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Sherr CJ, Beach D, Shapiro GI. Targeting CDK4 and CDK6: From Discovery to Therapy. Cancer Discov 2016; 6:353-67. [PMID: 26658964 PMCID: PMC4821753 DOI: 10.1158/2159-8290.cd-15-0894] [Citation(s) in RCA: 697] [Impact Index Per Article: 77.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2015] [Accepted: 10/09/2015] [Indexed: 12/12/2022]
Abstract
UNLABELLED Biochemical and genetic characterization of D-type cyclins, their cyclin D-dependent kinases (CDK4 and CDK6), and the polypeptide CDK4/6 inhibitor p16(INK4)over two decades ago revealed how mammalian cells regulate entry into the DNA synthetic (S) phase of the cell-division cycle in a retinoblastoma protein-dependent manner. These investigations provided proof-of-principle that CDK4/6 inhibitors, particularly when combined with coinhibition of allied mitogen-dependent signal transduction pathways, might prove valuable in cancer therapy. FDA approval of the CDK4/6 inhibitor palbociclib used with the aromatase inhibitor letrozole for breast cancer treatment highlights long-sought success. The newest findings herald clinical trials targeting other cancers. SIGNIFICANCE Rapidly emerging data with selective inhibitors of CDK4/6 have validated these cell-cycle kinases as anticancer drug targets, corroborating longstanding preclinical predictions. This review addresses the discovery of these CDKs and their regulators, as well as translation of CDK4/6 biology to positive clinical outcomes and development of rational combinatorial therapies.
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Affiliation(s)
- Charles J Sherr
- Howard Hughes Medical Institute, Chevy Chase, MD. Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee.
| | - David Beach
- The Blizard Institute, Barts and the London School of Medicine and Dentistry, London, United Kingdom
| | - Geoffrey I Shapiro
- Early Drug Development Center, Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts.
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102
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Zheng N, Wang Z, Wei W. Ubiquitination-mediated degradation of cell cycle-related proteins by F-box proteins. Int J Biochem Cell Biol 2016; 73:99-110. [PMID: 26860958 PMCID: PMC4798898 DOI: 10.1016/j.biocel.2016.02.005] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 02/05/2016] [Accepted: 02/05/2016] [Indexed: 02/06/2023]
Abstract
F-box proteins, subunits of SKP1-cullin 1-F-box protein (SCF) type of E3 ubiquitin ligase complexes, have been validated to play a crucial role in governing various cellular processes such as cell cycle, cell proliferation, apoptosis, migration, invasion and metastasis. Recently, a wealth of evidence has emerged that F-box proteins is critically involved in tumorigenesis in part through governing the ubiquitination and subsequent degradation of cell cycle proteins, and dysregulation of this process leads to aberrant cell cycle progression and ultimately, tumorigenesis. Therefore, in this review, we describe the critical role of F-box proteins in the timely regulation of cell cycle. Moreover, we discuss how F-box proteins involve in tumorigenesis via targeting cell cycle-related proteins using biochemistry studies, engineered mouse models, and pathological gene alternations. We conclude that inhibitors of F-box proteins could have promising therapeutic potentials in part through controlling of aberrant cell cycle progression for cancer therapies.
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Affiliation(s)
- Nana Zheng
- The Cyrus Tang Hematology Center and Collaborative Innovation Center of Hematology, Jiangsu Institute of Hematology, The First Affiliated Hospital, Soochow University, Suzhou 215123, China
| | - Zhiwei Wang
- The Cyrus Tang Hematology Center and Collaborative Innovation Center of Hematology, Jiangsu Institute of Hematology, The First Affiliated Hospital, Soochow University, Suzhou 215123, China; Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave., Boston, MA 02215, USA.
| | - Wenyi Wei
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave., Boston, MA 02215, USA.
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103
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Xi J, Zeng ST, Guo L, Feng J. High Expression of Cullin7 Correlates with Unfavorable Prognosis in Epithelial Ovarian Cancer Patients. Cancer Invest 2016; 34:130-6. [PMID: 26962950 DOI: 10.3109/07357907.2015.1114123] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Ubiquitin ligase Cullin7 has been has been suggested to act as an oncogene in some tumors; however, the prognostic role of Cullin7 has not been evaluated in cancer patients. In this study, we observed that the expression of Cullin7 mRNA was significantly higher in epithelial ovarian cancer (EOC) compared with normal ovarian surface tissues. In addition, Cullin7 expression was related to FIGO stage (p = .001) and lymph node metastasis (p = .033). Furthermore, Cullin7 overexpression inhibited the migration and invasion of ovarian cancer cells. These results suggest that Cullin7 may serve as an indicator of poor prognosis in patients with EOC.
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Affiliation(s)
- Jie Xi
- a Department of Gynecology , Cangzhou Central Hospital, Hebei Medical University , Cangzhou , China
| | - Sai-Tian Zeng
- a Department of Gynecology , Cangzhou Central Hospital, Hebei Medical University , Cangzhou , China
| | - Liang Guo
- a Department of Gynecology , Cangzhou Central Hospital, Hebei Medical University , Cangzhou , China
| | - Jing Feng
- a Department of Gynecology , Cangzhou Central Hospital, Hebei Medical University , Cangzhou , China
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104
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Koo J, Wang X, Owonikoko TK, Ramalingam SS, Khuri FR, Sun SY. GSK3 is required for rapalogs to induce degradation of some oncogenic proteins and to suppress cancer cell growth. Oncotarget 2016; 6:8974-87. [PMID: 25797247 PMCID: PMC4496196 DOI: 10.18632/oncotarget.3291] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 02/05/2015] [Indexed: 12/02/2022] Open
Abstract
The single-agent activity of rapalogs (rapamycin and its analogues) in most tumor types has been modest at best. The underlying mechanisms are largely unclear. In this report, we have uncovered a critical role of GSK3 in regulating degradation of some oncogenic proteins induced by rapalogs and cell sensitivity to rapalogs. The basal level of GSK3 activity was positively correlated with cell sensitivity of lung cancer cell lines to rapalogs. GSK3 inhibition antagonized rapamycin's growth inhibitory effects both in vitro and in vivo, while enforced activation of GSK3β sensitized cells to rapamycin. GSK3 inhibition rescued rapamcyin-induced reduction of several oncogenic proteins such as cyclin D1, Mcl-1 and c-Myc, without interfering with the ability of rapamycin to suppress mTORC1 signaling and cap binding. Interestingly, rapamycin induces proteasomal degradation of these oncogenic proteins, as evidenced by their decreased stabilities induced by rapamcyin and rescue of their reduction by proteasomal inhibition. Moreover, acute or short-time rapamycin treatment dissociated not only raptor, but also rictor from mTOR in several tested cell lines, suggesting inhibition of both mTORC1 and mTORC2. Thus, induction of GSK3-dependent degradation of these oncogenic proteins is likely secondary to mTORC2 inhibition; this effect should be critical for rapamycin to exert its anticancer activity.
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Affiliation(s)
- Junghui Koo
- Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA, USA
| | - Xuerong Wang
- Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Taofeek K Owonikoko
- Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA, USA
| | - Suresh S Ramalingam
- Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA, USA
| | - Fadlo R Khuri
- Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA, USA
| | - Shi-Yong Sun
- Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA, USA
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105
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Lian Z, Lee EK, Bass AJ, Wong KK, Klein-Szanto AJ, Rustgi AK, Diehl JA. FBXO4 loss facilitates carcinogen induced papilloma development in mice. Cancer Biol Ther 2016; 16:750-5. [PMID: 25801820 DOI: 10.1080/15384047.2015.1026512] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Cyclin D1 is frequently overexpressed in esophageal squamous cell carcinoma (ESCC) and is considered a key driver of this disease. Mutations in FBXO4, F-box specificity factor that directs SCF-mediated ubiquitylation of cyclin D1, occur in ESCC with concurrent overexpression of cyclin D1 suggesting a potential tumor suppressor role for FBXO4. To evaluate the contribution of FBXO4-dependent regulation cyclin D1 in esophageal squamous cell homeostasis, we exposed FBXO4 knockout mice to N-nitrosomethylbenzylamine (NMBA), an esophageal carcinogen. Our results revealed that loss of FBXO4 function facilitates NMBA induced papillomas in FBXO4 het (+/-) and null (-/-) mice both by numbers and sizes 11 months after single dose NMBA treatment at 2mg/kg by gavage when compared to that in wt (+/+) mice (P < 0.01). No significant difference was noted between heterozygous or nullizygous mice consistent with previous work. To assess cyclin D1/CDK4 dependence, mice were treated with the CDK4/6 specific inhibitor, PD0332991, for 4 weeks. PD0332991 treatment (150mg/kg daily), reduced tumor size and tumor number. Collectively, our data support a role for FBXO4 as a suppressor of esophageal tumorigenesis.
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Key Words
- BrdU, Bromodeoxyuridine
- CDK, Cyclin Dependent Kinase
- CDK4
- DMSO, Dimethyl Sulfoxide
- EGFR, Epidermal Growth Factor Receptor
- ESCC
- ESCC, Esophageal Squamous Cell Carcinoma
- FBXO4
- FBXO4, F box only protein 4
- GI, Gastrointestinal tract
- H&E, Hematoxylin and Eosin
- Het, Heterozygous
- NMBA, N-nitrosomethylbenzylamine
- PBS, Phosphate Buffered Saline
- PD0332991
- PE, Preneoplastic Esophagus
- PI, Propidium Iodide
- Rb, Retinoblastoma Protein
- SCC, Squamous Cell Carcinoma
- SCF, Skp1-Cul1-F box protein
- TNFa, Tumor Necrosis Factor alpha
- Wt, Wild Type
- cyclin D1
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Affiliation(s)
- Zhaorui Lian
- a Institute for Regenerative Medicine; University of Pennsylvania School of Medicine ; Philadelphia , PA , USA
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106
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New Insights Into the Mechanism of COP9 Signalosome-Cullin-RING Ubiquitin-Ligase Pathway Deregulation in Urological Cancers. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 323:181-229. [PMID: 26944622 DOI: 10.1016/bs.ircmb.2015.12.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Urological cancers are a very common type of cancer worldwide and have alarming high incidence and mortality rates, especially in kidney cancers, illustrate the urgent need for new therapeutic targets. Recent publications point to a deregulated COP9 signalosome (CSN)-cullin-RING ubiquitin-ligase (CRL) pathway which is here considered and investigated as potential target in urological cancers with strong focus on renal cell carcinomas (RCC). The CSN forms supercomplexes with CRLs in order to preserve protein homeostasis and was found deregulated in several cancer types. Examination of selected CSN-CRL pathway components in RCC patient samples and four RCC cell lines revealed an interesting deregulated p27(Kip1)-Skp2-CAND1 axis and two p27(Kip1) point mutations in 786-O cells; p27(Kip1)V109G and p27(Kip1)I119T. The p27(Kip1) mutants were detected in patients with RCC and appear to be responsible for an accelerated growth rate in 786-O cells. The occurrence of p27(Kip1)V109G and p27(Kip1)I119T in RCC makes the CSN-CRL pathway an attractive therapeutic target.
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107
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Eo HJ, Park GH, Jeong JB. The involvement of cyclin D1 degradation through GSK3β-mediated threonine-286 phosphorylation-dependent nuclear export in anti-cancer activity of mulberry root bark extracts. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2016; 23:105-113. [PMID: 26926171 DOI: 10.1016/j.phymed.2015.12.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 12/04/2015] [Accepted: 12/05/2015] [Indexed: 06/05/2023]
Abstract
BACKGROUND Mulberry root bark was shown to induce cyclin D1 proteasomal degradation in the human colorectal cancer cells. Still, the molecular mechanisms whereby mulberry root bark induces cyclin D1 proteasomal degradation remain largely unknown. PURPOSE In this study, the inhibitory effect of mulberry root bark (MRB) on the proliferation of human colorectal cancer cells and the mechanism of action were examined to evaluate its anti-cancer activity. METHODS Anti-proliferative effect was determined by MTT assay. RT-PCR and Western blotting were used to assess the mRNA and protein expression of related proteins. RESULTS MRB inhibited markedly the proliferation of human colorectal cancer cells (HCT116, SW480 and LoVo). In addition, the proliferation of human breast cancer cells (MDA-MB-231 and MCF-7) was suppressed by MRB treatment. However, MRB did not affect the growth of HepG-2 cells as a human hepatocellular carcinoma cell line. MRB effectively decreased cyclin D1 protein level in human colorectal cancer cells and breast cancer cells, but not in hepatocellular carcinoma cells. Contrast to protein levels, cyclin D1 mRNA level did not be changed by MRB treatment. Inhibition of proteasomal degradation by MG132 attenuated MRB-mediated cyclin D1 downregulation and the half-life of cyclin D1 was decreased in the cells treated with MRB. In addition, MRB increased phosphorylation of cyclin D1 at threonine-286 and a point mutation of threonine-286 to alanine attenuated MRB-mediated cyclin D1 degradation. Inhibition of GSK3β by LiCl suppressed cyclin D1 phosphorylation and downregulation by MRB. MRB decreased the nuclear level of cyclin D1 and the inhibition of nuclear export by LMB attenuated MRB-mediated cyclin D1 degradation. CONCLUSION MRB has anti-cancer activity by inducing cyclin D1 proteasomal degradation through cyclin D1 nuclear export via GSK3β-dependent threonine-286 phosphorylation. These findings suggest that possibly its extract could be used for treating colorectal cancer.
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Affiliation(s)
- Hyun Ji Eo
- Department of Bioresource Sciences, Andong National University, Andong 760749, Republic of Korea
| | - Gwang Hun Park
- Department of Bioresource Sciences, Andong National University, Andong 760749, Republic of Korea
| | - Jin Boo Jeong
- Department of Bioresource Sciences, Andong National University, Andong 760749, Republic of Korea.
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108
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Abstract
The cell cycle is the sequence of events through which a cell duplicates its genome, grows, and divides. Key cell cycle transitions are driven by oscillators comprising cyclin-dependent kinases and other kinases. Different cell cycle oscillators are inextricably linked to ensure orderly activation of oscillators. A recurring theme in their regulation is the abundance of auto-amplifying loops that ensure switch-like and unidirectional cell cycle transitions. The periodicity of many cell cycle oscillators is choreographed by inherent mechanisms that promote automatic inactivation, often involving dephosphorylation and ubiquitin-mediated protein degradation. These inhibitory signals are subsequently suppressed to enable the next cell cycle to occur. Although the activation and inactivation of cell cycle oscillators are in essence autonomous during the unperturbed cell cycle, a number of checkpoint mechanisms are able to halt the cell cycle until defects are addressed. Together, these mechanisms orchestrate orderly progression of the cell cycle to produce more cells and to safeguard genome integrity.
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Affiliation(s)
- Randy Y C Poon
- Division of Life Science, Center for Cancer Research, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong,
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109
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Liu Y, Mallampalli RK. Small molecule therapeutics targeting F-box proteins in cancer. Semin Cancer Biol 2015; 36:105-19. [PMID: 26427329 DOI: 10.1016/j.semcancer.2015.09.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 09/21/2015] [Accepted: 09/23/2015] [Indexed: 12/12/2022]
Abstract
The ubiquitin proteasome system (UPS) plays vital roles in maintaining protein equilibrium mainly through proteolytic degradation of targeted substrates. The archetypical SCF ubiquitin E3 ligase complex contains a substrate recognition subunit F-box protein that recruits substrates to the catalytic ligase core for its polyubiquitylation and subsequent proteasomal degradation. Several well-characterized F-box proteins have been demonstrated that are tightly linked to neoplasia. There is mounting information characterizing F-box protein-substrate interactions with the rationale to develop unique therapeutics for cancer treatment. Here we review that how F-box proteins function in cancer and summarize potential small molecule inhibitors for cancer therapy.
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Affiliation(s)
- Yuan Liu
- Department of Medicine, The Acute Lung Injury, Center of Excellence, University of Pittsburgh, Pittsburgh, PA 15213, United States
| | - Rama K Mallampalli
- Department of Medicine, The Acute Lung Injury, Center of Excellence, University of Pittsburgh, Pittsburgh, PA 15213, United States; Medical Specialty Service Line, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA 15240, United States.
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110
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Heo J, Eki R, Abbas T. Deregulation of F-box proteins and its consequence on cancer development, progression and metastasis. Semin Cancer Biol 2015; 36:33-51. [PMID: 26432751 DOI: 10.1016/j.semcancer.2015.09.015] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 09/25/2015] [Accepted: 09/25/2015] [Indexed: 01/28/2023]
Abstract
F-box proteins are substrate receptors of the SCF (SKP1-Cullin 1-F-box protein) E3 ubiquitin ligase that play important roles in a number of physiological processes and activities. Through their ability to assemble distinct E3 ubiquitin ligases and target key regulators of cellular activities for ubiquitylation and degradation, this versatile group of proteins is able to regulate the abundance of cellular proteins whose deregulated expression or activity contributes to disease. In this review, we describe the important roles of select F-box proteins in regulating cellular activities, the perturbation of which contributes to the initiation and progression of a number of human malignancies.
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Affiliation(s)
- Jinho Heo
- Department of Radiation Oncology, University of Virginia, Charlottesville, VA, USA
| | - Rebeka Eki
- Department of Radiation Oncology, University of Virginia, Charlottesville, VA, USA; Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA, USA
| | - Tarek Abbas
- Department of Radiation Oncology, University of Virginia, Charlottesville, VA, USA; Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA, USA; Center for Cell Signaling, University of Virginia, Charlottesville, VA, USA.
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111
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Bakthisaran R, Akula KK, Tangirala R, Rao CM. Phosphorylation of αB-crystallin: Role in stress, aging and patho-physiological conditions. Biochim Biophys Acta Gen Subj 2015; 1860:167-82. [PMID: 26415747 DOI: 10.1016/j.bbagen.2015.09.017] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 09/22/2015] [Accepted: 09/23/2015] [Indexed: 01/18/2023]
Abstract
BACKGROUND αB-crystallin, once thought to be a lenticular protein, is ubiquitous and has critical roles in several cellular processes that are modulated by phosphorylation. Serine residues 19, 45 and 59 of αB-crystallin undergo phosphorylation. Phosphorylation of S45 is mediated by p44/42 MAP kinase, whereas S59 phosphorylation is mediated by MAPKAP kinase-2. Pathway involved in S19 phosphorylation is not known. SCOPE OF REVIEW The review highlights the role of phosphorylation in (i) oligomeric structure, stability and chaperone activity, (ii) cellular processes such as apoptosis, myogenic differentiation, cell cycle regulation and angiogenesis, and (iii) aging, stress, cardiomyopathy-causing αB-crystallin mutants, and in other diseases. MAJOR CONCLUSIONS Depending on the context and extent of phosphorylation, αB-crystallin seems to confer beneficial or deleterious effects. Phosphorylation alters structure, stability, size distribution and dynamics of the oligomeric assembly, thus modulating chaperone activity and various cellular processes. Phosphorylated αB-crystallin has a tendency to partition to the cytoskeleton and hence to the insoluble fraction. Low levels of phosphorylation appear to be protective, while hyperphosphorylation has negative implications. Mutations in αB-crystallin, such as R120G, Q151X and 464delCT, associated with inherited myofibrillar myopathy lead to hyperphosphorylation and intracellular inclusions. An ongoing study in our laboratory with phosphorylation-mimicking mutants indicates that phosphorylation of R120GαB-crystallin increases its propensity to aggregate. GENERAL SIGNIFICANCE Phosphorylation of αB-crystallin has dual role that manifests either beneficial or deleterious consequences depending on the extent of phosphorylation and interaction with cytoskeleton. Considering that disease-causing mutants of αB-crystallin are hyperphosphorylated, moderation of phosphorylation may be a useful strategy in disease management. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
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Affiliation(s)
- Raman Bakthisaran
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Kranthi Kiran Akula
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Ramakrishna Tangirala
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Ch Mohan Rao
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.
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112
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Randle SJ, Laman H. F-box protein interactions with the hallmark pathways in cancer. Semin Cancer Biol 2015; 36:3-17. [PMID: 26416465 DOI: 10.1016/j.semcancer.2015.09.013] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 09/18/2015] [Accepted: 09/23/2015] [Indexed: 12/24/2022]
Abstract
F-box proteins (FBP) are the substrate specifying subunit of Skp1-Cul1-FBP (SCF)-type E3 ubiquitin ligases and are responsible for directing the ubiquitination of numerous proteins essential for cellular function. Due to their ability to regulate the expression and activity of oncogenes and tumour suppressor genes, FBPs themselves play important roles in cancer development and progression. In this review, we provide a comprehensive overview of FBPs and their targets in relation to their interaction with the hallmarks of cancer cell biology, including the regulation of proliferation, epigenetics, migration and invasion, metabolism, angiogenesis, cell death and DNA damage responses. Each cancer hallmark is revealed to have multiple FBPs which converge on common signalling hubs or response pathways. We also highlight the complex regulatory interplay between SCF-type ligases and other ubiquitin ligases. We suggest six highly interconnected FBPs affecting multiple cancer hallmarks, which may prove sensible candidates for therapeutic intervention.
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Affiliation(s)
- Suzanne J Randle
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom
| | - Heike Laman
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom.
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113
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Abstract
Cyclin D1 binds and activates cyclin-dependent kinases 4/6 (Cdk4/6) to phosphorylate the retinoblastoma (RB) family proteins, relieving E2F/DPs from the negative restraint of RB proteins and histone deacetylases. The cyclin D-Cdk4/6 complexes activate cyclin E/Cdk2 through titration of the Cdk inhibitors p21Cip1/p27Kip1. Cyclin E/Cdk2 further phosphorylates RBs, thereby activating E2F/DPs, and cells enter the S phase of the cell cycle. Cyclin D-Cdk4/6 also phosphorylates MEP50 subunit of the protein arginine methyltransferase 5 (PRMT5), which cooperates with cyclin D1 to drive lymphomagenesis in vivo. Activated PRMPT5 causes arginine methylation of p53 to suppress expression of pro-apoptotic and anti-proliferative target genes, explaining the molecular mechanism for tumorigenesis. Cyclin D1 physically interacts with transcription factors such as estrogen receptor, androgen receptor, and Myb family proteins to regulate gene expression in Cdk-independent fashion. Dmp1 is a Myb-like protein that quenches the oncogenic signals from activated Ras or HER2 by inducing Arf/p53-dependent cell cycle arrest. Cyclin D1 binds to Dmp1α to activate both Arf and Ink4a promoters to induce cell cycle arrest or apoptosis in non-transformed cells to prevent them from neoplastic transformation. Dmp1-deficiency significantly accelerates mouse mammary tumorigenesis with reduced apoptosis and increased metastasis. Cyclin D1 interferes with ligand activation of PPARγ involved in cellular differentiation; it also physically interacts with histone deacetylases (HDACs) and p300 to repress gene expression. It has also been shown that cyclin D1 accelerates tumorigenesis through transcriptional activation of miR-17/20 and Dicer1 which, in turn, represses cyclin D1 expression. Identification of cyclin D1-binding proteins/promoters will be essential for further clarification of its biological activities.
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Affiliation(s)
- Kazushi Inoue
- Department of Pathology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157 USA
| | - Elizabeth A Fry
- Department of Pathology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157 USA
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114
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Abstract
Mammalian tissues are always exposed to diverse threats from pathological conditions and
aging. Therefore, the molecular systems that protect the cells from these threats are
indispensable for cell survival. A variety of diseases, including neurodegenerative
diseases, cause intracellular damage and disturb homeostasis. Heat shock transcription
factor 1 (HSF1) positively regulates heat shock protein (Hsp) and maintains the precise
folding of proteins. Moreover, HSF1 induces the non-Hsp genes expression, and degrades
damaged/misfolded protein. Recently, my colleagues and I revealed non-Hsp genes have more
protective roles than Hsps at the cellular level. However, whether these protective
systems are similarly important to cellular defense in each tissue is still elusive. In
this study, I compared polyglutamine (polyQ) protein aggregations/inclusion development in
each tissue of WT- and HSF1KO-Huntington’s disease (HD) mice, and examined the expression
of the eight non-Hsp HSF1 target genes that have a strong suppressive effect on polyQ
protein aggregation. Of these genes, Nfatc2, Pdzk3, Cryab, Csrp2, and Prame were detected
in most tissues, but the other genes were not. Surprisingly, the obvious effect of HSF1
deficiency on the expression of these five genes was detected in only heart, spleen, and
stomach. In addition, polyQ protein aggregations/inclusion was not detected in any tissues
of WT-HD and HSF1KO-HD mice, but higher level of pre-aggregative polyQ protein was
detected in HSF1KO-HD tissues. These results indicate non-Hsp genes are indispensable for
the maintenance of intracellular homeostasis in mammalian tissues, resulting in whole body
homeostasis.
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Affiliation(s)
- Naoki Hayashida
- Department of Biochemistry and Molecular Biology, Yamaguchi University School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi 755-8505, Japan
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115
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Resibufogenin Induces G1-Phase Arrest through the Proteasomal Degradation of Cyclin D1 in Human Malignant Tumor Cells. PLoS One 2015; 10:e0129851. [PMID: 26121043 PMCID: PMC4488249 DOI: 10.1371/journal.pone.0129851] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 05/13/2015] [Indexed: 11/19/2022] Open
Abstract
Huachansu, a traditional Chinese medicine prepared from the dried toad skin, has been used in clinical studies for various cancers in China. Resibufogenin is a component of huachansu and classified as bufadienolides. Resibufogenin has been shown to exhibit the anti-proliferative effect against cancer cells. However, the molecular mechanism of resibufogenin remains unknown. Here we report that resibufogenin induces G1-phase arrest with hypophosphorylation of retinoblastoma (RB) protein and down-regulation of cyclin D1 expression in human colon cancer HT-29 cells. Since the down-regulation of cyclin D1 was completely blocked by a proteasome inhibitor MG132, the suppression of cyclin D1 expression by resibufogenin was considered to be in a proteasome-dependent manner. It is known that glycogen synthase kinase-3β (GSK-3β) induces the proteasomal degradation of cyclin D1. The addition of GSK-3β inhibitor SB216763 inhibited the reduction of cyclin D1 caused by resibufogenin. These effects on cyclin D1 by resibufogenin were also observed in human lung cancer A549 cells. These findings suggest that the anti-proliferative effect of resibufogenin may be attributed to the degradation of cyclin D1 caused by the activation of GSK-3β.
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Moreno SP, Gambus A. Regulation of Unperturbed DNA Replication by Ubiquitylation. Genes (Basel) 2015; 6:451-68. [PMID: 26121093 PMCID: PMC4584310 DOI: 10.3390/genes6030451] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 06/05/2015] [Accepted: 06/16/2015] [Indexed: 02/07/2023] Open
Abstract
Posttranslational modification of proteins by means of attachment of a small globular protein ubiquitin (i.e., ubiquitylation) represents one of the most abundant and versatile mechanisms of protein regulation employed by eukaryotic cells. Ubiquitylation influences almost every cellular process and its key role in coordination of the DNA damage response is well established. In this review we focus, however, on the ways ubiquitylation controls the process of unperturbed DNA replication. We summarise the accumulated knowledge showing the leading role of ubiquitin driven protein degradation in setting up conditions favourable for replication origin licensing and S-phase entry. Importantly, we also present the emerging major role of ubiquitylation in coordination of the active DNA replication process: preventing re-replication, regulating the progression of DNA replication forks, chromatin re-establishment and disassembly of the replisome at the termination of replication forks.
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Affiliation(s)
- Sara Priego Moreno
- School of Cancer Sciences, University of Birmingham, Vincent Drive, B15 2TT, Birmingham, UK
| | - Agnieszka Gambus
- School of Cancer Sciences, University of Birmingham, Vincent Drive, B15 2TT, Birmingham, UK.
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117
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Haslbeck M, Peschek J, Buchner J, Weinkauf S. Structure and function of α-crystallins: Traversing from in vitro to in vivo. Biochim Biophys Acta Gen Subj 2015; 1860:149-66. [PMID: 26116912 DOI: 10.1016/j.bbagen.2015.06.008] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 06/10/2015] [Accepted: 06/22/2015] [Indexed: 12/11/2022]
Abstract
BACKGROUND The two α-crystallins (αA- and αB-crystallin) are major components of our eye lenses. Their key function there is to preserve lens transparency which is a challenging task as the protein turnover in the lens is low necessitating the stability and longevity of the constituent proteins. α-Crystallins are members of the small heat shock protein family. αB-crystallin is also expressed in other cell types. SCOPE OF THE REVIEW The review summarizes the current concepts on the polydisperse structure of the α-crystallin oligomer and its chaperone function with a focus on the inherent complexity and highlighting gaps between in vitro and in vivo studies. MAJOR CONCLUSIONS Both α-crystallins protect proteins from irreversible aggregation in a promiscuous manner. In maintaining eye lens transparency, they reduce the formation of light scattering particles and balance the interactions between lens crystallins. Important for these functions is their structural dynamics and heterogeneity as well as the regulation of these processes which we are beginning to understand. However, currently, it still remains elusive to which extent the in vitro observed properties of α-crystallins reflect the highly crowded situation in the lens. GENERAL SIGNIFICANCE Since α-crystallins play an important role in preventing cataract in the eye lens and in the development of diverse diseases, understanding their mechanism and substrate spectra is of importance. To bridge the gap between the concepts established in vitro and the in vivo function of α-crystallins, the joining of forces between different scientific disciplines and the combination of diverse techniques in hybrid approaches are necessary. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
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Affiliation(s)
- Martin Haslbeck
- Center for Integrated Protein Science at the Department Chemie, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching, Germany
| | - Jirka Peschek
- Center for Integrated Protein Science at the Department Chemie, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching, Germany
| | - Johannes Buchner
- Center for Integrated Protein Science at the Department Chemie, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching, Germany.
| | - Sevil Weinkauf
- Center for Integrated Protein Science at the Department Chemie, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching, Germany.
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118
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Abstract
PURPOSE OF REVIEW Deregulated proteolysis is increasingly being implicated in pathogenesis of lymphoma. In this review, we highlight the major cellular processes that are affected by deregulated proteolysis of critical substrates that promote lymphoproliferative disorders. RECENT FINDINGS Emerging evidence supports the role of aberrant proteolysis by the ubiquitin proteasome system (UPS) in lymphoproliferative disorders. Several UPS mediators are identified to be altered in lymphomagenesis. However, the precise role of their alteration and comprehensive knowledge of their target substrate critical for lymphomagenesis is far from complete. SUMMARY Many E3 ligase and deubiquitinases that contribute to regulated proteolysis of substrates critical for major cellular processes are altered in various lineages of lymphoma. Understanding of the proteolytic regulatory mechanisms of these major cellular pathways may offer novel biomarkers and targets for lymphoma therapy.
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119
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Alpha crystallins in the retinal pigment epithelium and implications for the pathogenesis and treatment of age-related macular degeneration. Biochim Biophys Acta Gen Subj 2015; 1860:258-68. [PMID: 26026469 DOI: 10.1016/j.bbagen.2015.05.016] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 05/13/2015] [Accepted: 05/17/2015] [Indexed: 01/18/2023]
Abstract
BACKGROUND αA- and αB crystallins are principal members of the small heat shock protein family and elicit both a cell protective function and a chaperone function. α-Crystallins have been found to be prominent proteins in normal and pathological retina emphasizing the importance for in-depth understanding of their function and significance. SCOPE OF REVIEW Retinal pigment epithelial cells (RPE) play a vital role in the pathogenesis of age-related macular degeneration (AMD). This review addresses a number of cellular functions mediated by α-crystallins in the retina. Prominent expression of αB crystallin in mitochondria may serve to protect cells from oxidative injury. αB crystallin as secretory protein via exosomes can offer neuroprotection to adjacent RPE cells and photoreceptors. The availability of chaperone-containing minipeptides of αB crystallin could prove to be a valuable new tool for therapeutic treatment of retinal disorders. MAJOR CONCLUSIONS α-Crystallins are expressed in cytosol and mitochondria of RPE cells and are regulated during oxygen-induced retinopathy and during development. α-Crystallins protect RPE from oxidative-and ER stress-induced injury and autophagy. αB-Crystallin is a modulator of angiogenesis and vascular endothelial growth factor. αB Crystallin is secreted via exosomal pathway. Minichaperone peptides derived from αB Crystallin prevent oxidant induced cell death and have therapeutic potential. GENERAL SIGNIFICANCE Overall, this review summarizes several novel properties of α-crystallins and their relevance to maintaining normal retinal function. In particular, the use of α-crystallin derived peptides is a promising therapeutic strategy to combat retinal diseases such as AMD. This article is part of a Special Issue entitled Crystallin biochemistry in health and disease.
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120
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Abstract
Among the cell cycle-related mammalian cyclins, cyclin D1 is more closely connected with cell proliferation in response to extracellular signals than the cell cycle clock itself. Because both its mRNA and protein are labile, the intracellular abundance of cyclin D1 is thought to be largely regulated at the level of transcription. However, recent findings suggest that, in certain cell types, cyclin D1 is post-translationally regulated, and a disturbance of this regulatory mechanism induces aberrant entry into the cell cycle and proliferation, sometimes leading to diseases such as cancer. In this review, we summarize recent findings and discuss the physiological role and cellular function of the novel mechanism of regulation of cyclin D1 in terms of the control of cell proliferation.
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121
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Srinivasan A, Thangavel C, Liu Y, Shoyele S, Den RB, Selvakumar P, Lakshmikuttyamma A. Quercetin regulates β-catenin signaling and reduces the migration of triple negative breast cancer. Mol Carcinog 2015; 55:743-56. [PMID: 25968914 DOI: 10.1002/mc.22318] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 02/23/2015] [Accepted: 03/05/2015] [Indexed: 12/27/2022]
Abstract
Triple negative breast cancer (TNBC) is characterized by a lack in estrogen, progesterone, and epidermal growth factor 2 receptors. TNBC exhibits most of the characteristics of basal-like and claudin-low breast cancer subtypes. The main contributor in the mortality of TNBC is due to the higher invasive and migratory ability of these tumor cells. Some plant flavonoids inhibit the epithelial mesenchymal transition (EMT) of tumor cells and suppress cancer metastasis. In this study, we aimed to determine whether the flavonoid quercetin is effective in modulating the molecular signaling associated with EMT in TNBC. Our data indicated that quercetin can induce the expression of E-cadherin and also downregulate vimentin levels in TNBC. The ability of quercetin to modulate these EMT markers resulted in a mesenchymal-to-epithelial transition (MET). Quercetin-induced MET was linked with the alteration of nuclear localization of β-catenin and modulation of β-catenin target genes such as cyclin D1 and c-Myc. Furthermore, we observed that quercetin induced the anti-tumor activity of doxorubicin by inhibiting the migratory ability of TNBC cells. These results suggested that quercetin may inhibit TNBC metastasis and also improve the therapeutic efficacy of existing chemotherapeutic drugs.
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Affiliation(s)
- Asha Srinivasan
- Department of Pharmaceutical Sciences, Jefferson School of Pharmacy, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Chellappagounder Thangavel
- Department of Radiation Oncology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Yi Liu
- Department of Radiation Oncology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Sunday Shoyele
- Department of Pharmaceutical Sciences, Jefferson School of Pharmacy, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Robert B Den
- Department of Radiation Oncology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Ponniah Selvakumar
- Department of Pharmaceutical Sciences, Jefferson School of Pharmacy, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Ashakumary Lakshmikuttyamma
- Department of Pharmaceutical Sciences, Jefferson School of Pharmacy, Thomas Jefferson University, Philadelphia, Pennsylvania
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Chen X, Zhang L, Zheng S, Zhang T, Li M, Zhang X, Zeng Z, McCrae MA, Zhao J, Zhuang H, Lu F. Hepatitis B Virus X Protein Stabilizes Cyclin D1 and Increases Cyclin D1 Nuclear Accumulation through ERK-Mediated Inactivation of GSK-3β. Cancer Prev Res (Phila) 2015; 8:455-463. [PMID: 25712050 DOI: 10.1158/1940-6207.capr-14-0384] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 02/09/2015] [Indexed: 01/13/2023]
Abstract
The Hepatitis B virus X protein (HBx) contributes centrally to the pathogenesis of hepatocellular carcinoma (HCC). It has been suggested that the transcriptional activation of cyclin D1 by HBx is implicated in the development of HCC. However, numerous studies have shown that overexpression of cyclin D1 alone is not sufficient to drive oncogenic transformation. Herein, we investigated whether HBx can stabilize cyclin D1 and induce cyclin D1 protein nuclear accumulation, and thereby accelerate hepatocarcinogenesis. The effects of HBx on cyclin D1 stabilization were assessed in cell-based transfection, Western blot, immunoprecipitation, immunocytofluorescence staining, and flow-cytometric assays. The results demonstrated that ectopic expression of HBx in HCC cells could extend the half-life of cyclin D1 protein from 40-60 minutes to 80-110 minutes. HBx stabilized cyclin D1 primarily in the S phase of the cell cycle, in a manner dependent on the inactivation of GSK-3β, which was mediated by ERK activation. HBx also prompted the nuclear accumulation of cyclin D1, and cotransfection of the constitutively active mutant of GSK-3β along with HBx could reverse the nuclear accumulation and subsequent cell proliferation induced by HBx. Further, a positive correlation between HBx and nuclear cyclin D1 level was established in HCC specimens detected by an immunohistochemical assay. Taken together, our results indicated that HBx could stabilize and increase cyclin D1 nuclear accumulation through ERK-mediated inactivation of GSK-3β. This HBx-induced cyclin D1 upregulation might play an important role in HCC development and progression.
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Affiliation(s)
- Xiangmei Chen
- Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China
| | - Ling Zhang
- Department of Hepatobiliary Surgery, Henan Cancer Hospital, Zhengzhou, P.R. China
| | - Sujun Zheng
- Beijing YouAn hospital, Capital Medical University, Beijing, P.R. China
| | - Ting Zhang
- Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China
| | - Meng Li
- Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China
| | - Xiaolei Zhang
- Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China
| | - Zhenzhen Zeng
- Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China
| | | | - Jingmin Zhao
- Department of Pathology, Institute of Infectious Diseases, Beijing 302 Hospital, Beijing, P.R. China
| | - Hui Zhuang
- Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China
| | - Fengmin Lu
- Department of Microbiology and Infectious Disease Center, School of Basic Medical Science, Peking University Health Science Center, Beijing, P.R. China.
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Akçay Nİ, Bashirov R, Tüzmen Ş. Validation of signalling pathways: Case study of the p16-mediated pathway. J Bioinform Comput Biol 2015; 13:1550007. [DOI: 10.1142/s0219720015500079] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
p16 is recognized as a tumor suppressor gene due to the prevalence of its genetic inactivation in all types of human cancers. Additionally, p16 gene plays a critical role in controlling aging, regulating cellular senescence, detection and maintenance of DNA damage. The molecular mechanism behind these events involves p16-mediated signaling pathway (or p16- Rb pathway), the focus of our study. Understanding functional dependence between dynamic behavior of biological components involved in the p16-mediated pathway and aforesaid molecular-level events might suggest possible implications in the diagnosis, prognosis and treatment of human cancer. In the present work, we employ reverse-engineering approach to construct the most detailed computational model of p16-mediated pathway in higher eukaryotes. We implement experimental data from the literature to validate the model, and under various assumptions predict the dynamic behavior of p16 and other biological components by interpreting the simulation results. The quantitative model of p16-mediated pathway is created in a systematic manner in terms of Petri net technologies.
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Affiliation(s)
- Nimet İlke Akçay
- Department of Applied Mathematics and Computer Science, Eastern Mediterranean University, Famagusta, North Cyprus, Mersin-10, Turkey
| | - Rza Bashirov
- Department of Applied Mathematics and Computer Science, Eastern Mediterranean University, Famagusta, North Cyprus, Mersin-10, Turkey
| | - Şükrü Tüzmen
- Department of Biological Sciences, Eastern Mediterranean University, Famagusta, North Cyprus, Mersin-10, Turkey
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124
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Burmann BM, Hiller S. Chaperones and chaperone-substrate complexes: Dynamic playgrounds for NMR spectroscopists. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2015; 86-87:41-64. [PMID: 25919198 DOI: 10.1016/j.pnmrs.2015.02.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 02/19/2015] [Accepted: 02/19/2015] [Indexed: 05/20/2023]
Abstract
The majority of proteins depend on a well-defined three-dimensional structure to obtain their functionality. In the cellular environment, the process of protein folding is guided by molecular chaperones to avoid misfolding, aggregation, and the generation of toxic species. To this end, living cells contain complex networks of molecular chaperones, which interact with substrate polypeptides by a multitude of different functionalities: transport them towards a target location, help them fold, unfold misfolded species, resolve aggregates, or deliver them towards a proteolysis machinery. Despite the availability of high-resolution crystal structures of many important chaperones in their substrate-free apo forms, structural information about how substrates are bound by chaperones and how they are protected from misfolding and aggregation is very sparse. This lack of information arises from the highly dynamic nature of chaperone-substrate complexes, which so far has largely hindered their crystallization. This highly dynamic nature makes chaperone-substrate complexes good targets for NMR spectroscopy. Here, we review the results achieved by NMR spectroscopy to understand chaperone function in general and details of chaperone-substrate interactions in particular. We assess the information content and applicability of different NMR techniques for the characterization of chaperones and chaperone-substrate complexes. Finally, we highlight three recent studies, which have provided structural descriptions of chaperone-substrate complexes at atomic resolution.
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Affiliation(s)
- Björn M Burmann
- Biozentrum, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland
| | - Sebastian Hiller
- Biozentrum, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland.
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125
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Li Y, Chitnis N, Nakagawa H, Kita Y, Natsugoe S, Yang Y, Li Z, Wasik M, Klein-Szanto AJP, Rustgi AK, Diehl JA. PRMT5 is required for lymphomagenesis triggered by multiple oncogenic drivers. Cancer Discov 2015; 5:288-303. [PMID: 25582697 DOI: 10.1158/2159-8290.cd-14-0625] [Citation(s) in RCA: 115] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
UNLABELLED Protein arginine methyltransferase 5 (PRMT5) has been implicated as a key modulator of lymphomagenesis. Whether PRMT5 has overt oncogenic function in the context of leukemia/lymphoma and whether it represents a therapeutic target remains to be established. We demonstrate that inactivation of PRMT5 inhibits colony-forming activity by multiple oncogenic drivers, including cyclin D1, c-MYC, NOTCH1, and MLL-AF9. Furthermore, we demonstrate that PRMT5 overexpression specifically cooperates with cyclin D1 to drive lymphomagenesis in a mouse model, revealing inherent neoplastic activity. Molecular analysis of lymphomas revealed that arginine methylation of p53 selectively suppresses expression of crucial proapoptotic and antiproliferative target genes, thereby sustaining tumor cell self-renewal and proliferation and bypassing the need for the acquisition of inactivating p53 mutations. Critically, analysis of human tumor specimens reveals a strong correlation between cyclin D1 overexpression and p53 methylation, supporting the biomedical relevance of this pathway. SIGNIFICANCE We have identified and functionally validated a crucial role for PRMT5 for the inhibition of p53-dependent tumor suppression in response to oncogenic insults. The requisite role for PRMT5 in the context of multiple lymphoma/leukemia oncogenic drivers suggests a molecular rationale for therapeutic development.
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MESH Headings
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Amino Acid Substitution
- Animals
- Apoptosis/genetics
- Arginine/metabolism
- Cell Transformation, Neoplastic/genetics
- Cell Transformation, Neoplastic/metabolism
- Cluster Analysis
- Cyclin D1/genetics
- Cyclin D1/metabolism
- Cyclin-Dependent Kinase 4/genetics
- Cyclin-Dependent Kinase 4/metabolism
- Enzyme Activation
- Gene Expression Profiling
- Humans
- Leukemia, T-Cell/genetics
- Leukemia, T-Cell/metabolism
- Leukemia, T-Cell/pathology
- Lymphoma/genetics
- Lymphoma/pathology
- Lymphoma, T-Cell/genetics
- Lymphoma, T-Cell/metabolism
- Lymphoma, T-Cell/pathology
- Methylation
- Mice
- Mutation
- Oncogenes
- Phosphorylation
- Protein-Arginine N-Methyltransferases/genetics
- Protein-Arginine N-Methyltransferases/metabolism
- Tumor Suppressor Protein p53/genetics
- Tumor Suppressor Protein p53/metabolism
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Affiliation(s)
- Yan Li
- Department of Cancer Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - Nilesh Chitnis
- Department of Cancer Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - Hiroshi Nakagawa
- Division of Gastroenterology, Departments of Medicine and Genetics and Abramson Cancer Center, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - Yoshiaki Kita
- Department of Digestive Surgery, and Breast and Thyroid Surgery, Kagoshima University School of Medicine, Sakuragaoka, Kagoshima, Japan
| | - Shoji Natsugoe
- Department of Digestive Surgery, and Breast and Thyroid Surgery, Kagoshima University School of Medicine, Sakuragaoka, Kagoshima, Japan
| | - Yi Yang
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, South Carolina
| | - Zihai Li
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, South Carolina
| | - Mariusz Wasik
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania. Abramson Cancer Center, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, Pennsylvania
| | | | - Anil K Rustgi
- Division of Gastroenterology, Departments of Medicine and Genetics and Abramson Cancer Center, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania. Abramson Cancer Center, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, Pennsylvania
| | - J Alan Diehl
- Department of Cancer Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania.
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Abstract
Physical working capacity decreases with age and also in microgravity. Regardless of age, increased physical activity can always improve the physical adaptability of the body, although the mechanisms of this adaptability are unknown. Physical exercise produces various mechanical stimuli in the body, and these stimuli may be essential for cell survival in organisms. The cytoskeleton plays an important role in maintaining cell shape and tension development, and in various molecular and/or cellular organelles involved in cellular trafficking. Both intra and extracellular stimuli send signals through the cytoskeleton to the nucleus and modulate gene expression via an intrinsic property, namely the "dynamic instability" of cytoskeletal proteins. αB-crystallin is an important chaperone for cytoskeletal proteins in muscle cells. Decreases in the levels of αB-crystallin are specifically associated with a marked decrease in muscle mass (atrophy) in a rat hindlimb suspension model that mimics muscle and bone atrophy that occurs in space and increases with passive stretch. Moreover, immunofluorescence data show complete co-localization of αB-crystallin and the tubulin/microtubule system in myoblast cells. This association was further confirmed in biochemical experiments carried out in vitro showing that αB-crystallin acts as a chaperone for heat-denatured tubulin and prevents microtubule disassembly induced by calcium. Physical activity induces the constitutive expression of αB-crystallin, which helps to maintain the homeostasis of cytoskeleton dynamics in response to gravitational forces. This relationship between chaperone expression levels and regulation of cytoskeletal dynamics observed in slow anti-gravitational muscles as well as in mammalian striated muscles, such as those in the heart, diaphragm and tongue, may have been especially essential for human evolution in particular. Elucidation of the intrinsic properties of the tubulin/microtubule and chaperone αB-crystallin protein complex systems is expected to provide valuable information for high-pressure bioscience and gravity health science.
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Affiliation(s)
- Yoriko Atomi
- 204 Research Center for Science and Technology, Tokyo University of Agriculture and Technology, Koganei-shi, Tokyo, 184-8588, Japan,
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127
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Arrigo AP, Ducarouge B, Lavial F, Gibert B. Immense Cellular Implications Associated to Small Stress Proteins Expression: Impacts on Human Pathologies. HEAT SHOCK PROTEINS 2015. [DOI: 10.1007/978-3-319-16077-1_2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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128
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Der Perng M, Quinlan RA. The Dynamic Duo of Small Heat Proteins and IFs Maintain Cell Homeostasis, Resist Cellular Stress and Enable Evolution in Cells and Tissues. HEAT SHOCK PROTEINS 2015. [DOI: 10.1007/978-3-319-16077-1_17] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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129
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Bakthisaran R, Tangirala R, Rao CM. Small heat shock proteins: Role in cellular functions and pathology. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1854:291-319. [PMID: 25556000 DOI: 10.1016/j.bbapap.2014.12.019] [Citation(s) in RCA: 325] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Revised: 12/16/2014] [Accepted: 12/18/2014] [Indexed: 01/18/2023]
Abstract
Small heat shock proteins (sHsps) are conserved across species and are important in stress tolerance. Many sHsps exhibit chaperone-like activity in preventing aggregation of target proteins, keeping them in a folding-competent state and refolding them by themselves or in concert with other ATP-dependent chaperones. Mutations in human sHsps result in myopathies, neuropathies and cataract. Their expression is modulated in diseases such as Alzheimer's, Parkinson's and cancer. Their ability to bind Cu2+, and suppress generation of reactive oxygen species (ROS) may have implications in Cu2+-homeostasis and neurodegenerative diseases. Circulating αB-crystallin and Hsp27 in the plasma may exhibit immunomodulatory and anti-inflammatory functions. αB-crystallin and Hsp20 exhitbit anti-platelet aggregation: these beneficial effects indicate their use as potential therapeutic agents. sHsps have roles in differentiation, proteasomal degradation, autophagy and development. sHsps exhibit a robust anti-apoptotic property, involving several stages of mitochondrial-mediated, extrinsic apoptotic as well as pro-survival pathways. Dynamic N- and C-termini and oligomeric assemblies of αB-crystallin and Hsp27 are important factors for their functions. We propose a "dynamic partitioning hypothesis" for the promiscuous interactions and pleotropic functions exhibited by sHsps. Stress tolerance and anti-apoptotic properties of sHsps have both beneficial and deleterious consequences in human health and diseases. Conditional and targeted modulation of their expression and/or activity could be used as strategies in treating several human disorders. The review attempts to provide a critical overview of sHsps and their divergent roles in cellular processes particularly in the context of human health and disease.
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Affiliation(s)
- Raman Bakthisaran
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Ramakrishna Tangirala
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Ch Mohan Rao
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.
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130
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Gong Y, Chan TA. Molecular mechanisms orchestrating cyclin stability. Cell Cycle 2014; 13:2487-8. [PMID: 25486187 DOI: 10.4161/15384101.2014.946376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- Yongxing Gong
- a Human Oncology and Pathogenesis Program; Memorial Sloan Kettering Cancer Center ; New York , NY USA
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131
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Domitrović R, Cvijanović O, Šušnić V, Katalinić N. Renoprotective mechanisms of chlorogenic acid in cisplatin-induced kidney injury. Toxicology 2014; 324:98-107. [DOI: 10.1016/j.tox.2014.07.004] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 07/07/2014] [Accepted: 07/08/2014] [Indexed: 12/21/2022]
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132
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Soppa U, Schumacher J, Florencio Ortiz V, Pasqualon T, Tejedor FJ, Becker W. The Down syndrome-related protein kinase DYRK1A phosphorylates p27(Kip1) and Cyclin D1 and induces cell cycle exit and neuronal differentiation. Cell Cycle 2014; 13:2084-100. [PMID: 24806449 PMCID: PMC4111700 DOI: 10.4161/cc.29104] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 05/02/2014] [Accepted: 05/03/2014] [Indexed: 01/12/2023] Open
Abstract
A fundamental question in neurobiology is how the balance between proliferation and differentiation of neuronal precursors is maintained to ensure that the proper number of brain neurons is generated. Substantial evidence implicates DYRK1A (dual specificity tyrosine-phosphorylation-regulated kinase 1A) as a candidate gene responsible for altered neuronal development and brain abnormalities in Down syndrome. Recent findings support the hypothesis that DYRK1A is involved in cell cycle control. Nonetheless, how DYRK1A contributes to neuronal cell cycle regulation and thereby affects neurogenesis remains poorly understood. In the present study we have investigated the mechanisms by which DYRK1A affects cell cycle regulation and neuronal differentiation in a human cell model, mouse neurons, and mouse brain. Dependent on its kinase activity and correlated with the dosage of overexpression, DYRK1A blocked proliferation of SH-SY5Y neuroblastoma cells within 24 h and arrested the cells in G₁ phase. Sustained overexpression of DYRK1A induced G₀ cell cycle exit and neuronal differentiation. Furthermore, we provide evidence that DYRK1A modulated protein stability of cell cycle-regulatory proteins. DYRK1A reduced cellular Cyclin D1 levels by phosphorylation on Thr286, which is known to induce proteasomal degradation. In addition, DYRK1A phosphorylated p27(Kip1) on Ser10, resulting in protein stabilization. Inhibition of DYRK1A kinase activity reduced p27(Kip1) Ser10 phosphorylation in cultured hippocampal neurons and in embryonic mouse brain. In aggregate, these results suggest a novel mechanism by which overexpression of DYRK1A may promote premature neuronal differentiation and contribute to altered brain development in Down syndrome.
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Affiliation(s)
- Ulf Soppa
- Institute of Pharmacology and Toxicology; Medical Faculty; RWTH Aachen University; Aachen, Germany
- Instituto de Neurociencias; Consejo Superior de Investigaciones Cientificas (CSIC) and Universidad Miguel Hernandez; Alicante, Spain
| | - Julian Schumacher
- Institute of Pharmacology and Toxicology; Medical Faculty; RWTH Aachen University; Aachen, Germany
| | - Victoria Florencio Ortiz
- Instituto de Neurociencias; Consejo Superior de Investigaciones Cientificas (CSIC) and Universidad Miguel Hernandez; Alicante, Spain
| | - Tobias Pasqualon
- Institute of Pharmacology and Toxicology; Medical Faculty; RWTH Aachen University; Aachen, Germany
| | - Francisco J Tejedor
- Instituto de Neurociencias; Consejo Superior de Investigaciones Cientificas (CSIC) and Universidad Miguel Hernandez; Alicante, Spain
| | - Walter Becker
- Institute of Pharmacology and Toxicology; Medical Faculty; RWTH Aachen University; Aachen, Germany
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133
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Pan-cancer genetic analysis identifies PARK2 as a master regulator of G1/S cyclins. Nat Genet 2014; 46:588-94. [PMID: 24793136 DOI: 10.1038/ng.2981] [Citation(s) in RCA: 138] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 04/11/2014] [Indexed: 12/15/2022]
Abstract
Coordinate control of different classes of cyclins is fundamentally important for cell cycle regulation and tumor suppression, yet the underlying mechanisms are incompletely understood. Here we show that the PARK2 tumor suppressor mediates this coordination. The PARK2 E3 ubiquitin ligase coordinately controls the stability of both cyclin D and cyclin E. Analysis of approximately 5,000 tumor genomes shows that PARK2 is a very frequently deleted gene in human cancer and uncovers a striking pattern of mutual exclusivity between PARK2 deletion and amplification of CCND1, CCNE1 or CDK4-implicating these genes in a common pathway. Inactivation of PARK2 results in the accumulation of cyclin D and acceleration of cell cycle progression. Furthermore, PARK2 is a component of a new class of cullin-RING-containing ubiquitin ligases targeting both cyclin D and cyclin E for degradation. Thus, PARK2 regulates cyclin-CDK complexes, as does the CDK inhibitor p16, but acts as a master regulator of the stability of G1/S cyclins.
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134
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Koo J, Yue P, Gal AA, Khuri FR, Sun SY. Maintaining glycogen synthase kinase-3 activity is critical for mTOR kinase inhibitors to inhibit cancer cell growth. Cancer Res 2014; 74:2555-2568. [PMID: 24626091 PMCID: PMC4029841 DOI: 10.1158/0008-5472.can-13-2946] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
mTOR kinase inhibitors that target both mTORC1 and mTORC2 are being evaluated in cancer clinical trials. Here, we report that glycogen synthase kinase-3 (GSK3) is a critical determinant for the therapeutic response to this class of experimental drugs. Pharmacologic inhibition of GSK3 antagonized their suppressive effects on the growth of cancer cells similarly to genetic attenuation of GSK3. Conversely, expression of a constitutively activated form of GSK3β sensitized cancer cells to mTOR inhibition. Consistent with these findings, higher basal levels of GSK3 activity in a panel of human lung cancer cell lines correlated with more efficacious responses. Mechanistic investigations showed that mTOR kinase inhibitors reduced cyclin D1 levels in a GSK3β-dependent manner, independent of their effects on suppressing mTORC1 signaling and cap binding. Notably, selective inhibition of mTORC2 triggered proteasome-mediated cyclin D1 degradation, suggesting that mTORC2 blockade is responsible for GSK3-dependent reduction of cyclin D1. Silencing expression of the ubiquitin E3 ligase FBX4 rescued this reduction, implicating FBX4 in mediating this effect of mTOR inhibition. Together, our findings define a novel mechanism by which mTORC2 promotes cell growth, with potential implications for understanding the clinical action of mTOR kinase inhibitors.
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Affiliation(s)
- Junghui Koo
- Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA
| | - Ping Yue
- Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA
| | - Anthony A. Gal
- Department of Pathology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA
| | - Fadlo R. Khuri
- Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA
| | - Shi-Yong Sun
- Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA
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135
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Li S, Song W, Jiang M, Zeng L, Zhu X, Chen J. Phosphorylation of cyclin Y by CDK14 induces its ubiquitination and degradation. FEBS Lett 2014; 588:1989-96. [PMID: 24794231 DOI: 10.1016/j.febslet.2014.04.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 04/05/2014] [Accepted: 04/13/2014] [Indexed: 02/06/2023]
Abstract
Cyclin Y, a membrane associated cyclin, is capable of binding and activating CDK14. Here we report that human cyclin Y (CCNY) is a phosphoprotein in vivo and that phosphorylation of CCNY by CDK14 triggers its ubiquitination and degradation. Inactivation of either CDK14 or Cul1 results in accumulation of CCNY. An in vivo and in vitro mapping of CCNY phosphorylation sites by mass spectrometry revealed that the flanking regions of the conserved cyclin box are heavily phosphorylated. Phosphorylation of CCNY at Serines 71 and 73 creates a putative phospho-degron that controls its association with an SCF complex. Mutation of serine to alanine at these two sites stabilized CCNY and enhanced the activity of CCNY/CDK14 on phosphorylation of LRP6. Our results provide insight into autoregulation of the cyclin Y/CDK14 pair in CDK14 activation and cyclin Y turnover which is a process that is involved in membrane proximal signaling.
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Affiliation(s)
- Shan Li
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China
| | - Wei Song
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China
| | - Mei Jiang
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China
| | - Liyong Zeng
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China
| | - Xueliang Zhu
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China
| | - Jiangye Chen
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China.
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136
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Chu X, Zhang T, Wang J, Li M, Zhang X, Tu J, Sun S, Chen X, Lu F. Alternative splicing variants of human Fbx4 disturb cyclin D1 proteolysis in human cancer. Biochem Biophys Res Commun 2014; 447:158-64. [DOI: 10.1016/j.bbrc.2014.03.129] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2014] [Accepted: 03/25/2014] [Indexed: 11/15/2022]
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137
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Abstract
F-box proteins, which are the substrate-recognition subunits of SKP1-cullin 1-F-box protein (SCF) E3 ligase complexes, have pivotal roles in multiple cellular processes through ubiquitylation and subsequent degradation of target proteins. Dysregulation of F-box protein-mediated proteolysis leads to human malignancies. Notably, inhibitors that target F-box proteins have shown promising therapeutic potential, urging us to review the current understanding of how F-box proteins contribute to tumorigenesis. As the physiological functions for many of the 69 putative F-box proteins remain elusive, additional genetic and mechanistic studies will help to define the role of each F-box protein in tumorigenesis, thereby paving the road for the rational design of F-box protein-targeted anticancer therapies.
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Affiliation(s)
- Zhiwei Wang
- 1] Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA. [2] The Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, the First Affiliated Hospital, Soochow University, Suzhou 215123, P. R. China. [3]
| | - Pengda Liu
- 1] Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA. [2]
| | - Hiroyuki Inuzuka
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA
| | - Wenyi Wei
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA
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138
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Kwun HJ, Shuda M, Feng H, Camacho CJ, Moore PS, Chang Y. Merkel cell polyomavirus small T antigen controls viral replication and oncoprotein expression by targeting the cellular ubiquitin ligase SCFFbw7. Cell Host Microbe 2014; 14:125-35. [PMID: 23954152 DOI: 10.1016/j.chom.2013.06.008] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 05/09/2013] [Accepted: 06/10/2013] [Indexed: 10/26/2022]
Abstract
Merkel cell polyomavirus (MCV) causes an aggressive human skin cancer, Merkel cell carcinoma, through expression of small T (sT) and large T (LT) viral oncoproteins. MCV sT is also required for efficient MCV DNA replication by the multifunctional MCV LT helicase protein. We find that LT is targeted for proteasomal degradation by the cellular SCF(Fbw7) E3 ligase, which can be inhibited by sT through its LT-stabilization domain (LSD). Consequently, sT also stabilizes cellular SCF(Fbw7) targets, including the cell-cycle regulators c-Myc and cyclin E. Mutating the sT LSD decreases LT protein levels and eliminates synergism in MCV DNA replication as well as sT-induced cell transformation. SCF(Fbw7) knockdown mimics sT-mediated stabilization of LT, but this knockdown is insufficient to fully reconstitute the transforming activity of a mutant LSD sT protein. Thus, MCV has evolved a regulatory system involving SCF(Fbw7) that controls viral replication but also contributes to host cell transformation.
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Affiliation(s)
- Hyun Jin Kwun
- Cancer Virology Program, University of Pittsburgh, Pittsburgh, PA 15213, USA
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139
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Abbas T, Keaton M, Dutta A. Regulation of TGF-β signaling, exit from the cell cycle, and cellular migration through cullin cross-regulation: SCF-FBXO11 turns off CRL4-Cdt2. Cell Cycle 2014; 12:2175-82. [PMID: 23892434 DOI: 10.4161/cc.25314] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Deregulation of the cell cycle and genome instability are common features of cancer cells and various mechanisms exist to preserve the integrity of the genome and guard against cancer. The cullin 4-RING ubiquitin ligase (CRL4) with the substrate receptor Cdt2 (CRL4 (Cdt2)) promotes cell cycle progression and prevents genome instability through ubiquitylation and degradation of Cdt1, p21, and Set8 during S phase of the cell cycle and following DNA damage. Two recently published studies report the ubiquitin-dependent degradation of Cdt2 via the cullin 1-RING ubiquitin ligase (CRL1) in association with the substrate specificity factor and tumor suppressor FBXO11 (CRL1 (FBXO11)). The newly identified pathway restrains the activity of CRL4 (Cdt2) on p21 and Set8 and regulates cellular response to TGF-β, exit from the cell cycle and cellular migration. Here, we show that the CRL1 (FBXO11) also promotes the degradation of Cdt2 during an unperturbed cell cycle to promote efficient progression through S and G 2/M phases of the cell cycle. We discuss how this new method of regulating the abundance of Cdt2 participates in various cellular activities.
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Affiliation(s)
- Tarek Abbas
- Department of Radiation Oncology; School of Medicine, University of Virginia, Charlottesville, VA, USA.
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140
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Arrigo AP, Gibert B. HspB1, HspB5 and HspB4 in Human Cancers: Potent Oncogenic Role of Some of Their Client Proteins. Cancers (Basel) 2014; 6:333-65. [PMID: 24514166 PMCID: PMC3980596 DOI: 10.3390/cancers6010333] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Revised: 01/03/2014] [Accepted: 01/17/2014] [Indexed: 12/20/2022] Open
Abstract
Human small heat shock proteins are molecular chaperones that regulate fundamental cellular processes in normal unstressed cells as well as in many cancer cells where they are over-expressed. These proteins are characterized by cell physiology dependent changes in their oligomerization and phosphorylation status. These structural changes allow them to interact with many different client proteins that subsequently display modified activity and/or half-life. Nowdays, the protein interactomes of small Hsps are under intense investigations and will represent, when completed, key parameters to elaborate therapeutic strategies aimed at modulating the functions of these chaperones. Here, we have analyzed the potential pro-cancerous roles of several client proteins that have been described so far to interact with HspB1 (Hsp27) and its close members HspB5 (αB-crystallin) and HspB4 (αA-crystallin).
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Affiliation(s)
- André-Patrick Arrigo
- Apoptosis, Cancer and Development Laboratory, Lyon Cancer Research Center, INSERM U1052-CNRS UMR5286, Claude Bernard University Lyon 1, Lyon 69008, France.
| | - Benjamin Gibert
- Apoptosis, Cancer and Development Laboratory, Lyon Cancer Research Center, INSERM U1052-CNRS UMR5286, Claude Bernard University Lyon 1, Lyon 69008, France.
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141
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Zhang Q, Sakamoto K, Wagner KU. D-type Cyclins are important downstream effectors of cytokine signaling that regulate the proliferation of normal and neoplastic mammary epithelial cells. Mol Cell Endocrinol 2014; 382:583-592. [PMID: 23562856 PMCID: PMC3740091 DOI: 10.1016/j.mce.2013.03.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 03/19/2013] [Indexed: 02/07/2023]
Abstract
In response to the ligand-mediated activation of cytokine receptors, cells decide whether to proliferate or to undergo differentiation. D-type Cyclins (Cyclin D1, D2, or D3) and their associated Cyclin-dependent kinases (CDK4, CDK6) connect signals from cytokines to the cell cycle machinery, and they propel cells through the G1 restriction point and into the S phase, after which growth factor stimulation is no longer essential to complete cell division. D-type Cyclins are upregulated in many human malignancies including breast cancer to promote an uncontrolled proliferation of cancer cells. After summarizing important aspects of the cytokine-mediated transcriptional regulation and the posttranslational modification of D-type Cyclins, this review will highlight the physiological significance of these cell cycle regulators during normal mammary gland development as well as the initiation and promotion of breast cancer. Although the vast majority of published reports focus almost exclusively on the role of Cyclin D1 in breast cancer, we summarize here previous and recent findings that demonstrate an important contribution of the remaining two members of this Cyclin family, in particular Cyclin D3, for the growth of ErbB2-associated breast cancer cells in humans and in mouse models. New data from genetically engineered models as well as the pharmacological inhibition of CDK4/6 suggest that targeting the combined functions of D-type Cyclins could be a suitable strategy for the treatment of ErbB2-positive and potentially other types of breast cancer.
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Affiliation(s)
- Qian Zhang
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, 985950 Nebraska Medical Center, Omaha, NE 68198-5950, USA
| | - Kazuhito Sakamoto
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, 985950 Nebraska Medical Center, Omaha, NE 68198-5950, USA
| | - Kay-Uwe Wagner
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, 985950 Nebraska Medical Center, Omaha, NE 68198-5950, USA; Department of Pathology and Microbiology, University of Nebraska Medical Center, 985950 Nebraska Medical Center, Omaha, NE 68198-5950, USA.
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142
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Boularan C, Kamenyeva O, Cho H, Kehrl JH. Resistance to inhibitors of cholinesterase (Ric)-8A and Gαi contribute to cytokinesis abscission by controlling vacuolar protein-sorting (Vps)34 activity. PLoS One 2014; 9:e86680. [PMID: 24466196 PMCID: PMC3897744 DOI: 10.1371/journal.pone.0086680] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 12/12/2013] [Indexed: 11/18/2022] Open
Abstract
Resistance to inhibitors of cholinesterase (Ric)-8A is a guanine nucleotide exchange factor for Gαi, Gαq, and Gα12/13, which is implicated in cell signaling and as a molecular chaperone required for the initial association of nascent Gα subunits with cellular membranes. Ric-8A, Gαi subunits, and their regulators are localized at the midbody prior to abscission and linked to the final stages of cell division. Here, we identify a molecular mechanism by which Ric-8A affects cytokinesis and abscission by controlling Vps34 activity. We showed that Ric-8A protein expression is post-transcriptionally controlled during the cell cycle reaching its maximum levels at mitosis. A FRET biosensor created to measure conformational changes in Ric-8A by FLIM (Fluorescence Lifetime Imaging Microscopy) revealed that Ric-8A was in a close-state during mitosis and particularly so at cytokinesis. Lowering Ric-8A expression delayed the abscission time of dividing cells, which correlated with increased intercellular bridge length and multinucleation. During cytokinesis, Ric-8A co-localized with Vps34 at the midbody along with Gαi and LGN, where these proteins functioned to regulate Vps34 phosphatidylinositol 3-kinase activity.
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Affiliation(s)
- Cedric Boularan
- B-cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Olena Kamenyeva
- B-cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Hyeseon Cho
- B-cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - John H. Kehrl
- B-cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
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143
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Abstract
Cell division is controlled by a highly regulated program to accurately duplicate and segregate chromosomes. An important feature of the cell cycle regulatory program is that key cell cycle proteins are present and active during specific cell cycle stages but are later removed or inhibited to maintain appropriate timing. The ubiquitin-proteasome system has emerged as an important mechanism to target cell cycle proteins for degradation at critical junctures during cell division. Two key E3 ubiquitin ligase complexes that target key cell cycle proteins are the Skp1-Cul1-F-box protein complex and the anaphase-promoting complex/cyclosome. This chapter focuses on the role of these E3 ubiquitin ligases and how ubiquitin-dependent degradation of central cell cycle regulatory proteins advances the cell cycle.
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Affiliation(s)
- Deanna M Koepp
- Department of Genetics, Cell Biology and Development, University of Minnesota, 6-160 Jackson Hall, 321 Church St SE, Minneapolis, MN, 55455, USA,
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144
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A comparative analysis of the ubiquitination kinetics of multiple degrons to identify an ideal targeting sequence for a proteasome reporter. PLoS One 2013; 8:e78082. [PMID: 24205101 PMCID: PMC3812159 DOI: 10.1371/journal.pone.0078082] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2013] [Accepted: 09/09/2013] [Indexed: 01/03/2023] Open
Abstract
The ubiquitin proteasome system (UPS) is the primary pathway responsible for the recognition and degradation of misfolded, damaged, or tightly regulated proteins. The conjugation of a polyubiquitin chain, or polyubiquitination, to a target protein requires an increasingly diverse cascade of enzymes culminating with the E3 ubiquitin ligases. Protein recognition by an E3 ligase occurs through a specific sequence of amino acids, termed a degradation sequence or degron. Recently, degrons have been incorporated into novel reporters to monitor proteasome activity; however only a limited few degrons have successfully been incorporated into such reporters. The goal of this work was to evaluate the ubiquitination kinetics of a small library of portable degrons that could eventually be incorporated into novel single cell reporters to assess proteasome activity. After an intensive literary search, eight degrons were identified from proteins recognized by a variety of E3 ubiquitin ligases and incorporated into a four component degron-based substrate to comparatively calculate ubiquitination kinetics. The mechanism of placement of multiple ubiquitins on the different degron-based substrates was assessed by comparing the data to computational models incorporating first order reaction kinetics using either multi-monoubiquitination or polyubiquitination of the degron-based substrates. A subset of three degrons was further characterized to determine the importance of the location and proximity of the ubiquitination site lysine with respect to the degron. Ultimately, this work identified three candidate portable degrons that exhibit a higher rate of ubiquitination compared to peptidase-dependent degradation, a desired trait for a proteasomal targeting motif.
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145
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Lu A, Pfeffer SR. Golgi-associated RhoBTB3 targets cyclin E for ubiquitylation and promotes cell cycle progression. ACTA ACUST UNITED AC 2013; 203:233-50. [PMID: 24145166 PMCID: PMC3812982 DOI: 10.1083/jcb.201305158] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The Golgi protein RhoBTB3 in complex with CUL3 and RBX1 promotes Cyclin E ubiquitylation to allow its turnover during S phase and progression through the cell cycle. Cyclin E regulates the cell cycle transition from G1 to S phase and is degraded before entry into G2 phase. Here we show that RhoBTB3, a Golgi-associated, Rho-related ATPase, regulates the S/G2 transition of the cell cycle by targeting Cyclin E for ubiquitylation. Depletion of RhoBTB3 arrested cells in S phase, triggered Golgi fragmentation, and elevated Cyclin E levels. On the Golgi, RhoBTB3 bound Cyclin E as part of a Cullin3 (CUL3)-dependent RING–E3 ubiquitin ligase complex comprised of RhoBTB3, CUL3, and RBX1. Golgi association of this complex was required for its ability to catalyze Cyclin E ubiquitylation and allow normal cell cycle progression. These experiments reveal a novel role for a Ras superfamily member in catalyzing Cyclin E turnover during S phase, as well as an unexpected, essential role for the Golgi as a ubiquitylation platform for cell cycle control.
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Affiliation(s)
- Albert Lu
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305
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146
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Neumann J, Boerries M, Köhler R, Giaisi M, Krammer PH, Busch H, Li-Weber M. The natural anticancer compound rocaglamide selectively inhibits the G1-S-phase transition in cancer cells through the ATM/ATR-mediated Chk1/2 cell cycle checkpoints. Int J Cancer 2013; 134:1991-2002. [PMID: 24150948 DOI: 10.1002/ijc.28521] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 09/19/2013] [Indexed: 02/03/2023]
Abstract
Targeting the cancer cell cycle machinery is an important strategy for cancer treatment. Cdc25A is an essential regulator of cycle progression and checkpoint response. Over-expression of Cdc25A occurs often in human cancers. In this study, we show that Rocaglamide-A (Roc-A), a natural anticancer compound isolated from the medicinal plant Aglaia, induces a rapid phosphorylation of Cdc25A and its subsequent degradation and, thereby, blocks cell cycle progression of tumor cells at the G1-S phase. Roc-A has previously been shown to inhibit tumor proliferation by blocking protein synthesis. In this study, we demonstrate that besides the translation inhibition Roc-A can induce a rapid degradation of Cdc25A by activation of the ATM/ATR-Chk1/Chk2 checkpoint pathway. However, Roc-A has no influence on cell cycle progression in proliferating normal T lymphocytes. Investigation of the molecular basis of tumor selectivity of Roc-A by a time-resolved microarray analysis of leukemic vs. proliferating normal T lymphocytes revealed that Roc-A activates different sets of genes in tumor cells compared with normal cells. In particular, Roc-A selectively stimulates a set of genes responsive to DNA replication stress in leukemic but not in normal T lymphocytes. These findings further support the development of Rocaglamide for antitumor therapy.
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Affiliation(s)
- Jennifer Neumann
- Tumorimmunology Program (D030), German Cancer Research Center (DKFZ), Heidelberg, Germany
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147
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Crowe J, Aubareda A, McNamee K, Przybycien PM, Lu X, Williams RO, Bou-Gharios G, Saklatvala J, Dean JLE. Heat shock protein B1-deficient mice display impaired wound healing. PLoS One 2013; 8:e77383. [PMID: 24143227 PMCID: PMC3797036 DOI: 10.1371/journal.pone.0077383] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 09/05/2013] [Indexed: 01/27/2023] Open
Abstract
There is large literature describing in vitro experiments on heat shock protein (hsp)B1 but understanding of its function in vivo is limited to studies in mice overexpressing human hspB1 protein. Experiments in cells have shown that hspB1 has chaperone activity, a cytoprotective role, regulates inflammatory gene expression, and drives cell proliferation. To investigate the function of the protein in vivo we generated hspB1-deficient mice. HspB1-deficient fibroblasts display increased expression of the pro-inflammatory cytokine, interleukin-6, compared to wild-type cells, but reduced proliferation. HspB1-deficient fibroblasts exhibit reduced entry into S phase and increased expression of cyclin-dependent kinase inhibitors p27(kip1) and p21(waf1). The expression of hspB1 protein and mRNA is also controlled by the cell cycle. To investigate the physiological function of hspB1 in regulating inflammation and cell proliferation we used an excisional cutaneous wound healing model. There was a significant impairment in the rate of healing of wounds in hspB1-deficient mice, characterised by reduced re-epithelialisation and collagen deposition but also increased inflammation. HspB1 deficiency augments neutrophil infiltration in wounds, driven by increased chemokine (C-X-C motif) ligand 1 expression. This appears to be a general mechanism as similar results were obtained in the air-pouch and peritonitis models of acute inflammation.
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Affiliation(s)
- Jonathan Crowe
- Department of Medicine, Imperial College London, London, United Kingdom
| | - Anna Aubareda
- Kennedy Institute of Rheumatology, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom
| | - Kay McNamee
- Kennedy Institute of Rheumatology, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom
| | - Paulina M. Przybycien
- Kennedy Institute of Rheumatology, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom
| | - Xin Lu
- The Ludwig Institute for Cancer Research, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom
| | - Richard O. Williams
- Kennedy Institute of Rheumatology, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom
| | - George Bou-Gharios
- Kennedy Institute of Rheumatology, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom
| | - Jeremy Saklatvala
- Kennedy Institute of Rheumatology, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom
| | - Jonathan L. E. Dean
- Kennedy Institute of Rheumatology, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom
- * E-mail:
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148
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Achiwa Y, Hasegawa K, Udagawa Y. Effect of ursolic acid on MAPK in cyclin D1 signaling and RING-type E3 ligase (SCF E3s) in two endometrial cancer cell lines. Nutr Cancer 2013; 65:1026-33. [PMID: 24083669 DOI: 10.1080/01635581.2013.810292] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Cyclin D1 regulates G1 progression and is important in the development and proliferation of various human cancers. Cyclin D1 gene expression is activated by the Ras kinase cascade. Nuclear cyclin D1 levels are dependent on cytoplasmic degradation of cyclin D1 via ubiquitin-mediated proteolysis. We sought to determine whether the important MAPK signaling pathway, in the cyclin D1 cascade, including FBXW8, Cullin1, and the ubiquitination pathway mediated these effects. Ursolic acid (UA) treatment of SNG-2 cells, an endometrial cancer cell line, decreased cyclin D1, pERK1/2, FBXW8, and Cullin1 levels in a dose- and time-dependent manner. RING-type E3 ligase consists of CulIin1, Rbx, Skp1, and a member of the F-box protein family. In SNG-2, both dose- and time-dependent inhibition of Rbx 1 were observed following treatment with UA. Moreover, in HEC108 cells, another endometrial cancer cell line, UA treatment decreased cyclin D1, pERK1/2, and Cullin1 levels in a dose- and time-dependent manner and UA markedly inhibited FBXW8. Treatment of HEC108 cells moderately decreased Rbx1 in a dose- and-time-dependent fashion. In contrast, UA treatment increased ubiquitinated proteins in a dose- and time-dependent manner in both cell lines. RING-type E3 ligase accumulated in the cytoplasm following UA treatment of SNG-2cells. That in turn prevented cytoplasmic degradation of cyclin D1 via RING-type E3 (SCF E3s) ligase. In conclusion, our study found inhibition of the MAPK- cyclin D1 pathway and RING type E3 ligase (SCF E3s) in both endometrial cancer cell lines. Furthermore, CD36 was noted as a cell surface receptor for UA.
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Affiliation(s)
- Yumiko Achiwa
- a Faculty of Obstetrics and Gynecology, School of Medicine, Fujita Health University , Toyoake , Aichi , Japan
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149
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Regulated structural transitions unleash the chaperone activity of αB-crystallin. Proc Natl Acad Sci U S A 2013; 110:E3780-9. [PMID: 24043785 DOI: 10.1073/pnas.1308898110] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The small heat shock protein αB-crystallin is an oligomeric molecular chaperone that binds aggregation-prone proteins. As a component of the proteostasis system, it is associated with cataract, neurodegenerative diseases, and myopathies. The structural determinants for the regulation of its chaperone function are still largely elusive. Combining different experimental approaches, we show that phosphorylation-induced destabilization of intersubunit interactions mediated by the N-terminal domain (NTD) results in the remodeling of the oligomer ensemble with an increase in smaller, activated species, predominantly 12-mers and 6-mers. Their 3D structures determined by cryo-electron microscopy and biochemical analyses reveal that the NTD in these species gains flexibility and solvent accessibility. These modulated properties are accompanied by an increase in chaperone activity in vivo and in vitro and a more efficient cooperation with the heat shock protein 70 system in client folding. Thus, the modulation of the structural flexibility of the NTD, as described here for phosphorylation, appears to regulate the chaperone activity of αB-crystallin rendering the NTD a conformational sensor for nonnative proteins.
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150
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The FBXO4 tumor suppressor functions as a barrier to BRAFV600E-dependent metastatic melanoma. Mol Cell Biol 2013; 33:4422-33. [PMID: 24019069 DOI: 10.1128/mcb.00706-13] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Cyclin D1-cyclin-dependent kinase 4/6 (CDK4/6) dysregulation is a major contributor to melanomagenesis. Clinical evidence has revealed that p16(INK4A), an allosteric inhibitor of CDK4/6, is inactivated in over half of human melanomas, and numerous animal models have demonstrated that p16(INK4A) deletion promotes melanoma. FBXO4, a specificity factor for the E3 ligase that directs timely cyclin D1 proteolysis, has not been studied in melanoma. We demonstrate that Fbxo4 deficiency induces Braf-driven melanoma and that this phenotype depends on cyclin D1 accumulation in mice, underscoring the importance of this ubiquitin ligase in tumor suppression. Furthermore, we have identified a substrate-binding mutation, FBXO4 I377M, that selectively disrupts cyclin D1 degradation while preserving proteolysis of the other known FBXO4 substrate, TRF1. The I377M mutation and Fbxo4 deficiency result in nuclear accumulation of cyclin D1, a key transforming neoplastic event. Collectively, these data provide evidence that FBXO4 dysfunction, as a mechanism for cyclin D1 overexpression, is a contributor to human malignancy.
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