The involvement of nuclear factor-κappaB in the nuclear targeting and cyclin E1 upregulating activities of hepatoma upregulated protein

Single cell and bulk RNA expression analyses identify enhanced hexosamine biosynthetic pathway and O-GlcNAcylation in acute myeloid leukemia blasts and stem cells

Introduction

Acute myeloid leukemia (AML) is the most common acute leukemia in adults with an overall poor prognosis and high relapse rate. Multiple factors including genetic abnormalities, differentiation defects and altered cellular metabolism contribute to AML development and progression. Though the roles of oxidative phosphorylation and glycolysis are defined in AML, the role of the hexosamine biosynthetic pathway (HBP), which regulates the O-GlcNAcylation of cytoplasmic and nuclear proteins, remains poorly defined.

Methods

We studied the expression of the key enzymes involved in the HBP in AML blasts and stem cells by RNA sequencing at the single-cell and bulk level. We performed flow cytometry to study OGT protein expression and global O-GlcNAcylation. We studied the functional effects of inhibiting O-GlcNAcylation on transcriptional activation in AML cells by Western blotting and real time PCR and on cell cycle by flow cytometry.

Results

We found higher expression levels of the key enzymes in the HBP in AML as compared to healthy donors in whole blood. We observed elevated O-GlcNAc Transferase (OGT) and O-GlcNAcase (OGA) expression in AML stem and bulk cells as compared to normal hematopoietic stem and progenitor cells (HSPCs). We also found that both AML bulk cells and stem cells show significantly enhanced OGT protein expression and global O-GlcNAcylation as compared to normal HSPCs, validating our in silico findings. Gene set analysis showed substantial enrichment of the NF-κB pathway in AML cells expressing high OGT levels. Inhibition of O-GlcNAcylation decreased NF-κB nuclear translocation and the expression of selected NF-κB-dependent genes controlling cell cycle. It also blocked cell cycle progression suggesting a link between enhanced O-GlcNAcylation and NF-κB activation in AML cell survival and proliferation.

Discussion

Our study suggests the HBP may prove a potential target, alone or in combination with other therapeutic approaches, to impact both AML blasts and stem cells. Moreover, as insufficient targeting of AML stem cells by traditional chemotherapy is thought to lead to relapse, blocking HBP and O-GlcNAcylation in AML stem cells may represent a novel promising target to control relapse.

The crescent-like Golgi ribbon is shaped by the Ajuba/PRMT5/Aurora-A complex-modified HURP

BACKGROUND

Golgi apparatus (GA) is assembled as a crescent-like ribbon in mammalian cells under immunofluorescence microscope without knowing the shaping mechanisms. It is estimated that roughly 1/5 of the genes encoding kinases or phosphatases in human genome participate in the assembly of Golgi ribbon, reflecting protein modifications play major roles in building Golgi ribbon.

METHODS

To explore how Golgi ribbon is shaped as a crescent-like structure under the guidance of protein modifications, we identified a protein complex containing the scaffold proteins Ajuba, two known GA regulators including the protein kinase Aurora-A and the protein arginine methyltransferase PRMT5, and the common substrate of Aurora-A and PRMT5, HURP. Mutual modifications and activation of PRMT5 and Aurora-A in the complex leads to methylation and in turn phosphorylation of HURP, thereby producing HURP p725. The HURP p725 localizes to GA vicinity and its distribution pattern looks like GA morphology. Correlation study of the HURP p725 statuses and GA structure, site-directed mutagenesis and knockdown-rescue experiments were employed to identify the modified HURP as a key regulator assembling GA as a crescent ribbon.

RESULTS

The cells containing no or extended distribution of HURP p725 have dispersed GA membranes or longer GA. Knockdown of HURP fragmentized GA and HURP wild type could, while its phosphorylation deficiency mutant 725A could not, restore crescent Golgi ribbon in HURP depleted cells, collectively indicating a crescent GA-constructing activity of HURP p725. HURP p725 is transported, by GA membrane-associated ARF1, Dynein and its cargo adaptor Golgin-160, to cell center where HURP p725 forms crescent fibers, binds and stabilizes Golgi assembly factors (GAFs) including TRIP11, GRASP65 and GM130, thereby dictating the formation of crescent Golgi ribbon at nuclear periphery.

CONCLUSIONS

The Ajuba/PRMT5/Aurora-A complex integrates the signals of protein methylation and phosphorylation to HURP, and the HURP p725 organizes GA by stabilizing and recruiting GAFs to its crescent-like structure, therefore shaping GA as a crescent ribbon. Therefore, the HURP p725 fiber serves a template to construct GA according to its shape. Video Abstract.

DLGAP5 knockdown inactivates the Wnt/β-catenin signal to repress endometrial cancer cell malignant activities

Human discs large-associated protein 5 (DLGAP5), a microtubule-associated protein, has been reported to be upregulated in several tumors. However, the role of DLGAP5 in endometrial cancer (EC) progression and the related underlying mechanism were still unknown. A bioinformatics analysis was performed to analyze the expression and prognostic significance of DLGAP5 in EC tissues using TCGA, CPTAC, Human Protein Atlas, and GSE63678 databases, UALCAN web tool, and the Kaplan-Meier plotter. Effects of DLGAP on EC cell malignant properties were evaluated by CCK-8, flow cytometry analysis, TUNEL assay, caspase-3 activity assay, and Transwell invasion assay. The expression of DLGAP5, Wnt3, c-Myc, Ki67, and cleaved caspase-3 was detected by western blot analysis. DLGAP5 was highly expressed and correlated with poor prognosis in EC patients. DLGAP5 knockdown inhibited proliferation and invasion, triggered apoptosis, and increased caspase-3 activity in EC cells. Additionally, DLGAP5 knockdown inactivated the Wnt/β-catenin signaling pathway in EC cells. Moreover, β-catenin overexpression abolished the effects of DLGAP5 knockdown on the malignant phenotypes of EC cells. DLGAP5 silencing suppressed the malignant properties in EC cells by inactivating the Wnt/β-catenin pathway.

The JMJD6/HURP axis promotes cell migration via NF-κB-dependent centrosome repositioning and Cdc42-mediated Golgi repositioning

Golgi apparatus (GA) and centrosome reposition toward cell leading end during directional cell migration in a coupling way, thereby determining cell polarity by transporting essential factors to the proximal plasma membrane. The study provides mechanistic insights into how GA repositioning (GR) is regulated, and how GR and centrosome repositioning (CR) are coupled. Our previous published works reveals that PRMT5 methylates HURP at R122 and the HURP m122 inhibits GR and cell migration by stabilizing GA-associated acetyl-tubulin and then rigidifying GA. The current study further shows that the demethylase JMJD6-guided demethylation of HURP at R122 promotes GR and cell migration. The HURP methylation mimicking mutant 122 F blocks JMJD6-induced GR and cell migration, suggesting JMJD6 relays GR stimulating signal to HURP. Mechanistic studies reveal that the HURP methylation deficiency mutant 122 K promotes GR through NF-κB-induced CR and subsequently CR-dependent Cdc42 upregulation, where Cdc42 couples CR to GR. Taken together, HURP methylation statuses provide a unique opportunity to understand how GR is regulated, and the GA intrinsic mechanism controlling Golgi rigidity and the GA extrinsic mechanism involving NF-κB-CR-Cdc42 cascade collectively dictate GR.

The PRMT5/HURP axis retards Golgi repositioning by stabilizing acetyl-tubulin and Golgi apparatus during cell migration

The Golgi apparatus (GA) translocates to the cell leading end during directional migration, thereby determining cell polarity and transporting essential factors to the migration apparatus. The study provides mechanistic insights into how GA repositioning (GR) is regulated. We show that the methyltransferase PRMT5 methylates the microtubule regulator HURP at R122. The HURP methylation mimicking mutant 122F impairs GR and cell migration. Mechanistic studies revealed that HURP 122F or endogenous methylated HURP, that is, HURP m122, interacts with acetyl-tubulin. Overexpression of HURP 122F stabilizes the bundling pattern of acetyl-tubulin by decreasing the sensitivity of the latter to a microtubule disrupting agent nocodazole. HURP 122F also rigidifies GA via desensitizing the organelle to several GA disrupting chemicals. Similarly, the acetyl-tubulin mimicking mutant 40Q or tubulin acetyltransferase αTAT1 can rigidify GA, impair GR, and retard cell migration. Reversal of HURP 122F-induced GA rigidification, by knocking down GA assembly factors such as GRASP65 or GM130, attenuates 122F-triggered GR and cell migration. Remarkably, PRMT5 is found downregulated and the level of HURP m122 is decreased during the early hours of wound healing-based cell migration, collectively implying that the PRMT5-HURP-acetyl-tubulin axis plays the role of brake, preventing GR and cell migration before cells reach empty space.

Identification and prognostic value of DLGAP5 in endometrial cancer

Background

Endometrial cancer poses a serious threat to women’s health worldwide, and its pathogenesis, although actively explored, is not fully understood. DLGAP5 is a recently identified cell cycle-regulation gene not reported in endometrial cancer. This study was aiming to analyze the role of DLGAP5 in tumorigenesis and development and to investigate its prognostic significance of patients with endometrial cancer.

Methodology

Microarray datasets (GSE17025, GSE39099 and GSE63678) from the GEO database were used for comparative analysis, and their intersection was obtained by applying the Venn diagram, and DLGAP5 was selected as the target gene. Next, transcriptome data (n = 578) was downloaded from TCGA-UCEC to analyze the mRNA expression profile of DLGAP5. Then, immunohistochemical data provided by HPA were used to identify the different protein expression levels of DLGAP5 in tumor tissues and normal tissues. Subsequently, the prognostic meaning of DLGAP5 in patients with endometrial cancer was explored based on survival data from TCGA-UCEC (n = 541). Finally, the reliability of DLGAP5 expression was verified by RT-qPCR.

Results

Transcriptome data from TCGA-UCEC, immunohistochemical data from HPA, and RT-qPCR results from clinical samples were used for triple validation to confirm that the expression of DLGAP5 in endometrial cancer tissues was significantly higher than that in normal endometrial tissues. Kaplan–Meier survival analysis announced that the expression level of DLGAP5 was negatively correlated with the overall survival of patients with endometrial cancer.

Conclusions

DLGAP5 is a potential oncogene with cell cycle regulation, and its overexpression can predict the poor prognosis of patients with endometrial cancer. As a candidate target for the diagnosis and treatment of endometrial cancer, it is worthwhile to make further study to reveal the carcinogenicity of DLGAP5 and the mechanism of its resistance of organisms.

β-TrCP1 promotes cell proliferation via TNF-dependent NF-κB activation in diffuse large B cell lymphoma

Diffuse large B cell lymphoma (DLBCL), a heterogeneous group of invasive disease, is the most common type of B-cell non-Hodgkin's lymphomas. The mechanism of its development is closely related to the constitutive activation of NF-κB. In this study, we investigated the function and the mechanism of β-TRCP1 in DLBCL. CCK8 and EdU assays showed that β-TRCP1 could promote the growth of DLBCL cells under the stimulation of TNFα. Furthermore, overexpression of β-TRCP1 enhanced NF-κB activation in the presence of TNFα. Moreover, ectopic expression of β-TRCP1 decreased IκB-α expression but increased phospho-p65 expression. In addition, β-TRCP1 promoted cell cycle progression by accelerating G1-S phase transition. We also found that silencing of β-TrCP1 increased mitoxantrone-induced cell growth arrest and apoptosis. Based on these, we proposed that the expression of β-TRCP1 promoted cell proliferation via TNF-dependent NF-κB activation in DLBCL cells.

Identification and functional analysis of a core gene module associated with hepatitis C virus-induced human hepatocellular carcinoma progression

Hepatitis C virus (HCV)-induced human hepatocellular carcinoma (HCC) progression may be due to a complex multi-step processes. The developmental mechanism of these processes is worth investigating for the prevention, diagnosis and therapy of HCC. The aim of the present study was to investigate the molecular mechanism underlying the progression of HCV-induced hepatocarcinogenesis. First, the dynamic gene module, consisting of key genes associated with progression between the normal stage and HCC, was identified using the Weighted Gene Co-expression Network Analysis tool from R language. By defining those genes in the module as seeds, the change of co-expression in differentially expressed gene sets in two consecutive stages of pathological progression was examined. Finally, interaction pairs of HCV viral proteins and their directly targeted proteins in the identified module were extracted from the literature and a comprehensive interaction dataset from yeast two-hybrid experiments. By combining the interactions between HCV and their targets, and protein-protein interactions in the Search Tool for the Retrieval of Interacting Genes database (STRING), the HCV-key genes interaction network was constructed and visualized using Cytoscape software 3.2. As a result, a module containing 44 key genes was identified to be associated with HCC progression, due to the dynamic features and functions of those genes in the module. Several important differentially co-expressed gene pairs were identified between non-HCC and HCC stages. In the key genes, cyclin dependent kinase 1 (CDK1), NDC80, cyclin A2 (CCNA2) and rac GTPase activating protein 1 (RACGAP1) were shown to be targeted by the HCV nonstructural proteins NS5A, NS3 and NS5B, respectively. The four genes perform an intermediary role between the HCV viral proteins and the dysfunctional module in the HCV key genes interaction network. These findings provided valuable information for understanding the mechanism of HCV-induced HCC progression and for seeking drug targets for the therapy and prevention of HCC.

Prognostic and predictive value of HURP in non‑small cell lung cancer

Previous studies have revealed that HURP (also known as DLGAP5 or KIAA0008) is overexpressed in many types of human cancers, such as hepatocellular carcinoma, squamous cell bladder cancer, and transitional cell carcinoma, indicating that HURP is a putative oncoprotein that promotes carcinogenesis through various molecular mechanisms. However, the role of HURP in the pathogenesis of non-small cell lung cancer (NSCLC) has not been reported. In the present study, we investigated the prognostic value of HURP among NSCLC patients through the GEO database. The online tool of KM-plotter was used to identify the correlation of HURP expression and the survival of NSCLC patients. We found the HURP expression at the mRNA level was correlated with the clinicopathologic characteristics and prognosis of NSCLC patients. HURP was highly expressed in aggressive NSCLC cells, and its higher expression was associated with shorter survival. Further cytological experiments revealed that the silencing of HURP caused cell cycle arrest and inhibited the proliferation of NSCLC cells. Transwell assay showed that HURP shRNA inhibited cell migration and invasion in vitro. The bioinformatic analysis suggests that HURP promotes carcinogenesis in multiple manners. Taken together, we revealed the prognostic value of HURP in NSCLC patients and HURP may be a potential therapeutic target for NSCLC.

Downregulation of miR-16 via URGCP pathway contributes to glioma growth

Experimental and clinical evidence points to a critical role of Upregulator of cell proliferation (URGCP/URG4) in controlling the progression of multiple tumors. However, the oncogenic role of URGCP in glioma still remains elusive. In this study we tried to investigate the oncogenic roles and molecular mechanisms of URGCP in glioma. We found that the levels of URGCP were upregulated in glioma, and that the high-levels of URGCP indicated a worse prognosis in glioma patients. URGCP and miR-16 are critical for glioma growth: silencing URGCP (shURGCP) inhibited glioma growth, while, the shURGCP-mediated proliferative inhibition could be recovered by antagonizing miR-16 (anta-miR-16) in vivo and in vitro. Mechanically, URGCP repressed miR-16 expression via activating NF-κB/c-myc pathway in glioma; Cyclins D1 and Cyclin E1 were identified as the direct targets of miR-16, thus, URGCP-mediated miR-16 downregulation accelerated cell proliferation by upregulating Cyclin D1 and Cyclin E1 expression. All these results suggested that URGCP accelerates glioma growth through the NF-κB/c-myc/miR-16/Cyclin D1/E1 pathway, and both URGCP and miR-16 function as a novel cell cycle regulators in glioma and could be considered as potential targets for glioma therapy.