Structure of the Type VI Effector-Immunity Complex (Tae4-Tai4) Provides Novel Insights into the Inhibition Mechanism of the Effector by Its Immunity Protein

The type VI secretion system (T6SS), a multisubunit needle-like apparatus, has recently been found to play a role in interspecies interactions. The Gram-negative bacteria harboring T6SS (donor) deliver the effectors into their neighboring cells (recipient) to kill them. Meanwhile, the cognate immunity proteins were employed to protect the donor cells against the toxic effectors. Tae4 (type VI amidase effector 4) and Tai4 (type VI amidase immunity 4) are newly identified T6SS effector-immunity pairs. Here, we report the crystal structures of Tae4 from Enterobacter cloacae and Tae4-Tai4 complexes from both E. cloacae and Salmonella typhimurium. Tae4 acts as a dl-endopeptidase and displays a typical N1pC/P60 domain. Unlike Tsi1 (type VI secretion immunity 1), Tai4 is an all-helical protein and forms a dimer in solution. The small angle x-ray scattering study combined with the analytical ultracentrifugation reveal that the Tae4-Tai4 complex is a compact heterotetramer that consists of a Tai4 dimer and two Tae4 molecules in solution. Structure-based mutational analysis of the Tae4-Tai4 interface shows that a helix (α3) of one subunit in dimeric Tai4 plays a major role in binding of Tae4, whereas a protruding loop (L4) in the other subunit is mainly responsible for inhibiting Tae4 activity. The inhibition process requires collaboration between the Tai4 dimer. These results reveal a novel and unique inhibition mechanism in effector-immunity pairs and suggest a new strategy to develop antipathogen drugs.     

In vivo delivery of small interfering RNA targeting brain capillary endothelial cells

Brain capillary endothelial cells (BCECs) play an important role in blood-brain barrier (BBB) functions and pathophysiologic mechanisms in brain ischemia and inflammation. We try to suppress gene expression in BCECs by intravenous application of small interfering RNA (siRNA). After injection of large dose siRNA with hydrodynamic technique to mouse, suppression of endogenous protein and the BBB function of BCECs was investigated. The brain-to-blood transport function of organic anion transporter 3 (OAT3) that expressed in BCECs was evaluated by Brain Efflux Index method in mouse. The siRNA could be delivered to BCECs and efficiently inhibited endogenously expressed protein of BCECs. The suppression effect of siRNA to OAT3 is enough to reduce the brain-to-blood transport of OAT3 substrate, benzylpenicillin at BBB. The in vivo siRNA-silencing method with hydrodynamic technique may be useful for the study of BBB function and gene therapy targeting BCECs.     

Ultrasound promoted green synthesis,anticancer evaluation,and molecular docking studies of hydrazines: a pilot trial

We reported herein an efficient, environmentally friendly synthesis of hydrazine carboxamides (6a–l) in a water-glycerol (6:4) solvent system using ultrasonic irradiation. Ultrasonicated reactions were found to be much faster and more productive than conventional synthesis. The prepared compounds (6a–l) were tested against nine panels of 60 cancer cell lines according to the National Cancer Institute (NCI US) protocol. N-(4-Chlorophenyl)-2-(2-oxoindolin-3-ylidene)hydrazine-1-carboxamide (6b) was discovered to be promising anticancer agents with higher sensitivity against CCRF-CEM, HOP-92, UO-31, RMPI-8226, HL-60(TB), and MDA-MB-468 with percent growth inhibitions (%GIs) of 143.44, 33.46, 33.21, 33.09, 29.81, and 29.55 respectively. Compounds (6a–l) tested showed greater anticancer activity than Imatinib, except for compound 6k. Compounds 6b and 6c were found to be lethal on the CCRF-CEM leukaemia cell line, with %GIs of 143.44 and 108.91, respectively. Furthermore, molecular docking analysis was performed to investigate ligand binding affinity at the active site of epidermal growth factor (EGFR).     

美国州立公园体系的发展、特征与评估

美国州立公园与国家公园相比,更强调满足州内居民就近户外休闲游憩需求的功能,这使得其在美国整体公共户外休闲空间体系中占据特殊的位置。在中国第一次全面地研究了美国州立公园体系的发展、特征及与国家公园体系的关系,特别是以部分州为例研究了美国州立公园的分类、质量评估、可达性与空间分布评估等关键问题。研究认为,州立公园的意义在于既缓解了美国国家公园面临的巨大旅游游憩压力,也满足了大众户外休闲游憩的需求。这值得中国在目前构建国家公园与自然保护地体系的同时予以借鉴。最后基于中国的实际需求与挑战,探讨了在省域/区域层次加强构建地方公园、保护地和游憩地体系建设的必要性与途径。     

Nogo-B与Clusterin结合对细胞凋亡的影响

神经轴突生长抑制因子Nogo—B在体分布广泛,提示其除了具有抑制中枢神经系统轴突再生作用外,可能还扮演其他重要的功能角色。该研究为探讨Nogo-B下游新的结合分子及其功能开展相应研究。通过设计诱饵蛋白筛选人脑cDNA文库、免疫共沉淀方法,寻找Nogo-B下游结合分子：通过流式细胞术,检测结合对于细胞凋亡的影响：通过绿色荧光蛋白标记和免疫组织化学方法,探讨Nogo-B诱导细胞凋亡的机制。结果提示,Clusterin除了与Nogo-66功能域在酵母双杂交系统中存在结合,与Nogo—B在哺乳细胞中也能发生结合。过表达Nogo-B可明显诱导HEK293细胞凋亡,与Clusterin共表达可下调早期细胞凋亡率,但后期Nogo—B可通过调节Clusterin由胞浆到胞核转位,进一步诱导细胞凋亡进程。该研究首次提出Nogo—B与Clusterin之间存在结合,且结合参与了Nogo-B诱导的细胞凋亡进程。     

Ce3+对Cu2+胁迫下菹草叶片Cu毒害的缓解效应研究

在6种不同浓度的铈(C e3 )对0.1 m g.L-1的Cu2 毒害下,研究了菹草叶片中保护酶SOD、POD、CAT的活性,活性氧H2O2,膜脂过氧化产物M DA含量及叶绿素含量等的变化及影响.结果表明,在9~12 d之内,7.5 m g.L-1以下的C e3 可以增强SOD、CAT、POD活性,降低M DA的含量,提高叶片中叶绿素和可溶性蛋白含量,从而减轻Cu2 对菹草植物体的伤害.而随着C e3 作用时间的延长和浓度的增大,C e3 的缓解作用不断减弱,C e3 和Cu2 产生协同效应,加重毒害.本实验结果认为,5~7.5 m g.L-1的C e3 缓解菹草叶片Cu2 毒害效果最好.     

正常妊娠大鼠的Th2型免疫反应

采用流式细胞仪,^3H-TdR掺入和酶联免疫打点(enzyme-linked immunospot,ELISPOT)方法研究妊娠免疫学指标的改变。妊娠晚期大鼠脾脏单个核细胞表面分子主要组织相容性抗原Ⅱ(MHCⅡ)明显下调,外周血单个核细胞表达CD11c明显减少,共激活分子B7-1和B7-2未见改变;脾脏和外周血单个核细胞中Th2细胞因子IL-10、IL-4表达增多,TGFD阳性细胞数也明显增加,而Th1细胞因子IFNγ的产生未受抑制。此外,脾脏和外周血中单个核细胞的抗原特异性增殖未见改变,而腹腔淋巴结细胞的增殖明显升高。脾脏单个核细胞在妊娠晚期分泌较少的抗原特异性抗体。提示妊娠期性激素具有免疫调节作用,可能与怀孕时Th1细胞介导的自身免疫性疾病得到缓解有关。     

Infraciliature and myoneme system of Campanella umbellaria (Protozoa, Ciliophora, Peritrichida)

The infraciliature and myoneme system of Campanella umbellaria were revealed using the protargol impregnation technique. The main characteristics of the infraciliature are the peristomial ciliary rows (haplokinety and polykineties), which make four and a half turns around the peristomial disc before plunging into the infundibulum, and the aboral infraciliature, which is made up of the aboral ciliary wreath (trochal band) and the scopula. The myoneme system is composed of: 1) longitudinal fibers, which include 60-84 (mean 72.3) short longitudinal fibers, 40-56 (mean 45.8) medium-length longitudinal fibers, and numerous long longitudinal fibers; and 2) circular fibers, which include 8-12 (mean 9.3) peristomial ring fibers, linking fibers, support fibers, and peristomial disc fibers. The various fibers in C. umbellaria are interconnected to form a single myoneme system that may act as a cell skeleton as well as providing the mechanism by which the zooid contracts and relaxes.     

Cross-connections coordinate postural motoneuron activity in the crayfish abdomen

Intracellular recordings and dye injections were used to examine mutual coupling among slow abdominal postural motoneurons in the 4th abdominal ganglion in crayfish (Procambarus clarkii). Intracellular current injection into one motoneuron altered the spike firing rate of some of its synergists. Depending on the polarity of the injected current, the premotor effect on the synergists was excitatory or inhibitory. The magnitude of the effect was intensity dependent. No dye coupling was found among the motoneurons following injection of Lucifer yellow. The morphological basis of the coupling was examined by differential filling of motoneuron pairs, one with horseradish peroxidase and the other with Lucifer yellow. The stained motoneurons were simultaneously visualized under light microscopy to determine the proximity of their differently colored dendrites. It was thus possible to locate the site of the presumed monosynaptic contacts between them. Combined physiological and morphological evidence suggests that these neurons are mutually coupled, forming part of an integrative system for abdominal posture control in crayfish.     

细菌趋化信号通路中的磷酸酯酶CheZ

细菌通过趋化系统获得在复杂环境中的生存优势。趋化性在细菌致病性、病菌定殖、固氮细菌与宿主共生、植物与微生物互作等方面有重要的作用。作为趋化信号适应中不可或缺的调节蛋白,对CheZ的深入研究具有重要意义。本文主要对CheZ的结构、作用机制、功能调节、蛋白定位以及进化地位等方面的研究现状进行了综述,旨在为其它细菌中趋化系统的研究提供有益参考。