PPM1A functions as a Smad phosphatase to terminate TGFbeta signaling

TGF‑β/Smad signaling in chronic kidney disease: Exploring post‑translational regulatory perspectives (Review)

The TGF‑β/Smad signaling pathway plays a pivotal role in the onset of glomerular and tubulointerstitial fibrosis in chronic kidney disease (CKD). The present review delves into the intricate post‑translational modulation of this pathway and its implications in CKD. Specifically, the impact of the TGF‑β/Smad pathway on various biological processes was investigated, encompassing not only renal tubular epithelial cell apoptosis, inflammation, myofibroblast activation and cellular aging, but also its role in autophagy. Various post‑translational modifications (PTMs), including phosphorylation and ubiquitination, play a crucial role in modulating the intensity and persistence of the TGF‑β/Smad signaling pathway. They also dictate the functionality, stability and interactions of the TGF‑β/Smad components. The present review sheds light on recent findings regarding the impact of PTMs on TGF‑β receptors and Smads within the CKD landscape. In summary, a deeper insight into the post‑translational intricacies of TGF‑β/Smad signaling offers avenues for innovative therapeutic interventions to mitigate CKD progression. Ongoing research in this domain holds the potential to unveil powerful antifibrotic treatments, aiming to preserve renal integrity and function in patients with CKD.

Genome, HLA and polygenic risk score analyses for prevalent and persistent cervical human papillomavirus (HPV) infections

Genetic variants that underlie susceptibility to cervical high-risk human papillomavirus (hrHPV) infections are largely unknown. We conducted discovery genome-wide association studies (GWAS), replication, meta-analysis and colocalization, generated polygenic risk scores (PRS) and examined the association of classical HLA alleles and cervical hrHPV infections in a cohort of over 10,000 women. We identified genome-wide significant variants for prevalent hrHPV around LDB2 and for persistent hrHPV near TPTE2, SMAD2, and CDH12, which code for proteins that are significantly expressed in the human endocervix. Genetic variants associated with persistent hrHPV are in genes enriched for the antigen processing and presentation gene set. HLA-DRB1*13:02, HLA-DQB1*05:02 and HLA-DRB1*03:01 were associated with increased risk, and HLA-DRB1*15:03 was associated with decreased risk of persistent hrHPV. The analyses of peptide binding predictions showed that HLA-DRB1 alleles that were positively associated with persistent hrHPV showed weaker binding with peptides derived from hrHPV proteins and vice versa. The PRS for persistent hrHPV with the best model fit, had a P-value threshold (PT) of 0.001 and a p-value of 0.06 (-log10(0.06) = 1.22). The findings of this study expand our understanding of genetic risk factors for hrHPV infection and persistence and highlight the roles of MHC class II molecules in hrHPV infection.

Receptor-activated transcription factors and beyond: multiple modes of Smad2/3-dependent transmission of TGF-β signaling

Transforming growth factor β (TGF-β) is a pleiotropic cytokine that is widely distributed throughout the body. Its receptor proteins, TGF-β type I and type II receptors, are also ubiquitously expressed. Therefore, the regulation of various signaling outputs in a context-dependent manner is a critical issue in this field. Smad proteins were originally identified as signal-activated transcription factors similar to signal transducer and activator of transcription proteins. Smads are activated by serine phosphorylation mediated by intrinsic receptor dual specificity kinases of the TGF-β family, indicating that Smads are receptor-restricted effector molecules downstream of ligands of the TGF-β family. Smad proteins have other functions in addition to transcriptional regulation, including post-transcriptional regulation of micro-RNA processing, pre-mRNA splicing, and m6A methylation. Recent technical advances have identified a novel landscape of Smad-dependent signal transduction, including regulation of mitochondrial function without involving regulation of gene expression. Therefore, Smad proteins are receptor-activated transcription factors and also act as intracellular signaling modulators with multiple modes of function. In this review, we discuss the role of Smad proteins as receptor-activated transcription factors and beyond. We also describe the functional differences between Smad2 and Smad3, two receptor-activated Smad proteins downstream of TGF-β, activin, myostatin, growth and differentiation factor (GDF) 11, and Nodal.

Advances and Challenges in Targeting TGF-β Isoforms for Therapeutic Intervention of Cancer: A Mechanism-Based Perspective

The TGF-β family is a group of 25 kDa secretory cytokines, in mammals consisting of three dimeric isoforms (TGF-βs 1, 2, and 3), each encoded on a separate gene with unique regulatory elements. Each isoform plays unique, diverse, and pivotal roles in cell growth, survival, immune response, and differentiation. However, many researchers in the TGF-β field often mistakenly assume a uniform functionality among all three isoforms. Although TGF-βs are essential for normal development and many cellular and physiological processes, their dysregulated expression contributes significantly to various diseases. Notably, they drive conditions like fibrosis and tumor metastasis/progression. To counter these pathologies, extensive efforts have been directed towards targeting TGF-βs, resulting in the development of a range of TGF-β inhibitors. Despite some clinical success, these agents have yet to reach their full potential in the treatment of cancers. A significant challenge rests in effectively targeting TGF-βs' pathological functions while preserving their physiological roles. Many existing approaches collectively target all three isoforms, failing to target just the specific deregulated ones. Additionally, most strategies tackle the entire TGF-β signaling pathway instead of focusing on disease-specific components or preferentially targeting tumors. This review gives a unique historical overview of the TGF-β field often missed in other reviews and provides a current landscape of TGF-β research, emphasizing isoform-specific functions and disease implications. The review then delves into ongoing therapeutic strategies in cancer, stressing the need for more tools that target specific isoforms and disease-related pathway components, advocating mechanism-based and refined approaches to enhance the effectiveness of TGF-β-targeted cancer therapies.

TGF-β signaling in health, disease, and therapeutics

Transforming growth factor (TGF)-β is a multifunctional cytokine expressed by almost every tissue and cell type. The signal transduction of TGF-β can stimulate diverse cellular responses and is particularly critical to embryonic development, wound healing, tissue homeostasis, and immune homeostasis in health. The dysfunction of TGF-β can play key roles in many diseases, and numerous targeted therapies have been developed to rectify its pathogenic activity. In the past decades, a large number of studies on TGF-β signaling have been carried out, covering a broad spectrum of topics in health, disease, and therapeutics. Thus, a comprehensive overview of TGF-β signaling is required for a general picture of the studies in this field. In this review, we retrace the research history of TGF-β and introduce the molecular mechanisms regarding its biosynthesis, activation, and signal transduction. We also provide deep insights into the functions of TGF-β signaling in physiological conditions as well as in pathological processes. TGF-β-targeting therapies which have brought fresh hope to the treatment of relevant diseases are highlighted. Through the summary of previous knowledge and recent updates, this review aims to provide a systematic understanding of TGF-β signaling and to attract more attention and interest to this research area.

Targeting SMAD-Dependent Signaling: Considerations in Epithelial and Mesenchymal Solid Tumors

SMADs are the canonical intracellular effector proteins of the TGF-β (transforming growth factor-β). SMADs translocate from plasma membrane receptors to the nucleus regulated by many SMAD-interacting proteins through phosphorylation and other post-translational modifications that govern their nucleocytoplasmic shuttling and subsequent transcriptional activity. The signaling pathway of TGF-β/SMAD exhibits both tumor-suppressing and tumor-promoting phenotypes in epithelial-derived solid tumors. Collectively, the pleiotropic nature of TGF-β/SMAD signaling presents significant challenges for the development of effective cancer therapies. Here, we review preclinical studies that evaluate the efficacy of inhibitors targeting major SMAD-regulating and/or -interacting proteins, particularly enzymes that may play important roles in epithelial or mesenchymal compartments within solid tumors.

The BHLHE40‒PPM1F‒AMPK pathway regulates energy metabolism and is associated with the aggressiveness of endometrial cancer

BHLHE40 is a basic helix-loop-helix transcription factor that is involved in multiple cell activities including differentiation, cell cycle, and epithelial-to-mesenchymal transition. While there is growing evidence to support the functions of BHLHE40 in energy metabolism, little is known about the mechanism. In this study, we found that BHLHE40 expression was downregulated in cases of endometrial cancer of higher grade and advanced disease. Knockdown of BHLHE40 in endometrial cancer cells resulted in suppressed oxygen consumption and enhanced extracellular acidification. Suppressed pyruvate dehydrogenase (PDH) activity and enhanced lactated dehydrogenase (LDH) activity were observed in the knockdown cells. Knockdown of BHLHE40 also led to dephosphorylation of AMPKα Thr172 and enhanced phosphorylation of pyruvate dehydrogenase E1 subunit alpha 1 (PDHA1) Ser293 and lactate dehydrogenase A (LDHA) Tyr10. These results suggested that BHLHE40 modulates PDH and LDH activity by regulating the phosphorylation status of PDHA1 and LDHA. We found that BHLHE40 enhanced AMPKα phosphorylation by directly suppressing the transcription of an AMPKα-specific phosphatase, PPM1F. Our immunohistochemical study showed that the expression of BHLHE40, PPM1F, and phosphorylated AMPKα correlated with the prognosis of endometrial cancer patients. Because AMPK is a central regulator of energy metabolism in cancer cells, targeting the BHLHE40‒PPM1F‒AMPK axis may represent a strategy to control cancer development.

Optimal Performance Objectives in the Highly Conserved Bone Morphogenetic Protein Signaling Pathway

Throughout development, complex networks of cell signaling pathways drive cellular decision-making across different tissues and contexts. The transforming growth factor β (TGF-β) pathways, including the BMP/Smad pathway, play crucial roles in these cellular responses. However, as the Smad pathway is used reiteratively throughout the life cycle of all animals, its systems-level behavior varies from one context to another, despite the pathway connectivity remaining nearly constant. For instance, some cellular systems require a rapid response, while others require high noise filtering. In this paper, we examine how the BMP- Smad pathway balances trade-offs among three such systems-level behaviors, or "Performance Objectives (POs)": response speed, noise amplification, and the sensitivity of pathway output to receptor input. Using a Smad pathway model fit to human cell data, we show that varying non-conserved parameters (NCPs) such as protein concentrations, the Smad pathway can be tuned to emphasize any of the three POs and that the concentration of nuclear phosphatase has the greatest effect on tuning the POs. However, due to competition among the POs, the pathway cannot simultaneously optimize all three, but at best must balance trade-offs among the POs. We applied the multi-objective optimization concept of the Pareto Front, a widely used concept in economics to identify optimal trade-offs among various requirements. We show that the BMP pathway efficiently balances competing POs across species and is largely Pareto optimal. Our findings reveal that varying the concentration of NCPs allows the Smad signaling pathway to generate a diverse range of POs. This insight identifies how signaling pathways can be optimally tuned for each context.

Therapeutic potential for renal fibrosis by targeting Smad3-dependent noncoding RNAs

Renal fibrosis is a characteristic hallmark of chronic kidney disease (CKD) that ultimately results in renal failure, leaving patients with few therapeutic options. TGF-β is a master regulator of renal fibrosis and mediates progressive renal fibrosis via both canonical and noncanonical signaling pathways. In the canonical Smad signaling, Smad3 is a key mediator in tissue fibrosis and mediates renal fibrosis via a number of noncoding RNAs (ncRNAs). In this regard, targeting Smad3-dependent ncRNAs may offer a specific therapy for renal fibrosis. This review highlights the significance and innovation of TGF-β/Smad3-associated ncRNAs as biomarkers and therapeutic targets in renal fibrogenesis. In addition, the underlying mechanisms of these ncRNAs and their future perspectives in the treatment of renal fibrosis are discussed.

Osteoarthritis year in review 2023: Biology

Great progress continues to be made in our understanding of the multiple facets of osteoarthritis (OA) biology. Here, we review the major advances in this field and progress towards therapy development over the past year, highlighting a selection of relevant published literature from a PubMed search covering the year from the end of April 2022 to the end of April 2023. The selected articles have been arranged in themes. These include 1) molecular regulation of articular cartilage and implications for OA, 2) mechanisms of subchondral bone remodelling, 3) role of synovium and inflammation, 4) role of age-related changes including cartilage matrix stiffening, cellular senescence, mitochondrial dysfunction, metabolic dysfunction, and impaired autophagy, and 5) peripheral mechanisms of OA pain. Progress in the understanding of the cellular and molecular mechanisms responsible for the multiple aspects of OA biology is unravelling novel therapeutic targets for disease modification.

Smad4 sequestered in SFPQ condensates prevents TGF-β tumor-suppressive signaling

Loss of TGF-β growth-inhibitory responses is a hallmark of human cancer. However, the molecular mechanisms underlying the TGF-β resistance of cancer cells remain to be fully elucidated. Splicing factor proline- and glutamine-rich (SFPQ) is a prion-like RNA-binding protein that is frequently upregulated in human cancers. In this study, we identified SFPQ as a potent suppressor of TGF-β signaling. The ability of SFPQ to suppress TGF-β responses depends on its prion-like domain (PrLD) that drives liquid-liquid phase separation (LLPS). Mechanistically, SFPQ physically restrained Smad4 in its condensates, which excluded Smad4 from the Smad complex and chromatin occupancy and thus functionally dampened Smad-dependent transcriptional responses. Accordingly, SFPQ deficiency or loss of phase separation activities rendered human cells hypersensitive to TGF-β responses. Together, our data identify an important function of SFPQ through LLPS that suppresses Smad transcriptional activation and TGF-β tumor-suppressive activity.

HCV and HCC Tango-Deciphering the Intricate Dance of Disease: A Review Article

Hepatitis C virus (HCV) is a major cause of hepatocellular carcinoma (HCC) accounting for around one-third of all HCC cases. Prolonged inflammation in chronic hepatitis C (CHC), maintained through a variety of pro- and anti-inflammatory mediators, is one of the aspects of carcinogenesis, followed by mitochondrial dysfunction and oxidative stress. Immune response dysfunction including the innate and adaptive immunity also plays a role in the development, as well as in the recurrence of HCC after treatment. Some of the tumor suppressor genes inhibited by the HCV proteins are p53, p73, and retinoblastoma 1. Mutations in the telomerase reverse transcriptase promoter and the oncogene catenin beta 1 are two more important carcinogenic signaling pathways in HCC associated with HCV. Furthermore, in HCV-related HCC, numerous tumor suppressor and seven oncogenic genes are dysregulated by epigenetic changes. Epigenetic regulation of gene expression is considered as a lasting "epigenetic memory", suggesting that HCV-induced changes persist and are associated with liver carcinogenesis even after cure. Epigenetic changes and immune response dysfunction are recognized targets for potential therapy of HCC.

Intricacies of TGF-β signaling in Treg and Th17 cell biology

Balanced immunity is pivotal for health and homeostasis. CD4+ helper T (Th) cells are central to the balance between immune tolerance and immune rejection. Th cells adopt distinct functions to maintain tolerance and clear pathogens. Dysregulation of Th cell function often leads to maladies, including autoimmunity, inflammatory disease, cancer, and infection. Regulatory T (Treg) and Th17 cells are critical Th cell types involved in immune tolerance, homeostasis, pathogenicity, and pathogen clearance. It is therefore critical to understand how Treg and Th17 cells are regulated in health and disease. Cytokines are instrumental in directing Treg and Th17 cell function. The evolutionarily conserved TGF-β (transforming growth factor-β) cytokine superfamily is of particular interest because it is central to the biology of both Treg cells that are predominantly immunosuppressive and Th17 cells that can be proinflammatory, pathogenic, and immune regulatory. How TGF-β superfamily members and their intricate signaling pathways regulate Treg and Th17 cell function is a question that has been intensely investigated for two decades. Here, we introduce the fundamental biology of TGF-β superfamily signaling, Treg cells, and Th17 cells and discuss in detail how the TGF-β superfamily contributes to Treg and Th17 cell biology through complex yet ordered and cooperative signaling networks.

FOXO3 regulates Smad3 and Smad7 through SPON1 circular RNA to inhibit idiopathic pulmonary fibrosis

Forkhead box protein O3 (FOXO3) has good inhibition ability toward fibroblast activation and extracellular matrix, especially for the treatment of idiopathic pulmonary fibrosis. How FOXO3 regulates pulmonary fibrosis remains unclear. In this study, we reported that FOXO3 had binding sequences with F-spondin 1 (SPON1) promoter, which can activate its transcription and selectively promote the expression of SPON1 circRNA (circSPON1) but not mRNA expression. We further demonstrated that circSPON1 was involved in the extracellular matrix deposition of HFL1. In the cytoplasm, circSPON1 directly interacted with TGF-β1-induced Smad3 and inhibited the activation of fibroblasts by inhibiting nuclear translocation. Moreover, circSPON1 bound to miR-942-5p and miR-520f-3p that interfered with Smad7 mRNA and promoted Smad7 expression. This study revealed the mechanism of FOXO3-regulated circSPON1 in the development of pulmonary fibrosis. Potential therapeutic targets and new insights into the diagnosis and treatment of idiopathic pulmonary fibrosis based on circRNA were also provided.

The Emerging Role of Protein Phosphatase in Regeneration

Maintaining normal cellular behavior is essential for the survival of organisms. One of the main mechanisms to control cellular behavior is protein phosphorylation. The process of protein phosphorylation is reversible under the regulation of protein kinases and protein phosphatases. The importance of kinases in numerous cellular processes has been well recognized. In recent years, protein phosphatases have also been demonstrated to function actively and specifically in various cellular processes and thus have gained more and more attention from researchers. In the animal kingdom, regeneration frequently occurs to replace or repair damaged or missing tissues. Emerging evidence has revealed that protein phosphatases are crucial for organ regeneration. In this review, after providing a brief overview of the classification of protein phosphatases and their functions in several representative developmental processes, we highlight the critical roles that protein phosphatases play in organ regeneration by summarizing the most recent research on the function and underlying mechanism of protein phosphatase in the regeneration of the liver, bone, neuron, and heart in vertebrates.

Imatinib blocks tyrosine phosphorylation of Smad4 and restores TGF-β growth-suppressive signaling in BCR-ABL1-positive leukemia

Loss of TGF-β-mediated growth suppression is a major contributor to the development of cancers, best exemplified by loss-of-function mutations in genes encoding components of the TGF-β signaling pathway in colorectal and pancreatic cancers. Alternatively, gain-of-function oncogene mutations can also disrupt antiproliferative TGF-β signaling. However, the molecular mechanisms underlying oncogene-induced modulation of TGF-β signaling have not been extensively investigated. Here, we show that the oncogenic BCR-ABL1 of chronic myelogenous leukemia (CML) and the cellular ABL1 tyrosine kinases phosphorylate and inactivate Smad4 to block antiproliferative TGF-β signaling. Mechanistically, phosphorylation of Smad4 at Tyr195, Tyr301, and Tyr322 in the linker region interferes with its binding to the transcription co-activator p300/CBP, thereby blocking the ability of Smad4 to activate the expression of cyclin-dependent kinase (CDK) inhibitors and induce cell cycle arrest. In contrast, the inhibition of BCR-ABL1 kinase with Imatinib prevented Smad4 tyrosine phosphorylation and re-sensitized CML cells to TGF-β-induced antiproliferative and pro-apoptotic responses. Furthermore, expression of phosphorylation-site-mutated Y195F/Y301F/Y322F mutant of Smad4 in Smad4-null CML cells enhanced antiproliferative responses to TGF-β, whereas the phosphorylation-mimicking Y195E/Y301E/Y322E mutant interfered with TGF-β signaling and enhanced the in vivo growth of CML cells. These findings demonstrate the direct role of BCR-ABL1 tyrosine kinase in suppressing TGF-β signaling in CML and explain how Imatinib-targeted therapy restored beneficial TGF-β anti-growth responses.

Protein phosphatase PPM1A inhibition attenuates osteoarthritis via regulating TGF-β/Smad2 signaling in chondrocytes

TGF-β signaling is crucial for modulating osteoarthritis (OA), and protein phosphatase magnesium-dependent 1A (PPM1A) has been reported as a phosphatase of SMAD2 and regulates TGF-β signaling, while the role of PPM1A in cartilage homeostasis and OA development remains largely unexplored. In this study, we found increased PPM1A expression in OA chondrocytes and confirmed the interaction between PPM1A and phospho-SMAD2 (p-SMAD2). Importantly, our data show that PPM1A KO substantially protected mice treated with destabilization of medial meniscus (DMM) surgery against cartilage degeneration and subchondral sclerosis. Additionally, PPM1A ablation reduced the cartilage catabolism and cell apoptosis after the DMM operation. Moreover, p-SMAD2 expression in chondrocytes from KO mice was higher than that in WT controls with DMM induction. However, intraarticular injection with SD-208, repressing TGF-β/SMAD2 signaling, dramatically abolished protective phenotypes in PPM1A-KO mice. Finally, a specific pharmacologic PPM1A inhibitor, Sanguinarine chloride (SC) or BC-21, was able to ameliorate OA severity in C57BL/6J mice. In summary, our study identified PPM1A as a pivotal regulator of cartilage homeostasis and demonstrated that PPM1A inhibition attenuates OA progression via regulating TGF-β/SMAD2 signaling in chondrocytes and provided PPM1A as a potential target for OA treatment.

Indole-derived compound SIS3 targets a subset of activated Smad complexes

Smad2 and Smad3 are receptor-regulated Smad proteins that transmit signals from cytokines belonging to the transforming growth factor (TGF)-β family, which are vital for adult tissue homeostasis. The overactivation of such proteins often engenders the development of pathological conditions. Smad3 reportedly mediates TGF-β–induced fibrosis. Although various potential Smad3-specific inhibitors are being developed, their specificity and action mechanisms remain largely unknown. This study aimed to establish a biochemical platform to monitor Smad2- or Smad3-dependent TGF-β signaling using SMAD2, SMAD3 and SMAD2/3 knockout cell lines alongside TGF-β–dependent luciferase reporters and Smad mutant proteins. Using this platform, SIS3, an indole-derived compound widely used as a specific Smad3 inhibitor, was observed to preferentially suppress a subset of activated Smad complexes. However, its inhibition did not favor Smad3 signaling over Smad2 signaling. These findings indicate that SIS3 can be employed as a probe to examine the heterogeneous nature of Smad signaling that induces gene expression. However, its use as a Smad3-specific inhibitor should be avoided.

Energy sensor AMPK gamma regulates translation via phosphatase PPP6C independent of AMPK alpha

Maintenance of energy level to drive movements and material exchange with the environment is a basic principle of life. AMP-activated protein kinase (AMPK) senses energy level and is a major regulator of cellular energy responses. The gamma subunit of AMPK senses elevated ratio of AMP to ATP and allosterically activates the alpha catalytic subunit to phosphorylate downstream effectors. Here, we report that knockout of AMPKγ, but not AMPKα, suppressed phosphorylation of eukaryotic translation elongation factor 2 (eEF2) induced by energy starvation. We identified PPP6C as an AMPKγ-regulated phosphatase of eEF2. AMP-bound AMPKγ sequesters PPP6C, thereby blocking dephosphorylation of eEF2 and thus inhibiting translation elongation to preserve energy and to promote cell survival. Further phosphoproteomic analysis identified additional targets of PPP6C regulated by energy stress in an AMPKγ-dependent manner. Thus, AMPKγ senses cellular energy availability to regulate not only AMPKα kinase, but also PPP6C phosphatase and possibly other effectors.

Dysregulation of the immune response in TGF-β signalopathies

The transforming growth factor-β (TGF-β) family of cytokines exerts pleiotropic functions during embryonic development, tissue homeostasis and repair as well as within the immune system. Single gene defects in individual component of this signaling machinery cause defined Mendelian diseases associated with aberrant activation of TGF-β signaling, ultimately leading to impaired development, immune responses or both. Gene defects that affect members of the TGF-β cytokine family result in more restricted phenotypes, while those affecting downstream components of the signaling machinery induce broader defects. These rare disorders, also known as TGF-β signalopathies, provide the unique opportunity to improve our understanding of the role and the relevance of the TGF-β signaling in the human immune system. Here, we summarize this elaborate signaling pathway, review the diverse clinical presentations and immunological phenotypes observed in these patients and discuss the phenotypic overlap between humans and mice genetically deficient for individual components of the TGF-β signaling cascade.

To Ub or not to Ub: a regulatory question in TGF-β signaling

The transforming growth factor β (TGF-β) superfamily controls a wide spectrum of biological processes in metazoans, including cell proliferation, apoptosis, differentiation, cell-fate determination, and embryonic development. Deregulation of TGF-β-Smad signaling contributes to developmental anomalies and a variety of disorders and diseases such as tumorigenesis, fibrotic disorders, and immune diseases. In cancer, TGF-β has dual effects through its antiproliferative and prometastatic actions. At the cellular level, TGF-β functions mainly through the canonical Smad-dependent pathway in a cell type-specific and context-dependent manner. Accumulating evidence has demonstrated that ubiquitination plays a vital role in regulating TGF-β-Smad signaling. We summarize current progress on ubiquitination (Ub) and the ubiquitin ligases that regulate TGF-β-Smad signaling.

Targeting HSP47 and HSP70: promising therapeutic approaches in liver fibrosis management

Liver fibrosis is a liver disease in which there is an excessive buildup of extracellular matrix proteins, including collagen. By regulating cytokine production and the inflammatory response, heat shock proteins (HSPs) contribute significantly to a wider spectrum of fibrotic illnesses, such as lung, liver, and idiopathic pulmonary fibrosis by aiding in the folding and assembly of freshly synthesized proteins, HSPs serve as chaperones. HSP70 is one of the key HSPs in avoiding protein aggregation which induces its action by sending unfolded and/or misfolded proteins to the ubiquitin–proteasome degradation pathway and antagonizing influence on epithelial-mesenchymal transition. HSP47, on the other hand, is crucial for boosting collagen synthesis, and deposition, and fostering the emergence of fibrotic disorders. The current review aims to provide light on how HSP70 and HSP47 affect hepatic fibrogenesis. Additionally, our review looks into new therapeutic approaches that target HSP70 and HSP47 and could potentially be used as drug candidates to treat liver fibrosis, especially in cases of comorbidities.

Induced retinal pigment epithelial cells with anti-epithelial-to-mesenchymal transition ability delay retinal degeneration

The hostile microenvironment of the retina in patients with age-related macular degeneration (AMD) may trigger epithelial-to-mesenchymal transition (EMT) of grafted retinal pigment epithelial (RPE) cells, thus attenuating the therapeutic outcome. Here, we transformed human dedifferentiated induced pluripotent stem cell-derived RPE (iPSC-RPE) cells into induced RPE (iRPE) cells using a cocktail of four transcription factors (TFs)—CRX, MITF-A, NR2E1, and C-MYC. These critical TFs maintained the epithelial property of iRPE cells by regulating the expression of bmp7, forkhead box f2, lin7a, and pard6b, and conferred resistance to TGF-β-induced EMT in iRPE cells by targeting ppm1a. The iRPE cells with Tet-on system-regulated c-myc expression exhibited EMT resistance and better therapeutic function compared with iPSC-RPE cells in rat AMD model. Our study demonstrates that endowing RPE cells with anti-EMT property avoids the risk of EMT after cells are grafted into the subretinal space, and it may provide a suitable candidate for AMD treatment.

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CRX, MITF-A, NR2E1, and C-MYC transform De-iPSC-RPE cells into iRPE cells

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iRPE cells have resistance to TGF-β-induced EMT

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BMP7, FOXF2, LIN7A, PARD6B, and PPM1A mediate the functions of TFs in iRPE cells

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iRPE cells have better retinal protective function than iPSC-RPE cells

Astrocytic NDRG2-PPM1A interaction exacerbates blood-brain barrier disruption after subarachnoid hemorrhage

Blood-brain barrier (BBB) injury critically exacerbates the poor prognosis of patients with subarachnoid hemorrhage (SAH). The massively increased matrix metalloproteinases 9 (MMP-9) plays a deleterious role in BBB. However, the main source and mechanism of MMP-9 production after SAH remain unclear. We reported that the increased MMP-9 was mainly derived from reactive astrocytes after SAH. Ndrg2 knockout in astrocytes inhibited MMP-9 expression after SAH and attenuated BBB damage. Astrocytic Ndrg2 knockout decreased the phosphorylation of Smad2/3 and the transcription of MMP-9. Notably, cytoplasmic NDRG2 bound to the protein phosphatase PPM1A and restricted the dephosphorylation of Smad2/3. Accordingly, TAT-QFNP12, a novel engineered peptide that could block the NDRG2-PPM1A binding and reduce Smad2/3 dephosphorylation, decreased astrocytic MMP-9 production and BBB disruption after SAH. In conclusion, this study identified NDRG2-PPM1A signaling in reactive astrocytes as a key switch for MMP-9 production and provided a novel therapeutic avenue for BBB protection after SAH.

Direct conversion of human umbilical cord mesenchymal stem cells into retinal pigment epithelial cells for treatment of retinal degeneration

Age-related macular degeneration (AMD) is a major vision-threatening disease. Although mesenchymal stem cells (MSCs) exhibit beneficial neural protective effects, their limited differentiation capacity in vivo attenuates their therapeutic function. Therefore, the differentiation of MSCs into retinal pigment epithelial (RPE) cells in vitro and their subsequent transplantation into the subretinal space is expected to improve the outcome of cell therapy. Here, we transdifferentiated human umbilical cord MSCs (hUCMSCs) into induced RPE (iRPE) cells using a cocktail of five transcription factors (TFs): CRX, NR2E1, C-MYC, LHX2, and SIX6. iRPE cells exhibited RPE specific properties, including phagocytic ability, epithelial polarity, and gene expression profile. In addition, high expression of PTPN13 in iRPE cells endows them with an epithelial-to-mesenchymal transition (EMT)-resistant capacity through dephosphorylating syntenin1, and subsequently promoting the internalization and degradation of transforming growth factor-β receptors. After grafting into the subretinal space of the sodium iodate-induced rat AMD model, iRPE cells demonstrated a better therapeutic function than hUCMSCs. These results suggest that hUCMSC-derived iRPE cells may be promising candidates to reverse AMD pathophysiology.

RGS6 suppresses TGF-β-induced epithelial-mesenchymal transition in non-small cell lung cancers via a novel mechanism dependent on its interaction with SMAD4

Regulator of G-protein signaling 6 (RGS6) is a newly discovered tumor suppressor that has been shown to be protective in development of various cancers such as breast cancer and bladder cancer. But the mechanisms underlying these tumor-suppressing functions of RGS6 are not fully understood. Here, we discover a novel function of RGS6 in suppressing TGF-β-induced epithelial-mesenchymal transition (EMT) of non-small cell lung cancer (NSCLC) cells and in vivo NSCLC metastasis. Using both bioinformatics and experimental tools, we showed that RGS6 was downregulated in lung cancer tissues compared to noncancerous counterparts, and low expression of RGS6 was associated with poor survival of lung cancer patients. Overexpression of RGS6 suppressed TGF-β-induced EMT in vitro and TGF-β-promoted metastasis in vivo, by impairing gene expression of downstream effectors induced by the canonical TGF-β-SMAD signaling. The ability of RGS6 to suppress TGF-β-SMAD-mediated gene expression relied on its binding to SMAD4 to prevent complex formation between SMAD4 and SMAD2/3, but independent of its regulation of the G-protein signaling. Interaction between RGS6 and SMAD4 caused less nuclear entry of p-SMAD3 and SMAD4, resulting in inefficient SMAD3-mediated gene expression. Taken together, our findings reveal a novel and noncanonical role of RGS6 in regulation of TGF-β-induced EMT and metastasis of NSCLC and identify RGS6 as a prognostic marker and a potential novel target for NSCLC therapy.

TRPM7 deficiency exacerbates cardiovascular and renal damage induced by aldosterone-salt

Hyperaldosteronism causes cardiovascular disease as well as hypomagnesemia. Mechanisms are ill-defined but dysregulation of TRPM7, a Mg²⁺-permeable channel/α-kinase, may be important. We examined the role of TRPM7 in aldosterone-dependent cardiovascular and renal injury by studying aldosterone-salt treated TRPM7-deficient (TRPM7^+/Δkinase) mice. Plasma/tissue [Mg²⁺] and TRPM7 phosphorylation were reduced in vehicle-treated TRPM7^+/Δkinase mice, effects recapitulated in aldosterone-salt-treated wild-type mice. Aldosterone-salt treatment exaggerated vascular dysfunction and amplified cardiovascular and renal fibrosis, with associated increased blood pressure in TRPM7^+/Δkinase mice. Tissue expression of Mg²⁺-regulated phosphatases (PPM1A, PTEN) was downregulated and phosphorylation of Smad3, ERK1/2, and Stat1 was upregulated in aldosterone-salt TRPM7-deficient mice. Aldosterone-induced phosphorylation of pro-fibrotic signaling was increased in TRPM7^+/Δkinase fibroblasts, effects ameliorated by Mg²⁺ supplementation. TRPM7 deficiency amplifies aldosterone-salt-induced cardiovascular remodeling and damage. We identify TRPM7 downregulation and associated hypomagnesemia as putative molecular mechanisms underlying deleterious cardiovascular and renal effects of hyperaldosteronism.

Deficiency of the Mg2+-permeable channel/α-kinase TRPM7 in mice increases susceptibility to cardiovascular and renal fibrosis induced by aldosterone and salt.

Myoneurin regulates BMP signaling by competing with Ppm1a for Smad binding

A delicate balance of BMP activity is critical for tissue formation and organogenesis. However, the mechanical molecular details in ensuring the proper duration and intensity of BMP signaling have yet to be fully elucidated. Here, we identified a zebrafish mutant with a disrupted gene encoding for the BTB/POZ and zinc finger protein myoneurin (Mynn). mynn^−/− mutants exhibited severe loss of pharyngeal cartilage elements, owing to poor proliferation, blocked differentiation, and low viability of cranial neural crest cells. Depletion of mynn in both zebrafish embryos and mammalian cells led to a reduction of the BMP signal activity. Mechanistically, Mynn interacts with Smad proteins in the nucleus, thereby disrupting the association between Smad protein and the phosphatase Ppm1a. Ultimately, this interaction prevents Smad dephosphorylation. More broadly, our findings may provide a new strategy to balance BMP signal activity via competitive binding of Mynn and Ppm1a to Smad proteins during pharyngeal cartilage formation.

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mynn gene is essential for pharyngeal cartilage development

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mynn is required for the proliferation, differentiation, and survival of the CNCCs

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Mynn has an evolutionarily conserved function in supporting BMP signal

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Mynn maintains BMP signal activity by competing with Ppm1a for Smad binding

Knockdown of TRIM65 suppressed the proliferation and invasiveness of gastric cancer cells by restricting the ubiquitin degradation of PPM1A

Gastric cancer is a type of serious malignant tumors all around the world. TCGA data showed that the expression of TRIM65 (E3 ubiquitin ligase) was enhanced in the gastric cancer tissues. The role of TRIM65 in the tumorigenesis of gastric cancer remains unclear. In this study, we successfully established TRIM65-knockdown gastric cancer cells. Next, CCK-8, colony formation assays and transwell assays were performed to detect the cell proliferation and invasion. The results showed that suppression of TRIM65 inhibited the proliferation and invasion of gastric cancer cells. Interestingly, the Western blot assay confirmed that downregulation of TRIM65 increased the level of PPM1A and decreased the level of p-TBK1 in gastric cancer cells. Mechanistically, immunoprecipitation assay revealed that knockdown of TRIM65 inhibited the ubiquitin degradation of PPM1A. In rescue experiments, suppression of PPM1A promoted the proliferation and invasion of gastric cancer cells transfected with sh-TRIM65. Therefore, our results suggested that knockdown of TRIM65 inhibited the proliferation and invasion of gastric cancer cells by suppressing the ubiquitin degradation of PPM1A and phosphorylation of TBK1.

A selective PPM1A inhibitor activates autophagy to restrict the survival of Mycobacterium tuberculosis

Metal-dependent protein phosphatases (PPMs) have essential roles in a variety of cellular processes, including inflammation, proliferation, differentiation, and stress responses, which are intensively investigated in cancer and metabolic diseases. Targeting PPMs to modulate host immunity in response to pathogens is an ambitious proposition. The feasibility of such a strategy is unproven because development of inhibitors against PPMs is challenging and suffers from poor selectivity. Combining a biomimetic modularization strategy with function-oriented synthesis, we design, synthesize and screen more than 500 pseudo-natural products, resulting in the discovery of a potent, selective, and non-cytotoxic small molecule inhibitor for PPM1A, SMIP-30. Inhibition of PPM1A with SMIP-30 or its genetic ablation (ΔPPM1A) activated autophagy through a mechanism dependent on phosphorylation of p62-SQSTM1, which restricted the intracellular survival of Mycobacterium tuberculosis in macrophages and in the lungs of infected mice. SMIP-30 provides proof of concept that PPMs are druggable and promising targets for the development of host-directed therapies against tuberculosis.

YAP Targets the TGFβ Pathway to Mediate High-Fat/High-Sucrose Diet-Induced Arterial Stiffness

BACKGROUND

Metabolic syndrome is related to cardiovascular diseases, which is attributed in part, to arterial stiffness; however, the mechanisms remain unclear. The present study aimed to investigate the molecular mechanisms of metabolic syndrome-induced arterial stiffness and to identify new therapeutic targets.

METHODS

Arterial stiffness was induced by high-fat/high-sucrose diet in mice, which was quantified by Doppler ultrasound. Four-dimensional label-free quantitative proteomic analysis, affinity purification and mass spectrometry, and immunoprecipitation and GST pull-down experiments were performed to explore the mechanism of YAP (Yes-associated protein)-mediated TGF (transforming growth factor) β pathway activation.

RESULTS

YAP protein was upregulated in the aortic tunica media of mice fed a high-fat/high-sucrose diet for 2 weeks and precedes arterial stiffness. Smooth muscle cell-specific YAP knockdown attenuated high-fat/high-sucrose diet-induced arterial stiffness and activation of TGFβ-Smad2/3 signaling pathway in arteries. By contrast, Myh11Cre^ERT2-Yap^Tg mice exhibited exacerbated high-fat/high-sucrose diet-induced arterial stiffness and enhanced TGFβ-activated Smad2/3 phosphorylation in arteries. PPM1B (protein phosphatase, Mg²⁺/Mn²⁺-dependent 1B) was identified as a YAP-bound phosphatase that translocates into the nucleus to dephosphorylate Smads in response to TGFβ. This process was inhibited by YAP through removal of the K63-linked ubiquitin chain of PPM1B at K326.

CONCLUSIONS

This study provides a new mechanism by which smooth muscle cell YAP regulates the TGFβ pathway and a potential therapeutic target in metabolic syndrome-associated arterial stiffness.

Curcumin Inhibition of TGFβ signaling in bone metastatic breast cancer cells and the possible role of oxidative metabolites

TGFβ signaling promotes progression of bone-metastatic (BMET) breast cancer (BCa) cells by driving tumor-associated osteolysis, a hallmark of BCa BMETs, thus allowing for tumor expansion within bone. Turmeric-derived bioactive curcumin, enriched in bone via local enzymatic deconjugation of inactive circulating curcumin-glucuronides, inhibits osteolysis and BMET progression in human xenograft BCa BMET models by blocking tumoral TGFβ signaling pathways mediating osteolysis. This is a unique antiosteolytic mechanism in contrast to current osteoclast-targeting therapeutics. Therefore, experiments were undertaken to elucidate the mechanism for curcumin inhibition of BCa TGFβ signaling and the application of this finding across multiple BCa cell lines forming TGFβ-dependent BMETs, including a possible role for bioactive curcumin metabolites in mediating these effects. Immunoblot analysis of TGFβ signaling proteins in bone tropic human (MDA-SA, MDA-1833, MDA-2287) and murine (4T1) BCa cells revealed uniform curcumin blockade of TGFβ-induced Smad activation due to down-regulation of plasma membrane associated TGFβR2 and cellular receptor Smad proteins that propagate Smad-mediated gene expression, resulting in downregulation of PTHrP expression, the osteolytic factor driving in vivo BMET progression. With the exception of early decreases in TGFβR2, inhibitory effects appeared to be mediated by oxidative metabolites of curcumin and involved inhibition of gene expression. Interestingly, while not contributing to changes in Smad-mediated TGFβ signaling, curcumin caused early activation of MAPK signaling in all cell lines, including JNK, an effect possibly involving interactions with TGFβR2 within lipid rafts. Treatment with curcumin or oxidizable analogs of curcumin may have clinical relevancy in the management of TGFβ-dependent BCa BMETs.

A comprehensive overview of PPM1A: From structure to disease

PPM1A (magnesium-dependent phosphatase 1 A, also known as PP2Cα) is a member of the Ser/Thr protein phosphatase family. Protein phosphatases catalyze the removal of phosphate groups from proteins via hydrolysis, thus opposing the role of protein kinases. The PP2C family is generally considered a negative regulator in the eukaryotic stress response pathway. PPM1A can bind and dephosphorylate various proteins and is therefore involved in the regulation of a wide range of physiological processes. It plays a crucial role in transcriptional regulation, cell proliferation, and apoptosis and has been suggested to be closely related to the occurrence and development of cancers of the lung, bladder, and breast, amongst others. Moreover, it is closely related to certain autoimmune diseases and neurodegenerative diseases. In this review, we provide an insight into currently available knowledge of PPM1A, including its structure, biological function, involvement in signaling pathways, and association with diseases. Lastly, we discuss whether PPM1A could be targeted for therapy of certain human conditions.

HSPA13 facilitates NF-κB-mediated transcription and attenuates cell death responses in TNFα signaling

RIP1 has emerged as a master regulator in TNFα signaling that controls two distinct cellular fates: cell survival versus programmed cell death. Because the default response of most cells to TNFα is NF-κB–mediated inflammation and survival, a specific mechanism must exist to control the divergence of signaling outcome. Here, we identify HSPA13 as a transcription-independent checkpoint to modulate the role of RIP1 in TNFα signaling. Through specific binding to TNFR1 and RIP1, HSPA13 enhances TNFα-induced recruitment of RIP1 to TNFR1, and consequently promotes downstream NF-κB transcriptional responses. Meanwhile, HSPA13 attenuates the participation of RIP1 in cytosolic complex II and prevents cells from programmed death. Loss of HSPA13 shifts the transition of RIP1 from complex I to complex II and promotes both apoptosis and necroptosis. Thus, our study provides compelling evidence for the cellular protective function of HSPA13 in fine-tuning TNFα responses.

Phospho-Smad3L promotes progression of hepatocellular carcinoma through decreasing miR-140-5p level and stimulating epithelial-mesenchymal transition

BACKGROUND

The transforming growth factor β (TGF-β) activates JNK, phosphorylates Smad3 to linker-phosphorylated Smad3 (pSmad3L), resulting in liver tumorigenesis. However, the effect of pSmad3L on hepatocellular carcinoma (HCC) prognosis is obscure.

AIM

To detect the effect of pSmad3L on HCC prognosis and investigate the mechanism.

METHODS

The expressions of pSmad3L, E-cadherin, vimentin and MicroRNA-140-5p (miR-140-5p) were detected by using immunohistochemistry, immunofluorescence and in situ hybridization. Next, the relationships of pSmad3L and HCC patients' prognoses, pSmad3L and EMT markers, pSmad3L and miR-140-5p were analyzed using Spearman's rank correlation test. JNK/pSmad3L specific inhibitor SP600125 or Smad3 mutant plasmid was used to suppress JNK/pSmad3L pathway, and QPCR assay was performed to investigate the effect of pSmad3L on miR-140-5p level. The proliferation and invasion of hepatoma cells were observed using colony formation assay and transwell assay.

RESULTS

We demonstrated that patient with high level of pSmad3L predicted poor prognosis. Next, we verified that pSmad3L promoted EMT of hepatoma cells in vivo and in vitro. In order to investigate the mechanism, we verified a negative correlation between pSmad3L and miR-140-5p, which was an EMT inhibitor, in the liver tissues of HCC patient and diethylnitrosamine (DEN)-induced rat HCC model. We further used SP600125 or pSmad3L mutant plasmid to decrease pSmad3L level of hepatoma cells, and inhibition of pSmad3L increased miR-140-5p level and suppressed EMT of hepatoma cells.

CONCLUSIONS

JNK/pSmad3L pathway induces EMT by inhibiting miR-140-5p in HCC progression.

Negative regulators of TGF-β1 signaling in renal fibrosis; pathological mechanisms and novel therapeutic opportunities

Elevated expression of the multifunctional cytokine transforming growth factor β1 (TGF-β1) is causatively linked to kidney fibrosis progression initiated by diabetic, hypertensive, obstructive, ischemic and toxin-induced injury. Therapeutically relevant approaches to directly target the TGF-β1 pathway (e.g., neutralizing antibodies against TGF-β1), however, remain elusive in humans. TGF-β1 signaling is subjected to extensive negative control at the level of TGF-β1 receptor, SMAD2/3 activation, complex assembly and promoter engagement due to its critical role in tissue homeostasis and numerous pathologies. Progressive kidney injury is accompanied by the deregulation (loss or gain of expression) of several negative regulators of the TGF-β1 signaling cascade by mechanisms involving protein and mRNA stability or epigenetic silencing, further amplifying TGF-β1/SMAD3 signaling and fibrosis. Expression of bone morphogenetic proteins 6 and 7 (BMP6/7), SMAD7, Sloan-Kettering Institute proto-oncogene (Ski) and Ski-related novel gene (SnoN), phosphate tensin homolog on chromosome 10 (PTEN), protein phosphatase magnesium/manganese dependent 1A (PPM1A) and Klotho are dramatically decreased in various nephropathies in animals and humans albeit with different kinetics while the expression of Smurf1/2 E3 ligases are increased. Such deregulations frequently initiate maladaptive renal repair including renal epithelial cell dedifferentiation and growth arrest, fibrotic factor (connective tissue growth factor (CTGF/CCN2), plasminogen activator inhibitor type-1 (PAI-1), TGF-β1) synthesis/secretion, fibroproliferative responses and inflammation. This review addresses how loss of these negative regulators of TGF-β1 pathway exacerbates renal lesion formation and discusses the therapeutic value in restoring the expression of these molecules in ameliorating fibrosis, thus, presenting novel approaches to suppress TGF-β1 hyperactivation during chronic kidney disease (CKD) progression.

PGC1α is required for the renoprotective effect of lncRNA Tug1 in vivo and links Tug1 with urea cycle metabolites

lncRNA taurine-upregulated gene 1 (Tug1) is a promising therapeutic target in the progression of diabetic nephropathy (DN), but the molecular basis of its protection remains poorly understood. Here, we generate a triple-mutant diabetic mouse model coupled with metabolomic profiling data to interrogate whether Tug1 interaction with peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α) is required for mitochondrial remodeling and progression of DN in vivo. We find that, compared with diabetic conditional deletion of Pgc1α in podocytes alone (db/db; Pgc1αPod-f/f), diabetic Pgc1α knockout combined with podocyte-specific Tug1 overexpression (db/db; TugPodTg; Pgc1αPod-f/f) reverses the protective phenotype of Tug1 overexpression, suggesting that PGC1α is required for the renoprotective effect of Tug1. Using unbiased metabolomic profiling, we find that altered urea cycle metabolites and mitochondrial arginase 2 play an important role in Tug1/PGC1α-induced mitochondrial remodeling. Our work identifies a functional role of the Tug1/PGC1α axis on mitochondrial metabolic homeostasis and urea cycle metabolites in experimental models of diabetes.

AMBRA1 promotes TGF-β signaling via non-proteolytic polyubiquitylation of Smad4

Transforming growth factor-β (TGF-β) is pro-metastatic in advanced cancers and its biological activities are mainly mediated by the Smad family of proteins. Smad4 is the central signal transducer and transcription factor in the TGF-β pathway, yet the underlying mechanisms that govern transcriptional activities of Smad4 are not fully understood. Here, we show that AMBRA1, a member of the DDB1 and CUL4-associated factor (DCAF) family of proteins, serves as the substrate receptor for Smad4 in the CUL4-RING (CRL4) ubiquitin ligase complex. The CRL4-AMBRA1 ubiquitin ligase mediates non-proteolytic polyubiquitylation of Smad4 to enhance its transcriptional functions. Consequently, AMBRA1 potentiated TGF-β signaling and critically promoted TGF-β-induced epithelial-to-mesenchymal transition, migration, and invasion of breast cancer cells. Mouse models of breast cancer demonstrated that AMBRA1 promotes metastasis. Collectively, these results show that CRL4-AMBRA1 facilitates TGF-β-driven metastasis by increasing Smad4 polyubiquitylation, suggesting AMBRA1 may serve as a new therapeutic target in metastatic breast cancer.

Can serum matrix metalloproteinase-9 and SMAD-2 levels predict lamina propria invasion in bladder urothelial carcinoma?

INTRODUCTION

Matrix metalloproteinase-9 (MMP-9) has a role in the destruction of lamina propria (LP) of the bladder wall and SMAD-2 promotes cell-to-cell adhesion. This study aimed to investigate the association between LP invasion and serum protein and mRNA expression levels of MMP-9 and SMAD-2 in bladder cancer (BC) patients.

METHODS

Serum samples were taken from 57 patients with suspicious BC before TUR-BT (Group 1) and 20 patients with benign diseases as control (Group 2). The mRNA expression and serum protein levels of MMP-9 and SMAD-2 were analyzed using Real-Time PCR and ELISA methods, respectively. The comparison of protein and mRNA expression levels of MMP-9 and SMAD-2 were done statistically between Group 1 and 2, as well as for different T stages of BC.

RESULTS

The protein levels of MMP-9 (2448 vs 637.5 pg/mL, P = .0001) and SMAD-2 (6.85 vs 1.61 P = .0001) were significantly higher in Group 1 compared to Group 2. The mRNA expression levels of MMP-9 (P = .89) and SMAD-2 (P = .99) did not significantly differ between the groups. The protein levels of MMP-9 in T1 patients were significantly higher from both of pTa patients (P = .018) and pT2 (P = .02). The protein levels of SMAD-2 were not statistically different between T stages. Similarly, the mRNA expression levels of MMP-9 and SMAD-2 were not different between T stages.

CONCLUSIONS

The protein levels of MMP-9 and SMAD-2 were increased in BC patients while mRNA expressions were not different. Furthermore, the increased protein level of MMP-9 in T1 patients was more pronounced which may be related to LP invasion of the tumor.

The Role of TGF-β Signaling Pathways in Cancer and Its Potential as a Therapeutic Target

The transforming growth factor-β (TGF-β) signaling pathway mediates various biological functions, and its dysregulation is closely related to the occurrence of malignant tumors. However, the role of TGF-β signaling in tumorigenesis and development is complex and contradictory. On the one hand, TGF-β signaling can exert antitumor effects by inhibiting proliferation or inducing apoptosis of cancer cells. On the other hand, TGF-β signaling may mediate oncogene effects by promoting metastasis, angiogenesis, and immune escape. This review summarizes the recent findings on molecular mechanisms of TGF-β signaling. Specifically, this review evaluates TGF-β's therapeutic potential as a target by the following perspectives: ligands, receptors, and downstream signaling. We hope this review can trigger new ideas to improve the current clinical strategies to treat tumors related to the TGF-β signaling pathway.

Dual Roles of the Activin Signaling Pathway in Pancreatic Cancer

Activin, a member of the TGF-β superfamily, is involved in many physiological processes, such as embryonic development and follicle development, as well as in multiple human diseases including cancer. Genetic mutations in the activin signaling pathway have been reported in many cancer types, indicating that activin signaling plays a critical role in tumorigenesis. Recent evidence reveals that activin signaling may function as a tumor-suppressor in tumor initiation, and a promoter in the later progression and metastasis of tumors. This article reviews many aspects of activin, including the signaling cascade of activin, activin-related proteins, and its role in tumorigenesis, particularly in pancreatic cancer development. The mechanisms regulating its dual roles in tumorigenesis remain to be elucidated. Further understanding of the activin signaling pathway may identify potential therapeutic targets for human cancers and other diseases.

Fenofibrate inhibits TGF-β-induced myofibroblast differentiation and activation in human lung fibroblasts in vitro

Fenofibrate (FF), a peroxisome proliferator-activated receptor-alpha (PPAR-α) agonist and a lipid-lowering agent, can decrease experimental pulmonary fibrosis. However, the mechanisms underlying the antifibrotic effect of FF remain unknown. Hence, this study was conducted to evaluate the effects of FF on transforming growth factor-beta (TGF-β)-induced myofibroblast differentiation and activation in lung fibroblasts. The results showed that FF inhibited alpha-smooth muscle actin (α-SMA) and connective tissue growth factor expression, collagen production, cell motility, SMAD3 phosphorylation and nuclear translocation, and metabolic reprogramming in TGF-β-exposed cells. The inhibitory effect of FF did not decrease with the addition of a PPAR-α antagonist. Moreover, the inhibitory effect given by FF could not be reproduced with the addition of an alternative PPAR-α agonist. FF inhibited mitochondrial respiration. However, rotenone, a complex I inhibitor, did not suppress TGF-β-induced myofibroblast differentiation. Furthermore, the TGF-β-induced nuclear reduction of protein phosphatase, Mg²⁺ /Mn²⁺ -dependent 1A (PPM1A), a SMAD phosphatase, was inhibited by FF. These results showed that FF suppressed TGF-β-induced myofibroblast differentiation and activation independent of PPAR-α activation and impaired mitochondrial respiration. In conclusion, this study provides information on the effects of FF on anti-TGF-β mechanisms.

DUSP5 promotes osteogenic differentiation through SCP1/2-dependent phosphorylation of SMAD1

Dual‐specificity phosphatases (DUSPs) are defined by their capability to dephosphorylate both phosphoserine/phosphothreonine (pSer/pThr) and phosphotyrosine (pTyr). DUSP5, a member of DUSPs superfamily, is located in the nucleus and plays crucially regulatory roles in the signaling pathway transduction. In our present study, we discover that DUSP5 significantly promotes osteogenic differentiation of mesenchymal stromal cells (MSCs) by activating SMAD1 signaling pathway. Mechanistically, DUSP5 physically interacts with the phosphatase domain of small C‐terminal phosphatase 1/2 (SCP1/2, SMAD1 phosphatases) by the linker region. In addition, we further confirm that DUSP5 activates SMAD1 signaling through a SCP1/2‐dependent manner. Specifically, DUSP5 attenuates the SCP1/2‐SMAD1 interaction by competitively binding to SCP1/2, which is responsible for the SMAD1 dephosphorylation, and thus results in the activation of SMAD1 signaling. Importantly, DUSP5 expression in mouse bone marrow MSCs is significantly reduced in ovariectomized (OVX) mice in which osteogenesis is highly passive, and overexpression of Dusp5 via tail vein injection reverses the bone loss of OVX mice efficiently. Collectively, this work demonstrates that the linker region of DUSP5 maybe a novel chemically modifiable target for controlling MSCs fate choices and for osteoporosis treatment.

PPM1A suppresses the proliferation and invasiveness of RCC cells via Smad2/3 signaling inhibition

BACKGROUND

Cytokine therapies show promise in treating renal cell carcinoma (RCC). Transforming growth factor beta 1 (TGF-β1) is a cytokine whose downstream Smad2/3 signaling activity is inhibited by the protein phosphatase Mg2+/Mn2+-dependent 1 A (PPM1A). Here, we hypothesized that PPM1A may be involved in suppressing RCC cell aggressiveness through its negative regulation of Smad2/3.

METHODS

We quantified PPM1A expression from RCC tumors and matching healthy tissue and performed a Kaplan-Meier survival analysis. In silico analysis on PPM1A was performed using Cancer Genome Atlas-Kidney Renal Clear Cell Carcinoma and Clinical Proteomic Tumor Analysis Consortium RCC cohort data. We tested four RCC cell lines and selected the ACNH and A498 cells lines as expressing the greatest PPM1A levels. We assayed the effects of RNAi-mediated PPM1A silencing on invasiveness, proliferation, colony formation, and Smad2/3 phosphorylation in untreated and TGF-β1-stimulated ACNH and A498 cells. A nude mouse A498 xenograft tumor model was constructed to validate PPM1A's effects in vivo.

RESULTS

PPM1A levels are reduced in RCC tumors and are negatively correlated with RCC grade and stage. Below-median PPM1A expression is associated with reduced overall survival in RCC patients. PPM1A silencing promoted cellular invasiveness, proliferation, colony formation, and Smad2/3 phosphorylation under TGF-β1-stimulated conditions but not under untreated conditions. These effects of PPM1A were shown to be dependent on Smad2/3. Intratumor PPM1A overexpression inhibited A498 xenograft tumor growth.

CONCLUSIONS

This study establishes a direct link between PPM1A's suppression of Smad2/3 signaling and RCC cell aggressiveness. PPM1A could potentially serve as a biomarker for RCC cell aggressiveness.

Hepatitis B Virus-Encoded MicroRNA (HBV-miR-3) Regulates Host Gene PPM1A Related to Hepatocellular Carcinoma

BACKGROUND

Hepatitis B is a liver infection disease caused by the Hepatitis B Virus (HBV) that can become chronic and develop into hepatocellular carcinoma. HBV was classified as a double-stranded DNA virus. Currently, there is a report showing that HBV virus-encoded miRNA called HBV-miR-3 controls the replication of HBV. However, the regulation of HBV-miR-3 in host cells remains unclear.

OBJECTIVE

This study aimed to investigate the regulation of HBV-miR-3 in host gene target which is related to chronic HBV infection and HCC process.

METHODS

In this study, we analyzed the read count of HBV-miR-3 from next-generation sequencing of chronic hepatitis patients in Pegylated interferon alpha-2a (PEG-IFN-α-2a) treatment. To understand the regulation of HBV-miR-3 in host cells, the HBV-miR-3 recognition sites were predicted in host target genes using miRDB. The effect of HBV-miR-3 in host cells was examined using qPCR and 3' UTR dual luciferase assay.

RESULTS

The read count of HBV-miR-3 was found in chronic hepatitis patients before treatment. Moreover, the decrease of HBV-miR-3 was correlated with response group of chronic hepatitis patients after treatment. On the other hand, the abundance of HBV-miR-3 showed no difference in nonresponse group of chronic patients after PEG-IFN-α-2a treatment. To study the role of HBV-miR-3 in patients, four HBV-miR-3 target regions from Protein phosphatase 1A (PPM1A) and DIX domain containing 1 (DIXDC1) were identified in the human genome using miRDB. Interestingly, we found that HBV-miR-3 hybridized with PPM1A mRNA. The mRNA expression from RT-qPCR showed no difference between HepG2 transfected with pSilencer_scramble or pSilencer_HBV-miR-3. However, the reporter assay showed that PPM1A mRNA was suppressed by HBV-miR-3. The protein expression of PPM1A showed a decrease in cells overexpressing HBV-miR-3. Finally, the HBV-miR-3 can promote cell proliferation in cells overexpressing HBV-miR-3.

CONCLUSION

This study is the first report showed the HBV encoded miRNA can regulate host gene expression. HBV-miR-3 silenced PPM1A by inhibiting the translation process of PPM1A. The downregulation of PPM1A promotes cell proliferation related to HCC development.

MicroRNA-487a-3p inhibits the growth and invasiveness of oral squamous cell carcinoma by targeting PPM1A

Oral squamous cell carcinoma (OSCC) forms the majority of the entire cancerous tumors which occur in the mouth. Current treatment advances, such as surgical resection, chemotherapy, and radiotherapy, have significantly helped reduce OSCC. However, the overall patient survival rate remains relatively low. MiRNAs, a non-coding RNA group, are essential for multiple biological functions, which are essential for the progression of cancer, including survival of the cell, migration, multiplication, differentiation, and apoptosis. The study aimed to explore the existing association between miR-487a-3p and PPM1A and elucidating their role in modulation of proliferation in OSCC cell lines. In this study, we used CAL-27 and TCA-8113 OSCC cell lines and human samples to validate our results. The manifestation of miR-487a-3p and PPM1A was checked using quantitative real-time PCR. The miR-487a-3p and PPM1A binding was investigated through western blot assay and dual-luciferase reporter gene. Functional experiments, including colony formation, CCK-8, and transwell experimentations, were undertaken to validate cells' growth and invasion activities. According to the results, the expression of miR-487a-3p is regulated in the OSCC cell lines compared to normal cells. Moreover, the mimicking of miR-487a-3p significantly reduces the OSCC cell growth and invasion, and PPM1A overexpression exerts oncogenic effects and hinders the anti-oncogenic effects of miR-487a-3p. In conclusion, the study demonstrated that miR-487a-3p might act as a tumor suppressor by inhibiting the growth and invasion of OSCC via regulating PPM1A expression.

STMN2 mediates nuclear translocation of Smad2/3 and enhances TGFβ signaling by destabilizing microtubules to promote epithelial-mesenchymal transition in hepatocellular carcinoma

Metastasis remains the major obstacle of improving the survival of patients with hepatocellular carcinoma (HCC). Epithelial-mesenchymal transition (EMT) is critical to cancer metastasis. Successful induction of EMT requires dramatic cytoskeleton rearrangement. However, the significance of microtubule (MT), one of the core components of cell cytoskeleton, in this process remains largely unknown. Here we revealed that STMN2, an important MT dynamics regulator, is barely expressed in normal live tissues but markedly up-regulated in HCCs, especially in those with early recurrence. High STMN2 expression correlates with aggressive clinicopathological features and predicts poor prognosis of HCC patients. STMN2 overexpression in HCC cells promotes EMT, invasion and metastasis in vitro and in vivo, whereas STMN2 knockdown has opposite results. Mechanistically, STMN2 modulates MTs disassembly, disrupts MT-Smad complex, and facilitates release from MT network, phosphorylation and nuclear translocation of Smad2/3 even independent of TGFβ stimulation, thereby enhancing TGFβ signaling. Collectively, STMN2 orchestrates MT disassembly to facilitate EMT via TGF-β signaling, providing a novel insight into the mechanisms underlying cancer metastasis. STMN2 is a promising prognostic biomarker and potential therapeutic target for HCC.

The phosphorylation of the Smad2/3 linker region by nemo-like kinase regulates TGF-β signaling

Smad2 and Smad3 (Smad2/3) are structurally similar proteins that primarily mediate the transforming growth factor-β (TGF-β) signaling responsible for driving cell proliferation, differentiation, and migration. The dynamics of the Smad2/3 phosphorylation provide the key mechanism for regulating the TGF-β signaling pathway, but the details surrounding this phosphorylation remain unclear. Here, using in vitro kinase assay coupled with mass spectrometry, we identified for the first time that nemo-like kinase (NLK) regulates TGF-β signaling via modulation of Smad2/3 phosphorylation in the linker region. TGF-β-mediated transcriptional and cellular responses are suppressed by NLK overexpression, whereas NLK depletion exerts opposite effects. Specifically, we discovered that NLK associates with Smad3 and phosphorylates the designated serine residues located in the linker region of Smad2 and Smad3, which inhibits phosphorylation at the C terminus, thereby decreasing the duration of TGF-β signaling. Overall, this work demonstrates that phosphorylation on the linker region of Smad2/3 by NLK counteracts the canonical phosphorylation in response to TGF-β signals, thus providing new insight into the mechanisms governing TGF-β signaling transduction.