Angiogenesis is a multistep process that requires coordinated migration, proliferation, and junction formation of vascular endothelial cells (ECs) to form new vessel branches in response to growth ...stimuli. Major intracellular signaling pathways that regulate angiogenesis have been well elucidated, but key transcriptional regulators that mediate these signaling pathways and control EC behaviors are only beginning to be understood. Here, we show that YAP/TAZ, a transcriptional coactivator that acts as an end effector of Hippo signaling, is critical for sprouting angiogenesis and vascular barrier formation and maturation. In mice, endothelial-specific deletion of Yap/Taz led to blunted-end, aneurysm-like tip ECs with fewer and dysmorphic filopodia at the vascular front, a hyper-pruned vascular network, reduced and disarranged distributions of tight and adherens junction proteins, disrupted barrier integrity, subsequent hemorrhage in growing retina and brain vessels, and reduced pathological choroidal neovascularization. Mechanistically, YAP/TAZ activates actin cytoskeleton remodeling, an important component of filopodia formation and junction assembly. Moreover, YAP/TAZ coordinates EC proliferation and metabolic activity by upregulating MYC signaling. Overall, these results show that YAP/TAZ plays multifaceted roles for EC behaviors, proliferation, junction assembly, and metabolism in sprouting angiogenesis and barrier formation and maturation and could be a potential therapeutic target for treating neovascular diseases.
This paper presents a ZnO–CuO p–n heterojunction chemiresistive sensor that comprises CuO hollow nanocubes attached to ZnO spherical cores as active materials. These ZnO–CuO core-hollow cube ...nanostructures exhibit a remarkable response of 11.14 at 1 ppm acetone and 200 °C, which is a superior result to those reported by other metal-oxide-based sensors. The response can be measured up to 40 ppb, and the limit of detection is estimated as 9 ppb. ZnO–CuO core-hollow cube nanostructures also present high selectivity toward acetone against other volatile organic compounds and demonstrate excellent stability for up to 40 days. The outstanding gas-sensing performance of the developed nanocubes is attributed to their uniform and unique morphology. Their core–shell-like structures allow the main charge transfer pathways to pass the interparticle p–p junctions, and the p–n junctions in each particle increase the sensitivity of the reactions to gas molecules. The small grain size and high surface area of each domain also enhance the surface gas adsorption.
YAP and TAZ play oncogenic roles in various organs, but the role of YAP/TAZ in gastric cancer remains unclear. Here, we show that YAP/TAZ activation initiates gastric tumorigenesis
and verify its ...significance in human gastric cancer. In mice, YAP/TAZ activation in the pyloric stem cell led to step-wise tumorigenesis. RNA sequencing identified MYC as a decisive target of YAP, which controls MYC at transcriptional and posttranscriptional levels. These mechanisms tightly regulated MYC in homeostatic conditions, but YAP activation altered this balance by impeding miRNA processing, causing a shift towards MYC upregulation. Pharmacologic inhibition of MYC suppressed YAP-dependent phenotypes
and
, verifying its functional role as a key mediator. Human gastric cancer samples also displayed a significant correlation between YAP and MYC. We reanalyzed human transcriptome data to verify enrichment of YAP signatures in a subpopulation of gastric cancers and found that our model closely reflected the molecular pattern of patients with high YAP activity. Overall, these results provide genetic evidence of YAP/TAZ as oncogenic initiators and drivers for gastric tumors with MYC as the key downstream mediator. These findings are also evident in human gastric cancer, emphasizing the significance of YAP/TAZ signaling in gastric carcinogenesis.
YAP/TAZ activation initiates gastric carcinogenesis with MYC as the key downstream mediator.
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Actin cytoskeletal damage induces inactivation of the oncoprotein YAP (Yes‐associated protein). It is known that the serine/threonine kinase LATS (large tumour suppressor) inactivates YAP by ...phosphorylating its Ser127 and Ser381 residues. However, the events downstream of actin cytoskeletal changes that are involved in the regulation of the LATS–YAP pathway and the mechanism by which LATS differentially phosphorylates YAP on Ser127 and Ser381 in vivo have remained elusive. Here, we show that cyclic AMP (cAMP)‐dependent protein kinase (PKA) phosphorylates LATS and thereby enhances its activity sufficiently to phosphorylate YAP on Ser381. We also found that PKA activity is involved in all contexts previously reported to trigger the LATS–YAP pathway, including actin cytoskeletal damage, G‐protein‐coupled receptor activation, and engagement of the Hippo pathway. Inhibition of PKA and overexpression of YAP cooperate to transform normal cells and amplify neural progenitor pools in developing chick embryos. We also implicate neurofibromin 2 as an AKAP (A‐kinase‐anchoring protein) scaffold protein that facilitates the function of the cAMP/PKA–LATS–YAP pathway. Our study thus incorporates PKA as novel component of the Hippo pathway.
Actin cytoskeletal damage triggers inactivation of the oncoprotein YAP through phosphorylation by the LATS kinase downstream of PKA. Indeed, PKA is a Hippo pathway component implicated ubiquitously in LATS–YAP signalling.
The Hippo pathway is a central regulator of organ size and tumorigenesis and is commonly depicted as a kinase cascade, with an increasing number of regulatory and adaptor proteins linked to its ...regulation over recent years. Here, we propose that two Hippo signaling modules, MST1/2–SAV1–WWC1‐3 (HPO1) and MAP4K1‐7–NF2 (HPO2), together regulate the activity of LATS1/2 kinases and YAP/TAZ transcriptional co‐activators. In mouse livers, the genetic inactivation of either HPO1 or HPO2 module results in partial activation of YAP/TAZ, bile duct hyperplasia, and hepatocellular carcinoma (HCC). On the contrary, inactivation of both HPO1 and HPO2 modules results in full activation of YAP/TAZ, rapid development of intrahepatic cholangiocarcinoma (iCCA), and early lethality. Interestingly, HPO1 has a predominant role in regulating organ size. HPO1 inactivation causes a homogenous YAP/TAZ activation and cell proliferation across the whole liver, resulting in a proportional and rapid increase in liver size. Thus, this study has reconstructed the order of the Hippo signaling network and suggests that LATS1/2 and YAP/TAZ activities are finetuned by HPO1 and HPO2 modules to cause different cell fates, organ size changes, and tumorigenesis trajectories.
Synopsis
The Hippo pathway inhibits YAP/TAZ transcriptional co‐activators to regulate organ size and tumorigenesis. This study shows that upstream kinases and associated adaptor proteins of the Hippo pathway form two signaling modules that differentially regulate YAP/TAZ activity and its function in the liver.
The HPO1 module is formed by MST1/2 kinases and the adaptor proteins SAV1 and WWC1‐3, while the HPO2 module includes MAP4K1‐7 and the adaptor protein NF2.
Simultaneous deletion of HPO1 and HPO2 components leads to full activation of YAP/TAZ in a manner comparable with LATS1/2 deficiency.
Liver‐specific inactivation of either HPO1 or HPO2 module results in partial YAP/TAZ activation, bile duct hyperplasia, and hepatocellular carcinoma.
Inactivation of both HPO1 and HPO2 modules in the liver results in intrahepatic cholangiocarcinoma and early lethality.
HPO1 is the major organ size regulator, and its inactivation causes rapid hepatomegaly.
Two distinct Hippo signaling pathway modules converge on the kinases LATS1/2 to differentially regulate YAP/TAZ activation.
Yes‐associated protein (YAP) and myocardin‐related transcription factor (MRTF) play similar roles and exhibit significant crosstalk in directing transcriptional responses to chemical and physical ...extracellular cues. The mechanism underlying this crosstalk, however, remains unclear. Here, we show MRTF family proteins bind YAP via a conserved PPXY motif that interacts with the YAP WW domain. This interaction allows MRTF to recruit NcoA3 to the TEAD‐YAP transcriptional complex and potentiate its transcriptional activity. We show this interaction of MRTF and YAP is critical for LPA‐induced cancer cell invasion in vitro and breast cancer metastasis to the lung in vivo. We also demonstrate the significance of MRTF‐YAP binding in regulation of YAP activity upon acute actin cytoskeletal damage. Acute actin disruption induces nucleo‐cytoplasmic shuttling of MRTF, and this process underlies the LATS‐independent regulation of YAP activity. Our results provide clear evidence of crosstalk between MRTF and YAP independent of the LATS kinases that normally act upstream of YAP signaling. Our results also suggest a mechanism by which extracellular stimuli can coordinate physiological events downstream of YAP.
Synopsis
Oncogenic activity of TEAD‐YAP transcription complex is enhanced by MRTF proteins, which recruit NcoA3. MRTF–YAP interaction highlights a novel mode of signal transduction that regulates YAP activity independently of subcellular localization.
MRTF family proteins activate TEAD‐YAP by direct binding through PPXY–WW domain interaction.
MRTF–YAP interaction is required for TEAD‐YAP target gene expression and promotion of cancer cell invasion and metastasis.
MRTF binding to TEAD‐YAP recruits NcoA3 for full potentiation of TEAD‐YAP activity.
MRTF–YAP interaction constitutes a LATS‐independent regulatory mechanism on TEAD‐YAP activity.
Crosstalk with transcription factor MRTF enhances TEAD‐YAP oncogenic activity, coordinating signal transduction of extracellular GPCR ligands involved in cancer cell invasion or actin cytoskeletal disruption.
Hypoxia is a main driver of sprouting angiogenesis, but how tip endothelial cells are directed to hypoxic regions remains poorly understood. Here, we show that an endothelial MST1-FOXO1 cascade is ...essential for directional migration of tip cells towards hypoxic regions. In mice, endothelial-specific deletion of either MST1 or FOXO1 leads to the loss of tip cell polarity and subsequent impairment of sprouting angiogenesis. Mechanistically, MST1 is activated by reactive oxygen species (ROS) produced in mitochondria in response to hypoxia, and activated MST1 promotes the nuclear import of FOXO1, thus augmenting its transcriptional regulation of polarity and migration-associated genes. Furthermore, endothelial MST1-FOXO1 cascade is required for revascularization and neovascularization in the oxygen-induced retinopathy model. Together, the results of our study delineate a crucial coupling between extracellular hypoxia and an intracellular ROS-MST1-FOXO1 cascade in establishing endothelial tip cell polarity during sprouting angiogenesis.
Mechanical tensions are usually generated during development at spatially defined regions within tissues. Such physical cues dictate the cellular decisions of proliferation or cell cycle arrest. Yet, ...the mechanisms by which mechanical stress controls the cell cycle are not yet fully understood. Here, we report that mechanical cues function upstream of Skp2 transcription in human breast cancer cells. We found that YAP, the mechano‐responsive oncogenic Hippo signaling effector, directly promotes Skp2 transcription. YAP inactivation induces cell cycle exit (G0) by down‐regulating Skp2, causing p21/p27 to accumulate. Both Skp2 reconstitution and p21/p27 depletion can rescue the observed defect in cell cycle progression. In the context of a tissue‐mimicking 3D culture system, Skp2 inactivation effectively suppresses YAP‐driven oncogenesis and aberrant stiff 3D matrix‐evoked epithelial tissue behaviors. Finally, we also found that the expression of Skp2 and YAP is positively correlated in breast cancer patients. Our results not only reveal the molecular mechanism by which mechanical cues induce Skp2 transcription, but also uncover a role for YAP‐Skp2 oncogenic signaling in the relationship between tissue rigidity and cancer progression.
Synopsis
The cell cycle regulator and F‐box protein Skp2 is a direct target of the Hippo pathway effector YAP, and required for YAP's oncogenic activity upon mechanoregulation.
Mechanical cues function upstream of Skp2 transcription.
YAP and TEAD directly promote Skp2 transcription in response to mechanical cues.
YAP inactivation induces cell cycle exit (G0) by down‐regulating Skp2, causing accumulation of p21/p27.
Both Skp2 reconstitution and p21/p27 depletion rescue the defective cell cycle progression.
Skp2 inactivation suppresses YAP‐driven tumor‐spheroid‐like acini and aberrant tissue behaviors in a 3D stiff matrix.
YAP and Skp2 expression positively correlate in breast cancer patients.
YAP links mechanical stress and Skp2 transcription to instruct cell cycle progression and oncogenic functions in breast cancer growth.
Here we show that Mst1, a proapoptotic kinase, impairs protein quality control mechanisms in the heart through inhibition of autophagy. Stress-induced activation of Mst1 in cardiomyocytes promoted ...accumulation of p62 and aggresome formation, accompanied by the disappearance of autophagosomes. Mst1 phosphorylated the Thr108 residue in the BH3 domain of Beclin1, which enhanced the interaction between Beclin1 and Bcl-2 and/or Bcl-xL, stabilized the Beclin1 homodimer, inhibited the phosphatidylinositide 3-kinase activity of the Atg14L-Beclin1-Vps34 complex and suppressed autophagy. Furthermore, Mst1-induced sequestration of Bcl-2 and Bcl-xL by Beclin1 allows Bax to become active, thereby stimulating apoptosis. Mst1 promoted cardiac dysfunction in mice subjected to myocardial infarction by inhibiting autophagy, associated with increased levels of Thr108-phosphorylated Beclin1. Moreover, dilated cardiomyopathy in humans was associated with increased levels of Thr108-phosphorylated Beclin1 and signs of autophagic suppression. These results suggest that Mst1 coordinately regulates autophagy and apoptosis by phosphorylating Beclin1 and consequently modulating a three-way interaction among Bcl-2 proteins, Beclin1 and Bax.
LKB1 plays important roles in governing energy homeostasis by regulating AMP-activated protein kinase (AMPK) and other AMPK-related kinases, including the salt-inducible kinases (SIKs). However, the ...roles and regulation of LKB1 in lipid metabolism are poorly understood. Here we show that Drosophila LKB1 mutants display decreased lipid storage and increased gene expression of brummer, the Drosophila homolog of adipose triglyceride lipase (ATGL). These phenotypes are consistent with those of SIK3 mutants and are rescued by expression of constitutively active SIK3 in the fat body, suggesting that SIK3 is a key downstream kinase of LKB1. Using genetic and biochemical analyses, we identify HDAC4, a class IIa histone deacetylase, as a lipolytic target of the LKB1-SIK3 pathway. Interestingly, we found that the LKB1-SIK3-HDAC4 signaling axis is modulated by dietary conditions. In short-term fasting, the adipokinetic hormone (AKH) pathway, related to the mammalian glucagon pathway, inhibits the kinase activity of LKB1 as shown by decreased SIK3 Thr196 phosphorylation, and consequently induces HDAC4 nuclear localization and brummer gene expression. However, under prolonged fasting conditions, AKH-independent signaling decreases the activity of the LKB1-SIK3 pathway to induce lipolytic responses. We also identify that the Drosophila insulin-like peptides (DILPs) pathway, related to mammalian insulin pathway, regulates SIK3 activity in feeding conditions independently of increasing LKB1 kinase activity. Overall, these data suggest that fasting stimuli specifically control the kinase activity of LKB1 and establish the LKB1-SIK3 pathway as a converging point between feeding and fasting signals to control lipid homeostasis in Drosophila.
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