1
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Chien YC, Yoon GM. Subcellular dynamics of ethylene signaling drive plant plasticity to growth and stress: Spatiotemporal control of ethylene signaling in Arabidopsis. Bioessays 2024; 46:e2400043. [PMID: 38571390 DOI: 10.1002/bies.202400043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Revised: 03/15/2024] [Accepted: 03/19/2024] [Indexed: 04/05/2024]
Abstract
Volatile compounds, such as nitric oxide and ethylene gas, play a vital role as signaling molecules in organisms. Ethylene is a plant hormone that regulates a wide range of plant growth, development, and responses to stress and is perceived by a family of ethylene receptors that localize in the endoplasmic reticulum. Constitutive Triple Response 1 (CTR1), a Raf-like protein kinase and a key negative regulator for ethylene responses, tethers to the ethylene receptors, but undergoes nuclear translocation upon activation of ethylene signaling. This ER-to-nucleus trafficking transforms CTR1 into a positive regulator for ethylene responses, significantly enhancing stress resilience to drought and salinity. The nuclear trafficking of CTR1 demonstrates that the spatiotemporal control of ethylene signaling is essential for stress adaptation. Understanding the mechanisms governing the spatiotemporal control of ethylene signaling elements is crucial for unraveling the system-level regulatory mechanisms that collectively fine-tune ethylene responses to optimize plant growth, development, and stress adaptation.
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Affiliation(s)
- Yuan-Chi Chien
- Department of Botany and Plant Pathology and Center for Plant Biology, Purdue University, West Lafayette, Indiana, USA
| | - Gyeong Mee Yoon
- Department of Botany and Plant Pathology and Center for Plant Biology, Purdue University, West Lafayette, Indiana, USA
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2
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Belenichev I, Popazova O, Bukhtiyarova N, Savchenko D, Oksenych V, Kamyshnyi O. Modulating Nitric Oxide: Implications for Cytotoxicity and Cytoprotection. Antioxidants (Basel) 2024; 13:504. [PMID: 38790609 PMCID: PMC11118938 DOI: 10.3390/antiox13050504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 04/19/2024] [Accepted: 04/20/2024] [Indexed: 05/26/2024] Open
Abstract
Despite the significant progress in the fields of biology, physiology, molecular medicine, and pharmacology; the designation of the properties of nitrogen monoxide in the regulation of life-supporting functions of the organism; and numerous works devoted to this molecule, there are still many open questions in this field. It is widely accepted that nitric oxide (•NO) is a unique molecule that, despite its extremely simple structure, has a wide range of functions in the body, including the cardiovascular system, the central nervous system (CNS), reproduction, the endocrine system, respiration, digestion, etc. Here, we systematize the properties of •NO, contributing in conditions of physiological norms, as well as in various pathological processes, to the mechanisms of cytoprotection and cytodestruction. Current experimental and clinical studies are contradictory in describing the role of •NO in the pathogenesis of many diseases of the cardiovascular system and CNS. We describe the mechanisms of cytoprotective action of •NO associated with the regulation of the expression of antiapoptotic and chaperone proteins and the regulation of mitochondrial function. The most prominent mechanisms of cytodestruction-the initiation of nitrosative and oxidative stresses, the production of reactive oxygen and nitrogen species, and participation in apoptosis and mitosis. The role of •NO in the formation of endothelial and mitochondrial dysfunction is also considered. Moreover, we focus on the various ways of pharmacological modulation in the nitroxidergic system that allow for a decrease in the cytodestructive mechanisms of •NO and increase cytoprotective ones.
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Affiliation(s)
- Igor Belenichev
- Department of Pharmacology and Medical Formulation with Course of Normal Physiology, Zaporizhzhia State Medical and Pharmaceutical University, 69000 Zaporizhzhia, Ukraine
| | - Olena Popazova
- Department of Histology, Cytology and Embryology, Zaporizhzhia State Medical and Pharmaceutical University, 69000 Zaporizhzhia, Ukraine
| | - Nina Bukhtiyarova
- Department of Clinical Laboratory Diagnostics, Zaporizhzhia State Medical and Pharmaceutical University, 69000 Zaporizhzhia, Ukraine
| | - Dmytro Savchenko
- Department of Pharmacy and Industrial Drug Technology, Bogomolets National Medical University, 01601 Kyiv, Ukraine
| | - Valentyn Oksenych
- Broegelmann Research Laboratory, Department of Clinical Science, University of Bergen, 5020 Bergen, Norway
| | - Oleksandr Kamyshnyi
- Department of Microbiology, Virology and Immunology, I. Horbachevsky Ternopil State Medical University, 46001 Ternopil, Ukraine;
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3
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Chien YC, Reyes A, Park HL, Xu SL, Yoon GM. Uncovering the proximal proteome of CTR1 through TurboID-mediated proximity labeling. Proteomics 2024; 24:e2300212. [PMID: 37876141 DOI: 10.1002/pmic.202300212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 08/25/2023] [Accepted: 10/09/2023] [Indexed: 10/26/2023]
Abstract
Protein-protein interactions play a crucial role in driving cellular processes and enabling appropriate physiological responses in organisms. The plant hormone ethylene signaling pathway is complex and regulated by the spatiotemporal regulation of its signaling molecules. Constitutive Triple Response 1 (CTR1), a key negative regulator of the pathway, regulates the function of Ethylene-Insensitive 2 (EIN2), a positive regulator of ethylene signaling, at the endoplasmic reticulum (ER) through phosphorylation. Our recent study revealed that CTR1 can also translocate from the ER to the nucleus in response to ethylene and positively regulate ethylene responses by stabilizing EIN3. To gain further insights into the role of CTR1 in plants, we used TurboID-based proximity labeling and mass spectrometry to identify the proximal proteomes of CTR1 in Nicotiana benthamiana. The identified proximal proteins include known ethylene signaling components, as well as proteins involved in diverse cellular processes such as mitochondrial respiration, mRNA metabolism, and organelle biogenesis. Our study demonstrates the feasibility of proximity labeling using the N. benthamiana transient expression system and identifies the potential interactors of CTR1 in vivo, uncovering the potential roles of CTR1 in a wide range of cellular processes.
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Affiliation(s)
- Yuan-Chi Chien
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
- The Center for Plant Biology, Purdue University, West Lafayette, Indiana, USA
| | - Andres Reyes
- Department of Plant Biology, Carnegie Institution for Science, Stanford University, Stanford, California, USA
- Carnegie Mass Spectrometry Facility, Carnegie Institution for Science, Stanford, California, USA
| | - Hye Lin Park
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
- The Center for Plant Biology, Purdue University, West Lafayette, Indiana, USA
| | - Shou-Ling Xu
- Department of Plant Biology, Carnegie Institution for Science, Stanford University, Stanford, California, USA
- Carnegie Mass Spectrometry Facility, Carnegie Institution for Science, Stanford, California, USA
| | - Gyeong Mee Yoon
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
- The Center for Plant Biology, Purdue University, West Lafayette, Indiana, USA
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4
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Li Q, Li Z, Luo T, Shi H. Targeting the PI3K/AKT/mTOR and RAF/MEK/ERK pathways for cancer therapy. MOLECULAR BIOMEDICINE 2022; 3:47. [PMID: 36539659 PMCID: PMC9768098 DOI: 10.1186/s43556-022-00110-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 11/10/2022] [Indexed: 12/24/2022] Open
Abstract
The PI3K/AKT/mTOR and RAF/MEK/ERK pathways are commonly activated by mutations and chromosomal translocation in vital targets. The PI3K/AKT/mTOR signaling pathway is dysregulated in nearly all kinds of neoplasms, with the component in this pathway alternations. RAF/MEK/ERK signaling cascades are used to conduct signaling from the cell surface to the nucleus to mediate gene expression, cell cycle processes and apoptosis. RAS, B-Raf, PI3K, and PTEN are frequent upstream alternative sites. These mutations resulted in activated cell growth and downregulated cell apoptosis. The two pathways interact with each other to participate in tumorigenesis. PTEN alterations suppress RAF/MEK/ERK pathway activity via AKT phosphorylation and RAS inhibition. Several inhibitors targeting major components of these two pathways have been supported by the FDA. Dozens of agents in these two pathways have attracted great attention and have been assessed in clinical trials. The combination of small molecular inhibitors with traditional regimens has also been explored. Furthermore, dual inhibitors provide new insight into antitumor activity. This review will further comprehensively describe the genetic alterations in normal patients and tumor patients and discuss the role of targeted inhibitors in malignant neoplasm therapy. We hope this review will promote a comprehensive understanding of the role of the PI3K/AKT/mTOR and RAF/MEK/ERK signaling pathways in facilitating tumors and will help direct drug selection for tumor therapy.
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Affiliation(s)
- Qingfang Li
- grid.13291.380000 0001 0807 1581Laboratory of Aging Research and Cancer Drug Target, State Key Laboratory of Biotherapy, West China Hospital, National Clinical Research Center for Geriatrics, Sichuan University, Chengdu, China
| | - Zhihui Li
- Department of Oncology, The General Hospital of Western Theater Command, Chengdu, PR China
| | - Ting Luo
- grid.13291.380000 0001 0807 1581Department of Breast, Cancer Center, West China Hospital, Sichuan University, 610041 Chengdu, P. R. China
| | - Huashan Shi
- grid.13291.380000 0001 0807 1581Department of Biotherapy, Cancer Center, West China Hospital, Sichuan University, 610041 Chengdu, P. R. China
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5
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Rajpurohit T, Bhattacharya S. Moving Towards Dawn: KRas Signaling and Treatment in Pancreatic Ductal Adenocarcinoma. Curr Mol Pharmacol 2022; 15:904-928. [PMID: 35088684 DOI: 10.2174/1874467215666220128161647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 10/20/2021] [Accepted: 11/17/2021] [Indexed: 12/24/2022]
Abstract
"Pancreatic ductal adenocarcinoma (PDAC)" is robust, nearly clueless, and all-around deadly among all tumors. Below 10 %, the general 5-year endurance period has remained adamantly unaltered in the last 30 years, regardless of enormous clinical and therapeutic endeavors. The yearly number of deaths is more than the number of recently analyzed cases. Not a classic one, but "Carbohydrate Antigen CA19- 9" remains the prevailing tool for diagnosis. MicroRNAs and non-invasive techniques are now incorporated for the effective prognosis of PDAC than just CA19-9. Mutated "Rat sarcoma virus Ras" conformation "V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog KRas" is 95 % accountable for PDAC, and its active (GTP-bound) formation activates signaling cascade comprising "Rapidly accelerated fibrosarcoma Raf"/"Mitogen-activated protein kinase MEK"/ "Extracellular signal-regulated kinase ERK" with "Phosphoinositide 3-kinase PI3K"/ "protein kinase B Akt"/ "mammalian target of rapamycin mTOR" pathways. KRas has acquired the label of 'undruggable' since the crosstalk in the nexus of pathways compensates for Raf and PI3K signaling cascade blocking. It is arduous to totally regulate KRascoordinated PDAC with traditional medicaments like "gemcitabine GEM" plus nabpaclitaxel/ FOLFIRINOX. For long-haul accomplishments aiming at KRas, future endeavors should be directed to combinatorial methodologies to adequately block KRas pathways at different standpoints. Currently they are contributing to healing PDAC. In this review article, we outline the function of KRas in carcinogenesis in PDAC, its signaling cascade, former techniques utilized in hindering Kras, current and future possibilities for targeting Kras.
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Affiliation(s)
- Tarun Rajpurohit
- Department of Pharmaceutics, School of Pharmacy & Technology Management, SVKM'S NMIMS Deemed-to-be University, Shirpur, Maharashtra 425405, India
| | - Sankha Bhattacharya
- Department of Pharmaceutics, School of Pharmacy & Technology Management, SVKM'S NMIMS Deemed-to-be University, Shirpur, Maharashtra 425405, India
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6
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Wiechmann S, Maisonneuve P, Grebbin BM, Hoffmeister M, Kaulich M, Clevers H, Rajalingam K, Kurinov I, Farin HF, Sicheri F, Ernst A. Conformation-specific inhibitors of activated Ras GTPases reveal limited Ras dependency of patient-derived cancer organoids. J Biol Chem 2020; 295:4526-4540. [PMID: 32086379 DOI: 10.1074/jbc.ra119.011025] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 02/18/2020] [Indexed: 12/13/2022] Open
Abstract
The small GTPases H, K, and NRAS are molecular switches indispensable for proper regulation of cellular proliferation and growth. Several mutations in the genes encoding members of this protein family are associated with cancer and result in aberrant activation of signaling processes caused by a deregulated recruitment of downstream effector proteins. In this study, we engineered variants of the Ras-binding domain (RBD) of the C-Raf proto-oncogene, Ser/Thr kinase (CRAF). These variants bound with high affinity with the effector-binding site of Ras in an active conformation. Structural characterization disclosed how the newly identified RBD mutations cooperate and thereby enhance affinity with the effector-binding site in Ras compared with WT RBD. The engineered RBD variants closely mimicked the interaction mode of naturally occurring Ras effectors and acted as dominant-negative affinity reagents that block Ras signal transduction. Experiments with cancer cells showed that expression of these RBD variants inhibits Ras signaling, reducing cell growth and inducing apoptosis. Using these optimized RBD variants, we stratified patient-derived colorectal cancer organoids with known Ras mutational status according to their response to Ras inhibition. These results revealed that the presence of Ras mutations was insufficient to predict sensitivity to Ras inhibition, suggesting that not all of these tumors required Ras signaling for proliferation. In summary, by engineering the Ras/Raf interface of the CRAF-RBD, we identified potent and selective inhibitors of Ras in its active conformation that outcompete binding of Ras-signaling effectors.
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Affiliation(s)
- Svenja Wiechmann
- Institute of Biochemistry II, Goethe University Frankfurt-Medical Faculty, University Hospital, 60596 Frankfurt am Main, Germany.,Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Project Group Translational Medicine and Pharmacology TMP, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany
| | - Pierre Maisonneuve
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, Ontario M5G 1X5, Canada
| | - Britta M Grebbin
- German Cancer Consortium (DKTK), 69120 Heidelberg, Germany.,Georg-Speyer-Haus, Institute for Tumor Biology and Experimental Therapy, 60596 Frankfurt am Main, Germany.,German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - Meike Hoffmeister
- Institute of Biochemistry II, Goethe University Frankfurt-Medical Faculty, University Hospital, 60596 Frankfurt am Main, Germany.,Institute of Biochemistry, Brandenburg Medical School (MHB) Theodor Fontane, 14770 Brandenburg an der Havel, Germany
| | - Manuel Kaulich
- Institute of Biochemistry II, Goethe University Frankfurt-Medical Faculty, University Hospital, 60596 Frankfurt am Main, Germany.,Frankfurt Cancer Institute, 60596 Frankfurt am Main, Germany
| | - Hans Clevers
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW) and University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands.,Cancer Genomics Netherlands, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands.,Center for Molecular Medicine, Department of Genetics, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands
| | | | - Igor Kurinov
- Department of Chemistry and Chemical Biology, Cornell University, NE-CAT, Argonne, Illinois 60439
| | - Henner F Farin
- German Cancer Consortium (DKTK), 69120 Heidelberg, Germany.,Georg-Speyer-Haus, Institute for Tumor Biology and Experimental Therapy, 60596 Frankfurt am Main, Germany.,German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - Frank Sicheri
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, Ontario M5G 1X5, Canada
| | - Andreas Ernst
- Institute of Biochemistry II, Goethe University Frankfurt-Medical Faculty, University Hospital, 60596 Frankfurt am Main, Germany .,Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Project Group Translational Medicine and Pharmacology TMP, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany
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7
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Herrero A, Reis-Cardoso M, Jiménez-Gómez I, Doherty C, Agudo-Ibañez L, Pinto A, Calvo F, Kolch W, Crespo P, Matallanas D. Characterisation of HRas local signal transduction networks using engineered site-specific exchange factors. Small GTPases 2018; 11:371-383. [PMID: 29172991 DOI: 10.1080/21541248.2017.1406434] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Ras GTPases convey signals from different types of membranes. At these locations, different Ras isoforms, interactors and regulators generate different biochemical signals and biological outputs. The study of Ras localisation-specific signal transduction networks has been hampered by our inability to specifically activate each of these Ras pools. Here, we describe a new set of site-specific tethered exchange factors, engineered by fusing the RasGRF1 CDC25 domain to sub-localisation-defining cues, whereby Ras pools at specific locations can be precisely activated. We show that the CDC25 domain has a high specificity for activating HRas but not NRas and KRas. This unexpected finding means that our constructs mainly activate endogenous HRas. Hence, their use enabled us to identify distinct pathways regulated by HRas in endomembranes and plasma membrane microdomains. Importantly, these new constructs unveil different patterns of HRas activity specified by their subcellular localisation. Overall, the targeted GEFs described herein constitute ideal tools for dissecting spatially-defined HRas biochemical and biological functions.
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Affiliation(s)
- Ana Herrero
- Systems Biology Ireland, University College Dublin , Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin , Dublin, Ireland
| | | | - Iñaki Jiménez-Gómez
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Consejo Superior de Investigaciones Científicas (CSIC) - Universidad de Cantabria, Santander , Spain
| | - Carolanne Doherty
- Systems Biology Ireland, University College Dublin , Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin , Dublin, Ireland
| | - Lorena Agudo-Ibañez
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Consejo Superior de Investigaciones Científicas (CSIC) - Universidad de Cantabria, Santander , Spain
| | - Adán Pinto
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Consejo Superior de Investigaciones Científicas (CSIC) - Universidad de Cantabria, Santander , Spain
| | - Fernando Calvo
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Consejo Superior de Investigaciones Científicas (CSIC) - Universidad de Cantabria, Santander , Spain
| | - Walter Kolch
- Systems Biology Ireland, University College Dublin , Dublin, Ireland.,Conway Institute, University College Dublin , Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin , Dublin, Ireland
| | - Piero Crespo
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Consejo Superior de Investigaciones Científicas (CSIC) - Universidad de Cantabria, Santander , Spain.,Centro de Investigación Biomédica en Red CIBERONC, Instituto de Salud Calos III , Madrid, Spain
| | - David Matallanas
- Systems Biology Ireland, University College Dublin , Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin , Dublin, Ireland
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8
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Mahapatra DK, Asati V, Bharti SK. MEK inhibitors in oncology: a patent review (2015-Present). Expert Opin Ther Pat 2017; 27:887-906. [DOI: 10.1080/13543776.2017.1339688] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Debarshi Kar Mahapatra
- Dadasaheb Balpande College of Pharmacy, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur, India
| | - Vivek Asati
- Institute of Pharmaceutical Sciences, Guru Ghasidas Vishwavidyalaya (A Central University), Bilaspur, India
| | - Sanjay Kumar Bharti
- Institute of Pharmaceutical Sciences, Guru Ghasidas Vishwavidyalaya (A Central University), Bilaspur, India
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9
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Abstract
The RAF-MAPK signaling pathway regulates several very diverse cellular processes such as proliferation, differentiation, apoptosis, and transformation. While the canonical function of RAF kinases within the MAPK pathway is the activation of MEK, our group could demonstrate an important crosstalk between RAF signaling and the pro-apoptotic mammalian sterile 20-like kinase (MST2) tumor suppressor pathway in several cancer entities, including head and neck, colon, and breast. Here, the RAF kinases CRAF and ARAF sequester and inhibit the pro-apoptotic kinase MST2 independently of their own kinase activity. In our recent study, we showed that the ARAF-MST2 complex is regulated by subcellular compartmentalization during epithelial differentiation. Proliferating cells of the basal cell layer in squamous epithelia and tumor cells express ARAF at the mitochondria thus allowing for efficient sequestration of MST2. In contrast, non-malignant squamous epithelia have ARAF localized at the plasma membrane, where the control of MST2-mediated apoptosis is compromised. This re-distribution is regulated by the scaffold protein kinase suppressor of Ras 2 (KSR2). Here, we summarize how spatial and temporal regulation of RAF signaling complexes affect cellular signaling and functions.
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Affiliation(s)
- Jens Rauch
- a Systems Biology Ireland, University College Dublin , Ireland
| | - Walter Kolch
- a Systems Biology Ireland, University College Dublin , Ireland.,b School of Medicine and Medical Science, University College Dublin , Belfield, Dublin , Ireland
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10
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Differential localization of A-Raf regulates MST2-mediated apoptosis during epithelial differentiation. Cell Death Differ 2016; 23:1283-95. [PMID: 26891695 DOI: 10.1038/cdd.2016.2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2015] [Revised: 12/20/2016] [Accepted: 01/05/2016] [Indexed: 12/12/2022] Open
Abstract
A-Raf belongs to the family of oncogenic Raf kinases that are involved in mitogenic signaling by activating the MEK-ERK pathway. Low kinase activity of A-Raf toward MEK suggested that A-Raf might have alternative functions. We recently identified A-Raf as a potent inhibitor of the proapoptotic mammalian sterile 20-like kinase (MST2) tumor suppressor pathway in several cancer entities including head and neck, colon, and breast. Independent of kinase activity, A-Raf binds to MST2 thereby efficiently inhibiting apoptosis. Here, we show that the interaction of A-Raf with the MST2 pathway is regulated by subcellular compartmentalization. Although in proliferating normal cells and tumor cells A-Raf localizes to the mitochondria, differentiated non-carcinogenic cells of head and neck epithelia, which express A-Raf at the plasma membrane. The constitutive or induced re-localization of A-Raf to the plasma membrane compromises its ability to efficiently sequester and inactivate MST2, thus rendering cells susceptible to apoptosis. Physiologically, A-Raf re-localizes to the plasma membrane upon epithelial differentiation in vivo. This re-distribution is regulated by the scaffold protein kinase suppressor of Ras 2 (KSR2). Downregulation of KSR2 during mammary epithelial cell differentiation or siRNA-mediated knockdown re-localizes A-Raf to the plasma membrane causing the release of MST2. By using the MCF7 cell differentiation system, we could demonstrate that overexpression of A-Raf in MCF7 cells, which induces differentiation. Our findings offer a new paradigm to understand how differential localization of Raf complexes affects diverse signaling functions in normal cells and carcinomas.
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11
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Asati V, Mahapatra DK, Bharti SK. PI3K/Akt/mTOR and Ras/Raf/MEK/ERK signaling pathways inhibitors as anticancer agents: Structural and pharmacological perspectives. Eur J Med Chem 2016; 109:314-41. [PMID: 26807863 DOI: 10.1016/j.ejmech.2016.01.012] [Citation(s) in RCA: 383] [Impact Index Per Article: 47.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 01/08/2016] [Accepted: 01/09/2016] [Indexed: 12/17/2022]
Abstract
The protein kinases regulate cellular functions such as transcription, translation, proliferation, growth and survival by the process of phosphorylation. Over activation of signaling pathways play a major role in oncogenesis. The PI3K signaling pathway is dysregulated almost in all cancers due to the amplification, genetic mutation of PI3K gene and the components of the PI3K pathway themselves. Stimulation of the PI3K/Akt/mTOR and Ras/Raf/MEK/ERK pathways enhances growth, survival, and metabolism of cancer cells. Recently, the PI3K/Akt/mTOR and Ras/Raf/MEK/ERK signaling pathways have been identified as promising therapeutic targets for cancer therapy. The kinase inhibitors with enhanced specificity and improved pharmacokinetics have been considered for design and development of anticancer agents. This review focuses primarily on the Ras/Raf/MEK/ERK and PI3K/Akt/mTOR signaling pathways as therapeutic targets of anticancer drugs, their specific and dual inhibitors, structure activity relationships (SARs) and inhibitors under clinical trials.
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Affiliation(s)
- Vivek Asati
- Institute of Pharmaceutical Sciences, Guru Ghasidas Vishwavidyalaya (A Central University), Bilaspur 495009, Chhattisgarh, India
| | - Debarshi Kar Mahapatra
- Institute of Pharmaceutical Sciences, Guru Ghasidas Vishwavidyalaya (A Central University), Bilaspur 495009, Chhattisgarh, India
| | - Sanjay Kumar Bharti
- Institute of Pharmaceutical Sciences, Guru Ghasidas Vishwavidyalaya (A Central University), Bilaspur 495009, Chhattisgarh, India.
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12
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An S, Yang Y, Ward R, Liu Y, Guo XX, Xu TR. A-Raf: A new star of the family of raf kinases. Crit Rev Biochem Mol Biol 2015; 50:520-31. [PMID: 26508523 DOI: 10.3109/10409238.2015.1102858] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The Ras-Raf-MEK-MAPK (mitogen-activated protein kinase)-signaling pathway plays a key role in the regulation of many cellular functions, including cell proliferation, differentiation and transformation, by transmitting signals from membrane receptors to various cytoplasmic and nuclear targets. One of the key components of this pathway is the serine/threonine protein kinase, Raf. The Raf family kinases (A-Raf, B-Raf and C-Raf) have been intensively studied since being identified in the early 1980s as retroviral oncogenes, especially with respect to the discovery of activating mutations of B-Raf in a large number of tumors which led to intensified efforts to develop drugs targeting Raf kinases. This also resulted in a rapid increase in our knowledge of the biological functions of the B-Raf and C-Raf isoforms, which may in turn be contrasted with the little that is known about A-Raf. The biological functions of A-Raf remain mysterious, although it appears to share some of the basic properties of the other two isoforms. Recently, emerging evidence has begun to reveal the functions of A-Raf, of which some are kinase-independent. These include the inhibition of apoptosis by binding to MST2, acting as safeguard against oncogenic transformation by suppressing extracellular signal-regulated kinases (ERK) activation and playing a role in resistance to Raf inhibitors. In this review, we discuss the regulation of A-Raf protein expression, and the roles of A-Raf in apoptosis and cancer, with a special focus on its role in resistance to Raf inhibitors. We also describe the scaffold functions of A-Raf and summarize the unexpected complexity of Raf signaling.
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Affiliation(s)
- Su An
- a Faculty of Life Science and Technology , Kunming University of Science and Technology , Kunming , Yunnan , China and
| | - Yang Yang
- a Faculty of Life Science and Technology , Kunming University of Science and Technology , Kunming , Yunnan , China and
| | - Richard Ward
- b Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow , Scotland , UK
| | - Ying Liu
- a Faculty of Life Science and Technology , Kunming University of Science and Technology , Kunming , Yunnan , China and
| | - Xiao-Xi Guo
- a Faculty of Life Science and Technology , Kunming University of Science and Technology , Kunming , Yunnan , China and
| | - Tian-Rui Xu
- a Faculty of Life Science and Technology , Kunming University of Science and Technology , Kunming , Yunnan , China and
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13
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Baburina YL, Krestinina OV, Azarashvili TS. 2′,3′-cyclic nucleotide phosphodiesterase (CNPase) as a target in neurodegenerative diseases. NEUROCHEM J+ 2013. [DOI: 10.1134/s1819712412040034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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14
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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: 3.5] [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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15
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VDAC, a multi-functional mitochondrial protein regulating cell life and death. Mol Aspects Med 2010; 31:227-85. [PMID: 20346371 DOI: 10.1016/j.mam.2010.03.002] [Citation(s) in RCA: 530] [Impact Index Per Article: 37.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Accepted: 03/17/2010] [Indexed: 01/22/2023]
Abstract
Research over the past decade has extended the prevailing view of the mitochondrion to include functions well beyond the generation of cellular energy. It is now recognized that mitochondria play a crucial role in cell signaling events, inter-organellar communication, aging, cell proliferation, diseases and cell death. Thus, mitochondria play a central role in the regulation of apoptosis (programmed cell death) and serve as the venue for cellular decisions leading to cell life or death. One of the mitochondrial proteins controlling cell life and death is the voltage-dependent anion channel (VDAC), also known as mitochondrial porin. VDAC, located in the mitochondrial outer membrane, functions as gatekeeper for the entry and exit of mitochondrial metabolites, thereby controlling cross-talk between mitochondria and the rest of the cell. VDAC is also a key player in mitochondria-mediated apoptosis. Thus, in addition to regulating the metabolic and energetic functions of mitochondria, VDAC appears to be a convergence point for a variety of cell survival and cell death signals mediated by its association with various ligands and proteins. In this article, we review what is known about the VDAC channel in terms of its structure, relevance to ATP rationing, Ca(2+) homeostasis, protection against oxidative stress, regulation of apoptosis, involvement in several diseases and its role in the action of different drugs. In light of our recent findings and the recently solved NMR- and crystallography-based 3D structures of VDAC1, the focus of this review will be on the central role of VDAC in cell life and death, addressing VDAC function in the regulation of mitochondria-mediated apoptosis with an emphasis on structure-function relations. Understanding structure-function relationships of VDAC is critical for deciphering how this channel can perform such a variety of functions, all important for cell life and death. This review also provides insight into the potential of VDAC1 as a rational target for new therapeutics.
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16
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Zehorai E, Yao Z, Plotnikov A, Seger R. The subcellular localization of MEK and ERK--a novel nuclear translocation signal (NTS) paves a way to the nucleus. Mol Cell Endocrinol 2010; 314:213-20. [PMID: 19406201 DOI: 10.1016/j.mce.2009.04.008] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2009] [Accepted: 04/20/2009] [Indexed: 10/20/2022]
Abstract
The ERK cascade is a central signaling pathway that regulates a large number of intracellular processes including proliferation, differentiation, development and also survival or apoptosis. The induction of so many distinct and even opposing cellular processes raises the question as to how the signaling specificity of the cascade is regulated. In the past few years, subcellular localization of components of the ERK cascade was shown to play an important role in specificity determination. Here we describe the dynamic subcellular localization of Raf kinases, MEKs, and particularly ERKs, which translocate into the nucleus during many cellular processes to induce transcription. We also describe in details the recent identification of a novel nuclear translocation mechanism for ERKs, which is based on a nuclear translocation sequence (NTS) within their kinase insert domain (KID). Phosphorylation of this domain, mainly upon stimulation, allows ERKs to interact with the nuclear importing protein - importin7, which mediates the penetration of the interacting ERKs into the nucleus via nuclear pores. Interestingly, the NTS is not specific to ERKs, and seems to be a general signal for regulating nuclear accumulation of various proteins, including MEKs, upon their stimulation. Better understanding of this mechanism may clarify the role of the massive nuclear translocation of many regulatory proteins shortly after their stimulation.
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Affiliation(s)
- Eldar Zehorai
- Department of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
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17
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Can BAD pores be good? New insights from examining BAD as a target of RAF kinases. ACTA ACUST UNITED AC 2009; 50:147-59. [PMID: 19895838 DOI: 10.1016/j.advenzreg.2009.10.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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18
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Abstract
The extracellular signal-regulated kinase cascade is a central signaling pathway that is stimulated by various extracellular stimuli. The signals of these stimuli are then transferred by the cascade's components to a large number of targets at distinct subcellular compartments, which in turn induce and regulate a large number of cellular processes. To achieve these functions, the cascade exhibits versatile and dynamic subcellular distribution that allows proper temporal and spatial modulation of the appropriate processes. In this review, we discuss the intracellular localizations of different components of the ERK cascade, and the impact of these localizations on their activation and specificity.
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Affiliation(s)
- Zhong Yao
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
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19
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Simpkins JW, Yang SH, Sarkar SN, Pearce V. Estrogen actions on mitochondria--physiological and pathological implications. Mol Cell Endocrinol 2008; 290:51-9. [PMID: 18571833 PMCID: PMC2737506 DOI: 10.1016/j.mce.2008.04.013] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Revised: 04/08/2008] [Accepted: 04/10/2008] [Indexed: 02/07/2023]
Abstract
Estrogens are potent neuroprotective hormones and mitochondria are the site of cellular life-death decisions. As such, it is not surprising that we and others have shown that estrogens have remarkable effects on mitochondrial function. Herein we provide evidence for a primary effect of estrogens on mitochondrial function, achieved in part by the import of estrogen receptor beta (ERbeta) into the mitochondria where it mediates a number of estrogen actions on this vital organelle. ERbeta is imported into the mitochondria, through tethering to cytosolic chaperone protein and/or through direct interaction with mitochondrial import proteins. In the mitochondria, ERbeta can affect transcription of critical mitochondrial genes through the interaction with estrogen response elements (ERE) or through protein-protein interactions with mitochondrially imported transcription factors. The potent effects of estrogens on mitochondrial function, particularly during mitochondrial stress, argues for a role of estrogens in the treatment of mitochondrial defects in chronic neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD) and more acute conditions of mitochondrial compromise, like cerebral ischemia and traumatic brain injury.
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Affiliation(s)
- James W Simpkins
- Department of Pharmacology & Neuroscience, Institute for Aging and Alzheimer's Disease Research, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA.
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20
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Galmiche A, Fueller J, Santel A, Krohne G, Wittig I, Doye A, Rolando M, Flatau G, Lemichez E, Rapp UR. Isoform-specific interaction of C-RAF with mitochondria. J Biol Chem 2008; 283:14857-66. [PMID: 18356164 DOI: 10.1074/jbc.m709098200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The proteins of the RAF family (A-RAF, B-RAF, and C-RAF) are serine/threonine kinases that play important roles in development, mature cell regulation, and cancer. Although it is widely held that their localization on membranes is an important aspect of their function, there are few data that address this aspect of their mode of action. Here, we report that each member of the RAF family exhibits a specific distribution at the level of cellular membranes and that C-RAF is the only isoform that directly targets mitochondria. We found that the RAF kinases exhibit intrinsic differences in terms of mitochondrial affinity and that C-RAF is the only isoform that binds this organelle efficiently. This affinity is conferred by the C-RAF amino-terminal domain and does not depend on the presence of RAS GTPases on the surface of mitochondria. Finally, we analyzed the consequences of C-RAF activation on mitochondria and observed that this event dramatically changes their morphology and their subcellular distribution. Our observations indicate that: (i) RAF kinases exhibit different localizations at the level of cellular membranes; (ii) C-RAF is the only isoform that directly binds mitochondria; and (iii) through its functional coupling with MEK, C-RAF regulates the shape and the cellular distribution of mitochondria.
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Affiliation(s)
- Antoine Galmiche
- Institut für Medizinische Strahlenkunde und Zellforschung, University of Würzburg, Würzburg, Germany.
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21
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Omerovic J, Laude AJ, Prior IA. Ras proteins: paradigms for compartmentalised and isoform-specific signalling. Cell Mol Life Sci 2007; 64:2575-89. [PMID: 17628742 PMCID: PMC2561238 DOI: 10.1007/s00018-007-7133-8] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Ras GTPases mediate a wide variety of cellular processes by converting a multitude of extracellular stimuli into specific biological responses including proliferation, differentiation and survival. In mammalian cells, three ras genes encode four Ras isoforms (H-Ras, K-Ras4A, K-Ras4B and N-Ras) that are highly homologous but functionally distinct. Differences between the isoforms, including their post-translational modifications and intracellular sorting, mean that Ras has emerged as an important model system of compartmentalised signalling and membrane biology. Ras isoforms in different subcellular locations are proposed to recruit distinct upstream and downstream accessory proteins and activate multiple signalling pathways. Here, we summarise data relating to isoform-specific signalling, its role in disease and the mechanisms promoting compartmentalised signalling. Further understanding of this field will reveal the role of Ras signalling in development, cellular homeostasis and cancer and may suggest new therapeutic approaches.
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Affiliation(s)
- J. Omerovic
- Physiological Laboratory, University of Liverpool, Crown St., Liverpool, L69 3BX UK
| | - A. J. Laude
- Physiological Laboratory, University of Liverpool, Crown St., Liverpool, L69 3BX UK
| | - I. A. Prior
- Physiological Laboratory, University of Liverpool, Crown St., Liverpool, L69 3BX UK
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22
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Galmiche A, Fueller J. RAF kinases and mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2007; 1773:1256-62. [PMID: 17442414 DOI: 10.1016/j.bbamcr.2006.10.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Revised: 10/19/2006] [Accepted: 10/20/2006] [Indexed: 01/29/2023]
Abstract
Over the past decade, several investigators reported that a fraction of the RAF kinases are recruited to the mitochondria. Although we are still far from a global understanding of the molecular consequences of RAF translocation on mitochondrial physiology and metabolism, the recent description of some molecular interactions that are established by C-RAF in this organelle, principally with the proteins Bcl-2 and Bag-1, provides some clues. Here, we discuss the possible contribution of RAF targeting to mitochondria to their modulation of apoptosis signaling, as well as to this organelle's physiology. In addition, we discuss the possible modulation of the mitochondrial metabolism by RAF oncogenes in the context of cancer.
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Affiliation(s)
- Antoine Galmiche
- Institut für Medizinische Strahlenkunde und Zellforschung (MSZ), University of Würzburg, D-97078 Würzburg, Germany.
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23
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Yokoyama T, Takano K, Yoshida A, Katada F, Sun P, Takenawa T, Andoh T, Endo T. DA-Raf1, a competent intrinsic dominant-negative antagonist of the Ras-ERK pathway, is required for myogenic differentiation. ACTA ACUST UNITED AC 2007; 177:781-93. [PMID: 17535970 PMCID: PMC2064279 DOI: 10.1083/jcb.200703195] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ras activates Raf, leading to the extracellular-regulated kinase (ERK)–mitogen-activated protein kinase pathway, which is involved in a variety of cellular, physiological, and pathological responses. Thus, regulators of this Ras–Raf interaction play crucial roles in these responses. In this study, we report a novel regulator of the Ras–Raf interaction named DA-Raf1. DA-Raf1 is a splicing isoform of A-Raf with a wider tissue distribution than A-Raf. It contains the Ras-binding domain but lacks the kinase domain, which is responsible for activation of the ERK pathway. As inferred from its structure, DA-Raf1 bound to activated Ras as well as M-Ras and interfered with the ERK pathway. The Ras–ERK pathway is essential for the negative regulation of myogenic differentiation induced by growth factors. DA-Raf1 served as a positive regulator of myogenic differentiation by inducing cell cycle arrest, the expression of myogenin and other muscle-specific proteins, and myotube formation. These results imply that DA-Raf1 is the first identified competent, intrinsic, dominant-negative antagonist of the Ras–ERK pathway.
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Affiliation(s)
- Takashi Yokoyama
- Department of Biology, Graduate School of Science, Chiba University, Chiba 263-8522, Japan
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24
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Camarero G, Tyrsin OY, Xiang C, Pfeiffer V, Pleiser S, Wiese S, Götz R, Rapp UR. Cortical migration defects in mice expressing A-RAF from the B-RAF locus. Mol Cell Biol 2006; 26:7103-15. [PMID: 16980614 PMCID: PMC1592881 DOI: 10.1128/mcb.00424-06] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have previously shown that mice lacking the protein kinase B-RAF have defects in both neural and endothelial cell lineages and die around embryonic day 12 (E12). To delineate the function of B-RAF in the brain, B-RAF KIN/KIN mice lacking B-RAF and expressing A-RAF under the control of the B-RAF locus were created. B-RAF KIN/KIN embryos displayed no vascular defects, no endothelial and neuronal apoptosis, or gross developmental abnormalities, and a significant proportion of these animals survived for up to 8 weeks. Cell proliferation in the neocortex was reduced from E14.5 onwards. Newborn cortical neurons were impaired in their migration toward the cortical plate, causing a depletion of Brn-2-expressing pyramidal neurons in layers II, III, and V of the postnatal cortex. Our data reveal that B-RAF is an important mediator of neuronal survival, migration, and dendrite formation and that A-RAF cannot fully compensate for these functions.
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Affiliation(s)
- Guadalupe Camarero
- Institut für Medizinische Strahlenkunde und Zellforschung, Bayerische Julius-Maximilians-Universität, Versbacher-Str. 5, D-97078 Würzburg, Germany
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25
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Caraglia M, Tassone P, Marra M, Budillon A, Venuta S, Tagliaferri P. Targeting Raf-kinase: molecular rationales and translational issues. Ann Oncol 2006; 17 Suppl 7:vii124-7. [PMID: 16760274 DOI: 10.1093/annonc/mdl964] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Target-based therapy has been a promising anti-cancer strategy in the preclinical setting, but its efficacy is still limited in clinical practice. The latter was probably due to the lack of identification of molecular targets in order to predict clinical response and for the existence of multiple survival compensatory downstream pathways. Therefore, the use of downstream targets could be useful in order to avoid these overcoming pathways. One of these targets is Raf-kinase. In this review we describe the structure and functions of the components of Raf-kinase family and their relevance in proliferation and survival of tumor cells. Moreover, we illustrate the signal transduction pathways regulated by Raf-kinases. The main preclinical and clinical results obtained with the use of the Raf-kinase inhibitor BAY 43-9006 or sorafenib are also described. The multi-target function of sorafenib is also explained and the disclosure of new therapeutic opportunities based on the dual inhibition of cancer proliferation and neo-angiogenesis is discussed. In conclusion, Raf-kinase appears an appealing therapeutic target, even it other preclinical and clinical studies are warranted in order to evaluate the activity of sorafenib both in monotherapy and in combination with other agents.
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Affiliation(s)
- M Caraglia
- National Cancer Institute Fondazione G. Pascale, Experimental Oncology Department, Experimental Pharmacology Unit, Naples, Italy
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26
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Forrest ARR, Taylor DF, Crowe ML, Chalk AM, Waddell NJ, Kolle G, Faulkner GJ, Kodzius R, Katayama S, Wells C, Kai C, Kawai J, Carninci P, Hayashizaki Y, Grimmond SM. Genome-wide review of transcriptional complexity in mouse protein kinases and phosphatases. Genome Biol 2006; 7:R5. [PMID: 16507138 PMCID: PMC1431701 DOI: 10.1186/gb-2006-7-1-r5] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Revised: 11/02/2005] [Accepted: 12/16/2005] [Indexed: 11/25/2022] Open
Abstract
A systematic study of the transcript variants of all protein kinase- and phosphatase-like loci in mouse shows that at least 75% of them generate alternative transcripts, many of which encode different domain structures. Background Alternative transcripts of protein kinases and protein phosphatases are known to encode peptides with altered substrate affinities, subcellular localizations, and activities. We undertook a systematic study to catalog the variant transcripts of every protein kinase-like and phosphatase-like locus of mouse . Results By reviewing all available transcript evidence, we found that at least 75% of kinase and phosphatase loci in mouse generate alternative splice forms, and that 44% of these loci have well supported alternative 5' exons. In a further analysis of full-length cDNAs, we identified 69% of loci as generating more than one peptide isoform. The 1,469 peptide isoforms generated from these loci correspond to 1,080 unique Interpro domain combinations, many of which lack catalytic or interaction domains. We also report on the existence of likely dominant negative forms for many of the receptor kinases and phosphatases, including some 26 secreted decoys (seven known and 19 novel: Alk, Csf1r, Egfr, Epha1, 3, 5,7 and 10, Ephb1, Flt1, Flt3, Insr, Insrr, Kdr, Met, Ptk7, Ptprc, Ptprd, Ptprg, Ptprl, Ptprn, Ptprn2, Ptpro, Ptprr, Ptprs, and Ptprz1) and 13 transmembrane forms (four known and nine novel: Axl, Bmpr1a, Csf1r, Epha4, 5, 6 and 7, Ntrk2, Ntrk3, Pdgfra, Ptprk, Ptprm, Ptpru). Finally, by mining public gene expression data (MPSS and microarrays), we confirmed tissue-specific expression of ten of the novel isoforms. Conclusion These findings suggest that alternative transcripts of protein kinases and phosphatases are produced that encode different domain structures, and that these variants are likely to play important roles in phosphorylation-dependent signaling pathways.
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Affiliation(s)
- Alistair RR Forrest
- Institute for Molecular Bioscience and ARC Centre in Bioinformatics, University of Queensland, Brisbane, QLD 4072, Australia
| | - Darrin F Taylor
- Institute for Molecular Bioscience and ARC Centre in Bioinformatics, University of Queensland, Brisbane, QLD 4072, Australia
| | - Mark L Crowe
- Institute for Molecular Bioscience and ARC Centre in Bioinformatics, University of Queensland, Brisbane, QLD 4072, Australia
| | - Alistair M Chalk
- Institute for Molecular Bioscience and ARC Centre in Bioinformatics, University of Queensland, Brisbane, QLD 4072, Australia
- Queensland Institute for Medical Research, PO Royal Brisbane Hospital, Brisbane, QLD 4029, Australia
- Center for Genomics and Bioinformatics, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Nic J Waddell
- Institute for Molecular Bioscience and ARC Centre in Bioinformatics, University of Queensland, Brisbane, QLD 4072, Australia
- Queensland Institute for Medical Research, PO Royal Brisbane Hospital, Brisbane, QLD 4029, Australia
| | - Gabriel Kolle
- Institute for Molecular Bioscience and ARC Centre in Bioinformatics, University of Queensland, Brisbane, QLD 4072, Australia
| | - Geoffrey J Faulkner
- Institute for Molecular Bioscience and ARC Centre in Bioinformatics, University of Queensland, Brisbane, QLD 4072, Australia
- Queensland Institute for Medical Research, PO Royal Brisbane Hospital, Brisbane, QLD 4029, Australia
| | - Rimantas Kodzius
- Genome Exploration Research Group (Genome Network Project Core Group), RIKEN Genomic Sciences Center (GSC), RIKEN Yokohama Institute, Yokohama, Kanagawa, 230-0045, Japan
- Genome Science Laboratory, Discovery Research Institute, RIKEN Wako Institute, Wako, Saitama, 351-0198, Japan
| | - Shintaro Katayama
- Genome Exploration Research Group (Genome Network Project Core Group), RIKEN Genomic Sciences Center (GSC), RIKEN Yokohama Institute, Yokohama, Kanagawa, 230-0045, Japan
| | - Christine Wells
- Institute for Molecular Bioscience and ARC Centre in Bioinformatics, University of Queensland, Brisbane, QLD 4072, Australia
- The Eskitis Institute for Cell and Molecular Therapies, Griffith University, QLD 4111, Australia
| | - Chikatoshi Kai
- Genome Exploration Research Group (Genome Network Project Core Group), RIKEN Genomic Sciences Center (GSC), RIKEN Yokohama Institute, Yokohama, Kanagawa, 230-0045, Japan
| | - Jun Kawai
- Genome Exploration Research Group (Genome Network Project Core Group), RIKEN Genomic Sciences Center (GSC), RIKEN Yokohama Institute, Yokohama, Kanagawa, 230-0045, Japan
- Genome Science Laboratory, Discovery Research Institute, RIKEN Wako Institute, Wako, Saitama, 351-0198, Japan
| | - Piero Carninci
- Genome Exploration Research Group (Genome Network Project Core Group), RIKEN Genomic Sciences Center (GSC), RIKEN Yokohama Institute, Yokohama, Kanagawa, 230-0045, Japan
- Genome Science Laboratory, Discovery Research Institute, RIKEN Wako Institute, Wako, Saitama, 351-0198, Japan
| | - Yoshihide Hayashizaki
- Genome Exploration Research Group (Genome Network Project Core Group), RIKEN Genomic Sciences Center (GSC), RIKEN Yokohama Institute, Yokohama, Kanagawa, 230-0045, Japan
- Genome Science Laboratory, Discovery Research Institute, RIKEN Wako Institute, Wako, Saitama, 351-0198, Japan
| | - Sean M Grimmond
- Institute for Molecular Bioscience and ARC Centre in Bioinformatics, University of Queensland, Brisbane, QLD 4072, Australia
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27
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Lee J, O'Neill RC, Park MW, Gravel M, Braun PE. Mitochondrial localization of CNP2 is regulated by phosphorylation of the N-terminal targeting signal by PKC: implications of a mitochondrial function for CNP2 in glial and non-glial cells. Mol Cell Neurosci 2005; 31:446-62. [PMID: 16343930 DOI: 10.1016/j.mcn.2005.10.017] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2004] [Revised: 10/25/2005] [Accepted: 10/25/2005] [Indexed: 10/25/2022] Open
Abstract
Both 2',3'-cyclic nucleotide-3'-phosphodiesterase (CNP) isoforms are abundantly expressed in myelinating cells. CNP2 differs from CNP1 by a 20 amino acid N-terminal extension and is also expressed at much lower levels in non-myelinating tissues. The functional role of CNP2, apart from CNP1, and the significance for CNP2 expression in non-myelinating tissues are unknown. Here, we demonstrate that CNP2 is translocated to mitochondria by virtue of a mitochondrial targeting signal at the N-terminus. PKC-mediated phosphorylation of the targeting signal inhibits CNP2 translocation to mitochondria, thus retaining it in the cytoplasm. CNP2 is imported into mitochondria and the targeting signal cleaved, yielding a mature, truncated form similar in size to CNP1. CNP2 is entirely processed in adult liver and embryonic brain, indicating that it is localized specifically to mitochondria in non-myelinating cells. Our results point to a broader biological role for CNP2 in mitochondria that is likely to be different from its specific role in the cytoplasm, along with CNP1, during myelination.
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Affiliation(s)
- John Lee
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada H3G 1Y6.
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28
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Abstract
The Ras-Raf-MEK-ERK (ERK) pathway is a logical therapeutic target because it represents a common downstream pathway for several key growth factor tyrosine kinase receptors which are often mutated or overexpressed in human cancers. Although considered mainly growth-promoting, in certain contexts, this pathway also seems to be apoptosis-suppressing. Several novel agents targeting this pathway have now been developed and are in clinical trials. One of the most interesting new agents is BAY 43-9006. Although initially developed as a Raf kinase inhibitor, it can also target several other important tyrosine kinases including VEGFR-2, Flt-3, and c-Kit, which contributes to its antiproliferative and antiangiogenic properties. To date, encouraging results have been seen with BAY 43-9006, particularly in renal cell cancers which are highly vascular tumors. This review will provide an overview of the ERK signaling pathway in normal and neoplastic tissue, with a specific focus on novel therapies targeting the ERK pathway at the level of Raf kinase.
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Affiliation(s)
- Srikala S Sridhar
- Department of Medical Oncology and Hematology, Princess Margaret Hospital, University Health Network, 610 University Avenue, Suite 5-210, Toronto, Ontario, Canada M5G 2M9
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29
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Beeram M, Patnaik A, Rowinsky EK. Raf: A Strategic Target for Therapeutic Development Against Cancer. J Clin Oncol 2005; 23:6771-90. [PMID: 16170185 DOI: 10.1200/jco.2005.08.036] [Citation(s) in RCA: 199] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The mitogen-activated protein kinase (MAPK) signaling pathway plays a critical role in transmitting proliferative signals generated by cell surface receptors and cytoplasmic signaling elements to the nucleus. Several important signaling elements of the MAPK pathway, particularly Ras and Raf, are encoded by oncogenes, and as such, their structures and functions can be modified, rendering them constitutively active. Because the MAPK pathway is dysregulated in a notable proportion of human malignancies, many of its aberrant and critical components represent strategic targets for therapeutic development against cancer. Raf, which is an essential serine/threonine kinase constituent of the MAPK pathway and a downstream effector of the central signal transduction mediator Ras, is activated in a wide range of human malignancies by aberrant signaling upstream of the protein (eg, growth factor receptors and mutant Ras) and activating mutations of the protein itself, both of which confer a proliferative advantage. Three isoforms of Raf have been identified, and therapeutics targeting Raf, including small-molecule inhibitors and antisense oligodeoxyribonucleotides (ASON), are undergoing clinical evaluation. The outcomes of these investigations may have far-reaching implications in the management of many types of human cancer. This review outlines the structure and diverse functions of Raf, the rationale for targeting Raf as a therapeutic strategy against cancer, and the present status of various therapeutic approaches including ASONs and small molecules, particularly sorafenib (BAY 43-9006).
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Affiliation(s)
- Muralidhar Beeram
- University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
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30
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Salvi M, Brunati AM, Toninello A. Tyrosine phosphorylation in mitochondria: a new frontier in mitochondrial signaling. Free Radic Biol Med 2005; 38:1267-77. [PMID: 15855046 DOI: 10.1016/j.freeradbiomed.2005.02.006] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2005] [Revised: 02/01/2005] [Accepted: 02/03/2005] [Indexed: 11/25/2022]
Abstract
Mitochondria are multifunctional organelles that participate in a range of cellular processes such as energy production, proliferation, death, and senescence. The involvement of mitochondria in such distinct aspects of cell life requires the existence of an integrated system of signals that enter and exit the organelle according to the diverse needs of the cell. The recent discovery of several protein kinases and phosphatases that localize partially or predominantly inside mitochondria opens new perspectives into the regulation of these signals. This review focuses on tyrosine phosphorylation in mitochondria. A description of the protein tyrosine kinases and phosphatases which regulate this process along with the mitochondrial tyrosine-phosphorylated proteins identified to date is followed by a discussion of the possible involvement of tyrosine phosphorylation in mitochondrial signaling and future perspectives for developments in this emerging field.
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Affiliation(s)
- Mauro Salvi
- Dipartimento di Chimica Biologica, Università di Padova, Istituto di Neuroscienze del CNR, Unità per lo Studio delle Biomembrane, Viale G. Colombo 3, 35121 Padua, Italy
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31
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Kuznetsov AV, Janakiraman M, Margreiter R, Troppmair J. Regulating cell survival by controlling cellular energy production: novel functions for ancient signaling pathways? FEBS Lett 2005; 577:1-4. [PMID: 15527752 DOI: 10.1016/j.febslet.2004.10.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2004] [Revised: 09/15/2004] [Accepted: 10/01/2004] [Indexed: 11/25/2022]
Abstract
Cell survival is maintained by growth factors and critically depends on sufficient energy supply. New evidence suggests that a rise in cellular energy production is not merely a homeostatic response to increased demand but subject to regulation by extrinsic factors. The mechanisms operating in this control are largely enigmatic. Work on transformed cells identified direct targeting of glycolytic enzymes by signaling proteins as one possibility. But mitochondrial oxidative phosphorylation and biogenesis may also be subject to regulation by growth and survival factors. Both, positive and negative regulators of cell survival impinge on the processes of cellular energy production to regulate growth and survival versus death.
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Affiliation(s)
- Andrey V Kuznetsov
- Daniel-Swarovski-Research Laboratory (DSL), Department of General and Transplant Surgery, Innsbruck Medical University, Innsbruck, Austria
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32
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Mahon ES, Hawrysh AD, Chagpar RB, Johnson LM, Anderson DH. A-Raf associates with and regulates platelet-derived growth factor receptor signalling. Cell Signal 2004; 17:857-68. [PMID: 15763428 DOI: 10.1016/j.cellsig.2004.11.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Revised: 11/03/2004] [Accepted: 11/03/2004] [Indexed: 11/25/2022]
Abstract
Raf kinases are important intermediates in epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) mediated activation of the mitogen-activated protein kinase (MAPK) pathway. In this report, we show that the A-Raf kinase is associated with activated EGF receptor complexes and with PDGF receptor (PDGFR) complexes independent of prior PDGF treatment. The ability of A-Raf to associate with receptor tyrosine kinases could provide a Ras-GTP-independent mechanism for the membrane localization of A-Raf. Expression of a partially activated A-Raf mutant resulted in decreased tyrosine phosphorylation of the PDGFR, specifically on Y857 (autophosphorylation site) and Y1021 (phospholipase Cgamma1 (PLCgamma1) binding site), but not the binding sites for other signalling proteins (Nck, phosphatidylinositol 3'-kinase (PI3K), RasGAP, Grb2, SHP). Activated A-Raf expression also altered the activation of PLCgamma1, and p85-associated PI3K. Thus, A-Raf can regulate PLCgamma1 signalling via a PDGFR-dependent mechanism and may also regulate PI3K signalling via a PDGFR-independent mechanism.
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Affiliation(s)
- Elizabeth S Mahon
- Department of Biochemistry, University of Saskatchewan, 107 Wiggins Ave., Saskatoon, Saskatchewan, Canada S7N 5E5
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33
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Rapp UR, Rennefahrt U, Troppmair J. Bcl-2 proteins: master switches at the intersection of death signaling and the survival control by Raf kinases. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2004; 1644:149-58. [PMID: 14996499 DOI: 10.1016/j.bbamcr.2003.10.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2003] [Accepted: 10/27/2003] [Indexed: 01/22/2023]
Abstract
Bcl-2 family members are central to the control of cell survival. Work of the last years has established that the function of these proteins can be regulated by mitogenic signaling cascades. Within the scope of this review, we will discuss the contribution of Bcl-2-dependent signaling pathways to cell survival by Raf kinases and also address the underlying mechanisms.
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Affiliation(s)
- Ulf R Rapp
- Institut für Medizinische Strahlenkunde und Zellforschung (MSZ), Universität Würzburg, Versbacher Str. 5, 97078 Würzburg, Germany.
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34
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Abstract
The Raf-MEK-ERK signalling pathway controls fundamental cellular processes including proliferation, differentiation and survival. It remains enigmatic how this pathway can reliably convert a myriad of extracellular stimuli in specific biological responses. Recent results have shown that the Raf family isoforms A-Raf, B-Raf and Raf-1 have different physiological functions. Here we review how Raf isozyme diversity contributes to the specification of functional diversity, in particular regarding the role of Raf isozymes in cancer.
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Affiliation(s)
- E O'Neill
- Beatson Institute for Cancer Research, Switchback Road, Glasgow G61 1BD, UK.
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35
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Liu W, Shen X, Yang Y, Yin X, Xie J, Yan J, Jiang J, Liu W, Wang H, Sun M, Zheng Y, Gu J. Trihydrophobin 1 Is a New Negative Regulator of A-Raf Kinase. J Biol Chem 2004; 279:10167-75. [PMID: 14684750 DOI: 10.1074/jbc.m307994200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Our previous work indicated that instead of binding to B-Raf or C-Raf, trihydrophobin 1 (TH1) specifically binds to A-Raf kinase both in vitro and in vivo. In this work, we investigated its function further. Using confocal microscopy, we found that TH1 colocalizes with A-Raf, which confirms our former results. The region of TH1 responsible for the interaction with A-Raf is mapped to amino acids 1-372. Coimmunoprecipitation experiments demonstrate that TH1 is associated with A-Raf in both quiescent and serum-stimulated cells. Wild type A-Raf binds increasingly to TH1 when it is activated by serum and/or upstream oncogenic Ras/Src compared with that of "kinase-dead" A-Raf. The latter can still bind to TH1 under the same experimental condition. The binding pattern of A-Raf implies that this interaction is mediated in part by the A-Raf kinase activity. As indicated by Raf protein kinase assays, TH1 inhibits A-Raf kinase, whereas neither B-Raf nor C-Raf kinase activity is influenced. Furthermore, we observed that TH1 inhibited cell cycle progression in TH1 stably transfected 7721 cells compared with mock cells, and flow cell cytometry analysis suggested that the TH1 stably transfected 7721 cells were G(0)/G(1) phase-arrested. Taken together, our data provide a clue to understanding the cellular function of TH1 on Raf isoform-specific regulation.
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Affiliation(s)
- Weicheng Liu
- State Key laboratory of Genetic Engineering and Gene Research Center, Shanghai Medical College of Fudan University, Shanghai 200032, People's Republic of China
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36
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Steelman LS, Pohnert SC, Shelton JG, Franklin RA, Bertrand FE, McCubrey JA. JAK/STAT, Raf/MEK/ERK, PI3K/Akt and BCR-ABL in cell cycle progression and leukemogenesis. Leukemia 2004; 18:189-218. [PMID: 14737178 DOI: 10.1038/sj.leu.2403241] [Citation(s) in RCA: 499] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The roles of the JAK/STAT, Raf/MEK/ERK and PI3K/Akt signal transduction pathways and the BCR-ABL oncoprotein in leukemogenesis and their importance in the regulation of cell cycle progression and apoptosis are discussed in this review. These pathways have evolved regulatory proteins, which serve to limit their proliferative and antiapoptotic effects. Small molecular weight cell membrane-permeable drugs that target these pathways have been developed for leukemia therapy. One such example is imatinib mesylate, which targets the BCR-ABL kinase as well as a few structurally related kinases. This drug has proven to be effective in the treatment of CML patients. However, leukemic cells have evolved mechanisms to become resistant to this drug. A means to combat drug resistance is to target other prominent signaling components involved in the pathway or to inhibit BCR-ABL by other mechanisms. Treatment of imatinib-resistant leukemia cells with drugs that target Ras (farnysyl transferase inhibitors) or with the protein destabilizer geldanamycin has proven to be a means to inhibit the growth of resistant cells. This review will tie together three important signal transduction pathways involved in the regulation of hematopoietic cell growth and indicate how their expression is dysregulated by the BCR-ABL oncoprotein.
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Affiliation(s)
- L S Steelman
- Department of Microbiology and Immunology, Brody School of Medicine at East Carolina University, Greenville, NC 27858, USA
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37
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Ventura A, Maccarana M, Raker VA, Pelicci PG. A Cryptic Targeting Signal Induces Isoform-specific Localization of p46Shc to Mitochondria. J Biol Chem 2004; 279:2299-306. [PMID: 14573619 DOI: 10.1074/jbc.m307655200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human Src homology and collagen (Shc) gene encodes three protein isoforms of 46, 52, and 66 kDa that belong to a family of molecular adapters involved in several signal transduction pathways. Recently, the 66-kDa isoform has been shown to play a central role in controlling reactive oxygen species metabolism and life span in mammals. Despite the large amount of information available on the biology and biochemistry of Shc proteins, very little is known regarding the regulation of their subcellular localization. Here we demonstrate the specific and selective localization of p46Shc to the mitochondrial matrix. Through deletion mapping experiments, we show that targeting of p46Shc to mitochondria is mediated by its first 32 amino acids, which behave as a bona fide mitochondrial targeting sequence. We further demonstrate that the N-terminal location of the signal peptide is critical for its function. This accounts for the observation that p52Shc and p66Shc, containing the same sequence but more internally located, display a remarkably different subcellular localization. These findings indicate that p46Shc may exert a non-redundant biological function in signal transduction pathways involving mitochondria.
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Affiliation(s)
- Andrea Ventura
- Department of Experimental Oncology, European Institute of Oncology, Via Ripamonti 435, Milan 20141, Italy
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38
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Hekman M, Wiese S, Metz R, Albert S, Troppmair J, Nickel J, Sendtner M, Rapp UR. Dynamic changes in C-Raf phosphorylation and 14-3-3 protein binding in response to growth factor stimulation: differential roles of 14-3-3 protein binding sites. J Biol Chem 2003; 279:14074-86. [PMID: 14688280 DOI: 10.1074/jbc.m309620200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Phosphorylation events play a crucial role in Raf activation. Phosphorylation of serines 259 and 621 in C-Raf and serines 364 and 728 in B-Raf has been suggested to be critical for association with 14-3-3 proteins. To study the functional consequences of Raf phosphorylations at these positions, we developed and characterized phosphospecific antibodies directed against 14-3-3 binding epitopes: a monoclonal phosphospecific antibody (6B4) directed against pS621 and a polyclonal antibody specific for B-Raf-pS364 epitope. Although 6B4 detected both C- and B-Raf in Western blots, it specifically recognizes the native form of C-Raf but not B-Raf. Contrary to B-Raf, a kinase-dead mutant of C-Raf was found to be only poorly phosphorylated in the Ser-621 position. Moreover, serine 259 to alanine mutation prevented the Ser-621 phosphorylation suggesting an interdependence between these two 14-3-3 binding domains. Direct C-Raf.14-3-3 binding studies with purified proteins combined with competition assays revealed that the 14-3-3 binding domain surrounding pS621 represents the high affinity binding site, whereas the pS259 epitope mediates lower affinity binding. Raf isozymes differ in their 14-3-3 association rates. The time course of endogenous C-Raf activation in mammalian cells by nerve growth factor (NGF) has been examined using both phosphospecific antibodies directed against 14-3-3 binding sites (6B4 and anti-pS259) as well as phosphospecific antibodies directed against the activation domain (anti-pS338 and anti-pY340/pY341). Time course of Ser-621 phosphorylation, in contrast to Ser-259 phosphorylation, exhibited unexpected pattern reaching maximal phosphorylation within 30 s of NGF stimulation. Phosphorylation of tyrosine 340/341 reached maximal levels subsequent to Ser-621 phosphorylation and was coincident with emergence of kinase activity. Taken together, we found substantial differences between C-Raf.14-3-3 binding epitopes pS259 and pS621 and visualized for the first time the sequence of the essential C-Raf phosphorylation events in mammalian cells in response to growth factor stimulation.
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Affiliation(s)
- Mirko Hekman
- Institute for Medical Radiation and Cell Research, University of Wuerzburg, 97078 Wuerzburg
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39
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Garlid KD, Dos Santos P, Xie ZJ, Costa ADT, Paucek P. Mitochondrial potassium transport: the role of the mitochondrial ATP-sensitive K(+) channel in cardiac function and cardioprotection. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2003; 1606:1-21. [PMID: 14507424 DOI: 10.1016/s0005-2728(03)00109-9] [Citation(s) in RCA: 253] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Coronary artery disease and its sequelae-ischemia, myocardial infarction, and heart failure-are leading causes of morbidity and mortality in man. Considerable effort has been devoted toward improving functional recovery and reducing the extent of infarction after ischemic episodes. As a step in this direction, it was found that the heart was significantly protected against ischemia-reperfusion injury if it was first preconditioned by brief ischemia or by administering a potassium channel opener. Both of these preconditioning strategies were found to require opening of a K(ATP) channel, and in 1997 we showed that this pivotal role was mediated by the mitochondrial ATP-sensitive K(+) channel (mitoK(ATP)). This paper will review the evidence showing that opening mitoK(ATP) is cardioprotective against ischemia-reperfusion injury and, moreover, that mitoK(ATP) plays this role during all three phases of the natural history of ischemia-reperfusion injury preconditioning, ischemia, and reperfusion. We discuss two distinct mechanisms by which mitoK(ATP) opening protects the heart-increased mitochondrial production of reactive oxygen species (ROS) during the preconditioning phase and regulation of intermembrane space (IMS) volume during the ischemic and reperfusion phases. It is likely that cardioprotection by ischemic preconditioning (IPC) and K(ATP) channel openers (KCOs) arises from utilization of normal physiological processes. Accordingly, we summarize the results of new studies that focus on the role of mitoK(ATP) in normal cardiomyocyte physiology. Here, we observe the same two mechanisms at work. In low-energy states, mitoK(ATP) opening triggers increased mitochondrial ROS production, thereby amplifying a cell signaling pathway leading to gene transcription and cell growth. In high-energy states, mitoK(ATP) opening prevents the matrix contraction that would otherwise occur during high rates of electron transport. MitoK(ATP)-mediated volume regulation, in turn, prevents disruption of the structure-function of the IMS and facilitates efficient energy transfers between mitochondria and myofibrillar ATPases.
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Affiliation(s)
- Keith D Garlid
- Department of Biology, Portland State University, 1719 SW 10th Avenue, PO Box 751, Portland, OR 97207, USA.
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40
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Abstract
The MAP Kinase pathway is a key signalling mechanism that regulates many cellular functions such as cell growth, transformation and apoptosis. One of the essential components of this pathway is the serine/threonine kinase, Raf. Raf (MAPKK kinase, MAPKKK) relays the extracellular signal from the receptor/Ras complex to a cascade of cytosolic kinases by phosphorylating and activating MAPK/ERK kinase (MEK; MAPK kinase, MAPKK) that phosphorylates and activates extracellular signal regulated kinase (ERK; mitogen-activated protein kinase, MAPK), which phosphorylates various cytoplasmic and nuclear proteins. Regulation of both Ras and Raf is crucial in the proper maintenance of cell growth as oncogenic mutations in these genes lead to high transforming activity. Ras is mutated in 30% of all human cancers and B-Raf is mutated in 60% of malignant melanomas. The mechanisms that regulate the small GTPase Ras as well as the downstream kinases MEK and extracellular signal regulated kinase (ERK) are well understood. However, the regulation of Raf is complex and involves the integration of other signalling pathways as well as intramolecular interactions, phosphorylation, dephosphorylation and protein-protein interactions. From studies using mammalian isoforms of Raf, as well as C. elegans lin45-Raf, common patterns and unique differences of regulation have emerged. This review will summarize recent findings on the regulation of Raf kinase.
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Affiliation(s)
- Huira Chong
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
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41
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Chang F, Lee JT, Navolanic PM, Steelman LS, Shelton JG, Blalock WL, Franklin RA, McCubrey JA. Involvement of PI3K/Akt pathway in cell cycle progression, apoptosis, and neoplastic transformation: a target for cancer chemotherapy. Leukemia 2003; 17:590-603. [PMID: 12646949 DOI: 10.1038/sj.leu.2402824] [Citation(s) in RCA: 896] [Impact Index Per Article: 42.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The PI3K/Akt signal transduction cascade has been investigated extensively for its roles in oncogenic transformation. Initial studies implicated both PI3K and Akt in prevention of apoptosis. However, more recent evidence has also associated this pathway with regulation of cell cycle progression. Uncovering the signaling network spanning from extracellular environment to the nucleus should illuminate biochemical events contributing to malignant transformation. Here, we discuss PI3K/Akt-mediated signal transduction including its mechanisms of activation, signal transducing molecules, and effects on gene expression that contribute to tumorigenesis. Effects of PI3K/Akt signaling on important proteins controlling cellular proliferation are emphasized. These targets include cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors. Furthermore, strategies used to inhibit the PI3K/Akt pathway are presented. The potential for cancer treatment with agents inhibiting this pathway is also addressed.
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Affiliation(s)
- F Chang
- Department of Microbiology & Immunology, Brody School of Medicine at East Carolina University, Greenville 27858, USA
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42
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Yuryev A, Wennogle LP. Novel raf kinase protein-protein interactions found by an exhaustive yeast two-hybrid analysis. Genomics 2003; 81:112-25. [PMID: 12620389 DOI: 10.1016/s0888-7543(02)00008-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We have performed an exhaustive unbiased yeast two-hybrid analysis to identify interaction partners of two human Raf kinase isoforms, A-Raf and C-Raf, using their N-terminal regulatory domain as "bait." A total of 20 different human proteins were found to interact with Raf isoforms. Several of these interactions were novel and an extensive bioinformatics evaluation was performed for each. The novel putative interactions include a signalosome component, TOPK/PBK kinase, and two new putative protein phosphatases. The cysteine-rich zinc-binding domain (CRD) of Raf was found to interact with all 20 proteins and to achieve isoform-specific interactions. Since similar putative CRDs are present in a variety of protein serine-threonine kinases, the data suggest that the CRD may function as a major protein-protein interaction domain of these kinases. We propose possible functional consequences of these novel Raf interactions.
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Affiliation(s)
- Anton Yuryev
- Novartis Institute for Biomedical Research, Summit, NJ 07901, USA
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43
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Hindley A, Kolch W. Extracellular signal regulated kinase (ERK)/mitogen activated protein kinase (MAPK)-independent functions of Raf kinases. J Cell Sci 2002; 115:1575-81. [PMID: 11950876 DOI: 10.1242/jcs.115.8.1575] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Raf comprises a family of three kinases, A-Raf, B-Raf and Raf-1, which are best known as key regulators of the MEK—MAPK/ERK cascade. This module is often perceived as a linear pathway in which ERK is the effector. However,recent advances have unveiled a role for Raf outside this established signalling unit. Current evidence, including gene-knockout studies in mice,suggests that there are ERK-independent functions of Raf kinases. Regulation of apoptosis is one area in which Raf may function independently of ERK,although its substrates remain to be identified. Other studies have suggested that Raf has kinase-independent functions and may act as a scaffold protein.
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Affiliation(s)
- Alison Hindley
- The Beatson Institute for Cancer Research, CRC Beatson Laboratories, Glasgow, G61 1BD, UK
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44
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Spina Purrello V, Cormaci G, Denaro L, Reale S, Costa A, Lalicata C, Sabbatini M, Marchetti B, Avola R. Effect of growth factors on nuclear and mitochondrial ADP-ribosylation processes during astroglial cell development and aging in culture. Mech Ageing Dev 2002; 123:511-20. [PMID: 11796136 DOI: 10.1016/s0047-6374(01)00354-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), insulin-like growth factor-I (IGF-I) and insulin (INS) are powerful mitogens and may regulate gene expression in cultured astrocytes by ADP-ribosylation process. Nuclear poly-ADP ribose polymerase (PARP) and mitochondrial monoADP-ribosyltransferase (ADPRT) are the key enzymes involved in poly-ADP-ribosylation and mono ADP-ribosylation, respectively. In this investigation the effect of EGF, bFGF, IGF-I or INS on nuclear PARP and mitochondrial ADPRT activities were assessed in nuclei and mitochondria purified from developing (30 DIV) or aging (90 and 190 DIV) primary rat astrocyte cultures. A marked increase of PARP activity in bFGF or IGF-I treated astroglial cell cultures at 30 DIV was found. Nuclear PARP and mitochondrial ADPRT activities were greatly stimulated by treatment with EGF or INS alone or together in astrocyte cultures at 30 DIV. Nuclear PARP and mitochondrial ADPRT activities showed a more remarkable increase in control untreated astrocyte cultures at 190 DIV than at 90 DIV. These findings suggest that ADP-ribosylation process is involved in DNA damage and repair during cell differentiation and aging in culture. Twelve hours treatment with EGF, INS or bFGF significantly stimulated nuclear PARP and mitochondrial ADPRT activities in 190 DIV aging astrocyte cultures. The above results indicate that EGF, INS and bFGF may play a crucial role in the post-translational modification of chromosomal proteins including ADP-ribosylation process in in vitro models. This suggests that growth factors regulate genomic stability in glial cells during development and maturation, stimulating nuclear and mitochondrial ADP-ribosylation processes in developing or aging astrocyte cultures.
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Affiliation(s)
- Vittoria Spina Purrello
- Department of Chemical Sciences, Section of Biochemistry and Molecular Biology, Viale Andrea Doria, 6, University of Catania, 95125, Catania, Italy
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45
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Mercer K, Chiloeches A, Hüser M, Kiernan M, Marais R, Pritchard C. ERK signalling and oncogene transformation are not impaired in cells lacking A-Raf. Oncogene 2002; 21:347-55. [PMID: 11821947 DOI: 10.1038/sj.onc.1205101] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2001] [Revised: 10/19/2001] [Accepted: 10/27/2001] [Indexed: 11/09/2022]
Abstract
Previous studies have indicated an important role for the Raf family of protein kinases in controlling cellular responses to extracellular stimuli and activated oncogenes, through their ability to activate the MEK/ERKs. To investigate the specific role of A-Raf in this process we generated A-Raf deficient mouse embryonic fibroblasts (MEFs) and embryonic stem (ES) cells by gene targeting and characterized their ability to undergo proliferation, differentiation, apoptosis, ERK activation, and transformation by oncogenic Ras and Src. The A-Raf deficient cells are not disrupted for any of these processes, despite the fact that this protein is normally expressed at high levels in both cell types. This implies either that A-Raf plays no role in MEK/ERK activation, that its function is fully compensated by other Raf proteins or MEK kinases or that its role in MEK/ERK activation is highly tissue-specific. Interestingly, B-Raf and Raf-1 activity towards MEK as measured by the immunoprecipitation kinase cascade assay are both significantly increased in the A-Raf deficient MEFs.
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Affiliation(s)
- Kathryn Mercer
- Department of Biochemistry, University of Leicester, University Road, Leicester LE1 7RH, UK
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46
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Mikula M, Schreiber M, Husak Z, Kucerova L, Rüth J, Wieser R, Zatloukal K, Beug H, Wagner EF, Baccarini M. Embryonic lethality and fetal liver apoptosis in mice lacking the c-raf-1 gene. EMBO J 2001; 20:1952-62. [PMID: 11296228 PMCID: PMC125416 DOI: 10.1093/emboj/20.8.1952] [Citation(s) in RCA: 232] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Raf kinases play a key role in relaying signals elicited by mitogens or oncogenes. Here, we report that c-raf-1(-/-) embryos are growth retarded and die at midgestation with anomalies in the placenta and in the fetal liver. Although hepatoblast proliferation does not appear to be impaired, c-raf-1(-/-) fetal livers are hypocellular and contain numerous apoptotic cells. Similarly, the poor proliferation of Raf-1(-/-) fibroblasts and hematopoietic cells cultivated in vitro is due to an increase in the apoptotic index of these cultures rather than to a cell cycle defect. Furthermore, Raf-1- deficient fibroblasts are more sensitive than wild- type cells to specific apoptotic stimuli, such as actinomycin D or Fas activation, but not to tumor necrosis factor-alpha. MEK/ERK activation is normal in Raf-1-deficient cells and embryos, and is probably mediated by B-RAF. These results indicate that the essential function of Raf-1 is to counteract apoptosis rather than to promote proliferation, and that effectors distinct from the MEK/ERK cascade must mediate the anti-apoptotic function of Raf-1.
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Affiliation(s)
| | - Martin Schreiber
- Department of Cell- and Microbiology, Institute of Microbiology and Genetics and
Research Institute of Molecular Pathology, Vienna Biocenter, 1030 Vienna and Department of Pathology, University of Graz, A-8036 Graz, Austria Present address: Department of Obstetrics and Gynecology, University of Vienna, Währinger Gürtel 18–20, A-1090 Vienna, Austria Present address: Department of Medical Biology, University of Vienna, Währinger Straße 10, A-1090 Vienna, Austria Corresponding author e-mail:
| | | | | | | | - Rotraud Wieser
- Department of Cell- and Microbiology, Institute of Microbiology and Genetics and
Research Institute of Molecular Pathology, Vienna Biocenter, 1030 Vienna and Department of Pathology, University of Graz, A-8036 Graz, Austria Present address: Department of Obstetrics and Gynecology, University of Vienna, Währinger Gürtel 18–20, A-1090 Vienna, Austria Present address: Department of Medical Biology, University of Vienna, Währinger Straße 10, A-1090 Vienna, Austria Corresponding author e-mail:
| | - Kurt Zatloukal
- Department of Cell- and Microbiology, Institute of Microbiology and Genetics and
Research Institute of Molecular Pathology, Vienna Biocenter, 1030 Vienna and Department of Pathology, University of Graz, A-8036 Graz, Austria Present address: Department of Obstetrics and Gynecology, University of Vienna, Währinger Gürtel 18–20, A-1090 Vienna, Austria Present address: Department of Medical Biology, University of Vienna, Währinger Straße 10, A-1090 Vienna, Austria Corresponding author e-mail:
| | - Hartmut Beug
- Department of Cell- and Microbiology, Institute of Microbiology and Genetics and
Research Institute of Molecular Pathology, Vienna Biocenter, 1030 Vienna and Department of Pathology, University of Graz, A-8036 Graz, Austria Present address: Department of Obstetrics and Gynecology, University of Vienna, Währinger Gürtel 18–20, A-1090 Vienna, Austria Present address: Department of Medical Biology, University of Vienna, Währinger Straße 10, A-1090 Vienna, Austria Corresponding author e-mail:
| | - Erwin F. Wagner
- Department of Cell- and Microbiology, Institute of Microbiology and Genetics and
Research Institute of Molecular Pathology, Vienna Biocenter, 1030 Vienna and Department of Pathology, University of Graz, A-8036 Graz, Austria Present address: Department of Obstetrics and Gynecology, University of Vienna, Währinger Gürtel 18–20, A-1090 Vienna, Austria Present address: Department of Medical Biology, University of Vienna, Währinger Straße 10, A-1090 Vienna, Austria Corresponding author e-mail:
| | - Manuela Baccarini
- Department of Cell- and Microbiology, Institute of Microbiology and Genetics and
Research Institute of Molecular Pathology, Vienna Biocenter, 1030 Vienna and Department of Pathology, University of Graz, A-8036 Graz, Austria Present address: Department of Obstetrics and Gynecology, University of Vienna, Währinger Gürtel 18–20, A-1090 Vienna, Austria Present address: Department of Medical Biology, University of Vienna, Währinger Straße 10, A-1090 Vienna, Austria Corresponding author e-mail:
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Hüser M, Luckett J, Chiloeches A, Mercer K, Iwobi M, Giblett S, Sun XM, Brown J, Marais R, Pritchard C. MEK kinase activity is not necessary for Raf-1 function. EMBO J 2001; 20:1940-51. [PMID: 11296227 PMCID: PMC125235 DOI: 10.1093/emboj/20.8.1940] [Citation(s) in RCA: 239] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Raf-1 protein kinase has been identified as an integral component of the Ras/Raf/MEK/ERK signalling pathway in mammals. Activation of Raf-1 is achieved by RAS:GTP binding and other events at the plasma membrane including tyrosine phosphorylation at residues 340/341. We have used gene targeting to generate a 'knockout' of the raf-1 gene in mice as well as a rafFF mutant version of endogenous Raf-1 with Y340FY341F mutations. Raf-1(-/-) mice die in embryogenesis and show vascular defects in the yolk sac and placenta as well as increased apoptosis of embryonic tissues. Cell proliferation is not affected. Raf-1 from cells derived from raf-1(FF/FF) mice has no detectable activity towards MEK in vitro, and yet raf-1(FF/FF) mice survive to adulthood, are fertile and have an apparently normal phenotype. In cells derived from both the raf-1(-/-) and raf-1(FF/FF) mice, ERK activation is normal. These results strongly argue that MEK kinase activity of Raf-1 is not essential for normal mouse development and that Raf-1 plays a key role in preventing apoptosis.
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Affiliation(s)
| | | | - Antonio Chiloeches
- Department of Biochemistry,
MRC Toxicology Unit and Division of Biomedical Services, University of Leicester, University Road, Leicester LE1 7RH and Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, UK Corresponding author e-mail:
M.Hüser, J.Luckett and A.Chiloeches contributed equally to this work
| | | | | | | | - Xiao-Ming Sun
- Department of Biochemistry,
MRC Toxicology Unit and Division of Biomedical Services, University of Leicester, University Road, Leicester LE1 7RH and Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, UK Corresponding author e-mail:
M.Hüser, J.Luckett and A.Chiloeches contributed equally to this work
| | - Jane Brown
- Department of Biochemistry,
MRC Toxicology Unit and Division of Biomedical Services, University of Leicester, University Road, Leicester LE1 7RH and Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, UK Corresponding author e-mail:
M.Hüser, J.Luckett and A.Chiloeches contributed equally to this work
| | - Richard Marais
- Department of Biochemistry,
MRC Toxicology Unit and Division of Biomedical Services, University of Leicester, University Road, Leicester LE1 7RH and Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, UK Corresponding author e-mail:
M.Hüser, J.Luckett and A.Chiloeches contributed equally to this work
| | - Catrin Pritchard
- Department of Biochemistry,
MRC Toxicology Unit and Division of Biomedical Services, University of Leicester, University Road, Leicester LE1 7RH and Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, UK Corresponding author e-mail:
M.Hüser, J.Luckett and A.Chiloeches contributed equally to this work
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Jesenberger V, Procyk KJ, Rüth J, Schreiber M, Theussl HC, Wagner EF, Baccarini M. Protective role of Raf-1 in Salmonella-induced macrophage apoptosis. J Exp Med 2001; 193:353-64. [PMID: 11157055 PMCID: PMC2195927 DOI: 10.1084/jem.193.3.353] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Invasive Salmonella induces macrophage apoptosis via the activation of caspase-1 by the bacterial protein SipB. Here we show that infection of macrophages with Salmonella causes the activation and degradation of Raf-1, an important intermediate in macrophage proliferation and activation. Raf-1 degradation is SipB- and caspase-1-dependent, and is prevented by proteasome inhibitors. To study the functional significance of Raf-1 in this process, the c-raf-1 gene was inactivated by Cre-loxP-mediated recombination in vivo. Macrophages lacking c-raf-1 are hypersensitive towards pathogen-induced apoptosis. Surprisingly, activation of the antiapoptotic mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) and nuclear factor kappaB pathways is normal in Raf-1-deficient macrophages, and mitochondrial fragility is not increased. Instead, pathogen-mediated activation of caspase-1 is enhanced selectively, implying that Raf-1 antagonizes stimulus-induced caspase-1 activation and apoptosis.
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Affiliation(s)
| | | | - Jochen Rüth
- Department of Cell and Microbiology, Institute of Microbiology and Genetics
| | - Martin Schreiber
- Department of Cell and Microbiology, Institute of Microbiology and Genetics
| | | | - Erwin F. Wagner
- Research Institute of Molecular Pathology, Vienna Biocenter, 1030 Vienna, Austria
| | - Manuela Baccarini
- Department of Cell and Microbiology, Institute of Microbiology and Genetics
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Abstract
One of the near-to-invariant hallmarks of early apoptosis (programmed cell death) is mitochondrial membrane permeabilization (MMP). It appears that mitochondria fulfill a dual role during the apoptotic process. On the one hand, they integrate multiple different pro-apoptotic signal transducing cascades into a common pathway initiated by MMP. On the other hand, they coordinate the catabolic reactions accompanying late apoptosis by releasing soluble proteins that are normally sequestered within the intermembrane space. In a recent study, Li et al. described a nuclear transcription factor (Nur77/TR1/NGFI-B) that can translocate to mitochondrial membranes to induce MMP. Moreover, two groups identified a novel intermembrane protein (Smac/DIABLO) that specifically neutralizes the inhibitor of apoptosis (IAP) proteins, thereby facilitating the activation of caspases, a class of proteases activated during apoptosis. These findings refine our knowledge how MMP connects to the cellular suicide machinery.
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Affiliation(s)
- K F Ferri
- Centre National de la Recherche Scientifique, Institut Gustave Roussy, Villejuif, France
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50
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Abstract
Cells sense and respond to extracellular factors via receptors on the cell surface that trigger intracellular signaling pathways. The signals received by the receptors on hematopoietic cells often determine if the cell proliferates, survives or undergoes apoptosis. Apoptosis can be induced by almost any cytotoxic stimuli. These stimuli may be an absence of signals arising from cellular receptors, stimulation of specific ligand receptors on the cell surface, chemotherapeutic agents, and ionizing radiation or oxygen radicals, as well as a number of other factors. Cellular kinases and phosphatases participate in signaling cascades that influence this process. We review the ability of the calmodulin-dependent-kinases, I-kappaB kinases, PI3-kinases, Jakkinases, PKC, PKA, and MAP kinase signaling pathways (Erk, Jnk, and p38), to influence the apoptotic process. In addition, we discuss the cross-talk that exists between signaling cascades that are pro-apoptotic and anti-apoptotic.
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Affiliation(s)
- R A Franklin
- Department of Microbiology and Immunology and the Leo Jenkins Cancer Center, Brody School of Medicine at East Carolina, Greenville, NC 27858, USA
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