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Borkowsky S, Gass M, Alavizargar A, Hanewinkel J, Hallstein I, Nedvetsky P, Heuer A, Krahn MP. Phosphorylation of LKB1 by PDK1 Inhibits Cell Proliferation and Organ Growth by Decreased Activation of AMPK. Cells 2023; 12:cells12050812. [PMID: 36899949 PMCID: PMC10000615 DOI: 10.3390/cells12050812] [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: 08/19/2022] [Revised: 02/24/2023] [Accepted: 03/03/2023] [Indexed: 03/08/2023] Open
Abstract
The master kinase LKB1 is a key regulator of se veral cellular processes, including cell proliferation, cell polarity and cellular metabolism. It phosphorylates and activates several downstream kinases, including AMP-dependent kinase, AMPK. Activation of AMPK by low energy supply and phosphorylation of LKB1 results in an inhibition of mTOR, thus decreasing energy-consuming processes, in particular translation and, thus, cell growth. LKB1 itself is a constitutively active kinase, which is regulated by posttranslational modifications and direct binding to phospholipids of the plasma membrane. Here, we report that LKB1 binds to Phosphoinositide-dependent kinase (PDK1) by a conserved binding motif. Furthermore, a PDK1-consensus motif is located within the kinase domain of LKB1 and LKB1 gets phosphorylated by PDK1 in vitro. In Drosophila, knockin of phosphorylation-deficient LKB1 results in normal survival of the flies, but an increased activation of LKB1, whereas a phospho-mimetic LKB1 variant displays decreased AMPK activation. As a functional consequence, cell growth as well as organism size is decreased in phosphorylation-deficient LKB1. Molecular dynamics simulations of PDK1-mediated LKB1 phosphorylation revealed changes in the ATP binding pocket, suggesting a conformational change upon phosphorylation, which in turn can alter LKB1's kinase activity. Thus, phosphorylation of LKB1 by PDK1 results in an inhibition of LKB1, decreased activation of AMPK and enhanced cell growth.
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Affiliation(s)
- Sarah Borkowsky
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149 Münster, Germany
| | - Maximilian Gass
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149 Münster, Germany
| | - Azadeh Alavizargar
- Institute of Physical Chemistry, University of Münster, Corrensstr. 28/30, 48149 Münster, Germany
| | - Johannes Hanewinkel
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149 Münster, Germany
| | - Ina Hallstein
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149 Münster, Germany
| | - Pavel Nedvetsky
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149 Münster, Germany
| | - Andreas Heuer
- Institute of Physical Chemistry, University of Münster, Corrensstr. 28/30, 48149 Münster, Germany
| | - Michael P. Krahn
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149 Münster, Germany
- Correspondence: ; Tel.: +49-251-8357052
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2
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The Distinct Roles of LKB1 and AMPK in p53-Dependent Apoptosis Induced by Cisplatin. Int J Mol Sci 2022; 23:ijms231710064. [PMID: 36077459 PMCID: PMC9456506 DOI: 10.3390/ijms231710064] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 06/27/2022] [Accepted: 08/31/2022] [Indexed: 11/17/2022] Open
Abstract
Liver kinase B1 (LKB1) is a serine/threonine protein kinase that acts as a key tumor suppressor protein by activating its downstream kinases, such as AMP-activated protein kinase (AMPK). However, the regulatory actions of LKB1 and AMPK on DNA damage response (DDR) remain to be explored. In this study, we investigated the function of LKB1 in DDR induced by cisplatin, a representative DNA-damaging agent, and found that LKB1 stabilizes and activates p53 through the c-Jun N-terminal kinase (JNK) pathway, which promotes cisplatin-induced apoptosis in human fibrosarcoma cell line HT1080. On the other hand, we found that AMPKα1 and α2 double knockout (DKO) cells showed enhanced stabilization of p53 and increased susceptibility to apoptosis induced by cisplatin, suggesting that AMPK negatively regulates cisplatin-induced apoptosis. Moreover, the additional stabilization of p53 and subsequent apoptosis in AMPK DKO cells were clearly canceled by the treatment with the antioxidants, raising the possibility that AMPK suppresses the p53 activation mediated by oxidative stress. Thus, our findings unexpectedly demonstrate the reciprocal regulation of p53 by LKB1 and AMPK in DDR, which provides insights into the molecular mechanisms of DDR.
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3
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Rackley B, Seong CS, Kiely E, Parker RE, Rupji M, Dwivedi B, Heddleston JM, Giang W, Anthony N, Chew TL, Gilbert-Ross M. The level of oncogenic Ras determines the malignant transformation of Lkb1 mutant tissue in vivo. Commun Biol 2021; 4:142. [PMID: 33514834 PMCID: PMC7846793 DOI: 10.1038/s42003-021-01663-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 01/06/2021] [Indexed: 01/30/2023] Open
Abstract
The genetic and metabolic heterogeneity of RAS-driven cancers has confounded therapeutic strategies in the clinic. To address this, rapid and genetically tractable animal models are needed that recapitulate the heterogeneity of RAS-driven cancers in vivo. Here, we generate a Drosophila melanogaster model of Ras/Lkb1 mutant carcinoma. We show that low-level expression of oncogenic Ras (RasLow) promotes the survival of Lkb1 mutant tissue, but results in autonomous cell cycle arrest and non-autonomous overgrowth of wild-type tissue. In contrast, high-level expression of oncogenic Ras (RasHigh) transforms Lkb1 mutant tissue resulting in lethal malignant tumors. Using simultaneous multiview light-sheet microcopy, we have characterized invasion phenotypes of Ras/Lkb1 tumors in living larvae. Our molecular analysis reveals sustained activation of the AMPK pathway in malignant Ras/Lkb1 tumors, and demonstrate the genetic and pharmacologic dependence of these tumors on CaMK-activated Ampk. We further show that LKB1 mutant human lung adenocarcinoma patients with high levels of oncogenic KRAS exhibit worse overall survival and increased AMPK activation. Our results suggest that high levels of oncogenic KRAS is a driving event in the malignant transformation of LKB1 mutant tissue, and uncovers a vulnerability that may be used to target this aggressive genetic subset of RAS-driven tumors.
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Affiliation(s)
- Briana Rackley
- Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA, USA
- Cancer Biology Graduate Program, Emory University, Atlanta, GA, USA
| | - Chang-Soo Seong
- Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA, USA
| | - Evan Kiely
- Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA, USA
- Winship Research Informatics, Winship Cancer Institute of Emory University, Atlanta, GA, USA
| | - Rebecca E Parker
- Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA, USA
- Cancer Biology Graduate Program, Emory University, Atlanta, GA, USA
| | - Manali Rupji
- Biostatistics Shared Resource, Winship Cancer Institute of Emory University, Atlanta, GA, USA
| | - Bhakti Dwivedi
- Bioinformatics and Systems Biology Shared Resource, Winship Cancer Institute of Emory University, Atlanta, GA, USA
| | - John M Heddleston
- Advanced Imaging Center, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - William Giang
- Integrated Cellular Imaging Core, Emory University School of Medicine, Emory University, Atlanta, GA, USA
| | - Neil Anthony
- Integrated Cellular Imaging Core, Emory University School of Medicine, Emory University, Atlanta, GA, USA
| | - Teng-Leong Chew
- Advanced Imaging Center, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Melissa Gilbert-Ross
- Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA, USA.
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4
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Zhang K, Shi Y, Xu P, Huang C, Zhou C, Liu P, Hu R, Zhuang Y, Li G, Hu G, Guo X. Cloning and prokaryotic expression of the chicken liver kinase B1 (LKB1) and its localization in liver, heart and hypothalamus. Int J Biol Macromol 2020; 169:513-520. [PMID: 33385449 DOI: 10.1016/j.ijbiomac.2020.12.195] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 12/23/2020] [Accepted: 12/26/2020] [Indexed: 01/02/2023]
Abstract
Liver kinase B1 (LKB1) is a member of the serine/threonine kinase family, which plays an indispensable role in the organism of animals. In the current study, the chicken LKB1 protein gene was amplified by PCR based on the primers and cDNA templates. Then, the cloning vector was constructed and the target gene was cloned. After that, the target gene was inserted into the expression vector to construct the recombinant plasmid. The recombinant plasmid was transformed into BL21 (DE3) host cells and the LKB1 recombinant proteins were successfully expressed by using Isopropyl-β-D-thiogalactopyranoside (IPTG). Finally, purified LKB1 proteins were used as antigen and the rabbit-derived antiserums were collected. The antiserum titer determined by ELISA was not less than 1:128000. The results of Western blot suggested that the polyclonal antibody is highly specific to chicken LKB1 protein. Immunofluorescence indicated that the LKB1 protein is mainly expressed in the cytoplasm of liver, heart and hypothalamus cells of chicken. Our study showed that the LKB1 polyclonal antibodies produced by this method are effective and can be used to further study the role of LKB1 in the pathogenesis of chicken disease.
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Affiliation(s)
- Kun Zhang
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, Jiangxi, China
| | - Yan Shi
- School of Computer and Information Engineering, Jiangxi Agricultural University, Nanchang, Jiangxi, China
| | - Puzhi Xu
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, Jiangxi, China
| | - Cheng Huang
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, Jiangxi, China
| | - Changming Zhou
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, Jiangxi, China
| | - Ping Liu
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, Jiangxi, China
| | - Ruiming Hu
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, Jiangxi, China
| | - Yu Zhuang
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, Jiangxi, China
| | - Guyue Li
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, Jiangxi, China
| | - Guoliang Hu
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, Jiangxi, China
| | - Xiaoquan Guo
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, Jiangxi, China.
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5
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Khezri R, Rusten TE. Autophagy and Tumorigenesis in Drosophila. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1167:113-127. [PMID: 31520352 DOI: 10.1007/978-3-030-23629-8_7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The resurgence of Drosophila as a recognized model for carcinogenesis has contributed greatly to our conceptual advance and mechanistic understanding of tumor growth in vivo. With its powerful genetics, Drosophila has emerged as a prime model organism to study cell biology and physiological functions of autophagy. This has enabled exploration of the contributions of autophagy in several tumor models. Here we review the literature of autophagy related to tumorigenesis in Drosophila. Functional analysis of core autophagy components does not provide proof for a classical tumor suppression role for autophagy alone. Autophagy both serve to suppress or support tumor growth. These effects are context-specific, depending on cell type and oncogenic or tumor suppressive lesion. Future delineation of how autophagy impinges on tumorigenesis will demand to untangle in detail, the regulation and flux of autophagy in the respective tumor models. The downstream tumor-regulative roles of autophagy through organelle homeostasis, metabolism, selective autophagy or alternative mechanisms remain largely unexplored.
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Affiliation(s)
- Rojyar Khezri
- Center for Cancer Cell Reprogramming (CanCell), Institute for Clinical Medicine, The Medical Faculty, University of Oslo, Oslo, Norway
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Tor Erik Rusten
- Center for Cancer Cell Reprogramming (CanCell), Institute for Clinical Medicine, The Medical Faculty, University of Oslo, Oslo, Norway.
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.
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6
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Expression profiling of ubiquitin-related genes in LKB1 mutant lung adenocarcinoma. Sci Rep 2018; 8:13221. [PMID: 30185829 PMCID: PMC6125361 DOI: 10.1038/s41598-018-31592-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 08/20/2018] [Indexed: 12/12/2022] Open
Abstract
Liver kinase B1 (LKB1) is a tumor suppressor, and there is a very high proportion of LKB1 mutation in lung adenocarcinoma. The function of LKB1 is closely related to that of ubiquitin related genes. Our objective is to analyze the changes in ubiquitin-related genes in LKB1 mutant lung adenocarcinoma. We searched The Cancer Genome Atlas (TCGA) and obtained gene expression profiles from 230 lung adenocarcinoma patients, which were then analyzed using R software. Kaplan–Meier curves and Cox proportional hazards regression were applied to estimate survival. Real-time reverse transcription PCR was used to verify gene expression. Gene function was explored by gene set enrichment analysis. There were significantly expressed differences in the ubiquitin-related gene SH3RF1 between the LKB1 mutant and wild-type lung adenocarcinoma patients (p = 9.78013E-05). Patients with LKB1 mutation and high expression of SH3RF1 had a better prognosis than the low expression group (HR 0.356, 95% CI 0.136–0.929, p = 0.035). SH3RF1 can influence cell cycle, apoptosis, DNA replication and the p53 signaling pathway. SH3RF1 might have great clinical value act as a diagnostic biomarker and indicator to evaluate the prognosis of LKB1 mutant lung adenocarcinoma patients. This gene also can become a new treatment target for LKB1 mutant lung adenocarcinoma patients.
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7
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Ma X, Lu JY, Dong Y, Li D, Malagon JN, Xu T. PP6 Disruption Synergizes with Oncogenic Ras to Promote JNK-Dependent Tumor Growth and Invasion. Cell Rep 2018; 19:2657-2664. [PMID: 28658615 DOI: 10.1016/j.celrep.2017.05.092] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 05/10/2017] [Accepted: 05/29/2017] [Indexed: 01/21/2023] Open
Abstract
RAS genes are frequently mutated in cancers, yet an effective treatment has not been developed, partly because of an incomplete understanding of signaling within Ras-related tumors. To address this, we performed a genetic screen in Drosophila, aiming to find mutations that cooperate with oncogenic Ras (RasV12) to induce tumor overgrowth and invasion. We identified fiery mountain (fmt), a regulatory subunit of the protein phosphatase 6 (PP6) complex, as a tumor suppressor that synergizes with RasV12 to drive c-Jun N-terminal kinase (JNK)-dependent tumor growth and invasiveness. We show that Fmt negatively regulates JNK upstream of dTAK1. We further demonstrate that disruption of PpV, the catalytic subunit of PP6, mimics fmt loss-of-function-induced tumorigenesis. Finally, Fmt synergizes with PpV to inhibit JNK-dependent tumor progression. Our data here further highlight the power of Drosophila as a model system to unravel molecular mechanisms that may be relevant to human cancer biology.
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Affiliation(s)
- Xianjue Ma
- Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06519, USA
| | - Jin-Yu Lu
- Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06519, USA
| | - Yongli Dong
- Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06519, USA
| | - Daming Li
- Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06519, USA
| | - Juan N Malagon
- Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06519, USA
| | - Tian Xu
- Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06519, USA; State Key Laboratory of Genetic Engineering and National Center for International Research, Fudan-Yale Biomedical Research Center, Institute of Developmental Biology and Molecular Medicine, School of Life Sciences, Fudan University, Shanghai 200433, China.
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8
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Saito Y, Desai RR, Muthuswamy SK. Reinterpreting polarity and cancer: The changing landscape from tumor suppression to tumor promotion. Biochim Biophys Acta Rev Cancer 2018; 1869:103-116. [DOI: 10.1016/j.bbcan.2017.12.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 12/08/2017] [Indexed: 12/21/2022]
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9
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Hilu-Dadia R, Hakim-Mishnaevski K, Levy-Adam F, Kurant E. Draper-mediated JNK signaling is required for glial phagocytosis of apoptotic neurons during Drosophila metamorphosis. Glia 2018. [PMID: 29520845 DOI: 10.1002/glia.23322] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Development of the central nervous system involves elimination of superfluous neurons through apoptosis and subsequent phagocytosis. In Drosophila, this occurs mainly during three developmental stages: embryogenesis, metamorphosis and emerging adult. Two transmembrane glial phagocytic receptors, SIMU (homolog of the mammalian Stabilin-2) and Draper (homolog of the mammalian MEGF10 and Jedi), mediate glial phagocytosis of apoptotic neurons during embryogenesis. However, less is known about the removal of apoptotic neurons during later stages of development. Here we show that during metamorphosis, Draper plays a critical role in apoptotic cell clearance by glia, whereas SIMU, which is mostly expressed in pupal macrophages outside the brain, is not involved in glial phagocytosis. We found that Draper activates Drosophila c-Jun N-terminal kinase (dJNK) signaling predominantly in the ensheathing glia and astrocytes, where it is required for efficient removal of apoptotic neurons. Our data suggest that besides the dJNK pathway, Draper also triggers an additional signaling pathway capable of removing apoptotic neurons in the pupal brain. This study thus reveals that SIMU unexpectedly is not involved in glial phagocytosis of apoptotic neurons during metamorphosis and highlights the novel role of dJNK signaling in developmental apoptotic cell clearance downstream of Draper.
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Affiliation(s)
- Reut Hilu-Dadia
- Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Haifa, 34988, Israel.,Department of Genetics and Developmental Biology, The Rappaport Family Institute for Research in the Medical Sciences, Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, 31096, Israel
| | - Ketty Hakim-Mishnaevski
- Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Haifa, 34988, Israel
| | - Flonia Levy-Adam
- Department of Genetics and Developmental Biology, The Rappaport Family Institute for Research in the Medical Sciences, Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, 31096, Israel
| | - Estee Kurant
- Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Haifa, 34988, Israel.,Department of Genetics and Developmental Biology, The Rappaport Family Institute for Research in the Medical Sciences, Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, 31096, Israel
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10
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Zhang X, Song H, Qiao S, Liu J, Xing T, Yan X, Li H, Wang N. MiR-17-5p and miR-20a promote chicken cell proliferation at least in part by upregulation of c-Myc via MAP3K2 targeting. Sci Rep 2017; 7:15852. [PMID: 29158522 PMCID: PMC5696470 DOI: 10.1038/s41598-017-15626-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 10/30/2017] [Indexed: 12/14/2022] Open
Abstract
The miR-17-92 cluster has been well studied in mammals but less extensively studied in birds. Here, we demonstrated that miR-17-92 cluster overexpression promoted the proliferation of DF1 cells and immortalized chicken preadipocytes (ICPA-1), and miR-17-5p and miR-20a, members of the miR-17-92 cluster, targeted MAP3K2. Further analysis showed that MAP3K2 overexpression reduced the proliferation of DF1 and ICPA-1 cells and attenuated the promotive effect of the miR-17-92 cluster on cell proliferation. Downstream gene expression analysis of the MAPK signalling pathway showed that MAP3K2 overexpression decreased c-Myc expression; in contrast, MAP3K2 knockdown using RNA interference and miR-17-92 cluster overexpression increased c-Myc expression. Furthermore, c-Myc overexpression promoted miR-17-92 cluster expression and DF1 cell proliferation. Taken together, these data indicated that miR-17-92 promotes chicken cell proliferation at least in part by the upregulation of c-Myc via targeting MAP3K2, and the miR-17-92 cluster, c-Myc and E2F1 form a complex regulatory network in chicken cell proliferation.
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Affiliation(s)
- Xiaofei Zhang
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Cells and Genetic Engineering of Heilongjiang Province, Harbin, 150030, Heilongjiang, China
| | - He Song
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Cells and Genetic Engineering of Heilongjiang Province, Harbin, 150030, Heilongjiang, China
| | - Shupei Qiao
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Cells and Genetic Engineering of Heilongjiang Province, Harbin, 150030, Heilongjiang, China
| | - Jing Liu
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Cells and Genetic Engineering of Heilongjiang Province, Harbin, 150030, Heilongjiang, China
| | - Tianyu Xing
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Cells and Genetic Engineering of Heilongjiang Province, Harbin, 150030, Heilongjiang, China
| | - Xiaohong Yan
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Cells and Genetic Engineering of Heilongjiang Province, Harbin, 150030, Heilongjiang, China
| | - Hui Li
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin, 150030, Heilongjiang, China.,Key Laboratory of Animal Cells and Genetic Engineering of Heilongjiang Province, Harbin, 150030, Heilongjiang, China
| | - Ning Wang
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture, Harbin, 150030, Heilongjiang, China. .,Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin, 150030, Heilongjiang, China. .,Key Laboratory of Animal Cells and Genetic Engineering of Heilongjiang Province, Harbin, 150030, Heilongjiang, China.
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11
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Li R, Wang Z, Liu S, Wu B, Zeng D, Zhang Y, Gong L, Deng F, Zheng H, Wang Y, Chen C, Chen J, Jiang B. Two novel STK11 missense mutations induce phosphorylation of S6K and promote cell proliferation in Peutz-Jeghers syndrome. Oncol Lett 2017; 15:717-726. [PMID: 29399144 DOI: 10.3892/ol.2017.7436] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 01/19/2017] [Indexed: 01/23/2023] Open
Abstract
Peutz-Jeghers syndrome (PJS) is a rare hereditary disease caused by mutations in serine threonine kinase 11 (STK11) and characterized by an increased risk of developing cancer. Inactivation of STK11 has been associated with the mammalian target of rapamycin (mTOR) pathway. Hyperactivation and phosphorylation of the key downstream target genes ribosomal protein S6 kinase 1 (S6K1) and S6 promote protein synthesis and cell proliferation. To better understand the effects of STK11 dysfunction in the pathogenesis of PJS, genomic DNA samples from 21 patients with PJS from 11 unrelated families were investigated for STK11 mutations in the present study. The results revealed 6 point mutations and 2 large deletions in 8 (72.7%, 8/11) of the unrelated families. Notably, 3 novel mutations were identified, which included 2 missense mutations [c.88G>A (p.Asp30Asn) and c.869T>C (p.Leu290Pro)]. Subsequent immunohistochemical analysis revealed staining for phosphorylated-S6 protein in colonic hamartoma and breast benign tumor tissues from patients with PJS carrying the two respective missense mutations. Additionally, the novel missense STK11 mutants induced phosphorylation of S6K1 and S6, determined using western blot analysis, and promoted the proliferation of HeLa and SW1116 cells, determined using Cell Counting Kit-8 and colony formation assays. Collectively, these findings extend the STK11 mutation spectrum and confirm the pathogenicity of two novel missense mutations. This study represents a valuable insight into the molecular mechanisms implicated in the pathogenesis of PJS.
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Affiliation(s)
- Ran Li
- Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Zhiqing Wang
- Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Shu Liu
- Medical Genetics Center, Guangdong Women and Children's Hospital, Guangzhou, Guangdong 510010, P.R. China
| | - Baoping Wu
- Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Di Zeng
- Department of Gastroenterology, Guangzhou Panyu Central Hospital, Guangzhou, Guangdong 511400, P.R. China
| | - Yali Zhang
- Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Lanbo Gong
- Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Feihong Deng
- Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Haoxuan Zheng
- Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Yadong Wang
- Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Chudi Chen
- Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Junsheng Chen
- Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
| | - Bo Jiang
- Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China.,Department of Gastroenterology, Beijing Tsinghua Changgung Hospital, Beijing 102218, P.R. China
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12
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Class III phosphatidylinositol-3-OH kinase controls epithelial integrity through endosomal LKB1 regulation. Nat Cell Biol 2017; 19:1412-1423. [DOI: 10.1038/ncb3631] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 09/18/2017] [Indexed: 12/18/2022]
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13
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Drosophila LKB1 is required for the assembly of the polarized actin structure that allows spermatid individualization. PLoS One 2017; 12:e0182279. [PMID: 28767695 PMCID: PMC5540607 DOI: 10.1371/journal.pone.0182279] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 07/14/2017] [Indexed: 01/24/2023] Open
Abstract
In mammals, a testis-specific isoform of the protein kinase LKB1 is required for spermiogenesis, but its exact function and specificity are not known. Human LKB1 rescues the functions of Drosophila Lkb1 essential for viability, but these males are sterile, revealing a new function for this genes in fly. We also identified a testis-specific transcript generated by an alternative promoter and that only differs by a longer 5'UTR. We show that dLKB1 is required in the germline for the formation of the actin cone, the polarized structure that allows spermatid individualization and cytoplasm excess extrusion during spermiogenesis. Three of the nine LKB1 classical targets in the Drosophila genome (AMPK, NUAK and KP78b) are required for proper spermiogenesis, but later than dLKB1. dLkb1 mutant phenotype is reminiscent of that of myosin V mutants, and both proteins show a dynamic localization profile before actin cone formation. Together, these data highlight a new dLKB1 function and suggest that dLKB1 posttranscriptional regulation in testis and involvement in spermatid morphogenesis are evolutionarily conserved features.
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14
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Raja E, Tzavlaki K, Vuilleumier R, Edlund K, Kahata K, Zieba A, Morén A, Watanabe Y, Voytyuk I, Botling J, Söderberg O, Micke P, Pyrowolakis G, Heldin CH, Moustakas A. The protein kinase LKB1 negatively regulates bone morphogenetic protein receptor signaling. Oncotarget 2016; 7:1120-43. [PMID: 26701726 PMCID: PMC4811448 DOI: 10.18632/oncotarget.6683] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 12/08/2015] [Indexed: 01/24/2023] Open
Abstract
The protein kinase LKB1 regulates cell metabolism and growth and is implicated in intestinal and lung cancer. Bone morphogenetic protein (BMP) signaling regulates cell differentiation during development and tissue homeostasis. We demonstrate that LKB1 physically interacts with BMP type I receptors and requires Smad7 to promote downregulation of the receptor. Accordingly, LKB1 suppresses BMP-induced osteoblast differentiation and affects BMP signaling in Drosophila wing longitudinal vein morphogenesis. LKB1 protein expression and Smad1 phosphorylation analysis in a cohort of non-small cell lung cancer patients demonstrated a negative correlation predominantly in a subset enriched in adenocarcinomas. Lung cancer patient data analysis indicated strong correlation between LKB1 loss-of-function mutations and high BMP2 expression, and these two events further correlated with expression of a gene subset functionally linked to apoptosis and migration. This new mechanism of BMP receptor regulation by LKB1 has ramifications in physiological organogenesis and disease.
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Affiliation(s)
- Erna Raja
- Ludwig Institute for Cancer Research, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Kalliopi Tzavlaki
- Department of Medical Biochemistry and Microbiology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Robin Vuilleumier
- BIOSS, Centre for Biological Signaling Studies and Institute for Biology I, Faculty of Biology, Albert-Ludwigs-University of Freiburg, Freiburg, Germany
| | - Karolina Edlund
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Kaoru Kahata
- Ludwig Institute for Cancer Research, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Agata Zieba
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Anita Morén
- Ludwig Institute for Cancer Research, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Yukihide Watanabe
- Ludwig Institute for Cancer Research, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Iryna Voytyuk
- Ludwig Institute for Cancer Research, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Johan Botling
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Ola Söderberg
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Patrick Micke
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - George Pyrowolakis
- BIOSS, Centre for Biological Signaling Studies and Institute for Biology I, Faculty of Biology, Albert-Ludwigs-University of Freiburg, Freiburg, Germany
| | - Carl-Henrik Heldin
- Ludwig Institute for Cancer Research, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Aristidis Moustakas
- Ludwig Institute for Cancer Research, Science for Life Laboratory, Uppsala University, Uppsala, Sweden.,Department of Medical Biochemistry and Microbiology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
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15
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Laws KM, Drummond-Barbosa D. AMP-activated protein kinase has diet-dependent and -independent roles in Drosophila oogenesis. Dev Biol 2016; 420:90-99. [PMID: 27729213 DOI: 10.1016/j.ydbio.2016.10.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 09/16/2016] [Accepted: 10/07/2016] [Indexed: 12/31/2022]
Abstract
Multiple aspects of organismal physiology influence the number and activity of stem cells and their progeny, including nutritional status. Previous studies demonstrated that Drosophila germline stem cells (GSCs), follicle stem cells (FSCs), and their progeny sense and respond to diet via complex mechanisms involving many systemic and local signals. AMP-activated protein kinase, or AMPK, is a highly conserved regulator of energy homeostasis known to be activated under low cellular energy conditions; however, its role in the ovarian response to diet has not been investigated. Here, we describe nutrient-dependent and -independent requirements for AMPK in Drosophila oogenesis. We found that AMPK is cell autonomously required for the slow down in GSC and follicle cell proliferation that occurs on a poor diet. Similarly, AMPK activity is necessary in the germline for the degeneration of vitellogenic stages in response to nutrient deprivation. In contrast, AMPK activity is not required within the germline to modulate its growth. Instead, AMPK acts in follicle cells to negatively regulate their growth and proliferation, thereby indirectly limiting the size of the underlying germline cyst within developing follicles. Paradoxically, AMPK is required for GSC maintenance in well-fed flies (when AMPK activity is presumably at its lowest), suggesting potentially important roles for basal AMPK activity in specific cell types. Finally, we identified a nutrient-independent, developmental role for AMPK in cyst encapsulation by follicle cells. These results uncover specific AMPK requirements in multiple cell types in the ovary and suggest that AMPK can function outside of its canonical nutrient-sensing role in specific developmental contexts.
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Affiliation(s)
- Kaitlin M Laws
- Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Room W3118, Baltimore, MD 21205, USA.
| | - Daniela Drummond-Barbosa
- Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Room W3118, Baltimore, MD 21205, USA; Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Room W3118, Baltimore, MD 21205, USA.
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16
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Kim M, Semple I, Kim B, Kiers A, Nam S, Park HW, Park H, Ro SH, Kim JS, Juhász G, Lee JH. Drosophila Gyf/GRB10 interacting GYF protein is an autophagy regulator that controls neuron and muscle homeostasis. Autophagy 2016; 11:1358-72. [PMID: 26086452 DOI: 10.1080/15548627.2015.1063766] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Autophagy is an essential process for eliminating ubiquitinated protein aggregates and dysfunctional organelles. Defective autophagy is associated with various degenerative diseases such as Parkinson disease. Through a genetic screening in Drosophila, we identified CG11148, whose product is orthologous to GIGYF1 (GRB10-interacting GYF protein 1) and GIGYF2 in mammals, as a new autophagy regulator; we hereafter refer to this gene as Gyf. Silencing of Gyf completely suppressed the effect of Atg1-Atg13 activation in stimulating autophagic flux and inducing autophagic eye degeneration. Although Gyf silencing did not affect Atg1-induced Atg13 phosphorylation or Atg6-Pi3K59F (class III PtdIns3K)-dependent Fyve puncta formation, it inhibited formation of Atg13 puncta, suggesting that Gyf controls autophagy through regulating subcellular localization of the Atg1-Atg13 complex. Gyf silencing also inhibited Atg1-Atg13-induced formation of Atg9 puncta, which is accumulated upon active membrane trafficking into autophagosomes. Gyf-null mutants also exhibited substantial defects in developmental or starvation-induced accumulation of autophagosomes and autolysosomes in the larval fat body. Furthermore, heads and thoraxes from Gyf-null adults exhibited strongly reduced expression of autophagosome-associated Atg8a-II compared to wild-type (WT) tissues. The decrease in Atg8a-II was directly correlated with an increased accumulation of ubiquitinated proteins and dysfunctional mitochondria in neuron and muscle, which together led to severe locomotor defects and early mortality. These results suggest that Gyf-mediated autophagy regulation is important for maintaining neuromuscular homeostasis and preventing degenerative pathologies of the tissues. Since human mutations in the GIGYF2 locus were reported to be associated with a type of familial Parkinson disease, the homeostatic role of Gyf-family proteins is likely to be evolutionarily conserved.
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Affiliation(s)
- Myungjin Kim
- a Department of Molecular and Integrative Physiology ; University of Michigan ; Ann Arbor , MI USA
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17
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Jones TI, Parilla M, Jones PL. Transgenic Drosophila for Investigating DUX4 and FRG1, Two Genes Associated with Facioscapulohumeral Muscular Dystrophy (FSHD). PLoS One 2016; 11:e0150938. [PMID: 26942723 PMCID: PMC4778869 DOI: 10.1371/journal.pone.0150938] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 02/22/2016] [Indexed: 11/19/2022] Open
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is typically an adult onset dominant myopathy. Epigenetic changes in the chromosome 4q35 region linked to both forms of FSHD lead to a relaxation of repression and increased somatic expression of DUX4-fl (DUX4-full length), the pathogenic alternative splicing isoform of the DUX4 gene. DUX4-fl encodes a transcription factor expressed in healthy testis and pluripotent stem cells; however, in FSHD, increased levels of DUX4-fl in myogenic cells lead to aberrant regulation of target genes. DUX4-fl has proven difficult to study in vivo; thus, little is known about its normal and pathogenic roles. The endogenous expression of DUX4-fl in FSHD-derived human muscle and myogenic cells is extremely low, exogenous expression of DUX4-fl in somatic cells rapidly induces cytotoxicity, and, due in part to the lack of conservation beyond primate lineages, viable animal models based on DUX4-fl have been difficult to generate. By contrast, the FRG1 (FSHD region gene 1), which is linked to FSHD, is evolutionarily conserved from invertebrates to humans, and has been studied in several model organisms. FRG1 expression is critical for the development of musculature and vasculature, and overexpression of FRG1 produces a myopathic phenotype, yet the normal and pathological functions of FRG1 are not well understood. Interestingly, DUX4 and FRG1 were recently linked when the latter was identified as a direct transcriptional target of DUX4-FL. To better understand the pathways affected in FSHD by DUX4-fl and FRG1, we generated transgenic lines of Drosophila expressing either gene under control of the UAS/GAL4 binary system. Utilizing these lines, we generated screenable phenotypes recapitulating certain known consequences of DUX4-fl or FRG1 overexpression. These transgenic Drosophila lines provide resources to dissect the pathways affected by DUX4-fl or FRG1 in a genetically tractable organism and may provide insight into both muscle development and pathogenic mechanisms in FSHD.
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Affiliation(s)
- Takako I. Jones
- The Department of Cell and Developmental Biology, University of Massachusetts Medical School Worcester, Massachusetts, United States of America
- The Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Megan Parilla
- The Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Peter L. Jones
- The Department of Cell and Developmental Biology, University of Massachusetts Medical School Worcester, Massachusetts, United States of America
- The Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
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18
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Men Y, Zhang A, Li H, Jin Y, Sun X, Li H, Gao J. LKB1 Regulates Cerebellar Development by Controlling Sonic Hedgehog-mediated Granule Cell Precursor Proliferation and Granule Cell Migration. Sci Rep 2015; 5:16232. [PMID: 26549569 PMCID: PMC4637891 DOI: 10.1038/srep16232] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 10/12/2015] [Indexed: 02/04/2023] Open
Abstract
The Liver Kinase B1 (LKB1) gene plays crucial roles in cell differentiation, proliferation and the establishment of cell polarity. We created LKB1 conditional knockout mice (LKB1Atoh1 CKO) to investigate the function of LKB1 in cerebellar development. The LKB1Atoh1 CKO mice displayed motor dysfunction. In the LKB1Atoh1 CKO cerebellum, the overall structure had a larger volume and morelobules. LKB1 inactivationled to an increased proliferation of granule cell precursors (GCPs), aberrant granule cell migration and overproduction of unipolar brush cells. To investigate the mechanism underlying the abnormal foliation, we examined sonic hedgehog signalling (Shh) by testing its transcriptional mediators, the Gli proteins, which regulate the GCPs proliferation and cerebellar foliation during cerebellar development. The expression levels of Gli genes were significantly increased in the mutant cerebellum. In vitro assays showed that the proliferation of cultured GCPs from mutant cerebellum significantly increased, whereas the proliferation of mutant GCPs significantly decreased in the presence of a Shh inhibitor GDC-0049. Thus, LKB1 deficiency in the LKB1Atoh1 CKO mice enhanced Shh signalling, leading to the excessive GCP proliferation and the formation of extra lobules. We proposed that LKB1 regulates cerebellar development by controlling GCPs proliferation through Shh signalling during cerebellar development.
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Affiliation(s)
- Yuqin Men
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan 250100, China
| | - Aizhen Zhang
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan 250100, China
| | - Haixiang Li
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan 250100, China
| | - Yecheng Jin
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan 250100, China
| | - Xiaoyang Sun
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan 250100, China
| | - Huashun Li
- SARITEX Center for Stem Cell, Engineering Translational Medicine, Shanghai East Hospital, Advanced Institute of Translational Medicine, Tongji University School of Medicine, Shanghai 200123, China.,Center for Stem Cell&Nano-Medicine, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 200123, China.,Shenzhen Key Laboratory for Molecular Biology of Neural Development, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518000, Guangdong, China
| | - Jiangang Gao
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan 250100, China
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19
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Gailite I, Aerne BL, Tapon N. Differential control of Yorkie activity by LKB1/AMPK and the Hippo/Warts cascade in the central nervous system. Proc Natl Acad Sci U S A 2015; 112:E5169-78. [PMID: 26324895 PMCID: PMC4577147 DOI: 10.1073/pnas.1505512112] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The Hippo (Hpo) pathway is a highly conserved tumor suppressor network that restricts developmental tissue growth and regulates stem cell proliferation and differentiation. At the heart of the Hpo pathway is the progrowth transcriptional coactivator Yorkie [Yki-Yes-activated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) in mammals]. Yki activity is restricted through phosphorylation by the Hpo/Warts core kinase cascade, but increasing evidence indicates that core kinase-independent modes of regulation also play an important role. Here, we examine Yki regulation in the Drosophila larval central nervous system and uncover a Hpo/Warts-independent function for the tumor suppressor kinase liver kinase B1 (LKB1) and its downstream effector, the energy sensor AMP-activated protein kinase (AMPK), in repressing Yki activity in the central brain/ventral nerve cord. Although the Hpo/Warts core cascade restrains Yki in the optic lobe, it is dispensable for Yki target gene repression in the late larval central brain/ventral nerve cord. Thus, we demonstrate a dramatically different wiring of Hpo signaling in neighboring cell populations of distinct developmental origins in the central nervous system.
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Affiliation(s)
- Ieva Gailite
- Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, London WC2A 3LY, United Kingdom
| | - Birgit L Aerne
- Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, London WC2A 3LY, United Kingdom
| | - Nicolas Tapon
- Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, Lincoln's Inn Fields Laboratory, London WC2A 3LY, United Kingdom
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20
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Choi S, Lim DS, Chung J. Feeding and Fasting Signals Converge on the LKB1-SIK3 Pathway to Regulate Lipid Metabolism in Drosophila. PLoS Genet 2015; 11:e1005263. [PMID: 25996931 PMCID: PMC4440640 DOI: 10.1371/journal.pgen.1005263] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 05/05/2015] [Indexed: 12/26/2022] Open
Abstract
LKB1 plays important roles in governing energy homeostasis by regulating AMP-activated protein kinase (AMPK) and other AMPK-related kinases, including the salt-inducible kinases (SIKs). However, the roles and regulation of LKB1 in lipid metabolism are poorly understood. Here we show that Drosophila LKB1 mutants display decreased lipid storage and increased gene expression of brummer, the Drosophila homolog of adipose triglyceride lipase (ATGL). These phenotypes are consistent with those of SIK3 mutants and are rescued by expression of constitutively active SIK3 in the fat body, suggesting that SIK3 is a key downstream kinase of LKB1. Using genetic and biochemical analyses, we identify HDAC4, a class IIa histone deacetylase, as a lipolytic target of the LKB1-SIK3 pathway. Interestingly, we found that the LKB1-SIK3-HDAC4 signaling axis is modulated by dietary conditions. In short-term fasting, the adipokinetic hormone (AKH) pathway, related to the mammalian glucagon pathway, inhibits the kinase activity of LKB1 as shown by decreased SIK3 Thr196 phosphorylation, and consequently induces HDAC4 nuclear localization and brummer gene expression. However, under prolonged fasting conditions, AKH-independent signaling decreases the activity of the LKB1-SIK3 pathway to induce lipolytic responses. We also identify that the Drosophila insulin-like peptides (DILPs) pathway, related to mammalian insulin pathway, regulates SIK3 activity in feeding conditions independently of increasing LKB1 kinase activity. Overall, these data suggest that fasting stimuli specifically control the kinase activity of LKB1 and establish the LKB1-SIK3 pathway as a converging point between feeding and fasting signals to control lipid homeostasis in Drosophila. Liver kinase B1 (LKB1), a serine/threonine kinase, controls 14 different AMP-activated protein kinase (AMPK) family kinases, including salt-inducible kinase 3 (SIK3), suggesting that it plays a variety of roles. Using the fruit fly as an in vivo model system, we reveal that LKB1 kinase activity is critical for lipid storage and controls the lipolysis pathway in the fat body, which is equivalent to mammalian adipose and liver tissue. We find that the lipolytic defects of LKB1 mutants are rescued by the expression of constitutively active SIK3 in the fat body. We show that LKB1 and SIK3 regulate lipid storage by altering the gene expression of brummer, the Drosophila homolog of human adipose triglyceride lipase (ATGL), a critical lipolytic gene. We also identify that LKB1-SIK3 signaling controls the nuclear and cytosolic localization of the class IIa deacetylase HDAC4 via SIK3-dependent phosphorylation in feeding and fasting conditions, respectively. Collectively, these data suggest that the LKB1-SIK3-HDAC4 pathway plays a critical role in maintaining fly lipid homeostasis in response to dietary conditions.
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Affiliation(s)
- Sekyu Choi
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejon, Republic of Korea
- National Creative Research Initiatives Center for Energy Homeostasis Regulation, Seoul National University, Seoul, Republic of Korea
- Institute of Molecular Biology and Genetics, Seoul National University, Seoul, Republic of Korea
| | - Dae-Sik Lim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejon, Republic of Korea
- National Creative Research Initiatives Center for Cell Division and Differentiation, Korea Advanced Institute of Science and Technology, Daejon, Republic of Korea
| | - Jongkyeong Chung
- National Creative Research Initiatives Center for Energy Homeostasis Regulation, Seoul National University, Seoul, Republic of Korea
- Institute of Molecular Biology and Genetics, Seoul National University, Seoul, Republic of Korea
- School of Biological Sciences, Seoul National University, Seoul, Republic of Korea
- * E-mail:
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21
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Shklover J, Mishnaevski K, Levy-Adam F, Kurant E. JNK pathway activation is able to synchronize neuronal death and glial phagocytosis in Drosophila. Cell Death Dis 2015; 6:e1649. [PMID: 25695602 PMCID: PMC4669801 DOI: 10.1038/cddis.2015.27] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 01/12/2015] [Accepted: 01/13/2015] [Indexed: 02/07/2023]
Abstract
Glial phagocytosis of superfluous neurons and damaged or aberrant neuronal material is crucial for normal development and maintenance of the CNS. However, the molecular mechanisms underlying the relationship between neuronal death and glial phagocytosis are poorly understood. We describe a novel mechanism that is able to synchronize neuronal cell death and glial phagocytosis of dying neurons in the Drosophila embryonic CNS. This mechanism involves c-Jun N-terminal kinase (JNK) signaling, which is required for developmental apoptosis of specific neurons during embryogenesis. We demonstrate that the dJNK pathway gain-of-function in neurons leads to dJNK signaling in glia, which results in upregulation of glial phagocytosis. Importantly, this promotion of phagocytosis is not mediated by upregulation of the glial phagocytic receptors SIMU and DRPR, but by increasing glial capacity to degrade apoptotic particles inside phagosomes. The proposed mechanism may be important for removal of damaged neurons in the developing and mature CNS.
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Affiliation(s)
- J Shklover
- Department of Genetics and Developmental Biology, Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Haifa 31096, Israel
| | - K Mishnaevski
- Department of Genetics and Developmental Biology, Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Haifa 31096, Israel
| | - F Levy-Adam
- Department of Genetics and Developmental Biology, Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Haifa 31096, Israel
| | - E Kurant
- Department of Genetics and Developmental Biology, Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Haifa 31096, Israel
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22
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Recent progress on liver kinase B1 (LKB1): expression, regulation, downstream signaling and cancer suppressive function. Int J Mol Sci 2014; 15:16698-718. [PMID: 25244018 PMCID: PMC4200829 DOI: 10.3390/ijms150916698] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 08/12/2014] [Accepted: 08/28/2014] [Indexed: 12/15/2022] Open
Abstract
Liver kinase B1 (LKB1), known as a serine/threonine kinase, has been identified as a critical cancer suppressor in many cancer cells. It is a master upstream kinase of 13 AMP-activated protein kinase (AMPK)-related protein kinases, and possesses versatile biological functions. LKB1 gene is mutated in many cancers, and its protein can form different protein complexes with different cellular localizations in various cell types. The expression of LKB1 can be regulated through epigenetic modification, transcriptional regulation and post-translational modification. LKB1 dowcnstream pathways mainly include AMPK, microtubule affinity regulating kinase (MARK), salt-inducible kinase (SIK), sucrose non-fermenting protein-related kinase (SNRK) and brain selective kinase (BRSK) signalings, etc. This review, therefore, mainly discusses recent studies about the expression, regulation, downstream signaling and cancer suppressive function of LKB1, which can be helpful for better understanding of this molecular and its significance in cancers.
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23
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Zhang T, Liao Y, Hsu FN, Zhang R, Searle JS, Pei X, Li X, Ryoo HD, Ji JY, Du W. Hyperactivated Wnt signaling induces synthetic lethal interaction with Rb inactivation by elevating TORC1 activities. PLoS Genet 2014; 10:e1004357. [PMID: 24809668 PMCID: PMC4014429 DOI: 10.1371/journal.pgen.1004357] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 03/24/2014] [Indexed: 12/31/2022] Open
Abstract
Inactivation of the Rb tumor suppressor can lead to increased cell proliferation or cell death depending on specific cellular context. Therefore, identification of the interacting pathways that modulate the effect of Rb loss will provide novel insights into the roles of Rb in cancer development and promote new therapeutic strategies. Here, we identify a novel synthetic lethal interaction between Rb inactivation and deregulated Wg/Wnt signaling through unbiased genetic screens. We show that a weak allele of axin, which deregulates Wg signaling and increases cell proliferation without obvious effects on cell fate specification, significantly alters metabolic gene expression, causes hypersensitivity to metabolic stress induced by fasting, and induces synergistic apoptosis with mutation of fly Rb ortholog, rbf. Furthermore, hyperactivation of Wg signaling by other components of the Wg pathway also induces synergistic apoptosis with rbf. We show that hyperactivated Wg signaling significantly increases TORC1 activity and induces excessive energy stress with rbf mutation. Inhibition of TORC1 activity significantly suppressed synergistic cell death induced by hyperactivated Wg signaling and rbf inactivation, which is correlated with decreased energy stress and decreased induction of apoptotic regulator expression. Finally the synthetic lethality between Rb and deregulated Wnt signaling is conserved in mammalian cells and that inactivation of Rb and APC induces synergistic cell death through a similar mechanism. These results suggest that elevated TORC1 activity and metabolic stress underpin the evolutionarily conserved synthetic lethal interaction between hyperactivated Wnt signaling and inactivated Rb tumor suppressor. Inactivation of Rb tumor suppressor is common in cancers. Therefore, identification of genes and pathways that are synthetic lethal with Rb will provide new insights into the role of Rb in cancer development and promote the development of novel therapeutic approaches. Here we identified a novel synthetic lethal interaction between Rb inactivation and hyperactivated Wnt signaling and showed that this synthetic lethal interaction is conserved in mammalian systems. We demonstrate that hyperactivated Wnt signaling activate TORC1 activity and induce excessive energy stress with inactivated Rb tumor suppressor, which underpins the evolutionarily conserved synthetic lethal interaction. This study provides novel insights into the interactions between the Rb, Wnt, and mTOR pathways in regulating cellular energy balance, cell growth, and survival.
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Affiliation(s)
- Tianyi Zhang
- Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America
| | - Yang Liao
- Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America
| | - Fu-Ning Hsu
- Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M Health Science Center, College Station, Texas, United States of America
| | - Robin Zhang
- Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America
| | - Jennifer S Searle
- Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America
| | - Xun Pei
- Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America
| | - Xuan Li
- Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America
| | - Hyung Don Ryoo
- Department of Cell Biology, New York University School of Medicine, New York, New York, United States of America
| | - Jun-Yuan Ji
- Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M Health Science Center, College Station, Texas, United States of America
| | - Wei Du
- Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America
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Kim M, Park HL, Park HW, Ro SH, Nam SG, Reed JM, Guan JL, Lee JH. Drosophila Fip200 is an essential regulator of autophagy that attenuates both growth and aging. Autophagy 2013; 9:1201-13. [PMID: 23819996 DOI: 10.4161/auto.24811] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Autophagy-related 1 (Atg1)/Unc-51-like protein kinases (ULKs) are evolutionarily conserved proteins that play critical physiological roles in controlling autophagy, cell growth and neurodevelopment. RB1-inducible coiled-coil 1 (RB1CC1), also known as PTK2/FAK family-interacting protein of 200 kDa (FIP200) is a recently discovered binding partner of ULK1. Here we isolated the Drosophila RB1CC1/FIP200 homolog (Fip200/CG1347) and showed that it mediates Atg1-induced autophagy as a genetically downstream component in diverse physiological contexts. Fip200 loss-of-function mutants experienced severe mobility loss associated with neuronal autophagy defects and neurodegeneration. The Fip200 mutants were also devoid of both developmental and starvation-induced autophagy in salivary gland and fat body, while having no defects in axonal transport and projection in developing neurons. Interestingly, moderate downregulation of Fip200 accelerated both developmental growth and aging, accompanied by target of rapamycin (Tor) signaling upregulation. These results suggest that Fip200 is a critical downstream component of Atg1 and specifically mediates Atg1's autophagy-, aging- and growth-regulating functions.
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Affiliation(s)
- Myungjin Kim
- Department of Molecular and Integrative Physiology; University of Michigan; Ann Arbor, MI USA
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Gordon GM, Zhang T, Zhao J, Du W. Deregulated G1-S control and energy stress contribute to the synthetic-lethal interactions between inactivation of RB and TSC1 or TSC2. J Cell Sci 2013; 126:2004-13. [PMID: 23447678 DOI: 10.1242/jcs.121301] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Synthetic lethality is a potential strategy for cancer treatment by specifically promoting the death of cancer cells with particular defects such as the loss of the RB (RB1) tumor suppressor. We previously showed that inactivation of both RB and TSC2 induces synergistic apoptosis during the development of Drosophila melanogaster and in cancer cells. However, the in vivo mechanism of this synthetic-lethal interaction is not clear. Here, we show that synergistic cell death in tissues that have lost the RB and TSC orthologs rbf and dtsc1/gig, respectively, or overexpress Rheb and dE2F1, are correlated with synergistic defects in G1-S control, which causes cells to accumulate DNA damage. Coexpression of the G1-S inhibitor Dap, but not the G2-M inhibitor dWee1, decreases DNA damage and reduces cell death. In addition, we show that rbf and dtsc1 mutant cells are under energy stress, are sensitive to decreased energy levels and depend on the cellular energy stress-response pathway for survival. Decreasing mitochondrial ATP synthesis by inactivating cova or abrogating the energy-stress response by removing the metabolic regulator LKB1 both enhance the elimination of cells lacking either rbf or dtsc1. These observations, in conjunction with the finding that deregulation of TORC1 induces activation of JNK, indicate that multiple cellular stresses are induced and contribute to the synthetic-lethal interactions between RB and TSC1/TSC2 inactivation. The insights gained from this study suggest new approaches for targeting RB-deficient cancers.
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Affiliation(s)
- Gabriel M Gordon
- Ben May Department for Cancer Research, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA
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Villicaña C, Cruz G, Zurita M. The genetic depletion or the triptolide inhibition of TFIIH in p53 deficient cells induce a JNK-dependent cell death in Drosophila. J Cell Sci 2013; 126:2502-15. [DOI: 10.1242/jcs.122721] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
TFIIH participates in transcription, nucleotide excision repair and the control of the cell cycle. In this work, we demonstrate that the Dmp52 subunit of TFIIH in Drosophila physically interacts with the fly p53 homologue, Dp53. The depletion of Dmp52 in the wing disc generates chromosome fragility, increases apoptosis and produces wings with a reduced number of cells; cellular proliferation, however, is not affected. Interestingly, instead of suppressing the apoptotic phenotype, the depletion of Dp53 in Dmp52-depleted wing disc cells increases apoptosis and the number of cells that suffer from chromosome fragility. The apoptosis induced by the depletion of Dmp52 alone is partially dependent on the JNK pathway. In contrast, the enhanced apoptosis caused by the simultaneous depletion of Dp53 and Dmp52 is absolutely JNK-dependent. In this study, we also show that the anti-proliferative drug triptolide, which inhibits the ATPase activity of the XPB subunit of TFIIH, phenocopies the JNK-dependent massive apoptotic phenotype of Dp53-depleted wing disc cells; this observation suggests that the mechanism by which triptolide induces apoptosis in p53-deficient cancer cells involves the activation of the JNK death pathway.
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Korsse SE, Peppelenbosch MP, van Veelen W. Targeting LKB1 signaling in cancer. Biochim Biophys Acta Rev Cancer 2012; 1835:194-210. [PMID: 23287572 DOI: 10.1016/j.bbcan.2012.12.006] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 12/18/2012] [Accepted: 12/20/2012] [Indexed: 12/13/2022]
Abstract
The serine/threonine kinase LKB1 is a master kinase involved in cellular responses such as energy metabolism, cell polarity and cell growth. LKB1 regulates these crucial cellular responses mainly via AMPK/mTOR signaling. Germ-line mutations in LKB1 are associated with the predisposition of the Peutz-Jeghers syndrome in which patients develop gastrointestinal hamartomas and have an enormously increased risk for developing gastrointestinal, breast and gynecological cancers. In addition, somatic inactivation of LKB1 has been associated with sporadic cancers such as lung cancer. The exact mechanisms of LKB1-mediated tumor suppression remain so far unidentified; however, the inability to activate AMPK and the resulting mTOR hyperactivation has been detected in PJS-associated lesions. Therefore, targeting LKB1 in cancer is now mainly focusing on the activation of AMPK and inactivation of mTOR. Preclinical in vitro and in vivo studies show encouraging results regarding these approaches, which have even progressed to the initiation of a few clinical trials. In this review, we describe the functions, regulation and downstream signaling of LKB1, and its role in hereditary and sporadic cancers. In addition, we provide an overview of several AMPK activators, mTOR inhibitors and additional mechanisms to target LKB1 signaling, and describe the effect of these compounds on cancer cells. Overall, we will explain the current strategies attempting to find a way of treating LKB1-associated cancer.
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Affiliation(s)
- S E Korsse
- Dept. of Gastroenterology and Hepatology, Erasmus Medical University Center, Rotterdam, The Netherlands
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Enhanced antitumor effect of cisplatin in human NSCLC cells by tumor suppressor LKB1. Cancer Gene Ther 2012; 19:489-98. [DOI: 10.1038/cgt.2012.18] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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The HIV-1 Vpu protein induces apoptosis in Drosophila via activation of JNK signaling. PLoS One 2012; 7:e34310. [PMID: 22479597 PMCID: PMC3315533 DOI: 10.1371/journal.pone.0034310] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 02/26/2012] [Indexed: 01/19/2023] Open
Abstract
The genome of the human immunodeficiency virus type 1 (HIV-1) encodes the canonical retroviral proteins, as well as additional accessory proteins that enhance the expression of viral genes, the infectivity of the virus and the production of virions. The accessory Viral Protein U (Vpu), in particular, enhances viral particle production, while also promoting apoptosis of HIV-infected human T lymphocytes. Some Vpu effects rely on its interaction with the ubiquitin-proteasome protein degradation system, but the mechanisms responsible for its pro-apoptotic effects in vivo are complex and remain largely to be elucidated.We took advantage of the Drosophila model to study the effects of Vpu activity in vivo. Expression of Vpu in the developing Drosophila wing provoked tissue loss due to caspase-dependent apoptosis. Moreover, Vpu induced expression of the pro-apoptotic gene reaper, known to down-regulate Inhibitor of Apoptosis Proteins (IAPs) which are caspase-antagonizing E3 ubiquitin ligases. Indeed, Vpu also reduced accumulation of Drosophila IAP1 (DIAP1). Though our results demonstrate a physical interaction between Vpu and the proteasome-addressing SLIMB/β-TrCP protein, as in mammals, both SLIMB/βTrCP-dependent and -independent Vpu effects were observed in the Drosophila wing. Lastly, the pro-apoptotic effect of Vpu in this tissue was abrogated upon inactivation of the c-Jun N-terminal Kinase (JNK) pathway. Our results in the fly thus provide the first functional evidence linking Vpu pro-apoptotic effects to activation of the conserved JNK pathway.
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Abstract
The Peutz-Jeghers syndrome (PJS) culprit kinase LKB1 phosphorylates and activates multiple intracellular kinases regulating cell metabolism and polarity. The relevance of each of these pathways is highly variable depending on the tissue type, but typically represents functions of differentiated cells. These include formation and maintenance of specialized cell compartments in nerve axons, swift refunneling of metabolites and restructuring of cell architecture in response to environmental cues in committed lymphocytes, and ensuring energy-efficient oxygen-based energy expenditure. Such features are often lost or reduced in cancer cells, and indeed LKB1 defects in PJS-associated and sporadic cancers and even the benign PJS polyps lead to differentiation defects, including expansion of partially differentiated epithelial cells in PJS polyps and epithelial-to-mesenchymal transition in carcinomas. This review focuses on the involvement of LKB1 in the differentiation of epithelial, mesenchymal, hematopoietic and germinal lineages.
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Affiliation(s)
- Lina Udd
- Institute of Biotechnology and Genome-Scale Biology Research Program, University of Helsinki, P.O. Box 56 (Biocenter 1), 00014, Helsinki, Finland
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Schulte J, Sepp KJ, Wu C, Hong P, Littleton JT. High-content chemical and RNAi screens for suppressors of neurotoxicity in a Huntington's disease model. PLoS One 2011; 6:e23841. [PMID: 21909362 PMCID: PMC3166080 DOI: 10.1371/journal.pone.0023841] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Accepted: 07/26/2011] [Indexed: 11/27/2022] Open
Abstract
To identify Huntington's Disease therapeutics, we conducted high-content small molecule and RNAi suppressor screens using a Drosophila primary neural culture Huntingtin model. Drosophila primary neurons offer a sensitive readout for neurotoxicty, as their neurites develop dysmorphic features in the presence of mutant polyglutamine-expanded Huntingtin compared to nonpathogenic Huntingtin. By tracking the subcellular distribution of mRFP-tagged pathogenic Huntingtin and assaying neurite branch morphology via live-imaging, we identified suppressors that could reduce Huntingtin aggregation and/or prevent the formation of dystrophic neurites. The custom algorithms we used to quantify neurite morphologies in complex cultures provide a useful tool for future high-content screening approaches focused on neurodegenerative disease models. Compounds previously found to be effective aggregation inhibitors in mammalian systems were also effective in Drosophila primary cultures, suggesting translational capacity between these models. However, we did not observe a direct correlation between the ability of a compound or gene knockdown to suppress aggregate formation and its ability to rescue dysmorphic neurites. Only a subset of aggregation inhibitors could revert dysmorphic cellular profiles. We identified lkb1, an upstream kinase in the mTOR/Insulin pathway, and four novel drugs, Camptothecin, OH-Camptothecin, 18β-Glycyrrhetinic acid, and Carbenoxolone, that were strong suppressors of mutant Huntingtin-induced neurotoxicity. Huntingtin neurotoxicity suppressors identified through our screen also restored viability in an in vivo Drosophila Huntington's Disease model, making them attractive candidates for further therapeutic evaluation.
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Affiliation(s)
- Joost Schulte
- Department of Biology, Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.
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Bensimon A, Aebersold R, Shiloh Y. Beyond ATM: the protein kinase landscape of the DNA damage response. FEBS Lett 2011; 585:1625-39. [PMID: 21570395 DOI: 10.1016/j.febslet.2011.05.013] [Citation(s) in RCA: 164] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Revised: 05/04/2011] [Accepted: 05/04/2011] [Indexed: 01/18/2023]
Abstract
The DNA of all organisms is constantly subjected to damaging agents, both exogenous and endogenous. One extremely harmful lesion is the double-strand break (DSB), which activates a massive signaling network - the DNA damage response (DDR). The chief activator of the DSB response is the ATM protein kinase, which phosphorylates numerous key players in its various branches. Recent phosphoproteomic screens have extended the scope of damage-induced phosphorylations beyond the direct ATM substrates. We review the evidence for the involvement of numerous other protein kinases in the DDR, obtained from documentation of specific pathways as well as high-throughput screens. The emerging picture of the protein phosphorylation landscape in the DDR broadens the current view on the role of this protein modification in the maintenance of genomic stability. Extensive cross-talk between many of these protein kinases forms an interlaced signaling network that spans numerous cellular processes. Versatile protein kinases in this network affect pathways that are different from those they have been identified with to date. The DDR appears to be one of the most extensive signaling responses to cellular stimuli.
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Affiliation(s)
- Ariel Bensimon
- Institute of Molecular Systems Biology, Department of Biology, ETH Zurich, Zurich, Switzerland.
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Robich MP, Chu LM, Feng J, Burgess TA, Laham RJ, Bianchi C, Sellke FW. Effects of selective cyclooxygenase-2 and nonselective cyclooxygenase inhibition on ischemic myocardium. J Thorac Cardiovasc Surg 2010; 140:1143-52. [PMID: 20804993 DOI: 10.1016/j.jtcvs.2010.06.057] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 05/28/2010] [Accepted: 06/28/2010] [Indexed: 01/06/2023]
Abstract
OBJECTIVE We explored effects of nonselective cyclooxygenase and selective cyclooxygenase 2 inhibition on collateral development in a model of chronic myocardial ischemia. We hypothesized that cyclooxygenase 2 inhibitors would negatively effect angiogenic and inflammatory pathways. METHODS Yorkshire swine were made chronically ischemic by placing an ameroid constrictor on the left circumflex coronary artery. Swine were divided into 3 groups and given no drug (control, n = 7), a nonselective cyclooxygenase inhibitor (naproxen 400 mg daily, n = 7), or a selective cyclooxygenase 2 inhibitor (celecoxib 200 mg daily, n = 7). After 7 weeks, coronary angiography was performed. Myocardial function and microvascular reactivity were assessed. Serum and myocardial tissue were analyzed for prostaglandin levels and markers of inflammation and angiogenesis. RESULTS The celecoxib group demonstrated significantly increased mean arterial pressure and decreased left ventricular function. Myocardial perfusion in the celecoxib group was similar to control value but less than in the naproxen group. Coronary microvascular contraction in the collateral-dependent territory was increased in the naproxen group but minimally affected in the celecoxib group. Oxidative stress and apoptosis were increased in the celecoxib group. Expression of angiogenic markers vascular endothelial growth factor and phospho-endothelial nitric oxide synthase (ser1177) and tissue levels of prostacyclin were decreased in both celecoxib and naproxen groups. The naproxen group had diminished endostatin expression. CONCLUSIONS Selective and nonselective cyclooxygenase inhibition are more complex in effect than previously published, but they did not decrease collateral-dependent blood flow to the myocardium in our model of chronic myocardial ischemia.
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Affiliation(s)
- Michael P Robich
- Department of Surgery, Division of Cardiothoracic Surgery, Warren Alpert School of Medicine, Brown University, Providence, RI 02903, USA
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Kim YI, Ryu T, Lee J, Heo YS, Ahnn J, Lee SJ, Yoo O. A genetic screen for modifiers of Drosophila caspase Dcp-1 reveals caspase involvement in autophagy and novel caspase-related genes. BMC Cell Biol 2010; 11:9. [PMID: 20100334 PMCID: PMC2822743 DOI: 10.1186/1471-2121-11-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 01/25/2010] [Indexed: 12/01/2022] Open
Abstract
Background Caspases are cysteine proteases with essential functions in the apoptotic pathway; their proteolytic activity toward various substrates is associated with the morphological changes of cells. Recent reports have described non-apoptotic functions of caspases, including autophagy. In this report, we searched for novel modifiers of the phenotype of Dcp-1 gain-of-function (GF) animals by screening promoter element- inserted Drosophila melanogaster lines (EP lines). Results We screened ~15,000 EP lines and identified 72 Dcp-1-interacting genes that were classified into 10 groups based on their functions and pathways: 4 apoptosis signaling genes, 10 autophagy genes, 5 insulin/IGF and TOR signaling pathway genes, 6 MAP kinase and JNK signaling pathway genes, 4 ecdysone signaling genes, 6 ubiquitination genes, 11 various developmental signaling genes, 12 transcription factors, 3 translation factors, and 11 other unclassified genes including 5 functionally undefined genes. Among them, insulin/IGF and TOR signaling pathway, MAP kinase and JNK signaling pathway, and ecdysone signaling are known to be involved in autophagy. Together with the identification of autophagy genes, the results of our screen suggest that autophagy counteracts Dcp-1-induced apoptosis. Consistent with this idea, we show that expression of eGFP-Atg5 rescued the eye phenotype caused by Dcp-1 GF. Paradoxically, we found that over-expression of full-length Dcp-1 induced autophagy, as Atg8b-GFP, an indicator of autophagy, was increased in the eye imaginal discs and in the S2 cell line. Taken together, these data suggest that autophagy suppresses Dcp-1-mediated apoptotic cell death, whereas Dcp-1 positively regulates autophagy, possibly through feedback regulation. Conclusions We identified a number of Dcp-1 modifiers that genetically interact with Dcp-1-induced cell death. Our results showing that Dcp-1 and autophagy-related genes influence each other will aid future investigations of the complicated relationships between apoptosis and autophagy.
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Affiliation(s)
- Young-Il Kim
- Bio Medical Research Center, Department of Biological Science, KAIST, 373-1, 305-701, Daejeon, Korea
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Integrative genome analysis reveals an oncomir/oncogene cluster regulating glioblastoma survivorship. Proc Natl Acad Sci U S A 2010; 107:2183-8. [PMID: 20080666 DOI: 10.1073/pnas.0909896107] [Citation(s) in RCA: 185] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Using a multidimensional genomic data set on glioblastoma from The Cancer Genome Atlas, we identified hsa-miR-26a as a cooperating component of a frequently occurring amplicon that also contains CDK4 and CENTG1, two oncogenes that regulate the RB1 and PI3 kinase/AKT pathways, respectively. By integrating DNA copy number, mRNA, microRNA, and DNA methylation data, we identified functionally relevant targets of miR-26a in glioblastoma, including PTEN, RB1, and MAP3K2/MEKK2. We demonstrate that miR-26a alone can transform cells and it promotes glioblastoma cell growth in vitro and in the mouse brain by decreasing PTEN, RB1, and MAP3K2/MEKK2 protein expression, thereby increasing AKT activation, promoting proliferation, and decreasing c-JUN N-terminal kinase-dependent apoptosis. Overexpression of miR-26a in PTEN-competent and PTEN-deficient glioblastoma cells promoted tumor growth in vivo, and it further increased growth in cells overexpressing CDK4 or CENTG1. Importantly, glioblastoma patients harboring this amplification displayed markedly decreased survival. Thus, hsa-miR-26a, CDK4, and CENTG1 comprise a functionally integrated oncomir/oncogene DNA cluster that promotes aggressiveness in human cancers by cooperatively targeting the RB1, PI3K/AKT, and JNK pathways.
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Igaki T. Correcting developmental errors by apoptosis: lessons from Drosophila JNK signaling. Apoptosis 2009; 14:1021-8. [PMID: 19466550 DOI: 10.1007/s10495-009-0361-7] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Spatio-temporal regulation of the cell death machinery is essential for normal development and homeostasis of multicellular organisms. While the molecular basis for the central cell death machinery driven by caspases is now well documented, its regulatory mechanisms, especially in the context of living animals, remain to be clarified. The c-Jun N-terminal kinase (JNK) pathway is an evolutionarily conserved kinase cascade that regulates the apoptotic machinery. In mammals, JNK signaling has been implicated in stress-induced apoptosis. Drosophila genetics has now provided evidence of a novel role for JNK-mediated cell death signaling in eliminating developmentally aberrant cells from a tissue. The JNK-dependent cell-elimination system is orchestrated by cell-cell communication between normal and aberrant cells and is essential for ensuring developmental robustness, as well as for protecting organisms against fatal abnormalities such as neoplastic development. These processes are mediated by cell competition, morphogenetic apoptosis, and intrinsic tumor suppression. A combinatorial approach using both genetic and live-imaging systems in Drosophila will be extremely powerful to decipher how JNK-mediated apoptosis works within multicellular communities.
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Affiliation(s)
- Tatsushi Igaki
- Department of Cell Biology, G-COE, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
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Fan D, Ma C, Zhang H. The molecular mechanisms that underlie the tumor suppressor function of LKB1. Acta Biochim Biophys Sin (Shanghai) 2009; 41:97-107. [PMID: 19204826 DOI: 10.1093/abbs/gmn011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Germline mutations of the LKB1 tumor suppressor gene result in Peutz-Jeghers syndrome (PJS) characterized by intestinal hamartomas and increased incidence of epithelial cancers. Inactivating mutations in LKB1 have also been found in certain sporadic human cancers and with particularly high frequency in lung cancer. LKB1 has now been demonstrated to play a crucial role in pulmonary tumorigenesis, controlling initiation, differentiation, and metastasis. Recent evidences showed that LKB1 is a multitasking kinase, with great potential in orchestrating cell activity. Thus far, LKB1 has been found to play a role in cell polarity, energy metabolism, apoptosis, cell cycle arrest, and cell proliferation, all of which may require the tumor suppressor function of this kinase and/or its catalytic activity. This review focuses on remarkable recent findings concerning the molecular mechanism by which the LKB1 protein kinase operates as a tumor suppressor and discusses the rational treatment strategies to individuals suffering from PJS and other common disorders related to LKB1 signaling.
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Affiliation(s)
- Dahua Fan
- Department of Biochemistry and Molecular Biology, Guangdong Medical College, Zhanjiang, China
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Jang C, Lee G, Chung J. LKB1 induces apical trafficking of Silnoon, a monocarboxylate transporter, in Drosophila melanogaster. ACTA ACUST UNITED AC 2008; 183:11-7. [PMID: 18838551 PMCID: PMC2557035 DOI: 10.1083/jcb.200807052] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Silnoon (Sln) is a monocarboxylate transporter (MCT) that mediates active transport of metabolic monocarboxylates such as butyrate and lactate. Here, we identify Sln as a novel LKB1-interacting protein using Drosophila melanogaster genetic modifier screening. Sln expression does not affect cell cycle progression or cell size but specifically enhances LKB1-dependent apoptosis and tissue size reduction. Conversely, down-regulation of Sln suppresses LKB1-dependent apoptosis, implicating Sln as a downstream mediator of LKB1. The kinase activity of LKB1 induces apical trafficking of Sln in polarized cells, and LKB1-dependent Sln trafficking is crucial for triggering apoptosis induced by extracellular butyrate. Given that LKB1 functions to control both epithelial polarity and cell death, we propose Sln is an important downstream target of LKB1.
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Affiliation(s)
- Cholsoon Jang
- National Creative Research Initiatives Center for Cell Growth Regulation, Korea Advanced Institute of Science and Technology, Yusong-gu, Taejon 305-701, Korea
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Filippi BM, Alessi DR. Novel role for the LKB1 pathway in controlling monocarboxylate fuel transporters. ACTA ACUST UNITED AC 2008; 183:7-9. [PMID: 18838550 PMCID: PMC2557034 DOI: 10.1083/jcb.200809056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A question preoccupying many researchers is how signal transduction pathways control metabolic processes and energy production. A study by Jang et al. (Jang, C., G. Lee, and J. Chung. 2008. J. Cell Biol. 183:11–17) provides evidence that in Drosophila melanogaster a signaling network controlled by the LKB1 tumor suppressor regulates trafficking of an Sln/dMCT1 monocarboxylate transporter to the plasma membrane. This enables cells to import additional energy sources such as lactate and butyrate, enhancing the repertoire of fuels they can use to power vital activities.
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Affiliation(s)
- Beatrice Maria Filippi
- Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
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Bonaccorsi S, Mottier V, Giansanti MG, Bolkan BJ, Williams B, Goldberg ML, Gatti M. The Drosophila Lkb1 kinase is required for spindle formation and asymmetric neuroblast division. Development 2008; 134:2183-93. [PMID: 17507418 DOI: 10.1242/dev.02848] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We have isolated lethal mutations in the Drosophila lkb1 gene (dlkb1), the homolog of C. elegans par-4 and human LKB1 (STK11), which is mutated in Peutz-Jeghers syndrome. We show that these mutations disrupt spindle formation, resulting in frequent polyploid cells in larval brains. In addition, dlkb1 mutations affect asymmetric division of larval neuroblasts (NBs); they suppress unequal cytokinesis, abrogate proper localization of Bazooka, Par-6, DaPKC and Miranda, but affect neither Pins/Galphai localization nor spindle rotation. Most aspects of the dlkb1 phenotype are exacerbated in dlkb1 pins double mutants, which exhibit more severe defects than those observed in either single mutant. This suggests that Dlkb1 and Pins act in partially redundant pathways to control the asymmetry of NB divisions. Our results also indicate that Dlkb1 and Pins function in parallel pathways controlling the stability of spindle microtubules. The finding that Dlkb1 mediates both the geometry of stem cell division and chromosome segregation provides novel insight into the mechanisms underlying tumor formation in Peutz-Jeghers patients.
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Affiliation(s)
- Silvia Bonaccorsi
- Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università di Roma La Sapienza, P.le A. Moro 5, 00185 Roma, Italy
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Lee G, Chung J. Discrete functions of rictor and raptor in cell growth regulation in Drosophila. Biochem Biophys Res Commun 2007; 357:1154-9. [PMID: 17462592 DOI: 10.1016/j.bbrc.2007.04.086] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2007] [Accepted: 04/12/2007] [Indexed: 11/27/2022]
Abstract
The TOR signaling pathway regulates cell growth and metabolism in response to various nutrient signals by forming complexes with either rictor or raptor. To distinguish the physiological roles of the complexes formed by the two different TOR partners, we compared the in vivo functions of rictor and raptor in Drosophila. In rictor-null mutants, Akt-induced tissue hyperplasia was reduced and Akt-Ser-505 phosphorylation was decreased. Furthermore, FOXO-dependent apoptosis, which is inhibited by Akt, was augmented in the rictor-null background, indicating that rictor is essential for the Akt-FOXO signaling module. We found that neither S6K-dependent cell growth nor S6K-Thr-398 phosphorylation was affected in rictor-null mutants. However, the knockdown of another TOR binding partner, raptor, decreased S6K-Thr-398 phosphorylation and inhibited S6K-induced cell overgrowth. Collectively, our findings strongly support that the association of TOR with rictor or raptor plays pivotal roles in TOR-mediated cell apoptosis and growth control by differentially regulating Akt- and S6K-dependent signaling pathways, respectively.
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Affiliation(s)
- Gina Lee
- National Creative Research Initiatives Center for Cell Growth Regulation, Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 373-1 Kusong-Dong, Yusong-Gu, Taejon 305-701, Republic of Korea
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Liu W, Silverstein AM, Shu H, Martinez B, Mumby MC. A functional genomics analysis of the B56 isoforms of Drosophila protein phosphatase 2A. Mol Cell Proteomics 2006; 6:319-32. [PMID: 17121811 DOI: 10.1074/mcp.m600272-mcp200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the B56 family of protein phosphatase 2A (PP2A) regulatory subunits play crucial roles in Drosophila cell survival. Distinct functions of two B56 subunits were investigated using a combination of RNA interference, DNA microarrays, and proteomics. RNA interference-mediated knockdown of the B56-1 subunit (PP2A-B') but not the catalytic (mts) or B56-2 subunit (wdb) of PP2A resulted in increased expression of the apoptotic inducers reaper and sickle. Co-knockdown of B56-1 with reaper, but not with sickle, reduced the apoptosis caused by depletion of the B56 subunits. Two-dimensional gel electrophoresis and mass spectrometry identified proteins modified in cells depleted of PP2A subunits. These included generation of caspase-dependent cleavage products, increases in protein abundance, and covalent modifications. Results suggested that up-regulation of the ribosome-associated protein stubarista can serve as a sensitive marker of apoptosis. Up-regulation of transcripts for multiple glutathione transferases and other proteins suggested that loss of PP2A affected pathways involved in the response to oxidative stress. Knockdown of PP2A elevated basal JNK activity and substantially decreased activation of ERK in response to oxidative stress. The results reveal that the B56-containing isoform of PP2A functions within multiple signaling pathways, including those that regulate expression of reaper and the response to oxidative stress, thus promoting cell survival in Drosophila.
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Affiliation(s)
- Wei Liu
- Department of Pharmacology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041, USA
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Kim M, Lee JH, Lee SY, Kim E, Chung J. Caspar, a suppressor of antibacterial immunity in Drosophila. Proc Natl Acad Sci U S A 2006; 103:16358-63. [PMID: 17050695 PMCID: PMC1637587 DOI: 10.1073/pnas.0603238103] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Drosophila has a primitive yet highly effective innate immune system. Although the infection-dependent activation mechanisms of the Drosophila immune system are well understood, its inhibitory regulation remains elusive. To find novel suppressors of the immune system, we performed a genetic screening for Drosophila mutants with hyperactivated immune responses and isolated a loss-of-function mutant of caspar whose product is homologous to Fas-associating factor 1 in mammals. Interestingly, caspar mutant flies showed increased antibacterial immune responses including increased resistance to bacterial infection and a constitutive expression of diptericin, a representative antibacterial peptide gene. Conversely, ectopic expression of caspar strongly suppressed the infection-dependent gene expression of diptericin, which allowed bacterial outgrowth. Consistent with these physiological phenotypes, Caspar negatively regulated the immune deficiency (Imd)-mediated immune responses by blocking nuclear translocation of Relish, an NF-kappaB transcription factor. In addition, we further demonstrated that Dredd-dependent cleavage of Relish, a prerequisite event for the nuclear entry of Relish, is the target of the Caspar-mediated suppression of the Imd pathway. Remarkably, Caspar was highly specific for the Imd pathway and did not affect the Toll pathway, which is crucial for antifungal immunity. Collectively, our elucidation of an inhibitory mechanism of the Imd pathway by Caspar will provide a valuable insight into understanding complex regulatory mechanisms of the innate immune systems in both Drosophila and mammals.
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Affiliation(s)
- Myungjin Kim
- *National Creative Research Initiatives Center for Cell Growth Regulation and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 373-1 Kusong-dong, Yusong, Taejon 305-701, Korea; and
| | - Jun Hee Lee
- *National Creative Research Initiatives Center for Cell Growth Regulation and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 373-1 Kusong-dong, Yusong, Taejon 305-701, Korea; and
| | - Soo Young Lee
- *National Creative Research Initiatives Center for Cell Growth Regulation and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 373-1 Kusong-dong, Yusong, Taejon 305-701, Korea; and
| | - Eunhee Kim
- School of Bioscience and Biotechnology, Chungnam National University, 220 Gung-dong, Yusong, Taejon 305-764, Korea
| | - Jongkyeong Chung
- *National Creative Research Initiatives Center for Cell Growth Regulation and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 373-1 Kusong-dong, Yusong, Taejon 305-701, Korea; and
- To whom correspondence should be addressed. E-mail:
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Kim M, Lee JH, Koh H, Lee SY, Jang C, Chung CJ, Sung JH, Blenis J, Chung J. Inhibition of ERK-MAP kinase signaling by RSK during Drosophila development. EMBO J 2006; 25:3056-67. [PMID: 16763554 PMCID: PMC1500987 DOI: 10.1038/sj.emboj.7601180] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2005] [Accepted: 05/15/2006] [Indexed: 11/09/2022] Open
Abstract
Although p90 ribosomal S6 kinase (RSK) is known as an important downstream effector of the ribosomal protein S6 kinase/extracellular signal-regulated kinase (Ras/ERK) pathway, its endogenous role, and precise molecular function remain unclear. Using gain-of-function and null mutants of RSK, its physiological role was successfully characterized in Drosophila. Surprisingly, RSK-null mutants were viable, but exhibited developmental abnormalities related to an enhanced ERK-dependent cellular differentiation such as ectopic photoreceptor- and vein-cell formation. Conversely, overexpression of RSK dramatically suppressed the ERK-dependent differentiation, which was further augmented by mutations in the Ras/ERK pathway. Consistent with these physiological phenotypes, RSK negatively regulated ERK-mediated developmental processes and gene expressions by blocking the nuclear localization of ERK in a kinase activity-independent manner. In addition, we further demonstrated that the RSK-dependent inhibition of ERK nuclear migration is mediated by the physical association between ERK and RSK. Collectively, our study reveals a novel regulatory mechanism of the Ras/ERK pathway by RSK, which negatively regulates ERK activity by acting as a cytoplasmic anchor in Drosophila.
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Affiliation(s)
- Myungjin Kim
- National Creative Research Initiatives Center for Cell Growth Regulation and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Yusong, Taejon, Korea
| | - Jun Hee Lee
- National Creative Research Initiatives Center for Cell Growth Regulation and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Yusong, Taejon, Korea
| | - Hyongjong Koh
- National Creative Research Initiatives Center for Cell Growth Regulation and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Yusong, Taejon, Korea
| | - Soo Young Lee
- National Creative Research Initiatives Center for Cell Growth Regulation and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Yusong, Taejon, Korea
| | - Cholsoon Jang
- National Creative Research Initiatives Center for Cell Growth Regulation and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Yusong, Taejon, Korea
| | - Cecilia J Chung
- National Creative Research Initiatives Center for Cell Growth Regulation and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Yusong, Taejon, Korea
| | - Jung Hwan Sung
- National Creative Research Initiatives Center for Cell Growth Regulation and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Yusong, Taejon, Korea
| | - John Blenis
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Jongkyeong Chung
- National Creative Research Initiatives Center for Cell Growth Regulation and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Yusong, Taejon, Korea
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 373-1 Kusong-Dong, Yusong, Taejon 305-701, Korea. Tel.: +82 42 869 2620; Fax: +82 42 869 8260; E-mail:
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