101
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O'Reilly LP, Perlmutter DH, Silverman GA, Pak SC. α1-antitrypsin deficiency and the hepatocytes - an elegans solution to drug discovery. Int J Biochem Cell Biol 2014; 47:109-12. [PMID: 24355812 PMCID: PMC3970812 DOI: 10.1016/j.biocel.2013.12.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 11/29/2013] [Accepted: 12/08/2013] [Indexed: 11/24/2022]
Abstract
Hepatocytes are metabolically active cells of the liver that play an important role in the biosynthesis of proteins including α1-antitrypsin. Mutations in the α1-antitrypsin gene can lead to protein misfolding, polymerization/aggregation and retention of protein within the endoplasmic reticulum of hepatocytes. The intracellular accumulation of α1-antitrypsin aggregates can lead to liver disease and increased likelihood of developing hepatocellular carcinomas. Of note, only ~10% of individuals with α1-antitrypsin-deficiency develop severe liver disease suggesting that there are other genetic and/or environmental factors that determine disease outcome. The nematode, Caenorhabditis elegans, is a powerful genetic model organism to study molecular aspects of human disease. In this review, we discuss the functional similarities between the intestinal cells of C. elegans and human hepatocytes and how a C. elegans model of α1-antitrypsin-deficiency can be used as a tool for identifying genetic modifiers and small molecule drugs.
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Affiliation(s)
- Linda P O'Reilly
- Department of Pediatrics, Cell Biology and Physiology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - David H Perlmutter
- Department of Pediatrics, Cell Biology and Physiology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Gary A Silverman
- Department of Pediatrics, Cell Biology and Physiology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Stephen C Pak
- Department of Pediatrics, Cell Biology and Physiology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224, USA.
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102
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Martina JA, Diab HI, Li H, Puertollano R. Novel roles for the MiTF/TFE family of transcription factors in organelle biogenesis, nutrient sensing, and energy homeostasis. Cell Mol Life Sci 2014; 71:2483-97. [PMID: 24477476 DOI: 10.1007/s00018-014-1565-8] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 01/14/2014] [Accepted: 01/14/2014] [Indexed: 01/22/2023]
Abstract
The MiTF/TFE family of basic helix-loop-helix leucine zipper transcription factors includes MITF, TFEB, TFE3, and TFEC. The involvement of some family members in the development and proliferation of specific cell types, such as mast cells, osteoclasts, and melanocytes, is well established. Notably, recent evidence suggests that the MiTF/TFE family plays a critical role in organelle biogenesis, nutrient sensing, and energy metabolism. The MiTF/TFE family is also implicated in human disease. Mutations or aberrant expression of most MiTF/TFE family members has been linked to different types of cancer. At the same time, they have recently emerged as novel and very promising targets for the treatment of neurological and lysosomal diseases. The characterization of this fascinating family of transcription factors is greatly expanding our understanding of how cells synchronize environmental signals, such as nutrient availability, with gene expression, energy production, and cellular homeostasis.
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Affiliation(s)
- José A Martina
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, 9000 Rockville Pike, Bldg. 50/3537, Bethesda, MD, 20892, USA
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103
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Wang Y, Perlmutter DH. Targeting intracellular degradation pathways for treatment of liver disease caused by α1-antitrypsin deficiency. Pediatr Res 2014; 75:133-9. [PMID: 24226634 PMCID: PMC4174576 DOI: 10.1038/pr.2013.190] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 08/06/2013] [Indexed: 02/06/2023]
Abstract
The classic form of α1-antitrypsin deficiency (ATD) is a well-known genetic cause of severe liver disease in childhood. A point mutation alters the folding of a hepatic secretory glycoprotein such that the protein is prone to misfolding and polymerization. Liver injury, characterized predominantly by fibrosis/cirrhosis and carcinogenesis, is caused by the proteotoxic effect of polymerized mutant α1-antitrypsin Z (ATZ), which accumulates in the endoplasmic reticulum (ER) of hepatocytes. Several intracellular pathways have been shown to be responsible for disposal of ATZ after it accumulates in the ER, but autophagy appears to be specialized for disposal of insoluble ATZ polymers. Recently, we have found that drugs that enhance the activity of the autophagic pathway reduce the cellular load of mutant ATZ and reverse hepatic fibrosis in a mouse model of ATD. Because several of these autophagy enhancers have been used safely in humans for other reasons, we have been able to initiate a clinical trial of one of these drugs, carbamazepine, to determine its efficacy in severe liver disease due to ATD. In this review, we discuss the autophagy enhancer drugs as a new therapeutic strategy that targets cell biological mechanisms integral to the pathogenesis of liver disease due to ATD.
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Affiliation(s)
- Yan Wang
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - David H. Perlmutter
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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104
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Bowes Rickman C, Farsiu S, Toth CA, Klingeborn M. Dry age-related macular degeneration: mechanisms, therapeutic targets, and imaging. Invest Ophthalmol Vis Sci 2013; 54:ORSF68-80. [PMID: 24335072 DOI: 10.1167/iovs.13-12757] [Citation(s) in RCA: 184] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Age-related macular degeneration is the leading cause of irreversible visual dysfunction in individuals over 65 in Western Society. Patients with AMD are classified as having early stage disease (early AMD), in which visual function is affected, or late AMD (generally characterized as either "wet" neovascular AMD, "dry" atrophic AMD or both), in which central vision is severely compromised or lost. Until recently, there have been no therapies available to treat the disorder(s). Now, the most common wet form of late-stage AMD, choroidal neovascularization, generally responds to treatment with anti-vascular endothelial growth factor therapies. Nevertheless, there are no current therapies to restore lost vision in eyes with advanced atrophic AMD. Oral supplementation with the Age-Related Eye Disease Study (AREDS) or AREDS2 formulation (antioxidant vitamins C and E, lutein, zeaxanthin, and zinc) has been shown to reduce the risk of progression to advanced AMD, although the impact was in neovascular rather than atrophic AMD. Recent findings, however, have demonstrated several features of early AMD that are likely to be druggable targets for treatment. Studies have established that much of the genetic risk for AMD is associated with complement genes. Consequently, several complement-based therapeutic treatment approaches are being pursued. Potential treatment strategies against AMD deposit formation and protein and/or lipid deposition will be discussed, including anti-amyloid therapies. In addition, the role of autophagy in AMD and prevention of oxidative stress through modulation of the antioxidant system will be explored. Finally, the success of these new therapies in clinical trials and beyond relies on early detection, disease typing, and predicting disease progression, areas that are currently being rapidly transformed by improving imaging modalities and functional assays.
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105
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Füllgrabe J, Klionsky DJ, Joseph B. The return of the nucleus: transcriptional and epigenetic control of autophagy. Nat Rev Mol Cell Biol 2013; 15:65-74. [PMID: 24326622 DOI: 10.1038/nrm3716] [Citation(s) in RCA: 353] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Autophagy is a conserved process by which cytoplasmic components are degraded by the lysosome. It is commonly seen as a cytoplasmic event and, until now, nuclear events were not considered of primary importance for this process. However, recent studies have unveiled a transcriptional and epigenetic network that regulates autophagy. The identification of tightly controlled transcription factors (such as TFEB and ZKSCAN3), microRNAs and histone marks (especially acetylated Lys16 of histone 4 (H4K16ac) and dimethylated H3K9 (H3K9me2)) associated with the autophagic process offers an attractive conceptual framework to understand the short-term transcriptional response and potential long-term responses to autophagy.
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Affiliation(s)
- Jens Füllgrabe
- Department of Oncology Pathology, Cancer Centrum Karolinska, Karolinska Institutet, Stockholm 17176, Sweden
| | - Daniel J Klionsky
- Life Sciences Institute and Departments of Molecular, Cellular and Developmental Biology and Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Bertrand Joseph
- Department of Oncology Pathology, Cancer Centrum Karolinska, Karolinska Institutet, Stockholm 17176, Sweden
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106
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Eggenschwiler R, Loya K, Wu G, Sharma AD, Sgodda M, Zychlinski D, Herr C, Steinemann D, Teckman J, Bals R, Ott M, Schambach A, Schöler HR, Cantz T. Sustained knockdown of a disease-causing gene in patient-specific induced pluripotent stem cells using lentiviral vector-based gene therapy. Stem Cells Transl Med 2013; 2:641-54. [PMID: 23926210 DOI: 10.5966/sctm.2013-0017] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Patient-specific induced pluripotent stem cells (iPSCs) hold great promise for studies on disease-related developmental processes and may serve as an autologous cell source for future treatment of many hereditary diseases. New genetic engineering tools such as zinc finger nucleases and transcription activator-like effector nuclease allow targeted correction of monogenetic disorders but are very cumbersome to establish. Aiming at studies on the knockdown of a disease-causing gene, lentiviral vector-mediated expression of short hairpin RNAs (shRNAs) is a valuable option, but it is limited by silencing of the knockdown construct upon epigenetic remodeling during differentiation. Here, we propose an approach for the expression of a therapeutic shRNA in disease-specific iPSCs using third-generation lentiviral vectors. Targeting severe α-1-antitrypsin (A1AT) deficiency, we overexpressed a human microRNA 30 (miR30)-styled shRNA directed against the PiZ variant of A1AT, which is known to cause chronic liver damage in affected patients. This knockdown cassette is traceable from clonal iPSC lines to differentiated hepatic progeny via an enhanced green fluorescence protein reporter expressed from the same RNA-polymerase II promoter. Importantly, the cytomegalovirus i/e enhancer chicken β actin (CAG) promoter-driven expression of this construct is sustained without transgene silencing during hepatic differentiation in vitro and in vivo. At low lentiviral copy numbers per genome we confirmed a functional relevant reduction (-66%) of intracellular PiZ protein in hepatic cells after differentiation of patient-specific iPSCs. In conclusion, we have demonstrated that lentiviral vector-mediated expression of shRNAs can be efficiently used to knock down and functionally evaluate disease-related genes in patient-specific iPSCs.
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Affiliation(s)
- Reto Eggenschwiler
- Research Group Translational Hepatology and Stem Cell Biology, Hannover Medical School, Hannover, Germany
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107
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Signals from the lysosome: a control centre for cellular clearance and energy metabolism. Nat Rev Mol Cell Biol 2013; 14:283-96. [PMID: 23609508 DOI: 10.1038/nrm3565] [Citation(s) in RCA: 1148] [Impact Index Per Article: 104.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
For a long time, lysosomes were considered merely to be cellular 'incinerators' involved in the degradation and recycling of cellular waste. However, now there is compelling evidence indicating that lysosomes have a much broader function and that they are involved in fundamental processes such as secretion, plasma membrane repair, signalling and energy metabolism. Furthermore, the essential role of lysosomes in autophagic pathways puts these organelles at the crossroads of several cellular processes, with significant implications for health and disease. The identification of a master regulator, transcription factor EB (TFEB), that regulates lysosomal biogenesis and autophagy has revealed how the lysosome adapts to environmental cues, such as starvation, and targeting TFEB may provide a novel therapeutic strategy for modulating lysosomal function in human disease.
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108
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Thompson DA, Klionsky DJ. Autophagy and gene therapy combine in the treatment of liver disease. Autophagy 2013; 9:945-6. [PMID: 23590992 DOI: 10.4161/auto.24475] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Molecular biology holds the promise not only of increasing our understanding of basic cell biology, but also of advancing our ability to design targeted therapeutic methods for treating a range of diseases. One example that seems to hold tremendous potential is gene therapy, the use of exogenous DNA to replace or suppress a mutant gene in the patient's genome, or to boost the activity of a normal gene. A recent report (highlighted in a punctum in this issue of the journal) has brought autophagy into the gene therapy realm.
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Affiliation(s)
- Debra A Thompson
- Department of Ophthalmology and Visual Sciences and Department of Biological Chemistry; University of Michigan; Ann Arbor, MI USA
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109
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Kaarniranta K, Sinha D, Blasiak J, Kauppinen A, Veréb Z, Salminen A, Boulton ME, Petrovski G. Autophagy and heterophagy dysregulation leads to retinal pigment epithelium dysfunction and development of age-related macular degeneration. Autophagy 2013; 9:973-84. [PMID: 23590900 PMCID: PMC3722332 DOI: 10.4161/auto.24546] [Citation(s) in RCA: 239] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Age-related macular degeneration (AMD) is a complex, degenerative and progressive eye disease that usually does not lead to complete blindness, but can result in severe loss of central vision. Risk factors for AMD include age, genetics, diet, smoking, oxidative stress and many cardiovascular-associated risk factors. Autophagy is a cellular housekeeping process that removes damaged organelles and protein aggregates, whereas heterophagy, in the case of the retinal pigment epithelium (RPE), is the phagocytosis of exogenous photoreceptor outer segments. Numerous studies have demonstrated that both autophagy and heterophagy are highly active in the RPE. To date, there is increasing evidence that constant oxidative stress impairs autophagy and heterophagy, as well as increases protein aggregation and causes inflammasome activation leading to the pathological phenotype of AMD. This review ties together these crucial pathological topics and reflects upon autophagy as a potential therapeutic target in AMD.
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Affiliation(s)
- Kai Kaarniranta
- Department of Ophthalmology; Institute of Clinical Medicine; University of Eastern Finland; Kuopio, Finland; Department of Ophthalmology; Kuopio University Hospital; Kuopio, Finland
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