Bendless modulates JNK-mediated cell death and migration in Drosophila.
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ABSTRACT:
SUBMITTER: Ma X
PROVIDER: S-EPMC3921588 | biostudies-other | 2014 Mar
REPOSITORIES: biostudies-other
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Project description:Cell death plays a pivotal role in animal development and tissue homeostasis. Dysregulation of this process is associated with a wide variety of human diseases, including developmental and immunological disorders, neurodegenerative diseases and tumors. While the fundamental role of JNK pathway in cell death has been extensively studied, its down-stream regulators and the underlying mechanisms remain largely elusive. From a Drosophila genetic screen, we identified Snail (Sna), a Zinc-finger transcription factor, as a novel modulator of ectopic Egr-induced JNK-mediated cell death. In addition, sna is essential for the physiological function of JNK signaling in development. Our genetic epistasis data suggest that Sna acts downstream of JNK to promote cell death. Mechanistically, JNK signaling triggers dFoxO-dependent transcriptional activation of sna. Thus, our findings not only reveal a novel function and the underlying mechanism of Sna in modulating JNK-mediated cell death, but also provide a potential drug target and therapeutic strategies for JNK signaling-related diseases.
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Project description:Cell death is a fundamental progress that regulates cell number, tissue homeostasis and organ size in development. The c-Jun N-terminal kinase (JNK) pathway has been evolutionarily conserved from fly to human, and plays essential roles in regulating cell death. To characterize additional genes that regulate JNK signaling, we performed a genetic screen in Drosophila and identified dGLYAT, a novel gene whose function was previously unknown, as a modulator of JNK-mediated cell death. We found that loss of dGLYAT suppressed JNK activation and cell death triggered by over-expression of Egr or Hep, or depletion of puc or lgl in development, suggesting dGLYAT regulates both ectopic and physiological functions of JNK pathway. Furthermore, we showed that loss of dGLYAT inhibits JNK-mediated ROS production, suggesting dGLYAT regulates multiple functions of JNK signaling in vivo.
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Project description:ObjectivesThe evolutionary conserved JNK pathway plays crucial role in cell death, yet factors that modulate this signalling have not been fully disclosed. In this study, we aim to identify additional factors that regulate JNK signalling in cell death, and characterize the underlying mechanisms.Materials and methodsDrosophila were raised on standard media, and cross was carried out at 25°C. The Gal4/UAS system was used to express proteins or RNAi in a specific temporal and spatial pattern. Gene expression was revealed by GFP fluorescence, X-gal staining or immunostaining of 3rd instar larval eye and wing discs. Cell death was visualized by acridine orange (AO) staining. Images of fly eyes and wings were taken by OLYMPUS microscopes.ResultsWe found that licorne (lic) encoding the Drosophila MKK3 is an essential regulator of JNK-mediated cell death. Firstly, loss of lic suppressed ectopic Egr-triggered JNK activation and cell death in eye and wing development. Secondary, lic is necessary for loss-of-cell polarity-induced, physiological JNK-dependent cell death in wing development. Thirdly, Lic overexpression is sufficient to initiate JNK-mediated cell death in developing eyes and wings. Furthermore, ectopic Lic activates JNK signalling by promoting JNK phosphorylation. Finally, genetic epistatic analysis confirmed that Lic acts in parallel with Hep in the Egr-JNK pathway.ConclusionsThis study not only identified Lic as a novel component of the JNK signalling, but also disclosed the crucial roles and mechanism of Lic in cell death.
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Project description:The c-Jun N-terminal kinase (JNK) pathway plays essential roles in regulating a variety of cellular processes including proliferation, migration and survival. Previous genetic studies in Drosophila have identified numerous cell death regulating genes, providing new insights into the mechanisms for related diseases. Despite the known role of the small GTPase Rac1 in regulating cell death, the downstream components and underlying mechanism remain largely elusive. Here, we show that Rac1 promotes JNK-dependent cell death through Wallenda (Wnd). In addition, we find that Wnd triggers JNK activation and cell death via its kinase domain. Moreover, we show that both MKK4 and Hep are critical for Wnd-induced cell death. Furthermore, Wnd is essential for ectopic Egr- or Rho1-induced JNK activation and cell death. Finally, Wnd is physiologically required for loss of scribble-induced JNK-dependent cell death. Thus, our data suggest that wnd encodes a novel essential cell death regulator in Drosophila.
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Project description:Tumor necrosis factor (TNF) family ligands play essential roles in regulating a variety of cellular processes including proliferation, differentiation and survival. Expression of Drosophila TNF ortholog Eiger (Egr) induces JNK-dependent cell death, while the roles of caspases in this process remain elusive. To further delineate the Egr-triggered cell death pathway, we performed a genetic screen to identify dominant modifiers of the Egr-induced cell death phenotype. Here we report that Egr elicits a caspase-mediated cell death pathway independent of JNK signaling. Furthermore, we show NOPO, the Drosophila ortholog of TRIP (TRAF interacting protein) encoding an E3 ubiquitin ligase, modulates Egr-induced Caspase-mediated cell death through transcriptional activation of pro-apoptotic genes reaper and hid. Finally, we found Bendless and dUEV1a, an ubiquitin-conjugating E2 enzyme complex, regulates NOPO-triggered cell death. Our results indicate that the Ben-dUEV1a complex constitutes a molecular switch that bifurcates the Egr-induced cell death signaling into two pathways mediated by JNK and caspases respectively.
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Project description:Loss of the cell polarity gene could cooperate with oncogenic Ras to drive tumor growth and invasion, which critically depends on the c-Jun N-terminal Kinase (JNK) signaling pathway in Drosophila. By performing a genetic screen, we have identified Src42A, the ortholog of mammalian Src, as a key modulator of both Ras(V12)/lgl(-/-) triggered tumor invasion and loss of cell polarity gene-induced cell migration. Our genetic study further demonstrated that the Bendless (Ben)/dUev1a ubiquitin E2 complex is an essential regulator of Src42A-induced, JNK-mediated cell migration. Furthermore, we showed that ectopic Ben/dUev1a expression induced invasive cell migration along with increased MMP1 production in wing disc epithelia. Moreover, Ben/dUev1a could cooperate with Ras(V12) to promote tumor overgrowth and invasion. In addition, we found that the Ben/dUev1a complex is required for ectopic Src42A-triggered cell death and endogenous Src42A-dependent thorax closure. Our data not only provide a mechanistic insight into the role of Src in development and disease but also propose a potential oncogenic function for Ubc13 and Uev1a, the mammalian homologs of Ben and dUev1a.
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