701
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Bingol B, Sheng M. Deconstruction for reconstruction: the role of proteolysis in neural plasticity and disease. Neuron 2011; 69:22-32. [PMID: 21220096 DOI: 10.1016/j.neuron.2010.11.006] [Citation(s) in RCA: 225] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/11/2010] [Indexed: 12/17/2022]
Abstract
The brain changes in response to experience and altered environment. This neural plasticity is largely mediated by morphological and functional modification of synapses, a process that depends on both synthesis and degradation of proteins. It is now clear that regulated proteolysis plays a critical role in the remodeling of synapses, learning and memory, and neurodevelopment. Here, we highlight the mechanisms and functions of proteolysis in synaptic plasticity and discuss its alteration in disease states.
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Affiliation(s)
- Baris Bingol
- Department of Neuroscience, Genentech, Inc., South San Francisco, CA 94080, USA
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702
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Munoz-Sanjuan I, Bates GP. The importance of integrating basic and clinical research toward the development of new therapies for Huntington disease. J Clin Invest 2011; 121:476-83. [PMID: 21285520 DOI: 10.1172/jci45364] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Huntington disease (HD) is a dominantly inherited neurodegenerative disorder that results from expansion of the polyglutamine repeat in the huntingtin (HTT) gene. There are currently no effective treatments for this devastating disease. Given its monogenic nature, disease modification therapies for HD should be theoretically feasible. Currently, pharmacological therapies aimed at disease modification by altering levels of HTT protein are in late-stage preclinical development. Here, we review current efforts to develop new treatments for HD based on our current understanding of HTT function and the main pathological mechanisms. We emphasize the need to enhance translational efforts and highlight the importance of aligning the clinical and basic research communities to validate existing hypotheses in clinical studies. Human and animal therapeutic trials are presented with an emphasis on cellular and molecular mechanisms relevant to disease progression.
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Affiliation(s)
- Ignacio Munoz-Sanjuan
- CHDI Management Inc./CHDI Foundation Inc., 6080 Center Drive, Suite 100, Los Angeles, California 90046, USA.
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703
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Association of DAPK1 genetic variations with Alzheimer's disease in Han Chinese. Brain Res 2011; 1374:129-33. [DOI: 10.1016/j.brainres.2010.12.036] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 12/09/2010] [Accepted: 12/10/2010] [Indexed: 11/18/2022]
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704
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Ofengeim D, Miyawaki T, Suzanne zukin R. Molecular and Cellular Mechanisms of Ischemia-Induced Neuronal Death. Stroke 2011. [DOI: 10.1016/b978-1-4160-5478-8.10006-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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705
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Haigis MC, Yankner BA. The aging stress response. Mol Cell 2010; 40:333-44. [PMID: 20965426 DOI: 10.1016/j.molcel.2010.10.002] [Citation(s) in RCA: 371] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Revised: 09/28/2010] [Accepted: 10/01/2010] [Indexed: 12/25/2022]
Abstract
Aging is the outcome of a balance between damage and repair. The rate of aging and the appearance of age-related pathology are modulated by stress response and repair pathways that gradually decline, including the proteostasis and DNA damage repair networks and mitochondrial respiratory metabolism. Highly conserved insulin/IGF-1, TOR, and sirtuin signaling pathways in turn control these critical cellular responses. The coordinated action of these signaling pathways maintains cellular and organismal homeostasis in the face of external perturbations, such as changes in nutrient availability, temperature, and oxygen level, as well as internal perturbations, such as protein misfolding and DNA damage. Studies in model organisms suggest that changes in signaling can augment these critical stress response systems, increasing life span and reducing age-related pathology. The systems biology of stress response signaling thus provides a new approach to the understanding and potential treatment of age-related diseases.
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Affiliation(s)
- Marcia C Haigis
- Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.
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706
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Wong E, Cuervo AM. Integration of clearance mechanisms: the proteasome and autophagy. Cold Spring Harb Perspect Biol 2010; 2:a006734. [PMID: 21068151 DOI: 10.1101/cshperspect.a006734] [Citation(s) in RCA: 228] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Cells maintain a healthy proteome through continuous evaluation of the quality of each of their proteins. Quality control requires the coordinated action of chaperones and proteolytic systems. Chaperones identify abnormal or unstable conformations in proteins and often assist them to regain stability. However, if repair is not possible, the aberrant protein is eliminated from the cellular cytosol to prevent undesired interactions with other proteins or its organization into toxic multimeric complexes. Autophagy and the ubiquitin/proteasome system mediate the complete degradation of abnormal protein products. In this article, we describe each of these proteolytic systems and their contribution to cellular quality control. We also comment on the cellular consequences resulting from the dysfunction of these systems in common human protein conformational disorders and provide an overview on current therapeutic interventions based on the modulation of the proteolytic systems.
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Affiliation(s)
- Esther Wong
- Department of Developmental and Molecular Biology, Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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707
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Pimplikar SW, Nixon RA, Robakis NK, Shen J, Tsai LH. Amyloid-independent mechanisms in Alzheimer's disease pathogenesis. J Neurosci 2010; 30:14946-54. [PMID: 21068297 PMCID: PMC3426835 DOI: 10.1523/jneurosci.4305-10.2010] [Citation(s) in RCA: 212] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Revised: 09/15/2010] [Accepted: 09/16/2010] [Indexed: 12/17/2022] Open
Abstract
Despite the progress of the past two decades, the cause of Alzheimer's disease (AD) and effective treatments against it remain elusive. The hypothesis that amyloid-β (Aβ) peptides are the primary causative agents of AD retains significant support among researchers. Nonetheless, a growing body of evidence shows that Aβ peptides are unlikely to be the sole factor in AD etiology. Evidence that Aβ/amyloid-independent factors, including the actions of AD-related genes, also contribute significantly to AD pathogenesis was presented in a symposium at the 2010 Annual Meeting of the Society for Neuroscience. Here we summarize the studies showing how amyloid-independent mechanisms cause defective endo-lysosomal trafficking, altered intracellular signaling cascades, or impaired neurotransmitter release and contribute to synaptic dysfunction and/or neurodegeneration, leading to dementia in AD. A view of AD pathogenesis that encompasses both the amyloid-dependent and -independent mechanisms will help fill the gaps in our knowledge and reconcile the findings that cannot be explained solely by the amyloid hypothesis.
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Affiliation(s)
- Sanjay W Pimplikar
- Department of Neuroscience, Lerner Research Institute, Cleveland Clinic, and Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio 44195, USA.
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708
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Fabri M, Realegeno SE, Jo EK, Modlin RL. Role of autophagy in the host response to microbial infection and potential for therapy. Curr Opin Immunol 2010; 23:65-70. [PMID: 21071195 DOI: 10.1016/j.coi.2010.10.010] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Accepted: 10/15/2010] [Indexed: 12/21/2022]
Abstract
There is compelling evidence demonstrating a key role for autophagy in host defense against microbial infections. Induction and regulation of autophagy involves complex pathways including signaling molecules that have widespread roles in cell biological functions. For example, inhibiting mTOR by rapamycin, the most widely used chemical approach to induce autophagy, can also result in immunosupression. Nevertheless, advances in our understanding of autophagy provide a new opportunity to modulate host cellular responses as a potential therapeutic strategy to combat microbial infections in humans.
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Affiliation(s)
- Mario Fabri
- Division of Dermatology, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles, CA, USA.
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709
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Shen X, Ying H, Qiu Y, Park JS, Shyam R, Chi ZL, Iwata T, Yue BYJT. Processing of optineurin in neuronal cells. J Biol Chem 2010; 286:3618-29. [PMID: 21059646 DOI: 10.1074/jbc.m110.175810] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Optineurin is a gene linked to amyotrophic lateral sclerosis, Paget disease of bone, and glaucoma, a major blinding disease. Mutations such as E50K were identified in glaucoma patients. We investigated herein the involvement of ubiquitin-proteasome pathway (UPP) and autophagy, two major routes for protein clearance, in processing of optineurin in a retinal ganglion cell model line RGC5 and neuronal PC12 cells. It was found that the endogenous optineurin level in neuronal cells was increased by treatment of proteasomal inhibitor but not by autophagic and lysosomal inhibitors. Multiple bands immunoreactive to anti-ubiquitin were seen in the optineurin pulldown, indicating that optineurin was ubiquitinated. In cells overexpressing wild type and E50K optineurin, the level of the proteasome regulatory β5 subunit (PSMB5, indicative of proteasome activity) was reduced, whereas that for autophagy marker microtubule-associated protein 1 light chain 3 was enhanced compared with controls. Autophagosome formation was detected by electron microscopy. The foci formed after optineurin transfection were increased upon treatment of an autophagic inhibitor but were decreased by treatment of an inducer, rapamycin. Moreover, the level of optineurin-triggered apoptosis was reduced by rapamycin. This study thus provides compelling evidence that in a normal homeostatic situation, the turnover of endogenous optineurin involves mainly UPP. When optineurin is up-regulated or mutated, the UPP function is compromised, and autophagy comes into play. A decreased PSMB5 level and an induced autophagy were also demonstrated in vivo in retinal ganglion cells of E50K transgenic mice, validating and making relevant the in vitro findings.
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Affiliation(s)
- Xiang Shen
- Department of Ophthalmology and Visual Sciences, College of Medicine, University of Illinois, Chicago, Illinois 60612, USA
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710
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Williamson WR, Hiesinger PR. On the role of v-ATPase V0a1-dependent degradation in Alzheimer disease. Commun Integr Biol 2010; 3:604-7. [PMID: 21331254 DOI: 10.4161/cib.3.6.13364] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Accepted: 08/19/2010] [Indexed: 12/21/2022] Open
Abstract
Defective autophagy and lysosomal degradation are hallmarks of numerous neurodegenerative disorders. Vesicular ATPases are intracellular proton pumps that acidify autophagosomes and lysosomes. V0a1 is a key component of the v-ATPase that is only required in neurons in Drosophila melanogaster. We have recently shown that loss of V0a1 in Drosophila photoreceptor neurons leads to slow, adult-onset degeneration.1 Concurrently, Lee et al.2 reported that V0a1 fails to localize to lysosomal compartments in cells from Presenilin 1 knock-out cells. Together these two reports suggest that a neuronal V0a1-dependent degradation mechanism may be causally linked to Alzheimer pathology. Indeed, we now show that loss of V0a1 makes Drosophila neurons more susceptible to insult with human Alzheimer-related neurotoxic Aβ and tau proteins. Furthermore, we discuss the potential significance of the discovery of the neuron-specific degradation mechanism in Drosophila for intracellular degradation defects in Alzheimer Disease.
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Affiliation(s)
- W Ryan Williamson
- Department of Physiology and Green Center for Systems Biology; University of Texas Southwestern Medical Center at Dallas; Dallas, TX USA
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711
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Mariño G, Madeo F, Kroemer G. Autophagy for tissue homeostasis and neuroprotection. Curr Opin Cell Biol 2010; 23:198-206. [PMID: 21030235 DOI: 10.1016/j.ceb.2010.10.001] [Citation(s) in RCA: 156] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Accepted: 10/04/2010] [Indexed: 11/20/2022]
Abstract
Although autophagy has frequently been viewed as a cell death mechanism in the mammalian system, it is now considered as indispensable for the homeostasis of cells, tissues, and organisms. Basal or stress-induced autophagy plays essential and diverse roles in a variety of tissues, due to its cytoprotective properties. In this review, we briefly discuss the different homeostatic functions of autophagy that have been finely dissected in mammals through the generation and characterization of animal models with tissue-specific autophagic alterations. In addition, and given the importance of constitutive autophagy in neuronal tissues, we describe in more detail the specific roles of autophagy in the central nervous system (CNS). Finally, we discuss the contribution of autophagy malfunctions to the development of several common neurological disorders and the potential benefits of pharmacologically induced autophagy for the avoidance of neurodegeneration.
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712
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Abstract
Late endosome-lysosome trafficking plays a key role in regulating cell surface signaling and degradation of intracellular components by autophagy. New work by Cai and coworkers in this issue of Neuron provides evidence that snapin regulates the recruitment of late endosomes to the dynein motor complex for retrograde trafficking along microtubules and maturation of lysosomes.
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713
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Synaptic dysfunction in genetic models of Parkinson's disease: a role for autophagy? Neurobiol Dis 2010; 43:60-7. [PMID: 20969957 DOI: 10.1016/j.nbd.2010.10.011] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Revised: 10/08/2010] [Accepted: 10/13/2010] [Indexed: 11/21/2022] Open
Abstract
The past decade in Parkinson's disease (PD) research has been punctuated by numerous advances in understanding genetic factors that contribute to the disease. Common to most of the genetic models of Parkinsonian neurodegeneration are pathologic mechanisms of mitochondrial dysfunction, secretory vesicle dysfunction and oxidative stress that likely trigger common cell death mechanisms. Whereas presynaptic function is implicated in the function/dysfunction of α-synuclein, the first gene shown to contribute to PD, synaptic function has not comprised a major focus in most other genetic models. However, recent advances in understanding the impact of mutations in parkin and LRRK2 have also yielded insights into synaptic dysfunction as a possible early pathogenic mechanism. Autophagy is a common neuronal response in each of these genetic models of PD, participating in the clearance of protein aggregates and injured mitochondria. However, the potential consequences of autophagy upregulation on synaptic structure and function remain unknown. In this review, we discuss the evidence that supports a role for synaptic dysfunction in the neurodegenerative cascade in PD, and highlight unresolved questions concerning a potential role for autophagy in either pathological or compensatory synaptic remodeling. This article is part of a Special Issue entitled "Autophagy and protein degradation in neurological diseases."
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714
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Banerjee R, Beal MF, Thomas B. Autophagy in neurodegenerative disorders: pathogenic roles and therapeutic implications. Trends Neurosci 2010; 33:541-9. [PMID: 20947179 DOI: 10.1016/j.tins.2010.09.001] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Revised: 09/07/2010] [Accepted: 09/07/2010] [Indexed: 12/19/2022]
Abstract
Autophagy is a highly conserved intracellular pathway involved in the elimination of proteins and organelles by lysosomes. Known originally as an adaptive response to nutrient deprivation in mitotic cells, autophagy is now recognized as an arbiter of neuronal survival and death decisions in neurodegenerative diseases. Studies using postmortem human tissue, genetic and toxin-induced animal and cellular models indicate that many of the etiological factors associated with neurodegenerative disorders can perturb the autophagy process. Emerging data support the view that dysregulation of autophagy might play a critical role in the pathogenesis of neurodegenerative disorders. In this review, we highlight the pathophysiological roles of autophagy and its potential therapeutic implications in debilitating neurodegenerative disorders, including amyotrophic lateral sclerosis and Alzheimer's, Parkinson's and Huntington's diseases.
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Affiliation(s)
- Rebecca Banerjee
- Department of Neurology and Neuroscience, Weill Medical College of Cornell University, 525 East 68(th) Street, A-501, New York, NY 10065
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715
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Batlevi Y, La Spada AR. Mitochondrial autophagy in neural function, neurodegenerative disease, neuron cell death, and aging. Neurobiol Dis 2010; 43:46-51. [PMID: 20887789 DOI: 10.1016/j.nbd.2010.09.009] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Revised: 09/08/2010] [Accepted: 09/19/2010] [Indexed: 11/26/2022] Open
Abstract
Macroautophagy is a cellular process by which cytosolic components and organelles are degraded in double-membrane bound structures upon fusion with lysosomes. A pathway for selective degradation of mitochondria by autophagy, known as mitophagy, has been described, and is of particular importance to neurons, because of the constant need for high levels of energy production in this cell type. Although much remains to be learned about mitophagy, it appears that the regulation of mitophagy shares key steps with the macroautophagy pathway, while exhibiting distinct regulatory steps specific for mitochondrial autophagic turnover. Mitophagy is emerging as an important pathway in neurodegenerative disease, and has been linked to the pathogenesis of Parkinson's disease through the study of recessively inherited forms of this disorder, involving PINK1 and Parkin. Recent work indicates that PINK1 and Parkin together maintain mitochondrial quality control by regulating mitophagy. In the Purkinje cell degeneration (pcd) mouse, altered mitophagy may contribute to the dramatic neuron cell death observed in the cerebellum, suggesting that over-active mitophagy or insufficient mitophagy can both be deleterious. Finally, mitophagy has been linked to aging, as impaired macroautophagy over time promotes mitochondrial dysfunction associated with the aging process. Understanding the role of mitophagy in neural function, neurodegenerative disease, and aging represents an essential goal for future research in the autophagy field. This article is part of a Special Issue entitled "Autophagy and protein degradation in neurological diseases."
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Affiliation(s)
- Yakup Batlevi
- Division of Genetics, Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093-0642, USA
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