Role of the Hippo pathway in autoimmune diseases

Upregulated nicotinic ACh receptor signaling contributes to intestinal stem cell function through activation of Hippo and Notch signaling pathways

Despite recent advances in treatment in patients with inflammatory bowel diseases (IBDs), achieving mucosal healing remains challenging due to an incomplete understanding of disease pathobiology and heterogeneity. Intestinal stem cells (ISCs) are crucial for epithelial regeneration and repair, making them promising targets for regenerative therapies. E-cadherin, a transmembrane protein of the adherens junctions, plays a critical role in maintaining intestinal epithelial integrity. E-cadherin modulates key signaling pathways, including Wnt, Hippo, and Notch signaling pathways, which are essential for ISC homeostasis and regeneration. However, the role of E-cadherin in ISC function and its potential as a therapeutic target for IBD have been largely unexplored. In this study, we hypothesized that downregulation of E-cadherin affects colonic stem cell development and promotes regenerative responses by modulating Wnt and Hippo signaling pathways. Using mouse colonoids, we investigated the role of E-cadherin during intestinal homeostasis and regeneration using an IBD-like anoxia/cytokine model. We generated inducible E-cadherin shRNA knock-down mouse colonoids using lentiviral vectors. Acute injury was induced by subjecting colonoids to inflammatory cytokines, TNF-α and INF-γ, in anoxia, closely recapitulating the physiologic environment of IBD. Phenotypes and gene expression were analyzed by microscopy and real-time PCR. Our findings show that E-cadherin knockdown led to a more spherical and less differentiated morphology in colonoid cultures, accompanied by a significant increase in the mRNA expression of ISC marker Lgr5. The expression of reserve stem cell markers (Bmi1 and Hopx) remained unchanged, while markers for secretory progenitors were upregulated, and absorptive progenitor markers were downregulated. During regeneration after IBD-like anoxia/cytokine injury, characterized by increased area and bud number of colonoids, mRNA expression of reserve stem cell marker Hopx was considerably elevated with reduced E-cadherin expression. Notably, we observed increased expression of Wnt and YAP target genes and altered expression of Notch pathway genes in E-cadherin-deficient colonoids. These results suggest that E-cadherin regulates ISC development and intestinal regeneration through critical cellular pathways, including Wnt, Hippo, and Notch signaling pathways. Further studies on the mechanistic role of E-cadherin in ISC populations during regeneration, particularly in the context of IBD, may reveal novel therapeutic strategies aimed at enhancing mucosal healing and restoring intestinal homeostasis in IBD patients. Maryland Stem Cell Research Fund (Grant no. 2021-MSCRFL-5577) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Immuno-hippo: Research progress of the hippo pathway in autoimmune disease

The Hippo signaling pathway is critical for carcinogenesis. However, the roles of the Hippo signaling pathway in the tumor immune microenvironment have been rarely investigated. This study systematically analyzed the relationship between the Hippo signaling pathway and immune cell infiltration across 32 cancer types. Both bioinformatics analyses and biological experiments revealed that the downstream effector of Hippo signaling YAP1 might inhibit CD8+ T cell infiltration by upregulating the expression of the transcription factor CREB1 in uterine corpus endometrial carcinoma. In addition, esophageal carcinoma (ESCA) patients were classified into three subtypes based on the Hippo-immune gene panel. The subtypes of ESCA had distinct characteristics in immune cell infiltration, immune pathways, and prognosis. Thus, this study also reveals a new classification of the immune subtypes with prognostic characteristics in ESCA.

Changes in chromatin accessibility caused by histone modifications regulate gene transcription. However, little is known about associations between gene expression changes caused by histone modifications and viral infections. We investigate the midguts of silkworms infected with Bombyx mori cypovirus (BmCPV) at 48 h and 96 h post infection (CPV48 and CPV96), and corresponding midguts of uninfected silkworms (GUT48 and GUT96) using CUT&Tag-seq and RNA-seq. We report H3K9me3, H3K9ac, and gene expression profiles at the genome-wide level to change with BmCPV infection. Differential H3K9me3 peak-related genes were mainly enriched in MAPK, Wnt, and Hippo signalling pathways; Differential H3K9ac peaks-related genes were mainly enriched in the Hippo signalling, apoptosis, and citrate cycle pathways; and differentially expressed genes (DEGs) were mainly enriched in carbon metabolism, protein processing in endoplasmic reticulum, and glycolysis/gluconeogenesis pathways. Integration analysis between H3K9me3/H3K9ac peaks and gene expression revealed changes in gene expression profiles to be associated with alteration of H3K9me3/H3K9ac at promoters; gene expression correlates negatively with corresponding H3K9me3 signals in gene bodies, and positively with corresponding H3K9ac signals at the transcription start site. Intersection genes with log2foldchange of both CUT&Tag-seq peak and RNA-seq FPKM > 1 were screened and annotated. Genes shared by differential H3K9me3 peak-related genes and DEGs were enriched in insect hormone biosynthesis, MAPK signalling, and TGF-beta signalling pathways, and genes shared by differential H3K9ac peak-related genes and DEGs were enriched in glycolysis/gluconeogenesis, TGF-beta signalling, and mitophagy pathways. These results indicate that BmCPV regulates gene expression through H3K9me3/H3K9ac.

The Hippo pathway is recognized as an important regulator of tissue growth and cell fate [1-3]. Originally indentified in Drosophila, the Hippo pathway, also known as the Salvador–Warts–Hippo pathway, contains core kinases cascade, Hippo and Warts(Wts) coupled by the scaffold protein Salvador (Sav), as well as Mats. The activation of the Hippo pathway kinases results in phosphorylation and inactivation of the downstream transcriptional co-activator Yorkie which binds to the sequence-specific DNA-binding protein Scalloped and enhances the expression of proliferative and pro-survival genes. In general, the primary function of the Hippo signaling pathway is to inhibit the activation of Yorkie, inasmuch as deletion of Yki reverses the overgrowth phenotypes resulted from loss of Hippo, Warts, Salvador or Mats. Components of the Hippo pathway are highly conserved throughout evolution. The counterparts for the Hippo pathway in Drosophila can all be found in mammals, although they are more diverse and complex [4]. The Hippo orthologs Mst1 and Mst2 utilize the Salvador ortholog WW45/Sav1 to regulate the Warts orthologs Lats1/Lats2. Activated Lats kinases phosphorylate the transcriptional regulators TAZ/YAP (Yorkie orthologs) which promotes 14-3-3 binding to YAP, causing YAP nuclear exit, hereby inhibiting its function. In recent years, increasing numbers of mammalian studies have expanded the large proteins network of the Hippo signaling pathway that controls tissues growth during development and regeneration, as well as in pathological states such as cancer [5]. The upstream regulator of the Hippo pathway and the downstream of Mst1/Mst2 have been diversified considerably in mammals compared with the Drosophila Hippo pathway. Multiple cellular stresses can trigger an adaptive response by activating the Hippo signaling pathway, which may, in turn, maintain the cellular homeostasis. The Hippo/Warts/Mats/Yorkie pathway predicated in Drosophila is not universal in all mammalian tissues in which their regulation and function are different in selected cell types. For examples, Mst1/2 negatively regulates YAP1 in mammalian liver, however, Mst1/2 is not required for YAP1 phosporylation and nuclear exclusion resulted from the cell-cell contact in mouse embryonic fibroblasts(MEFs); Mst1/2 is dispensable for Lats1/2 signaling in MEFs, but not in HeLa cells [6]. Independent of YAP, Mst1 negatively regulates naive T cell proliferation upon the T cell receptor stimulation, as well as regulates peripheral naive T cell trafficking and thymus egress [7]. Furthermore, patients with Mst1 deficiency are reported to have a primary immunodeficiency phenotype [8,9]. During the tissues regeneration and tumorigenesis, the Hippo signaling pathway has been shown to cross talk with other signaling players such as Notch and Wnt [10]. Thus, not just for the organ size control, the Hippo pathway receives inputs from multiple extracellular or intracellular signals and interacts with other essential signaling pathways to play critical roles in many aspects for cell fate decisions. In this issue of the Cell & Bioscience, we have provided some updates on the regulations beyond the canonical Hippo signaling, and their implications in pathological states. Qin et al. will review the recent updates of the roles of Mst1/2 on the cellular redox state regulation, the effects of Mst1/2 deficiency on the development process and tumorigenesis in multiple organs, and their involvement in the immune regulation. The review by Hergovich will summarize the current understanding of mammalian Lats1/2 kinases together with their closest relatives, the NDR1/2 kinases. He will focus on discussion about the regulation of the LATS/NDR family of kinases and their currently known substrates, as well as the biological roles of LATS/NDR kinases. Guo and Zhao follows with a discussion of the function of YAP and TAZ as effectors of cell responses to several extracellular signals including mechanical stress, GPCR signaling, and the Wnt signaling pathway, emphasizing that YAP and TAZ might have different role with cell-type specificity in the promotion of specific cancers. Collectively, these reviews have provided additional information to address the complexity of the hippo signaling pathway in response to physiological signals for regulating cellular and tissues homeostasis.

Hippo signaling pathways are evolutionarily conserved signal transduction mechanisms mainly involved in organ size control, tissue regeneration, and tumor suppression. However, in mammals, the primary role of Hippo signaling seems to be regulation of immunity. As such, humans with null mutations in STK4 (mammalian homologue of Drosophila Hippo; also known as MST1) suffer from recurrent infections and autoimmune symptoms. Although dysregulated T cell homeostasis and functions have been identified in MST1-deficient human patients and mouse models, detailed cellular and molecular bases of the immune dysfunction remain to be elucidated. Although the canonical Hippo signaling pathway involves transcriptional co-activator Yes-associated protein (YAP) or transcriptional coactivator with PDZ motif (TAZ), the major Hippo downstream signaling pathways in T cells are YAP/TAZ-independent and they widely differ between T cell subsets. Here we will review Hippo signaling mechanisms in T cell immunity and describe their implications for immune defects found in MST1-deficient patients and animals. Further, we propose that mutual inhibition of Mst and Akt kinases and their opposing roles on the stability and function of forkhead box O and β-catenin may explain various immune defects discovered in mutant mice lacking Hippo signaling components. Understanding these diverse Hippo signaling pathways and their interplay with other evolutionarily-conserved signaling components in T cells may uncover molecular targets relevant to vaccination, autoimmune diseases, and cancer immunotherapies.

Cardiovascular diseases have become the leading cause of death in the world. Understanding the development of cardiovascular system and the pathogenesis of cardiovascular diseases will promote the generation of novel preventive and therapeutic strategy. The Hippo pathway is a recently identified signaling cascade that plays a critical role in organ size control, cell proliferation, apoptosis and fate determination of stem cells. Gene knockout and transgenic mouse models have revealed that the Hippo signaling pathway is involved in heart development, cardiomyocyte proliferation, apoptosis, hypertrophy and cardiac regeneration. The Hippo signaling pathway also regulates vascular development, differentiation and various functions of vascular cells. Dysregulation of the Hippo signaling pathway leads to different kinds of cardiovascular diseases, such as myocardial infarction, cardiac hypertrophy, neointima formation and atherosclerosis. In this review, we briefly summarize current research on the roles and regulation mechanisms of the Hippo signaling pathway in cardiovascular development and diseases.

The Hippo signaling pathway, also known as the Salvador-Warts-Hippo pathway, is a well-known oncogenic signaling pathway associated with organ size regulation, cell proliferation, and apoptosis. In this study, we analyzed the association of Hippo signaling pathway genes in patients with acute myeloid leukemia (AML) using whole-exome sequencing (WES) and whole-transcriptome sequencing (WTS) data. We used Seoul National University Hospital (SNUH) AML patient data (n=16) collected from December 2015 to January 2019 for analysis. Additionally, public datasets of AML patients, TCGA-LAML (n=179) and LeuceGene (n=110) were used. we performed hierarchical clustering using Hippo pathway gene expression from AML patient samples. As a result, we discovered a gene expression signature in which the expressions of tumor suppressor genes among the Hippo pathway genes were significantly decreased. We divided AML patients into the case group and the control group according to the presence or absence of the corresponding gene expression signature and attempted to identify differences in biological features between the two groups. First, in the process of comparing differences in genetic alteration, it was confirmed that the frequency of PML-RARA fusion was significantly higher in the case group. We further analyzed the data of the AML patients in the case group without PML-RARA fusion to discover other biological features. To discover the correlation between the Hippo pathway and other oncogenic signaling pathways on gene expression level, we performed a correlation analysis. As a result, it was confirmed that the expression of the Hippo pathway gene showed a high correlation with the gene expression of the Notch signaling pathway and the Myc signaling pathway in the patients of the case group. In addition, we performed DEGs analysis to find new therapeutic target candidate genes from the case group. As a result, we identified a significantly upregulated gene, LAMP5.In conclusion, we identified the gene expression signatures of the Hippo signaling pathway in AML patients. Also, we discovered a correlation between the Hippo pathway and other signaling pathways and suggested potential therapeutic candidate genes using gene expression signatures of the Hippo signaling pathway genes. And we will perform further analysis about validating therapeutic candidate genes related to the Hippo signaling pathway gene expression signature. Citation Format: Heejun Jang, Sungyoung Lee, Hongseok Yun, Yongil Koh, Sung-Soo Yoon. Association of Hippo signaling pathway in acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3359.

Integration of intercellular signaling through the Hippo pathway

Study question Does verteporfin, an inhibitor of YAP/TAZ activity, prevent from the impacts of chemotherapy exposure on signaling pathways governing follicle activation and survival? Summary answer Verteporfin treatment prevents from the chemotherapy-induced impairments of the Hippo pathway but also of PI3K and survival pathways. What is known already The Hippo pathway is a crucial regulator of the ovarian reserve. Disruption of this pathway occurring in non-physiological contexts, such as ovarian processing during ovarian tissue preservation or after chemotherapy exposure, leads to massive uncoordinated follicular growth and depletion of the ovarian stockpile. To prevent from the harmful impact of chemotherapy exposure, several studies assessed the potential of inhibition of the PI3K pathway, the major signaling pathway involved in physiological follicle activation. However, the protective effect of this inhibition appeared to be moderate in vitro, suggesting the involvement of other disrupted mechanisms, as Hippo pathway. Study design, size, duration This study was performed on post-natal day 3 mouse ovaries. Half-cut ovaries were first treated with 0, 0.2, 1.5 and 3 µM Verteporfin (VERT) during 3 hours in vitro culture to establish the efficient dose of VERT. Whole ovaries were then cultured for 24 and 48 hours and exposed to 10 µM 4-hydroperoxycyclophosphamide (4HC) and/or 3 µM VERT to assess the effect of this inhibitor on follicle activation and survival pathways. (N = 3-5) Participants/materials, setting, methods To assess the impacts of sectioning and VERT treatment on follicle activation, gene expression analyses (RT-qPCR) were used to assess Hippo, PI3K/AKT/mTOR and apoptosis signaling pathways. The potential preventive effect of VERT co-treatment with 4HC exposure was evaluated by gene (RT-qPCR) and protein expression (western blot) analyses of these three pathways, and completed with histological staining for DNA damages (TUNEL). Main results and the role of chance Following exposure to increased concentration of VERT for 3 hours, a significant impact of the inhibitor was observed at 3µM on Ccn2 (p = 0.003) and Cmyc (p = 0.045) expression levels compared to control, without impacting on apoptosis genes expression. Exposure to 10 µM 4HC induced a higher YAP/pYAP protein ratio and Ccn2 expression level compared to control after 24 and 48 hours of culture, confirming the Hippo pathway disruption. VERT co-treatment was able to prevent from this increase of protein levels and gene expression, although the impact on Ccn2 expression was moderated after 48 hours of culture. Assessment of PI3K signaling revealed an induction of mTOR signaling following 4HC exposure at both time of culture as shown by the higher pRPS6/RPS6 ratio compared to control. Surprisingly, VERT co-treatment significantly decreased this level compared to 4HC alone at 24 and 48 hours of culture. This result suggests an indirect impact of this inhibitor on the PI3K pathway. Despite Bax and Bcl2 gene levels remained stable among conditions, ovaries exposed to 4HC had a significant higher level of DNA damages at both culture timepoints compared to control. Notably, VERT co-treatment was able to decrease the 4HC-induced gonadotoxicity at 48 hours of culture. Limitations, reasons for caution This study evaluated the impact of an inhibitor to control follicle activation in mouse model, and was limited to the assessment of two main signaling. Although we completed our study with apoptosis analyses, the results should be interpreted with caution as other pathways may be involved into the activation process. Wider implications of the findings Our results suggest that verteporfin is a promising inhibitor to control acute signaling pathway impairments under unphysiological conditions. Moreover, this study sustains the presence of a potential interaction between the two main signaling pathways regulating follicle activation, PI3K and Hippo pathways. Trial registration number Not applicable

The Hippo signaling pathway is an evolutionarily conserved network that regulates cell proliferation, apoptosis, and stemness. It also plays an important role in tumorigenesis and cancer progression, and previous studies have indicated that Hippo signaling promotes trastuzumab resistance in breast cancer (BC). However, its clinical relevance in patients with BC remains unclear. Clinical and transcriptomics data from two large cohorts, METABRIC and TCGA, were analyzed. A Hippo pathway score was calculated by applying Gene Set Variation Analysis to the curated Kyoto Encyclopedia of Genes and Genomes (KEGG) Hippo pathway gene set (43 genes). Patients were stratified into high and low groups based on the top tertile of Hippo pathway scores in each cohort. High Hippo pathway scores were significantly associated with worse disease-specific survival (DSS) in HER2-positive BC. In both cohorts, the Hippo pathway score showed the largest hazard ratio (HR) for DSS in HER2-positive BC compared with YAP1 or TAZ, transcription co-activators that are key components in the Hippo pathway (HR = 2.47, p = 0.04, and HR = 41.8, p = 0.03). Breast cancers with high Hippo pathway activity were associated with enrichment of cell proliferation and metastasis-related gene sets, including epithelial-mesenchymal transition, Notch, Hedgehog, and TGF-β signaling. Moreover, high Hippo pathway scores correlated with lower infiltration of anti-cancer immune cells (Th1 cells, dendritic cells, and M1-macrophages). Notably, low Hippo pathway scores were linked to a higher pathological complete response following trastuzumab-based neoadjuvant chemotherapy (p = 0.035). Enhanced Hippo pathway activity in HER2-positive BC is associated with worse prognoses, metastasis-related gene enrichment, and reduced anti-cancer immune cell infiltration, potentially contributing to trastuzumab resistance.

Sophoridine inhibits lung cancer cell growth and enhances cisplatin sensitivity through activation of the p53 and Hippo signaling pathways.

Cell types have been established during organogenesis based on early mouse embryos. However, our understanding of cell types and molecular mechanisms in the early embryo development of Mongolian sheep has been hampered. This study presents the first comprehensive single-cell transcriptomic characterization at E16 in Ujumqin sheep and Hulunbuir short-tailed sheep. Thirteen major cell types were identified at E16 in Ujumqin sheep, and eight major cell types were identified at E16 in Hulunbuir short-tailed sheep. Function enrichment analysis showed that several pathways were significantly enriched in the TGF-beta signaling pathway, the Hippo signaling pathway, the platelet activation pathway, the riboflavin metabolism pathway, the Wnt signaling pathway, regulation of the actin cytoskeleton, and the insulin signaling pathway in the notochord cluster. Glutathione metabolism, glyoxylate, and dicarboxylate metabolism, the citrate cycle, thyroid hormone synthesis, pyruvate metabolism, cysteine and methionine metabolism, thermogenesis, and the VEGF signaling pathway were significantly enriched in the spinal cord cluster. Steroid biosynthesis, riboflavin metabolism, the cell cycle, the Hippo signaling pathway, the Hedgehog signaling pathway, the FoxO signaling pathway, the JAK-STAT signaling pathway, and the Wnt signaling pathway were significantly enriched in the paraxial mesoderm cluster. The notochord cluster, spinal cord cluster, and paraxial mesoderm cluster were found to be highly associated with tail development. Pseudo-time analysis demonstrated that the mesenchyme can translate to the notochord in Ujumqin sheep. Molecular assays revealed that the Hippo signaling pathway was enriched in Ujumqin sheep. This comprehensive single-cell map revealed previously unrecognized signaling pathways that will further our understanding of the mechanism of short-tailed sheep formation.

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