Project description:It has been shown that up regulation activity of CD81(TAPA-1, the portal of entry of Hepatitis C virus) by agonistic antibody results in phosphorylation of Ezrin. We have previously shown that in liver, Ezrin phosphorylation occurs via Syk kinase, causing suppression of hippo intensity, therefore increases sequential Yap activity. The opposite occurs when Glypican-3 (GPC3) or E2 protein of HCV bind to CD81. Mice over-expressing GPC3 in hepatocytes have decreased p-Ezrin(Thr567) and Yap, increased Hippo activity and suppressed liver regeneration. The role of Ezrin in these processes has been speculated, but not proven. We now provide dynamic picture of Ezrin regulates Hippo pathway and Yap. Forced expression of plasmids expressing mutant Ezrin (T567D) (which mimics p-Ezrin(Thr567)) suppressed Hippo activity and activated Yap signaling. And this mutant Ezrin drive more cell proliferation to cell division through up regulated Yap activity in vitro and in vivo. CD81 loses expression, while p-Ezrin(Thr567) increases in JM1 and JM2 hepatocellular carcinoma (HCC) cells. Administration with compound NSC668394, a characterized p-Ezrin(Thr567) antagonist, caused significant decrease in HCC cell proliferation. We additionally present evidence that pEzrin(T567) is also controlled by EGFR and MET. Conclusions: Ezrin phosphorylation, mediated by CD81 associated Syk kinase, is directly involved in regulation of Hippo pathway, Yap levels and growth rates of normal and neoplastic hepatocytes. The finding has mechanistic and potentially therapeutic applications in understanding and regulating growth of hepatocytes and HCC and HCV pathogenesis. We used microarrays to detail the global programme of gene expression in GFP positive hepatocytes of FVB mice adminstration with EzrinT567D plasmids
Project description:Splicing dysregulations extensively occur in cancers, yet the biological consequences of such alterations are mostly undefined. Here we report that the Hippo-YAP signaling, a key pathway that regulates cell proliferation and organ size, is under control of a new splicing switch. We show that TEAD4, the transcription factor that mediates Hippo-YAP signaling, undergoes alternative splicing facilitated by the tumor suppressor RBM4, producing a truncated isoform, TEAD4-S, which lacks N-terminal DNA-binding domain but maintains YAP-interaction domain. TEAD4-S is located in both nucleus and cytoplasm, acting as a dominant negative isoform to YAP activity. Consistently, TEAD4-S is reduced in cancer cells, and its re-expression suppresses cancer cell proliferation and migration, inhibiting tumor growth in xenograft mouse model. Furthermore, TEAD4-S is reduced in human cancers, and patients with elevated TEAD4-S levels have improved survival. Altogether these data reveal a novel RBM4-mediated splicing switch that serves to fine-tune Hippo-YAP pathway. Cell lines stably expressing YAP, YAP/TEAD4-S, YAP/TEAD4-FL, YAP/RBM4 and control vector were created, and the total RNA was purified from the cells using TRIzol reagents. The polyadenylated RNAs were purified for construction of sequencing library using kapa TruSeq Total RNA Sample Prep kits (UNC High Throughput Sequencing Facility).
Project description:Splicing dysregulations extensively occur in cancers, yet the biological consequences of such alterations are mostly undefined. Here we report that the Hippo-YAP signaling, a key pathway that regulates cell proliferation and organ size, is under control of a new splicing switch. We show that TEAD4, the transcription factor that mediates Hippo-YAP signaling, undergoes alternative splicing facilitated by the tumor suppressor RBM4, producing a truncated isoform, TEAD4-S, which lacks N-terminal DNA-binding domain but maintains YAP-interaction domain. TEAD4-S is located in both nucleus and cytoplasm, acting as a dominant negative isoform to YAP activity. Consistently, TEAD4-S is reduced in cancer cells, and its re-expression suppresses cancer cell proliferation and migration, inhibiting tumor growth in xenograft mouse model. Furthermore, TEAD4-S is reduced in human cancers, and patients with elevated TEAD4-S levels have improved survival. Altogether these data reveal a novel RBM4-mediated splicing switch that serves to fine-tune Hippo-YAP pathway.
Project description:The Hippo pathway plays an important role in regulating tissue homeostasis, and its effectors YAP and TAZ are responsible for mediating the vast majority of its physiological functions. Although YAP and TAZ are thought to be largely redundant and similarly regulated by Hippo signaling, they have developmental, structural, and physiological differences which suggest there may be differences in their regulation and downstream functions. To better understand the functions of YAP and TAZ in the Hippo pathway, we generated knockout cells and evaluated them in response to many conditions and stimuli. Here, we used RNA-seq to identify and compare differences in the transcriptional profiles between the YAP and TAZ.
Project description:Regulation of hepatocyte proliferation and liver morphology is of critical importance to tissue and whole-body homeostasis. However, the molecular mechanisms that underlie this complex process are incompletely understood. Here we describe a novel role for the ubiquitin ligase BRAP in regulation of hepatocyte morphology and turnover via regulation of MST2, a protein kinase in the Hippo pathway. The Hippo pathway has been implicated in control of liver morphology, inflammation and fibrosis. We demonstrate here that liver-specific ablation of Brap in mice results in gross and cellular morphological alterations of the liver. Brap-deficient livers exhibit increased hepatocyte proliferation, cell death, and inflammation. We show that loss of BRAP protein alters Hippo pathway signaling, causing a reduction in phosphorylation of YAP and increased expression of YAP target genes, including those regulating cell growth and interactions with the extracellular environment. Finally, increased Hippo signaling in Brap knockout mice alters the pattern of liver lipid accumulation in dietary models of obesity. These studies identify a role for BRAP as a modulator of the hepatic Hippo pathway with relevance to human liver disease. tissue and whole-body homeostasis. However, the molecular mechanisms that underlie this complex process are incompletely understood. Here we describe a novel role for the ubiquitin ligase BRAP in regulation of hepatocyte morphology and turnover via regulation of MST2, a protein kinase in the Hippo pathway. The Hippo pathway has been implicated in control of liver morphology, inflammation and fibrosis. We demonstrate here that liver-specific ablation of Brap in mice results in gross and cellular morphological alterations of the liver. Brap-deficient livers exhibit increased hepatocyte proliferation, cell death, and inflammation. We show that loss of BRAP protein alters Hippo pathway signaling, causing a reduction in phosphorylation of YAP and increased expression of YAP target genes, including those regulating cell growth and interactions with the extracellular environment. Finally, increased Hippo signaling in Brap knockout mice alters the pattern of liver lipid accumulation in dietary models of obesity. These studies identify a role for BRAP as a modulator of the hepatic Hippo pathway with relevance to human liver disease.
Project description:Background—YAP, the nuclear effector of Hippo signaling, regulates cellular growth and survival in multiple organs, including the heart, by interacting with TEAD sequence specific DNA-binding proteins. Recent studies showed that YAP stimulates cardiomyocyte proliferation and survival. However, the direct transcriptional targets through which YAP exerts its effects are poorly defined. Methods and Results—To identify genes directly regulated by YAP in cardiomyocytes, we combined differential gene expression analysis in YAP gain- and loss-of-function with genome-wide identification of YAP bound loci using chromatin immunoprecipitation and high throughput sequencing. This screen identified Pik3cb, encoding p110β, a catalytic subunit of phosphoinositol-3-kinase (PI3K), as a candidate YAP effector that promotes cardiomyocyte proliferation and survival. We validated YAP and TEAD occupancy of a conserved enhancer within the first intron of Pik3cb, and show that this enhancer drives YAP-dependent reporter gene expression. Yap gain- and loss-of-function studies indicated that YAP is necessary and sufficient to activate the PI3K-Akt pathway. Like Yap, Pik3cb gain-of-function stimulated cardiomyocyte proliferation, and Pik3cb knockdown dampened the YAP mitogenic activity. Reciprocally, Yap loss-of-function impaired heart function and reduced cardiomyocyte proliferation and survival, all of which were significantly rescued by AAV-mediated Pik3cb expression. Conclusion—Pik3cb is a crucial direct target of YAP, through which the YAP activates PI3K-AKT pathway and regulates cardiomyocyte proliferation and survival. Yap wild type ChIPseq and input
Project description:We identified the Hippo pathway and its effector YAP as a key pathway that controls stellate cell activation. YAP is a transcriptional co-activator and we found that it drives the earliest changes in gene expression during stellate cell activation. Activation of stellate cells in vivo by CCl4 or activation in vitro caused rapid activation of YAP as revealed by its nuclear translocation and the induction of YAP target genes.
Project description:Background—YAP, the nuclear effector of Hippo signaling, regulates cellular growth and survival in multiple organs, including the heart, by interacting with TEAD sequence specific DNA-binding proteins. Recent studies showed that YAP stimulates cardiomyocyte proliferation and survival. However, the direct transcriptional targets through which YAP exerts its effects are poorly defined. Methods and Results—To identify genes directly regulated by YAP in cardiomyocytes, we combined differential gene expression analysis in YAP gain- and loss-of-function with genome-wide identification of YAP bound loci using chromatin immunoprecipitation and high throughput sequencing. This screen identified Pik3cb, encoding p110β, a catalytic subunit of phosphoinositol-3-kinase (PI3K), as a candidate YAP effector that promotes cardiomyocyte proliferation and survival. We validated YAP and TEAD occupancy of a conserved enhancer within the first intron of Pik3cb, and show that this enhancer drives YAP-dependent reporter gene expression. Yap gain- and loss-of-function studies indicated that YAP is necessary and sufficient to activate the PI3K-Akt pathway. Like Yap, Pik3cb gain-of-function stimulated cardiomyocyte proliferation, and Pik3cb knockdown dampened the YAP mitogenic activity. Reciprocally, Yap loss-of-function impaired heart function and reduced cardiomyocyte proliferation and survival, all of which were significantly rescued by AAV-mediated Pik3cb expression. Conclusion—Pik3cb is a crucial direct target of YAP, through which the YAP activates PI3K-AKT pathway and regulates cardiomyocyte proliferation and survival. Two groups were involved in this study:TNTcreYapfl_het group and TNTcreYapfl_KO group. Each group contained three biological replicates. Embryo hearts were collected at E12.5 and dissociated. Cardiomyocytes were collected by FACS. The total RNA of cardiomyocytes were isolated for microarray analysis.
Project description:Inducing cardiac myocytes to proliferate is considered a potential therapy to target heart disease, however, modulating cardiac myocyte proliferation has proven to be a technical challenge. The Hippo pathway is a kinase signaling cascade that regulates cell proliferation during the growth of the heart. Inhibition of the Hippo pathway increases the activation of the transcription factors YAP/TAZ, which translocate to the nucleus and upregulate transcription of pro-proliferative genes. The Hippo pathway regulates the proliferation of cancer cells, pluripotent stem cells, and epithelial cells through a cell-cell contact-dependent manner, however, it is unclear if cell density-dependent cell proliferation is a consistent feature in cardiac myocytes. Here, we used cultured human iPSC-derived cardiac myocytes (hiCMs) as a model system to investigate this concept. hiCMs have a comparable transcriptome to the immature cardiac myocytes that proliferate during heart development in vivo. Our data indicate that a dense syncytium of hiCMs can regain cell cycle activity and YAP expression and activity when plated sparsely or when density is reduced through wounding. We found that combining two small molecules, XMU-MP-1 and S1P, increased YAP activity and further enhanced proliferation of low-density hiCMs. Importantly, these compounds had no effect on hiCMs within a dense syncytium. These data add to a growing body of literature that link Hippo pathway regulation with cardiac myocyte proliferation and demonstrate that regulation is restricted to cells with reduced contact inhibition.
Project description:Hippo effectors YAP/TAZ act as on-off mechanosensing switches by sensing modifications in extracellular matrix (ECM) composition and mechanics. The regulation of their activity has been described so far through a hierarchical model in which elements of Hippo pathway are under the control of Focal Adhesions (FAs). Here we unveiled the molecular mechanism by which cell spreading and RhoA GTPase control FA formation through YAP to stabilize the anchorage of actin cytoskeleton to cell membrane. This mechanism required YAP co-transcriptional function and involved the activation of genes encoding for integrins and FA docking proteins. Tuning YAP transcriptional activity led to the modification of cell mechanics, force development, adhesion strength, determined cell shaping, migration and differentiation. These results provide new insights into the mechanism of YAP mechanosensing activity and qualify Hippo effector as the key determinant of cell mechanics in response to ECM cues.