1
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Alquezar C, Schoch KM, Geier EG, Ramos EM, Scrivo A, Li KH, Argouarch AR, Mlynarski EE, Dombroski B, DeTure M, Dickson DW, Yokoyama JS, Cuervo AM, Burlingame AL, Schellenberg GD, Miller TM, Miller BL, Kao AW. TSC1 loss increases risk for tauopathy by inducing tau acetylation and preventing tau clearance via chaperone-mediated autophagy. Sci Adv 2021; 7:eabg3897. [PMID: 34739309 PMCID: PMC8570595 DOI: 10.1126/sciadv.abg3897] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Accepted: 09/17/2021] [Indexed: 05/20/2023]
Abstract
Age-associated neurodegenerative disorders demonstrating tau-laden intracellular inclusions are known as tauopathies. We previously linked a loss-of-function mutation in the TSC1 gene to tau accumulation and frontotemporal lobar degeneration. Now, we have identified genetic variants in TSC1 that decrease TSC1/hamartin levels and predispose to tauopathies such as Alzheimer’s disease and progressive supranuclear palsy. Cellular and murine models of TSC1 haploinsufficiency, as well as human brains carrying a TSC1 risk variant, accumulated tau protein that exhibited aberrant acetylation. This acetylation hindered tau degradation via chaperone-mediated autophagy, thereby leading to its accumulation. Aberrant tau acetylation in TSC1 haploinsufficiency resulted from the dysregulation of both p300 acetyltransferase and SIRT1 deacetylase. Pharmacological modulation of either enzyme restored tau levels. This study substantiates TSC1 as a novel tauopathy risk gene and includes TSC1 haploinsufficiency as a genetic model for tauopathies. In addition, these findings promote tau acetylation as a rational target for tauopathy therapeutics and diagnostic.
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Affiliation(s)
- Carolina Alquezar
- UCSF Memory and Aging Center, Department of Neurology, University of California San Francisco, San Francisco, CA 94158, USA
| | - Kathleen M. Schoch
- Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Ethan G. Geier
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA 94143, USA
| | - Eliana Marisa Ramos
- Department of Neurology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Aurora Scrivo
- Institute for Aging Research, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Kathy H. Li
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA 94158, USA
| | - Andrea R. Argouarch
- UCSF Memory and Aging Center, Department of Neurology, University of California San Francisco, San Francisco, CA 94158, USA
| | - Elisabeth E. Mlynarski
- Department of Pathology and Laboratory Medicine, Penn Neurodegeneration Genomics Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-4238, USA
| | - Beth Dombroski
- Department of Pathology and Laboratory Medicine, Penn Neurodegeneration Genomics Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-4238, USA
| | - Michael DeTure
- Department of Neuroscience, The Mayo Clinic Florida, 4500 San Pablo Road, Jacksonville, FL 32224, USA
| | - Dennis W. Dickson
- Department of Neuroscience, The Mayo Clinic Florida, 4500 San Pablo Road, Jacksonville, FL 32224, USA
| | - Jennifer S. Yokoyama
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA 94143, USA
| | - Ana M. Cuervo
- Institute for Aging Research, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Alma L. Burlingame
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA 94158, USA
| | - Gerard D. Schellenberg
- Department of Pathology and Laboratory Medicine, Penn Neurodegeneration Genomics Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-4238, USA
| | - Timothy M. Miller
- Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Bruce L. Miller
- UCSF Memory and Aging Center, Department of Neurology, University of California San Francisco, San Francisco, CA 94158, USA
| | - Aimee W. Kao
- UCSF Memory and Aging Center, Department of Neurology, University of California San Francisco, San Francisco, CA 94158, USA
- Corresponding author.
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2
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Dong S, Wang Q, Kao YR, Diaz A, Tasset I, Kaushik S, Thiruthuvanathan V, Zintiridou A, Nieves E, Dzieciatkowska M, Reisz JA, Gavathiotis E, D’Alessandro A, Will B, Cuervo AM. Chaperone-mediated autophagy sustains haematopoietic stem-cell function. Nature 2021; 591:117-123. [PMID: 33442062 PMCID: PMC8428053 DOI: 10.1038/s41586-020-03129-z] [Citation(s) in RCA: 123] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Accepted: 12/09/2020] [Indexed: 01/29/2023]
Abstract
The activation of mostly quiescent haematopoietic stem cells (HSCs) is a prerequisite for life-long production of blood cells1. This process requires major molecular adaptations to allow HSCs to meet the regulatory and metabolic requirements for cell division2-4. The mechanisms that govern cellular reprograming upon stem-cell activation, and the subsequent return of stem cells to quiescence, have not been fully characterized. Here we show that chaperone-mediated autophagy (CMA)5, a selective form of lysosomal protein degradation, is involved in sustaining HSC function in adult mice. CMA is required for protein quality control in stem cells and for the upregulation of fatty acid metabolism upon HSC activation. We find that CMA activity in HSCs decreases with age and show that genetic or pharmacological activation of CMA can restore the functionality of old mouse and human HSCs. Together, our findings provide mechanistic insights into a role for CMA in sustaining quality control, appropriate energetics and overall long-term HSC function. Our work suggests that CMA may be a promising therapeutic target for enhancing HSC function in conditions such as ageing or stem-cell transplantation.
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Affiliation(s)
- S Dong
- Department of Development and Molecular Biology, Albert Einstein College of Medicine, NY, USA;,Institute for Aging Studies, Albert Einstein College of Medicine, NY, USA
| | - Q Wang
- Department of Cell Biology, Albert Einstein College of Medicine, NY, USA
| | - YR Kao
- Department of Cell Biology, Albert Einstein College of Medicine, NY, USA
| | - A Diaz
- Department of Development and Molecular Biology, Albert Einstein College of Medicine, NY, USA;,Institute for Aging Studies, Albert Einstein College of Medicine, NY, USA
| | - I Tasset
- Department of Development and Molecular Biology, Albert Einstein College of Medicine, NY, USA;,Institute for Aging Studies, Albert Einstein College of Medicine, NY, USA
| | - S Kaushik
- Department of Development and Molecular Biology, Albert Einstein College of Medicine, NY, USA;,Institute for Aging Studies, Albert Einstein College of Medicine, NY, USA
| | - V Thiruthuvanathan
- Department of Cell Biology, Albert Einstein College of Medicine, NY, USA
| | - A Zintiridou
- Department of Cell Biology, Albert Einstein College of Medicine, NY, USA
| | - E Nieves
- Department of Development and Molecular Biology, Albert Einstein College of Medicine, NY, USA
| | - M Dzieciatkowska
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver – Anschutz Medical Campus, CO, USA
| | - JA Reisz
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver – Anschutz Medical Campus, CO, USA
| | - E Gavathiotis
- Institute for Aging Studies, Albert Einstein College of Medicine, NY, USA;,Department of Biochemistry, Albert Einstein College of Medicine, NY, USA;,Department of Medicine (Oncology), Albert Einstein College of Medicine, NY, USA
| | - A D’Alessandro
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver – Anschutz Medical Campus, CO, USA
| | - B Will
- Institute for Aging Studies, Albert Einstein College of Medicine, NY, USA;,Department of Cell Biology, Albert Einstein College of Medicine, NY, USA;,Department of Medicine (Oncology), Albert Einstein College of Medicine, NY, USA;,Ruth L. and David S. Gottesman Institute for Stem Cell Biology, Albert Einstein College of Medicine, NY, USA,Corresponding authors: Ana Maria Cuervo MD PhD, Dept. Developmental Mol Biol, Institute for Aging Studies, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, Phone: +1 718 430 2689, , Britta Will PhD, Department of Cell Biology, Institute for Aging Studies, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, Phone: +1 718 430 3786,
| | - AM Cuervo
- Department of Development and Molecular Biology, Albert Einstein College of Medicine, NY, USA;,Institute for Aging Studies, Albert Einstein College of Medicine, NY, USA;,Corresponding authors: Ana Maria Cuervo MD PhD, Dept. Developmental Mol Biol, Institute for Aging Studies, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, Phone: +1 718 430 2689, , Britta Will PhD, Department of Cell Biology, Institute for Aging Studies, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, Phone: +1 718 430 3786,
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3
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Zhang X, Ramírez CM, Aryal B, Madrigal-Matute J, Liu X, Diaz A, Torrecilla-Parra M, Suárez Y, Cuervo AM, Sessa WC, Fernández-Hernando C. Cav-1 (Caveolin-1) Deficiency Increases Autophagy in the Endothelium and Attenuates Vascular Inflammation and Atherosclerosis. Arterioscler Thromb Vasc Biol 2020; 40:1510-1522. [PMID: 32349535 PMCID: PMC7253189 DOI: 10.1161/atvbaha.120.314291] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Supplemental Digital Content is available in the text. Endothelial Cav-1 (caveolin-1) expression plays a relevant role during atherogenesis by controlling NO production, vascular inflammation, LDL (low-density lipoprotein) transcytosis, and extracellular matrix remodeling. Additional studies have identified cholesterol-rich membrane domains as important regulators of autophagy by recruiting ATGs (autophagy-related proteins) to the plasma membrane. Here, we investigate how the expression of Cav-1 in the aortic endothelium influences autophagy and whether enhanced autophagy contributes to the atheroprotective phenotype observed in Cav-1–deficient mice.
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Affiliation(s)
- Xinbo Zhang
- From the Vascular Biology and Therapeutics Program (X.Z., C.M.R., B.A., Y.S., W.C.S., C.F.-H.), Yale University School of Medicine, New Haven, CT.,Integrative Cell Signaling and Neurobiology of Metabolism Program, Department of Comparative Medicine and Department of Pathology (X.Z., C.M.R., B.A., Y.S., C.F.-H.), Yale University School of Medicine, New Haven, CT
| | - Cristina M Ramírez
- From the Vascular Biology and Therapeutics Program (X.Z., C.M.R., B.A., Y.S., W.C.S., C.F.-H.), Yale University School of Medicine, New Haven, CT.,Integrative Cell Signaling and Neurobiology of Metabolism Program, Department of Comparative Medicine and Department of Pathology (X.Z., C.M.R., B.A., Y.S., C.F.-H.), Yale University School of Medicine, New Haven, CT.,IMDEA Research Institute of Food and Health Sciences, Madrid, Spain (C.M.R., M.T.-P.)
| | - Binod Aryal
- From the Vascular Biology and Therapeutics Program (X.Z., C.M.R., B.A., Y.S., W.C.S., C.F.-H.), Yale University School of Medicine, New Haven, CT.,Integrative Cell Signaling and Neurobiology of Metabolism Program, Department of Comparative Medicine and Department of Pathology (X.Z., C.M.R., B.A., Y.S., C.F.-H.), Yale University School of Medicine, New Haven, CT
| | - Julio Madrigal-Matute
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY (J.M.-M., A.D., A.M.C.)
| | - Xinran Liu
- Department of Cell Biology (X.L.), Yale University School of Medicine, New Haven, CT
| | - Antonio Diaz
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY (J.M.-M., A.D., A.M.C.)
| | | | - Yajaira Suárez
- From the Vascular Biology and Therapeutics Program (X.Z., C.M.R., B.A., Y.S., W.C.S., C.F.-H.), Yale University School of Medicine, New Haven, CT.,Integrative Cell Signaling and Neurobiology of Metabolism Program, Department of Comparative Medicine and Department of Pathology (X.Z., C.M.R., B.A., Y.S., C.F.-H.), Yale University School of Medicine, New Haven, CT
| | - Ana M Cuervo
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY (J.M.-M., A.D., A.M.C.)
| | - William C Sessa
- From the Vascular Biology and Therapeutics Program (X.Z., C.M.R., B.A., Y.S., W.C.S., C.F.-H.), Yale University School of Medicine, New Haven, CT.,Department of Pharmacology (W.C.S.), Yale University School of Medicine, New Haven, CT
| | - Carlos Fernández-Hernando
- From the Vascular Biology and Therapeutics Program (X.Z., C.M.R., B.A., Y.S., W.C.S., C.F.-H.), Yale University School of Medicine, New Haven, CT.,Integrative Cell Signaling and Neurobiology of Metabolism Program, Department of Comparative Medicine and Department of Pathology (X.Z., C.M.R., B.A., Y.S., C.F.-H.), Yale University School of Medicine, New Haven, CT
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4
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Dong S, Aguirre-Hernandez C, Scrivo A, Eliscovich C, Arias E, Bravo-Cordero JJ, Cuervo AM. Monitoring spatiotemporal changes in chaperone-mediated autophagy in vivo. Nat Commun 2020; 11:645. [PMID: 32005807 PMCID: PMC6994528 DOI: 10.1038/s41467-019-14164-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 12/06/2019] [Indexed: 02/07/2023] Open
Abstract
Autophagy malfunctioning occurs in multiple human disorders, making attractive the idea of chemically modulating it with therapeutic purposes. However, for many types of autophagy, a clear understanding of tissue-specific differences in their activity and regulation is missing because of lack of methods to monitor these processes in vivo. Chaperone-mediated autophagy (CMA) is a selective type of autophagy that until now has only been studied in vitro and not in the tissue context at single cell resolution. Here, we develop a transgenic reporter mouse that allows dynamic measurement of CMA activity in vivo using image-based procedures. We identify previously unknown spatial and temporal differences in CMA activity in multiple organs and in response to stress. We illustrate the versatility of this model for monitoring CMA in live animals, organotypic cultures and cell cultures from these mice, and provide practical examples of multiorgan response to drugs that modulate CMA.
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Affiliation(s)
- S Dong
- Department of Development and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
- Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - C Aguirre-Hernandez
- Department of Development and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
- Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
- Department of Medicine, Division of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, 10029, NY, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, 10029, NY, USA
| | - A Scrivo
- Department of Development and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
- Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - C Eliscovich
- Department of Medicine Marion Liver Research Center, Albert Einstein College of Medicine, Bronx, 10461, NY, USA
| | - E Arias
- Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
- Department of Medicine Marion Liver Research Center, Albert Einstein College of Medicine, Bronx, 10461, NY, USA.
| | - J J Bravo-Cordero
- Department of Medicine, Division of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, 10029, NY, USA.
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, 10029, NY, USA.
| | - A M Cuervo
- Department of Development and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
- Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
- Department of Medicine, Division of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, 10029, NY, USA.
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5
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Guerrero-Ros I, Clement CC, Reynolds CA, Patel B, Santambrogio L, Cuervo AM, Macian F. The negative effect of lipid challenge on autophagy inhibits T cell responses. Autophagy 2019; 16:223-238. [PMID: 30982401 DOI: 10.1080/15548627.2019.1606635] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Obesity is associated with changes in the immune system that significantly hinder its ability to mount efficient immune responses. Previous studies have reported a dysregulation of immune responses caused by lipid challenge; however, the mechanisms underlying that dysregulation are still not completely understood. Autophagy is an essential catabolic process through which cellular components are degraded by the lysosomal machinery. In T cells, autophagy is an actively regulated process necessary to sustain homeostasis and activation. Here, we report that CD4+ T cell responses are inhibited when cells are challenged with increasing concentrations of fatty acids. Furthermore, analysis of T cells from diet-induced obese mice confirms that high lipid load inhibits activation-induced responses in T cells. We have found that autophagy is inhibited in CD4+ T cells exposed in vitro or in vivo to lipid stress, which causes decreased autophagosome formation and degradation. Supporting that inhibition of autophagy caused by high lipid load is a key mechanism that accounts for the effects on T cell function of lipid stress, we found that ATG7 (autophagy-related 7)-deficient T cells, unable to activate autophagy, did not show additional inhibitory effects on their responses to activation when subjected to lipid challenge. Our results indicate, thus, that increased lipid load can dysregulate autophagy and cause defective T cell responses, and suggest that inhibition of autophagy may underlie some of the characteristic obesity-associated defects in the T cell compartment.Abbreviations: ACTB: actin, beta; ATG: autophagy-related; CDKN1B: cyclin-dependent kinase inhibitor 1B; HFD: high-fat diet; IFNG: interferon gamma; IL: interleukin; MAPK1/ERK2: mitogen-activated protein kinase 1; MAPK3/ERK1: mitogen-activated protein kinase 3; MAPK8/JNK: mitogen-activated protein kinase 8; LC3-I: non-conjugated form of MAP1LC3B; LC3-II: phosphatidylethanolamine-conjugated form of MAP1LC3B; MAP1LC3B: microtubule-associated protein 1 light chain 3 beta; MS: mass spectrometry; MTOR: mechanistic target of rapamycin kinase; NFATC2: nuclear factor of activated T cells, cytoplasmic, calcineurin dependent 2; NLRP3: NLR family, pyrin domain containing 3; OA: oleic acid; PI: propidium iodide; ROS: reactive oxygen species; STAT5A: signal transducer and activator of transcription 5A; TCR: T cell receptor; TH1: T helper cell type 1.
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Affiliation(s)
| | - Cristina C Clement
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Cara A Reynolds
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Bindi Patel
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Laura Santambrogio
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA.,Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA.,Institute for Aging Research, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Ana M Cuervo
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY, USA.,Institute for Aging Research, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Fernando Macian
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA.,Institute for Aging Research, Albert Einstein College of Medicine, Bronx, NY, USA
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6
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Hernandez I, Luna G, Rauch JN, Reis SA, Giroux M, Karch CM, Boctor D, Sibih YE, Storm NJ, Diaz A, Kaushik S, Zekanowski C, Kang AA, Hinman CR, Cerovac V, Guzman E, Zhou H, Haggarty SJ, Goate AM, Fisher SK, Cuervo AM, Kosik KS. A farnesyltransferase inhibitor activates lysosomes and reduces tau pathology in mice with tauopathy. Sci Transl Med 2019; 11:eaat3005. [PMID: 30918111 PMCID: PMC7961212 DOI: 10.1126/scitranslmed.aat3005] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 08/15/2018] [Accepted: 11/30/2018] [Indexed: 11/02/2022]
Abstract
Tau inclusions are a shared feature of many neurodegenerative diseases, among them frontotemporal dementia caused by tau mutations. Treatment approaches for these conditions include targeting posttranslational modifications of tau proteins, maintaining a steady-state amount of tau, and preventing its tendency to aggregate. We discovered a new regulatory pathway for tau degradation that operates through the farnesylated protein, Rhes, a GTPase in the Ras family. Here, we show that treatment with the farnesyltransferase inhibitor lonafarnib reduced Rhes and decreased brain atrophy, tau inclusions, tau sumoylation, and tau ubiquitination in the rTg4510 mouse model of tauopathy. In addition, lonafarnib treatment attenuated behavioral abnormalities in rTg4510 mice and reduced microgliosis in mouse brain. Direct reduction of Rhes in the rTg4510 mouse by siRNA reproduced the results observed with lonafarnib treatment. The mechanism of lonafarnib action mediated by Rhes to reduce tau pathology was shown to operate through activation of lysosomes. We finally showed in mouse brain and in human induced pluripotent stem cell-derived neurons a normal developmental increase in Rhes that was initially suppressed by tau mutations. The known safety of lonafarnib revealed in human clinical trials for cancer suggests that this drug could be repurposed for treating tauopathies.
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Affiliation(s)
- Israel Hernandez
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Gabriel Luna
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Jennifer N Rauch
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Surya A Reis
- Department of Neurology, Massachusetts General Hospital, Chemical Neurobiology Lab, and Center for Genomic Medicine, Harvard Medical School, Boston, MA 02114, USA
| | - Michel Giroux
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Celeste M Karch
- Department of Psychiatry, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Daniel Boctor
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Youssef E Sibih
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Nadia J Storm
- Department of Developmental and Molecular Biology and Institute for Aging Studies, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Antonio Diaz
- Department of Developmental and Molecular Biology and Institute for Aging Studies, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Susmita Kaushik
- Department of Developmental and Molecular Biology and Institute for Aging Studies, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Cezary Zekanowski
- Laboratory of Neurogenetics, Mossakowski Medical Research Centre, Polish Academy of Sciences, 5 Pawinskiego St., 02-106 Warsaw, Poland
| | - Alexander A Kang
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Cassidy R Hinman
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Vesna Cerovac
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Elmer Guzman
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Honjun Zhou
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Stephen J Haggarty
- Department of Neurology, Massachusetts General Hospital, Chemical Neurobiology Lab, and Center for Genomic Medicine, Harvard Medical School, Boston, MA 02114, USA
| | - Alison M Goate
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Steven K Fisher
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Ana M Cuervo
- Department of Developmental and Molecular Biology and Institute for Aging Studies, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Kenneth S Kosik
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
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7
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Abstract
Chaperone-mediated autophagy (CMA) is a selective type of autophagy whereby a specific subset of intracellular proteins is targeted to the lysosome for degradation. These proteins are identified by a chaperone that targets them to lysosomes. There, they are translocated into the organelle lumen through a lysosomal membrane receptor/translocation complex. CMA plays an important role in maintaining cellular proteostasis by eliminating damaged and altered proteins. CMA also participates in the control of the cellular energetic balance through recycling of amino acids resulting from lysosomal proteolysis of the substrate proteins. Lastly, due to the intrinsic protein selectivity of CMA, this type of autophagy exerts regulatory functions by mediating timely degradation of key cellular proteins that participate in processes such as lipid and glucose metabolism, cell cycle, DNA repair, and cellular reprogramming, among others. Dysfunctional CMA occurs with age and has now been described in a growing list of human pathologies such as metabolic disorders, neurodegeneration, cancer, immunodeficiency, and diabetes. In this chapter, we describe current methodologies to quantitatively analyze CMA activity in different experimental models.
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Affiliation(s)
- Y R Juste
- Department of Developmental and Molecular Biology, Bronx, NY, USA
- Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY, USA
| | - A M Cuervo
- Department of Developmental and Molecular Biology, Bronx, NY, USA.
- Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY, USA.
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8
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Orhon I, Dupont N, Pampliega O, Cuervo AM, Codogno P. Autophagy and regulation of cilia function and assembly. Cell Death Differ 2014; 22:389-97. [PMID: 25361082 DOI: 10.1038/cdd.2014.171] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 09/05/2014] [Accepted: 09/10/2014] [Indexed: 12/21/2022] Open
Abstract
Motile and primary cilia (PC) are microtubule-based structures located at the cell surface of many cell types. Cilia govern cellular functions ranging from motility to integration of mechanical and chemical signaling from the environment. Recent studies highlight the interplay between cilia and autophagy, a conserved cellular process responsible for intracellular degradation. Signaling from the PC recruits the autophagic machinery to trigger autophagosome formation. Conversely, autophagy regulates ciliogenesis by controlling the levels of ciliary proteins. The cross talk between autophagy and ciliated structures is a novel aspect of cell biology with major implications in development, physiology and human pathologies related to defects in cilium function.
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Affiliation(s)
- I Orhon
- 1] INSERM U1151-CNRS UMR 8253, Paris, France [2] Institut Necker Enfants-Malades (INEM), Paris, France [3] Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - N Dupont
- 1] INSERM U1151-CNRS UMR 8253, Paris, France [2] Institut Necker Enfants-Malades (INEM), Paris, France [3] Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - O Pampliega
- 1] Department of Development and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY, USA [2] Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY, USA
| | - A M Cuervo
- 1] Department of Development and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY, USA [2] Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY, USA
| | - P Codogno
- 1] INSERM U1151-CNRS UMR 8253, Paris, France [2] Institut Necker Enfants-Malades (INEM), Paris, France [3] Université Paris Descartes, Sorbonne Paris Cité, Paris, France
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Yang DS, Stavrides P, Saito M, Kumar A, Rodriguez-Navarro JA, Pawlik M, Huo C, Walkley SU, Saito M, Cuervo AM, Nixon RA. Defective macroautophagic turnover of brain lipids in the TgCRND8 Alzheimer mouse model: prevention by correcting lysosomal proteolytic deficits. ACTA ACUST UNITED AC 2014; 137:3300-18. [PMID: 25270989 DOI: 10.1093/brain/awu278] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Autophagy, the major lysosomal pathway for the turnover of intracellular organelles is markedly impaired in neurons in Alzheimer's disease and Alzheimer mouse models. We have previously reported that severe lysosomal and amyloid neuropathology and associated cognitive deficits in the TgCRND8 Alzheimer mouse model can be ameliorated by restoring lysosomal proteolytic capacity and autophagy flux via genetic deletion of the lysosomal protease inhibitor, cystatin B. Here we present evidence that macroautophagy is a significant pathway for lipid turnover, which is defective in TgCRND8 brain where lipids accumulate as membranous structures and lipid droplets within giant neuronal autolysosomes. Levels of multiple lipid species including several sphingolipids (ceramide, ganglioside GM3, GM2, GM1, GD3 and GD1a), cardiolipin, cholesterol and cholesteryl esters are elevated in autophagic vacuole fractions and lysosomes isolated from TgCRND8 brain. Lipids are localized in autophagosomes and autolysosomes by double immunofluorescence analyses in wild-type mice and colocalization is increased in TgCRND8 mice where abnormally abundant GM2 ganglioside-positive granules are detected in neuronal lysosomes. Cystatin B deletion in TgCRND8 significantly reduces the number of GM2-positive granules and lowers the levels of GM2 and GM3 in lysosomes, decreases lipofuscin-related autofluorescence, and eliminates giant lipid-containing autolysosomes while increasing numbers of normal-sized autolysosomes/lysosomes with reduced content of undigested components. These findings have identified macroautophagy as a previously unappreciated route for delivering membrane lipids to lysosomes for turnover, a function that has so far been considered to be mediated exclusively through the endocytic pathway, and revealed that autophagic-lysosomal dysfunction in TgCRND8 brain impedes lysosomal turnover of lipids as well as proteins. The amelioration of lipid accumulation in TgCRND8 by removing cystatin B inhibition on lysosomal proteases suggests that enhancing lysosomal proteolysis improves the overall environment of the lysosome and its clearance functions, which may be possibly relevant to a broader range of lysosomal disorders beyond Alzheimer's disease.
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Affiliation(s)
- Dun-Sheng Yang
- 1 Centre for Dementia Research, Nathan Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA 2 Department of Psychiatry, New York University Langone Medical Centre, 550 First Avenue, New York, NY 10016, USA
| | - Philip Stavrides
- 1 Centre for Dementia Research, Nathan Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA
| | - Mitsuo Saito
- 1 Centre for Dementia Research, Nathan Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA 2 Department of Psychiatry, New York University Langone Medical Centre, 550 First Avenue, New York, NY 10016, USA
| | - Asok Kumar
- 1 Centre for Dementia Research, Nathan Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA 2 Department of Psychiatry, New York University Langone Medical Centre, 550 First Avenue, New York, NY 10016, USA
| | - Jose A Rodriguez-Navarro
- 3 Department of Developmental and Molecular Biology, Institute for Ageing Studies, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - Monika Pawlik
- 1 Centre for Dementia Research, Nathan Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA
| | - Chunfeng Huo
- 1 Centre for Dementia Research, Nathan Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA
| | - Steven U Walkley
- 4 Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - Mariko Saito
- 1 Centre for Dementia Research, Nathan Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA 2 Department of Psychiatry, New York University Langone Medical Centre, 550 First Avenue, New York, NY 10016, USA
| | - Ana M Cuervo
- 3 Department of Developmental and Molecular Biology, Institute for Ageing Studies, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - Ralph A Nixon
- 1 Centre for Dementia Research, Nathan Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA 2 Department of Psychiatry, New York University Langone Medical Centre, 550 First Avenue, New York, NY 10016, USA 5 Department of Cell Biology, New York University Langone Medical Centre, 550 First Avenue, New York, NY 10016, USA
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10
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Yang DS, Stavrides P, Mohan PS, Kaushik S, Kumar A, Ohno M, Schmidt SD, Wesson DW, Bandyopadhyay U, Jiang Y, Pawlik M, Peterhoff CM, Yang AJ, Wilson DA, St George-Hyslop P, Westaway D, Mathews PM, Levy E, Cuervo AM, Nixon RA. Therapeutic effects of remediating autophagy failure in a mouse model of Alzheimer disease by enhancing lysosomal proteolysis. Autophagy 2011; 7:788-9. [PMID: 21464620 DOI: 10.4161/auto.7.7.15596] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The extensive autophagic-lysosomal pathology in Alzheimer disease (AD) brain has revealed a major defect: in the proteolytic clearance of autophagy substrates. Autophagy failure contributes on several levels to AD pathogenesis and has become an important therapeutic target for AD and other neurodegenerative diseases. We recently observed broad therapeutic effects of stimulating autophagic-lysosomal proteolysis in the TgCRND8 mouse model of AD that exhibits defective proteolytic clearance of autophagic substrates, robust intralysosomal amyloid-β peptide (Aβ) accumulation, extracellular β-amyloid deposition and cognitive deficits. By genetically deleting the lysosomal cysteine protease inhibitor, cystatin B (CstB), to selectively restore depressed cathepsin activities, we substantially cleared Aβ, ubiquitinated proteins and other autophagic substrates from autolysosomes/lysosomes and rescued autophagic-lysosomal pathology, as well as reduced total Aβ40/42 levels and extracellular amyloid deposition, highlighting the underappreciated importance of the lysosomal system for Aβ clearance. Most importantly, lysosomal remediation prevented the marked learning and memory deficits in TgCRND8 mice. Our findings underscore the pathogenic significance of autophagic-lysosomal dysfunction in AD and demonstrate the value of reversing this dysfunction as an innovative therapeautic strategy for AD.
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11
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Abstract
Different mechanisms for delivery of intracellular components (proteins and organelles) to lysosomes and late endosomes for degradation co-exist in almost all cells and set the basis for distinct autophagic pathways. Cargo can be sequestered inside double-membrane vesicles (or autophagosomes) and reach the lysosomal compartment upon fusion of these vesicles to lysosomes through macroautophagy. In a different type of autophagy, known as chaperone-mediated autophagy (CMA), single individual soluble proteins can be targeted one by one to the lysosomal membrane and translocated into the lumen for degradation. Direct sequestration of proteins and organelles by invaginations at the lysosomal membrane that pinch off into the lumen has also been proposed. This process, known as microautophagy, remains poorly understood in mammalian cells. In our recent work, we demonstrate the occurrence of both "in bulk" and "selective" internalization of cytosolic components in late endosomes and identify some of the molecular players of this process that we have named endosomalmicroautophagy (e-MI) due to its resemblance to microautophagy.
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Affiliation(s)
- Laura Santambrogio
- Departments of Pathology, Albert Einstein College of Medicine; Bronx, NY, USA.
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12
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Yang DS, Stavrides P, Mohan PS, Kaushik S, Kumar A, Ohno M, Schmidt SD, Wesson D, Bandyopadhyay U, Jiang Y, Pawlik M, Peterhoff CM, Yang AJ, Wilson DA, St George-Hyslop P, Westaway D, Mathews PM, Levy E, Cuervo AM, Nixon RA. Reversal of autophagy dysfunction in the TgCRND8 mouse model of Alzheimer's disease ameliorates amyloid pathologies and memory deficits. ACTA ACUST UNITED AC 2011; 134:258-77. [PMID: 21186265 DOI: 10.1093/brain/awq341] [Citation(s) in RCA: 333] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Autophagy, a major degradative pathway for proteins and organelles, is essential for survival of mature neurons. Extensive autophagic-lysosomal pathology in Alzheimer's disease brain contributes to Alzheimer's disease pathogenesis, although the underlying mechanisms are not well understood. Here, we identified and characterized marked intraneuronal amyloid-β peptide/amyloid and lysosomal system pathology in the Alzheimer's disease mouse model TgCRND8 similar to that previously described in Alzheimer's disease brains. We further establish that the basis for these pathologies involves defective proteolytic clearance of neuronal autophagic substrates including amyloid-β peptide. To establish the pathogenic significance of these abnormalities, we enhanced lysosomal cathepsin activities and rates of autophagic protein turnover in TgCRND8 mice by genetically deleting cystatin B, an endogenous inhibitor of lysosomal cysteine proteases. Cystatin B deletion rescued autophagic-lysosomal pathology, reduced abnormal accumulations of amyloid-β peptide, ubiquitinated proteins and other autophagic substrates within autolysosomes/lysosomes and reduced intraneuronal amyloid-β peptide. The amelioration of lysosomal function in TgCRND8 markedly decreased extracellular amyloid deposition and total brain amyloid-β peptide 40 and 42 levels, and prevented the development of deficits of learning and memory in fear conditioning and olfactory habituation tests. Our findings support the pathogenic significance of autophagic-lysosomal dysfunction in Alzheimer's disease and indicate the potential value of restoring normal autophagy as an innovative therapeutic strategy for Alzheimer's disease.
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Affiliation(s)
- Dun-Sheng Yang
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY 10962, USA.
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13
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Abstract
Autophagy is an essential intracellular process that mediates degradation of intracellular proteins and organelles in lysosomes. Autophagy was initially identified for its role as alternative source of energy when nutrients are scarce but, in recent years, a previously unknown role for this degradative pathway in the cellular response to stress has gained considerable attention. In this review, we focus on the novel findings linking autophagic function with metabolic stress resulting either from proteins or lipids. Proper autophagic activity is required in the cellular defense against proteotoxicity arising in the cytosol and also in the endoplasmic reticulum, where a vast amount of proteins are synthesized and folded. In addition, autophagy contributes to mobilization of intracellular lipid stores and may be central to lipid metabolism in certain cellular conditions. In this review, we focus on the interrelation between autophagy and different types of metabolic stress, specifically the stress resulting from the presence of misbehaving proteins within the cytosol or in the endoplasmic reticulum and the stress following a lipogenic challenge. We also comment on the consequences that chronic exposure to these metabolic stressors could have on autophagic function and on how this effect may underlie the basis of some common metabolic disorders.
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Affiliation(s)
- S Kaushik
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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14
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Abstract
All cells count on precise mechanisms that regulate protein homeostasis to maintain a stable and functional proteome. Alterations in these fine-tuned mechanisms underlie the pathogenesis of severe human diseases including, among others, common neurodegenerative disorders such as Alzheimer's or Parkinson's disease. A progressive deterioration in the ability of cells to preserve the stability of their proteome occurs with age, even in the absence of disease, and it likely contributes to different aspects of "normal" aging. A group of experts in different aspects of the biology of aging met recently to discuss the implications of altered protein homeostasis in aging, the current gaps in our understanding of the mechanisms responsible for proteome maintenance, and future opportunities for discovery in this area. We summarize here some of the key topics and main outcomes of the discussions.
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Affiliation(s)
- Richard I Morimoto
- Department of Developmental and Molecular Biology, Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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15
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Yang DS, Stavrides P, Mohan P, Kumar A, Schmidt SD, Pawlik M, Bandyopadhyay U, Mathews PM, Levy E, Cuervo AM, Nixon RA. P1‐059: Cystatin B deletion in a mouse model of Alzheimer's disease, TgCRND8, ameliorates both autophagic‐lysosomal and amyloid pathologies. Alzheimers Dement 2008. [DOI: 10.1016/j.jalz.2008.05.645] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- Dun-Sheng Yang
- Nathan Kline InstituteOrangeburgNYUSA
- Department of PsychiatryNew York University School of MedicineNew YorkNYUSA
| | | | - Panaiyur Mohan
- Nathan Kline InstituteOrangeburgNYUSA
- Department of PsychiatryNew York University School of MedicineNew YorkNYUSA
| | - Asok Kumar
- Nathan Kline InstituteOrangeburgNYUSA
- Department of PsychiatryNew York University School of MedicineNew YorkNYUSA
| | | | - Monika Pawlik
- Nathan Kline InstituteOrangeburgNYUSA
- Department of PharmacologyNew York University School of MedicineNew YorkNYUSA
| | - Urmi Bandyopadhyay
- Department of Anatomy and Structural BiologyMarion Bessin Liver Research Center, Albert Einstein College of MedicineBronxNYUSA
| | - Paul M. Mathews
- Nathan Kline InstituteOrangeburgNYUSA
- Department of PsychiatryNew York University School of MedicineNew YorkNYUSA
| | - Efrat Levy
- Nathan Kline InstituteOrangeburgNYUSA
- Departments of Psychiatry and PharmacologyNew York University School of MedicineNew YorkNYUSA
| | - Ana M. Cuervo
- Department of Anatomy and Structural BiologyMarion Bessin Liver Research Center, Albert Einstein College of MedicineBronxNYUSA
| | - Ralph A. Nixon
- Nathan Kline InstituteOrangeburgNYUSA
- Departments of Psychiatry and Cell BiologyNew York University School of MedicineNew YorkNYUSA
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16
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Abstract
Chaperone-mediated autophagy (CMA) is the only type of autophagy in mammalian cells able to selectively degrade cytosolic proteins in lysosomes. CMA is maximally activated in response to stressors such as prolonged starvation, exposure to toxic compounds, or oxidative stress. We have found that CMA activity decreases in aging and in some age-related disorders such as Parkinson's disease. Impaired CMA under these conditions may be responsible for the accumulation of damaged proteins inside cells and for their higher vulnerability to stressors. In contrast to other forms of autophagy, where substrates are engulfed or sequestered along with other cytosolic components, CMA substrates are translocated one-by-one across the lysosomal membrane. Changes in the levels/activity of the lysosomal components required for substrate translocation can be used to stimulate CMA activity. However, the most unequivocal method to measure CMA is by directly tracking the translocation of substrate proteins into isolated lysosomes.
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Affiliation(s)
- S Kaushik
- Department of Anatomy and Structural Biology, Marion Bessin Liver Research Center, Albert Einstein College of Medicine, New York, NY, USA
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17
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Sparrow JR, Kim SR, Cuervo AM, Bandhyopadhyayand U. A2E, a pigment of RPE lipofuscin, is generated from the precursor, A2PE by a lysosomal enzyme activity. Adv Exp Med Biol 2008; 613:393-8. [PMID: 18188969 DOI: 10.1007/978-0-387-74904-4_46] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Janet R Sparrow
- Department of Ophthalmology, Columbia University, New York, NY 10032, USA.
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18
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Abstract
Proper removal of oxidized proteins is an important determinant of success when evaluating the ability of cells to handle oxidative stress. The ubiquitin/proteasome system has been considered the main responsible mechanism for the removal of oxidized proteins, as it can discriminate between normal and altered proteins, and selectively target the latter ones for degradation. A possible role for lysosomes, the other major intracellular proteolytic system, in the removal of oxidized proteins has been often refused, mostly on the basis of the lack of selectivity of this system. Although most of the degradation of intracellular components in lysosomes (autophagy) takes place through "in bulk" sequestration of complete cytosolic regions, selective targeting of proteins to lysosomes for their degradation is also possible via what is known as chaperone-mediated autophagy (CMA). In this work, we review recent evidence supporting the participation of CMA in the clearance of oxidized proteins in the forefront of the cellular response to oxidative stress. The consequences of an impairment in CMA activity, observed during aging and in some age-related disorders, are also discussed.
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Affiliation(s)
- S Kaushik
- Department of Anatomy and Structural Biology, Marion Bessin Liver Research Center, Albert Einstein College of Medicine, Ullmann Building room 611D, Bronx, NY 10461, USA
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19
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Yu WH, Kumar A, Peterhoff C, Shapiro Kulnane L, Uchiyama Y, Lamb BT, Cuervo AM, Nixon RA. Autophagic vacuoles are enriched in amyloid precursor protein-secretase activities: implications for β-amyloid peptide over-production and localization in Alzheimer’s disease. Int J Biochem Cell Biol 2004; 36:2531-40. [PMID: 15325590 DOI: 10.1016/j.biocel.2004.05.010] [Citation(s) in RCA: 194] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2004] [Revised: 05/20/2004] [Accepted: 05/21/2004] [Indexed: 10/26/2022]
Abstract
In Alzheimer's disease (AD), the neuropathologic hallmarks of beta-amyloid deposition and neurofibrillary degeneration are associated with early and progressive pathology of the endosomal-lysosomal system. Abnormalities of autophagy, a major pathway to lysosomes for protein and organelle turnover, include marked accumulations of autophagy-related vesicular compartments (autophagic vacuoles or AVs) in affected neurons. Here, we investigated the possibility that AVs contain the proteases and substrates necessary to cleave the amyloid precursor protein (APP) to A beta peptide that forms beta-amyloid, a key pathogenic factor in AD. AVs were highly purified using a well-established metrizamide gradient procedure from livers of transgenic YAC mice overexpressing wild-type human APP. By Western blot analysis, AVs contained APP, beta CTF - the beta-cleaved carboxyl-terminal domain of APP, and BACE, the protease-mediating beta-cleavage of APP. beta-Secretase activity measured against a fluorogenic peptide was significantly enriched in the AV fraction relative to whole-liver lysate. Compared to other recovered subcellular fractions, AVs exhibited the highest specific activity of gamma-secretase based on a fluorogenic assay and inhibition by a specific inhibitor of gamma-secretase, DAPT. AVs were also the most enriched subcellular fraction in levels of the gamma-secretase components presenilin and nicastrin. Immunoelectron microscopy demonstrated selective immunogold labeling of AVs with antibodies specific for the carboxyl termini of human A beta 40 and A beta 42. These data indicate that AVs are a previously unrecognized and potentially highly active compartment for A beta generation and suggest that the abnormal accumulation of AVs in affected neurons of the AD brain contributes to beta-amyloid deposition.
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Affiliation(s)
- W H Yu
- Center for Dementia Research, Nathan S. Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA
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20
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Abstract
Lamp2a acts as a receptor in the lysosomal membrane for substrate proteins of chaperone-mediated autophagy. Using antibodies specific for the cytosolic tail of lamp2a and others recognizing all lamp2 isoforms, we found that in rat liver lamp2a represents 25% of lamp2s in the lysosome. We show that lamp2a levels in the lysosomal membrane in rat liver and fibroblasts in culture directly correlate with rates of chaperone-mediated autophagy in a variety of physiological and pathological conditions. The concentration of other lamp2s in the lysosomal membrane show no correlation under the same conditions. Furthermore, substrate proteins bind to lamp2a but not to other lamp2s. Four positively-charged amino acids uniquely present in the cytosolic tail of lamp2a are required for the binding of substrate proteins. Lamp2a also distributes to an unique subpopulation of perinuclear lysosomes in cultured fibroblasts in response to serum withdrawal, and lamp2a, more than other lamp2s, tends to multimerize. These characteristics may be important for lamp2a to act as a receptor for chaperone-mediated autophagy.
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Affiliation(s)
- A M Cuervo
- Department of Physiology, Tufts University School of Medicine, Boston, MA, USA.
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21
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Abstract
Annexins are a family of proteins that bind phospholipids in a calcium-dependent manner. Analysis of the sequences of the different members of the annexin family revealed the presence of a pentapeptide biochemically related to KFERQ in some annexins but not in others. Such sequences have been proposed to be a targeting sequence for chaperone-mediated autophagy, a lysosomal pathway of protein degradation that is activated in confluent cells in response to removal of serum growth factors. We demonstrate that annexins II and VI, which contain KFERQ-like sequences, are degraded more rapidly in response to serum withdrawal, while annexins V and XI, without such sequences, are degraded at the same rate in the presence and absence of serum. Using isolated lysosomes, only the annexins containing KFERQ-like sequences are degraded by chaperone mediated-autophagy. Annexins V and XI could associate with lysosomes but did not enter the lysosomes and were not proteolytic substrates. Furthermore, four annexins containing KFERQ-like sequences, annexins I, II, IV, and VI, are enriched in lysosomes with high chaperone-mediated autophagy activity as expected for substrate proteins. These results provide striking evidence for the importance of KFERQ motifs in substrates of chaperone-mediated autophagy.
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Affiliation(s)
- A M Cuervo
- Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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22
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Abstract
Intracellular protein degradation rates decrease with age in many tissues and organs. In cultured cells, chaperone-mediated autophagy, which is responsible for the selective degradation of cytosolic proteins in lysosomes, decreases with age. In this work we use lysosomes isolated from rat liver to analyze age-related changes in the levels and activities of the main components of chaperone-mediated autophagy. Lysosomes from "old" (22-month-old) rats show lower rates of chaperone-mediated autophagy, and both substrate binding to the lysosomal membrane and transport into lysosomes decline with age. A progressive age-related decrease in the levels of the lysosome-associated membrane protein type 2a that acts as a receptor for chaperone-mediated autophagy was responsible for decreased substrate binding in lysosomes from old rats as well as from late passage human fibroblasts. The cytosolic levels and activity of the 73-kDa heat-shock cognate protein required for substrate targeting to lysosomes were unchanged with age. The levels of lysosome-associated hsc73 were increased only in the oldest rats. This increase may be an attempt to compensate for reduced activity of the pathway with age.
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Affiliation(s)
- A M Cuervo
- Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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23
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Abstract
The selective degradation of cytosolic proteins in lysosomes by chaperone-mediated autophagy depends, at least in part, on the levels of a substrate receptor at the lysosomal membrane. We have previously identified this receptor as the lysosome-associated membrane protein type 2a (lamp2a) and showed that levels of lamp2a at the lysosomal membrane directly correlate with the activity of the proteolytic pathway. Here we show that levels of lamp2a at the lysosomal membrane are mainly controlled by changes in its half-life and its distribution between the lysosomal membrane and the matrix. The lysosomal degradation of lamp2a requires the combined action of at least two different proteolytic activities at the lysosomal membrane. Lamp2a is released from the membrane by the action of these proteases, and then the truncated lamp2a is rapidly degraded within the lysosomal matrix. Membrane degradation of lamp2a is a regulated process that is inhibited in the presence of substrates for chaperone-mediated autophagy and under conditions that activate that type of autophagy. Uptake of substrate proteins also results in transport of some intact lamp2a from the lysosomal membrane into the matrix. This fraction of lamp2a can be reinserted back into the lysosomal membrane. The traffic of lamp2a through the lysosomal matrix is not mediated by vesicles, and lamp2a reinsertion requires the lysosomal membrane potential and protein components of the lysosomal membrane. The distribution of lamp2a between the lysosomal membrane and matrix is a dynamic process that contributes to the regulation of lysosomal membrane levels of lamp2a and consequently to the activity of the chaperone-mediated autophagic pathway.
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Affiliation(s)
- A M Cuervo
- Department of Physiology, Tufts University School of Medicine, Boston, MA, USA
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24
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Abstract
Changes in the lysosomes of senescent tissues and organisms are common and have been used as biomarkers of aging. Lysosomes are responsible for the degradation of many macromolecules, including proteins. At least five different pathways for the delivery of substrate proteins to lysosomes are known. Three of these pathways decline with age, and the molecular explanations for these deficiencies are currently being studied. Other aspects of lysosomal proteolysis increase or do not change with age in spite of marked changes in lysosomal morphology and biochemistry. Age-related changes in certain lysosomal pathways of proteolysis remain to be studied. This area of research is important because abnormalities in lysosomal protein degradation pathways may contribute to several characteristics and pathologies associated with aging.
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Affiliation(s)
- A M Cuervo
- Department of Physiology, Tufts University School of Medicine, Boston, MA, USA
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25
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Abstract
BACKGROUND An abnormal accumulation of alpha 2-microglobulin (alpha 2 mu) in kidney lysosomes of male rats has been described in the nephropathy resulting from exposure to a variety of chemicals. The increment in lysosomal levels of alpha 2 mu cannot be explained by a decrease in its proteolytic susceptibility. Because a portion of alpha 2 mu resides in the cytosol of kidney cells, we decided to analyze whether this cytosolic form also contributes to the abnormal lysosomal accumulation of alpha 2 mu after exposure to chemicals. METHODS Intact kidney lysosomes were isolated from untreated or 2,2,4-trimethylpentane (TMP) treated rats, and their ability to take up alpha 2 mu was compared. RESULTS alpha 2 mu can be directly transported into isolated lysosomes in the presence of the heat shock cognate protein of 73 kDa (hsc73). alpha 2 mu specifically binds to a lysosomal membrane glycoprotein of 96 kDa, previously identified as the receptor for the hsc73-mediated lysosomal pathway of protein degradation. In rats exposed to TMP, the specific lysosomal transport of alpha 2 mu increases, as well as the ability of lysosomes to directly transport other substrates for this pathway. The increased lysosomal transport is mainly due to an increase in the levels of the receptor protein in the lysosomal membrane. CONCLUSIONS The hsc73-mediated lysosomal pathway contributes to the normal degradation of alpha 2 mu in rat kidney and liver, and the activity of this pathway is increased after exposure to TMP. Our results suggest that the chemically induced accumulation of cytosolic alpha 2 mu in lysosomes is mediated by an increased rate of direct uptake into lysosomes.
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Affiliation(s)
- A M Cuervo
- Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts, USA.
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26
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Cuervo AM, Hu W, Lim B, Dice JF. IkappaB is a substrate for a selective pathway of lysosomal proteolysis. Mol Biol Cell 1998; 9:1995-2010. [PMID: 9693362 PMCID: PMC25451 DOI: 10.1091/mbc.9.8.1995] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/1997] [Accepted: 06/04/1998] [Indexed: 11/11/2022] Open
Abstract
In lysosomes isolated from rat liver and spleen, a percentage of the intracellular inhibitor of the nuclear factor kappa B (IkappaB) can be detected in the lysosomal matrix where it is rapidly degraded. Levels of IkappaB are significantly higher in a lysosomal subpopulation that is active in the direct uptake of specific cytosolic proteins. IkappaB is directly transported into isolated lysosomes in a process that requires binding of IkappaB to the heat shock protein of 73 kDa (hsc73), the cytosolic molecular chaperone involved in this pathway, and to the lysosomal glycoprotein of 96 kDa (lgp96), the receptor protein in the lysosomal membrane. Other substrates for this degradation pathway competitively inhibit IkappaB uptake by lysosomes. Ubiquitination and phosphorylation of IkappaB are not required for its targeting to lysosomes. The lysosomal degradation of IkappaB is activated under conditions of nutrient deprivation. Thus, the half-life of a long-lived pool of IkappaB is 4.4 d in serum-supplemented Chinese hamster ovary cells but only 0.9 d in serum-deprived Chinese hamster ovary cells. This increase in IkappaB degradation can be completely blocked by lysosomal inhibitors. In Chinese hamster ovary cells exhibiting an increased activity of the hsc73-mediated lysosomal degradation pathway due to overexpression of lamp2, the human form of lgp96, the degradation of IkappaB is increased. There are both short- and long-lived pools of IkappaB, and it is the long-lived pool that is subjected to the selective lysosomal degradation pathway. In the presence of antioxidants, the half-life of the long-lived pool of IkappaB is significantly increased. Thus, the production of intracellular reactive oxygen species during serum starvation may be one of the mechanisms mediating IkappaB degradation in lysosomes. This selective pathway of lysosomal degradation of IkappaB is physiologically important since prolonged serum deprivation results in an increase in the nuclear activity of nuclear factor kappa B. In addition, the response of nuclear factor kappa B to several stimuli increases when this lysosomal pathway of proteolysis is activated.
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Affiliation(s)
- A M Cuervo
- Department of Physiology, Tufts University, School of Medicine, Boston, Massachusetts 02111, USA
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27
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Abstract
Lysosomes, classically considered as nonspecific systems for protein degradation, have recently also been shown to be able selectively to degrade specific intracellular proteins. Here we review this selective pathway of lysosomal protein degradation that involves cytosolic and intralysosomal chaperones and a receptor in the lysosomal membrane. This pathway is highly selective for cytosolic proteins containing a lysosomal targeting signal. The selective lysosomal degradation pathway is active under conditions of nutrient deprivation and plays an important role in the regulation of intracellular protein levels in stress situations. Several physiological and pathological modifications in the activity of this selective lysosomal pathway of protein degradation are discussed.
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Affiliation(s)
- A M Cuervo
- Department of Physiology, School of Medicine, Tufts University, Boston, MA 02111, USA
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28
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Abstract
One of the common features of cells from senescent tissues is the accumulation of abnormal proteins. Several hypotheses have been proposed to explain the origin of those abnormal proteins. A defect in proteolytic systems usually responsible for the elimination of altered proteins from the cells could clearly contribute to such accumulation. Here we describe the effect of age on the major proteolytic systems within cells: the ubiquitin-proteasome pathway, the calcium-activated calpain pathways, and multiple lysosomal pathways. Our group has contributed to the characterization of a selective pathway of degradation of cytosolic proteins in lysosomes that is activated under conditions of nutrient deprivation. In this lysosomal pathway of proteolysis proteins are transported through the lysosomal membrane assisted by cytosolic and lysosomal molecular chaperones and a receptor protein in the lysosomal membrane. The activity of this pathway significantly decreases with age, and this decrease might account for the cytosolic accumulation of aberrant substrate proteins in senescent cells. The cellular consequences of the decline of this lysosomal pathway together with possible methods to restore the reduced function are also addressed in this review.
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Affiliation(s)
- A M Cuervo
- Department of Physiology Tufts University School of Medicine, Boston, USA
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29
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Abstract
Two populations of rat liver lysosomes can be distinguished on the basis of their density. A major difference between these populations is that one contains the heat shock cognate protein of 73 kDa (hsc73) within the lysosomal lumen. The lysosomal fraction containing hsc73 exhibits much higher efficiencies in the in vitro uptake and degradation of glyceraldehyde-3-phosphate dehydrogenase and ribonuclease A, two well established substrates of the selective lysosomal pathway of intracellular protein degradation. Preloading of the lysosomal population that is devoid of lumenal hsc73 with hsc73 isolated from cytosol activated the selective transport of substrate proteins into these lysosomes. Furthermore, treatment of animals with leupeptin, an inhibitor of lysosomal cathepsins, or 88 h of starvation also increased the amount of hsc73 within their lysosomal lumen, and these in vivo treatments also activated the selective transport of substrate proteins in vitro. Thus, the hsc73 located within lysosomes appears to be required for efficient uptake of cytosolic proteins by these organelles. The difference in hsc73 content between the lysosomal populations appears to be due to differences in their ability to take up hsc73 combined with differences in the intralysosomal degradation rates of hsc73. The increased stability of hsc73 in one population of lysosomes is primarily a consequence of this lysosomal population's more acidic pH.
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Affiliation(s)
- A M Cuervo
- Instituto de Investigaciones Citológicas, 46010 Valencia, Spain
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30
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Abstract
Multiple pathways of protein degradation operate within cells. A selective protein import pathway exists for the uptake and degradation of particular cytosolic proteins by lysosomes. Here, the lysosomal membrane glycoprotein LGP96 was identified as a receptor for the selective import and degradation of proteins within lysosomes. Specific substrates of this proteolytic pathway bound to the cytosolic tail of a 96-kilodalton lysosomal membrane protein in two different binding assays. Overexpression of human LGP96 in Chinese hamster ovary cells increased the activity of the selective lysosomal proteolytic pathway in vivo and in vitro.
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Affiliation(s)
- A M Cuervo
- Department of Physiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
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31
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Adra CN, Zhu S, Ko JL, Guillemot JC, Cuervo AM, Kobayashi H, Horiuchi T, Lelias JM, Rowley JD, Lim B. LAPTM5: a novel lysosomal-associated multispanning membrane protein preferentially expressed in hematopoietic cells. Genomics 1996; 35:328-37. [PMID: 8661146 DOI: 10.1006/geno.1996.0364] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
While a large body of knowledge about cell membrane proteins exists, much less is known about the repertoire and function of integral membrane proteins of intracellular organelles. In looking for novel classes of genes that are functionally important to hematopoietic cells, we have cloned the cDNA for a gene preferentially expressed in adult hematopoietic tissues. During embryonic development the gene is expressed in both hematopoietic and nonhematopoietic tissues. In cell lines the gene is expressed specifically in hematopoietic lineages, whereas in normal adult tissues the mRNA is preferentially detected at high levels in lymphoid and myeloid tissues. The predicted protein is a pentaspanner with no homology to known genes and conserved across evolution. Immunocytological and cell fractionation studies with a specific antibody revealed a protein localizing in lysosomes. The gene, provisionally named LAPTM5, maps to chromosome 1p34. The expression pattern of the gene together with preliminary evidence that the protein interacts with ubiquitin indicates that the protein may have a special functional role during embryogenesis and in adult hematopoietic cells.
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MESH Headings
- Adult
- Amino Acid Sequence
- Animals
- Antibodies
- Base Sequence
- Blotting, Western
- Cell Line
- Chromosome Mapping
- Chromosomes, Human, Pair 1
- Cloning, Molecular
- DNA, Complementary
- Embryo, Mammalian
- Embryonic and Fetal Development
- Female
- Gene Expression
- Gene Expression Regulation, Developmental
- Hematopoietic Stem Cells/metabolism
- Humans
- Immediate-Early Proteins
- Intracellular Membranes/metabolism
- Lysosomes/metabolism
- Membrane Proteins/analysis
- Membrane Proteins/biosynthesis
- Membrane Proteins/genetics
- Mice
- Molecular Sequence Data
- Peptides/chemistry
- Peptides/immunology
- Pregnancy
- RNA, Messenger/biosynthesis
- Rats
- Sequence Homology, Amino Acid
- Tumor Cells, Cultured
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Affiliation(s)
- C N Adra
- Division of Hematology/Oncology, Harvard Medical School, Boston, Massachusetts, 02215, USA
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32
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Abstract
Lysosomal uptake and degradation of polypeptides such as glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ribonuclease A (RNase A), and RNase S-peptide (residues 1-20 of RNase A) are progressively activated in rat liver by starvation before isolation of lysosomes. This pathway of proteolysis is selective, since it is stimulated by the heat shock cognate protein of 73 kDa (HSC73) and ATP-MgCl2, and lysosomal uptake of RNase A could be competed by GAPDH but not by ovalbumin. A portion of intracellular HSC73 is associated with certain lysosomes, and the amount of lysosomal HSC73 increases by 5- to 10-fold during prolonged starvation. The lysosome-associated HSC73 is primarily within the lysosomal lumen. Double immunogold labeling of lysosomes incubated in vitro with RNase A detects this protein substrate as well as HSC73 within lysosomes. More than two-thirds of the labeled lysosomes contain both RNase A and HSC73. The possible physiological significance of the activation of this selective pathway of lysosomal proteolysis in long-term starvation is discussed.
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Affiliation(s)
- A M Cuervo
- Instituto de Investigaciones Citológicas, Valencia, Spain
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33
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Abstract
Proteasomes are high-molecular-mass multisubunit complexes which are believed, either by themselves or as a part of the 26S proteinase complex, to play a central role in extralysosomal pathways of intracellular protein breakdown. We have addressed the degradation of proteasomes in rat liver, investigating the possible role of lysosomes. Affinity-purified antibodies against rat liver proteasomes were used for immunoblot analysis of isolated lysosomes. Although proteasomes are not found in lysosomes from normally fed rats, they were found to accumulate in lysosomes of rats treated with leupeptin (an inhibitor of lysosomal proteases) and could also be detected in lysosomes isolated from livers of starved (24 h) rats. Proteinase-K treatment of these fractions, as well as immunogold procedures, show that a proportion of the proteasomes are inside lysosomes. Comparison of the amount of proteasomes found in lysosomes by immunoblotting with their experimentally determined half life (8.3 days) is consistent with an important role of these organelles in the degradation of rat liver proteasomes. Nevertheless, these data do not exclude the possibility that some nonlysosomal degradation of proteasome components also occurs. Since proteasomes were localized in autophagic vacuoles, it is likely that they are taken up mainly by nonselective autophagy. However, using an in vitro system, it was found that, under conditions of starvation, proteasomes may also be taken up into lysosomes and degraded via the heat-shock cognate protein of 73 kDa (hsc73)-mediated transport.
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Affiliation(s)
- A M Cuervo
- Instituto de Investigaciones Citológicas, Fundación Valenciana de Investigaciones Biomédicas, Spain
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34
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Cuervo AM, Terlecky SR, Dice JF, Knecht E. Selective binding and uptake of ribonuclease A and glyceraldehyde-3-phosphate dehydrogenase by isolated rat liver lysosomes. J Biol Chem 1994; 269:26374-80. [PMID: 7929357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Ribonuclease A (RNase A) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) are selectively taken up and degraded by isolated rat liver lysosomes by very similar processes. The uptake and degradation of both of these proteins are stimulated by the heat shock cognate protein of 73 kDa and ATP/Mg2+. Both binding and uptake of RNase A and GAPDH by lysosomes are saturable, and uptake of RNase A and GAPDH requires a protease-sensitive component within the lysosomal membrane. GAPDH competes for binding and uptake of RNase A by lysosomes and vice versa while another protein, ovalbumin, does not compete. RNase S-peptide (amino acids 1-20 of RNase A) also competes for RNase A binding and uptake by lysosomes, while RNase S-protein (amino acids 21-124 of RNase A) does not compete. The uptake of RNase A by lysosomes appears to involve an intermediate step in which approximately 2 kDa of the polypeptide's COOH terminus remains outside lysosomes while the remainder is inside the lysosomal lumen.
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Affiliation(s)
- A M Cuervo
- Instituto de Investigaciones Citológicas, Fundación Valenciana de Investigaciones Biomédicas, Valencia, Spain
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35
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Raya A, Cuervo AM, Macián F, Romero FJ, Romá J. Nerve conduction velocity decrease and synaptic transmission alterations in caffeine-treated rats. Neurotoxicol Teratol 1994; 16:11-5. [PMID: 8183184 DOI: 10.1016/0892-0362(94)90003-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The action of caffeine on peripheral neuromuscular function was studied by means of in vivo determinations of electrophysiological parameters, i.e., amplitude of extracellularly recorded muscle action potentials and nerve conduction velocity in the dorsal skeletal muscle and caudal nerve of the rat tail, respectively. Repeated exposure of the rats was carried out by adding caffeine to the drinking water for 10 days. Here we report the novel finding that motor nerve conduction velocity showed a significant decrease in caffeine-treated animals, whereas no change was observed in the amplitude of indirectly evoked extracellular muscle action potentials. The physiological recovery of the amplitude of the compound muscle action potential observed in nonintoxicated rats after high-frequency stimulation (10 Hz) was not observed in intoxicated animals and is also discussed.
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Affiliation(s)
- A Raya
- Department of Physiology, School of Medicine and Dentistry, University of Valencia, Spain
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36
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Aniento F, Roche E, Cuervo AM, Knecht E. Uptake and degradation of glyceraldehyde-3-phosphate dehydrogenase by rat liver lysosomes. J Biol Chem 1993; 268:10463-70. [PMID: 8486700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The molecular mechanisms involved in the degradation of individual cellular proteins are probably unique and characteristic. We have investigated in rat liver the degradation of glyceraldehyde-3-phosphate dehydrogenase, an abundant cytosolic enzyme of the glycolytic pathway. Immunoblot analysis of isolated liver lysosomes from rats treated with lysosomal inhibitors show that this protein is degraded, at least in part, by a lysosomal pathway. This pathway was further investigated by incubating the enzyme with lysosomes in a cell-free system, followed by proteolysis measurements, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of lysosomes, and electron microscopic immunocytochemistry. We postulate that the degradative mechanism of glyceraldehyde-3-phosphate dehydrogenase includes a temperature-dependent lysosomal pathway, different from classical nonspecific macroautophagy. The postulated pathway involves: binding of the enzyme to the lysosomal membrane, entry into the lysosomal matrix, and degradation. This cell-free system, which can also incorporate in vitro synthesized proteins, should allow further advances toward clarifying the complex signals that regulate protein degradation as well as its close interrelationship with protein synthesis.
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Affiliation(s)
- F Aniento
- Instituto de Investigaciones Citológicas, Valencia, Spain
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37
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Romá J, Cuervo AM, Macian F, Raya A, Gallego J, Llopis JE, Romero FJ. Temperature dependence of the toxic effects of phenytoin on peripheral neuromuscular function of the rat tail. Neurotoxicol Teratol 1990; 12:627-31. [PMID: 2255306 DOI: 10.1016/0892-0362(90)90075-n] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We studied the acute effects of a single dose of phenytoin (250 mg/kg) on peripheral neuromuscular function. The evoked muscle action potentials of the dorsal segmental muscles in the rat tail, and the conduction velocity of the dorsal nerve trunk which innervates them, were measured before and after the intraperitoneal injection of phenytoin. The experiments were performed at different temperatures, 27 (physiological tail temperature), 36 and 37 degrees C (physiological central temperature) in different groups of animals. The amplitudes of the evoked muscle action potentials in the treated groups showed no significant modifications at 27 degrees C, at 36 degrees C a small nonsignificant decrease could be observed, and a complete block occurred at 37 degrees C. The mean blocking time was approximately one hour. No significant variations of conduction velocity were observed at 27 and 36 degrees C, whereas it decreased significantly after 30 minutes at 37 degrees C. The results presented confirm phenytoin toxicity. How far these results, especially the decrease of nerve conduction velocity observed at 37 degrees C, confirm a previous hypothesis which supported that peripheral and central nervous system are affected by phenytoin by similar mechanisms, is discussed.
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Affiliation(s)
- J Romá
- Department de Fisiologia, Facultat de Medicina i Odontologia, Universitat de València, Spain
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