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Laudadio E, Mangano L, Minnelli C. Chemical Scaffolds for the Clinical Development of Mutant-Selective and Reversible Fourth-Generation EGFR-TKIs in NSCLC. ACS Chem Biol 2024; 19:839-854. [PMID: 38552205 DOI: 10.1021/acschembio.4c00028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
In nonsmall cell lung cancer (NSCLC), as well as in other tumors, the targeted therapy is mainly represented by tyrosine kinase inhibitors (TKIs), small molecules able to target oncogenic driver alterations affecting the gene encoding the epidermal growth factor receptor (EGFR). Up to now, several different TKIs have been developed. However, cancer cells showed an incredible adaptive tumor response to the inhibition of the sequentially mutated EGFR (EGFRM+), triggering the need to explore novel pharmacochemical strategies. This Review summarizes the recent efforts in the development of new reversible next-generation EGFR TKIs to fight the resistance against T790M and C797S mutations. Specifically, after giving an overview of the role of the EGFR's signaling pathways in cancer progression, we are going to discuss the most relevant approved drugs and drug candidates in terms of chemical structure, binding modalities, and their potency and selectivity against the mutated EGFR over the wild-type form. This could provide important guidelines and rationale for the discovery and iterative development of new drugs.
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Affiliation(s)
- Emiliano Laudadio
- Department of Science and Engineering of Matter, Environment and Urban Planning, Marche Polytechnic University, 60131 Ancona, Italy
| | - Luca Mangano
- Roche Pharma Research and Early Development, Oncology Discovery, Roche Innovation Center Basel, 4070 Basel, Switzerland
| | - Cristina Minnelli
- Department of Life and Environmental Sciences, Marche Polytechnic University, 60131 Ancona, Italy
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Zhang Y, Lu Q, Li N, Xu M, Miyamoto T, Liu J. Sulforaphane suppresses metastasis of triple-negative breast cancer cells by targeting the RAF/MEK/ERK pathway. NPJ Breast Cancer 2022; 8:40. [PMID: 35332167 PMCID: PMC8948359 DOI: 10.1038/s41523-022-00402-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 02/22/2022] [Indexed: 12/15/2022] Open
Abstract
Breast cancer metastasis is the main cause of cancer death in women, so far, no effective treatment has inhibited breast cancer metastasis. Sulforaphane (SFN), a natural compound derived from broccoli, has shown potential health benefits in many cancers. However, research on breast cancer metastasis is still insufficient. Here, we showed that SFN, including its two isomers of R-SFN and S-SFN, significantly inhibited TGF-β1-induced migration and invasion in breast cancer cells. Proteomic and phosphoproteomic analysis showed that SFN affected the formation of the cytoskeleton. Subsequent experiments confirmed that SFN significantly inhibited TGF-β1-induced actin stress fiber formation and the expression of actin stress fiber formation-associated proteins, including paxillin, IQGAP1, FAK, PAK2, and ROCK. Additionally, SFN is directly bound to RAF family proteins (including ARAF, BRAF, and CRAF) and inhibited MEK and ERK phosphorylation. These in vitro results indicate that SFN targets the RAF/MEK/ERK signaling pathway to inhibit the formation of actin stress fibers, thereby inhibiting breast cancer cell metastasis.
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Affiliation(s)
- Ying Zhang
- Department of Molecular and Cellular Physiology, Yamaguchi University, Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi, 755-8505, Japan.
| | - Qian Lu
- Department of Molecular and Cellular Physiology, Yamaguchi University, Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Nan Li
- Department of Molecular and Cellular Physiology, Yamaguchi University, Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Ming Xu
- Department of Gastroenterological, Breast and Endocrine Surgery, Yamaguchi University, Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Tatsuo Miyamoto
- Department of Molecular and Cellular Physiology, Yamaguchi University, Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Jing Liu
- College of Pharmacy, Dalian Medical University, No.9 West Section Lvshun South Road, Dalian, 116044, China.
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Wang Q, Fan H, Li F, Skeeters SS, Krishnamurthy VV, Song Y, Zhang K. Optical control of ERK and AKT signaling promotes axon regeneration and functional recovery of PNS and CNS in Drosophila. eLife 2020; 9:57395. [PMID: 33021199 PMCID: PMC7567606 DOI: 10.7554/elife.57395] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 09/15/2020] [Indexed: 12/17/2022] Open
Abstract
Neuroregeneration is a dynamic process synergizing the functional outcomes of multiple signaling circuits. Channelrhodopsin-based optogenetics shows the feasibility of stimulating neural repair but does not pin down specific signaling cascades. Here, we utilized optogenetic systems, optoRaf and optoAKT, to delineate the contribution of the ERK and AKT signaling pathways to neuroregeneration in live Drosophila larvae. We showed that optoRaf or optoAKT activation not only enhanced axon regeneration in both regeneration-competent and -incompetent sensory neurons in the peripheral nervous system but also allowed temporal tuning and proper guidance of axon regrowth. Furthermore, optoRaf and optoAKT differ in their signaling kinetics during regeneration, showing a gated versus graded response, respectively. Importantly in the central nervous system, their activation promotes axon regrowth and functional recovery of the thermonociceptive behavior. We conclude that non-neuronal optogenetics targets damaged neurons and signaling subcircuits, providing a novel strategy in the intervention of neural damage with improved precision. Most cells have a built-in regeneration signaling program that allows them to divide and repair. But, in the cells of the central nervous system, which are called neurons, this program is ineffective. This is why accidents and illnesses affecting the brain and spinal cord can cause permanent damage. Reactivating regeneration in neurons could help them repair, but it is not easy. Certain small molecules can switch repair signaling programs back on. Unfortunately, these molecules diffuse easily through tissues, spreading around the body and making it hard to target individual damaged cells. This both hampers research into neuronal repair and makes treatments directed at healing damage to the nervous system more likely to have side-effects. It is unclear whether reactivating regeneration signaling in individual neurons is possible. One way to address this question is to use optogenetics. This technique uses genetic engineering to fuse proteins that are light-sensitive to proteins responsible for relaying signals in the cell. When specific wavelengths of light hit the light-sensitive proteins, the fused signaling proteins switch on, leading to the activation of any proteins they control, for example, those involved in regeneration. Wang et al. used optogenetic tools to determine if light can help repair neurons in fruit fly larvae. First, a strong laser light was used to damage an individual neuron in a fruit fly larva that had been genetically modified so that blue light would activate the regeneration program in its neurons. Then, Wang et al. illuminated the cell with dim blue light, switching on the regeneration program. Not only did this allow the neuron to repair itself, it also allowed the light to guide its regeneration. By focusing the blue light on the damaged end of the neuron, it was possible to guide the direction of the cell's growth as it regenerated. Regeneration programs in flies and mammals involve similar signaling proteins, but blue light does not penetrate well into mammalian tissues. This means that further research into LEDs that can be implanted may be necessary before neuronal repair experiments can be performed in mammals. In any case, the ability to focus treatment on individual neurons paves the way for future work into the regeneration of the nervous system, and the combination of light and genetics could reveal more about how repair signals work.
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Affiliation(s)
- Qin Wang
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, United States.,Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, United States
| | - Huaxun Fan
- Department of Biochemistry, Urbana, United States
| | - Feng Li
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, United States.,Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, United States
| | | | | | - Yuanquan Song
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, United States.,Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, United States
| | - Kai Zhang
- Department of Biochemistry, Urbana, United States.,Neuroscience Program, Urbana, United States.,Center for Biophysics and Quantitative Biology, Urbana, United States.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States
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Cyclin-Dependent Kinase-Like 5 (CDKL5): Possible Cellular Signalling Targets and Involvement in CDKL5 Deficiency Disorder. Neural Plast 2020; 2020:6970190. [PMID: 32587608 PMCID: PMC7293752 DOI: 10.1155/2020/6970190] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 05/12/2020] [Accepted: 05/14/2020] [Indexed: 12/29/2022] Open
Abstract
Cyclin-dependent kinase-like 5 (CDKL5, also known as STK9) is a serine/threonine protein kinase originally identified in 1998 during a transcriptional mapping project of the human X chromosome. Thereafter, a mutation in CDKL5 was reported in individuals with the atypical Rett syndrome, a neurodevelopmental disorder, suggesting that CDKL5 plays an important regulatory role in neuronal function. The disease associated with CDKL5 mutation has recently been recognised as CDKL5 deficiency disorder (CDD) and has been distinguished from the Rett syndrome owing to its symptomatic manifestation. Because CDKL5 mutations identified in patients with CDD cause enzymatic loss of function, CDKL5 catalytic activity is likely strongly associated with the disease. Consequently, the exploration of CDKL5 substrate characteristics and regulatory mechanisms of its catalytic activity are important for identifying therapeutic target molecules and developing new treatment. In this review, we summarise recent findings on the phosphorylation of CDKL5 substrates and the mechanisms of CDKL5 phosphorylation and dephosphorylation. We also discuss the relationship between changes in the phosphorylation signalling pathways and the Cdkl5 knockout mouse phenotype and consider future prospects for the treatment of mental and neurological disease associated with CDKL5 mutations.
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Regulation of c-Raf Stability through the CTLH Complex. Int J Mol Sci 2019; 20:ijms20040934. [PMID: 30795516 PMCID: PMC6412545 DOI: 10.3390/ijms20040934] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 02/14/2019] [Indexed: 12/23/2022] Open
Abstract
c-Raf is a central component of the extracellular signal-regulated kinase (ERK) pathway which is implicated in the development of many cancer types. RanBPM (Ran-Binding Protein M) was previously shown to inhibit c-Raf expression, but how this is achieved remains unclear. RanBPM is part of a recently identified E3 ubiquitin ligase complex, the CTLH (C-terminal to LisH) complex. Here, we show that the CTLH complex regulates c-Raf expression through a control of its degradation. Several domains of RanBPM were found necessary to regulate c-Raf levels, but only the C-terminal CRA (CT11-RanBPM) domain showed direct interaction with c-Raf. c-Raf ubiquitination and degradation is promoted by the CTLH complex. Furthermore, A-Raf and B-Raf protein levels are also regulated by the CTLH complex, indicating a common regulation of Raf family members. Finally, depletion of CTLH subunits RMND5A (required for meiotic nuclear division 5A) and RanBPM resulted in enhanced proliferation and loss of RanBPM promoted tumour growth in a mouse model. This study uncovers a new mode of control of c-Raf expression through regulation of its degradation by the CTLH complex. These findings also uncover a novel target of the CTLH complex, and suggest that the CTLH complex has activities that suppress cell transformation and tumour formation.
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78495111110.3390/cancers9050052" />
Abstract
The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is commonly upregulated in cancers such as in non-small-cell lung cancer, metastatic colorectal cancer, glioblastoma, head and neck cancer, pancreatic cancer, and breast cancer. Various mechanisms mediate the upregulation of EGFR activity, including common mutations and truncations to its extracellular domain, such as in the EGFRvIII truncations, as well as to its kinase domain, such as the L858R and T790M mutations, or the exon 19 truncation. These EGFR aberrations over-activate downstream pro-oncogenic signaling pathways, including the RAS-RAF-MEK-ERK MAPK and AKT-PI3K-mTOR pathways. These pathways then activate many biological outputs that are beneficial to cancer cell proliferation, including their chronic initiation and progression through the cell cycle. Here, we review the molecular mechanisms that regulate EGFR signal transduction, including the EGFR structure and its mutations, ligand binding and EGFR dimerization, as well as the signaling pathways that lead to G1 cell cycle progression. We focus on the induction of CYCLIN D expression, CDK4/6 activation, and the repression of cyclin-dependent kinase inhibitor proteins (CDKi) by EGFR signaling pathways. We also discuss the successes and challenges of EGFR-targeted therapies, and the potential for their use in combination with CDK4/6 inhibitors.
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Wee P, Wang Z. Epidermal Growth Factor Receptor Cell Proliferation Signaling Pathways. Cancers (Basel) 2017; 9:cancers9050052. [PMID: 28513565 PMCID: PMC5447962 DOI: 10.3390/cancers9050052] [Citation(s) in RCA: 1036] [Impact Index Per Article: 148.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 05/10/2017] [Accepted: 05/10/2017] [Indexed: 12/12/2022] Open
Abstract
The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is commonly upregulated in cancers such as in non-small-cell lung cancer, metastatic colorectal cancer, glioblastoma, head and neck cancer, pancreatic cancer, and breast cancer. Various mechanisms mediate the upregulation of EGFR activity, including common mutations and truncations to its extracellular domain, such as in the EGFRvIII truncations, as well as to its kinase domain, such as the L858R and T790M mutations, or the exon 19 truncation. These EGFR aberrations over-activate downstream pro-oncogenic signaling pathways, including the RAS-RAF-MEK-ERK MAPK and AKT-PI3K-mTOR pathways. These pathways then activate many biological outputs that are beneficial to cancer cell proliferation, including their chronic initiation and progression through the cell cycle. Here, we review the molecular mechanisms that regulate EGFR signal transduction, including the EGFR structure and its mutations, ligand binding and EGFR dimerization, as well as the signaling pathways that lead to G1 cell cycle progression. We focus on the induction of CYCLIN D expression, CDK4/6 activation, and the repression of cyclin-dependent kinase inhibitor proteins (CDKi) by EGFR signaling pathways. We also discuss the successes and challenges of EGFR-targeted therapies, and the potential for their use in combination with CDK4/6 inhibitors.
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Affiliation(s)
- Ping Wee
- Department of Medical Genetics and Signal Transduction Research Group, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| | - Zhixiang Wang
- Department of Medical Genetics and Signal Transduction Research Group, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
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Lee S, Wottrich S, Bonavida B. Crosstalks between Raf-kinase inhibitor protein and cancer stem cell transcription factors (Oct4, KLF4, Sox2, Nanog). Tumour Biol 2017; 39:1010428317692253. [PMID: 28378634 DOI: 10.1177/1010428317692253] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Raf-kinase inhibitor protein has been reported to inhibit both the Raf/mitogen extracellular signal-regulated kinase/extracellular signal-regulated kinase and nuclear factor kappa-light-chain of activated B cells pathways. It has also been reported in cancers that Raf-kinase inhibitor protein behaves as a metastatic suppressor as well as a chemo-immunosensitizing factor to drug/immune-mediated apoptosis. The majority of cancers exhibit low or no levels of Raf-kinase inhibitor protein. Hence, the activities of Raf-kinase inhibitor protein contrast, in part, to those mediated by several cancer stem cell transcription factors for their roles in resistance and metastasis. In this review, the existence of crosstalks in the signaling pathways between Raf-kinase inhibitor protein and several cancer stem cell transcription factors (Oct4, KLF4, Sox2 and Nanog) was assembled. Oct4 is induced by Lin28, and Raf-kinase inhibitor protein inhibits the microRNA binding protein Lin28. The expression of Raf-kinase inhibitor protein inversely correlates with the expression of Oct4. KLF4 does not interact directly with Raf-kinase inhibitor protein, but rather interacts indirectly via Raf-kinase inhibitor protein's regulation of the Oct4/Sox2/KLF4 complex through the mitogen-activated protein kinase pathway. The mechanism by which Raf-kinase inhibitor protein inhibits Sox2 is via the inhibition of the mitogen-activated protein kinase pathway by Raf-kinase inhibitor protein. Thus, Raf-kinase inhibitor protein's relationship with Sox2 is via its regulation of Oct4. Inhibition of extracellular signal-regulated kinase by Raf-kinase inhibitor protein results in the upregulation of Nanog. The inhibition of Oct4 by Raf-kinase inhibitor protein results in the failure of the heterodimer formation of Oct4 and Sox2 that is necessary to bind to the Nanog promoter for the transcription of Nanog. The findings revealed that there exists a direct correlation between the expression of Raf-kinase inhibitor protein and the expression of each of the above transcription factors. Based on these analyses, we suggest that the expression level of Raf-kinase inhibitor protein may be involved in the regulation of the cancer stem cell phenotype.
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Affiliation(s)
- SoHyun Lee
- Department of Microbiology, Immunology & Molecular Genetics, David Geffen School of Medicine, Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, CA, USA
| | - Stephanie Wottrich
- Department of Microbiology, Immunology & Molecular Genetics, David Geffen School of Medicine, Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, CA, USA
| | - Benjamin Bonavida
- Department of Microbiology, Immunology & Molecular Genetics, David Geffen School of Medicine, Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, CA, USA
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Abstract
SMYD3 is a member of the SET and MYND-domain family of methyl-transferases, the increased expression of which correlates with poor prognosis in various types of cancer. In liver and colon tumors, SMYD3 is localized in the nucleus, where it interacts with RNA Pol II and H3K4me3 and functions as a selective transcriptional amplifier of oncogenes and genes that control cell proliferation and metastatic spread. Smyd3 expression has a high discriminative power for the characterization of liver tumors and positively correlates with poor prognosis. In lung and pancreatic cancer, SMYD3 acts in the cytoplasm, potentiating oncogenic Ras/ERK signaling through the methylation of the MAP3K2 kinase and the subsequent release from its inhibitor. A clinico-pathological analysis of lung cancer patients uncovers prognostic significance of SMYD3 only for first progression survival. However, stratification of patients according to their smoking history significantly expands the prognostic value of SMYD3 to overall survival and other features, suggesting that smoking-related effects saturate the clinical analysis and mask the function of SMYD3 as an oncogenic potentiator.
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Zhou J, Du T, Li B, Rong Y, Verkhratsky A, Peng L. Crosstalk Between MAPK/ERK and PI3K/AKT Signal Pathways During Brain Ischemia/Reperfusion. ASN Neuro 2015; 7:7/5/1759091415602463. [PMID: 26442853 PMCID: PMC4601130 DOI: 10.1177/1759091415602463] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The epidermal growth factor receptor (EGFR) is linked to the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and Raf/mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK1/2) signaling pathways. During brain ischemia/reperfusion, EGFR could be transactivated, which stimulates these intracellular signaling cascades that either protect cells or potentiate cell injury. In the present study, we investigated the activation of EGFR, PI3K/AKT, and Raf/MAPK/ERK1/2 during ischemia or reperfusion of the brain using the middle cerebral artery occlusion model. We found that EGFR was phosphorylated and transactivated during both ischemia and reperfusion periods. During ischemia, the activity of PI3K/AKT pathway was significantly increased, as judged from the strong phosphorylation of AKT; this activation was suppressed by the inhibitors of EGFR and Zn-dependent metalloproteinase. Ischemia, however, did not induce ERK1/2 phosphorylation, which was dependent on reperfusion. Coimmunoprecipitation of Son of sevenless 1 (SOS1) with EGFR showed increased association between the receptor and SOS1 in ischemia, indicating the inhibitory node downstream of SOS1. The inhibitory phosphorylation site of Raf-1 at Ser259, but not its stimulatory phosphorylation site at Ser338, was phosphorylated during ischemia. Furthermore, ischemia prompted the interaction between Raf-1 and AKT, while both the inhibitors of PI3K and AKT not only abolished AKT phosphorylation but also restored ERK1/2 phosphorylation. All these findings suggest that Raf/MAPK/ERK1/2 signal pathway is inhibited by AKT via direct phosphorylation and inhibition at Raf-1 node during ischemia. During reperfusion, we observed a significant increase of ERK1/2 phosphorylation but no change in AKT phosphorylation. Inhibitors of reactive oxygen species and phosphatase and tensin homolog restored AKT phosphorylation but abolished ERK1/2 phosphorylation, suggesting that the reactive oxygen species-dependent increase in phosphatase and tensin homolog activity in reperfusion period relieves ERK1/2 from inhibition of AKT.
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Affiliation(s)
- Jing Zhou
- Laboratory of Metabolic Brain Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China
| | - Ting Du
- Laboratory of Metabolic Brain Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China
| | - Baoman Li
- Laboratory of Metabolic Brain Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China
| | - Yan Rong
- Laboratory of Metabolic Brain Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China
| | - Alexei Verkhratsky
- Faculty of Life Science, The University of Manchester, UK Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, Bilbao, Spain University of Nizhny Novgorod, Russia
| | - Liang Peng
- Laboratory of Metabolic Brain Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China
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Abstract
Ran-binding protein M (RanBPM) is a nucleocytoplasmic protein of yet unknown function. We have previously shown that RanBPM inhibits expression of the anti-apoptotic factor Bcl-2 and promotes apoptosis induced by DNA damage. Here we show that the effects of RanBPM on Bcl-2 expression occur through a regulation of the ERK signaling pathway. Transient and stable down-regulation of RanBPM stimulated ERK phosphorylation, leading to Bcl-2 up-regulation, while re-expression of RanBPM reversed these effects. RanBPM was found to inhibit MEK and ERK activation induced by ectopic expression of active RasV12. Activation of ERK by active c-Raf was also prevented by RanBPM. Expression of RanBPM correlated with a marked decrease in the protein levels of ectopically expressed active c-Raf and also affected the expression of endogenous c-Raf. RanBPM formed a complex with both active c-Raf, consisting of the C-terminal kinase domain, and endogenous c-Raf in mammalian cells. In addition, RanBPM was found to decrease the binding of Hsp90 to c-Raf. Finally, we show that loss of RanBPM expression confers increased cell proliferation and cell migration properties to HEK293 cells. Altogether, these findings establish RanBPM as a novel inhibitor of the ERK pathway through an interaction with the c-Raf complex and a regulation of c-Raf stability, and provide evidence that RanBPM loss of expression results in constitutive activation of the ERK pathway and promotes cellular events leading to cellular transformation and tumorigenesis.
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Affiliation(s)
| | - Caroline Schild-Poulter
- Robarts Research Institute and Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
- * E-mail:
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Cross-talk between mitogenic Ras/MAPK and survival PI3K/Akt pathways: a fine balance. Biochem Soc Trans 2012; 40:139-46. [PMID: 22260680 DOI: 10.1042/bst20110609] [Citation(s) in RCA: 347] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In the present paper, we describe multiple levels of cross-talk between the PI3K (phosphoinositide 3-kinase)/Akt and Ras/MAPK (mitogen-activated protein kinase) signalling pathways. Experimental data and computer simulations demonstrate that cross-talk is context-dependent and that both pathways can activate or inhibit each other. Positive influence of the PI3K pathway on the MAPK pathway is most effective at sufficiently low doses of growth factors, whereas negative influence of the MAPK pathway on the PI3K pathway is mostly pronounced at high doses of growth factors. Pathway cross-talk endows a cell with emerging capabilities for processing and decoding signals from multiple receptors activated by different combinations of extracellular cues.
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Matallanas D, Birtwistle M, Romano D, Zebisch A, Rauch J, von Kriegsheim A, Kolch W. Raf family kinases: old dogs have learned new tricks. Genes Cancer 2011; 2:232-60. [PMID: 21779496 PMCID: PMC3128629 DOI: 10.1177/1947601911407323] [Citation(s) in RCA: 272] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
First identified in the early 1980s as retroviral oncogenes, the Raf proteins have been the objects of intense research. The discoveries 10 years later that the Raf family members (Raf-1, B-Raf, and A-Raf) are bona fide Ras effectors and upstream activators of the ubiquitous ERK pathway increased the interest in these proteins primarily because of the central role that this cascade plays in cancer development. The important role of Raf in cancer was corroborated in 2002 with the discovery of B-Raf genetic mutations in a large number of tumors. This led to intensified drug development efforts to target Raf signaling in cancer. This work yielded not only recent clinical successes but also surprising insights into the regulation of Raf proteins by homodimerization and heterodimerization. Surprising insights also came from the hunt for new Raf targets. Although MEK remains the only widely accepted Raf substrate, new kinase-independent roles for Raf proteins have emerged. These include the regulation of apoptosis by suppressing the activity of the proapoptotic kinases, ASK1 and MST2, and the regulation of cell motility and differentiation by controlling the activity of Rok-α. In this review, we discuss the regulation of Raf proteins and their role in cancer, with special focus on the interacting proteins that modulate Raf signaling. We also describe the new pathways controlled by Raf proteins and summarize the successes and failures in the development of efficient anticancer therapies targeting Raf. Finally, we also argue for the necessity of more systemic approaches to obtain a better understanding of how the Ras-Raf signaling network generates biological specificity.
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Affiliation(s)
- David Matallanas
- Systems Biology Ireland, University College Dublin, Dublin, Ireland
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Zhou J, Yang Z, Tsuji T, Gong J, Xie J, Chen C, Li W, Amar S, Luo Z. LITAF and TNFSF15, two downstream targets of AMPK, exert inhibitory effects on tumor growth. Oncogene 2011; 30:1892-900. [PMID: 21217782 PMCID: PMC3431012 DOI: 10.1038/onc.2010.575] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF) α factor (LITAF) is a multiple functional molecule whose sequence is identical to the small integral membrane protein of the lysosome/late endosome. LITAF was initially identified as a transcription factor that activates transcription of proinflammatory cytokine in macrophages in response to LPS. Mutations of the LITAF gene are associated with a genetic disease, called Charcot-Marie-Tooth syndrome. Recently, we have reported that mRNA levels of LITAF and TNF superfamily member 15 (TNFSF15) are upregulated by 5' adenosine monophosphate (AMP)-activated protein kinase (AMPK). The present study further assesses their biological functions. Thus, we show that 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), a pharmacological activator of AMPK, increases the abundance of LITAF and TNFSF15 in LNCaP and C4-2 prostate cancer cells, which is abrogated by small hairpin RNA (shRNA) or the dominant-negative mutant of AMPK α1 subunit. Our data further demonstrate that AMPK activation upregulates the transcription of LITAF. Intriguingly, silencing LITAF by shRNA enhances proliferation, anchorage-independent growth of these cancer cells and tumor growth in the xenograft model. In addition, our study reveals that LITAF mediates the effect of AMPK by binding to a specific sequence in the promoter region. Furthermore, we show that TNFSF15 remarkably inhibits the growth of prostate cancer cells and bovine aortic endothelial cells in vitro, with a more potent effect toward the latter. In conjuncture, intratumoral injection of TNFSF15 significantly reduces the size of tumors and number of blood vessels and induces changes that are characteristic of tumor cell differentiation. Therefore, our studies for the first time establish the regulatory axis of AMPK-LITAF-TNFSF15 and also suggest that LITAF may function as a tumor suppressor.
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Affiliation(s)
- J Zhou
- Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118, USA
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15
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Hatzivassiliou G, Song K, Yen I, Brandhuber BJ, Anderson DJ, Alvarado R, Ludlam MJC, Stokoe D, Gloor SL, Vigers G, Morales T, Aliagas I, Liu B, Sideris S, Hoeflich KP, Jaiswal BS, Seshagiri S, Koeppen H, Belvin M, Friedman LS, Malek S. RAF inhibitors prime wild-type RAF to activate the MAPK pathway and enhance growth. Nature 2010; 464:431-5. [DOI: 10.1038/nature08833] [Citation(s) in RCA: 1256] [Impact Index Per Article: 89.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Accepted: 01/18/2010] [Indexed: 02/07/2023]
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16
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Systems-level interactions between insulin-EGF networks amplify mitogenic signaling. Mol Syst Biol 2009; 5:256. [PMID: 19357636 PMCID: PMC2683723 DOI: 10.1038/msb.2009.19] [Citation(s) in RCA: 155] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Accepted: 02/23/2009] [Indexed: 01/01/2023] Open
Abstract
Crosstalk mechanisms have not been studied as thoroughly as individual signaling pathways. We exploit experimental and computational approaches to reveal how a concordant interplay between the insulin and epidermal growth factor (EGF) signaling networks can potentiate mitogenic signaling. In HEK293 cells, insulin is a poor activator of the Ras/ERK (extracellular signal-regulated kinase) cascade, yet it enhances ERK activation by low EGF doses. We find that major crosstalk mechanisms that amplify ERK signaling are localized upstream of Ras and at the Ras/Raf level. Computational modeling unveils how critical network nodes, the adaptor proteins GAB1 and insulin receptor substrate (IRS), Src kinase, and phosphatase SHP2, convert insulin-induced increase in the phosphatidylinositol-3,4,5-triphosphate (PIP3) concentration into enhanced Ras/ERK activity. The model predicts and experiments confirm that insulin-induced amplification of mitogenic signaling is abolished by disrupting PIP3-mediated positive feedback via GAB1 and IRS. We demonstrate that GAB1 behaves as a non-linear amplifier of mitogenic responses and insulin endows EGF signaling with robustness to GAB1 suppression. Our results show the feasibility of using computational models to identify key target combinations and predict complex cellular responses to a mixture of external cues.
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17
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Wu X, Carr HS, Dan I, Ruvolo PP, Frost JA. p21 activated kinase 5 activates Raf-1 and targets it to mitochondria. J Cell Biochem 2008; 105:167-75. [PMID: 18465753 DOI: 10.1002/jcb.21809] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Raf-1 is an important effector of Ras mediated signaling and is a critical regulator of the ERK/MAPK pathway. Raf-1 activation is controlled in part by phosphorylation on multiple residues, including an obligate phosphorylation site at serine 338. Previously PAK1 and casein kinase II have been implicated as serine 338 kinases. To identify novel kinases that phosphorylate this site, we tested the ability of group II PAKs (PAKs 4-6) to control serine 338 phosphorylation. We observed that all group II PAKs were efficient serine 338 kinases, although only PAK1 and PAK5 significantly stimulated Raf-1 kinase activity. We also showed that PAK5 forms a tight complex with Raf-1 in the cell, but not A-Raf or B-Raf. Importantly, we also demonstrated that the association of Raf-1 with PAK5 targets a subpopulation of Raf-1 to mitochondria. These data indicate that PAK5 is a potent regulator of Raf-1 activity and may control Raf-1 dependent signaling at mitochondria.
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Affiliation(s)
- Xiaochong Wu
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, Texas 77030, USA
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18
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Gorelik G, Fang JY, Wu A, Sawalha AH, Richardson B. Impaired T cell protein kinase C delta activation decreases ERK pathway signaling in idiopathic and hydralazine-induced lupus. THE JOURNAL OF IMMUNOLOGY 2007; 179:5553-63. [PMID: 17911642 DOI: 10.4049/jimmunol.179.8.5553] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
T cells from patients with lupus or treated with the lupus-inducing drug hydralazine have defective ERK phosphorylation. The reason for the impaired signal transduction is unknown but important to elucidate, because decreased T cell ERK pathway signaling causes a lupus-like disease in animal models by decreasing DNA methyltransferase expression, leading to DNA hypomethylation and overexpression of methylation-sensitive genes with subsequent autoreactivity and autoimmunity. We therefore analyzed the PMA stimulated ERK pathway phosphorylation cascade in CD4(+) T cells from patients with lupus and in hydralazine-treated cells. The defect in these cells localized to protein kinase C (PKC)delta. Pharmacologic inhibition of PKCdelta or transfection with a dominant negative PKCdelta mutant caused demethylation of the TNFSF7 (CD70) promoter and CD70 overexpression similar to lupus and hydralazine-treated T cells. These results suggest that defective T cell PKCdelta activation may contribute to the development of idiopathic and hydralazine-induced lupus through effects on T cell DNA methylation.
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Affiliation(s)
- Gabriela Gorelik
- Department of Medicine, University of Michigan, Ann Arbor, MI 48109, USA
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19
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Feng L, Xie X, Ding Q, Luo X, He J, Fan F, Liu W, Wang Z, Chen Y. Spatial regulation of Raf kinase signaling by RKTG. Proc Natl Acad Sci U S A 2007; 104:14348-53. [PMID: 17724343 PMCID: PMC1964828 DOI: 10.1073/pnas.0701298104] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Subcellular compartmentalization has become an important theme in cell signaling such as spatial regulation of Ras by RasGRP1 and MEK/ERK by Sef. Here, we report spatial regulation of Raf kinase by RKTG (Raf kinase trapping to Golgi). RKTG is a seven-transmembrane protein localized at the Golgi apparatus. RKTG expression inhibits EGF-stimulated ERK and RSK phosphorylation, blocks NGF-mediated PC12 cell differentiation, and antagonizes Ras- and Raf-1-stimulated Elk-1 transactivation. Through interaction with Raf-1, RKTG changes the localization of Raf-1 from cytoplasm to the Golgi apparatus, blocks EGF-stimulated Raf-1 membrane translocation, and reduces the interaction of Raf-1 with Ras and MEK1. In RKTG-null mice, the basal ERK phosphorylation level is increased in the brain and liver. In RKTG-deleted mouse embryonic fibroblasts, EGF-induced ERK phosphorylation is enhanced. Collectively, our results reveal a paradigm of spatial regulation of Raf kinase by RKTG via sequestrating Raf-1 to the Golgi apparatus and thereby inhibiting the ERK signaling pathway.
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Affiliation(s)
- Lin Feng
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Xiaoduo Xie
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Qiurong Ding
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Xiaolin Luo
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Jing He
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Fengjuan Fan
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Weizhong Liu
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Zhenzhen Wang
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
| | - Yan Chen
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai 200031, China
- *To whom correspondence should be addressed at:
Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 294 Taiyuan Road, Shanghai 200031, China. E-mail:
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20
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Abstract
Cancer can be perceived as a disease of communication between and within cells. The aberrations are pleiotropic, but mitogen-activated protein kinase (MAPK) pathways feature prominently. Here, we discuss recent findings and hypotheses on the role of MAPK pathways in cancer. Cancerous mutations in MAPK pathways are frequently mostly affecting Ras and B-Raf in the extracellular signal-regulated kinase pathway. Stress-activated pathways, such as Jun N-terminal kinase and p38, largely seem to counteract malignant transformation. The balance and integration between these signals may widely vary in different tumours, but are important for the outcome and the sensitivity to drug therapy.
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Affiliation(s)
- A S Dhillon
- The Beatson Institute for Cancer Research, Bearsden, Glasgow, UK.
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21
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Park ER, Eblen ST, Catling AD. MEK1 activation by PAK: a novel mechanism. Cell Signal 2007; 19:1488-96. [PMID: 17314031 PMCID: PMC2233889 DOI: 10.1016/j.cellsig.2007.01.018] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2006] [Revised: 01/12/2007] [Accepted: 01/16/2007] [Indexed: 10/23/2022]
Abstract
Extracellular signal-Regulated Kinase (ERK) controls a variety of cellular processes, including cell proliferation and cell motility. While oncogenic mutations in Ras and B-Raf result in deregulated ERK activity and proliferation and migration in some tumor cells, other tumors exhibit elevated ERK signaling in the absence of these mutations. Here we provide evidence that PAK can directly activate MEK1 by a mechanism distinct from conventional Ras/Raf mediated activation. We find that PAK phosphorylation of MEK1 serine 298 stimulates MEK1 autophosphorylation on the activation loop, and activation of MEK1 activity towards ERK in in vitro reconstitution experiments. Serines 218 and/or 222 in the MEK1 activation loop are required for PAK-stimulated MEK1 activity towards ERK. MEK2, which is a poor target for PAK phosphorylation in cells, is not activated in this manner. Tissue culture experiments verify that this mechanism is used in suspended fibroblasts expressing mutationally activated PAK1. We speculate that aberrant signaling through PAK may directly induce anchorage-independent MEK1 activation in tumor cells lacking oncogenic Ras or Raf mutations, and that this mechanism may contribute to localized MEK signaling in focal contacts and adhesions during cell adhesion or migration.
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Affiliation(s)
- Electa R. Park
- Department of Biochemistry, Louisiana State University Health Sciences Center, New Orleans, LA 70112, United States
| | - Scott T. Eblen
- Department of Pharmacology, Medical University of South Carolina, Charleston, SC 29425, United States
| | - Andrew D. Catling
- Department of Pharmacology, Louisiana State University Health Sciences Center, New Orleans, LA 70112, United States
- Stanley S. Scott Cancer Center, Louisiana State University Health Sciences Center, New Orleans, LA 70112, United States
- *Corresponding author. Department of Pharmacology, Medical Education Building, 1901 Perdido Street, New Orleans, LA 70112, United States. Tel.: +1 504 568 4740; fax: +1 504 568 2361. E-mail address: (A.D. Catling)
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22
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Zhang S, Li Z, Wu X, Huang Q, Shen HM, Ong CN. Methyl-3-indolylacetate inhibits cancer cell invasion by targeting the MEK1/2-ERK1/2 signaling pathway. Mol Cancer Ther 2006; 5:3285-93. [PMID: 17172432 DOI: 10.1158/1535-7163.mct-06-0240] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Epidemiologic studies have suggested an inverse correlation between dietary intake of cruciferous vegetables and cancer risk. It is thus of interest to investigate the anticancer potential of phytochemicals presented in cruciferous vegetables. In this study, methyl-3-indolylacetate (MIA), a cruciferous indole for which the bioactivity has not been previously reported, was found to significantly suppress the invasion of cancer cells stimulated by the 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Our data show that MIA pretreatments inhibited matrix metalloproteinase 9 (MMP-9) expression in a concentration-dependent manner, resulting in decreased MMP-9 activity. By using real-time reverse transcription-PCR, luciferase reporter gene assay, and electrophoretic mobility shift assay, we provided convincing evidence that MIA suppresses MMP-9 gene transcription via targeting the activator protein-1 signaling but not the nuclear factor-kappaB pathway. The TPA-induced mitogen-activated protein kinase (MAPK) activation cascade was also analyzed. Despite extensive activation of major MAPKs [c-Jun NH2-terminal kinase, p38, and extracellular signal-regulated kinase-1/2 (ERK1/2)] under TPA stimulation, only the ERK1/2 activation and its consequent nuclear translocation were found to be diminished by MIA. Interestingly, MIA did not affect the TPA-induced phosphorylation of either c-Raf or MAPK/ERK kinase-1/2 (MEK1/2), two upstream kinases of ERK. Moreover, using the in vitro kinase assay, MIA was shown to inhibit the kinase activity of MEK1/2, the upstream kinases of ERK, suggesting that MEK is the major molecular target of MIA. In conclusion, data from this study provided new insight into the anticancer potential of MIA, a cruciferous vegetable-derived indole compound.
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Affiliation(s)
- Siyuan Zhang
- Department of Community, Occupational, and Family Medicine, Yong Loo Lin School of Medicine, National University of Singapore, 16 Medical Drive, Singapore 117597, Republic of Singapore
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23
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Park S, Rath O, Beach S, Xiang X, Kelly SM, Luo Z, Kolch W, Yeung KC. Regulation of RKIP binding to the N-region of the Raf-1 kinase. FEBS Lett 2006; 580:6405-12. [PMID: 17097642 PMCID: PMC1892598 DOI: 10.1016/j.febslet.2006.10.054] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2006] [Revised: 10/10/2006] [Accepted: 10/24/2006] [Indexed: 12/27/2022]
Abstract
The Raf kinase inhibitory protein (RKIP) binds to Raf-1 interfering with binding of the MEK substrate and potentially also Raf-1 activation. In response to mitogen stimulation RKIP dissociates from Raf-1 and later re-associates. Here, using a combination of mutational approaches, biochemical studies, peptide arrays and plasmon surface resonance (BIAcore), we fine map and characterize a minimal 24 amino acid long RKIP binding domain in the Raf-1 N-region, which consists of constitutive elements at both flanks and a center element that is regulated by phosphorylation and enhances the re-binding of RKIP to Raf-1 in the later phase of mitogen stimulation.
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Affiliation(s)
- Sungdae Park
- Medical University of Ohio, Department of Biochemistry and Cancer Biology, 3035 Arlington Avenue, Toledo, OH 43614-5804, USA
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24
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von Kriegsheim A, Pitt A, Grindlay GJ, Kolch W, Dhillon AS. Regulation of the Raf-MEK-ERK pathway by protein phosphatase 5. Nat Cell Biol 2006; 8:1011-6. [PMID: 16892053 DOI: 10.1038/ncb1465] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Accepted: 07/13/2006] [Indexed: 11/09/2022]
Abstract
The Raf-MEK-ERK pathway couples growth factor, mitogenic and extracellular matrix signals to cell fate decisions such as growth, proliferation, migration, differentiation and survival. Raf-1 is a direct effector of the Ras GTPase and is the initiating kinase in this signalling cascade. Although Raf-1 activation is well studied, little is known about how Raf-1 is inactivated. Here, we used a proteomic approach to identify molecules that may inactivate Raf-1 signalling. Protein phosphatase 5 (PP5) was identified as an inactivator that associates with Raf-1 on growth factor stimulation and selectively dephosphorylates an essential activating site, Ser 338. The PP5-mediated dephosphorylation of Ser 338 inhibited Raf-1 activity and downstream signalling to MEK, an effect that was prevented by phosphomimetic substitution of Ser 338, or by ablation of PP5 catalytic function. Furthermore, depletion of endogenous PP5 increased cellular phospho-Ser 338 levels. Our results suggest that PP5 is a physiological regulator of Raf-1 signalling pathways.
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Affiliation(s)
- Alex von Kriegsheim
- The Beatson Institute for Cancer Research, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
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25
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Brummer T, Martin P, Herzog S, Misawa Y, Daly RJ, Reth M. Functional analysis of the regulatory requirements of B-Raf and the B-Raf(V600E) oncoprotein. Oncogene 2006; 25:6262-76. [PMID: 16702958 DOI: 10.1038/sj.onc.1209640] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The BRAF(V600E) mutation is found in approximately 6% of human cancers and mimics the phosphorylation of the kinase domain activation segment. In wild-type B-Raf (B-Raf(wt)), activation segment phosphorylation is thought to cooperate with negative charges within the N-region for full activation. In contrast to Raf-1, the N-region of B-Raf is constitutively negatively charged owing to the presence of residues D447/D448 and the phosphorylation of S446. Therefore, it has been suggested that this hallmark predisposes B-Raf for oncogenic activation. In this study, we demonstrate that neutralizing mutations of these residues (in particular S446 and S447), or uncoupling of B-Raf from Ras-guanine 5'-triphosphate (GTP), strongly reduce the biological activity of B-Raf in a PC12 cell differentiation assay. We also confirm that S365 is a 14-3-3 binding site, and determine that mutation of this residue rescues the impaired biological activity of B-Raf proteins with a neutralized N-region, suggesting that the N-region opposes a 14-3-3-mediated transition into an inactive conformation. However, in the case of B-Raf(V600E), although complete N-region neutralization resulted in a 2.5-fold reduction in kinase activity in vitro, this oncoprotein strongly induced PC12 differentiation or transformation and epithelial-mesenchymal transition of MCF-10A cells regardless of its N-region charge. Furthermore, the biological activity of B-Raf(V600E) was independent of its ability to bind Ras-GTP. Our analysis identifies important regulatory differences between B-Raf(wt) and B-Raf(V600E) and suggests that B-Raf(V600E) cannot be inhibited by strategies aimed at blocking S446 phosphorylation or Ras activation.
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Affiliation(s)
- T Brummer
- Cancer Research Program, The Garvan Institute of Medical Research, Sydney, NSW, Australia.
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26
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Terai K, Matsuda M. Ras binding opens c-Raf to expose the docking site for mitogen-activated protein kinase kinase. EMBO Rep 2005; 6:251-5. [PMID: 15711535 PMCID: PMC1299259 DOI: 10.1038/sj.embor.7400349] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2004] [Revised: 12/06/2004] [Accepted: 01/11/2005] [Indexed: 11/08/2022] Open
Abstract
A key signalling molecule, c-Raf, is situated downstream from Ras and upstream from the mitogen-activated protein kinase kinase (MEK). We studied the mechanism underlying the signal transduction from Ras to MEK by using probes based on the principle of fluorescence resonance energy transfer. In agreement with previous models, it was found that c-Raf adopted two conformations: open active and closed inactive. Ras binding induced the c-Raf transition from closed to open conformation, which enabled c-Raf to bind to MEK. In the presence of a cytosolic Ras mutant, c-Raf bound to, but failed to phosphorylate, MEK in the cytoplasm. In contrast, the cytosolic Ras mutant significantly enhanced MEK phosphorylation by a membrane-targeted c-Raf. These results demonstrated the essential role of Ras-induced conformational change in MEK activation by c-Raf.
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Affiliation(s)
- Kenta Terai
- Department of Tumor Virology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Michiyuki Matsuda
- Department of Tumor Virology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan
- Tel: +81 6 6879 8316; Fax: +81 6 6879 8314; E-mail:
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27
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Edin ML, Juliano RL. Raf-1 serine 338 phosphorylation plays a key role in adhesion-dependent activation of extracellular signal-regulated kinase by epidermal growth factor. Mol Cell Biol 2005; 25:4466-75. [PMID: 15899852 PMCID: PMC1140616 DOI: 10.1128/mcb.25.11.4466-4475.2005] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Activation of the extracellular signal-regulated kinase (ERK) 1/2 cascade by polypeptide growth factors is tightly coupled to adhesion to extracellular matrix in nontransformed cells. Raf-1, the initial kinase in this cascade, is intricately regulated by phosphorylation, localization, and molecular interactions. We investigated the complex interactions between Raf-1, protein kinase A (PKA), and p21-activated kinase (PAK) to determine their roles in the adhesion dependence of signaling from epidermal growth factor (EGF) to ERK. We conclude that Raf-1 phosphorylation on serine 338 (S338) is a critical step that is inhibited in suspended cells. Restoration of phosphorylation at S338, either by expression of highly active PAK or by expression of an S338 phospho-mimetic Raf-1 mutation, led to a partial rescue of ERK activation in suspended cells. Raf-1 inhibition in suspension was not due to excessive negative regulation on inhibitory sites S43 and S259, as these serines were largely dephosphorylated in suspended cells. Finally, strong phosphorylation of Raf-1 S338 provided resistance to PKA-mediated inhibition of ERK activation. Phosphorylation at Raf-1 S43 and S259 by PKA only weakly inhibited EGF activation of Raf-1 and ERK when cells maintained high Raf-1 S338 phosphorylation.
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Affiliation(s)
- Matthew L Edin
- Department of Pharmacology, University of North Carolina, Chapel Hill, 1017 Mary Ellen Jones Building, CB 7365, Chapel Hill, NC 27599-7365, USA
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28
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Tsukamoto H, Irie A, Nishimura Y. B-Raf contributes to sustained extracellular signal-regulated kinase activation associated with interleukin-2 production stimulated through the T cell receptor. J Biol Chem 2004; 279:48457-65. [PMID: 15339934 DOI: 10.1074/jbc.m403087200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A T cell receptor (TCR) recognizes and responds to an antigenic peptide in the context of major histocompatibility complex-encoded molecules. This provokes T cells to produce interleukin-2 (IL-2) through extracellular signal-regulated kinase (ERK) activation. We investigated the roles of B-Raf in TCR-mediated IL-2 production coupled with ERK activation in the Jurkat human T cell line. We found that TCR cross-linking could induce up-regulation of both B-Raf and Raf-1 activities, but Raf-1 activity was decreased rapidly. On the other hand, TCR-stimulated kinase activity of B-Raf was sustained. Expression of a dominant-negative mutant of B-Raf abrogated sustained but not transient TCR-mediated MEK/ERK activation. The inhibition of sustained ERK activation by either expression of a dominant-negative B-Raf or treatment with a MEK inhibitor resulted in a decrease of the TCR-stimulated nuclear factor of activated T cells (NFAT) activity and IL-2 production. Collectively, our data provide the first direct evidence that B-Raf is a positive regulator of TCR-mediated sustained ERK activation, which is required for NFAT activation and the full production of IL-2.
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Affiliation(s)
- Hirotake Tsukamoto
- Department of Immunogenetics, Graduate School of Medical Sciences, Kumamoto University, Honjo 1-1-1, Kumamoto 860-8556, Japan
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29
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Slack-Davis JK, Parsons JT. Emerging views of integrin signaling: implications for prostate cancer. J Cell Biochem 2004; 91:41-6. [PMID: 14689580 DOI: 10.1002/jcb.10665] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Integrins are heterodimeric transmembrane cellular receptors that link the cell to its underlying substratum. Alterations in integrin expression and signaling have been implicated in many aspects of tumorigenesis and metastasis including cell survival, migration, and invasion. In prostate cancer, the progression from normal to metastatic cells is accompanied by changes in the repertoire of integrins expressed and up-regulation of key adhesion-dependent signaling pathways. Recent work from several laboratories indicates the emergence of new mechanisms for the regulation of growth and migratory pathways by integrin engagement. These pathways are likely to provide novel sites of therapeutic intervention for the treatment of prostate cancer.
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Affiliation(s)
- Jill K Slack-Davis
- Department of Microbiology, University of Virginia Health Sciences System, Charlottesville, Virginia 22908, USA.
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30
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Abstract
Stimulation of the erythropoietin (EPO) receptor triggers a cascade of signaling events. We reported that EPO upregulates c-myc expression through 2 pathways in BaF3-EpoR cells--a phosphatidylinositol 3-kinase (PI3K) pathway operating on transcriptional initiation and a Raf-1-mitogen-activated protein kinase (MAPK) pathway affecting elongation. We now show that EPO induces phosphorylation of Raf-1 at serine 338 and within the carboxy-terminal domain, resulting in an electrophoretic mobility change (hyperphosphorylation). Importantly, MEK 1 inhibitor PD98059 blocked only the hyperphosphorylation of Raf-1 but not the phosphorylation at serine 338. This inhibition of Raf-1 hyperphosphorylation resulted in increased kinase activity of Raf-1 and increased phosphorylation of MEK, suggesting that the hyperphosphorylation of Raf-1 inhibits its MEK kinase activity. Deletion of the first 184 amino acids of Raf-1, which are involved in its interaction with Ras, had no effect on EPO-induced phosphorylation. Introducing the dominant-negative N17Ras or GAP had no effect on EPO-induced kinase activity of Raf-1 and ELK activation. N17Ras failed to inhibit ELK activation in another cell line-Rauscher murine erythroleukemia- which expresses the EPO receptor endogenously and differentiates in response to the hormone. These results indicate the presence of a Ras-independent mechanism for Raf-1 and MEK activation in these cells.
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Affiliation(s)
- Changmin Chen
- Laboratory for Cell and Molecular Biology, Division of Hematology and Oncology, Beth Israel Deaconess Medical Center, and Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
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31
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Tran NH, Frost JA. Phosphorylation of Raf-1 by p21-activated kinase 1 and Src regulates Raf-1 autoinhibition. J Biol Chem 2003; 278:11221-6. [PMID: 12551923 DOI: 10.1074/jbc.m210318200] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Exposure of cells to mitogens or growth factors stimulates Raf-1 activity through a complex mechanism that involves binding to active Ras, phosphorylation on multiple residues, and protein-protein interactions. Recently it was shown that the amino terminus of Raf-1 contains an autoregulatory domain that can inhibit its activity in Xenopus oocytes. In the present work we show that expression of the Raf-1 autoinhibitory domain blocks extracellular signal-regulated kinase 2 activation by the Raf-1 catalytic domain in mammalian cells. We also show that phosphorylation of Raf-1 on serine 338 by PAK1 and tyrosines 340 and 341 by Src relieves autoinhibition and that this occurs through a specific decrease in the binding of the Raf-1 regulatory domain to its catalytic domain. In addition, we demonstrate that phosphorylation of threonine 491 and serine 494, two phosphorylation sites in the catalytic domain that are required for Raf-1 activation, is unlikely to regulate autoinhibition. These results demonstrate that the autoinhibitory domain of Raf-1 is functional in mammalian cells and that its interaction with the Raf-1 catalytic domain is regulated by phosphorylation of serine 338 and tyrosines 340 and 341.
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Affiliation(s)
- Nancy H Tran
- Department of Integrative Biology and Pharmacology, University of Texas Houston Health Science Center, Houston, Texas 77030, USA
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