In macrophages, the accumulation of cholesteryl esters synthesized by the activated acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT1) results in the foam cell formation, a hallmark of early atherosclerotic lesions...In macrophages, the accumulation of cholesteryl esters synthesized by the activated acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT1) results in the foam cell formation, a hallmark of early atherosclerotic lesions. In this study, with the treatment of a glucocorticoid hormone dexamethasone (Dex), lipid staining results clearly showed the large accumulation of lipid droplets containing cholesteryl esters in THP-1-derived macrophages exposed to lower concentration of the oxidized low-density lipoprotein (ox-LDL). More notably, when treated together with specific anti-ACAT inhibitors, the abundant cholesteryl ester accumulation was markedly diminished in THP-1-derived macrophages, confirming that ACAT is the key enzyme responsible for intracellular cholesteryl ester synthesis. RT-PCR and Western blot results indicated that Dex caused up-regulation of human ACAT1 expression at both the mRNA and protein levels in THP-1 and THP-1-derived macrophages. The luciferase activity assay demonstrated that Dex could enhance the activity of human ACAT1 gene P1 promoter, a major factor leading to the ACAT1 activation, in a cell-specific manner. Further experimental evidences showed that a glucocorticoid response element (GRE) located within human ACAT1 gene P1 promoter to response to the elevation of human ACAT1 gene expression by Dex could be functionally bound with glucocorticoid receptor (GR) proteins. These data supported the hypothesis that the clinical treatment with Dex, which increased the incidence of atherosclerosis, may in part due to enhancing the ACAT1 expression to promote the accumulation of cholesteryl esters during the macrophage-derived foam cell formation, an early stage of atherosclerosis.展开更多
Gastric cancer is one of the most common malignancies worldwide; however, the molecular mechanism in tumorigenesis still needs exploration. BCL2L11 belongs to the BCL-2 family, and acts as a central regulator of the i...Gastric cancer is one of the most common malignancies worldwide; however, the molecular mechanism in tumorigenesis still needs exploration. BCL2L11 belongs to the BCL-2 family, and acts as a central regulator of the intrinsic apoptotic cascade and mediates cell apoptosis. Although miRNAs have been reported to be involved in each stage of cancer development, the role of miR-24 in GC has not been reported yet. In the present study, miR- 24 was found to be up-regulated while the expression of BCL2L11 was inhibited in tumor tissues of GC. Studies from both in vitro and in vivo shown that miR-24 regulates BCL2L11 expression by directly binding with 3＇UTR of mRNA, thus promoting cell growth, migration while inhibiting cell apoptosis. Therefore, miR-24 is a novel onco-miRNA that can be potential drug targets for future clinical use.展开更多
CDK4 is crucial for Gl-to-S transition of cell cycle. It is well established that ubiquitin-mediated degradations of CDK inhibitors and cycUns are pivotal for the timely and unidirectional progression of cell cycle. H...CDK4 is crucial for Gl-to-S transition of cell cycle. It is well established that ubiquitin-mediated degradations of CDK inhibitors and cycUns are pivotal for the timely and unidirectional progression of cell cycle. However, how CDK4 itself is modulated by ubiquitin-mediated degradation has been elusive. Here we report that the steady-state level of CDK4 is controlled by PAQR4, a member of the progestin and adipoQ receptor family, and SKP2, an E3 ubiquitin ligase. Knockdown of PAQR4 leads to reduction of cell proliferation, accompanied by reduced protein level of CDK4. PAQR4 reduces polyubiquitination and degradation of CDK4. PAQR4 interacts with the C-terminal lobe of CDK4. On the other hand, SKP2 also interacts with the C-terminal lobe of CDK4 and enhances polyubiquitination and degradation of CDK4. importantly, PAQR4 and SKP2 bind to the same region in CDK4, and PAQR4 competes with SKP2 for the binding, thereby abrogating SKP2-mediated ubiquitination of CDK4. Using a two-stage DMBA/TPA-induced skin cancer model, we find that PAQR4-deleted mice are resistant to chemical carcinogen-induced tumor formation. Collectively, our findings reveal that the steady-state level of CDK4 is controlled by the antagonistic actions between PAQR4 and SKP2, contributing to modulation of cell proliferation and tumorigenesis.展开更多
基金supported by grants of the Major State Basic Research Development program of China(No.2002CB513000)National Scienses Foudation Center(No.30393110)+1 种基金State Science and Technology Committee(SSTC)(NO.02DJ14068)Chinese Academy of Science to Bo Liang LI,and NIH grant HL36709 to Ta Yuan CHANG.
文摘In macrophages, the accumulation of cholesteryl esters synthesized by the activated acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT1) results in the foam cell formation, a hallmark of early atherosclerotic lesions. In this study, with the treatment of a glucocorticoid hormone dexamethasone (Dex), lipid staining results clearly showed the large accumulation of lipid droplets containing cholesteryl esters in THP-1-derived macrophages exposed to lower concentration of the oxidized low-density lipoprotein (ox-LDL). More notably, when treated together with specific anti-ACAT inhibitors, the abundant cholesteryl ester accumulation was markedly diminished in THP-1-derived macrophages, confirming that ACAT is the key enzyme responsible for intracellular cholesteryl ester synthesis. RT-PCR and Western blot results indicated that Dex caused up-regulation of human ACAT1 expression at both the mRNA and protein levels in THP-1 and THP-1-derived macrophages. The luciferase activity assay demonstrated that Dex could enhance the activity of human ACAT1 gene P1 promoter, a major factor leading to the ACAT1 activation, in a cell-specific manner. Further experimental evidences showed that a glucocorticoid response element (GRE) located within human ACAT1 gene P1 promoter to response to the elevation of human ACAT1 gene expression by Dex could be functionally bound with glucocorticoid receptor (GR) proteins. These data supported the hypothesis that the clinical treatment with Dex, which increased the incidence of atherosclerosis, may in part due to enhancing the ACAT1 expression to promote the accumulation of cholesteryl esters during the macrophage-derived foam cell formation, an early stage of atherosclerosis.
基金This work was supported by grants from the National research platform of clinical evaluation technology for new anticancer drugs （No. 2013ZX09303001 ）, the National Natural Science Foundation of China （Grant Nos. 81201946 and 81372394） and Tianjin City High School Science ＆ Technology Fund Planning Project （20130122）. The funders had no role in study design collection, analysis, and interpretation of data+1 种基金 in the writing of the report and in the decision to submit this article for publication.
文摘Gastric cancer is one of the most common malignancies worldwide; however, the molecular mechanism in tumorigenesis still needs exploration. BCL2L11 belongs to the BCL-2 family, and acts as a central regulator of the intrinsic apoptotic cascade and mediates cell apoptosis. Although miRNAs have been reported to be involved in each stage of cancer development, the role of miR-24 in GC has not been reported yet. In the present study, miR- 24 was found to be up-regulated while the expression of BCL2L11 was inhibited in tumor tissues of GC. Studies from both in vitro and in vivo shown that miR-24 regulates BCL2L11 expression by directly binding with 3＇UTR of mRNA, thus promoting cell growth, migration while inhibiting cell apoptosis. Therefore, miR-24 is a novel onco-miRNA that can be potential drug targets for future clinical use.
文摘CDK4 is crucial for Gl-to-S transition of cell cycle. It is well established that ubiquitin-mediated degradations of CDK inhibitors and cycUns are pivotal for the timely and unidirectional progression of cell cycle. However, how CDK4 itself is modulated by ubiquitin-mediated degradation has been elusive. Here we report that the steady-state level of CDK4 is controlled by PAQR4, a member of the progestin and adipoQ receptor family, and SKP2, an E3 ubiquitin ligase. Knockdown of PAQR4 leads to reduction of cell proliferation, accompanied by reduced protein level of CDK4. PAQR4 reduces polyubiquitination and degradation of CDK4. PAQR4 interacts with the C-terminal lobe of CDK4. On the other hand, SKP2 also interacts with the C-terminal lobe of CDK4 and enhances polyubiquitination and degradation of CDK4. importantly, PAQR4 and SKP2 bind to the same region in CDK4, and PAQR4 competes with SKP2 for the binding, thereby abrogating SKP2-mediated ubiquitination of CDK4. Using a two-stage DMBA/TPA-induced skin cancer model, we find that PAQR4-deleted mice are resistant to chemical carcinogen-induced tumor formation. Collectively, our findings reveal that the steady-state level of CDK4 is controlled by the antagonistic actions between PAQR4 and SKP2, contributing to modulation of cell proliferation and tumorigenesis.
