The sphingosine kinases, SK1 and SK2, produce the potent signaling lipid sphingosine-1-phosphate (S1P). These enzymes have garnered increasing interest for their roles in tumorigenesis, inflammation, vascular diseases...The sphingosine kinases, SK1 and SK2, produce the potent signaling lipid sphingosine-1-phosphate (S1P). These enzymes have garnered increasing interest for their roles in tumorigenesis, inflammation, vascular diseases, and immunity, as well as other functions. The sphingosine kinases are considered signaling enzymes by producing S1P, and their activity is acutely regulated by a variety of agonists. However, these enzymes are also key players in the control of sphingolipid metabolism. A variety of sphingolipids, such as sphingosine and the ceramides, are potent signaling molecules in their own right. The role of sphingosine kinases in regulating sphingolipid metabolism is potentially a critical aspect of their signaling function. A central aspect of signaling lipids is that their hydrophobic nature constrains them to membranes. Most enzymes of sphingolipid metabolism, including the enzymes that degrade S1P, are membrane enzymes. Therefore the localization of the sphingosine kinases and S1P is likely to be important in S1P signaling. Sphingosine kinase localization affects sphingolipid signaling in several ways. Translocation of SK1 to theplasma membrane promotes extracellular secretion of S1P. SK1 and SK2 localization to specific sites appears to direct S1P to intracellular protein effectors. SK localization also determines the access of these enzymes to their substrates. This may be an important mechanism for the regulation of ceramide biosynthesis by diverting dihydrosphingosine, a precursor in the ceramide biosynthetic pathway, from the de novo production of ceramide.展开更多
丹参(Salviae Miltiorrhizae Radix et Rhizoma)是唇形科、鼠尾草属多年生直立草本植物,其干燥根和根茎常用于心血管疾病的治疗,为我国传统医学中的常见药材。研究结果表明,丹参提取物及主要活性成分丹酚酸、丹参酮等通过调节炎症、过...丹参(Salviae Miltiorrhizae Radix et Rhizoma)是唇形科、鼠尾草属多年生直立草本植物,其干燥根和根茎常用于心血管疾病的治疗,为我国传统医学中的常见药材。研究结果表明,丹参提取物及主要活性成分丹酚酸、丹参酮等通过调节炎症、过氧化等多靶点多信号途径改善糖脂代谢。本文梳理了近年来的研究成果,总结丹参及其活性物质调控糖脂代谢的作用与机制研究进展,以期为丹参应用于糖尿病与肥胖等代谢性疾病的防治提供参考。展开更多
The copper-binding, membrane-anchored, cellular prion protein （PrP~） has two constitutive cleavage sites producing distinct N- and C-terminal fragments （N1/C1 and N2/C2）. Using RK13 cells expressing either human P...The copper-binding, membrane-anchored, cellular prion protein （PrP~） has two constitutive cleavage sites producing distinct N- and C-terminal fragments （N1/C1 and N2/C2）. Using RK13 cells expressing either human PrPc, mouse PrPc or mouse PrP^C carrying the 3F4 epitope, this study explored the influence of the PrP^C primary sequence on endoproteolytic cleavage and one putative PrPc function, MAP kinase signal transduction, in response to exogenous copper with or without a perturbed membrane environment. PrPc primary sequence, especially that around the N1/C1 cleavage site, appeared to influence basal levels of proteolysis at this location and extracellular signal-regulat- ed kinase 1/2 （ERK1/2） phosphorylation, with increased processing demonstrating an inverse relationship with basal ERK1/2 activation. Human PrP^C showed increased N1/C1 cleavage in response to copper alone, accompanied by specific p38 and JNK/SAPK phosphorylation. Combined exposure to copper plus the cholesterol-sequestering antibiotic filipin resulted in a mouse PrP^C-specific substantial increase in signal protein phosphorylation, accompanied by an increase in N1/C1 cleavage. Mouse PrPc harboring the human N1/C1 cleavage site assumed more human-like profiles basally and in response to copper and altered membrane environments. Our results demonstrate that the PrPc pri- mary sequence around the N1/C1 cleavage site influences endoproteolytic processing at this location, which appears linked to MAP kinase signal transduction both basally and in response to copper. Further, the primary sequence appears to confer a mutual dependence of N1/C1 cleavage and membrane integrity on the fidelity of PrP^C-related signal transduction in response to exogenous stimuli.展开更多
AIM:To assess the regulatory effect of micro RNA-185(mi R-185)on lipid metabolism and the insulin signalling pathway in human Hep G2 hepatocytes and a high-fat diet mouse model.METHODS:Quantitative reverse transcripti...AIM:To assess the regulatory effect of micro RNA-185(mi R-185)on lipid metabolism and the insulin signalling pathway in human Hep G2 hepatocytes and a high-fat diet mouse model.METHODS:Quantitative reverse transcription-polymerase chain reaction was used to assess the m RNA levels of lipogenic genes after loss or gain of mi R-185.In addition,the amounts of insulin signalling intermediates were determined after transfection of Hep G2 cells with pre-mi R-185.RESULTS:Mi R-185 levels decreased in a time-and dose-dependent manner in response to palmitic acid in human Hep G2 hepatocytes.Transfection of Hep G2 cells with mi R-185 significantly decreased the m RNA levels of fatty acid synthase,3-hydroxy-3-methylglutaryl-Co A reductase,sterol-regulatory element binding protein-2,and sterol-regulatory element binding protein-1c,whereas inhibition of mi R-185 using an anti-mi R-185oligonucleotide produced the opposite effect in Hep G2cells.In a high-fat diet mouse model,the accumulation of lipids was significantly improved after treatment with mi R-185,compared with control animals.Induction of mi R-185 enhanced the insulin signalling pathway by upregulating the insulin-receptor substrate-2.CONCLUSION:These findings suggest that mi R-185plays an important role in regulating fatty-acid metabolism and cholesterol homeostasis in hepatocytes,as well as in improving insulin sensitivity,both in vitro and in vivo.展开更多
A growing body of epidemiologic research has demonstrated that metabolic derangement exists in patients with hepatitis B virus(HBV) infection, indicating that there are clinical associations between HBV infection and ...A growing body of epidemiologic research has demonstrated that metabolic derangement exists in patients with hepatitis B virus(HBV) infection, indicating that there are clinical associations between HBV infection and host metabolism. In order to understand the complex interplay between HBV and hepatic metabolism in greater depth, we systematically reviewed these alterations in different metabolic signaling pathways due to HBV infection. HBV infection interfered with most aspects of hepatic metabolic responses, including glucose, lipid, nucleic acid, bile acid and vitamin metabolism. Glucose and lipid metabolism is a particular focus due to the significant promotion of gluconeogenesis, glucose aerobic oxidation, the pentose phosphate pathway, fatty acid synthesis or oxidation, phospholipid and cholesterol biosynthesis affected by HBV. These altered metabolic pathways are involved in the pathological process of not only hepatitis B, but also metabolic disorders, increasing the occurrence of complications, such as hepatocellular carcinoma and liver steatosis. Thus, a clearer understanding of the hepatic metabolic pathways affected by HBV and its pathogenesis is necessary to develop more novel therapeutic strategies targeting viral eradication.展开更多
Lipid phosphorylation by diacylglycerol kinase(DGK)that produces phosphatidic acid(PA)plays important roles in various biological processes,including stress responses,but the underlying mechanisms remain elusive.Here,...Lipid phosphorylation by diacylglycerol kinase(DGK)that produces phosphatidic acid(PA)plays important roles in various biological processes,including stress responses,but the underlying mechanisms remain elusive.Here,we show that DGK5 and its lipid product PA suppress ABA biosynthesis by interacting withABA-DEFICIENT2(ABA2),a key ABA biosynthesis enzyme,to negatively modulate plant responseto abiotic stress tested in Arabidopsis thaliana.Loss of DGK5 function rendered plants less damaged,whereas overexpression(OE)of DGK5 enhanced plant damage to water and salt stress.The dgk5 mutant plants exhibited decreased total cellular and nuclear levels of PA with increased levels of diacylglycerol,whereas DGK5-OE plants displayed the opposite effect.Interestingly,we found that both DGK5 and PA bind to the ABA-synthesizing enzyme ABA2 and suppress its enzymatic activity.Consistently,the dgk5 mutant plants exhibited increased levels of ABA,while DGK5-OE plants showed reduced ABA levels.In addition,we showed that both DGK5 and ABA2 are detected in and outside the nuclei,and loss of DGK5 function decreased the nuclear association of ABA2.We found that both DGK5 activity and PA promote nuclear association of ABA2.Taken together,these results indicate that both DGK5 and PA interact with ABA2 to inhibit its enzymatic activity and promote its nuclear sequestration,thereby sup-pressing ABA production in response to abiotic stress.Our study reveals a sophisticated mechanism by which DGK5 and PA regulate plant stress responses.展开更多
To explore the intracellular signal pathways for β-VLDL induced very low density lipoprotein receptor (VLDL-R) transcription up-regulation and their effects on lipid accumulation in macrophages, Western Blot was used...To explore the intracellular signal pathways for β-VLDL induced very low density lipoprotein receptor (VLDL-R) transcription up-regulation and their effects on lipid accumulation in macrophages, Western Blot was used to examine phosphorylated ERK1/2 protein and regulated effects by different singal kinase inhibitants. It was found that β-VLDL induced an increase in ERK1/2 activity in a protein kinase C (PKC)-dependent manner in murine RAW264.7 macrophages. By using different protein kinases inhibitors or activators, it was observed that the effect of β-VLDL induced VLDL receptor transcription, which was monitored by RT-PCR analysis of VLDL receptor mRNA, was not affected by the inhibitor of p38 kinase and cAMP analog, but extremely abolished by pretreating cells with PD98059, an inhibitor of ERK and GF 109203X, an inhibitor of PKC. These results demonstrated that the PKC-ERK1/2 cascade is the essential signaling pathway by which β-VLDL activated VLDL-R mRNA expression. Inhibition of the ERK1/2 signaling cascade resulted in suppression of the cellular lipid accumulation induced by β-VLDL in macrophages.展开更多
基金Supported by The James Graham Brown Cancer Center and NIH, No. CA111987
文摘The sphingosine kinases, SK1 and SK2, produce the potent signaling lipid sphingosine-1-phosphate (S1P). These enzymes have garnered increasing interest for their roles in tumorigenesis, inflammation, vascular diseases, and immunity, as well as other functions. The sphingosine kinases are considered signaling enzymes by producing S1P, and their activity is acutely regulated by a variety of agonists. However, these enzymes are also key players in the control of sphingolipid metabolism. A variety of sphingolipids, such as sphingosine and the ceramides, are potent signaling molecules in their own right. The role of sphingosine kinases in regulating sphingolipid metabolism is potentially a critical aspect of their signaling function. A central aspect of signaling lipids is that their hydrophobic nature constrains them to membranes. Most enzymes of sphingolipid metabolism, including the enzymes that degrade S1P, are membrane enzymes. Therefore the localization of the sphingosine kinases and S1P is likely to be important in S1P signaling. Sphingosine kinase localization affects sphingolipid signaling in several ways. Translocation of SK1 to theplasma membrane promotes extracellular secretion of S1P. SK1 and SK2 localization to specific sites appears to direct S1P to intracellular protein effectors. SK localization also determines the access of these enzymes to their substrates. This may be an important mechanism for the regulation of ceramide biosynthesis by diverting dihydrosphingosine, a precursor in the ceramide biosynthetic pathway, from the de novo production of ceramide.
文摘丹参(Salviae Miltiorrhizae Radix et Rhizoma)是唇形科、鼠尾草属多年生直立草本植物,其干燥根和根茎常用于心血管疾病的治疗,为我国传统医学中的常见药材。研究结果表明,丹参提取物及主要活性成分丹酚酸、丹参酮等通过调节炎症、过氧化等多靶点多信号途径改善糖脂代谢。本文梳理了近年来的研究成果,总结丹参及其活性物质调控糖脂代谢的作用与机制研究进展,以期为丹参应用于糖尿病与肥胖等代谢性疾病的防治提供参考。
文摘The copper-binding, membrane-anchored, cellular prion protein （PrP~） has two constitutive cleavage sites producing distinct N- and C-terminal fragments （N1/C1 and N2/C2）. Using RK13 cells expressing either human PrPc, mouse PrPc or mouse PrP^C carrying the 3F4 epitope, this study explored the influence of the PrP^C primary sequence on endoproteolytic cleavage and one putative PrPc function, MAP kinase signal transduction, in response to exogenous copper with or without a perturbed membrane environment. PrPc primary sequence, especially that around the N1/C1 cleavage site, appeared to influence basal levels of proteolysis at this location and extracellular signal-regulat- ed kinase 1/2 （ERK1/2） phosphorylation, with increased processing demonstrating an inverse relationship with basal ERK1/2 activation. Human PrP^C showed increased N1/C1 cleavage in response to copper alone, accompanied by specific p38 and JNK/SAPK phosphorylation. Combined exposure to copper plus the cholesterol-sequestering antibiotic filipin resulted in a mouse PrP^C-specific substantial increase in signal protein phosphorylation, accompanied by an increase in N1/C1 cleavage. Mouse PrPc harboring the human N1/C1 cleavage site assumed more human-like profiles basally and in response to copper and altered membrane environments. Our results demonstrate that the PrPc pri- mary sequence around the N1/C1 cleavage site influences endoproteolytic processing at this location, which appears linked to MAP kinase signal transduction both basally and in response to copper. Further, the primary sequence appears to confer a mutual dependence of N1/C1 cleavage and membrane integrity on the fidelity of PrP^C-related signal transduction in response to exogenous stimuli.
基金Supported by National Natural Science Foundation of China,No.30950005the Department of Education of Heilongjiang Province,No.12511233
文摘AIM:To assess the regulatory effect of micro RNA-185(mi R-185)on lipid metabolism and the insulin signalling pathway in human Hep G2 hepatocytes and a high-fat diet mouse model.METHODS:Quantitative reverse transcription-polymerase chain reaction was used to assess the m RNA levels of lipogenic genes after loss or gain of mi R-185.In addition,the amounts of insulin signalling intermediates were determined after transfection of Hep G2 cells with pre-mi R-185.RESULTS:Mi R-185 levels decreased in a time-and dose-dependent manner in response to palmitic acid in human Hep G2 hepatocytes.Transfection of Hep G2 cells with mi R-185 significantly decreased the m RNA levels of fatty acid synthase,3-hydroxy-3-methylglutaryl-Co A reductase,sterol-regulatory element binding protein-2,and sterol-regulatory element binding protein-1c,whereas inhibition of mi R-185 using an anti-mi R-185oligonucleotide produced the opposite effect in Hep G2cells.In a high-fat diet mouse model,the accumulation of lipids was significantly improved after treatment with mi R-185,compared with control animals.Induction of mi R-185 enhanced the insulin signalling pathway by upregulating the insulin-receptor substrate-2.CONCLUSION:These findings suggest that mi R-185plays an important role in regulating fatty-acid metabolism and cholesterol homeostasis in hepatocytes,as well as in improving insulin sensitivity,both in vitro and in vivo.
基金Supported by the National Natural Science Foundation of China,No.81270500The State 12th 5-Year Plan S&T Projects of China,No.2012ZX10002007The National Basic Research Program(973 Program)in China,No.2013CB531400
文摘A growing body of epidemiologic research has demonstrated that metabolic derangement exists in patients with hepatitis B virus(HBV) infection, indicating that there are clinical associations between HBV infection and host metabolism. In order to understand the complex interplay between HBV and hepatic metabolism in greater depth, we systematically reviewed these alterations in different metabolic signaling pathways due to HBV infection. HBV infection interfered with most aspects of hepatic metabolic responses, including glucose, lipid, nucleic acid, bile acid and vitamin metabolism. Glucose and lipid metabolism is a particular focus due to the significant promotion of gluconeogenesis, glucose aerobic oxidation, the pentose phosphate pathway, fatty acid synthesis or oxidation, phospholipid and cholesterol biosynthesis affected by HBV. These altered metabolic pathways are involved in the pathological process of not only hepatitis B, but also metabolic disorders, increasing the occurrence of complications, such as hepatocellular carcinoma and liver steatosis. Thus, a clearer understanding of the hepatic metabolic pathways affected by HBV and its pathogenesis is necessary to develop more novel therapeutic strategies targeting viral eradication.
基金Research reported in this article was supported by the National Institute of General Medical Sciences of the National Institutes of Health under award number R01GM141374 and the National Science Foundation grants 2222157 and 2302424.
文摘Lipid phosphorylation by diacylglycerol kinase(DGK)that produces phosphatidic acid(PA)plays important roles in various biological processes,including stress responses,but the underlying mechanisms remain elusive.Here,we show that DGK5 and its lipid product PA suppress ABA biosynthesis by interacting withABA-DEFICIENT2(ABA2),a key ABA biosynthesis enzyme,to negatively modulate plant responseto abiotic stress tested in Arabidopsis thaliana.Loss of DGK5 function rendered plants less damaged,whereas overexpression(OE)of DGK5 enhanced plant damage to water and salt stress.The dgk5 mutant plants exhibited decreased total cellular and nuclear levels of PA with increased levels of diacylglycerol,whereas DGK5-OE plants displayed the opposite effect.Interestingly,we found that both DGK5 and PA bind to the ABA-synthesizing enzyme ABA2 and suppress its enzymatic activity.Consistently,the dgk5 mutant plants exhibited increased levels of ABA,while DGK5-OE plants showed reduced ABA levels.In addition,we showed that both DGK5 and ABA2 are detected in and outside the nuclei,and loss of DGK5 function decreased the nuclear association of ABA2.We found that both DGK5 activity and PA promote nuclear association of ABA2.Taken together,these results indicate that both DGK5 and PA interact with ABA2 to inhibit its enzymatic activity and promote its nuclear sequestration,thereby sup-pressing ABA production in response to abiotic stress.Our study reveals a sophisticated mechanism by which DGK5 and PA regulate plant stress responses.
文摘To explore the intracellular signal pathways for β-VLDL induced very low density lipoprotein receptor (VLDL-R) transcription up-regulation and their effects on lipid accumulation in macrophages, Western Blot was used to examine phosphorylated ERK1/2 protein and regulated effects by different singal kinase inhibitants. It was found that β-VLDL induced an increase in ERK1/2 activity in a protein kinase C (PKC)-dependent manner in murine RAW264.7 macrophages. By using different protein kinases inhibitors or activators, it was observed that the effect of β-VLDL induced VLDL receptor transcription, which was monitored by RT-PCR analysis of VLDL receptor mRNA, was not affected by the inhibitor of p38 kinase and cAMP analog, but extremely abolished by pretreating cells with PD98059, an inhibitor of ERK and GF 109203X, an inhibitor of PKC. These results demonstrated that the PKC-ERK1/2 cascade is the essential signaling pathway by which β-VLDL activated VLDL-R mRNA expression. Inhibition of the ERK1/2 signaling cascade resulted in suppression of the cellular lipid accumulation induced by β-VLDL in macrophages.
