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Yuan R, Hahn Y, Stempel MH, Sidibe DK, Laxton O, Chen J, Kulkarni A, Maday S. Proteasomal inhibition preferentially stimulates lysosome activity relative to autophagic flux in primary astrocytes. Autophagy 2023; 19:570-596. [PMID: 35722992 PMCID: PMC9851260 DOI: 10.1080/15548627.2022.2084884] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [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: 09/21/2021] [Revised: 05/23/2022] [Accepted: 05/26/2022] [Indexed: 01/22/2023] Open
Abstract
Neurons and astrocytes face unique demands on their proteome to enable proper function and survival of the nervous system. Consequently, both cell types are critically dependent on robust quality control pathways such as macroautophagy (hereafter referred to as autophagy) and the ubiquitin-proteasome system (UPS). We previously reported that autophagy is differentially regulated in astrocytes and neurons in the context of metabolic stress, but less is understood in the context of proteotoxic stress induced by inhibition of the UPS. Dysfunction of the proteasome or autophagy has been linked to the progression of various neurodegenerative diseases. Therefore, in this study, we explored the connection between autophagy and the proteasome in primary astrocytes and neurons. Prior studies largely in non-neural models report a compensatory relationship whereby inhibition of the UPS stimulates autophagy. To our surprise, inhibition of the proteasome did not robustly upregulate autophagy in astrocytes or neurons. In fact, the effects on autophagy are modest particularly in comparison to paradigms of metabolic stress. Rather, we find that UPS inhibition in astrocytes induces formation of Ub-positive aggregates that harbor the selective autophagy receptor, SQSTM1/p62, but these structures were not productive substrates for autophagy. By contrast, we observed a significant increase in lysosomal degradation in astrocytes in response to UPS inhibition, but this stimulation was not sufficient to reduce total SQSTM1 levels. Last, UPS inhibition was more toxic in neurons compared to astrocytes, suggesting a cell type-specific vulnerability to proteotoxic stress.Abbreviations: Baf A1: bafilomycin A1; CQ: chloroquine; Epox: epoxomicin; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; p-ULK1: phospho-ULK1; SQSTM1/p62: sequestosome 1; Ub: ubiquitin; ULK1: unc-51 like kinase 1; UPS: ubiquitin-proteasome system.
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Affiliation(s)
- Ruiyi Yuan
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Younghee Hahn
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Max H. Stempel
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - David K. Sidibe
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Olivia Laxton
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Jessica Chen
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Aditi Kulkarni
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Sandra Maday
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
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Sidibe DK, Vogel MC, Maday S. Organization of the autophagy pathway in neurons. Curr Opin Neurobiol 2022; 75:102554. [PMID: 35649324 PMCID: PMC9990471 DOI: 10.1016/j.conb.2022.102554] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 03/28/2022] [Accepted: 04/12/2022] [Indexed: 01/18/2023]
Abstract
Macroautophagy (hereafter referred to as autophagy) is an essential quality-control pathway in neurons, which face unique functional and morphological challenges in maintaining the integrity of organelles and the proteome. To overcome these challenges, neurons have developed compartment-specific pathways for autophagy. In this review, we discuss the organization of the autophagy pathway, from autophagosome biogenesis, trafficking, to clearance, in the neuron. We dissect the compartment-specific mechanisms and functions of autophagy in axons, dendrites, and the soma. Furthermore, we highlight examples of how steps along the autophagy pathway are impaired in the context of aging and neurodegenerative disease, which underscore the critical importance of autophagy in maintaining neuronal function and survival.
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Affiliation(s)
- David K Sidibe
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Maria C Vogel
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Sandra Maday
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, 19104, USA.
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Tichy ED, Sidibe DK, Greer CD, Oyster NM, Rompolas P, Rosenthal NA, Blau HM, Mourkioti F. A robust Pax7EGFP mouse that enables the visualization of dynamic behaviors of muscle stem cells. Skelet Muscle 2018; 8:27. [PMID: 30139374 PMCID: PMC6107960 DOI: 10.1186/s13395-018-0169-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [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: 04/12/2018] [Accepted: 07/04/2018] [Indexed: 01/10/2023] Open
Abstract
Background Pax7 is a transcription factor involved in the specification and maintenance of muscle stem cells (MuSCs). Upon injury, MuSCs leave their quiescent state, downregulate Pax7 and differentiate, contributing to skeletal muscle regeneration. In the majority of regeneration studies, MuSCs are isolated by fluorescence-activated sorting (FACS), based on cell surface markers. It is known that MuSCs are a heterogeneous population and only a small percentage of isolated cells are true stem cells that are able to self-renew. A strong Pax7 reporter line would be valuable to study the in vivo behavior of Pax7-expressing stem cells. Methods We generated and characterized the muscle properties of a new transgenic Pax7EGFP mouse. Utilizing traditional immunofluorescence assays, we analyzed whole embryos and muscle sections by fluorescence microscopy, in addition to whole skeletal muscles by 2-photon microscopy, to detect the specificity of EGFP expression. Skeletal muscles from Pax7EGFP mice were also evaluated in steady state and under injury conditions. Finally, MuSCs-derived from Pax7EGFP and control mice were sorted and analyzed by FACS and their myogenic activity was comparatively examined. Results Our studies provide a new Pax7 reporter line with robust EGFP expression, detectable by both flow cytometry and fluorescence microscopy. Pax7EGFP-derived MuSCs have identical properties to that of wild-type MuSCs, both in vitro and in vivo, excluding any positional effect due to the transgene insertion. Furthermore, we demonstrated high specificity of EGFP to label MuSCs in a temporal manner that recapitulates the reported Pax7 expression pattern. Interestingly, immunofluorescence analysis showed that the robust expression of EGFP marks cells in the satellite cell position of adult muscles in fixed and live tissues. Conclusions This mouse could be an invaluable tool for the study of a variety of questions related to MuSC biology, including but not limited to population heterogeneity, polarity, aging, regeneration, and motility, either by itself or in combination with mice harboring additional genetic alterations. Electronic supplementary material The online version of this article (10.1186/s13395-018-0169-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Elisia D Tichy
- Department of Orthopaedic Surgery, Perelman School of Medicine, The University of Pennsylvania, Philadelphia, PA, USA
| | - David K Sidibe
- Department of Orthopaedic Surgery, Perelman School of Medicine, The University of Pennsylvania, Philadelphia, PA, USA
| | - Christopher D Greer
- Department of Orthopaedic Surgery, Perelman School of Medicine, The University of Pennsylvania, Philadelphia, PA, USA.,Cell and Molecular Biology Graduate Program, The University of Pennsylvania, Philadelphia, PA, USA
| | - Nicholas M Oyster
- Department of Orthopaedic Surgery, Perelman School of Medicine, The University of Pennsylvania, Philadelphia, PA, USA
| | - Panteleimon Rompolas
- Cell and Molecular Biology Graduate Program, The University of Pennsylvania, Philadelphia, PA, USA.,Department of Dermatology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Nadia A Rosenthal
- The Jackson Laboratory, Bar Harbor, ME, USA.,Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, USA.,The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA.,Australian Regenerative Medicine Institute, Monash University, Melbourne, VIC, Australia.,National Heart and Lung Institute, Imperial College London, London, UK
| | - Helen M Blau
- Baxter Laboratory for Stem Cell Biology, Department of Microbiology and Immunology, Institute for Stem Cell Biology and Regenerative Medicine, Stanford School of Medicine, Stanford, CA, USA
| | - Foteini Mourkioti
- Department of Orthopaedic Surgery, Perelman School of Medicine, The University of Pennsylvania, Philadelphia, PA, USA. .,Cell and Molecular Biology Graduate Program, The University of Pennsylvania, Philadelphia, PA, USA. .,Department of Cell and Developmental Biology, Penn Institute of Regenerative Medicine, Musculoskeletal Regeneration Program, Perelman School of Medicine, The University of Pennsylvania, Philadelphia, PA, USA. .,Musculoskeletal Regeneration Program, Department of Orthopaedic Surgery and Cell and Developmental Biology, Penn Institute of Regenerative Medicine, The University of Pennsylvania, 3450 Hamilton Walk, 112A Stemmler Hall, Philadelphia, PA, 19104-6081, USA.
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Tichy ED, Sidibe DK, Tierney MT, Stec MJ, Sharifi-Sanjani M, Hosalkar H, Mubarak S, Johnson FB, Sacco A, Mourkioti F. Single Stem Cell Imaging and Analysis Reveals Telomere Length Differences in Diseased Human and Mouse Skeletal Muscles. Stem Cell Reports 2017; 9:1328-1341. [PMID: 28890163 PMCID: PMC5639167 DOI: 10.1016/j.stemcr.2017.08.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 08/08/2017] [Accepted: 08/11/2017] [Indexed: 12/12/2022] Open
Abstract
Muscle stem cells (MuSCs) contribute to muscle regeneration following injury. In many muscle disorders, the repeated cycles of damage and repair lead to stem cell dysfunction. While telomere attrition may contribute to aberrant stem cell functions, methods to accurately measure telomere length in stem cells from skeletal muscles have not been demonstrated. Here, we have optimized and validated such a method, named MuQ-FISH, for analyzing telomere length in MuSCs from either mice or humans. Our analysis showed no differences in telomere length between young and aged MuSCs from uninjured wild-type mice, but MuSCs isolated from young dystrophic mice exhibited significantly shortened telomeres. In corroboration, we demonstrated that telomere attrition is present in human dystrophic MuSCs, which underscores its importance in diseased regenerative failure. The robust technique described herein provides analysis at a single-cell resolution and may be utilized for other cell types, especially rare populations of cells. MuQ-FISH is a telomere analysis assay of mouse and human muscle stem cells Highly sensitive telomere analysis on small numbers of cells Detection of both telomere length and number of telomere foci with MuQ-FISH assay Telomere analysis is now possible in quiescent and/or cycling stem cells
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Affiliation(s)
- Elisia D Tichy
- Department of Orthopaedic Surgery, Perelman School of Medicine, The University of Pennsylvania, 112A Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104-6081, USA
| | - David K Sidibe
- Department of Orthopaedic Surgery, Perelman School of Medicine, The University of Pennsylvania, 112A Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104-6081, USA
| | - Matthew T Tierney
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Michael J Stec
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Maryam Sharifi-Sanjani
- Department of Orthopaedic Surgery, Perelman School of Medicine, The University of Pennsylvania, 112A Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104-6081, USA
| | - Harish Hosalkar
- Joint Preservation Center, Tricity Medical Center, Joint Preservation & Deformity Correction Center & Traumatic Brain Injury Program, Paradise Valley Hospital, National City, CA 91950, USA
| | - Scott Mubarak
- Department of Orthopedic Surgery, Rady Children's Hospital, 3030 Children's Way, San Diego, CA 92123, USA
| | - F Brad Johnson
- Department of Pathology and Laboratory Medicine, Institute on Aging, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Alessandra Sacco
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Foteini Mourkioti
- Department of Orthopaedic Surgery, Perelman School of Medicine, The University of Pennsylvania, 112A Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104-6081, USA; Department of Cell and Developmental Biology, Perelman School of Medicine, The University of Pennsylvania, Philadelphia, PA 19104, USA.
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