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Abstract
Tyrosine phosphorylation plays a significant role in a wide range of cellular processes. The Drosophila genome encodes more than 20 receptor tyrosine kinases and extensive studies in the past 20 years have illustrated their diverse roles and complex signaling mechanisms. Although some receptor tyrosine kinases have highly specific functions, others strikingly are used in rather ubiquitous manners. Receptor tyrosine kinases regulate a broad expanse of processes, ranging from cell survival and proliferation to differentiation and patterning. Remarkably, different receptor tyrosine kinases share many of the same effectors and their hierarchical organization is retained in disparate biological contexts. In this comprehensive review, we summarize what is known regarding each receptor tyrosine kinase during Drosophila development. Astonishingly, very little is known for approximately half of all Drosophila receptor tyrosine kinases.
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Affiliation(s)
- Richelle Sopko
- Department of Genetics, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
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Yu L, Daniels J, Glaser AE, Wolf MJ. Raf-mediated cardiac hypertrophy in adult Drosophila. Dis Model Mech 2013; 6:964-76. [PMID: 23580199 PMCID: PMC3701216 DOI: 10.1242/dmm.011361] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In response to stress and extracellular signals, the heart undergoes a process called cardiac hypertrophy during which cardiomyocytes increase in size. If untreated, cardiac hypertrophy can progress to overt heart failure that causes significant morbidity and mortality. The identification of molecular signals that cause or modify cardiomyopathies is necessary to understand how the normal heart progresses to cardiac hypertrophy and heart failure. Receptor tyrosine kinase (RTK) signaling is essential for normal human cardiac function, and the inhibition of RTKs can cause dilated cardiomyopathies. However, neither investigations of activated RTK signaling pathways nor the characterization of hypertrophic cardiomyopathy in the adult fly heart has been previously described. Therefore, we developed strategies using Drosophila as a model to circumvent some of the complexities associated with mammalian models of cardiovascular disease. Transgenes encoding activated EGFRA887T, Ras85DV12 and Ras85DV12S35, which preferentially signal to Raf, or constitutively active human or fly Raf caused hypertrophic cardiomyopathy as determined by decreased end diastolic lumen dimensions, abnormal cardiomyocyte fiber morphology and increased heart wall thicknesses. There were no changes in cardiomyocyte cell numbers. Additionally, activated Raf also induced an increase in cardiomyocyte ploidy compared with control hearts. However, preventing increases in cardiomyocyte ploidy using fizzy-related (Fzr) RNAi did not rescue Raf-mediated cardiac hypertrophy, suggesting that Raf-mediated polyploidization is not required for cardiac hypertrophy. Similar to mammals, the cardiac-specific expression of RNAi directed against MEK or ERK rescued Raf-mediated cardiac hypertrophy. However, the cardiac-specific expression of activated ERKD334N, which promotes hyperplasia in non-cardiac tissues, did not cause myocyte hypertrophy. These results suggest that ERK is necessary, but not sufficient, for Raf-mediated cardiac hypertrophy.
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Affiliation(s)
- Lin Yu
- Duke University Medical Center, 321 Sands Building, Research Drive, Durham, NC 27710, USA
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53
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Liu HY, Pfleger CM. Mutation in E1, the ubiquitin activating enzyme, reduces Drosophila lifespan and results in motor impairment. PLoS One 2013; 8:e32835. [PMID: 23382794 PMCID: PMC3558519 DOI: 10.1371/journal.pone.0032835] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 01/31/2012] [Indexed: 11/21/2022] Open
Abstract
Neurodegenerative diseases cause tremendous suffering for those afflicted and their families. Many of these diseases involve accumulation of mis-folded or aggregated proteins thought to play a causal role in disease pathology. Ubiquitinated proteins are often found in these protein aggregates, and the aggregates themselves have been shown to inhibit the activity of the proteasome. These and other alterations in the Ubiquitin Pathway observed in neurodegenerative diseases have led to the question of whether impairment of the Ubiquitin Pathway on its own can increase mortality or if ongoing neurodegeneration alters Ubiquitin Pathway function as a side-effect. To address the role of the Ubiquitin Pathway in vivo, we studied loss-of-function mutations in the Drosophila Ubiquitin Activating Enzyme, Uba1 or E1, the most upstream enzyme in the Ubiquitin Pathway. Loss of only one functional copy of E1 caused a significant reduction in adult lifespan. Rare homozygous hypomorphic E1 mutants reached adulthood. These mutants exhibited further reduced lifespan and showed inappropriate Ras activation in the brain. Removing just one functional copy of Ras restored the lifespan of heterozygous E1 mutants to that of wild-type flies and increased the survival of homozygous E1 mutants. E1 homozygous mutants also showed severe motor impairment. Our findings suggest that processes that impair the Ubiquitin Pathway are sufficient to cause early mortality. Reduced lifespan and motor impairment are seen in the human disease X-linked Infantile Spinal Muscular Atrophy, which is associated with mutation in human E1 warranting further analysis of these mutants as a potential animal model for study of this disease.
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Affiliation(s)
- Hsiu-Yu Liu
- Department of Oncological Sciences, The Mount Sinai School of Medicine, New York, New York, United States of America
| | - Cathie M. Pfleger
- Department of Oncological Sciences, The Mount Sinai School of Medicine, New York, New York, United States of America
- * E-mail:
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54
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Depleting gene activities in early Drosophila embryos with the "maternal-Gal4-shRNA" system. Genetics 2012; 193:51-61. [PMID: 23105012 DOI: 10.1534/genetics.112.144915] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In a developing Drosophila melanogaster embryo, mRNAs have a maternal origin, a zygotic origin, or both. During the maternal-zygotic transition, maternal products are degraded and gene expression comes under the control of the zygotic genome. To interrogate the function of mRNAs that are both maternally and zygotically expressed, it is common to examine the embryonic phenotypes derived from female germline mosaics. Recently, the development of RNAi vectors based on short hairpin RNAs (shRNAs) effective during oogenesis has provided an alternative to producing germline clones. Here, we evaluate the efficacies of: (1) maternally loaded shRNAs to knockdown zygotic transcripts and (2) maternally loaded Gal4 protein to drive zygotic shRNA expression. We show that, while Gal4-driven shRNAs in the female germline very effectively generate phenotypes for genes expressed maternally, maternally loaded shRNAs are not very effective at generating phenotypes for early zygotic genes. However, maternally loaded Gal4 protein is very efficient at generating phenotypes for zygotic genes expressed during mid-embryogenesis. We apply this powerful and simple method to unravel the embryonic functions of a number of pleiotropic genes.
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55
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Curtis BJ, Zraly CB, Dingwall AK. Drosophila LSD1-CoREST demethylase complex regulates DPP/TGFβ signaling during wing development. Genesis 2012; 51:16-31. [PMID: 22965777 DOI: 10.1002/dvg.22346] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Revised: 08/27/2012] [Accepted: 08/30/2012] [Indexed: 12/30/2022]
Abstract
The choice and timing of specific developmental pathways in organogenesis are determined by tissue-specific temporal and spatial cues that are acted upon to impart unique cellular and compartmental identities. A consequence of cellular signaling is the rapid transcriptional reprogramming of a wide variety of target genes. To overcome intrinsic epigenetic chromatin barriers to transcription modulation, histone modifying and remodeling complexes are employed. The deposition or erasure of specific covalent histone modifications, including acetylation, methylation, and ubiquitination are essential features of gene activation and repression. We have found that the activity of a specific class of histone demethylation enzymes is required for the specification of vein cell fates during Drosophila wing development. Genetic tests revealed that the Drosophila LSD1-CoREST complex is required for proper cell specification through regulation of the DPP/TGFβ pathway. An important finding from this analysis is that LSD1-CoREST functions through control of rhomboid expression in an EGFR-independent pathway.
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Affiliation(s)
- Brenda J Curtis
- Program in Molecular and Cellular Biochemistry, Stritch School of Medicine, Loyola University of Chicago, Maywood, Illinois, USA
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56
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Abstract
Synthetic biology is an area of biological research that combines science and engineering. Here, I merge the principles of synthetic biology and regulatory evolution to create a new species with a minimal set of known elements. Using preexisting transgenes and recessive mutations of Drosophila melanogaster, a transgenic population arises with small eyes and a different venation pattern that fulfils the criteria of a new species according to Mayr's Biological Species Concept. The population described here is the first transgenic organism that cannot hybridize with the original wild type population but remains fertile when crossed with other identical transgenic animals. I therefore propose the term "synthetic species" to distinguish it from "natural species", not only because it has been created by genetic manipulation, but also because it may never be able to survive outside the laboratory environment. The use of genetic engineering to design artificial species barriers could help us understand natural speciation and may have practical applications. For instance, the transition from transgenic organisms towards synthetic species could constitute a safety mechanism to avoid the hybridization of genetically modified animals with wild type populations, preserving biodiversity.
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Affiliation(s)
- Eduardo Moreno
- Institute of Cell Biology, University of Bern, Bern, Switzerland.
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57
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Abstract
Since the discovery of a single white-eyed male in a population of red eyed flies over 100 years ago (Morgan, 1910), the compound eye of the fruit fly, Drosophila melanogaster, has been a favorite experimental system for identifying genes that regulate various aspects of development. For example, a fair amount of what we know today about enzymatic pathways and vesicular transport is due to the discovery and subsequent characterization of eye color mutants such as white. Likewise, our present day understanding of organogenesis has been aided considerably by studies of mutations, such as eyeless, that either reduce or eliminate the compound eyes. But by far the phenotype that has provided levers into the greatest number of experimental fields has been the humble "rough" eye. The fly eye is composed of several hundred unit-eyes that are also called ommatidia. These unit eyes are packed into a hexagonal array of remarkable precision. The structure of the eye is so precise that it has been compared with that of a crystal (Ready et al., 1976). Even the slightest perturbations to the structure of the ommatidium can be visually detected by light or electron microscopy. The cause for this is two-fold: (1) any defect that affects the hexagonal geometry of a single ommatidium can and will disrupt the positioning of surrounding unit eyes thereby propagating structural flaws and (2) disruptions in genes that govern the development of even a single cell within an ommatidium will affect all unit eyes. In both cases, the effect is the visual magnification of even the smallest imperfection. Studies of rough eye mutants have provided key insights into the areas of cell fate specification, lateral inhibition, signal transduction, transcription factor networks, planar cell polarity, cell proliferation, and programmed cell death just to name a few. This review will attempt to summarize the key steps that are required to assemble each ommatidium.
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Affiliation(s)
- Justin P Kumar
- Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
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Maeng O, Son W, Chung J, Lee KS, Lee YH, Yoo OJ, Cha GH, Paik SG. The BTB/POZ-ZF transcription factor dPLZF is involved in Ras/ERK signaling during Drosophila wing development. Mol Cells 2012; 33:457-63. [PMID: 22544070 PMCID: PMC3887728 DOI: 10.1007/s10059-012-2179-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 02/29/2012] [Accepted: 03/09/2012] [Indexed: 10/28/2022] Open
Abstract
In Drosophila, broad complex, tramtrack, bric à brac (BTB)/poxvirus and zinc finger (POZ) transcription factors are essential regulators of development. We searched the Drosophila genome for BTB/POZ-ZF domains and discovered an unknown Drosophila gene, dPLZF, which encodes an orthologue of human PLZF. We then characterized the biological function of the dPLZF via genetic interaction analysis. Ectopic expression of dPLZF in the wing induced extra vein formation during wing development in Drosophila. Genetic interactions between dPLZF and Ras or extracellular signal-regulated kinase (ERK) significantly enhanced the formation of vein cells. On the other hand, loss-of-function mutations in dPLZF resulted in a dramatic suppression of the extra and ectopic vein formation induced by elevated Ras/ERK signaling. Moreover, dPLZF activity upregulated the expression of rhomboid (rho) and spitz, which perform crucial functions in vein cell formation in the developing wing. These results indicate that dPLZF is a transcription factor controlled by the Ras/ERK signaling pathway, which is a prominent regulator of vein cell formation during wing development in Drosophila.
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Affiliation(s)
- Oky Maeng
- Department of Infection Biology, College of Medicine and Brain Korea 21 Program for Medical Science, Chungnam National University, Daejeon 301-131,
Korea
| | - Wonseok Son
- Graduate School of Medical Science and Engineering, Biomedical Research Center, Korea Advanced Institute of Science and Technology, Daejeon 305-701,
Korea
| | - Jongkyeong Chung
- School of Biological Science, Seoul National University, Seoul 151-742,
Korea
| | - Kyu-Sun Lee
- Aging Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806,
Korea
| | - Young-Ha Lee
- Department of Infection Biology, College of Medicine and Brain Korea 21 Program for Medical Science, Chungnam National University, Daejeon 301-131,
Korea
| | - Ook-Joon Yoo
- Graduate School of Medical Science and Engineering, Biomedical Research Center, Korea Advanced Institute of Science and Technology, Daejeon 305-701,
Korea
| | - Guang-Ho Cha
- Department of Infection Biology, College of Medicine and Brain Korea 21 Program for Medical Science, Chungnam National University, Daejeon 301-131,
Korea
| | - Sang-Gi Paik
- Department of Biology, Chungnam National University, Daejeon 305-764,
Korea
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59
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Hamshou M, Van Damme EJM, Vandenborre G, Ghesquière B, Trooskens G, Gevaert K, Smagghe G. GalNAc/Gal-binding Rhizoctonia solani agglutinin has antiproliferative activity in Drosophila melanogaster S2 cells via MAPK and JAK/STAT signaling. PLoS One 2012; 7:e33680. [PMID: 22529896 PMCID: PMC3329507 DOI: 10.1371/journal.pone.0033680] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Accepted: 02/15/2012] [Indexed: 12/16/2022] Open
Abstract
Rhizoctonia solani agglutinin, further referred to as RSA, is a lectin isolated from the plant pathogenic fungus Rhizoctonia solani. Previously, we reported a high entomotoxic activity of RSA towards the cotton leafworm Spodoptera littoralis. To better understand the mechanism of action of RSA, Drosophila melanogaster Schneider S2 cells were treated with different concentrations of the lectin and FITC-labeled RSA binding was examined using confocal fluorescence microscopy. RSA has antiproliferative activity with a median effect concentration (EC(50)) of 0.35 µM. In addition, the lectin was typically bound to the cell surface but not internalized. In contrast, the N-acetylglucosamine-binding lectin WGA and the galactose-binding lectin PNA, which were both also inhibitory for S2 cell proliferation, were internalized whereas the mannose-binding lectin GNA did not show any activity on these cells, although it was internalized. Extracted DNA and nuclei from S2 cells treated with RSA were not different from untreated cells, confirming inhibition of proliferation without apoptosis. Pre-incubation of RSA with N-acetylgalactosamine clearly inhibited the antiproliferative activity by RSA in S2 cells, demonstrating the importance of carbohydrate binding. Similarly, the use of MEK and JAK inhibitors reduced the activity of RSA. Finally, RSA affinity chromatography of membrane proteins from S2 cells allowed the identification of several cell surface receptors involved in both signaling transduction pathways.
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Affiliation(s)
- Mohamad Hamshou
- Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
- Laboratory of Biochemistry and Glycobiology, Department of Molecular Biotechnology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Els J. M. Van Damme
- Laboratory of Biochemistry and Glycobiology, Department of Molecular Biotechnology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Gianni Vandenborre
- Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
- Laboratory of Biochemistry and Glycobiology, Department of Molecular Biotechnology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Bart Ghesquière
- Department of Medical Protein Research, VIB, Ghent, Belgium
- Department of Biochemistry, Ghent University, Ghent, Belgium
| | - Geert Trooskens
- Department of Mathematical Modelling, Statistics and Bioinformatics, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Kris Gevaert
- Department of Medical Protein Research, VIB, Ghent, Belgium
- Department of Biochemistry, Ghent University, Ghent, Belgium
| | - Guy Smagghe
- Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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60
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Kim SY, Kim JY, Malik S, Son W, Kwon KS, Kim C. Negative regulation of EGFR/MAPK pathway by Pumilio in Drosophila melanogaster. PLoS One 2012; 7:e34016. [PMID: 22514614 PMCID: PMC3326002 DOI: 10.1371/journal.pone.0034016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2011] [Accepted: 02/21/2012] [Indexed: 12/19/2022] Open
Abstract
In Drosophila melanogaster, specification of wing vein cells and sensory organ precursor (SOP) cells, which later give rise to a bristle, requires EGFR signaling. Here, we show that Pumilio (Pum), an RNA-binding translational repressor, negatively regulates EGFR signaling in wing vein and bristle development. We observed that loss of Pum function yielded extra wing veins and additional bristles. Conversely, overexpression of Pum eliminated wing veins and bristles. Heterozygotes for Pum produced no phenotype on their own, but greatly enhanced phenotypes caused by the enhancement of EGFR signaling. Conversely, over-expression of Pum suppressed the effects of ectopic EGFR signaling. Components of the EGFR signaling pathway are encoded by mRNAs that have Nanos Response Element (NRE)–like sequences in their 3’UTRs; NREs are known to bind Pum to confer regulation in other mRNAs. We show that these NRE-like sequences bind Pum and confer repression on a luciferase reporter in heterologous cells. Taken together, our evidence suggests that Pum functions as a negative regulator of EGFR signaling by directly targeting components of the pathway in Drosophila.
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Affiliation(s)
- Sung Yun Kim
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Yongbong-Dong, Gwangju, South Korea
| | - Ji Young Kim
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Yongbong-Dong, Gwangju, South Korea
- Aging Research Center, Korea Research Institute of Bioscience and Biotechnology, Yuseong-gu, Daejeon, South Korea
| | - Sumira Malik
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Yongbong-Dong, Gwangju, South Korea
| | - Wonseok Son
- Department of Biological Science, KAIST (Korea Advanced Institute of Science and Technology), Daejeon, South Korea
| | - Ki-Sun Kwon
- Aging Research Center, Korea Research Institute of Bioscience and Biotechnology, Yuseong-gu, Daejeon, South Korea
| | - Changsoo Kim
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Yongbong-Dong, Gwangju, South Korea
- * E-mail:
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61
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The role of the small GTPase Rap in Drosophila R7 photoreceptor specification. Proc Natl Acad Sci U S A 2012; 109:3844-9. [PMID: 22355117 DOI: 10.1073/pnas.1115108109] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Drosophila R7 photoreceptor provides an excellent model system with which to study how cells receive and "decode" signals that specify cell fate. R7 is specified by the combined actions of the receptor tyrosine kinase (RTK) and Notch (N) signaling pathways. These pathways interact in a complex manner that includes antagonistic effects on photoreceptor specification: RTK promotes the photoreceptor fate, whereas N inhibits. Although other photoreceptors are subject to only mild N activation, R7 experiences a high-level N signal. To counter this effect and to ensure that the cell is specified as a photoreceptor, a high RTK signal is transduced in the cell. Thus, there are two levels of RTK transduction in the photoreceptors: in R7 it is high, whereas in others it is low. Here, we address how this high-level RTK signal is transduced in R7 and find that, in addition to Ras, another small GTPase, Rap, is also engaged. Thus, when N activity is high, a robust RTK signal operates that uses both Ras and Rap, but when N activity is low, only a mild RTK signal is transduced and Ras alone suffices for the purpose.
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62
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Katanaev VL, Kryuchkov MV. The eye of Drosophila as a model system for studying intracellular signaling in ontogenesis and pathogenesis. BIOCHEMISTRY (MOSCOW) 2012; 76:1556-81. [DOI: 10.1134/s0006297911130116] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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63
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Gafuik C, Steller H. A gain-of-function germline mutation in Drosophila ras1 affects apoptosis and cell fate during development. PLoS One 2011; 6:e23535. [PMID: 21858158 PMCID: PMC3155559 DOI: 10.1371/journal.pone.0023535] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Accepted: 07/19/2011] [Indexed: 12/30/2022] Open
Abstract
The RAS/MAPK signal transduction pathway is an intracellular signaling cascade that transmits environmental signals from activated receptor tyrosine kinases (RTKs) on the cell surface and other endomembranes to transcription factors in the nucleus, thereby linking extracellular stimuli to changes in gene expression. Largely as a consequence of its role in oncogenesis, RAS signaling has been the subject of intense research efforts for many years. More recently, it has been shown that milder perturbations in Ras signaling during embryogenesis also contribute to the etiology of a group of human diseases. Here we report the identification and characterization of the first gain-of-function germline mutation in Drosophila ras1 (ras85D), the Drosophila homolog of human K-ras, N-ras and H-ras. A single amino acid substitution (R68Q) in the highly conserved switch II region of Ras causes a defective protein with reduced intrinsic GTPase activity, but with normal sensitivity to GAP stimulation. The ras1R68Q mutant is homozygous viable but causes various developmental defects associated with elevated Ras signaling, including cell fate changes and ectopic survival of cells in the nervous system. These biochemical and functional properties are reminiscent of germline Ras mutants found in patients afflicted with Noonan, Costello or cardio-facio-cutaneous syndromes. Finally, we used ras1R68Q to identify novel genes that interact with Ras and suppress cell death.
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Affiliation(s)
- Christopher Gafuik
- Howard Hughes Medical Institute, The Rockefeller University, New York, New York, United States of America
| | - Hermann Steller
- Howard Hughes Medical Institute, The Rockefeller University, New York, New York, United States of America
- * E-mail:
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Mouchel-Vielh E, Rougeot J, Decoville M, Peronnet F. The MAP kinase ERK and its scaffold protein MP1 interact with the chromatin regulator Corto during Drosophila wing tissue development. BMC DEVELOPMENTAL BIOLOGY 2011; 11:17. [PMID: 21401930 PMCID: PMC3062617 DOI: 10.1186/1471-213x-11-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Accepted: 03/14/2011] [Indexed: 11/12/2022]
Abstract
Background Mitogen-activated protein kinase (MAPK) cascades (p38, JNK, ERK pathways) are involved in cell fate acquisition during development. These kinase modules are associated with scaffold proteins that control their activity. In Drosophila, dMP1, that encodes an ERK scaffold protein, regulates ERK signaling during wing development and contributes to intervein and vein cell differentiation. Functional relationships during wing development between a chromatin regulator, the Enhancer of Trithorax and Polycomb Corto, ERK and its scaffold protein dMP1, are examined here. Results Genetic interactions show that corto and dMP1 act together to antagonize rolled (which encodes ERK) in the future intervein cells, thus promoting intervein fate. Although Corto, ERK and dMP1 are present in both cytoplasmic and nucleus compartments, they interact exclusively in nucleus extracts. Furthermore, Corto, ERK and dMP1 co-localize on several sites on polytene chromosomes, suggesting that they regulate gene expression directly on chromatin. Finally, Corto is phosphorylated. Interestingly, its phosphorylation pattern differs between cytoplasm and nucleus and changes upon ERK activation. Conclusions Our data therefore suggest that the Enhancer of Trithorax and Polycomb Corto could participate in regulating vein and intervein genes during wing tissue development in response to ERK signaling.
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Affiliation(s)
- Emmanuèle Mouchel-Vielh
- Université Pierre et Marie Curie-Paris 6; Centre National de la Recherche Scientifique; UMR7622, Laboratoire de Biologie du Développement, Equipe Chromatine et Développement, 75005 Paris, France.
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Biteau B, Jasper H. EGF signaling regulates the proliferation of intestinal stem cells in Drosophila. Development 2011; 138:1045-55. [PMID: 21307097 DOI: 10.1242/dev.056671] [Citation(s) in RCA: 222] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Precise control of somatic stem cell proliferation is crucial to ensure maintenance of tissue homeostasis in high-turnover tissues. In Drosophila, intestinal stem cells (ISCs) are essential for homeostatic turnover of the intestinal epithelium and ensure epithelial regeneration after tissue damage. To accommodate these functions, ISC proliferation is regulated dynamically by various growth factors and stress signaling pathways. How these signals are integrated is poorly understood. Here, we show that EGF receptor signaling is required to maintain the proliferative capacity of ISCs. The EGF ligand Vein is expressed in the muscle surrounding the intestinal epithelium, providing a permissive signal for ISC proliferation. We find that the AP-1 transcription factor FOS serves as a convergence point for this signal and for the Jun N-terminal kinase (JNK) pathway, which promotes ISC proliferation in response to stress. Our results support the notion that the visceral muscle serves as a functional 'niche' for ISCs, and identify FOS as a central integrator of a niche-derived permissive signal with stress-induced instructive signals, adjusting ISC proliferation to environmental conditions.
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Affiliation(s)
- Benoît Biteau
- Department of Biology, University of Rochester, River Campus Box 270211, Rochester, NY 14627, USA
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66
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Drosophila Ras/MAPK signalling regulates innate immune responses in immune and intestinal stem cells. EMBO J 2011; 30:1123-36. [PMID: 21297578 DOI: 10.1038/emboj.2011.4] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Accepted: 12/22/2010] [Indexed: 11/08/2022] Open
Abstract
Immune signalling pathways need to be tightly regulated as overactivation of these pathways can result in chronic inflammatory diseases and cancer. NF-κB signalling and associated innate immune pathways are crucial in the first line of defense against infection in all animals. In a genome-wide RNAi screen for modulators of Drosophila immune deficiency (IMD)/NF-κB signalling, we identified components of the Ras/MAPK pathway as essential for suppression of IMD pathway activity, even in the absence of an immune challenge. Downregulation of Ras/MAPK activity mimics the induction of innate immune responses by microbial patterns. Conversely, ectopic Ras/MAPK pathway activation results in the suppression of Drosophila IMD/NF-κB signalling. Mechanistically, we show that the Ras/MAPK pathway acts by inducing transcription of the IMD pathway inhibitor Pirk/Rudra/PIMS. Finally, in vivo experiments demonstrate a requirement for Ras/MAPK signalling in restricting innate immune responses in haemocytes, fat body and adult intestinal stem cells. Our observations provide an example of a pathway that promotes cell proliferation and has simultaneously been utilized to limit the immune response.
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67
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Overexpression of transglutaminase in the Drosophila wing imaginal disc induced an extra wing crossvein phenotype. Biosci Biotechnol Biochem 2010; 74:2494-6. [PMID: 21150110 DOI: 10.1271/bbb.100449] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
To determine the roles of Drosophila transglutaminase-A (dTG-A), we examined a phenotype induced through ectopic expression of dTG-A. Overexpression of dTG-A in the wing imaginal disc induced an extra wing crossvein phenotype. This phenotype was suppressed by crossing with epidermal growth factor receptor (Egfr) signaling pathway mutant flies. These results indicate that this phenotype, induced by dTG-A, is related to enhancement of the Egfr signaling pathway.
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68
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Morozova T, Hackett J, Sedaghat Y, Sonnenfeld M. The Drosophila jing gene is a downstream target in the Trachealess/Tango tracheal pathway. Dev Genes Evol 2010; 220:191-206. [PMID: 21061019 DOI: 10.1007/s00427-010-0339-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Accepted: 10/08/2010] [Indexed: 11/28/2022]
Abstract
Primary branching in the Drosophila trachea is regulated by the Trachealess (Trh) and Tango (Tgo) basic helix-loop-helix-PAS (bHLH-PAS) heterodimers, the POU protein Drifter (Dfr)/Ventral Veinless (Vvl), and the Pointed (Pnt) ETS transcription factor. The jing gene encodes a zinc finger protein also required for tracheal development. Three Trh/Tgo DNA-binding sites, known as CNS midline elements, in 1.5 kb of jing 5′ cis-regulatory sequence (jing1.5) previously suggested a downstream role for jing in the pathway. Here, we show that jing is a direct downstream target of Trh/Tgo and that Vvl and Pnt are also involved in jing tracheal activation. In vivo lacZ enhancer detection assays were used to identify cis-regulatory elements mediating embryonic expression patterns of jing. A 2.8-kb jing enhancer (jing2.8) drove lacZ expression in all tracheal cell lineages, the CNS midline and Engrailed-positive segmental stripes, mimicking endogenous jing expression. A 1.3-kb element within jing2.8 drove expression that was restricted to Engrailed-positive CNS midline cells and segmental ectodermal stripes. Surprisingly, jing1.5-lacZ expression was restricted to tracheal fusion cells despite the presence of consensus DNA-binding sites for bHLH-PAS, ETS, and POU domain transcription factors. Given the absence of Trh/Tgo DNA-binding sites in the jing1.3 enhancer, these results are consistent with previous observations suggesting a combinatorial basis to Trh-/Tgo-mediated transcriptional regulation in the trachea.
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Affiliation(s)
- Tatiana Morozova
- Faculty of Medicine, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
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69
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Sonnenfeld M, Morozova T, Hackett J, Sun X. Drosophila Jing is part of the breathless fibroblast growth factor receptor positive feedback loop. Dev Genes Evol 2010; 220:207-20. [PMID: 21061018 DOI: 10.1007/s00427-010-0342-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Accepted: 10/19/2010] [Indexed: 11/28/2022]
Abstract
In the developing Drosophila trachea, extensive cell migration lays the foundation for an elaborate network of tubules to form. This process is controlled by the Drosophila fibroblast growth factor receptor, known as Breathless (Btl), whose expression is activated by the Trachealess (Trh) and Tango (Tgo) basic helix-loop-helix (bHLH)-PAS transcription factors. We previously identified the jing zinc finger transcription factor as a gene sensitive to the dosage of bHLH-PAS transcriptional activity and showed that its mutations interact genetically with those of trh and btl. Here, we demonstrate that jing is required for btl expression in the branching trachea and dominantly interacts with known regulators of btl expression, including the ETS and POU transcription factors, pointed, and drifter/ventral veinless, respectively. Furthermore, the zinc finger-containing C-terminus of Jing associates with a btl tracheal enhancer in a Trh/Tgo-dependent manner in chromatin immunoprecipitation assays in vitro and interferes with btl in vitro and in vivo. Together, our results support a model by which Jing/Trh/Tgo complexes regulate btl transcript levels during primary tracheal branching.
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Affiliation(s)
- Margaret Sonnenfeld
- Faculty of Medicine, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada.
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70
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β-arrestin Kurtz inhibits MAPK and Toll signalling in Drosophila development. EMBO J 2010; 29:3222-35. [PMID: 20802461 DOI: 10.1038/emboj.2010.202] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2010] [Accepted: 07/26/2010] [Indexed: 01/14/2023] Open
Abstract
β-Arrestins have been implicated in the regulation of multiple signalling pathways. However, their role in organism development is not well understood. In this study, we report a new in vivo function of the Drosophila β-arrestin Kurtz (Krz) in the regulation of two distinct developmental signalling modules: MAPK ERK and NF-κB, which transmit signals from the activated receptor tyrosine kinases (RTKs) and the Toll receptor, respectively. Analysis of the expression of effectors and target genes of Toll and the RTK Torso in krz maternal mutants reveals that Krz limits the activity of both pathways in the early embryo. Protein interaction studies suggest a previously uncharacterized mechanism for ERK inhibition: Krz can directly bind and sequester an inactive form of ERK, thus preventing its activation by the upstream kinase, MEK. A simultaneous dysregulation of different signalling systems in krz mutants results in an abnormal patterning of the embryo and severe developmental defects. Our findings uncover a new in vivo function of β-arrestins and present a new mechanism of ERK inhibition by the Drosophila β-arrestin Krz.
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71
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Yan H, Jahanshahi M, Horvath EA, Liu HY, Pfleger CM. Rabex-5 ubiquitin ligase activity restricts Ras signaling to establish pathway homeostasis in Drosophila. Curr Biol 2010; 20:1378-82. [PMID: 20655224 DOI: 10.1016/j.cub.2010.06.058] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 06/18/2010] [Accepted: 06/18/2010] [Indexed: 01/01/2023]
Abstract
The Ras signaling pathway allows cells to translate external cues into diverse biological responses. Depending on context and the threshold reached, Ras signaling can promote growth, proliferation, differentiation, or cell survival. Failure to maintain precise control of Ras can have adverse physiological consequences. Indeed, excess Ras signaling disrupts developmental patterning and causes developmental disorders [1, 2], and in mature tissues, it can lead to cancer [3-5]. We identify Rabex-5 as a new component of Ras signaling crucial for achieving proper pathway outputs in multiple contexts in vivo. We show that Drosophila Rabex-5 restricts Ras signaling to establish organism size, wing vein pattern, and eye versus antennal fate. Rabex-5 has both Rab5 guanine nucleotide exchange factor (GEF) activity that regulates endocytic trafficking [6] and ubiquitin ligase activity [7, 8]. Surprisingly, overexpression studies demonstrate that Rabex-5 ubiquitin ligase activity, not its Rab5 GEF activity, is required to restrict wing vein specification and to suppress the eye phenotypes of oncogenic Ras expression. Furthermore, genetic interaction experiments indicate that Rabex-5 acts at the step of Ras, and tissue culture studies show that Rabex-5 promotes Ras ubiquitination. Together, these findings reveal a new mechanism for attenuating Ras signaling in vivo and suggest an important role for Rabex-5-mediated Ras ubiquitination in pathway homeostasis.
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Affiliation(s)
- Hua Yan
- Department of Oncological Sciences, The Mount Sinai School of Medicine, New York, NY 10029, USA
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72
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Aron L, Klein P, Pham TT, Kramer ER, Wurst W, Klein R. Pro-survival role for Parkinson's associated gene DJ-1 revealed in trophically impaired dopaminergic neurons. PLoS Biol 2010; 8:e1000349. [PMID: 20386724 PMCID: PMC2850379 DOI: 10.1371/journal.pbio.1000349] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Accepted: 02/24/2010] [Indexed: 12/16/2022] Open
Abstract
A mouse genetic study reveals a novel cell-survival role for the Parkinson's disease-associated gene DJ-1 in dopaminergic neurons that have reduced support from endogenous survival factors. The mechanisms underlying the selective death of substantia nigra (SN) neurons in Parkinson disease (PD) remain elusive. While inactivation of DJ-1, an oxidative stress suppressor, causes PD, animal models lacking DJ-1 show no overt dopaminergic (DA) neuron degeneration in the SN. Here, we show that aging mice lacking DJ-1 and the GDNF-receptor Ret in the DA system display an accelerated loss of SN cell bodies, but not axons, compared to mice that only lack Ret signaling. The survival requirement for DJ-1 is specific for the GIRK2-positive subpopulation in the SN which projects exclusively to the striatum and is more vulnerable in PD. Using Drosophila genetics, we show that constitutively active Ret and associated Ras/ERK, but not PI3K/Akt, signaling components interact genetically with DJ-1. Double loss-of-function experiments indicate that DJ-1 interacts with ERK signaling to control eye and wing development. Our study uncovers a conserved interaction between DJ-1 and Ret-mediated signaling and a novel cell survival role for DJ-1 in the mouse. A better understanding of the molecular connections between trophic signaling, cellular stress and aging could uncover new targets for drug development in PD. The major pathological event in Parkinson disease is the loss of dopaminergic neurons in a midbrain structure, the substantia nigra. The study of familial Parkinson disease has uncovered several disease-associated genes, including DJ-1. Subsequent studies have suggested that the DJ-1 protein is a suppressor of oxidative stress that might modify signaling pathways that regulate cell survival. However, because animal models lacking DJ-1 function do not show dopaminergic neurodegeneration, the function(s) of DJ-1 in vivo remain unclear. Using mouse genetics, we found that DJ-1 is required for survival of neurons of the substantia nigra only in aging conditions and only in neurons that are partially impaired in receiving trophic signals. Aging mice that lack DJ-1 and Ret, a receptor for a neuronal survival factor, lose more dopaminergic neurons in the substantia nigra as compared with aging mice that lack only Ret. Using the fruit fly Drosophila, we determined that DJ-1 interacts with constitutively active Ret and with its associated downstream signaling pathways. Therefore, understanding the molecular connections between trophic signaling, cellular stress and aging could facilitate the identification of new targets for drug development in Parkinson Disease.
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Affiliation(s)
- Liviu Aron
- Department of Molecular Neurobiology, Max Planck Institute of Neurobiology, Martinsried, Germany
| | - Pontus Klein
- Department of Molecular Neurobiology, Max Planck Institute of Neurobiology, Martinsried, Germany
| | - Thu-Trang Pham
- Helmholtz Center Munich, Technical University of Munich, National Center for Dementia Research, Neuherberg, Germany
| | | | - Wolfgang Wurst
- Helmholtz Center Munich, Technical University of Munich, National Center for Dementia Research, Neuherberg, Germany
| | - Rüdiger Klein
- Department of Molecular Neurobiology, Max Planck Institute of Neurobiology, Martinsried, Germany
- * E-mail:
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73
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Rodriguez MCS, Petersen M, Mundy J. Mitogen-activated protein kinase signaling in plants. ANNUAL REVIEW OF PLANT BIOLOGY 2010; 61:621-49. [PMID: 20441529 DOI: 10.1146/annurev-arplant-042809-112252] [Citation(s) in RCA: 676] [Impact Index Per Article: 48.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Eukaryotic mitogen-activated protein kinase (MAPK) cascades have evolved to transduce environmental and developmental signals into adaptive and programmed responses. MAPK cascades relay and amplify signals via three types of reversibly phosphorylated kinases leading to the phosphorylation of substrate proteins, whose altered activities mediate a wide array of responses, including changes in gene expression. Cascades may share kinase components, but their signaling specificity is maintained by spaciotemporal constraints and dynamic protein-protein interactions and by mechanisms that include crossinhibition, feedback control, and scaffolding. Plant MAPK cascades regulate numerous processes, including stress and hormonal responses, innate immunity, and developmental programs. Genetic analyses have uncovered several predominant MAPK components shared by several of these processes including the Arabidopsis thaliana MAPKs MPK3, 4, and 6 and MAP2Ks MKK1, 2, 4, and 5. Future work needs to focus on identifying substrates of MAPKs, and on understanding how specificity is achieved among MAPK signaling pathways.
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74
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Tsui MM, York JD. Roles of inositol phosphates and inositol pyrophosphates in development, cell signaling and nuclear processes. ACTA ACUST UNITED AC 2009; 50:324-37. [PMID: 20006638 DOI: 10.1016/j.advenzreg.2009.12.002] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Marco M Tsui
- Department of Pharmacology and Cancer Biology, Howard Hughes Medical Institute, Duke University Medical Center, Box 3813, Durham, NC 27710, USA
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75
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The tyrosine kinase Stitcher activates Grainy head and epidermal wound healing in Drosophila. Nat Cell Biol 2009; 11:890-5. [PMID: 19525935 DOI: 10.1038/ncb1898] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2008] [Accepted: 03/23/2009] [Indexed: 01/25/2023]
Abstract
Epidermal injury initiates a cascade of inflammation, epithelial remodelling and integument repair at wound sites. The regeneration of the extracellular barrier and damaged tissue repair rely on the precise orchestration of epithelial responses triggered by the injury. Grainy head (Grh) transcription factors induce gene expression to crosslink the extracellular barrier in wounded flies and mice. However, the activation mechanisms and functions of Grh factors in re-epithelialization remain unknown. Here we identify stitcher (stit), a new Grh target in Drosophila melanogaster. stit encodes a Ret-family receptor tyrosine kinase required for efficient epidermal wound healing. Live imaging analysis reveals that Stit promotes actin cable assembly during wound re-epithelialization. Stit activation also induces extracellular signal-regulated kinase (ERK) phosphorylation along with the Grh-dependent expression of stit and barrier repair genes at the wound sites. The transcriptional stimulation of stit on injury triggers a positive feedback loop increasing the magnitude of epithelial responses. Thus, Stit activation upon wounding coordinates cytoskeletal rearrangements and the level of Grh-mediated transcriptional wound responses.
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76
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Fischer M, Raabe T, Heisenberg M, Sendtner M. Drosophila RSK negatively regulates bouton number at the neuromuscular junction. Dev Neurobiol 2009; 69:212-20. [PMID: 19160443 DOI: 10.1002/dneu.20700] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Ribosomal S6 kinases (RSKs) are growth factor-regulated serine-threonine kinases participating in the RAS-ERK signaling pathway. RSKs have been implicated in memory formation in mammals and flies. To characterize the function of RSK at the synapse level, we investigated the effect of mutations in the rsk gene on the neuromuscular junction (NMJ) in Drosophila larvae. Immunostaining revealed transgenic expressed RSK in presynaptic regions. In mutants with a full deletion or an N-terminal partial deletion of rsk, an increased bouton number was found. Restoring the wild-type rsk function in the null mutant with a genomic rescue construct reverted the synaptic phenotype, and overexpression of the rsk-cDNA in motoneurons reduced bouton numbers. Based on previous observations that RSK interacts with the Drosophila ERK homologue Rolled, genetic epistasis experiments were performed with loss- and gain-of-function mutations in Rolled. These experiments provided evidence that RSK mediates its negative effect on bouton formation at the Drosophila NMJ by inhibition of ERK signaling.
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Affiliation(s)
- Matthias Fischer
- Institute for Clinical Neurobiology, University of Würzburg, Würzburg 97078, Germany.
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77
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Aberg E, Torgersen KM, Johansen B, Keyse SM, Perander M, Seternes OM. Docking of PRAK/MK5 to the atypical MAPKs ERK3 and ERK4 defines a novel MAPK interaction motif. J Biol Chem 2009; 284:19392-401. [PMID: 19473979 DOI: 10.1074/jbc.m109.023283] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ERK3 and ERK4 are atypical MAPKs in which the canonical TXY motif within the activation loop of the classical MAPKs is replaced by SEG. Both ERK3 and ERK4 bind, translocate, and activate the MAPK-activated protein kinase (MK) 5. The classical MAPKs ERK1/2 and p38 interact with downstream MKs (RSK1-3 and MK2-3, respectively) through conserved clusters of acidic amino acids, which constitute the common docking (CD) domain. In contrast to the classical MAPKs, the interaction between ERK3/4 and MK5 is strictly dependent on phosphorylation of the SEG motif of these kinases. Here we report that the conserved CD domain is dispensable for the interaction of ERK3 and ERK4 with MK5. Using peptide overlay assays, we have defined a novel MK5 interaction motif (FRIEDE) within both ERK4 and ERK3 that is essential for binding to the C-terminal region of MK5. This motif is located within the L16 extension lying C-terminal to the CD domain in ERK3 and ERK4 and a single isoleucine to lysine substitution in FRIEDE totally abrogates binding, activation, and translocation of MK5 by both ERK3 and ERK4. These findings are the first to demonstrate binding of a physiological substrate via this region of the L16 loop in a MAPK. Furthermore, the link between activation loop phosphorylation and accessibility of the FRIEDE interaction motif suggests a switch mechanism for these atypical MAPKs in which the phosphorylation status of the activation loop regulates the ability of both ERK3 and ERK4 to bind to a downstream effector.
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Affiliation(s)
- Espen Aberg
- Institutes of Pharmacy, Medical Biology, University of Tromsø, N-9037 Tromsø, Norway
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78
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Terriente-Félix A, de Celis JF. Osa, a subunit of the BAP chromatin-remodelling complex, participates in the regulation of gene expression in response to EGFR signalling in the Drosophila wing. Dev Biol 2009; 329:350-61. [PMID: 19306864 DOI: 10.1016/j.ydbio.2009.03.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Revised: 03/05/2009] [Accepted: 03/12/2009] [Indexed: 01/27/2023]
Abstract
Gene expression is regulated in part by protein complexes containing ATP-dependent chromatin-remodelling factors of the SWI/SNF family. In Drosophila there is only one SWI/SNF protein, named Brahma, which forms the catalytic subunit of two complexes composed of different proteins. The protein Osa defines the BAP complex, and the proteins Polybromo and Bap170 are only present in the complex named PBAP. In this work we have analysed the functional requirements of Osa during Drosophila wing development, and found that osa is needed for cell growth and survival in the wing imaginal disc, and for the correct patterning of sensory organs, veins and the wing margin. Other members of the BAP complex, such as Snr1, Bap55, Mor and Brm, also share these functions of Osa. We focused on the requirement of Osa during the formation of the wing veins. Genetic interactions between osa alleles and mutations affecting the activity of the EGFR pathway suggest that one aspect of Osa is intimately related to the response to EGFR activity. Thus, loss of osa and EGFR signalling results in similar wing vein phenotypes, and osa alleles enhance the loss of veins caused by reduced EGFR activity. In addition, Osa is required for the expression of several targets of EGFR signalling, such as Delta, rhomboid and argos. We suggest that one role of Osa and Brm in the wing is to establish a chromatin environment in the regulatory regions of EGFR target genes, making them available for both activators and repressors and facilitating transcription in response to EGFR signalling.
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Affiliation(s)
- Ana Terriente-Félix
- Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
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79
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Armstrong SP, Caunt CJ, McArdle CA. Gonadotropin-releasing hormone and protein kinase C signaling to ERK: spatiotemporal regulation of ERK by docking domains and dual-specificity phosphatases. Mol Endocrinol 2009; 23:510-9. [PMID: 19179479 DOI: 10.1210/me.2008-0333] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Activated ERK translocates to the nucleus to regulate transcription. Spatiotemporal aspects of this response dictate biological consequences and are influenced by dual-specificity phosphatases (DUSPs) that can scaffold and dephosphorylate ERK. In HeLa cells, GnRH causes transient and protein kinase C (PKC)-dependent ERK activation, but termination mechanisms are unknown. We now explore DUSP roles using short inhibitory RNA to knock down endogenous ERK, adenoviruses to express GnRH receptors and add-back ERK2-GFP, and automated microscopy to monitor ERK location and activation. GnRH caused rapid and transient increases in dual phosphorylated ERK2 (ppERK2) and nuclear to cytoplasmic ERK2-green fluorescent protein (GFP) ratio, whereas responses to a PKC-activating phorbol ester were more sustained. In cells expressing D319N ERK2-GFP (D319N mutation impairs docking-domain-dependent binding to DUSPs), GnRH caused more sustained increases in ppERK2 and nuclear to cytoplasmic ERK2-GFP ratio and also had more pronounced effects on Egr-1 luciferase (a transcriptional reporter for ERK activation). Cycloheximide caused more sustained effects of GnRH and phorbol ester on ppERK, suggesting termination by nuclear-inducible DUSPs. GnRH also increased expression of nuclear-inducible DUSP1 and -4, but their knockdown did not alter GnRH-mediated ERK signaling. Screening a short inhibitory RNA library targeting 16 DUSPs (nuclear-inducible DUSPs, cytoplasmic ERK MAPK phosphatases, c-Jun N-terminal kinase/p38 MAPK phosphatases, and atypical DUSPs) revealed GnRH effects to be influenced by DUSPs 5, 9, 10, 16, and 3 (i.e. by each DUSP class). Thus, GnRH-mediated ERK responses (like PKC-mediated ERK responses) are dependent on protein neosynthesis and docking-domain-dependent binding, but for GnRH activation (unlike PKC activation), this does not reflect dependence on nuclear-inducible DUSPs. Termination of these GnRH effects is apparently dependent upon a preexisting rapid turnover protein.
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Affiliation(s)
- Stephen Paul Armstrong
- Department of Clinical Sciences at South Bristol, University of Bristol, Bristol BS1 3NY, UK
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80
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Levin-Salomon V, Kogan K, Ahn NG, Livnah O, Engelberg D. Isolation of intrinsically active (MEK-independent) variants of the ERK family of mitogen-activated protein (MAP) kinases. J Biol Chem 2008; 283:34500-10. [PMID: 18829462 PMCID: PMC3259889 DOI: 10.1074/jbc.m806443200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Revised: 09/29/2008] [Indexed: 11/06/2022] Open
Abstract
MAPKs are key components of cell signaling pathways with a unique activation mechanism: i.e. dual phosphorylation of neighboring threonine and tyrosine residues. The ERK enzymes form a subfamily of MAPKs involved in proliferation, differentiation, development, learning, and memory. The exact role of each Erk molecule in these processes is not clear. An efficient strategy for addressing this question is to activate individually each molecule, for example, by expressing intrinsically active variants of them. However, such molecules were not produced so far. Here, we report on the isolation, via a specifically designed genetic screen, of six variants (each carries a point mutation) of the yeast MAPK Mpk1/Erk that are active, independent of upstream phosphorylation. One of the activating mutations, R68S, occurred in a residue conserved in the mammalian Erk1 (Arg-84) and Erk2 (Arg-65) and in the Drosophila ERK Rolled (Arg-80). Replacing this conserved Arg with Ser rendered these MAPKs intrinsically active to very high levels when tested in vitro as recombinant proteins. Combination of the Arg to Ser mutation with the sevenmaker mutation (producing Erk2(R65S+D319N) and Rolled(R80S+D334N)) resulted in even higher activity (45 and 70%, respectively, in reference to fully active dually phosphorylated Erk2 or Rolled). Erk2(R65S) and Erk2(R65S+D319N) were found to be spontaneously active also when expressed in human HEK293 cells. We further revealed the mechanism of action of the mutants and show that it involves acquisition of autophosphorylation activity. Thus, a first generation of Erk molecules that are spontaneously active in vitro and in vivo has been obtained.
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Affiliation(s)
- Vered Levin-Salomon
- The Department of Biological Chemistry,
The Alexander Silberman Institute of Life Sciences, The Hebrew University of
Jerusalem, Jerusalem 91904, Israel, The Wolfson
Centre for Applied Structural Biology, The Hebrew University of Jerusalem,
Jerusalem 91904, Israel, and the Department of
Chemistry and Biochemistry, Howard Hughes Medical Institute, University of
Colorado, Boulder, Colorado 80309
| | - Konstantin Kogan
- The Department of Biological Chemistry,
The Alexander Silberman Institute of Life Sciences, The Hebrew University of
Jerusalem, Jerusalem 91904, Israel, The Wolfson
Centre for Applied Structural Biology, The Hebrew University of Jerusalem,
Jerusalem 91904, Israel, and the Department of
Chemistry and Biochemistry, Howard Hughes Medical Institute, University of
Colorado, Boulder, Colorado 80309
| | - Natalie G. Ahn
- The Department of Biological Chemistry,
The Alexander Silberman Institute of Life Sciences, The Hebrew University of
Jerusalem, Jerusalem 91904, Israel, The Wolfson
Centre for Applied Structural Biology, The Hebrew University of Jerusalem,
Jerusalem 91904, Israel, and the Department of
Chemistry and Biochemistry, Howard Hughes Medical Institute, University of
Colorado, Boulder, Colorado 80309
| | - Oded Livnah
- The Department of Biological Chemistry,
The Alexander Silberman Institute of Life Sciences, The Hebrew University of
Jerusalem, Jerusalem 91904, Israel, The Wolfson
Centre for Applied Structural Biology, The Hebrew University of Jerusalem,
Jerusalem 91904, Israel, and the Department of
Chemistry and Biochemistry, Howard Hughes Medical Institute, University of
Colorado, Boulder, Colorado 80309
| | - David Engelberg
- The Department of Biological Chemistry,
The Alexander Silberman Institute of Life Sciences, The Hebrew University of
Jerusalem, Jerusalem 91904, Israel, The Wolfson
Centre for Applied Structural Biology, The Hebrew University of Jerusalem,
Jerusalem 91904, Israel, and the Department of
Chemistry and Biochemistry, Howard Hughes Medical Institute, University of
Colorado, Boulder, Colorado 80309
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81
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Mouchel-Vielh E, Bloyer S, Salvaing J, Randsholt NB, Peronnet F. Involvement of the MP1 scaffold protein in ERK signaling regulation during Drosophila wing development. Genes Cells 2008; 13:1099-111. [PMID: 18823331 DOI: 10.1111/j.1365-2443.2008.01231.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Mitogen-activated protein kinase (MAPK) cascades are evolutionary conserved transduction pathways involved in many cellular processes. Kinase modules are associated with scaffold proteins that regulate signaling by providing critical spatial and temporal specificities. Some of these scaffold proteins have been shown to be conserved, both in sequence and function. In mouse, the scaffold MP1 (MEK Partner 1) forms a signaling complex with MEK1 and ERK1. In this work, we focus on Drosophila MP1 (dMP1). We show that dMP1 is expressed ubiquitously during embryonic and larval development. By in vitro and in vivo experiments, we show that dMP1 is located in the cytoplasm and the nuclei, and that it interacts with MEK and ERK. Genetic studies with transgenic Drosophila lines allowing either dMP1 over-expression or dMP1 down-regulation by RNA interference highlight dMP1 function in the control of cell differentiation during development of the Drosophila wing.
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Affiliation(s)
- Emmanuèle Mouchel-Vielh
- UMR 7622-Biologie du Développement; CNRS-Université Pierre et Marie Curie Paris 6 (UPMC), 9, quai Saint-Bernard, 75005 Paris, France.
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82
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Caunt CJ, Armstrong SP, Rivers CA, Norman MR, McArdle CA. Spatiotemporal regulation of ERK2 by dual specificity phosphatases. J Biol Chem 2008; 283:26612-23. [PMID: 18650424 PMCID: PMC2546534 DOI: 10.1074/jbc.m801500200] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Although many stimuli activate extracellular signal-regulated kinases 1 and
2 (ERK1/2), the kinetics and compartmentalization of ERK1/2 signals are
stimulus-dependent and dictate physiological consequences. ERKs can be
inactivated by dual specificity phosphatases (DUSPs), notably the MAPK
phosphatases (MKPs) and atypical DUSPs, that can both dephosphorylate and
scaffold ERK1/2. Using a cell imaging model (based on knockdown of endogenous
ERKs and add-back of wild-type or mutated ERK2-GFP reporters), we explored
possible effects of DUSPs on responses to transient or sustained ERK2
activators (epidermal growth factor and phorbol 12,13-dibutyrate,
respectively). For both stimuli, a D319N mutation (which impairs DUSP binding)
increased ERK2 activity and reduced nuclear accumulation. These stimuli also
increased mRNA levels for eight DUSPs. In a short inhibitory RNA screen, 12 of
16 DUSPs influenced ERK2 responses. These effects were evident among nuclear
inducible MKP, cytoplasmic ERK MKP, JNK/p38 MKP, and atypical DUSP subtypes
and, with the exception of the nuclear inducible MKPs, were paralleled by
corresponding changes in Egr-1 luciferase activation. Simultaneous removal of
all JNK/p38 MKPs or nuclear inducible MKPs revealed them as positive and
negative regulators of ERK2 signaling, respectively. The effects of JNK/p38
MKP short inhibitory RNAs were not dependent on protein neosynthesis but were
reversed in the presence of JNK and p38 kinase inhibitors, indicating
DUSP-mediated cross-talk between MAPK pathways. Overall, our data reveal that
a large number of DUSPs influence ERK2 signaling. Together with the known
tissue-specific expression of DUSPs and the importance of ERK1/2 in cell
regulation, our data support the potential value of DUSPs as targets for drug
therapy.
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Affiliation(s)
- Christopher J Caunt
- Laboratory for Integrated Neuroscience and Endocrinology, Department of Clinical Sciences at South Bristol, University of Bristol, Whitson Street, Bristol BS1 3NY, United Kingdom
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83
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Two adjacent docking sites in the yeast Hog1 mitogen-activated protein (MAP) kinase differentially interact with the Pbs2 MAP kinase kinase and the Ptp2 protein tyrosine phosphatase. Mol Cell Biol 2008; 28:2481-94. [PMID: 18212044 DOI: 10.1128/mcb.01817-07] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Functional interactions between a mitogen-activated protein kinase (MAPK) and its regulators require specific docking interactions. Here, we investigated the mechanism by which the yeast osmoregulatory Hog1 MAPK specifically interacts with its activator, the MAPK kinase Pbs2, and its major inactivator, the protein phosphatase Ptp2. We found, in the N-terminal noncatalytic region of Pbs2, a specific Hog1-binding domain, termed HBD-1. We also defined two adjacent Pbs2-binding sites in Hog1, namely, the common docking (CD) domain and Pbs2-binding domain 2 (PBD-2). The PBD-2 docking site appears to be sterically blocked in the intact Hog1 molecule, but its affinity to Pbs2 is apparent in shorter fragments of Hog1. Both the CD and the PBD-2 docking sites are required for the optimal activation of Hog1 by Pbs2, and in the absence of both sites, Hog1 cannot be activated by Pbs2. These data suggest that the initial interaction of Pbs2 with the CD site might induce a conformational change in Hog1 so that the PBD-2 site becomes accessible. The CD and PBD-2 docking sites are also involved in the specific interaction between Hog1 and Ptp2 and govern the dynamic dephosphorylation of activated Hog1. Thus, the CD and the PBD-2 docking sites play critical roles in both the activation and inactivation of Hog1.
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84
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Caunt CJ, Rivers CA, Conway-Campbell BL, Norman MR, McArdle CA. Epidermal growth factor receptor and protein kinase C signaling to ERK2: spatiotemporal regulation of ERK2 by dual specificity phosphatases. J Biol Chem 2008; 283:6241-52. [PMID: 18178562 DOI: 10.1074/jbc.m706624200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Spatiotemporal aspects of ERK activation are stimulus-specific and dictate cellular consequences. They are dependent upon dual specificity phosphatases (DUSPs) that bind ERK via docking domains and can both inactivate and anchor ERK in cellular compartments. Using high throughput fluorescence microscopy in combination with a system where endogenous ERKs are removed and replaced with wild-type or mutated ERK2-green fluorescent protein (GFP), we show that ERK2 activation responses to epidermal growth factor (EGF) and protein kinase C (PKC) are transient and sustained, respectively. PKC-mediated ERK2 activation is associated with prolonged nuclear localization in the dephosphorylated form, whereas EGF-stimulated ERK2 activation mediates only transient nuclear accumulation. By using short inhibitory RNAs to nuclear inducible DUSP1, -2, or -4 (alone or in combination), we demonstrate that all three of these enzymes contribute to the dephosphorylation of PKC (but not EGF)-activated ERK2 in the nucleus but that they have opposing effects on localization. DUSP2 and -4 inactivate and anchor ERK2, whereas DUSP1 dephosphorylates ERK in the nucleus but allows its traffic back to the cytoplasm. Overexpression of DUSP1, -2, or -4 prevented ERK2 activation, but only DUSP2 and -4 caused ERK2-GFP nuclear accumulation or could be immunoprecipitated with ERK2. Furthermore, protein synthesis inhibition or replacement of wild-type ERK2-GFP with docking domain mutants selectively increased PKC effects on ERK activity and altered ERK2-GFP localization. These mutations also impaired the ability of ERK2-GFP to bind DUSP2 and -4. Together, our data reveal a novel, stimulus-specific, and phosphatase-specific mechanism of ERK2 regulation in the nucleus by DUSP1, -2, and -4.
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Affiliation(s)
- Christopher J Caunt
- Laboratories for Integrated Neuroscience and Endocrinology, Department of Clinical Sciences at South Bristol, University of Bristol, Whitson Street, Bristol, U.K
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85
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Yazicioglu MN, Goad DL, Ranganathan A, Whitehurst AW, Goldsmith EJ, Cobb MH. Mutations in ERK2 Binding Sites Affect Nuclear Entry. J Biol Chem 2007; 282:28759-28767. [PMID: 17656361 DOI: 10.1074/jbc.m703460200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The MAPK ERK2 can enter and exit the nucleus by an energy-independent process that is facilitated by direct interactions with nuclear pore proteins. Several studies also suggest that the localization of ERK2 can be influenced by carrier proteins. Using import reconstitution assays, we examined a group of ERK2 mutants defective in known protein interactions to determine structural properties of ERK2 that contribute to its nuclear entry. ERK2 mutants defective in binding to substrates near the active site or to basic/hydrophobic docking (D) motifs were imported normally. Several ERK2 mutants defective in interactions with FXF motifs displayed slowed rates of nuclear import. The import-impaired mutants also showed reduced binding to a recombinant C-terminal fragment of nucleoporin 153 that is rich in FXF motifs. Despite the deficit revealed in some mutants via reconstitution assays, all but one of the ERK2 mutants accumulated in nuclei of stimulated cells in a manner comparable with the wild type protein; the mutant most defective in import remained in the cytoplasm. These results further support the idea that direct interactions with nucleoporins are involved in ERK2 nuclear entry and that multiple events contribute to the ligand-dependent relocalization of these protein kinases.
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Affiliation(s)
- Mustafa N Yazicioglu
- Departments of Pharmacology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9041
| | - Daryl L Goad
- Departments of Pharmacology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9041
| | - Aarati Ranganathan
- Departments of Pharmacology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9041
| | - Angelique W Whitehurst
- Departments of Pharmacology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9041
| | - Elizabeth J Goldsmith
- Departments of Biochemistry, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9041
| | - Melanie H Cobb
- Departments of Pharmacology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9041.
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86
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O’Keefe DD, Prober DA, Moyle PS, Rickoll WL, Edgar BA. Egfr/Ras signaling regulates DE-cadherin/Shotgun localization to control vein morphogenesis in the Drosophila wing. Dev Biol 2007; 311:25-39. [PMID: 17888420 PMCID: PMC2128780 DOI: 10.1016/j.ydbio.2007.08.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Revised: 08/01/2007] [Accepted: 08/02/2007] [Indexed: 12/31/2022]
Abstract
Egfr/Ras signaling promotes vein cell fate specification in the developing Drosophila wing. While the importance of Ras signaling in vein determination has been extensively documented, the mechanisms linking Ras activity to vein differentiation remain unclear. We found that Ras signaling regulates both the levels and subcellular localization of the cell adhesion molecule DE-cadherin/Shotgun (Shg) in the differentiating wing epithelium. High Ras activity in presumptive vein cells directs the apical localization of Shg containing adherens junctions, whereas low Ras activity in intervein cells allows Shg to relocalize basally. These alterations in Shg-mediated adhesion control cell shape changes that are essential for vein morphogenesis. While Decapentaplegic (Dpp) acts downstream of Ras to maintain vein cell identity in the pupal wing, our results indicate that Ras controls Shg localization via a Dpp-independent mechanism. Ras, therefore, regulates both the transcriptional responses necessary for vein cell identity, and the cell adhesive changes that determine vein and intervein cell morphology.
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Affiliation(s)
- David D. O’Keefe
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109
| | - David A. Prober
- Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195
| | | | | | - Bruce A. Edgar
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109
- Corresponding author: , phone: (206) 667-4185, FAX: (206) 667-3308
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87
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Zeng YA, Rahnama M, Wang S, Sosu-Sedzorme W, Verheyen EM. DrosophilaNemo antagonizes BMP signaling by phosphorylation of Mad and inhibition of its nuclear accumulation. Development 2007; 134:2061-71. [PMID: 17507407 DOI: 10.1242/dev.02853] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Drosophila Nemo is the founding member of the Nemo-like kinase(Nlk) family of serine/threonine protein kinases that are involved in several Wnt signal transduction pathways. Here we report a novel function for Nemo in the inhibition of bone morphogenetic protein (BMP) signaling. Genetic interaction studies demonstrate that nemo can antagonize BMP signaling and can inhibit the expression of BMP target genes during wing development. Nemo can bind to and phosphorylate the BMP effector Mad. In cell culture, phosphorylation by Nemo blocks the nuclear accumulation of Mad by promoting export of Mad from the nucleus in a kinase-dependent manner. This is the first example of the inhibition of Drosophila BMP signaling by a MAPK and represents a novel mechanism of Smad inhibition through the phosphorylation of a conserved serine residue within the MH1 domain of Mad.
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Affiliation(s)
- Yi Arial Zeng
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
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88
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Astigarraga S, Grossman R, Díaz-Delfín J, Caelles C, Paroush Z, Jiménez G. A MAPK docking site is critical for downregulation of Capicua by Torso and EGFR RTK signaling. EMBO J 2007; 26:668-77. [PMID: 17255944 PMCID: PMC1794389 DOI: 10.1038/sj.emboj.7601532] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Accepted: 12/07/2006] [Indexed: 11/09/2022] Open
Abstract
Early Drosophila development requires two receptor tyrosine kinase (RTK) pathways: the Torso and the Epidermal growth factor receptor (EGFR) pathways, which regulate terminal and dorsal-ventral patterning, respectively. Previous studies have shown that these pathways, either directly or indirectly, lead to post-transcriptional downregulation of the Capicua repressor in the early embryo and in the ovary. Here, we show that both regulatory effects are direct and depend on a MAPK docking site in Capicua that physically interacts with the MAPK Rolled. Capicua derivatives lacking this docking site cause dominant phenotypes similar to those resulting from loss of Torso and EGFR activities. Such phenotypes arise from inappropriate repression of genes normally expressed in response to Torso and EGFR signaling. Our results are consistent with a model whereby Capicua is the main nuclear effector of the Torso pathway, but only one of different effectors responding to EGFR signaling. Finally, we describe differences in the modes of Capicua downregulation by Torso and EGFR signaling, raising the possibility that such differences contribute to the tissue specificity of both signals.
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Affiliation(s)
- Sergio Astigarraga
- Institut de Biologia Molecular de Barcelona-CSIC, Parc Científic de Barcelona, Barcelona, Spain
| | - Rona Grossman
- Department of Biochemistry, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Julieta Díaz-Delfín
- Institut de Recerca Biomèdica, Parc Científic de Barcelona, Barcelona, Spain
| | - Carme Caelles
- Institut de Recerca Biomèdica, Parc Científic de Barcelona, Barcelona, Spain
| | - Ze'ev Paroush
- Department of Biochemistry, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Gerardo Jiménez
- Institut de Biologia Molecular de Barcelona-CSIC, Parc Científic de Barcelona, Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
- Department of Molecular and Cellular Biology, Institut de Biologia Molecular de Barcelona-CSIC, Parc Cientific de Barcelona, Josep Samitier, 1-5, Barcelona 08028, Spain. Tel.: +34 934 034 970; Fax: +34 934 034 979; E-mail:
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89
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Doroquez DB, Rebay I. Signal integration during development: mechanisms of EGFR and Notch pathway function and cross-talk. Crit Rev Biochem Mol Biol 2007; 41:339-85. [PMID: 17092823 DOI: 10.1080/10409230600914344] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Metazoan development relies on a highly regulated network of interactions between conserved signal transduction pathways to coordinate all aspects of cell fate specification, differentiation, and growth. In this review, we discuss the intricate interplay between the epidermal growth factor receptor (EGFR; Drosophila EGFR/DER) and the Notch signaling pathways as a paradigm for signal integration during development. First, we describe the current state of understanding of the molecular architecture of the EGFR and Notch signaling pathways that has resulted from synergistic studies in vertebrate, invertebrate, and cultured cell model systems. Then, focusing specifically on the Drosophila eye, we discuss how cooperative, sequential, and antagonistic relationships between these pathways mediate the spatially and temporally regulated processes that generate this sensory organ. The common themes underlying the coordination of the EGFR and Notch pathways appear to be broadly conserved and should, therefore, be directly applicable to elucidating mechanisms of information integration and signaling specificity in vertebrate systems.
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Affiliation(s)
- David B Doroquez
- Department of Biology, Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge, MA, USA
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90
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Gaziova I, Bhat KM. Generating asymmetry: with and without self-renewal. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2007; 45:143-78. [PMID: 17585500 DOI: 10.1007/978-3-540-69161-7_7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
At some point during the history of organismal evolution, unicellular, unipotent and mitotically active cells acquired an ability to undergo a special type of cell division called asymmetric division. By this special type of cell division, these cells could divide to generate two different progeny or to self-renew and at the same time generate a progeny that is committed to become a cell different from the mother cell. This type of cell division, which forms the basis for the functioning of totipotent or multipotent stem cells, underlies the fundamental basis for the developmental evolution of organisms. It is not clear if the asymmetric division without self-renewal preceded the asymmetric division with self-renewal. It is reasonable to assume that the asymmetric division without self-renewal preceded the asymmetric division with self-renewal. In this review we explore the genetic regulation of these two types of asymmetric divisions using the Drosophila central nervous system (CNS) as a model system. The results from recent studies argue that for cells to undergo a self-renewing asymmetric division, certain "stem cell" proteins must be maintained or up-regulated, while genes encoding proteins responsible for differentiation must be repressed or down-regulated. As long as a balance between these two classes of proteins is maintained via asymmetric segregation and activation/repression, the progeny that receives stem cell proteins/maintains stem cell competence will have the potential to undergo self-renewing asymmetric division. The other progeny will commit to differentiate. In non-self-renewing asymmetric division, down-regulation of stem cell proteins/competence combined with asymmetric segregation of cell identity specifying factors (either cell-autonomous or a combination of cell autonomous and non-cell autonomous signals) cause the two progeny to assume different differentiated identities. Identification of mutations that confer a stem cell type of division to nonstem cell precursors, or mutations that eliminate asymmetric division, has led the way in elucidating the molecular basis for these divisions. Given that there is a considerable degree of conservation of genes and their function, these studies should provide clear insight into how the self-renewing asymmetric division of stem cells in neural and other lineages is regulated not only in Drosophila but also in vertebrates including humans.
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Affiliation(s)
- Ivana Gaziova
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch School of Medicine, Galveston, Texas 77555, USA
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91
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Tresini M, Lorenzini A, Torres C, Cristofalo VJ. Modulation of replicative senescence of diploid human cells by nuclear ERK signaling. J Biol Chem 2006; 282:4136-51. [PMID: 17145763 DOI: 10.1074/jbc.m604955200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Normal somatic cells have a limited replicative lifespan, and serial subcultivation ultimately results in senescence. Senescent cells are irreversibly growth-arrested and show impaired responses to mitogens. Activation of the ERK signaling pathway, an absolute requirement for cell proliferation, results in nuclear relocalization of active ERKs, an event impaired in senescent fibroblasts. This impairment coincides with increased activity of the nuclear ERK phosphatase MKP2. Here we show that replicative lifespan can be altered by changes in nuclear ERK activity. Ectopic expression of MKP2 results in premature senescence. In contrast, knock-down of MKP2 expression, through transduction of MKP2 sequence-specific short hairpin RNA, or expression of the phosphatase resistant ERK2(D319N) mutant, abrogates the effects of increased endogenous MKP2 levels and senescence is postponed. Nuclear targeting of ERK2(D319N) significantly augments its effects and the transduced cultures show higher than 60% increase in replicative lifespan compared with cultures transduced with wt ERK2. Long-lived cultures senesce with altered molecular characteristics and retain the ability to express c-fos, and Rb is maintained in its inactive form. Our results support that MKP2-mediated inactivation of nuclear ERK2 represents a key event in the establishment of replicative senescence. Although it is evident that senescence can be imposed through multiple mechanisms, restoration of nuclear ERK activity can bypass a critical senescence checkpoint and, thus, extend replicative lifespan.
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Affiliation(s)
- Maria Tresini
- Lankenau Institute for Medical Research, Wynnewood, Pennsylvania 19096, USA.
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92
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Askari N, Diskin R, Avitzour M, Yaakov G, Livnah O, Engelberg D. MAP-quest: could we produce constitutively active variants of MAP kinases? Mol Cell Endocrinol 2006; 252:231-40. [PMID: 16672172 DOI: 10.1016/j.mce.2006.03.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Constitutively active mutants that acquired intrinsic activity and escaped regulation, serve as powerful tools for revealing the biochemical, biological and pathological functions of proteins. Such mutants are not available for mitogen-activated protein kinases (MAPKs). It is not known how to mimic the unusual mode of MAPK activation and to enforce, by mutations, their active conformation. In this review we describe the strategies employed in attempts to overcome this obstacle. We focus on a recent breakthrough with the p38 family that suggests that active variants of all MAPKs will soon be available.
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Affiliation(s)
- Nadav Askari
- The Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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93
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Zhou H, Zheng M, Chen J, Xie C, Kolatkar AR, Zarubin T, Ye Z, Akella R, Lin S, Goldsmith EJ, Han J. Determinants that control the specific interactions between TAB1 and p38alpha. Mol Cell Biol 2006; 26:3824-34. [PMID: 16648477 PMCID: PMC1489000 DOI: 10.1128/mcb.26.10.3824-3834.2006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous studies have revealed that transforming growth factor-beta-activated protein kinase 1 (TAB1) interacts with p38alpha and induces p38alpha autophosphorylation. Here, we examine the sequence requirements in TAB1 and p38alpha that drive their interaction. Deletion and point mutations in TAB1 reveal that a proline residue in the C terminus of TAB1 (Pro412) is necessary for its interaction with p38alpha. Furthermore, a cryptic D-domain-like docking site was identified adjacent to the N terminus of Pro412, putting Pro412 in the phi(B)+3 position of the docking site. Through mutational analysis, we found that the previously identified hydrophobic docking groove in p38alpha is involved in this interaction, whereas the CD domain and ED domain are not. Furthermore, chimeric analysis with p38beta (which does not bind to TAB1) revealed a previously unidentified locus of p38alpha comprising Thr218 and Ile275 that is essential for specific binding of p38alpha to TAB1. Converting either of these residues to the corresponding amino acid of p38beta abolishes p38alpha interaction with TAB1. These p38alpha mutants still can be fully activated by p38alpha upstream activating kinase mitogen-activated protein kinase kinase 6, but their basal activity and activation in response to some extracellular stimuli are reduced. Adjacent to Thr218 and Ile275 is a site where large conformational changes occur in the presence of docking-site peptides derived from p38alpha substrates and activators. This suggests that TAB1-induced autophosphorylation of p38alpha results from conformational changes that are similar but unique to those seen in p38alpha interactions with its substrates and activating kinases.
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Affiliation(s)
- Huamin Zhou
- The Key Laboratory of the Ministry of Education for Cell Biology and Tumor Cell Engineering, School of Life Sciences, Xiamen University, Fujian, China
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94
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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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95
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Baril C, Therrien M. Alphabet, a Ser/Thr phosphatase of the protein phosphatase 2C family, negatively regulates RAS/MAPK signaling in Drosophila. Dev Biol 2006; 294:232-45. [PMID: 16600208 DOI: 10.1016/j.ydbio.2006.02.046] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Revised: 02/16/2006] [Accepted: 02/25/2006] [Indexed: 11/16/2022]
Abstract
Signal transduction through the RAS/mitogen-activated protein kinase (MAPK) pathway depends on a diverse collection of proteins regulating positively and negatively signaling flow. We previously conducted a genetic screen in Drosophila to identify novel components of this signaling pathway. Here, we present the identification and characterization of a new gene, alphabet (alph), whose activity negatively regulates RAS/MAPK-dependent developmental processes in Drosophila and this, at a step downstream or in parallel to RAS. alph encodes a protein phosphatase 2C (PP2C) family member closely related to the mammalian PP2C alpha and beta isoforms. Interestingly, although alph gene product does not appear to be essential for viability, its elimination leads to weak but significant developmental defects reminiscent of an overactivated RAS/MAPK pathway. Consistent with this interpretation, strong genetic interactions are observed between alph alleles and mutations in bona fide components of the pathway. Together, this work identifies a PP2C of the alpha/beta subfamily as a novel negative regulator of the RAS/MAPK pathway and suggests that these evolutionarily conserved enzymes play a similar role in other metazoans. Finally, despite the relatively large size of the PP2C gene family in metazoans, this study represents only the second genetic characterization of a PP2C in these organisms.
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Affiliation(s)
- Caroline Baril
- Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, C.P. 6128 Succursale Centre-Ville, Montréal, Québec, Canada H3C 3J7
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96
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Martín H, Flández M, Nombela C, Molina M. Protein phosphatases in MAPK signalling: we keep learning from yeast. Mol Microbiol 2006; 58:6-16. [PMID: 16164545 DOI: 10.1111/j.1365-2958.2005.04822.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Because of their key role in cell signalling, a rigorous regulation of mitogen-activated protein kinases (MAPKs) is essential in eukaryotic physiology. Whereas the use of binding motifs and scaffold proteins guarantees the selective activation of a specific MAPK pathway, activating kinases and downregulating phosphatases control the appropriate intensity and timing of MAPK activation. Tyrosine, serine/threonine and dual-specificity phosphatases co-ordinately dephosphorylate and thereby inactivate MAPKs. In budding yeast, enzymes that belong to these three types of phosphatases have been shown to counteract the MAPKs that govern the cellular response to varied extracellular stimuli. Studies carried out with these yeast phosphatases have expanded our knowledge of essential key aspects of the biology of these negative regulators, such as their function, the mechanisms that operate in their modulation by MAPK pathways and their binding to MAPK substrates. Furthermore, yeast MAPK phosphatases have been shown to play additional and essential roles in MAPK-mediated signalling, controlling MAPK localization or cross-talk among pathways. This review stresses the importance of these negative regulators in eukaryotic signalling by discussing the recent developments and perspectives in the study of yeast MAPK phosphatases.
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Affiliation(s)
- Humberto Martín
- Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense, 28040-Madrid, Spain
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97
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Liu S, Sun JP, Zhou B, Zhang ZY. Structural basis of docking interactions between ERK2 and MAP kinase phosphatase 3. Proc Natl Acad Sci U S A 2006; 103:5326-31. [PMID: 16567630 PMCID: PMC1459354 DOI: 10.1073/pnas.0510506103] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mitogen-activated protein (MAP) kinases are central components of signal transduction pathways for cell proliferation, stress responses, and differentiation. Signaling efficiency and specificity are modulated in large part by docking interactions between individual MAP kinase and the kinase interaction motif (KIM), (R/K)(2-3)-X(1-6)-Phi(A)-X-Phi(B), in its cognate kinases, phosphatases, scaffolding proteins, and substrates. We have determined the crystal structure of extracellular signal-regulated protein kinase 2 bound to the KIM peptide from MAP kinase phosphatase 3, an extracellular signal-regulated protein kinase 2-specific phosphatase. The structure reveals that the KIM docking site, situated in a noncatalytic region opposite of the kinase catalytic pocket, is comprised of a highly acidic patch and a hydrophobic groove, which engage the basic and Phi(A)-X-Phi(B) residues, respectively, in the KIM sequence. The specific docking interactions observed in the structure consolidate all known biochemical data. In addition, structural comparison indicates that the KIM docking site is conserved in all MAP kinases. The results establish a structural model for understanding how MAP kinases interact with their regulators and substrates and provide new insights into how MAP kinase docking specificity can be achieved.
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Affiliation(s)
- Sijiu Liu
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202
| | - Jin-Peng Sun
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202
| | - Bo Zhou
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202
| | - Zhong-Yin Zhang
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202
- *To whom correspondence should be addressed. E-mail:
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98
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Ranganathan A, Pearson GW, Chrestensen CA, Sturgill TW, Cobb MH. The MAP kinase ERK5 binds to and phosphorylates p90 RSK. Arch Biochem Biophys 2006; 449:8-16. [PMID: 16626623 DOI: 10.1016/j.abb.2006.02.023] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2006] [Revised: 02/24/2006] [Accepted: 02/24/2006] [Indexed: 11/15/2022]
Abstract
We showed previously that p90 RSK was activated in cells expressing an activated mutant of MEK5, the activator of the MAP kinase ERK5. Based on the following evidence, we suggest that ERK5 can directly activate RSK in cells. ERK5 binds to RSK in vitro and co-immunoprecipitates from cell extracts; activation of ERK5 weakens its binding to RSK, suggesting that RSK is released upon activation. Phosphorylation of RSK by ERK5 in vitro causes its activation, indicating that RSK is a substrate of ERK5. In cells activation of ERK5 but not p38 or the c-Jun N-terminal kinase is associated with RSK activation. The large C-terminal domain of ERK5 is not required for binding or activation of RSK by ERK5; however, the common docking or CD domain of ERK5 and the docking or D domain of RSK are important for their association.
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Affiliation(s)
- Aarati Ranganathan
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9041, USA
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99
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Guichard A, Park JM, Cruz-Moreno B, Karin M, Bier E. Anthrax lethal factor and edema factor act on conserved targets in Drosophila. Proc Natl Acad Sci U S A 2006; 103:3244-9. [PMID: 16455799 PMCID: PMC1413899 DOI: 10.1073/pnas.0510748103] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Many bacterial toxins act on conserved components of essential host-signaling pathways. One consequence of this conservation is that genetic model organisms such as Drosophila melanogaster can be used for analyzing the mechanism of toxin action. In this study, we characterize the activities of two anthrax virulence factors, lethal factor (LF) and edema factor, in transgenic Drosophila. LF is a zinc metalloprotease that cleaves and inactivates most human mitogen-activated protein kinase (MAPK) kinases (MAPKKs). We found that LF similarly cleaves the Drosophila MAPK kinases Hemipterous (Hep) and Licorne in vitro. Consistent with these observations, expression of LF in Drosophila inhibited the Hep/c-Jun N-terminal kinase pathway during embryonic dorsal closure and the related process of adult thoracic closure. Epistasis experiments confirmed that LF acts at the level of Hep. We also found that LF inhibits Ras/MAPK signaling during wing development and that LF acts upstream of MAPK and downstream of Raf, consistent with LF acting at the level of Dsor. In addition, we found that edema factor, a potent adenylate cyclase, inhibits the hh pathway during wing development, consistent with the known role of cAMP-dependent PKA in suppressing the Hedgehog response. These results demonstrate that anthrax toxins function in Drosophila as they do in mammalian cells and open the way to using Drosophila as a multicellular host system for studying the in vivo function of diverse toxins and virulence factors.
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Affiliation(s)
- Annabel Guichard
- Section of Cell and Developmental Biology,
University of California at San Diego, 9500 Gilman Drive, La Jolla, CA
92093-0349
| | - Jin Mo Park
- Laboratory of Gene Regulation and Signal
Transduction, Department of Pharmacology, School of Medicine, University of
California at San Diego, La Jolla, CA 92093; and
- Cutaneous Biology Research Center,
Massachusetts General Hospital, Harvard Medical School, Charlestown, MA
02129
| | - Beatriz Cruz-Moreno
- Section of Cell and Developmental Biology,
University of California at San Diego, 9500 Gilman Drive, La Jolla, CA
92093-0349
| | - Michael Karin
- Laboratory of Gene Regulation and Signal
Transduction, Department of Pharmacology, School of Medicine, University of
California at San Diego, La Jolla, CA 92093; and
- To whom correspondence may be addressed.
E-mail: ,
, or
| | - Ethan Bier
- Section of Cell and Developmental Biology,
University of California at San Diego, 9500 Gilman Drive, La Jolla, CA
92093-0349
- To whom correspondence may be addressed.
E-mail: ,
, or
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100
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Liu J, Qian L, Wessells RJ, Bidet Y, Jagla K, Bodmer R. Hedgehog and RAS pathways cooperate in the anterior–posterior specification and positioning of cardiac progenitor cells. Dev Biol 2006; 290:373-85. [PMID: 16387294 DOI: 10.1016/j.ydbio.2005.11.033] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Revised: 11/03/2005] [Accepted: 11/18/2005] [Indexed: 10/25/2022]
Abstract
The Drosophila heart is a highly ordered structure with only a limited number of cell types, which are arranged in a stereotyped metameric pattern. Ras signaling has previously been implicated in contributing to heart formation, but how positional information is integrated with this pathway to specify, distinguish and precisely position individual cardiac progenitors within the presumptive heart-forming region are not known. Here, we present evidence that the striped pattern of the secreted factor Hedgehog (Hh), in combination with the RAS pathway, specifies and positions neighboring groups of cardiac progenitors within each segment: the anterior ladybird (lbe)- and the posterior even skipped (eve)-expressing cardiac progenitors. Loss of hh function (while maintaining wg activity) results in the absence of the Eve cells, whereas the Lbe cells are expanded within the cardiac mesoderm. Overexpressing the repressor form of Cubitus interruptus (Ci), a Hh pathway antagonist, also results in expansion of Lbe at the expense of Eve, as does lowering Ras signaling. Conversely, overexpression of Hh or increasing Ras signaling eliminates Lbe expression while expanding Eve within the cardiogenic mesoderm. Increasing Ras signaling in the absence of Hh suggests that the Ras pathway is in part epistatic to Hh. Hh controls dorsal mesodermal Ras signaling by transcriptional regulation of the EGF receptor ligand protease, encoded by rhomboid (rho). Conversely, Hh overexpression can fully inhibit Lbe even when Ras signaling is much reduced, suggesting that Hh also acts in parallel to Ras. We propose that the Eve precursors next to the Hh stripe are distinguished from more distant Lbe precursors by locally augmenting Ras signaling via elevating rho transcripts. Thus, the spatial precision of cell type specification within an organ depends on multiple phases of inductive interaction between the ectoderm and the mesoderm.
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Affiliation(s)
- Jiandong Liu
- The Burnham Institute, Center for Neurosciences and Aging, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
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