Membrane lipids in invadopodia and podosomes: key structures for cancer invasion and metastasis

Invadopodia are extracellular matrix (ECM)-degrading protrusions formed by invasive cancer cells. Podosomes are structures functionally similar to invadopodia that are found in oncogene-transformed fibroblasts and monocyte-derived cells, including macrophages and osteoclasts. These structures are thought to play important roles in the pericellular remodeling of ECM during cancer invasion and metastasis. Much effort has been directed toward identification of the molecular components and regulators of invadopodia/podosomes, which could be therapeutic targets in the treatment of malignant cancers. However, it remains largely unknown how these components are assembled into invadopodia/podosomes and how the assembly process is spatially and temporally regulated. This review will summarize recent progress on the molecular mechanisms of invadopodia/podosome formation, with strong emphasis on the roles of lipid rafts and phosphoinositides.     

参与P-gp膜定位和功能调控的相关蛋白研究进展

P-糖蛋白(P-gp)作为ABC转运体家族的成员之一,只有定位在细胞膜上才具有外排药物及毒物的功能.P-gp在细胞膜上的定位和功能受到多种机制调控.P-gp通过ERM(ezrin/radixin/moesin)蛋白家族锚定在膜上,其中脂筏区域在P-gp转运通道的形成中起重要作用,微囊蛋白-1(Cav-1)定位于小窝,作...     

Abnormal lipid rafts related ganglioside expression and signaling in T lymphocytes in immune thrombocytopenia patients

Aberrant T lymphocytes signaling is considered to play a crucial role in the abnormal immune state of primary immune thrombocytopenia (ITP). Lipid raft has been verified to engage in the T cell receptor (TCR)-mediated T lymphocytes signal transduction. Whether lipid raft-associated T cells signal transduction has impact on the pathogenesis of ITP is still unconfirmed. In this study, we aimed to reveal the abnormality in structure and function of lipid rafts (LRs) in CD4⁺ and CD8⁺ T lymphocytes of patients with ITP. Our results showed that there was an increased lipid raft aggregation in ITP patients, while this kind of increase would not be influenced by platelet counts or therapeutic regimes. Stimulation by anti-CD3/CD28 monoclonal antibodies promoted enhanced lipid raft clustering in T lymphocytes of ITP patients compared with negative controls. Methyl-β-cyclodextrin (MβCD) could block the abnormal lipid raft aggregation and disrupt the TCR-mediated T cells proliferation and cytokines secretion, including both proinflammatory cytokines and anti-inflammatory cytokines. The spontaneous activation of T lymphocytes from ITP patients might be due to the elevated co-localization of protein tyrosine phosphatase (PTP) CD45 and lipid rafts in patients’ CD4⁺ and CD8⁺ T lymphocytes. These findings suggest that the autoactivation of T lymphocytes from ITP patients may lead to the abnormality in lipid raft structure and raft-anchored proteins, and the changes conversely promote the TCR-mediated T cells activation of ITP patients.     

脂筏特异性AIE荧光探针的设计、合成及其应用

脂筏（lipid raft）是由饱和磷脂、鞘磷脂以及胆固醇组成的位于细胞膜的液态有序微区，与细胞的许多生理/病理过程密切相关。基于脂筏区与非脂筏区脂质组成与分布的差异，本研究设计并合成了一种具有聚集诱导发光（aggregation-induced emission，AIE）特性的脂筏探针胆固醇-三聚乙二醇-四苯乙烯（TCHS-TPE）用于细胞膜上脂筏区的便捷特异性成像。本研究首先成功合成了TCHS-TPE，同时测定了TCHS-TPE的光物理性质以评价其AIE特性，最后采用激光共聚焦显微镜研究了TCHS-TPE对B16F10黑色素瘤细胞膜上脂筏区的特异性成像。与现有脂筏探针霍乱毒素B（CTxB）相比，TCHS-TPE脂筏探针具有操作简单、特异性高等优势。该荧光探针的成功合成将为研究脂筏区相关生理、病理过程提供有利工具，并为其他脂筏区成像探针的设计奠定了理论基础。     

鱼油脂肪乳对肠外营养大鼠小肠黏膜紧密连接形态结构的影响

目的:探讨鱼油脂肪乳剂(富含ω-3多不饱和脂肪酸)对肠外营养(PN)大鼠肠上皮细胞紧密连接(TJ)形态和紧密连接蛋白occludin表达的影响。方法:将大鼠随机分为四组,即对照组(正常喂食),PN(禁食5d行PN支持)组,小剂量鱼油治疗(1 ml/kg鱼油静脉注射+PN)组和大剂量鱼油治疗(2 ml/kg鱼油静脉注射+PN)组。观察大鼠术后小肠黏膜上皮细胞TJ形态,以及紧密连接蛋白occludin的表达分布。结果:PN组大鼠治疗5 d后肠上皮细胞TJ结构部分缺失、间隙增宽;大剂量鱼油治疗组TJ形态基本完整,小剂量鱼油治疗组TJ部分缺失。各组occludin蛋白总量无明显差异。提取脂筏组分,发现与对照组比,三个实验组脂筏区域中occludin蛋白表达均明显减少,但大剂量鱼油治疗组较PN组明显升高(P<0.01)。结论:长期PN可导致TJ结构的缺失,脂筏区域紧密连接蛋白occludin表达减少。大剂量鱼油脂肪乳剂可维持occludin蛋白在脂筏区域的表达,保护小肠黏膜细胞TJ的结构和功能。     

Differential Pathomechanisms of Desmoglein 1 Transmembrane Domain Mutations in Skin Disease

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Persistence of psychosine in brain lipid rafts is a limiting factor in the therapeutic recovery of a mouse model for Krabbe disease

Sphingolipids are intrinsic components of membrane lipid rafts. The abnormal accumulation of these molecules may introduce architectural and functional changes in these domains, leading to cellular dysfunction. Galactosylsphingosine (psychosine) is a pathogenic lipid raft-associated molecule whose accumulation leads to brain deterioration and irreversible neurological handicap in the incurable leukodystrophy Krabbe disease (KD). The relevance of clearing excessive levels of pathogenic psychosine from lipid rafts in therapy for KD has not been investigated. The work presented here demonstrates that psychosine inhibits raft-mediated endocytosis in neural cells. In addition, although in vitro enzyme reconstitution is sufficient for the reversal of related endocytic defects in affected neural cells, traditional in vivo enzyme therapies in the mouse model of KD appear to be insufficient for complete removal of pathogenic levels of raft-associated psychosine. This work describes a mechanism that may contribute to limiting the in vivo efficacy of traditional therapies for KD.     

脂筏在肿瘤发生发展中的作用及其作为药物靶点的研究

脂筏是细胞膜上具有特殊功能的微区域,通过动态聚集、募集及靶向运输作用为蛋白分子提供功能平台,调节细胞功能,该过程受到脂筏结构、内在组分及动态定位分子的多重调节。肿瘤的发生发展与凋亡异常、侵袭转移力增强等因素密切相关,而脂筏可调节上述因素,因此成为近年来肿瘤治疗研究中的新靶点。     

Inhibitory effect of NAP-22 on the phosphatase activity of synaptojanin-1

Endocytosis of the synaptic vesicle is a complicated process, in which many proteins and lipids participate. Phosphatidylinositol 4,5-bisphosphate (PIP(2) ) plays important roles in the process, and the dynamic regulation of this lipid is one of the key events. Synaptojanin is a PIP(2) phosphatase, and dephosphorylation of PIP(2) of the clathrin coated-vesicle results in the uncoating of the vesicle. NAP-22 is one of the major proteins of the neuronal detergent-resistant membrane microdomain and localizes in both the presynaptic plasma membrane and the synaptic vesicle. To elucidate the role of NAP-22 in synaptic function, a screening of the NAP-22 binding proteins through pull-down assay was performed. In addition to CapZ protein, synaptojanin-1 was detected by LC-MS/MS, and Western blotting using antisynaptojanin-1 confirmed this result. The interaction seems to be important in the course of synaptic vesicle endocytosis, because NAP-22 inhibited the phosphatase activity of synaptojanin in a dose-dependent manner. The inhibitory region for 5-phosphatase and the binding region for PIP(2) overlapped in the amino acid sequence of NAP-22, so elucidation of the regulatory mechanism of the PIP(2) binding ability of NAP-22 could be important in understanding the membrane dynamics at the presynaptic region.