HL-60细胞诱导分化期间细胞表面ConA受体结合量变化的研究

 <正> 在用二甲亚砜(DMSO)诱导人急性早幼粒细胞性白血病细胞系(HL-60 Cell)沿粒系统分化成熟的实验基础上,我们用受体荧光标记技术和荧光分光光度法,进一步观察了HL-60细胞诱导分化期间,细胞膜流动性动态降低对膜上伴刀豆球蛋白(ConA)受体结合量的影响。     

Role of adipocytokines in obesity-associated insulin resistance

The rapid increase of obese population in the United States has made obesity into epidemic proportion. Obesity is a strong risk factor for metabolic syndrome, type 2 diabetes mellitus, cardiovascular diseases, cancer and other diseases. Compelling evidence has demonstrated that increased adipose tissue mass is not only the consequence of obesity, but also plays a central role in the development of obesity-associated diseases. Recent studies have profoundly changed the concept of adipose tissue from being an energy depot to an active endocrine organ. The development of obesity alters adipocyte-derived hormones or cytokines expression, which provide a link between obesity and impaired insulin sensitivity and metabolic defects in other tissues. This review summarizes the current knowledge on how major adipose-derived hormones or adipocytokines influence insulin sensitivity.     

Cryo-atomic force microscopy of unphosphorylated and thiophosphorylated single smooth muscle myosin molecules

The purpose of this study was to determine whether steric blockage of one head by the second head of native two-headed myosin was responsible for the inactivity of nonphosphorylated two-headed myosin compared with the high activity of single-headed myosin, as suggested on the basis of electron microscopy of two-dimensional crystals of heavy meromyosin (Wendt, T., Taylor, D., Messier, T., Trybus, K. M., and Taylor, K. A. (1999) J. Cell Biol. 147, 1385-1390; and Wendt, T., Taylor, D., Trybus, K. M., and Taylor, K. (2001) Proc. Natl. Acad. Sci. U. S. A. 98, 4361-4366). Our earlier cryo-atomic force microscopy (cryo-AFM) (Zhang, Y., Shao, Z., Somlyo, A. P., and Somlyo, A. V. (1997) Biophys. J. 72, 1308-1318) indicates that thiophosphorylation of the regulatory light chain increases the separation of the two heads of a single myosin molecule, but the thermodynamic probability of steric hindrance by strong binding between the two heads was not determined. We now report this probability determined by cryo-AFM of single whole myosin molecules shown to have normal low ATPase activity (0.007 s-1). We found that the thermodynamic probability of the relative head positions of nonphosphorylated myosin was approximately equal between separated heads as compared with closely apposed heads (energy difference of 0.24 kT (where k is a Boltzman constant and T is the absolute temperature)), and thiophosphorylation increased the number of molecules having separated heads (energy advantage of -1.2 kT (where k is a Boltzman constant and I is the absolute temperature)). Our results do not support the suggestion that strong binding of one head to the other stabilizes the blocked conformation against thermal fluctuations resulting in steric blockage that can account for the low activity of nonphosphorylated two-headed myosin.     

RIG-I mediates the co-induction of tumor necrosis factor and type I interferon elicited by myxoma virus in primary human macrophages

The sensing of pathogen infection and subsequent triggering of innate immunity are key to controlling zoonotic infections. Myxoma virus (MV) is a cytoplasmic DNA poxvirus that in nature infects only rabbits. Our previous studies have shown that MV infection of primary mouse cells is restricted by virus-induced type I interferon (IFN). However, little is known about the innate sensor(s) involved in activating signaling pathways leading to cellular defense responses in primary human immune cells. Here, we show that the complete restriction of MV infection in the primary human fibroblasts requires both tumor necrosis factor (TNF) and type I IFN. We also demonstrate that MV infection of primary human macrophages (pHMs) activates the cytoplasmic RNA sensor called retinoic acid inducible gene I (RIG-I), which coordinately induces the production of both TNF and type I IFN. Of note, RIG-I sensing of MV infection in pHMs initiates a sustained TNF induction through the sequential involvement of the downstream IFN-regulatory factors 3 and 7 (IRF3 and IRF7). Thus, RIG-I-mediated co-induction of TNF and type I IFN by virus-infected pHMs represents a novel innate defense mechanism to restrict viral infection in human cells. These results also reveal a new regulatory mechanism for TNF induction following viral infection.     

Core–shell structured CdTe/CdS@SiO2@CdTe@SiO2 composite fluorescent spheres: Synthesis and application for Cd2+ detection

Core–shell structured quantum dot (QD)–silica fluorescent nanoparticles have attracted a great deal of attention due to the excellent optical properties of QDs and the stability of silica. In this study, core–shell structured CdTe/CdS@SiO₂@CdTe@SiO₂ fluorescent nanospheres were synthesized based on the Stöber method using multistep silica encapsulation. The second silica layer on the CdTe QDs maintained the optical stability of nanospheres and decreased adverse influences on the probe during subsequent processing. Red‐emissive CdTe/CdS QDs (630 nm) were used as a built‐in reference signal and green‐emissive CdTe QDs (550 nm) were used as a responding probe. The fluorescence of CdTe QDs was greatly quenched by added S^2?, owing to a S^2?‐induced change in the CdTe QDs surface state in the shell. Upon addition of Cd²⁺ to the S^2?‐quenched CdTe/CdS@SiO₂@CdTe@SiO₂ system, the responding signal at 550 nm was dramatically restored, whereas the emission at 630 nm remained almost unchanged; this response could be used as a ratiometric ‘off–on’ fluorescent probe for the detection of Cd²⁺. The sensing mechanism was suggested to be: the newly formed CdS‐like cluster with a higher band gap facilitated exciton/hole recombination and effectively enhanced the fluorescence of the CdTe QDs. The proposed probe shows a highly sensitive and selective response to Cd²⁺ and has potential application in the detection of Cd²⁺ in environmental or biological samples.     

Mitochondrial DNA phylogeography of Glyptothorax fokiensis and Glyptothorax hainanensis in Asia

Whole mitochondrial DNA cytochrome b sequences in 62 fish from 13 locations in Southeast China identified two major clades corresponding to two allopatric taxa, Glyptothorax fokiensis fokiensis and Glyptothorax fokiensis hainanensis . Reciprocal monophyly and a molecular clock separation between these two taxa of 2·3 million years indicate these taxa should be elevated to species. Mismatch distributions and Fu's F _S statistic suggest that both G. fokiensis and G. hainanensis have experienced recent population expansions. Analysis of molecular variance indicates that most of the genetic variation resides among populations within both species, with Φ _ST= 0·645 for G. fokiensis and 0·801 for G. hainanensis , suggesting restricted gene flow among populations. Significant correlations between the geographic and the genetic distances provide support for the importance of geographic isolations between populations. Nested clade analysis also confirms low levels of genetic exchanges between the two major groups and between populations within each group. The phylogeographical pattern among populations of Glyptothorax in East Asia can be attributed to historical fragmentations, demographic expansions and occasional long-distance dispersals stimulated by tectonic activity and Ice Age climate changes.     

The use of avidin-biotinylglycan as the model for in vitro glycoprotein processing

In an attempt to evaluate the effects of the protein matrix on the specificity of glycoprotein processing in Golgi membranes, we have developed a model neoglycoprotein consisting of biotinylated glycans bound noncovalently to avidin (Chen, V. J., and Wold, F. (1986) Biochemistry 25, 939-444) with which the protein effect on processing can be evaluated as the difference in substrate efficiency between a free biotinylated glycan and the same biotinylated glycan bound to avidin. The avidin (streptavidin)-glycan complex stability was found to be proper for the experimental design; the complex remains intact for extended periods of incubation at the concentrations used, but the glycan can be completely liberated and recovered by heating the complex at 95 degrees C for 10 min in the presence of a 10-fold molar excess of biotin. By measuring the relative rates of [14C]sugar incorporation into the free and bound substrates it was demonstrated that the protein indeed influences the processing reactions; under conditions where free glycans such as biotinyl-Asn-Glc-NAc2-Man5 and 6-(biotinamido)hexanoyl-Asn-Glc-NAc2-Man5 could be converted to the biantennary products R-Asn-GlcNAc2-Man3-GlcNAc2-Gal2-sialyl2 in the presence of UDP-GlcNAc, UDP-Gal and CMP-sialic acid and Golgi enzymes, the avidin-bound derivative without the extension arm gave only low levels of product and the streptavidin-bound one remained unaltered. The presence of the extension arm in the substrates significantly improved the yield of some products in the complex, apparently by reducing or eliminating the avidin inhibition of the early steps, but not of the late ones. There are consequently two types of effect of the protein matrix on processing efficiency. One is expressed only when the glycan is close to the protein surface and affecting primarily early steps (mannosidases and GlcNAc transferases). The other is apparently independent of the proximity of the glycan core and the protein, and affects primarily late steps, in particular the incorporation of the second sialic acid residue into a biantennary complex glycan.     

Quantifying HDL proteins by mass spectrometry: how many proteins are there and what are their functions?

Introduction: Many lines of evidence indicate that low levels of HDL cholesterol increase the risk of cardiovascular disease (CVD). However, recent clinical studies of statin-treated subjects with established atherosclerosis cast doubt on the hypothesis that elevating HDL cholesterol levels reduces CVD risk.

Areas covered: It is critical to identify new HDL metrics that capture HDL’s proposed cardioprotective effects. One promising approach is quantitative MS/MS-based HDL proteomics. This article focuses on recent studies of the feasibility and challenges of using this strategy in translational studies. It also discusses how lipid-lowering therapy and renal disease alter HDL’s functions and proteome, and how HDL might serve as a platform for binding proteins with specific functional properties.

Expert commentary: It is clear that HDL has a diverse protein cargo and that its functions extend well beyond its classic role in lipid transport and reverse cholesterol transport. MS/MS analysis has demonstrated that HDL might contain >80 different proteins. Key challenges are demonstrating that these proteins truly associate with HDL, are functionally important, and that MS-based HDL proteomics can reproducibly detect biomarkers in translational studies of disease risk.