Cyclic di-GMP sensing via the innate immune signaling protein STING

Detection of foreign materials is the first step of successful immune responses. Stimulator of interferon genes (STING) was shown to directly bind cyclic diguanylate monophosphate (c-di-GMP), a bacterial second messenger, and to elicit strong interferon responses. Here we elucidate the structural features of the cytosolic c-di-GMP binding domain (CBD) of STING and its complex with c-di-GMP. The CBD exhibits an α + β fold and is a dimer in the crystal and in solution. Surprisingly, one c-di-GMP molecule binds to the central crevice of a STING dimer, using a series of stacking and hydrogen bonding interactions. We show that STING is autoinhibited by an intramolecular interaction between the CBD and the C-terminal tail (CTT) and that c-di-GMP releases STING from this autoinhibition by displacing the CTT. The structures provide a remarkable example of pathogen-host interactions in which a unique microbial molecule directly engages the innate immune system.     

羽叶三七根茎的三萜皂甙成分及其化学分类学意义

羽叶三七(Panax japonicus C. A. Meyer var. bipinnalifidus (Scem.) Wu et Feng)又称疙瘩七,产我国西北部至西南部山区,是人参届植物中分布海拔和纬度均较高的一个种类。在陕西省秦岭地区主要产于南北坡海拔2100—2900米的针叶林下阴湿处。民间以其根茎入药,具有清热解毒、顺气健胃、活血祛瘀、滋补强壮之效。作为国产人参属植物皂甙成分系统研究的一个部分,本文报告秦岭产羽叶三七根茎的皂甙成分,并讨论其化学分类学意义。     

Structural and catalytic role of two conserved tyrosines in Delta-class glutathione S-transferase from Locusta migratoria

Glutathione S-transferases (GSTs) are an important family of detoxifying enzymes and play a key role in pesticide resistance in the insect. Tyrosine is essential for its detoxification function. In the present study, two conserved tyrosine residues are located at positions 108 and 116 in H-site of LmGSTD1. To elucidate how the two residues participate in the catalytic process and keeping structural stability, four mutants, Y108A, Y108E, Y116A, and Y116E, were generated. It was found that the four mutants affected the specific activity of LmGSTD1 in various degrees, depending on the types of substrate and reaction mechanism. Steady-state kinetics assay revealed that Y108E and Y116E had a significant influence on GSH-binding ability, which indicates the two tyrosine residues of H-site contribute to topology rearrangement of G-site. Both Y116A and Y116E exhibited lower CDNB-binding affinity, suggesting that Y116 takes part in hydrophobic substrate binding. The thermostability assay, intrinsic, and 8-anilino-1-naphthalenesulfonic acid (ANS) florescence results showed that the two tyrosine residues were involved in regulation of active-site conformation. Finally, homology modeling provided evidence that the two tyrosines in H-site participate in hydrophobic substrate binding. Furthermore, Y108 is closer to the S atom of S-hexylglutathione. In conclusion, the two tyrosines in LmGSTD1 are important residues in both the catalytic process and protein stability.     

Leucine aminopeptidase 3 promotes migration and invasion of breast cancer cells through upregulation of fascin and matrix metalloproteinases-2/9 expression

Overexpression of leucine aminopeptidase 3 (LAP3) is involved in proliferation, migration, and invasion of several tumor cells and plays a crucial role in tumor metastasis. However, the related mechanism remains unknown. In this study, we used MDA-MB-231 and MCF7 breast cancer cell lines to explore the role of LAP3 in the regulation of cancer cell migration and invasion by employing the natural LAP3 inhibitor bestatin and a lentivirus vector that overexpresses or knocks down LAP3. Bestatin inhibited tumor cell migration and invasion in a dose-dependent manner. Western blot assay showed that bestatin and knockdown of LAP3 upregulated phosphorylation of Hsp27 and downregulated expression of fascin. Phosphorylation of Akt and expression of matrix metalloproteinase-2/9 can also be downregulated. LAP3 overexpression showed the opposite results. Immunohistochemistry analysis was conducted to detect expression levels of LAP3 in breast cancer tissues. High LAP3 expression was correlated with the grade of malignancy. Findings of this study uncovered the molecular mechanism of LAP3 on breast cancer metastasis and indicated that LAP3 may act as a potential antimetastasis therapeutic target.     

基于PI3K/PKB通路研究EGCG对CVB3感染致病毒性心肌炎小鼠细胞凋亡的影响

细胞凋亡是造成病毒性心肌炎(VMC)发病过程中心肌损伤的重要因素;表没食子儿茶素没食子酸酯(EGCG)对缺血再灌注引起的细胞凋亡具有抑制作用,但是否抑制VMC发病过程中的心肌细胞凋亡尚不明确.因此,本研究将分析EGCG对VMC小鼠细胞凋亡的影响及分子机制.BALB/c小鼠随机分为对照组、VMC组(腹腔注射CVB3悬液造模)、VMC+EGCG组(腹腔注射CVB3悬液造模后腹腔注射EGCG)、VMC+EGCG+LY组(腹腔注射CVB3悬液造模后腹腔注射EGCG及P13K抑制剂LY294002).检测血清心肌损伤标志物肌钙蛋白I(cTnI)及乳酸脱氢酶(LDH),心肌中CVB3滴度及RNA表达、HE染色、凋亡基因及p-PI3K、p-PKB表达.结果显示,与对照组比较,VMC组血清cTnI、LDH含量、心肌中CVB3滴度及RNA表达、细胞凋亡率、cleaved caspase-3表达升高,心肌中Survivin、p-PI3K、p-PKB表达降低(P＜0.05);与VMC组比较,VMC+EGCG组血清cTnI、LDH含量及心肌中细胞凋亡率、cleaved caspase-3表达降低,心肌中Survivin、p-PI3K、p-PKB表达升高(P＜0.05),心肌中CVB3滴度及RNA表达无明显变化(P＞0.05);与VMC+EGCG组比较,VMC+EGCG+LY组血清cTnI、LDH含量、心肌中细胞凋亡率、cleaved caspase-3表达升高,心肌中Survivin、p-PI3K、p-PKB表达降低(P＜0.05),心肌中CVB3滴度及RNA表达无明显变化(P＞0.05).以上结果表明EGCG对VMC小鼠心肌细胞凋亡具有抑制作用且该作用与激活PI3K/PKB通路有关.     

Crystal structure of a coiled-coil domain from human ROCK I

The small GTPase Rho and one of its targets, Rho-associated kinase (ROCK), participate in a variety of actin-based cellular processes including smooth muscle contraction, cell migration, and stress fiber formation. The ROCK protein consists of an N-terminal kinase domain, a central coiled-coil domain containing a Rho binding site, and a C-terminal pleckstrin homology domain. Here we present the crystal structure of a large section of the central coiled-coil domain of human ROCK I (amino acids 535-700). The structure forms a parallel α-helical coiled-coil dimer that is structurally similar to tropomyosin, an actin filament binding protein. There is an unusual discontinuity in the coiled-coil; three charged residues (E613, R617 and D620) are positioned at what is normally the hydrophobic core of coiled-coil packing. We speculate that this conserved irregularity could function as a hinge that allows ROCK to adopt its autoinhibited conformation.     

New organoantimony complexes with the isomers of chlorophenylacetic acid: Syntheses, characterizations and crystal structures of 1D polymeric chain, 2D network structure and 3D framework

A series of novel organoantimony(V) complexes have been synthesised by the reactions of the isomers of chlorophenylacetic acids with triphenylantimony(V) dichloride or tetraphenylantimony(V) bromide in 1:2 or 1:1 stoichiometries. All the complexes have been characterized by elemental analysis, IR and NMR (¹H, ¹³C) spectra analyses; furthermore, complexes 1, 2, 3 and 4 have been determined by X-ray single crystal diffraction. The structure of complexes show that the five-coordinated and six-coordinated antimony(V) atoms adopt distorted trigonal bipyramidal geometry and octahedral geometry. And the structural analyses show that complexes 1 and 3 have 2D network structures; complex 2 possesses a 1D polymeric chain structure and complex 4 has a 3D supramolecular framework.     

Synthesis and characterization of a novel spring-like organotin complex containing guest benzene molecules

A novel spring-like organotin complex [(Ph₃Sn)(C₇H₅ClNO₂)]_n·3C₆H₆ (1), has been synthesized by treatment of 6-chloro-3-pyridineacetic acid bis(triphenyltin)oxide on the condition of reflux. The complex was characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy, and X-ray crystallography diffraction analysis. The structure analyses reveals that complex 1 is an 1D infinite chain linked by intermolecular Sn-O bonds, in which the guest benzene molecules are established in the cavity of this helical chain; all the tin atoms of complex 1 are five-coordinated.