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Velagala V, Soundarrajan DK, Unger MF, Gazzo D, Kumar N, Li J, Zartman J. The multimodal action of G alpha q in coordinating growth and homeostasis in the Drosophila wing imaginal disc. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.08.523049. [PMID: 36711848 PMCID: PMC9881979 DOI: 10.1101/2023.01.08.523049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Background G proteins mediate cell responses to various ligands and play key roles in organ development. Dysregulation of G-proteins or Ca 2+ signaling impacts many human diseases and results in birth defects. However, the downstream effectors of specific G proteins in developmental regulatory networks are still poorly understood. Methods We employed the Gal4/UAS binary system to inhibit or overexpress Gαq in the wing disc, followed by phenotypic analysis. Immunohistochemistry and next-gen RNA sequencing identified the downstream effectors and the signaling cascades affected by the disruption of Gαq homeostasis. Results Here, we characterized how the G protein subunit Gαq tunes the size and shape of the wing in the larval and adult stages of development. Downregulation of Gαq in the wing disc reduced wing growth and delayed larval development. Gαq overexpression is sufficient to promote global Ca 2+ waves in the wing disc with a concomitant reduction in the Drosophila final wing size and a delay in pupariation. The reduced wing size phenotype is further enhanced when downregulating downstream components of the core Ca 2+ signaling toolkit, suggesting that downstream Ca 2+ signaling partially ameliorates the reduction in wing size. In contrast, Gαq -mediated pupariation delay is rescued by inhibition of IP 3 R, a key regulator of Ca 2+ signaling. This suggests that Gαq regulates developmental phenotypes through both Ca 2+ -dependent and Ca 2+ -independent mechanisms. RNA seq analysis shows that disruption of Gαq homeostasis affects nuclear hormone receptors, JAK/STAT pathway, and immune response genes. Notably, disruption of Gαq homeostasis increases expression levels of Dilp8, a key regulator of growth and pupariation timing. Conclusion Gαq activity contributes to cell size regulation and wing metamorphosis. Disruption to Gαq homeostasis in the peripheral wing disc organ delays larval development through ecdysone signaling inhibition. Overall, Gαq signaling mediates key modules of organ size regulation and epithelial homeostasis through the dual action of Ca 2+ -dependent and independent mechanisms.
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Maheshvara regulates JAK/STAT signaling by interacting and stabilizing hopscotch transcripts which leads to apoptosis in Drosophila melanogaster. Cell Death Dis 2021; 12:363. [PMID: 33824299 PMCID: PMC8024297 DOI: 10.1038/s41419-021-03649-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 02/01/2023]
Abstract
Maheshvara (mahe), an RNA helicase that is widely conserved across taxa, regulates Notch signaling and neuronal development in Drosophila. In order to identify novel components regulated by mahe, transcriptome profiling of ectopic mahe was carried out and this revealed striking upregulation of JAK/STAT pathway components like upd1, upd2, upd3, and socs36E. Further, significant downregulation of the pathway components in mahe loss-of-function mutant as well as upon lowering the level of mahe by RNAi, supported and strengthened our transcriptome data. Parallelly, we observed that mahe, induced caspase-dependent apoptosis in photoreceptor neurons, and this phenotype was significantly modulated by JAK/STAT pathway components. RNA immunoprecipitation unveiled the presence of JAK/STAT tyrosine kinase hopscotch (hop) transcripts in the complex immunoprecipitated with Mahe, which ultimately resulted in stabilization and elevation of hop transcripts. Additionally, we also observed the surge in activity of downstream transcription factor Stat92E, which is indicative of activation of the JAK/STAT signaling, and this in turn led to apoptosis via upregulation of hid. Taken together, our data provide a novel regulation of JAK/STAT pathway by RNA helicase Maheshvara, which ultimately promotes apoptosis.
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Control of Cell Growth and Proliferation by the Tribbles Pseudokinase: Lessons from Drosophila. Cancers (Basel) 2021; 13:cancers13040883. [PMID: 33672471 PMCID: PMC7923445 DOI: 10.3390/cancers13040883] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 02/09/2021] [Accepted: 02/14/2021] [Indexed: 12/13/2022] Open
Abstract
Simple Summary Tribbles pseudokinases represent a sub-branch of the CAMK (Ca2+/calmodulin-dependent protein kinase) subfamily and are associated with disease-associated signaling pathways associated with various cancers, including melanoma, lung, liver, and acute leukemia. The ability of this class of molecules to regulate cell proliferation was first recognized in the model organism Drosophila and the fruit fly genetic model and continues to provide insight into the molecular mechanism by which this family of adapter molecules regulates both normal development and disease associated with corruption of their proper regulation and function. Abstract The Tribbles (Trib) family of pseudokinase proteins regulate cell growth, proliferation, and differentiation during normal development and in response to environmental stress. Mutations in human Trib isoforms (Trib1, 2, and 3) have been associated with metabolic disease and linked to leukemia and the formation of solid tumors, including melanomas, hepatomas, and lung cancers. Drosophila Tribbles (Trbl) was the first identified member of this sub-family of pseudokinases and shares a conserved structure and similar functions to bind and direct the degradation of key mediators of cell growth and proliferation. Common Trib targets include Akt kinase (also known as protein kinase B), C/EBP (CAAT/enhancer binding protein) transcription factors, and Cdc25 phosphatases, leading to the notion that Trib family members stand athwart multiple pathways modulating their growth-promoting activities. Recent work using the Drosophila model has provided important insights into novel facets of conserved Tribbles functions in stem cell quiescence, tissue regeneration, metabolism connected to insulin signaling, and tumor formation linked to the Hippo signaling pathway. Here we highlight some of these recent studies and discuss their implications for understanding the complex roles Tribs play in cancers and disease pathologies.
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CRISPR/Cas9 mediated genetic resource for unknown kinase and phosphatase genes in Drosophila. Sci Rep 2020; 10:7383. [PMID: 32355295 PMCID: PMC7193564 DOI: 10.1038/s41598-020-64253-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 04/13/2020] [Indexed: 11/09/2022] Open
Abstract
Kinases and phosphatases are crucial for cellular processes and animal development. Various sets of resources in Drosophila have contributed significantly to the identification of kinases, phosphatases and their regulators. However, there are still many kinases, phosphatases and associate genes with unknown functions in the Drosophila genome. In this study, we utilized a CRISPR/Cas9 strategy to generate stable mutants for these unknown kinases, phosphatases and associate factors in Drosophila. For all the 156 unknown gene loci, we totally obtained 385 mutant alleles of 105 candidates, with 18 failure due to low efficiency of selected gRNAs and other 33 failure due to few recovered F0, which indicated high probability of lethal genes. From all the 105 mutated genes, we observed 9 whose mutants were lethal and another 4 sterile, most of which with human orthologs referred in OMIM, representing their huge value for human disease research. Here, we deliver these mutants as an open resource for more interesting studies.
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Fisher KH, Fragiadaki M, Pugazhendhi D, Bausek N, Arredondo MA, Thomas SJ, Brown S, Zeidler MP. A genome-wide RNAi screen identifies MASK as a positive regulator of cytokine receptor stability. J Cell Sci 2018; 131:jcs.209551. [PMID: 29848658 DOI: 10.1242/jcs.209551] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 05/16/2018] [Indexed: 01/01/2023] Open
Abstract
Cytokine receptors often act via the Janus kinase and signal transducer and activator of transcription (JAK/STAT) pathway to form a signalling cascade that is essential for processes such as haematopoiesis, immune responses and tissue homeostasis. In order to transduce ligand activation, cytokine receptors must dimerise. However, mechanisms regulating their dimerisation are poorly understood. In order to better understand the processes regulating cytokine receptor levels, and their activity and dimerisation, we analysed the highly conserved JAK/STAT pathway in Drosophila, which acts via a single receptor, known as Domeless. We performed a genome-wide RNAi screen in Drosophila cells, identifying MASK as a positive regulator of Domeless dimerisation and protein levels. We show that MASK is able to regulate receptor levels and JAK/STAT signalling both in vitro and in vivo We also show that its human homologue, ANKHD1, is also able to regulate JAK/STAT signalling and the levels of a subset of pathway receptors in human cells. Taken together, our results identify MASK as a novel regulator of cytokine receptor levels, and suggest functional conservation, which may have implications for human health.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Katherine H Fisher
- The Bateson Centre, Department of Biomedical Science, The University of Sheffield, Firth Court, Sheffield, S10 2TN, UK
| | - Maria Fragiadaki
- The Bateson Centre, Department of Biomedical Science, The University of Sheffield, Firth Court, Sheffield, S10 2TN, UK
| | - Dhamayanthi Pugazhendhi
- The Bateson Centre, Department of Biomedical Science, The University of Sheffield, Firth Court, Sheffield, S10 2TN, UK
| | - Nina Bausek
- The Bateson Centre, Department of Biomedical Science, The University of Sheffield, Firth Court, Sheffield, S10 2TN, UK
| | - Maria A Arredondo
- Department of Oncology & Human Metabolism, The University of Sheffield, Sheffield, S10 2RX, UK
| | - Sally J Thomas
- Department of Oncology & Human Metabolism, The University of Sheffield, Sheffield, S10 2RX, UK
| | - Stephen Brown
- The Sheffield RNAi Screening Facility, Department of Biomedical Science, The University of Sheffield, S10 2TN, UK
| | - Martin P Zeidler
- The Bateson Centre, Department of Biomedical Science, The University of Sheffield, Firth Court, Sheffield, S10 2TN, UK
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6
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Chen Q, Giedt M, Tang L, Harrison DA. Tools and methods for studying the Drosophila JAK/STAT pathway. Methods 2014; 68:160-72. [DOI: 10.1016/j.ymeth.2014.03.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 03/17/2014] [Accepted: 03/19/2014] [Indexed: 12/29/2022] Open
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Myllymäki H, Rämet M. JAK/STAT Pathway inDrosophilaImmunity. Scand J Immunol 2014; 79:377-85. [DOI: 10.1111/sji.12170] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 03/21/2014] [Indexed: 12/24/2022]
Affiliation(s)
- H. Myllymäki
- Laboratory of Experimental Immunology; BioMediTech; University of Tampere; Tampere Finland
| | - M. Rämet
- Laboratory of Experimental Immunology; BioMediTech; University of Tampere; Tampere Finland
- Department of Pediatrics; Tampere University Hospital; Tampere Finland
- Department of Pediatrics; Medical Research Center Oulu; University of Oulu; Oulu Finland
- Department of Children and Adolescents; Oulu University Hospital; Oulu Finland
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Amoyel M, Anderson AM, Bach EA. JAK/STAT pathway dysregulation in tumors: a Drosophila perspective. Semin Cell Dev Biol 2014; 28:96-103. [PMID: 24685611 PMCID: PMC4037387 DOI: 10.1016/j.semcdb.2014.03.023] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 03/17/2014] [Accepted: 03/20/2014] [Indexed: 12/18/2022]
Abstract
Sustained activation of the JAK/STAT pathway is causal to human cancers. This pathway is less complex in Drosophila, and its dysregulation has been linked to several tumor models in this organism. Here, we discuss models of metastatic epithelial and hematopoietic tumors that are causally linked to dysregulation of JAK/STAT signaling in Drosophila. First, we focus on cancer models in imaginal discs where ectopic expression of the JAK/STAT pathway ligand Unpaired downstream of distinct tumor suppressors has emerged as an unexpected mediator of neoplastic transformation. We also discuss the collaboration between STAT and oncogenic Ras in epithelial transformation. Second, we examine hematopoietic tumors, where mutations that cause hyperactive JAK/STAT signaling are necessary and sufficient for "fly leukemia". We highlight the important contributions that genetic screens in Drosophila have made to understanding the JAK/STAT pathway, its developmental roles, and how its function is co-opted during tumorigenesis.
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Affiliation(s)
- Marc Amoyel
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, 550 First Avenue, MSB 497B, New York, NY 10016, USA
| | - Abigail M Anderson
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, 550 First Avenue, MSB 497B, New York, NY 10016, USA
| | - Erika A Bach
- The Helen L. and Martin S. Kimmel Center for Stem Cell Biology, New York University School of Medicine.
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Morin-Poulard I, Vincent A, Crozatier M. The Drosophila JAK-STAT pathway in blood cell formation and immunity. JAKSTAT 2013; 2:e25700. [PMID: 24069567 PMCID: PMC3772119 DOI: 10.4161/jkst.25700] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 07/09/2013] [Accepted: 07/10/2013] [Indexed: 12/17/2022] Open
Abstract
Genetic alterations affecting the JAK-STAT signaling pathway are linked to several malignancies and hematological disorders in humans. Despite being one of the most extensively studied pathways, there remain many gaps to fill. JAK-STAT components are widely conserved during evolution. Here, we review the known roles of the JAK-STAT pathway in Drosophila immunity: controlling the different steps of hematopoiesis, both under physiological conditions and in response to immune challenge, and contributing to antiviral responses. We then summarize what is currently known about JAK-STAT signaling in renewal of the adult intestine, under physiological conditions or in response to ingestion of pathogenic bacteria.
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Affiliation(s)
- Ismaël Morin-Poulard
- Centre de Biologie du Développement; UMR 5547 CNRS/Université Toulouse III and Fédération de Recherche de Biologie de Toulouse; Toulouse, France
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Muñoz-Soriano V, Ruiz C, Pérez-Alonso M, Mlodzik M, Paricio N. Nemo regulates cell dynamics and represses the expression of miple, a midkine/pleiotrophin cytokine, during ommatidial rotation. Dev Biol 2013; 377:113-25. [PMID: 23428616 DOI: 10.1016/j.ydbio.2013.02.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Revised: 02/07/2013] [Accepted: 02/11/2013] [Indexed: 01/18/2023]
Abstract
Ommatidial rotation is one of the most important events for correct patterning of the Drosophila eye. Although several signaling pathways are involved in this process, few genes have been shown to specifically affect it. One of them is nemo (nmo), which encodes a MAP-like protein kinase that regulates the rate of rotation throughout the entire process, and serves as a link between core planar cell polarity (PCP) factors and the E-cadherin-β-catenin complex. To determine more precisely the role of nmo in ommatidial rotation, live-imaging analyses in nmo mutant and wild-type early pupal eye discs were performed. We demonstrate that ommatidial rotation is not a continuous process, and that rotating and non-rotating interommatidial cells are very dynamic. Our in vivo analyses also show that nmo regulates the speed of rotation and is required in cone cells for correct ommatidial rotation, and that these cells as well as interommatidial cells are less dynamic in nmo mutants. Furthermore, microarray analyses of nmo and wild-type larval eye discs led us to identify new genes and signaling pathways related to nmo function during this process. One of them, miple, encodes the Drosophila ortholog of the midkine/pleiotrophin secreted cytokines that are involved in cell migration processes. miple is highly up-regulated in nmo mutant discs. Indeed, phenotypic analyses reveal that miple overexpression leads to ommatidial rotation defects. Genetic interaction assays suggest that miple is signaling through Ptp99A, the Drosophila ortholog of the vertebrate midkine/pleiotrophin PTPζ receptor. Accordingly, we propose that one of the roles of Nmo during ommatial rotation is to repress miple expression, which may in turn affect the dynamics in E-cadherin-β-catenin complexes.
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Affiliation(s)
- Verónica Muñoz-Soriano
- Departamento de Genética, Facultad de CC Biológicas, Universidad de Valencia, Doctor Moliner 50, E-46100 Burjassot, Valencia, Spain
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Hayashi Y, Sexton TR, Dejima K, Perry DW, Takemura M, Kobayashi S, Nakato H, Harrison DA. Glypicans regulate JAK/STAT signaling and distribution of the Unpaired morphogen. Development 2013; 139:4162-71. [PMID: 23093424 DOI: 10.1242/dev.078055] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In Drosophila, ligands of the Unpaired (Upd) family activate the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway. The JAK/STAT pathway controls many developmental events, including multiple functions in the ovary. These include an early role in the germarium for specification of stalk cells and a later role in the vitellarium to pattern the follicular epithelium surrounding each cyst. In this latter role, graded JAK/STAT activation specifies three distinct anterior follicular cell fates, suggesting that Upd is a morphogen in this system. Consistent with the JAK/STAT activation pattern in the vitellarium, Upd forms a concentration gradient on the apical surface of the follicular epithelium with a peak at its source, the polar cells. Like many morphogens, signaling and distribution of Upd are regulated by the heparan sulfate proteoglycans (HSPGs) Dally and Dally-like. Mutations in these glypican genes and in heparan sulfate biosynthetic genes result in disruption of JAK/STAT signaling, loss or abnormal formation of the stalk and significant reduction in the accumulation of extracellular Upd. Conversely, forced expression of Dally causes ectopic accumulation of Upd in follicular cells. Furthermore, biochemical studies reveal that Upd and Dally bind each other on the surface of the cell membrane. Our findings demonstrate that Drosophila glypicans regulate formation of the follicular gradient of the Upd morphogen, Upd. Furthermore, we establish the follicular epithelium as a new model for morphogen signaling in complex organ development.
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Affiliation(s)
- Yoshiki Hayashi
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA
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12
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Dobens LL, Bouyain S. Developmental roles of tribbles protein family members. Dev Dyn 2012; 241:1239-48. [PMID: 22711497 DOI: 10.1002/dvdy.23822] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/11/2012] [Indexed: 12/15/2022] Open
Abstract
The gene tribbles (trbl), identified 12 years ago in genetic screens for mutations that control both cell division and cell migration during embryonic Drosophila development, is the founding member of the Tribbles (Trib) family of kinase-like proteins that have diverse roles in cell signaling, tissue homeostasis, and cancer. Trib proteins share three motifs: (1) a divergent kinase region (Trib domain) with undetermined catalytic activity, (2) a COP1 site used to direct key target proteins to the proteosome for degradation, and (3) a MEK1 site that binds and modulates MAPKK kinase activity. The notion that Tribs act as scaffolding proteins to balance signaling levels in multiple pathways retains an attractive simplicity, but given recent data showing that divergent kinases act by means of novel catalytic mechanisms, the enzymatic activity of Tribs remains untested. Here, we focus on the role of Tribs during development. Developmental analysis of Drosophila trbl phenotypes reveals tissue-specific, sometimes contradictory roles. In mammals, multiple Trib isoforms exhibit overlapping and tissue-specific functions. Recent data indicate the mechanism of Trib activity is conserved and requires the Trib domain. Finally, we discuss the connections between Tribs in disease and cancer that have implications for their normal roles during organogenesis.
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Affiliation(s)
- Leonard L Dobens
- Division of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri, USA.
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Wang YH, Huang ML. Organogenesis and tumorigenesis: insight from the JAK/STAT pathway in the Drosophila eye. Dev Dyn 2011; 239:2522-33. [PMID: 20737505 PMCID: PMC2972639 DOI: 10.1002/dvdy.22394] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The Janus kinase (JAK) signal transducer and activator of transcription (STAT) pathway is one of the main signaling pathways in eukaryotic cells. This pathway is used during diverse growth and developmental processes in multiple tissues to control cell proliferation, differentiation, survival, and apoptosis. In addition to its role during development, the JAK/STAT pathway has also been implicated in tumorigenesis. Drosophila melanogaster is a powerful genetic tool, and its eyes have been used extensively as a platform to study signaling pathways. Many reports have demonstrated that the JAK/STAT pathway plays pleiotropic roles in Drosophila eye development. Its functions and activation are decided by its interplay with other signal pathways and the epigenetic status. In this review, we focus on the functions and regulation of the JAK/STAT pathway during eye development and provide some insights into the study of this pathway in tumorigenesis. Developmental Dynamics 239:2522–2533, 2010. © 2010 Wiley-Liss, Inc.
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Affiliation(s)
- Ying-Hsuan Wang
- Department of Life Science and Institute of Molecular Biology, National Chung-Cheng University, Chia-Yi, Taiwan
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Bronstein R, Levkovitz L, Yosef N, Yanku M, Ruppin E, Sharan R, Westphal H, Oliver B, Segal D. Transcriptional regulation by CHIP/LDB complexes. PLoS Genet 2010; 6:e1001063. [PMID: 20730086 PMCID: PMC2921152 DOI: 10.1371/journal.pgen.1001063] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Accepted: 07/12/2010] [Indexed: 01/18/2023] Open
Abstract
It is increasingly clear that transcription factors play versatile roles in turning genes "on" or "off" depending on cellular context via the various transcription complexes they form. This poses a major challenge in unraveling combinatorial transcription complex codes. Here we use the powerful genetics of Drosophila combined with microarray and bioinformatics analyses to tackle this challenge. The nuclear adaptor CHIP/LDB is a major developmental regulator capable of forming tissue-specific transcription complexes with various types of transcription factors and cofactors, making it a valuable model to study the intricacies of gene regulation. To date only few CHIP/LDB complexes target genes have been identified, and possible tissue-dependent crosstalk between these complexes has not been rigorously explored. SSDP proteins protect CHIP/LDB complexes from proteasome dependent degradation and are rate-limiting cofactors for these complexes. By using mutations in SSDP, we identified 189 down-stream targets of CHIP/LDB and show that these genes are enriched for the binding sites of APTEROUS (AP) and PANNIER (PNR), two well studied transcription factors associated with CHIP/LDB complexes. We performed extensive genetic screens and identified target genes that genetically interact with components of CHIP/LDB complexes in directing the development of the wings (28 genes) and thoracic bristles (23 genes). Moreover, by in vivo RNAi silencing we uncovered novel roles for two of the target genes, xbp1 and Gs-alpha, in early development of these structures. Taken together, our results suggest that loss of SSDP disrupts the normal balance between the CHIP-AP and the CHIP-PNR transcription complexes, resulting in down-regulation of CHIP-AP target genes and the concomitant up-regulation of CHIP-PNR target genes. Understanding the combinatorial nature of transcription complexes as presented here is crucial to the study of transcription regulation of gene batteries required for development.
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Affiliation(s)
- Revital Bronstein
- Department of Microbiology and Biotechnology, Tel Aviv University, Tel Aviv, Israel
| | - Liron Levkovitz
- Department of Physiology and Pharmacology, Tel Aviv University, Tel Aviv, Israel
- Balvatnik School of Computer Science, Tel Aviv University, Tel Aviv, Israel
| | - Nir Yosef
- Balvatnik School of Computer Science, Tel Aviv University, Tel Aviv, Israel
| | - Michaela Yanku
- Department of Microbiology and Biotechnology, Tel Aviv University, Tel Aviv, Israel
| | - Eytan Ruppin
- Department of Physiology and Pharmacology, Tel Aviv University, Tel Aviv, Israel
- Balvatnik School of Computer Science, Tel Aviv University, Tel Aviv, Israel
| | - Roded Sharan
- Balvatnik School of Computer Science, Tel Aviv University, Tel Aviv, Israel
| | - Heiner Westphal
- Section on Mammalian Molecular Genetics, Program in Genomics of Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Brian Oliver
- Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Daniel Segal
- Department of Microbiology and Biotechnology, Tel Aviv University, Tel Aviv, Israel
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Kallio J, Myllymäki H, Grönholm J, Armstrong M, Vanha-aho LM, Mäkinen L, Silvennoinen O, Valanne S, Rämet M. Eye transformer is a negative regulator of Drosophila JAK/STAT signaling. FASEB J 2010; 24:4467-79. [PMID: 20624926 DOI: 10.1096/fj.10-162784] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
JAK/STAT signaling pathway is evolutionarily conserved and tightly regulated. We carried out a reporter-based genome-wide RNAi in vitro screen to identify genes that regulate Drosophila JAK/STAT pathway and found 5 novel regulators. Of these, CG14225 is a negative regulator structurally related to the Drosophila JAK/STAT pathway receptor Domeless, especially in the extracellular domain, and to the mammalian IL-6 receptor and the signal transducer gp130. CG14225 coimmunoprecipitates with Domeless and its associated kinase hopscotch in S2 cells. CG14225 RNAi caused hyperphosphorylation of the transcription factor Stat92E in S2 cells on stimulation with the Drosophila JAK/STAT pathway ligand unpaired. CG14225 RNAi in vivo hyperactivated JAK/STAT target genes on septic injury and enhanced unpaired-induced eye overgrowth, and was thus named the eye transformer (ET). In the gastrointestinal infection model, where JAK/STAT signaling is important for stem cell renewal, CG14225/ET RNAi was protective in vivo. In conclusion, we have identified ET as a novel negative regulator of the Drosophila JAK/STAT pathway both in vitro and in vivo, and it functions in regulating Stat92E phosphorylation.
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Affiliation(s)
- Jenni Kallio
- Laboratory of Experimental Immunology, Institute of Medical Technology, Tampere University, Tampere, Finland
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Transcriptional targets of Drosophila JAK/STAT pathway signalling as effectors of haematopoietic tumour formation. EMBO Rep 2010; 11:201-7. [PMID: 20168330 DOI: 10.1038/embor.2010.1] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Revised: 12/11/2009] [Accepted: 12/11/2009] [Indexed: 01/26/2023] Open
Abstract
Although many signal transduction pathways have been implicated in the development of human disease, the identification of pathway targets and the biological processes that mediate disease progression remains challenging. One such disease-related pathway is the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) cascade whose constitutive misactivation by the JAK2 V617F mutation underlies most human myeloproliferative disorders. Here, we use transcript profiling of Drosophila haemocyte-like cells to identify JAK/STAT target genes, combined with an in vivo model for JAK-induced blood cell overproliferation, to identify the main effectors required for haematopoietic tumour development. The identified human homologues of the Drosophila effectors were tested for potential V617F-mediated transcriptional regulation in human HeLa cells and compared with small interfering RNA-derived data, quantify their role in regulating the proliferation of cancer-derived cell lines. Such an inter-species approach is an effective way to identify factors with conserved functions that might be central to human disease.
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Stofanko M, Kwon SY, Badenhorst P. A misexpression screen to identify regulators of Drosophila larval hemocyte development. Genetics 2008; 180:253-67. [PMID: 18757933 PMCID: PMC2535679 DOI: 10.1534/genetics.108.089094] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Accepted: 07/14/2008] [Indexed: 12/19/2022] Open
Abstract
In Drosophila, defense against foreign pathogens is mediated by an effective innate immune system, the cellular arm of which is composed of circulating hemocytes that engulf bacteria and encapsulate larger foreign particles. Three hemocyte types occur: plasmatocytes, crystal cells, and lamellocytes. The most abundant larval hemocyte type is the plasmatocyte, which is responsible for phagocytosis and is present either in circulation or in adherent sessile domains under the larval cuticle. The mechanisms controlling differentiation of plasmatocytes and their migration toward these sessile compartments are unclear. To address these questions we have conducted a misexpression screen using the plasmatocyte-expressed GAL4 driver Peroxidasin-GAL4 (Pxn-GAL4) and existing enhancer-promoter (EP) and EP yellow (EY) transposon libraries to systematically misexpress approximately 20% of Drosophila genes in larval hemocytes. The Pxn-GAL4 strain also contains a UAS-GFP reporter enabling hemocyte phenotypes to be visualized in the semitransparent larvae. Among 3412 insertions screened we uncovered 101 candidate hemocyte regulators. Some of these are known to control hemocyte development, but the majority either have no characterized function or are proteins of known function not previously implicated in hemocyte development. We have further analyzed three candidate genes for changes in hemocyte morphology, cell-cell adhesion properties, phagocytosis activity, and melanotic tumor formation.
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Affiliation(s)
- Martin Stofanko
- Institute of Biomedical Research, University of Birmingham, Edgbaston B15 2TT, United Kingdom
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Sehgal PB. Paradigm shifts in the cell biology of STAT signaling. Semin Cell Dev Biol 2008; 19:329-40. [PMID: 18691663 DOI: 10.1016/j.semcdb.2008.07.003] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Revised: 07/15/2008] [Accepted: 07/17/2008] [Indexed: 01/25/2023]
Abstract
In recent years several of the key tenets of the original cytokine-STAT-signaling paradigm had to be revised. First, the notion that nonphosphorylated "inactive" STATs are present in the cytoplasm as free monomers which dimerized only subsequent to Tyr-phosphorylation has been replaced by the understanding that nonphosphorylated STATs in the cytoplasm exist largely as dimers and high molecular mass "statosome" complexes. Second, the notion that phosphorylation, either of Tyr or Ser residues or both, in STAT species is required for transcriptional activation has been replaced by the realization that nonphosphorylated STATs can be transcriptionally active albeit with respect to sets of target genes distinct from phosphorylated STATs. Third, the notion that it is the activation by phosphorylation of STATs at the plasma membrane that then leads to their import into the nucleus has been replaced by the recognition that even nonphosphorylated STATs shuttle between the cytoplasm and nucleus at all times in a constitutive manner. Fourth, the notion that the trans-cytoplasmic transit of STATs from the plasma membrane to the nuclear import machinery takes place exclusively as a free cytosolic process has been replaced by the understanding that at least a portion of this trans-cytoplasmic transit is mediated via membrane-associated caveolar and endocytic trafficking (the "signaling endosome" hypothesis). Fifth, the targeting and sequestration of activated STAT3 to long-lived endosomes in the cytoplasm requires consideration of STAT3-mediated "signal transduction" from the plasma membrane to cytoplasmic membrane destinations potentially for function(s) in the cytoplasm. Indeed, in tissue sections many discrete histologic cell types display PY-STAT3 almost exclusively in the cytoplasm with little, if any, in the nucleus. New challenges include determining the structural bases for the recruitment of nonphosphorylated dimeric STAT species to the cytosolic face of membranes including at the cytoplasmic tails of respective receptor complexes, the conformational changes subsequent to phosphorylation and the structural bases for the targeting and functions of STAT proteins within the cytoplasm per se.
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Affiliation(s)
- Pravin B Sehgal
- Department of Cell Biology & Anatomy, New York Medical College, Valhalla, NY 10595, United States.
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Müller P, Boutros M, Zeidler MP. Identification of JAK/STAT pathway regulators--insights from RNAi screens. Semin Cell Dev Biol 2008; 19:360-9. [PMID: 18586112 PMCID: PMC2631610 DOI: 10.1016/j.semcdb.2008.06.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2008] [Revised: 06/02/2008] [Accepted: 06/04/2008] [Indexed: 12/30/2022]
Abstract
While many core JAK/STAT pathway components have been discovered in Drosophila via classical genetic approaches, the identification of pathway regulators has been more challenging. Recently two cell-based RNAi screens for JAK/STAT pathway regulators have been undertaken using libraries of double-stranded RNAs targeting a large proportion of the predicted Drosophila transcriptome. While both screens identified multiple regulators, only relatively few loci are common to both data sets. Here we compare the two screens and discuss these differences. Although many factors are likely to be contributory, differences in the assay design are of key importance. Low levels of stimulation favouring the identification of negative pathway regulators and high levels of stimulation favouring the identification of positively acting factors. Ultimately, the results from both screens are likely to be largely complementary and have identified a range of novel candidate regulators of JAK/STAT pathway activity as a starting point for new research directions in the future.
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Affiliation(s)
- Patrick Müller
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA
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20
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Devergne O, Ghiglione C, Noselli S. The endocytic control of JAK/STAT signalling in Drosophila. J Cell Sci 2007; 120:3457-64. [PMID: 17855388 DOI: 10.1242/jcs.005926] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Domeless (Dome) is an IL-6-related cytokine receptor that activates a conserved JAK/STAT signalling pathway during Drosophila development. Despite good knowledge of the signal transduction pathway in several models, the role of receptor endocytosis in JAK/STAT activation remains poorly understood. Using both in vivo genetic analysis and cell culture assays, we show that ligand binding of Unpaired 1 (Upd1) induces clathrin-dependent endocytosis of receptor-ligand complexes and their subsequent trafficking through the endosomal compartment towards the lysosome. Surprisingly, blocking trafficking in distinct endosomal compartments using mutants affecting either Clathrin heavy chain, rab5, Hrs or deep orange led to an inhibition of the JAK/STAT pathway, whereas this pathway was unchanged when rab11 was affected. This suggests that internalization and trafficking are both required for JAK/STAT activity. The requirement for clathrin-dependent endocytosis to activate JAK/STAT signalling suggests a model in which the signalling `on' state relies not only on ligand binding to the receptor at the cell surface, but also on the recruitment of the complex into endocytic vesicles on their way to lysozomes. Selective activation of the pool of receptors marked for degradation thus provides a way to tightly control JAK/STAT activity.
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Affiliation(s)
- Olivier Devergne
- Institute of Developmental Biology and Cancer, CNRS-UMR 6543, University of Nice Sophia-Antipolis, Parc Valrose 06108 Nice cedex 2, France
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21
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Arbouzova NI, Zeidler MP. JAK/STAT signalling in Drosophila: insights into conserved regulatory and cellular functions. Development 2006; 133:2605-16. [PMID: 16794031 DOI: 10.1242/dev.02411] [Citation(s) in RCA: 298] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
High levels of interspecies conservation characterise all signal transduction cascades and demonstrate the significance of these pathways over evolutionary time. Here, we review advances in the field of JAK/STAT signalling, focusing on recent developments in Drosophila. In particular, recent results from genetic and genome-wide RNAi screens, as well as studies into the developmental roles played by this pathway, highlight striking levels of physical and functional conservation in processes such as cellular proliferation, immune responses and stem cell maintenance. These insights underscore the value of model organisms for improving our understanding of this human disease-relevant pathway.
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Affiliation(s)
- Natalia I Arbouzova
- Department of Molecular Developmental Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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