Tension-dependent regulation of mammalian Hippo signaling through LIMD1.
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ABSTRACT:
SUBMITTER: Ibar C
PROVIDER: S-EPMC5897721 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Mechanical forces have been proposed to modulate organ growth, but a molecular mechanism that links them to growth regulation in vivo has been lacking. We report that increasing tension within the cytoskeleton increases Drosophila wing growth, whereas decreasing cytoskeletal tension decreases wing growth. These changes in growth can be accounted for by changes in the activity of Yorkie, a transcription factor regulated by the Hippo pathway. The influence of myosin activity on Yorkie depends genetically on the Ajuba LIM protein Jub, a negative regulator of Warts within the Hippo pathway. We further show that Jub associates with ?-catenin and that its localization to adherens junctions and association with ?-catenin are promoted by cytoskeletal tension. Jub recruits Warts to junctions in a tension-dependent manner. Our observations delineate a mechanism that links cytoskeletal tension to regulation of Hippo pathway activity, providing a molecular understanding of how mechanical forces can modulate organ growth.
| S-EPMC4082802 | biostudies-literature
Project description:EGFR and Hippo signaling pathways both control growth and, when dysregulated, contribute to tumorigenesis. We find that EGFR activates the Hippo pathway transcription factor Yorkie and demonstrate that Yorkie is required for the influence of EGFR on cell proliferation in Drosophila. EGFR regulates Yorkie through the influence of its Ras-MAPK branch on the Ajuba LIM protein Jub. Jub is epistatic to EGFR and Ras for Yorkie regulation, Jub is subject to MAPK-dependent phosphorylation, and EGFR-Ras-MAPK signaling enhances Jub binding to the Yorkie kinase Warts and the adaptor protein Salvador. An EGFR-Hippo pathway link is conserved in mammals, as activation of EGFR or RAS activates the Yorkie homolog YAP, and EGFR-RAS-MAPK signaling promotes phosphorylation of the Ajuba family protein WTIP and also enhances WTIP binding to the Warts and Salvador homologs LATS and WW45. Our observations implicate the Hippo pathway in EGFR-mediated tumorigenesis and identify a molecular link between these pathways.
| S-EPMC3624988 | biostudies-literature
Project description:Mechanical forces affect all the tissues of our bodies. Experiments conducted mainly on cultured cells have established that altering these forces influences cell behaviors, including migration, differentiation, apoptosis, and proliferation [1, 2]. The transcriptional coactivator YAP has been identified as a nuclear relay of mechanical signals, but the molecular mechanisms that lead to YAP activation were not identified [3]. YAP is the main transcriptional effector of the Hippo signaling pathway, a major growth regulatory pathway within metazoa [4], but at least in some instances, the influence of mechanical strain on YAP was reported to be independent of Hippo signaling [5, 6]. Here, we identify a molecular pathway that can promote the proliferation of cultured mammary epithelial cells in response to cyclic or static stretch. These mechanical stimuli are associated with increased activity of the transcriptional coactivator YAP, which is due at least in part to inhibition of Hippo pathway activity. Much of this influence on Hippo signaling can be accounted for by the activation of c-Jun N-terminal kinase (JNK) activity by mechanical strain and subsequent inhibition of Hippo signaling by JNK. LATS1 is a key negative regulator of YAP within the Hippo pathway, and we further show that cyclic stretch is associated with a JNK-dependent increase in binding of a LATS inhibitor, LIMD1, to the LATS1 kinase and that reduction of LIMD1 expression suppresses the activation of YAP by cyclic stretch. Together, these observations establish a pathway for mechanical regulation of cell proliferation via JNK-mediated inhibition of Hippo signaling.
| S-EPMC4160395 | biostudies-literature
Project description:The transcriptional co-activator YAP controls cell proliferation, survival, and tissue regeneration in response to changes in the mechanical environment. It is not known how mechanical stimuli such as tension are sensed and how the signal is transduced to control YAP activity. Here, we show that the LIM domain protein TRIP6 acts as part of a mechanotransduction pathway at adherens junctions to promote YAP activity by inhibiting the LATS1/2 kinases. Previous studies showed that vinculin at adherens junctions becomes activated by mechanical tension. We show that vinculin inhibits Hippo signaling by recruiting TRIP6 to adherens junctions and stimulating its binding to and inhibition of LATS1/2 in response to tension. TRIP6 competes with MOB1 for binding to LATS1/2 thereby blocking MOB1 from recruiting the LATS1/2 activating kinases MST1/2. Together, these findings reveal a novel pathway that responds to tension at adherens junctions to control Hippo pathway signaling.
| S-EPMC5797958 | biostudies-literature
Project description:We have previously shown that overexpression of SKI, an endogenous TGF-β1 repressor, deactivates the pro-fibrotic myofibroblast phenotype in the heart. We now show that SKI also functions independently of SMAD/TGF-β signaling, by activating the Hippo tumor-suppressor pathway and inhibiting the Transcriptional co-Activator with PDZ-binding motif (TAZ or WWTR1). The mechanism(s) by which SKI targets TAZ to inhibit cardiac fibroblast activation and fibrogenesis remain undefined. A rat model of post-myocardial infarction was used to examine the expression of TAZ during acute fibrogenesis and chronic heart failure. Results were then corroborated with primary rat cardiac fibroblast cell culture performed both on plastic and on inert elastic substrates, along with the use of siRNA and adenoviral expression vectors for active forms of SKI, YAP, and TAZ. Gene expression was examined by qPCR and luciferase assays, while protein expression was examined by immunoblotting and fluorescence microscopy. Cell phenotype was further assessed by functional assays. Finally, to elucidate SKI's effects on Hippo signaling, the SKI and TAZ interactomes were captured in human cardiac fibroblasts using BioID2 and mass spectrometry. Potential interactors were investigated in vitro to reveal novel mechanisms of action for SKI. In vitro assays on elastic substrates revealed the ability of TAZ to overcome environmental stimuli and induce the activation of hypersynthetic cardiac myofibroblasts. Further cell-based assays demonstrated that SKI causes specific proteasomal degradation of TAZ, but not YAP, and shifts actin cytoskeleton dynamics to inhibit myofibroblast activation. These findings were supported by identifying the bi-phasic expression of TAZ in vivo during post-MI remodeling and fibrosis. BioID2-based interactomics in human cardiac fibroblasts suggest that SKI interacts with actin-modifying proteins and with LIM Domain-containing protein 1 (LIMD1), a negative regulator of Hippo signaling. Furthermore, we found that LATS2 interacts with TAZ, whereas LATS1 does not, and that LATS2 knockdown prevented TAZ downregulation with SKI overexpression. Our findings indicate that SKI's capacity to regulate cardiac fibroblast activation is mediated, in part, by Hippo signaling. We postulate that the interaction between SKI and TAZ in cardiac fibroblasts is arbitrated by LIMD1, an important intermediary in focal adhesion-associated signaling pathways. This study contributes to the understanding of the unique physiology of cardiac fibroblasts, and of the relationship between SKI expression and cell phenotype.
| S-EPMC8043893 | biostudies-literature
Project description:The Hippo pathway is an emerging signaling cascade involved in the regulation of organ size control. It consists of evolutionally conserved protein kinases that are sequentially phosphorylated and activated. The active Hippo pathway subsequently phosphorylates a transcription coactivator, YAP, which precludes its nuclear localization and transcriptional activation. Identification of transcriptional targets of YAP in diverse cellular contexts is therefore critical to the understanding of the molecular mechanisms in which the Hippo pathway restricts tissue growth. We used microarrays to profile the gene expression patterns upon acute siRNA knockdown of Hippo pathway components in multiple mammalian cell lines and identified a set of genes representing immediate transcriptional targets of the Hippo/Yap signaling pathway. Three mammalian cell lines (HEK293T, HepG2, HaCaT) were transfected with scramble siRNA controls or siRNAs against NF2 and LATS2, two core components of the Hippo pathway, simultaneously. Total RNAs were harvested four days after transfection to reveal the gene expression pattern unsing microarry. YAP and TAZ siRNAs were also transfected along with NF2 and LATS2 siRNAs to identify YAP/TAZ-dependent transcriptional targets upon loss of NF2/LATS2.
2013-12-31 | E-GEOD-49384 | biostudies-arrayexpress
Project description:Although extracellular force has a profound effect on cell shape, cytoskeleton tension, and cell proliferation through the Hippo signaling effector Yki/YAP/TAZ, how intracellular force regulates these processes remains poorly understood. Here, we report an essential role for spectrin in specifying cell shape by transmitting intracellular actomyosin force to cell membrane. While activation of myosin II in Drosophila melanogaster pupal retina leads to increased cortical tension, apical constriction, and Yki-mediated hyperplasia, spectrin mutant cells, despite showing myosin II activation and Yki-mediated hyperplasia, paradoxically display decreased cortical tension and expanded apical area. Mechanistically, we show that spectrin is required for tethering cortical F-actin to cell membrane domains outside the adherens junctions (AJs). Thus, in the absence of spectrin, the weakened attachment of cortical F-actin to plasma membrane results in a failure to transmit actomyosin force to cell membrane, causing an expansion of apical surfaces. These results uncover an essential mechanism that couples cell shape, cortical tension, and Hippo signaling and highlight the importance of non-AJ membrane domains in dictating cell shape in tissue morphogenesis.
| S-EPMC7147103 | biostudies-literature
Project description:Overwhelming studies show that dysregulation of the Hippo pathway is positively correlated with cell proliferation, growth, and tumorigenesis. Paradoxically, the detailed molecular roles of the Hippo pathway in cell invasion remain debatable. Using a Drosophila invasion model in wing epithelium, we show herein that activated Hippo signaling promotes cell invasion and epithelial-mesenchymal transition through JNK, as inhibition of JNK signaling dramatically blocked Hippo pathway activation-induced matrix metalloproteinase 1 expression and cell invasion. Furthermore, we identify bantam-Rox8 modules as essential components downstream of Yorkie in mediating JNK-dependent cell invasion. Finally, we confirm that YAP (Yes-associated protein) expression negatively regulates TIA1 (Rox8 ortholog) expression and cell invasion in human cancer cells. Together, these findings provide molecular insights into Hippo pathway-mediated cell invasion and also raise a noteworthy concern in therapeutic interventions of Hippo-related cancers, as simply inhibiting Yorkie or YAP activity might paradoxically accelerate cell invasion and metastasis.
| S-EPMC5338425 | biostudies-other
Project description:The Hippo and c-Jun N-terminal kinase (JNK) pathway both regulate growth and contribute to tumorigenesis when dysregulated. Whereas the Hippo pathway acts via the transcription coactivator Yki/YAP to regulate target gene expression, JNK signaling, triggered by various modulators including Rho GTPases, activates the transcription factors Jun and Fos. Here, we show that impaired Hippo signaling induces JNK activation through Rho1. Blocking Rho1-JNK signaling suppresses Yki-induced overgrowth in the wing disk, whereas ectopic Rho1 expression promotes tissue growth when apoptosis is prohibited. Furthermore, Yki directly regulates Rho1 transcription via the transcription factor Sd. Thus, our results have identified a novel molecular link between the Hippo and JNK pathways and implicated the essential role of the JNK pathway in Hippo signaling-related tumorigenesis.
| S-EPMC4313816 | biostudies-other
Project description:BackgroundNon-small cell lung cancer (NSCLC) occupies the majority of lung cancer cases and is notorious for the awful prognosis. LIM domains-containing 1 (LIMD1) is suggested as a tumor suppressor in lung cancer, but its mechanism in NSCLC remains elusive. Present study aimed to uncover the mechanism of LIMD1 in NSCLC.MethodsqRT-PCR was performed to analyze the level of LIMD1. The functions of LIMD1 in NSCLC cells were evaluated by CCK-8, EdU, and caspase-3 activity assays. RIP and pull-down assays were applied to determine the interaction of LIMD1 with heterogeneous nuclear ribonucleoprotein U (hnRNP U) and LIMD1-AS1.ResultsLIMD1 was downregulated in NSCLC samples and cells. Functionally, LIMD1 hindered proliferation and drove apoptosis in NSCLC cells. Moreover, long noncoding RNA (lncRNA) LIMD1 antisense RNA 1 (LIMD1-AS1) was downregulated in NSCLC samples and cell lines. LIMD1-AS1 knockdown abrogated NSCLC cell growth in vitro and in vivo. Mechanistically, LIMD1-AS1 stabilized LIMD1 mRNA through interacting with hnRNP U. Rescue experiments suggested that LIMD1-AS1 repressed NSCLC progression through LIMD1.ConclusionsLIMD1-AS1 suppressed NSCLC progression through stabilizing LIMD1 mRNA via hnRNP U, providing new thoughts for the improvement of molecular-targeted therapy for NSCLC.
| S-EPMC7286462 | biostudies-literature