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Somlapura M, Gottschalk B, Lahiri P, Kufferath I, Pabst D, Rülicke T, Graier WF, Denk H, Zatloukal K. Different Roles of p62 (SQSTM1) Isoforms in Keratin-Related Protein Aggregation. Int J Mol Sci 2021; 22:ijms22126227. [PMID: 34207662 PMCID: PMC8227998 DOI: 10.3390/ijms22126227] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 06/01/2021] [Accepted: 06/05/2021] [Indexed: 12/03/2022] Open
Abstract
p62/Sequestosome-1 (p62) is a multifunctional adaptor protein and is also a constant component of disease-associated protein aggregates, including Mallory–Denk bodies (MDBs), in steatohepatitis and hepatocellular carcinoma. We investigated the interaction of the two human p62 isoforms, p62-H1 (full-length isoform) and p62-H2 (partly devoid of PB1 domain), with keratins 8 and 18, the major components of MDBs. In human liver, p62-H2 is expressed two-fold higher compared to p62-H1 at the mRNA level and is present in slightly but not significantly higher concentrations at the protein level. Co-transfection studies in CHO-K1 cells, PLC/PRF/5 cells as well as p62− total-knockout and wild-type mouse fibroblasts revealed marked differences in the cytoplasmic distribution and aggregation behavior of the two p62 isoforms. Transfection-induced overexpression of p62-H2 generated large cytoplasmic aggregates in PLC/PRF/5 and CHO-K1 cells that mostly co-localized with transfected keratins resembling MDBs or (transfection without keratins) intracytoplasmic hyaline bodies. In fibroblasts, however, transfected p62-H2 was predominantly diffusely distributed in the cytoplasm. Aggregation of p62-H2 and p62ΔSH2 as well as the interaction with K8 (but not with K18) involves acquisition of cross-β-sheet conformation as revealed by staining with luminescent conjugated oligothiophenes. These results indicate the importance of considering p62 isoforms in protein aggregation disease.
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Affiliation(s)
- Meghana Somlapura
- Diagnostic and Research Center for Molecular Biomedicine, Institute of Pathology, Medical University of Graz, 8010 Graz, Austria; (M.S.); (I.K.); (D.P.); (H.D.)
| | - Benjamin Gottschalk
- Gottfried Schatz Research Center for Cell Signaling, Metabolism and Aging, Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria; (B.G.); (W.F.G.)
| | - Pooja Lahiri
- School of Medical Science and Technology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India;
| | - Iris Kufferath
- Diagnostic and Research Center for Molecular Biomedicine, Institute of Pathology, Medical University of Graz, 8010 Graz, Austria; (M.S.); (I.K.); (D.P.); (H.D.)
| | - Daniela Pabst
- Diagnostic and Research Center for Molecular Biomedicine, Institute of Pathology, Medical University of Graz, 8010 Graz, Austria; (M.S.); (I.K.); (D.P.); (H.D.)
| | - Thomas Rülicke
- Department of Biomedical Sciences, University of Veterinary Medicine Vienna, 1210 Vienna, Austria;
| | - Wolfgang F. Graier
- Gottfried Schatz Research Center for Cell Signaling, Metabolism and Aging, Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria; (B.G.); (W.F.G.)
| | - Helmut Denk
- Diagnostic and Research Center for Molecular Biomedicine, Institute of Pathology, Medical University of Graz, 8010 Graz, Austria; (M.S.); (I.K.); (D.P.); (H.D.)
| | - Kurt Zatloukal
- Diagnostic and Research Center for Molecular Biomedicine, Institute of Pathology, Medical University of Graz, 8010 Graz, Austria; (M.S.); (I.K.); (D.P.); (H.D.)
- Correspondence: ; Tel.: +43-(0)316-385-71731
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Liput KP, Lepczyński A, Nawrocka A, Poławska E, Ogłuszka M, Jończy A, Grzybek W, Liput M, Szostak A, Urbański P, Roszczyk A, Pareek CS, Pierzchała M. Effects of Three-Month Administration of High-Saturated Fat Diet and High-Polyunsaturated Fat Diets with Different Linoleic Acid (LA, C18:2n-6) to α-Linolenic Acid (ALA, C18:3n-3) Ratio on the Mouse Liver Proteome. Nutrients 2021; 13:1678. [PMID: 34063343 PMCID: PMC8156955 DOI: 10.3390/nu13051678] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Accepted: 05/12/2021] [Indexed: 12/13/2022] Open
Abstract
The aim of the study was to evaluate the effect of different types of high-fat diets (HFDs) on the proteomic profile of mouse liver. The analysis included four dietary groups of mice fed a standard diet (STD group), a high-fat diet rich in SFAs (SFA group), and high-fat diets dominated by PUFAs with linoleic acid (LA, C18:2n-6) to α-linolenic acid (ALA, C18:3n-3) ratios of 14:1 (14:1 group) and 5:1 (5:1 group). After three months of diets, liver proteins were resolved by two-dimensional gel electrophoresis (2DE) using 17 cm non-linear 3-10 pH gradient strips. Protein spots with different expression were identified by MALDI-TOF/TOF. The expression of 13 liver proteins was changed in the SFA group compared to the STD group (↓: ALB, APOA1, IVD, MAT1A, OAT and PHB; ↑: ALDH1L1, UniProtKB-Q91V76, GALK1, GPD1, HMGCS2, KHK and TKFC). Eleven proteins with altered expression were recorded in the 14:1 group compared to the SFA group (↓: ARG1, FTL1, GPD1, HGD, HMGCS2 and MAT1A; ↑: APOA1, CA3, GLO1, HDHD3 and IVD). The expression of 11 proteins was altered in the 5:1 group compared to the SFA group (↓: ATP5F1B, FTL1, GALK1, HGD, HSPA9, HSPD1, PC and TKFC; ↑: ACAT2, CA3 and GSTP1). High-PUFA diets significantly affected the expression of proteins involved in, e.g., carbohydrate metabolism, and had varying effects on plasma total cholesterol and glucose levels. The outcomes of this study revealed crucial liver proteins affected by different high-fat diets.
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Affiliation(s)
- Kamila P. Liput
- Department of Genomics and Biodiversity, Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, ul. Postepu 36A, Jastrzebiec, 05-552 Magdalenka, Poland; (K.P.L.); (A.N.); (E.P.); (M.O.); (A.S.); (P.U.); (A.R.)
- Department of Molecular Biology, Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, ul. Postepu 36A, Jastrzebiec, 05-552 Magdalenka, Poland;
| | - Adam Lepczyński
- Department of Physiology, Cytobiology and Proteomics, West Pomeranian University of Technology, K. Janickiego 32 Str., 71-270 Szczecin, Poland;
| | - Agata Nawrocka
- Department of Genomics and Biodiversity, Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, ul. Postepu 36A, Jastrzebiec, 05-552 Magdalenka, Poland; (K.P.L.); (A.N.); (E.P.); (M.O.); (A.S.); (P.U.); (A.R.)
- Department of Experimental Genomics, Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, ul. Postepu 36A, Jastrzebiec, 05-552 Magdalenka, Poland
| | - Ewa Poławska
- Department of Genomics and Biodiversity, Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, ul. Postepu 36A, Jastrzebiec, 05-552 Magdalenka, Poland; (K.P.L.); (A.N.); (E.P.); (M.O.); (A.S.); (P.U.); (A.R.)
| | - Magdalena Ogłuszka
- Department of Genomics and Biodiversity, Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, ul. Postepu 36A, Jastrzebiec, 05-552 Magdalenka, Poland; (K.P.L.); (A.N.); (E.P.); (M.O.); (A.S.); (P.U.); (A.R.)
| | - Aneta Jończy
- Department of Molecular Biology, Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, ul. Postepu 36A, Jastrzebiec, 05-552 Magdalenka, Poland;
| | - Weronika Grzybek
- Department of Biotechnology and Nutrigenomics, Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, ul. Postepu 36A, Jastrzebiec, 05-552 Magdalenka, Poland;
| | - Michał Liput
- Department of Stem Cell Bioengineering, Mossakowski Medical Research Institute of the Polish Academy of Sciences, 02-106 Warsaw, Poland;
| | - Agnieszka Szostak
- Department of Genomics and Biodiversity, Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, ul. Postepu 36A, Jastrzebiec, 05-552 Magdalenka, Poland; (K.P.L.); (A.N.); (E.P.); (M.O.); (A.S.); (P.U.); (A.R.)
| | - Paweł Urbański
- Department of Genomics and Biodiversity, Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, ul. Postepu 36A, Jastrzebiec, 05-552 Magdalenka, Poland; (K.P.L.); (A.N.); (E.P.); (M.O.); (A.S.); (P.U.); (A.R.)
| | - Agnieszka Roszczyk
- Department of Genomics and Biodiversity, Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, ul. Postepu 36A, Jastrzebiec, 05-552 Magdalenka, Poland; (K.P.L.); (A.N.); (E.P.); (M.O.); (A.S.); (P.U.); (A.R.)
| | - Chandra S. Pareek
- Institute of Veterinary Medicine, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, 87-100 Toruń, Poland;
- Division of Functional Genomics in Biological and Biomedical Research, Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University, 87-100 Torun, Poland
| | - Mariusz Pierzchała
- Department of Genomics and Biodiversity, Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, ul. Postepu 36A, Jastrzebiec, 05-552 Magdalenka, Poland; (K.P.L.); (A.N.); (E.P.); (M.O.); (A.S.); (P.U.); (A.R.)
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Honma Y, Miyagawa K, Hara Y, Hayashi T, Kusanaga M, Ogino N, Minami S, Oe S, Ikeda M, Hino K, Harada M. Correlation of hepatitis C virus-mediated endoplasmic reticulum stress with autophagic flux impairment and hepatocarcinogenesis. Med Mol Morphol 2021; 54:108-121. [PMID: 33386512 DOI: 10.1007/s00795-020-00271-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 11/13/2020] [Indexed: 12/29/2022]
Abstract
Hepatitis C virus (HCV) infection has been known to use autophagy for its replication. However, the mechanisms by which HCV modulates autophagy remain controversial. We used HCV-Japanese fulminant hepatitis-1-infected Huh7 cells. HCV infection induced the accumulation of autophagosomes. Morphological analyses of monomeric red fluorescent protein (mRFP)-green fluorescent protein (GFP) tandem fluorescent-tagged LC3 transfection showed HCV infection impaired autophagic flux. Autophagosome-lysosome fusion assessed by transfection of mRFP- or GFP-LC3 and immunostaining of lysosomal-associated membrane protein 1 was inhibited by HCV infection. Decrease of HCV-induced endoplasmic reticulum (ER) stress by 4-phenylbutyric acid, a chemical chaperone, improved the HCV-mediated autophagic flux impairment. HCV infection-induced oxidative stress and subsequently DNA damage, but not apoptosis. Furthermore, HCV induced cytoprotective effects against the cellular stress by facilitating the formation of cytoplasmic inclusion bodies as shown by p62 expression and by modulating keratin protein expression and activated nuclear factor erythroid 2-related factor 2. HCV eradication by direct-acting antivirals improved autophagic flux, but DNA damage persisted. In conclusion, HCV-induced ER stress correlates with autophagic flux impairment. Decrease of ER stress is considered to be a promising therapeutic strategy for HCV-related chronic liver diseases. However, we should be aware that the risk of hepatocarcinogenesis remains even after HCV eradication.
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Affiliation(s)
- Yuichi Honma
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan.
| | - Koichiro Miyagawa
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan
| | - Yuichi Hara
- Department of Hepatology and Pancreatology, Kawasaki Medical School, Kurashiki, Japan
| | - Tsuguru Hayashi
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan
| | - Masashi Kusanaga
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan
| | - Noriyoshi Ogino
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan
| | - Sota Minami
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan
| | - Shinji Oe
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan
| | - Masanori Ikeda
- Department of Persistent and Oncogenic Viruses, Center for Chronic Viral Diseases, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Keisuke Hino
- Department of Hepatology and Pancreatology, Kawasaki Medical School, Kurashiki, Japan
| | - Masaru Harada
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan.
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Zhong B, Dong J, Zhang R, He M, Zeng W, Pan J, He J, Tao A, Yang R, Fu B, French SW, Liu H. Altered regulation of LncRNA analysis of human alcoholic hepatitis with Mallory-Denk Bodies (MDBs) is revealed by RNA sequencing. Exp Mol Pathol 2020; 117:104559. [PMID: 33121977 DOI: 10.1016/j.yexmp.2020.104559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 10/09/2020] [Accepted: 10/22/2020] [Indexed: 02/07/2023]
Abstract
Mallory-Denk Bodies (MDBs) are prevalent in a variety of liver diseases including alcoholic hepatitis (AH) and are formed in mice livers by feeding DDC. Long noncoding RNAs (lncRNAs) are considered as emerging new gene regulators, which participates in many functional activities through diverse mechanisms. We previously reported the mechanisms involved in the formation of liver MDBs in mouse model and in AH livers where MDBs had formed. To investigate the regulation of mRNAs expression and the probable role of lncRNAs in AH livers with MDBs, RNA-Seq analyses was further conducted to determine the mRNA and lncRNA expression profiles of the AH livers compared with the normal livers. It showed that different lncRNAs have different information contribution degrees by principal component analysis, and the integrated analysis of lncRNA-mRNA co-expression networks were linked to endocytosis, cell cycle, p53 signaling pathways in the human. Based on the co-expression networks, we identify 36 mRNAs that could be as potential biomarkers of alcoholic liver disease (ALD) and hepatocellular carcinoma (HCC). To our knowledge, this is the first report on the regulatory network of lncRNAs associated with liver MDB formation in human, and these results might offer new insights into the molecular mechanisms of liver MDB formation and the progression of AH to HCC.
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Affiliation(s)
- Bei Zhong
- The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital; School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou 510182, China
| | - Jun Dong
- The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital; School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou 510182, China
| | - Rong Zhang
- The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital; School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou 510182, China
| | - Menghua He
- The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital; School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou 510182, China
| | - Wuyi Zeng
- The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital; School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou 510182, China
| | - Jiayi Pan
- The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital; School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou 510182, China
| | - Jiashan He
- The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital; School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou 510182, China
| | - Ailin Tao
- The State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou 510260, China
| | - Rirong Yang
- Department of Immunology, School of Preclinical Medicine, Center for Genomic and Personalized Medicine, Guangxi Medical University, Nanning 530021, China
| | - Bishi Fu
- The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital; School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou 510182, China
| | - Samuel W French
- University of California, Harbor UCLA Medical Center, Department of Pathology, Torrance, CA 90509, USA.
| | - Hui Liu
- The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital; School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou 510182, China; The State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou 510260, China.
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Honma Y, Sato-Morita M, Katsuki Y, Mihara H, Baba R, Hino K, Kawashima A, Ariyasu T, Harada M. Trehalose alleviates oxidative stress-mediated liver injury and Mallor-Denk body formation via activating autophagy in mice. Med Mol Morphol 2020; 54:41-51. [PMID: 32588144 DOI: 10.1007/s00795-020-00258-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 06/16/2020] [Indexed: 02/06/2023]
Abstract
Autophagy is a degradation pathway for long-lived cytoplasmic proteins or damaged organelles and also for many aggregate-prone and disease-causing proteins. Endoplasmic reticulum (ER) stress and oxidative stress are associated with the pathophysiology of various liver diseases. These stresses induce the accumulation of abnormal proteins, Mallory-Denk body (MDB) formation and apoptosis in hepatocytes. A disaccharide trehalose had been reported to induce autophagy and decrease aggregate-prone proteins and cytotoxicity in neurodegenerative disease models. But the effects of trehalose in hepatocytes have not been fully understood. We examined the effect of trehalose on autophagy, ER stress and oxidative stress-mediated cytotoxicity and MDB formation in hepatocytes using mice model with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) treatment for 3 months. We administered trehalose by intraperitoneal injection of water containing 10% trehalose (0.02 mg/g body weight) every other day for 3 months. Our results demonstrated that trehalose induced autophagy and reduced ER stress, oxidative stress, MDB formation and apoptosis in hepatocytes of DDC-fed mice by Western blotting and immunostaining analyses. Electron microscopy revealed that trehalose induced autolysosome formation, which located is close to the MDBs. Thus, our findings suggest that trehalose can become a therapeutic agent for oxidative stress-related liver diseases via activating autophagy.
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Affiliation(s)
- Yuichi Honma
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan.
| | - Miyuki Sato-Morita
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan
| | - Yuka Katsuki
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan
| | - Hitomi Mihara
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan
| | - Ryoko Baba
- Department of Anatomy, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Katsuhiko Hino
- Core Technology Division, R&D Center, Hayashibara Co., Ltd., Okayama, Japan
| | - Akira Kawashima
- Applied Technology Division, R&D Center, Hayashibara Co., Ltd., Okayama, Japan
| | - Toshio Ariyasu
- Applied Technology Division, R&D Center, Hayashibara Co., Ltd., Okayama, Japan
| | - Masaru Harada
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555, Japan
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Jang KH, Yoon HN, Lee J, Yi H, Park SY, Lee SY, Lim Y, Lee HJ, Cho JW, Paik YK, Hancock WS, Ku NO. Liver disease-associated keratin 8 and 18 mutations modulate keratin acetylation and methylation. FASEB J 2019; 33:9030-9043. [PMID: 31199680 DOI: 10.1096/fj.201800263rr] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Keratin 8 (K8) and keratin 18 (K18) are the intermediate filament proteins whose phosphorylation/transamidation associate with their aggregation in Mallory-Denk bodies found in patients with various liver diseases. However, the functions of other post-translational modifications in keratins related to liver diseases have not been fully elucidated. Here, using a site-specific mutation assay combined with nano-liquid chromatography-tandem mass spectrometry, we identified K8-Lys108 and K18-Lys187/426 as acetylation sites, and K8-Arg47 and K18-Arg55 as methylation sites. Keratin mutation (Arg-to-Lys/Ala) at the methylation sites, but not the acetylation sites, led to decreased stability of the keratin protein. We compared keratin acetylation/methylation in liver disease-associated keratin variants. The acetylation of K8 variants increased or decreased to various extents, whereas the methylation of K18-del65-72 and K18-I150V variants increased. Notably, the highly acetylated/methylated K18-I150V variant was less soluble and exhibited unusually prolonged protein stability, which suggests that additional acetylation of highly methylated keratins has a synergistic effect on prolonged stability. Therefore, the different levels of acetylation/methylation of the liver disease-associated variants regulate keratin protein stability. These findings extend our understanding of how disease-associated mutations in keratins modulate keratin acetylation and methylation, which may contribute to disease pathogenesis.-Jang, K.-H., Yoon, H.-N., Lee, J., Yi, H., Park, S.-Y., Lee, S.-Y., Lim, Y., Lee, H.-J., Cho, J.-W., Paik, Y.-K., Hancock, W. S., Ku, N.-O. Liver disease-associated keratin 8 and 18 mutations modulate keratin acetylation and methylation.
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Affiliation(s)
- Kwi-Hoon Jang
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul, Korea
| | - Han-Na Yoon
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul, Korea
| | - Jongeun Lee
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul, Korea
| | - Hayan Yi
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul, Korea
| | - Sang-Yoon Park
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, USA
| | - So-Young Lee
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul, Korea
| | - Younglan Lim
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul, Korea
| | - Hyoung-Joo Lee
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul, Korea
| | - Jin-Won Cho
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul, Korea
| | - Young-Ki Paik
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul, Korea
| | - Williams S Hancock
- Barnett Institute and Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts, USA
| | - Nam-On Ku
- Interdisciplinary Program of Integrated OMICS for Biomedical Science, Graduate School, Yonsei University, Seoul, Korea.,Department of Bio-Convergence Integrated Science and Engineering Division, Underwood International College, Yonsei University, Seoul, Korea
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Effect of heme oxygenase-1 on the protection of ischemia reperfusion injury of bile duct in rats after liver transplantation. Clin Res Hepatol Gastroenterol 2018; 42:245-254. [PMID: 29174380 DOI: 10.1016/j.clinre.2017.09.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2017] [Revised: 09/13/2017] [Accepted: 09/19/2017] [Indexed: 02/04/2023]
Abstract
OBJECTIVE To investigate the effect of heme oxygenase-1 (HO-1) on the ischemic reperfusion injury (IRI) of bile duct in rat models after liver transplantation. METHODS 320 SD rats were equally and randomly divided into 5 groups, which were group A receiving injection of 3×108/pfu/ml adenovirus (adv), group B with donor receiving Adv-HO-1 and recipient receiving Adv-HO-1-siRNA, group C with donor and recipient both receiving Adv-HO-1, group D with donor receiving Adv-HO-1-siRNA and recipient receiving Adv-HO-1, and group E with donor and recipient both receiving Adv-HO-1-siRNA at 24h before liver transplantation. Donor liver was stored in UW liquid at 4°C followed by measuring HO-1 level by western blot before transplantation. On d1, d3, d7 and d14, serum and liver was isolated for analysis of liver function, inflammatory cell infiltration by H&E staining, ultrastructure of liver by transmission electron microscopy as well as the expression of HO-1, Bsep, Mrp2 and Ntcp by western blot. RESULTS Compared with group D and E, group B and C displayed improved liver function as demonstrated by lower level of ALT, AST, LDH, TBIL, ALP and GGT, increased secretion of TBA and PL as well as expression of transporter proteins (Bsep, Mrp2 and Ntcp), reduced inflammatory cells infiltration and liver injury. CONCLUSION Our study demonstrated that overexpression of HO-1 in donor liver can ameliorate the damage to bile duct and liver, and improved liver function, suggesting HO-1 might be a new therapeutic target in the treatment of IRI after liver transplantation.
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Aigelsreiter A, Neumann J, Pichler M, Halasz J, Zatloukal K, Berghold A, Douschan P, Rainer F, Stauber R, Haybaeck J, Denk H, Lackner C. Hepatocellular carcinomas with intracellular hyaline bodies have a poor prognosis. Liver Int 2017; 37:600-610. [PMID: 27885796 DOI: 10.1111/liv.13325] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 11/13/2016] [Indexed: 01/03/2023]
Abstract
BACKGROUND & AIMS Mallory-Denk bodies (MDBs) and intracellular hyaline bodies (IHBs) are cytoplasmic inclusions found in a subset of hepatocellular carcinoma (HCC). MDBs are mainly composed of the intermediate filament proteins keratin (K) 8 and K18, the cellular stress- and adapter-protein sequestosome 1/p62 (p62) and ubiquitin, whereas IHBs consist of p62 and/or ubiquitin. Of note, cytoplasmic inclusions containing p62 can serve as markers of suppressed autophagy, which in turn has been associated with poor prognosis. The aim of this study was to evaluate the prognostic significance of p62-containing MDB and IHB in patients with HCC. METHODS Ninety resected HCCs were assessed by H&E histology for MDB or IHB, and their presence was confirmed by immunohistochemistry using K8/18, p62 and ubiquitin antibodies. The prognostic impact of inclusions was assessed using Kaplan-Meier and multivariate Cox proportional model. RESULTS Mallory-Denk bodies and/or IHB were found in about 50% of HCC. Both types of inclusions were seen in 21%, MDB only in 19% and IHB only in 10% of cases. The presence of MDB in tumours was associated with the steatohepatitic variant of HCC, which also showed fatty change, ballooning of tumour cells, MDBs, inflammation and pericellular fibrosis (P<.001). In contrast, IHBs were not associated with steatohepatitic morphology but were associated with significantly shorter overall survival (P=.006). Multivariate analysis revealed macroscopic vascular invasion (P=.045) and presence of IHB in HCC cells (P=.005) as independently associated with overall survival. CONCLUSIONS Intracellular hyaline bodies and macroscopic vascular invasion identify a subset of HCC patients with poor prognosis.
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Affiliation(s)
| | - Jens Neumann
- Institute of Pathology, Medical University of Graz, Graz, Austria.,Institute of Pathology, Ludwig-Maximilian University of Munich, Munich, Germany
| | - Martin Pichler
- Department of Internal Medicine, Division of Oncology, Medical University of Graz, Graz, Austria
| | - Judith Halasz
- 2nd Department of Pathology, Semmelweis University of Budapest, Budapest, Hungary
| | - Kurt Zatloukal
- Institute of Pathology, Medical University of Graz, Graz, Austria
| | - Andrea Berghold
- Institute for Medical Informatics Statistics and Documentation, Medical University of Graz, Graz, Austria
| | - Philipp Douschan
- Department of Internal Medicine, Division of Gastroenterology and Hepatology, Medical University of Graz, Graz, Austria
| | - Florian Rainer
- Department of Internal Medicine, Division of Gastroenterology and Hepatology, Medical University of Graz, Graz, Austria
| | - Rudolf Stauber
- Department of Internal Medicine, Division of Gastroenterology and Hepatology, Medical University of Graz, Graz, Austria
| | | | - Helmut Denk
- Institute of Pathology, Medical University of Graz, Graz, Austria
| | - Carolin Lackner
- Institute of Pathology, Medical University of Graz, Graz, Austria
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Three-dimensional Organization of Layered Apical Cytoskeletal Networks Associated with Mouse Airway Tissue Development. Sci Rep 2017; 7:43783. [PMID: 28272499 PMCID: PMC5363704 DOI: 10.1038/srep43783] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 01/30/2017] [Indexed: 01/11/2023] Open
Abstract
The cytoskeleton is an essential cellular component that enables various sophisticated functions of epithelial cells by forming specialized subcellular compartments. However, the functional and structural roles of cytoskeletons in subcellular compartmentalization are still not fully understood. Here we identified a novel network structure consisting of actin filaments, intermediate filaments, and microtubules directly beneath the apical membrane in mouse airway multiciliated cells and in cultured epithelial cells. Three-dimensional imaging by ultra-high voltage electron microscopy and immunofluorescence revealed that the morphological features of each network depended on the cell type and were spatiotemporally integrated in association with tissue development. Detailed analyses using Odf2 mutant mice, which lack ciliary basal feet and apical microtubules, suggested a novel contribution of the intermediate filaments to coordinated ciliary beating. These findings provide a new perspective for viewing epithelial cell differentiation and tissue morphogenesis through the structure and function of apical cytoskeletal networks.
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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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11
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12
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Hiura M, Honma Y, Miyagawa K, Oe S, Shimajiri S, Mihara H, Oe M, Sato-Morita M, Katsuki Y, Harada M. Alleviation mechanisms against hepatocyte oxidative stress in patients with chronic hepatic disorders. Hepatol Res 2015; 45:1124-35. [PMID: 25581125 DOI: 10.1111/hepr.12478] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 01/05/2015] [Accepted: 01/06/2015] [Indexed: 02/08/2023]
Abstract
AIM Autophagy induction and Mallory-Denk body (MDB) formation have been considered to have cytoprotective effects from cellular stress in liver diseases. We investigated the relations among oxidative stress, autophagy and MDB formation in patients with chronic hepatitis B (CHB), chronic hepatitis C (CHC) and non-alcoholic fatty liver disease (NAFLD) to clarify the alleviation mechanisms against oxidative stress of hepatocytes. METHODS First, we treated cultured cells with proteasome inhibitor (PI) or free fatty acid (FFA) and evaluated endoplasmic reticulum (ER) stress, oxidative stress, ubiquitinated proteins and p62 by western blotting. Then, we used human liver biopsy samples to evaluate oxidative stress, autophagy and MDB formation by immunohistochemical analysis. RESULTS Treatment with PI or FFA increased ER stress, oxidative stress, ubiquitinated proteins and p62 in cultured cells. Human liver biopsy samples of CHC and NAFLD showed that MDB formed in areas with strong oxidative stress and that the MDB-containing cells circumvented oxidative stress. Keratin 8 (K8) expression was strong in MDB-containing cells in CHC and NAFLD. However, in CHB samples, the expression of K8 was not increased in response to oxidative stress and MDB aggregates did not appear. Aminotransferase values were significantly lower in patients with CHC and NAFLD in whom light chain 3 antibody expression was increased in response to oxidative stress. CONCLUSION Strong expression of K8 was considered to be important for MDB formation. MDB protect liver cells from oxidative stress at a cellular level and autophagy reduced hepatic damage when it was induced in the hepatocytes exposed to strong oxidative stress.
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Affiliation(s)
- Masaaki Hiura
- Third Department of Internal Medicine, Kitakyushu, Japan
| | - Yuichi Honma
- Third Department of Internal Medicine, Kitakyushu, Japan
| | | | - Shinji Oe
- Third Department of Internal Medicine, Kitakyushu, Japan
| | - Shohei Shimajiri
- Department of Pathology and Cell Biology, University of Occupational and Environmental Health, School of Medicine, Kitakyushu, Japan
| | - Hitomi Mihara
- Third Department of Internal Medicine, Kitakyushu, Japan
| | - Masami Oe
- Third Department of Internal Medicine, Kitakyushu, Japan
| | | | - Yuka Katsuki
- Third Department of Internal Medicine, Kitakyushu, Japan
| | - Masaru Harada
- Third Department of Internal Medicine, Kitakyushu, Japan
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Honma Y, Harada M. New therapeutic strategy for hepatocellular carcinoma by molecular targeting agents via inhibition of cellular stress defense mechanisms. J UOEH 2014; 36:229-235. [PMID: 25501753 DOI: 10.7888/juoeh.36.229] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The prognosis of advanced hepatocellular carcinoma (HCC) has remained very poor.It has recently been reported that the molecular targeting agent sorafenib can improve the prognosis of patients with advanced HCC. However, the detailed mechanisms of sorafenib, especially its direct effects on hepatoma and hepatocyte cells, are poorly understood, making a more detailed investigation about the molecular mechanism of sorafenib necessary. Endoplasmic reticulum (ER) stress is related to the pathophysiology of various liver diseases, including chronic viral hepatitis, alcoholic and nonalcoholic steatohepatitis and HCC. In this regard, our recent data examining the molecular effects of sorafenib focused on the cellular defense mechanisms from ER stress, the unfolded protein response (UPR) and keratin phosphorylation, demonstrated that sorafenib inhibited both important cytoprotective mechanisms, UPR and keratin phosphorylation, and enhances the anti-tumor effect in combination with proteasome inhibitors. This review summarizes the cytoprotective mechanisms from ER stress and our results about the direct effect of sorafenib on the cytoprotective mechanisms.
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Affiliation(s)
- Yuichi Honma
- Third Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, Japan
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Strnad P, Nuraldeen R, Guldiken N, Hartmann D, Mahajan V, Denk H, Haybaeck J. Broad Spectrum of Hepatocyte Inclusions in Humans, Animals, and Experimental Models. Compr Physiol 2013; 3:1393-436. [DOI: 10.1002/cphy.c120032] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Honma Y, Harada M. Sorafenib enhances proteasome inhibitor-mediated cytotoxicity via inhibition of unfolded protein response and keratin phosphorylation. Exp Cell Res 2013; 319:2166-78. [PMID: 23727131 DOI: 10.1016/j.yexcr.2013.05.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 05/17/2013] [Accepted: 05/18/2013] [Indexed: 12/19/2022]
Abstract
Hepatocellular carcinoma (HCC) is highly resistant to conventional systemic therapies and prognosis for advanced HCC patients remains poor. Recent studies of the molecular mechanisms responsible for tumor initiation and progression have identified several potential molecular targets in HCC. Sorafenib is a multi-kinase inhibitor shown to have survival benefits in advanced HCC. It acts by inhibiting the serine/threonine kinases and the receptor type tyrosine kinases. In preclinical experiments sorafenib had anti-proliferative activity in hepatoma cells and it reduced tumor angiogenesis and increased apoptosis. Here, we demonstrate for the first time that the cytotoxic mechanisms of sorafenib include its inhibitory effects on protein ubiquitination, unfolded protein response (UPR) and keratin phosphorylation in response to endoplasmic reticulum (ER) stress. Moreover, we show that combined treatment with sorafenib and proteasome inhibitors (PIs) synergistically induced a marked increase in cell death in hepatoma- and hepatocyte-derived cells. These observations may open the way to potentially interesting treatment combinations that may augment the effect of sorafenib, possibly including drugs that promote ER stress. Because sorafenib blocked the cellular defense mechanisms against hepatotoxic injury not only in hepatoma cells but also in hepatocyte-derived cells, we must be careful to avoid severe liver injury.
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Affiliation(s)
- Yuichi Honma
- Third Department of Internal Medicine, University of Occupational and Environmental Health, School of Medicine, Kitakyushu, Japan
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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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Österreicher CH, Trauner M. Xenobiotic-induced liver injury and fibrosis. Expert Opin Drug Metab Toxicol 2012; 8:571-80. [PMID: 22452290 DOI: 10.1517/17425255.2012.674511] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
INTRODUCTION Many different drugs and xenobiotics (chemical compounds foreign to an organism) can injure the bile duct epithelium and cause inflammatory bile duct diseases (cholangiopathies) ranging from transient cholestasis to vanishing bile duct syndrome, sclerosing cholangitis with development of biliary fibrosis and cirrhosis. Animal models of xenobiotic-induced liver injury have provided major mechanistic insights into the molecular mechanisms of xenobiotic-induced cholangiopathies and biliary fibrosis including primary biliary cirrhosis and primary sclerosing cholangitis. AREAS COVERED In this review, the authors discuss the basic principles of xenobiotic-induced liver and bile duct injury and biliary fibrosis with emphasis on animal models. A PubMed search was performed using the search terms "xenobiotic," "liver injury," "cholestasis," and "biliary fibrosis." Reference lists of retrieved articles were also searched for relevant literature. EXPERT OPINION Xenobiotic-induced cholangiopathies are underestimated and frequently overlooked medical conditions due to their often transient nature. However, biliary disease may progress to vanishing bile duct syndrome, biliary fibrosis, and cirrhosis. Moreover, xenobiotics may prime the liver for subsequent liver disease by other agents and may also contribute to the development of hepatobiliary cancer though interaction with resident stem cells.
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Affiliation(s)
- Christoph H Österreicher
- Medical University of Vienna, Institute of Pharmacology, Center for Physiology and Pharmacology, Vienna, Austria
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Kwan R, Hanada S, Harada M, Strnad P, Li DH, Omary MB. Keratin 8 phosphorylation regulates its transamidation and hepatocyte Mallory-Denk body formation. FASEB J 2012; 26:2318-26. [PMID: 22362895 DOI: 10.1096/fj.11-198580] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Mallory-Denk bodies (MDBs) are hepatocyte inclusions that are associated with poor liver disease prognosis. The intermediate filament protein keratin 8 (K8) and its cross-linking by transglutaminase-2 (TG2) are essential for MDB formation. K8 hyperphosphorylation occurs in association with liver injury and MDB formation, but the link between keratin phosphorylation and MDB formation is unknown. We used a mutational approach to identify K8 Q70 as a residue that is important for K8 cross-linking to itself and other liver proteins. K8 cross-linking is markedly enhanced on treating cells with a phosphatase inhibitor and decreases dramatically on K8 S74A or Q70N mutation in the presence of phosphatase inhibition. K8 Q70 cross-linking, in the context of synthetic peptides or intact proteins transfected into cells, is promoted by phosphorylation at K8 S74 or by an S74D substitution and is inhibited by S74A mutation. Transgenic mice that express K8 S74A or a K8 G62C liver disease variant that inhibits K8 S74 phosphorylation have a markedly reduced ability to form MDBs. Our findings support a model in which the stress-triggered phosphorylation of K8 S74 induces K8 cross-linking by TG2, leading to MDB formation. These findings may extend to neuropathies and myopathies that are characterized by intermediate filament-containing inclusions.
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Affiliation(s)
- Raymond Kwan
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0622, USA.
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Molnar A, Haybaeck J, Lackner C, Strnad P. The cytoskeleton in nonalcoholic steatohepatitis: 100 years old but still youthful. Expert Rev Gastroenterol Hepatol 2011; 5:167-77. [PMID: 21476912 DOI: 10.1586/egh.11.5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The hepatocellular cytoskeleton consists of three filamentous systems: microfilaments, microtubules and keratins (Ks). While the alterations in microfilaments and microtubules during nonalcoholic steatohepatitis (NASH) are largely unexplored, K8/K18 reorganization into Mallory-Denk bodies (MDBs) represents a NASH hallmark, and serological K18 fragments constitute an established tool to monitor NASH severity. To commemorate the 100th anniversary of the first description of MDBs, this article summarizes the composition and function of the hepatocellular cytoskeleton, as well as the importance of cytoskeletal alterations in NASH. The significance of MDBs in clinical routine is illustrated, as are the findings from MDB mouse models, which shape our current view of MDB pathogenesis. Even after 100 years, the cytoskeleton represents a fascinating but greatly understudied area of NASH biology.
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Affiliation(s)
- Agnes Molnar
- Department of Internal Medicine I, University Hospital Ulm, Germany
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Autophagy is involved in the elimination of intracellular inclusions, Mallory-Denk bodies, in hepatocytes. Med Mol Morphol 2010; 43:13-8. [PMID: 20340001 DOI: 10.1007/s00795-009-0476-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Accepted: 09/28/2009] [Indexed: 12/19/2022]
Abstract
Several human liver diseases are associated with formation of hepatocyte Mallory-Denk bodies (MDB) composed of keratins and ubiquitin. Similar inclusions are found in various other diseases, neurodegenerative and muscle disorders. However, the mechanisms of MDB formation have been unclear. Autophagy is a degradation process of intracellular proteins and organelles. In the present study we examined the association of autophagy with the formation of MDB. We fed wild-type and keratin 8-transgenic mice with a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-containing diet for 9 days. The livers were analyzed by immunohistochemistry and conventional and immune electron microscopy. Short-term DDC feeding induced MDB in keratin 8-transgenic but not in nontransgenic mouse livers. Electron microscopy revealed inclusions composed of electron-dense materials and filaments in hepatocyte cytoplasm and many autophagolysosomes in hepatocytes. Inclusions were positive for keratin 8/18 and ubiquitin examined by immunoelectron microscopy. Gold particles for keratin 8/18 or ubiquitin were found in the autophagic vacuoles near or in the inclusions. Keratin 8 overexpression accelerates MDB formation, and the keratin 8-transgenic mouse is a useful tool for the study of MDB formation. Autophagy apparently participates in the elimination of components of MDB. Manipulation of autophagy may be a possible therapeutic strategy for various inclusion-associated diseases.
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Omary MB, Ku NO, Strnad P, Hanada S. Toward unraveling the complexity of simple epithelial keratins in human disease. J Clin Invest 2009; 119:1794-805. [PMID: 19587454 DOI: 10.1172/jci37762] [Citation(s) in RCA: 204] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Simple epithelial keratins (SEKs) are found primarily in single-layered simple epithelia and include keratin 7 (K7), K8, K18-K20, and K23. Genetically engineered mice that lack SEKs or overexpress mutant SEKs have helped illuminate several keratin functions and served as important disease models. Insight into the contribution of SEKs to human disease has indicated that K8 and K18 are the major constituents of Mallory-Denk bodies, hepatic inclusions associated with several liver diseases, and are essential for inclusion formation. Furthermore, mutations in the genes encoding K8, K18, and K19 predispose individuals to a variety of liver diseases. Hence, as we discuss here, the SEK cytoskeleton is involved in the orchestration of several important cellular functions and contributes to the pathogenesis of human liver disease.
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Affiliation(s)
- M Bishr Omary
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
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Mallory-Denk-bodies: lessons from keratin-containing hepatic inclusion bodies. Biochim Biophys Acta Mol Basis Dis 2008; 1782:764-74. [PMID: 18805482 DOI: 10.1016/j.bbadis.2008.08.008] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 08/25/2008] [Accepted: 08/26/2008] [Indexed: 01/08/2023]
Abstract
Inclusion bodies are characteristic morphological features of various neuronal, muscular and other human disorders. They share common molecular constituents such as p62, chaperones and proteasome subunits. The proteins within aggregates are misfolded with increased beta-sheet structure, they are heavily phosphorylated, ubiquitinylated and partially degraded. Furthermore, involvement of proteasomal system represents a common feature of virtually all inclusions. Multiple aggregates contain intermediate filament proteins as their major constituents. Among them, Mallory-Denk bodies (MDBs) are the best studied. MDBs represent hepatic inclusions observed in diverse chronic liver diseases such as alcoholic and non-alcoholic steatohepatitis, chronic cholestasis, metabolic disorders and hepatocellular neoplasms. MDBs are induced in mice fed griseofulvin or 3,5-diethoxycarbonyl-1,4-dihydrocollidine and resolve after discontinuation of toxin administration. The availability of a drug-induced model makes MDBs a unique tool for studying inclusion formation. Our review summarizes the recent advances gained from this model and shows how they relate to observations in other aggregates. The MDB formation-underlying mechanisms include protein misfolding, chaperone alterations, disproportional protein expression with keratin 8>keratin 18 levels and subsequent keratin 8 crosslinking via transglutaminase. p62 presence is crucial for MDB formation. Proteasome inhibitors precipitate MDB formation, whereas stimulation of autophagy with rapamycin attenuates their formation.
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Hanada S, Strnad P, Brunt EM, Omary MB. The genetic background modulates susceptibility to mouse liver Mallory-Denk body formation and liver injury. Hepatology 2008; 48:943-52. [PMID: 18697208 DOI: 10.1002/hep.22436] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
UNLABELLED Mallory-Denk bodies (MDBs) are hepatocyte inclusions found in several liver diseases and consist primarily of keratins 8 and 18 (K8/K18) and ubiquitin that are cross-linked by transglutaminase-2. We hypothesized that genetic variables contribute to the extent of MDB formation, because not all patients with an MDB-associated liver disease develop inclusions. We tested this hypothesis using five strains of mice (FVB/N, C3H/He, Balb/cAnN, C57BL/6, 129X1/Sv) fed for three months (eight mice per strain) the established MDB-inducing agent 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). MDB formation was compared using hematoxylin-and-eosin staining, or immunofluorescence staining with antibodies to K8/K18/ubiquitin, or biochemically by blotting with antibodies to transglutaminase-2/p62 proteins and to K8/K18/ubiquitin to detect keratin cross-linking. DDC feeding induced MDBs in all mouse strains, but there were dramatic strain differences that quantitatively varied 2.5-fold (P < 0.05). MDB formation correlated with hepatocyte ballooning, and most ballooned hepatocytes had MDBs. Immunofluorescence assessment was far more sensitive than hematoxylin-and-eosin staining in detecting small MDBs, which out-numbered (by approximately 30-fold to 90-fold) but did not parallel their large counterparts. MDB scores partially reflected the biochemical presence of cross-linked keratin-ubiquitin species but not the changes in liver size or injury in response to DDC. The extent of steatosis correlated with the total (large+small) number of MDBs, and there was a limited correlation between large MDBs and acidophil bodies. CONCLUSION Mouse MDB formation has important genetic contributions that do not correlate with the extent of DDC-induced liver injury. If extrapolated to humans, the genetic contributions help explain why some patients develop MDBs whereas others are less likely to do so. Detection and classification of MDBs using MDB-marker-selective staining may offer unique links to specific histological features of DDC-induced liver injury.
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Affiliation(s)
- Shinichiro Hanada
- Department of Medicine, Veterans Administration Palo Alto Health Care System and Stanford University, Palo Alto, CA, USA
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Abstract
PURPOSE OF REVIEW Studies are reviewed from the past year concerning the histopathology of liver and biliary diseases and their pathogenesis. RECENT FINDINGS Several cases of acute hepatitis E showed portal and periportal hepatitis, with polarization of neutrophils to the interface region and lymphocytes more centrally in the portal tracts. Transfection of hepatitis C virus into cultured fetal hepatocytes resulted in sustained growth of 50-90 nm diameter viral particles. The ductular reaction in nonalcoholic steatohepatitis appears to evolve with fibrosis in response to hepatocyte replicative senescence. Hepatocellular release of hepcidin is critical for iron homeostasis in a manner analogous to pancreatic insulin for glucose homeostasis; this 'endocrine' focus was elaborated in an overview of hemochromatosis. Specific microscopic features of liver-cell adenomas combined with genetic analysis for hepatocyte nuclear factor 1alpha and beta-catenin mutations allows differentiation into four variants. Steroid-sensitive biliary strictures resembling primary sclerosing cholangitis but with increased serum immunoglobulin G4 and infiltrating immunoglobulin G4-positive plasma cells ('immunoglobulin associated cholangitis') are part of a spectrum of disorders including autoimmune pancreatitis and inflammatory pseudotumor. SUMMARY Pathologic features of viral hepatitis C and E, immunohistochemistry for the ductular reaction and malignant liver tumors and several systemic disorders are among recent important pathology studies.
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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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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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Ku NO, Strnad P, Zhong BH, Tao GZ, Omary MB. Keratins let liver live: Mutations predispose to liver disease and crosslinking generates Mallory-Denk bodies. Hepatology 2007; 46:1639-49. [PMID: 17969036 DOI: 10.1002/hep.21976] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Keratin polypeptides 8 and 18 (K8/K18) are the cytoskeletal intermediate filament proteins of hepatocytes while K8/K18/K19 are the keratins of hepatobiliary ductal cells. Hepatocyte K8/K18 are highly abundant and behave as stress proteins with injury-inducible expression. Human association studies show that K8/K18 germline heterozygous mutations predispose to end-stage liver disease of multiple etiologies ( approximately 3 fold increased risk), and to liver disease progression in patients with chronic hepatitis C infection. These findings are supported by extensive transgenic mouse and ex vivo primary hepatocyte culture studies showing that K8 or K18 mutations predispose the liver to acute or subacute injury and promote apoptosis and fibrosis. Mutation-associated predisposition to liver injury is likely related to mechanical and nonmechanical keratin functions including maintenance of cell integrity, protection from apoptosis and oxidative injury, serving as a phosphate sponge, regulation of mitochondrial organization/function and protein targeting. These functions are altered by mutation-induced changes in keratin phosphorylation, solubility and filament organization/reorganization. Keratins are also the major constituents of Mallory-Denk bodies (MDBs). A toxin-induced K8>K18 ratio, and keratin crosslinking by transglutaminase-2 play essential roles in MDB formation. Furthermore, intracellular or cell-released K18 fragments, generated by caspase-mediated proteolysis during apoptosis serve as markers of liver injury. Therefore, K8 and K18 are cytoprotective stress proteins that play a central role in guarding hepatocytes from apoptosis. Keratin involvement in liver disease is multi-faceted and includes modulating disease progression upon mutation, formation of MDBs in response to unique forms of injury, and serving as markers of epithelial cell death.
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Affiliation(s)
- Nam-On Ku
- Department of Medicine, Palo Alto VA Medical Center and Stanford University Digestive Disease Center, Palo Alto, CA
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Stumptner C, Fuchsbichler A, Zatloukal K, Denk H. In vitro production of Mallory bodies and intracellular hyaline bodies: the central role of sequestosome 1/p62. Hepatology 2007; 46:851-60. [PMID: 17685470 DOI: 10.1002/hep.21744] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
UNLABELLED Mallory bodies (MBs) and intracellular hyaline bodies (IHBs) are characteristic hepatocellular inclusions. MBs are hallmarks of steatohepatitis, whereas IHBs have first been detected in hepatocellular carcinoma. MBs and IHBs contain ubiquitin and sequestosome 1/p62 (p62), a stress-inducible adapter protein with affinity to polyubiquitinated proteins. MBs differ from IHBs by their keratin content and morphology. In vitro transfections were undertaken to study under defined conditions MB and IHB formation, their pathogenesis, and relationship. CHO-K1, TIB73, and HeLa cells were transfected with keratin 8, keratin 18, ubiquitin, p62, and p62 lacking the ubiquitin binding domain (p62DeltaUBA) and analyzed by immunofluorescence, immunoelectron microscopy, and immunoblotting. Transfection of p62 complementary deoxyribonucleic acid (cDNA) alone led to cytoplasmic aggregates consisting of filaments mostly arranged in parallel arrays resembling amyloid and type 1 MBs. Transfection of p62 and ubiquitin resulted in globular cytoplasmic aggregates with indistinct fibrillar ultrastructure resembling IHBs. Cotransfection of p62, keratin 8, and ubiquitin was necessary to produce in vitro type 2 MBs-like aggregates consisting of randomly oriented 10- to 15-nm filaments. A similar result was obtained when keratin 8 was replaced by keratin 18. After cotransfection of p62DeltaUBA, keratin 8, and ubiquitin, keratin formed irregular aggregates with electron-dense granular-amorphous ultrastructure (resembling type 3 MBs), whereas p62DeltaUBA remained in diffuse cytoplasmic distribution. CONCLUSION Our studies show that in vitro development of classical type 2 MBs requires overexpression of keratin 8 (or keratin 18), ubiquitin, and p62 containing the ubiquitin binding domain, whereas IHBs result from overexpression of p62 together with ubiquitin without keratin involvement.
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Affiliation(s)
- Conny Stumptner
- Institute of Pathology, Medical University of Graz, Graz, Austria
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Zatloukal K, French SW, Stumptner C, Strnad P, Harada M, Toivola DM, Cadrin M, Omary MB. From Mallory to Mallory–Denk bodies: What, how and why? Exp Cell Res 2007; 313:2033-49. [PMID: 17531973 DOI: 10.1016/j.yexcr.2007.04.024] [Citation(s) in RCA: 235] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Revised: 04/02/2007] [Accepted: 04/03/2007] [Indexed: 12/16/2022]
Abstract
Frank B. Mallory described cytoplasmic hyaline inclusions in hepatocytes of patients with alcoholic hepatitis in 1911. These inclusions became known as Mallory bodies (MBs) and have since been associated with a variety of other liver diseases including non-alcoholic fatty liver disease. Helmut Denk and colleagues described the first animal model of MBs in 1975 that involves feeding mice griseofulvin. Since then, mouse models have been instrumental in helping understand the pathogenesis of MBs. Given the tremendous contributions made by Denk to the field, we propose renaming MBs as Mallory-Denk bodies (MDBs). The major constituents of MDBs include keratins 8 and 18 (K8/18), ubiquitin, and p62. The relevant proteins and cellular processes that contribute to MDB formation and accumulation include the type of chronic stress, the extent of stress-induced protein misfolding and consequent proteasome overload, a K8-greater-than-K18 ratio, transamidation of K8 and other proteins, presence of p62 and autophagy. Although it remains unclear whether MDBs serve a bystander, protective or injury promoting function, they do serve an important role as histological and potential progression markers in several liver diseases.
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Affiliation(s)
- Kurt Zatloukal
- Institute of Pathology, Medical University of Graz, Auenbruggerplatz 25, A-8036 Graz, Austria
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Strnad P, Harada M, Siegel M, Terkeltaub RA, Graham RM, Khosla C, Omary MB. Transglutaminase 2 regulates mallory body inclusion formation and injury-associated liver enlargement. Gastroenterology 2007; 132:1515-26. [PMID: 17408647 DOI: 10.1053/j.gastro.2007.02.020] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2006] [Accepted: 12/14/2006] [Indexed: 12/23/2022]
Abstract
BACKGROUND & AIMS Mallory body (MB) inclusions are a characteristic feature of several liver disorders and share similarities with cytoplasmic inclusions observed in neural diseases and myopathies. MBs consist primarily of keratins 8 and 18 (K8/K18), require a K8-greater-than-K18 ratio for their formation, and contain glutamine-lysine cross-links generated by transglutaminase (TG). We hypothesized that protein transamidation is essential for MB formation. METHODS Because TG2 is the most abundant hepatocyte TG, we tested our hypothesis using TG2(-/-) and their wild-type counterpart mice fed 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC), an established MB inducer. Keratin cross-linking was further examined using recombinant proteins or transgenic mice that overexpress K8 or K18. RESULTS TG2(-/-) livers have markedly reduced TG2 activity as compared with TG2(+/+) livers. The DDC-fed TG2(-/-) mice have dramatic decreases in MB formation and liver hypertrophy response as contrasted with DDC-fed TG2(+/+) mice. Despite similar hepatocellular damage, TG2(-/-) mice had more gallstones, jaundice, and ductal proliferation than wild-type mice. Inhibition of MB formation in TG2(-/-) mice was associated with marked attenuation of ubiquitination and K8-containing protein cross-linking. MB formation and resolution paralleled the generation then disappearance of cross-linked K8, respectively. K8 is a preferential TG2 substrate when compared to K18, as examined in vitro or in DDC-fed transgenic mice that overexpress K8 or K18. CONCLUSIONS We demonstrate an essential role for TG2 in determining injury-mediated liver enlargement and the necessity of K8 and TG2 for generating cross-linked keratins and MBs. The role of TG in inclusion formation might extend to nonkeratin intermediate filament protein-related diseases.
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Affiliation(s)
- Pavel Strnad
- Department of Medicine, Palo Alto VA Medical Center, Palo Alto, California, USA
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Oriolo AS, Wald FA, Ramsauer VP, Salas PJI. Intermediate filaments: a role in epithelial polarity. Exp Cell Res 2007; 313:2255-64. [PMID: 17425955 PMCID: PMC1986643 DOI: 10.1016/j.yexcr.2007.02.030] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2007] [Revised: 02/19/2007] [Accepted: 02/22/2007] [Indexed: 11/24/2022]
Abstract
Intermediate filaments have long been considered mechanical components of the cell that provide resistance to deformation stress. Practical experimental problems, including insolubility, lack of good pharmacological antagonists, and the paucity of powerful genetic models have handicapped the research of other functions. In single-layered epithelial cells, keratin intermediate filaments are cortical, either apically polarized or apico-lateral. This review analyzes phenotypes of genetic manipulations of simple epithelial cell keratins in mice and Caenorhabditis elegans that strongly suggest a role of keratins in apico-basal polarization and membrane traffic. Published evidence that intermediate filaments can act as scaffolds for proteins involved in membrane traffic and signaling is also discussed. Such a scaffolding function would generate a highly polarized compartment within the cytoplasm of simple epithelial cells. While in most cases mechanistic explanations for the keratin-null or overexpression phenotypes are still missing, it is hoped that investigators will be encouraged to study these as yet poorly understood functions of intermediate filaments.
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Affiliation(s)
- Andrea S Oriolo
- Department of Cell Biology and Anatomy, University of Miami, Miller School of Medicine, 1600 NW 10th Ave.-RMSB, Miami, FL 33136, USA
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