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Vu NT, Kim M, Stephenson DJ, MacKnight HP, Chalfant CE. Ceramide Kinase Inhibition Drives Ferroptosis and Sensitivity to Cisplatin in Mutant KRAS Lung Cancer by Dysregulating VDAC-Mediated Mitochondria Function. Mol Cancer Res 2022; 20:1429-1442. [PMID: 35560154 PMCID: PMC9444881 DOI: 10.1158/1541-7786.mcr-22-0085] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 04/15/2022] [Accepted: 05/11/2022] [Indexed: 11/16/2022]
Abstract
Ceramide kinase (CERK) is the mammalian lipid kinase from which the bioactive sphingolipid, ceramide-1-phosphate (C1P), is derived. CERK has been implicated in several promalignant phenotypes with little known as to mechanistic underpinnings. In this study, the mechanism of how CERK inhibition decreases cell survival in mutant (Mut) KRAS non-small cell lung cancer (NSCLC), a major lung cancer subtype, was revealed. Specifically, NSCLC cells possessing a KRAS mutation were more responsive to inhibition, downregulation, and genetic ablation of CERK compared with those with wild-type (WT) KRAS regarding a reduction in cell survival. Inhibition of CERK induced ferroptosis in Mut KRAS NSCLC cells, which required elevating VDAC-regulated mitochondria membrane potential (MMP) and the generation of cellular reactive oxygen species (ROS). Importantly, through modulation of VDAC, CERK inhibition synergized with the first-line NSCLC treatment, cisplatin, in reducing cell survival and in vivo tumor growth. Further mechanistic studies indicated that CERK inhibition affected MMP and cell survival by limiting AKT activation and translocation to mitochondria, and thus, blocking VDAC phosphorylation and tubulin recruitment. IMPLICATIONS Our findings depict how CERK inhibition may serve as a new key point in combination therapeutic strategy for NSCLC, specifically precision therapeutics targeting NSCLC possessing a KRAS mutation.
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Affiliation(s)
- Ngoc T. Vu
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, USA,Institute of Biotechnology and Food Technology, Industrial University of Ho Chi Minh City, Vietnam
| | - Minjung Kim
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, USA
| | - Daniel J. Stephenson
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, USA,Department of Medicine, Division of Hematology & Oncology, University of Virginia, Charlottesville, VA, 22903
| | - H. Patrick MacKnight
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, USA,Department of Medicine, Division of Hematology & Oncology, University of Virginia, Charlottesville, VA, 22903
| | - Charles E. Chalfant
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, USA,Department of Medicine, Division of Hematology & Oncology, University of Virginia, Charlottesville, VA, 22903,Department of Cell Biology, University of Virginia, Charlottesville, VA, 22903,Program in Cancer Biology, University of Virginia Cancer Center, Charlottesville, VA, 22903,Research Service, Richmond Veterans Administration Medical Center, Richmond VA, 23298,To whom correspondence should be addressed: Charles E. Chalfant, Professor, Department of Medicine, Division of Hematology & Oncology, P.O. Box 801398, University of Virginia, Charlottesville, VA, 22903, or
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2
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Geetha N, Bhavya G, Abhijith P, Shekhar R, Dayananda K, Jogaiah S. Insights into nanomycoremediation: Secretomics and mycogenic biopolymer nanocomposites for heavy metal detoxification. JOURNAL OF HAZARDOUS MATERIALS 2021; 409:124541. [PMID: 33223321 DOI: 10.1016/j.jhazmat.2020.124541] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 10/02/2020] [Accepted: 11/06/2020] [Indexed: 05/21/2023]
Abstract
Our environment thrives on the subtle balance achieved by the forever cyclical nature of building and rebuilding life through natural processes. Fungi, being the evident armor of bioremediation, is the indispensable element of the soil food web, contribute to be the nature's most dynamic arsenal with non-specific enzymes like peroxidase (POX), glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), non-enzymatic compounds like thiol (-SH) groups and non-protein compounds such as glutathione (GSH) and metallothionein (MT). Recently, the area of nanomycoremediation has been gaining momentum as a powerful tool for environmental clean-up strategies with its ability to detoxify heavy metals with its unique characteristics to adapt mechanisms such as biosorption, bioconversion, and biodegradation to harmless end products. The insight into the elaborate secretomic processes provides us with huge opportunities for creating a magnificent living bioremediation apparatus. This review discusses the scope and recent advances in the lesser understood area, nanomycoremediation, the state-of-the-art, innovative, cost-effective and promising tool for detoxification of heavy metal pollutants and focuses on the metabolic capabilities and secretomics with nanobiotechnological interventions.
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Affiliation(s)
- Nagaraja Geetha
- Nanobiotechnology Laboratory, Department of Studies in Biotechnology, University of Mysore, Manasagangotri, Mysuru 570006, Karnataka, India
| | - Gurulingaiah Bhavya
- Nanobiotechnology Laboratory, Department of Studies in Biotechnology, University of Mysore, Manasagangotri, Mysuru 570006, Karnataka, India
| | - Padukana Abhijith
- Nanobiotechnology Laboratory, Department of Studies in Biotechnology, University of Mysore, Manasagangotri, Mysuru 570006, Karnataka, India
| | - Ravikant Shekhar
- Nanobiotechnology Laboratory, Department of Studies in Biotechnology, University of Mysore, Manasagangotri, Mysuru 570006, Karnataka, India
| | - Karigowda Dayananda
- Nanobiotechnology Laboratory, Department of Studies in Biotechnology, University of Mysore, Manasagangotri, Mysuru 570006, Karnataka, India
| | - Sudisha Jogaiah
- Laboratory of Plant Healthcare and Diagnostics, P.G. Department of Biotechnology and Microbiology, Karnatak University, Dharwad 580003, Karnataka, India.
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Pareja F, Toss MS, Geyer FC, da Silva EM, Vahdatinia M, Sebastiao APM, Selenica P, Szatrowski A, Edelweiss M, Wen HY, Mihai R, Varga Z, Foschini MP, Rubin BP, Ellis IO, Chandarlapaty S, Jungbluth AA, Brogi E, Weigelt B, Reis-Filho JS, Rakha EA. Immunohistochemical assessment of HRAS Q61R mutations in breast adenomyoepitheliomas. Histopathology 2021; 76:865-874. [PMID: 31887226 DOI: 10.1111/his.14057] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Revised: 12/27/2019] [Accepted: 12/29/2019] [Indexed: 12/13/2022]
Abstract
AIMS Breast adenomyoepitheliomas (AMEs) are uncommon tumours. Most oestrogen receptor (ER)-positive AMEs have mutations in phosphoinositide 3-kinase (PI3K) pathway genes, whereas ER-negative AMEs usually harbour concurrent mutations affecting the HRAS Q61 hotspot and PI3K pathway genes. Here, we sought to determine the sensitivity and specificity of RAS Q61R immunohistochemical (IHC) analysis for detection of HRAS Q61R mutations in AMEs. METHODS AND RESULTS Twenty-six AMEs (14 ER-positive; 12 ER-negative) previously subjected to massively parallel sequencing (n = 21) or Sanger sequencing (n = 5) of the HRAS Q61 hotspot locus were included in this study. All AMEs were subjected to IHC analysis with a monoclonal (SP174) RAS Q61R-specific antibody, in addition to detailed histopathological analysis. Nine ER-negative AMEs harboured HRAS mutations, including Q61R (n = 7) and Q61K (n = 2) mutations. Five of seven (71%) AMEs with HRAS Q61R mutations were immunohistochemically positive, whereas none of the AMEs lacking HRAS Q61R mutations (n = 17) were immunoreactive. RAS Q61R immunoreactivity was restricted to the myoepithelium in 80% (4/5) of cases, whereas one case showed immunoreactivity in both the epithelial component and the myoepithelial component. RAS Q61R immunohistochemically positive AMEs were associated with infiltrative borders (P < 0.001), necrosis (P < 0.01) and mitotic index in the epithelial (P < 0.05) and myoepithelial (P < 0.01) components. RAS Q61R IHC assessment did not reveal Q61K mutations (0/2). CONCLUSIONS IHC analysis of RAS Q61R shows high specificity (100%) and moderate sensitivity (71%) for detection of HRAS Q61R mutations in breast AMEs, and appears not to detect HRAS Q61K mutations. IHC analysis of RAS Q61R may constitute a useful technique in the diagnostic workup of ER-negative AMEs.
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Affiliation(s)
- Fresia Pareja
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Michael S Toss
- Department of Histopathology, Nottingham University Hospitals NHS Trust, Nottingham, UK
| | - Felipe C Geyer
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Edaise M da Silva
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Mahsa Vahdatinia
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | | | - Pier Selenica
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Austin Szatrowski
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Marcia Edelweiss
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Hannah Y Wen
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Raluca Mihai
- Department of Histopathology, Nottingham University Hospitals NHS Trust, Nottingham, UK
| | - Zsuzsanna Varga
- Institute of Surgical Pathology, University Hospital Zurich, Zurich, Switzerland
| | - Maria P Foschini
- Department of Biomedical and Neuromotor Sciences, Section of Anatomical Pathology, Bellaria Hospital, University of Bologna, Bologna, Italy
| | - Brian P Rubin
- Department of Pathology, Cleveland Clinic, Cleveland, OH, USA
| | - Ian O Ellis
- Department of Histopathology, Nottingham University Hospitals NHS Trust, Nottingham, UK
| | - Sarat Chandarlapaty
- Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Achim A Jungbluth
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Edi Brogi
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Britta Weigelt
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Jorge S Reis-Filho
- Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Emad A Rakha
- Department of Histopathology, Nottingham University Hospitals NHS Trust, Nottingham, UK
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Xu Z, Duan F, Lu H, Abdulkadhim Dragh M, Xia Y, Liang H, Hong L. UBIAD1 suppresses the proliferation of bladder carcinoma cells by regulating H-Ras intracellular trafficking via interaction with the C-terminal domain of H-Ras. Cell Death Dis 2018; 9:1170. [PMID: 30518913 PMCID: PMC6281600 DOI: 10.1038/s41419-018-1215-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 10/28/2018] [Accepted: 10/30/2018] [Indexed: 12/13/2022]
Abstract
UbiA prenyltransferase domain-containing protein 1 (UBIAD1) plays a key role in biosynthesis of vitamin K2 and coenzyme Q10 using geranylgeranyl diphosphate (GGPP). However, the mechanism by which UBIAD1 participates in tumorigenesis remains unknown. This study show that UBIAD1 interacts with H-Ras, retains H-Ras in the Golgi apparatus, prevents H-Ras trafficking from the Golgi apparatus to the plasma membrane, blocks the aberrant activation of Ras/MAPK signaling, and inhibits the proliferation of bladder cancer cells. In addition, GGPP was required to maintain the function of UBIAD1 in regulating the Ras/ERK signaling pathway. A Drosophila model was employed to confirm the function of UBIAD1/HEIX in vivo. The activation of Ras/ERK signaling at the plasma membrane induced melanotic masses in Drosophila larvae. Our study suggests that UBIAD1 serves as a tumor suppressor in cancer and tentatively reveals the underlying mechanism of melanotic mass formation in Drosophila.
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Affiliation(s)
- Zhiliang Xu
- Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Fengsen Duan
- Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Huiai Lu
- Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Maytham Abdulkadhim Dragh
- Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Yanzhi Xia
- Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Huageng Liang
- Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Ling Hong
- Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China.
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5
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Dhatwalia SK, Kumar M, Dhawan DK. Role of EGCG in Containing the Progression of Lung Tumorigenesis - A Multistage Targeting Approach. Nutr Cancer 2018; 70:334-349. [PMID: 29570987 DOI: 10.1080/01635581.2018.1445762] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Lung cancer is a prominent form among various types of cancers, irrespective of the sex worldwide. Treatment of lung cancer involves the intensive phase of chemotherapy/radiotherapy which is associated with high rate of adverse events. There is a need of safe and reliable treatment/adjunctive therapy to apprehend the cancer by reducing the undesirable outcome of primary therapy. Epigallocatechin-3-gallate (EGCG), which is a potent antioxidant and anticancer compound extracted from the plant camellia sinensis has proved to be a novel agent to control or reduce lung tumorigenesis by affecting the signaling molecules of cell cycle regulation and apoptotic pathways. In vitro studies have revealed that EGCG can contain carcinogenesis by altering the molecules involved in multiple signal transduction pathways like ERK, VEGF, COX2, NEAT, Ras-GTPase, and kinases. The animal studies have also demonstrated effectiveness of EGCG by inhibiting various molecular pathways which include AKT, NFkB, MAPK, Bcl/Bax, DNMT1, and HIF-1α. Various attempts have been made to see the adjunctive role of EGCG in human lung cancer. Phase I/II clinical studies have recommended that EGCG is quite safe and effective in providing protection against cancer. In this review, we will discuss the role of EGCG and its molecular mechanisms in lung carcinogenesis.
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Affiliation(s)
| | | | - Devinder K Dhawan
- a Department of Biophysics , Panjab University , Chandigarh , India.,c Nuclear Medicine, Panjab University , Chandigarh , India
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6
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Bender RHF, Haigis KM, Gutmann DH. Activated k-ras, but not h-ras or N-ras, regulates brain neural stem cell proliferation in a raf/rb-dependent manner. Stem Cells 2016; 33:1998-2010. [PMID: 25788415 DOI: 10.1002/stem.1990] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 02/08/2015] [Accepted: 02/19/2015] [Indexed: 12/19/2022]
Abstract
Neural stem cells (NSCs) give rise to all the major cell types in the brain, including neurons, oligodendrocytes, and astrocytes. However, the intracellular signaling pathways that govern brain NSC proliferation and differentiation have been incompletely characterized to date. Since some neurodevelopmental brain disorders (Costello syndrome and Noonan syndrome) are caused by germline activating mutations in the RAS genes, Ras small GTPases are likely critical regulators of brain NSC function. In the mammalian brain, Ras exists as three distinct molecules (H-Ras, K-Ras, and N-Ras), each with different subcellular localizations, downstream signaling effectors, and biological effects. Leveraging a novel series of conditional-activated Ras molecule-expressing genetically engineered mouse strains, we demonstrate that activated K-Ras, but not H-Ras or N-Ras, expression increases brain NSC growth in a Raf-dependent, but Mek-independent, manner. Moreover, we show that activated K-Ras regulation of brain NSC proliferation requires Raf binding and suppression of retinoblastoma (Rb) function. Collectively, these observations establish tissue-specific differences in activated Ras molecule regulation of brain cell growth that operate through a noncanonical mechanism.
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Affiliation(s)
- R Hugh F Bender
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Kevin M Haigis
- Department of Medicine, Cancer Research Institute, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
| | - David H Gutmann
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, USA
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7
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Doi A, Kita A, Kanda Y, Uno T, Asami K, Satoh R, Nakano K, Sugiura R. Geranylgeranyltransferase Cwg2-Rho4/Rho5 module is implicated in the Pmk1 MAP kinase-mediated cell wall integrity pathway in fission yeast. Genes Cells 2015; 20:310-23. [DOI: 10.1111/gtc.12222] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2014] [Accepted: 12/15/2014] [Indexed: 11/27/2022]
Affiliation(s)
- Akira Doi
- Laboratory of Molecular Pharmacogenomics; School of Pharmaceutical Sciences; Kinki University; Kowakae 3-4-1 Higashi-Osaka 577-8502 Japan
- Japan Society for the Promotion of Science; 1-8 Chiyoda-ku Tokyo 102-8472 Japan
| | - Ayako Kita
- Laboratory of Molecular Pharmacogenomics; School of Pharmaceutical Sciences; Kinki University; Kowakae 3-4-1 Higashi-Osaka 577-8502 Japan
| | - Yuki Kanda
- Laboratory of Molecular Pharmacogenomics; School of Pharmaceutical Sciences; Kinki University; Kowakae 3-4-1 Higashi-Osaka 577-8502 Japan
| | - Takaya Uno
- Laboratory of Molecular Pharmacogenomics; School of Pharmaceutical Sciences; Kinki University; Kowakae 3-4-1 Higashi-Osaka 577-8502 Japan
| | - Keita Asami
- Laboratory of Molecular Pharmacogenomics; School of Pharmaceutical Sciences; Kinki University; Kowakae 3-4-1 Higashi-Osaka 577-8502 Japan
| | - Ryosuke Satoh
- Laboratory of Molecular Pharmacogenomics; School of Pharmaceutical Sciences; Kinki University; Kowakae 3-4-1 Higashi-Osaka 577-8502 Japan
| | - Kentaro Nakano
- Department of Biological Sciences; Graduate School of Life and Environmental Sciences; University of Tsukuba; 1-1-1 Tennohdai Tsukuba Ibaraki 305-8577 Japan
| | - Reiko Sugiura
- Laboratory of Molecular Pharmacogenomics; School of Pharmaceutical Sciences; Kinki University; Kowakae 3-4-1 Higashi-Osaka 577-8502 Japan
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8
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Janardhan SV, Marks R, Gajewski TF. Primary murine CD4+ T cells fail to acquire the ability to produce effector cytokines when active Ras is present during Th1/Th2 differentiation. PLoS One 2014; 9:e112831. [PMID: 25397617 PMCID: PMC4232516 DOI: 10.1371/journal.pone.0112831] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 10/16/2014] [Indexed: 01/10/2023] Open
Abstract
Constitutive Ras signaling has been shown to augment IL-2 production, reverse anergy, and functionally replace many aspects of CD28 co-stimulation in CD4+ T cells. These data raise the possibility that introduction of active Ras into primary T cells might result in improved functionality in pathologic situations of T cell dysfunction, such as cancer or chronic viral infection. To test the biologic effects of active Ras in primary T cells, CD4+ T cells from Coxsackie-Adenovirus Receptor Transgenic mice were transduced with an adenovirus encoding active Ras. As expected, active Ras augmented IL-2 production in naive CD4+ T cells. However, when cells were cultured for 4 days under conditions to promote effector cell differentiation, active Ras inhibited the ability of CD4+ T cells to acquire a Th1 or Th2 effector cytokine profile. This differentiation defect was not due to deficient STAT4 or STAT6 activation by IL-12 or IL-4, respectively, nor was it associated with deficient induction of T-bet and GATA-3 expression. Impaired effector cytokine production in active Ras-transduced cells was associated with deficient demethylation of the IL-4 gene locus. Our results indicate that, despite augmenting acute activation of naïve T cells, constitutive Ras signaling inhibits the ability of CD4+ T cells to properly differentiate into Th1/Th2 effector cytokine-producing cells, in part by interfering with epigenetic modification of effector gene loci. Alternative strategies to potentiate Ras pathway signaling in T cells in a more regulated fashion should be considered as a therapeutic approach to improve immune responses in vivo.
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Affiliation(s)
- Sujit V. Janardhan
- Department of Pathology, The University of Chicago, Chicago, Illinois, United States of America
| | - Reinhard Marks
- Department of Pathology, The University of Chicago, Chicago, Illinois, United States of America
| | - Thomas F. Gajewski
- Department of Pathology, The University of Chicago, Chicago, Illinois, United States of America
- Department of Medicine, The University of Chicago, Chicago, Illinois, United States of America
- * E-mail:
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9
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Activated Ras as a Therapeutic Target: Constraints on Directly Targeting Ras Isoforms and Wild-Type versus Mutated Proteins. ISRN ONCOLOGY 2013; 2013:536529. [PMID: 24294527 PMCID: PMC3833460 DOI: 10.1155/2013/536529] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Accepted: 10/04/2013] [Indexed: 12/12/2022]
Abstract
The ability to selectively and directly target activated Ras would provide immense utility for treatment of the numerous cancers that are driven by oncogenic Ras mutations. Patients with disorders driven by overactivated wild-type Ras proteins, such as type 1 neurofibromatosis, might also benefit from progress made in that context. Activated Ras is an extremely challenging direct drug target due to the inherent difficulties in disrupting the protein:protein interactions that underlie its activation and function. Major investments have been made to target Ras through indirect routes. Inhibition of farnesyl transferase to block Ras maturation has failed in large clinical trials. Likely reasons for this disappointing outcome include the significant and underappreciated differences in the isoforms of Ras. It is still plausible that inhibition of farnesyl transferase will prove effective for disease that is driven by activated H-Ras. The principal current focus of drugs entering clinic trial is inhibition of pathways downstream of activated Ras, for example, trametinib, a first-in-class MEK inhibitor. The complexity of signaling that is driven by activated Ras indicates that effective inhibition of oncogenic transduction through this approach will be difficult, with resistance being likely to emerge through switch to parallel pathways. Durable disease responses will probably require combinatorial block of several downstream targets.
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10
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Oz S, Benmocha A, Sasson Y, Sachyani D, Almagor L, Lee A, Hirsch JA, Dascal N. Competitive and non-competitive regulation of calcium-dependent inactivation in CaV1.2 L-type Ca2+ channels by calmodulin and Ca2+-binding protein 1. J Biol Chem 2013; 288:12680-91. [PMID: 23530039 DOI: 10.1074/jbc.m113.460949] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CaV1.2 interacts with the Ca(2+) sensor proteins, calmodulin (CaM) and calcium-binding protein 1 (CaBP1), via multiple, partially overlapping sites in the main subunit of CaV1.2, α1C. Ca(2+)/CaM mediates a negative feedback regulation of Cav1.2 by incoming Ca(2+) ions (Ca(2+)-dependent inactivation (CDI)). CaBP1 eliminates this action of CaM through a poorly understood mechanism. We examined the hypothesis that CaBP1 acts by competing with CaM for common interaction sites in the α1C- subunit using Förster resonance energy transfer (FRET) and recording of Cav1.2 currents in Xenopus oocytes. FRET detected interactions between fluorescently labeled CaM or CaBP1 with the membrane-attached proximal C terminus (pCT) and the N terminus (NT) of α1C. However, mutual overexpression of CaM and CaBP1 proved inadequate to quantitatively assess competition between these proteins for α1C. Therefore, we utilized titrated injection of purified CaM and CaBP1 to analyze their mutual effects. CaM reduced FRET between CaBP1 and pCT, but not NT, suggesting competition between CaBP1 and CaM for pCT only. Titrated injection of CaBP1 and CaM altered the kinetics of CDI, allowing analysis of their opposite regulation of CaV1.2. The CaBP1-induced slowing of CDI was largely eliminated by CaM, corroborating a competition mechanism, but 15-20% of the effect of CaBP1 was CaM-resistant. Both components of CaBP1 action were present in a truncated α1C where N-terminal CaM- and CaBP1-binding sites have been deleted, suggesting that the NT is not essential for the functional effects of CaBP1. We propose that CaBP1 acts via interaction(s) with the pCT and possibly additional sites in α1C.
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Affiliation(s)
- Shimrit Oz
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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11
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Grunwald A, Gottfried I, Cox AD, Haklai R, Kloog Y, Ashery U. Rasosomes originate from the Golgi to dispense Ras signals. Cell Death Dis 2013; 4:e496. [PMID: 23412389 PMCID: PMC3734827 DOI: 10.1038/cddis.2013.16] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Ras proteins undergo an incompletely understood trafficking process in the cell. Rasosomes are protein nanoparticles of 80–100 nm diameter that carry lipidated Ras isoforms (H-Ras and N-Ras) as well as their effectors through the cytoplasm and near the plasma membrane (PM). In this study, we identified the subcellular origin of rasosomes and how they spread Ras proteins through the cell. We found no dependency of rasosome formation on galectins, or on the GDP-/GTP-bound state of Ras. We found that significantly more rasosomes are associated with forms of Ras that are localized to the Golgi, namely N-Ras or the singly palmitoylated H-Ras mutant (C181S). To explore the possibility that rasosome originate from the Golgi, we used photoactivatable (PA)-GFP-H-Ras mutants and showed that rasosomes bud from the Golgi in a two-step mechanism. Newly released rasosomes first move in an energy-dependent directed fashion and then convert to randomly diffusing rasosomes. Dual fluorescence time-lapse imaging revealed the appearance of dually labeled rasosomes, indicating a dynamic exchange of cytoplasmic and PM-associated Ras with rasosome-associated Ras. Finally, higher levels of rasosomes correlate with higher levels of ERK phosphorylation, a key marker of Ras downstream signaling. We suggest that H-Ras and N-Ras proteins exchange with rasosomes that can function as carriers of palmitoylated Ras and its signals.
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Affiliation(s)
- A Grunwald
- Department of Neurobiology, Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Israel
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12
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Holst CM, Johansson VM, Alm K, Oredsson SM. Novel anti-apoptotic effect of Bcl-2: Prevention of polyamine depletion-induced cell death. Cell Biol Int 2013; 32:66-74. [DOI: 10.1016/j.cellbi.2007.08.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 06/29/2007] [Accepted: 08/22/2007] [Indexed: 10/22/2022]
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13
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Cancino J, Luini A. Signaling Circuits on the Golgi Complex. Traffic 2012; 14:121-34. [DOI: 10.1111/tra.12022] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 10/12/2012] [Accepted: 10/12/2012] [Indexed: 01/21/2023]
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Boaglio AC, Zucchetti AE, Toledo FD, Barosso IR, Sánchez Pozzi EJ, Crocenzi FA, Roma MG. ERK1/2 and p38 MAPKs are complementarily involved in estradiol 17ß-D-glucuronide-induced cholestasis: crosstalk with cPKC and PI3K. PLoS One 2012; 7:e49255. [PMID: 23166621 PMCID: PMC3498151 DOI: 10.1371/journal.pone.0049255] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Accepted: 10/04/2012] [Indexed: 12/17/2022] Open
Abstract
Objective The endogenous, cholestatic metabolite estradiol 17ß-d-glucuronide (E217G) induces endocytic internalization of the canalicular transporters relevant to bile formation, Bsep and Mrp2. We evaluated here whether MAPKs are involved in this effect. Design ERK1/2, JNK1/2, and p38 MAPK activation was assessed by the increase in their phosphorylation status. Hepatocanalicular function was evaluated in isolated rat hepatocyte couplets (IRHCs) by quantifying the apical secretion of fluorescent Bsep and Mrp2 substrates, and in isolated, perfused rat livers (IPRLs), using taurocholate and 2,4-dinitrophenyl-S-glutathione, respectively. Protein kinase participation in E217G-induced secretory failure was assessed by co-administering selective inhibitors. Internalization of Bsep/Mrp2 was assessed by confocal microscopy and image analysis. Results E217G activated all kinds of MAPKs. The PI3K inhibitor wortmannin prevented ERK1/2 activation, whereas the cPKC inhibitor Gö6976 prevented p38 activation, suggesting that ERK1/2 and p38 are downstream of PI3K and cPKC, respectively. The p38 inhibitor SB203580 and the ERK1/2 inhibitor PD98059, but not the JNK1/2 inhibitor SP600125, partially prevented E217G-induced changes in transporter activity and localization in IRHCs. p38 and ERK1/2 co-inhibition resulted in additive protection, suggesting complementary involvement of these MAPKs. In IPRLs, E217G induced endocytosis of canalicular transporters and a rapid and sustained decrease in bile flow and biliary excretion of Bsep/Mrp2 substrates. p38 inhibition prevented this initial decay, and the internalization of Bsep/Mrp2. Contrarily, ERK1/2 inhibition accelerated the recovery of biliary secretion and the canalicular reinsertion of Bsep/Mrp2. Conclusions cPKC/p38 MAPK and PI3K/ERK1/2 signalling pathways participate complementarily in E217G-induced cholestasis, through internalization and sustained intracellular retention of canalicular transporters, respectively.
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Affiliation(s)
| | | | | | | | | | - Fernando A. Crocenzi
- Institute of Experimental Physiology, National Scientific and Technical Research Council/National University of Rosario, Rosario, Argentina
- * E-mail: (FAC); (MGR)
| | - Marcelo G. Roma
- Institute of Experimental Physiology, National Scientific and Technical Research Council/National University of Rosario, Rosario, Argentina
- * E-mail: (FAC); (MGR)
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15
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Zhuravliova E, Barbakadze T, Jojua N, Zaalishvili E, Shanshiashvili L, Natsvlishvili N, Kalandadze I, Narmania N, Chogovadze I, Mikeladze D. Synaptic and non-synaptic mitochondria in hippocampus of adult rats differ in their sensitivity to hypothyroidism. Cell Mol Neurobiol 2012; 32:1311-21. [PMID: 22706894 PMCID: PMC11498642 DOI: 10.1007/s10571-012-9857-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Accepted: 05/31/2012] [Indexed: 11/28/2022]
Abstract
Hypothyroidism in humans provokes various neuropsychiatric disorders, movement, and cognitive abnormalities that may greatly depend on the mitochondrial energy metabolism. Brain cells contain at least two major populations of mitochondria that include the non-synaptic mitochondria, which originate from neuronal and glial cell bodies (CM), and the synaptic (SM) mitochondria, which primarily originate from the nerve terminals. Several parameters of oxidative stress and other parameters in SM and CM fractions of hippocampus of adult rats were compared among euthyroid (control), hypothyroid (methimazol-treated), and thyroxine (T4)-treated hypothyroid states. nNOS translocation to CM was observed with concomitant increase of mtNOS's activity in hypothyroid rats. In parallel, oxidation of cytochrome c oxidase and production of peroxides with substrates of complex I (glutamate + malate) were enhanced in CM, whereas the activity of aconitase and mitochondrial membrane potential (ΔΨm) were decreased. Furthermore, the elevation of mitochondrial hexokinase activity in CM was also found. No differences in these parameters between control and hypothyroid animals were observed in SM. However, in contrast to CM, hypothyroidism increases the level of pro-apoptotic K-Ras and Bad in SM. Our results suggest that hypothyroidism induces moderate and reversible oxidative/nitrosative stress in hippocampal CM, leading to the compensatory elevation of hexokinase activity and aerobic glycolysis. Such adaptive activation in glycolytic metabolism does not occur in SM, suggesting that synaptic mitochondria differ in their sensitivity to the energetic disturbance in hypothyroid conditions.
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Affiliation(s)
- E. Zhuravliova
- I. Beritashvili Center of Experimental Biomedicine, Tbilisi, Georgia
- Ilia State University, 3/5 Cholokashvili Av., 0150 Tbilisi, Georgia
| | - T. Barbakadze
- I. Beritashvili Center of Experimental Biomedicine, Tbilisi, Georgia
- Ilia State University, 3/5 Cholokashvili Av., 0150 Tbilisi, Georgia
| | - N. Jojua
- Ilia State University, 3/5 Cholokashvili Av., 0150 Tbilisi, Georgia
| | - E. Zaalishvili
- I. Beritashvili Center of Experimental Biomedicine, Tbilisi, Georgia
| | - L. Shanshiashvili
- I. Beritashvili Center of Experimental Biomedicine, Tbilisi, Georgia
- Ilia State University, 3/5 Cholokashvili Av., 0150 Tbilisi, Georgia
| | - N. Natsvlishvili
- I. Beritashvili Center of Experimental Biomedicine, Tbilisi, Georgia
- Ilia State University, 3/5 Cholokashvili Av., 0150 Tbilisi, Georgia
| | - I. Kalandadze
- I. Beritashvili Center of Experimental Biomedicine, Tbilisi, Georgia
| | - N. Narmania
- Ilia State University, 3/5 Cholokashvili Av., 0150 Tbilisi, Georgia
| | - I. Chogovadze
- I. Beritashvili Center of Experimental Biomedicine, Tbilisi, Georgia
| | - D. Mikeladze
- I. Beritashvili Center of Experimental Biomedicine, Tbilisi, Georgia
- Ilia State University, 3/5 Cholokashvili Av., 0150 Tbilisi, Georgia
- Life Science Research Center, 14 Gotua St., 0160 Tbilisi, Georgia
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Fillatre J, Delacour D, Van Hove L, Bagarre T, Houssin N, Soulika M, Veitia RA, Moreau J. Dynamics of the subcellular localization of RalBP1/RLIP through the cell cycle: the role of targeting signals and of protein-protein interactions. FASEB J 2012; 26:2164-74. [PMID: 22319010 DOI: 10.1096/fj.11-196451] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The small G protein Ras regulates many cell processes, such as gene expression, proliferation, apoptosis, and cell differentiation. Its mutations are associated with one-third of all cancers. Ras functions are mediated, at least in part, by Ral proteins and their downstream effector the Ral-binding protein 1 (RalBP1). RalBP1 is involved in endocytosis and in regulating the dynamics of the actin cytoskeleton. It also regulates early development since it is required for the completion of gastrulation in Xenopus laevis. RalBP1 has also been reported to be the main transporter of glutathione electrophiles, and it is involved in multidrug resistance. Such a variety of functions could be explained by a differential regulation of RalBP1 localization. In this study, we have detected endogenous RalBP1 in the nucleus of interphasic cells. This nuclear targeting is mediated by nuclear localization sequences that map to the N-terminal third of the protein. Moreover, in X. laevis embryos, a C-terminal coiled-coil sequence mediates RalBP1 retention in the nucleus. We have also observed RalBP1 at the level of the actin cytoskeleton, a localization that depends on interaction of the protein with active Ral. During mitosis RalBP1 also associates with the mitotic spindle and the centrosome, a localization that could be negatively regulated by active Ral. Finally, we demonstrate the presence of post-transcriptional and post-translational isoforms of RalBP1 lacking the Ral-binding domain, which opens new possibilities for the existence of Ral-independent functions.
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Affiliation(s)
- Jonathan Fillatre
- Mécanismes Moléculaires du Développement, Institut Jacques Monod, CNRS, UMR 7592, Université Paris Diderot, Sorbonne Paris Cité. 15, rue Hélène Brion. 75205 Paris, France
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17
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Galectin-3 mediates cross-talk between K-Ras and Let-7c tumor suppressor microRNA. PLoS One 2011; 6:e27490. [PMID: 22102901 PMCID: PMC3216962 DOI: 10.1371/journal.pone.0027490] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 10/18/2011] [Indexed: 01/02/2023] Open
Abstract
Background Galectin-3 (Gal-3) and active (GTP-bound) K-Ras contribute to the malignant phenotype of many human tumors by increasing the rate of cell proliferation, survival, and migration. These Gal-3-mediated effects result from a selective binding to K-Ras.GTP, causing increased nanoclustering in the cell membrane and leading to robust Ras signaling. Regulation of the interactions between Gal-3 and active K-Ras is not fully understood. Methods and Findings To gain a better understanding of what regulates the critical interactions between these two proteins, we examined the role of Gal-3 in the regulation of K-Ras by using Gal-3-knockout mouse embryonic-fibroblasts (Gal-3-/- MEFs) and/or Gal-3/Gal-1 double-knockout MEFs. We found that knockout of Gal-3 induced strong downregulation (∼60%) of K-Ras and K-Ras.GTP. The downregulation was somewhat more marked in the double-knockout MEFs, in which we also detected robust inhibition(∼50%) of ERK and Akt activation. These additional effects are probably attributable to inhibition of the weak interactions of K-Ras.GTP with Gal-1. Re-expression of Gal-3 reversed the phenotype of the Gal-3-/- MEFs and dramatically reduced the disappearance of K-Ras in the presence of cycloheximide to the levels seen in wild-type MEFs. Furthermore, phosphorylation of Gal-3 by casein kinase-1 (CK-1) induced translocation of Gal-3 from the nucleus to the cytoplasm and the plasma membrane, leading to K-Ras stabilization accompanied by downregulation of the tumor suppressor miRNA let-7c, known to negatively control K-Ras transcription. Conclusions Our results suggest a novel cross-talk between Gal-3-mediated downregulation of let 7c microRNA (which in turn negatively regulates K-Ras transcription) and elucidates the association among Gal-3 let-7c and K-Ras transcription/translation, cellular compartmentalization and activity.
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Arozarena I, Calvo F, Crespo P. Ras, an actor on many stages: posttranslational modifications, localization, and site-specified events. Genes Cancer 2011; 2:182-94. [PMID: 21779492 DOI: 10.1177/1947601911409213] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Among the wealth of information that we have gathered about Ras in the past decade, the introduction of the concept of space in the field has constituted a major revolution that has enabled many pieces of the Ras puzzle to fall into place. In the early days, it was believed that Ras functioned exclusively at the plasma membrane. Today, we know that within the plasma membrane, the 3 Ras isoforms-H-Ras, K-Ras, and N-Ras-occupy different microdomains and that these isoforms are also present and active in endomembranes. We have also discovered that Ras proteins are not statically associated with these localizations; instead, they traffic dynamically between compartments. And we have learned that at these localizations, Ras is under site-specific regulatory mechanisms, distinctively engaging effector pathways and switching on diverse genetic programs to generate different biological responses. All of these processes are possible in great part due to the posttranslational modifications whereby Ras proteins bind to membranes and to regulatory events such as phosphorylation and ubiquitination that Ras is subject to. As such, space and these control mechanisms act in conjunction to endow Ras signals with an enormous signal variability that makes possible its multiple biological roles. These data have established the concept that the Ras signal, instead of being one single, homogeneous entity, results from the integration of multiple, site-specified subsignals, and Ras has become a paradigm of how space can differentially shape signaling.
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Affiliation(s)
- Imanol Arozarena
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Consejo Superior de Investigaciones Científicas (CSIC)-IDICAN-Universidad de Cantabria, Departamento de Biología Molecular, Facultad de Medicina, Cantabria, Spain
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19
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Janardhan SV, Praveen K, Marks R, Gajewski TF. Evidence implicating the Ras pathway in multiple CD28 costimulatory functions in CD4+ T cells. PLoS One 2011; 6:e24931. [PMID: 21949793 PMCID: PMC3176298 DOI: 10.1371/journal.pone.0024931] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Accepted: 08/24/2011] [Indexed: 12/28/2022] Open
Abstract
CD28 costimulation is a critical event in the full activation of CD4+ T cells that augments cytokine gene transcription, promotes cytokine mRNA stability, prevents induction of anergy, increases cellular metabolism, and increases cell survival. However, despite extensive biochemical analysis of the signaling events downstream of CD28, molecular pathways sufficient to functionally replace the diverse aspects of CD28-mediated costimulation in normal T cells have not been identified. Ras/MAPK signaling is a critical pathway downstream of T cell receptor stimulation, but its role in CD28-mediated costimulation has been controversial. We observed that physiologic CD28 costimulation caused a relocalization of the RasGEF RasGRP to the T cell-APC interface by confocal microscopy. In whole cell biochemical analysis, CD28 cross-linking with either anti-CD28 antibody or B7.1-Ig augmented TCR-induced Ras activation. To determine whether Ras signaling was sufficient to functionally mimic CD28 costimulation, we utilized an adenoviral vector encoding constitutively active H-Ras (61L) to transduce normal, Coxsackie-Adenovirus Receptor (CAR) transgenic CD4+ T cells. Like costimulation via CD28, active Ras induced AKT, JNK and ERK phosphorylation. In addition, constitutive Ras signaling mimicked the ability of CD28 to costimulate IL-2 protein secretion, prevent anergy induction, increase glucose uptake, and promote cell survival. Importantly, we also found that active Ras mimicked the mechanism by which CD28 costimulates IL-2 production: by increasing IL-2 gene transcription, and promoting IL-2 mRNA stability. Finally, active Ras was able to induce IL-2 production when combined with ionomycin stimulation in a MEK-1-dependent fashion. Our results are consistent with a central role for Ras signaling in CD28-mediated costimulation.
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Affiliation(s)
- Sujit V. Janardhan
- Department of Pathology, The University of Chicago, Chicago, Illinois, United States of America
| | - Kesavannair Praveen
- Department of Pathology, The University of Chicago, Chicago, Illinois, United States of America
| | - Reinhard Marks
- Department of Pathology, The University of Chicago, Chicago, Illinois, United States of America
| | - Thomas F. Gajewski
- Department of Pathology, The University of Chicago, Chicago, Illinois, United States of America
- Department of Medicine, The University of Chicago, Chicago, Illinois, United States of America
- * E-mail:
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20
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Rotblat B, Leprivier G, Sorensen PHB. A possible role for long non-coding RNA in modulating signaling pathways. Med Hypotheses 2011; 77:962-5. [PMID: 21903344 DOI: 10.1016/j.mehy.2011.08.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Accepted: 08/14/2011] [Indexed: 01/10/2023]
Abstract
Signaling proteins often engage in multiple protein-protein interactions that are dependent upon cellular context. Little is known about how signaling proteins select their interacting targets. The Ras GTPase is an example of a protein that can activate a large number of distinct and interconnected downstream signaling pathways. Hyperactive forms of Ras are commonly found in a variety of different cancers, often due to somatic mutations within the RAS gene. Despite extensive studies to identify Ras-regulated pathways, it is still not known exactly which pathways might be activated by hyperactive Ras in a given cellular and disease context. Long non-coding RNAs (lncRNAs) are RNA transcripts longer than 200 bp exhibiting spatially and temporally-regulated expression patterns. LncRNAs have been shown to harbor biological activities but the functions of the great majority of lncRNAs are not known. We hypothesize that long non-coding RNAs serve as signaling modulators linking Ras and potentially other signaling proteins to their specific downstream targets and may therefore play a key role in how signals are propagated in a specific cellular environment. In support of our hypothesis we argue that lncRNAs have been shown to bind and regulate protein complexes targeting their enzymatic activity towards specific substrates. It has also been demonstrated that specific lncRNAs are expressed in particular types of cancers where they may influence tumor progression. Studies suggest that lncRNAs have evolved to help regulate complex biological processes that require the ability to stringently discriminate between a large number of potential effectors. If our hypothesis is correct, we envision that it will be possible to predict the target pathway of a mutant protein based on the lncRNA profile in a specific cancer. More generally, this will expand our understanding of how signal transduction networks are wired within a given biological context.
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Affiliation(s)
- Barak Rotblat
- Department of Molecular Oncology, BC Cancer Research Center, University of British Columbia, Vancouver, BC, Canada
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21
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Mor A, Aizman E, George J, Kloog Y. Ras inhibition induces insulin sensitivity and glucose uptake. PLoS One 2011; 6:e21712. [PMID: 21738773 PMCID: PMC3126849 DOI: 10.1371/journal.pone.0021712] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Accepted: 06/06/2011] [Indexed: 02/06/2023] Open
Abstract
Background Reduced glucose uptake due to insulin resistance is a pivotal mechanism in the pathogenesis of type 2 diabetes. It is also associated with increased inflammation. Ras inhibition downregulates inflammation in various experimental models. The aim of this study was to examine the effect of Ras inhibition on insulin sensitivity and glucose uptake, as well as its influence on type 2 diabetes development. Methods and Findings The effect of Ras inhibition on glucose uptake was examined both in vitro and in vivo. Ras was inhibited in cells transfected with a dominant-negative form of Ras or by 5-fluoro-farnesylthiosalicylic acid (F-FTS), a small-molecule Ras inhibitor. The involvement of IκB and NF-κB in Ras-inhibited glucose uptake was investigated by immunoblotting. High fat (HF)-induced diabetic mice were treated with F-FTS to test the effect of Ras inhibition on induction of hyperglycemia. Each of the Ras-inhibitory modes resulted in increased glucose uptake, whether in insulin-resistant C2C12 myotubes in vitro or in HF-induced diabetic mice in vivo. Ras inhibition also caused increased IκB expression accompanied by decreased expression of NF-κB . In fat-induced diabetic mice treated daily with F-FTS, both the incidence of hyperglycemia and the levels of serum insulin were significantly decreased. Conclusions Inhibition of Ras apparently induces a state of heightened insulin sensitization both in vitro and in vivo. Ras inhibition should therefore be considered as an approach worth testing for the treatment of type 2 diabetes.
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Affiliation(s)
- Adi Mor
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel-Aviv, Israel
| | - Elizabeta Aizman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel-Aviv, Israel
| | - Jacob George
- Department of Cardiology, Kaplan Medical Center, Rehovot, affiliated to the Hebrew University—Hadassah Medical School, Jerusalem, Israel
| | - Yoel Kloog
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel-Aviv, Israel
- * E-mail:
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22
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Limnander A, Depeille P, Freedman TS, Liou J, Leitges M, Kurosaki T, Roose JP, Weiss A. STIM1, PKC-δ and RasGRP set a threshold for proapoptotic Erk signaling during B cell development. Nat Immunol 2011; 12:425-33. [PMID: 21441934 PMCID: PMC3623929 DOI: 10.1038/ni.2016] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Accepted: 03/02/2011] [Indexed: 01/05/2023]
Abstract
Clonal deletion of autoreactive B cells is crucial for the prevention of autoimmunity, but the signaling mechanisms that regulate this checkpoint remain undefined. Here we characterize a previously unrecognized Ca(2+)-driven pathway for activation of the kinase Erk, which was proapoptotic and biochemically distinct from Erk activation induced by diacylglycerol (DAG). This pathway required protein kinase C-δ (PKC-δ) and the guanine nucleotide-exchange factor RasGRP and depended on the concentration of the Ca(2+) sensor STIM1, which controls the magnitude of Ca(2+) entry. Developmental regulation of these proteins was associated with selective activation of the pathway in B cells prone to negative selection. This checkpoint was impaired in PKC-δ-deficient mice, which developed B cell autoimmunity. Conversely, overexpression of STIM1 conferred a competitive disadvantage to developing B cells. Our findings establish Ca(2+)-dependent Erk signaling as a critical proapoptotic pathway that mediates the negative selection of B cells.
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Affiliation(s)
- Andre Limnander
- Department of Medicine, Howard Hughes Medical Institute, Rosalind Russell Medical Research Center for Arthritis, University of California at San Francisco, San Francisco, California, USA
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Farin K, Schokoroy S, Haklai R, Cohen-Or I, Elad-Sfadia G, Reyes-Reyes ME, Bates PJ, Cox AD, Kloog Y, Pinkas-Kramarski R. Oncogenic synergism between ErbB1, nucleolin, and mutant Ras. Cancer Res 2011; 71:2140-51. [PMID: 21257709 DOI: 10.1158/0008-5472.can-10-2887] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Alterations in the ErbB family of growth factor receptors, their signaling components, and mutational activation of Ras proteins are major contributors to malignant transformation. Recently, mutant Ras was shown to be capable of activating ErbB receptors in a ligand-independent manner. Furthermore, it was observed that nucleolin, a transcriptional regulator and ribosome biogenesis factor, can bind both K-Ras and the cytoplasmic tail of ErbB receptors to enhance ErbB receptor activation. However, the functional significance of these interactions to cancer pathogenesis has not been probed. Here, we show that endogenous nucleolin interacts simultaneously in vivo with endogenous Ras and ErbB1 (EGFR) in cancer cells. The C-terminal 212 amino acids of nucleolin were determined to be sufficient to interact with ErbB1 and all Ras protein isoforms (H-, N-, and K-Ras). Nucleolin partially colocalizes with Ras at the plasma membrane. Moreover, activated but not wild-type Ras facilitates nucleolin interaction with ErbB1 and stabilizes ErbB1 receptor levels. Most importantly, these three oncogenes synergistically facilitate anchorage-independent cell growth in vitro and tumor growth in vivo. Our findings suggest strategies to target nucleolin as a general approach to inhibiting ErbB- and Ras-driven cancers.
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Affiliation(s)
- Keren Farin
- Department of Neurobiology, Tel-Aviv University, Ramat-Aviv, Israel
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Abstract
Ras GTPases are best known for their ability to serve as molecular switches regulating cell growth, differentiation and survival. Gene mutations that result in expression of constitutively active forms of Ras have been linked to oncogenesis in animal models and humans. However, over the past two decades, evidence has gradually accumulated to support a paradoxical role for Ras proteins in the initiation of cell death pathways. In this review we survey the literature pointing to the ability of activated Ras to promote cell death under conditions where cancer cells encounter apoptotic stimuli or Ras is ectopically expressed. In some of these cases Ras acts through known effectors and well defined apoptotic death pathways. However, in other cases it appears that Ras operates by triggering novel non-apoptotic death mechanisms that are just beginning to be characterized. Understanding these mechanisms and the factors that go into changing the nature of Ras signaling from pro-survival to pro-death could set the stage for development of novel therapeutic approaches aimed at manipulating pro-death Ras signaling pathways in cancer.
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Affiliation(s)
- Jean H Overmeyer
- Department of Biochemistry and Cancer Biology, University of Toledo College of Medicine, Toledo, Ohio 43614, USA
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Bustinza-Linares E, Kurzrock R, Tsimberidou AM. Salirasib in the treatment of pancreatic cancer. Future Oncol 2010; 6:885-91. [PMID: 20528225 DOI: 10.2217/fon.10.71] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The Ras family of genes is involved in the cellular regulation of proliferation, differentiation, cell adhesion and apoptosis. The K-ras gene is mutated in over 90% of pancreatic cancer cases. Salirasib (S-trans,trans-farnesylthiosalycilic acid [FTS]) is a synthetic small molecule that acts as a potent Ras inhibitor. It is a farnesylcysteine mimetic that selectively disrupts the association of active RAS proteins with the plasma membrane. Animal studies demonstrated that salirasib inhibited tumor growth, downregulated gene expression in the cell cycle and Ras signaling pathways. In a clinical study of salirasib combined with standard doses of gemcitabine, it was demonstrated that the two drugs have no overlapping pharmacokinetics. The salirasib recommended dose was 600 mg twice daily and the progression-free survival was 4.7 months. Future studies will determine whether salirasib adds to the anti-tumor activity of drugs approved by the US FDA for pancreatic cancer.
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Affiliation(s)
- Ernesto Bustinza-Linares
- Department of Investigational Cancer Therapeutics, The Phase I Clinical Trials Program, Unit 455, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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Ketschek A, Gallo G. Nerve growth factor induces axonal filopodia through localized microdomains of phosphoinositide 3-kinase activity that drive the formation of cytoskeletal precursors to filopodia. J Neurosci 2010; 30:12185-97. [PMID: 20826681 PMCID: PMC2944214 DOI: 10.1523/jneurosci.1740-10.2010] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Revised: 07/19/2010] [Accepted: 07/22/2010] [Indexed: 01/02/2023] Open
Abstract
The initiation of axonal filopodia is the first step in the formation of collateral branches and synaptic structures. In sensory neurons, nerve growth factor (NGF) promotes the formation of axonal filopodia and branches. However, the signaling and cytoskeletal mechanisms of NGF-induced initiation of axonal filopodia are not clear. Axonal filopodia arise from precursor axonal cytoskeletal structures termed filamentous actin (F-actin) patches. Patches form spontaneously and are transient. Although filopodia emerge from patches, only a fraction of patches normally gives rise to filopodia. Using chicken sensory neurons and live imaging of enhanced yellow fluorescent protein (eYFP)-actin dynamics, we report that NGF promotes the formation of axonal filopodia by increasing the rate of F-actin patch formation but not the fraction of patches that give rise to filopodia. We also demonstrate that activation of the phosphatidylinositol 3-kinase (PI3K)-Akt pathway is sufficient and required for driving the formation of axonal F-actin patches, filopodia, and axon branches. Using the green fluorescent protein-plekstrin homology domain of Akt, which targets to PI3K-generated phosphatidylinositol-3,4,5-triphosphate (PIP(3)), we report localized microdomains of PIP(3) accumulation that form in synchrony with F-actin patches and that NGF promotes the formation of microdomains of PIP(3) and patches. Finally, we find that, in NGF, F-actin patches form in association with axonal mitochondria and oxidative phosphorylation is required for patch formation. This investigation demonstrates that surprisingly NGF promotes formation of axonal filopodia by increasing the formation of cytoskeletal filopodial precursors (patches) through localized microdomains of PI3K signaling but not the emergence of filopodia from patches.
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Affiliation(s)
- Andrea Ketschek
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129
| | - Gianluca Gallo
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129
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Aizman E, Mor A, George J, Kloog Y. Ras inhibition attenuates pancreatic cell death and experimental type 1 diabetes: Possible role of regulatory T cells. Eur J Pharmacol 2010; 643:139-44. [DOI: 10.1016/j.ejphar.2010.06.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2010] [Revised: 05/05/2010] [Accepted: 06/15/2010] [Indexed: 10/19/2022]
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Manandhar SP, Hildebrandt ER, Jacobsen WH, Santangelo GM, Schmidt WK. Chemical inhibition of CaaX protease activity disrupts yeast Ras localization. Yeast 2010; 27:327-43. [PMID: 20162532 DOI: 10.1002/yea.1756] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Proteins possessing a C-terminal CaaX motif, such as the Ras GTPases, undergo extensive post-translational modification that includes attachment of an isoprenoid lipid, proteolytic processing and carboxylmethylation. Inhibition of the enzymes involved in these processes is considered a cancer-therapeutic strategy. We previously identified nine in vitro inhibitors of the yeast CaaX protease Rce1p in a chemical library screen (Manandhar et al., 2007). Here, we demonstrate that these agents disrupt the normal plasma membrane distribution of yeast GFP-Ras reporters in a manner that pharmacologically phenocopies effects observed upon genetic loss of CaaX protease function. Consistent with Rce1p being the in vivo target of the inhibitors, we observe that compound-induced delocalization is suppressed by increasing the gene dosage of RCE1. Moreover, we observe that Rce1p biochemical activity associated with inhibitor-treated cells is inversely correlated with compound dose. Genetic loss of CaaX proteolysis results in mistargeting of GFP-Ras2p to subcellular foci that are positive for the endoplasmic reticulum marker Sec63p. Pharmacological inhibition of CaaX protease activity also delocalizes GFP-Ras2p to foci, but these foci are not as strongly positive for Sec63p. Lastly, we demonstrate that heterologously expressed human Rce1p can mediate proper targeting of yeast Ras and that its activity can also be perturbed by some of the above inhibitors. Together, these results indicate that disrupting the proteolytic modification of Ras GTPases impacts their in vivo trafficking.
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Affiliation(s)
- Surya P Manandhar
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
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30
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Calvo F, Agudo-Ibáñez L, Crespo P. The Ras-ERK pathway: understanding site-specific signaling provides hope of new anti-tumor therapies. Bioessays 2010; 32:412-21. [PMID: 20414899 DOI: 10.1002/bies.200900155] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Recent discoveries have suggested the concept that intracellular signals are the sum of multiple, site-specified subsignals, rather than single, homogeneous entities. In the context of cancer, searching for compounds that selectively block subsignals essential for tumor progression, but not those regulating "house-keeping" functions, could help in producing drugs with reduced side effects compared to compounds that block signaling completely. The Ras-ERK pathway has become a paradigm of how space can differentially shape signaling. Today, we know that Ras proteins are found in different plasma membrane microdomains and endomembranes. At these localizations, Ras is subject to site-specific regulatory mechanisms, distinctively engaging effector pathways and switching-on diverse genetic programs to generate different biological responses. The Ras effector pathway leading to ERKs activation is also under strict, space-related regulatory processes. These findings may open a gate for aiming at the Ras-ERK pathway in a spatially restricted fashion, in our quest for new anti-tumor therapies.
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Affiliation(s)
- Fernando Calvo
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Consejo Superior de Investigaciones Científicas (CSIC), IDICAN, Universidad de Cantabria, Cantabria, Spain
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31
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Lau KS, Haigis KM. Non-redundancy within the RAS oncogene family: insights into mutational disparities in cancer. Mol Cells 2009; 28:315-20. [PMID: 19812895 PMCID: PMC3976423 DOI: 10.1007/s10059-009-0143-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Accepted: 09/11/2009] [Indexed: 12/11/2022] Open
Abstract
The RAS family of oncoproteins has been studied extensively for almost three decades. While we know that activation of RAS represents a key feature of malignant transformation for many cancers, we are only now beginning to understand the complex underpinnings of RAS biology. Here, we will discuss emerging cancer genome sequencing data in the context of what is currently known about RAS function. Taken together, retrospective studies of primary human tissues and prospective studies of experimental models support the notion that the variable mutation frequencies exhibited by the RAS oncogenes reflect unique functions of the RAS oncoproteins.
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Affiliation(s)
- Ken S. Lau
- Molecular Pathology Unit and Center for Cancer Research, Massachusetts General Hospital and Department of Pathology, Harvard Medical School, USA
| | - Kevin M. Haigis
- Molecular Pathology Unit and Center for Cancer Research, Massachusetts General Hospital and Department of Pathology, Harvard Medical School, USA
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32
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Gurry T, Kahramanoğulları O, Endres RG. Biophysical mechanism for ras-nanocluster formation and signaling in plasma membrane. PLoS One 2009; 4:e6148. [PMID: 19587789 PMCID: PMC2704371 DOI: 10.1371/journal.pone.0006148] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Accepted: 06/07/2009] [Indexed: 01/02/2023] Open
Abstract
Ras GTPases are lipid-anchored G proteins, which play a fundamental role in cell signaling processes. Electron micrographs of immunogold-labeled Ras have shown that membrane-bound Ras molecules segregate into nanocluster domains. Several models have been developed in attempts to obtain quantitative descriptions of nanocluster formation, but all have relied on assumptions such as a constant, expression-level independent ratio of Ras in clusters to Ras monomers (cluster/monomer ratio). However, this assumption is inconsistent with the law of mass action. Here, we present a biophysical model of Ras clustering based on short-range attraction and long-range repulsion between Ras molecules in the membrane. To test this model, we performed Monte Carlo simulations and compared statistical clustering properties with experimental data. We find that we can recover the experimentally-observed clustering across a range of Ras expression levels, without assuming a constant cluster/monomer ratio or the existence of lipid rafts. In addition, our model makes predictions about the signaling properties of Ras nanoclusters in support of the idea that Ras nanoclusters act as an analog-digital-analog converter for high fidelity signaling.
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Affiliation(s)
- Thomas Gurry
- Centre for Integrated Systems Biology at Imperial College, Imperial College London, London, United Kingdom
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | - Ozan Kahramanoğulları
- Centre for Integrated Systems Biology at Imperial College, Imperial College London, London, United Kingdom
- Department of Computing, Imperial College London, London, United Kingdom
| | - Robert G. Endres
- Centre for Integrated Systems Biology at Imperial College, Imperial College London, London, United Kingdom
- Division of Molecular Biosciences, Imperial College London, London, United Kingdom
- * E-mail:
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33
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Abstract
The three closely related mammalian ras genes, Hras, Nras and Kras, have each been implicated in human tumorigenesis by virtue of mutational activation. However, while these genes encode proteins with very similar biochemical properties, activating ras alleles corresponding to the various isoforms have been linked to particular malignancies. Accumulating evidence suggests that these proteins exert distinct activities in a tissue-specific context, apparently reflecting developmental lineage-specific roles for the various ras isoforms. Some of these distinct functions appear to reflect differences in their C-termini, which determine distinct subcellular localization, thereby suggesting a role for compartmentalized signaling. In this review, we discuss the biological functions of the ras isoforms in the context of tissue-specific function as it relates to ras function in development and human cancer.
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Affiliation(s)
- Margaret P Quinlan
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
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34
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Kang BH, Plescia J, Song HY, Meli M, Colombo G, Beebe K, Scroggins B, Neckers L, Altieri DC. Combinatorial drug design targeting multiple cancer signaling networks controlled by mitochondrial Hsp90. J Clin Invest 2009; 119:454-64. [PMID: 19229106 DOI: 10.1172/jci37613] [Citation(s) in RCA: 196] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Accepted: 01/07/2009] [Indexed: 12/11/2022] Open
Abstract
Although therapeutically targeting a single signaling pathway that drives tumor development and/or progression has been effective for a number of cancers, in many cases this approach has not been successful. Targeting networks of signaling pathways, instead of isolated pathways, may overcome this problem, which is probably due to the extreme heterogeneity of human tumors. However, the possibility that such networks may be spatially arranged in specialized subcellular compartments is not often considered in pathway-oriented drug discovery and may influence the design of new agents. Hsp90 is a chaperone protein that controls the folding of proteins in multiple signaling networks that drive tumor development and progression. Here, we report the synthesis and properties of Gamitrinibs, a class of small molecules designed to selectively target Hsp90 in human tumor mitochondria. Gamitrinibs were shown to accumulate in the mitochondria of human tumor cell lines and to inhibit Hsp90 activity by acting as ATPase antagonists. Unlike Hsp90 antagonists not targeted to mitochondria, Gamitrinibs exhibited a "mitochondriotoxic" mechanism of action, causing rapid tumor cell death and inhibiting the growth of xenografted human tumor cell lines in mice. Importantly, Gamitrinibs were not toxic to normal cells or tissues and did not affect Hsp90 homeostasis in cellular compartments other than mitochondria. Therefore, combinatorial drug design, whereby inhibitors of signaling networks are targeted to specific subcellular compartments, may generate effective anticancer drugs with novel mechanisms of action.
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Affiliation(s)
- Byoung Heon Kang
- Department of Cancer Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
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35
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Zhuravliova E, Barbakadze T, Narmania N, Sepashvili M, Mikeladze DG. Hypoinsulinemia alleviates the GRF1/Ras/Akt anti-apoptotic pathway and induces alterations of mitochondrial ras trafficking in neuronal cells. Neurochem Res 2008; 34:1076-82. [PMID: 19002579 DOI: 10.1007/s11064-008-9877-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/23/2008] [Indexed: 02/04/2023]
Abstract
Recent observations have established that interruption of insulin production causes deficits in learning and memory formation. We have studied the mechanism of insulin's neuroprotective effect on primary neuronal cells and in streptozotocin (STZ)-induced diabetic rat brain. We have found that in hippocampal neuronal cells insulin increases the content of farnesylated Ras and phosphorylated form of Akt. Besides, the treatment of cells by insulin leads to the activation of mitochondrial cytochrome oxidase, which is inhibited by manumycin, a farnesyltransferase inhibitor. During experimental diabetes, the content of membrane-bound GRF1 was decreased in rat hippocampus that was correlated with the reduction in mitochondrial Ras and phosphorylated forms of Akt. This redistribution in Ras-GRF system was accompanied by the alteration in the activities of CREB, NF-kB (p65) and c-Rel transcription factors. We have proposed that hypoinsulinemia induces the inhibition of Ras signalling in the neuronal cells additionally by abnormality of Ras trafficking into mitochondria.
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Affiliation(s)
- E Zhuravliova
- Department of Biochemistry, I. Beritashvili Institute of Physiology, Tbilisi, Georgia
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36
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Ji H, Erfani N, Tauro BJ, Kapp EA, Zhu HJ, Moritz RL, Lim JWE, Simpson RJ. Difference gel electrophoresis analysis of Ras-transformed fibroblast cell-derived exosomes. Electrophoresis 2008; 29:2660-71. [PMID: 18494037 DOI: 10.1002/elps.200800015] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Exosomes are membrane vesicles of endocytic origin released by many cell types. The molecular composition of exosomes reflects the specialised functions of their original cells. For example, these vesicles can mediate communication through their ability to bind to target cells, facilitating processes such as vascular homeostasis and antigen presentation. Although the proteomes of exosomes from several cell types are known, exploration of exosomes from additional cell types may improve our understanding of their potential physiological roles. Here, we describe the isolation and characterisation of exosomes isolated from the culture medium of murine fibroblast NIH3T3 cells and Ras-transformed NIH3T3 cells. The vesicular nature and size (30-100 nm) of the purified fibroblast exosomes was confirmed by electron microscopy. 2-D difference gel electrophoresis (DIGE) was used to compare protein profiles of exosomes secreted from NIH3T3 cells and Ras-transformed NIH3T3 cells. LC-MS/MS sequencing identified proteins in 188 protein spots in the exosomes from the two cell lines, many of which have been previously identified in exosomes from other cell types. However, some proteins identified are novel for fibroblast exosomes, such as Serpin B6. Over 34 proteins, including milk fat globule EGF factor 8 (lactadherin), collagen alpha-1 (VI), 14-3-3 isoforms, guanine nucleotide-binding proteins (G proteins), the eukaryotic translation initiation factors elF-3 gamma and elF-5A accumulated (>2-fold) in exosomes upon Ras-induced oncogenic transformation. Significantly, the 10.4-fold increase in v-Ha-Ras p21 protein in exosomes derived from Ras-transformed NIH3T3 cells suggests that exosome secretion may be implicated in eradication of obsolete proteins.
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Affiliation(s)
- Hong Ji
- Joint ProteomicS Laboratory, Ludwig Institute for Cancer Research, Parkville, Victoria, Australia
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37
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GTPase-mediated regulation of the unfolded protein response in Caenorhabditis elegans is dependent on the AAA+ ATPase CDC-48. Mol Cell Biol 2008; 28:4261-74. [PMID: 18458060 DOI: 10.1128/mcb.02252-07] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
When endoplasmic reticulum (ER) homeostasis is perturbed, an adaptive mechanism is triggered and named the unfolded protein response (UPR). Thus far, three known UPR signaling branches (IRE-1, PERK, and ATF-6) mediate the reestablishment of ER functions but can also lead to apoptosis if ER stress is not alleviated. However, the understanding of the molecular mechanisms integrating the UPR to other ER functions, such as membrane traffic or endomembrane signaling, remains incomplete. We consequently sought to identify new regulators of UPR-dependent transcriptional mechanisms and focused on a family of proteins known to mediate, among other, ER-related functions: the small GTP-binding proteins of the RAS superfamily. To this end, we used transgenic UPR reporter Caenorhabditis elegans strains as a model to specifically silence small-GTPase expression. We show that the Rho subfamily member CRP-1 is an essential component of UPR-induced transcriptional events through its physical and genetic interactions with the AAA+ ATPase CDC-48. In addition, we describe a novel signaling module involving CRP-1 and CDC-48 which may directly link the UPR to DNA remodeling and transcription control.
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38
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Shalom-Feuerstein R, Levy R, Makovski V, Raz A, Kloog Y. Galectin-3 regulates RasGRP4-mediated activation of N-Ras and H-Ras. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:985-93. [PMID: 18413234 DOI: 10.1016/j.bbamcr.2008.03.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2007] [Revised: 03/05/2008] [Accepted: 03/06/2008] [Indexed: 01/19/2023]
Abstract
Galectin-3 (Gal-3) is a pleiotropic beta-galactoside-binding protein expressed at relatively high levels in human neoplasms. Its carbohydrate recognition domain (CRD) contains a hydrophobic pocket that can accommodate the farnesyl moiety of K-Ras. Binding of K-Ras to Gal-3 stabilizes K-Ras in its active (GTP-bound) state. Gal-3, which does not interact with N-Ras, was nevertheless shown to reduce N-Ras-GTP in BT-549 cells by an unknown mechanism that we explored here. First, comparative analysis of various cancer cell lines (glioblastomas, breast cancer cells and ovarian carcinomas) showed a positive correlation between low N-Ras-GTP/high K-Ras-GTP phenotype and Gal-3 expression levels. Next we found that epidermal growth factor-stimulated GTP loading of N-Ras, but not of K-Ras, is blocked in cells expressing high levels of Gal-3. Activation of Ras guanine nucleotide releasing proteins (RasGRPs) by phorbol 12-myristate 13-acetate (PMA) or downregulation of Gal-3 by Gal-3 shRNA increased the levels of N-Ras-GTP in Gal-3 expressing cells. We further show that the N-terminal domain of Gal-3 interacts with and inhibits RasGRP4-mediated GTP loading on N-Ras and H-Ras proteins. Growth of BT-549 cells stably expressing the Gal-3 N-terminal domain was strongly attenuated. Overall, these experiments demonstrate a new control mechanism of Ras activation in cancer cells whereby the Gal-3 N-terminal domain inhibits activation of N-Ras and H-Ras proteins.
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Affiliation(s)
- Ruby Shalom-Feuerstein
- Department of Neurobiochemistry, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, 69978 Tel-Aviv, Israel
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39
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Rotblat B, Ehrlich M, Haklai R, Kloog Y. The Ras inhibitor farnesylthiosalicylic acid (Salirasib) disrupts the spatiotemporal localization of active Ras: a potential treatment for cancer. Methods Enzymol 2008; 439:467-89. [PMID: 18374183 DOI: 10.1016/s0076-6879(07)00432-6] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Chronic activation of Ras proteins by mutational activation or by growth factor stimulation is a common occurrence in many human cancers and was shown to induce and be required for tumor growth. Even if additional genetic defects are present, "correction" of the Ras defect has been shown to reverse Ras-dependent tumorigenesis. One way to block Ras protein activity is by interfering with their spatiotemporal localization in cellular membranes or in membrane microdomains, a prerequisite for Ras signaling and biological activity. Detailed reports describe the use of this method in studies employing farnesylthiosalicylic acid (FTS, Salirasib), a Ras farnesylcysteine mimetic, which selectively disrupts the association of chronically active Ras proteins with the plasma membrane. FTS competes with Ras for binding to Ras-escort proteins, which possess putative farnesyl-binding domains and interact only with the activated form of Ras proteins, thereby promoting Ras nanoclusterization in the plasma membrane and robust signals. This chapter presents three-dimensional time-lapse images that track the FTS-induced inhibition of membrane-activated Ras in live cells on a real-time scale. It also describes a mechanistic model that explains FTS selectivity toward activated Ras. Selective blocking of activated Ras proteins results in the inhibition of Ras transformation in vitro and in animal models, with no accompanying toxicity. Phase I clinical trials have demonstrated a safe profile for oral FTS, with minimal side effects and promising activity in hematological malignancies. Salirasib is currently undergoing trials in patients with pancreatic cancer and with nonsmall cell lung cancer, with or without identified K-Ras mutations. The findings might indicate whether with the disruption of the spatiotemporal localization of oncogenic Ras proteins and the targeting of prenyl-binding domains by anticancer drugs is worth developing as a means of cancer treatment.
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Affiliation(s)
- Barak Rotblat
- Department of Neurobiochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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40
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Mor A, Philips MR, Pillinger MH. The role of Ras signaling in lupus T lymphocytes: biology and pathogenesis. Clin Immunol 2007; 125:215-23. [PMID: 17913587 DOI: 10.1016/j.clim.2007.08.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Revised: 08/11/2007] [Accepted: 08/13/2007] [Indexed: 12/17/2022]
Abstract
Ras is a GTP-binding protein that plays multiple important roles in cell activation, including proliferative and inflammatory responses. Ras regulation is complex and depends upon post-translational processing, organelle-specific localization and the activation/deactivation of Ras by a number of regulatory molecules. Ras activation in T lymphocytes demonstrates unique features, including its dependence on the T cell receptor and the ability of Ras to signal from both the plasma membrane and the Golgi. Abnormalities of Ras expression, activation and signaling pathways in T lymphocytes appear to play important roles in the development of autoimmunity in general, and systemic lupus erythematosus in particular. In this manuscript, we review the basic biology of Ras in T lymphocytes, and the ways in which T lymphocyte Ras abnormalities may contribute to the development of a lupus phenotype.
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Affiliation(s)
- Adam Mor
- Department of Medicine, Division of Rheumatology, New York University School of Medicine, the NYU Hospital for Joint Diseases, NY 10003, USA.
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41
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Abstract
Cancer can be perceived as a disease of communication between and within cells. The aberrations are pleiotropic, but mitogen-activated protein kinase (MAPK) pathways feature prominently. Here, we discuss recent findings and hypotheses on the role of MAPK pathways in cancer. Cancerous mutations in MAPK pathways are frequently mostly affecting Ras and B-Raf in the extracellular signal-regulated kinase pathway. Stress-activated pathways, such as Jun N-terminal kinase and p38, largely seem to counteract malignant transformation. The balance and integration between these signals may widely vary in different tumours, but are important for the outcome and the sensitivity to drug therapy.
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Affiliation(s)
- A S Dhillon
- The Beatson Institute for Cancer Research, Bearsden, Glasgow, UK.
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42
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Wang S, Narendra S, Fedoroff N. Heterotrimeric G protein signaling in the Arabidopsis unfolded protein response. Proc Natl Acad Sci U S A 2007; 104:3817-22. [PMID: 17360436 PMCID: PMC1820667 DOI: 10.1073/pnas.0611735104] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We present evidence that heterotrimeric G protein signaling is involved in cell death associated with the unfolded protein response (UPR) in Arabidopsis. Seedlings of homozygous agb1-2 (Gbeta-null mutation) mutant plants are markedly more resistant to growth inhibition by the protein glycosylation inhibitor tunicamycin (Tm) than either wild-type plants or gpa1-4 (Galpha-null mutation) mutants. Leaves of older Gbeta mutant plants show much less cell death when infiltrated with Tm than leaves of wild-type plants. The transcriptional response of Gbeta mutant plants to Tm is less pronounced than that of wild-type plants, as is the accumulation of BiP chaperone proteins. A majority of the Arabidopsis Gbeta protein is associated with the endoplasmic reticulum (ER) and cofractionates with membrane-associated ER luminal BiP. Consistent with its ER localization, Gbeta protein is degraded during the UPR, whereas Galpha protein is not. Taken together, these observations imply that the Gbeta protein, which forms a stable heterodimer with the Ggamma subunit, is involved in the signaling events that trigger UPR-associated cell death. The different Tm sensitivities of Galpha and Gbeta mutants, the ER localization of Gbeta, and the differential stabilities of Galpha and Gbeta proteins during the UPR suggest that the Gbetagamma complex serves a signaling function in the ER independent of its function in the Galphabetagamma heterotrimer.
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Affiliation(s)
- Shiyu Wang
- *Biology Department and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802; and
| | - Savitha Narendra
- *Biology Department and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802; and
| | - Nina Fedoroff
- *Biology Department and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802; and
- Santa Fe Institute, Santa Fe, NM 87501
- To whom correspondence should be addressed at:
219 Wartik Laboratory, Pennsylvania State University, University Park, PA 16802. E-mail:
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43
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Affiliation(s)
- Andrea I. McClatchey
- Center for Cancer Research, Massachusetts General Hospital, Charlestown, Massachusetts 02129 and Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115;
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44
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Marq JB, Brini A, Kolakofsky D, Garcin D. Targeting of the Sendai virus C protein to the plasma membrane via a peptide-only membrane anchor. J Virol 2007; 81:3187-97. [PMID: 17229713 PMCID: PMC1866060 DOI: 10.1128/jvi.02465-06] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Several cellular proteins are synthesized in the cytosol on free ribosomes and then associate with membranes due to the presence of short peptide sequences. These membrane-targeting sequences contain sites to which lipid chains are attached, which help direct the protein to a particular membrane domain and anchor it firmly in the bilayer. The intracellular concentration of these proteins in particular cellular compartments, where their interacting partners are also concentrated, is essential to their function. This paper reports that the apparently unmodified N-terminal sequence of the Sendai virus C protein (MPSFLKKILKLRGRR . . .; letters in italics represent hydrophobic residues; underlined letters represent basic residues, which has a strong propensity to form an amphipathic alpha-helix in a hydrophobic environment) also function as a membrane targeting signal and membrane anchor. Moreover, the intracellular localization of the C protein at the plasma membrane is essential for inducing the interferon-independent phosphorylation of Stat1 as part of the viral program to prevent the cellular antiviral response.
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Affiliation(s)
- Jean-Baptiste Marq
- Department of Microbiology and Molecular Medicine, University of Geneva School of Medicine, 11 Ave de Champel, CH-1211 Geneva, Switzerland
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45
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Xiang Z, Kreisel F, Cain J, Colson A, Tomasson MH. Neoplasia driven by mutant c-KIT is mediated by intracellular, not plasma membrane, receptor signaling. Mol Cell Biol 2006; 27:267-82. [PMID: 17060458 PMCID: PMC1800644 DOI: 10.1128/mcb.01153-06] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Activating mutations in c-KIT are associated with gastrointestinal stromal tumors, mastocytosis, and acute myeloid leukemia. In attempting to establish a murine model of human KIT(D816V) (hKIT(D816V))-mediated leukemia, we uncovered an unexpected relationship between cellular transformation and intracellular trafficking. We found that transport of hKIT(D816V) protein was blocked at the endoplasmic reticulum in a species-specific fashion. We exploited these species-specific trafficking differences and a set of localization domain-tagged KIT mutants to explore the relationship between subcellular localization of mutant KIT and cellular transformation. The protein products of fully transforming KIT mutants localized to the Golgi apparatus and to a lesser extent the plasma membrane. Domain-tagged KIT(D816V) targeted to the Golgi apparatus remained constitutively active and transforming. Chemical inhibition of intracellular transport demonstrated that Golgi localization is sufficient, but plasma membrane localization is dispensable, for downstream signaling mediated by KIT mutation. When expressed in murine bone marrow, endoplasmic reticulum-localized hKIT(D816V) failed to induce disease in mice, while expression of either Golgi-localized HyKIT(D816V) or cytosol-localized, ectodomain-deleted KIT(D816V) uniformly caused fatal myeloproliferative diseases. Taken together, these data demonstrate that intracellular, non-plasma membrane receptor signaling is sufficient to drive neoplasia caused by mutant c-KIT and provide the first animal model of myelomonocytic neoplasia initiated by human KIT(D816V).
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Affiliation(s)
- Zhifu Xiang
- Washington University School of Medicine, Campus Box 8007, 660 South Euclid Avenue, St. Louis, MO 63110, USA
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46
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Abstract
Protein kinase C (PKC) comprises a superfamily of isoenzymes, many of which are activated by cofactors such as diacylglycerol and phosphatidylserine. In order to be capable of activation, PKC must first undergo a series of phosphorylations. In turn, activated PKC phosphorylates a wide variety of intracellular target proteins and has multiple functions in signal transduced cellular regulation. A role for PKC activation had been noted in several renal diseases, but two that have had most investigation are diabetic nephropathy and kidney cancer. In diabetic nephropathy, an elevation in diacylglycerol and/or other cofactor stimulants leads to an increase in activity of certain PKC isoforms, changes that are linked to the development of dysfunctional vasculature. The ability of isoform-specific PKC inhibitors to antagonize diabetes-induced vascular disease is a new avenue for treatment of this disorder. In the development and progressive invasiveness of kidney cancer, increased activity of several specific isoforms of PKC has been noted. It is thought that this may promote the kidney cancer's inherent resistance to apoptosis, in natural regression or after treatments, or it may promote the invasiveness of renal cancers via cellular differentiation pathways. In general, however, a more complete understanding of the functions of individual PKC isoforms in the kidney, and development or recognition of specific inhibitors or promoters of their activation, will be necessary to apply this knowledge for treatment of cellular dysregulation in renal disease.
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Affiliation(s)
- Jun Li
- Discipline of Molecular and Cellular Pathology, School of Medicine, University of Queensland, Brisbane, Queensland, Australia
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47
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Trampont P, Zhang L, Ravichandran KS. ShcA mediates the dominant pathway to extracellular signal-regulated kinase activation during early thymic development. Mol Cell Biol 2006; 26:9035-44. [PMID: 16982683 PMCID: PMC1636838 DOI: 10.1128/mcb.00988-06] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
During thymic development, the beta selection checkpoint is regulated by pre-T-cell receptor-initiated signals. Progression through this checkpoint is influenced by phosphorylation and activation of the serine/threonine kinases extracellular signal-regulated kinase 1 (ERK1) and ERK2, but the in vivo relevance of specific upstream players leading to ERK activation is not known. Here, using mice with a conditional loss of the shc1 gene or expressing mutants of ShcA, we demonstrate that the adapter protein ShcA is responsible for up to 70% of ERK activation in double-negative (DN) thymocytes in vivo and ex vivo. We also identify two specific tyrosines on ShcA that promote ERK phosphorylation in vivo, and mice expressing ShcA with mutations of these tyrosines show impaired DN thymocyte development. This work provides the first in vivo demonstration of the relative requirement of upstream adapters in controlling ERK activation during beta selection and suggests a dominant role for ShcA.
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Affiliation(s)
- Paul Trampont
- Carter Immunology Center, MR4-4072D, Box 801386, University of Virginia, Charlottesville, VA 22908, USA
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Denoyelle C, Abou-Rjaily G, Bezrookove V, Verhaegen M, Johnson TM, Fullen DR, Pointer JN, Gruber SB, Su LD, Nikiforov MA, Kaufman RJ, Bastian BC, Soengas MS. Anti-oncogenic role of the endoplasmic reticulum differentially activated by mutations in the MAPK pathway. Nat Cell Biol 2006; 8:1053-63. [PMID: 16964246 DOI: 10.1038/ncb1471] [Citation(s) in RCA: 274] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2006] [Accepted: 08/08/2006] [Indexed: 12/30/2022]
Abstract
Dysfunction of the endoplasmic reticulum (ER) has been reported in a variety of human pathologies, including cancer. However, the contribution of the ER to the early stages of normal cell transformation is largely unknown. Using primary human melanocytes and biopsies of human naevi (moles), we show that the extent of ER stress induced by cellular oncogenes may define the mechanism of activation of premature senescence. Specifically, we found that oncogenic forms of HRAS (HRAS(G12V)) but not its downstream target BRAF (BRAF(V600E)), engaged a rapid cell-cycle arrest that was associated with massive vacuolization and expansion of the ER. However, neither p53, p16(INK4a) nor classical senescence markers--such as foci of heterochromatin or DNA damage--were able to account for the specific response of melanocytes to HRAS(G12V). Instead, HRAS(G12V)-driven senescence was mediated by the ER-associated unfolded protein response (UPR). The impact of HRAS on the UPR was selective, as it was poorly induced by activated NRAS (more frequently mutated in melanoma than HRAS). These results argue against premature senescence as a converging mechanism of response to activating oncogenes and support a direct role of the ER as a gatekeeper of tumour control.
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Affiliation(s)
- Christophe Denoyelle
- Department of Dermatology and Comprehensive Cancer Center, University of Michigan, 1500E Medical Center Drive, 4217 CCGC, Ann Arbor, MI 48109, USA
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Wolfman JC, Planchon SM, Liao J, Wolfman A. Structural and functional consequences of c-N-Ras constitutively associated with intact mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:1108-24. [PMID: 16996152 DOI: 10.1016/j.bbamcr.2006.07.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2006] [Revised: 07/19/2006] [Accepted: 07/27/2006] [Indexed: 12/22/2022]
Abstract
We demonstrate that both c-N-Ras and c-K(B)-Ras are constitutively associated with purified mitochondria. c-K(B)-Ras is associated with the mitochondrial outer membrane, and c-N-Ras is associated with both the outer membrane and inner mitochondrial compartments. The mitochondrial morphology is abnormal in both c-N-Ras negative and K-Ras negative cells. Normal mitochondrial morphology was restored by targeting N-Ras to both the inner and outer mitochondrial compartments, or by ectopically expressing c-K(B)-Ras. Impaired mitochondrial function can result in increased CHOP and NFkappaB activity, typical for a retrograde signaling response. Both are constitutively elevated in the N-Ras negative cells, but not in the K-Ras negative background, and are restored by c-N-Ras targeted exclusively to the inner mitochondrial compartment. Surprisingly, both targeting and the ability to functionally reduce retrograde transcriptional activity were found to be independent of c-N-Ras farnesylation. Overall, these data demonstrate for the first time a (1) farnesylation independent function for c-N-Ras and (2) that N-Ras within the inner mitochondrial compartment is an essential component of the retrograde signaling system between the mitochondria and nucleus.
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Affiliation(s)
- Janice C Wolfman
- Department of Cell Biology, NC10, Cleveland Clinic Lerner College of Medicine, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
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Ashery U, Yizhar O, Rotblat B, Kloog Y. Nonconventional Trafficking of Ras Associated with Ras Signal Organization. Traffic 2006; 7:119-26. [PMID: 16824054 DOI: 10.1111/j.1600-0854.2006.00459.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Ras signaling to its downstream effectors appears to include combinations of extracellular-signal-regulated Ras activation at the plasma membrane (PM) and endomembranes, dynamic lateral segregation in the PM, and translocation of Ras from the PM to intracellular compartments. These processes are governed by the C-terminal polybasic farnesyl domain in K-Ras 4B and by the cysteine-palmitoylated C-terminal farnesyl domains in H-Ras and N-Ras. K-Ras 4B has no palmitoylated cysteines. Depalmitoylation/repalmitoylation of H-/N-Ras proteins promotes their cellular redistribution and signaling by mechanisms as yet unknown, possibly involving chaperones. Palmitoylation of H-/N-Ras also promotes their association with 'rasosomes', randomly diffusing nanoparticles that apparently provide a means by which multiple copies of activated Ras and its signal can spread rapidly. Ubiquitination of H-Ras evidently targets it to the endosomes. The polybasic farnesyl domain of K-Ras 4B was shown to act as a target for Ca++/calmodulin, which sequesters the active protein from the PM, thereby facilitating its trafficking to Golgi apparatus and early endosomes. Protein kinase C-dependent phosphorylation of S181 in K-Ras 4B was shown to provide a regulated farnesyl-electrostatic switch on K-Ras 4B, which promotes its translocation to the mitochondria. All these translocation events are characterized by nonconventional trafficking of the farnesyl-modified Ras proteins and seem to govern the selectivity and probably also the robustness of the Ras signal. In this review, we discuss the various modifications and interactions of the farnesylated C-terminus, the trafficking of Ras proteins in the PM and between the PM and the endomembranes, and the relevance of the subcellular localization of Ras for Ras function.
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Affiliation(s)
- Uri Ashery
- Department of Neurobiochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv, Israel
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