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Wijerathne SVT, Pandit R, Ipinmoroti AO, Crenshaw BJ, Matthews QL. Feline coronavirus influences the biogenesis and composition of extracellular vesicles derived from CRFK cells. Front Vet Sci 2024; 11:1388438. [PMID: 39091390 PMCID: PMC11292801 DOI: 10.3389/fvets.2024.1388438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Accepted: 07/02/2024] [Indexed: 08/04/2024] Open
Abstract
Introduction Coronavirus (CoV) has become a public health crisis that causes numerous illnesses in humans and certain animals. Studies have identified the small, lipid-bound structures called extracellular vesicles (EVs) as the mechanism through which viruses can enter host cells, spread, and evade the host's immune defenses. EVs are able to package and carry numerous viral compounds, including proteins, genetic substances, lipids, and receptor proteins. We proposed that the coronavirus could alter EV production and content, as well as influence EV biogenesis and composition in host cells. Methods In the current research, Crandell-Rees feline kidney (CRFK) cells were infected with feline coronavirus (FCoV) in an exosome-free media at a multiplicity of infection (MOI) of 2,500 infectious units (IFU) at 48 h and 72 h time points. Cell viability was analyzed and found to be significantly decreased by 9% (48 h) and 15% (72 h) due to FCoV infection. EVs were isolated by ultracentrifugation, and the surface morphology of isolated EVs was analyzed via Scanning Electron Microscope (SEM). Results NanoSight particle tracking analysis (NTA) confirmed that the mean particle sizes of control EVs were 131.9 nm and 126.6 nm, while FCoV infected-derived EVs were 143.4 nm and 120.9 nm at 48 and 72 h, respectively. Total DNA, RNA, and protein levels were determined in isolated EVs at both incubation time points; however, total protein was significantly increased at 48 h. Expression of specific protein markers such as TMPRSS2, ACE2, Alix, TSG101, CDs (29, 47, 63), TLRs (3, 6, 7), TNF-α, and others were altered in infection-derived EVs when compared to control-derived EVs after FCoV infection. Discussion Our findings suggested that FCoV infection could alter the EV production and composition in host cells, which affects the infection progression and disease evolution. One purpose of studying EVs in various animal coronaviruses that are in close contact with humans is to provide significant information about disease development, transmission, and adaptation. Hence, this study suggests that EVs could provide diagnostic and therapeutic applications in animal CoVs, and such understanding could provide information to prevent future coronavirus outbreaks.
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Affiliation(s)
| | - Rachana Pandit
- Microbiology Program, Alabama State University, Montgomery, AL, United States
| | | | | | - Qiana L. Matthews
- Microbiology Program, Alabama State University, Montgomery, AL, United States
- Department of Biological Sciences, College of Science, Technology, Engineering, and Mathematics, Alabama State University, Montgomery, AL, United States
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Shahi S, Kang T, Fonseka P. Extracellular Vesicles in Pathophysiology: A Prudent Target That Requires Careful Consideration. Cells 2024; 13:754. [PMID: 38727289 PMCID: PMC11083420 DOI: 10.3390/cells13090754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 04/22/2024] [Accepted: 04/24/2024] [Indexed: 05/13/2024] Open
Abstract
Extracellular vesicles (EVs) are membrane-bound particles released by cells to perform multitudes of biological functions. Owing to their significant implications in diseases, the pathophysiological role of EVs continues to be extensively studied, leading research to neglect the need to explore their role in normal physiology. Despite this, many identified physiological functions of EVs, including, but not limited to, tissue repair, early development and aging, are attributed to their modulatory role in various signaling pathways via intercellular communication. EVs are widely perceived as a potential therapeutic strategy for better prognosis, primarily through utilization as a mode of delivery vehicle. Moreover, disease-associated EVs serve as candidates for the targeted inhibition by pharmacological or genetic means. However, these attempts are often accompanied by major challenges, such as off-target effects, which may result in adverse phenotypes. This renders the clinical efficacy of EVs elusive, indicating that further understanding of the specific role of EVs in physiology may enhance their utility. This review highlights the essential role of EVs in maintaining cellular homeostasis under different physiological settings, and also discusses the various aspects that may potentially hinder the robust utility of EV-based therapeutics.
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Affiliation(s)
| | | | - Pamali Fonseka
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia; (S.S.); (T.K.)
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The Multifaceted Roles of the Tumor Susceptibility Gene 101 (TSG101) in Normal Development and Disease. Cancers (Basel) 2020; 12:cancers12020450. [PMID: 32075127 PMCID: PMC7073217 DOI: 10.3390/cancers12020450] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 02/07/2020] [Accepted: 02/10/2020] [Indexed: 12/13/2022] Open
Abstract
The multidomain protein encoded by the Tumor Susceptibility Gene 101 (TSG101) is ubiquitously expressed and is suggested to function in diverse intracellular processes. In this review, we provide a succinct overview of the main structural features of the protein and their suggested roles in molecular and cellular functions. We then summarize, in more detail, key findings from studies using genetically engineered animal models that demonstrate essential functions of TSG101 in cell proliferation and survival, normal tissue homeostasis, and tumorigenesis. Despite studies on cell lines that provide insight into the molecular underpinnings by which TSG101 might function as a negative growth regulator, a biologically significant role of TSG101 as a tumor suppressor has yet to be confirmed using genuine in vivo cancer models. More recent observations from several cancer research teams suggest that TSG101 might function as an oncoprotein. A potential role of post-translational mechanisms that control the expression of the TSG101 protein in cancer is being discussed. In the final section of the review, we summarize critical issues that need to be addressed to gain a better understanding of biologically significant roles of TSG101 in cancer.
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Deng S, Essandoh K, Wang X, Li Y, Huang W, Chen J, Peng J, Jiang DS, Mu X, Wang C, Peng T, Guan JL, Wang Y, Jegga A, Huang K, Fan GC. Tsg101 positively regulates P62-Keap1-Nrf2 pathway to protect hearts against oxidative damage. Redox Biol 2020; 32:101453. [PMID: 32057709 PMCID: PMC7264471 DOI: 10.1016/j.redox.2020.101453] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 02/01/2020] [Accepted: 02/05/2020] [Indexed: 12/17/2022] Open
Abstract
Currently, most antioxidants do not show any favorable clinical outcomes in reducing myocardial ischemia-reperfusion (I/R) injury, suggesting an urgent need for exploring a new regulator of redox homeostasis in I/R hearts. Here, using heart-specific transgenic (TG) and knockdown (KD) mouse models, tumor susceptibility gene 101 (Tsg101) is defined as a novel cardiac-protector against I/R-triggered oxidative stress. RNA sequencing and bioinformatics data surprisingly reveal that most upregulated genes in Tsg101-TG hearts are transcribed by Nrf2. Accordingly, pharmacological inhibition of Nrf2 offsets Tsg101-elicited cardio-protection. Mechanistically, Tsg101 interacts with SQSTM1/p62 through its PRR domain, and promotes p62 aggregation, leading to recruitment of Keap1 for degradation by autophagosomes and release of Nrf2 to the nucleus. Furthermore, knockout of p62 abrogates Tsg101-induced cardio-protective effects during I/R. Hence, our findings uncover a previously unrecognized role of Tsg101 in the regulation of p62/Keap1/Nrf2 signaling cascades and provide a new strategy for the treatment of ischemic heart disease.
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Affiliation(s)
- Shan Deng
- Department of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China; Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA; Clinical Center for Human Genomic Research, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Kobina Essandoh
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA
| | - Xiaohong Wang
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA
| | - Yutian Li
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA
| | - Wei Huang
- Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA
| | - Jing Chen
- Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA
| | - Jiangtong Peng
- Department of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China; Clinical Center for Human Genomic Research, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Ding-Sheng Jiang
- Division of Cardiothoracic and Vascular Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Xingjiang Mu
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA
| | - Chenran Wang
- Department of Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA
| | - Tianqing Peng
- Critical Illness Research, Lawson Health Research Institute, Ontario, Canada
| | - Jun-Lin Guan
- Department of Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA
| | - Yigang Wang
- Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA
| | - Anil Jegga
- Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA
| | - Kai Huang
- Department of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China; Clinical Center for Human Genomic Research, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Guo-Chang Fan
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA.
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Wang H, Chen F, Mi T, Liu Q, Yu Z, Zhen Y. Responses of Marine Diatom Skeletonema marinoi to Nutrient Deficiency: Programmed Cell Death. Appl Environ Microbiol 2020; 86:e02460-19. [PMID: 31757826 PMCID: PMC6974647 DOI: 10.1128/aem.02460-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 11/15/2019] [Indexed: 11/20/2022] Open
Abstract
Diatoms are important phytoplankton and contribute greatly to the primary productivity of marine ecosystems. Despite the ecological significance of diatoms and the importance of programmed cell death (PCD) in the fluctuation of diatom populations, little is known about the molecular mechanisms of PCD triggered by different nutrient stresses. Here we describe the physiological, morphological, biochemical, and molecular changes in response to low levels of nutrients in the ubiquitous diatom Skeletonema marinoi The levels of gene expression involved in oxidation resistance and PCD strongly increased upon nitrogen (N) or phosphorus (P) starvation. The enzymatic activity of caspase 3-like protein also increased. Differences in mRNA levels and protein activities were observed between the low-N and low-P treatments, suggesting that PCD could have a differential response to different nutrient stresses. When cultures were replete with N or P, the growth inhibition stopped. Meanwhile, the enzymatic activity of caspase 3-like protein and the number of cells with damaged membranes decreased. These results suggest that PCD is an important cell fate decision mechanism in the marine diatom S. marinoi Our results provide important insight into how diatoms adjust phenotypic and genotypic features of their cell-regulated death programs when stressed by nutrient limitations. Overall, this study could allow us to better understand the molecular mechanism behind the formation and termination of diatom blooms in the marine environment.IMPORTANCE Our study showed how the ubiquitous diatom S. marinoi responded to different nutrient limitations with PCD in terms of physiological, morphological, biochemical, and molecular characteristics. Some PCD-related genes (PDCD4, GOX, and HSP90) induced by N deficiency were relatively upregulated compared to those induced by P deficiency. In contrast, the expression of the TSG101 gene in S. marinoi showed a clear and constant increase during P limitation compared to N limitation. These findings suggest that PCD is a complex mechanism involving several different proteins. The systematic mRNA level investigations provide new insight into understanding the oxidative stress- and cell death-related functional genes of diatoms involved in the response to nutrient fluctuations (N or P stress) in the marine environment.
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Affiliation(s)
- Hualong Wang
- College of Marine Life Science, Ocean University of China, Qingdao, China
- Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, Maryland, USA
| | - Feng Chen
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, Maryland, USA
| | - Tiezhu Mi
- Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Key Laboratory of Marine Environment and Ecology, Ministry of Education, Qingdao, China
- College of Environmental Science and Engineering, Ocean University of China, Qingdao, China
| | - Qian Liu
- College of Marine Life Science, Ocean University of China, Qingdao, China
| | - Zhigang Yu
- Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Key Laboratory of Marine Chemical Theory and Technology, Ministry of Education, Qingdao, China
| | - Yu Zhen
- Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Key Laboratory of Marine Environment and Ecology, Ministry of Education, Qingdao, China
- College of Environmental Science and Engineering, Ocean University of China, Qingdao, China
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Minaidou A, Nicolaou P, Christodoulou K. Deregulation of LRSAM1 expression impairs the levels of TSG101, UBE2N, VPS28, MDM2 and EGFR. PLoS One 2019; 14:e0211814. [PMID: 30726272 PMCID: PMC6364939 DOI: 10.1371/journal.pone.0211814] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 01/22/2019] [Indexed: 11/20/2022] Open
Abstract
CMT is the most common hereditary neuromuscular disorder of the peripheral nervous system with a prevalence of 1/2500 individuals and it is caused by mutations in more than 80 genes. LRSAM1, a RING finger ubiquitin ligase also known as TSG101-associated ligase (TAL), has been associated with Charcot-Marie-Tooth disease type 2P (CMT2P) and to date eight causative mutations have been identified. Little is currently known on the pathogenetic mechanisms that lead to the disease. We investigated the effect of LRSAM1 deregulation on possible LRSAM1 interacting molecules in cell based models. Possible LRSAM1 interacting molecules were identified using protein-protein interaction databases and literature data. Expression analysis of these molecules was performed in both CMT2P patient and control lymphoblastoid cell lines as well as in LRSAM1 and TSG101 downregulated SH-SY5Y cells.TSG101, UBE2N, VPS28, EGFR and MDM2 levels were significantly decreased in the CMT2P patient lymphoblastoid cell line as well as in LRSAM1 downregulated cells. TSG101 downregulation had a significant effect only on the expression of VPS28 and MDM2 and it did not affect the levels of LRSAM1. This study confirms that LRSAM1 is a regulator of TSG101 expression. Furthermore, deregulation of LRSAM1 significantly affects the levels of UBE2N, VPS28, EGFR and MDM2.
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Affiliation(s)
- Anna Minaidou
- Neurogenetics Department, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
- Cyprus School of Molecular Medicine, Nicosia, Cyprus
| | - Paschalis Nicolaou
- Neurogenetics Department, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
- Cyprus School of Molecular Medicine, Nicosia, Cyprus
| | - Kyproula Christodoulou
- Neurogenetics Department, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
- Cyprus School of Molecular Medicine, Nicosia, Cyprus
- * E-mail:
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Minaidou A, Nicolaou P, Christodoulou K. LRSAM1 Depletion Affects Neuroblastoma SH-SY5Y Cell Growth and Morphology: The LRSAM1 c.2047-1G>A Loss-of-Function Variant Fails to Rescue The Phenotype. CELL JOURNAL 2018; 20:340-347. [PMID: 29845787 PMCID: PMC6004992 DOI: 10.22074/cellj.2018.5352] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 10/25/2017] [Indexed: 12/13/2022]
Abstract
Objective Deleterious variants in LRSAM1, a RING finger ubiquitin ligase which is also known as TSG101-associated ligase
(TAL), have recently been associated with Charcot-Marie-Tooth disease type 2P (CMT2P). The mechanism by which mutant
LRSAM1 contributes to the development of neuropathy is currently unclear. The aim of this study was to induce LRSAM1
deficiency in a neuronal cell model, observe its effect on cell growth and morphology and attempt to rescue the phenotype with
ancestral and mutant LRSAM1 transfections.
Materials and Methods In this experimental study, we investigated the effect of LRSAM1 downregulation on
neuroblastoma SH-SY5Y cells by siRNA technology where cells were transfected with siRNA against LRSAM1.
The effects on the expression levels of TSG101, the only currently known LRSAM1 interacting molecule, were also
examined. An equal dosage of ancestral or mutant LRSAM1 construct was transfected in LRSAM1-downregulated cells
to investigate its effect on the phenotype of the cells and whether cell proliferation and morphology could be rescued.
Results A significant reduction in TSG101 levels was observed with the downregulation of LRSAM1. In addition,
LRSAM1 knockdown significantly decreased the growth rate of SH-SY5Y cells which is caused by a decrease in cell
proliferation. An effect on cell morphology was also observed. Furthermore, we overexpressed the ancestral and the
c.2047-1G>A mutant LRSAM1 in knocked down cells. Ancestral LRSAM1 recovered cell proliferation and partly the
morphology, however, the c.2047-1G>A mutant did not recover cell proliferation and further aggravated the observed
changes in cell morphology.
Conclusion Our findings suggest that depletion of LRSAM1 affects neuroblastoma cells growth and morphology and
that overexpression of the c.2047-1G>A mutant form, unlike the ancestral LRSAM1, fails to rescue the phenotype.
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Affiliation(s)
- Anna Minaidou
- Department of Neurogenetics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus.,Cyprus School of Molecular Medicine, Nicosia, Cyprus
| | - Paschalis Nicolaou
- Department of Neurogenetics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus.,Cyprus School of Molecular Medicine, Nicosia, Cyprus
| | - Kyproula Christodoulou
- Department of Neurogenetics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus.,Cyprus School of Molecular Medicine, Nicosia, Cyprus.Electronic Address:
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Park MH, Lee HJ, Lee HL, Son DJ, Ju JH, Hyun BK, Jung SH, Song JK, Lee DH, Hwang CJ, Han SB, Kim S, Hong JT. Parkin Knockout Inhibits Neuronal Development via Regulation of Proteasomal Degradation of p21. Am J Cancer Res 2017; 7:2033-2045. [PMID: 28656059 PMCID: PMC5485421 DOI: 10.7150/thno.19824] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2017] [Accepted: 03/31/2017] [Indexed: 11/05/2022] Open
Abstract
PARK2 encodes for the E3 ubiquitin ligase parkin and is implicated in the development of Parkinson's disease (PD). Although the neuroprotective role of parkin is well known, the mechanism of PARK2's function in neural stem differentiation has not yet been thoroughly studied. Co-expressions network analysis showed that synaptosomal-associated protein 25 (SNAP-25) and brain-derived neurotrophic factor (BDNF) were positively correlated with parkin, but negatively correlated with p21 in human patient brain. We investigated a link between the ubiquitin E3 ligase parkin and proteasomal degradation of p21 for the control of neural stem cell differentiation. We found that the neurogenesis was lowered in PARK2 knockout (KO) mice compared with non-tg mice. Expression of the marker protein for neural cell differentiation such as class III beta tubulin (TUBBIII), glial fibrillary acidic protein (GFAP) and neurofilament, as well as SNAP25 and BDNF, was down regulated in PARK2 KO mice. Associated with the loss of differentiation function, p21 protein was highly accumulated in the neural stem cells of PARK2 KO mice. We discovered that p21 directly binds with parkin and is ubiquitinated by parkin which resulted in the loss of cell differentiation ability. Introduction of p21 shRNA in PARK2 KO mice significantly rescued the differentiation efficacy as well as SNAP25 and BDNF expression. c-Jun N-terminal kinase (JNK) pathway is implicated in neurogenesis and p21 degradation. We also defined the decreased p21 ubiquitination and differentiation ability were reversed after treatment with JNK inhibitor, SP600125 in PARK2 KO mice derived neural stem cells. Thus, the present study indicated that parkin knockout inhibits neural stem cell differentiation by JNK-dependent proteasomal degradation of p21.
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Gasulla F, Barreno E, Parages ML, Cámara J, Jiménez C, Dörmann P, Bartels D. The Role of Phospholipase D and MAPK Signaling Cascades in the Adaption of Lichen Microalgae to Desiccation: Changes in Membrane Lipids and Phosphoproteome. PLANT & CELL PHYSIOLOGY 2016; 57:1908-20. [PMID: 27335354 DOI: 10.1093/pcp/pcw111] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Accepted: 06/06/2016] [Indexed: 05/27/2023]
Abstract
Classically, lichen phycobionts are described as poikilohydric organisms able to undergo desiccation due to the constitutive presence of molecular protection mechanisms. However, little is known about the induction of cellular responses in lichen phycobionts during drying. The analysis of the lipid composition of the desiccated lichen microalga Asterochloris erici revealed the unusual accumulation of highly polar lipids (oligogalactolipids and phosphatidylinositol), which prevents the fusion of membranes during stress, but also the active degradation of cone-shaped lipids (monogalactosyldiacylglycerol and phosphatidylethanolamine) to stabilize membranes in desiccated cells. The level of phosphatidic acid increased 7-fold during desiccation, implicating a possible role for phospholipase D (PLD) in the response to osmotic stress. Inhibition of PLD with 1-butanol markedly impaired the recovery of photosynthesis activity in A. erici upon desiccation and salt stress (2 M NaCl). These two hyperosmotic stresses caused the phosphorylation of c-Jun N-terminal kinase (JNK) and p38-like mitogen-activated protein kinase (MAPK) and the dephosphorylation of extracellular signal-regulated kinase (ERK). The incubation with 1-butanol reduced the phosphorylation of JNK-like proteins and increased the dephosphorylation of ERK-like proteins, which indicates an upstream control of MAPK cascades by PLD. The phosphoproteome showed that desiccation caused the phosphorylation of several proteins in A. erici, most of them involved in protein turnover. The results demonstrate that lichen phycobionts possess both constitutive and inducible protective mechanisms to acquire desiccation tolerance. Among others, these responses are controlled by the PLD pathway through the activation of MAPK cascades.
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Affiliation(s)
- Francisco Gasulla
- Departamento de Botánica & ICBIBE, Fac. C. Biológicas, Universitat de València, 46100 Burjassot, Spain Institute of Molecular Physiology and Biotechnology of Plants (IMBIO), University of Bonn, D-53115 Bonn, Germany
| | - Eva Barreno
- Departamento de Botánica & ICBIBE, Fac. C. Biológicas, Universitat de València, 46100 Burjassot, Spain
| | - María L Parages
- Departamento de Ecología, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain
| | - Joaquín Cámara
- Departamento de Ecología, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain
| | - Carlos Jiménez
- Departamento de Ecología, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain
| | - Peter Dörmann
- Institute of Molecular Physiology and Biotechnology of Plants (IMBIO), University of Bonn, D-53115 Bonn, Germany
| | - Dorothea Bartels
- Institute of Molecular Physiology and Biotechnology of Plants (IMBIO), University of Bonn, D-53115 Bonn, Germany
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Insights into possible cell-death markers in the diatom Skeletonema marinoi in response to senescence and silica starvation. Mar Genomics 2015; 24 Pt 1:81-8. [DOI: 10.1016/j.margen.2015.06.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 05/18/2015] [Accepted: 06/15/2015] [Indexed: 10/23/2022]
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11
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Yates SC, Zafar A, Rabai EM, Foxall JB, Nagy S, Morrison KE, Clarke C, Esiri MM, Christie S, Smith AD, Nagy Z. The effects of two polymorphisms on p21cip1 function and their association with Alzheimer's disease in a population of European descent. PLoS One 2015; 10:e0114050. [PMID: 25625488 PMCID: PMC4308198 DOI: 10.1371/journal.pone.0114050] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 10/09/2014] [Indexed: 01/23/2023] Open
Abstract
With the exception of ApoE4, genome-wide association studies have failed to identify strong genetic risk factors for late-onset Alzheimer’s disease, despite strong evidence of heritability, suggesting that many low penetrance genes may be involved. Additionally, the nature of the identified genetic risk factors and their relation to disease pathology is also largely obscure. Previous studies have found that a cancer-associated variant of the cell cycle inhibitor gene p21cip1 is associated with increased risk of Alzheimer’s disease. The aim of this study was to confirm this association and to elucidate the effects of the variant on protein function and Alzheimer-type pathology. We examined the association of the p21cip1 variant with Alzheimer’s disease and Parkinson’s disease with dementia. The genotyping studies were performed on 719 participants of the Oxford Project to Investigate Memory and Ageing, 225 participants of a Parkinson’s disease DNA bank, and 477 participants of the Human Random Control collection available from the European Collection of Cell Cultures. The post mortem studies were carried out on 190 participants. In the in-vitro study, human embryonic kidney cells were transfected with either the common or rare p21cip1 variant; and cytometry was used to assess cell cycle kinetics, p21cip1 protein expression and sub-cellular localisation. The variant was associated with an increased risk of Alzheimer’s disease, and Parkinson’s disease with dementia, relative to age matched controls. Furthermore, the variant was associated with an earlier age of onset of Alzheimer’s disease, and a more severe phenotype, with a primary influence on the accumulation of tangle pathology. In the in-vitro study, we found that the SNPs reduced the cell cycle inhibitory and anti-apoptotic activity of p21cip1. The results suggest that the cancer-associated variant of p21cip1 may contribute to the loss of cell cycle control in neurons that may lead to Alzheimer-type neurodegeneration.
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Affiliation(s)
- Sharon C. Yates
- Neuropharmacology and Neurobiology, College of Medical and Dental Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, B15 2TT, United Kingdom
| | - Amen Zafar
- Neuropharmacology and Neurobiology, College of Medical and Dental Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, B15 2TT, United Kingdom
| | - Erzsebet M. Rabai
- Neuropharmacology and Neurobiology, College of Medical and Dental Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, B15 2TT, United Kingdom
| | - James B. Foxall
- Neuropharmacology and Neurobiology, College of Medical and Dental Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, B15 2TT, United Kingdom
| | - Sheila Nagy
- Neuropharmacology and Neurobiology, College of Medical and Dental Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, B15 2TT, United Kingdom
| | - Karen E. Morrison
- Neuropharmacology and Neurobiology, College of Medical and Dental Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, B15 2TT, United Kingdom
| | - Carl Clarke
- Neuropharmacology and Neurobiology, College of Medical and Dental Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, B15 2TT, United Kingdom
| | - Margaret M. Esiri
- Department of Neuropathology, University of Oxford, Level 1, John Radcliffe Hospital, Oxford, OX3 9DU, United Kingdom
| | - Sharon Christie
- OPTIMA, University of Oxford, Level 4, John Radcliffe Hospital, Oxford, OX3 9DU, United Kingdom
| | - A. David Smith
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, United Kingdom
| | - Zsuzsanna Nagy
- Neuropharmacology and Neurobiology, College of Medical and Dental Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, B15 2TT, United Kingdom
- * E-mail:
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12
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Lin YS, Chen YJ, Cohen SN, Cheng TH. Identification of TSG101 functional domains and p21 loci required for TSG101-mediated p21 gene regulation. PLoS One 2013; 8:e79674. [PMID: 24244542 PMCID: PMC3823576 DOI: 10.1371/journal.pone.0079674] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Accepted: 10/02/2013] [Indexed: 11/25/2022] Open
Abstract
TSG101 (tumor susceptibility gene 101) is a multi-domain protein known to act in the cell nucleus, cytoplasm, and periplasmic membrane. Remarkably, TSG101, whose location within cells varies with the stage of the cell cycle, affects biological events as diverse as cell growth and proliferation, gene expression, cytokinesis, and endosomal trafficking. The functions of TSG101 additionally are recruited for viral and microvesicle budding and for intracellular survival of invading bacteria. Here we report that the TSG101 protein also interacts with and down-regulates the promoter of the p21CIP1/WAF1tumor suppressor gene, and identify a p21 locus and TSG101 domains that mediate this interaction. TSG101 deficiency in Saos-2 human osteosarcoma cells was accompanied by an increased abundance of p21 mRNA and protein and the retardation of cell proliferation. A cis-acting element in the p21 promoter that interacts with TSG101 and is required for promoter repression was located using chromatin immunoprecipitation (ChIP) analysis and p21-driven luciferase reporter gene expression, respectively. Additional analysis of TSG101 deletion mutants lacking specific domains established the role of the central TSG101 domains in binding to the p21 promoter and demonstrated the additional essentiality of the TSG101 C-terminal steadiness box (SB) in the repression of p21 promoter activity. Neither binding of TSG101 to the p21 promoter nor repression of this promoter required the TSG101 N-terminal UEV domain, which mediates the ubiquitin-recognition functions of TSG101 and its actions as a member of ESCRT endocytic trafficking complexes, indicating that regulation of the p21 promoter by TSG101 is independent of its role in such trafficking.
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Affiliation(s)
- Yu-Shiuan Lin
- Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan
| | - Yin-Ju Chen
- Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan
| | - Stanley N. Cohen
- Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Tzu-Hao Cheng
- Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan
- * E-mail:
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13
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An CH, Kim YR, Kim HS, Kim SS, Yoo NJ, Lee SH. Frameshift mutations of vacuolar protein sorting genes in gastric and colorectal cancers with microsatellite instability. Hum Pathol 2012; 43:40-7. [DOI: 10.1016/j.humpath.2010.03.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2010] [Revised: 03/04/2010] [Accepted: 03/17/2010] [Indexed: 11/29/2022]
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Abstract
The idea that the gap junction family of proteins, connexins, are tumour suppressors has been widely supported through numerous cancer models. However, the paradigm that connexins and enhanced gap junctional intercellular communication is of universal benefit by restricting tumour growth has been challenged by more recent evidence that suggests a role for connexins in facilitating tumour progression and metastasis. Therefore, connexins might be better classified as conditional tumour suppressors that modulate cell proliferation, as well as adhesion and migration.
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Affiliation(s)
- Christian C Naus
- Life Sciences Institute, Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia V6T-1Z3, Canada.
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15
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Abstract
Components of the ESCRT (endosomal sorting complex required for transport) machinery mediate endosomal sorting of ubiquitinated membrane proteins. They are key regulators of biological processes important for cell growth and survival, such as growth-factor-mediated signalling and cytokinesis. In addition, enveloped viruses, such as HIV-1, hijack and utilize the ESCRTs for budding during virus release and infection. Obviously, the ESCRT-facilitated pathways require tight regulation, which is partly mediated by a group of interacting proteins, for which our knowledge is growing. In this review we discuss the different ESCRT-modulating proteins and how they influence ESCRT-dependent processes, for example, by acting as positive or negative regulators or by providing temporal and spatial control. A number of the interactors influence the classical ESCRT-mediated process of endosomal cargo sorting, for example, by modulating the interaction between ubiquitinated cargo and the ESCRTs. Certain accessory proteins have been implicated in regulating the activity or steady-state expression levels of the ESCRT components, whereas other interactors control the cellular localization of the ESCRTs, for example, by inducing shuttling between cytosol and nucleus or endosomes. In conclusion, the discovery of novel interactors has and will extend our knowledge of the biological roles of ESCRTs.
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16
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Auth T, Schlüter S, Urschel S, Kussmann P, Sonntag S, Höher T, Kreuzberg MM, Dobrowolski R, Willecke K. The TSG101 protein binds to connexins and is involved in connexin degradation. Exp Cell Res 2009; 315:1053-62. [PMID: 19210987 DOI: 10.1016/j.yexcr.2008.12.025] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 12/08/2008] [Accepted: 12/27/2008] [Indexed: 11/16/2022]
Abstract
Gap junctions mediate electrical and metabolic communication between cells in almost all tissues and are proposed to play important roles in cellular growth control, differentiation and embryonic development. Gap junctional communication and channel assembly were suggested to be regulated by interaction of connexins with different proteins including kinases and phosphatases. Here, we identified the tumor susceptibility gene 101 (TSG101) protein to bind to the carboxyterminal tail of connexin45 in a yeast two-hybrid protein interaction screen. Glutathione S-transferase pull down experiments and immunoprecipitation revealed that not only connexin45 but also connexin30.2, -36, and -43 carboxyterminal regions were associated with TSG101 protein in pull down analyses and that connexin31, -43 and -45 co-precipitate with endogenous TSG101 protein in lysates from HM1 embryonic stem cells. TSG101 has been shown to be involved in cell cycle control, transcriptional regulation and turnover of endocytosed proteins. Thus, we decided to study the functional role of this interaction. SiRNA mediated knock down of TSG101 in HM1 embryonic stem cells led to increased levels of connexin43 and -45, prolonged half life of these connexins and increased transfer of microinjected Lucifer yellow. Our results suggest that TSG101 is involved in the degradation of connexins via interaction with connexin proteins.
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Affiliation(s)
- Tanja Auth
- Institute of Genetics, Division of Molecular Genetics, University of Bonn, 53117 Bonn, Germany.
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17
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Abstract
HIV infection of macrophages is a critically important component of viral pathogenesis and progression to AIDS. Although the virus follows the same life cycle in macrophages and T lymphocytes, several aspects of the virus-host relationship are unique to macrophage infection. Examples of these are the long-term persistence of productive infection, sustained by the absence of cell death, and the ability of progeny virus to bud into and accumulate in endocytic compartments designated multivesicular bodies (MVBs). Recently, the hypothesis that viral exploitation of the macrophage endocytic machinery is responsible for perpetuating the chronic state of infection unique to this cell type has been challenged in several independent studies employing a variety of experimental strategies. This review examines the evidence supporting and refuting the canonical hypothesis and highlights recently identified cellular factors that may contribute to the unique aspects of the HIV-macrophage interaction.
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Affiliation(s)
- Carol A Carter
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York 11794, USA.
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18
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Abstract
First identified as cell cycle inhibitors mediating the growth inhibitory cues of upstream signaling pathways, the cyclin-CDK inhibitors of the Cip/Kip family p21Cip1, p27Kip1, and p57Kip2 have emerged as multifaceted proteins with functions beyond cell cycle regulation. In addition to regulating the cell cycle, Cip/Kip proteins play important roles in apoptosis, transcriptional regulation, cell fate determination, cell migration and cytoskeletal dynamics. A complex phosphorylation network modulates Cip/Kip protein functions by altering their subcellular localization, protein-protein interactions, and stability. These functions are essential for the maintenance of normal cell and tissue homeostasis, in processes ranging from embryonic development to tumor suppression.
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McDonald B, Martin-Serrano J. Regulation of Tsg101 expression by the steadiness box: a role of Tsg101-associated ligase. Mol Biol Cell 2007; 19:754-63. [PMID: 18077552 DOI: 10.1091/mbc.e07-09-0957] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
As part of the endosomal sorting complex required for transport (ESCRT) machinery, Tsg101 is essential for endosomal sorting, membrane receptor degradation and the final stages of cytokinesis. Depletion or overproduction of the protein can cause disruption of these vital processes and results in severe consequences for the cell. Tsg101 expression is thus controlled posttranslationally within a narrow range and this autoregulation has been mapped to the C-terminus of the protein. Here we elucidate further the mechanisms of this regulation and describe a novel function of Tsg101-associated ligase (Tal) in mediating this control. We show that Tal polyubiquitinates lysine residues in the C-terminus of uncomplexed Tsg101, resulting in proteasomal degradation. However, accessibility to these lysines is prevented by the presence of the other ESCRT-I proteins. We show that VPS28 is a limiting factor, and consequently Tsg101 expression surplus to ESCRT-I function is vulnerable to degradation. The role of Tal in the regulation of Tsg101 steady-state control is highlighted when Tsg101 is overexpressed; however, our data also suggest that additional ligases regulate Tsg101 expression under normal conditions. Lastly, we demonstrate that while the C-terminal lysines are targets for polyubiquitination, they are not required for any additional function necessary for ESCRT activity.
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Affiliation(s)
- Bethan McDonald
- Department of Infectious Diseases, King's College London School of Medicine, London SE19RT, United Kingdom
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20
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Young TW, Rosen DG, Mei FC, Li N, Liu J, Wang XF, Cheng X. Up-regulation of tumor susceptibility gene 101 conveys poor prognosis through suppression of p21 expression in ovarian cancer. Clin Cancer Res 2007; 13:3848-54. [PMID: 17606716 DOI: 10.1158/1078-0432.ccr-07-0337] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE The function of tumor susceptibility gene 101 (TSG101) in ovarian carcinogenesis is largely unexplored. The aim of this study is to investigate the role of TSG101 in human ovarian cancer development, to examine the expression levels of TSG101 in ovarian carcinomas, and to correlate the results with clinicopathologic variables and survival. EXPERIMENTAL DESIGN Human ovarian cancer tissue arrays that contain duplicates of 422 cases of primary ovarian carcinoma were used to probe the expression levels of TSG101 and p21 in epithelial ovarian cancer. In vitro studies in ovarian cancer cells using TSG101-specific small interfering RNA (siRNA) were done to further elucidate the mechanism of TSG101-mediated p21 regulation. RESULTS We show that TSG101 is increasingly overexpressed in borderline tumors and low-grade and high-grade carcinomas. Patients with low expression of TSG101 survive longer than those with high expression. Suppressing TSG101 by siRNA in ovarian cancer cells led to growth inhibition, cell cycle arrest, and apoptosis with concurrent increases in p21 mRNA and protein. Consistent with this negative association between TSG101 and p21, expression levels of these two markers are inversely correlated in ovarian cancer. CONCLUSIONS TSG101 negatively regulates p21 levels, and up-regulation of TSG101 is associated with poor prognosis in ovarian cancer.
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Affiliation(s)
- Travis W Young
- Department of Pharmacology and Toxicology, Sealy Center for Cancer Cell Biology, The University of Texas Medical Branch, Galveston, Texas 77555-1031, USA
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21
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Passananti C, Fanciulli M. The anti-apoptotic factor Che-1/AATF links transcriptional regulation, cell cycle control, and DNA damage response. Cell Div 2007; 2:21. [PMID: 17634135 PMCID: PMC1948887 DOI: 10.1186/1747-1028-2-21] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Accepted: 07/16/2007] [Indexed: 12/29/2022] Open
Abstract
Che-1 is a RNA polymerase II binding protein involved in the transcriptional regulation of E2F target genes and in cell proliferation. Recently, it has been shown that Che-1 accumulates in cells responding to genotoxic agents such as Doxorubicin and ionizing radiation. The DNA damage-activated checkpoint kinases ATM and Chk2 interact with and phosphorylate Che-1, enhancing its accumulation and stability, and promoting Che-1-mediated transcription of p53-responsive genes and of p53 itself, as evidenced by microarray analysis. This transcriptional response is suppressed by expression of a Che-1 mutant lacking ATM and Chk2 phosphorylation amino acid residues, or by depletion of Che-1 by RNA silencing. In addition, chromatin immunoprecipitation analysis has shown that Che-1 is released from E2F target genes and recruited to the p21 and p53 promoters after DNA damage. Che-1 contributes to the maintenance of the G2/M checkpoint in response to genotoxic stress. These findings identify a new mechanism by which the checkpoint kinases regulate, via the novel effector Che-1, the p53 pathway. Lastly, increasing evidence suggests that Che-1 may be involved in apoptotic signaling in neural tissues. In cortical neurons, Che-1 exhibits anti-apoptotic activity, protecting cells from neuronal damage induced by amyloid β-peptide. In cerebellar granule neurons, Che-1 interacts with Tau in the cytoplasmic compartment and this interaction is modulated during neuronal apoptosis. Finally, Che-1 directly interacts with the neuronal cell-death inducer "NRAGE" which downregulates endogenous Che-1 by targeting it for proteasome-dependent degradation. These findings identify Che-1 as a novel cytoprotective factor against apoptotic insults and suggest that Che-1 may represent a potential target for therapeutic application.
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Affiliation(s)
- Claudio Passananti
- Instituto di Biologia e Patologia Molecolare, CNR, c/o Regina Elena Cancer Institute, Via Delle Messi d'oro 156, 00158 Rome, Italy
- Rome Oncogenomic Center, Regina Elena Cancer Institute, Rome, Italy
| | - Maurizio Fanciulli
- Laboratory "B", Department of Therapeutic Programs Development, Regina Elena Cancer Institute, Via Delle Messi d'oro 156, 00158 Rome, Italy
- Rome Oncogenomic Center, Regina Elena Cancer Institute, Rome, Italy
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22
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You HL, Eng HL, Hsu SF, Chen CM, Ye TC, Liao WT, Huang MY, Baer R, Cheng JT. A PKC-Sp1 signaling pathway induces early differentiation of human keratinocytes through upregulation of TSG101. Cell Signal 2007; 19:1201-11. [PMID: 17321722 DOI: 10.1016/j.cellsig.2007.01.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2006] [Revised: 12/18/2006] [Accepted: 01/08/2007] [Indexed: 11/15/2022]
Abstract
The TSG101 protein has been implicated in multiple biological functions including regulation of gene transcription, vesicular trafficking, cellular growth and differentiation. However, the cellular signals that control TSG101 functions are unclear. Here, we demonstrate that TSG101 is upregulated during keratinocyte differentiation in both human foreskin tissue and reconstructed organotypic skin cultures. In addition, we found that TSG101 siRNA inhibits calcium-induced early differentiation of human foreskin keratinocytes, indicating an essential and downstream role for TSG101 in this process. Furthermore, the PKC agonist TPA promotes expression of TSG101 and keratin 10 in keratinocytes under low calcium conditions, while co-treatment with the PKC inhibitor GF 109203X blocks TPA-induced TSG101 and keratin 10 upregulation. Previous work has established that the TSG101 gene is controlled by a TATA-less promoter that harbors a Sp1-binding site. Here we show that both calcium and TPA activate PKC, stimulate phosphorylation of Sp1, and augment the activity of the TSG101 promoter in a manner dependent on its Sp1-binding site. Release of calcium from intracellular stores with thapsigargin, an endoplasmic reticulum Ca2+-ATPase inhibitor that elevates intracellular free Ca2+ without activating PKC, does not affect Sp1 phosphorylation and TSG101 promoter activity. Taken together, these data suggest that an intracellular calcium store independent PKC-Sp1 signaling pathway induces early keratinocyte differentiation through upregulation of TSG101.
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Affiliation(s)
- Huey-Ling You
- Department of Biological Sciences, National Sun Yat-Sen University, 70 Lien Hai Road, and Department of Pathology, Chang Gung Memorial Hospital, Kaohsiung, Taiwan 80833, Republic of China
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23
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De Nicola F, Bruno T, Iezzi S, Di Padova M, Floridi A, Passananti C, Del Sal G, Fanciulli M. The prolyl isomerase Pin1 affects Che-1 stability in response to apoptotic DNA damage. J Biol Chem 2007; 282:19685-91. [PMID: 17468107 DOI: 10.1074/jbc.m610282200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
We have previously demonstrated that DNA damage leads to stabilization and accumulation of Che-1, an RNA polymerase II-binding protein that plays an important role in transcriptional activation of p53 and in maintenance of the G(2)/M checkpoint. Here we show that Che-1 is down-regulated during the apoptotic process. We found that the E3 ligase HMD2 physically and functionally interacts with Che-1 and promotes its degradation via the ubiquitin-dependent proteasomal system. Furthermore, we found that in response to apoptotic stimuli Che-1 interacts with the peptidyl-prolyl isomerase Pin1 and that conformational changes generated by Pin1 are required for Che-1/HDM2 interaction. Notably, a Che-1 mutant lacking the capacity to bind Pin1 exhibits an increased half-life and this correlates with a diminished apoptosis in response to genotoxic stress. Our results establish Che-1 as a new Pin1 and HDM2 target and confirm its important role in the cellular response to DNA damage.
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Affiliation(s)
- Francesca De Nicola
- Laboratory B, Experimental Research Center and Rome Oncogenomic Center, Regina Elena Cancer Institute, Via delle Messi d'Oro 156, 00158 Rome, Italy
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24
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Spitzer C, Schellmann S, Sabovljevic A, Shahriari M, Keshavaiah C, Bechtold N, Herzog M, Müller S, Hanisch FG, Hülskamp M. The Arabidopsis elch mutant reveals functions of an ESCRT component in cytokinesis. Development 2007; 133:4679-89. [PMID: 17090720 DOI: 10.1242/dev.02654] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recently, an alternative route to the proteasomal protein-degradation pathway was discovered that specifically targets transmembrane proteins marked with a single ubiquitin to the endosomal multivesicular body (MVB) and, subsequently, to the vacuole (yeast) or lysosome (animals), where they are degraded by proteases. Vps23p/TSG101 is a key component of the ESCRT I-III machinery in yeast and animals that recognizes mono-ubiquitylated proteins and sorts them into the MVB. Here, we report that the Arabidopsis ELCH (ELC) gene encodes a Vps23p/TSG101 homolog, and that homologs of all known ESCRT I-III components are present in the Arabidopsis genome. As with its animal and yeast counterparts, ELC binds ubiquitin and localizes to endosomes. Gel-filtration experiments indicate that ELC is a component of a high-molecular-weight complex. Yeast two-hybrid and immunoprecipitation assays showed that ELC interacts with Arabidopsis homologs of the ESCRT I complex. The elc mutant shows multiple nuclei in various cell types, indicating a role in cytokinesis. Double-mutant analysis with kaktus shows that increased ploidy levels do not influence the cytokinesis effect of elc mutants, suggesting that ELC is only important during the first endoreduplication cycle. Double mutants with tubulin folding cofactor a mutants show a synergistic phenotype, suggesting that ELC regulates cytokinesis through the microtubule cytoskeleton.
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Affiliation(s)
- Christoph Spitzer
- University of Köln, Botanical Institute III, Gyrhofstr. 15, 50931 Köln, Germany
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25
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Bashirova AA, Bleiber G, Qi Y, Hutcheson H, Yamashita T, Johnson RC, Cheng J, Alter G, Goedert JJ, Buchbinder S, Hoots K, Vlahov D, May M, Maldarelli F, Jacobson L, O'brien SJ, Telenti A, Carrington M. Consistent effects of TSG101 genetic variability on multiple outcomes of exposure to human immunodeficiency virus type 1. J Virol 2006; 80:6757-63. [PMID: 16809281 PMCID: PMC1489017 DOI: 10.1128/jvi.00094-06] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tumor susceptibility gene 101 (TSG101) encodes a host cellular protein that is appropriated by human immunodeficiency virus type 1 (HIV-1) in the budding process of viral particles from infected cells. Variation in the coding or noncoding regions of the gene could potentially affect the degree of TSG101-mediated release of viral particles. While the coding regions of the gene were found to lack nonsynonymous variants, two polymorphic sites in the TSG101 5' area were identified that were associated with the rate of AIDS progression among Caucasians. These single-nucleotide polymorphisms (SNPs), located at positions -183 and +181 relative to the translation start, specify three haplotypes termed A, B, and C, which occur at frequencies of 67%, 21%, and 12%, respectively. Haplotype C is associated with relatively rapid AIDS progression, while haplotype B is associated with slower disease progression. Both effects were dominant over the intermediate haplotype A. The haplotypes also demonstrated parallel effects on the rate of CD4 T-cell depletion and viral load increase over time, as well as a possible influence on HIV-1 infection. The data raise the hypothesis that noncoding variation in TSG101 affects the efficiency of TSG101-mediated release of viral particles from infected cells, thereby altering levels of plasma viral load and subsequent disease progression.
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Affiliation(s)
- Arman A Bashirova
- Laboratory of Genomic Diversity, SAIC-Frederick, Inc., National Cancer Institute, Frederick, Maryland 21702, USA
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26
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Devgan V, Nguyen BC, Oh H, Dotto GP. p21WAF1/Cip1 suppresses keratinocyte differentiation independently of the cell cycle through transcriptional up-regulation of the IGF-I gene. J Biol Chem 2006; 281:30463-70. [PMID: 16912042 DOI: 10.1074/jbc.m604684200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
p21 plays a dual role in keratinocyte growth and differentiation control. It restricts the number of keratinocyte stem cell populations while inhibiting the later stages of differentiation independently of the cell cycle. The molecular/biochemical mechanism for the differentiation suppressive function of p21 is unknown. Here we show that elevated p21 expression leads to activation of MAPK family members in a keratinocyte-specific and cell cycle-independent manner, and up-regulation of MAPK activity can explain the inhibitory effects of p21 on differentiation. p21 induces transcription of several genes with MAPK activation potential. Although several of these genes are induced by p21 in a MAPK-dependent manner, expression of IGF-I is induced upstream of MAPK activation. IGF-I stimulation is by itself sufficient to cause MAPK activation and inhibit differentiation and suppression of IGF-I signaling by knock down of the cognate receptor (IGF-R1), diminishing the ability of p21 to activate MAPK and suppress differentiation. Thus, in keratinocytes, the ability of p21 to suppress differentiation can be explained by cell type-specific activation of the MAPK cascade by transcriptional up-regulation of the IGF-I gene.
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Affiliation(s)
- Vikram Devgan
- Cutaneous Biology Research Center, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA
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27
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Slagsvold T, Pattni K, Malerød L, Stenmark H. Endosomal and non-endosomal functions of ESCRT proteins. Trends Cell Biol 2006; 16:317-26. [PMID: 16716591 DOI: 10.1016/j.tcb.2006.04.004] [Citation(s) in RCA: 195] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2006] [Revised: 03/16/2006] [Accepted: 04/13/2006] [Indexed: 12/30/2022]
Abstract
The three endosomal sorting complexes required for transport (ESCRTs) are integral to the degradation of endocytosed membrane proteins and multivesicular body (MVB) biogenesis. Here, we review evidence that ESCRTs have evolved as a specialized machinery for the degradative sorting of ubiquitinated membrane proteins and we highlight recent studies that have shed light on the mechanisms by which these complexes mediate protein sorting, MVB biogenesis, tumour suppression and viral budding. We also discuss evidence that some ESCRT subunits have evolved additional functions that are unrelated to membrane trafficking.
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Affiliation(s)
- Thomas Slagsvold
- Department of Biochemistry, the Norwegian Radium Hospital and the University of Oslo, Montebello, N-0310 Oslo, Norway
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28
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Ellsworth DL, Ellsworth RE, Love B, Deyarmin B, Lubert SM, Mittal V, Shriver CD. Genomic patterns of allelic imbalance in disease free tissue adjacent to primary breast carcinomas. Breast Cancer Res Treat 2005; 88:131-9. [PMID: 15564796 DOI: 10.1007/s10549-004-1424-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mammary stroma plays an important role in facilitating the neoplastic transformation of epithelial cells, modulating integrity of the extracellular matrix, and maintaining genomic stability, but molecular mechanisms by which stroma affects epithelial structure and function are not well-defined. We used laser-assisted microdissection of paraffin-embedded breast tissues from 30 patients with breast disease and a panel of 52 microsatellite markers defining 26 chromosomal regions to characterize genomic patterns of allelic imbalance (AI) in disease-free tissue adjacent to sites of breast disease and to define genomic regions that may contain genes associated with early carcinogenic processes. The mean frequency of AI in histologically normal tissue adjacent to the primary carcinomas (15.4%) was significantly higher than that in distant tissue from the same breast (3.7%). The pattern of AI across all chromosomal regions differed between the adjacent tissue and primary tumor in every case. Unique AI events, observed only in tumor (15% of informative markers) or only in adjacent cells (10% of informative markers), were far more common than AI events shared between tumor and adjacent cells (approximately 4%). Levels of AI characteristic of advanced invasive carcinomas were already present in non-invasive ductal carcinomas in situ, and appreciable levels of AI were observed in adjacent non-neoplastic tissue at all pathological stages. Chromosome 11p15.1 showed significantly higher levels of AI in adjacent cells (p < 0.01), suggesting that this region may harbor genes involved in breast cancer development and progression. Our data indicate that genomic instability may be inherently greater in disease-free tissue close to developing tumors, which may have important implications for defining surgical margins and predicting recurrence.
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Affiliation(s)
- Darrell L Ellsworth
- Clinical Breast Care Project, Windber Research Institute, Windber, PA 15963, USA.
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29
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Ismaili N, Blind R, Garabedian MJ. Stabilization of the unliganded glucocorticoid receptor by TSG101. J Biol Chem 2005; 280:11120-6. [PMID: 15657031 DOI: 10.1074/jbc.m500059200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The glucocorticoid receptor (GR) has been shown to undergo hormone-dependent down-regulation via transcriptional, post-transcriptional, and posttranslational mechanisms. However, the mechanisms involved in modulating GR levels in the absence of hormone remain enigmatic. Here we demonstrate that TSG101, a previously identified GR-interacting protein, stabilizes the hypophosphorylated form of GR in the absence of ligand. We found that a non-phosphorylated version of GR (S203A/S211A) showed enhanced interaction with TSG101 as compared with the wild type GR, suggesting that TSG101 interacts more favorably with GR when it is not phosphorylated. A significant accumulation of GR S203A/S211A protein is detected in the absence of ligand when TSG101 is overexpressed, whereas no increase in the wild type phosphorylated GR or phosphomimetic GR S203E/S211E was observed in mammalian cells. In contrast, down-regulation of TSG101 expression by siRNA renders the hypophosphorylated form of GR unstable. We further show that TSG101 stabilizes GR by impeding its degradation by the proteasome and extending receptor half-life. Thus, in absence of a ligand, TSG101 binds GR and protects the non-phosphorylated receptor from degradation.
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Affiliation(s)
- Naima Ismaili
- Department of Microbiology, New York Univeristy Cancer Institute, New York University School of Medicine, New York, New York 10016, USA
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Carstens MJ, Krempler A, Triplett AA, van Lohuizen M, Wagner KU. Cell cycle arrest and cell death are controlled by p53-dependent and p53-independent mechanisms in Tsg101-deficient cells. J Biol Chem 2004; 279:35984-94. [PMID: 15210712 PMCID: PMC1201394 DOI: 10.1074/jbc.m400408200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Our previous studies have shown that cells conditionally deficient in Tsg101 arrested at the G(1)/S cell cycle checkpoint and died. We created a series of Tsg101 conditional knock-out cell lines that lack p53, p21(Cip1), or p19(Arf) to determine the involvement of the Mdm2-p53 circuit as a regulator for G(1)/S progression and cell death. In this new report we show that the cell cycle arrest in Tsg101-deficient cells is p53-dependent, but a null mutation of the p53 gene is unable to maintain cell survival. The deletion of the Cdkn1a gene in Tsg101 conditional knock-out cells resulted in G(1)/S progression, suggesting that the p53-dependent G(1) arrest in the Tsg101 knock-out is mediated by p21(Cip1). The Cre-mediated excision of Tsg101 in immortalized fibroblasts that lack p19(Arf) seemed not to alter the ability of Mdm2 to sequester p53, and the p21-mediated G(1) arrest was not restored. Based on these findings, we propose that the p21-dependent cell cycle arrest in Tsg101-deficient cells is an indirect consequence of cellular stress and not caused by a direct effect of Tsg101 on Mdm2 function as previously suggested. Finally, the deletion of Tsg101 from primary tumor cells that express mutant p53 and that lack p21(Cip1) expression results in cell death, suggesting that additional transforming mutations during tumorigenesis do not affect the important role of Tsg101 for cell survival.
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Affiliation(s)
- Marissa J. Carstens
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Nebraska Medical Center, Omaha, Nebraska 68198-6805 and
| | - Andrea Krempler
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Nebraska Medical Center, Omaha, Nebraska 68198-6805 and
| | - Aleata A. Triplett
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Nebraska Medical Center, Omaha, Nebraska 68198-6805 and
| | - Maarten van Lohuizen
- The Netherlands Cancer Institute, Department of Molecular Genetics, H5, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Kay-Uwe Wagner
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Nebraska Medical Center, Omaha, Nebraska 68198-6805 and
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31
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Ismaili N, Garabedian MJ. Modulation of glucocorticoid receptor function via phosphorylation. Ann N Y Acad Sci 2004; 1024:86-101. [PMID: 15265775 DOI: 10.1196/annals.1321.007] [Citation(s) in RCA: 213] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The glucocorticoid receptor (GR) is phosphorylated at multiple serine residues in a hormone-dependent manner. It has been suggested that GR phosphorylation affects turnover, subcellular trafficking, or the transcriptional regulatory functions of the receptor, yet the contribution of individual GR phosphorylation sites to the modulation of GR activity remains enigmatic. This review critically evaluates the literature on GR phosphorylation and presents more recent work on the mechanism of GR phosphorylation from studies using antibodies that recognize GR only when it is phosphorylated. In addition, we present support for the notion that GR phosphorylation modifies protein-protein interactions, which can stabilize the hypophosphorylated form of the receptor in the absence of ligand, as well as facilitate transcriptional activation by the hyperphosphorylation of GR via cofactor recruitment upon ligand binding. Finally, we propose that GR phosphorylation also participates in the nongenomic activation of cytoplasmic signaling pathways evoked by GR. Thus, GR phosphorylation is a versatile mechanism for modulating and integrating multiple receptor functions.
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Affiliation(s)
- Naima Ismaili
- Department of Microbiology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA
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32
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Marks MS, Theos AC, Raposo G. Melanosomes and MHC class II antigen-processing compartments: a tinted view of intracellular trafficking and immunity. Immunol Res 2004; 27:409-26. [PMID: 12857985 DOI: 10.1385/ir:27:2-3:409] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Melanosomes are specialized intracellular compartments within melanocytes and retinal pigment epithelial cells that function in the synthesis, storage, and secretion of melanins, which are the major pigments made by mammals. The mechanisms that regulate the formation of melanosomes, and the pathways by which constituent proteins are targeted to them, are related to those involved in the biogenesis of major histocompatibility complex (MHC) class II antigen-processing compartments. Consequently, diseases that affect pigmentation may also affect antigen presentation to T cells. Moreover, many of the tissue-specific proteins that localize to melanosomes and participate in melanin formation double as tumor-associated antigens that are targets for T cells in patients with melanoma. Our studies on melanosome biogenesis are providing new ways of thinking about antigen-processing compartments and the mechanisms regulating presentation of tumor-associated antigens.
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Affiliation(s)
- Michael S Marks
- Department of Pathology, University of Pennsylvania, Philadelphia, PA 19104-6082, USA.
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33
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Burgdorf S, Leister P, Scheidtmann KH. TSG101 interacts with apoptosis-antagonizing transcription factor and enhances androgen receptor-mediated transcription by promoting its monoubiquitination. J Biol Chem 2004; 279:17524-34. [PMID: 14761944 DOI: 10.1074/jbc.m313703200] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Apoptosis-antagonizing transcription factor (AATF), also termed Che-1, was identified as interacting protein of Dlk/ZIP kinase and RNA polymerase II, respectively. Che-1 has additionally been shown to bind Rb, thereby activating transcription factor E2F and promoting cell cycle progression. Moreover, AATF enhances steroid receptor-mediated transactivation in a hormone- and dose-dependent manner (Leister, P., Burgdorf, S., and Scheidtmann, K. H., (2003) Signal Transduction 3, 18-25). These data suggest that AATF exerts its functions through interaction with different transcription factors. In search of novel interaction partners of AATF, we identified the tumor susceptibility gene product TSG101, which had also been recognized as a co-regulator of nuclear hormone receptors. Interestingly, TSG101 and AATF functioned as cooperative coactivators in androgen receptor-mediated transcription. Because TSG101 was also shown to play a role in regulation of ubiquitin conjugation, we asked whether its coactivating function might be linked to ubiquitination. Indeed, TSG101 enhanced monoubiquitination of the androgen receptor in a ligand-dependent manner, and this correlated with enhanced transactivating capacity. Furthermore, a dominant-negative mutant of ubiquitin preventing polyubiquitination also stimulated androgen receptor-mediated transcription, which in this case could not be enhanced by TSG101. We propose that TSG101 activates androgen receptor-induced transcription by transient stabilization of the monoubiquitinated state, thus revealing a novel regulatory mechanism for nuclear receptors.
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MESH Headings
- Amino Acid Motifs
- Animals
- Apoptosis
- Apoptosis Regulatory Proteins
- Blotting, Western
- Cell Line, Tumor
- Cell Nucleus/metabolism
- DNA, Complementary/metabolism
- DNA-Binding Proteins/chemistry
- DNA-Binding Proteins/metabolism
- Dose-Response Relationship, Drug
- Endosomal Sorting Complexes Required for Transport
- Gene Deletion
- Gene Library
- Genes, Dominant
- Hormones/metabolism
- Humans
- Ligands
- Microscopy, Fluorescence
- Models, Biological
- Models, Genetic
- Plasmids/metabolism
- Promoter Regions, Genetic
- Protein Binding
- Protein Structure, Tertiary
- Rats
- Receptors, Androgen/metabolism
- Repressor Proteins/metabolism
- Transcription Factors/chemistry
- Transcription Factors/metabolism
- Transcription, Genetic
- Transcriptional Activation
- Transfection
- Two-Hybrid System Techniques
- Ubiquitin/metabolism
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Affiliation(s)
- Sven Burgdorf
- Institute of Genetics, University of Bonn, D-53117 Bonn, Germany
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34
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Affiliation(s)
- Nadir R Farid
- Osancor Biotech Inc, 31 Woodland Drive, Watford, Herts, UK, WD17 3BY
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35
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Zhu G, Gilchrist R, Borley N, Chng HW, Morgan M, Marshall JF, Camplejohn RS, Muir GH, Hart IR. Reduction of TSG101 protein has a negative impact on tumor cell growth. Int J Cancer 2004; 109:541-7. [PMID: 14991575 DOI: 10.1002/ijc.20014] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
TSG101 was defined originally as a tumor-suppressor gene, raising the expectation that absence of the encoded protein should lead to increased tumor cell growth and, perhaps, increased tumor cell aggressiveness. We have used the RNA interference (RNAi) technique to downregulate TSG101 in PC3 (prostate cancer) and MDA-MB-231 (breast cancer) cells. An approximately 85% selective downregulation at the protein level was achieved in both cell lines over a period of 12 days as detected by Western blotting. This treatment resulted in inhibition of tumor cell growth, with a decreased level of TSG101 causing partial cell cycle arrest at the G(1)/S boundary and a reduction in the rate at which cells passed from G(2) through mitosis and back into G(1). In both cell lines, the percentage of cells in S-phase was reduced significantly at day 4 after the TSG101 siRNA transfection (27% vs. 41% in MDA-MB-231 cells; 22% vs. 39% in PC3 cells). Additionally, RNAi-mediated downregulation of TSG101 reduced the colony formation capacities of both cancer cell lines. Rather more surprisingly, TSG101 downregulation affected the migratory activity of the MDA-MB-231 cells, independent of any effect on proliferation. Thus, in a Transwell assay, after 4-hr incubation, 36.0% of control MDA-MB-231 cells had migrated to the lower chamber vs. 7.3% of TSG101-downregulated cells (p < 0.001; scrambled control, 36.5%). These results show that the TSG101 gene does not comply with the usual characteristics of a tumor-suppressor gene; rather, its expression may be necessary for activities associated with aspects of tumor progression.
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Affiliation(s)
- Gang Zhu
- Richard Dimbleby Department of Cancer Research/Cancer Research U.K. Laboratory, GKT School of Medicine, St. Thomas' Hospital, London, United Kingdom
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36
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Lu Q, Hope LW, Brasch M, Reinhard C, Cohen SN. TSG101 interaction with HRS mediates endosomal trafficking and receptor down-regulation. Proc Natl Acad Sci U S A 2003; 100:7626-31. [PMID: 12802020 PMCID: PMC164637 DOI: 10.1073/pnas.0932599100] [Citation(s) in RCA: 252] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Down-regulation of mitogenic signaling in mammalian cells relies in part on endosomal trafficking of activated receptors into lysosomes, where the receptors are degraded. These events are mediated by ubiquitination of the endosomal cargo and its consequent sorting into multivesicular bodies that form at the surfaces of late endosomes. Tumor susceptibility gene 101 (tsg101) recently was found to be centrally involved in this process. Here we report that TSG101 interacts with hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), an early endosomal protein, and that disruption of this interaction impedes endosomal trafficking and endocytosis-mediated degradation of mitogenic receptors. TSG101/HRS interaction occurs between a ubiquitin-binding domain of TSG101 and two distinct proline-rich regions of HRS, and is modulated by a C-terminal TSG101 sequence that resembles a motif targeted in HRS. Mutational perturbation of TSG101/HRS interaction prevented delivery of epidermal growth factor receptor (EGFR) to late endosomes, resulted in the cellular accumulation of ubiquitinated EGFR in early endosomes, and inhibited ligand-induced down-regulation of EGFR. Our results reveal the TSG101 interaction with HRS as a crucial step in endocytic down-regulation of mitogenic signaling and suggest a role for this interaction in linking the functions of early and late endosomes.
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Affiliation(s)
- Quan Lu
- Department of Genetics, Program in Cancer Biology, Stanford University School of Medicine, Stanford, CA 94305-5120, USA
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37
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Blanco S, Lazo PA. Human TSG101 does not replace Saccharomyces cerevisiae VPS23 role in the quality control of plasma membrane proteins. FEMS Microbiol Lett 2003; 221:151-4. [PMID: 12725919 DOI: 10.1016/s0378-1097(03)00179-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Saccharomyces cerevisiae VPS23 (STP22) gene is implicated in the control of vesicle movement and quality of plasma membrane proteins. VPS23 mutants have defects either in removing defective membrane proteins such as alpha-mating factor receptor and arginine permease. The human ortholog TSG101 and its variants, isolated from tumor cells, do not substitute VPS23 in its ability to rescue the phenotype of defective plasma membrane proteins.
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Affiliation(s)
- Sandra Blanco
- Centro de Investigación del Cáncer, Instituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas - Universidad de Salamanca, Campus Miguel de Unamuno, 37007 Salamanca, Spain
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38
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Fehrmann F, Klumpp DJ, Laimins LA. Human papillomavirus type 31 E5 protein supports cell cycle progression and activates late viral functions upon epithelial differentiation. J Virol 2003; 77:2819-31. [PMID: 12584305 PMCID: PMC149771 DOI: 10.1128/jvi.77.5.2819-2831.2003] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The function of the E5 protein of human papillomaviruses (HPV) is not well characterized, and controversies exist about its role in the viral life cycle. To determine the function of E5 within the life cycle of HPV type 31 (HPV31) we first constructed HPV31 mutant genomes that contained an altered AUG initiation codon or stop codons in E5. Cell lines were established which harbored transfected wild-type or E5 mutant HPV31 genomes. These cell lines all maintained episomal copies of HPV31 and revealed similar phenotypes with respect to growth rate, early gene expression, and viral copy number in undifferentiated monolayer cultures. Following epithelial differentiation, genome amplification and differentiation-dependent late gene expression were observed in mutant cell lines, but at a rate significantly reduced from that observed in cells containing the wild-type genomes. Organotypic raft cultures indicated that E5 does not effect the expression of differentiation markers but does reduce expression of late viral proteins. Western analysis and immunofluorescence staining for cyclins during epithelial differentiation revealed a decreased expression of cyclin A and B in E5 mutant cells compared to HPV wild-type cells. Using a replating assay, a significant reduction in colony-forming ability was detected in the absence of E5 expression when cells containing wild-type or E5 mutant HPV genomes were allowed to proliferate following 24 h in suspension-induced differentiation. This suggests that HPV E5 modifies the differentiation-induced cell cycle exit and supports the ability of HPV31-positive keratinocytes to retain proliferative competence. In these studies, E5 was found to have little effect on the levels of the epidermal growth factor receptor (EGFR) or on its phosphorylation status. This indicates that EGFR is not a target of E5 action. Our results propose a role for high risk HPV E5 in modulation of late viral functions through activation of proliferative capacity in differentiated cells. We suspect that the primary target of E5 is a membrane protein or receptor that then acts to alter the levels or activities of cell cycle regulators.
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Affiliation(s)
- Frauke Fehrmann
- Department of Microbiology-Immunology, The Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
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39
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Wagner KU, Krempler A, Qi Y, Park K, Henry MD, Triplett AA, Riedlinger G, Rucker III EB, Hennighausen L. Tsg101 is essential for cell growth, proliferation, and cell survival of embryonic and adult tissues. Mol Cell Biol 2003; 23:150-62. [PMID: 12482969 PMCID: PMC140677 DOI: 10.1128/mcb.23.1.150-162.2003] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tumor susceptibility gene 101 (Tsg101) was identified in a random mutagenesis screen for potential tumor suppressors in NIH 3T3 cells. Altered transcripts of this gene have been detected in sporadic breast cancers and many other human malignancies. However, the involvement of this gene in neoplastic transformation and tumorigenesis is still elusive. Using gene targeting, we generated genetically engineered mice with a floxed allele of Tsg101. We investigated essential functions of this gene in vivo and examined whether the loss of function of Tsg101 results in tumorigenesis. Conventional knockout mice were generated through Cre-mediated excision of the first coding exon in the germ line of mouse mammary tumor virus (MMTV)-Cre transgenic mice. The complete ablation of Tsg101 in the developing embryo resulted in death around implantation. In contrast, mammary gland-specific knockout mice developed normally but were unable to nurse their young as a result of impaired mammogenesis during late pregnancy. Neither heterozygous null mutants nor somatic knockout mice developed mammary tumors after a latency of 2 years. The Cre-mediated deletion of Tsg101 in primary cells demonstrated that this gene is essential for the growth, proliferation, and survival of mammary epithelial cells. In summary, our results suggest that Tsg101 is required for normal cell function of embryonic and adult tissues but that this gene is not a tumor suppressor for sporadic forms of breast cancer.
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Affiliation(s)
- Kay-Uwe Wagner
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha 68198-6805, USA.
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40
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Scott MT, Ingram A, Ball KL. PDK1-dependent activation of atypical PKC leads to degradation of the p21 tumour modifier protein. EMBO J 2002; 21:6771-80. [PMID: 12485998 PMCID: PMC139104 DOI: 10.1093/emboj/cdf684] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
p21(WAF1/CIP1) Contributes to positive and negative growth control on multiple levels. We previously mapped phosphorylation sites within the C-terminal domain of p21 that regulate proliferating cell nuclear antigen binding. In the current study, a kinase has been fractionated from mammalian cells that stoichiometrically phosphorylates p21 at the Ser146 site, and the enzyme has been identified as an insulin-responsive atypical protein kinase C (aPKC). Expression of PKCzeta or activation of the endogenous kinase by 3-phosphoinositide dependent protein kinase-1 (PDK1) decreased the half-life of p21. Conversely, dnPKCzeta or dnPDK1 increased p21 protein half-life, and a PDK1-dependent increase in the rate of p21 degradation was mediated by aPKC. Insulin stimulation gave a biphasic response with a rapid transient decrease in p21 protein levels during the initial signalling phase that was dependent on phosphatidylinositol 3- kinase, PKC and proteasome activity. Thus, aPKC provides a physiological signal for the degradation of p21. The rapid degradation of p21 protein during the signalling phase of insulin stimulation identifies a novel link between energy metabolism and a key modulator of cell cycle progression.
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Affiliation(s)
| | | | - Kathryn L. Ball
- Cancer Research UK Laboratories, University of Dundee Medical School, Dundee DD1 9SY, UK
Corresponding author e-mail:
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41
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Abstract
To spread infection, enveloped viruses must bud from infected host cells. Recent research indicates that HIV and other enveloped RNA viruses bud by appropriating the cellular machinery that is normally used to create vesicles that bud into late endosomal compartments called multivesicular bodies. This new model of virus budding has many potential implications for cell biology and viral pathogenesis.
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Affiliation(s)
- Owen Pornillos
- Dept of Biochemistry, University of Utah, Salt Lake City, UT 84132, USA
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42
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Krempler A, Henry MD, Triplett AA, Wagner KU. Targeted deletion of the Tsg101 gene results in cell cycle arrest at G1/S and p53-independent cell death. J Biol Chem 2002; 277:43216-23. [PMID: 12205095 PMCID: PMC1201509 DOI: 10.1074/jbc.m207662200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The tumor susceptibility gene 101 (Tsg101) was originally discovered in a screen for potential tumor suppressors using insertional mutagenesis in immortalized fibroblasts. To investigate essential functions of this gene in cell growth and neoplastic transformation, we derived primary mouse embryonic fibroblasts from Tsg101 conditional knockout mice. Expression of Cre recombinase from a retroviral vector efficiently down-regulated Tsg101. The deletion of Tsg101 caused growth arrest and cell death but did not result in increased proliferation and cellular transformation. Inactivation of p53 had no influence on the deleterious phenotype, but Tsg101(-/-) cells were rescued through expression of exogenous Tsg101. Fluorescence-activated cell sorting, proliferation assays, and Western blot analysis of crucial regulators of the cell cycle revealed that Tsg101 deficiency resulted in growth arrest at the G(1)/S transition through inactivation of cyclin-dependent kinase 2. As a consequence, DNA replication was not initiated in Tsg101-deficient cells. Our results clearly demonstrate that Tsg101 is not a primary tumor suppressor in mouse embryonic fibroblasts. However, the protein is crucial for cell proliferation and cell survival.
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Affiliation(s)
| | | | | | - Kay-Uwe Wagner
- § To whom correspondence should be addressed: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, 986805 Nebraska Medical Center, Rm. 8009, Omaha, NE 68198-6805. Tel.: 402-559-3288; Fax: 402-559-4651; E-mail:
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43
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Kwon YH, Jovanovic A, Serfas MS, Kiyokawa H, Tyner AL. P21 functions to maintain quiescence of p27-deficient hepatocytes. J Biol Chem 2002; 277:41417-22. [PMID: 12202477 DOI: 10.1074/jbc.m203388200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hepatocytes rarely proliferate in the healthy adult liver. We explored the roles of the cyclin kinase inhibitors p21 and p27 in maintaining hepatocyte quiescence. p27 is expressed throughout the wild-type liver, but the related protein p21 was not detected. However, p21 was detected in livers of p27-deficient mice. Increased p21 protein levels did not result from an increase in p21 mRNA expression, indicating that p21 expression is regulated post-transcriptionally. p21 protein levels increased in cultured primary hepatocytes treated with the proteasome inhibitor MG132 and cycloheximide, indicating that p21 expression is regulated at the level of protein stability in liver cells. Although increased expression of cyclin-dependent kinase (Cdk) 4, Cdk2, and proliferating cell nuclear antigen was detected in p27-deficient livers, increased hepatocyte proliferation was detected only in livers of mice deficient for both p21 and p27. In p27-deficient livers, p21 was found in complexes with Cdk2 and CdK4 and can compensate for the absence of p27. Our data indicate that cyclin kinase inhibitor activity is important for maintaining hepatocyte quiescence in the adult liver. Significant increases in p21 were detected in multiple tissues of mature p27-deficient mice compared with wild-type mice, suggesting that the ability of p21 to functionally substitute for p27 is not liver-specific.
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Affiliation(s)
- Young Hye Kwon
- Department of Molecular Genetics, University of Illinois, Chicago 60607, USA
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