The Hippo Signaling Pathway in Development and Disease

ADH1C maintains the homeostasis of metabolic microenvironment to inhibit steatotic hepatocellular carcinoma

Steatotic hepatocellular carcinoma (HCC) has emerged as a significant subtype of HCC. Understanding the complex tumor microenvironment in HCC is particularly important for stratifying patients and improving treatment response. In this study, we performed proteomic analysis on clinical samples of steatotic HCC and identified human-specific gene alcohol dehydrogenase 1C (ADH1C) as a key factor. ADH1C is a favorable prognostic factor in both steatotic and non-steatotic HCC. ADH1C promotes fatty acid degradation through a novel non-enzymatic function, inhibiting the development of hepatocellular carcinoma. Specifically, in vitro experiments revealed that ADH1C interacts with splicing factor retinitis pigmentosa 9 (RP9) to enhance the splicing of key transcription factor peroxisome proliferator activated receptor alpha (PPARa) pre-mRNA, which is crucial for fatty acid degradation. The regulation of the ADH1C/RP9/PPARa axis was supported by in vivo experiments and clinical relevance. This leads to a reduction in the critical metabolite palmitic acid, subsequently decreasing the palmitoylation levels of oncogenic protein TEA domain transcription factor 1 (TEAD1), thereby regulating the hippo pathway and subsequent cell proliferation inhibition. Additionally, we found that ADH1C and PPARa can serve as combined biomarkers to distinguish between patients with steatotic and non-steatotic HCC. Combination therapy targeting ADH1C and anti-programmed cell death protein 1 (PD1) enhances the response of steatotic HCC to anti- PD1 immunotherapy. Our study revealed a central role of ADH1C/PPARa in lipid metabolism and HCC suppression. Targeting lipid metabolism via ADH1C/PPARa may provide new therapeutic strategies for the treatment of liver cancer.

Neuroendocrine regulatory network underlying physiological shifts between reproduction and aestivation of sea cucumber Apostichopus japonicus: Insights from transcriptome analysis

The sea cucumber Apostichopus japonicus is an economically significant marine species in China, with numerous studies focusing on its diverse physiological processes, including seasonal reproduction and aestivation. The neuroendocrine system plays a critical role in regulating these physiological transitions. In this study, we utilized transcriptomic techniques and bioinformatics tools to identify key functional genes in the nerve ring of A. japonicus during four distinct physiological phases: pre-reproduction, post-reproduction, aestivation, and recovery from aestivation. Totally 33 neuropeptide precursors and 521 G protein-coupled receptors (GPCRs) were identified. Highlighted key genes, such as AjCRZP, AjPDFP1b, AjSSP1, AjSSP2, and AjSSTR4, were proposed to contribute to transitions of reproduction to aestivation. The temporal trends and functions of differentially expressed genes (DEGs) were validated through qRT-PCR assays. Additionally, we constructed a preliminary neuroendocrine regulatory network, with AjGALR2 and AjCHRM5 identified as central hub genes. These findings offer valuable insights into the neuroendocrine regulation of reproduction and aestivation in A. japonicus, providing a foundation for further mechanistic studies and enhancing our understanding of sea cucumber biology.

VGLL2 and TEAD1 fusion proteins identified in human sarcoma drive YAP/TAZ-independent tumorigenesis by engaging EP300

Studies on Hippo pathway regulation of tumorigenesis largely center on YAP and TAZ, the transcriptional co-regulators of TEADs. Here, we present an oncogenic mechanism involving VGLL and TEAD fusions that is Hippo pathway-related but YAP/TAZ-independent. We characterize two recurrent fusions, VGLL2-NCOA2 and TEAD1-NCOA2, recently identified in human spindle cell rhabdomyosarcoma. We demonstrate that in contrast to VGLL2 and TEAD1 the fusion proteins are potent activators of TEAD-dependent transcription, and the function of these fusion proteins does not require YAP/TAZ. Furthermore, we identify that VGLL2 and TEAD1 fusions engage specific epigenetic regulation by recruiting histone acetyltransferase EP300 to control TEAD-mediated transcriptional and epigenetic landscapes. We show that small-molecule EP300 inhibition can suppress fusion protein-induced oncogenic transformation both in vitro and in vivo in mouse models. Overall, our study reveals a molecular basis for VGLL involvement in cancer and provides a framework for targeting tumors carrying VGLL, TEAD, or NCOA translocations.

Inhibition of YAP can down-regulate NLRP3 inflammasome and improve anti-tuberculosis drug-induced liver injury

Yes-associated protein (YAP) is a core effector molecule in the Hippo signalling pathway, but its role in antituberculosis drug-induced liver injury (ADLI) is unclear. We aimed to explore the regulatory effects of YAP on the NLRP3 inflammasome in ADLI and its potential hepatoprotective effects.An ADLI animal model was established. Various indicators of experimental animals were detected at 0, 7, 14, and 21 days. On day 7, HE staining observed liver tissue, and liver index, ALT, and AST levels confirmed the ADLI model. YAP's mRNA and protein levels were examined, YAP inhibitor effects were observed, and NLRP3 inflammasome, inflammation, and oxidative stress indicators were analysed.It was found that the mRNA and protein levels of YAP increased during ADLI and then decreased due to the action of YAP inhibitors. YAP caused an elevation in NLRP3 inflammasome indicators, as well as increased expression of inflammation and oxidative stress. After feeding with YAP inhibitors, these indicators were reduced.The results suggest that targeting YAP may be a novel therapeutic strategy for alleviating antituberculosis drug-induced liver injury.

Microtubule associated serine/threonine kinase-3 inhibits the malignant phenotype of breast cancer by promoting phosphorylation-mediated ubiquitination degradation of yes-associated protein

BACKGROUND

Microtubule associated series/threonine kinase-3 (MAST3) is a member of microtubule associated serine/threonine kinase family (MAST1-4, MAST-like), and the expression and underlying molecular mechanism of MAST3 in human tumors, including breast cancer, is not yet elucidated.

METHODS

We employed immunohistochemistry to assess the significant expression of MAST3 in breast cancer tissue samples. Additionally, we utilized an overexpression vector and shRNA to bi-directionally regulate MAST3 expression, aiming to observe the impact of MAST3 on the proliferation, migration, and invasion capabilities of breast cancer cells. Furthermore, we employed immunoprecipitation, immunoblotting, luciferase reporter genes and real-time quantitative PCR to investigate the interaction between MAST3 and YAP, as well as the regulatory effects on the expression of Hippo pathway-related target genes.

RESULTS

Low MAST3 expression was observed both in breast cancer cells and tissues, which was significantly associated with advanced tumor T stage, lymph node metastasis, and poor patient prognosis. Functional experiments found that overexpression of MAST3 can gradually inhibit the proliferation and invasion of breast cancer cells, knocking-out MAST3 showed the opposite functional effect. Immunoprecipitation showed that MAST3 interacts with the key effector factor, yes-associated protein (YAP), in the Hippo pathway. The combination of MAST3-YAP promoted the phosphorylation of YAP, which led to its degradation through the ubiquitin-proteasome pathway and reduced nuclear translocation.

CONCLUSIONS

MAST3 was identified as a novel tumor suppressor protein in breast cancer, which directly regulates the expression of YAP through the non-dependent mammalian sterile-20-like (MST)-large tumor suppressor (LATS) classical signaling pathway, providing a theoretical and experimental basis for the development of small-molecule tumor inhibitors in breast cancer.

The enigma of maladaptation in gastric pathophysiology

Despite a decline in global incidence, gastric cancer (GC) remains a major health concern. The development of GC is a sequential, multistage maladaptive process involving numerous different factors. Understanding the complexity of GC development is crucial for early detection, effective treatment, and, ultimately, prevention. In this respect, identifying the impact of risk factors contributing to the emergence or progression of GC, such as Helicobacter pylori infection, host and bacterial genetics, alcohol consumption, smoking, and preserved foods, will aid in combatting this disease. In this review, we focus on recent developments in understanding the role of the microbiome, dysfunctional molecular pathways, and immune evasion in gastric pathophysiology. We also highlight challenges and advances in treatment of GC.

Role of ferroptosis mediated by abnormal membrane structure in DEHP-induced reproductive injury

Di-(2-ethylhexyl) phthalate (DEHP), a commonly used plasticizer, has been demonstrated to possess reproductive toxicity; however, the precise mechanisms underlying this effect have yet to be fully elucidated. This study aimed to investigate the potential mechanisms by which prepubertal DEHP exposure impairs testicular development and to provide possible therapeutic targets. We exposed BALB/c male mice from postnatal days 22-35 to different doses of DEHP (0, 250, and 500 mg/kg/day) and utilized lipid metabolomics and other methods to elucidate the reproductive damage caused by DEHP from a multidimensional tissue-cell-molecule perspective. Our findings indicate that DEHP exposure induces ferroptosis in testicular tissue by remodeling membrane lipid structure, in which the imbalance of phospholipid-polyunsaturated fatty acids (PL-PUFA) and phospholipid-monounsaturated fatty acids (PL-MUFA) playing a crucial role. DEHP exposure altered the expression of ACSL4 and MBOAT2 via HIPPO and androgen receptor pathways, thereby impacting PL-PUFA/PL-MUFA synthesis. In conclusion, this study highlights a link between DEHP-induced reproductive damage and lipid metabolism reprogramming, suggesting new targets for preventing DEHP-induced reproductive toxicity.

The mechanism of YAP/TAZ transactivation and dual targeting for cancer therapy

Transcriptional coactivators Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) play key roles in cancers through transcriptional outputs. However, their transactivation mechanisms remain unclear, and effective targeting strategies are lacking. Here, we show that YAP/TAZ possess a hydrophobic transactivation domain (TAD). TAD knockout prevents tumor establishment due to growth defects and enhances immune attack. Mechanistically, TADs facilitate preinitiation complex (PIC) assembly by recruiting the TATA-binding protein-associated factor 4 (TAF4)-dependent TFIID complex and enhance RNA polymerase II (Pol II) elongation through mediator complex subunit 15 (MED15)-dependent mediator recruitment for the expressions of oncogenic/immune-suppressive programs. The synthesized peptide TJ-M11 selectively disrupts TAD interactions with MED15 and TAF4, suppressing tumor growth and sensitizing tumors to immunotherapy. Our findings demonstrate that YAP/TAZ TADs exhibit dual functions in PIC assembly and Pol II elongation via hydrophobic interactions, which represent actionable targets for cancer therapy and combination immunotherapy.

Hippo Signaling Is Essential for the Maintenance of Zona Glomerulosa Cell Fate in the Murine Adrenal Cortex

Cells of the zona glomerulosa (zG), the outermost zone of the adrenal cortex, secrete aldosterone and transdifferentiate into glucocorticoid-producing cells of the zona fasciculata (zF) during adrenal homeostasis. However, our understanding of the signaling pathways mediating zG cell maintenance or their transdifferentiation into zF cells is incomplete. Hippo is a major pathway that regulates cell proliferation/differentiation during embryogenesis and postnatal tissue homeostasis. Hypothesizing that Hippo signaling could be involved in zG cell maintenance or transdifferentiation, we generated a mouse model in which the two main kinases of the Hippo signaling cascade large tumor suppressor homolog kinases 1/2 (Lats1 and Lats2) are specifically inactivated in zG cells. Here we show that loss of function of Lats1 and Lats2 impairs zG steroidogenesis and leads to zG cell transdifferentiation into cells sharing characteristics with chondroblasts/osteoblasts rather than zF cells. Furthermore, we demonstrate that this phenotype can be rescued by the concomitant inactivation of the transcriptional coactivators Yes-associated protein (Yap) and transcriptional coactivator with PDZ-binding motif (Taz) with Lats1 and Lats2. Finally, we show that expression of a constitutively active form of YAP (YAP5SA) in zG cells does not alter their fate as severely as the loss of Lats1 and Lats2 but leads to adrenal hyperplasia. Together, these findings highlight the critical role of Hippo signaling in maintaining zG cell fate and function and provide key insights into broader mechanisms underlying cellular differentiation.

The Hippo pathway in bone and cartilage: implications for development and disease

Bone is the main structure of the human body; it mainly plays a supporting role and participates in metabolic processes. The Hippo signaling pathway is composed of a series of protein kinases, including the mammalian STE20-like kinase MST1/2 and the large tumor suppressor LATS1/2, which are widely involved in pathophysiological processes, including cell proliferation, differentiation, apoptosis and death, especially those related to biomechanical transduction in vivo. However, the role of it in regulating skeletal system development and the evolution of bone-related diseases remains poorly understood. The pathway can intervene in and regulate the physiological activities of bone-related cells such as osteoclasts and chondrocytes through its own or other bone-related signaling pathways, such as the Wnt pathway, the Notch pathway, and receptor activator of nuclear factor-κB ligand (RANKL), thereby affecting the occurrence and development of bone diseases. This article discusses the role of the Hippo signaling pathway in bone development and disease to provide new insights into the treatment of bone-related diseases by targeting the Hippo signaling pathway.

Cancer chemoprevention: signaling pathways and strategic approaches

Although cancer chemopreventive agents have been confirmed to effectively protect high-risk populations from cancer invasion or recurrence, only over ten drugs have been approved by the U.S. Food and Drug Administration. Therefore, screening potent cancer chemopreventive agents is crucial to reduce the constantly increasing incidence and mortality rate of cancer. Considering the lengthy prevention process, an ideal chemopreventive agent should be nontoxic, inexpensive, and oral. Natural compounds have become a natural treasure reservoir for cancer chemoprevention because of their superior ease of availability, cost-effectiveness, and safety. The benefits of natural compounds as chemopreventive agents in cancer prevention have been confirmed in various studies. In light of this, the present review is intended to fully delineate the entire scope of cancer chemoprevention, and primarily focuses on various aspects of cancer chemoprevention based on natural compounds, specifically focusing on the mechanism of action of natural compounds in cancer prevention, and discussing in detail how they exert cancer prevention effects by affecting classical signaling pathways, immune checkpoints, and gut microbiome. We also introduce novel cancer chemoprevention strategies and summarize the role of natural compounds in improving chemotherapy regimens. Furthermore, we describe strategies for discovering anticancer compounds with low abundance and high activity, revealing the broad prospects of natural compounds in drug discovery for cancer chemoprevention. Moreover, we associate cancer chemoprevention with precision medicine, and discuss the challenges encountered in cancer chemoprevention. Finally, we emphasize the transformative potential of natural compounds in advancing the field of cancer chemoprevention and their ability to introduce more effective and less toxic preventive options for oncology.

Platinum(II) and ruthenium(II) coordination complexes equipped with an anchoring site for binding the protein kinase enzyme pockets: synthesis, molecular docking and biological assays

To mimic the structural aspects of staurosporine, a potent but unspecific kinase inhibitor, several coordination compounds based on two readily available diimine ligands containing hydrogen bonding donor/acceptor sites (NH-CO fragment) have been designed and synthesized. These complexes are constructed around Ru(II) and Pt(II) metal centers. A total of 9 compounds, named Ru(1)-(5) and Pt(1)-(4), were obtained through straightforward synthetic approaches. The cytotoxicity of the compounds was evaluated on AGS gastric cancer cells (GC) through standard MTT assays. All ruthenium and platinum complexes with low toxicity, i.e.Ru(3), Ru(5), Pt(3) and Pt(4), were docked in the ATP binding pocket of two protein kinases (S6K1 and MST2). The docking scores highlighted a preferred affinity of Ru(5) for the MST2 binding pocket, whereas the platinum compounds are predicted to bind stronger to the S6K1 binding site. Inhibitory activity of the metal complexes on the MST2 and S6K1 signaling pathways was evaluated by analyzing via western blot experiments the phosphorylation state of YAP, a downstream component of the Hippo pathway and the protein expression of S6 and its phosphorylated analogue p-S6. A clear difference of behavior between the Pt(II) and the Ru(II) complexes depending on the type of kinase was observed.

Disrupting bile acid metabolism by suppressing Fxr causes hepatocellular carcinoma induced by YAP activation

Disruption of bile acid (BA) metabolism causes various liver diseases including hepatocellular carcinoma (HCC). However, the underlying molecular mechanism remains elusive. Here, we report that BA metabolism is directly controlled by a repressor function of YAP, which induces cholestasis by altering BA levels and composition via inhibiting the transcription activity of Fxr, a key physiological BA sensor. Elevated BA levels further activate hepatic YAP, resulting in a feedforward cycle leading to HCC. Mechanistically, Teads are found to bind Fxr in a DNA-binding-independent manner and recruit YAP to epigenetically suppress Fxr. Promoting BA excretion, or alleviating YAP repressor function by pharmacologically activating Fxr and inhibiting HDAC1, or overexpressing an Fxr target gene Bsep to promote BA exportation, alleviate cholestasis and HCC caused by YAP activation. Our results identify YAP's transcriptional repressor role in BA metabolism as a key driver of HCC and suggest its potential as a therapeutic target.

NEK8, a NIMA-family protein kinase at the core of the ciliary INV complex

Here we describe the current knowledge about the ciliary kinase NEK8, highlighting what we know and what we don't know about its regulation, substrates and potential functions. We also review the literature about the pathological consequences of different NEK8 variants in patients of nephronophthisis, renal-hepatic-pancreatic dysplasia and autosomal dominant polycystic kidney disease, three different types of ciliopathies. NEK8 belongs to the NIMA family of serine/threonine protein kinases. Like its closest relative, NEK9, it contains a protein kinase and an RCC1 domain, but lacks the C-terminal region that is key for NEK9's regulation as a G2/M kinase. Importantly, NEK8 localizes to cilia as part of a multimeric protein complex that assembles in a fibrillar fashion at the proximal half of this signaling organelle, defining what is known as the INV compartment. NEK8 and its INV compartment partners inversin, ANKS6 and NPHP3 are necessary for left-right determination and the correct development of different organs such as the kidney, the heart and the liver. But the kinase substrates, regulatory mechanism and activating cues and thus the molecular basis of NEK8 important physiological roles remain elusive. We present the current findings regarding NEK8 and also highlight what we miss in order to progress towards the understanding of the kinase and the function of the INV complex at the cilia.

Neuroprotective role of Hippo signaling by microtubule stability control in Caenorhabditis elegans

The evolutionarily conserved Hippo (Hpo) pathway has been shown to impact early development and tumorigenesis by governing cell proliferation and apoptosis. However, its post-developmental roles are relatively unexplored. Here, we demonstrate its roles in post-mitotic cells by showing that defective Hpo signaling accelerates age-associated structural and functional decline of neurons in Caenorhabditis elegans. Loss of wts-1/LATS, the core kinase of the Hpo pathway, resulted in premature deformation of touch neurons and impaired touch responses in a yap-1/YAP-dependent manner, the downstream transcriptional co-activator of LATS. Decreased movement as well as microtubule destabilization by treatment with colchicine or disruption of microtubule-stabilizing genes alleviated the neuronal deformation of wts-1 mutants. Colchicine exerted neuroprotective effects even during normal aging. In addition, the deficiency of a microtubule-severing enzyme spas-1 also led to precocious structural deformation. These results consistently suggest that hyper-stabilized microtubules in both wts-1-deficient neurons and normally aged neurons are detrimental to the maintenance of neuronal structural integrity. In summary, Hpo pathway governs the structural and functional maintenance of differentiated neurons by modulating microtubule stability, raising the possibility that the microtubule stability of fully developed neurons could be a promising target to delay neuronal aging. Our study provides potential therapeutic approaches to combat age- or disease-related neurodegeneration.

Inhibition of thioredoxin reductase 1 sensitizes glucose-starved glioblastoma cells to disulfidptosis

Disulfidptosis is a recently identified form of cell death characterized by the aberrant accumulation of cellular disulfides. This process primarily occurs in glucose-starved cells expressing higher levels of SLC7A11 and has been proposed as a therapeutic strategy for cancers with hyperactive SCL7A11. However, the potential for inducing disulfidptosis through other mechanisms in cancers remains unclear. Here, we found that inhibiting thioredoxin reductase 1 (TrxR1), a key enzyme in the thioredoxin system, induces disulfidptosis in glioblastoma (GBM) cells. TrxR1 expression is elevated in GBM with activated transcriptional coactivator with PDZ-binding motif (TAZ) and correlates with poor prognosis. TrxR1 inhibitors induced GBM cell death that can be rescued by disulfide reducers but not by ROS scavengers or inhibitors of apoptosis, ferroptosis, or necroptosis. Glucose-starved cells, but not those deprived of oxygen or glutamine, increased TrxR1 expression in an NRF2-dependent manner and were more sensitive to TrxR1 inhibition-induced cell death. The dying cells initially exhibited highly dynamic lamellipodia, followed by actin cytoskeleton collapse. This process involved the accumulation of cytosolic peroxisomes and micropinocytic caveolae, as well as small gaps in the plasma membrane. Depletion of the WAVE complex component NCKAP1 partially rescued the cells, whereas Rac inhibition enhanced cell death. In an orthotopic xenograft GBM mouse model, TrxR1 depletion inhibited tumor growth and improved survival. Furthermore, cells undergoing TrxR1 inhibition exhibited features of immunogenic cell death. Therefore, this study suggests the potential of targeting TrxR1 as a therapeutic strategy in GBM.

Developmental instability, body mass, and reproduction predict immunological response in short-tailed bats

Developmental instability (DI) is a phenomenon whereby organisms are unable to buffer developmental disturbances, resulting in asymmetric variation of paired traits. Previous research has demonstrated a negative relationship between DI, measured as forearm asymmetry, and survival in the bat Carollia perspicillata. This study aims to test the hypothesis that individuals with higher DI exhibit a lower immune response. We measured a delayed-type hypersensitivity to the antigen phytohemagglutinin (PHA) on 74 males and 65 females of C. perspicillata before and after the breeding season (BS). Linear models were used to predict the immunological response based on body mass (BM), forearm asymmetry, sex, BS, and testicle length. The best-fitting model accounted for 29% of the variation in immune response and included asymmetry, BM, sex, and BS as predictors. The immune response was negatively associated with asymmetry and testicle length in males but positively related to asymmetry in females. Both sexes showed a reduced immune response in the late BS. Additionally, the association between immune response and BM changed direction seasonally, with heavier individuals showing weaker responses early in the BS and stronger responses later. Individual variation in male immunity was predicted by individual attributes, whereas variation in immune response in females was mostly seasonal. Our results support the link between DI, survival, and immune response in short-tailed bats, and suggest that the immunological component measured by the PHA response may be under finer selection in males due to its stronger correlation with individual traits.

PDLIM3 Regulates Migration and Invasion of Head and Neck Squamous Cell Carcinoma via YAP-Mediated Epithelial-Mesenchymal Transition

Despite significant progress in characterizing the omics landscape of head and neck squamous cell carcinoma (HNSCC), the development of precision therapies remains limited. One key factor contributing to this challenge is the marked molecular heterogeneity of HNSCC. Further investigation of molecular profiles within HNSCC may facilitate the improvement in more effective precision treatments. Here, we focus on the dysregulation of PDZ and LIM domain protein 3 (PDLIM3) in HNSCC. The expression levels of PDLIM3 were analyzed using public datasets to assess its potential role in tumor progression. We found that PDLIM3 was downregulated in pan-cancer and HNSCC. The prognostic significance of PDLIM3 was evaluated through tissue microarray, and the downregulation of PDLIM3 was correlated with poor HNSCC prognosis. Investigating the implications of PDLIM3 for tumor metastatic ability in vitro, we found that PDLIM3 suppressed the migration and invasion of HNSCC, accompanied by partially impeding the process of epithelial-mesenchymal transition (EMT). Furthermore, PDLIM3 inhibited the transcriptional activity of Yes-associated protein (YAP), suggesting that YAP may be involved in the PDLIM3-mediated suppression of HNSCC metastatic ability. Our findings identify a potential signaling axis wherein PDLIM3 regulates YAP-EMT, thereby influencing tumor metastatic ability, and suggest the potential role of PDLIM3 as a tumor suppressor and prognostic biomarker for HNSCC.

Targeting the disrupted Hippo signaling to prevent neoplastic renal epithelial cell immune evasion

Large-scale cancer genetic/genomic studies demonstrated that papillary renal cell carcinoma (pRCC) is featured with a frequent shallow deletion of the upstream tumor suppressors of the Hippo/YAP signaling pathway, suggesting that this signaling pathway may play a role in pRCC development. Here we develop a transgenic mouse model with a renal epithelial cell-specific hyperactivation of YAP1 and find that hyperactivation of YAP1 can induce dedifferentiation and transformation of renal tubular epithelial cells leading to the development of pRCC. We analyze at the single-cell resolution the cellular landscape alterations during cancer initiation and progression. Our data indicate that the hyperactivated YAP1, via manipulating multiple signaling pathways, induces epithelial cell transformation, MDSC (Myeloid-derived suppressor cells) accumulation, and pRCC development. Interestingly, we find that depletion of MDSC blocks YAP1-induced kidney overgrowth and tumorigenesis. Inhibiting YAP1 activity with MGH-CP1, a recently developed TEAD inhibitor, impedes MDSC accumulation and suppresses tumor development. Our results identify the disrupted Hippo/YAP signaling as a major contributor to pRCC and suggest that targeting the disrupted Hippo pathway represents a plausible strategy to prevent and treat pRCC.

Human Satellite 3 DNA encodes megabase-scale transcription factor binding platforms

Eukaryotic genomes frequently contain large arrays of tandem repeats, called satellite DNA. While some satellite DNAs participate in centromere function, others do not. For example, Human Satellite 3 (HSat3) forms the largest satellite DNA arrays in the human genome, but these multi-megabase regions were almost fully excluded from genome assemblies until recently, and their potential functions remain understudied and largely unknown. To address this, we performed a systematic screen for HSat3 binding proteins. Our work revealed that HSat3 contains millions of copies of transcription factor (TF) motifs bound by over a dozen TFs from various signaling pathways, including the growth-regulating transcription effector family TEAD1-4 from the Hippo pathway. Imaging experiments show that TEAD recruits the co-activator YAP to HSat3 regions in a cell-state specific manner. Using synthetic reporter assays, targeted repression of HSat3, inducible degradation of YAP, and super-resolution microscopy, we show that HSat3 arrays can localize YAP/TEAD inside the nucleolus, enhancing RNA Polymerase I activity. Beyond discovering a direct relationship between the Hippo pathway and ribosomal DNA regulation, this work demonstrates that satellite DNA can encode multiple transcription factor binding motifs, defining an important functional role for these enormous genomic elements.

The Hippo pathway effector YAP inhibits NF-κB signaling and ccRCC growth by opposing ZHX2

The prevailing view in the cancer field is that Hippo (Hpo) signaling pathway functions as a tumor suppressor pathway by blocking the oncogenic potential of the pathway effectors Yes1-associated transcriptional regulator (YAP)/transcriptional coactivator with PDZ-binding motif. However, YAP can also function as a context-dependent tumor suppressor in several types of cancer including clear cell renal cell carcinomas (ccRCCs). We find that, in addition to inhibiting hypoxia-inducible factor 2α, a major oncogenic driver in Von Hippel-Lindau-/- ccRCC, YAP also blocks nuclear factor κB (NF-κB) signaling in ccRCC to inhibit cancer cell growth under conditions where hypoxia-inducible factor 2α is dispensable. Mechanistically, YAP inhibits the expression of Zinc fingers and homeoboxes 2 (ZHX2), a Von Hippel-Lindau substrate and critical cofactor of NF-κB in ccRCC. Furthermore, YAP competes with ZHX2 for binding to the NF-κB subunit p65. Consequently, elevated nuclear YAP blocks the cooperativity between ZHX2 and the NF-κB subunit p65, leading to diminished NF-κB target gene expression. Pharmacological inhibition of Hpo kinase blocked NF-κB transcriptional program and suppressed ccRCC cell growth, which can be rescued by overexpression of ZHX2 or p65. Our study uncovers a crosstalk between the Hpo and NF-κB/ZHX2 pathways and its involvement in ccRCC growth inhibition, suggesting that targeting the Hpo pathway may provide a therapeutical opportunity for ccRCC treatment.

YAP1 facilitates the pathogenesis of psoriasis via modulating keratinocyte proliferation and inflammation

Psoriasis is an autoinflammatory skin disease characterized by the abnormal activation of epidermal keratinocytes. The Hippo-YAP pathway is an evolutionarily conserved pathway that plays important roles in organ size control and tumorigenesis. Recently, accumulating evidence demonstrated that YAP1, the core downstream component of Hippo-YAP pathway, was up-regulated in psoriasis patients, suggesting its possible role in psoriasis development. However, its precise function and mechanism in psoriasis pathogenesis are still not well-clarified. In the present study, we confirmed the up-regulation of YAP1 in psoriasis keratinocytes by measuring its expression in psoriatic patient skins, psoriatic-like cellular model, and IMQ-induced mouse model. Further functional studies showed that YAP1 promoted keratinocyte proliferation and inflammation in vitro. Meanwhile, VP, a selective YAP1 antagonist, inhibited keratinocyte proliferation and inflammatory factor production in a dose-dependent way. Moreover, intradermal injection of si-Yap1 or VP hindered psoriasis development by impeding epidermal hyperplasia and relieving systemic inflammatory response in the IMQ-induced mouse model. Therefore, our findings suggest that YAP1 plays a crucial role in psoriasis pathogenesis through modulating keratinocyte activation and may serve as a novel target for the treatment of psoriasis.

YAP Regulates HER3 Signaling-Driven Adaptive Resistance to RET Inhibitors in RET-Aberrant Cancers

PURPOSE

Rearranged during transfection (RET) aberrations represent a targetable oncogene in several tumor types, with RET inhibitors displaying marked efficacy. However, some patients with RET-aberrant cancer are insensitive to RET tyrosine kinase inhibitors (TKI). Recently, drug-tolerant mechanisms have attracted attention as targets for initial therapies to overcome drug resistance. The underlying mechanisms of drug-tolerant cell emergence treated with RET-TKIs derived from RET-aberrant cancer cells remain unknown. This study investigated the role of YAP-mediated HER3 signaling in the underlying mechanisms of adaptive resistance to RET-TKIs in RET-aberrant cancer cells.

EXPERIMENTAL DESIGN

Four RET-aberrant cancer cell lines were used to assess sensitivity to the RET-TKIs selpercatinib and pralsetinib and to elucidate the molecular mechanisms underlying adaptive resistance using RNA sequencing, phospho-receptor tyrosine kinase antibody arrays, chromatin immunoprecipitation assay, and luciferase reporter assays. Clinical specimens from patients with RET fusion-positive lung cancer were analyzed for pretreatment YAP expression and correlated with treatment outcomes.

RESULTS

In high YAP-expressing RET-aberrant cancer cells, YAP-mediated HER3 signaling activation maintained cell survival and induced the emergence of cells tolerant to the RET-TKIs selpercatinib and pralsetinib. The pan-ErBB inhibitor afatinib and YAP/tea domain inhibitors verteporfin and K-975 sensitized YAP-expressing RET-aberrant cancer cells to the RET-TKIs selpercatinib and pralsetinib. Pretreatment YAP expression in clinical specimens obtained from patients with RET fusion-positive lung cancer was associated with poor RET-TKI treatment outcomes.

CONCLUSIONS

The YAP-HER3 axis is crucial for the survival and adaptive resistance of high YAP-expressing RET-aberrant cancer cells treated with RET-TKIs. Combining YAP/HER3 inhibition with RET-TKIs represents a highly potent strategy for initial treatment. See related commentary by Ortiz-Cuaran and Leonce, p. 958.

Proto-oncogene DEK binds to pre-mRNAs and regulates the alternative splicing of Hippo signaling genes in HeLa cells

Our study aimed to explore how DEK, a carcinogenic protein with chromatin architectural function, genome-widely binds to RNA and affects the alternative splicing in cancer cells to decipher its molecular functions. To achieve this goal, cell phenotype experiments, RNA sequencing (RNA-seq), and improved RNA immunoprecipitation sequencing (iRIP-seq) were conducted to identify the function and regulated targets of DEK in HeLa cells. The results showed DEK overexpression promoted cell proliferation and invasion of HeLa cells. Meanwhile, DEK hardly affected transcript level expression of those high expressed genes, but splicing pattern of 411 genes was regulated by DEK in HeLa cells, which were enriched in Hippo signaling pathway. Moreover, DEK broadly bind the RNA of a total of 11, 112 genes, with a biased binding the 5' splice site (5'SS) consensus GGUAA motifs at the CDS and intronic regions. In addition, 297 DEK-binding genes showed different splicing pattern after DEK overexpression in HeLa cells. These genes were enriched in Hippo signaling pathway including CSNK1D. The RT-qPCR and RIP-PCR confirmed that DEK can bind to CSNK1D to regulate its alternative splicing in HeLa cells. In summary, our results indicated DEK could broadly bind and regulate the pre-mRNA splicing process, which provide new insights of mechanisms that DEK functions in various biological processes including cancer.

Mechanical forces in the tumor microenvironment: roles, pathways, and therapeutic approaches

Tumors often exhibit greater stiffness compared to normal tissues, primarily due to increased deposition within the tumor stroma. Collagen, proteoglycans, laminin, and fibronectin are key components of the extracellular matrix (ECM), interacting to facilitate ECM assembly. Enhanced fiber density and cross-linking within the ECM result in elevated matrix stiffness and interstitial fluid pressure, subjecting tumors to significant physical stress during growth. This mechanical stress is transduced intracellularly via integrins, the Rho signaling pathway, and the Hippo signaling pathway, thereby promoting tumor invasion. Additionally, mechanical pressure fosters glycolysis in tumor cells, boosting energy production to support metastasis. Mechanical cues also regulate macrophage polarization, maintaining an inflammatory microenvironment conducive to tumor survival. In summary, mechanical signals within tumors play a crucial role in tumor growth and invasion. Understanding these signals and their involvement in tumor progression is essential for advancing our knowledge of tumor biology and enhancing therapeutic approaches.

Characterization of Hippo signaling components in the early dorsal pancreatic bud

All pancreatic lineages originate from a transitory structure known as the multipotent progenitor epithelium (MPE), which is an endodermal placode formed via epithelial stratification. Cells within the MPE undergo de novo lumenogenesis to give rise to an epithelial plexus, which serves as a progenitor niche for subsequent development of endocrine, ductal and acinar cell types. Recent evidence suggests that Hippo signaling is required for pancreatic cell differentiation, but little is known about the function of Hippo signaling in the development of the MPE. Here, we characterize the expression of YAP1, TAZ, and the Hippo regulators LATS1/2 kinases and MERLIN in early murine pancreatic epithelium, during epithelial stratification, plexus development and emergence of endocrine cells. We find that YAP1 expression is relatively low in the pancreas bud during stratification but increases by E11.5. Intriguingly, we find differing patterns of TAZ and YAP1 immunoreactivty throughout pancreatic development. We further find that MERLIN and LATS1/2 kinases are expressed during the period of rapid stratification and become markedly apical at nascent lumens. To gain a better understanding of how Hippo signaling and lumen formation are connected, we analyzed the subcellular localization of Hippo signaling components during varying stages of lumen formation and found that they are dynamically localized during lumenogenesis. Together, our results point to a previously unsuspected relationship between Hippo signaling and lumen formation during pancreatic development.

Phosphorylation of an RNA-Binding Protein Rck/Me31b by Hippo Is Essential for Adipose Tissue Aging

The metazoan lifespan is determined in part by a complex signaling network that regulates energy metabolism and stress responses. Key signaling hubs in this network include insulin/IGF-1, AMPK, mTOR, and sirtuins. The Hippo/Mammalian Ste20-like Kinase1 (MST1) pathway has been reported to maintain lifespan in Caenorhabditis elegans, but its role has not been studied in higher metazoans. In this study, we report that overexpression of Hpo, the MST1 homolog in Drosophila melanogaster, decreased lifespan with concomitant changes in lipid metabolism and aging-associated gene expression, while RNAi Hpo depletion increased lifespan. These effects were mediated primarily by Hpo-induced transcriptional activation of the RNA-binding protein maternal expression at 31B (Me31b)/RCK, resulting in stabilization of mRNA-encoding a lipolytic hormone, Akh. In mouse adipocytes, Hpo/Mst1 mediated adipocyte differentiation, phosphorylation of RNA-binding proteins such as Rck, decapping MRNA 2 (Dcp2), enhancer Of MRNA decapping 3 (Edc3), nucleolin (NCL), and glucagon mRNA stability by interacting with Rck. Decreased lifespan in Hpo-overexpressing Drosophila lines required expression of Me31b, but not DCP2, which was potentially mediated by recovering expression of lipid metabolic genes and formation of lipid droplets. Taken together, our findings suggest that Hpo/Mst1 plays a conserved role in longevity by regulating adipogenesis and fatty acid metabolism.

PICK1 links KIBRA and AMPA receptor subunit GluA2 in coiled-coil-driven supramolecular complexes

The human memory-associated protein KIBRA regulates synaptic plasticity and trafficking of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors, and is implicated in multiple neuropsychiatric and cognitive disorders. How KIBRA forms complexes with and regulates AMPA receptors remains unclear. Here, we show that KIBRA does not interact directly with the AMPA receptor subunit GluA2, but that protein interacting with C kinase 1 (PICK1), a key regulator of AMPA receptor trafficking, can serve as a bridge between KIBRA and GluA2. In contrast, KIBRA can form a complex with GluA1 independent of PICK1. We identified structural determinants of KIBRA-PICK1-AMPAR complexes by investigating interactions and cellular expression patterns of different combinations of KIBRA and PICK1 domain mutants. We find that the PICK1 BAR domain, a coiled-coil structure, is sufficient for interaction with KIBRA, whereas mutation of the PICK1 BAR domain disrupts KIBRA-PICK1-GluA2 complex formation. In addition, KIBRA recruits PICK1 into large supramolecular complexes, a process which requires KIBRA coiled-coil domains. These findings reveal molecular mechanisms by which KIBRA can organize key synaptic signaling complexes.

ARHGEF17/TEM4 regulates the cell cycle through control of G1 progression

The Ras homolog (Rho) small GTPases coordinate diverse cellular functions including cell morphology, adhesion and motility, cell cycle progression, survival, and apoptosis via their role in regulating the actin cytoskeleton. The upstream regulators for many of these functions are unknown. ARHGEF17 (also known as TEM4) is a Rho family guanine nucleotide exchange factor (GEF) implicated in cell migration, cell-cell junction formation, and the mitotic checkpoint. In this study, we characterize the regulation of the cell cycle by TEM4. We demonstrate that TEM4-depleted cells exhibit multiple defects in mitotic entry and duration, spindle morphology, and spindle orientation. In addition, TEM4 insufficiency leads to excessive cortical actin polymerization and cell rounding defects. Mechanistically, we demonstrate that TEM4-depleted cells delay in G1 as a consequence of decreased expression of the proproliferative transcriptional co-activator YAP. TEM4-depleted cells that progress through to mitosis do so with decreased levels of cyclin B as a result of attenuated expression of CCNB1. Importantly, cyclin B overexpression in TEM4-depleted cells largely rescues mitotic progression and chromosome segregation defects in anaphase. Our study thus illustrates the consequences of Rho signaling imbalance on cell cycle progression and identifies TEM4 as the first GEF governing Rho GTPase-mediated regulation of G1/S.

The Hippo pathway: Organ size control and beyond

The Hippo signaling pathway is a highly conserved signaling network for controlling organ size, tissue homeostasis, and regeneration. It integrates a wide range of intracellular and extracellular signals, such as cellular energy status, cell density, hormonal signals, and mechanical cues, to modulate the activity of YAP/TAZ transcriptional coactivators. A key aspect of Hippo pathway regulation involves its spatial organization at the plasma membrane, where upstream regulators localize to specific membrane subdomains to regulate the assembly and activation of the pathway components. This spatial organization is critical for the precise control of Hippo signaling, as it dictates the dynamic interactions between pathway components and their regulators. Recent studies have also uncovered the role of biomolecular condensation in regulating Hippo signaling, adding complexity to its control mechanisms. Dysregulation of the Hippo pathway is implicated in various pathological conditions, particularly cancer, where alterations in YAP/TAZ activity contribute to tumorigenesis and drug resistance. Therapeutic strategies targeting the Hippo pathway have shown promise in both cancer treatment, by inhibiting YAP/TAZ signaling, and regenerative medicine, by enhancing YAP/TAZ activity to promote tissue repair. The development of small molecule inhibitors targeting the YAP-TEAD interaction and other upstream regulators offers new avenues for therapeutic intervention. SIGNIFICANCE STATEMENT: The Hippo signaling pathway is a key regulator of organ size, tissue homeostasis, and regeneration, with its dysregulation linked to diseases such as cancer. Understanding this pathway opens new possibilities for therapeutic approaches in regenerative medicine and oncology, with the potential to translate basic research into improved clinical outcomes.

Live-cell FRET assay on the stoichiometry and affinity of the YAP complexes in MCF-7 cells

Yes-associated protein (YAP), a focal point of current biological research, is involved in regulating various life processes. In this report, live-cell fluorescence resonance energy transfer (FRET) imaging was employed to unravel the YAP complexes in MCF-7 cells. Fluorescence imaging of living cells co-expressing CFP (cyan fluorescent protein)-YAP and YFP (yellow fluorescent protein)-LATS1 (large tumor suppressor 1) plasmids revealed that YAP promoted LATS1 oligomerization around mitochondria. Moreover, FRET two-hybrid assay showed that YAP directly interacted with LATS1 to form dimer. Similarly, we found that YAP directly interacted with large tumor suppressor 2 (LATS2) to form a heterotrimer with 1:2 in cytoplasm and around mitochondria. In addition, YAP directly interacted with angiomotin (AMOT) to form a heterodimer in cytoplasm. However, YAP did not interact with O-linked N-acetylglucosamine transferase (OGT). Furthermore, FRET assay also indicated that YAP exhibited a higher affinity with AMOT, followed by LATS1, and least with LATS2. In summary, YAP directly interacts with LATS1 and AMOT to form a heterodimer, with LATS2 to form a heterotrimer with 1:2, and shows a preference for binding to AMOT, followed by LATS1, and lastly LATS2, providing new insights into the Hippo-YAP signaling pathway.

Ultraviolet B Exposure Does Not Influence the Expression of YAP mRNA in Human Epidermal Keratinocytes-Preliminary Study

Background: The causal relationship between exposure to ultraviolet radiation and the development of skin cancers requires constant research for possible orchestrating mechanisms. In recent years, the Hippo pathway, along with its effector protein YAP, became implicated in cutaneous carcinogenesis; however, Hippo pathway regulation by ultraviolet radiation has not been described thoroughly. In order to address this issue, we focused on how different doses of ultraviolet B affect Hippo signaling pathway components and its upstream regulators, JNK1/2 and ABL1, in human keratinocytes. Additionally, we decided to determine how silencing of YAP influences Hippo pathway component expression. Methods: Primary epidermal keratinocytes were irradiated using UVB lamps with increasing doses of ultraviolet B radiation (including 311 nm UVB). Real-time PCR was used to determine the mRNA levels of each investigated gene. The experiment was then performed after YAP silencing using siRNA transfection. Additionally, we determined the mRNA expression of Hippo pathway components in an A431 cSCC cell line. Results: We observed that YAP mRNA expression in the A431 cell line was insignificant in comparison to control, while in the case of LATS1/2, a significant increase was noted. UVB irradiation did not change the levels of YAP mRNA expression in human epidermal keratinocytes. LATS1, LATS2, ABL1 and MAP4K4 mRNA expression was significantly upregulated after UVB irradiation in non-YAP-silenced keratinocytes in a dose-dependent manner, while after YAP silencing, only LATS2 and ABL1 showed significant mRNA upregulation. The 311 nm UVB irradiation resulted in significant, dose-dependent mRNA upregulation in non-YAP-silenced keratinocytes for LATS1, ABL1 and MAP4K4. After YAP silencing, a significant change in mRNA expression was present only in the case of ABL1. Conclusions: YAP mRNA expression does not significantly increase after exposure to UVB; however, it upregulates the expression of its proven (LATS1/2, JNK1/2) regulators, suggesting that in real-life settings, UV-induced dysregulation of the Hippo pathway may not be limited to YAP.

Extracellular matrix: Dystroglycan interactions-Roles for the dystrophin-associated glycoprotein complex in skeletal tissue dynamics

Contributions made by the dystrophin-associated glycoprotein complex (DGC) to cell-cell and cell-extracellular matrix (ECM) interactions are vital in development, homeostasis and pathobiology. This review explores how DGC functions may extend to skeletal pathophysiology by appraising the known roles of its major ECM ligands, and likely associated DGC signalling pathways, in regulating cartilage and bone cell behaviour and emergent skeletal phenotypes. These considerations will be contextualised by highlighting the potential of studies into the role of the DGC in isolated chondrocytes, osteoblasts and osteoclasts, and by fuller deliberation of skeletal phenotypes that may emerge in very young mice lacking vital, yet diverse core elements of the DGC. Our review points to roles for individual DGC components-including the glycosylation of dystroglycan itself-beyond the establishment of membrane stability which clearly accounts for severe muscle phenotypes in muscular dystrophy. It implies that the short stature, low bone mineral density, poor bone health and greater fracture risk in these patients, which has been attributed due to primary deficiencies in muscle-evoked skeletal loading, may instead arise due to primary roles for the DGC in controlling skeletal tissue (re)modelling.

Spheroids from Epithelial and Mesenchymal Cell Phenotypes as Building Blocks in Bioprinting (Review)

Most tissues and organs are based on cells of the epithelial and mesenchymal phenotypes. Epithelial cells build protective barriers, have a key role in absorption and secretion, and participate in metabolism. Characterized by high plasticity and ability to migrate, mesenchymal cells ensure structural support, promote tissue restoration and are important for matrix remodeling. Interaction between these two cell types is critical for maintaining the body integrity and functioning. Modern tissue engineering is aimed at creation of artificial tissues and organs that have the required cellular composition, mechanical properties and functional potential for medical usage. One of the most popular methods of tissue engineering is 3D bioprinting, which allows creating complex three-dimensional structures with specified characteristics. Recently, special attention has been paid to bioprinting with spheroids being three-dimensional cellular aggregates that can be used as building blocks for tissue-engineered structures. Due to numerous cell-to-cell contacts and accumulation of extracellular matrix, spheroids ensure conditions allowing to form anatomical tissues and organs. To optimize bioprinting conditions, one shall precisely understand the mechanical properties of spheroids, as they directly affect the ability of cells to migrate and fuse, and thus the rate of construct formation and its overall morphology. This review summarizes the available data on the differences in mechanical properties of epithelial and mesenchymal spheroids, examines methods for their co-culturing in various applications of regenerative medicine, as well as analyzes the peculiarities of their use in different bioprinting methods to obtain high-quality tissue constructs.

8q24 derived ZNF252P promotes tumorigenesis by driving phase separation to activate c-Myc mediated feedback loop

As a well-known cancer risk region, the 8q24 locus is frequently amplified in a variety of solid tumors. Here we identify a pseudogene-derived oncogenic lncRNA, ZNF252P, which is upregulated in a variety of cancer types by copy number gain as well as c-Myc-mediated transcriptional activation. Mechanistically, ZNF252P binds and drives "phase separation" of HNRNPK and ILF3 protein in the nucleus and cytoplasm, respectively, to transcriptionally and posttranscriptionally activate c-Myc, thus forming a c-Myc/ZNF252P/c-Myc positive feedback loop. These findings expand the understanding of the relationship between genomic instability in the 8q24 region and tumorigenesis and clarify a regulatory mechanism involved in transcription and posttranscription from the perspective of RNA-mediated nuclear and cytoplasmic protein phase separation, which sheds light on the dialogue with the driver oncogene c-Myc. The pivotal regulatory axis of ZNF252P/c-Myc has potential as a promising biomarker and therapeutic target in cancer development.

The deubiquitylating enzyme Fat facets promotes Fat signalling and restricts tissue growth

Tissue growth is regulated by many signals, including polarity cues. The Hippo signalling pathway restricts tissue growth and receives inputs from the planar cell polarity-controlling Fat signalling pathway. The atypical cadherin Fat restricts growth via several mechanisms that ultimately control the activity of the pro-growth transcriptional co-activator Yorkie. Fat signalling activates the Yorkie inhibitory kinase Warts, and modulates the function of the FERM protein Expanded, which promotes Hippo signalling and also directly inhibits Yorkie. Although several Fat pathway activity modulators are known to be involved in ubiquitylation, the role of this post-translational modification in the pathway remains unclear. Moreover, no deubiquitylating enzymes have been described in this pathway. Here, using in vivo RNAi screening, we identify the deubiquitylating enzyme Fat facets as a positive regulator of Fat signalling with roles in tissue growth control. Fat facets interacts genetically and physically with Fat signalling components and regulates Yorkie target gene expression. Thus, we uncover a role for reversible ubiquitylation in the control of Fat signalling and tissue growth regulation.

Mesenchymal Hippo signaling regulates intestinal homeostasis in adult mice

Intestinal homeostasis is tightly regulated by the reciprocal interaction between the gut epithelium and adjacent mesenchyme. The Hippo pathway is intimately associated with intestinal epithelial homeostasis and regeneration; however, its role in postnatal gut mesenchyme remains poorly defined. Here, we find that removal of the core Hippo kinases Lats1/2 or activation of YAP in adult intestinal smooth muscle layers has largely no effect; however, Hippo-YAP signaling in the niche-forming Gli1+ mesenchymal cells plays intrinsic roles in regulating intestinal homeostasis. We find that Lats1/2 deletion drives robust mesenchymal over-proliferation, and YAP activation in Gli1+ pericryptal cells disrupts the intestinal epithelial-mesenchymal crosstalk via promoting Wnt ligand production. We show that YAP is upregulated in the stroma during dextran sodium sulfate (DSS)-induced injury, and mesenchymal YAP activation facilitates intestinal epithelial regeneration. Altogether, our data suggest an important role for mesenchymal Hippo-YAP signaling in the stem cell niche during intestinal homeostasis and pathogenesis.

VGLL2 and TEAD1 fusion proteins drive YAP/TAZ-independent tumorigenesis by engaging p300

Studies on Hippo pathway regulation of tumorigenesis largely center on YAP and TAZ, the transcriptional co-regulators of TEAD. Here, we present an oncogenic mechanism involving VGLL and TEAD fusions that is Hippo pathway-related but YAP/TAZ-independent. We characterize two recurrent fusions, VGLL2-NCOA2 and TEAD1-NCOA2, recently identified in spindle cell rhabdomyosarcoma. We demonstrate that in contrast to VGLL2 and TEAD1, the fusion proteins are strong activators of TEAD-dependent transcription, and their function does not require YAP/TAZ. Furthermore, we identify that VGLL2 and TEAD1 fusions engage specific epigenetic regulation by recruiting histone acetyltransferase p300 to control TEAD-mediated transcriptional and epigenetic landscapes. We showed that small molecule p300 inhibition can suppress fusion proteins-induced oncogenic transformation both in vitro and in vivo. Overall, our study reveals a molecular basis for VGLL involvement in cancer and provides a framework for targeting tumors carrying VGLL, TEAD, or NCOA translocations.

Cooperation between the Hippo and MAPK pathway activation drives acquired resistance to TEAD inhibition

TEAD (transcriptional enhanced associate domain) transcription factors (TEAD1-4) serve as the primary effectors of the Hippo signaling pathway in various cancers. Targeted therapy leads to the emergence of resistance and the underlying mechanism of resistance to TEAD inhibition in cancers is less characterized. We uncover that upregulation of the AP-1 (activator protein-1) transcription factors, along with restored YAP (yes-associated protein) and TEAD activity, drives resistance to GNE-7883, a pan-TEAD inhibitor. Acute GNE-7883 treatment abrogates YAP-TEAD binding and attenuates FOSL1 (FOS like 1) activity. TEAD inhibitor resistant cells restore YAP and TEAD chromatin occupancy, acquire additional FOSL1 binding and exhibit increased MAPK (mitogen-activated protein kinase) pathway activity. FOSL1 is required for the chromatin binding of YAP and TEAD. This study describes a clinically relevant interplay between the Hippo and MAPK pathway and highlights the key role of MAPK pathway inhibitors in mitigating resistance to TEAD inhibition in Hippo pathway dependent cancers.

Cell enlargement modulated by GATA4 and YAP instructs the senescence-associated secretory phenotype

Dynamic changes in cell size are associated with development and pathological conditions, including aging. Although cell enlargement is a prominent morphological feature of cellular senescence, its functional implications are unknown; moreover, how senescent cells maintain their enlargement state is less understood. Here we show that an extensive remodeling of actin cytoskeleton is necessary for establishing senescence-associated cell enlargement and pro-inflammatory senescence-associated secretory phenotype (SASP). This remodeling is attributed to a balancing act between the SASP regulator GATA4 and the mechanosensor YAP on the expression of the Rho family of GTPase RHOU. Genetic or pharmacological interventions that reduce cell enlargement attenuate SASP with minimal effect on senescence growth arrest. Mechanistically, actin cytoskeleton remodeling couples cell enlargement to the nuclear localization of GATA4 and NF-κB via the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex. RhoU protein accumulates in mouse adipose tissue under senescence-inducing conditions. Furthermore, RHOU expression correlates with SASP expression in adipose tissue during human aging. Thus, our study highlights an unexpected instructive role of cell enlargement in modulating the SASP and reveals a mechanical branch in the senescence regulatory network.

Cell signaling in Ehrlichia infection and cancer: Parallels in pathogenesis

Ehrlichia chaffeensis (E. chaffeensis) has recently emerged as an intracellular bacterial pathogen with sophisticated survival mechanisms that include repurposing evolutionarily conserved eukaryotic cell signaling pathways for immune evasion. E. chaffeensis exploits four major developmental signaling pathways (Wnt, Notch, Hedgehog, and Hippo) using short linear motif (SLiM) ligand mimicry to initiate signaling cascades. Dysregulation of these major signaling pathways leading to unchecked cell survival is implicated in various diseases, most notably cancer. E. chaffeensis exploits Wnt, Notch, Hedgehog and Hippo signaling pathways to inhibit apoptosis and co-opt other cellular functions to promote infection. This review will explore the signaling pathways exploited during Ehrlichia infection and the new discoveries that have illuminated this interesting example of the cell signaling convergence in cellular infection and cancer biology.

Mechanosignaling via Integrins: Pivotal Players in Liver Fibrosis Progression and Therapy

Liver fibrosis, a consequence of chronic liver injury, represents a major global health burden and is the leading cause of liver failure, morbidity, and mortality. The pathological hallmark of this condition is excessive extracellular matrix deposition, driven primarily by integrin-mediated mechanotransduction. Integrins, transmembrane heterodimeric proteins that serve as primary ECM receptors, orchestrate complex mechanosignaling networks that regulate the activation, differentiation, and proliferation of hepatic stellate cells and other ECM-secreting myofibroblasts. These mechanical signals create self-reinforcing feedback loops that perpetuate the fibrotic response. Recent advances have provided insight into the roles of specific integrin subtypes in liver fibrosis and revealed their regulation of key downstream effectors-including transforming growth factor beta, focal adhesion kinase, RhoA/Rho-associated, coiled-coil containing protein kinase, and the mechanosensitive Hippo pathway. Understanding these mechanotransduction networks has opened new therapeutic possibilities through pharmacological manipulation of integrin-dependent signaling.

The Hippo pathway effector YAP inhibits NF-κB signaling and ccRCC growth by opposing ZHX2

The prevailing view in the cancer field is that Hippo signaling pathway functions as a tumor suppressor pathway by blocking the oncogenic potential of the pathway effectors Yes1 associated transcriptional regulator (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ). However, YAP can also function as a context-dependent tumor suppressor in several types of cancer including clear cell renal cell carcinomas (ccRCC). We find that, in additional to inhibiting hypoxia-inducible factor 2α (HIF2α), a major oncogenic driver in Von Hippel-Lindau (VHL)-/- ccRCC, YAP also blocks nuclear factor κB (NF-κB ) signaling in ccRCC to inhibit cancer cell growth under conditions where HIF2α is dispensable. Mechanistically, YAP inhibits the expression of Zinc fingers and homeoboxes 2 (ZHX2), a VHL substrate and critical co-factor of NF-κB in ccRCC. Furthermore, YAP competes with ZHX2 for binding to the NF-κB subunit p65. Consequently, elevated nuclear YAP blocks the cooperativity between ZHX2 and the NF-κB subunit p65, leading to diminished NF-κB target gene expression. Pharmacological inhibition of Hippo kinase blocked NF-κB transcriptional program and suppressed ccRCC cancer cell growth, which can be rescued by overexpression of ZHX2 or p65. Our study uncovers a crosstalk between the Hippo and NF-κB/ZHX2 pathways and its involvement in ccRCC growth inhibition, suggesting that targeting the Hippo pathway may provide a therapeutical opportunity for ccRCC treatment.

The Moonlighting Function of Glutaminase 2 Promotes Immune Evasion of Pancreatic Ductal Adenocarcinoma by Tubulin Tyrosine Ligase-like 1-Mediated Yes1 Associated Transcriptional Regulator Glutamylation

BACKGROUND & AIMS

Elevated programmed cell death-ligand 1 (PD-L1) expression in tumor cells facilitates immune evasion. However, the mechanism via which PD-L1 expression is regulated in pancreatic ductal adenocarcinoma (PDAC) cells remains inadequately elucidated.

METHODS

Immunoprecipitation, pull-down assays, and mass spectrometry were used to identify glutaminase 2 (GLS2) and yes1 associated transcriptional regulator (YAP1) binding proteins and modification sites. Immunoblotting, immunofluorescence, chromatin immunoprecipitation, and luciferase reporter assays were used to analyze YAP1 activation. Protein expression levels were assessed using immunoblotting, immunoprecipitation, immunofluorescence, and immunohistochemistry. RNA expression levels were analyzed using real-time quantitative polymerase chain reaction.

RESULTS

Hypoxia-induced general control nondepressible 5 (GCN5)-mediated acetylation of GLS2 at K151, which enhanced GLS2 interaction with YAP1. Subsequently, tubulin tyrosine ligase-like 1 mediated YAP1 glutamylation at E100 and promoted its nuclear translocation and the activation-dependent transcriptional up-regulation of PD-L1 expression. The expression of GLS2-K151R or YAP1-E100A mutants in PDAC cells blocked hypoxia-induced PD-L1 expression and enhanced CD4+ and CD8+ T-cell activation and tumor infiltration, thereby suppressing PDAC tumor growth. Simultaneous administration of MB-3, a GCN5 inhibitor, and an anti-programmed cell death 1 (PD-1) antibody abolished tumor immune evasion, boosting the anti-tumor efficacy of immune checkpoint blockade. Furthermore, GLS2-K151 acetylation and YAP1 E100 glutamylation levels correlated positively with PD-L1 expression and poor prognosis in PDAC patients.

CONCLUSIONS

The present study revealed a novel mechanism by which hypoxia up-regulates PD-L1 expression and highlighted the involvement of GLS2 in noncanonical metabolic pathways involved in tumor immune evasion, with implications for PDAC treatment.

ROS-induced cytosolic release of mitochondrial PGAM5 promotes colorectal cancer progression by interacting with MST3

Aberrant release of mitochondrial reactive oxygen species (mtROS) in response to cellular stress is well known for promoting cancer progression. However, precise molecular mechanism by which mtROS contribute to epithelial cancer progression remains only partially understood. Here, using colorectal cancer (CRC) models, we show that upon sensing excessive mtROS, phosphatase PGAM5, which normally localizes to the mitochondria, undergoes aberrant cleavage by presenilin-associated rhomboid-like protein (PARL), becoming released into the cytoplasm. Cytosolic PGAM5 then directly binds to and dephosphorylates MST3 kinase. This, in turn, prevents STK25-mediated LATS1/2 phosphorylation, leading to YAP activation and CRC progression. Importantly, depletion of MST3 reciprocally promotes accumulation of cytosolic PGAM5 by inducing mitochondrial damage. Taken together, these findings demonstrate how mtROS promotes CRC progression by activating YAP via a post-transcriptional positive feedback loop between PGAM5 and MST3, both of which can serve as potential targets for developing next-generation anti-colon cancer therapeutics.

CircINADL promotes nasopharyngeal carcinoma metastasis by inhibiting HuR ubiquitin degradation and disrupting the hippo signaling pathway

Distant metastasis is a primary factor contributing to the low survival rate of patients with nasopharyngeal carcinoma (NPC). Circular RNAs (circRNAs) are increasingly recognized for their roles in cancer initiation and progression. However, the mechanisms underlying the abnormal expression and biological function of circRNA in NPC remain unclear. In this study, we identified a new circRNA, circINADL, which was upregulated in NPC tissues and positively correlated with the clinical stage of NPC. We found that the FUS RNA binding protein (FUS) promoted the transcription of circINADL in NPC cells. Elevated circINADL levels were shown to enhance NPC cells metastasis. Mechanistically, circINADL attenuated the interaction between human antigen R (HuR) and the E3 ubiquitin ligase β-TrCP, thereby inhibited the ubiquitination and degradation of HuR. Consequently, CircINADL enhanced the stability of the HuR target gene Yes1-associated transcriptional regulator (YAP1), leading to the dysregulation of the Hippo signaling pathway. In conclusion, our study reveals the function of circINADL in promoting NPC metastasis and highlights its potential as a biomarker and therapeutic target for NPC treatment.

Important molecular mechanisms in ferroptosis

Ferroptosis is a type of cell death that is caused by the oxidation of lipids and is dependent on the presence of iron. It was first characterized by Brent R. Stockwell in 2012, and since then, research in the field of ferroptosis has rapidly expanded. The process of ferroptosis-induced cell death is genetically, biochemically, and morphologically distinct from other forms of cellular death, such as apoptosis, necroptosis, and non-programmed cell death. Extensive research has been devoted to comprehending the intricate process of ferroptosis and the various factors that contribute to it. While the majority of these studies have focused on examining the effects of lipid metabolism and mitochondria on ferroptosis, recent findings have highlighted the significant involvement of signaling pathways and associated proteins, including Nrf2, P53, and YAP/TAZ, in this process. This review provides a concise summary of the crucial signaling pathways associated with ferroptosis based on relevant studies. It also elaborates on the drugs that have been employed in recent years to treat ferroptosis-related diseases by targeting the relevant signaling pathways. The established and potential therapeutic targets for ferroptosis-related diseases, such as cancer and ischemic heart disease, are systematically addressed.

Inhibition of MST1/2 Kinases of the Hippo Signaling Pathway Enhances Antitumor Chemotherapy in Hematological Cancers

Primary drug resistance of tumor cells or resistance acquired during treatment is among the main factors that significantly limit the efficacy of antitumor chemotherapy, along with severe side effects depending on the drug dose. To increase the efficacy, chemotherapeutics can be used in combination with substances that modulate the functions of cell signaling pathways. In this work, the substance XMU-MP-1, an inhibitor of key MST1/2 kinases of the Hippo signaling pathway, was shown to enhance the antitumor activity of two genotoxic chemotherapeutics, etoposide and cisplatin, against Namalwa Burkitt's B-cell lymphoma cells. XMU-MP-1 increased the cytotoxicity of the agents and significantly reduced their CTD50. The drug efficacy is therefore possible to increase significantly, and a therapeutic effect might be achieved at a lower drug concentration to reduce the likelihood of life-threatening side effects.

Regulatory roles of RNA binding proteins in the Hippo pathway

The Hippo pathway represents a highly conserved evolutionary pathway, dysfunction of which has been implicated in various diseases. RNA-binding proteins (RBPs) intricately modulate gene expression through interacting with non-coding RNAs or other proteins. To data, while an array of RBPs have been identified as modulators of the Hippo pathway, there remains a notable absence of a comprehensive review addressing the mechanistic regulations of RBPs in the transduction of Hippo signaling. Herein, this review aims to consolidate recent advances and elucidate the intricate mechanisms underlying RBPs binding to target RNA. It also explores the dynamic interplay between RBPs, non-coding RNAs, TFs, and DNA on chromatin. Additionally, it also outlines future perspectives, including the essential non-canonical functions of RBPs and emerging roles of non-canonical RBPs as transcription factors (TFs) in genes transcription. Overall, this review provides mechanistic insights into the roles of eukaryotic RBP proteins in the regulation of crucial signaling cascades.

YAP/TAZ-associated cell signaling - at the crossroads of cancer and neurodevelopmental disorders

YAP/TAZ (Yes-associated protein/paralog transcriptional co-activator with PDZ-binding domain) are transcriptional cofactors that are the key and major downstream effectors of the Hippo signaling pathway. Both are known to play a crucial role in defining cellular outcomes, including cell differentiation, cell proliferation, and apoptosis. Aside from the canonical Hippo signaling cascade with the key components MST1/2 (mammalian STE20-like kinase 1/2), SAV1 (Salvador homologue 1), MOB1A/B (Mps one binder kinase activator 1A/B) and LATS1/2 (large tumor suppressor kinase 1/2) upstream of YAP/TAZ, YAP/TAZ activation is also influenced by numerous other signaling pathways. Such non-canonical regulation of YAP/TAZ includes well-known growth factor signaling pathways such as the epidermal growth factor receptor (EGFR)/ErbB family, Notch, and Wnt signaling as well as cell-cell adhesion, cell-matrix interactions and mechanical cues from a cell's microenvironment. This puts YAP/TAZ at the center of a complex signaling network capable of regulating developmental processes and tissue regeneration. On the other hand, dysregulation of YAP/TAZ signaling has been implicated in numerous diseases including various cancers and neurodevelopmental disorders. Indeed, in recent years, parallels between cancer development and neurodevelopmental disorders have become apparent with YAP/TAZ signaling being one of these pathways. This review discusses the role of YAP/TAZ in brain development, cancer and neurodevelopmental disorders with a special focus on the interconnection in the role of YAP/TAZ in these different conditions.