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Autophagy Aug 2020Ferroptosis is a recently discovered form of programmed cell death, but its regulatory mechanisms remain poorly understood. Here, we show that the RNA-binding protein...
UNLABELLED
Ferroptosis is a recently discovered form of programmed cell death, but its regulatory mechanisms remain poorly understood. Here, we show that the RNA-binding protein ZFP36/TTP (ZFP36 ring finger protein) plays a crucial role in regulating ferroptosis in hepatic stellate cells (HSCs). Upon exposure to ferroptosis-inducing compounds, the ubiquitin ligase FBXW7/CDC4 (F-box and WD repeat domain containing 7) decreased ZFP36 protein expression by recognizing SFSGLPS motif. plasmid contributed to classical ferroptotic events, whereas plasmid impaired plasmid-induced HSC ferroptosis. Interestingly, plasmid inhibited macroautophagy/autophagy activation by destabilizing ATG16L1 (autophagy related 16 like 1) mRNA. plasmid eliminated the inhibitory action of plasmid on ferroptosis, and plasmid enhanced the effect of plasmid on autophagy. Importantly, plasmid promoted mRNA decay via binding to the AU-rich elements (AREs) within the 3'-untranslated region. The internal mutation of the ARE region abrogated the ZFP36-mediated mRNA instability, and prevented plasmid-mediated ferroptosis resistance. In mice, treatment with erastin and sorafenib alleviated murine liver fibrosis by inducing HSC ferroptosis. HSC-specific overexpression of impaired erastin- or sorafenib-induced HSC ferroptosis. Noteworthy, we analyzed the effect of sorafenib on HSC ferroptosis in fibrotic patients with hepatocellular carcinoma receiving sorafenib monotherapy. Attractively, sorafenib monotherapy led to ZFP36 downregulation, ferritinophagy activation, and ferroptosis induction in human HSCs. Overall, these results revealed novel molecular mechanisms and signaling pathways of ferroptosis, and also identified ZFP36-autophagy-dependent ferroptosis as a potential target for the treatment of liver fibrosis.
ABBREVIATIONS
ARE: AU-rich elements; ATG: autophagy related; BECN1: beclin 1; CHX: cycloheximide; COL1A1: collagen type I alpha 1 chain; ELAVL1/HuR: ELAV like RNA binding protein 1; FBXW7/CDC4: F-box and WD repeat domain containing 7; FN1: fibronectin 1; FTH1: ferritin heavy chain 1; GPX4/PHGPx: glutathione peroxidase 4; GSH: glutathione; HCC: hepatocellular carcinoma; HSC: hepatic stellate cell; LSEC: liver sinusoidal endothelial cell; MAP1LC3A: microtubule associated protein 1 light chain 3 alpha; MDA: malondialdehyde; NCOA4: nuclear receptor coactivator 4; PTGS2/COX2: prostaglandin-endoperoxide synthase 2; RBP: RNA-binding protein; ROS: reactive oxygen species; SLC7A11/xCT: solute carrier family 7 member 11; SQSTM1/p62: sequestosome 1; TNF: tumor necrosis factor; TP53/p53: tumor protein p53; UTR: untranslated region; ZFP36/TTP: ZFP36 ring finger protein.
Topics: AU Rich Elements; Adult; Aged; Aged, 80 and over; Amino Acid Motifs; Animals; Autophagy; Autophagy-Related Proteins; Collagen Type I, alpha 1 Chain; Down-Regulation; Female; Ferroptosis; Hepatic Stellate Cells; Humans; Liver Cirrhosis; Male; Mice, Inbred C57BL; Middle Aged; Piperazines; Plasmids; Protein Binding; RNA Stability; Rats; Signal Transduction; Sorafenib; Tristetraprolin
PubMed: 31679460
DOI: 10.1080/15548627.2019.1687985 -
Acta Pharmaceutica Sinica. B Mar 2022The immune checkpoint blockade (ICB) targeting on PD-1/PD-L1 has shown remarkable promise in treating cancers. However, the low response rate and frequently observed... (Review)
Review
The immune checkpoint blockade (ICB) targeting on PD-1/PD-L1 has shown remarkable promise in treating cancers. However, the low response rate and frequently observed severe side effects limit its broad benefits. It is partially due to less understanding of the biological regulation of PD-L1. Here, we systematically and comprehensively summarized the regulation of PD-L1 from nuclear chromatin reorganization to extracellular presentation. In PD-L1 and PD-L2 highly expressed cancer cells, a new TAD (topologically associating domain) (chr9: 5,400,000-5,600,000) around and was discovered, which includes a reported super-enhancer to drive synchronous transcription of PD-L1 and PD-L2. The re-shaped TAD allows transcription factors such as STAT3 and IRF1 recruit to PD-L1 locus in order to guide the expression of PD-L1. After transcription, the PD-L1 is tightly regulated by miRNAs and RNA-binding proteins the long 3'UTR. At translational level, PD-L1 protein and its membrane presentation are tightly regulated by post-translational modification such as glycosylation and ubiquitination. In addition, PD-L1 can be secreted exosome to systematically inhibit immune response. Therefore, fully dissecting the regulation of PD-L1/PD-L2 and thoroughly detecting PD-L1/PD-L2 as well as their regulatory networks will bring more insights in ICB and ICB-based combinational therapy.
PubMed: 35530130
DOI: 10.1016/j.apsb.2021.09.010 -
Cell Sep 2018The metabolic state of a cell is influenced by cell-extrinsic factors, including nutrient availability and growth factor signaling. Here, we present extracellular matrix...
The metabolic state of a cell is influenced by cell-extrinsic factors, including nutrient availability and growth factor signaling. Here, we present extracellular matrix (ECM) remodeling as another fundamental node of cell-extrinsic metabolic regulation. Unbiased analysis of glycolytic drivers identified the hyaluronan-mediated motility receptor as being among the most highly correlated with glycolysis in cancer. Confirming a mechanistic link between the ECM component hyaluronan and metabolism, treatment of cells and xenografts with hyaluronidase triggers a robust increase in glycolysis. This is largely achieved through rapid receptor tyrosine kinase-mediated induction of the mRNA decay factor ZFP36, which targets TXNIP transcripts for degradation. Because TXNIP promotes internalization of the glucose transporter GLUT1, its acute decline enriches GLUT1 at the plasma membrane. Functionally, induction of glycolysis by hyaluronidase is required for concomitant acceleration of cell migration. This interconnection between ECM remodeling and metabolism is exhibited in dynamic tissue states, including tumorigenesis and embryogenesis.
Topics: Carbohydrate Metabolism; Carrier Proteins; Cell Line, Tumor; Extracellular Matrix; Glucose; Glucose Transporter Type 1; Glycolysis; Humans; Hyaluronic Acid; Hyaluronoglucosaminidase; Intercellular Signaling Peptides and Proteins; Signal Transduction; Tristetraprolin
PubMed: 30197082
DOI: 10.1016/j.cell.2018.08.017 -
Immunity Dec 2017The immunosuppressive protein PD-L1 is upregulated in many cancers and contributes to evasion of the host immune system. The relative importance of the tumor...
The immunosuppressive protein PD-L1 is upregulated in many cancers and contributes to evasion of the host immune system. The relative importance of the tumor microenvironment and cancer cell-intrinsic signaling in the regulation of PD-L1 expression remains unclear. We report that oncogenic RAS signaling can upregulate tumor cell PD-L1 expression through a mechanism involving increases in PD-L1 mRNA stability via modulation of the AU-rich element-binding protein tristetraprolin (TTP). TTP negatively regulates PD-L1 expression through AU-rich elements in the 3' UTR of PD-L1 mRNA. MEK signaling downstream of RAS leads to phosphorylation and inhibition of TTP by the kinase MK2. In human lung and colorectal tumors, RAS pathway activation is associated with elevated PD-L1 expression. In vivo, restoration of TTP expression enhances anti-tumor immunity dependent on degradation of PD-L1 mRNA. We demonstrate that RAS can drive cell-intrinsic PD-L1 expression, thus presenting therapeutic opportunities to reverse the innately immunoresistant phenotype of RAS mutant cancers.
Topics: Animals; B7-H1 Antigen; Cell Line, Tumor; Colorectal Neoplasms; Epithelial Cells; Female; Gene Expression Regulation, Neoplastic; Humans; Intracellular Signaling Peptides and Proteins; Lung Neoplasms; MAP Kinase Kinase Kinases; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Neoplasm Transplantation; Protein Binding; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins p21(ras); RNA Cleavage; RNA Stability; RNA, Messenger; Signal Transduction; Tristetraprolin; Tumor Escape
PubMed: 29246442
DOI: 10.1016/j.immuni.2017.11.016 -
Science Immunology Oct 2022RNA binding proteins are important regulators of T cell activation, proliferation, and cytokine production. The zinc finger protein 36 (ZFP36) family genes (, , and )...
RNA binding proteins are important regulators of T cell activation, proliferation, and cytokine production. The zinc finger protein 36 (ZFP36) family genes (, , and ) encode RNA binding proteins that promote the degradation of transcripts containing AU-rich elements. Numerous studies have demonstrated both individual and shared functions of the ZFP36 family in immune cells, but their collective function in T cells remains unclear. Here, we found a redundant and critical role for the ZFP36 proteins in regulating T cell quiescence. T cell-specific deletion of all three ZFP36 family members in mice resulted in early lethality, immune cell activation, and multiorgan pathology characterized by inflammation of the eyes, central nervous system, kidneys, and liver. Mice with T cell-specific deletion of any two genes were protected from this spontaneous syndrome. Triply deficient T cells overproduced proinflammatory cytokines, including IFN-γ, TNF, and GM-CSF, due to increased mRNA stability of these transcripts. Unexpectedly, T cell-specific deletion of both and rendered mice resistant to experimental autoimmune encephalomyelitits due to failed priming of antigen-specific CD4 T cells. ZFP36L1 and ZFP36L2 double-deficient CD4 T cells had poor proliferation during in vitro T helper cell polarization. Thus, the ZFP36 family redundantly regulates T cell quiescence at homeostasis, but ZFP36L1 and ZFP36L2 are specifically required for antigen-specific T cell clonal expansion.
Topics: Animals; Mice; Cytokines; Granulocyte-Macrophage Colony-Stimulating Factor; Homeostasis; RNA-Binding Proteins; Tristetraprolin; T-Lymphocytes
PubMed: 36269839
DOI: 10.1126/sciimmunol.abo0981 -
Cell Reports May 2023Cellular metabolism is tightly regulated by growth factor signaling, which promotes metabolic rewiring to support growth and proliferation. While growth factor-induced...
Cellular metabolism is tightly regulated by growth factor signaling, which promotes metabolic rewiring to support growth and proliferation. While growth factor-induced transcriptional and post-translational modes of metabolic regulation have been well defined, whether post-transcriptional mechanisms impacting mRNA stability regulate this process is less clear. Here, we present the ZFP36/L1/L2 family of RNA-binding proteins and mRNA decay factors as key drivers of metabolic regulation downstream of acute growth factor signaling. We quantitatively catalog metabolic enzyme and nutrient transporter mRNAs directly bound by ZFP36 following growth factor stimulation-many of which encode rate-limiting steps in metabolic pathways. Further, we show that ZFP36 directly promotes the mRNA decay of Enolase 2 (Eno2), altering Eno2 protein expression and enzymatic activity, and provide evidence of a ZFP36/Eno2 axis during VEGF-stimulated developmental retinal angiogenesis. Thus, ZFP36-mediated mRNA decay serves as an important mode of metabolic regulation downstream of growth factor signaling within dynamic cell and tissue states.
Topics: RNA-Binding Proteins; Signal Transduction; Intercellular Signaling Peptides and Proteins; RNA Stability; Tristetraprolin
PubMed: 37086408
DOI: 10.1016/j.celrep.2023.112411 -
Proceedings of the National Academy of... Oct 2023Externalized histones erupt from the nucleus as extracellular traps, are associated with several acute and chronic lung disorders, but their implications in the...
Externalized histones erupt from the nucleus as extracellular traps, are associated with several acute and chronic lung disorders, but their implications in the molecular pathogenesis of interstitial lung disease are incompletely defined. To investigate the role and molecular mechanisms of externalized histones within the immunologic networks of pulmonary fibrosis, we studied externalized histones in human and animal bronchoalveolar lavage (BAL) samples of lung fibrosis. Neutralizing anti-histone antibodies were administered in bleomycin-induced fibrosis of C57BL/6 J mice, and subsequent studies used conditional/constitutive knockout mouse strains for TGFβ and IL-27 signaling along with isolated platelets and cultured macrophages. We found that externalized histones (citH3) were significantly ( < 0.01) increased in cell-free BAL fluids of patients with idiopathic pulmonary fibrosis (IPF; = 29) as compared to healthy controls ( = 10). The pulmonary sources of externalized histones were Ly6GCD11b neutrophils and nonhematopoietic cells after bleomycin in mice. Neutralizing monoclonal anti-histone H2A/H4 antibodies reduced the pulmonary collagen accumulation and hydroxyproline concentration. Histones activated platelets to release TGFβ1, which signaled through the TGFbRI/TGFbRII receptor complex on LysM cells to antagonize macrophage-derived IL-27 production. TGFβ1 evoked multiple downstream mechanisms in macrophages, including p38 MAPK, tristetraprolin, IL-10, and binding of SMAD3 to the IL-27 promotor regions. IL-27RA-deficient mice displayed more severe collagen depositions suggesting that intact IL-27 signaling limits fibrosis. In conclusion, externalized histones inactivate a safety switch of antifibrotic, macrophage-derived IL-27 by boosting platelet-derived TGFβ1. Externalized histones are accessible to neutralizing antibodies for improving the severity of experimental pulmonary fibrosis.
Topics: Humans; Mice; Animals; Mice, Inbred C57BL; Histones; Interleukin-27; Blood Platelets; Idiopathic Pulmonary Fibrosis
PubMed: 37756334
DOI: 10.1073/pnas.2215421120 -
Frontiers in Immunology 2021Post-transcriptional regulation is involved in the regulation of many inflammatory genes. Zinc finger protein 36 (ZFP36) family proteins are RNA-binding proteins... (Review)
Review
Post-transcriptional regulation is involved in the regulation of many inflammatory genes. Zinc finger protein 36 (ZFP36) family proteins are RNA-binding proteins involved in messenger RNA (mRNA) metabolism pathways. The ZFP36 family is composed of ZFP36 (also known as tristetraprolin, TTP), ZFP36L1, ZFP36L2, and ZFP36L3 (only in rodents). The ZFP36 family proteins contain two tandemly repeated CCCH-type zinc-finger motifs, bind to adenine uridine-rich elements in the 3'-untranslated regions (3' UTR) of specific mRNA, and lead to target mRNA decay. Although the ZFP36 family members are structurally similar, they are known to play distinct functions and regulate different target mRNAs, probably due to their cell-type-specific expression patterns. For instance, ZFP36 has been well-known to function as an anti-inflammatory modulator in murine models of systemic inflammatory diseases by down-regulating the production of various pro-inflammatory cytokines, including TNF-α. Meanwhile, ZFP36L1 is required for the maintenance of the marginal-zone B cell compartment. Recently, we found that ZFP36L2 reduces the expression of (encoding HELIOS) and suppresses regulatory T cell function. This review summarizes the current understanding of the post-transcriptional regulation of immunological responses and inflammatory diseases by RNA-binding ZFP36 family proteins.
Topics: 3' Untranslated Regions; Animals; Autoimmune Diseases; Cytokines; Genetic Therapy; Genetic Vectors; Genome-Wide Association Study; Humans; Hypersensitivity; Immunity; Inflammation; Mice; Multigene Family; Polymorphism, Single Nucleotide; RNA Interference; RNA Stability; RNA, Messenger; RNA-Binding Proteins; Structure-Activity Relationship; Tristetraprolin; Zinc Fingers
PubMed: 34276705
DOI: 10.3389/fimmu.2021.711633 -
Metabolism: Clinical and Experimental Apr 2023Emerging evidence suggests that crosstalk between Kupffer cells (KCs) and hepatocytes protects against non-alcoholic fatty liver disease (NAFLD). However, the underlying...
OBJECTIVE
Emerging evidence suggests that crosstalk between Kupffer cells (KCs) and hepatocytes protects against non-alcoholic fatty liver disease (NAFLD). However, the underlying mechanisms that lead to the reduction of steatosis in NAFLD remain obscure.
METHODS
Ttp and Ttp mice were fed with a high-fat diet. Hepatic steatosis was analyzed by Nile Red staining and measurement of inflammatory cytokines. Lipid accumulation and cell death were evaluated in co-culture systems with primary hepatocytes and KCs derived from either Ttp or Ttp mice.
RESULTS
Tristetraprolin (TTP), an mRNA binding protein, was essential for the protective effects of metformin in NAFLD. Metformin activated TTP via the AMPK-Sirt1 pathway in hepatocytes and KCs. TTP inhibited TNF-α production in KCs, which in turn decreased hepatocyte necroptosis. Downregulation of Rheb expression by TTP promoted hepatocyte lipophagy via mTORC1 inhibition and increased nuclear translocation of transcription factor-EB (TFEB). Consistently, TTP-deficient NAFLD mice failed to respond to metformin with respect to alleviation of hepatic steatosis, protection of hepatocyte necroptosis, or induction of lipophagy.
CONCLUSIONS
TTP, which is essential for the protective effects of metformin, may represent a novel primary therapeutic target in NAFLD.
Topics: Mice; Animals; Non-alcoholic Fatty Liver Disease; Liver; Kupffer Cells; Metformin; Necroptosis; Hepatocytes; Communication; Autophagy; Diet, High-Fat; Mice, Inbred C57BL; Lipid Metabolism
PubMed: 36773805
DOI: 10.1016/j.metabol.2023.155516 -
International Journal of Molecular... Oct 2018Genetic loss or mutations in tumor suppressor genes promote tumorigenesis. The prospective tumor suppressor tristetraprolin (TTP) has been shown to negatively regulate... (Review)
Review
Genetic loss or mutations in tumor suppressor genes promote tumorigenesis. The prospective tumor suppressor tristetraprolin (TTP) has been shown to negatively regulate tumorigenesis through destabilizing the messenger RNAs of critical genes implicated in both tumor onset and tumor progression. Regulation of TTP has therefore emerged as an important issue in tumorigenesis. Similar to other tumor suppressors, TTP expression is frequently downregualted in various human cancers, and its low expression is correlated with poor prognosis. Additionally, disruption in the regulation of TTP by various mechanisms results in the inactivation of TTP protein or altered TTP expression. A recent study showing alleviation of Myc-driven lymphomagenesis by the forced expression of TTP has shed light on new therapeutic avenues for cancer prevention and treatment through the restoration of TTP expression. In this review, we summarize key oncogenes subjected to the TTP-mediated mRNA degradation, and discuss how dysregulation of TTP can contribute to tumorigenesis. In addition, the control mechanism underlying TTP expression at the posttranscriptional and posttranslational levels will be discussed.
Topics: Animals; Carcinogenesis; Disease Progression; Gene Expression Regulation, Neoplastic; Genes, Tumor Suppressor; Humans; Neoplasms; RNA Stability; RNA, Messenger; Tristetraprolin
PubMed: 30380668
DOI: 10.3390/ijms19113384