Dynamic Hippo pathway activity underlies mesenchymal differentiation during lung alveolar morphogenesis.

Alveologenesis, the final stage in lung development, substantially remodels the distal lung, expanding the alveolar surface area for efficient gas exchange. Secondary crest myofibroblasts (SCMF) exist transiently in the neonatal distal lung and are crucial for alveologenesis. However, the pathways that regulate SCMF function, proliferation and temporal identity remain poorly understood. To address this, we purified SCMFs from reporter mice, performed bulk RNA-seq and found dynamic changes in Hippo-signaling components during alveologenesis. We deleted the Hippo effectors Yap/Taz from Acta2-expressing cells at the onset of alveologenesis, causing a significant arrest in alveolar development. Using single cell RNA-seq, we identified a distinct cluster of cells in mutant lungs with altered expression of marker genes associated with proximal mesenchymal cell types, airway smooth muscle and alveolar duct myofibroblasts. In vitro studies confirmed that Yap/Taz regulates myofibroblast-associated gene signature and contractility. Together, our findings show that Yap/Taz is essential for maintaining functional myofibroblast identity during postnatal alveologenesis.

Genome-wide CRISPR screens identify the YAP/TEAD axis as a driver of persister cells in EGFR mutant lung cancer.

Most lung cancer patients with metastatic cancer eventually relapse with drug-resistant disease following treatment and EGFR mutant lung cancer is no exception. Genome-wide CRISPR screens, to either knock out or overexpress all protein-coding genes in cancer cell lines, revealed the landscape of pathways that cause resistance to the EGFR inhibitors osimertinib or gefitinib in EGFR mutant lung cancer. Among the most recurrent resistance genes were those that regulate the Hippo pathway. Following osimertinib treatment a subpopulation of cancer cells are able to survive and over time develop stable resistance. These 'persister' cells can exploit non-genetic (transcriptional) programs that enable cancer cells to survive drug treatment. Using genetic and pharmacologic tools we identified Hippo signalling as an important non-genetic mechanism of cell survival following osimertinib treatment. Further, we show that combinatorial targeting of the Hippo pathway and EGFR is highly effective in EGFR mutant lung cancer cells and patient-derived organoids, suggesting a new therapeutic strategy for EGFR mutant lung cancer patients.

N6-methyladenosine-modified circTEAD1 stabilizes Yap1 mRNA to promote chordoma tumorigenesis.

BACKGROUND: Chordoma, a rare bone tumour with aggressive local invasion and high recurrence rate with limited understanding of its molecular mechanisms. Circular RNAs (circRNAs) have been extensively implicated in tumorigenesis, yet their involvement in chordoma remains largely unexplored. N6-methyladenosine (m6A) modification holds a crucial function in regulating protein translation, RNA degradation and transcription. METHODS: Initially, screening and validation of circTEAD1 in chordoma were conducted by high-throughput sequencing. Subsequently, sh-circTEAD1 and an overexpression plasmid were constructed. Colony formation assays, cell counting kit-8, Transwell and wound healing assays were utilized to validate the function of circTEAD1 in vitro. RNA pull-down assays identified the binding proteins of circTEAD1, which underwent verification through RNA immunoprecipitation (RIP). Methylated RIP assays were conducted to detect the m6A binding sites. Following this, luciferase assay, RT-qPCR, RIP and Western blotting analyses were conducted, revealing that Yap1 was the direct target of circTEAD1. Afterwards, the same methods were utilized for the validation of the function of Yap1 in chordoma in vitro. Finally, the regulatory relationship between circTEAD1 and Yap1 in chordoma was verified by an in vivo tumour formation assay. RESULTS: CircTEAD1 was identified as an upregulated circRNA in chordoma specimens, with heightened circTEAD1 expression emerging as a prognostic indicator. In vitro experiments convincingly demonstrated that circTEAD1 significantly promoted chordoma cell invasion, migration and aggressiveness. Furthermore, the analysis revealed that methyltransferase-like 3-mediated m6A modification facilitated the cytoplasmic export of circTEAD1. The circTEAD1/IGF2BP3/Yap1 mRNA RNA-protein ternary complex not only bolstered the stability of Yap1 mRNA but also exerted a pivotal role in driving chordoma tumorigenesis. CONCLUSIONS: In this study, the role of m6A-modified circTEAD1 in chordoma was identified. The findings offer novel insights into the potential molecular targets for chordoma therapy, shedding light on the intricate interplay between circRNAs, m6A modification and Yap1 mRNA in chordoma pathogenesis.

SRY-Box transcription factor 9 triggers YAP nuclear entry via direct interaction in tumors.

The translocation of YAP from the cytoplasm to the nucleus is critical for its activation and plays a key role in tumor progression. However, the precise molecular mechanisms governing the nuclear import of YAP are not fully understood. In this study, we have uncovered a crucial role of SOX9 in the activation of YAP. SOX9 promotes the nuclear translocation of YAP by direct interaction. Importantly, we have identified that the binding between Asp-125 of SOX9 and Arg-124 of YAP is essential for SOX9-YAP interaction and subsequent nuclear entry of YAP. Additionally, we have discovered a novel asymmetrical dimethylation of YAP at Arg-124 (YAP-R124me2a) catalyzed by PRMT1. YAP-R124me2a enhances the interaction between YAP and SOX9 and is associated with poor prognosis in multiple cancers. Furthermore, we disrupted the interaction between SOX9 and YAP using a competitive peptide, S-A1, which mimics an α-helix of SOX9 containing Asp-125. S-A1 significantly inhibits YAP nuclear translocation and effectively suppresses tumor growth. This study provides the first evidence of SOX9 as a pivotal regulator driving YAP nuclear translocation and presents a potential therapeutic strategy for YAP-driven human cancers by targeting SOX9-YAP interaction.

Dynamic YAP expression in the non-parenchymal liver cell compartment controls heterologous cell communication.

INTRODUCTION: The Hippo pathway and its transcriptional effectors yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are targets for cancer therapy. It is important to determine if the activation of one factor compensates for the inhibition of the other. Moreover, it is unknown if YAP/TAZ-directed perturbation affects cell-cell communication of non-malignant liver cells. MATERIALS AND METHODS: To investigate liver-specific phenotypes caused by YAP and TAZ inactivation, we generated mice with hepatocyte (HC) and biliary epithelial cell (BEC)-specific deletions for both factors (YAPKO, TAZKO and double knock-out (DKO)). Immunohistochemistry, single-cell sequencing, and proteomics were used to analyze liver tissues and serum. RESULTS: The loss of BECs, liver fibrosis, and necrosis characterized livers from YAPKO and DKO mice. This phenotype was weakened in DKO tissues compared to specimens from YAPKO animals. After depletion of YAP in HCs and BECs, YAP expression was induced in non-parenchymal cells (NPCs) in a cholestasis-independent manner. YAP positivity was detected in subgroups of Kupffer cells (KCs) and endothelial cells (ECs). The secretion of pro-inflammatory chemokines and cytokines such as C-X-C motif chemokine ligand 11 (CXCL11), fms-related receptor tyrosine kinase 3 ligand (FLT3L), and soluble intercellular adhesion molecule-1 (ICAM1) was increased in the serum of YAPKO animals. YAP activation in NPCs could contribute to inflammation via TEA domain transcription factor (TEAD)-dependent transcriptional regulation of secreted factors. CONCLUSION: YAP inactivation in HCs and BECs causes liver damage, and concomitant TAZ deletion does not enhance but reduces this phenotype. Additionally, we present a new mechanism by which YAP contributes to cell-cell communication originating from NPCs.

YAP knockdown repressed autophagy in fibroblasts to accelerate wound healing through regulating En1/mTOR axis.

OBJECTIVE: Wound repair dysfunction is becoming a major public health issue worldwide. Yes-associated protein (YAP) has previously been reported to be closely related to wound healing, while how YAP accelerates wound healing via regulating autophagy needs to be further probed. MATERIALS AND METHODS: ICR male mice were involved in two independent animal experiments; the mice were randomly allocated into control, autophagy inhibitor (3-MA) (injection), and 3-MA (drip) group or control, si-NC, si-YAP group (8 mice for each). Full-thickness excisional wounds (8 mm) in mice were created by punch to construct an in vivo wound model to observe the effects of autophagy inhibitor (3-MA) (by injection and drip) and si-YAP by electrotransfection. RESULTS: Firstly, we found that the autophagy inhibitor (3-MA) accelerated wound closure in vivo. Loss-of-function experiments subsequently revealed that YAP knockdown led to increased proliferation and migration of fibroblasts as well as reduced autophagy, resulting in accelerated wound healing. In addition, our results revealed that YAP could positively regulate Engrailed-1 (En1) expression in fibroblasts. En1 knockdown also promoted the proliferation and migration of fibroblasts, meanwhile resulting in increased mammalian target of rapamycin (mTOR) levels and reduced autophagy in fibroblasts. CONCLUSIONS: YAP knockdown repressed autophagy in fibroblasts to accelerate wound closure by regulating the En1/mTOR axis.

Blockade of ZFX Alleviates Hypoxia-Induced Pulmonary Vascular Remodeling by Regulating the YAP Signaling.

High expression of the zinc finger X-chromosomal protein (ZFX) correlates with proliferation, aggressiveness, and development in many types of cancers. In the current report, we investigated the efficacy of ZFX in mouse pulmonary artery smooth muscle cells (PASMCs) proliferation during pulmonary arterial hypertension (PAH). PASMCs were cultured in hypoxic conditions. Real-time PCR and western blotting were conducted to detect the expression of ZFX. Cell proliferation, apoptosis, migration, and invasion were, respectively, measured by CCK-8, flow cytometry, wound scratchy, and transwell assays. Glycolytic ability was validated by the extracellular acidification rate and oxygen consumption rate. Transcriptome sequencing technology was used to explore the genes affected by ZFX knockdown. Luciferase and chromatin immunoprecipitation assays were utilized to verify the possible binding site of ZFX and YAP1. Mice were subjected to hypoxia for 21 days to induce PAH. The right ventricular systolic pressure (RVSP) was measured and ratio of RV/LV + S was calculated. The results show that ZFX was increased in hypoxia-induced PASMCs and mice. ZFX knockdown inhibited the proliferation, migration, and invasion of PASMC. Using RNA sequencing, we identify glycolysis and YAP as a key signaling of ZFX. ZFX knockdown inhibited Glycolytic ability. ZFX strengthened the transcription activity of YAP1, thereby regulating the YAP signaling. YAP1 overexpression reversed the effect of ZFX knockdown on hypoxia-treated PASMCs. In conclusion, ZFX knockdown protected mice from hypoxia-induced PAH injury. ZFX knockdown dramatically reduced RVSP and RV/(LV + S) in hypoxia-treated mice.

DNMT3A Cooperates with YAP/TAZ to Drive Gallbladder Cancer Metastasis.

Gallbladder cancer (GBC) is an extremely lethal malignancy with aggressive behaviors, including liver or distant metastasis; however, the underlying mechanisms driving the metastasis of GBC remain poorly understood. In this study, it is found that DNA methyltransferase DNMT3A is highly expressed in GBC tumor tissues compared to matched adjacent normal tissues. Clinicopathological analysis shows that DNMT3A is positively correlated with liver metastasis and poor overall survival outcomes in patients with GBC. Functional analysis confirms that DNMT3A promotes the metastasis of GBC cells in a manner dependent on its DNA methyltransferase activity. Mechanistically, DNMT3A interacts with and is recruited by YAP/TAZ to recognize and access the CpG island within the CDH1 promoter and generates hypermethylation of the CDH1 promoter, which leads to transcriptional silencing of CDH1 and accelerated epithelial-to-mesenchymal transition. Using tissue microarrays, the association between the expression of DNMT3A, YAP/TAZ, and CDH1 is confirmed, which affects the metastatic ability of GBC. These results reveal a novel mechanism through which DNMT3A recruitment by YAP/TAZ guides DNA methylation to drive GBC metastasis and provide insights into the treatment of GBC metastasis by targeting the functional connection between DNMT3A and YAP/TAZ.

Chromatin accessibility complex subunit 1 enhances tumor growth by regulating the oncogenic transcription of YAP in breast and cervical cancer.

Background: As a component of chromatin remodeling complex, chromatin accessibility complex subunit 1 (CHRAC1) is critical in transcription and DNA replication. However, the significance of CHRAC1 in cancer progression has not been investigated extensively. This research aimed to determine the function of CHRAC1 in breast and cervical cancer and elucidate the molecular mechanism. Methods: The Bio-ID method was used to identify the interactome of transcriptional activator Yes-associated protein (YAP) and the binding between YAP and CHRAC1 was verified by immunofluorescence. CCK8, colony formation and subcutaneous xenograft assays were conducted to explore the function of CHRAC1 in cancer cell proliferation. RNA-seq analysis and RT-PCR were used to analyze the transcription program change after CHRAC1 ablation. The diagnostic value of CHRAC1 was analyzed by TCGA database and further validated by immunohistochemistry staining. Results: In the current study, we found that the chromatin remodeler CHRAC1 was a potential YAP interactor. CHRAC1 depletion suppressed breast and cervical cancer cell proliferation and tumor growth. The potential mechanism may be that CHRAC1 interacts with YAP to facilitate oncogenic transcription of YAP target genes in Hippo pathway, thereby promoting tumorigenesis. CHRAC1 was elevated in cervical and breast cancer biopsies and the upregulation correlated with shorter survival, poor pathological stages and metastasis of cancer patients. Moreover, CHRAC1 expression was statistically associated with YAP in breast and cervical cancer biopsies. Conclusions: These findings highlight that CHRAC1 contributes to cancer progression through regulating the oncogenic transcription of YAP, which makes it a potential therapeutic target for cancer treatment.

Androgen receptor promotes cell stemness via interacting with co-factor YAP1 in gastric cancer.

Cancer stem cells (CSCs) have been proposed to explain tumor relapse and chemoresistance in various types of cancers, and androgen receptor (AR) has been emerged as a potential regulator of stemness in cancers. However, the underlying mechanism of AR-regulated CSCs properties and chemoresistance in gastric cancer (GC) remains unknown. Here, we shown that AR is upregulated in GC tissues and correlates with poor survival rate and CSCs phenotypes of GC patients. According to our experimental data, overexpression of AR upregulated the expression of CSCs markers and this was consistent with the result concluded from data analysis that the expression of AR was positively correlated with CD44 in GC patients. In addition, AR overexpression obviously enhanced the tumor sphere formation ability and chemoresistance of GC cells in vitro. Whereas these effects were attenuated by inhibition of AR. These results were further validated in vivo that MGC-803 cells overexpressing AR had stronger properties to initiate gastric tumorigenesis than the control cells, and inhibition of AR increased the chemosensitivity of GC cells. Mechanically, AR upregulated CD44 expression by directly binding to its promoter region and Yes-associated protein 1 (YAP1) served as the co-factor of AR, which was demonstrated by the fact that the promoting effects of AR on GC cells stemness were partially counteracted by YAP1 knockdown. Thus, this study revealed that AR facilitates CSCs properties and chemoresistance of GC cells via forming complex with YAP1and indicates a potential therapeutic approach to GC patients.

Deep annotation of long noncoding RNAs by assembling RNA-seq and small RNA-seq data.

Long noncoding RNAs (lncRNAs) are increasingly being recognized as modulators in various biological processes. However, due to their low expression, their systematic characterization is difficult to determine. Here, we performed transcript annotation by a newly developed computational pipeline, termed RNA-seq and small RNA-seq combined strategy (RSCS), in a wide variety of cellular contexts. Thousands of high-confidence potential novel transcripts were identified by the RSCS, and the reliability of the transcriptome was verified by analysis of transcript structure, base composition, and sequence complexity. Evidenced by the length comparison, the frequency of the core promoter and the polyadenylation signal motifs, and the locations of transcription start and end sites, the transcripts appear to be full length. Furthermore, taking advantage of our strategy, we identified a large number of endogenous retrovirus-associated lncRNAs, and a novel endogenous retrovirus-lncRNA that was functionally involved in control of Yap1 expression and essential for early embryogenesis was identified. In summary, the RSCS can generate a more complete and precise transcriptome, and our findings greatly expanded the transcriptome annotation for the mammalian community.

Loss of TAZ after YAP deletion severely impairs foregut development and worsens cholestatic hepatocellular injury.

BACKGROUND: We previously showed that loss of yes-associated protein 1 (YAP) in early liver development (YAPKO) leads to an Alagille syndrome-like phenotype, with failure of intrahepatic bile duct development, severe cholestasis, and chronic hepatocyte adaptations to reduce liver injury. TAZ, a paralog of YAP, was significantly upregulated in YAPKO hepatocytes and interacted with TEA domain family member (TEAD) transcription factors, suggesting possible compensatory activity. METHODS: We deleted both Yap1 and Wwtr1 (which encodes TAZ) during early liver development using the Foxa3 promoter to drive Cre expression, similar to YAPKO mice, resulting in YAP/TAZ double knockout (DKO) and YAPKO with TAZ heterozygosity (YAPKO TAZHET). We evaluated these mice using immunohistochemistry, serum biochemistry, bile acid profiling, and RNA sequencing. RESULTS: DKO mice were embryonic lethal, but their livers were similar to YAPKO, suggesting an extrahepatic cause of death. Male YAPKO TAZHET mice were also embryonic lethal, with insufficient samples to determine the cause. However, YAPKO TAZHET females survived and were phenotypically similar to YAPKO mice, with increased bile acid hydrophilicity and similar global gene expression adaptations but worsened the hepatocellular injury. TAZ heterozygosity in YAPKO impacted the expression of canonical YAP targets Ctgf and Cyr61, and we found changes in pathways regulating cell division and inflammatory signaling correlating with an increase in hepatocyte cell death, cell cycling, and macrophage recruitment. CONCLUSIONS: YAP loss (with or without TAZ loss) aborts biliary development. YAP and TAZ play a codependent critical role in foregut endoderm development outside the liver, but they are not essential for hepatocyte development. TAZ heterozygosity in YAPKO livers increased cell cycling and inflammatory signaling in the setting of chronic injury, highlighting genes that are especially sensitive to TAZ regulation.

Mechanical control of the mammalian circadian clock via YAP/TAZ and TEAD.

Autonomous circadian clocks exist in nearly every mammalian cell type. These cellular clocks are subjected to a multilayered regulation sensitive to the mechanochemical cell microenvironment. Whereas the biochemical signaling that controls the cellular circadian clock is increasingly well understood, mechanisms underlying regulation by mechanical cues are largely unknown. Here we show that the fibroblast circadian clock is mechanically regulated through YAP/TAZ nuclear levels. We use high-throughput analysis of single-cell circadian rhythms and apply controlled mechanical, biochemical, and genetic perturbations to study the expression of the clock gene Rev-erbα. We observe that Rev-erbα circadian oscillations are disrupted with YAP/TAZ nuclear translocation. By targeted mutations and overexpression of YAP/TAZ, we show that this mechanobiological regulation, which also impacts core components of the clock such as Bmal1 and Cry1, depends on the binding of YAP/TAZ to the transcriptional effector TEAD. This mechanism could explain the impairment of circadian rhythms observed when YAP/TAZ activity is upregulated, as in cancer and aging.

YES-associated protein-regulated Smad7 worsen epithelial barrier injury of chronic sinusitis with nasal polyps.

BACKGROUND: Chronic rhinosinusitis with nasal polyps (CRSwNP) was potentially due to the epithelial barrier injury. YES-associated protein (YAP) is a multifunctional transcriptional factor and plays versatile roles in the regulation and maintenance of epithelial barrier in different organs and tissues. The purpose of this study is to elucidate possible effect and mechanism of YAP on the epithelial barrier of CRSwNP. METHODS: Patients were divided into CRSwNP group (n = 12) and control group (n = 9). The location of YAP, PDZ-binding transcriptional co-activator (TAZ), and Smad7 were estimated by immunohistochemistry and immunofluorescence. Meanwhile, the expression of YAP, TAZ, Zona occludens-1 (ZO-1), E-cadherin, and transforming growth factor-beta1 (TGF-ß1) were detected by Western blot. After primary human nasal epithelial cells were treated with YAP inhibitor, the expression level of YAP, TAZ, ZO-1, E-cadherin, TGF-ß1, and Smad7 were measured by Western blot. RESULTS: Compared with the control group, the protein levels of YAP, TAZ, and Smad7 were significantly upregulated, while TGF-ß1, ZO-1, and E-cadherin were downregulated in CRSwNP. YAP and Smad7 demonstrated lower levels, while the expression of ZO-1, E-cadherin, and TGF-ß1 rose slightly after YAP inhibitor treatment in primary nasal epithelial cells. CONCLUSIONS: Higher level of YAP may lead to CRSwNP epithelial barrier injury via the TGF-ß1 signaling pathway, and the inhibition of YAP can partially reverse epithelial barrier function.

The oncogenic role of NF1 in gallbladder cancer through regulation of YAP1 stability by direct interaction with YAP1.

BACKGROUND: Gallbladder cancer (GBC) is the most prevalent and invasive biliary tract malignancy. As a GTPase-activating protein, Neurofibromin 1 (NF1) is a tumor suppressor that negatively regulates the RAS signaling pathway, and its abnormality leads to neurofibromatosis type 1 (NF-1) disease. However, the role of NF1 playing in GBC and the underlying molecular mechanism has not been defined yet. METHODS: A combination of NOZ and EH-GB1 cell lines as well as nude mice, were utilized in this study. mRNA expression and protein levels of NF1 and YAP1 were evaluated by quantitative real-time PCR (qRT-PCR), western blot (WB), and immunohistochemistry (IHC). In vitro and in vivo assays were performed to explore the biological effects of NF1 in NOZ and EH-GB1 cells via siRNA or lv-shRNA mediated knockdown. Direct interaction between NF1 and YAP1 was detected by confocal microscopy and co-immunoprecipitation (Co-IP), and further confirmed by GST pull-down assay and isothermal titration calorimetry assay (ITC). The stability of proteins was measured by western blot (WB) in the presence of cycloheximide. RESULTS: This study showed that a higher level of NF1 and YAP1 was found in GBC samples than in normal tissues and associated with worse prognoses. The NF1 knockdown impaired the proliferation and migration of NOZ in vivo and in vitro by downregulating YAP1 expression. Moreover, NF1 co-localized with YAP1 in NOZ and EH-GB1 cells, and the WW domains of YAP1 specifically recognized the PPQY motif of NF1. The structural modeling also indicated the hydrophobic interactions between YAP1 and NF1. On the other hand, YAP1 knockdown also impaired the proliferation of NOZ in vitro, phenocopying the effects of NF1 knockdown. Overexpression of YAP1 can partially rescue the impaired proliferation in NF1 stably knockdown cells. In mechanism, NF1 interacted with YAP1 and increased the stability of YAP1 by preventing ubiquitination. CONCLUSIONS: Our findings discovered a novel oncogenic function of NF1 by directly interacting with YAP1 protein and stabilizing YAP1 to protect it from proteasome degradation in NOZ cells. NF1 may serve as a potential therapeutic target in GBC.

Mechanoepigenetic regulation of extracellular matrix homeostasis via Yap and Taz.

Cells integrate mechanical cues to direct fate specification to maintain tissue function and homeostasis. While disruption of these cues is known to lead to aberrant cell behavior and chronic diseases, such as tendinopathies, the underlying mechanisms by which mechanical signals maintain cell function are not well understood. Here, we show using a model of tendon de-tensioning that loss of tensile cues in vivo acutely changes nuclear morphology, positioning, and expression of catabolic gene programs, resulting in subsequent weakening of the tendon. In vitro studies using paired ATAC/RNAseq demonstrate that the loss of cellular tension rapidly reduces chromatin accessibility in the vicinity of Yap/Taz genomic targets while also increasing expression of genes involved in matrix catabolism. Concordantly, the depletion of Yap/Taz elevates matrix catabolic expression. Conversely, overexpression of Yap results in a reduction of chromatin accessibility at matrix catabolic gene loci, while also reducing transcriptional levels. The overexpression of Yap not only prevents the induction of this broad catabolic program following a loss of cellular tension, but also preserves the underlying chromatin state from force-induced alterations. Taken together, these results provide novel mechanistic details by which mechanoepigenetic signals regulate tendon cell function through a Yap/Taz axis.

Recent advances in the role of Yes-associated protein in dermatosis.

BACKGROUND: Dermatosis is a general term for diseases of the skin and skin appendages including scleroderma, psoriasis, bullous disease, atopic dermatitis, basal cell carcinoma, squamous cell carcinoma, and melanoma. These diseases affect millions of individuals globally and are a serious public health concern. However, the pathogenesis of skin diseases is not fully understood, and treatments are not optimal. Yes-associated protein (YAP) is a transcriptional coactivator that plays a role in the regulation of gene transcription and signal transduction. AIMS: To study the role of Yes-associated protein in skin diseases. MATERIALS AND METHODS: The present review summarizes recent advances in our understanding of the role of YAP in skin diseases, current treatments that target YAP, and potential avenues for novel therapies. RESULTS: Abnormal YAP expression has been implicated in occurrence and development of dermatosis. YAP regulates the cell homeostasis, proliferation, differentiation, apoptosis, angiopoiesis, and epithelial-to-mesenchymal transition, among other processes. As well as, it serves as a potential target in many biological processes for treating dermatosis. CONCLUSIONS: The effects of YAP on the skin are complex and require multidimensional investigational approaches. YAP functions as an oncoprotein that can promote the occurrence and development of cancer, but there is currently limited information on the therapeutic potential of YAP inhibition for cancer treatment. Additional studies are also needed to clarify the role of YAP in the development and maturation of dermal fibroblasts; skin barrier function, homeostasis, aging, and melanin production; and dermatosis.

Lipophilic Statins Inhibit YAP Nuclear Localization, Coactivator Activity, and Migration in Response to Ligation of HLA Class I Molecules in Endothelial Cells: Role of YAP Multisite Phosphorylation.

Solid-organ transplant recipients exhibiting HLA donor-specific Abs are at risk for graft loss due to chronic Ab-mediated rejection. HLA Abs bind HLA molecules expressed on the surface of endothelial cells (ECs) and induce intracellular signaling pathways, including the activation of the transcriptional coactivator yes-associated protein (YAP). In this study, we examined the impact of lipid-lowering drugs of the statin family on YAP localization, multisite phosphorylation, and transcriptional activity in human ECs. Exposure of sparse cultures of ECs to cerivastatin or simvastatin induced striking relocalization of YAP from the nucleus to the cytoplasm and inhibited the expression of the YAP/TEA domain DNA-binding transcription factor-regulated genes connective tissue growth factor and cysteine-rich angiogenic inducer 61. In dense cultures of ECs, statins prevented YAP nuclear import and expression of connective tissue growth factor and cysteine-rich angiogenic inducer 61 stimulated by the mAb W6/32 that binds HLA class I. Exposure of ECs to either cerivastatin or simvastatin completely blocked the migration of ECs stimulated by ligation of HLA class I. Exogenously supplied mevalonic acid or geranylgeraniol reversed the inhibitory effects of statins on YAP localization either in low-density ECs or high-density ECs challenged with W6/32. Mechanistically, cerivastatin increased the phosphorylation of YAP at Ser127, blunted the assembly of actin stress fiber, and inhibited YAP phosphorylation at Tyr357 in ECs. Using mutant YAP, we substantiated that YAP phosphorylation at Tyr357 is critical for YAP activation. Collectively, our results indicate that statins restrain YAP activity in EC models, thus providing a plausible mechanism underlying their beneficial effects in solid-organ transplant recipients.

Circ_0091537 promotes gefitinib chemoresistance in non-small cell lung cancer by mediating the miR-520h/YAP1 network.

Chemoresistance is the leading cause of poor outcomes of non-small cell lung cancer (NSCLC). Circular RNA (circRNA) plays a vital role in NSCLC resistance progression. Our study aimed to uncover the role of circRNA PDZ domain containing 8 (circ_0091537) in NSCLC with gefitinib resistance. The expression of circ_0091537, microRNA-520h (miR-520h), and Yes-associated protein 1 (YAP1) mRNA were detected using quantitative real-time PCR. Cell viability and cell proliferation were assessed by MTT assay and colony formation assay. Colony formation ability was detected by colony formation assay. Cell cycle distribution and cell apoptosis were determined by flow cytometry assay. Cell migration and cell invasion were detected by transwell assay. The potential relationship between miR-520h and circ_0091537 or YAP1 was verified by dual-luciferase reporter assay. Tumor formation assay in nude mice was performed to test the role of circ_0091537 in vivo . Circ_0091537 and YAP1 were upregulated, while miR-520h was downregulated in gefitinib-resistant NSCLC cells. Circ_0091537 knockdown inhibited gefitinib resistance in NSCLC cells and then inhibited NSCLC cell growth, migration, and invasion. MiR-520h was a target of circ_0091537, and miR-520h inhibition reversed the effects of circ_0091537 knockdown. Moreover, YAP1 was a target of miR-520h, and circ_0091537 competitively combined with miR-520h to enrich YAP1 expression. MiR-520h restoration impaired gefitinib resistance and suppressed NSCLC cell proliferation, migration, and invasion by repressing YAP1. Circ_0091537 overexpression weakened gefitinib sensitivity in vivo to promote tumor growth. Circ_0091537 strengthens gefitinib chemoresistance to promote NSCLC progression by mediating the miR-520h/YAP1 network, suggesting that circ_0091537 may be a key indicator in resistance to treatment of NSCLC.

The YAP-TEAD4 complex promotes tumor lymphangiogenesis by transcriptionally upregulating CCBE1 in colorectal cancer.

The secreted protein collagen and calcium-binding EGF domain 1 (CCBE1) is critical for embryonic lymphatic development through its role in the proteolytic activation of mature vascular endothelial growth factor C (VEGFC). We previously reported that CCBE1 is overexpressed in colorectal cancer (CRC) and that its transcription is negatively regulated by the TGFß-SMAD pathway, but the transcriptional activation mechanism of CCBE1 in CRC remains unknown. Recent studies have revealed the vital role of the hippo effectors YAP/TAZ in lymphatic development; however, the role of YAP/TAZ in tumor lymphangiogenesis has not been clarified. In this study, we found that high nuclear expression of transcription factor TEAD4 is associated with lymph node metastasis and high lymphatic vessel density in patients with CRC. YAP/TAZ-TEAD4 complexes transcriptionally upregulated the expression of CCBE1 by directly binding to the enhancer region of CCBE1 in both CRC cells and cancer-associated fibroblasts, which resulted in enhanced VEGFC proteolysis and induced tube formation and migration of human lymphatic endothelial cells in vitro and lymphangiogenesis in a CRC cell-derived xenograft model in vivo. In addition, the bromodomain and extraterminal domain (BET) inhibitor JQ1 significantly inhibited the transcription of CCBE1, suppressed VEGFC proteolysis, and inhibited tumor lymphangiogenesis in vitro and in vivo. Collectively, our study reveals a new positive transcriptional regulatory mechanism of CCBE1 via YAP/TAZ-TEAD4-BRD4 complexes in CRC, which exposes the protumor lymphangiogenic role of YAP/TAZ and the potential inhibitory effect of BET inhibitors on tumor lymphangiogenesis.