang Y, Li PL. Enhancement of dynein-mediated autophagosome trafficking and autophagy maturation by ROS in mouse coronary arterial myocytes. J Cell Mol Med 2014; 18:2165-75. [PMID: 24912985 PMCID: PMC4213304 DOI: 10.1111/jcmm.12326] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Accepted: 04/15/2014] [Indexed: 01/18/2023] Open
Abstract
Dynein-mediated autophagosome (AP) trafficking was recently demonstrated to contribute to the formation of autophagolysosomes (APLs) and autophagic flux process in coronary arterial myocytes (CAMs). However, it remains unknown how the function of dynein as a motor protein for AP trafficking is regulated under physiological and pathological conditions. The present study tested whether the dynein-mediated autophagy maturation is regulated by a redox signalling associated with lysosomal Ca2+ release machinery. In primary cultures of CAMs, reactive oxygen species (ROS) including H2O2 and O2−. (generated by xanthine/xanthine oxidase) significantly increased dynein ATPase activity and AP movement, which were accompanied by increased lysosomal fusion with AP and APL formation. Inhibition of dynein activity by (erythro-9-(2-hydroxy-3-nonyl)adenine) (EHNA) or disruption of the dynein complex by dynamitin (DCTN2) overexpression blocked ROS-induced dynein activation, AP movement and APL formation, and resulted in an accumulation of AP along with a failed breakdown of AP. Antagonism of nicotinic acid adenine dinucleotide phosphate (NAADP)-mediated Ca2+ signalling with NED-19 and PPADS abolished ROS-enhanced lysosomal Ca2+ release and dynein activation in CAMs. In parallel, all these changes were also enhanced by overexpression of NADPH oxidase-1 (Nox1) gene in CAMs. Incubation with high glucose led to a marked O2−. production compared with normoglycaemic CAMs, while Nox1 inhibitor ML117 abrogated this effect. Moreover, ML117 and NED-19 and PPADS significantly suppressed dynein activity and APL formation caused by high glucose. Taken together, these data suggest that ROS function as important players to regulate dynein-dependent AP trafficking leading to efficient autophagic maturation in CAMs.
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Affiliation(s)
- Ming Xu
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA
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165
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Regulation of autophagy by mTOR-dependent and mTOR-independent pathways: autophagy dysfunction in neurodegenerative diseases and therapeutic application of autophagy enhancers. Biochem Soc Trans 2014; 41:1103-30. [PMID: 24059496 DOI: 10.1042/bst20130134] [Citation(s) in RCA: 269] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Autophagy is an intracellular degradation pathway essential for cellular and energy homoeostasis. It functions in the clearance of misfolded proteins and damaged organelles, as well as recycling of cytosolic components during starvation to compensate for nutrient deprivation. This process is regulated by mTOR (mammalian target of rapamycin)-dependent and mTOR-independent pathways that are amenable to chemical perturbations. Several small molecules modulating autophagy have been identified that have potential therapeutic application in diverse human diseases, including neurodegeneration. Neurodegeneration-associated aggregation-prone proteins are predominantly degraded by autophagy and therefore stimulating this process with chemical inducers is beneficial in a wide range of transgenic disease models. Emerging evidence indicates that compromised autophagy contributes to the aetiology of various neurodegenerative diseases related to protein conformational disorders by causing the accumulation of mutant proteins and cellular toxicity. Combining the knowledge of autophagy dysfunction and the mechanism of drug action may thus be rational for designing targeted therapy. The present review describes the cellular signalling pathways regulating mammalian autophagy and highlights the potential therapeutic application of autophagy inducers in neurodegenerative disorders.
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166
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Zientara-Rytter K, Sirko A. Selective autophagy receptor Joka2 co-localizes with cytoskeleton in plant cells. PLANT SIGNALING & BEHAVIOR 2014; 9:e28523. [PMID: 24705105 PMCID: PMC4091515 DOI: 10.4161/psb.28523] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 03/12/2014] [Accepted: 03/12/2014] [Indexed: 05/08/2023]
Abstract
Autophagy, especially selective autophagy, is poorly characterized in plants compared with mammals and yeasts, where numerous factors required for the proper regulation of autophagy have been identified. The evidence for the importance of the cytoskeleton (both actin filaments and microtubules) in various aspects of autophagy comes mostly from work on yeasts and mammals, while in plant cells these links are poorly explored. In this report we demonstrate that tobacco protein Joka2, a member of a family of selective autophagy cargo receptors closely related to mammalian NBR1 and p62 colocalizes with both major cytoskeletal components, microtubules and microfilaments and, additionally, resides in close proximity of the ER.
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Affiliation(s)
| | - Agnieszka Sirko
- Institute of Biochemistry and Biophysics; Polish Academy of Sciences; Warsaw, Poland
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167
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Liu Y, Yuan YH, Sun JD, Li J, Li ZP, Chen NH. Nigrostriatal dynein changes in A53T alpha-synuclein transgenic mice. F1000Res 2014; 3:68. [PMID: 25210616 PMCID: PMC4156029 DOI: 10.12688/f1000research.3507.1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/10/2014] [Indexed: 12/02/2022] Open
Abstract
The accumulation of misfolded a-synuclein is mechanistically linked to neurodegeneration in Parkinson’s disease (PD) and other alpha-synucleinopathies. However, how alpha-synuclein causes neurodegeneration is unresolved. Several studies have supported the involvement of dynein, the major motor for retrograde axonal transport in alpha-synuclein-dependent neurodegeneration, especially in the nigrostriatal system. Therefore, we examined the nigrostriatal dyneins in transgenic mice that overexpress human A53T alpha-synuclein and recapitulate key features of a PD-like neuronal synucleinopathy. Age-matched nontransgenic littermates were used as controls. The results demonstrated that the protein level of dynein was decreased in the striatum, whereas it was elevated in the substantia nigra. Double immunostaining results revealed that the reduction in dynein level was associated with aggregation of A53T a-synuclein in the striatum. Furthermore, we performed a quantitative analysis of motor behaviors in A53T alpha-synuclein transgenic mice and controls using a modified open field test. We demonstrated that the protein level of dynein in the striatum was significantly correlated with the motor behaviors. Together, our data indicate that dynein changes in the nigrostriatal system of A53T alpha-synuclein transgenic mice may contribute to their severe movement disorder.
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Affiliation(s)
- Yan Liu
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Department of Pharmacology, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100050, China
| | - Yu-He Yuan
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Department of Pharmacology, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100050, China
| | - Jian-Dong Sun
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Department of Pharmacology, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100050, China
| | - Jing Li
- Tianjin University of Traditional Chinese Medicine, Tianjin, 300193, China
| | - Zhi-Peng Li
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Department of Pharmacology, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100050, China
| | - Nai-Hong Chen
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Department of Pharmacology, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100050, China
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168
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The regulation of autophagosome dynamics by huntingtin and HAP1 is disrupted by expression of mutant huntingtin, leading to defective cargo degradation. J Neurosci 2014; 34:1293-305. [PMID: 24453320 DOI: 10.1523/jneurosci.1870-13.2014] [Citation(s) in RCA: 265] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Autophagy is an essential cellular pathway for degrading defective organelles and aggregated proteins. Defects in autophagy have been implicated in the neurodegenerative disorder Huntington's disease (HD), in which polyglutamine-expanded huntingtin (polyQ-htt) is predominantly cleared by autophagy. In neurons, autophagosomes form constitutively at the axon tip and undergo robust retrograde axonal transport toward the cell body, but the factors regulating autophagosome dynamics and autophagosome maturation are not well understood. Here, we show that both huntingtin (htt) and its adaptor protein huntingtin-associated protein-1 (HAP1) copurify and colocalize with autophagosomes in neurons. We use live-cell imaging and RNAi in primary neurons from GFP-LC3 transgenic mice to show that htt and HAP1 control autophagosome dynamics, regulating dynein and kinesin motors to promote processive transport. Expression of polyQ-htt in either primary neurons or striatal cells from HD knock-in mice is sufficient to disrupt the axonal transport of autophagosomes. Htt is not required for autophagosome formation or cargo loading. However, the defective autophagosome transport observed in both htt-depleted neurons and polyQ-htt-expressing neurons is correlated with inefficient degradation of engulfed mitochondrial fragments. Together, these studies identify htt and HAP1 as regulators of autophagosome transport in neurons and suggest that misregulation of autophagosome transport in HD leads to inefficient autophagosome maturation, potentially due to inhibition of autophagosome/lysosome fusion along the axon. The resulting defective clearance of both polyQ-htt aggregates and dysfunctional mitochondria by neuronal autophagosomes may contribute to neurodegeneration and cell death in HD.
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169
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Mandillo S, Heise I, Garbugino L, Tocchini-Valentini GP, Giuliani A, Wells S, Nolan PM. Early motor deficits in mouse disease models are reliably uncovered using an automated home-cage wheel-running system: a cross-laboratory validation. Dis Model Mech 2014; 7:397-407. [PMID: 24423792 PMCID: PMC3944499 DOI: 10.1242/dmm.013946] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Deficits in motor function are debilitating features in disorders affecting neurological, neuromuscular and musculoskeletal systems. Although these disorders can vary greatly with respect to age of onset, symptomatic presentation, rate of progression and severity, the study of these disease models in mice is confined to the use of a small number of tests, most commonly the rotarod test. To expand the repertoire of meaningful motor function tests in mice, we tested, optimised and validated an automated home-cage-based running-wheel system, incorporating a conventional wheel with evenly spaced rungs and a complex wheel with particular rungs absent. The system enables automated assessment of motor function without handler interference, which is desirable in longitudinal studies involving continuous monitoring of motor performance. In baseline studies at two test centres, consistently significant differences in performance on both wheels were detectable among four commonly used inbred strains. As further validation, we studied performance in mutant models of progressive neurodegenerative diseases – Huntington’s disease [TgN(HD82Gln)81Dbo; referred to as HD mice] and amyotrophic lateral sclerosis [Tg(SOD1G93A)dl1/GurJ; referred to as SOD1 mice] – and in a mutant strain with subtle gait abnormalities, C-Snap25Bdr/H (Blind-drunk, Bdr). In both models of progressive disease, as with the third mutant, we could reliably and consistently detect specific motor function deficits at ages far earlier than any previously recorded symptoms in vivo: 7–8 weeks for the HD mice and 12 weeks for the SOD1 mice. We also conducted longitudinal analysis of rotarod and grip strength performance, for which deficits were still not detectable at 12 weeks and 23 weeks, respectively. Several new parameters of motor behaviour were uncovered using principal component analysis, indicating that the wheel-running assay could record features of motor function that are independent of rotarod performance. This represents a powerful new method to detect motor deficits at pre-symptomatic stages in mouse disease models and should be considered as a valid tool to investigate the efficacy of therapeutic agents.
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Affiliation(s)
- Silvia Mandillo
- CNR - Institute of Cell Biology and Neurobiology - EMMA, 00015 Monterotondo Scalo, Italy
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170
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Alteration of dynein function affects α-synuclein degradation via the autophagosome-lysosome pathway. Int J Mol Sci 2013; 14:24242-54. [PMID: 24351814 PMCID: PMC3876108 DOI: 10.3390/ijms141224242] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 11/26/2013] [Accepted: 12/03/2013] [Indexed: 11/17/2022] Open
Abstract
Growing evidence suggests that dynein dysfunction may be implicated in the pathogenesis of neurodegeneration. It plays a central role in aggresome formation, the delivery of autophagosome to lysosome for fusion and degradation, which is a pro-survival mechanism essential for the bulk degradation of misfolded proteins and damaged organells. Previous studies reported that dynein dysfuntion was associated with aberrant aggregation of α-synuclein, which is a major component of inclusion bodies in Parkinson's disease (PD). However, it remains unclear what roles dynein plays in α-synuclein degradation. Our study demonstrated a decrease of dynein expression in neurotoxin-induced PD models in vitro and in vivo, accompanied by an increase of α-synuclein protein level. Dynein down-regulation induced by siRNA resulted in a prolonged half-life of α-synuclein and its over-accumulation in A53T overexpressing PC12 cells. Dynein knockdown also prompted the increase of microtubule-associated protein 1 light chain 3 (LC3-II) and sequestosome 1 (SQSTM1, p62) expression, and the accumulation of autophagic vacuoles. Moreover, dynein suppression impaired the autophagosome fusion with lysosome. In summary, our findings indicate that dynein is critical for the clearance of aberrant α-synuclein via autophagosome-lysosome pathway.
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171
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Ribeiro FM, Devries RA, Hamilton A, Guimaraes IM, Cregan SP, Pires RGW, Ferguson SSG. Metabotropic glutamate receptor 5 knockout promotes motor and biochemical alterations in a mouse model of Huntington's disease. Hum Mol Genet 2013; 23:2030-42. [PMID: 24282028 DOI: 10.1093/hmg/ddt598] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Huntington's disease (HD) is an autosomal-dominant neurodegenerative disorder caused by a polyglutamine expansion in the amino-terminal region of the huntingtin protein, which promotes progressive neuronal cell loss, neurological symptoms and death. In the present study, we show that blockade of mGluR5 with MTEP promotes increased locomotor activity in both control (Hdh(Q20/Q20)) and mutant HD (Hdh(Q111/Q111)) mice. Although acute injection of MTEP increases locomotor activity in both control and mutant HD mice, locomotor activity is increased in only control mice, not mutant HD mice, following the genetic deletion of mGluR5. Interestingly, treatment of mGluR5 knockout mice with either D1 or D2 dopamine antagonists eliminates the increased locomotor activity of mGluR5 knockout mice. Amphetamine treatment increases locomotor activity in control mice, but not mGluR5 null mutant HD mice. However, the loss of mGluR5 expression improves rotarod performance and decreases the number of huntingtin intranuclear inclusions in mutant HD mice. These adaptations may be due to mutant huntingtin-dependent alterations in gene expression, as microarray studies have identified several genes that are altered in mutant, but not wild-type HD mice lacking mGluR5 expression. qPCR experiments confirm that the mRNA transcript levels of dynein heavy chain, dynactin 3 and dynein light chain-6 are altered following the genetic deletion of mGluR5 in mutant HD mice, as compared with wild-type mutant HD mice. Thus, our data suggest that mutant huntingtin protein and mGluR5 exhibit a functional interaction that may be important for HD-mediated alterations in locomotor behavior and the development of intranuclear inclusions.
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Affiliation(s)
- Fabiola M Ribeiro
- Departamento de Bioquimica e Imunologia, ICB, Universidade Federal de Minas Gerais, Belo Horizonte 31270-901, Brazil
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172
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Role of protein misfolding and proteostasis deficiency in protein misfolding diseases and aging. Int J Cell Biol 2013; 2013:638083. [PMID: 24348562 PMCID: PMC3855986 DOI: 10.1155/2013/638083] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 10/08/2013] [Accepted: 10/09/2013] [Indexed: 11/29/2022] Open
Abstract
The misfolding, aggregation, and tissue accumulation of proteins are common events in diverse chronic diseases, known as protein misfolding disorders. Many of these diseases are associated with aging, but the mechanism for this connection is unknown. Recent evidence has shown that the formation and accumulation of protein aggregates may be a process frequently occurring during normal aging, but it is unknown whether protein misfolding is a cause or a consequence of aging. To combat the formation of these misfolded aggregates cells have developed complex and complementary pathways aiming to maintain protein homeostasis. These protective pathways include the unfolded protein response, the ubiquitin proteasome system, autophagy, and the encapsulation of damaged proteins in aggresomes. In this paper we review the current knowledge on the role of protein misfolding in disease and aging as well as the implication of deficiencies in the proteostasis cellular pathways in these processes. It is likely that further understanding of the mechanisms involved in protein misfolding and the natural defense pathways may lead to novel strategies for treatment of age-dependent protein misfolding disorders and perhaps aging itself.
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173
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Mackeh R, Perdiz D, Lorin S, Codogno P, Poüs C. Autophagy and microtubules - new story, old players. J Cell Sci 2013; 126:1071-80. [PMID: 23620510 DOI: 10.1242/jcs.115626] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Both at a basal level and after induction (especially in response to nutrient starvation), the function of autophagy is to allow cells to degrade and recycle damaged organelles, proteins and other biological constituents. Here, we focus on the role microtubules have in autophagosome formation, autophagosome transport across the cytoplasm and in the formation of autolysosomes. Recent insights into the exact relationship between autophagy and microtubules now point to the importance of microtubule dynamics, tubulin post-translational modifications and microtubule motors in the autophagy process. Such factors regulate signaling pathways that converge to stimulate autophagosome formation. They also orchestrate the movements of pre-autophagosomal structures and autophagosomes or more globally organize and localize immature and mature autophagosomes and lysosomes. Most of the factors that now appear to link microtubules to autophagosome formation or to autophagosome dynamics and fate were identified initially without the notion that sequestration, recruitment and/or interaction with microtubules contribute to their function. Spatial and temporal coordination of many stages in the life of autophagosomes thus underlines the integrative role of microtubules and progressively reveals hidden parts of the autophagy machinery.
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Affiliation(s)
- Rafah Mackeh
- UPRES EA4530, Université Paris-Sud, Faculté de Pharmacie, 92296 Châtenay-Malabry, France
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174
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175
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Bhutia SK, Mukhopadhyay S, Sinha N, Das DN, Panda PK, Patra SK, Maiti TK, Mandal M, Dent P, Wang XY, Das SK, Sarkar D, Fisher PB. Autophagy: cancer's friend or foe? Adv Cancer Res 2013; 118:61-95. [PMID: 23768510 DOI: 10.1016/b978-0-12-407173-5.00003-0] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The functional relevance of autophagy in tumor formation and progression remains controversial. Autophagy can promote tumor suppression during cancer initiation and protect tumors during progression. Autophagy-associated cell death may act as a tumor suppressor, with several autophagy-related genes deleted in cancers. Loss of autophagy induces genomic instability and necrosis with inflammation in mouse tumor models. Conversely, autophagy enhances survival of tumor cells subjected to metabolic stress and may promote metastasis by enhancing tumor cell survival under environmental stress. Unraveling the complex molecular regulation and multiple diverse roles of autophagy is pivotal in guiding development of rational and novel cancer therapies.
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Affiliation(s)
- Sujit K Bhutia
- Department of Life Science, National Institute of Technology Rourkela, Rourkela, Odisha, India.
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176
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Xu M, Li XX, Xiong J, Xia M, Gulbins E, Zhang Y, Li PL. Regulation of autophagic flux by dynein-mediated autophagosomes trafficking in mouse coronary arterial myocytes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:3228-3236. [PMID: 24095928 DOI: 10.1016/j.bbamcr.2013.09.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 09/23/2013] [Accepted: 09/24/2013] [Indexed: 02/06/2023]
Abstract
Autophagic flux is an important process during autophagy maturation in coronary arterial myocytes (CAMs). Here, we defined the role and molecular mechanism of the motor protein dynein in the regulation of autophagic flux in CAMs. In mouse CAMs, dynein protein is abundantly expressed. Pharmacological or genetic inhibition of dynein activity dramatically enhanced 7-ketocholesterol (7-Ket)-induced expression of the autophagic marker LC3B and increased the cellular levels of p62, a selective substrate for autophagy. Inhibition of dynein activity increased 7-Ket-induced formation of autophagosomes (APs), but reduced the number of autophagolysosomes (APLs) in CAMs. Furthermore, 7-Ket increased the fusion of APs with lysosomes and the velocity of APs movement in mouse CAMs, which was abolished when the dynein activity in these cells was inhibited. Interestingly, 7-Ket increased lysosomal Ca(2+) release and stimulated dynein ATPase activity, both of which were abolished by NAADP antagonists, NED-19 and PPADS. Taken together, our data suggest that NAADP-mediated Ca(2+) release plays a crucial role in regulating dynein activity, which mediates APs trafficking and fusion with lysosomes to form APLs thus regulating autophagic flux in CAMs under atherogenic stimulation.
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Affiliation(s)
- Ming Xu
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Xiao-Xue Li
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Jing Xiong
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Min Xia
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Erich Gulbins
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse, 55, 45122 Essen, Germany
| | - Yang Zhang
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Pin-Lan Li
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA.
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177
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Vantaggiato C, Crimella C, Airoldi G, Polishchuk R, Bonato S, Brighina E, Scarlato M, Musumeci O, Toscano A, Martinuzzi A, Santorelli FM, Ballabio A, Bresolin N, Clementi E, Bassi MT. Defective autophagy in spastizin mutated patients with hereditary spastic paraparesis type 15. ACTA ACUST UNITED AC 2013; 136:3119-39. [PMID: 24030950 DOI: 10.1093/brain/awt227] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Hereditary spastic paraparesis type 15 is a recessive complicated form of the disease clinically characterized by slowly progressive spastic paraparesis and mental deterioration with onset between the first and second decade of life. Thinning of corpus callosum is the neuroradiological distinctive sign frequently associated with white matter abnormalities. The causative gene, ZFYVE26, encodes a large protein of 2539 amino acid residues, termed spastizin, containing three recognizable domains: a zinc finger, a leucine zipper and a FYVE domain. Spastizin protein has a diffuse cytoplasmic distribution and co-localizes partially with early endosomes, the endoplasmic reticulum, microtubules and vesicles involved in protein trafficking. In addition, spastizin localizes to the mid-body during the final step of mitosis and contributes to successful cytokinesis. Spastizin interacts with Beclin 1, a protein required for cytokinesis and autophagy, which is the major lysosome-mediated degradation process in the cell. In view of the Beclin 1-spastizin interaction, we investigated the possible role of spastizin in autophagy. We carried out this analysis by using lymphoblast and fibroblast cells derived from four different spastizin mutated patients (p.I508N, p.L243P, p.R1209fsX, p.S1312X) and from control subjects. Of note, the truncating p.R1209fsX and p.S1312X mutations lead to loss of spastizin protein. The results obtained indicate that spastizin interacts with the autophagy related Beclin 1-UVRAG-Rubicon multiprotein complex and is required for autophagosome maturation. In cells lacking spastizin or with mutated forms of the protein, spastizin interaction with Beclin 1 is lost although the formation of the Beclin 1-UVRAG-Rubicon complex can still be observed. However, in these cells we demonstrate an impairment of autophagosome maturation and an accumulation of immature autophagosomes. Autophagy defects with autophagosome accumulation can be observed also in neuronal cells upon spastizin silencing. These results indicate that autophagy is a central process in the pathogenesis of complicated forms of hereditary spastic paraparesis with thin corpus callosum.
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Affiliation(s)
- Chiara Vantaggiato
- 1 Scientific Institute IRCCS E. Medea, Laboratory of Molecular Biology, 23842 Bosisio Parini, Lecco, Italy
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178
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Schiavo G, Greensmith L, Hafezparast M, Fisher EMC. Cytoplasmic dynein heavy chain: the servant of many masters. Trends Neurosci 2013; 36:641-51. [PMID: 24035135 PMCID: PMC3824068 DOI: 10.1016/j.tins.2013.08.001] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 07/23/2013] [Accepted: 08/05/2013] [Indexed: 12/20/2022]
Abstract
The cytoplasmic dynein complex is the main retrograde motor in all eukaryotic cells. This complex is built around a dimer of cytoplasmic dynein heavy chains (DYNC1H1). Mouse DYNC1H1 mutants have sensory defects, but motor defects have been controversial. Now human DYNC1H1 mutations with sensory, motor, and cognitive deficits are being found. The study of these mutations will give us new insight into DYNC1H1 function in the nervous system.
Cytoplasmic dynein is the main retrograde motor in all eukaryotic cells. This complex comprises different subunits assembled on a cytoplasmic dynein heavy chain 1 (DYNC1H1) dimer. Cytoplasmic dynein is particularly important for neurons because it carries essential signals and organelles from distal sites to the cell body. In the past decade, several mouse models have helped to dissect the numerous functions of DYNC1H1. Additionally, several DYNC1H1 mutations have recently been found in human patients that give rise to a broad spectrum of developmental and midlife-onset disorders. Here, we discuss the effects of mutations of mouse and human DYNC1H1 and how these studies are giving us new insight into the many critical roles DYNC1H1 plays in the nervous system.
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Affiliation(s)
- Giampietro Schiavo
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, National Hospital for Neurology and Neurosurgery, University College London, Queen Square, London WC1N 3BG, UK; Molecular NeuroPathobiology, Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3LY, UK.
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179
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Nixon RA. The role of autophagy in neurodegenerative disease. Nat Med 2013; 19:983-97. [PMID: 23921753 DOI: 10.1038/nm.3232] [Citation(s) in RCA: 1443] [Impact Index Per Article: 131.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 05/03/2013] [Indexed: 02/08/2023]
Abstract
Autophagy is a lysosomal degradative process used to recycle obsolete cellular constituents and eliminate damaged organelles and protein aggregates. These substrates reach lysosomes by several distinct mechanisms, including delivery within endosomes as well as autophagosomes. Completion of digestion involves dynamic interactions among compartments of the autophagic and endocytic pathways. Neurons are particularly vulnerable to disruptions of these interactions, especially as the brain ages. Not surprisingly, mutations of genes regulating autophagy cause neurodegenerative diseases across the age spectrum with exceptional frequency. In late-onset disorders such as Alzheimer's disease, amyotrophic lateral sclerosis and familial Parkinson's disease, defects arise at different stages of the autophagy pathway and have different implications for pathogenesis and therapy. This Review provides an overview of the role of autophagy in neurodegenerative disease, focusing particularly on less frequently considered lysosomal clearance mechanisms and their considerable impact on disease. Various therapeutic strategies for modulating specific stages of autophagy and the current state of drug development for this purpose are also evaluated.
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Affiliation(s)
- Ralph A Nixon
- Center for Dementia Research, Nathan S. Kline Institute, Orangeburg, New York, USA.
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180
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Xu Z, Graham K, Foote M, Liang F, Rizkallah R, Hurt M, Wang Y, Wu Y, Zhou Y. 14-3-3 protein targets misfolded chaperone-associated proteins to aggresomes. J Cell Sci 2013; 126:4173-86. [PMID: 23843611 DOI: 10.1242/jcs.126102] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The aggresome is a key cytoplasmic organelle for sequestration and clearance of toxic protein aggregates. Although loading misfolded proteins cargos to dynein motors has been recognized as an important step in the aggresome formation process, the molecular machinery that mediates the association of cargos with the dynein motor is poorly understood. Here, we report a new aggresome-targeting pathway that involves isoforms of 14-3-3, a family of conserved regulatory proteins. 14-3-3 interacts with both the dynein-intermediate chain (DIC) and an Hsp70 co-chaperone Bcl-2-associated athanogene 3 (BAG3), thereby recruiting chaperone-associated protein cargos to dynein motors for their transport to aggresomes. This molecular cascade entails functional dimerization of 14-3-3, which we show to be crucial for the formation of aggresomes in both yeast and mammalian cells. These results suggest that 14-3-3 functions as a molecular adaptor to promote aggresomal targeting of misfolded protein aggregates and may link such complexes to inclusion bodies observed in various neurodegenerative diseases.
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Affiliation(s)
- Zhe Xu
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL 32306, USA
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181
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Zavodszky E, Vicinanza M, Rubinsztein DC. Biology and trafficking of ATG9 and ATG16L1, two proteins that regulate autophagosome formation. FEBS Lett 2013; 587:1988-96. [PMID: 23669359 DOI: 10.1016/j.febslet.2013.04.025] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Revised: 04/24/2013] [Accepted: 04/24/2013] [Indexed: 01/16/2023]
Abstract
Autophagy is a highly conserved intracytoplasmic degradation pathway for proteins, oligomers, organelles and pathogens. It initiates with the formation of a cup-shaped double membrane structure called the phagophore. The membrane origin for autophagosomes has been a key question for the field. ATG9 and ATG16L1, or their yeast orthologues, are key proteins that regulate autophagosome biogenesis, and may be associated with distinct membrane sources. Here we review the biology of autophagy with a focus on ATG16L1 and ATG9, and we summarise the current knowledge of their trafficking in relation to autophagic stimuli and autophagosome formation.
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Affiliation(s)
- Eszter Zavodszky
- Department of Medical Genetics, University of Cambridge, Cambridge Institute for Medical Research, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
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182
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Yan WJ, Dong HL, Xiong LZ. The protective roles of autophagy in ischemic preconditioning. Acta Pharmacol Sin 2013; 34:636-43. [PMID: 23603984 DOI: 10.1038/aps.2013.18] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Autophagy, a process for the degradation of protein aggregates and dysfunctional organelles, is required for cellular homeostasis and cell survival in response to stress and is implicated in endogenous protection. Ischemic preconditioning is a brief and nonlethal episode of ischemia, confers protection against subsequent ischemia-reperfusion through the up-regulation of endogenous protective mechanisms. Emerging evidence shows that autophagy is associated with the protective effect of ischemic preconditioning. This review summarizes recent progress in research on the functions and regulations of the autophagy pathway in preconditioning-induced protection and cellular survival.
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183
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Zhang XJ, Chen S, Huang KX, Le WD. Why should autophagic flux be assessed? Acta Pharmacol Sin 2013; 34:595-9. [PMID: 23474710 PMCID: PMC4002868 DOI: 10.1038/aps.2012.184] [Citation(s) in RCA: 221] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Accepted: 12/05/2012] [Indexed: 12/19/2022] Open
Abstract
As autophagy is involved in cell growth, survival, development and death, impaired autophagic flux has been linked to a variety of human pathophysiological processes, including neurodegeneration, cancer, myopathy, cardiovascular and immune-mediated disorders. There is a growing need to identify and quantify the status of autophagic flux in different pathological conditions. Given that autophagy is a highly dynamic and complex process that is regulated at multiple steps, it is often assessed accurately. This perspective review article will focus on the autophagic flux defects in different human disorders and update the current methods of monitoring autophagic flux. This knowledge is essential for developing autophagy-related therapeutics for treating the diseases.
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Affiliation(s)
- Xiao-jie Zhang
- Institute of Neurology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences-Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Sheng Chen
- Institute of Neurology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Kai-xing Huang
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences-Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Wei-dong Le
- Institute of Neurology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences-Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
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184
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Hochfeld WE, Lee S, Rubinsztein DC. Therapeutic induction of autophagy to modulate neurodegenerative disease progression. Acta Pharmacol Sin 2013; 34:600-4. [PMID: 23377551 PMCID: PMC3647215 DOI: 10.1038/aps.2012.189] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
There is accumulating evidence that aggregating, misfolded proteins may have an impact on autophagic function, suggesting that this could be a secondary pathological mechanism in many diseases. In this review, we focus on the role of autophagy in four major neurodegenerative diseases: Alzheimer disease (AD), Huntington's disease (HD), Parkinson's disease (PD) and amyotropic lateral sclerosis.
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185
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Banduseela VC, Chen YW, Kultima HG, Norman HS, Aare S, Radell P, Eriksson LI, Hoffman EP, Larsson L. Impaired autophagy, chaperone expression, and protein synthesis in response to critical illness interventions in porcine skeletal muscle. Physiol Genomics 2013; 45:477-86. [PMID: 23572537 DOI: 10.1152/physiolgenomics.00141.2012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Critical illness myopathy (CIM) is characterized by a preferential loss of the motor protein myosin, muscle wasting, and impaired muscle function in critically ill intensive care unit (ICU) patients. CIM is associated with severe morbidity and mortality and has a significant negative socioeconomic effect. Neuromuscular blocking agents, corticosteroids, sepsis, mechanical ventilation, and immobilization have been implicated as important risk factors, but the causal relationship between CIM and the risk factors has not been established. A porcine ICU model has been used to determine the immediate molecular and cellular cascades that may contribute to the pathogenesis prior to myosin loss and extensive muscle wasting. Expression profiles have been compared between pigs exposed to the ICU interventions, i.e., mechanically ventilated, sedated, and immobilized for 5 days, with pigs exposed to critical illness interventions, i.e., neuromuscular blocking agents, corticosteroids, and induced sepsis in addition to the ICU interventions for 5 days. Impaired autophagy as well as impaired chaperone expression and protein synthesis were observed in the skeletal muscle in response to critical illness interventions. A novel finding in this study is impaired core autophagy machinery in response to critical illness interventions, which when in concert with downregulated chaperone expression and protein synthesis may collectively affect the proteostasis in skeletal muscle and may exacerbate the disease progression in CIM.
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Affiliation(s)
- Varuna C Banduseela
- Department of Neuroscience, Clinical Neurophysiology, Uppsala University, Uppsala, Sweden.
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186
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Zhou J, Tan SH, Nicolas V, Bauvy C, Yang ND, Zhang J, Xue Y, Codogno P, Shen HM. Activation of lysosomal function in the course of autophagy via mTORC1 suppression and autophagosome-lysosome fusion. Cell Res 2013; 23:508-23. [PMID: 23337583 PMCID: PMC3616426 DOI: 10.1038/cr.2013.11] [Citation(s) in RCA: 314] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 11/27/2012] [Accepted: 11/30/2012] [Indexed: 12/11/2022] Open
Abstract
Lysosome is a key subcellular organelle in the execution of the autophagic process and at present little is known whether lysosomal function is controlled in the process of autophagy. In this study, we first found that suppression of mammalian target of rapamycin (mTOR) activity by starvation or two mTOR catalytic inhibitors (PP242 and Torin1), but not by an allosteric inhibitor (rapamycin), leads to activation of lysosomal function. Second, we provided evidence that activation of lysosomal function is associated with the suppression of mTOR complex 1 (mTORC1), but not mTORC2, and the mTORC1 localization to lysosomes is not directly correlated to its regulatory role in lysosomal function. Third, we examined the involvement of transcription factor EB (TFEB) and demonstrated that TFEB activation following mTORC1 suppression is necessary but not sufficient for lysosomal activation. Finally, Atg5 or Atg7 deletion or blockage of the autophagosome-lysosome fusion process effectively diminished lysosomal activation, suggesting that lysosomal activation occurring in the course of autophagy is dependent on autophagosome-lysosome fusion. Taken together, this study demonstrates that in the course of autophagy, lysosomal function is upregulated via a dual mechanism involving mTORC1 suppression and autophagosome-lysosome fusion.
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Affiliation(s)
- Jing Zhou
- Department of Physiology, Yong Loo Lin School of Medicine and Saw Swee Hock School of Public Health, National University of Singapore, Singapore 117597
| | - Shi-Hao Tan
- Department of Physiology, Yong Loo Lin School of Medicine and Saw Swee Hock School of Public Health, National University of Singapore, Singapore 117597
- NUS Graduate School for Integrative Sciences and Engineering National University of Singapore, Singapore 117597
| | - Valérie Nicolas
- Microscopy Facility-IFR-141-IPSIT, rue JB Clément, 92296 Châtenay-Malabry, France
- University Paris-Sud, Orsay, France
| | - Chantal Bauvy
- University Paris-Sud, Orsay, France
- INSERM U984, 92296 Châtenay-Malabry, France
| | - Nai-Di Yang
- Department of Physiology, Yong Loo Lin School of Medicine and Saw Swee Hock School of Public Health, National University of Singapore, Singapore 117597
| | - Jianbin Zhang
- Department of Physiology, Yong Loo Lin School of Medicine and Saw Swee Hock School of Public Health, National University of Singapore, Singapore 117597
| | - Yuan Xue
- Reed College, Portland, OR 97202, USA
| | - Patrice Codogno
- University Paris-Sud, Orsay, France
- INSERM U984, 92296 Châtenay-Malabry, France
| | - Han-Ming Shen
- Department of Physiology, Yong Loo Lin School of Medicine and Saw Swee Hock School of Public Health, National University of Singapore, Singapore 117597
- NUS Graduate School for Integrative Sciences and Engineering National University of Singapore, Singapore 117597
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187
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Bánréti A, Sass M, Graba Y. The emerging role of acetylation in the regulation of autophagy. Autophagy 2013; 9:819-29. [PMID: 23466676 DOI: 10.4161/auto.23908] [Citation(s) in RCA: 143] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Autophagy is an evolutionarily conserved catabolic process through which different components of the cells are sequestered into double-membrane cytosolic vesicles called autophagosomes, and fated to degradation through fusion with lysosomes. Autophagy plays a major function in many physiological processes including response to different stress factors, energy homeostasis, elimination of cellular organelles and tissue remodeling during development. Consequently, autophagy is strictly controlled and post-translational modifications such as phosphorylation and ubiquitination have long been associated with autophagy regulation. In contrast, the importance of acetylation in autophagy control has only emerged in the last few years. In this review, we summarize how previously identified histone acetylases and deacetylases modify key autophagic effector proteins, and discuss how this has an impact on physiological and pathological cellular processes.
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Affiliation(s)
- Agnes Bánréti
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary.
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188
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Brice A, Moseley GW. Viral interactions with microtubules: orchestrators of host cell biology? Future Virol 2013. [DOI: 10.2217/fvl.12.137] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Viral interaction with the microtubule (MT) cytoskeleton is critical to infection by many viruses. Most data regarding virus–MT interaction indicate key roles in the subcellular transport of virions/viral genomic material to sites of replication, assembly and egress. However, the MT cytoskeleton orchestrates diverse processes in addition to subcellular cargo transport, including regulation of signaling pathways, cell survival and mitosis, suggesting that viruses, expert manipulators of the host cell, may use the virus–MT interface to control multiple aspects of cell biology. Several lines of evidence support this idea, indicating that specific viral proteins can modify MT dynamics and/or structure and regulate processes such as apoptosis and innate immune signaling through MT-dependent mechanisms. Here, the authors review general aspects of virus–MT interactions, with emphasis on viral mechanisms that modify MT dynamics and functions to affect processes beyond virion transport. The emerging importance of discrete viral protein–MT interactions in pathogenic processes indicates that these interfaces may represent new targets for future therapeutics and vaccine development.
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Affiliation(s)
- Aaron Brice
- Viral Immune Evasion & Pathogenicity Laboratory, Department of Biochemistry & Molecular Biology, Monash University, Victoria 3800, Australia
| | - Gregory W Moseley
- Viral Immune Evasion & Pathogenicity Laboratory, Department of Biochemistry & Molecular Biology, Monash University, Victoria 3800, Australia.
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189
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Iguchi Y, Katsuno M, Niwa JI, Takagi S, Ishigaki S, Ikenaka K, Kawai K, Watanabe H, Yamanaka K, Takahashi R, Misawa H, Sasaki S, Tanaka F, Sobue G. Loss of TDP-43 causes age-dependent progressive motor neuron degeneration. Brain 2013; 136:1371-82. [DOI: 10.1093/brain/awt029] [Citation(s) in RCA: 132] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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190
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Chauhan S, Goodwin JG, Chauhan S, Manyam G, Wang J, Kamat AM, Boyd DD. ZKSCAN3 is a master transcriptional repressor of autophagy. Mol Cell 2013; 50:16-28. [PMID: 23434374 DOI: 10.1016/j.molcel.2013.01.024] [Citation(s) in RCA: 198] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2012] [Revised: 12/05/2012] [Accepted: 01/18/2013] [Indexed: 12/31/2022]
Abstract
Autophagy constitutes a major cell-protective mechanism that eliminates damaged components and maintains energy homeostasis via recycling nutrients under normal/stressed conditions. Although the core components of autophagy have been well studied, regulation of autophagy at the transcriptional level is poorly understood. Herein, we establish ZKSCAN3, a zinc finger family DNA-binding protein, as a transcriptional repressor of autophagy. Silencing of ZKSCAN3 induced autophagy and increased lysosome biogenesis. Importantly, we show that ZKSCAN3 represses transcription of a large gene set (>60) integral to, or regulatory for, autophagy and lysosome biogenesis/function and that a subset of these genes, including Map1lC3b and Wipi2, represent direct targets. Interestingly, ZKSCAN3 and TFEB are oppositely regulated by starvation and in turn oppositely regulate lysosomal biogenesis and autophagy, suggesting that they act in conjunction. Altogether, our study uncovers an autophagy master switch regulating the expression of a transcriptional network of genes integral to autophagy and lysosome biogenesis/function.
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Affiliation(s)
- Santosh Chauhan
- Department of Cancer Biology, MD Anderson Cancer Center, Houston, TX 77030, USA
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191
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dnc-1/dynactin 1 knockdown disrupts transport of autophagosomes and induces motor neuron degeneration. PLoS One 2013; 8:e54511. [PMID: 23408943 PMCID: PMC3567092 DOI: 10.1371/journal.pone.0054511] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 12/12/2012] [Indexed: 11/25/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive loss of motor neurons. We previously showed that the expression of dynactin 1, an axon motor protein regulating retrograde transport, is markedly reduced in spinal motor neurons of sporadic ALS patients, although the mechanisms by which decreased dynactin 1 levels cause neurodegeneration have yet to be elucidated. The accumulation of autophagosomes in degenerated motor neurons is another key pathological feature of sporadic ALS. Since autophagosomes are cargo of dynein/dynactin complexes and play a crucial role in the turnover of several organelles and proteins, we hypothesized that the quantitative loss of dynactin 1 disrupts the transport of autophagosomes and induces the degeneration of motor neuron. In the present study, we generated a Caenorhabditis elegans model in which the expression of DNC-1, the homolog of dynactin 1, is specifically knocked down in motor neurons. This model exhibited severe motor defects together with axonal and neuronal degeneration. We also observed impaired movement and increased number of autophagosomes in the degenerated neurons. Furthermore, the combination of rapamycin, an activator of autophagy, and trichostatin which facilitates axonal transport dramatically ameliorated the motor phenotype and axonal degeneration of this model. Thus, our results suggest that decreased expression of dynactin 1 induces motor neuron degeneration and that the transport of autophagosomes is a novel and substantial therapeutic target for motor neuron degeneration.
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192
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Nunes P, Ernandez T, Roth I, Qiao X, Strebel D, Bouley R, Charollais A, Ramadori P, Foti M, Meda P, Féraille E, Brown D, Hasler U. Hypertonic stress promotes autophagy and microtubule-dependent autophagosomal clusters. Autophagy 2013; 9:550-67. [PMID: 23380587 DOI: 10.4161/auto.23662] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Osmotic homeostasis is fundamental for most cells, which face recurrent alterations of environmental osmolality that challenge cell viability. Protein damage is a consequence of hypertonic stress, but whether autophagy contributes to the osmoprotective response is unknown. Here, we investigated the possible implications of autophagy and microtubule organization on the response to hypertonic stress. We show that hypertonicity rapidly induced long-lived protein degradation, LC3-II generation and Ptdlns3K-dependent formation of LC3- and ATG12-positive puncta. Lysosomotropic agents chloroquine and bafilomycin A 1, but not nutrient deprivation or rapamycin treatment, further increased LC3-II generation, as well as ATG12-positive puncta, indicating that hypertonic stress increases autophagic flux. Autophagy induction upon hypertonic stress enhanced cell survival since cell death was increased by ATG12 siRNA-mediated knockdown and reduced by rapamycin. We additionally showed that hypertonicity induces fast reorganization of microtubule networks, which is associated with strong reorganization of microtubules at centrosomes and fragmentation of Golgi ribbons. Microtubule remodeling was associated with pericentrosomal clustering of ATG12-positive autolysosomes that colocalized with SQSTM1/p62 and ubiquitin, indicating that autophagy induced by hypertonic stress is at least partly selective. Efficient autophagy by hypertonic stress required microtubule remodeling and was DYNC/dynein-dependent as autophagosome clustering was enhanced by paclitaxel-induced microtubule stabilization and was reduced by nocodazole-induced tubulin depolymerization as well as chemical (EHNA) or genetic [DCTN2/dynactin 2 (p50) overexpression] interference of DYNC activity. The data document a general and hitherto overlooked mechanism, where autophagy and microtubule remodeling play prominent roles in the osmoprotective response.
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Affiliation(s)
- Paula Nunes
- Department of Cellular Physiology and Metabolism, University of Geneva, Geneva, Switzerland
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193
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Lionaki E, Markaki M, Tavernarakis N. Autophagy and ageing: insights from invertebrate model organisms. Ageing Res Rev 2013; 12:413-28. [PMID: 22634332 DOI: 10.1016/j.arr.2012.05.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 05/03/2012] [Accepted: 05/08/2012] [Indexed: 12/11/2022]
Abstract
Ageing in diverse species ranging from yeast to humans is associated with the gradual, lifelong accumulation of molecular and cellular damage. Autophagy, a conserved lysosomal, self-destructive process involved in protein and organelle degradation, plays an essential role in both cellular and whole-animal homeostasis. Accumulating evidence now indicates that autophagic degradation declines with age and this gradual reduction of autophagy might have a causative role in the functional deterioration of biological systems during ageing. Indeed, loss of autophagy gene function significantly influences longevity. Moreover, genetic or pharmacological manipulations that extend lifespan in model organisms often activate autophagy. Interestingly, conserved signalling pathways and environmental factors that regulate ageing, such as the insulin/IGF-1 signalling pathway and oxidative stress response pathways converge on autophagy. In this article, we survey recent findings in invertebrates that contribute to advance our understanding of the molecular links between autophagy and the regulation of ageing. In addition, we consider related mechanisms in other organisms and discuss their similarities and idiosyncratic features in a comparative manner.
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194
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Abstract
Compartmentalization is essential in the eukaryotic cell and this is most often achieved by sequestering specific components that perform a related function in a membrane-bound organelle. To function normally these organelles must transiently fuse with other compartments in order to transfer protein and lipid that is needed for them to function. These events must be highly coordinated otherwise non-specific fusion could occur leading to loss of compartment identity and function. The autophagosome is a specialized membrane compartment that delivers cytosolic components to the lysosome for degradation. Likewise, this delivery is coordinated so that only when the autophagosome is fully formed is it imparted with the information to allow it to specifically fuse with the endocytic system and deliver its contents to the lysosome. In the present chapter, I discuss our current understanding of how this happens.
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Affiliation(s)
- Ian G Ganley
- MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K
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195
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Abstract
Autophagy, or autophagocytosis, is a selective intracellular degradative process involving the cell's own lysosomal apparatus. An essential component in cell development, homeostasis, repair and resistance to stress, autophagy may result in either cell death or survival. The targeted region of the cell is sequestered within a membrane structure, the autophagosome, for regulation of the catabolic process. A key factor in both autophagosome formation and autophagosome maturation is a protein encoded by the ultraviolet irradiation resistance-associated gene (UVRAG). Conversely, the serine/threonine-specific protein kinase B (PKB, also known as Akt), which regulates survival in various cancers, inhibits autophagy through mTOR activation. We found that Akt1 may also directly inhibit autophagy by down-regulating UVRAG both in a 293T transient transfection system and breast cancer cells stably expressing Akt1. The UVRAG with mutations at putative Akt1-phosphorylation sites were still inhibited by Akt1, and dominant-negative Akt1 also inhibited UVRAG expression, suggesting that Akt1 down-regulates UVRAG by a kinase activity-independent mechanism. We showed that Akt1 overexpression in MDA-MB-231 breast cancer cells down-regulated UVRAG transcription. Cells over-expressing Akt1 were more resistant than control cells to ultraviolet light-induced autophagy and exhibited the associated reduction in cell viability. Levels of the autophagosome indicator protein LC3B-II and mRFP-GFP-LC3 were reduced in cells that over-expressing Akt1. Inhibiting Akt1 by siRNA or reintroducing UVRAG gene rescued the level of LC3B-II in UV-irradiation. Altogether, these data suggest that Akt1 may inhibit autophagy by decreasing UVRAG expression, which also sensitizes cancer cells to UV irradiation.
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196
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Dynein mediates the localization and activation of mTOR in normal and human cytomegalovirus-infected cells. Genes Dev 2012; 26:2015-26. [PMID: 22987636 DOI: 10.1101/gad.196147.112] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Activation of stress signaling pathways normally leads to inhibition of the mammalian target of rapamycin complex 1 (mTORC1); however, human cytomegalovirus (HCMV) infection maintains mTORC1 activity in the presence of numerous types of stress. We previously demonstrated that HCMV infection maintains mTORC1 activity during amino acid deprivation through a Ras-related GTP-binding (Rag) protein-independent mechanism. This depends on the colocalization of mTOR and its activator, Rheb (Ras homology enriched in brain)-GTP, to a perinuclear position that corresponds to the viral cytoplasmic assembly compartment (AC). The data presented here show that the HCMV-induced, amino acid depletion-resistant perinuclear localization and activation of mTORC1 occurs as early as 8 h post-infection, prior to AC formation. We show that the molecular motor dynein is required for perinuclear localization of mTORC1 in both uninfected and HCMV-infected cells. Association between dynein and mTOR is shown by coimmunoprecipitation, and inhibition of dynein function using RNAi or the small molecule inhibitor ciliobrevin A inhibits mTORC1 activity in both uninfected and HCMV-infected cells. The data suggest that mTORC1 activation requires dynein-dependent transport to a position in the cell where it can be activated. Thus, the HCMV commandeers a cellular dynein-dependent mTORC1 activation mechanism to maintain stress-resistant mTORC1 activity during infection and to form the AC.
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197
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Abstract
Autophagy is a membrane trafficking pathway responsible for the breakdown of unwanted intracellular materials and crucial for the cell healthiness and survival. In the autophagic flux, various dynamic membrane rearrangements occurs starting with the elongation of the phagophore and its closure to build an autophagosome and ending with its fusion with late endosomes and lysosomes to form an autolysosome. Although Ca2+ is a well established regulator of membrane fusion events, little is known about its role in these processes during autophagy. Recent studies, based on proteomic analyses of lysosomal membranes, have provided new insights into this field of study. Thus, the levels on lysosomal membranes of annexin A1, annexin A5 and copine 1, three proteins that bind to phospholipid membranes in a Ca2+-dependent manner, increased under nutrient deprivation, a condition that promotes autophagic degradation. In addition, two different studies showed that annexin A5 and annexin A1 are involved in autophagosome maturation. Here, we discuss the molecular mechanisms by which the fusion of autophagosomes with endosomes and lysosomes could be regulated by these three proteins and Ca2+.
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Affiliation(s)
- Ghita Ghislat
- Laboratorio de Biología Celular; Centro de Investigación Príncipe; Valencia, Spain
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198
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Abstract
Autophagy is implicated in the pathogenesis of major neurodegenerative disorders although concepts about how it influences these diseases are still evolving. Once proposed to be mainly an alternative cell death pathway, autophagy is now widely viewed as both a vital homeostatic mechanism in healthy cells and as an important cytoprotective response mobilized in the face of aging- and disease-related metabolic challenges. In Alzheimer's, Parkinson's, Huntington's, amyotrophic lateral sclerosis, and other diseases, impairment at different stages of autophagy leads to the buildup of pathogenic proteins and damaged organelles, while defeating autophagy's crucial prosurvival and antiapoptotic effects on neurons. The differences in the location of defects within the autophagy pathway and their molecular basis influence the pattern and pace of neuronal cell death in the various neurological disorders. Future therapeutic strategies for these disorders will be guided in part by understanding the manifold impact of autophagy disruption on neurodegenerative diseases.
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199
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Rubinsztein DC, Codogno P, Levine B. Autophagy modulation as a potential therapeutic target for diverse diseases. Nat Rev Drug Discov 2012; 11:709-30. [PMID: 22935804 PMCID: PMC3518431 DOI: 10.1038/nrd3802] [Citation(s) in RCA: 1160] [Impact Index Per Article: 96.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Autophagy is an essential, conserved lysosomal degradation pathway that controls the quality of the cytoplasm by eliminating protein aggregates and damaged organelles. It begins when double-membraned autophagosomes engulf portions of the cytoplasm, which is followed by fusion of these vesicles with lysosomes and degradation of the autophagic contents. In addition to its vital homeostatic role, this degradation pathway is involved in various human disorders, including metabolic conditions, neurodegenerative diseases, cancers and infectious diseases. This article provides an overview of the mechanisms and regulation of autophagy, the role of this pathway in disease and strategies for therapeutic modulation.
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Affiliation(s)
- David C. Rubinsztein
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Hills Road, Cambridge CB2 OXY, UK
| | - Patrice Codogno
- Faculté de Pharmacie, Institut National de la Santé et de la Recherche Médicale (INSERM) UMR984, Université Paris-Sud 11, 5 rue Jean-Baptiste Clément, 92296 Châtenay-Malabry, France
| | - Beth Levine
- Departments of Internal Medicine and Microbiology, Center for Autophagy Research, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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200
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Abstract
Autophagy is an intracellular lysosomal degradation process, which plays an important role in cell growth and development, and keeping cellular homeostasis in all eukaryotes. Autophagy has multiple physiological functions, including protein degradation, organelle turnover and response to stress. Emerging evidences support the notion that dysregulation of autophagy might be critical for pathogenesis of amyotrophic lateral sclerosis (ALS). The autophagy dysregulation in motor neurons of ALS may occur in different steps of the autophagic process. Recent studies have shown that two ALS associated proteins, TDP-43 and superoxide dismutase 1 (SOD1), are involved in the abnormal autophagy regulation. Furthermore, it is reported that several genetic mutations in ALS disturb the autophagic process in the motor neurons. This review will provide new evidence of autophagy dysregulation as a critical pathogenic process leading to ALS, and will discuss the prospect of future therapeutic targets using autophagic regulation to treat this disease.
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Affiliation(s)
- Sheng Chen
- Department of Neurology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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