Identification of metastasis-associated proteins by proteomic analysis and functional exploration of interleukin-18 in metastasis

Very little is currently known about mechanisms underlying cancer metastasis. In the present study, metastasis-associated proteomes were separated and identified by comparative proteomic analysis, and the metastasis-related function of candidate protein interleukin-18 (IL-18) was further elucidated. First, a pair of highly and poorly metastatic sublines (termed PLA801D and PLA801C, respectively), originating from the same parental PLA801 cell line, was identified by spontaneous tumorigenicity and metastasis in vivo and characterized by metastatic phenotypes analysis in vitro. Subsequently, a proteomic approach was used to compare the protein expression profiles between PLA801C and PLA801D sublines. Eleven proteins were identified and further verified by one-dimensional Western blotting, Northern blot and/or semiquantitative reverse transciptase polymerase chain reaction analysis. Compared with those in poorly metastatic PLA801C subline, cytokeratin 18, tissue transglutaminase, Rho GDP-dissociation inhibitor 1, tropomyosin, fibroblast type, IL-18 and annexin I were significantly up-regulated, while protein disulfide isomerase, heat shock protein 60, peroxiredoxin 1, chlorine intracellular channel protein 1 (CLI1) and creatine kinase, B chain were significantly down-regulated in the highly metastatic PLA801D subline. Intriguingly, all the identified candidate proteins except for CLI1 have been shown to be somehow associated with distinct aspects of tumor metastasis such as cell growth, motility, invasion, adhesion, apoptosis and tumor immunity, etc. Considering that IL-18 was present in highly metastatic PLA801D but absent in poorly metastatic PLA801C, the association of IL-18 with metastasis was further elucidated by introducing IL-18 sense/IL-18 antisense into PLA801C/PLA801D sublines simultaneously. The results demonstrated that ectopically expressed IL-18 promoted cell motility in vitro and down-regulated E-cadherin expression of PLA801C transfectants, while IL-18 antisense remarkably decreased cell invasion potency in vitro and notably increased E-cadherin expression of PLA801D transfectants, indicating that IL-18 might play a role in metastasis by inhibiting E-cadherin expression.     

Defining the native disulfide topology in the somatomedin B domain of human vitronectin

The N-terminal 44 amino acid residues of the human plasma glycoprotein vitronectin, known as the somatomedin B (SMB) domain, mediates the interaction between vitronectin and plasminogen activator inhibitor 1 (PAI-1) in a variety of important biological processes. Despite the functional importance of the Cys-rich SMB domain, how its four disulfide bridges are arranged in the molecule remains highly controversial, as evidenced by three different disulfide connectivities reported by several laboratories. Using native chemical ligation and orthogonal protection of selected Cys residues, we chemically synthesized all three topological analogs of SMB with predefined disulfide connectivities corresponding to those previously published. In addition, we oxidatively folded a fully reduced SMB in aqueous solution, and prepared, by CNBr cleavage, the N-terminal segment of 51 amino acid residues of intact vitronectin purified from human blood. Proteolysis coupled with mass spectrometric analysis and functional characterization using a surface plasmon resonance based vitronectin-PAI-1-SMB competition assay allowed us to conclude that 1) only the Cys(5)-Cys(21), Cys(9)-Cys(39), Cys(19)-Cys(32), and Cys(25)-Cys(31) connectivity is present in native vitronectin; 2) only the native disulfide connectivity is functional; and 3) the native disulfide pairings can be readily formed during spontaneous (oxidative) folding of the SMB domain in vitro. Our results unequivocally define the native disulfide topology in the SMB domain of human vitronectin, providing biochemical as well as functional support to the structural findings on a recombinant SMB domain by Read and colleagues (Zhou, A., Huntington, J. A., Pannu, N. S., Carrell, R. W., and Read, R. J. (2003) Nat. Struct. Biol. 10, 541-544).     

Systematic and comprehensive strategy for reducing matrix effects in LC/MS/MS analyses

A systematic, comprehensive strategy that optimizes sample preparation and chromatography to minimize matrix effects in bioanalytical LC/MS/MS assays was developed. Comparisons were made among several sample preparation methods, including protein precipitation (PPT), liquid-liquid extraction (LLE), pure cation exchange solid-phase extraction (SPE), reversed-phase SPE and mixed-mode SPE. The influence of mobile phase pH and gradient duration on the selectivity and sensitivity for both matrix components and basic analytes was investigated. Matrix effects and overall sensitivity and resolution between UPLC technology and HPLC were compared. The amount of specific matrix components, or class of matrix components, was measured in the sample preparation extracts by LC/MS/MS with electrospray ionization (ESI) using both precursor ion scanning mode and multiple reaction monitoring (MRM). PPT is the least effective sample preparation technique, often resulting in significant matrix effects due to the presence of many residual matrix components. Reversed-phase and pure cation exchange SPE methods resulted in cleaner extracts and reduced matrix effects compared to PPT. The cleanest extracts, however, were produced with polymeric mixed-mode SPE (both reversed-phase and ion exchange retention mechanisms). These mixed-mode sorbents dramatically reduced the levels of residual matrix components from biological samples, leading to significant reduction in matrix effects. LLE also provided clean final extracts. However, analyte recovery, particularly for polar analytes, was very low. Mobile phase pH was manipulated to alter the retention of basic compounds relative to phospholipids, whose retention tends to be relatively independent of pH. In addition to the expected resolution, speed and sensitivity benefits of UPLC technology, a paired t-test demonstrated a statistically significant improvement with respect to matrix effects when this technology was chosen over traditional HPLC. The combination of polymeric mixed-mode SPE, the appropriate mobile phase pH and UPLC technology provides significant advantages for reducing matrix effects resulting from plasma matrix components and in improving the ruggedness and sensitivity of bioanalytical methods.     

Bimodal occurrence of aspartoacylase in myelin and cytosol of brain

The growing use of N-acetylaspartate as an indicator of neuronal viability has fostered interest in the biological function(s) of this unusual amino acid derivative. In considering the various physiological roles that have been proposed for this relatively abundant molecule one is obliged to take into account its unusual metabolic compartmentalization, according to which synthesis and storage occur in the neuron and hydrolytic cleavage in the oligodendrocyte. The latter reaction, catalyzed by aspartoacylase (ASPA), produces acetyl groups plus aspartate and has been proposed to occur in both soluble and membranous subfractions of white matter. Our study supports such bimodal occurrence and we now present immunoblot, proteomic, and biochemical evidence that the membrane-bound form of ASPA is intrinsic to purified myelin membranes. This was supported by a novel TLC-based method for the assay of ASPA. That observation, together with previous demonstrations of numerous lipid-synthesizing enzymes in myelin, suggests utilization of acetyl groups liberated by myelin-localized ASPA for lipid synthesis within the myelin sheath. Such synthesis might be selective and could explain the deficit of myelin lipids in animals lacking ASPA.     

LTP inhibits LTD in the hippocampus via regulation of GSK3beta

Glycogen synthase kinase-3 (GSK3) has been implicated in major neurological disorders, but its role in normal neuronal function is largely unknown. Here we show that GSK3beta mediates an interaction between two major forms of synaptic plasticity in the brain, N-methyl-D-aspartate (NMDA) receptor-dependent long-term potentiation (LTP) and NMDA receptor-dependent long-term depression (LTD). In rat hippocampal slices, GSK3beta inhibitors block the induction of LTD. Furthermore, the activity of GSK3beta is enhanced during LTD via activation of PP1. Conversely, following the induction of LTP, there is inhibition of GSK3beta activity. This regulation of GSK3beta during LTP involves activation of NMDA receptors and the PI3K-Akt pathway and disrupts the ability of synapses to undergo LTD for up to 1 hr. We conclude that the regulation of GSK3beta activity provides a powerful mechanism to preserve information encoded during LTP from erasure by subsequent LTD, perhaps thereby permitting the initial consolidation of learnt information.     

Synthesis of 3-(1H-benzimidazol-2-yl)-5-isoquinolin-4-ylpyrazolo[1,2-b]pyridine, a potent cyclin dependent kinase 1 (CDK1) inhibitor

The novel compound 3-(1H-benzimidazol-2-yl)-5-isoquinolin-4-ylpyrazolo[1,2-b]pyridine was discovered to be a potent CDK1 inhibitor. Described here is the chemistry for its synthesis, including Pd(II) catalyzed Stille coupling reaction and sulfur(0) induced benzimidazole formation. Its effects on VEGFR-2 kinase activity and tumour cell proliferation are also described.     

Function and oligomerization study of the leucine zipper-like domain in P13 from Leucania separata multiple nuclear polyhedrosis virus

The p13 gene is uniquely present in Group II nucleopolyhedroviruses (NPVs) and some granuloviruses, but not in Group I NPVs. p13 gene was first described by our laboratory in Leucania separatamultiple nuclear polyhedrosis virus (Ls-p13) in 1995. However, the functions of Ls-P13 and of its homologues are unknown. When Ls-p13 was inserted into Autographa californica nucleopolyhedrovirus, a Group I NPV, polyhedra yield was inhibited. However, this inhibition was prevented when the leucine zipper-like domain of Ls-p13 was mutated. To determine the cause of this marked difference between Ls-P13 and leucine zipper mutated Ls-P13 (Ls-P13mL), oligomerization and secondary structure analyses were performed. High performance liquid chromatography and yeast two-hybrid assays indicated that neither Ls-P13 nor Ls-P13mL could form oligomers. Informatics and circular dichroism spectropolarimetry results further indicated marked secondary structural differences between Ls-P13 and Ls-P13mL. The LZLD of Ls-P13 has two extended heptad repeat units which form a hydrophobic surface, but it is short of a third hydrophobic heptad repeat unit for oligomerization. However, the mutated LZLD of Ls-P13mL lacks the above hydrophobic surface, and its secondary structure is markedly different. This difference in its secondary structure may explain why Ls-P13mL is unable to inhibit polyhedra yield.     

以油体作为生物反应器的研究进展

获得安全、经济、稳定具有生物活性的重组蛋白,应用于基础研究及临床应用是一个重大的战略课题,现在可以利用酵母、细菌和动物细胞生产多种药物蛋白,但这些蛋白的生产过程还存在许多问题.利用植物作为生物反应器生产药用蛋白和疫苗是目前生物反应器研究的热点.油体蛋白在油料作物种子中高水平表达且易于分离,经过改造后是生产目的蛋白的一种理想栽体.介绍了油体、油体蛋白的结构以及利用植物油体蛋白表达体系这一新型植物生物反应器生产目的蛋白的研究进展和前景.     

兴安落叶松鞘蛾触角及其感器的扫描电镜观察

应用扫描电镜对兴安落叶松鞘蛾Coleophora obducta(Meyrick)触角及其感器进行观察和研究。结果表明,兴安落叶松鞘蛾触角为丝状,其上共有8种感器:板形感器、锥形感器、腔锥形感器、栓锥形感器、毛形感器、鳞形感器、叉形感器和Bhm氏鬃毛,对各种感器的形态、分布特点进行描述,推测其可能具有的功能。雌雄蛾触角有明显的性二型现象,表现为雌雄触角大小不同,触角感器类型、大小、数量、分布不同。