CD36与脂类味觉感受

CD36是一种脂类结合蛋白,在大鼠和小鼠的舌上皮细胞中均被发现,与长链脂肪酸（LCFA）具有高度亲和力,是啮齿类动物感受脂类的重要因子之一。研究表明这种蛋白质受体在口腔的脂类感受中起着至关重要的作用。CD36位于啮齿类口腔味蕾部分神经感受细胞的顶端部分,任轮廓状乳头中有特别高的表达,在叶状乳头中有少量表达,而在菌状乳头中几乎没有表达。     

CD36调控脂质代谢作用及机制

脂质代谢是机体的重要代谢过程,其紊乱会导致众多疾病的发生。人类白细胞分化抗原36(cluster of differentiation 36,CD36)是一种在单核细胞、巨噬细胞、平滑肌细胞以及脂肪细胞高度表达的清道夫受体,是识别氧化低密度脂蛋白及长链脂肪酸的主要受体和转运蛋白,在脂质代谢过程中发挥着重要作用。本文综述了CD36基因及蛋白的结构和生理功能,阐述了清道夫受体CD36在脂质代谢过程中发挥的作用,并系统地总结了其级联AMPK、mTOR和MAPK信号通路参与脂质代谢过程的分子机制,为相关生物学研究提供了理论基础。     

Soluble CD36- a marker of the (pathophysiological) role of CD36 in the metabolic syndrome?

CD36 is a class B scavenger receptor observed in many cell types and tissues throughout the body. Recent literature has implicated CD36 in the pathogenesis of metabolic dysregulation such as found in obesity, insulin resistance, and atherosclerosis. Genetic variation at the CD36 loci have been associated with obesity and lipid components of the metabolic syndrome, with risk of heart disease and type 2 diabetes. Recently, non-cell bound CD36 was identified in human plasma and was termed soluble CD36 (sCD36). In this review we will describe the functions of CD36 in tissues and address the role of sCD36 in the context of the metabolic syndrome. We will also highlight recent findings from human genetic studies looking at the CD36 locus in relation to metabolic profile in the general population. Finally, we present a model in which insulin resistance, oxLDL, low-grade inflammation and liver steatosis may contribute to elevated levels of sCD36.     

KLF9通过上调CD36调节肝脏脂代谢

非酒精性脂肪性肝病(nonalcoholic fatty liver disease, NAFLD)的发生和发展与脂肪酸的摄取密切相关。本研究旨在探索Krüppel样转录因子9 (Krüppel-like factor 9, KLF9)对脂肪酸转位酶CD36、肝细胞的脂代谢以及非酒精性脂肪肝的发生和发展所产生的影响。采用高脂饮食构建的高脂模型C57BL/6J小鼠和db/db糖尿病小鼠,检测其肝脏内Klf9和Cd36基因和蛋白表达水平的变化。分离C57BL/6J小鼠原代肝细胞进行体外培养,分别给予Ad-GFP、Ad-Klf9、Ad-shCtrl或Ad-shKlf9处理,然后利用油酸和棕榈酸进行24 h的诱导;同时构建肝脏特异性Klf9基因敲除小鼠,采用Western blot检测KLF9蛋白表达水平的变化,real-time PCR检测Klf9和Cd36 mRNA表达水平的变化,试剂盒测定甘油三酯含量的变化,油红O染色检测脂质含量的变化。结果显示:(1)与对照组相比,高脂饮食诱导的肥胖小鼠或db/db糖尿病小鼠肝脏Klf9的表达显著增加;(2)在小鼠原代肝脏细胞中过量表达Klf9会增加Cd36表达水平,导致细胞脂肪含量增加;(3)相反,在小鼠原代肝脏细胞中敲低Klf9的表达则降低Cd36表达水平,从而减少肝细胞脂肪含量;(4)小鼠肝脏Klf9敲除能降低肝脏Cd36表达,改善高脂饮食诱导的脂肪肝表型。上述结果表明,肝脏KLF9通过促进CD36的表达影响肝脏的脂代谢。     

Amyloid-β inhibits No-cGMP signaling in a CD36- and CD47-dependent manner

Amyloid-β interacts with two cell surface receptors, CD36 and CD47, through which the matricellular protein thrombospondin-1 inhibits soluble guanylate cyclase activation. Here we examine whether amyloid-β shares this inhibitory activity. Amyloid-β inhibited both drug and nitric oxide-mediated activation of soluble guanylate cyclase in several cell types. Known cGMP-dependent functional responses to nitric oxide in platelets and vascular smooth muscle cells were correspondingly inhibited by amyloid-β. Functional interaction of amyloid-β with the scavenger receptor CD36 was indicated by inhibition of free fatty acid uptake via this receptor. Both soluble oligomer and fibrillar forms of amyloid-β were active. In contrast, amyloid-β did not compete with the known ligand SIRPα for binding to CD47. However, both receptors were necessary for amyloid-β to inhibit cGMP accumulation. These data suggest that amyloid-β interaction with CD36 induces a CD47-dependent signal that inhibits soluble guanylate cyclase activation. Combined with the pleiotropic effects of inhibiting free fatty acid transport via CD36, these data provides a molecular mechanism through which amyloid-β can contribute to the nitric oxide signaling deficiencies associated with Alzheimer's disease.     

CD36原核表达载体的构建及生物信息学分析

[目的]对CD36基因进行体外克隆表达,建立CD36基因cDNA在大肠杆菌中表达的实验技术以及进行CD36蛋白三级结构的预测并利用生物信息学方法进行分析。[方法]以人血液RNA为模板,RT-PCR扩增CD36的基因序列;并构建原核表达质粒pET-32a-CD36转化到大肠杆菌DE3中后,经过IPTG诱导表达后进行SDS-PAGE验证。[结果]成功克隆了人CD36基因并构建出原核表达质粒,成功转入表达菌大肠杆菌DE3中后经IPTG诱导成功表达,且在1 mmol/L的诱导剂浓度下培养6 h表达量最佳。利用Phyre2和Abcpred软件预测蛋白质结构和B细胞抗原表位,B细胞抗原表位评分大于0.85的CD36的B细胞抗原表位有8个。[结论]成功建立了人CD36基因的原核表达的实验技术,并对CD36的结构及B细胞抗原表位进行了预测,为后续研究CD36基因的功能和抗体制备提供方向和奠定基础。     

CD36在炎症反应和脂质代谢中的作用

白细胞分化抗原36 (cluster of differentiation 36, CD36)是一种高度糖基化的单链跨膜蛋白,属B型清道夫受体。其功能较为广泛,不仅可以识别"异己"成分,诱发免疫应答,还参与多种生理、病理过程。CD36作为膜受体与其他膜蛋白和胞质蛋白组成不同的信号通路。CD36是TRL4的辅助受体,可识别病原体相关分子模式,级联NF-κB信号通路,在天然免疫过程发挥作用;作为修饰脂蛋白受体,级联MAPK通路,诱发无菌性炎症及脂代谢紊乱,并参与动脉粥样硬化病变;作为外源长链脂肪酸受体,通过AMPK/mTOR信号通路在能量代谢及脂质蓄积过程中发挥调控作用。该文综述了CD36的分子特征及其偶联相关信号通路在天然免疫和脂代谢等方面的作用与机制,展示CD36的多功能特点,为相关生物医学研究提供依据。     

鸭CD36表达与血清生化指标相关性研究

CD36是一种多肽单链的跨膜糖蛋白,属于B类清道夫受体。为更深入了解CD36基因的功能并能更好地为鸭分子育种方面提供基础参考,本研究采用相对定量PCR法检测樱桃谷鸭CD36 m RNA的组织表达谱,分析樱桃谷鸭各组织CD36 m RNA表达水平差异显著性及其与血清生化指标的相关性。结果表明:CD36 m RNA在16个组织中表达水平上存在显著差异,在皮脂、垂体、大肠和腹脂均呈高度特异表达,在下丘脑及胸肌呈中度特异表达,在心、肝、脾、肺、肾、腺胃、肌胃、小脑、大脑和小肠中呈低度特异表达;相关分析结果显示:CD36与甘油三酯呈极显著正相关(p0.01),与总蛋白、球蛋白、低密度脂蛋白及总胆固醇呈极显著负相关(p0.01)。由此推测鸭CD36基因可作为脂质性状选择的候选基因。     

重组斑马鱼CD36蛋白的原核表达及纯化

目的：在大肠杆菌中重组表达斑马鱼CD36蛋白胞外区38～432氨基酸残基段并纯化。方法：PCR扩增斑马鱼CD36蛋白的基因编码区,连接到带有6~His标签的原核表达载体pET-28a中,构建重组表达质粒pET28a-CD36,并转化大肠杆菌BL21（DE3）,用IPTG诱导表达,优化表达条件后用Ni^2＋柱进行纯化。结果：构建了pET28a-CD36重组质粒;目的蛋白在大肠杆菌中获得表达,亲和纯化后,SDS-PAGE显示相对分子质量为预期的46．8×10^3。结论：获得了斑马鱼CD36融合蛋白,为其生物学功能研究奠定了基础。     

肝脏特异性CD36基因敲除小鼠的制备及鉴定

目的:运用Cre/Loxp重组酶系统构建肝脏特异性CD36基因敲除小鼠并进行鉴定和验证,为研究CD36的生物学功能奠定基础。方法:构建CD36打靶载体,电转转染胚胎干细胞,通过长链PCR筛选出正确同源重组的阳性克隆,阳性胚胎干细胞克隆经扩增后,注射入C57BL/6J小鼠的囊胚中,获得嵌合小鼠,再与Flp小鼠交配筛选获得Flox杂合子小鼠,该小鼠与引进的Alb-Cre小鼠交配,在F3代获得CD36fl/fl:Alb-Cre+基因型小鼠,即为肝脏特异性CD36敲除小鼠。采用PCR鉴定小鼠基因型,PCR、实时荧光定量PCR和Western blot验证小鼠肝脏CD36敲除效果,Western blot检测小鼠肾脏、脂肪和心肌组织CD36表达情况,HE染色观察小鼠肝脏形态学改变。结果:建立了CD36基因的Flox杂合子小鼠,与Alb-Cre小鼠交配后,在F3代筛选出CD36fl/fl:AlbCre-和CD36fl/fl:Alb-Cre+基因型小鼠,DNA水平证实CD36fl/fl:Alb-Cre+基因型小鼠肝脏CD36基因通过Cre/Loxp重组酶系统被敲除。与CD36fl/fl:Alb-Cre-基因型小鼠相比,CD36fl/fl:Alb-Cre+基因型小鼠肝脏CD36mRNA和蛋白表达水平显著降低,肾脏、脂肪和心肌组织CD36蛋白表达无差别,肝脏形态学特征无明显差异。结论:通过Cre/Loxp重组酶系统成功构建了肝脏特异性CD36基因敲除小鼠,为研究CD36在肝脏代谢和肝脏疾病中的功能提供了动物模型。     

氧化低密度脂蛋白诱导巨噬细胞内质网应激及CD36的可能作用

本文旨在研究在鼠源巨噬细胞泡沫化过程中氧化低密度脂蛋白(oxidized low density lipoprotein,ox-LDL)对巨噬细胞内质网应激(endoplasmic reticulum stress,ERS)的诱导作用及其机制。体外培养RAW264.7巨噬细胞,分别给予ox-LDL(25、50和100mg/L)、抗CD36抗体+ox-LDL和衣霉素(tunicamycin,TM)等不同处理。采用油红O染色观察细胞内脂质蓄积情况,酶比色法测定细胞内总胆固醇含量,免疫细胞化学法检测ERS标志分子糖调节蛋白94(glucose-regulated protein94,GRP94)表达,免疫印迹法检测GRP94及未折叠蛋白反应关键分子p-IRE1(phosphorylated inositol-requiring enzyme1)和X盒结合蛋白1(X box binding protein1,XBP1)蛋白表达水平。结果显示,不同浓度(25、50和100mg/L)ox-LDL处理细胞24h后,胞浆内可见大量油红O染色阳性脂质颗粒,细胞内总胆固醇含量明显增加,分别为空白对照组的2.1倍、2.8倍和3.1倍;使用抗CD36抗体阻断ox-LDL的摄入,可显著减少100mg/Lox-LDL所致的细胞内胆固醇蓄积。不同浓度ox-LDL和ERS诱导剂TM均可显著增加GRP94及其上游信号分子p-IRE1和XBP1蛋白表达,且表达强度随着ox-LDL诱导浓度的增加而增强;抗CD36抗体显著抑制100mg/Lox-LDL所致的上述3种蛋白表达上调。上述结果提示,ox-LDL可呈剂量依赖性诱导RAW264.7巨噬细胞产生ERS,激活未折叠蛋白反应信号通路;该过程可能由清道夫受体CD36所介导。     

鸭CD36基因表达对前列腺癌PC3细胞增殖的影响

为了探讨鸭CD36基因表达对前列腺癌PC3细胞增殖的效应,通过克隆鸭CD36基因CDS区,构建真核表达载体pEGFP-N3+CD36+His,空载体pEGFP-N3为对照,转染培养的前列腺癌PC3细胞。结果表明:前列腺癌PC3细胞均被pEGFP-N3+CD36+His和pEGFP-N3成功转染,转染效率均较高;通过检测转染48 h的CD36+His-tag融合蛋白表达量和细胞数量,CD36+His-tag融合蛋白表达量为98.81 pg/m L,pEGFP-N3+CD36+His组细胞数为0.72×10~6个,pEGFP-N3组细胞数为0.61×10~6个,pEGFP-N3+CD36+His组细胞数显著高于pEGFP-N3组。研究结果揭示,鸭CD36基因的表达对前列腺癌PC3细胞增殖和生长可能有促进作用。     

动脉粥样硬化早期病变过程CD36的表达与oxLDL的摄取作用

清道夫受体CD36最初被认为是一种血小板膜糖蛋白和一种血栓反应蛋白受体(TSP-1)。近来,CD36也被认为是单核细胞产生的活性氮物质修饰的低密度脂蛋白(LDL)的主要受体,参与包括动脉粥样硬化(AS)在内的许多病理生理过程。该文介绍CD36的生物学特性及其在巨噬细胞源性泡沫细胞形成和AS形成中的作用,以及CD36表达的调控机制。     

抑制CD36与Nogo-B表达抑制三阴性乳腺癌细胞增殖与迁移

分化聚类36（cluster of differentiation 36,CD36）是一种位于细胞表面的膜蛋白受体,可以结合并转运脂肪酸。内质网膜蛋白4B （Nogo-B）在肝脏中调控脂肪酸代谢而影响肝癌的发展。目前并不清楚CD36和Nogo-B的相互作用是否能够影响乳腺癌细胞的增殖和迁移。本研究在三阴性乳腺癌（triple-negative breast cancer,TNBC）细胞中同时干预CD36与Nogo-B的表达来探索它们对细胞增殖与迁移的影响。结果表明在三阴性乳腺癌细胞中,单独抑制CD36或Nogo-B的表达都能够抑制细胞的增殖与迁移;同时抑制CD36与Nogo-B的表达时,这种抑制效果更加明显,且Vimentin、B细胞淋巴瘤-2（B-cell lympoma-2,BCL2）和增殖细胞核抗原（proliferating cell nuclear antigen,PCNA）的表达受到抑制。在小鼠移植瘤模型中,E0771细胞转染CD36或Nogo-B的siRNA后成瘤能力降低;同时敲减CD36和Nogo-B时,肿瘤生长速度显著减慢。机制研究发现,抑制CD36和Nogo-B表达能够抑制脂肪酸结合蛋白4（fatty acid binding protein 4,FABP4）和脂肪酸转运蛋白4（fatty acid transport protein 4,FATP4） mRNA的含量,同时CD36和Nogo-B过表达刺激的细胞增殖被FABP4的siRNA降低,预示着抑制乳腺癌细胞中CD36与Nogo-B的表达可能通过抑制脂肪酸的吸收和转运而抑制细胞的生长和迁移。此外,抑制CD36与Nogo-B的表达可激活P53-P21-Rb信号通路,参与抑制CD36与Nogo-B表达而抑制的细胞增殖与迁移。本研究证明同时抑制CD36和Nogo-B的表达能够协同抑制三阴性乳腺癌细胞的增殖和迁移,为临床抗三阴性乳腺癌药物的开发提供了新的靶点。     

Suppression of FAT/CD36 mRNA by human growth hormone in pancreatic β-cells

Fatty acid-induced damage in pancreatic β-cells is assumed to play an important role in the development of type 2 diabetes. Lactogens (prolactin, placental lactogen and growth hormone) improve β-cell survival via STAT5 activation but the molecular targets are incompletely characterized. The aim of this study was to examine the effect of human growth hormone (hGH) on mRNAs of fatty acid transport and binding proteins expressed in pancreatic β-cells, and to examine this in relation to β-cell survival after exposure to fatty acids. hGH decreased mRNA levels of FAT/CD36, whereas mRNAs of GPR40, FASN, FABP2, FATP1 and FATP4 were unchanged. RNAi against FAT/CD36 decreased fatty acid-induced apoptosis. Over-expression of constitutively active STAT5 was able to mimic hGH’s suppression of FAT/CD36 expression, whereas dominant negative STAT5 was unable to block the effect of hGH indicating that STAT5 did not bind directly to the FAT/CD36 promoter. The hGH-mediated suppression of FAT/CD36 mRNA was associated with a decrease in palmitate uptake and fatty acid-induced basal hyper-secretion of insulin resulting in improved glucose-stimulated insulin secretion. This study suggests that hGH can protect β-cells against fatty acid-induced damages.