Recent progress on the effects of structured lipids and fluidity of plasma membrane on tumor metastasis / 药学学报

The lipid composition of cell plasma membranes of aggressive tumors is significantly altered from normal, affecting the membrane fluidity and function. Plasma membrane fluidity involves multiple steps in tumor invasion and metastasis, including cell movement, adhesion, lateral diffusion of membrane molecules, signal transduction, material exchange and so on. This review highlights the difference in plasma membrane lipid composition and fluidity between normal and cancer cells, as well as the correlation with the invasion and metastasis potential of cancer. We also point out that the proliferation, invasion and metastasis of tumors can be inhibited by improving membrane fluidity or interfering with the membrane structured lipid composition, this focusing more on changing the biophysical properties of cancer cell membranes, and providing a novel strategy that works for treatment of tumor metastasis.

Coarse-Grained Molecular Dynamics of Protein-lipid Interaction between CD3ε and PIP2 in Lipid Raft Nanodomains / 中国生物化学与分子生物学报

Lipid raft nanodomains of plasma membrane are rich in saturated lipids‚ cholesterol‚ sphingolipids‚ functioning as multimolecular platforms to recruit signaling and trafficking proteins involved in an array of physiological processes‚ which are critical for regulating signal transduction in cell. The staggering complexity of cell membranes and the transient formation of nanodomains greatly hinder research on lipid rafts by traditional experimental means. Molecular dynamics simulations have provided important insight into the organizational principles of cell membranes recently. Simulated membrane systems are under a transition from simple membrane models to multicomponent systems‚ culminating in realistic models of various cell types. Coarse-grained models have been extensively adopted as a powerful tool to explore membrane organization and interactions between lipids and proteins‚ providing efficient computational speed and enabling complex systems. In this work‚ coarse-grained molecular dynamics simulations with MARTINI force field were performed to build a raft-forming membrane with mixed lipids‚ including negatively charged lipid PIP2. Mixed lipids in this model were spontaneously partitioned into binary-phase membrane during 5 μs simulations by low temperature (295 K) treatment‚ forming lipid ordered (Lo) and liquid-disordered (Ld) nanodomains. Results of membrane thickness‚ lipid distribution‚ membrane fluidity‚ order parameters of the acyl tails‚ radial distribution functions were consistent with simulation and experimental data. Addition of small amounts of PIP2 did not affect the raft formation‚ and it showed remarkable affinity to lipid raft nanodomains. Simulations of the signaling transmembrane protein CD3ε in our raft-forming membranes were further performed to study the protein-lipid interaction as well. Results showed that the cytoplasmic tail of CD3ε was recruited to the Lo/ Ld boundary due to PIP2 binding‚ and this binding was regulated by Ca

Design, synthesis and application of AIE fluorescent probe for lipid raft / 中国药科大学学报

@#Lipid rafts composed of saturated phospholipids,sphingomyelin,and cholesterol are usually defined as liquid ordered microdomains located in the cell membrane. Lipid rafts are involved in many physiological and pathological processes of cells. Based on the difference in composition and distribution between lipid raft and non-raft domains,a lipid raft probe with aggregation-induced emission (AIE),cholesterol-triethylene glycol-tetraphenylethylene (TCHS-TPE),was designed and synthesized for convenient and specific imaging of lipid raft domains on cell membranes in this study. In this paper,TCHS-TPE was successfully synthesized,and the photophysical properties of TCHS-TPE were measured to evaluate its AIE characteristics. And finally the specific imaging of TCHS-TPE on the lipid raft region of B16F10 melanoma cell membrane was studied using confocal laser scanning microscopy. Compared with the existing lipid raft probe cholera toxin B (CTxB),the TCHS-TPE lipid raft probe has the advantages of simple operation and high specificity. The successful synthesis of the fluorescent probe will provide a useful tool for studying the physiological and pathological processes related to lipid raft domains,and offer a theoretical basis for the design of imaging probes for other lipid raft domains.

Roles of flotillins in tumors / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

The identification and use of molecular biomarkers have greatly improved the diagnosis and treatment of malignant tumors. However, a much deeper understanding of oncogenic proteins is needed for the benefit to cancer patients. The lipid raft marker proteins, flotillin-1 and flotillin-2, were first found in goldfish retinal ganglion cells during axon regeneration. They have since been found in a variety of cells, mainly on the inner surface of cell membranes, and not only act as a skeleton to provide a platform for protein-protein interactions, but also are involved in signal transduction, nerve regeneration, endocytosis, and lymphocyte activation. Previous studies have shown that flotillins are closely associated with tumor development, invasion, and metastasis. In this article, we review the functions of flotillins in relevant cell processes, their underlying mechanisms of action in a variety of tumors, and their potential applications to tumor molecular diagnosis and targeted therapy.

The role of galectin-4 in physiology and diseases

Galectin-4, a tandem repeat member of the β-galactoside-binding proteins, possesses two carbohydrate-recognition domains (CRD) in a single peptide chain. This lectin is mostly expressed in epithelial cells of the intestinal tract and secreted to the extracellular. The two domains have 40% similarity in amino acid sequence, but distinctly binding to various ligands. Just because the two domains bind to different ligands simultaneously, galectin-4 can be a crosslinker and crucial regulator in a large number of biological processes. Recent evidence shows that galectin-4 plays an important role in lipid raft stabilization, protein apical trafficking, cell adhesion, wound healing, intestinal inflammation, tumor progression, etc. This article reviews the physiological and pathological features of galectin-4 and its important role in such processes.

Angiostatin Works as Immune Modulatory Molecules via Inhibition of Neutrophil Activation and Migration

Angiostatin is derived from enzymatic degradation of plasminogen and it has endogenous anti-angiogenic properties. Although tumor cells, macrophages, platelets, and neutrophils generate high amount of angiostatin, its expression is increased in inflammatory conditions. Moreover, angiostatin binds to integrin alpha(v)beta(3), ATP synthase, and angiomotin, which expressed on neutrophils. Activated neutrophils are essential to innate immune response, but also cause tissue damage through production of reactive oxygen species (ROS) and increase lifespan. In this article, it suggests several mechanism of angiostatin as immune regulator for neutrophils in inflammatory conditions; complex with integrin alpha(v)beta(3) and F(1)F(0) ATP synthase on lipid raft, attenuate polarization, and ROS production. These data provide possible exploit of double-edged role of neutrophils in acute inflammatory pathologies to preserve beneficial effect and minimize tissue damage.

Clathrin and Lipid Raft-dependent Internalization of Porphyromonas gingivalis in Endothelial Cells

Porphyromonas gingivalis is one of the most important periodontal pathogens and has been to known to invade various types of cells, including endothelial cells. The present study investigated the mechanisms involved in the internalization of P. gingivalis in human umbilical vein endothelial cells (HUVEC). P. gingivalis internalization was reduced by clathrin and lipid raft inhibitors, as well as a siRNA knockdown of caveolin-1, a principal molecule of lipid raft-related caveolae. The internalization was also reduced by perturbation of actin rearrangement, while microtubule polymerization was not required. Furthermore, we found that Src kinases are critical for the internalization of P. gingivalis into HUVEC, while neither Rho family GTPases nor phosphatidylinositol 3-kinase are required. Taken together, this study indicated that P. gingivalis internalization into endothelial cells involves clathrin and lipid rafts and requires actin rearrangement associated with Src kinase activation.

Properties of Lipid Rafts from Cerebral Cortex Based on HPLC MS/MS Proteomics / 天津医药

Objective To verify the validity of the sucrose density gradient ultracentrifugation method for lipid rafts from cerebral cortex. Methods Extract lipid rafts from cerebral cortex in mouse were extracted by the sucrose density gradi-ent ultracentrifugation method. The properties of lipid rafts were detected by Western blotting method, double enzyme and light scattering methods. HPLC MS/MS proteomics and bioinformatics were used to locate proteins of lipid rafts in cells. Re-sults Lipid rafts from cerebral cortex were provided with the model properties of lipid rafts such as high light scattering and cholesterol and high expression of Flotillin-1. HPLC MS/MS proteomics identified total 647 proteins. Most of these pro-teins were from plasma membrane, endoplasmic reticulum, cytoskeleton and cytosol, however, there were 21% proteins among total 647 proteins were from nucleus, mitochondria and ribosomes. Conclusion The sucrose density gradient ultra-centrifugation method is a effective method to extract lipid rafts from cerebral cortex, however, the properties of mixture should be considered.

Effect of lipid raft on the growth of cervical cancer cells / 肿瘤研究与临床

Objective To explore the effect of lipid raft on cervical cancer cell growth and its mechanisms Methods HeLa cells in logarithmic phase were divided into three groups including control group, lipid raft interference agent group,and NADPH oxidase inhibitors group.Cells were treated with fre sh medium,3 μmol/L Apocynin and 1 mmol/L M-beta CD, respectively, for 24 h.Cell survival rate was detected using the MTT method, and the HIF-1α level was examined by Western-blot. Results Cell growths of the lipid raft interference agent group and NADPH oxidase inhibitors group were significantly slower than control group,(0.612±0.051 vs 0.984±0.034,0.591 ±0.074 vs 0.984±0.034,t=4.062,P＜0.05).HIF-1α expression in the lipid raft interference agent group and NADPH oxidase inhibitors group was also significantly reduced compared with control group (1.79±0.14 vs 2.56±0.22 and 1.54±0.12 vs 2.56±0.22) and the difference was significant (t=2.423,P＜0.05). Conclusion Lipid raft-NADPH oxidase pathway may activate HIF-1α and downstream protocarcinogenic gene expression to promote the growth of cervical cancer cells. The inhibitors of lipid raft and NADPH oxidase may become a new research direction for cervical cancer chemotherapy.

Lipid raft involved in drug resistance: Relationship between multidrug resistance ATP-binding cassette transporters and lipid raft / 第二军医大学学报

Lipid rafts have been implicated in many cellular functions, including protein and lipid transport and signal transduction. Recently ATP-binding cassette (ABC) transporters, which are associated with multidrug resistance, have been found in lipid rafts; therefore they might be related to drug resistance. Here we introduce the relationship between the localization and functions of three multi-drug related ABC transporters, including two relevant to multidrug resistance in tumor cells(Pgp/ABCB1 and MRP1/ABCC1) and one relevant to multidrug resistance in Candida albicans (Cdrlp). We also discuss the influence of sphingolipids and cholesterol, two major components of lipid rafts, on the localization and function of the above three ABC transporters.

Ape1/Ref-1 Stimulates GDNF/GFR alpha1-mediated Downstream Signaling and Neuroblastoma Proliferation

We previously reported that glial cell line-derived neurotropic factor (GDNF) receptor alpha1 (GFR alpha1) is a direct target of apurinic/apyrimidinic endonuclease 1 (Ape1/Ref-1). In the present study, we further analyzed the physiological roles of Ape1/Ref-1-induced GFRalpha1 expression in Neuro2a mouse neuroblastoma cells. Ape1/Ref-1 expression caused the clustering of GFR alpha1 immunoreactivity in lipid rafts in response to GDNF. We also found that Ret, a downstream target of GFRalpha1, was functionally activated by GDNF in Ape1/Ref-1-expressing cells. Moreover, GDNF promoted the proliferation of Ape1/Ref-1-expressing Neuro2a cells. Furthermore, GFR alpha1-specific RNA experiments demonstrated that the downregulation of GFR alpha1 by siRNA in Ape1/Ref-1-expressing cells impaired the ability of GDNF to phosphorylate Akt and PLC gamma-1 and to stimulate cellular proliferation. These results show an association between Ape1/Ref-1 and GDNF/GFR alpha signaling, and suggest a potential molecular mechanism for the involvement of Ape1/Ref-1 in neuronal proliferation.

The Effect of Methyl-β-cyclodextrin on the Differentiation of RAW264 Cells into Osteoclasts / Oral Science International

Bone is continuously remodeled by bone resorption and formation and, accordingly, bone metabolism is tightly regulated to maintain homeostasis. Deviation from the normal conditions of bone resorption can result in bone diseases. Lipid rafts are specialized plasma membrane microdomains that are enriched with glycosphingolipids, sphingomyelin and cholesterol. Lipid rafts are important for the transport of select membranes and relay stations involved in intracellular signaling.To investigate the role of lipid rafts in RAW264 cells signaling, lipid rafts were disrupted by depleting cholesterol through the introduction of methyl-β-cyclodextrin (MβCD). We found that sRANKL-induced differentiation into osteoclasts was markedly inhibited by MβCD in a dose-dependent manner. MβCD enhanced the sRANKL-induced phosphorylation of ERK1/2 MAP kinase. In contrast, MβCD blocked the phosphorylation of IκB. These findings suggest that cholesterol might play a crucial role in the regulation of the sRANKL-mediated signaling pathway and in osteoclast differentiation of RAW264 cells, thereby reflecting its importance in the formation of plasma membrane lipid rafts.