scholarly journals The COP9 Signalosome Regulates Skp2 Levels and Proliferation of Human Cells

2006 ◽  
Vol 281 (43) ◽  
pp. 32188-32196 ◽  
Author(s):  
Simona Denti ◽  
Maria Elena Fernandez-Sanchez ◽  
Lars Rogge ◽  
Elisabetta Bianchi
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Kinase Inhibitor ◽  
Human Cells ◽  
Cop9 Signalosome ◽  
Mammalian Development ◽  
Down Regulation ◽  
Protein Levels

The COP9 signalosome (CSN) is a conserved, multisubunit complex first identified as a developmental regulator in plants. Gene inactivation of single CSN subunits results in early embryonic lethality in mice, indicating that the CSN is essential for mammalian development. The pleiotropic function of the CSN may be related to its ability to remove the ubiquitin-like peptide Nedd8 from cullin-RING ubiquitin ligases, such as the SCF complex, and therefore regulate their activity. However, the mechanism of CSN regulatory action on cullins has been debated, since, paradoxically, the CSN has an inhibitory role in vitro, while genetic evidence supports a positive regulatory role in vivo. We have targeted expression of CSN subunits 4 and 5 in human cells by lentivirus-mediated small hairpin RNA delivery. Down-regulation of either subunit resulted in disruption of the CSN complex and in Cullin1 hyperneddylation. Functional consequences of CSN down-regulation were decreased protein levels of Skp2, the substrate recognition subunit of SCFSkp2, and stabilization of a Skp2 target, the cyclin-dependent kinase inhibitor p27Kip1. CSN down-regulation caused an impairment in cell proliferation, which could be partially reversed by suppression of p27Kip1. Moreover, restoring Skp2 levels in CSN-deficient cells recovered cell cycle progression, indicating that loss of Skp2 in these cells plays an important role in their proliferation defect. Our data indicate that the CSN is necessary to ensure the assembly of a functional SCFSkp2 complex and therefore contributes to cell cycle regulation of human cells.

scholarly journals The Cak1p Protein Kinase Is Required at G1/S and G2/M in the Budding Yeast Cell Cycle

Genetics ◽  
1997 ◽  
Vol 147 (1) ◽  
pp. 57-71 ◽  
Author(s):  
Ann Sutton ◽  
Richard Freiman
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Cell Cycle Progression ◽  
Budding Yeast ◽  
Protein Kinase Activity ◽  
Synthetic Lethal ◽  
Protein Levels ◽  
M Phase

Abstract The CAK1 gene encodes the major CDK-activating kinase (CAK) in budding yeast and is required for activation of Cdc28p for cell cycle progression from G2 to M phase. Here we describe the isolation of a mutant allele of CAK1 in a synthetic lethal screen with the Sit4 protein phosphatase. Analysis of several different cak1 mutants shows that although the G2 to M transition appears most sensitive to loss of Cak1p function, Cak1p is also required for activation of Cdc28p for progression from G1 into S phase. Further characterization of these mutants suggests that, unlike the CAK identified from higher eukaryotes, Cak1p of budding yeast may not play a role in general transcription. Finally, although Cak1 protein levels and in vitro protein kinase activity do not fluctuate during the cell cycle, at least a fraction of Cak1p associates with higher molecular weight proteins, which may be important for its in vivo function.

scholarly journals Rho-associated Protein Kinase 2 Confers Epileptogenesis through the Activation of Astroglial Stat3 Pathway

2020 ◽  
Author(s):  
Li-jia Song ◽  
Hua Zhang ◽  
Jun-gong Jin ◽  
Chao Wang ◽  
Xiao-Peng Qu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Kinase Inhibitor ◽  
Expression Profiles ◽  
Control Group ◽  
Drug Resistant ◽  
Cycle Progression ◽  
Stat3 Pathway

Abstract Patients with temporal lobe epilepsy (TLE) are prone to tolerance to antiepileptic drugs. Based on the perspective of molecular targets for drug resistance, it is necessary to explore effective drug resistant genes and signaling pathways for the treatment of TLE. We performed gene expression profiles in hippocampus of patients with drug-resistant TLE and identified ROCK2 as one of the 20 most significantly increased genes in hippocampus. In vitro and in vivo experiments were performed to identify the potential role of ROCK2 in epileptogenesis. In addition, the activity of Stat3 pathway was tested in hippocampal tissues and primary cultured astrocytes. The expression levels of ROCK2 in the hippocampus of TLE patients were significantly increased compared with the control group, which was due to the hypomethylation of ROCK2 promoter. Fasudil, a specific Rho-kinase inhibitor, alleviated epileptic seizures in the pilocarpine rat model of TLE. Furthermore, ROCK2 activated the Stat3 pathway in pilocarpine-treated epilepsy rats, and the spearman correlation method confirmed that ROCK2 is associated with Stat3 activation in TLE patients. In addition, ROCK2 was predominantly expressed in astrocytes during epileptogenesis, and induced epileptogenesis by activating astrocyte cell cycle progression via Stat3 pathway. The overexpressed ROCK2 plays an important role in the pathogenesis of drug-resistant epilepsy. ROCK2 accelerates astrocytes cell cycle progression via the activation of Stat3 pathway likely provides the key to explaining the process of epileptogenesis.

scholarly journals A Circular RNA from the MDM2 Locus Controls Cell Cycle Progression by Suppressing p53 Levels

2020 ◽  
Vol 40 (9) ◽  
Author(s):  
Ritu Chaudhary ◽  
Bruna R. Muys ◽  
Ioannis Grammatikakis ◽  
Supriyo De ◽  
Kotb Abdelmohsen ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
P53 Protein ◽  
Circular Rnas ◽  
Small Interfering Rnas ◽  
Cycle Progression ◽  
Protein Levels

ABSTRACT Circular RNAs (circRNAs) are a class of noncoding RNAs produced by a noncanonical form of alternative splicing called back-splicing. To investigate a potential role of circRNAs in the p53 pathway, we analyzed RNA sequencing (RNA-seq) data from colorectal cancer cell lines (HCT116, RKO, and SW48) that were untreated or treated with a DNA-damaging agent. Surprisingly, unlike the strong p53-dependent induction of hundreds of p53-induced mRNAs upon DNA damage, only a few circRNAs were upregulated from p53-induced genes. circ-MDM2, an annotated circRNA from the MDM2 locus, was one of the handful of circRNAs that originated from a p53-induced gene. Given the central role of MDM2 in suppressing p53 protein levels and p53 activity, we investigated the function of circ-MDM2. Knocking down circ-MDM2 with small interfering RNAs (siRNAs) that targeted circ-MDM2 did not alter MDM2 mRNA or MDM2 protein levels but resulted in increased basal p53 levels and growth defects in vitro and in vivo. Consistent with these results, transcriptome profiling showed increased expression of several direct p53 targets, reduced retinoblastoma protein (Rb) phosphorylation, and defects in G1-S progression upon silencing circ-MDM2. Our results on the initial characterization of circ-MDM2 identify a new player from the MDM2 locus that suppresses p53 levels and cell cycle progression.

scholarly journals ID: 1023 All-trans retinoic acid targets gastric cancer stem cells and inhibits patient-derived gastric carcinoma tumor growth

2017 ◽  
Vol 4 (S) ◽  
pp. 98
Author(s):  
P H Nguyen ◽  
J Giraud ◽  
C Staedel ◽  
L Chambonnier ◽  
P Dubus ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Cancer Stem Cells ◽  
Gastric Carcinoma ◽  
Tumor Growth ◽  
Cell Cycle Progression ◽  
3D Culture ◽  
All Trans Retinoic Acid

Gastric carcinoma is the third leading cause of cancer-related death worldwide. This cancer, most of the time metastatic, is essentially treated by surgery associated with conventional chemotherapy, and has a poor prognosis. The existence of cancer stem cells (CSC) expressing CD44 and a high aldehyde dehydrogenase (ALDH) activity has recently been demonstrated in gastric carcinoma and has opened new perspectives to develop targeted therapy. In this study, we evaluated the effects of all-transretinoic acid (ATRA) on CSCs in human gastric carcinoma. ATRA effects were evaluated on the proliferation and tumorigenic properties of gastric carcinoma cells from patient-derived tumors and cell lines in conventional 2D cultures, in 3D culture systems (tumorsphere assay) and in mouse xenograft models. ATRA inhibited both tumorspheres initiation and growth in vitro, which was associated with a cell-cycle arrest through the upregulation of cyclin-dependent kinase (CDK) inhibitors and the downregulation of cell-cycle progression activators. More importantly, ATRA downregulated the expression of the CSC markers CD44 and ALDH as well as stemness genes such as Klf4 and Sox2 and induced differentiation of tumorspheres. Finally, 2 weeks of daily ATRA treatment were sufficient to inhibit gastric tumor progression in vivo, which was associated with a decrease in CD44, ALDH1, Ki67 and PCNA expression in the remaining tumor cells. Administration of ATRA appears to be a potent strategy to efficiently inhibit tumor growth and more importantly to target gastric CSCs in both intestinal and diffuse types of gastric carcinoma.

Upregulation of SGOL2 Predicts Poor Prognosis and Facilitates Hepatocellular Carcinoma Progression via Dysregulating the Cell Cycle by Directly Activating MAD2

2021 ◽  
Author(s):  
Qingqing Hu ◽  
Xiaochu Hu ◽  
Yalei Zhao ◽  
Lingjian Zhang ◽  
Ya Yang ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Cell Cycle ◽  
The Cancer Genome Atlas ◽  
Loss Of Function ◽  
Protein Levels ◽  
Cancer Genome Atlas ◽  
Centromeric Protein ◽  
Hcc Cells

Abstract Background: Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Shugoshin-like protein 2 (SGOL2) is a centromeric protein that ensures the correct and orderly process of mitosis by protecting and maintaining centripetal adhesions during meiosis and mitosis. However, the role of SGOL2 in cancer is not well understood. Methods: The mRNA and protein levels of SGOL2 and survival analysis were conducted in The Cancer Genome Atlas (TCGA) and further validated in 2 independent cohorts. Differential genes correlated with SGOL2 and mitotic arrest deficient 2 like 1 (MAD2) were obtained using LinkedOmics. Subsequently, loss-of-function and rescue assays were carried out in vitro and in vivo to assess the functions of SGOL2 in hepatic tumorigenisis. Findings: We found that SGOL2 was significantly overexpressed in HCC and predicted unfavorable overall survival in HCC patients. Next, we identified 47 differentially expressed genes positively correlated with both SGOL2 and MAD2 to be mainly involved in the cell cycle. In addition, SGOL2 downregulation suppressed the migration, invasion, proliferation, stemness and EMT of HCC cells and inhibited tumorigenesis in vivo. Furthermore, SGOL2 promoted tumor proliferation by activating MAD2-induced cell cycle dysregulation, which could be reversed by the MAD2 inhibitor M2I-1. We also proved that SGOL2 activated MAD2 by directly binding with MAD2. Conclusions: The results of this study showed that SGOL2 acts as an oncogene in HCC cells by directly activating MAD2 and then dysregulating the cell cycle, thereby providing a potential target for HCC patients in the future.

scholarly journals CDK4/6 inhibitors: a novel strategy for tumor radiosensitization

2020 ◽  
Vol 39 (1) ◽  
Author(s):  
Yilan Yang ◽  
Jurui Luo ◽  
Xingxing Chen ◽  
Zhaozhi Yang ◽  
Xin Mei ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Clinical Studies ◽  
Cell Cycle Progression ◽  
Combined Therapy ◽  
Small Sample ◽  
Combination Strategies ◽  
Novel Strategy ◽  
Underlying Mechanisms

Abstract Recently, the focus of enhancing tumor radiosensitivity has shifted from chemotherapeutics to targeted therapies. Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors are a novel class of selective cell cycle therapeutics that target the cyclin D-CDK4/6 complex and induce G1 phase arrest. These agents have demonstrated favorable effects when used as monotherapy or combined with endocrine therapy and targeted inhibitors, stimulating further explorations of other combination strategies. Multiple preclinical studies have indicated that CDK4/6 inhibitors exhibit a synergistic effect with radiotherapy both in vitro and in vivo. The principal mechanisms of radiosensitization effects include inhibition of DNA damage repair, enhancement of apoptosis, and blockade of cell cycle progression, which provide the rationale for clinical use. CDK4/6 inhibitors also induce cellular senescence and promote anti-tumor immunity, which might represent potential mechanisms for radiosensitization. Several small sample clinical studies have preliminarily indicated that the combination of CDK4/6 inhibitors and radiotherapy exhibited well-tolerated toxicity and promising efficacy. However, most clinical trials in combined therapy remain in the recruitment stage. Further work is required to seek optimal radiotherapy-drug combinations. In this review, we describe the effects and underlying mechanisms of CDK4/6 inhibitors as a radiosensitizer and discuss previous clinical studies to evaluate the prospects and challenges of this combination.

Effect and mechanism of YB-1 knockdown on glioma cell growth, migration, and apoptosis

2020 ◽  
Vol 52 (2) ◽  
pp. 168-179 ◽  
Author(s):  
Huilin Gong ◽  
Shan Gao ◽  
Chenghuan Yu ◽  
Meihe Li ◽  
Ping Liu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Cell Growth ◽  
Glioma Cell ◽  
Cell Transformation ◽  
Malignant Cell ◽  
Protein Levels ◽  
Glioma Progression

Abstract Y-box binding protein 1 (YB-1) is manifested as its involvement in cell proliferation and differentiation and malignant cell transformation. Overexpression of YB-1 is associated with glioma progression and patient survival. The aim of this study is to investigate the influence of YB-1 knockdown on glioma cell progression and reveal the mechanisms of YB-1 knockdown on glioma cell growth, migration, and apoptosis. It was found that the knockdown of YB-1 decreased the mRNA and protein levels of YB-1 in U251 glioma cells. The knockdown of YB-1 significantly inhibited cell proliferation, colony formation, and migration in vitro and tumor growth in vivo. Proteome and phosphoproteome data revealed that YB-1 is involved in glioma progression through regulating the expression and phosphorylation of major proteins involved in cell cycle, adhesion, and apoptosis. The main regulated proteins included CCNB1, CCNDBP1, CDK2, CDK3, ADGRG1, CDH-2, MMP14, AIFM1, HO-1, and BAX. Furthermore, it was also found that YB-1 knockdown is associated with the hypo-phosphorylation of ErbB, mTOR, HIF-1, cGMP-PKG, and insulin signaling pathways, and proteoglycans in cancer. Our findings indicated that YB-1 plays a key role in glioma progression in multiple ways, including regulating the expression and phosphorylation of major proteins associated with cell cycle, adhesion, and apoptosis.

scholarly journals Dynamic Structural Modeling Revealed That Nilotinib Inhibits Smoothened Signaling

Neurosurgery ◽  
2019 ◽  
Vol 66 (Supplement_1) ◽  
Author(s):  
Kirti Kandhwal Chahal ◽  
Jie Li ◽  
Irina Kufareva ◽  
Donald Durden ◽  
Robert Wechsler Reya ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Computational Modeling ◽  
Kinase Inhibitor ◽  
Acquired Resistance ◽  
Protein Docking ◽  
High Rate ◽  
Protein Levels ◽  
Matching Criteria

Abstract INTRODUCTION Dysregulation of the 7-transmembrane receptors Smoothened (SMO) and other components of the Hedgehog (Hh) signaling pathway causes several cancers, including medulloblastoma (MB) and glioblastoma. However, SMO-specific antagonists produced mixed results in clinical trials, marked by a limited efficacy and a high rate of acquired resistance in tumors. METHODS Computational modeling of protein docking sites, analytical configuration modeling of crystallographic data, and in Vitro and in Vivo xenograft experiments. RESULTS Using computational modeling of SMO structure, we discovered that Nilotinib, an FDA-approved receptor tyrosine kinase inhibitor, directly binds to SMO. Furthermore, Nilotinib was more efficacious than the SMO-specific antagonist Vismodegib in inhibiting cell growth and Gli-1 mRNA and protein levels in Hh-dependent MB cells and glioblastoma cells. It also reduced tumor growth in the Hh-dependent MB and glioblastoma mouse xenograft models. These results indicate that in addition to its ability to inhibit several tyrosine kinase-mediated proliferative pathways, Nilotinib is active against the Hh pathway. CONCLUSION The newly discovered extension of Nilotinib target profile holds promise for the treatment of Hh-dependent cancers. It also calls for comprehensive characterization of pharmacology for other drugs and incorporation of their multitarget profiles into drug-disease matching criteria for personalized medicine.

Sign in / Sign up

Export Citation Format

Share Document