负载光敏剂D-甘露糖修饰胶束的制备及其在靶向光动力治疗中的应用

本研究合成了D-甘露糖修饰的两亲性β-环糊精(C_3-CD-Man7)和三臂金刚烷共价键连的BODIPY光敏剂(BTA),并利用β-环糊精(β-CD)与金刚烷(Ad)之间超分子主客体识别作用制备表面D-甘露糖修饰的高负载光敏剂胶束(BTA@C_3-CD-Man7)。利用透射电镜和动态光散射对BTA@C_3-CD-Man7胶束形貌、粒径和稳定性进行表征;并采用MTT细胞毒性评价方法考察其对人乳腺癌MDA-MB-231细胞的摄入、光动力治疗效果和光毒性。结果表明BTA@C_3-CD-Man7粒径均一,在溶液中稳定性良好;甘露糖受体过度表达的乳腺癌细胞MDA-MB-231能够特异性识别并大量摄取BTA@C_3-CD-Man7,并在665 nm LED灯照射下表现出对MDAMB-231细胞靶向光动力治疗的效果。     

车前子多糖对骨髓来源树突状细胞表型和吞噬功能的影响

目的:探讨车前子多糖对小鼠骨髓来源树突状细胞(BMDCs)表型和功能的影响。方法:从小鼠骨髓中分离单核细胞,加入细胞因子rmGM-CSF、rmIL-4诱导分化成未成熟树突状细胞,收集细胞加入促成熟刺激剂LPS(阳性对照组)或车前子多糖。倒置显微镜观察树突状细胞的形态,流式细胞术检测成熟树突状细胞的表面标志CD11c和MHCII的表达及吞噬FITC-dextran的变化。结果:经4种不同的车前子多糖作用40h后,显著促进CD11c+MHCII+双阳性细胞的比率,在浓度(0～50μg/ml)范围内呈现剂量依赖性,当浓度高于50μg/ml时,双阳性细胞表达率呈现降低趋势。经多糖作用后吞噬FITC-dextran的能力降低,其中PS3的作用效果最明显,表达PE-CD11c×FITC-dextran的细胞比率只有11.53%。结论:车前子多糖促进CD11c+MHCII+双阳性细胞的比率,降低对FITC-dextran的吞噬能力,初步表明车前子多糖可以促进树突状细胞的成熟。     

Moving EM: the Rapid Transfer System as a new tool for correlative light and electron microscopy and high throughput for high-pressure freezing

In this paper, the Rapid Transfer System (RTS), an attachment to the Leica EMPACT2 high‐pressure freezer, is described as a new tool for special applications within the cryofixation field. The RTS is an automated system that allows for fast processing of samples (<5 s) that make it possible for the first time to use high‐pressure freezing in combination with high time resolution correlative light and electron microscopy. In addition, with a working cycle of 30 s this rapid turn over time allows one to acquire more samples of biopsy material before it deteriorates than with other HPF machines with longer cycle times. With the use of the RTS it was possible to obtain three samples each of four different tissues in 6 min. Together with the finding that 90% of samples of cells grown on sapphire discs were well frozen, the RTS was both fast and reliable. Most important, together with other newly developed accessories, the RTS made it possible to capture specific events occurring live in the cell as observed by light microscopy, to cryofix that sample/event within 4 s, and then to analyze that event at high resolution in the electron microscope with excellent preservation of ultra‐structure. These developments should give us the tools to unravel intracellular processes that can be observed by live cell imaging but are too rare or fast to be picked up by routine EM methods or where the history of a structure is necessary to be able to discern its nature.     

FRET analysis of transmembrane flipping of FM4-64 in plant cells: is FM4-64 a robust marker for endocytosis?

Although the styryl dye FM4–64 is now used routinely to monitor endocytosis in plants, the argument about its potential to cytoplasmically and non-endocytically relocate into a selective set of vesicular compartments persists. To address this question, we determined whether fluorescence resonance energy transfer (FRET) could occur between a cytoplasmically expressed, short-wavelength excitation green fluorescent protein (GFP) and FM4–64 in Nicotiana benthaminana . After exposure to FM4–64, the root hair plasma membrane and internal organelles became labelled. Under these conditions, no FRET with cytoplasmic GFP was seen. However, if the cells were treated with a low concentration of quillajasaponin, a membrane permeabilization agent, the cells continued to stream and FRET was detected. Thereby, we demonstrate that under conditions that do not severely compromise cell viability, the FM4–64 dye becomes a suitable FRET partner for the cytoplasmically localized GFP. Under normal conditions, FM4–64 does not significantly enter the cytosolic side of the membrane, but remains at the plasma membrane or trapped in the organelles of the endocytic pathway. Hence, when the structure or permeability of the plasma membrane is unaltered, FM4–64 dye is a robust marker for endocytosis.     

Identification of Receptor‐Interacting Regions of Vitellogenin within Evolutionarily Conserved β‐Sheet Structures by Using a Peptide Array

Vitellogenesis, a key process in oviparous animals, is characterized by enhanced synthesis of the lipoprotein vitellogenin, which serves as the major yolk‐protein precursor. In most oviparous animals, and specifically in crustaceans, vitellogenin is mainly synthesized in the hepatopancreas, secreted to the hemolymph, and taken up into the ovary by receptor‐mediated endocytosis. In the present study, localization of the vitellogenin receptor and its interaction with vitellogenin were investigated in the freshwater prawn Macrobrachium rosenbergii. The receptor was immuno‐histochemically localized to the cell periphery and around yolk vesicles. A receptor blot assay revealed that the vitellogenin receptor interacts with most known vitellogenin subunits, the most prominent being the 79 kDa subunit. The receptor was, moreover, able to interact with trypsin‐digested vitellogenin peptides. By combining a novel peptide‐array approach with tandem mass spectrometry, eleven vitellogenin‐derived peptides that interacted with the receptor were identified. A 3D model of vitellogenin indicated that four of the identified peptides are N‐terminally localized. One of the peptides is homologous to the receptor‐recognized site of vertebrate vitellogenin, and assumes a conserved β‐sheet structure. These findings suggest that this specific β‐sheet region in the vitellogenin N‐terminal lipoprotein domain is the receptor‐interacting site, with the rest of the protein serving to enhance affinity for the receptor. The conservation of the receptor recognition site in invertebrate and vertebrate vitellogenin might have vast implications for oviparous species reproduction, development, immunity, and pest management.     

Membrane Trafficking of Death Receptors: Implications on Signalling

Death receptors were initially recognised as potent inducers of apoptotic cell death and soon ambitious attempts were made to exploit selective ignition of controlled cellular suicide as therapeutic strategy in malignant diseases. However, the complexity of death receptor signalling has increased substantially during recent years. Beyond activation of the apoptotic cascade, involvement in a variety of cellular processes including inflammation, proliferation and immune response was recognised. Mechanistically, these findings raised the question how multipurpose receptors can ensure selective activation of a particular pathway. A growing body of evidence points to an elegant spatiotemporal regulation of composition and assembly of the receptor-associated signalling complex. Upon ligand binding, receptor recruitment in specialized membrane compartments, formation of receptor-ligand clusters and internalisation processes constitute key regulatory elements. In this review, we will summarise the current concepts of death receptor trafficking and its implications on receptor-associated signalling events.