1
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Sun J, Li P, Gui H, Rittié L, Lombard DB, Rietscher K, Magin TM, Xie Q, Liu L, Omary MB. Deacetylation via SIRT2 prevents keratin-mutation-associated injury and keratin aggregation. JCI Insight 2023; 8:e166314. [PMID: 37485877 PMCID: PMC10443796 DOI: 10.1172/jci.insight.166314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 06/02/2023] [Indexed: 07/25/2023] Open
Abstract
Keratin (K) and other intermediate filament (IF) protein mutations at conserved arginines disrupt keratin filaments into aggregates and cause human epidermolysis bullosa simplex (EBS; K14-R125C) or predispose to mouse liver injury (K18-R90C). The challenge for more than 70 IF-associated diseases is the lack of clinically utilized IF-targeted therapies. We used high-throughput drug screening to identify compounds that normalized mutation-triggered keratin filament disruption. Parthenolide, a plant sesquiterpene lactone, dramatically reversed keratin filament disruption and protected cells and mice expressing K18-R90C from apoptosis. K18-R90C became hyperacetylated compared with K18-WT and treatment with parthenolide normalized K18 acetylation. Parthenolide upregulated the NAD-dependent SIRT2, and increased SIRT2-keratin association. SIRT2 knockdown or pharmacologic inhibition blocked the parthenolide effect, while site-specific Lys-to-Arg mutation of keratin acetylation sites normalized K18-R90C filaments. Treatment of K18-R90C-expressing cells and mice with nicotinamide mononucleotide had a parthenolide-like protective effect. In 2 human K18 variants that associate with human fatal drug-induced liver injury, parthenolide protected K18-D89H- but not K8-K393R-induced filament disruption and cell death. Importantly, parthenolide normalized K14-R125C-mediated filament disruption in keratinocytes and inhibited dispase-triggered keratinocyte sheet fragmentation and Fas-mediated apoptosis. Therefore, keratin acetylation may provide a novel therapeutic target for some keratin-associated diseases.
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Affiliation(s)
- Jingyuan Sun
- Center for Advanced Biotechnology and Medicine, Rutgers University, Piscataway, New Jersey, USA
- Department of Radiation Oncology, Nanfang Hospital, Southern Medical University, Guangzhou, PR China
| | - Pei Li
- Center for Advanced Biotechnology and Medicine, Rutgers University, Piscataway, New Jersey, USA
| | - Honglian Gui
- Department of Infectious Diseases, Ruijin Hospital, Jiaotong University School of Medicine, Shanghai, PR China
| | - Laure Rittié
- Department of Dermatology, University of Michigan, Ann Arbor, Michigan, USA
| | - David B. Lombard
- Sylvester Comprehensive Cancer Center, and Department of Pathology & Laboratory Medicine, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Katrin Rietscher
- Division of Cell and Developmental Biology, Institute of Biology, Leipzig University, Leipzig, Germany
| | - Thomas M. Magin
- Division of Cell and Developmental Biology, Institute of Biology, Leipzig University, Leipzig, Germany
| | - Qing Xie
- Department of Infectious Diseases, Ruijin Hospital, Jiaotong University School of Medicine, Shanghai, PR China
| | - Li Liu
- Hepatology Unit and Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, PR China
| | - M. Bishr Omary
- Center for Advanced Biotechnology and Medicine, Rutgers University, Piscataway, New Jersey, USA
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
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2
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Zhu JG, Xie P, Zheng MD, Meng Y, Wei ML, Liu Y, Liu TW, Gong DQ. Dynamic changes in protein concentrations of keratins in crop milk and related gene expression in pigeon crops during different incubation and chick rearing stages. Br Poult Sci 2023; 64:100-109. [PMID: 36069156 DOI: 10.1080/00071668.2022.2119836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
1. The objective of this study was to examine the keratin composition of crop milk, the variation of epithelial thickness and keratin (K) gene expression in samples from young pigeon during incubation and chick rearing.2. Crop milk was collected from 1-, 3- and 5-day-old squab crops for keratin content analysis. Results showed that K4 accounted for the highest proportion of all detected keratins.3. In total, 42 pairs of adult pigeons were allocated to seven groups according to different stages to collect crop samples. Gene expression studies showed that the K3 gene expression was maximised at rearing Day 15 (15) and R1 in males and females, respectively. K6a gene level was the greatest at R15 in females, whereas it peaked at incubation Day 4 (I4) in males. The K12, K13, K23 and K80 gene levels were inhibited at the peak period of crop milk formation in comparison with I4. In females, K cochleal expression peaked at I10, whereas it was the greatest at R25 in males. K4 and K14 gene expression was the highest at I10 in females, while K4 and K14 were minimised at I17 and R7 in males, respectively. Gene expressions of K5, K8, K19 and K20 in males and K19 in females were maximised at R1. The K5, K20 and K75 gene levels in females peaked at R7. K75 and K8 expressions in males and females reached a maximum value at R25 and I17, respectively.4. The epithelial thickness of male and female crops reached their greatest levels at R1 and had the highest correlation with K19.5. These results emphasised the importance of keratinisation in crop milk formation, and different keratins probably play various roles during this period. The K19 was probably a marker for pigeon crop epithelium development. The sex of the parent pigeon affected keratin gene expression profiles.
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Affiliation(s)
- J G Zhu
- College of Animal Science and Technology, Yangzhou University, Yangzhou, Jiangsu, China
- Jiangsu Collaborative Innovation Center of Regional Modern Agriculture & Environmental Protection, Huaiyin Normal University, Huaian, Huaiyin, China
| | - P Xie
- Jiangsu Collaborative Innovation Center of Regional Modern Agriculture & Environmental Protection, Huaiyin Normal University, Huaian, Huaiyin, China
- Jiangsu Key Laboratory for Eco-Agricultural Biotechnology around Hongze Lake, Huaiyin Normal University, Huaian, Huaiyin, China
| | - M D Zheng
- College of Animal Science and Technology, Yangzhou University, Yangzhou, Jiangsu, China
| | - Y Meng
- College of Animal Science and Technology, Yangzhou University, Yangzhou, Jiangsu, China
| | - M L Wei
- Jiangsu Collaborative Innovation Center of Regional Modern Agriculture & Environmental Protection, Huaiyin Normal University, Huaian, Huaiyin, China
| | - Y Liu
- Jiangsu Collaborative Innovation Center of Regional Modern Agriculture & Environmental Protection, Huaiyin Normal University, Huaian, Huaiyin, China
- Jiangsu Key Laboratory for Eco-Agricultural Biotechnology around Hongze Lake, Huaiyin Normal University, Huaian, Huaiyin, China
| | - T W Liu
- Jiangsu Collaborative Innovation Center of Regional Modern Agriculture & Environmental Protection, Huaiyin Normal University, Huaian, Huaiyin, China
- Jiangsu Key Laboratory for Eco-Agricultural Biotechnology around Hongze Lake, Huaiyin Normal University, Huaian, Huaiyin, China
| | - D Q Gong
- College of Animal Science and Technology, Yangzhou University, Yangzhou, Jiangsu, China
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3
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Li P, Maitra D, Kuo N, Kwan R, Song Y, Tang W, Chen L, Xie Q, Liu L, Omary MB. PP2 protects from keratin mutation-associated liver injury and filament disruption via SRC kinase inhibition in male but not female mice. Hepatology 2023; 77:144-158. [PMID: 35586977 DOI: 10.1002/hep.32574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2022] [Revised: 05/04/2022] [Accepted: 05/05/2022] [Indexed: 02/03/2023]
Abstract
BACKGROUND AND AIMS Hepatocyte keratin polypeptides 8/18 (K8/K18) are unique among intermediate filaments proteins (IFs) in that their mutation predisposes to, rather than causes, human disease. Mice that overexpress human K18 R90C manifest disrupted hepatocyte keratin filaments with hyperphosphorylated keratins and predisposition to Fas-induced liver injury. We hypothesized that high-throughput screening will identify compounds that protect the liver from mutation-triggered predisposition to injury. APPROACH AND RESULTS Using A549 cells transduced with a lentivirus K18 construct and high-throughput screening, we identified the SRC-family tyrosine kinases inhibitor, PP2, as a compound that reverses keratin filament disruption and protects from apoptotic cell death caused by K18 R90C mutation at this highly conserved arginine. PP2 also ameliorated Fas-induced apoptosis and liver injury in male but not female K18 R90C mice. The PP2 male selectivity is due to its lower turnover in male versus female livers. Knockdown of SRC but not another kinase target of PP2, protein tyrosine kinase 6, in A549 cells abrogated the hepatoprotective effect of PP2. Phosphoproteomic analysis and validation showed that the protective effect of PP2 associates with Ser/Thr but not Tyr keratin hypophosphorylation, and differs from the sex-independent effect of the Ser/Thr kinase inhibitor PKC412. Inhibition of RAF kinase, a downstream target of SRC, by vemurafenib had a similar protective effect to PP2 in A549 cells and male K18 R90C mice. CONCLUSIONS PP2 protects, in a male-selective manner, keratin mutation-induced mouse liver injury by inhibiting SRC-triggered downstream Ser/Thr phosphorylation of K8/K18, which is phenocopied by RAF kinase inhibitor vemurafenib. The PP2/vemurafenib-associated findings, and their unique mechanisms of action, further support the potential role of select kinase inhibition as therapeutic opportunities for keratin and other IF-associated human diseases.
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Affiliation(s)
- Pei Li
- Robert Wood Johnson Medical School , Rutgers University , New Brunswick , New Jersey , USA
- Center for Advanced Biotechnology & Medicine , Rutgers University , Piscataway , New Jersey , USA
| | - Dhiman Maitra
- Robert Wood Johnson Medical School , Rutgers University , New Brunswick , New Jersey , USA
- Center for Advanced Biotechnology & Medicine , Rutgers University , Piscataway , New Jersey , USA
- Early-Stage Method Development & Characterization Unit , Bristol Myers Squibb , New Brunswick , New Jersey , USA
| | - Ning Kuo
- Robert Wood Johnson Medical School , Rutgers University , New Brunswick , New Jersey , USA
- Center for Advanced Biotechnology & Medicine , Rutgers University , Piscataway , New Jersey , USA
| | - Raymond Kwan
- Robert Wood Johnson Medical School , Rutgers University , New Brunswick , New Jersey , USA
- Center for Advanced Biotechnology & Medicine , Rutgers University , Piscataway , New Jersey , USA
| | - Yang Song
- Department of Radiation Oncology , Nanfang Hospital, Southern Medical University , Guangzhou , People's Republic of China
| | - Weiliang Tang
- Department of Infectious Diseases , Ruijin Hospital, Jiao Tong University School of Medicine , Shanghai , People's Republic of China
| | - Lu Chen
- Department of Infectious Diseases , Ruijin Hospital, Jiao Tong University School of Medicine , Shanghai , People's Republic of China
| | - Qing Xie
- Department of Infectious Diseases , Ruijin Hospital, Jiao Tong University School of Medicine , Shanghai , People's Republic of China
| | - Li Liu
- Hepatology Unit and Department of Infectious Diseases, Nanfang Hospital , Southern Medical University , Guangzhou , People's Republic of China
| | - M Bishr Omary
- Robert Wood Johnson Medical School , Rutgers University , New Brunswick , New Jersey , USA
- Center for Advanced Biotechnology & Medicine , Rutgers University , Piscataway , New Jersey , USA
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4
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Boricic N, Boricic I, Soldatovic I, Milovanovic J, Trivic A, Terzic T. Utility of CK8, CK10, CK13, and CK17 in Differential Diagnostics of Benign Lesions, Laryngeal Dysplasia, and Laryngeal Squamous Cell Carcinoma. Diagnostics (Basel) 2022; 12:diagnostics12123203. [PMID: 36553210 PMCID: PMC9777365 DOI: 10.3390/diagnostics12123203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 12/07/2022] [Accepted: 12/14/2022] [Indexed: 12/24/2022] Open
Abstract
There are no reliable immunohistochemical markers for diagnosing laryngeal squamous cell carcinoma (SCC) or diagnosing and grading laryngeal dysplasia. We aimed to evaluate the diagnostic utility of CK8, CK10, CK13, and CK17 in benign laryngeal lesions, laryngeal dysplasia, and laryngeal SCC. This retrospective study included 151 patients diagnosed with laryngeal papilloma, laryngeal polyps, laryngeal dysplasia, and laryngeal SCC who underwent surgical treatment between 2010 and 2020. Immunohistochemistry (IHC) was carried out using specific monoclonal antibodies against CK8, CK10, CK13, and CK17. Two experienced pathologists performed semi-quantitative scoring of IHC positivity. The diagnostic significance of the markers was analyzed. CK13 showed a sensitivity of 100% and a specificity of 82.5% for distinguishing between laryngeal SCC and laryngeal dysplasia and benign lesions. CK17 showed a sensitivity of 78.3% and specificity of 57.1% for the detection of laryngeal SCC vs. laryngeal dysplasia. CK10 showed a sensitivity of 80.0% for discriminating between low-grade and high-grade dysplasia, and a specificity of 61.1%. Loss of CK13 expression is a reliable diagnostic tool for diagnosing laryngeal lesions with malignant potential and determining resection lines. In lesions with diminished CK13 expression, CK17 could be used as an auxiliary immunohistochemical marker in diagnosing laryngeal SCC. In CK13-negative and CK17-positive lesions, CK10 positivity could be used to determine low-grade dysplasia. CK8 is not a useful IHC marker in differentiating between benign laryngeal lesions, laryngeal dysplasia, and laryngeal SCC.
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Affiliation(s)
- Novica Boricic
- Institute of Pathology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
- Correspondence:
| | - Ivan Boricic
- Institute of Pathology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Ivan Soldatovic
- Faculty of Medicine, Institute of Medical Statistics and Informatics, University of Belgrade, 11000 Belgrade, Serbia
| | - Jovica Milovanovic
- Clinic for Otorhinolaryngology and Maxillofacial Surgery, Clinical Centre Serbia, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Aleksandar Trivic
- Clinic for Otorhinolaryngology and Maxillofacial Surgery, Clinical Centre Serbia, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Tatjana Terzic
- Institute of Pathology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
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5
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Ni JH, Yang WX. Extracellular and Intracellular Skeletons: How Do They Involve in Apoptosis. DNA Cell Biol 2021; 41:80-90. [PMID: 34847739 DOI: 10.1089/dna.2021.0613] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Apoptosis plays a key role in removing abnormal or senescent cells, maintaining the overall health of the tissue, and coordinating individual development. Recently, it has been discovered that the intracellular cytoskeleton plays a role in the apoptotic process. In addition, the regulatory role of extracellular matrix (ECM) fibrous proteins, which can be considered as the extracellular skeleton, in the process of apoptosis is rarely summarized. In this review, we collect the latest knowledge about how fibrous proteins inside and outside cells regulate apoptosis. We describe how ECM fibrous proteins participate in the regulation of death receptor and mitochondrial pathways through various signaling cascades mediated by integrins. We then explore the molecular mechanisms by which intracellular intermediate filaments regulate cell apoptosis by regulating death receptors on the cell membrane surface. Similarly, we report on novel supporting functions of microtubules in the execution phase of apoptosis and discuss their formation mechanisms. Finally, we discuss that the polypeptide fragments formed by caspase degradation of ECM fibrous proteins and intracellular intermediate filament act as local regulatory signals to play different regulatory roles in apoptosis.
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Affiliation(s)
- Jia-Hao Ni
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Wan-Xi Yang
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
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6
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Kim S, Lim Y, Lee SY, Yoon HN, Yi H, Jang KH, Ku NO. Keratin 8 mutations in transgenic mice predispose to lung injury. J Cell Sci 2021; 134:jcs250167. [PMID: 34342355 DOI: 10.1242/jcs.250167] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 06/28/2021] [Indexed: 11/20/2022] Open
Abstract
Keratin 8 (K8) is the cytoskeletal intermediate filament protein of simple-type epithelia. Mutations in K8 predispose the affected individual and transgenic mouse to liver disease. However, the role of K8 in the lung has not been reported in mutant transgenic mouse models. Here, we investigated the susceptibility of two different transgenic mice expressing K8 Gly62-Cys (Gly62 replaced with Cys) or Ser74-Ala (Ser74 replaced with Ala) to lung injury. The mutant transgenic mice were highly susceptible to two independent acute and chronic lung injuries compared with control mice. Both K8 Gly62-Cys mice and K8 Ser74-Ala mice showed markedly increased mouse lethality (∼74% mutant mice versus ∼34% control mice) and more severe lung damage, with increased inflammation and apoptosis, under L-arginine-mediated acute lung injury. Moreover, the K8 Ser74-Ala mice had more severe lung damage, with extensive hemorrhage and prominent fibrosis, under bleomycin-induced chronic lung injury. Our study provides the first direct evidence that K8 mutations predispose to lung injury in transgenic mice.
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Affiliation(s)
- Sujin Kim
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul 03722, Korea
| | - Younglan Lim
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul 03722, Korea
| | - So-Young Lee
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul 03722, Korea
| | - Han-Na Yoon
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul 03722, Korea
| | - Hayan Yi
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul 03722, Korea
| | - Kwi-Hoon Jang
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul 03722, Korea
| | - Nam-On Ku
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul 03722, Korea
- Department of Bio-Convergence ISED, Underwood International College, Yonsei University, Seoul 03722, Korea
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7
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Alam CM, Baghestani S, Pajari A, Omary MB, Toivola DM. Keratin 7 Is a Constituent of the Keratin Network in Mouse Pancreatic Islets and Is Upregulated in Experimental Diabetes. Int J Mol Sci 2021; 22:ijms22157784. [PMID: 34360548 PMCID: PMC8346022 DOI: 10.3390/ijms22157784] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/08/2021] [Accepted: 07/13/2021] [Indexed: 11/16/2022] Open
Abstract
Keratin (K) 7 is an intermediate filament protein expressed in ducts and glands of simple epithelial organs and in urothelial tissues. In the pancreas, K7 is expressed in exocrine ducts, and apico-laterally in acinar cells. Here, we report K7 expression with K8 and K18 in the endocrine islets of Langerhans in mice. K7 filament formation in islet and MIN6 β-cells is dependent on the presence and levels of K18. K18-knockout (K18‒/‒) mice have undetectable islet K7 and K8 proteins, while K7 and K18 are downregulated in K8‒/‒ islets. K7, akin to F-actin, is concentrated at the apical vertex of β-cells in wild-type mice and along the lateral membrane, in addition to forming a fine cytoplasmic network. In K8‒/‒ β-cells, apical K7 remains, but lateral keratin bundles are displaced and cytoplasmic filaments are scarce. Islet K7, rather than K8, is increased in K18 over-expressing mice and the K18-R90C mutation disrupts K7 filaments in mouse β-cells and in MIN6 cells. Notably, islet K7 filament networks significantly increase and expand in the perinuclear regions when examined in the streptozotocin diabetes model. Hence, K7 represents a significant component of the murine islet keratin network and becomes markedly upregulated during experimental diabetes.
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Affiliation(s)
- Catharina M. Alam
- Department of Biosciences, Cell Biology, Åbo Akademi University, Tykistökatu 6A, BioCity 2nd Floor, FIN-20520 Turku, Finland; (S.B.); (A.P.)
- Correspondence: (C.M.A.); (D.M.T.)
| | - Sarah Baghestani
- Department of Biosciences, Cell Biology, Åbo Akademi University, Tykistökatu 6A, BioCity 2nd Floor, FIN-20520 Turku, Finland; (S.B.); (A.P.)
| | - Ada Pajari
- Department of Biosciences, Cell Biology, Åbo Akademi University, Tykistökatu 6A, BioCity 2nd Floor, FIN-20520 Turku, Finland; (S.B.); (A.P.)
| | - M. Bishr Omary
- Center for Advanced Biotechnology and Medicine, Rutgers University, Piscataway, NJ 08854, USA;
| | - Diana M. Toivola
- Department of Biosciences, Cell Biology, Åbo Akademi University, Tykistökatu 6A, BioCity 2nd Floor, FIN-20520 Turku, Finland; (S.B.); (A.P.)
- Turku Center for Disease Modeling, University of Turku, Kiinamyllynkatu 10, FIN-20520 Turku, Finland
- Correspondence: (C.M.A.); (D.M.T.)
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8
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Lim Y, Ku NO. Revealing the Roles of Keratin 8/18-Associated Signaling Proteins Involved in the Development of Hepatocellular Carcinoma. Int J Mol Sci 2021; 22:6401. [PMID: 34203895 PMCID: PMC8232640 DOI: 10.3390/ijms22126401] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 06/08/2021] [Accepted: 06/11/2021] [Indexed: 02/08/2023] Open
Abstract
Although hepatocellular carcinoma (HCC) is developed with various etiologies, protection of hepatocytes seems basically essential to prevent the incidence of HCC. Keratin 8 and keratin 18 (K8/K18) are cytoskeletal intermediate filament proteins that are expressed in hepatocytes. They maintain the cell shape and protect cells under stress conditions. Their protective roles in liver damage have been described in studies of mouse models, and K8/K18 mutation frequency in liver patients. Interestingly, K8/K18 bind to signaling proteins such as transcription factors and protein kinases involved in HCC development. Since K8/K18 are abundant cytoskeletal proteins, K8/K18 binding with the signaling factors can alter the availability of the factors. Herein, we discuss the potential roles of K8/K18 in HCC development.
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Affiliation(s)
- Younglan Lim
- Interdisciplinary Program of Integrated OMICS for Biomedical Sciences, Yonsei University, Seoul 03722, Korea;
| | - Nam-On Ku
- Interdisciplinary Program of Integrated OMICS for Biomedical Sciences, Yonsei University, Seoul 03722, Korea;
- Department of Bio-Convergence ISED, Underwood International College, Yonsei University, Seoul 03722, Korea
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9
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Sundaram B, Behnke K, Belancic A, Al-Salihi MA, Thabet Y, Polz R, Pellegrino R, Zhuang Y, Shinde PV, Xu HC, Vasilevska J, Longerich T, Herebian D, Mayatepek E, Bock HH, May P, Kordes C, Aghaeepour N, Mak TW, Keitel V, Häussinger D, Scheller J, Pandyra AA, Lang KS, Lang PA. iRhom2 inhibits bile duct obstruction-induced liver fibrosis. Sci Signal 2019; 12:12/605/eaax1194. [PMID: 31662486 DOI: 10.1126/scisignal.aax1194] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Chronic liver disease can induce prolonged activation of hepatic stellate cells, which may result in liver fibrosis. Inactive rhomboid protein 2 (iRhom2) is required for the maturation of A disintegrin and metalloprotease 17 (ADAM17, also called TACE), which is responsible for the cleavage of membrane-bound tumor necrosis factor-α (TNF-α) and its receptors (TNFRs). Here, using the murine bile duct ligation (BDL) model, we showed that the abundance of iRhom2 and activation of ADAM17 increased during liver fibrosis. Consistent with this, concentrations of ADAM17 substrates were increased in plasma samples from mice after BDL and in patients suffering from liver cirrhosis. We observed increased liver fibrosis, accelerated disease progression, and an increase in activated stellate cells after BDL in mice lacking iRhom2 (Rhbdf2-/- ) compared to that in controls. In vitro primary mouse hepatic stellate cells exhibited iRhom2-dependent shedding of the ADAM17 substrates TNFR1 and TNFR2. In vivo TNFR shedding after BDL also depended on iRhom2. Treatment of Rhbdf2-/- mice with the TNF-α inhibitor etanercept reduced the presence of activated stellate cells and alleviated liver fibrosis after BDL. Together, these data suggest that iRhom2-mediated inhibition of TNFR signaling protects against liver fibrosis.
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Affiliation(s)
- Balamurugan Sundaram
- Department of Molecular Medicine II, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Kristina Behnke
- Department of Molecular Medicine II, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Andrea Belancic
- Department of Molecular Medicine II, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Mazin A Al-Salihi
- Department of Molecular Medicine II, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Yasser Thabet
- Department of Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine-University Düsseldorf, Moorenstrasse 5, 40225 Düsseldorf, Germany
| | - Robin Polz
- Institute of Biochemistry and Molecular Biology II, Medical Faculty, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany
| | - Rossella Pellegrino
- Institute of Pathology, University Hospital Heidelberg, Im Neuenheimer Feld 224, 69120 Heidelberg, Germany
| | - Yuan Zhuang
- Department of Molecular Medicine II, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Prashant V Shinde
- Department of Molecular Medicine II, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Haifeng C Xu
- Department of Molecular Medicine II, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Jelena Vasilevska
- Department of Molecular Medicine II, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Thomas Longerich
- Institute of Pathology, University Hospital Heidelberg, Im Neuenheimer Feld 224, 69120 Heidelberg, Germany
| | - Diran Herebian
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany
| | - Ertan Mayatepek
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany
| | - Hans H Bock
- Department of Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine-University Düsseldorf, Moorenstrasse 5, 40225 Düsseldorf, Germany
| | - Petra May
- Department of Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine-University Düsseldorf, Moorenstrasse 5, 40225 Düsseldorf, Germany
| | - Claus Kordes
- Department of Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine-University Düsseldorf, Moorenstrasse 5, 40225 Düsseldorf, Germany.,Institute for Experimental Regenerative Hepatology, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany
| | - Nima Aghaeepour
- Stanford University, 300 Pasteur Drive, Grant S280, Stanford, CA 94305-5117, USA
| | - Tak W Mak
- Department of Medical Biophysics, University of Toronto, 1 King's Circle, Toronto, ON M5S 1A8, Canada.,Department of Pathology, University of Hong Kong, Hong Kong
| | - Verena Keitel
- Department of Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine-University Düsseldorf, Moorenstrasse 5, 40225 Düsseldorf, Germany
| | - Dieter Häussinger
- Department of Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine-University Düsseldorf, Moorenstrasse 5, 40225 Düsseldorf, Germany.,Institute for Experimental Regenerative Hepatology, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany
| | - Jürgen Scheller
- Institute of Biochemistry and Molecular Biology II, Medical Faculty, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany
| | - Aleksandra A Pandyra
- Department of Molecular Medicine II, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany.,Department of Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine-University Düsseldorf, Moorenstrasse 5, 40225 Düsseldorf, Germany
| | - Karl S Lang
- Institute of Immunology, Medical Faculty, University of Duisburg-Essen, Hufelandstr. 55, Essen 45147, Germany
| | - Philipp A Lang
- Department of Molecular Medicine II, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
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10
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Cheng Y, Qin K, Huang N, Zhou Z, Xiong H, Zhao J, Zhang Y, Yu S. Cytokeratin 18 regulates the transcription and alternative splicing of apoptotic‑related genes and pathways in HeLa cells. Oncol Rep 2019; 42:301-312. [PMID: 31115582 PMCID: PMC6549092 DOI: 10.3892/or.2019.7166] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 05/13/2019] [Indexed: 02/07/2023] Open
Abstract
Cytokeratin 18 (CK18), one of the major components of intermediate filaments (IF) in simple epithelial cells, undergoes caspase-mediated cleavage upon epithelial cell necrosis and apoptosis. CK18 has been used as a biomarker of several cancers and has been reported to be dysregulated in cervical cancers. The effects of dysregulated expression of CK18 at a molecular level are, however, unclear. In the present study, the function of CK18 in HeLa cells, a cell line derived from a cervical cancer cells, was investigated using shRNA knockdown. Reduced levels of CK18 led to a significant decrease in cell apoptosis, compared with control cells. Notably, RNA-seq analysis of the transcriptomes of HeLa cells, with or without CK18 knockdown, revealed that genes in the NF-κB pathway, and certain apoptosis pathways, were under global transcriptional and alternative splicing regulation. Quantitative RT-PCR confirmed the CK18-regulated transcription of apoptotic genes FAS and FADD, as well as immune genes CXCL2 and CD79B, in addition to alternative splicing of FAS and CTNNB1. Western blot analysis further revealed that CK18 knockdown led to reduced expression of CASP8. In conclusion, the present study indicated that CK18 played a role in apoptosis, which may be mediated via a feed-back regulation loop and may involve regulation of transcription and alternative splicing of a number of genes in apoptotic pathways.
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Affiliation(s)
- Yi Cheng
- Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Kai Qin
- Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Nan Huang
- Department of Allergy, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Zhipeng Zhou
- Laboratory for Genome Regulation and Human Health, ABLife, Inc., Optics Valley International Biomedical Park, East Lake High‑Tech Development Zone, Wuhan, Hubei 430075, P.R. China
| | - Huihua Xiong
- Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Jing Zhao
- Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
| | - Yi Zhang
- Laboratory for Genome Regulation and Human Health, ABLife, Inc., Optics Valley International Biomedical Park, East Lake High‑Tech Development Zone, Wuhan, Hubei 430075, P.R. China
| | - Shiying Yu
- Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
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11
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The role of keratins in the digestive system: lessons from transgenic mouse models. Histochem Cell Biol 2018; 150:351-359. [PMID: 30039330 DOI: 10.1007/s00418-018-1695-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/17/2018] [Indexed: 01/17/2023]
Abstract
Keratins are the largest subfamily of intermediate filament proteins. They are either type I acidic or type II basic keratins. Keratins form obligate heteropolymer in epithelial cells and their expression patterns are tissue-specific. Studies have shown that keratin mutations are the cause of many diseases in humans or predispose humans to acquiring them. Using mouse models to study keratin-associated human diseases is critical, because they allow researchers to get a better understanding of these diseases and their progressions, and so many such studies have been conducted. Acknowledging the importance, researches with genetically modified mice expressing human disease-associated keratin mutants have been widely done. Numerous studies using keratin knockout mice, keratin-overexpressed mice, or transgenic mice expressing keratin mutants have been conducted. This review summarizes the mouse models that have been used to study type I and type II keratin expression in the digestive organs, namely, the liver, pancreas, and colon.
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12
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Consequences of Keratin Phosphorylation for Cytoskeletal Organization and Epithelial Functions. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2017; 330:171-225. [DOI: 10.1016/bs.ircmb.2016.09.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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13
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Proteomics-Based Identification of the Molecular Signatures of Liver Tissues from Aged Rats following Eight Weeks of Medium-Intensity Exercise. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2016; 2016:3269405. [PMID: 28116034 PMCID: PMC5223045 DOI: 10.1155/2016/3269405] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2016] [Revised: 09/05/2016] [Accepted: 11/28/2016] [Indexed: 02/07/2023]
Abstract
Physical activity has emerged as a powerful intervention that promotes healthy aging by maintaining the functional capacity of critical organ systems. Here, by combining functional and proteomics analyses, we examined how hepatic phenotypes might respond to exercise treatment in aged rats. 16 male aged (20 months old) SD rats were divided into exercise and parallel control groups at random; the exercise group had 8 weeks of treadmill training with medium intensity. Whole protein samples of the liver were extracted from both groups and separated by two-dimensional gel electrophoresis. Alternatively objective protein spots with >2-fold difference in expression were selected for enzymological extraction and MS/MS identification. Results show increased activity of the manganese superoxide dismutase and elevated glutathione levels in the livers of exercise-treated animals, but malondialdehyde contents obviously decreased in the liver of the exercise group. Proteomics-based identification of differentially expressed proteins provided an integrated view of the metabolic adaptations occurring in the liver proteome during exercise, which significantly altered the expression of several proteins involved in key liver metabolic pathways including mitochondrial sulfur, glycolysis, methionine, and protein metabolism. These findings indicate that exercise may be beneficial to aged rats through modulation of hepatic protein expression profiles.
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14
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Bettermann K, Mehta AK, Hofer EM, Wohlrab C, Golob-Schwarzl N, Svendova V, Schimek MG, Stumptner C, Thüringer A, Speicher MR, Lackner C, Zatloukal K, Denk H, Haybaeck J. Keratin 18-deficiency results in steatohepatitis and liver tumors in old mice: A model of steatohepatitis-associated liver carcinogenesis. Oncotarget 2016; 7:73309-73322. [PMID: 27689336 PMCID: PMC5341981 DOI: 10.18632/oncotarget.12325] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 09/19/2016] [Indexed: 02/06/2023] Open
Abstract
Backround: Steatohepatitis (SH)-associated liver carcinogenesis is an increasingly important issue in clinical medicine. SH is morphologically characterized by steatosis, hepatocyte injury, ballooning, hepatocytic cytoplasmic inclusions termed Mallory-Denk bodies (MDBs), inflammation and fibrosis. RESULTS 17-20-months-old Krt18-/- and Krt18+/- mice in contrast to wt mice spontaneously developed liver lesions closely resembling the morphological spectrum of human SH as well as liver tumors. The pathologic alterations were more pronounced in Krt18-/- than in Krt18+/- mice. The frequency of liver tumors with male predominance was significantly higher in Krt18-/- compared to age-matched Krt18+/- and wt mice. Krt18-deficient tumors in contrast to wt animals displayed SH features and often pleomorphic morphology. aCGH analysis of tumors revealed chromosomal aberrations in Krt18-/- liver tumors, affecting loci of oncogenes and tumor suppressor genes. MATERIALS AND METHODS Livers of 3-, 6-, 12- and 17-20-months-old aged wild type (wt), Krt18+/- and Krt18-/- (129P2/OlaHsd background) mice were analyzed by light and immunofluorescence microscopy as well as immunohistochemistry. Liver tumors arising in aged mice were analyzed by array comparative genomic hybridization (aCGH). CONCLUSIONS Our findings show that K18 deficiency of hepatocytes leads to steatosis, increasing with age, and finally to SH. K18 deficiency and age promote liver tumor development in mice, frequently on the basis of chromosomal instability, resembling human HCC with stemness features.
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Affiliation(s)
- Kira Bettermann
- Institute of Pathology, Medical University of Graz, Graz 8036, Austria
| | | | - Eva M. Hofer
- Institute of Pathology, Medical University of Graz, Graz 8036, Austria
| | - Christina Wohlrab
- Institute of Pathology, Medical University of Graz, Graz 8036, Austria
| | | | - Vendula Svendova
- Institute for Medical Informatics, Statistics and Documentation, Medical University of Graz, Graz 8036, Austria
| | - Michael G. Schimek
- Institute for Medical Informatics, Statistics and Documentation, Medical University of Graz, Graz 8036, Austria
| | | | - Andrea Thüringer
- Institute of Pathology, Medical University of Graz, Graz 8036, Austria
| | | | - Carolin Lackner
- Institute of Pathology, Medical University of Graz, Graz 8036, Austria
| | - Kurt Zatloukal
- Institute of Pathology, Medical University of Graz, Graz 8036, Austria
| | - Helmut Denk
- Institute of Pathology, Medical University of Graz, Graz 8036, Austria
| | - Johannes Haybaeck
- Institute of Pathology, Medical University of Graz, Graz 8036, Austria
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15
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Prognostic Value of Serum Caspase-Cleaved Cytokeratin-18 Levels before Liver Transplantation for One-Year Survival of Patients with Hepatocellular Carcinoma. Int J Mol Sci 2016; 17:ijms17091524. [PMID: 27618033 PMCID: PMC5037799 DOI: 10.3390/ijms17091524] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 09/01/2016] [Accepted: 09/05/2016] [Indexed: 12/30/2022] Open
Abstract
Cytokeratin (CK)-18 is the major intermediate filament protein in the liver and during hepatocyte apoptosis is cleaved by the action of caspases; the resulting fragments are released into the blood as caspase-cleaved cytokeratin (CCCK)-18. Higher circulating levels of CCCK-18 have been found in patients with hepatocellular carcinoma (HCC) than in healthy controls and than in cirrhotic patients. However, it is unknown whether serum CCCK-18 levels before liver transplantation (LT) in patients with HCC could be used as a prognostic biomarker of one-year survival, and this was the objective of our study with 135 patients. At one year after LT, non-survivors showed higher serum CCCK-18 levels than survivors (p = 0.001). On binary logistic regression analysis, serum CCCK-18 levels >384 U/L were associated with death at one year (odds ratio = 19.801; 95% confidence interval = 5.301–73.972; p < 0.001) after controlling for deceased donor age. The area under the receiver operating characteristic (ROC) curve of serum CCCK-18 levels to predict death at one year was 77% (95% CI = 69%–84%; p < 0.001). The new finding of our study was that serum levels of CCCK-18 before LT in patients with HCC could be used as prognostic biomarker of survival.
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16
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Siemionow K, Teul J, Drągowski P, Pałka J, Miltyk W. New potential biomarkers of acetaminophen-induced hepatotoxicity. Adv Med Sci 2016; 61:325-330. [PMID: 27471017 DOI: 10.1016/j.advms.2016.05.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 02/29/2016] [Accepted: 05/16/2016] [Indexed: 12/26/2022]
Abstract
Acetaminophen (APAP) is one of the most common antipyretic and analgesic drugs. Despite various precautions patients use APAP in amounts exceeding acceptable daily doses. APAP overdosing contributes to APAP intoxication, which leads to acute liver injury or necessity of exigent liver transplantation. Biomarkers that can be helpful in early diagnosis of liver injury during APAP overdosing are studied worldwide. This review presents recent reports on new potential biomarkers and their prospective application in clinical practice.
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17
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Ku NO, Strnad P, Bantel H, Omary MB. Keratins: Biomarkers and modulators of apoptotic and necrotic cell death in the liver. Hepatology 2016; 64:966-76. [PMID: 26853542 PMCID: PMC4977204 DOI: 10.1002/hep.28493] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Revised: 01/28/2016] [Accepted: 02/03/2016] [Indexed: 12/14/2022]
Abstract
UNLABELLED Keratins, formerly known as cytokeratins, are the major epithelial-specific subgroup of intermediate filament proteins. Adult hepatocytes express keratin polypeptides 8 and 18 (K8/K18), whereas cholangiocytes express K8/K18 and keratins 7 and 19 (K7/K19). Keratins function primarily to protect hepatocytes from apoptosis and necrosis, which was revealed using several genetic mouse models. This cytoprotective function was further clarified by the identification of natural human keratin variants that are normally silent, but become pathogenic by predisposing their carriers to apoptosis during acute or chronic liver injury mediated by toxins, virus infection, or metabolic stress. During apoptosis, caspases cleave K18 and K19 at conserved aspartates (human K18/K19: (235) Val-Glu-Val-Asp(↓) ) and K18 at a unique aspartate (human K18: (394) Asp-Ala-Leu-Asp(↓) ), with the latter exposed epitope becoming recognized by the M30 antibody in blood and tissues. Additional K18-containing protein backbone epitopes are detected using the M6 and M5 (termed M65) antibodies. Intact K18 and its associated fragments, which are released into blood during apoptosis and necrosis in various diseases, have been analyzed by enzyme-linked immunosorbent assay using the M30/M65 antibodies or their signal ratios. Furthermore, M30/M65 levels have been used as diagnostic and prognostic biomarkers in acute and chronic liver diseases, including nonalcoholic steatohepatitis and acute liver failure. Other keratin biomarkers include K8/K18/K19-related tissue polypeptide antigen, K18-related tissue polypeptide-specific antigen, and K19-related CYFRA-21-1, which have been evaluated mostly in patients with epithelial tumors. CONCLUSION Keratins and their fragments are released into blood during liver and other epithelial tissue injury. The epithelial specificity of K18/K19, epitope unmasking upon caspase digestion, keratin abundance, and relative keratin stability render them useful biomarkers for hepatocyte and cholangiocyte apoptosis and necrosis. However, the precise biochemical nature and release mechanism of circulating keratins remain unknown. (Hepatology 2016;64:966-976).
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Affiliation(s)
- Nam-On Ku
- Department of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul 120-749, Korea
| | - Pavel Strnad
- Department of Internal Medicine III and IZKF, University Hospital Aachen, Aachen, Germany
| | - Heike Bantel
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - M. Bishr Omary
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, 7744 Medical Science II, 1301 E. Catherine Street, Ann Arbor, MI 48109-5622,Department of Medicine, University of Michigan Medical School, 7744 Medical Science II, 1301 E. Catherine Street, Ann Arbor, MI 48109-5622; and VA Ann Arbor Health Care System, Ann Arbor MI, 48105
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18
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Gilbert S, Loranger A, Omary MB, Marceau N. Keratin impact on PKCδ- and ASMase-mediated regulation of hepatocyte lipid raft size - implication for FasR-associated apoptosis. J Cell Sci 2016; 129:3262-73. [PMID: 27422101 DOI: 10.1242/jcs.171124] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 07/13/2016] [Indexed: 11/20/2022] Open
Abstract
Keratins are epithelial cell intermediate filament (IF) proteins that are expressed as pairs in a cell-differentiation-regulated manner. Hepatocytes express the keratin 8 and 18 pair (denoted K8/K18) of IFs, and a loss of K8 or K18, as in K8-null mice, leads to degradation of the keratin partner. We have previously reported that a K8/K18 loss in hepatocytes leads to altered cell surface lipid raft distribution and more efficient Fas receptor (FasR, also known as TNFRSF6)-mediated apoptosis. We demonstrate here that the absence of K8 or transgenic expression of the K8 G62C mutant in mouse hepatocytes reduces lipid raft size. Mechanistically, we find that the lipid raft size is dependent on acid sphingomyelinase (ASMase, also known as SMPD1) enzyme activity, which is reduced in absence of K8/K18. Notably, the reduction of ASMase activity appears to be caused by a less efficient redistribution of surface membrane PKCδ toward lysosomes. Moreover, we delineate the lipid raft volume range that is required for an optimal FasR-mediated apoptosis. Hence, K8/K18-dependent PKCδ- and ASMase-mediated modulation of lipid raft size can explain the more prominent FasR-mediated signaling resulting from K8/K18 loss. The fine-tuning of ASMase-mediated regulation of lipid rafts might provide a therapeutic target for death-receptor-related liver diseases.
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Affiliation(s)
- Stéphane Gilbert
- Centre de recherche sur le cancer de l'Université Laval and Centre de recherche du CHU de Québec (HDQ), Québec, Canada G1R 2J6
| | - Anne Loranger
- Centre de recherche sur le cancer de l'Université Laval and Centre de recherche du CHU de Québec (HDQ), Québec, Canada G1R 2J6
| | - M Bishr Omary
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Normand Marceau
- Centre de recherche sur le cancer de l'Université Laval and Centre de recherche du CHU de Québec (HDQ), Québec, Canada G1R 2J6
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Salas PJ, Forteza R, Mashukova A. Multiple roles for keratin intermediate filaments in the regulation of epithelial barrier function and apico-basal polarity. Tissue Barriers 2016; 4:e1178368. [PMID: 27583190 PMCID: PMC4993576 DOI: 10.1080/21688370.2016.1178368] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 04/05/2016] [Accepted: 04/07/2016] [Indexed: 12/27/2022] Open
Abstract
As multicellular organisms evolved a family of cytoskeletal proteins, the keratins (types I and II) expressed in epithelial cells diversified in more than 20 genes in vertebrates. There is no question that keratin filaments confer mechanical stiffness to cells. However, such a number of genes can hardly be explained by evolutionary advantages in mechanical features. The use of transgenic mouse models has revealed unexpected functional relationships between keratin intermediate filaments and intracellular signaling. Accordingly, loss of keratins or mutations in keratins that cause or predispose to human diseases, result in increased sensitivity to apoptosis, regulation of innate immunity, permeabilization of tight junctions, and mistargeting of apical proteins in different epithelia. Precise mechanistic explanations for these phenomena are still lacking. However, immobilization of membrane or cytoplasmic proteins, including chaperones, on intermediate filaments (“scaffolding”) appear as common molecular mechanisms and may explain the need for so many different keratin genes in vertebrates.
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Affiliation(s)
- Pedro J Salas
- Department of Cell Biology, Miller School of Medicine, University of Miami , Miami, FL, USA
| | - Radia Forteza
- Department of Cell Biology, Miller School of Medicine, University of Miami , Miami, FL, USA
| | - Anastasia Mashukova
- Department of Cell Biology, Miller School of Medicine, University of Miami, Miami, FL, USA; Department of Physiology, Nova Southeastern University, Fort Lauderdale, FL, USA
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20
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Kwan R, Chen L, Looi K, Tao GZ, Weerasinghe SV, Snider NT, Conti MA, Adelstein RS, Xie Q, Omary MB. PKC412 normalizes mutation-related keratin filament disruption and hepatic injury in mice by promoting keratin-myosin binding. Hepatology 2015; 62:1858-69. [PMID: 26126491 PMCID: PMC4681638 DOI: 10.1002/hep.27965] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 06/29/2015] [Indexed: 12/22/2022]
Abstract
UNLABELLED Keratins, among other cytoskeletal intermediate filament proteins, are mutated at a highly conserved arginine with consequent severe disease phenotypes due to disruption of keratin filament organization. We screened a kinase inhibitor library, using A549 cells that are transduced with a lentivirus keratin 18 (K18) construct, to identify compounds that normalize filament disruption due to K18 Arg90Cys mutation at the conserved arginine. High-throughput screening showed that PKC412, a multikinase inhibitor, ameliorated K18 Arg90Cys-mediated keratin filament disruption in cells and in the livers of previously described transgenic mice that overexpress K18 Arg90Cys. Furthermore, PKC412 protected cultured A549 cells that express mutant or wild-type K18 and mouse livers of the K18 Arg90Cys-overexpressing transgenic mice from Fas-induced apoptosis. Proteomic analysis of proteins that associated with keratins after exposure of K18-expressing A549 cells to PKC412 showed that nonmuscle myosin heavy chain-IIA (NMHC-IIA) partitions with the keratin fraction. The nonmuscle myosin-IIA (NM-IIA) association with keratins was confirmed by immune staining and by coimmunoprecipitation. The keratin-myosin association is myosin dephosphorylation-dependent; occurs with K8, the obligate K18 partner; is enhanced by PKC412 in cells and mouse liver; and is blocked by hyperphosphorylation conditions in cultured cells and mouse liver. Furthermore, NMHC-IIA knockdown inhibits PKC412-mediated normalization of K18 R90C filaments. CONCLUSION The inhibitor PKC412 normalizes K18 Arg90Cys mutation-induced filament disruption and disorganization by enhancing keratin association with NM-IIA in a myosin dephosphorylation-regulated manner. Targeting of intermediate filament disorganization by compounds that alter keratin interaction with their associated proteins offers a potential novel therapeutic approach for keratin and possibly other intermediate filament protein-associated diseases.
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Affiliation(s)
- Raymond Kwan
- Departments of Molecular & Integrative Physiology and Medicine, University of Michigan, Ann Arbor, Michigan, USA,VA Ann Arbor Healthcare System, Ann Arbor, Michigan, USA
| | - Lu Chen
- Departments of Molecular & Integrative Physiology and Medicine, University of Michigan, Ann Arbor, Michigan, USA,Infectious Diseases Department, Ruijin Hospital, Shanghai Jiao Tong University Medical School, Shanghai, Peoples Republic of China
| | - Koksun Looi
- Departments of Molecular & Integrative Physiology and Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Guo-Zhong Tao
- Department of Surgery, Stanford University, Palo Alto, California, USA
| | - Sujith V Weerasinghe
- Departments of Molecular & Integrative Physiology and Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Natasha T Snider
- Departments of Molecular & Integrative Physiology and Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Mary Anne Conti
- The Laboratory of Molecular Cardiology, NHLBI, National Institutes of Health, Bethesda, Maryland, USA
| | - Robert S Adelstein
- The Laboratory of Molecular Cardiology, NHLBI, National Institutes of Health, Bethesda, Maryland, USA
| | - Qing Xie
- Infectious Diseases Department, Ruijin Hospital, Shanghai Jiao Tong University Medical School, Shanghai, Peoples Republic of China
| | - M Bishr Omary
- Departments of Molecular & Integrative Physiology and Medicine, University of Michigan, Ann Arbor, Michigan, USA,VA Ann Arbor Healthcare System, Ann Arbor, Michigan, USA
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Yunusbaeva MM, Yunusbaev BB, Valiev RR, Khammatova AA, Khusnutdinova EK. Широкое многообразие кератинов человека. VESTNIK DERMATOLOGII I VENEROLOGII 2015. [DOI: 10.25208/0042-4609-2015-91-5-42-52] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
А review presents systematic data about the diversity of human keratins. The results of numerous studies concerning the structure and functions of keratins, their distribution in various cells and tissues were summarized. The role of these proteins in the development of human hereditary diseases, as well as modern approaches in use keratins in immunohistochemistry and perspectives of their further studies are discussed.
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22
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Roux A, Gilbert S, Loranger A, Marceau N. Impact of keratin intermediate filaments on insulin-mediated glucose metabolism regulation in the liver and disease association. FASEB J 2015; 30:491-502. [PMID: 26467793 DOI: 10.1096/fj.15-277905] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 09/21/2015] [Indexed: 12/17/2022]
Abstract
In all cells, a tight regulation exists between glucose uptake and utilization to prevent diseases related to its perturbed metabolism. In insulin-targeted cells, such as hepatocytes, proper glucose utilization requires an elaborate interplay between the insulin receptor, the glucose transporter, and mitochondria that involves the participation of actin microfilaments and microtubules. In addition, there is increasing evidence of an involvement of the third cytoskeletal network provided by intermediate filaments (IFs). Keratins belong to the multigene family of IF proteins, coordinately expressed as distinct pairs within the context of epithelial cell differentiation. Hepatocyte IFs are made up of the [keratin (K)8/K18] pair only, whereas pancreatic β-cell IFs additionally include small amounts of K7. There are accumulating examples of K8/K18 involvement in the glucose-insulin cross-talk, including the modulation of plasma glucose levels, insulin release from pancreatic β-cells, and insulin-mediated glucose uptake and glycogen production in hepatocytes after a K8/K18 loss. This review integrates the mechanistic features that support such an impact of K8/K18 IFs on insulin-dependent glucose metabolism regulation in liver and its implication in glucose- or insulin-associated diseases.
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Affiliation(s)
- Alexandra Roux
- Centre de Recherche sur le Cancer, Université Laval, and Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec City, Québec, Canada
| | - Stéphane Gilbert
- Centre de Recherche sur le Cancer, Université Laval, and Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec City, Québec, Canada
| | - Anne Loranger
- Centre de Recherche sur le Cancer, Université Laval, and Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec City, Québec, Canada
| | - Normand Marceau
- Centre de Recherche sur le Cancer, Université Laval, and Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec City, Québec, Canada
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23
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Abou-Kheir W, Eid A, El-Merahbi R, Assaf R, Daoud G. A Unique Expression of Keratin 14 in a Subset of Trophoblast Cells. PLoS One 2015; 10:e0139939. [PMID: 26430881 PMCID: PMC4592186 DOI: 10.1371/journal.pone.0139939] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 08/25/2015] [Indexed: 12/20/2022] Open
Abstract
The placenta, a transient organ in human, is essential for pregnancy maintenance and for fetal growth and development. Trophoblast and stromal cells are the main cell types present in human placenta. Trophoblast cells are present in different subtypes depending on their differentiation state and their temporal and spatial location during pregnancy. The stromal cells are of extraembryonic mesenchymal origin and are important for villous formation and maintenance. Interestingly, many pregnancy–related diseases are associated with defect in trophoblast differentiation and villous integrity. Therefore, it's crucial to specifically identify each type of placental cells using specific markers. Keratins (CK) are widely used as marker of epithelial cells, cancer origin identification and in some cases as marker of stem/progenitor cells. Vimentin is widely used as marker of mesenchymal cells. The aim of this study is to characterize the presence of different keratins in human trophoblast cells and vimentin in stromal cells. Using immunohistochemistry on term placental sections, our results show that vimentin is solely expressed in stromal-mesenchymal cells while keratins 5, 7, 8, 14 and 19 are expressed in trophoblast cells. Interestingly, all keratins tested, except for keratin 14, were evenly expressed in all trophoblast cells. Keratin 14 was expressed in a subset of CK7 positive cells. Moreover, the same results were obtained when using freshly isolated cytotrophoblast cells or BeWo cells. In conclusion, this study is a crucial step in the advancement of our knowledge in placental cell type identification and characterization.
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Affiliation(s)
- Wassim Abou-Kheir
- Department of Anatomy, Cell Biology and Physiological Sciences, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
- * E-mail: (WAK); (GD)
| | - Assaad Eid
- Department of Anatomy, Cell Biology and Physiological Sciences, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Rabih El-Merahbi
- Department of Anatomy, Cell Biology and Physiological Sciences, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Rebecca Assaf
- Department of Anatomy, Cell Biology and Physiological Sciences, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Georges Daoud
- Department of Anatomy, Cell Biology and Physiological Sciences, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
- * E-mail: (WAK); (GD)
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Toivola DM, Habtezion A, Misiorek JO, Zhang L, Nyström JH, Sharpe O, Robinson WH, Kwan R, Omary MB. Absence of keratin 8 or 18 promotes antimitochondrial autoantibody formation in aging male mice. FASEB J 2015; 29:5081-9. [PMID: 26399787 DOI: 10.1096/fj.14-269795] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 09/08/2015] [Indexed: 12/16/2022]
Abstract
Human mutations in keratin 8 (K8) and keratin 18 (K18), the intermediate filament proteins of hepatocytes, predispose to several liver diseases. K8-null mice develop chronic liver injury and fragile hepatocytes, dysfunctional mitochondria, and Th2-type colitis. We tested the hypothesis that autoantibody formation accompanies the liver damage that associates with K8/K18 absence. Sera from wild-type control, K8-null, and K18-null mice were analyzed by immunoblotting and immunofluorescence staining of cell and mouse tissue homogenates. Autoantibodies to several antigens were identified in 81% of K8-null male mice 8 mo or older. Similar autoantibodies were detected in aging K18-null male mice that had a related liver phenotype but normal colon compared with K8-null mice, suggesting that the autoantibodies are linked to liver rather than colonic disease. However, these autoantibodies were not observed in nontransgenic mice subjected to 4 chronic injury models. The autoantigens are ubiquitous and partition with mitochondria. Mass spectrometry and purified protein analysis identified, mitochondrial HMG-CoA synthase, aldehyde dehydrogenase, and catalase as the primary autoantigens, and glutamate dehydrogenase and epoxide hydrolase-2 as additional autoantigens. Therefore, absence of the hepatocyte keratins results in production of anti-mitochondrial autoantibodies (AMA) that recognize proteins involved in energy metabolism and oxidative stress, raising the possibility that AMA may be found in patients with keratin mutations that associate with liver and other diseases.
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Affiliation(s)
- Diana M Toivola
- *Department of Science and Engineering, Department of Biosciences, and Department of Cell Biology, Åbo Akademi University, Turku, Finland; Division of Gastroenterology and Hepatology, Division of Immunology and Rheumatology, Stanford University School of Medicine, Palo Alto, California, USA; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA; Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA; and Veterans Affairs Ann Arbor Health Care System, Ann Arbor, Michigan, USA
| | - Aida Habtezion
- *Department of Science and Engineering, Department of Biosciences, and Department of Cell Biology, Åbo Akademi University, Turku, Finland; Division of Gastroenterology and Hepatology, Division of Immunology and Rheumatology, Stanford University School of Medicine, Palo Alto, California, USA; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA; Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA; and Veterans Affairs Ann Arbor Health Care System, Ann Arbor, Michigan, USA
| | - Julia O Misiorek
- *Department of Science and Engineering, Department of Biosciences, and Department of Cell Biology, Åbo Akademi University, Turku, Finland; Division of Gastroenterology and Hepatology, Division of Immunology and Rheumatology, Stanford University School of Medicine, Palo Alto, California, USA; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA; Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA; and Veterans Affairs Ann Arbor Health Care System, Ann Arbor, Michigan, USA
| | - Linxing Zhang
- *Department of Science and Engineering, Department of Biosciences, and Department of Cell Biology, Åbo Akademi University, Turku, Finland; Division of Gastroenterology and Hepatology, Division of Immunology and Rheumatology, Stanford University School of Medicine, Palo Alto, California, USA; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA; Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA; and Veterans Affairs Ann Arbor Health Care System, Ann Arbor, Michigan, USA
| | - Joel H Nyström
- *Department of Science and Engineering, Department of Biosciences, and Department of Cell Biology, Åbo Akademi University, Turku, Finland; Division of Gastroenterology and Hepatology, Division of Immunology and Rheumatology, Stanford University School of Medicine, Palo Alto, California, USA; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA; Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA; and Veterans Affairs Ann Arbor Health Care System, Ann Arbor, Michigan, USA
| | - Orr Sharpe
- *Department of Science and Engineering, Department of Biosciences, and Department of Cell Biology, Åbo Akademi University, Turku, Finland; Division of Gastroenterology and Hepatology, Division of Immunology and Rheumatology, Stanford University School of Medicine, Palo Alto, California, USA; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA; Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA; and Veterans Affairs Ann Arbor Health Care System, Ann Arbor, Michigan, USA
| | - William H Robinson
- *Department of Science and Engineering, Department of Biosciences, and Department of Cell Biology, Åbo Akademi University, Turku, Finland; Division of Gastroenterology and Hepatology, Division of Immunology and Rheumatology, Stanford University School of Medicine, Palo Alto, California, USA; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA; Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA; and Veterans Affairs Ann Arbor Health Care System, Ann Arbor, Michigan, USA
| | - Raymond Kwan
- *Department of Science and Engineering, Department of Biosciences, and Department of Cell Biology, Åbo Akademi University, Turku, Finland; Division of Gastroenterology and Hepatology, Division of Immunology and Rheumatology, Stanford University School of Medicine, Palo Alto, California, USA; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA; Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA; and Veterans Affairs Ann Arbor Health Care System, Ann Arbor, Michigan, USA
| | - M Bishr Omary
- *Department of Science and Engineering, Department of Biosciences, and Department of Cell Biology, Åbo Akademi University, Turku, Finland; Division of Gastroenterology and Hepatology, Division of Immunology and Rheumatology, Stanford University School of Medicine, Palo Alto, California, USA; Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA; Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA; and Veterans Affairs Ann Arbor Health Care System, Ann Arbor, Michigan, USA
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Guldiken N, Zhou Q, Kucukoglu O, Rehm M, Levada K, Gross A, Kwan R, James LP, Trautwein C, Omary MB, Strnad P. Human keratin 8 variants promote mouse acetaminophen hepatotoxicity coupled with c-jun amino-terminal kinase activation and protein adduct formation. Hepatology 2015; 62:876-86. [PMID: 25963979 PMCID: PMC4549164 DOI: 10.1002/hep.27891] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 04/15/2015] [Accepted: 05/03/2015] [Indexed: 12/21/2022]
Abstract
UNLABELLED Keratins 8 and 18 (K8/K18) are the intermediate filaments proteins of simple-type digestive epithelia and provide important cytoprotective function. K8/K18 variants predispose humans to chronic liver disease progression and poor outcomes in acute acetaminophen (APAP)-related liver failure. Given that K8 G62C and R341H/R341C are common K8 variants in European and North American populations, we studied their biological significance using transgenic mice. Mice that overexpress the human K8 variants, R341H or R341C, were generated and used together with previously described mice that overexpress wild-type K8 or K8 G62C. Mice were injected with 600 mg/kg of APAP or underwent bile duct ligation (BDL). Livers were evaluated by microarray analysis, quantitative real-time polymerase chain reaction, immunoblotting, histological and immunological staining, and biochemical assays. Under basal conditions, the K8 G62C/R341H/R341C variant-expressing mice did not show an obvious liver phenotype or altered keratin filament distribution, whereas K8 G62C/R341C animals had aberrant disulphide cross-linked keratins. Animals carrying the K8 variants displayed limited gene expression changes, but had lower nicotinamide N-methyl transferase (NNMT) levels and were predisposed to APAP-induced hepatotoxicity. NNMT represents a novel K8/K18-associated protein that becomes up-regulated after K8/K18 transfection. The more pronounced liver damage was accompanied by increased and prolonged JNK activation; elevated APAP protein adducts; K8 hyperphosphorylation at S74/S432 with enhanced keratin solubility; and prominent pericentral keratin network disruption. No differences in APAP serum levels, glutathione, or adenosine triphosphate levels were noted. BDL resulted in similar liver injury and biliary fibrosis in all mouse genotypes. CONCLUSION Expression of human K8 variants G62C, R341H, or R341C in mice predisposes to acute APAP hepatotoxicity, thereby providing direct evidence for the importance of these variants in human acute liver failure.
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Affiliation(s)
- Nurdan Guldiken
- IZKF and Department of Internal Medicine III, University Hospital Aachen, Germany,Department of Internal Medicine I, University Hospital Ulm, Ulm Germany
| | - Qin Zhou
- Department of Medicine, Palo Alto VA Medical Center, CA; and Stanford University Digestive Disease Center, USA
| | - Ozlem Kucukoglu
- Department of Internal Medicine I, University Hospital Ulm, Ulm Germany
| | - Melanie Rehm
- Department of Internal Medicine I, University Hospital Ulm, Ulm Germany
| | - Kateryna Levada
- IZKF and Department of Internal Medicine III, University Hospital Aachen, Germany
| | - Annika Gross
- IZKF and Department of Internal Medicine III, University Hospital Aachen, Germany
| | - Raymond Kwan
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, and the VA Ann Arbor Health Care System, Ann Arbor, MI, USA
| | - Laura P. James
- Arkansas Children's Hospital Research Institute and Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Christian Trautwein
- IZKF and Department of Internal Medicine III, University Hospital Aachen, Germany
| | - M. Bishr Omary
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, and the VA Ann Arbor Health Care System, Ann Arbor, MI, USA
| | - Pavel Strnad
- IZKF and Department of Internal Medicine III, University Hospital Aachen, Germany,Department of Internal Medicine I, University Hospital Ulm, Ulm Germany,To whom correspondence should be addressed. Corresponding author: Pavel Strnad, Department of Internal Medicine III and IZKF, University Hospital Aachen, Pauwelsstraße 30, D-52074 Aachen, Tel.: +49(241) 80-35324, Fax: +49(241) 80-82455,
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Lipid rafts and raft-mediated supramolecular entities in the regulation of CD95 death receptor apoptotic signaling. Apoptosis 2015; 20:584-606. [DOI: 10.1007/s10495-015-1104-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Weerasinghe SVW, Ku NO, Altshuler PJ, Kwan R, Omary MB. Mutation of caspase-digestion sites in keratin 18 interferes with filament reorganization, and predisposes to hepatocyte necrosis and loss of membrane integrity. J Cell Sci 2014; 127:1464-75. [PMID: 24463813 DOI: 10.1242/jcs.138479] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Keratin 18 (K18 or KRT18) undergoes caspase-mediated cleavage during apoptosis, the significance of which is poorly understood. Here, we mutated the two caspase-cleavage sites (D238E and D397E) in K18 (K18-DE), followed by transgenic overexpression of the resulting mutant. We found that K18-DE mice develop extensive Fas-mediated liver damage compared to wild-type mice overexpressing K18 (K18-WT). Fas-stimulation of K18-WT mice or isolated hepatocytes caused K18 degradation. By contrast, K18-DE livers or hepatocytes maintained intact keratins following Fas-stimulation, but showed hypo-phosphorylation at a major stress-kinase-related keratin 8 (K8) phosphorylation site. Although K18-WT and K18-DE hepatocytes showed similar Fas-mediated caspase activation, K18-DE hepatocytes were more 'leaky' after a mild hypoosmotic challenge and were more susceptible to necrosis after Fas-stimulation or severe hypoosmotic stress. K8 hypophosphorylation was not due to the inhibition of kinase binding to the keratin but was due to mutation-induced inaccessibility to the kinase that phosphorylates K8. A stress-modulated keratin phospho-mutant expressed in hepatocytes phenocopied the hepatocyte susceptibility to necrosis but was found to undergo keratin filament reorganization during apoptosis. Therefore, the caspase cleavage of keratins might promote keratin filament reorganization during apoptosis. Interference with keratin caspase cleavage shunts hepatocytes towards necrosis and increases liver injury through the inhibition of keratin phosphorylation. These findings might extend to other intermediate filament proteins that undergo proteolysis during apoptosis.
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Affiliation(s)
- Sujith V W Weerasinghe
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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Fortier AM, Asselin E, Cadrin M. Keratin 8 and 18 loss in epithelial cancer cells increases collective cell migration and cisplatin sensitivity through claudin1 up-regulation. J Biol Chem 2013; 288:11555-71. [PMID: 23449973 DOI: 10.1074/jbc.m112.428920] [Citation(s) in RCA: 145] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Keratins 8 and 18 (K8/18) are simple epithelial cell-specific intermediate filament proteins. Keratins are essential for tissue integrity and are involved in intracellular signaling pathways that regulate cell response to injuries, cell growth, and death. K8/18 expression is maintained during tumorigenesis; hence, they are used as a diagnostic marker in tumor pathology. In recent years, studies have provided evidence that keratins should be considered not only as markers but also as regulators of cancer cell signaling. The loss of K8/18 expression during epithelial-mesenchymal transition (EMT) is associated with metastasis and chemoresistance. In the present study, we investigated whether K8/18 expression plays an active role in EMT. We show that K8/18 stable knockdown using shRNA increased collective migration and invasiveness of epithelial cancer cells without modulating EMT markers. K8/18-depleted cells showed PI3K/Akt/NF-κB hyperactivation and increased MMP2 and MMP9 expression. K8/18 deletion also increased cisplatin-induced apoptosis. Increased Fas receptor membrane targeting suggests that apoptosis is enhanced via the extrinsic pathway. Interestingly, we identified the tight junction protein claudin1 as a regulator of these processes. This is the first indication that modulation of K8/18 expression can influence the phenotype of epithelial cancer cells at a transcriptional level and supports the hypothesis that keratins play an active role in cancer progression.
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Affiliation(s)
- Anne-Marie Fortier
- Molecular Oncology and Endocrinology Research Group, Department of Medical Biology, University of Québec at Trois-Rivières, Trois-Rivières, Québec G9A 5H7, Canada
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Duncan A, Forcina J, Birt A, Townson D. Estrous cycle-dependent changes of Fas expression in the bovine corpus luteum: influence of keratin 8/18 intermediate filaments and cytokines. Reprod Biol Endocrinol 2012; 10:90. [PMID: 23113883 PMCID: PMC3567950 DOI: 10.1186/1477-7827-10-90] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 10/26/2012] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Fas expression and Fas-induced apoptosis are mechanisms attributed to the selective destruction of cells of the corpus luteum (CL) during luteal regression. In certain cell-types, sensitivity to these death-inducing mechanisms is due to the loss or cleavage of keratin-containing intermediate filaments. Specifically, keratin 8/18 (K8/K18) filaments are hypothesized to influence cell death in part by regulating Fas expression at the cell surface. METHODS Here, Fas expression on bovine luteal cells was quantified by flow cytometry during the early (Day 5, postovulation) and late stages (Days 16-18, postovulation) of CL function, and the relationship between Fas expression, K8/K18 filament expression and cytokine-induced cell death in vitro was evaluated. RESULTS Both total and cell surface expression of Fas on luteal cells was greater for early versus late stage bovine CL (89% vs. 44% of cells for total Fas; 65% vs.18% of cells for cell surface Fas; respectively, P<0.05, n=6-9 CL/stage). A similar increase in the steady-state concentration of mRNA for Fas, as detected by quantitative real-time polymerase chain reaction, however, was not observed. Transient disruption of K8/K18 filaments in the luteal cells with acrylamide (5 mM), however, had no effect on the surface expression of Fas (P>0.05, n=4 CL/stage), despite evidence these conditions increased Fas expression on HepG2 cells (P<0.05, n= 3 expts). Exposure of the luteal cells to cytokines induced cell death (P<0.05) as expected, but there was no effect of K8/K18 filament disruption by acrylamide (P>0.05) or stage of CL (P>0.05, n= 4 CL/stage) on this outcome. CONCLUSION In conclusion, we rejected our null hypothesis that the cell surface expression of Fas does not differ between luteal cells of early and late stage CL. The results also did not support the idea that K8/K18 filaments influence the expression of Fas on the surface of bovine luteal cells. Potential downstream effects of these filaments on death signaling, however, remain a possibility. Importantly, the elevated expression of Fas observed on cells of early stage bovine CL compared to late stage bovine CL raises a provocative question concerning the physiological role(s) of Fas in the corpus luteum, particularly during early luteal development.
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Affiliation(s)
- Alice Duncan
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH, USA
| | - Jennifer Forcina
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH, USA
| | - Alyssa Birt
- Department of Dairy and Animal Science, The Pennsylvania State University, University Park, PA, USA
| | - David Townson
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH, USA
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Gilbert S, Loranger A, Lavoie JN, Marceau N. Cytoskeleton keratin regulation of FasR signaling through modulation of actin/ezrin interplay at lipid rafts in hepatocytes. Apoptosis 2012; 17:880-94. [PMID: 22585043 DOI: 10.1007/s10495-012-0733-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
FasR stimulation by Fas ligand leads to rapid formation of FasR microaggregates, which become signaling protein oligomerization transduction structures (SPOTS), through interactions with actin and ezrin, a structural step that triggers death-inducing signaling complex formation, in association with procaspase-8 activation. In some cells, designated as type I, caspase 8 directly activates effector caspases, whereas in others, known as type II, the caspase-mediated death signaling is amplified through mitochondria. Keratins are the intermediate filament (IF) proteins of epithelial cells, expressed as pairs in a lineage/differentiation manner. Hepatocyte IFs are made solely of keratins 8/18 (K8/K18), the hallmark of all simple epithelia. We have shown recently that in comparison to type II wild-type (WT) mouse hepatocytes, the absence of K8/K18 IFs in K8-null hepatocytes leads to more efficient FasR-mediated apoptosis, in link with a type II/type I-like switch in FasR-death signaling. Here, we demonstrate that the apoptotic process occurring in type I-like K8-null hepatocytes is associated with accelerated SPOTS elaboration at surface membrane, along with manifestation of FasR cap formation and internalization. In addition, the lipid raft organization is altered in K8-null hepatocytes. While lipid raft inhibition impairs SPOTS formation in both WT and K8-null hepatocytes, the absence of K8/K18 IFs in the latter sensitizes SPOTS to actin de-polymerization, and perturbs ezrin compartmentalization. Overall, the results indicate that the K8/K18 IF loss in hepatocytes alters the initial FasR activation steps through perturbation of ezrin/actin interplay and lipid raft organization, which leads to a type II/type I switch in FasR-death signaling.
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Affiliation(s)
- Stéphane Gilbert
- Centre de Recherche en Cancérologie de l'Université Laval, and Centre de Recherche du Centre Hospitalier de Québec (CRCHUQ)/HDQ, 9 rue McMahon, Quebec, G1R 2J6, Canada
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Brouillard F, Fritsch J, Edelman A, Ollero M. Contribution of proteomics to the study of the role of cytokeratins in disease and physiopathology. Proteomics Clin Appl 2012; 2:264-85. [PMID: 21136830 DOI: 10.1002/prca.200780018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Cytokeratins (CKs), the most abundant group of cytoskeletal intermediate filaments, and proteomics are strongly connected. On the one hand, proteomics has been extremely useful to uncover new features and functions of CKs, on the other, the highly abundant CKs serve as an exceptional tool to test new technological developments in proteomics. As a result, proteomics has contributed to finding valuable associations of CKs with diseases as diverse as cancer, cystic fibrosis, steatohepatitis, viral and bacterial infection, keratoconus, vitreoretinopathy, preeclampsia or the chronic fatigue syndrome, as well as to characterizing their participation in a number of physiopathological processes, including drug resistance, response to toxicants, inflammation, stem cell differentiation, embryo development, and tissue repair. In some cases, like in cystic fibrosis, CKs have been described as potential therapeutic targets. The development of a specific field of proteomics where CKs become the main subject of research aims and hypotheses is suggested.
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Affiliation(s)
- Franck Brouillard
- INSERM, Unité 845, Paris, France; Faculté de Médecine René Descartes, Université Paris-Descartes, Plateau Protéomes IFR94, Paris, France
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Genetic background effects of keratin 8 and 18 in a DDC-induced hepatotoxicity and Mallory-Denk body formation mouse model. J Transl Med 2012; 92:857-67. [PMID: 22449798 DOI: 10.1038/labinvest.2012.49] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Keratin 8 (K8) and keratin 18 (K18) form the major hepatocyte cytoskeleton. We investigated the impact of genetic loss of either K8 or K18 on liver homeostasis under toxic stress with the hypothesis that K8 and K18 exert different functions. krt8⁻/⁻ and krt18⁻/⁻ mice crossed into the same 129-ola genetic background were treated by acute and chronic administration of 3,5-diethoxy-carbonyl-1,4-dihydrocollidine (DDC). In acutely DDC-intoxicated mice, macrovesicular steatosis was more pronounced in krt8⁻/⁻ and krt18⁻/⁻ compared with wild-type (wt) animals. Mallory-Denk bodies (MDBs) appeared in krt18⁻/⁻ mice already at an early stage of intoxication in contrast to krt8⁻/⁻ mice that did not display MDB formation when fed with DDC. Keratin-deficient mice displayed significantly lower numbers of apoptotic hepatocytes than wt animals. krt8⁻/⁻, krt18⁻/⁻ and control mice displayed comparable cell proliferation rates. Chronically DDC-intoxicated krt18⁻/⁻ and wt mice showed a similarly increased degree of steatohepatitis with hepatocyte ballooning and MDB formation. In krt8⁻/⁻ mice, steatosis was less, ballooning, and MDBs were absent. krt18⁻/⁻ mice developed MDBs whereas krt8⁻/⁻ mice on the same genetic background did not, highlighting the significance of different structural properties of keratins. They are independent of the genetic background as an intrinsic factor. By contrast, toxicity effects may depend on the genetic background. krt8⁻/⁻ and krt18⁻/⁻ mice on the same genetic background show similar sensitivity to DDC intoxication and almost resemble wt animals regarding survival, degree of porphyria, liver-to-body weight ratio, serum bilirubin and liver enzyme levels. This stands in contrast to previous work where krt8⁻/⁻ and krt18⁻/⁻ mice on different genetic backgrounds were investigated.
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Strnad P, Kucukoglu O, Lunova M, Guldiken N, Lienau TC, Stickel F, Omary MB. Non-coding keratin variants associate with liver fibrosis progression in patients with hemochromatosis. PLoS One 2012; 7:e32669. [PMID: 22412904 PMCID: PMC3296740 DOI: 10.1371/journal.pone.0032669] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2011] [Accepted: 02/02/2012] [Indexed: 01/08/2023] Open
Abstract
Background Keratins 8 and 18 (K8/K18) are intermediate filament proteins that protect the liver from various forms of injury. Exonic K8/K18 variants associate with adverse outcome in acute liver failure and with liver fibrosis progression in patients with chronic hepatitis C infection or primary biliary cirrhosis. Given the association of K8/K18 variants with end-stage liver disease and progression in several chronic liver disorders, we studied the importance of keratin variants in patients with hemochromatosis. Methods The entire K8/K18 exonic regions were analyzed in 162 hemochromatosis patients carrying homozygous C282Y HFE (hemochromatosis gene) mutations. 234 liver-healthy subjects were used as controls. Exonic regions were PCR-amplified and analyzed using denaturing high-performance liquid chromatography and DNA sequencing. Previously-generated transgenic mice overexpressing K8 G62C were studied for their susceptibility to iron overload. Susceptibility to iron toxicity of primary hepatocytes that express K8 wild-type and G62C was also assessed. Results We identified amino-acid-altering keratin heterozygous variants in 10 of 162 hemochromatosis patients (6.2%) and non-coding heterozygous variants in 6 additional patients (3.7%). Two novel K8 variants (Q169E/R275W) were found. K8 R341H was the most common amino-acid altering variant (4 patients), and exclusively associated with an intronic KRT8 IVS7+10delC deletion. Intronic, but not amino-acid-altering variants associated with the development of liver fibrosis. In mice, or ex vivo, the K8 G62C variant did not affect iron-accumulation in response to iron-rich diet or the extent of iron-induced hepatocellular injury. Conclusion In patients with hemochromatosis, intronic but not exonic K8/K18 variants associate with liver fibrosis development.
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Affiliation(s)
- Pavel Strnad
- Department of Internal Medicine I, University Medical Center Ulm, Ulm, Germany.
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Pan TL, Wang PW, Chen CC, Fang JY, Sintupisut N. Functional proteomics reveals hepatotoxicity and the molecular mechanisms of different forms of chromium delivered by skin administration. Proteomics 2012; 12:477-89. [DOI: 10.1002/pmic.201100055] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 11/09/2011] [Accepted: 11/17/2011] [Indexed: 12/11/2022]
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Farnesoid X receptor protects human and murine gastric epithelial cells against inflammation-induced damage. Biochem J 2011; 438:315-23. [PMID: 21619550 DOI: 10.1042/bj20102096] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Bile acids from duodenogastric reflux promote inflammation and increase the risk for gastro-oesophageal cancers. FXR (farnesoid X receptor/NR1H4) is a transcription factor regulated by bile acids such as CDCA (chenodeoxycholic acid). FXR protects the liver and the intestinal tract against bile acid overload; however, a functional role for FXR in the stomach has not been described. We detected FXR expression in the normal human stomach and in GC (gastric cancer). FXR mRNA and protein were also present in the human GC cell lines MKN45 and SNU5, but not in the AGS cell line. Transfection of FXR into AGS cells protected against TNFα (tumour necrosis factor α)-induced cell damage. We identified K13 (keratin 13), an anti-apoptotic protein of desmosomes, as a novel CDCA-regulated FXR-target gene. FXR bound to a conserved regulatory element in the proximal human K13 promoter. Gastric expression of K13 mRNA was increased in an FXR-dependent manner by a chow diet enriched with 1% (w/w) CDCA and by indomethacin (35 mg/kg of body weight intraperitoneal) in C57BL/6 mice. FXR-deficient mice were more susceptible to indomethacin-induced gastric ulceration than their WT (wild-type) littermates. These results suggest that FXR increases the resistance of human and murine gastric epithelial cells to inflammation-mediated damage and may thus participate in the development of GC.
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Absence of keratin 8 confers a paradoxical microflora-dependent resistance to apoptosis in the colon. Proc Natl Acad Sci U S A 2011; 108:1445-50. [PMID: 21220329 DOI: 10.1073/pnas.1010833108] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Keratin 8 (K8) is a major intermediate filament protein present in enterocytes and serves an antiapoptotic function in hepatocytes. K8-null mice develop colonic hyperplasia and colitis that are reversed after antibiotic treatment. To investigate the pathways that underlie the mechanism of colonocyte hyperplasia and the normalization of the colonic phenotype in response to antibiotics, we performed genome-wide microarray analysis. Functional annotation of genes that are differentially regulated in K8(-/-) and K8(+/+) isolated colon crypts (colonocytes) identified apoptosis as a major altered pathway. Exposure of K8(-/-) colonocytes or colon organ ("organoid") cultures, but not K8(-/-) small intestine organoid cultures, to apoptotic stimuli showed, surprisingly, that they are resistant to apoptosis compared with their wild-type counterparts. This resistance is not related to inflammation per se because T-cell receptor α-null (TCR-α(-/-)) and wild-type colon cultures respond similarly upon induction of apoptosis. Following antibiotic treatment, K8(-/-) colonocytes and organ cultures become less resistant to apoptosis and respond similarly to the wild-type colonocytes. Antibiotics also normalize most differentially up-regulated genes, including survivin and β4-integrin. Treatment of K8(-/-) mice with anti-β4-integrin antibody up-regulated survivin, and induced phosphorylation of focal adhesion kinase with decreased activation of caspases. Therefore, unlike the proapoptotic effect of K8 mutation or absence in hepatocytes, lack of K8 confers resistance to colonocyte apoptosis in a microflora-dependent manner.
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Kupffer cells are associated with apoptosis, inflammation and fibrotic effects in hepatic fibrosis in rats. J Transl Med 2010; 90:1805-16. [PMID: 20921949 DOI: 10.1038/labinvest.2010.123] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Hepatocellular apoptosis, hepatic inflammation, and fibrosis are prominent features in chronic liver diseases. However, the linkage among these processes remains mechanistically unclear. In this study, we examined the apoptosis and activation of Kupffer cells (KCs) as well as their pathophysiological involvement in liver fibrosis process. Hepatic fibrosis was induced in rats by dimethylnitrosamine (DMN) or carbon tetrachloride (CCl4) treatment. KCs were isolated from normal rats and incubated with lipopolysaccharide (LPS) or from fibrotic rats. The KCs were stained immunohistochemically with anti-CD68 antibody, a biomarker for KC. The level of expression of CD68 was analyzed by western blot and real-time PCR methods. The apoptosis and pathophysiological involvement of KCs in the formation of liver fibrosis were studied using confocal microscopy. The mRNA and protein expression of CD68 were significantly increased in DMN- and CCL4-treated rats. Confocal microscopy analysis showed that CD68-positive KCs, but not α-smooth muscle actin (SMA)-positive cells, underwent apoptosis in the liver of DMN- and CCL4-treated rats. It was also revealed that the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and CD68-double-positive apoptotic KCs located in the portal or fibrotic septa area were situated next to hepatic stellate cells (HSCs). Tumor necrosis factor-α (TNF-α) and KC co-localized in the liver in the neighbor of HSCs. The double α-SMA- and collagen type I-positive cells predominantly existed in fibrotic septa, and those cells were co-localized clearly with CD68-positive cells. Interestingly, some CD68 and Col (1) double positive, but completely negative for α-SMA, were found in the portal areas and hepatic sinusoids; this phenomenon was also validated in primary isolated KCs after 6 h LPS exposure or fibrotic rats in vitro. These results show that KCs are associated with hepatocellular apoptosis, inflammation, and fibrosis process in a liver fibrosis models.
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Abstract
Keratins are the intermediate filament (IF)-forming proteins of epithelial cells. Since their initial characterization almost 30 years ago, the total number of mammalian keratins has increased to 54, including 28 type I and 26 type II keratins. Keratins are obligate heteropolymers and, similarly to other IFs, they contain a dimeric central α-helical rod domain that is flanked by non-helical head and tail domains. The 10-nm keratin filaments participate in the formation of a proteinaceous structural framework within the cellular cytoplasm and, as such, serve an important role in epithelial cell protection from mechanical and non-mechanical stressors, a property extensively substantiated by the discovery of human keratin mutations predisposing to tissue-specific injury and by studies in keratin knockout and transgenic mice. More recently, keratins have also been recognized as regulators of other cellular properties and functions, including apico-basal polarization, motility, cell size, protein synthesis and membrane traffic and signaling. In cancer, keratins are extensively used as diagnostic tumor markers, as epithelial malignancies largely maintain the specific keratin patterns associated with their respective cells of origin, and, in many occasions, full-length or cleaved keratin expression (or lack there of) in tumors and/or peripheral blood carries prognostic significance for cancer patients. Quite intriguingly, several studies have provided evidence for active keratin involvement in cancer cell invasion and metastasis, as well as in treatment responsiveness, and have set the foundation for further exploration of the role of keratins as multifunctional regulators of epithelial tumorigenesis.
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Affiliation(s)
- V Karantza
- Department of Medicine, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, NJ, USA.
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Ku NO, Toivola DM, Strnad P, Omary MB. Cytoskeletal keratin glycosylation protects epithelial tissue from injury. Nat Cell Biol 2010; 12:876-85. [PMID: 20729838 DOI: 10.1038/ncb2091] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Accepted: 07/27/2010] [Indexed: 12/25/2022]
Abstract
Keratins 8 and 18 (K8 and K18) are heteropolymeric intermediate filament phosphoglycoproteins of simple-type epithelia. Mutations in K8 and K18 predispose the affected individual to liver disease as they protect hepatocytes from apoptosis. K18 undergoes dynamic O-linked N-acetylglucosamine glycosylation at Ser 30, 31 and 49. We investigated the function of K18 glycosylation by generating mice that overexpress human K18 S30/31/49A substitution mutants that cannot be glycosylated (K18-Gly(-)), and compared the susceptibility of these mice to injury with wild-type and other keratin-mutant mice. K18-Gly(-) mice are more susceptible to liver and pancreatic injury and apoptosis induced by streptozotocin or to liver injury by combined N-acetyl-D-glucosaminidase inhibition and Fas administration. The enhanced apoptosis in the livers of mice that express K18-Gly(-) involves the inactivation of Akt1 and protein kinase Ctheta as a result of their site-specific hypophosphorylation. Akt1 binds to K8, which probably contributes to the reciprocal hyperglycosylation and hypophosphorylation of Akt1 that occurs on K18 hypoglycosylation, and leads to decreased Akt1 kinase activity. Therefore, K18 glycosylation provides a unique protective role in epithelial injury by promoting the phosphorylation and activation of cell-survival kinases.
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Affiliation(s)
- Nam-On Ku
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, 7744 Medical Science II, 1301 East Catherine Street, Ann Arbor, MI 48109-5622, USA.
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Fortier AM, Riopel K, Désaulniers M, Cadrin M. Novel insights into changes in biochemical properties of keratins 8 and 18 in griseofulvin-induced toxic liver injury. Exp Mol Pathol 2010; 89:117-25. [PMID: 20643122 DOI: 10.1016/j.yexmp.2010.07.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 07/08/2010] [Accepted: 07/08/2010] [Indexed: 12/11/2022]
Abstract
Keratins 8 and 18 (K8/18) intermediate filament proteins are believed to play an essential role in the protection of hepatocytes against mechanical and toxic stress. This assertion is mainly based on increased hepatocyte fragility observed in transgenic mice deficient in K8/18, or carrying mutations on K8/18. The molecular mechanism by which keratins accomplish their protective functions has not been totally elucidated. Liver diseases such as alcoholic hepatitis and copper metabolism diseases are associated with modifications, in hepatocytes, of intermediate filament organisation and the formation of K8/18 containing aggregates named Mallory-Denk bodies. Treatment of mice with a diet containing griseofulvin induces the formation of Mallory-Denk bodies in hepatocytes. This provides a reliable animal model for assessing the molecular mechanism by which keratins accomplish their protective role in the response of hepatocytes to chemical injuries. In this study, we found that griseofulvin intoxication induced changes in keratin solubility and that there was a 5% to 25% increase in the relative amounts of soluble keratin. Keratin phosphorylation on specific sites (K8 pS79, K8 pS436 and K18 pS33) was increased and prominent in the insoluble protein fractions. Since at least six K8 phosphoepitopes were detected after GF treatment, phosphorylation sites other than the ones studied need to be accounted for. Immunofluorescence staining showed that K8 pS79 epitope was present in clusters of hepatocytes that surrounded apoptotic cells. Activated p38 MAPK was associated with, but not present in K8 pS79-positive cells. These results indicate that griseofulvin intoxication mediates changes in the physicochemical properties of keratin, which result in the remodelling of keratin intermediate filaments which in turn could modulate the signalling pathways in which they are involved by modifying their binding to signalling proteins.
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Affiliation(s)
- Anne-Marie Fortier
- Molecular oncology and endocrinology research group, Department of Chemistry-Biology, University of Quebec at Trois-Rivières, 3351 Blv Des Forges, Trois-Rivières, Québec, Canada G9A 5H7
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Shi Y, Sun S, Liu Y, Li J, Zhang T, Wu H, Chen X, Chen D, Zhou Y. Keratin 18 phosphorylation as a progression marker of chronic hepatitis B. Virol J 2010; 7:70. [PMID: 20334631 PMCID: PMC2853512 DOI: 10.1186/1743-422x-7-70] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Accepted: 03/24/2010] [Indexed: 04/21/2023] Open
Abstract
Background The intermediate filament proteins keratins 18 (K18) and 8 (K8) polymerize to form the cytoskeletal network in the mature hepatocytes. It has been shown that the phosphorylation of K18 at two serine residues, 33 and 52, correlates with the progression of hepatitis C, but little is known of chronic hepatitis B (CHB). In this study, we examined K18 phosphorylation in relation to CHB. Results Site-specific phosphorylation of K18 was determined in livers of twelve healthy donors, and non-cirrhosis (n = 40) and cirrhosis (n = 21) patients. On average, progressively higher level of Ser52 phosphorylation was observed in non-cirrhotic and cirrhotic livers, while elevated Ser33 phosphorylation was detected in both livers but no significant difference. Progressive increase of Ser33 and Ser52 phosphorylation correlated with the elevation of both histological lesions and enzymatic activities of alanine aminotransferase in non-cirrhotic livers. In the hepatocytes of an inactive HBV carrier, strong signals of Ser33 phosphorylation were co-localized with viral infection, while only basal level of Ser52 phosphorylation was detected in infected cells. Conclusion Assuming all obtained data, our data suggest that K18 phosphorylation is a progression marker for CHB.
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Affiliation(s)
- Ying Shi
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
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Tao GZ, Looi KS, Toivola DM, Strnad P, Zhou Q, Liao J, Wei Y, Habtezion A, Omary MB. Keratins modulate the shape and function of hepatocyte mitochondria: a mechanism for protection from apoptosis. J Cell Sci 2009; 122:3851-5. [PMID: 19825937 DOI: 10.1242/jcs.051862] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Absence or mutation of keratins 8 (K8) or 18 (K18) cause predisposition to liver injury and apoptosis. We assessed the mechanisms of hepatocyte keratin-mediated cytoprotection by comparing the protein expression profiles of livers from wild-type and K8-null mice using two-dimensional differential-in-gel-electrophoresis (2D-DIGE) and mass spectrometry. Prominent among the alterations were those of mitochondrial proteins, which were confirmed using 2D-DIGE of purified mitochondria. Ultrastructural analysis showed that mitochondria of livers that lack or have disrupted keratins are significantly smaller than mitochondria of wild-type livers. Immunofluorescence staining showed irregular distribution of mitochondria in keratin-absent or keratin-mutant livers. K8-null livers have decreased ATP content; and K8-null mitochondria have less cytochrome c, increased release of cytochrome c after exposure to Ca(2+) and oxidative stimulation, and a higher sensitivity to Ca(2+)-induced permeability transition. Therefore, keratins play a direct or indirect role in regulating the shape and function of mitochondria. The effects of keratin mutation on mitochondria are likely to contribute to hepatocyte predisposition to apoptosis and oxidative injury, and to play a pathogenic role in keratin-mutation-related human liver disease.
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Affiliation(s)
- Guo-Zhong Tao
- Department of Surgery, Stanford University, Palo Alto, CA 94305, USA
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Fickert P, Fuchsbichler A, Wagner M, Silbert D, Zatloukal K, Denk H, Trauner M. The role of the hepatocyte cytokeratin network in bile formation and resistance to bile acid challenge and cholestasis in mice. Hepatology 2009; 50:893-9. [PMID: 19585611 DOI: 10.1002/hep.23068] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
UNLABELLED The intermediate filament cytoskeleton of hepatocytes is composed of keratin (K) 8 and K18 and has important mechanical and nonmechanical functions. However, the potential role of the K8/K18 network for proper membrane targeting of hepatocellular adenosine triphosphate-binding cassette transporters and bile formation is unknown. We therefore designed a comparative study in K8 and K18 knockout mice and respective wild-type controls to test the hypothesis that intermediate filaments of hepatocytes play a role in normal bile formation. In addition, we challenged mice either with a 1% cholic acid-supplemented diet or a diet containing the porphyrinogenic xenobiotic 3,5-diethoxycarbonyl-1,4-dihydrocollidine to determine the effect of K8/K18 loss on bile flow/composition and liver injury under different physiological and toxic stress stimuli. Protein expression levels and membrane localization of various transporters and anion exchangers were compared using western blotting and immunofluorescence microscopy, respectively, and bile flow and composition were determined under various experimental conditions. Our results demonstrate that loss of the intermediate filament network had no significant effect on bile formation and composition, as well as expression levels and membrane targeting of key hepatobiliary transporters under baseline and stress conditions. However, loss of K8 significantly increased liver injury in response to toxic stress. CONCLUSION The intermediate filament network of hepatocytes is not specifically required for proper bile formation in mice.
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Affiliation(s)
- Peter Fickert
- Laboratory of Experimental and Molecular Hepatology, Division of Gastroenterology and Hepatology, Medical University of Graz, Graz, Austria
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Leifeld L, Kothe S, Söhl G, Hesse M, Sauerbruch T, Magin TM, Spengler U. Keratin 18 provides resistance to Fas-mediated liver failure in mice. Eur J Clin Invest 2009; 39:481-8. [PMID: 19397691 DOI: 10.1111/j.1365-2362.2009.02133.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Keratins are intermediate filament proteins of epithelial cells with pivotal functions for cell integrity. They comprise keratins 18 [K18] and 8 [K8] in hepatocytes. Keratins are of major importance for an intact cellular microarchitecture and have protective functions in human liver diseases. In mice, K8 has been demonstrated to protect against Fas-antibody-induced liver failure by direct interaction with apoptotic regulators, while the role of K18 remains unresolved. MATERIALS AND METHODS We analysed effects of K18 deficiency on Fas-induced liver failure in mice. We determined survival and analysed induction of apoptosis after injection of the agonistic Fas antibody Jo2 into K18(-/-) and wild-type control mice by TUNEL assay and fluorometrically analysed caspase-3, -8 and -9 activities 1, 2 and 3 h after Jo2 injection. RESULTS In K18(-/-) mice, survival of Fas-antibody treated mice was significantly shorter than that of wild-type controls (P = 0.02). However, shortened survival of K18(-/-) mice was caused by increased hepatic damage but was not correlated to enhanced induction of apoptotic pathways, as neither numbers of TUNEL positive apoptotic cells nor activities of caspases-3, -8 and -9 differed between K18(-/-) and K18(+/+) mice at any point of time. CONCLUSION K18(-/-) mice are significantly more susceptible to Fas-antibody-induced liver failure. The cytoprotective effect of K18 is not explained by a differential activation of caspases-3, -8 and -9, suggesting that K18 does not directly interfere with apoptotic regulators. Importantly, however, K18 exerts significant protective functions by other mechanisms.
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Affiliation(s)
- L Leifeld
- Evangelisches Krankenhaus Kalk, Cologne, Germany.
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Lucchese A, Serpico R. Effect of SP3 silencing on cytokeratin expression pattern in HPV-positive cells. Int J Immunopathol Pharmacol 2009; 22:163-8. [PMID: 19309563 DOI: 10.1177/039463200902200118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
In an attempt to understand the molecular factors underlying squamous cell carcinogenesis in HPV-infected oral and cervical tissues, we examined the Sp3-dependent cytokeratin expression in HPV-positive CaSki cells. Two sets of cytokeratins were examined: the simple epithelial CK 7, 8, 18, 19, and 20, which are generally expressed in simple epithelia and CK4, 10, 13, and 17, which are expressed in squamous epithelia. Two additional CK pairs, i.e. CK6/CK16 and CK4/CK13 were analyzed as controls of the proliferation/differentiation cell status, respectively. We report that Sp3 gene silencing specifically hits CK18 and CK19, which are markers of oral and cervical squamous tumors. These data may be of help in immunopathological definition of squamous carcinogenesis.
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Affiliation(s)
- A Lucchese
- Department of Odontostomatology, Orthodontics and Surgical Disciplines, University of Naples (SUN), Naples, Italy.
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Switch in Fas-activated death signaling pathway as result of keratin 8/18-intermediate filament loss. Apoptosis 2008; 13:1479-93. [PMID: 19002587 DOI: 10.1007/s10495-008-0274-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Fas-induced apoptosis is initiated through the recruitment of FADD and procaspase 8 to form the death-inducing signaling complex (DISC). In some cells (type I cells) the initiator caspase 8 directly activates effector caspases such as procaspase 3, whereas in others (type II cells) the death signal is amplified through mitochondria. In epithelial cells, Fas-induced hierarchic caspase activation is also linked with DEDD, a member of the DED family that binds to keratin (K) intermediate filaments (IFs). Hepatocytes are type II cells and their IFs are made exclusively of K8/K18. We have shown previously that K8-null mouse hepatocytes, lacking K8/K18 IFs, are more sensitive than their wild-type counterparts to Fas-induced apoptosis. Here, by examining the cell-death kinetics and death-signaling ordering, we found that K8-null hepatocytes exhibited prominent DISC formation, higher procaspase 8 activation and direct procaspase 3 activation as reported for type I cells; however they experienced a reduced Bid cleavage and a stronger procaspase 9 activation. In addition, the K8/K18 loss altered the DEDD ubiquitination status and nuclear/cytoplasmic distribution. Together, the results suggest that the K8/K18 loss induces a switch in Fas-induced death signaling, likely through a DEDD involvement.
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Abstract
The keratins are the typical intermediate filament proteins of epithelia, showing an outstanding degree of molecular diversity. Heteropolymeric filaments are formed by pairing of type I and type II molecules. In humans 54 functional keratin genes exist. They are expressed in highly specific patterns related to the epithelial type and stage of cellular differentiation. About half of all keratins—including numerous keratins characterized only recently—are restricted to the various compartments of hair follicles. As part of the epithelial cytoskeleton, keratins are important for the mechanical stability and integrity of epithelial cells and tissues. Moreover, some keratins also have regulatory functions and are involved in intracellular signaling pathways, e.g. protection from stress, wound healing, and apoptosis. Applying the new consensus nomenclature, this article summarizes, for all human keratins, their cell type and tissue distribution and their functional significance in relation to transgenic mouse models and human hereditary keratin diseases. Furthermore, since keratins also exhibit characteristic expression patterns in human tumors, several of them (notably K5, K7, K8/K18, K19, and K20) have great importance in immunohistochemical tumor diagnosis of carcinomas, in particular of unclear metastases and in precise classification and subtyping. Future research might open further fields of clinical application for this remarkable protein family.
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Strnad P, Stumptner C, Zatloukal K, Denk H. Intermediate filament cytoskeleton of the liver in health and disease. Histochem Cell Biol 2008; 129:735-49. [PMID: 18443813 PMCID: PMC2386529 DOI: 10.1007/s00418-008-0431-x] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2008] [Indexed: 02/06/2023]
Abstract
Intermediate filaments (IFs) represent the largest cytoskeletal gene family comprising approximately 70 genes expressed in tissue specific manner. In addition to scaffolding function, they form complex signaling platforms and interact with various kinases, adaptor, and apoptotic proteins. IFs are established cytoprotectants and IF variants are associated with >30 human diseases. Furthermore, IF-containing inclusion bodies are characteristic features of several neurodegenerative, muscular, and other disorders. Acidic (type I) and basic keratins (type II) build obligatory type I and type II heteropolymers and are expressed in epithelial cells. Adult hepatocytes contain K8 and K18 as their only cytoplasmic IF pair, whereas cholangiocytes express K7 and K19 in addition. K8/K18-deficient animals exhibit a marked susceptibility to various toxic agents and Fas-induced apoptosis. In humans, K8/K18 variants predispose to development of end-stage liver disease and acute liver failure (ALF). K8/K18 variants also associate with development of liver fibrosis in patients with chronic hepatitis C. Mallory-Denk bodies (MDBs) are protein aggregates consisting of ubiquitinated K8/K18, chaperones and sequestosome1/p62 (p62) as their major constituents. MDBs are found in various liver diseases including alcoholic and non-alcoholic steatohepatitis and can be formed in mice by feeding hepatotoxic substances griseofulvin and 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). MDBs also arise in cell culture after transfection with K8/K18, ubiquitin, and p62. Major factors that determine MDB formation in vivo are the type of stress (with oxidative stress as a major player), the extent of stress-induced protein misfolding and resulting chaperone, proteasome and autophagy overload, keratin 8 excess, transglutaminase activation with transamidation of keratin 8 and p62 upregulation.
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Affiliation(s)
- P Strnad
- Department of Internal Medicine I, University of Ulm, Robert-Koch-Strabe 8, 89081, Ulm, Germany.
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49
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Strnad P, Tao GZ, Zhou Q, Harada M, Toivola DM, Brunt EM, Omary MB. Keratin mutation predisposes to mouse liver fibrosis and unmasks differential effects of the carbon tetrachloride and thioacetamide models. Gastroenterology 2008; 134:1169-79. [PMID: 18395095 PMCID: PMC2692280 DOI: 10.1053/j.gastro.2008.01.035] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Accepted: 01/04/2008] [Indexed: 01/07/2023]
Abstract
BACKGROUND & AIMS Keratins 8 and 18 (K8/K18) are important hepatoprotective proteins. Animals expressing K8/K18 mutants show a marked susceptibility to acute/subacute liver injury. K8/K18 variants predispose to human end-stage liver disease and associate with fibrosis progression during chronic hepatitis C infection. We sought direct evidence for a keratin mutation-related predisposition to liver fibrosis using transgenic mouse models because the relationship between keratin mutations and cirrhosis is based primarily on human association studies. METHODS Mouse hepatofibrosis was induced by carbon tetrachloride (CCl(4)) or thioacetamide. Nontransgenic mice, or mice that over express either human Arg89-to-Cys (R89C mice) or wild-type K18 (WT mice) were used. The extent of fibrosis was evaluated by quantitative real-time reverse-transcription polymerase chain reaction of fibrosis-related genes, liver hydroxyproline measurement, and Picro-Sirius red staining and collagen immunofluorescence staining. RESULTS Compared with control animals, CCl(4) led to similar liver fibrosis but increased injury in K18 R89C mice. In contrast, thioacetamide caused more severe liver injury and fibrosis in K18 R89C as compared with WT and nontransgenic mice and resulted in increased messenger RNA levels of collagen, tissue inhibitor of metalloproteinase 1, matrix metalloproteinase 2, and matrix metalloproteinase 13. Analysis in nontransgenic mice showed that thioacetamide and CCl(4) have dramatically different molecular expression responses involving cytoskeletal and chaperone proteins. CONCLUSIONS Over expression of K18 R89C predisposes transgenic mice to thioacetamide- but not CCl(4)-induced liver fibrosis. Differences in the keratin mutation-associated fibrosis response among the 2 models raise the hypothesis that keratin variants may preferentially predispose to fibrosis in unique human liver diseases. Findings herein highlight distinct differences in the 2 widely used fibrosis models.
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Affiliation(s)
| | | | | | - Masaru Harada
- Department of Medicine, Kurume University School of Medicine, Kurume 830-0011, Japan
| | | | - Elizabeth M. Brunt
- Department of Pathology and Immunology, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8118, St. Louis, MO 63110
| | - M. Bishr Omary
- Corresponding Author Address: Bishr Omary, Palo Alto VA Medical Center, 3801 Miranda Avenue, Mail code 154J, Palo Alto, CA 94304, Tel: (650) 493-5000, x63140; Fax: (650) 852-3259, E-Mail:
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50
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Toivola DM, Nakamichi I, Strnad P, Michie SA, Ghori N, Harada M, Zeh K, Oshima RG, Baribault H, Omary MB. Keratin overexpression levels correlate with the extent of spontaneous pancreatic injury. THE AMERICAN JOURNAL OF PATHOLOGY 2008; 172:882-92. [PMID: 18349119 DOI: 10.2353/ajpath.2008.070830] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mutation of the adult hepatocyte keratins K8 and K18 predisposes to liver disease. In contrast, exocrine pancreas K8 and K18 are dispensable and are co-expressed with limited levels of membrane-proximal K19 and K20. Overexpression of mutant K18 or genetic ablation of K8 in mouse pancreas is well tolerated whereas overexpression of K8 causes spontaneous chronic pancreatitis. To better understand the effect of exocrine pancreatic keratin overexpression, we compared transgenic mice that overexpress K18, K8, or K8/K18, associated with minimal, modest, or large increases in keratin expression, respectively, with nontransgenic wild-type (WT) mice. Overexpression of the type-II keratin K8 up-regulated type-I keratins K18, K19, and K20 and generated K19/K20-containing neocytoplasmic typical or short filaments; however, overexpression of K18 had no effect on K8 levels. K8- and K18-overexpressing pancreata were histologically similar to WT, whereas K8/K18 pancreata displayed age-enhanced vacuolization and atrophy of the exocrine pancreas and exhibited keratin hyperphosphorylation. Zymogen granules in K8/K18 pancreata were 50% smaller and more dispersed than their normal apical concentration but were twice as numerous as in WT controls. Therefore, modest keratin overexpression has minor effects on the exocrine pancreas whereas significant keratin overexpression alters zymogen granule organization and causes aging-associated exocrine atrophy. Keratin absence or mutation is well tolerated after pancreatic but not liver injury, whereas excessive overexpression is toxic to the pancreas but not the liver when induced under basal conditions.
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Affiliation(s)
- Diana M Toivola
- Department of Medicine, Veterans Administration Palo Alto Health Care System, Palo Alto, CA, USA.
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