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Molecular and Cellular Biochemistry [journal]
- Moderate grade hyperammonemia activates lactate dehydrogenase-4 and 6-phosphofructo-2-kinase to support increased lactate turnover in the brain slices. [JOURNAL ARTICLE]
- Mol Cell Biochem 2013 May 24.
Rapid metabolism of lactate is an important aspect of bioenergetic adaptation in the brain during non-physiological conditions. The low grade hyperammonemia (HA) is a common condition in the patients with chronic hepatic encephalopathy (HE); however, biochemistry of lactate turnover during low grade HA remains poorly defined. The present article describes profile of lactate dehydrogenase (LDH) isozymes vis-a-vis lactate level in the brain slices exposed with 0.1-0.5 mM ammonia, found to exist in the brain during chronic HE. A significant increment in LDH activity coincided with a similar increase in lactate level in the brain slices exposed with 0.5 mM ammonia. This was consistent with a selective increment of LDH-4 that synthesizes lactate from pyruvate with a concomitant decline in LDH-1 which catalyzes conversion of lactate to pyruvate; resulting into ~3-fold increase in LDH-4/LDH-1 ratio in those brain slices. The PFK2 domain of PFK2/FBPase2 (6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase) regulates glycolysis to maintain the pyruvate pool for lactate synthesis. The PFK2 expression was also observed to be increased ~2-fold (P < 0.001) in 0.5 mM ammonia treated brain slices. These findings provide enzymatic regulation of increased lactate turnover in the brain exposed with moderate HA.
- Endoplasmic reticulum stress leads to lipid accumulation through upregulation of SREBP-1c in normal hepatic and hepatoma cells. [JOURNAL ARTICLE]
- Mol Cell Biochem 2013 May 24.
Endoplasmic reticulum stress (ERS) has been found in non-alcoholic fatty liver disease. The study was to further explore the mechanistic relationship between ERS and lipid accumulation. To induce ERS, the hepatoblastoma cell line HepG2 and the normal human L02 cell line were exposed to Tg for 48 h. RT-PCR and Western blot were performed to evaluate glucose-regulated protein (GRP-78) expression as a marker of ERS. ER ultrastructure was assessed by electron microscopy. Triglyceride content was examined by Oil Red O staining and quantitative intracellular triglyceride assay. The hepatic nuclear sterol regulatory element-binding protein (SREBP-1c), liver X receptor (LXRs), fatty acid synthase (FAS), and acetyl-coA carboxylase (ACC1) expressions were examined by real-time PCR and Western blot. 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF) was used to inhibit S1P serine protease inhibitor, and SREBP-1c cleavage was evaluated under ERS. SREBP-1c was knockdown and its effect on lipid metabolism was observed. Tg treatment upregulated GRP-78 expression and severely damaged the ER structure in L02 and HepG2 cells. ERS increased triglyceride deposition and enhanced the expression of SREBP-1c, FAS, and ACC1, but have no influence on LXR. AEBSF pretreatment abolished Tg-induced SREBP-1c cleavage. Moreover, SREBP-1c silencing reduced triglycerides and downregulated FAS expression. Pharmacological ERS induced by Tg leads to lipid accumulation through upregulation of SREBP-1c in L02 and HepG2 cells.
- Altered methylation of IGF2 DMR0 is associated with neural tube defects. [JOURNAL ARTICLE]
- Mol Cell Biochem 2013 May 21.
Neural tube defects (NTDs) are serious congenital malformation of fusion failure of the neural tube during early embryogenesis. DNA methylation disorders have been found in NTD-affected fetuses, and are correlated to the risk of NTDs. The insulin-like growth factor 2 (IGF2) gene, maternally imprinted, has a key role in fetal development. IGF2 transcription is partly controlled by differentially methylated regions (DMRs) 0 and 2. To assess whether disturbed methylation pattern increases the incidence of NTDs, we employed matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) to quantify CpG methylation levels of DMR2 and 0 in fetuses with or without NTDs. We found that the methylation level of IGF2 DMR0 increased significantly in the brain tissues of NTD-affected fetuses. And hypermethylation of DMR0 was associated with an increased risk of NTDs, with an odds ratio of 5.375 (95 % CI: 1.447-19.965; p = 0.007). IGF2 mRNA expression was negatively correlated with the methylation level of DMR0 (R (2) = 0.893; p = 0.000) in HCT15 cells. These results highlights that IGF2 DMR0 hypermethylation is a potential risk factor of NTD, and IGF2 gene is a promising candidate gene to study for a greater understanding of the cause of NTDs.
- RNA interference mediated pten knock-down inhibit the formation of polycystic ovary. [JOURNAL ARTICLE]
- Mol Cell Biochem 2013 May 19.
Pten (phosphatase and tensin homolog deleted on chromosome 10), a kind of tumor suppressor gene, plays important roles in female reproductive system. But its expression and roles in the formation of polycystic ovaries are yet to be known. In this study, we constructed a rat model of PCOS using norethindrone and HCG injections and found the expressions of pten mRNA and PTEN protein increased significantly in the polycystic ovary tissue by immunohistochemistry, RT-PCR, and western blot. Furthermore, the results showed that in vivo ovaries could be effectively transfected by lentiviral vectors through the ovarian microinjection method and indicated that pten shRNA may inhibit the formation of polycystic ovaries by pten down-regulation. Our study provides new information regarding the role of PTEN in female reproductive disorders, such as polycystic ovary syndrome.
- Subnuclear distribution of SSX regulates its function. [JOURNAL ARTICLE]
- Mol Cell Biochem 2013 May 18.
SSX, a family of genes clustered on the X chromosome, has been identified as a cancer-testis antigen and also forms a part of the SYT-SSX fusion gene found in synovial sarcoma, implying that it has an important role in tumorigenesis. However, knowledge of the molecular regulation of SSX is still limited. In this study, we demonstrate that SSX or its SYT fusion protein is distributed as nuclear speckles, in which it is co-localized with B cell-specific Moloney murine leukemia virus insertion site 1 (Bmi1), which is a core factor of polycomb repressor complex 1. The C-terminal residues of SSX are indispensable for the nuclear speckle distribution, while the N-terminal domain is necessary for the recruitment of Bmi1, indicating that intact SSX must be needed for interaction with Bmi1 both spatially and functionally. In addition, the N-terminus of SSX also proved to contain an intrinsic nucleolar localization signal, which mediates the nucleolar translocation of SSX in particular kinds of cell stress such as the oxidation of hydrogen peroxide or heat shock. This stress-induced translocation is reversible and accompanied by HSP 70 or p14ARF traffic, suggesting that SSX is a stress response gene. It is of note that nucleolar translocation of SSX can result in disassociation of SSX from Bmi1, with consequent down-regulation of Bmi1 activity. These novel findings regarding distinct domains of SSX and its interaction with Bmi1 may shed light on the mechanism by which synovial sarcoma develops and on the up-regulation of SSX in cancer cells.
- miR-17-92 cluster: an apoptosis inducer or proliferation enhancer. [JOURNAL ARTICLE]
- Mol Cell Biochem 2013 May 17.
Study of the non-coding RNA roles in the regulation of adaptive immune responses through T cells could be the basis of novel therapeutic applications. MicroRNAs (miRNAs) are a class of short non-coding RNAs that control the cell's functions and destination. To investigate the role of miRNAs in T cell activation, herein the expressions of miR-17-92 cluster and its paralogs were studied in naïve CD4(+)T cells that were activated by anti-CD2, -CD3, -CD28 microbeads and induced with or without IL-2. Proliferation and apoptosis rate of the cultured cells were determined by BrdU incorporation assay (ELISA) and propidium iodide staining, respectively. In continuation the expressions of eight miRNAs of the mentioned clusters were analyzed quantitatively. In addition their potential targets were predicted using multiple algorithms; as a confirmation, the transcription of PIK3R3 (a putative target of modulated miRNAs) was evaluated. Stimulation index (SI) of activated cells was decreased on day 6; whereas, the IL-2 induced cells showed increase in SI in the assay time. Evaluation of eight members of the aforementioned cluster showed upregulation of miR-92a-2* (~15 times) in IL-2 un-induced (activated) cells relative to the IL-2 induced cells. In silico investigations revealed that the suggested miRNAs targeted genes that were involved in cell proliferation, survival, and apoptosis. Transcriptional analysis of PIK3R3 illustrated decrease in activated cells relative to IL-2 induced cells. According to our findings, it seems that multiple members of miR-17-92 families in activated CD4(+)T cells inhibited negative regulators of IL-2 such as DUSP, PTPN, and SOCS families after IL-2 induction. According to our findings, it seems that multiple genes of cell proliferation-related families such as MAPK, E2F, AKT, STAT, and JAK as well as PIK3R3 are inhibited by miR-17-92 cluster in activated cells. As FASL is a putative target of over-expressed miRNAs in activated cell, antigen-induced cell death (AICD) might be occurred in FASL-independent manner. Altogether this study suggested that clonal expansion through IL-2 signaling pathway does not depend on the members of miR-17-92 family; while, it appears that AICD in activated CD4(+)T cells without IL-2 induction is affected by these miRNA clusters.
- Promotion of autophagy at the maturation step by IL-6 is associated with the sustained mitogen-activated protein kinase/extracellular signal-regulated kinase activity. [JOURNAL ARTICLE]
- Mol Cell Biochem 2013 May 16.
Increased autophagic vacuoles (AVs) occur in injured or degenerating neurons, under both developmental and pathological situations. Although an induced autophagy has been shown in inflammation response to cell factors, the underlying mechanism(s) remain(s) unknown. Here, we show that both cell factor IL-6 and environmental toxin MPP(+) promote the formation of vacuolation in SHSY5Y cells. By electron and immunofluorescent microscopy analyses, we showed that these structures are acid autolysosomes, containing cellular debris, and labeled by LC3 or LAMP1, markers of autophagosomes or lysosomes, respectively. Combining MPP(+) and IL-6 do not further increase vacuolation of SHSY5Y cells, and the vacuolation is less than that in the MPP(+)-treated group. MPP(+)-induced vacuolation results from significant increase in autophagy formation and delay in autophagy degradation, in relation to a decline of the lysosomal activity of arylsulfatase A. At molecular level, we show that this defect in autolysosomal maturation is independent of mammalian target of rapamycin and p38 inhibitions. Most importantly, we provide the first evidence that activation of ERK pathway is sufficient to commit cell to autophagic vacuolation. The sustained activation is required for MPP(+) to disrupt the autophagic pathway. IL-6 also induces a temporary and significant activation of ERK, but not sustained activation, and change sustained activation in MPP(+)-treated group into temporary activation. Taken together, these findings strongly support that IL-6 promotes the maturation of autophagosomes into functional autolysosomes by regulating ERK.
- VAMP4 is required to maintain the ribbon structure of the Golgi apparatus. [JOURNAL ARTICLE]
- Mol Cell Biochem 2013 May 16.
The Golgi apparatus forms a twisted ribbon-like network in the juxtanuclear region of vertebrate cells. Vesicle-associated membrane protein 4 (VAMP4), a v-SNARE protein expressed exclusively in the vertebrate trans-Golgi network (TGN), plays a role in retrograde trafficking from the early endosome to the TGN, although its precise function within the Golgi apparatus remains unclear. To determine whether VAMP4 plays a functional role in maintaining the structure of the Golgi apparatus, we depleted VAMP4 gene expression using RNA interference technology. Depletion of VAMP4 from HeLa cells led to fragmentation of the Golgi ribbon. These fragments were not uniformly distributed throughout the cytoplasm, but remained in the juxtanuclear area. Electron microscopy and immunohistochemistry showed that in the absence of VAMP4, the length of the Golgi stack was shortened, but Golgi stacking was normal. Anterograde trafficking was not impaired in VAMP4-depleted cells, which contained intact microtubule arrays. Depletion of the cognate SNARE partners of VAMP4, syntaxin 6, syntaxin 16, and Vti1a also disrupted the Golgi ribbon structure. Our findings suggested that the maintenance of Golgi ribbon structure requires normal retrograde trafficking from the early endosome to the TGN, which is likely to be mediated by the formation of VAMP4-containing SNARE complexes.
- MicroRNA-148a suppresses epithelial-to-mesenchymal transition by targeting ROCK1 in non-small cell lung cancer cells. [JOURNAL ARTICLE]
- Mol Cell Biochem 2013 May 14.
Recent studies have implied that miRNAs act as crucial modulators for epithelial-to-mesenchymal transition (EMT). We found that miR-148a is significantly downregulated in non-small cell lung cancer (NSCLC) compared to adjacent non-cancerous lung tissues, and the downregulated miR-148a was significantly associated with lymph-node metastasis. Functional assays demonstrated that miR-148a inhibited EMT in NSCLC cells. Moreover, miR-148a decreased 3'-untranslated region luciferase activity of ROCK1 and ROCK1 protein expression. Knockdown of ROCK1 reversed EMT resembling that of miR-148a overexpression. Furthermore, ROCK1 was widely upregulated in NSCLC, and its mRNA levels were inversely correlated with miR-148a expression. These findings suggest that miR-148a acts as a novel EMT suppressor in NSCLC cells, at least in part by modulation of ROCK1.
- MicroRNA-19a targets tissue factor to inhibit colon cancer cells migration and invasion. [JOURNAL ARTICLE]
- Mol Cell Biochem 2013 May 12.
The over-expression of tissue factor (TF) and its roles in colon cancer progression have attracted much attention. However, the mechanisms regulating TF expression have not yet been shown in detail. In this study, we over-expressed miR-19a, miR20a and miR-106b in colon cancer cells, and evaluated their impact on TF expression and cellular function. We provide evidence demonstrating that miR-19a inhibited TF expression in vitro. Luciferase reporter assay confirmed that TF was a direct target of miR-19a because the miR-19a mediated repression of luciferase activity was abolished by mutation of the putative binding site. Moreover, miR-19a suppressed colon cancer cell migration and invasion. This effect was due to the indirect down-regulation of matrix metalloproteinase 9. Finally, we investigated the relevance of TF and miR-19a expression in a total of 48 paired colon cancer samples and revealed that miR-19a was inversely correlated with TF expression in stages I and II cases. Therefore, our results suggested that miR-19a was capable of suppressing TF expression in vitro and inhibiting cell migration and invasion. Although it was not the unique mechanism responsible for the expression of TF in vivo, miR-19a was inversely correlated with TF expression in early stage colon cancer patients.