Lipid rafts participate in aberrant degradative autophagic-lysosomal pathway of amyloid-beta peptide in Alzheimer's disease

Amyloid-beta peptide is the main component of amyloid plaques, which are found in Alzhei- mer＇s disease. The generation and deposition of amyloid-beta is one of the crucial factors for the onset and progression of Alzheimer＇s disease. Lipid rafts are glycolipid-rich liquid domains of the plasma membrane, where certain types of protein tend to aggregate and intercalate. Lipid rafts are involved in the generation of amyloid-beta oligomers and the formation of amyloid-beta peptides. In this paper, we review the mechanism by which lipid rafts disturb the aberrant deg- radative autophagic-lysosomal pathway of amyloid-beta, which plays an important role in the pathological process of Alzheimer＇s disease. Moreover, we describe this mechanism from the view of the Two-system Theory of fasciology and thus, suggest that lipid rafts may be a new target of Alzheimer＇s disease treatment.

Glut-4 is translocated to both caveolae and non-caveolar lipid rafts, but is partially internalized through caveolae in insulin-stimulated adipocytes

Caveolae and non-caveolar lipid rafts are two types of membrane lipid microdomains that play important roles in insulin-stimulated glucose uptake in adipocytes. In order to ascertain their specific functions in this process, caveolae were ablated by caveolin-1 RNA interference. In Cav-1 RNAi adipocytes, neither insulin-stimulated glucose uptake nor Glut-4 （glucose transporter 4） translocation to membrane lipid microdomains was affected by the ablation of caveolae. With a modified sucrose density gradient, caveolae and non-caveolar lipid rafts could be separated. In the wild-type 3T3- L l adipocytes, Glut-4 was found to be translocated into both caveolae and non-caveolar lipid rafts. However, in Cav1 RNAi adipocytes, Glut-4 was localized predominantly in non-caveolar lipid rafts. After the removal of insulin, caveolaelocalized Glut-4 was internalized faster than non-caveolar lipid raft-associated Glut-4. The internalization of Glut-4 from plasma membrane was significantly decreased in Cav-1 RNAi adipocytes. These results suggest that insulin-stimulated Glut-4 translocation and glucose uptake are caveolae-independent events. Caveolae play a role in the internalization of Glut-4 from plasma membrane after the removal of insulin.

Involvement of Lipid Rafts and Cellular Actin in AcMNPV GP64 Distribution and Virus Budding

GP64 is the major envelope glycoprotein associated with the budded virus (BV) of Autographa californica nucleopolyhedrovirus (AcMNPV) and is essential for attachment and budding of BV particles. Confocal microscopy and flotation assays established the presence of lipid raft domains within the plasma membranes of AcMNPV-infected Sf9 cells and suggested the association of GP64 with lipid rafts during infection. GP64 and filamentous actin (F-actin) were found to co-localise at the cell cortex at 24 and 48 hpi and an additional restructuring of F-actin during infection was visualised, resulting in a strongly polarised distribution of both F-actin and GP64 at the cell cortex. Depletion of F-actin, achieved by treatment of Sf9 cells with latrunculin B (LB), resulted in the redistribution of GP64 with significant cytoplasmic aggregation and reduced presence at the plasma membrane. Treatment with LB also resulted in reduced production of BV in Sf9 cells. Analysis of virus gene transcription confirmed this reduction was not due to decreased trafficking of nucleocapsids to the nucleus or to decreased production of infectious progeny nucleocapsids. Reduced BV production due to a lack of GP64 at the plasma membrane of AcMNPV-infected Sf9 cells treated with LB, suggests a key role for F-actin in the egress of BV.

Interaction of hyperlipidemia and reactive oxygen species:Insights from the lipid-raft platform

Reactive oxygen species(ROS) and oxidative stress are closely associated with the development of atherosclerosis,and the most important regulator of ROS production in endothelial cells is NADPH oxidase.Activation of NADPH oxidase requires the assembly of multiple subunits into lipid rafts,which include specific lipid components,including free cholesterol and specific proteins.Disorders of lipid metabolism such as hyperlipidemia affect the cellular lipid components included in rafts,resulting in modification of cellular reactions that produce ROS.In the similar manner,several pathways associating ROS production are affected by the presence of lipid disorder through raft compartments.In this manuscript,we review the pathophysiological implications of hyperlipidemia and lipid rafts in the production of ROS.

Membrane lipid raft organization during cotton fiber development

Background:Cotton fiber is a single-celled seed trichome that originates from the ovule epidermis.It is an excellent model for studying cell elongation.Along with the elongation of cotton fiber cell,the plasma membrane is also extremely expanded.Despite progress in understanding cotton fiber cell elongation,knowledge regarding the relationship of plasma membrane in cotton fiber cell development remains elusive.Methods:The plasma membrane of cotton fiber cells was marked with a low toxic fluorescent dye,di-4-ANEPPDHQ,at different stages of development.Fluorescence images were obtained using a confocal laser scanning microscopy.Subsequently,we investigated the relationship between lipid raft activity and cotton fiber development by calculating generalized polarization(GP values)and dual-channel ratio imaging.Results:We demonstrated that the optimum dyeing conditions were treatment with 3μmol·L-1 di-4-ANEPPDHQ for 5 min at room temperature,and the optimal fluorescence images were obtained with 488 nm excitation and500–580 nm and 620–720 nm dual channel emission.First,we examined lipid raft organization in the course of fiber development.The GP values were high in the fiber elongation stage(5–10 DPA,days past anthesis)and relatively low in the initial(0 DPA),secondary cell wall synthesis(20 DPA),and stable synthesis(30 DPA)stages.The GP value peaked in the 10 DPA fiber,and the value in 30 DPA fiber was the lowest.Furthermore,we examined the differences in lipid raft activity in fiber cells between the short fiber cotton mutant,Li-1,and its wild-type.The GP values of the Li-1 mutant fiber were lower than those of the wild type fiber at the elongation stage,and the GP values of 10 DPA fibers were lower than those of 5 DPA fibers in the Li-1 mutant.Conclusions:We established a system for examining membrane lipid raft activity in cotton fiber cells.We verified that lipid raft activity exhibited a low-high-low change regularity during the development of cotton fiber cell,and the pattern was disrupted in the short lint fiber Li-1 mutant,suggesting that membrane lipid order and lipid raft activity are closely linked to fiber cell development.

The Stability of Lipid Rafts-Like Micro-Domains Is Dependent on the Available Amount of Cholesterol

Lipid rafts are sterol and sphingolipid rich membrane domains that possibly may play roles in multiple cellular processes. These domains are still the matter of debate and it is still unknown by which mechanism if any and organisms promote their formation. This study centers on the ease of in vitro formation of lipid rafts-like structures as it relates to the relative availability of sphingolipids, phospholipids, cholesterol, and membrane proteins. Following a 12 h incubation period, isolation and extraction of the lipid rafts-like assemblies, the composition of the structures was evaluated using HPLC. Cholesterol and sphingomyelin were detected at 206 nm and phosphatidylcholine was detected at 254 nm. Identification of lactose permease, a typical membrane protein, was done using FTIR. The thermal stability of the produced structures was also determined. Results show that the addition of cholesterol significantly increased both the amount of insoluble lipid rafts-like structures and their stability, and that the availability of a minimum amount of sphingolipid was necessary to produce larger amounts of more stable structures. However, the addition of phospholipids hindered the formation of lipid rafts-like assemblies and those formed were generally less stable.

Designing the lipid raft marker protein for synaptic vesicles

Lipid rafts are cholesterol-enriched microdomains and implicated in many essential physiological ac-tivities such as the neurotransmitter release.Many studies have been carried out on the function of rafts inthe plasma membranes,whereas little is known about the information of such microdomains in subcellularcompartments especially synaptic vesicles(SVs).In the well-studied plasma membranes,several proteinshave been recognized as raft markers,which are used to label or trace rafts.But the raft marker proteinon SVs has not been identified yet.Although some SV proteins,including VAMP and CPE,have beenfound in raft fractions,they cannot be used as markers due to their low abundance in rafts.In this work,we designed several chimera proteins and tested their characteristics for using as SV raft makers.First,we detected whether they located in SVs,and then the chimeras exhibiting the better localization in SVswere further examined for their enrichment in raft using detergent treatment and gradient density floatationanalysis.Our results indicate that one of the chimeric proteins is primarily located in SVs and distributedin raft microdomains,which strongly suggests that it could be served as a raft marker for SVs.

Emodin suppresses LPS-induced proinflammatory responses and nuclear factor-B activation by disruption of lipid rafts and TLR-4 recruitment in endothelial cells

Emodin [1,3,8-Trihydroxy-6-methylanthraquinone] has been reported to exhibit vascular anti-inflammatory properties.However,the relevant anti-inflammatory mechanisms are not well understood.The present study was design to explore the molecular target(s) of emodin

The differential protein and lipid compositions of noncaveolar lipid microdomains and caveolae

Morphologically, caveolae and lipid rafts are two different membrane structures. They are often reported to share similar lipid and protein compositions, and are considered to be two subtypes of membrane lipid microdomains. By modifying sucrose density gradient flotation centrifugation, which is used to isolate lipid microdomains, we were able to separate caveolae and noncaveolar lipid microdomains into two distinct fractions. The caveolar membranes are membrane vesicles of 100-nm diameter, enriched with caveolin-1 and flotillin-1. The noncaveolar lipid microdomains are amorphous membranes and most likely the coalescence of heterogeneous lipid rafts. They are depleted of caveo- lin-1 and are more enriched with cholesterol and sphingolipids than the caveolae. Many membrane proteins, such as insulin-like growth factor-1 receptor （membrane receptor）, aquaporin-1 （membrane transporter）, Thy-1 and N- cadherin （glycosylphosphatidylinositol-anchored membrane protein and membrane glycoprotein）, are specifically as- sociated with noncaveolar lipid microdomains, but not with caveolae. These results indicate that the lipid and protein compositions of caveolae differ from those of noncaveolar lipid microdomains. The difference in their protein compo- sitions implies that these two membrane microdomains may have different cellular functions.

Curvature-driven lipid sorting: coarse-grained dynamics simulations of a membrane mimicking a hemifusion intermediate

How membrane curvature influences lipid distribution is under intensive research. In this short report, after a brief review of recent studies, the results of our coarse-grained (CG) molecular dynamics simulations of membranes with “hemifused ribbons” geometry are discussed. When membranes of a binary mixture of (dipalmitoyl-phosphatidylcholine (DPPC) / diol-eoyl-phosphatidylethanolamine (DOPE) were used, DOPE accumulated in the negatively curved region of the monolayer that formed as the proximal monolayers fused (i.e., cis leaflets). However, the enrichment was dependent on the presence of tethering molecules which kept the curvature high (the curvature radius of ~1 nm), placing the cis monolayers ~2-2.5 nm from each other. Simulations in which DOPE was replaced with dioleoyl-phosphatidylcholine (DOPC) showed an insignificant degree of DOPC accumulation, suggesting the importance of lateral interaction among DOPE molecules for the curvature sorting. The above composition was not close to a demixing point and our radial distribution function analysis suggested that the DOPE accumulation was not assisted by the lipid phase separation which has been shown to promote curvature-driven lipid sorting. Relevance of curvature-driven lipid sorting to biological membrane fusion is discussed.

Curvature-induced lipid segregation

We investigate how an externally imposed curvature influences lipid segregation on two-phase-coexistent membranes. We show that the bending-modulus contrast of the two phases and the curvature act together to yield a reduced effective line tension. On largely curved membranes, a state of multiple domains （or rafts） forms due to a mechanism analogous to that causing magnetic-vortex formation in type-II superconductors. We determine the criterion for such a multi-domain state to occur; we then calculate respectively the size of the domains formed on cylindrically and spherically curved membranes.

Linking Lipid Metabolism with Cell Transformation and Tumor Progression

Carbohydrates,lipids,and proteins are the three major nutrients required by the human body.The lipids,comprising triglycerides,phospholipids,and sterols,provide energy and essential fatty acids for the body,and are required for the growth and maintenance of human cells and tissues.A variety of lipid molecules and their intermediates are involved in cell signaling and inflammation,and have been reported to promote tumor transformation and progression.Fatty acid biosynthetic enzymes are also involved in the lipid metabolism of tumors.Dyslipidemia is closely related to many solid tumors,and may both play a role in both tumorigenesis and be a consequence of tumor development.Therefore,abnormal lipid metabolism is strongly associated with tumor transformation and progression.This review discusses the signaling pathways,related genes,enzymes,and inflammatory cell factors involved in tumor lipid metabolism,as well as the roles of dyslipidemia in tumor transformation and progression.We believe the information provided will serve as valuable reference highlighting molecules that can be targeted to improve the treatment of tumors.

微RNA-152靶向调控内质网脂质Raft关联蛋白1对甲状腺乳头状癌细胞增殖和迁移的影响

目的探讨微RNA-152(miR-152)对甲状腺乳头状癌(PTC)细胞增殖、侵袭和迁移的影响及其作用机制。方法将对数生长期PTC TPC-1细胞随机分为空白对照组、miR-con组(转染miRNA-mimics阴性对照)和miR-152组(转染miR-152-mimics),另取对数生长期正常甲状腺细胞株Nthy-ori 3-1作为Nthy-ori 3-1组。采用实时荧光定量聚合酶链反应法检测各组细胞中miR-152、内质网脂质Raft关联蛋白1(ERLIN1)mRNA表达,四唑盐比色法及平板克隆形成实验检测各组TPC-1细胞增殖能力,流式细胞仪检测各组TPC-1细胞凋亡情况,Transwell实验检测各组TPC-1细胞迁移、侵袭能力,Western blot法检测各组TPC-1细胞中ERLIN1蛋白表达。结果空白对照组与miR-con组TPC-1细胞中miR-152、ERLIN1 mRNA和蛋白相对表达量、TPC-1细胞增殖抑制率、细胞克隆数、细胞凋亡率、细胞迁移数及侵袭数比较差异均无统计学意义(P>0.05)。空白对照组、miR-con组、miR-152组TPC-1细胞中miR-152相对表达量显著低于Nthy-ori 3-1组(P<0.05);miR-152组TPC-1细胞中miR-152相对表达量显著高于空白对照组和miR-con组(P<0.05)。与空白对照组、miR-con组比较,miR-152组TPC-1细胞增殖抑制率、细胞凋亡率显著升高,细胞克隆数、细胞迁移数及侵袭数显著降低(P<0.05)。miR-152组TPC-1细胞中ERLIN1 mRNA及蛋白相对表达量均显著低于空白对照组和miR-con组(P<0.05)。结论过表达miR-152可下调TPC-1细胞中ERLIN1的表达,抑制TPC-1细胞增殖、侵袭和迁移,miR-152可能通过靶向调控ERLIN1参与PTC进展和转移。

Coarse-grained simulations of branched bilayer membranes: effects of cholesterol-dependent phase separation on curvature-driven lipid sorting

Our recent coarse-grained (CG) molecular dynamics (MD) simulations of membranes with a hemifused-ribbon (λ-shaped) geometry showed curvature-driven demixing leading to enrich ment in dioleoyl-phosphatidylethanolamine (DOPE) in a negatively-curved region (at C = –0.8 nm–1) of a DOPE/dipalmitoyl-phosphati-dylcholine (DPPC) membrane. Here we extend the analysis with respect to lipid composition and simulation time. Simulations of 12 – 20 μs effective time show that, compared with DOPE of the DOPE/DPPC system, a DPPC/dilinoleyl-PC [di(18:2)PC] membrane showed a similar degree of enrichment of di(18:2)PC in the curved region with C=–0.8 nm–1. For the latter mixture, even weak negative curvatures (C=–0.5 – 0.6 nm–1) caused significant degrees of di(18:2)PC enrichment. In agreement with recent studies of a planar bilayer, a ternary DPPC/ di(18:2)PC/cholesterol 0.42:0.28:0.3 mixture phase-separated into nanoscale raft-like liquid-ordered (Lo) and non-raft liquid-disordered (Ld) phases on a sub-microsecond time scale. The Lo domains were preferentially localized at planar portions, whereas the Ld domains were positioned mainly in curved regions of the membrane. Unlike binary dioleoylphosphatidylcho-line (DOPC)/cholesterol and DPPC/cholesterol mixtures, which showed only a slight enrich ment of cholesterol in the curved region, the ternary mixtures showed considerable migra tion of cholesterol and DPPC from the curved to the planar region. A pronounced degree of lipid segregation due to the preferential distribution of the Ld and Lo domains in the curved and planar regions, respectively, was observed even when the curvature of the fused monolayers (originally ‘cis’ leaflets) was weakened (C= –0.5 nm-1). Overall, the results are consistent with theoretical predictions based on spontaneous curvature of the constituent lipids and the difference in rigidity between the Ld and Lo domains, whereas lipid-lipid interactions, such as PE-PE or DPPC-cholesterol, as well as propensity for interleaflet colocalization (registration) of the Lo and Ld domains appear to significantly amplify curvature-induced lipid demixing in the λ system. Intriguingly, for the DPPC/ di(18:2)PC/cholesterol ternary mixtures, a Lo/Ld domain boundary often moved to the branched point of the membrane, suggesting enhanced flexibility at the domain boundary. We hypothesize that curvature-driven lipid sorting and energetically favored localization of domain boundaries at sharp bends in the membranes may collaborate to assist intracellular lipid sorting.

The diterpenoid esters from Euphorbia lathyris L. induce intestinal inflammation via LXRα/ABCA1-regulated lipid rafts and TLR4-mediated pathway

Background:Diterpenoid esters are considered to be the main toxic components and bioactive constituents of Euphorbia lathyris L.(EL).Euphorbia factors L1(EF1),L2(EF2),and L3(EF3),the main diterpenoid esters of EL,have been found to cause intestinal diarrhea and induce intestinal inflammation in mice.This research aimed to explore the effects of major diterpenoid esters from EL on intestinal inflammation,as well as to clarify their possible targets and molecular mechanisms in vivo and vitro.Methods:Caco-2 cells and BALB/c mice were intervened with EFL1,EFL2,and EFL3,respectively.The expressions of TLR4,NLRP3,NF-κB p65,LXRα,ABCA1,TNF-αand IL-1βwere measured by Real-time PCR and ELISA.Cholesterol efflux levels were examined using cholesterol efflux kit.Flow cytometry was applied to detect lipid rafts abundance.Confocal microscopy was applied to investigate co-localization of lipid rafts and TLR4.Results:Our results revealed that EFL1,EFL2,and EFL3 inhibited LXRα,ABCA1 expression,and cholesterol efflux,promoted colocalization of TLR4 and lipid rafts,and up-regulated TLR4,NLRP3,NF-κB p65,TNF-αand IL-1βexpressions.Conclusion:These findings reveal that the mechanisms by which EFL1,EFL2,and EFL3 induce intestinal inflammation may be associated with LXRα/ABCA1-regulated lipid rafts and TLR4-mediated pathways.

miR-29c-3p调控ERLIN2抑制肺腺癌发展的作用

目的:探讨miR-29c-3p在肺腺癌(lung adenocarcinoma,LUAD)发生发展中的作用。方法:利用公共数据库分析miR-29c-3p和ERLIN2在肺腺癌中的表达及其与临床病理参数的相关性。采用qRT-PCR检测miR-29c-3p在LUAD细胞系和正常支气管上皮细胞系中的表达,CCK8、细胞克隆形成、Transwell和伤口愈合实验评估miR-29c-3p在细胞增殖、迁移和侵袭中的作用,利用生物信息学工具预测miR-29c-3p下游靶基因,并通过双荧光素酶报告基因分析验证靶向关系。结果:miR-29c-3p在肺腺癌组织和细胞中低表达。miR-29c-3p低表达患者的预后较差,miR-29c-3p是肺腺癌患者的独立预后因素,并与淋巴结转移状态和临床分期密切相关。细胞实验表明,抑制miR-29c-3p可促进A549细胞的增殖、迁移和侵袭。生物信息学分析表明,ERLIN2是miR-29c-3p的靶基因,二者表达呈负相关。通过双荧光素酶报告基因测定验证了上述靶向关系。在UALCAN数据库中,ERLIN2在肺腺癌组织中高表达,并与患者年龄、性别、吸烟、肿瘤分期、淋巴结转移和TP53突变状态密切相关,ERLIN2高表达患者总生存率低于低表达患者。结论:miR-29c-3p通过靶向ERLIN2抑制肺腺癌细胞的增殖、迁移和侵袭,是肺腺癌患者的独立预后因素。

基于脂筏治疗相关疾病的研究进展

“LR微区域”又称LR(lipid raft,LR)是细胞膜上的一类功能区域,富含糖脂、鞘磷脂以及胆固醇。在机体的免疫和炎症过程中,LR是重要的参与者。癌症、神经系统疾病、传染病和心血管等疾病常伴随LR的失调或缺陷等病理表现。本文基于细胞和及分子层面概述LR的结构及组成,挖掘靶向LR治疗相关疾病的方法和机制并探讨其相关性,对比了基于LR机制的中药和西药发挥药效的差异,以期对相关疾病的研究和临床治疗提供新的思路。

血小板胆固醇、脂筏与功能间的关系探究

[目的]探究胆固醇对血小板脂筏含量和血小板功能的调控作用。[方法]利用体外孵育甲基β环糊精(MβCD)和体内提升外周血总胆固醇水平来移除和负载血小板胆固醇。霍乱毒素B染色联合流式细胞术检测血小板脂筏含量;荧光抗体染色结合流式细胞术检测P选择素和活化型整合素αⅡbβ3的表达水平;Annexin V标记结合流式细胞术检测磷脂外翻水平;体外实验体系及鼠尾出血实验检测血小板的聚集能力。[结果]B淋巴细胞上脂筏的含量随着胆固醇的移除而降低,体外孵育MβCD移除血小板胆固醇反而显著提高其脂筏水平(P<0.05)。与此一致,体内胆固醇负载增加B淋巴细胞上的脂筏含量却降低血小板的脂筏含量(P<0.05)。移除胆固醇后增加的脂筏并不利于血小板的活化与聚集功能。体内胆固醇的负载下调血小板脂筏含量(P<0.05),增强其应答低浓度刺激剂的活化聚集与凝血能力,此增强作用在移除胆固醇后消失。[结论]血小板胆固醇是调控血小板脂筏含量和血小板功能的关键调节因子,可负向调节脂筏,促进血小板活化并增强其凝血功能。

Trichosanthin can spontaneously penetrate phospholipid monolayer under acid condition

Tianhuafen is a kind of traditional Chinese medicine for abortion, which has long been used in China. The basic protein trichosanthin (TCS) is responsible for such activity. As a ribosome inactivating protein (RIP), trichosanthin removes A4304 in the 28s rRNA via the N-glycosidase activity and inactivates the ribosome. However, it remains unclear how TCS

外周血液中脂筏标记蛋白表达水平与重性抑郁障碍全病程相关性的研究

目的探讨外周血液中脂筏标记蛋白(FLOT)1表达水平与重性抑郁障碍(MDD)全病程的相关性,以及是否能起到预测MDD复发与难治性MDD的作用。方法选取福建省福州神经精神病防治院2022年9月至2023年8月收治的100例MDD患者为试验组,以同期50名健康体检者为对照组。分别采取不同时期(急性期、巩固期、稳定期)MDD患者及对照组的外周血样本,采用实时荧光定量PCR(qRT-PCR)法测定外周血单核细胞FLOT1表达水平,分析FLOT1表达水平变化与生活事件(主要为负性事件)的相关性。结果试验组FLOT1 mRNA相对表达量高于对照组,差异有统计学意义(P<0.05);与治疗前比较,试验组治疗后的FLOT1 mRNA相对表达量明显下降,差异有统计学意义(P<0.05);试验组急性期的FLOT1 mRNA相对表达量明显高于巩固期与稳定期,差异有统计学意义(P<0.05)。试验组急性期汉密顿抑郁量表-17(HAMD-17)评分均高于巩固期、稳定期,差异有统计学意义(P<0.05);稳定期与巩固期比较,差异无统计学意义(P>0.05)。FLOT1 mRNA相对表达量与MDD患者不同时期的HAMD-17评分呈正相关(P<0.05),FLOT1 mRNA相对表达量与负性事件刺激量、生活事件应激总分呈正相关(P<0.05)。结论外周血液中FLOT1表达水平与MDD全病程有相关性,可能是MDD发病的一种生物学标志物。