Acetylation of beta-catenin by p300 regulates beta-catenin-Tcf4 interaction

The role and mechanism of protein post‑translational modification in vascular calcification (Review)

Vascular calcification is closely associated with morbidity and mortality in patients with chronic kidney disease, atherosclerosis and diabetes. In the past few decades, vascular calcification has been studied extensively and the findings have shown that the mechanism of vascular calcification is not merely a consequence of a high-phosphorus and high-calcium environment but also an active process characterized by abnormal calcium phosphate deposition on blood vessel walls that involves various molecular mechanisms. Recent advances in bioinformatics approaches have led to increasing recognition that aberrant post-translational modifications (PTMs) play important roles in vascular calcification. This review presents the latest progress in clarifying the roles of PTMs, such as ubiquitination, acetylation, carbamylation and glycosylation, as well as signaling pathways, such as the Wnt/β-catenin pathway, in vascular calcification.

Cell signaling and transcriptional regulation of osteoblast lineage commitment, differentiation, bone formation, and homeostasis

The initiation of osteogenesis primarily occurs as mesenchymal stem cells undergo differentiation into osteoblasts. This differentiation process plays a crucial role in bone formation and homeostasis and is regulated by two intricate processes: cell signal transduction and transcriptional gene expression. Various essential cell signaling pathways, including Wnt, BMP, TGF-β, Hedgehog, PTH, FGF, Ephrin, Notch, Hippo, and Piezo1/2, play a critical role in facilitating osteoblast differentiation, bone formation, and bone homeostasis. Key transcriptional factors in this differentiation process include Runx2, Cbfβ, Runx1, Osterix, ATF4, SATB2, and TAZ/YAP. Furthermore, a diverse array of epigenetic factors also plays critical roles in osteoblast differentiation, bone formation, and homeostasis at the transcriptional level. This review provides an overview of the latest developments and current comprehension concerning the pathways of cell signaling, regulation of hormones, and transcriptional regulation of genes involved in the commitment and differentiation of osteoblast lineage, as well as in bone formation and maintenance of homeostasis. The paper also reviews epigenetic regulation of osteoblast differentiation via mechanisms, such as histone and DNA modifications. Additionally, we summarize the latest developments in osteoblast biology spurred by recent advancements in various modern technologies and bioinformatics. By synthesizing these insights into a comprehensive understanding of osteoblast differentiation, this review provides further clarification of the mechanisms underlying osteoblast lineage commitment, differentiation, and bone formation, and highlights potential new therapeutic applications for the treatment of bone diseases.

Wnt/β-catenin signaling pathway in carcinogenesis and cancer therapy

The Wnt/β-catenin signaling pathway plays a crucial role in various physiological processes, encompassing development, tissue homeostasis, and cell proliferation. Under normal physiological conditions, the Wnt/β-catenin signaling pathway is meticulously regulated. However, aberrant activation of this pathway and downstream target genes can occur due to mutations in key components of the Wnt/β-catenin pathway, epigenetic modifications, and crosstalk with other signaling pathways. Consequently, these dysregulations contribute significantly to tumor initiation and progression. Therapies targeting the Wnt/β-catenin signaling transduction have exhibited promising prospects and potential for tumor treatment. An increasing number of medications targeting this pathway are continuously being developed and validated. This comprehensive review aims to summarize the latest advances in our understanding of the role played by the Wnt/β-catenin signaling pathway in carcinogenesis and targeted therapy, providing valuable insights into acknowledging current opportunities and challenges associated with targeting this signaling pathway in cancer research and treatment.

Proximal tubular FHL2, a novel downstream target of hypoxia inducible factor 1, is a protector against ischemic acute kidney injury

Four-and-a-half LIM domains protein 2 (FHL2) is an adaptor protein that may interact with hypoxia inducible factor 1α (HIF-1α) or β-catenin, two pivotal protective signaling in acute kidney injury (AKI). However, little is known about the regulation and function of FHL2 during AKI. We found that FHL2 was induced in renal tubular cells in patients with acute tubular necrosis and mice model of ischemia-reperfusion injury (IRI). In cultured renal proximal tubular cells (PTCs), hypoxia induced FHL2 expression and promoted the binding of HIF-1 to FHL2 promoter. Compared with control littermates, mice with PTC-specific deletion of FHL2 gene displayed worse renal function, more severe morphologic lesion, more tubular cell death and less cell proliferation, accompanying by downregulation of AQP1 and Na, K-ATPase after IRI. Consistently, loss of FHL2 in PTCs restricted activation of HIF-1 and β-catenin signaling simultaneously, leading to attenuation of glycolysis, upregulation of apoptosis-related proteins and downregulation of proliferation-related proteins during IRI. In vitro, knockdown of FHL2 suppressed hypoxia-induced activation of HIF-1α and β-catenin signaling pathways. Overexpression of FHL2 induced physical interactions between FHL2 and HIF-1α, β-catenin, GSK-3β or p300, and the combination of these interactions favored the stabilization and nuclear translocation of HIF-1α and β-catenin, enhancing their mediated gene transcription. Collectively, these findings identify FHL2 as a direct downstream target gene of HIF-1 signaling and demonstrate that FHL2 could play a critical role in protecting against ischemic AKI by promoting the activation of HIF-1 and β-catenin signaling through the interactions with its multiple protein partners.

Protein lysine acetyltransferase CBP/p300: A promising target for small molecules in cancer treatment

CBP and p300 are homologous proteins exhibiting remarkable structural and functional similarity. Both proteins function as acetyltransferase and coactivator, underscoring their significant roles in cellular processes. The function of histone acetyltransferases is to facilitate the release of DNA from nucleosomes and act as transcriptional co-activators to promote gene transcription. Transcription factors recruit CBP/p300 by co-condensation and induce transcriptional bursting. Disruption of CBP or p300 functions is associated with different diseases, especially cancer, which can result from either loss of function or gain of function. CBP and p300 are multidomain proteins containing HAT (histone acetyltransferase) and BRD (bromodomain) domains, which perform acetyltransferase activity and maintenance of HAT signaling, respectively. Inhibitors targeting HAT and BRD have been explored for decades, and some BRD inhibitors have been evaluated in clinical trials for treating hematologic malignancies or advanced solid tumors. Here, we review the development and application of CBP/p300 inhibitors. Several inhibitors have been evaluated in vivo, exhibiting notable potency but limited selectivity. Exploring these inhibitors emphasizes the promise of targeting CBP and p300 with small molecules in cancer therapy.

α-Catenin acetylation is essential for its stability and blocks its tumor suppressor effects in breast cancer through Yap1

α-Catenin plays a critical role in tissue integrity, repair, and embryonic development. However, the post-translational modifications of α-catenin and the correlative roles in regulating cancer progression remain unclear. Here, we report that α-catenin is acetylated by p300, and identify three acetylation sites, K45, K866, and K881. Conversely, α-catenin acetylation can be reversed by deacetylase HDAC6. Mechanistically, α-catenin acetylation releases the transcriptional coactivator Yes-associated protein 1 (Yap1) by blocking the interaction between α-catenin and Yap1, and promotes the accumulation of Yap1 in the nucleus. Through this mechanism, acetylation weakens the capacity of α-catenin to inhibit breast cancer cell proliferation and tumor growth in mice. Meanwhile, we show that CDDP induces acetylation of α-catenin, and acetylated α-catenin resists the apoptosis under CDDP conditions. Additionally, acetylation inhibits the proteasome-dependent degradation of α-catenin, thus enhancing the stability of α-catenin for storage. Taken together, our results demonstrate that α-catenin can be acetylated, an event that is key for the subcellular distribution of Yap1 and subsequent facilitation of breast tumorigenesis.

Novel mechanism for zinc inducing hepatic lipolysis via the HDAC3-mediated deacetylation of β-catenin at lysine 311

Zinc (Zn) is a multipurpose trace element indispensable for vertebrates and possesses essential regulatory roles in lipid metabolism, but the fundamental mechanism remains largely unknown. In the current study, we found that a high-Zn diet significantly increased hepatic Zn content and influenced the expression of Zn transport-relevant genes. Dietary Zn addition facilitated lipolysis, inhibited lipogenesis, and controlled β-catenin signal; Zn also promoted T-cell factor 7-like 2 (TCF7L2) to interact with β-catenin and regulating its transcriptional activity, thereby inducing lipolysis and inhibiting lipogenesis; Zn-induced lipid degradation was mediated by histone deacetylase 3 (HDAC3) which was responsible for β-catenin deacetylation and the regulation of β-catenin signal under the Zn treatment. Mechanistically, Zn promoted lipid degradation via stimulating HDAC3-mediated deacetylation of β-catenin at lysine 311 (K311), which enhanced the interaction between β-catenin and TCF7L2 and then transcriptionally inhibited fatty acid synthase (FAS), 2-acylglycerol O-acyltransferase 2 (MOGAT2), and sterol regulatory element-binding protein 1 (SREBP1) expression, but elevated the mRNA abundance of adipose triglyceride lipase (ATGL), hormone-sensitive lipase a (HSLA) and carnitine palmitoyltransferase 1a1b (CPT1A1B). Overall, our research reveals a novel mechanism into the important roles of HDAC3/β-catenin pathway in Zn promoting lipolysis and inhibiting lipogenesis, and highlights the essential roles of K311 deacetylation in β-catenin actions and lipolytic metabolism, and accordingly provides novel insight into the prevention and treatment of steatosis in the vertebrates.

ENO2-derived phosphoenolpyruvate functions as an endogenous inhibitor of HDAC1 and confers resistance to antiangiogenic therapy

Metabolic reprogramming is associated with resistance to antiangiogenic therapy in cancer. However, its molecular mechanisms have not been clearly elucidated. Here, we identify the glycolytic enzyme enolase 2 (ENO2) as a driver of resistance to antiangiogenic therapy in colorectal cancer (CRC) mouse models and human participants. ENO2 overexpression induces neuroendocrine differentiation, promotes malignant behaviour in CRC and desensitizes CRC to antiangiogenic drugs. Mechanistically, the ENO2-derived metabolite phosphoenolpyruvate (PEP) selectively inhibits histone deacetylase 1 (HDAC1) activity, which increases the acetylation of β-catenin and activates the β-catenin pathway in CRC. Inhibition of ENO2 with enolase inhibitors AP-III-a4 or POMHEX synergizes the efficacy of antiangiogenic drugs in vitro and in mice bearing drug-resistant CRC xenograft tumours. Together, our findings reveal that ENO2 constitutes a useful predictive biomarker and therapeutic target for resistance to antiangiogenic therapy in CRC, and uncover a previously undefined and metabolism-independent role of PEP in regulating resistance to antiangiogenic therapy by functioning as an endogenous HDAC1 inhibitor.

Mechanistic insights into the dual role of CCAR2/DBC1 in cancer

Cell cycle and apoptosis regulator 2 (CCAR2), also known as deleted in breast cancer 1 (DBC1), has been recently identified as a master regulator of transcriptional processes and plays diverse roles in physiology and pathophysiology, including as a regulator of apoptosis, DNA repair, metabolism, and tumorigenesis. CCAR2 functions as a coregulator of various transcription factors and a critical regulator of numerous epigenetic modifiers. Based on its ability to stimulate apoptosis by activating and stabilizing p53, CCAR2 was initially considered to be a tumor suppressor. However, an increasing number of studies have shown that CCAR2 also functions as a tumor-promoting coregulator by activating oncogenic transcription factors and regulating the enzymatic activity of epigenetic modifiers, indicating that CCAR2 may play a dual role in cancer progression by acting as a tumor suppressor and tumor promoter. Here, we review recent progress in understanding the dual tumor-suppressing and oncogenic roles of CCAR2 in cancer. We discuss CCAR2 domain structures, its interaction partners, and the molecular mechanisms by which it regulates the activities of transcription factors and epigenetic modifiers.

Genetic heterogeneity of liver cancer stem cells

Cancer cell heterogeneity is a serious problem in the control of tumor progression because it can cause chemoresistance and metastasis. Heterogeneity can be generated by various mechanisms, including genetic evolution of cancer cells, cancer stem cells (CSCs), and niche heterogeneity. Because the genetic heterogeneity of CSCs has been poorly characterized, the genetic mutation status of CSCs was examined using Exome-Seq and RNA-Seq data of liver cancer. Here we show that different surface markers for liver cancer stem cells (LCSCs) showed a unique propensity for genetic mutations. Cluster of differentiation 133 (CD133)-positive cells showed frequent mutations in the IRF2, BAP1, and ERBB3 genes. However, leucine-rich repeat-containing G protein-coupled receptor 5-positive cells showed frequent mutations in the CTNNB1, RELN, and ROBO1 genes. In addition, some genetic mutations were frequently observed irrespective of the surface markers for LCSCs. BAP1 mutations was frequently observed in CD133-, CD24-, CD13-, CD90-, epithelial cell adhesion molecule-, or keratin 19-positive LCSCs. ASXL2, ERBB3, IRF2, TLX3, CPS1, and NFATC2 mutations were observed in more than three types of LCSCs, suggesting that common mechanisms for the development of these LCSCs. The present study provides genetic heterogeneity depending on the surface markers for LCSCs. The genetic heterogeneity of LCSCs should be considered in the development of LCSC-targeting therapeutics.

Role of primary aging hallmarks in Alzheimer´s disease

Alzheimer's disease (AD) is the most common neurodegenerative disease, which severely threatens the health of the elderly and causes significant economic and social burdens. The causes of AD are complex and include heritable but mostly aging-related factors. The primary aging hallmarks include genomic instability, telomere wear, epigenetic changes, and loss of protein stability, which play a dominant role in the aging process. Although AD is closely associated with the aging process, the underlying mechanisms involved in AD pathogenesis have not been well characterized. This review summarizes the available literature about primary aging hallmarks and their roles in AD pathogenesis. By analyzing published literature, we attempted to uncover the possible mechanisms of aberrant epigenetic markers with related enzymes, transcription factors, and loss of proteostasis in AD. In particular, the importance of oxidative stress-induced DNA methylation and DNA methylation-directed histone modifications and proteostasis are highlighted. A molecular network of gene regulatory elements that undergoes a dynamic change with age may underlie age-dependent AD pathogenesis, and can be used as a new drug target to treat AD.

Cardiac fibroblasts and mechanosensation in heart development, health and disease

The term 'mechanosensation' describes the capacity of cells to translate mechanical stimuli into the coordinated regulation of intracellular signals, cellular function, gene expression and epigenetic programming. This capacity is related not only to the sensitivity of the cells to tissue motion, but also to the decryption of tissue geometric arrangement and mechanical properties. The cardiac stroma, composed of fibroblasts, has been historically considered a mechanically passive component of the heart. However, the latest research suggests that the mechanical functions of these cells are an active and necessary component of the developmental biology programme of the heart that is involved in myocardial growth and homeostasis, and a crucial determinant of cardiac repair and disease. In this Review, we discuss the general concept of cell mechanosensation and force generation as potent regulators in heart development and pathology, and describe the integration of mechanical and biohumoral pathways predisposing the heart to fibrosis and failure. Next, we address the use of 3D culture systems to integrate tissue mechanics to mimic cardiac remodelling. Finally, we highlight the potential of mechanotherapeutic strategies, including pharmacological treatment and device-mediated left ventricular unloading, to reverse remodelling in the failing heart.

Activation of Drp1 promotes fatty acids-induced metabolic reprograming to potentiate Wnt signaling in colon cancer

Cancer cells are known for their ability to adapt variable metabolic programs depending on the availability of specific nutrients. Our previous studies have shown that uptake of fatty acids alters cellular metabolic pathways in colon cancer cells to favor fatty acid oxidation. Here, we show that fatty acids activate Drp1 to promote metabolic plasticity in cancer cells. Uptake of fatty acids (FAs) induces mitochondrial fragmentation by promoting ERK-dependent phosphorylation of Drp1 at the S616 site. This increased phosphorylation of Drp1 enhances its dimerization and interaction with Mitochondrial Fission Factor (MFF) at the mitochondria. Consequently, knockdown of Drp1 or MFF attenuates fatty acid-induced mitochondrial fission. In addition, uptake of fatty acids triggers mitophagy via a Drp1- and p62-dependent mechanism to protect mitochondrial integrity. Moreover, results from metabolic profiling analysis reveal that silencing Drp1 disrupts cellular metabolism and blocks fatty acid-induced metabolic reprograming by inhibiting fatty acid utilization. Functionally, knockdown of Drp1 decreases Wnt/β-catenin signaling by preventing fatty acid oxidation-dependent acetylation of β-catenin. As a result, Drp1 depletion inhibits the formation of tumor organoids in vitro and xenograft tumor growth in vivo. Taken together, our study identifies Drp1 as a key mediator that connects mitochondrial dynamics with fatty acid metabolism and cancer cell signaling.

Crosstalk between age accumulated DNA-damage and the SIRT1-AKT-GSK3ß axis in urine derived renal progenitor cells

The aging process is manifested by a multitude of inter-linked biological processes. These processes contribute to genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, de-regulated nutrient-sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. The mammalian ortholog of the yeast silent information regulator (Sir2) SIRT1 is a NAD+-dependent class III histone deacetylase and has been recognized to be involved in many of the forementioned processes. Furthermore, the physiological activity of several Sirtuin family members has been connected to the regulation of life span of lower organisms (Caenorhabditis elegans and Drosophila melanogaster) as well as mammals.

In the present study, we provide evidence that SIX2-positive urine derived renal progenitor cells-UdRPCs isolated directly from human urine show typical hallmarks of aging. This includes the subsequent transcriptional downregulation of SIRT1 and its downstream targets AKT and GSK3ß with increased donor age. This transcriptional downregulation is accompanied by an increase in DNA damage and transcriptional levels of several cell cycle inhibitors such as P16. We provide evidence that the renal progenitor transcription factor SIX2 binds to the coding sequence of SIRT1. Furthermore, we show that the SIRT1 promoter region is methylation sensitive and becomes methylated during aging, dividing them into SIRT1-high and -low expressing UdRPCs. Our results highlight the importance of SIRT1 in DNA damage repair recognition in UdRPCs and the control of differentiation by regulating the activation of GSK3β through AKT.

SIRT4-Catalyzed Deacetylation of Axin1 Modulates the Wnt/β-Catenin Signaling Pathway

Axin1 is a fundamental scaffolding protein of the destruction complex in the canonical Wnt signaling pathway, which plays a critical role in various biological processes. However, how Axin1 is regulated in the activation of the canonical Wnt signaling pathway remains elusive. Here, we report that Axin1 is constitutively acetylated in resting cells. Upon stimulation with Wnt, SIRT4 translocates from mitochondria to the cytoplasm and catalyzes Axin1 deacetylation, thus turning off the destruction complex. In this process, Lys147, a residue in the RGS domain of Axin1, plays a key role. We proved that the Axin1-K147R mutant impairs the assembly of β-TrCP to the destruction complex, which leads to β-catenin accumulation even without Wnt stimulation. In summary, our work proposes a new model for better understanding the initial stage of the canonical Wnt signaling pathway in which SIRT4 translocates from mitochondria into the cytoplasm to deacetylate Axin1-K147 after Wnt stimulation, which results in reduced assembly of β-TrCP to the destruction complex.

Cross-Talk between Wnt Signaling and Src Tyrosine Kinase

Src, a non-receptor tyrosine kinase, was first discovered as a prototype oncogene and has been shown to critical for cancer progression for a variety of tissues. Src activity is regulated by a number of post-translational modifications in response to various stimuli. Phosphorylations of Src Tyr419 (human; 416 in chicken) and Src Tyr530 (human; 527 in chicken) have been known to be critical for activation and inactivation of Src, respectively. Wnt signaling regulates a variety of cellular functions including for development and cell proliferation, and has a role in certain diseases such as cancer. Wnt signaling is carried out through two pathways: β-catenin-dependent canonical and β-catenin-independent non-canonical pathways as Wnt ligands bind to their receptors, Frizzled, LRP5/6, and ROR1/2. In addition, many signaling components including Axin, APC, Damm, Dishevelled, JNK kinase and Rho GTPases contribute to these canonical and non-canonical Wnt pathways. However, the communication between Wnt signaling and Src tyrosine kinase has not been well reviewed as Src regulates Wnt signaling through LRP6 tyrosine phosphorylation. GSK-3β phosphorylated by Wnt also regulates Src activity. As Wnt signaling and Src mutually regulate each other, it is noted that aberrant regulation of these components give rise to various diseases including typically cancer, and as such, merit a closer look.

The CK1δ/ϵ-Tip60 Axis Enhances Wnt/β-Catenin Signaling via Regulating β-Catenin Acetylation in Colon Cancer

Casein kinase 1δ/ϵ (CK1δ/ϵ) are well-established positive modulators of the Wnt/β-catenin signaling pathway. However, the molecular mechanisms involved in the regulation of β-catenin transcriptional activity by CK1δ/ϵ remain unclear. In this study, we found that CK1δ/ϵ could enhance β-catenin-mediated transcription through regulating β-catenin acetylation. CK1δ/ϵ interacted with Tip60 and facilitated the recruitment of Tip60 to β-catenin complex, resulting in increasing β-catenin acetylation at K49. Importantly, Tip60 significantly enhanced the SuperTopFlash reporter activity induced by CK1δ/ϵ or/and β-catenin. Furthermore, a CK1δ/CK1ϵ/β-catenin/Tip60 complex was detected in colon cancer cells. Simultaneous knockdown of CK1δ and CK1ϵ significantly attenuated the interaction between β-catenin and Tip60. Notably, inhibition of CK1δ/ϵ or Tip60, with shRNA or small molecular inhibitors downregulated the level of β-catenin acetylation at K49 in colon cancer cells. Finally, combined treatment with CK1 inhibitor SR3029 and Tip60 inhibitor MG149 had more potent inhibitory effect on β-catenin acetylation, the transcription of Wnt target genes and the viability and proliferation in colon cancer cells. Taken together, our results revealed that the transcriptional activity of β-catenin could be modulated by the CK1δ/ϵ-β-catenin-Tip60 axis, which may be a potential therapeutic target for colon cancer.

Resveratrol ameliorates high-phosphate-induced VSMCs to osteoblast-like cells transdifferentiation and arterial medial calcification in CKD through regulating Wnt/β-catenin signaling

Vascular smooth muscle cells (VSMCs) to osteoblast-like cells transdifferentiation induced by high-phosphate is a crucial step in the development of arterial medial calcification (AMC) in patients with chronic kidney disease (CKD), and previous studies implicate Wnt/β-catenin signaling in osteogenic transdifferentiation of VSMCs and AMC. Given that resveratrol's ability to modulate Wnt/β-catenin signaling in other types of cell, we tested the effect of resveratrol on high-phosphate-induced osteogenic transdifferentiation of VSMCs and AMC in CKD. Resveratrol ameliorated AMC in rats with chronic renal failure and calcium deposition in aortic rings and VSMCs cultured in a high-phosphate environment. Resveratrol also diminished high-phosphate-induced osteogenic transdifferentiation of VSMCs in cultured aortic rings and VSMCs. In vitro, resveratrol attenuated the activation of β-catenin induced by high-phosphate and inhibited the expression of Runx2, a downstream effector of Wnt/β-catenin signaling during osteogenic transdifferentiation of VSMCs. Intriguingly, resveratrol inhibited high-phosphate-induced phosphorylation of LRP6 (Ser1490), but didn't inhibit Wnt3a-induced phosphorylation of LRP6 (Ser1490) and Runx2 expression. The expression of several Wnts was induced by high-phosphate, but the expression of Wnt7a, not Wnt2b and Wnt10a could be suppressed by resveratrol. In addition, the expression of both porcupine and wntless, two obligatory proteins for Wnt secretion, was induced by high-phosphate in cultured aortic rings and VSMCs, which could be suppressed by resveratrol. In summary, these findings suggest that resveratrol possesses a vascular protective effect on retarding high-phosphate-induced osteogenic transdifferentiation of VSMCs and AMC in CKD by targeting Wnt/β-catenin signaling, which may, to a large extent, via impeding Wnt secretion.

Involvement of activator protein-1 family members in β-catenin and p300 association on the genome of PANC-1 cells

Wnt/β-catenin is believed to regulate different sets of genes with different coactivators, cAMP response element-binding protein (CREB)-binding protein (CBP) or p300. However, the factors that determine which coactivators act on a particular promoter remain elusive. ICG-001 is a specific inhibitor for β-catenin/CBP but not for β-catenin/p300. By taking advantage of the action of ICG-001, we sought to investigate regulatory mechanisms underlying β-catenin coactivator usage in human pancreatic carcinoma PANC-1 cells through combinatorial analysis of chromatin immunoprecipitation-sequencing and RNA-sequencing. CBP and p300 preferentially bound to regions with the TCF motif alone and with both the TCF and AP-1 motifs, respectively. ICG-001 increased β-catenin binding to regions with both the TCF and AP-1 motifs, flanking the genes induced by ICG-001, concomitant with the increments of the p300 and AP-1 component c-JUN binding. Taken together, AP-1 possibly coordinates β-catenin coactivator usage in PANC-1 cells. These results would further our understanding of the canonical Wnt/β-catenin signaling divergence.

PRMT7 ablation in cardiomyocytes causes cardiac hypertrophy and fibrosis through β-catenin dysregulation

Angiotensin II (AngII) has potent cardiac hypertrophic effects mediated through activation of hypertrophic signaling like Wnt/β-Catenin signaling. In the current study, we examined the role of protein arginine methyltransferase 7 (PRMT7) in cardiac function. PRMT7 was greatly decreased in hypertrophic hearts chronically infused with AngII and cardiomyocytes treated with AngII. PRMT7 depletion in rat cardiomyocytes resulted in hypertrophic responses. Consistently, mice lacking PRMT7 exhibited the cardiac hypertrophy and fibrosis. PRMT7 overexpression abrogated the cellular hypertrophy elicited by AngII, while PRMT7 depletion exacerbated the hypertrophic response caused by AngII. Similar with AngII treatment, the cardiac transcriptome analysis of PRMT7-deficient hearts revealed the alteration in gene expression profile related to Wnt signaling pathway. Inhibition of PRMT7 by gene deletion or an inhibitor treatment enhanced the activity of β-catenin. PRMT7 deficiency decreases symmetric dimethylation of β-catenin. Mechanistic studies reveal that methylation of arginine residue 93 in β-catenin decreases the activity of β-catenin. Taken together, our data suggest that PRMT7 is important for normal cardiac function through suppression of β-catenin activity.

The interaction of canonical Wnt/β-catenin signaling with protein lysine acetylation

Canonical Wnt/β-catenin signaling is a complex cell-communication mechanism that has a central role in the progression of various cancers. The cellular factors that participate in the regulation of this signaling are still not fully elucidated. Lysine acetylation is a significant protein modification which facilitates reversible regulation of the target protein function dependent on the activity of lysine acetyltransferases (KATs) and the catalytic function of lysine deacetylases (KDACs). Protein lysine acetylation has been classified into histone acetylation and non-histone protein acetylation. Histone acetylation is a kind of epigenetic modification, and it can modulate the transcription of important biological molecules in Wnt/β-catenin signaling. Additionally, as a type of post-translational modification, non-histone acetylation directly alters the function of the core molecules in Wnt/β-catenin signaling. Conversely, this signaling can regulate the expression and function of target molecules based on histone or non-histone protein acetylation. To date, various inhibitors targeting KATs and KDACs have been discovered, and some of these inhibitors exert their anti-tumor activity via blocking Wnt/β-catenin signaling. Here, we discuss the available evidence in understanding the complicated interaction of protein lysine acetylation with Wnt/β-catenin signaling, and lysine acetylation as a new target for cancer therapy via controlling this signaling.

Testosterone Deficiency Promotes Hypercholesteremia and Attenuates Cholesterol Liver Uptake via AR/PCSK9/LDLR Pathways

BACKGROUND

Testosterone deficiency is reportedly correlated with an elevation of cholesterol in plasma, but the mechanism remains unclear. Our objective was to investigate the effects of testosterone deficiency on cholesterol metabolism and the corresponding molecular changes in vivo and in vitro.

METHODS

SD rats were randomized into three groups: sham-operated (SHAM), subtotal orchiectomized (SO), and orchiectomized (ORX) and fed for 8 weeks. HepG2 cells were cultured with medium containing testosterone with the final concentrations of 0, 10, 30, and 300 nM. Method of isotope tracing and fluorescence labelling was adopted to investigate cholesterol metabolism. Several key molecules of cholesterol metabolism were also analyzed.

RESULTS

SO and ORX rats displayed dysfunctional liver uptake of cholesterol. HepG2 cells incubated with testosterone of lower and excessive level exhibited reduced capacity of cholesterol uptake. Further investigation revealed that lack of testosterone induced increased proprotein convertase subtilisin/kexin type 9 (PCSK9) and decreased low-density lipoprotein receptor (LDLR) both in vivo and in vitro. Moreover, the androgen receptor (AR) antagonist flutamide mimicked the effects of testosterone deficiency on PCSK9 and LDLR indicating the role of AR as a mediator in triggering attenuating liver cholesterol uptake in which testosterone instead of dihydrotestosterone (DHT) is the major functional form of androgen.

CONCLUSION

Testosterone deficiency attenuated cholesterol liver uptake mediated by the PCSK9-LDLR pathway, in which AR and testosterone without transforming to DHT play important roles.

The transcription factor activity gradient (TAG) model: contemplating a contact-independent mechanism for enhancer-promoter communication

How distal cis-regulatory elements (e.g., enhancers) communicate with promoters remains an unresolved question of fundamental importance. Although transcription factors and cofactors are known to mediate this communication, the mechanism by which diffusible molecules relay regulatory information from one position to another along the chromosome is a biophysical puzzle-one that needs to be revisited in light of recent data that cannot easily fit into previous solutions. Here we propose a new model that diverges from the textbook enhancer-promoter looping paradigm and offer a synthesis of the literature to make a case for its plausibility, focusing on the coactivator p300.

Autophagy-Induced HDAC6 Activity During Hypoxia Regulates Mitochondrial Energy Metabolism Through the β-Catenin/COUP-TFII Axis in Hepatocellular Carcinoma Cells

Hypoxia is one of the main driving forces that results in poor outcomes and drug resistance in hepatocellular carcinoma (HCC). As the critical cellular oxygen sensor, mitochondria respond to hypoxic stress by sending retrograde signals to the nucleus that initiate adaptive metabolic responses and maintain the survival of HCC cells. Increasing evidence suggested autophagy contributes to sustain mitochondrial metabolic and quality control. Understanding how mitochondria communicate with the nucleus and alter transcription may provide promising targets for HCC treatment. In this study, we found mitochondrial undergoes selective degradation by autophagy under hypoxia. Furthermore, autophagy-activated HDAC6 not only promoted the nuclear translocation of β-catenin but also increased the affinity of β-catenin to the transcription repressor chicken ovalbumin upstream promoter-transcription factor 2 (COUP-TF II), which suppressed mitochondrial oxidative phosphorylation-related genes transcription. Our data showed that autophagy served as a critical mediator of integrating mitochondrial energy metabolism and nuclear transcription. HDAC6 may be a potential target for reducing the survival of HCC cells by interrupting mitochondria-nucleus crosstalk.

Genetic Code Expansion Tools to Study Lysine Acylation

Lysine acylation is a ubiquitous protein modification that controls various aspects of protein function, such as the activity, localization, and stability of enzymes. Mass spectrometric identification of lysine acylations has witnessed tremendous improvements in sensitivity over the last decade, facilitating the discovery of thousands of lysine acylation sites in proteins involved in all essential cellular functions across organisms of all domains of life. However, the vast majority of currently known acylation sites are of unknown function. Semi-synthetic methods for installing lysine derivatives are ideally suited for in vitro experiments, while genetic code expansion (GCE) allows the installation and study of such lysine modifications, especially their dynamic properties, in vivo. An overview of the current state of the art is provided, and its potential is illustrated with case studies from recent literature. These include the application of engineered enzymes and GCE to install lysine modifications or photoactivatable crosslinker amino acids. Their use in the context of central metabolism, bacterial and viral pathogenicity, the cytoskeleton and chromatin dynamics, is investigated.

Wnt/β-catenin signaling in cancers and targeted therapies

Wnt/β-catenin signaling has been broadly implicated in human cancers and experimental cancer models of animals. Aberrant activation of Wnt/β-catenin signaling is tightly linked with the increment of prevalence, advancement of malignant progression, development of poor prognostics, and even ascendence of the cancer-associated mortality. Early experimental investigations have proposed the theoretical potential that efficient repression of this signaling might provide promising therapeutic choices in managing various types of cancers. Up to date, many therapies targeting Wnt/β-catenin signaling in cancers have been developed, which is assumed to endow clinicians with new opportunities of developing more satisfactory and precise remedies for cancer patients with aberrant Wnt/β-catenin signaling. However, current facts indicate that the clinical translations of Wnt/β-catenin signaling-dependent targeted therapies have faced un-neglectable crises and challenges. Therefore, in this study, we systematically reviewed the most updated knowledge of Wnt/β-catenin signaling in cancers and relatively targeted therapies to generate a clearer and more accurate awareness of both the developmental stage and underlying limitations of Wnt/β-catenin-targeted therapies in cancers. Insights of this study will help readers better understand the roles of Wnt/β-catenin signaling in cancers and provide insights to acknowledge the current opportunities and challenges of targeting this signaling in cancers.

Breast milk nutrients driving intestinal epithelial layer maturation via Wnt and Notch signaling: Implications for necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is an often lethal, inflammatory disease of the preterm intestine. The underdeveloped immune system plays an important role; however, the initial trigger for NEC development is likely a damaged intestinal epithelial layer. We hypothesize that due to incomplete maturation of different epithelial cell lineages, nutrients and bacteria are able to damage the epithelial cells and cause the (immature) inflammatory response, food intolerance and malabsorption seen in NEC. Intestinal organoid research has shown that maturation of intestinal epithelial cell lineages is orchestrated by two key signaling pathways: Wnt and Notch. In NEC, these pathways are dysregulated by hyperactivation of Toll-like-receptor-4. Breastfeeding decreases the risk of developing NEC compared to formula milk. Here, we review the intricate link between breast milk components, Wnt and Notch signaling and intestinal epithelial maturation. We argue that (nutritional) interventions regulating these pathways may decrease the risk of NEC development in preterm infants.

CBP/p300: Critical Co-Activators for Nuclear Steroid Hormone Receptors and Emerging Therapeutic Targets in Prostate and Breast Cancers

The CREB-binding protein (CBP) and p300 are two paralogous lysine acetyltransferases (KATs) that were discovered in the 1980s-1990s. Since their discovery, CBP/p300 have emerged as important regulatory proteins due to their ability to acetylate histone and non-histone proteins to modulate transcription. Work in the last 20 years has firmly established CBP/p300 as critical regulators for nuclear hormone signaling pathways, which drive tumor growth in several cancer types. Indeed, CBP/p300 are critical co-activators for the androgen receptor (AR) and estrogen receptor (ER) signaling in prostate and breast cancer, respectively. The AR and ER are stimulated by sex hormones and function as transcription factors to regulate genes involved in cell cycle progression, metabolism, and other cellular functions that contribute to oncogenesis. Recent structural studies of the AR/p300 and ER/p300 complexes have provided critical insights into the mechanism by which p300 interacts with and activates AR- and ER-mediated transcription. Breast and prostate cancer rank the first and forth respectively in cancer diagnoses worldwide and effective treatments are urgently needed. Recent efforts have identified specific and potent CBP/p300 inhibitors that target the acetyltransferase activity and the acetytllysine-binding bromodomain (BD) of CBP/p300. These compounds inhibit AR signaling and tumor growth in prostate cancer. CBP/p300 inhibitors may also be applicable for treating breast and other hormone-dependent cancers. Here we provide an in-depth account of the critical roles of CBP/p300 in regulating the AR and ER signaling pathways and discuss the potential of CBP/p300 inhibitors for treating prostate and breast cancer.

ATP-citrate lyase regulates stemness and metastasis in hepatocellular carcinoma via the Wnt/β-catenin signaling pathway

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most highly malignant tumors. Liver tumor-initiating cells (LTICs) have been considered to contribute to HCC progression and metastasis. ATP-citrate lyase (ACLY), as a key enzyme for de novo lipogenesis, has been reported to be upregulated in various tumors. However, its expression and role in HCC and LTICs remain unknown.

METHODS

The expressions of ACLY in HCC tissues were detected by quantitative real-time PCR (qRT-PCR), Western blotting and immunohistochemistry. Kaplan-Meier curves and Chi-square test were used to determine the clinical significance of ACLY expression in HCC patients. A series of assays were performed to determine the function of ACLY on stemness, migration and invasion of HCC cells. Luciferase reporter assay, Western blotting and immunoprecipitation were used to study the regulation of the Wnt/β-catenin signaling by ACLY. Rescue experiments were performed to investigate whether β-catenin was the mediator of ACLY-regulated stemness and migration in HCC cells.

RESULTS

ACLY was highly expressed in HCC tissues and LTICs. Overexpression of ACLY was significantly correlated with poor prognosis, progression and metastasis of HCC patients. Knockdown of ACLY remarkably suppressed stemness properties, migration and invasion in HCC cells. Mechanistically, ACLY could regulate the canonical Wnt pathway by affecting the stability of β-catenin, and Lys49 acetylation of β-catenin might mediate ACLY-regulated β-catenin level in HCC cells.

CONCLUSIONS

ACLY is a potent regulator of Wnt/β-catenin signaling in modulating LTICs stemness and metastasis in HCC. ACLY may serve as a new target for the diagnosis and treatment of HCC.

Promotion of Momordica Charantia polysaccharides on neural stem cell proliferation by increasing SIRT1 activity after cerebral ischemia/reperfusion in rats

The deacetylase SIRT1 has been reported to play a critical role in regulating neurogenesis, which may be an adaptive processes contributing to recovery after stroke. Our previous work showed that the antioxidant capacity of Momordica charantia polysaccharides (MCPs) could protect against cerebral ischemia/reperfusion (I/R) after stroke. However, whether the protective effect of MCPs on I/R injury is related to neural stem cell (NSC) proliferation remains unclear. In the present study, we designed invivo and invitro experiments to elucidate the underlying mechanisms by which MCPs promote endogenous NSC proliferation during cerebral I/R. Invivo results showed that MCPs rescued the memory and learning abilities of rats after I/R damage and enhanced NSC proliferation in the rat subventricular zone (SVZ) and subgrannular zone (SGZ) during I/R. Invitro experiments demonstrated that MCPs could stimulate the proliferation of C17.2 cells under oxygen-glucose deprivation (OGD) conditions. Further studies revealed that the proliferation-promoting mechanism of MCPs relied on increasing the activity of SIRT1, decreasing the level of acetylation of β-catenin in the cytoplasm, and then triggering the translocation of β-catenin into the nucleus. These data provide experimental evidence that the up-regulation of SIRT1 activity by MCPs led to an increased cytoplasmic deacetylation of β-catenin, which promoted translocation of β-catenin to the nucleus to participate in the signaling pathway involved in NSC proliferation. The present study reveals that MCPs function as a therapeutic drug to promote stroke recovery by increasing the activity of SIRT1, decreasing the level of acetylated β-catenin, promoting the nuclear translocation of β-catenin and thereby increasing endogenous NSC proliferation.

Walking the tight wire between cell adhesion and WNT signalling: a balancing act for β-catenin

CTNNB1 (catenin β-1, also known as β-catenin) plays a dual role in the cell. It is the key effector of WNT/CTNNB1 signalling, acting as a transcriptional co-activator of TCF/LEF target genes. It is also crucial for cell adhesion and a critical component of cadherin-based adherens junctions. Two functional pools of CTNNB1, a transcriptionally active and an adhesive pool, can therefore be distinguished. Whether cells merely balance the distribution of available CTNNB1 between these functional pools or whether interplay occurs between them has long been studied and debated. While interplay has been indicated upon artificial modulation of cadherin expression levels and during epithelial-mesenchymal transition, it is unclear to what extent CTNNB1 exchange occurs under physiological conditions and in response to WNT stimulation. Here, we review the available evidence for both of these models, discuss how CTNNB1 binding to its many interaction partners is controlled and propose avenues for future studies.

Chromatin Dynamics in Intestinal Epithelial Homeostasis: A Paradigm of Cell Fate Determination versus Cell Plasticity

The rapid renewal of intestinal epithelium is mediated by a pool of stem cells, located at the bottom of crypts, giving rise to highly proliferative progenitor cells, which in turn differentiate during their migration along the villus. The equilibrium between renewal and differentiation is critical for establishment and maintenance of tissue homeostasis, and is regulated by signaling pathways (Wnt, Notch, Bmp…) and specific transcription factors (TCF4, CDX2…). Such regulation controls intestinal cell identities by modulating the cellular transcriptome. Recently, chromatin modification and dynamics have been identified as major actors linking signaling pathways and transcriptional regulation in the control of intestinal homeostasis. In this review, we synthesize the many facets of chromatin dynamics involved in controlling intestinal cell fate, such as stemness maintenance, progenitor identity, lineage choice and commitment, and terminal differentiation. In addition, we present recent data underlying the fundamental role of chromatin dynamics in intestinal cell plasticity. Indeed, this plasticity, which includes dedifferentiation processes or the response to environmental cues (like microbiota’s presence or food ingestion), is central for the organ’s physiology. Finally, we discuss the role of chromatin dynamics in the appearance and treatment of diseases caused by deficiencies in the aforementioned mechanisms, such as gastrointestinal cancer, inflammatory bowel disease or irritable bowel syndrome.

Transcriptional Regulation of Wnt/β-Catenin Pathway in Colorectal Cancer

The Wnt/β-catenin signaling pathway exerts integral roles in embryogenesis and adult homeostasis. Aberrant activation of the pathway is implicated in growth-associated diseases and cancers, especially as a key driver in the initiation and progression of colorectal cancer (CRC). Loss or inactivation of Adenomatous polyposis coli (APC) results in constitutive activation of Wnt/β-catenin signaling, which is considered as an initiating event in the development of CRC. Increased Wnt/β-catenin signaling is observed in virtually all CRC patients, underscoring the importance of this pathway for therapeutic intervention. Prior studies have deciphered the regulatory networks required for the cytoplasmic stabilisation or degradation of the Wnt pathway effector, β-catenin. However, the mechanism whereby nuclear β-catenin drives or inhibits expression of Wnt target genes is more diverse and less well characterised. Here, we describe a brief synopsis of the core canonical Wnt pathway components, set the spotlight on nuclear mediators and highlight the emerging role of chromatin regulators as modulators of β-catenin-dependent transcription activity and oncogenic output.

Upregulation of CPT1A is essential for the tumor-promoting effect of adipocytes in colon cancer

Colon tumors grow in an adipose tissue-enriched microenvironment. Locally advanced colon cancers often invade into surrounding adipose tissue with a direct contact with adipocytes. We have previously shown that adipocytes promote tumor growth by modulating cellular metabolism. Here we demonstrate that carnitine palmitoyltransferase I (CPT1A), a key enzyme controlling fatty acid oxidation (FAO), was upregulated in colon cancer cells upon exposure to adipocytes or fatty acids. In addition, CPT1A expression was increased in invasive tumor cells within the adipose tissue compared to tumors without direct contact with adipocytes. Silencing CPT1A abolished the protective effect provided by fatty acids against nutrient deprivation and reduced tumor organoid formation in 3D culture and the expression of genes associated with cancer stem cells downstream of Wnt/β-catenin. Mechanistically, CPT1A-dependent FAO promoted the acetylation and nuclear translocation of β-catenin. Furthermore, knockdown of CPT1A blocked the tumor-promoting effect of adipocytes in vivo and inhibited xenograft tumor initiation. Taken together, our findings identify CPT1A-depedent FAO as an essential metabolic pathway that enables the interaction between adipocytes and colon cancer cells.

Waterborne Cu exposure increased lipid deposition and lipogenesis by affecting Wnt/β-catenin pathway and the β-catenin acetylation levels of grass carp Ctenopharyngodon idella

Lipid metabolism could be used as a biomarker for environmental monitoring of metal pollution, including Cu. Given the potential role of the Wnt/β-catenin signaling pathway and acetylation in lipid metabolism, the aim of this study was to investigate the mechanism of Wnt signaling and acetylation mediating Cu-induced lipogenesis. Grass carp Ctenopharyngodon idella, widely distributed freshwater teleost, were used as the model. We found that waterborne Cu exposure increased the accumulation of Cu and lipid, up-regulated lipogenesis, suppressed Wnt signaling, reduced β-catenin protein level and its nuclear location, reduced the sirt1 mRNA levels and up-regulated the β-catenin acetylation level. Further investigation found that Cu up-regulated lipogenesis through Wnt/β-catenin pathway; Cu regulated the β-catenin acetylation, and K311 was the key acetylated residue after Cu incubation. SIRT1 mediated Cu-induced changes of acetylated β-catenin and played an essential role in nuclear accumulation of β-catenin and Cu-induced lipogenesis. Cu facilitated lipid accumulation via the regulation of Wnt pathway by SIRT1. For the first time, our study uncovered the novel mechanism for Wnt/β-catenin pathway and β-catenin acetylation levels mediating Cu-induced lipid deposition, which provided insights into the association between Cu exposure and lipid metabolism in fish and had important environmental implications for monitoring metal pollution in the water by using new biomarkers involved in lipid metabolism.

Chlorquinaldol targets the β-catenin and T-cell factor 4 complex and exerts anti-colorectal cancer activity

Aberrant activation of Wnt signaling plays a critical role in the initiation and progression of colorectal cancer (CRC). Chlorquinaldol (CQD) is a topical antimicrobial agent used to treat skin infections. Little is known about the anticancer activity of CQD and its underlying mechanisms. In this study, CQD was demonstrated to inhibit Wnt/β-catenin signaling through targeting the downstream part of this pathway. The results showed that CQD could inhibit the acetylation of β-catenin and disrupt the interaction of β-catenin with T-cell factor 4 (TCF4), leading to reduced binding of β-catenin to the promoters of Wnt target genes and downregulation of the expression of these target genes. Moreover, treatment with CQD suppressed the proliferation, migration, invasion and stemness of CRC cells. In APC^min/+ mice and CRC cell xenografts, administration of CQD suppressed tumor growth and the expression of Wnt target genes c-Myc and Leucine-rich G protein-coupled receptor-5 (LGR5). These results strongly suggest that CQD may be a promising therapeutic agent in the treatment of CRC.

Bcl-3 promotes Wnt signaling by maintaining the acetylation of β-catenin at lysine 49 in colorectal cancer

Wnt/β-catenin signaling plays a critical role in colorectal cancer (CRC) tumorigenesis and the homeostasis of colorectal cancer stem cells (CSCs), but its molecular mechanism remains unclear. B-cell lymphoma 3 (Bcl-3), a member of the IκB family, is overexpressed in CRC and promotes tumorigenicity. Here, we report a novel function of Bcl-3 in maintaining colorectal CSC homeostasis by activating Wnt/β-catenin signaling. Silencing Bcl-3 suppresses the self-renewal capacity of colorectal CSCs and sensitizes CRC cells to chemotherapeutic drugs through a decrease in Wnt/β-catenin signaling. Moreover, our data show that Bcl-3 is a crucial component of Wnt/β-catenin signaling and is essential for β-catenin transcriptional activity in CRC cells. Interestingly, Wnt3a increases the level and nuclear translocation of Bcl-3, which binds directly to β-catenin and enhances the acetylation of β-catenin at lysine 49 (Ac-K49-β-catenin) and transcriptional activity. Bcl-3 depletion decreases the Ac-K49-β-catenin level by increasing the level of histone deacetylase 1 to remove acetyl groups from β-catenin, thus interrupting Wnt/β-catenin activity. In CRC clinical specimens, Bcl-3 expression negatively correlates with the overall survival of CRC patients. A significantly positive correlation was found between the expression of Bcl-3 and Ac-K49-β-catenin. Collectively, our data reveal that Bcl-3 plays a crucial role in CRC chemoresistance and colorectal CSC maintenance via its modulation of the Ac-K49-β-catenin, which serves as a promising therapeutic target for CRC.

ZBP1 (DAI/DLM-1) promotes osteogenic differentiation while inhibiting adipogenic differentiation in mesenchymal stem cells through a positive feedback loop of Wnt/β-catenin signaling

The lineage specification of mesenchymal stem/stromal cells (MSCs) is tightly regulated by a wide range of factors. Recently, the versatile functions of ZBP1 (also known as DAI or DLM-1) have been reported in the blood circulation and immune systems. However, the biological function of ZBP1 during the lineage specification of MSCs is still unknown. In the present study, we found that ZBP1 was upregulated during osteogenesis but downregulated during adipogenesis in mouse bone marrow-derived MSCs (mBMSCs). ZBP1 was highly expressed in osteoblasts but expressed at a relatively low level in marrow adipocytes. Knockdown of ZBP1 inhibited alkaline phosphataseactivity, extracellular matrix mineralization, and osteogenesis-related gene expression in vitro and reduced ectopic bone formation in vivo. Knockdown of ZBP1 also promoted adipogenesis in MSCs in vitro. Conversely, the overexpression of ZBP1 increased the osteogenesis but suppressed the adipogenesis of MSCs. When the expression of ZBP1 was rescued, the osteogenic capacity of ZBP1-depleted mBMSCs was restored at both the molecular and phenotypic levels. Furthermore, we demonstrated that ZBP1, a newly identified target of Wnt/β-catenin signaling, was required for β-catenin translocation into nuclei. Collectively, our results indicate that ZBP1 is a novel regulator of bone and fat transdifferentiation via Wnt/β-catenin signaling.

Proteogenomic Characterization of Endometrial Carcinoma

We undertook a comprehensive proteogenomic characterization of 95 prospectively collected endometrial carcinomas, comprising 83 endometrioid and 12 serous tumors. This analysis revealed possible new consequences of perturbations to the p53 and Wnt/β-catenin pathways, identified a potential role for circRNAs in the epithelial-mesenchymal transition, and provided new information about proteomic markers of clinical and genomic tumor subgroups, including relationships to known druggable pathways. An extensive genome-wide acetylation survey yielded insights into regulatory mechanisms linking Wnt signaling and histone acetylation. We also characterized aspects of the tumor immune landscape, including immunogenic alterations, neoantigens, common cancer/testis antigens, and the immune microenvironment, all of which can inform immunotherapy decisions. Collectively, our multi-omic analyses provide a valuable resource for researchers and clinicians, identify new molecular associations of potential mechanistic significance in the development of endometrial cancers, and suggest novel approaches for identifying potential therapeutic targets.

β-Catenin Is Required for the cGAS/STING Signaling Pathway but Antagonized by the Herpes Simplex Virus 1 US3 Protein

The cGAS/STING-mediated DNA-sensing signaling pathway is crucial for interferon (IFN) production and host antiviral responses. Herpes simplex virus I (HSV-1) is a DNA virus that has evolved multiple strategies to evade host immune responses. Here, we demonstrate that the highly conserved β-catenin protein in the Wnt signaling pathway is an important factor to enhance the transcription of type I interferon (IFN-I) in the cGAS/STING signaling pathway, and the production of IFN-I mediated by β-catenin was antagonized by HSV-1 US3 protein via its kinase activity. Infection by US3-deficienct HSV-1 and its kinase-dead variants failed to downregulate IFN-I and IFN-stimulated gene (ISG) production induced by β-catenin. Consistent with this, absence of β-catenin enhanced the replication of US3-deficienct HSV-1, but not wild-type HSV-1. The underlying mechanism was the interaction of US3 with β-catenin and its hyperphosphorylation of β-catenin at Thr556 to block its nuclear translocation. For the first time, HSV-1 US3 has been shown to inhibit IFN-I production through hyperphosphorylation of β-catenin and to subvert host antiviral innate immunity.IMPORTANCE Although increasing evidence has demonstrated that HSV-1 subverts host immune responses and establishes lifelong latent infection, the molecular mechanisms by which HSV-1 interrupts antiviral innate immunity, especially the cGAS/STING-mediated cellular DNA-sensing signaling pathway, have not been fully explored. Here, we show that β-catenin promotes cGAS/STING-mediated activation of the IFN pathway, which is important for cellular innate immune responses and intrinsic resistance to DNA virus infection. The protein kinase US3 antagonizes the production of IFN by targeting β-catenin via its kinase activity. The findings in this study reveal a novel mechanism for HSV-1 to evade host antiviral immunity and add new knowledge to help in understanding the interaction between the host and HSV-1 infection.

Tau acetylates and stabilizes β-catenin thereby promoting cell survival

Overexpressing Tau counteracts apoptosis and increases dephosphorylated β-catenin levels, but the underlying mechanisms are elusive. Here, we show that Tau can directly and robustly acetylate β-catenin at K49 in a concentration-, time-, and pH-dependent manner. β-catenin K49 acetylation inhibits its phosphorylation and its ubiquitination-associated proteolysis, thus increasing β-catenin protein levels. K49 acetylation further promotes nuclear translocation and the transcriptional activity of β-catenin, and increases the expression of survival-promoting genes (bcl2 and survivin), counteracting apoptosis. Mutation of Tau's acetyltransferase domain or co-expressing non-acetylatable β-catenin-K49R prevents increased β-catenin signaling and abolishes the anti-apoptotic function of Tau. Our data reveal that Tau preserves β-catenin by acetylating K49, and upregulated β-catenin/survival signaling in turn mediates the anti-apoptotic effect of Tau.

Hypothesis: Retinoblastoma protein inactivation mediates effects of histone deacetylase inhibitor-induced Wnt hyperactivation in colorectal cancer cells

Butyrate, a product of dietary fiber and a histone deacetylase inhibitor, induces apoptosis of colorectal cancer cells; this effect of butyrate is in part mediated by its ability to hyperactivate Wnt signaling, and may in part explain the preventive action of dietary fiber against colorectal cancer. However, the mechanisms by which Wnt hyperactivation promotes apoptosis are unknown. Inactivation of the retinoblastoma tumor suppressor occurs in some cancers and can lead to context-dependent cell proliferation or cell death/apoptosis. The function of retinoblastoma protein (Rb) in normal cells is modulation of cell cycle; inactivation of Rb allows for cell cycle progression and, hence, cell proliferation. Wnt signaling is upregulated in a variety of cancers, and deregulated Wnt signaling is a key initiating event in most cases of sporadic colorectal cancer. It has been shown that Wnt signaling activated by APC inactivation can synergize with the inactivation of Rb to induce apoptosis in a manner mediated by increased TORC1 activity, leading to induced metabolic and energy stress. Rb is typically not inactivated in colorectal cancer; however, Rb is phosphorylated and deactivated during cell cycle G1/S transition. This manuscript posits that it is during this time that butyrate/histone deacetylase inhibitor-induced Wnt hyperactivation induces apoptosis in colorectal cancer cells. Thus, the inactivation of Rb in cell cycle progression may synergize with Wnt hyperactivation to induce apoptosis in response to histone deacetylase inhibitors. The hypothesis is that hyperactivation of Wnt signaling enhances colorectal cancer cell apoptosis via the interaction between upregulated Wnt signaling and inactivated Rb during cell cycle progression. This paper discusses this hypothesis and offers initial experimental approaches for testing the hypothesis. A better understanding of how histone deacetylase inhibitors induce colorectal cancer cell apoptosis through hyperactivation of Wnt signaling, and of cross-talk between repression of cell cycle and induction of apoptosis that occurs with treatment with histone deacetylase inhibitors, can assist in the development of novel therapies for colorectal cancer.

Deacetylation of β-catenin by SIRT1 regulates self-renewal and oncogenesis of liver cancer stem cells

Hepatocellular carcinoma (HCC) is a highly malignant liver tumor. The presence of cancer stem cells (CSCs) figures prominently in tumor invasion, therapeutic resistance and tumor recurrence resulting in poor outcome and limited therapeutic options. Wnt/β-catenin signaling is essential for cancer stem cell regulation and tumorigenesis in HCC, but its molecular mechanisms are not fully understood. Here, we demonstrate that β-catenin is overexpressed in liver CSCs, and its expression level is positively correlated with SIRT1 in HCC specimens. SIRT1 regulates the protein stability of β-catenin, thereby affecting the transcriptional activity of Wnt/β-catenin signaling in liver CSCs. Mechanistically, we show that nuclear accumulation of β-catenin results from deacetylation mediated by SIRT1. Further, nuclear β-catenin promotes the transcription of Nanog to help maintain self-renewal of liver CSCs. Taken together, our findings indicate that the deacetylation of β-catenin by SIRT1 represents a critical mechanism for regulating liver CSCs self-renewal and tumorigenesis. It provides an improved understanding of molecular mechanisms underlying β-catenin activation and tumorigenesis in HCC.

Building a schizophrenia genetic network: transcription factor 4 regulates genes involved in neuronal development and schizophrenia risk

The transcription factor 4 (TCF4) locus is a robust association finding with schizophrenia (SCZ), but little is known about the genes regulated by the encoded transcription factor. Therefore, we conducted chromatin immunoprecipitation sequencing (ChIP-seq) of TCF4 in neural-derived (SH-SY5Y) cells to identify genome-wide TCF4 binding sites, followed by data integration with SCZ association findings. We identified 11 322 TCF4 binding sites overlapping in two ChIP-seq experiments. These sites are significantly enriched for the TCF4 Ebox binding motif (>85% having ≥1 Ebox) and implicate a gene set enriched for genes downregulated in TCF4 small-interfering RNA (siRNA) knockdown experiments, indicating the validity of our findings. The TCF4 gene set was also enriched among (1) gene ontology categories such as axon/neuronal development, (2) genes preferentially expressed in brain, in particular pyramidal neurons of the somatosensory cortex and (3) genes downregulated in postmortem brain tissue from SCZ patients (odds ratio, OR = 2.8, permutation P < 4x10-5). Considering genomic alignments, TCF4 binding sites significantly overlapped those for neural DNA-binding proteins such as FOXP2 and the SCZ-associated EP300. TCF4 binding sites were modestly enriched among SCZ risk loci from the Psychiatric Genomic Consortium (OR = 1.56, P = 0.03). In total, 130 TCF4 binding sites occurred in 39 of the 108 regions published in 2014. Thirteen genes within the 108 loci had both a TCF4 binding site ±10kb and were differentially expressed in siRNA knockdown experiments of TCF4, suggesting direct TCF4 regulation. These findings confirm TCF4 as an important regulator of neural genes and point toward functional interactions with potential relevance for SCZ.

p300/CBP-associated factor promotes autophagic degradation of δ-catenin through acetylation and decreases prostate cancer tumorigenicity

δ-Catenin shares common binding partners with β-catenin. As acetylation and deacetylation regulate β-catenin stability, we searched for histone acetyltransferases (HATs) or histone deacetylases (HDACs) affecting δ-catenin acetylation status and protein levels. We showed that p300/CBP-associated factor (PCAF) directly bound to and acetylated δ-catenin, whereas several class I and class II HDACs reversed this effect. Unlike β-catenin, δ-catenin was downregulated by PCAF-mediated acetylation and upregulated by HDAC-mediated deacetylation. The HDAC inhibitor trichostatin A attenuated HDAC1-mediated δ-catenin upregulation, whereas HAT or autophagy inhibitors, but not proteasome inhibitors, abolished PCAF-mediated δ-catenin downregulation. The results suggested that PCAF-mediated δ-catenin acetylation promotes its autophagic degradation in an Atg5/LC3-dependent manner. Deletions or point mutations identified several lysine residues in different δ-catenin domains involved in PCAF-mediated δ-catenin downregulation. PCAF overexpression in prostate cancer cells markedly reduced δ-catenin levels and suppressed cell growth and motility. PCAF-mediated δ-catenin downregulation inhibited E-cadherin processing and decreased the nuclear distribution of β-catenin, resulting in the suppression of β-catenin/LEF-1-mediated downstream effectors. These data demonstrate that PCAF downregulates δ-catenin by promoting its autophagic degradation and suppresses δ-catenin-mediated oncogenic signals.

The Interplay of SIRT1 and Wnt Signaling in Vascular Calcification

Vascular calcification is a major health risk and is highly correlated with atherosclerosis, diabetes, and chronic kidney disease. The development of vascular calcification is an active and complex process linked with a multitude of signaling pathways, which regulate promoters and inhibitors of osteogenesis, the balance of which become deregulated in disease conditions. SIRT1, a protein deacetylase, known to be protective in inhibiting oxidative stress and inflammation within the vessel wall, has been shown as a possible key player in modulating the cell-fate determining canonical Wnt signaling pathways. Suppression of SIRT1 has been reported in patients suffering with cardiovascular pathologies, suggesting that the sustained acetylation of osteogenic factors could contribute to their activation and in turn, lead to the progression of calcification. There is clear evidence of the synergy between β-Catenin and elevated Runx2, and with Wnt signaling being β-Catenin dependent, further understanding is needed as to how these molecular pathways converge and interact, in order to provide novel insight into the mechanism by which smooth muscle cells switch to an osteogenic differentiation programme. Therefore, this review will describe the current concepts of pathological soft tissue mineralization, with a focus on the contribution of SIRT1 as a regulator of Wnt signaling and its targets, discussing SIRT1 as a potential target for manipulation and therapy.

Active mitochondria support osteogenic differentiation by stimulating β-catenin acetylation

Bone marrow stromal (a.k.a. mesenchymal stem) cells (BMSCs) can differentiate into osteoblasts (OBs), adipocytes, or chondrocytes. As BMSCs undergo OB differentiation, they up-regulate mitochondrial oxidative phosphorylation (OxPhos). Here, we investigated the mechanism(s) connecting mitochondrial OxPhos to OB differentiation. First, we found that treating BMSC-like C3H10T1/2 cells with an OxPhos inhibitor reduces their osteogenic potential. Interestingly, ATP levels were not reduced, as glycolysis compensated for the decreased OxPhos. Thus, mitochondria support OB differentiation not only by supplying ATP, but also by other mechanisms. To uncover these mechanisms, we stimulated OxPhos in C3H10T1/2 cells by replacing media glucose with galactose and observed that this substitution increases both OxPhos and osteogenesis even in the absence of osteoinducers. β-Catenin, an important signaling pathway in osteogenesis, was found to be responsive to OxPhos stimulation. β-Catenin activity is maintained by acetylation, and mitochondria generate the acetyl donor acetyl-CoA, which upon entering the Krebs cycle is converted to citrate capable of exiting mitochondria. Cytosolic citrate is converted back to acetyl-CoA by ATP citrate lyase (ACLY). We found that inhibiting ACLY with SB204990 (SB) reverses the galactose-induced β-catenin activity and OB differentiation. This suggested that acetylation is involved in β-catenin activation after forced OxPhos stimulation, and using immunoprecipitation, we indeed detected SB-sensitive β-catenin acetylation. Both β-catenin acetylation and activity increased during osteoinduction coincident with OxPhos activation. These findings suggest that active mitochondria support OB differentiation by promoting β-catenin acetylation and thus activity.

Salvianolic acid A alleviates chronic ethanol-induced liver injury via promotion of β-catenin nuclear accumulation by restoring SIRT1 in rats

In recent years, alcoholic liver disease (ALD) has emerged as a growing public health problem worldwide. β-catenin plays an important role in the growth, development, regeneration and metabolic activity of the liver. Salvianolic acid A (SalA) is a water-soluble component from the root extract of Salvia miltiorrhiza Bunge, and its effect on ALD has not yet been investigated. This study aimed to investigate the effect of SalA on chronic alcohol-induced liver injury and to explore the role of SIRT1-mediated β-catenin deacetylation in such an effect. In this study, SalA treatment significantly alleviated the accumulation of lipid droplets and reduced the plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC), triglyceride (TG), alcohol and ammonia levels in rats. SalA enhanced ethanol and ammonia metabolism and maintained mitochondrial homeostasis. Moreover, SalA restored the activity of the major ethanol-metabolizing enzymes and oxidative stress functions in the liver. Importantly, we found that SalA treatment effectively inhibited the ethanol-mediated decrease in nuclear β-catenin by upregulating SIRT1 in the liver. SIRT1 then deacetylated β-catenin to promote its accumulation in the nucleus, thereby preventing alcohol-induced liver injury. The results demonstrate that the SIRT1/β-catenin pathway is a key therapeutic target in liver injury caused by chronic alcohol exposure and that SalA protects against alcohol-induced liver injury via the SIRT1-mediated deacetylation of β-catenin.