Endocytosis is enhanced in Tangier fibroblasts: possible role of ATP-binding cassette protein A1 in endosomal vesicular transport

A human genetic disorder, Tangier disease, has been linked recently to mutations in ATP-binding cassette protein A1 (ABCA1). In addition to its function in apoprotein A-I-mediated lipid removal, ABCA1 was also shown to be a phosphatidylserine (PS) translocase that facilitates PS exofacial flipping. This PS translocation is crucial for the plasma membrane to produce protrusions enabling the engulfment of apoptotic cells. In this report, we show that ABCA1 also plays a role in endocytosis. Receptor-mediated endocytosis, probed by both transferrin and low density lipoprotein, is up-regulated by more than 50% in homozygous Tangier fibroblasts in comparison with controls. Fluid-phase uptake is increased similarly. We also demonstrate that bulk membrane flow, including lipid endocytosis and exocytosis, is accelerated greatly in Tangier cells. Moreover, endocytosis is similarly enhanced in normal fibroblasts when ABCA1 function is inhibited by glyburide, whereas glyburide has no effect on endocytosis in Tangier cells. In addition, we demonstrate a decreased annexin V binding in Tangier fibroblasts as compared with controls, supporting the notion that PS transmembrane distribution is indeed defective in the presence of ABCA1 mutations. Furthermore, adding a PS analog to the exofacial leaflet of the plasma membrane normalizes endocytosis in Tangier cells. Taken together, these data demonstrate that ABCA1 plays an important role in endocytosis. We speculate that this is related to the PS translocase function of ABCA1. A loss of functional ABCA1, as in the case of Tangier cells, enhances membrane inward bending and facilitates endocytosis.     

Seasonal and annual stem respiration of Scots pine trees under boreal conditions

BACKGROUND AND AIMS: Stem respiration of trees is a major, but poorly assessed component of the carbon balance of forests, and important for geo-chemistry. Measurements are required under naturally changing seasonal conditions in different years. Therefore, intra- and inter-annual carbon fluxes of stems in forests were measured continuously from April to November in three consecutive years. METHODS: Stem respiratory CO2 fluxes of 50-year-old Scots pine (Pinus sylvestris) trees were continuously measured with a CO2 analyser, and, concomitantly, stem circumference, stem and air temperature and other environmental factors and photosynthesis, were also measured automatically. KEY RESULTS: There were diurnal, seasonal and inter-annual changes in stem respiration, which peaked at 1600 h during the day and was highest in July. The temperature coefficient of stem respiration (Q10) was greater during the growing season than when growth was slow or had stopped, and more sensitive to temperature in the growing season. The annual Q10 remained relatively constant at about 2 over the three years, while respiration at a reference temperature of 15 degrees C (R15) was higher in the growing than in the non-growing season (1.09 compared with 0.78 micromol m(-2) stem surface s(-1)), but was similar between the years. Maintenance respiration was 76 %, 82 % and 80 % of the total respiration of 17.46, 17.26 and 19.35 mol m2 stem surface in 2001, 2002 and 2003, respectively. The annual total stem respiration of the stand per unit ground area was 75.97 gC m(-2) in 2001 and 74.28 gC m(-2) in 2002. CONCLUSIONS: Stem respiration is an important component in the annual carbon balance of a Scots pine stand, contributing 9 % to total carbon loss from the ecosystem and consuming about 8 % of the carbon of the ecosystem gross primary production. Stem (or air) temperature was the most important predictor of stem carbon flux. The magnitude of stem respiration is modified by photosynthesis and tree growth. Solar radiation indirectly affects stem respiration through its effect on photosynthesis.     

Lupane‐ and Friedelane‐Type Triterpenoids from Celastrus stylosus

Two new triterpenoids, 30‐hydroxylup‐20(29)‐ene 3β‐caffeate ( 1 ) and 24‐nor‐friedelan‐6α,10‐dihydroxy‐1,2‐dioxo‐4,7‐dien‐29‐oic acid ( 2 ), together with eight known compounds 3 – 10 , were isolated from the roots of Celastrus stylosus. The structures of these compounds were elucidated on the basis of spectroscopic analyses. To the best of our knowledge, this represents the first study on the chemical constituents of C. stylosus. The antiproliferative activities of the triterpenoids against six human cancer cell lines (PANC‐1, A549, PC‐3, HepG2, SGC‐7901, and HCCLM3) were evaluated. Compounds 3, 4 , and 10 exhibited comparable activities against PC‐3 and HCCLM3 cell lines as the positive control taxol.     

Nonrigid Registration Regularized by Shape Information: Application to Atlas Construction of Cardiac CT Images

Cardiac atlases play an important role in the computer-aided diagnosis of cardiovascular diseases, in particular they need to deal with large and highly variable image datasets. In this paper, we propose a new nonrigid registration algorithm incorporating shape information, to produce comprehensive atlases. For one thing, the multiscale gradient orientation features of images are combined to form the construction of multifeature mutual information. Additionally, the shape information of multiple-objects in images is incorporated into the cost function for registration. We demonstrate the merits of the new registration algorithm on the 3D data sets of 15 patients. The experimental results show that the new registration algorithm can outperform the conventional intensity-based registration method. The obtained atlas can represent the cardiac structures more accurately.     

URG11 promotes gastric cancer growth and invasion by activation of β‐catenin signalling pathway

Upregulated gene 11 (URG11), a new gene upregulated by Heptatitis B Virus X protein (HBx), was previously shown to activate β‐catenin and promote hepatocellular growth and tumourigenesis. Although the oncogenic role of URG11 in the development of hepatocellular carcinoma has been well documented, its relevance to other human malignancies and the underlying molecular mechanisms remain largely unknown. Here we reported a novel function of URG11 to promote gastric cancer growth and metastasis. URG11 was found to be highly expressed in gastric cancer tissues compared with adjacent nontumourous ones by immunohistochemical staining and western blot. Knockdown of URG11 expression by small interfering RNA (siRNA) effectively attenuated the proliferation, anchorage‐independent growth, invasiveness and metastatic potential of gastric cancer cells. URG11 inhibition led to decreased expression of β‐catenin and its nuclear accumulation in gastric cancer cells and extensive costaining between URG11 and β‐catenin was observed in gastric cancer tissues. Transient transfection assays with the β‐catenin promoter showed that it was inhibited by URG11‐specific small inhibitory RNA. Moreover, suppression of endogenous URG11 expression results in decreased activation of β‐catenin/TCF and its downstream effector genes, cyclinD1 and membrane type 1 matrix metallopeptidase (MT1‐MMP), which are known to be involved in cell proliferation and invasion, respectively. Taken together, our data suggest that URG11 contributes to gastric cancer growth and metastasis at least partially through activation of β‐catenin signalling pathway. These findings also propose a promising target for gene therapy in gastric cancer.     

Efficacy of Chromium(III) Supplementation on Growth,Body Composition,Serum Parameters,and Tissue Chromium in Rats

Chromium(III) is often claimed to have a positive effect on body composition, while the responses in researches with supplementation of different chemical form of chromium are various and inconsistent. We have studied the effects of 6 weeks of treatment with three different forms of chromium (300 μg/kg) as chromium chloride, chromium tripicolinate, and chromium nanocomposite (CrNano) on growth, body composition, serum parameters, and tissue chromium in rats. The supplementataion of CrNano significantly increased average daily gain, food efficiency, and lean body mass and decreased fat mass and body fat proportion and serum levels of glucose, urea nitrogen, triglyceride, and insulin. Chromium contents in liver, kidney, and hind leg muscle were increased significantly with the addition of CrNano in diet. The results indicate that chromium nanocomposite has higher efficacy on growth and body composition compared to the traditional chromium agents.     

Phosphatidylinositol 3-kinase/protein kinase B pathway stabilizes DNA methyltransferase I protein and maintains DNA methylation

DNA methylation, which affects gene expression and chromatin stability, is catalyzed by DNA methyltransferases (DNMTs) of which DNMT1 possesses most abundant activity. PI3K/PKB pathway is an important pathway involved in cell proliferation, viability, and metabolism and often disrupted in cancer. Here we investigated the impact of PKB on DNMT1 and DNA methylation. Positive correlation between PKB-Ser473-phosphorylation and DNMT1 protein level in 17 human cell lines (p<0.01) and in 27 human bladder cancer tissues (p<0.05) was found. With activator, inhibitor, siRNA and constitutively active or dominant-negative plasmids of PKB, we found that PKB increased the protein level of DNMT1 without coordinate mRNA change, which was specific rather than due to cell-cycle change. PKB enhanced DNMT1 protein stability independent of de novo synthesis of any protein, which was attributed to down-regulation of N-terminal-120-amino-acids-dependent DNMT1 degradation via ubiquitin-proteasome pathway. Gsk3beta inhibitor rescued the decrease of DNMT1 by PKB inhibition, suggesting that Gsk3beta mediated the stabilization of DNMT1 by PKB. Then role of PKB regulating DNMT1 was investigated. Inhibition of PKB caused observable DNA hypomethylation and chromatin decondensation and DNMT1 overexpression partially reversed cell growth inhibition by PKB inhibition. In conclusion, our results suggested that PKB enhanced DNMT1 stability and maintained DNA methylation and chromatin structure, which might contribute to cancer cell growth.