Relationship between LTP and the nuclear protein induced by calcineurin

Results demonstrate that calcineurin plays a role in long term potentiatibn (LTP) in the hippocampus. A 45 ku enzyme was administered, which exhibits Ca²⁺ /calmodulin independent activity to rats, and the protein components of nuclear extracts from the cell-free system of rat hippocampus were tested. It is found that the level of a component significantly increased in nuclear extracts following the activation of calcineurin. The concentration of the component in the nucleus is also markedly increased following hippocampal LTP elicited by ginsenosides. These results suggest that the activation of calcineurin induces a preexisting protein component to translocate to the nucleus in the hippocampus. The nuclear translocation of the component may be required for LTP in the hippocampus.     

Tumour maintenance is mediated by eNOS

Tumour cells become addicted to the expression of initiating oncogenes like Ras, such that loss of oncogene expression in established tumours leads to tumour regression. HRas, NRas or KRas are mutated to remain in the active GTP-bound oncogenic state in many cancers. Although Ras activates several proteins to initiate human tumour growth, only PI3K, through activation of protein kinase B (PKB; also known as AKT), must remain activated by oncogenic Ras to maintain this growth. Here we show that blocking phosphorylation of the AKT substrate, endothelial nitric oxide synthase (eNOS or NOS3), inhibits tumour initiation and maintenance. Moreover, eNOS enhances the nitrosylation and activation of endogenous wild-type Ras proteins, which are required throughout tumorigenesis. We suggest that activation of the PI3K-AKT-eNOS-(wild-type) Ras pathway by oncogenic Ras in cancer cells is required to initiate and maintain tumour growth.     

CREB在姜黄素改善gp120所致大鼠学习记忆障碍中的作用

目的:探讨cAMP反应元件结合蛋白(CREB)在姜黄素改善gp120所致大鼠学习记忆障碍中的作用.方法:SD大鼠随机分为6组:对照组、假手术组、模型组、姜黄素低、中和高剂量治疗组;除对照组、假手术组外其余4组侧脑室缓慢注射5μL的gp120,连续3 d.第4天开始,低、中、高剂量治疗组分别每天给予50、100、200 mg/kg的姜黄素灌胃,对照组、假手术组和模型组大鼠用双蒸水灌胃,连续灌胃14 d.各组大鼠进行水迷宫测试,并分组进行海马磷酸化的CREB(pCREB)免疫组化染色.结果:①Morris水迷宫空间探索实验显示模型组大鼠反应迟钝,寻找目标象限所需的时间较长,在目标象限停留的时间及穿越次数明显短于对照组(P<0.05);姜黄素低、中、高剂量治疗组大鼠寻找目标象限所需时间缩短,在目标象限停留的时间及穿越次数明显长于模型组(P<0.05),其中姜黄素低剂量组效果更好(P<0.05).②免疫组化结果显示模型组大鼠海马内pCREB的表达与对照组相比有所降低(P<0.01),姜黄素各剂量治疗组pCREB的表达有所上调.结论:姜黄素具有改善gp120所致大鼠学习记忆障碍的作用,其机制可能与增加海马CREB的磷酸化水平有关.     

Macrophage-induced angiogenesis is mediated by tumour necrosis factor-alpha

Macrophages are important in the induction of new blood vessel growth during wound repair, inflammation and tumour growth. We show here that tumour necrosis factor-alpha (TNF-alpha), a secretory product of activated macrophages that is believed to mediate tumour cytotoxicity, is a potent inducer of new blood vessel growth (angiogenesis). In vivo, TNF-alpha induces capillary blood vessel formation in the rat cornea and the developing chick chorioallantoic membrane at very low doses. In vitro, TNF-alpha stimulates chemotaxis of bovine adrenal capillary endothelial cells and induces cultures of these cells grown on type-1 collagen gels to form capillary-tube-like structures. The angiogenic activity produced by activated murine peritoneal macrophages is completely neutralized by a polyclonal antibody to TNF-alpha, suggesting immunological features are common to TNF-alpha and the protein responsible for macrophage-derived angiogenic activity. In inflammation and wound repair, TNF-alpha could augment repair by stimulating new blood vessel growth; in tumours, TNF-alpha might both stimulate tumour development by promoting vessel growth and participate in tumour destruction by direct cytotoxicity.     

Phagocytosis and clearance of apoptotic cells is mediated by MER

Apoptosis is fundamental to the development and maintenance of animal tissues and the immune system. Rapid clearance of apoptotic cells by macrophages is important to inhibit inflammation and autoimmune responses against intracellular antigens. Here we report a new function for Mer, a member of the Axl/Mer/Tyro3 receptor tyrosine kinase family. mer(kd) mice with a cytoplasmic truncation of Mer had macrophages deficient in the clearance of apoptotic thymocytes. This was corrected in chimaeric mice reconstituted with bone marrow from wild-type animals. Primary macrophages isolated from mer(kd) mice showed that the phagocytic deficiency was restricted to apoptotic cells and was independent of Fc receptor-mediated phagocytosis or ingestion of other particles. The inability to clear apoptotic cells adequately may be linked to an increased number of nuclear autoantibodies in mer(kd) mice. Thus, the Mer receptor tyrosine kinase seems to be critical for the engulfment and efficient clearance of apoptotic cells. This has implications for inflammation and autoimmune diseases such as systemic lupus erythematosus.     

Photoreceptor light adaptation is mediated by cytoplasmic calcium concentration

The vertebrate visual system can operate over a large range of light intensities. This is possible in part because the sensitivity of photoreceptors decreases approximately in inverse proportion to the background light intensity. This process, called photoreceptor light adaptation, is known to be mediated by a diffusible intracellular messenger, but the identity of the messenger is still unclear. There has been considerable speculation that decreased cytoplasmic Ca2+ concentration (Cai2+) may play a role in light adaptation, and recent experiments in which Ca2+ buffer was incorporated into rod-cells have supported this notion. The extent of the contribution of calcium, however, remains unresolved. We now show that light-dependent changes in sensitivity in amphibian photoreceptors can be abolished by preventing movements of Ca2+ across the outer-segment plasma membrane. These experiments demonstrate that light adaptation in photoreceptors is mediated in cones primarily, and in rods perhaps exclusively, by changes in Cai2+.     

Obtained transgenic wheat expressing pac1 mediated by Agrobacterium is resistant against Barley yellow dwarf virus-GPV

At present, genes used to transform wheat for the virus resistance are mostly from the virus, such as coat protein gene[1,2], replicase gene[3] and movement gene[4], and transformed wheat with these genes showed resis-tance to the corresponding virus. How…     

Obtained transgenic wheat expressing pac1 mediated by Agrobacterium is resistant against Barley yellow dwarf virus-GPV

In fission yeast （Schizosaccharomyces pombe）, pacl gene was cloned with 99.3% nucleotide sequence similarity with published pacl in GenBank. In pET-5α expression system, the expression product of cloned pacl in E. coil showed activity to degrade the double-strand RNA. Harboring the binary vector pBI121, which contains pacl gene, Agrobacterium tumefaciens strain LBA4404 was used to transform the wheat immature embryos precultured 7-10 d. After preregeneration, regeneration and selection culture stage, totally 41 G418 resistant plants were obtained, in which 25 lines were proved to integrate with transgene and express transgene normally by PCR, Dot blot, RT-PCR and ELISA detection. Antivirus test carried out on 25 positive lines with high dose of Barley yellow dwarf virus-GPV revealed that 12 lines had resistance to BVDV-GPV in low level, another 12 lines had resistance to BVDV- GPV in middle level, and 1 line showed resistance to BVDV-GPV in high level. However, both low and middle level of resistance plants showed no symptoms when infected by viruses at low dose, which suggested the dose-dependent effect of the resistance mediated by pacl to BYDV-GPV.     

基于一类完备格诱导的直觉模糊集的多元扩展运算

基于一种二元序完备格引入了直觉模糊集的截集的概念,给出了直觉模糊集的加、减和乘法等算术运算,获得了这种截集的算术运算性质,并通过实例说明这些包含关系可以严格成立.此外,在完备格诱导的直觉模糊集的截集基础上,得到了直觉模糊集的多元扩展原理,进而讨论了多元扩展运算的2个基本性质.     

Clathrin self-assembly is mediated by a tandemly repeated superhelix.

Clathrin is a triskelion-shaped cytoplasmic protein that polymerizes into a polyhedral lattice on intracellular membranes to form protein-coated membrane vesicles. Lattice formation induces the sorting of membrane proteins during endocytosis and organelle biogenesis by interacting with membrane-associated adaptor molecules. The clathrin triskelion is a trimer of heavy-chain subunits (1,675 residues), each binding a single light-chain subunit, in the hub domain (residues 1,074-1,675). Light chains negatively modulate polymerization so that intracellular clathrin assembly is adaptor-dependent. Here we report the atomic structure, to 2.6 A resolution, of hub residues 1,210-1,516 involved in mediating spontaneous clathrin heavy-chain polymerization and light-chain association. The hub fragment folds into an elongated coil of alpha-helices, and alignment analyses reveal a 145-residue motif that is repeated seven times along the filamentous leg and appears in other proteins involved in vacuolar protein sorting. The resulting model provides a three-dimensional framework for understanding clathrin heavy-chain self-assembly, light-chain binding and trimerization.     

Host recognition by the tobacco hornworm is mediated by a host plant compound

It is generally believed that animals make decisions about the selection of mates, kin or food on the basis of pre-constructed recognition templates. These templates can be innate or acquired through experience. An example of an acquired template is the feeding preference exhibited by larvae of the moth, Manduca sexta. Naive hatchlings will feed and grow successfully on many different plants or artificial diets, but once they have fed on a natural host they become specialist feeders. Here we show that the induced feeding preference of M. sexta involves the formation of a template to a steroidal glycoside, indioside D, that is present in solanaceous foliage. This compound is both necessary and sufficient to maintain the induced feeding preference. The induction of host plant specificity is at least partly due to a tuning of taste receptors to indioside D. The taste receptors of larvae fed on host plants show an enhanced response to indioside D as compared with other plant compounds tested.     

Draper-dependent glial phagocytic activity is mediated by Src and Syk family kinase signalling

The cellular machinery promoting phagocytosis of corpses of apoptotic cells is well conserved from worms to mammals. An important component is the Caenorhabditis elegans engulfment receptor CED-1 (ref. 1) and its Drosophila orthologue, Draper. The CED-1/Draper signalling pathway is also essential for the phagocytosis of other types of 'modified self' including necrotic cells, developmentally pruned axons and dendrites, and axons undergoing Wallerian degeneration. Here we show that Drosophila Shark, a non-receptor tyrosine kinase similar to mammalian Syk and Zap-70, binds Draper through an immunoreceptor tyrosine-based activation motif (ITAM) in the Draper intracellular domain. We show that Shark activity is essential for Draper-mediated signalling events in vivo, including the recruitment of glial membranes to severed axons and the phagocytosis of axonal debris and neuronal cell corpses by glia. We also show that the Src family kinase (SFK) Src42A can markedly increase Draper phosphorylation and is essential for glial phagocytic activity. We propose that ligand-dependent Draper receptor activation initiates the Src42A-dependent tyrosine phosphorylation of Draper, the association of Shark and the activation of the Draper pathway. These Draper-Src42A-Shark interactions are strikingly similar to mammalian immunoreceptor-SFK-Syk signalling events in mammalian myeloid and lymphoid cells. Thus, Draper seems to be an ancient immunoreceptor with an extracellular domain tuned to modified self, and an intracellular domain promoting phagocytosis through an ITAM-domain-SFK-Syk-mediated signalling cascade.     

Structure of mammalian AMPK and its regulation by ADP

The heterotrimeric AMP-activated protein kinase (AMPK) has a key role in regulating cellular energy metabolism; in response to a fall in intracellular ATP levels it activates energy-producing pathways and inhibits energy-consuming processes. AMPK has been implicated in a number of diseases related to energy metabolism including type 2 diabetes, obesity and, most recently, cancer. AMPK is converted from an inactive form to a catalytically competent form by phosphorylation of the activation loop within the kinase domain: AMP binding to the γ-regulatory domain promotes phosphorylation by the upstream kinase, protects the enzyme against dephosphorylation, as well as causing allosteric activation. Here we show that ADP binding to just one of the two exchangeable AXP (AMP/ADP/ATP) binding sites on the regulatory domain protects the enzyme from dephosphorylation, although it does not lead to allosteric activation. Our studies show that active mammalian AMPK displays significantly tighter binding to ADP than to Mg-ATP, explaining how the enzyme is regulated under physiological conditions where the concentration of Mg-ATP is higher than that of ADP and much higher than that of AMP. We have determined the crystal structure of an active AMPK complex. The structure shows how the activation loop of the kinase domain is stabilized by the regulatory domain and how the kinase linker region interacts with the regulatory nucleotide-binding site that mediates protection against dephosphorylation. From our biochemical and structural data we develop a model for how the energy status of a cell regulates AMPK activity.     

Regulation of cell movement is mediated by stretch-activated calcium channels.

Intracellular calcium regulates many of the molecular processes that are essential for cell movement. It is required for the production of actomyosin-based contractile forces, the regulation of the structure and dynamics of the actin cytoskeletons, and the formation and disassembly of cell-substratum adhesions. Calcium also serves as a second messenger in many biochemical signal-transduction pathways. However, despite the pivotal role of calcium in motile processes, it is not clear how calcium regulates overall cell movement. Here we show that transient increases in intracellular calcium, [Ca2+]i, during the locomotion of fish epithelial keratocytes, occur more frequently in cells that become temporarily 'stuck' to the substratum or when subjected to mechanical stretching. We find that calcium transients arise from the activation of stretch-activated calcium channels, which triggers an influx of extracellular calcium. In addition, the subsequent increase in [Ca2+]i is involved in detachment of the rear cell margin. Thus, we have defined a mechanism by which cells can detect and transduce mechanical forces into biochemical signals that can modulate locomotion.     

Shoot control of root development and nodulation is mediated by a receptor-like kinase

In legumes, root nodule organogenesis is activated in response to morphogenic lipochitin oligosaccharides that are synthesized by bacteria, commonly known as rhizobia. Successful symbiotic interaction results in the formation of highly specialized organs called root nodules, which provide a unique environment for symbiotic nitrogen fixation. In wild-type plants the number of nodules is regulated by a signalling mechanism integrating environmental and developmental cues to arrest most rhizobial infections within the susceptible zone of the root. Furthermore, a feedback mechanism controls the temporal and spatial susceptibility to infection of the root system. This mechanism is referred to as autoregulation of nodulation, as earlier nodulation events inhibit nodulation of younger root tissues. Lotus japonicus plants homozygous for a mutation in the hypernodulation aberrant root (har1) locus escape this regulation and form an excessive number of nodules. Here we report the molecular cloning and expression analysis of the HAR1 gene and the pea orthologue, Pisum sativum, SYM29. HAR1 encodes a putative serine/threonine receptor kinase, which is required for shoot-controlled regulation of root growth, nodule number, and for nitrate sensitivity of symbiotic development.