The REST Gene Signature Predicts Drug Sensitivity in Neuroblastoma Cell Lines and Is Significantly Associated with Neuroblastoma Tumor Stage

Neuroblastoma is the most common and deadly solid tumor in children, and there is currently no effective treatment available for neuroblastoma patients. The repressor element-1 silencing transcription (REST) factor has been found to play important roles in the regulation of neural differentiation and tumorigenesis. Recently, a REST signature consisting of downstream targets of REST has been reported to have clinical relevance in both breast cancer and glioblastoma. However it remains unclear how the REST signature works in neuroblastoma. Publicly available datasets were mined and bioinformatic approaches were used to investigate the utility of the REST signature in neuroblastoma with both preclinical and real patient data. The REST signature was found to be associated with drug sensitivity in neuroblastoma cell lines. Further, neuroblastoma patients with enhanced REST activity are significantly associated with higher clinical stages. Loss of heterozygosity on chromosome 11q23, which occurs in a large subset of high-risk neuroblastomas, tends to be correlated with high REST activity, with marginal significance. In conclusion, the REST signature has important implications for targeted therapy, and it is a prognostic factor in neuroblastoma patients

Identification of Ubr1 as an amino acid sensor of steatosis in liver and muscle

Abstract Background Malnutrition is implicated in human metabolic disorders, including hepatic steatosis and myosteatosis. The corresponding nutrient signals and sensors as well as signalling pathways have not yet been well studied. This study aimed to unravel the nutrient‐sensing mechanisms in the pathogenesis of steatosis. Methods Plin2, a lipid droplet (LD) protein‐inhibiting lipolysis, is associated with steatosis in liver and muscle. Taking advantage of the Gal4‐UAS system, we used the Drosophila melanogaster wing imaginal disc as an in vivo model to study the regulation of Plin2 proteostasis and LD homeostasis. Drosophila Schneider 2 (S2) cells were used for western blotting, immunoprecipitation assays, amino acid‐binding assays and ubiquitination assays to further investigate the regulatory mechanisms of Plin2 in response to nutrient signals. Mouse AML12 hepatocytes, human JHH‐7 and SNU‐475 hepatoma cells were used for immunofluorescence, western blotting and immunoprecipitation to demonstrate that the mode of Plin2 regulation is evolutionarily conserved. In addition, we purified proteins from HEK293 cells and reconstituted in vitro cell‐free systems in amino acid‐binding assays, pulldown assays and ubiquitination assays to directly demonstrate the molecular mechanism by which Ubr1 senses amino acids to regulate Plin2 proteostasis. Results As a lipolysis inhibitor, Plin2 was significantly elevated in liver (P < 0.05) and muscle (P < 0.05) in patients with steatosis. Consistently, we found that the ubiquitin moiety can be conjugated to any Lys residue in Plin2, ensuring robust clearance of Plin2 by protein degradation. We further demonstrated that the E3 ubiquitin ligase Ubr1 targets Plin2 for degradation in an amino acid‐dependent manner. Ubr1 uses two canonical substrate‐binding pockets, independent of each other, to bind basic and bulky hydrophobic amino acids, respectively. Mechanistically, amino acid binding allosterically activates Ubr1 by alleviating Ubr1's auto‐inhibition. In the absence of amino acids, or when the amino acid‐binding capacity of Ubr1 is diminished, Ubr1‐mediated Plin2 degradation is inactivated, leading to steatosis. Conclusions We identified Ubr1 as an amino acid sensor regulating Plin2 proteostasis, bridging the knowledge gap between steatosis and nutrient sensing. Our work may provide new strategies for the prevention and treatment of steatosis

Protein kinase C and protein kinase A are involved in the protection of recombinant human glucagon‐like peptide‐1 on glomeruli and tubules in diabetic rats

Abstract Aims/Introduction Blockade or reversal the progression of diabetic nephropathy is a clinical challenge. The aim of the present study was to examine whether recombinant human glucagon‐like peptide‐1 (rhGLP‐1) has an effect on alleviating urinary protein and urinary albumin levels in diabetic rats. Materials and Methods Streptozotocin‐induced diabetes rats were treated with rhGLP‐1 insulin and saline. Using immunostaining, hematoxylin–eosin, electron microscopy and periodic acid–Schiff staining to study the pathology of diabetic nephropathy, and we carried out quantitative reverse transcription polymerase chain reaction, western blot and immunohistochemistry to identify the differentially expressed proteins. The mechanism was studied through advanced glycation end‐products‐induced tubular epithelial cells. Results rhGLP‐1 inhibits protein kinase C (PKC)‐β, but increases protein kinase A (PKA), which reduces oxidative stress in glomeruli and in cultured glomerular microvascular endothelial cells. In tubules, rhGLP‐1 increased the expression of two key proteins related to re‐absorption – megalin and cubilin – which was accompanied by downregulation of PKC‐β and upregulation of PKA. On human proximal tubular epithelial cells, rhGLP‐1 enhanced the absorption of albumin, and this was blocked by a PKC activator or PKA inhibitor. Conclusions These findings suggest that rhGLP‐1 can reverse diabetic nephropathy by protecting both glomeruli and tubules by inhibiting PKC and activating PKA