Laminin 332 processing impacts cellular behavior

Laminin 332, composed of the α3, β3 and γ2 chains, is an epithelial-basement membrane specific laminin variant. Its main role in normal tissues is the maintenance of epithelial-mesenchymal cohesion in tissues exposed to external forces, including skin and stratified squamous mucosa. After being secreted and deposited in the extracellular matrix, laminin 332 undergoes physiological maturation processes consisting in the proteolytic processing of domains located within the α3 and the γ2 chains. These maturation events are essential for laminin 332 integration into the basement membrane where it plays an important function in the nucleation and maintenance of anchoring structures. Studies in normal and pathological situations have revealed that laminin 332 can trigger distinct cellular events depending on the level of its proteolytic cleavages. In this review, the biological and structural characteristics of laminin 332 domains are presented and we discuss whether they trigger specific functions.     

STGC3基因缺失突变对CNE2细胞生长增殖能力的影响

为探讨鼻咽癌候选抑癌基因STGC3中层粘连蛋白G结构域(LG domain)对CNE2生长增殖能力的影响,应用基因定点突变技术将该结构域缺失,亚克隆至真核表达载体上,并将野生型及突变型STGC3稳定转染人鼻咽癌细胞系CNE2,检测其对CNE2细胞系表型的影响,包括测定稳转细胞系的生长曲线、细胞集落形成能力和细胞周期分布.研究发现,LGdomain的缺失明显降低了STGC3的肿瘤抑制活性,使受其稳定转染的细胞系恶性度显著增强,提示该结构域在STGC3发挥肿瘤抑制功能中起着重要作用.     

Genetic,epigenetic, and gene-by-diet interaction effects underlie variation in serum lipids in a LG/J×SM/J murine model

Variation in serum cholesterol, free-fatty acids, and triglycerides is associated with cardiovascular disease (CVD) risk factors. There is great interest in characterizing the underlying genetic architecture of these risk factors, because they vary greatly within and among human populations and between the sexes. We present results of a genome-wide scan for quantitative trait loci (QTL) affecting serum cholesterol, free-fatty acids, and triglycerides in an F₁₆ advanced intercross line of LG/J and SM/J (Wustl:LG,SM-G16). Half of the population was fed a high-fat diet and half was fed a relatively low-fat diet. Context-dependent genetic (additive and dominance) and epigenetic (imprinting) effects were characterized by partitioning animals into sex, diet, and sex-by-diet cohorts. Here we examine genetic, environmental, and genetic-by-environmental interactions of QTL overlapping previously identified loci associated with CVD risk factors, and we add to the serum lipid QTL landscape by identifying new loci.     

Differential impact of glucose levels and advanced glycation end-products on tubular cell viability and pro-inflammatory/profibrotic functions

High glucose (HG) or synthetic advanced glycation end-products (AGE) conditions are generally used to mimic diabetes in cellular models. Both models have shown an increase of apoptosis, oxidative stress and pro-inflammatory cytokine production in tubular cells. However, the impact of the two conditions combined has rarely been studied. In addition, the impact of glucose level variation due to cellular consumption is not clearly characterized in such experiments. Therefore, the aim of this study was to compare the effect of HG and AGE separately and of both on tubular cell phenotype changes in the HK2 cell line. Moreover, glucose consumption was monitored every hour to maintain the glucose level by supplementation throughout the experiments. We thus observed a significant decrease of apoptosis and H₂O₂ production in the HK2 cell. HG or AGE treatment induced an increase of total and mitochondrial apoptosis as well as TGF-β release compared to control conditions; however, AGE or HG led to apoptosis preferentially involving the mitochondria pathway. No cumulative effect of HG and AGE treatment was observed on apoptosis. However, a pretreatment with RAGE antibodies partially abolished the apoptotic effect of HG and completely abolished the apoptotic effect of AGE. In conclusion, tubular cells are sensitive to the lack of glucose as well as to the HG and AGE treatments, the AGE effect being more deleterious than the HG effect. Absence of a potential synergistic effect of HG and AGE could indicate that they act through a common pathway, possibly via the activation of the RAGE receptors.     

Purification and Properties of Catalasc from a Methanol-utilizing Yeast,Candida sp. N-16

Defatted soybean extract was fractionated into protein fractions and low molecular weight fractions with gel filtration. NAD-dependent aldehyde dehydrogenase from bovine liver mitochondria and from yeast was found to oxidize aldehyde in both fractions. These enzymes, therefore, were used to determine the quantity of aldehyde. When the protein fraction obtained by gel filtration was subjected to gel filtration again, aldehyde was recovered in the protein fractions. The level of aldehyde in the protein fractions was unchanged before and after digestion of the protein with pepsin. When the soybean extract was incubated beforehand with aldehyde dehydrogenase and NAD⁺ and the subjected to gel filtration, no aldehyde was detected in the protein fractions. These results indicate that aldehyde dehydrogenase acts on the soybean protein-bound aldehyde. Alcohol dehydrogenase from horse liver in the presence of NADH did not convert the bound aldehyde to alcohol.

A large portion of the aldehyde in the extract was separated from the protein by acid precipitation of the protein. Aldehyde dehydrogenase acts on the aldehyde remaining in the protein after acid precipitation. Thus acid precipitation helps to save NAD⁺ required for complete removal of aldehyde from the soybean protein by aldehyde dehydrogenase.     

A minimal element in 5'UTR of insulin mRNA mediates its translational regulation by glucose

Glucose induced translation of insulin in pancreatic beta cells is mediated by the 5'UTR of insulin mRNA. We determined the minimal sequence/structure in the 5'UTR of rat insulin gene1 for this regulation. We show that specific factors in the pancreatic islets bind to the 5'UTR of the insulin mRNA upon glucose stimulation. We identified a minimal 29-nucleotide element in the 5'UTR that is sufficient to form the complex, and confer glucose mediated translation activation. Conserved residues in the predicted stem loop region of the un-translated region (UTR) seem to be important for the complex formation and the translation regulation.     

The roles of ABCA12 in epidermal lipid barrier formation and keratinocyte differentiation

ATP-binding cassette (ABC) transporters form a large superfamily of transporters that bind and hydrolyze ATP to transport various molecules across limiting membranes or into vesicles. The ABCA subfamily members are thought to transport lipid materials. ABCA12 is a keratinocyte transmembrane lipid transporter protein associated with the transport of lipids via lamellar granules. ABCA12 is considered to transport lipids including ceramides to form extracellular lipid layers in the stratum corneum of the epidermis, which is essential for skin barrier function. ABCA12 mutations are known to underlie the three major types of autosomal recessive congenital ichthyoses: harlequin ichthyosis, lamellar ichthyosis and congenital ichthyosiform erythroderma. ABCA12 mutations result in defective lipid transport via lamellar granules in the keratinocytes, leading to ichthyosis phenotypes from malformation of the stratum corneum lipid barrier. Studies on ABCA12-deficient bioengineered models have revealed that lipid transport by ABCA12 is required for keratinocyte differentiation and epidermal morphogenesis. Defective lipid transport due to loss of ABCA12 function leads to the accumulation of intracellular lipids, including glucosylceramides and gangliosides, in the epidermal keratinocytes. The accumulation of gangliosides seems to result in the apoptosis of Abca12^−/− keratinocytes. It was reported that AKT activation occurs in Abca12^−/− granular-layer keratinocytes, which suggests that AKT activation serves to prevent the cell death of Abca12^−/− keratinocytes. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.