Na+-K+--ATPase-mediated signal transduction: from protein interaction to cellular function

The Na+-K+--ATPase, or Na+ pump, is a member of the P-type ATPase superfamily. In addition to pumping ions, Na+-K+--ATPase is engaged in assembly of multiple protein complexes that transmit signals to different intracellular compartments. The signaling function of the enzyme appears to have been acquired through the evolutionary incorporation of many specific binding motifs that interact with proteins and ligands. In some cell types the signaling Na+ --ATPase and its protein partners are compartmentalized in coated pits (i.e., caveolae) the plasma membrane. Binding of ouabain to the signaling Na+-K+--ATPase activates the cytoplasmic tyrosine kinase Src, resulting in the formation of an active "binary receptor" that phosphorylates and assembles other proteins into different signaling modules. This in turn activates multiple protein kinase cascades including mitogen-activated protein kinases and protein kinase C isozymes in a cell-specific manner. It also increases mitochondrial production of reactive oxygen species (ROS)and regulates intracellular calcium concentration. Crosstalk among the activated pathways eventually results in changes in the expression of a number of genes. Although ouabain stimulates hypertrophic growth in cardiac myocytes and proliferation in smooth muscle cells, it also induces apoptosis in many malignant cells. Finally, the signaling function of the enzyme is also pivotal to ouabain-induced nongenomic effects on cardiac myocytes.     

Cortisol secretion in the elderly. Influence of age,sex and cardiovascular disease in a Chinese population

Adrenal function and aging have been the object of intense interest in recent years. In this study we analyzed morning (08:00 h) serum cortisol concentrations from a sample of Chinese subjects aged from 31 to 110 years. These levels differed according to age, health status and sex, although the sex difference was confirmed only among the healthy elderly. These results suggest that age (older than 60 years), disease and male sex are associated with increased morning serum cortisol levels in a Chinese population.     

A recombinant anti-erbB2, scFv-Fc-IL-2 fusion protein retains antigen specificity and cytokine function

Elevated erbB2 expression is detected in many in situ and invasive human ductal carcinomas. Anti-erbB2 antibody directed at the extracellular domain of erbB2 can result in an antitumor response in some patients with tumors overexpressing erbB2 oncoprotein. By combining interleukin 2 (IL-2) activities with a tumor specific antibody, immunotherapy of tumors might be more effective in the future. In this study, a fusion protein consisting of erbB2 single chain antibody (scFv), Fc fragment of human IgG1 and IL-2 was constructed. The molecular weight of fusion proteins is 66 kDa, only one third of whole antibody-IL-2 fusion protein or 44% whole Ig molecule. The fusion proteins retained the activities of both antigen binding and IL-2. The scFv-Fc-IL-2 fusion protein may have advantages over whole antibody-IL-2 fusion proteins, such as smaller molecule, better activity of penetration, more favorable pharmacokinetic properties.     

Angiostatin production in cultivation of recombinant Pichia pastoris fed with mixed carbon sources

A recombinant strain of Pichia pastoris with a phenotype of Mut^S was used to produce angiostatin. Due to the low methanol consumption rate of this strain, both methanol and glycerol feedings, that produced oscillation in dissolved O₂ concentration, were used during the expression phase to improve cell growth and angiostatin expression. However, enhanced cell growth led to nitrogen limitation that suppressed further production of angiostatin, but addition of ammonia allowed angiostatin concentration to reach 108 mg l^–1 after an expression period of 96 h. The ratio of consumed glycerol to methanol of 1.5:1 (w/w) in the expression phase suggested that methanol played an important role in the metabolism of carbon sources.     

Effects of La3+ on growth,transformation, and gene expression of Escherichia coli

Rare earth elements have been emitted into the environment largely as fertilizer components. This has caused much fear about whether they would influence our environment, especially on the metabolism and genetics of microorganisms. In this article, the trivalent ion of a rare earth element, lanthanum, was studied for the effects on growth, transformation, and gene expression of Escherichia coli. The results showed that La³⁺ at concentrations from 50 to 150 μg/mL stimulated the endogenic metabolism and ectogenic metabolism, but had few effects on gene expression. La³⁺ at lower concentrations from 0.5 to 30 μg/mL inhibit intensively E. coli-absorbing external DNA, decreasing the transformation efficiency. It is also supported by observations using transmission electron microscopy. Our results are significant in understanding the function of rare earth elements to microorganisms and assessing the risk of application of rare earth compounds.     

Relationships of endogenous plant hormones to accumulation of grain protein and starch in winter wheat under different post-anthesis soil water statusses

Accumulation of protein and starch in grain is a key process determining grain yield and quality in wheat. Under drought or waterlogging, endogenous plant hormone levels will change and may have an impact on the yield and quality of wheat. In a greenhouse experiment, four winter wheat (Triticum aestivum L.) varieties differing in grain protein content, Heimai 76, Wanmai 38, Yangmai 10 and Yangmai 9, were subjected to drought (SRWC = 4550%, DR), waterlogging (WL) and moderate water supply (SRWC = 7580%, CK), beginning from 4 days post-anthesis (DPA) to maturity. On the 10 (grain enlargement stage) and 20 (grain filling stage) DPA, endogenous abscisic acid (ABA), gibberellins (GA₁₊₃), indole-3-acetic acid (IAA) and zeatin riboside (ZR) were determined in sink and source organs of wheat plants by enzyme linked immunosorbent assay (ELISA). The patterns of hormonal changes were similar in four varieties. The ABA levels were much higher under DR and WL than under CK. Compared with CK, GA₁₊₃ levels in whole-plant under DR and WL changed a little at 10 DPA, but markedly decreased under DR and WL at 20 DPA. Changes of endogenous IAA level under DR and WL exhibited a complicated pattern, depending on organs and growth stages. Particularly at the 20 DPA, the mean levels of IAA in roots, leaves and grains decreased significantly under DR and WL. In comparison with CK, ZR levels in all organs significantly decreased under DR and WL at both stages. The correlation analyses between yields and contents of starch and protein in grains and levels and ratios of four hormones in source and sink organs indicated that the changes in yield and content of grain starch and protein under DR and WL were associated with the reduced IAA, ZR and GA₁₊₃ levels and elevated ABA level in plants, especially in grains. It was proposed that the changed levels of endogenous hormones under post-anthesis DR and WL might indirectly affect protein and starch accumulation in grains by influencing the regulatory enzymes and processes.