Ribosomal protein L10A and signaling pathway

Silencing RPL8 inhibits the progression of hepatocellular carcinoma by down-regulating the mTORC1 signalling pathway

This study aimed to explore the role of ribosomal protein L8 (RPL8) in controlling hepatocellular carcinoma (LIHC) development. We measured RPL8 expression, apoptosis, cell viability, proliferation, migration, invasion, glucose uptake, lactate production, and the ATP/ADP ratio of LIHC cells to investigate the effect of RPL8 on LIHC. Bioinformatic analysis was employed to analyse RPL8 expression and its potential mechanism in LIHC. RPL8 was upregulated in LIHC tissues and cells. RPL8 silencing accelerated apoptosis and suppressed viability, growth, and movement of LIHC cells. Additionally, RPL8 silencing inhibited glycolysis in LIHC cells. Bioinformatic analysis revealed that RPL8 is regulated by the upstream transcription factor upstream stimulating factor 1 (USF1) and activates the mTORC1 signalling pathway. USF1 overexpression eliminated the inhibitory effect of RPL8 silencing in LIHC cells. RPL8 overexpression increased cell growth, movement, and glycolysis in LIHC. However, inhibition of the mTORC1 signalling pathway eliminated the effect of RPL8 overexpression on LIHC cells. In conclusion, RPL8 may affect LIHC progression by regulating the mTORC1 signalling pathway.

Misregulation of the Nucleoporins 98 and 96 lead to defects in protein synthesis that promote hallmarks of tumorigenesis

Nucleoporin 98KD (Nup98) is a promiscuous translocation partner in hematological malignancies. Most disease models of Nup98 translocations involve ectopic expression of the fusion protein under study, leaving the endogenous Nup98 loci unperturbed. Overlooked in these approaches is the loss of one copy of normal Nup98 in addition to the loss of Nup96 – a second Nucleoporin encoded within the same mRNA and reading frame as Nup98 – in translocations. Nup98 and Nup96 are also mutated in a number of other cancers, suggesting that their disruption is not limited to blood cancers. We found that reducing Nup98-96 function in Drosophila melanogaster (in which the Nup98-96 shared mRNA and reading frame is conserved) de-regulates the cell cycle. We found evidence of overproliferation in tissues with reduced Nup98-96, counteracted by elevated apoptosis and aberrant signaling associated with chronic wounding. Reducing Nup98-96 function led to defects in protein synthesis that triggered JNK signaling and contributed to hallmarks of tumorigenesis when apoptosis was inhibited. We suggest that partial loss of Nup98-96 function in translocations could de-regulate protein synthesis, leading to signaling that cooperates with other mutations to promote tumorigenesis.

Editor's choice: Compromising Nucleoporins 98 and 96 leads to defects in protein synthesis and stress signaling via JNK that triggers compensatory and apoptosis-induced proliferation.

DNA methylation-based profiling reveals distinct clusters with survival heterogeneity in high-grade serous ovarian cancer

High-grade serous ovarian cancer (HGSOC) is the most common type of epigenetically heterogeneous ovarian cancer. Methylation typing has previously been used in many tumour types but not in HGSOC. Methylation typing in HGSOC may promote the development of personalized care. The present study used DNA methylation data from The Cancer Genome Atlas database and identified four unique methylation subtypes of HGSOC. With the poorest prognosis and high frequency of residual tumours, cluster 4 featured hypermethylation of a panel of genes, which indicates that demethylation agents may be tested in this group and that neoadjuvant chemotherapy may be used to reduce the possibility of residual lesions. Cluster 1 and cluster 2 were significantly associated with metastasis genes and metabolic disorders, respectively. Two feature CpG sites, cg24673765 and cg25574024, were obtained through Cox proportional hazards model analysis of the CpG sites. Based on the methylation level of the two CpG sites, the samples were classified into high- and low-risk groups to identify the prognostic information. Similar results were obtained in the validation set. Taken together, these results explain the epigenetic heterogeneity of HGSOC and provide guidance to clinicians for the prognosis of HGSOC based on DNA methylation sites.

Sox9 Determines Translational Capacity During Early Chondrogenic Differentiation of ATDC5 Cells by Regulating Expression of Ribosome Biogenesis Factors and Ribosomal Proteins

Introduction

In addition to the well-known cartilage extracellular matrix-related expression of Sox9, we demonstrated that chondrogenic differentiation of progenitor cells is driven by a sharply defined bi-phasic expression of Sox9: an immediate early and a late (extracellular matrix associated) phase expression. In this study, we aimed to determine what biological processes are driven by Sox9 during this early phase of chondrogenic differentiation.

Materials

Sox9 expression in ATDC5 cells was knocked down by siRNA transfection at the day before chondrogenic differentiation or at day 6 of differentiation. Samples were harvested at 2 h and 7 days of differentiation. The transcriptomes (RNA-seq approach) and proteomes (Label-free proteomics approach) were compared using pathway and network analyses. Total protein translational capacity was evaluated with the SuNSET assay, active ribosomes were evaluated with polysome profiling, and ribosome modus was evaluated with bicistronic reporter assays.

Results

Early Sox9 knockdown severely inhibited chondrogenic differentiation weeks later. Sox9 expression during the immediate early phase of ATDC5 chondrogenic differentiation regulated the expression of ribosome biogenesis factors and ribosomal protein subunits. This was accompanied by decreased translational capacity following Sox9 knockdown, and this correlated to lower amounts of active mono- and polysomes. Moreover, cap- versus IRES-mediated translation was altered by Sox9 knockdown. Sox9 overexpression was able to induce reciprocal effects to the Sox9 knockdown.

Conclusion

Here, we identified an essential new function for Sox9 during early chondrogenic differentiation. A role for Sox9 in regulation of ribosome amount, activity, and/or composition may be crucial in preparation for the demanding proliferative phase and subsequent cartilage extracellular matrix production of chondroprogenitors in the growth plate in vivo.

Dual Inhibition of DKC1 and MEK1/2 Synergistically Restrains the Growth of Colorectal Cancer Cells

Colorectal cancer, one of the most commonly diagnosed cancers worldwide, is often accompanied by uncontrolled proliferation of tumor cells. Dyskerin pseudouridine synthase 1 (DKC1), screened using the genome-wide RNAi strategy, is a previously unidentified key regulator that promotes colorectal cancer cell proliferation. Enforced expression of DKC1, but not its catalytically inactive mutant D125A, accelerates cell growth in vitro and in vivo. DKC1 knockdown or its inhibitor pyrazofurin attenuates cell proliferation. Proteomics, RNA immunoprecipitation (RIP)-seq, and RNA decay analyses reveal that DKC1 binds to and stabilizes the mRNA of several ribosomal proteins (RPs), including RPL10A, RPL22L1, RPL34, and RPS3. DKC1 depletion significantly accelerates mRNA decay of these RPs, which mediates the oncogenic function of DKC1. Interestingly, these DKC1-regulated RPs also interact with HRAS and suppress the RAS/RAF/MEK/ERK pathway. Pyrazofurin and trametinib combination synergistically restrains colorectal cancer cell growth in vitro and in vivo. Furthermore, DKC1 is markedly upregulated in colorectal cancer tissues compared to adjacent normal tissues. Colorectal cancer patients with higher DKC1 expression has consistently poorer overall survival and progression-free survival outcomes. Taken together, these data suggest that DKC1 is an essential gene and candidate therapeutic target for colorectal cancer.

Effect of the interaction between ribosomal protein L10a and insulin receptor on carbohydrate metabolism

The number of patients with insulin-resistant diabetes has significantly increased. Thus, alternative insulin mimetics are required for such patients. Some evidences indicate that ribosomal protein L10a (RpL10a) is involved in the insulin pathway. In addition, we previously demonstrated that recombinant RpL10a from Fenneropenaeus merguiensis (Fm-RpL10a) could stimulate cell proliferation and trehalose metabolism in RpL10a–over-expressing flies by inducing insulin receptor (InR) expression and some insulin signaling mediators phosphorylation. In this study, we investigated the in silico binding between Fm-RpL10a and InR. The results indicated that Fm-RpL10a bound to InR at residues 635–640 and 697–702 of the FnIII2 domain. This binding was confirmed using a pull-down and immunofluorescence assay. Further analysis indicated that Fm-RpL10a could stimulate glucose utilisation by insulin-resistant cells (IRCs) and healthy cells. Additionally, Fm-RpL10a at a low concentration (1 μg/ml) altered some glucose metabolism-related genes expression in Fm-RpL10a treated IRCs. The qRT-PCR result revealed the up-regulation of Hk1, which encode key enzymes in glycolysis. Conversely, the expression of G6pc3, which participates in gluconeogenesis, was down-regulated. Overall, the results suggest that Fm-RpL10a can alleviate insulin resistance by stimulating insulin signaling via the FnIII2 domain of InR and activate glycolysis. Therefore, Fm-RpL10a may be a candidate insulin mimetic for the treatment of diabetes.