Project description:Aging involves morphological and functional changes across different organs, but how these changes are linked among the different organs remains to be elucidated. Here, we uncover a central role of platelets in sys temic aging. In aged mice, the levels of platelet secreted pro inflammatory factors (PSPF) increased greatly in the serum and platelets, leading to a diffuse increase of platelet infiltration in brain, liver, lung, kidney, and aortic root. The RNA binding protein HuR/ELAVL1, a major regulator of R NA metabolism, promoted the production of PSPF in platelets. Platelet specific deletion of HuR reduced the expression of PSPF in platelets, alleviated platelet infiltration in brain, liver, lung, kidney, and aortic root, and delayed systemic aging. Our findings highlight a role of platelets in coordinating aging traits across organs.
Project description:Background and Aims: Recent studies have implicated platelets, particularly α-granules, in the development of steatohepatitis (NASH). However, the specific mechanisms involved have yet to be determined. Notably, thrombospondin 1 (TSP1) is a major component of the platelet α-granules released during platelet activation. The role of platelet-derived TSP1 in NASH remains unknown and was investigated in this study. Approach and Results: Platelet-specific TSP1 knockout mice (TSP1Δpf4) and their wild type littermates (TSP1F/F) were used. NASH was induced by feeding the mice a diet enriched in fat, sucrose, fructose, and cholesterol (AMLN diet). A human liver NASH organoid model was also employed. Although TSP1 deletion in platelets did not affect diet-induced steatosis, TSP1Δpf4 mice exhibited attenuated NASH and liver fibrosis, accompanied by improvements in plasma glucose and lipid homeostasis. Moreover, intrahepatic platelet accumulation, activation and chemokine production were reduced in TSP1Δpf4 mice, which was correlated with decreased immune cell infiltration into the liver. Consequently, this leads to diminished pro-inflammatory signaling in the liver and mitigated the progression of NAFLD. Moreover, in vitro data revealed that co-culturing TSP1-deficient platelets in a human liver NASH organoid model attenuated hepatic stellate cell activation and NASH progression. Additionally, TSP1 deficient platelets play a role in regulating brown fat endocrine function, specifically affecting Nrg4 production. Crosstalk between brown fat and the liver may also influence NAFLD progression. Conclusions: These data suggest that platelet α-granule-derived TSP1 is a significant contributor to diet-induced NASH and fibrosis, and may serve as a new therapeutic target for this severe liver disease.
Project description:RNA-binding proteins coordinate the fates of multiple RNAs, but the principles underlying these global interactions remain poorly understood. We elucidated regulatory mechanisms of the RNA-binding protein HuR, by integrating data from diverse high-throughput targeting technologies, specifically PAR-CLIP, RIP-chip, and whole-transcript expression profiling. The number of binding sites per transcript, degree of HuR-association, and degree of HuR-dependent RNA stabilization were positively correlated. Pre-mRNA and mature mRNA containing both intronic and 3' UTR binding sites were more highly stabilized than transcripts with only 3' UTR or only intronic binding sites, suggesting that HuR couples pre-mRNA processing with mature mRNA stability. We also observed HuR-dependent splicing changes and substantial binding of HuR in poly-pyrimidine tracts of pre-mRNAs. Comparison of the spatial patterns surrounding HuR and miRNA binding sites provided functional evidence for HuR-dependent antagonism of proximal miRNA-mediated repression. We conclude that HuR coordinates gene expression outcomes at multiple interconnected steps of RNA processing. HuR (ELAVL1) PAR-CLIP
Project description:The Human antigen R protein (HuR) is a RNA-binding protein that recognizes U/AU-rich elements in diverse RNAs through two RNA-recognition motifs, RRM1 and RRM2, and post-transcriptionally regulates the fate of target RNAs. The natural product Dihydrotanshinone-I (DHTS) prevents the association of HuR and target RNAs in vitro and in cultured cells by interfering with the binding of HuR to RNA. Here, we report the structural determinants of the interaction between DHTS and HuR and the impact of DHTS on HuR binding to target mRNAs transcriptome-wide. NMR titration and Molecular Dynamic simulation identified the residues within RRM1 and RRM2 responsible for the interaction between DHTS and HuR. RNA Electromobility Shifts and Alpha Screen Assays showed that DHTS interacts with HuR through the same binding regions as target RNAs, stabilizing HuR in a locked conformation that hampers RNAs binding competitively. HuR ribonucleoprotein immunoprecipitation followed by microarray (RIP-chip) analysis showed that DHTS treatment of HeLa cells paradoxically enriched HuR binding to mRNAs with longer 3’UTR and with higher density of U/AU-rich elements, suggesting that DHTS inhibits the association of HuR to weaker target mRNAs. In vivo, DHTS potently inhibited xenograft tumor growth in a HuR-dependent model without systemic toxicity.
Project description:Identify mRNA targets of the RNA-binding protein HuR in vivo during Schwann cell development using RIP-chip analysis. IP protocol of endogenous mRNA-transfected HuR complexes was performed as described in Keene et al. (2006). In brief, 500 mg of whole-cell lysate obtained from a pool of NB or P5 sciatic nerves from C57BL6J mice were incubated with a suspension of Protein Sepharose beads (Sigma-Aldrich), pre-coated with 15 mg of either IgG1 (BD Pharmingen) or anti-HuR (Santa Cruz Biotechnology) antibodies. mRNAs were isolated using the phenol-chloroform method.
Project description:RNA-binding proteins coordinate the fates of multiple RNAs, but the principles underlying these global interactions remain poorly understood. We elucidated regulatory mechanisms of the RNA-binding protein HuR, by integrating data from diverse high-throughput targeting technologies, specifically PAR-CLIP, RIP-chip, and whole-transcript expression profiling. The number of binding sites per transcript, degree of HuR-association, and degree of HuR-dependent RNA stabilization were positively correlated. Pre-mRNA and mature mRNA containing both intronic and 3' UTR binding sites were more highly stabilized than transcripts with only 3' UTR or only intronic binding sites, suggesting that HuR couples pre-mRNA processing with mature mRNA stability. We also observed HuR-dependent splicing changes and substantial binding of HuR in poly-pyrimidine tracts of pre-mRNAs. Comparison of the spatial patterns surrounding HuR and miRNA binding sites provided functional evidence for HuR-dependent antagonism of proximal miRNA-mediated repression. We conclude that HuR coordinates gene expression outcomes at multiple interconnected steps of RNA processing.
Project description:Human antigen R (HuR) protein, a RNA binding protein (RBP), has been reported to regulate essential steps in RNA metabolism and immune response in a variety of cell types, but its function in metabolism remains unclear. This study identifies HuR as a major repressor during adipogenesis. Knockdown and overexpression of HuR in primary adipocyte culture enhances and inhibits adipogenesis in vitro, respectively. Fat-specific knockout of HuR significantly enhances adipogenic gene program in all three major adipose tissues including epidydimal, inguinal white and brown adipose tissue, accompanied with systemic glucose intolerance and insulin resistance. Conversely, transgenic overexpression of HuR in adipose tissue prevents the HFD induced obesity by repressing adipogenesis. Mechanistically, HuR may inhibit adipogenesis by recognizing and modulating the stability of hundreds of adipocyte transcripts, including the mRNA of Insig1, a negative regulator during adipogenesis. Taken together, our work establishes HuR as a novel posttranscriptional regulator of adipogenesis and provides a new insight into how RNA processing contributes to adipocyte development.
Project description:Human antigen R (HuR) protein, a RNA binding protein (RBP), has been reported to regulate essential steps in RNA metabolism and immune response in a variety of cell types, but its function in metabolism remains unclear. This study identifies HuR as a major repressor during adipogenesis. Knockdown and overexpression of HuR in primary adipocyte culture enhances and inhibits adipogenesis in vitro, respectively. Fat-specific knockout of HuR significantly enhances adipogenic gene program in all three major adipose tissues including epidydimal, inguinal white and brown adipose tissue, accompanied with systemic glucose intolerance and insulin resistance. Conversely, transgenic overexpression of HuR in adipose tissue prevents the HFD induced obesity by repressing adipogenesis. Mechanistically, HuR may inhibit adipogenesis by recognizing and modulating the stability of hundreds of adipocyte transcripts, including the mRNA of Insig1, a negative regulator during adipogenesis. Taken together, our work establishes HuR as a novel posttranscriptional regulator of adipogenesis and provides a new insight into how RNA processing contributes to adipocyte development.
Project description:Human antigen R (HuR) protein, a RNA binding protein (RBP), has been reported to regulate essential steps in RNA metabolism and immune response in a variety of cell types, but its function in metabolism remains unclear. This study identifies HuR as a major repressor during adipogenesis. Knockdown and overexpression of HuR in primary adipocyte culture enhances and inhibits adipogenesis in vitro, respectively. Fat-specific knockout of HuR significantly enhances adipogenic gene program in all three major adipose tissues including epidydimal, inguinal white and brown adipose tissue, accompanied with systemic glucose intolerance and insulin resistance. Conversely, transgenic overexpression of HuR in adipose tissue prevents the HFD induced obesity by repressing adipogenesis. Mechanistically, HuR may inhibit adipogenesis by recognizing and modulating the stability of hundreds of adipocyte transcripts, including the mRNA of Insig1, a negative regulator during adipogenesis. Taken together, our work establishes HuR as a novel posttranscriptional regulator of adipogenesis and provides a new insight into how RNA processing contributes to adipocyte development.