基于siRNA技术的TRPC6基因沉默对血管紧张素Ⅱ诱导的足细胞自噬和凋亡的影响

目的采用小分子干扰RNA(siRNA)干扰技术沉默足细胞相关分子瞬时受体电位阳离子通道蛋白6(TRPC6)对血管紧张素Ⅱ(AngⅡ)诱导的自噬和凋亡的影响。方法设计、构建siRNA,转染足细胞,使TRPC6基因沉默,采用流式细胞术、激光共聚焦、透射电镜及Western Blot技术检测不同浓度siRNA转染后TRPC6基因表达,优化获得TRPC6基因沉默最佳效果的条件。体外培养小鼠肾小球足细胞,设立对照组、AngⅡ组、空载体组、沉默TRPC6基因组和AngⅡ+沉默TRPC6基因组。对照组用含0.02%DMSO的RPMI 1640培养液培养;AngⅡ组加入AngⅡ(10~(-8)M)刺激足细胞;空载体组加入空载体至足细胞;沉默TRPC6基因组运用siRNA干扰技术沉默TRPC6基因;AngⅡ+沉默TRPC6基因组同时加入AngⅡ(10~(-8)M)及沉默TRPC6基因。处理12、24 h和48 h后分别收集细胞,采用流式细胞仪检测足细胞凋亡率,Western Blot检测TRPC6及自噬相关蛋白的表达,透射电镜及激光共聚焦电子显微镜观察自噬相关蛋白的分布。结果自噬在正常足细胞的表达量很微弱,AngⅡ组足细胞凋亡率明显升高,沉默TRPC6使足细胞凋亡率明显降低,与对照组比较差异有统计学意义(P0.05)。透射电镜下AngⅡ组示足细胞超微结构发生改变,自噬表达增加,胞质中出现独立双层膜结构,胞质成分及溶酶体等细胞器形成双层及多层膜结构的自噬体。沉默TRPC6使自噬表达下降,与AngⅡ组比较差异有统计学意义(P0.05)。激光共聚焦检测AngⅡ组LC3-Ⅱ的表达增加,沉默TRPC6使LC3-Ⅱ表达趋于稳定,与对照组比较差异有统计学意义(P0.05)。结论AngⅡ促进足细胞的凋亡,沉默TRPC6基因能有效保护AngⅡ诱导的肾小球足细胞损伤,发挥保护足细胞的作用。     

足突裂孔隔膜相关蛋白分子研究进展

肾小球足细胞的足突裂孔隔膜是肾小球滤过屏障的重要结构 ,其特异的结构及功能蛋白分子是维持肾小球滤过屏障功能的基础 ,已获得的裂孔隔膜相关蛋白的信息资料增进了对足细胞及其足突裂孔隔膜生物学作用的认识 ,有利于进一步揭示蛋白尿的发生机制 ,为肾脏病基础与临床研究开辟了新的广阔的前景。     

肾脏足细胞裂孔隔膜的分子组成

足细胞裂孔隔膜结构的改变是导致肾小球疾病产生蛋白尿的主要原因 ,已陆续发现包括nephrin在内的与裂孔隔膜相关的多个蛋白分子 ,如ZO 1,CD2AP ,P cadherin ,podocin ,NEPH1,FAT及Filtrin等 ,它们的存在及相互作用对于保证裂孔隔膜的完整性和滤过功能有着直接或间接的作用 ,这些蛋白分子的发现有利于进一步阐明蛋白尿的发病机制 ,同时也为临床监测蛋白尿进展及制定治疗方案提供新的思路     

足细胞抗原与肾小球疾病

肾小球足细胞的损伤及其相关蛋白的表达异常是蛋白尿形成的主要原因, 足细胞表面抗原在肾小球疾病发病机制中发挥了重要作用.人类膜性肾病第一个足细胞抗原-中性内肽酶以及第一个裂孔隔膜组成分子Nephrin的发现开辟了足细胞研究的新纪元.随着足细胞抗原在肾小球疾病及蛋白尿产生机制中的深入研究, 将为临床进一步揭示肾小球疾病的发病机制和寻找特异有效的防治蛋白尿的新的分子靶点提供理论依据.     

CD2相关蛋白在肾脏细胞中的分布及其在足细胞中的作用

目的 观察CD2相关蛋白(cD2AP)在肾脏不同细胞系中的表达分布,及其与足细胞裂孔隔膜分子nephrin和细胞骨架蛋白F-actin之间的联系.方法 以DMEM培养基培养人肾小球系膜细胞(HMC)和人肾小管上皮细胞系(HK-2),RPMI 1640培养基培养条件永生化小鼠足细胞系.以RT-PCR及Western blotting方法检测足细胞内CD2AP和nephrin的表达.间接免疫荧光结合激光共焦方法观察CD2AP在HMC、HK-2、未分化及已分化足细胞中的表达情况,及CD2AP与nephtin在足细胞中的共存.直接免疫荧光结合激光共焦方法观察F-actin在足细胞的表达及其与CD2AP的共存.结果 CD2AP均匀分布于HK-2及未分化足细胞的核周及胞浆,而不表达于HMC细胞.在足细胞分化过程中,CD2AP的分布发生了变化,出现向周边聚集的现象.CD2AP与足细胞裂孔隔膜分子nephrin及细胞骨架蛋白F-actin在足细胞中存在共定位关系.结论 CD2AP表达于上皮来源的肾脏固有细胞.CD2AP在足细胞中的分布特点,提示CD2AP可能参与足细胞的分化过程,并与裂孔隔膜分子功能及细胞骨架凋节有关.     

Podocin及其生物学意义

Podocin是一种新发现的肾小球足细胞跨膜蛋白 ,定位于足突裂孔隔膜 (SD)插入足突膜的部位。Podocin属于stomatin蛋白家族 ,可能具有离子通道、信号转导功能 ,在足细胞形态形成和SD结构组织与功能调节中发挥重要作用。     

膜性肾病肾活检组织中TRPC6和podocalyxin表达改变及其意义

目的检测膜性肾病(membranous nephropathy,MN)患者肾活检组织中肾小球足细胞瞬时受体电位阳离子通道蛋白6(transient receptor potential cation channel 6,TRPC6)和podocalyxin的表达和分布,探讨足细胞蛋白TRPC6和podocalyxin在MN蛋白尿发生中的作用。方法采用常规组织病理以及免疫组化检查,并行免疫荧光双套色染色于激光共聚焦显微镜下观察TRPC6、podocalyxin在各组肾组织中表达及分布的改变,以计算机图像分析系统进行半定量分析。结果对照组肾组织podocalyxin沿肾小球毛细血管壁连续均匀分布,阳性荧光信号表达强,MN组表达减弱,且分布不均或节段性缺失,部分呈点状、短线状不连续分布,肾病综合征组较非肾病综合征组减弱更明显;TRPC6在对照组肾小球有一定的表达,沿肾小球基膜呈均匀连续线型分布,MN组TRPC6荧光强度有不同程度增强,且呈点状、团块状不均匀分布,肾病综合征组较非肾病综合征组更明显。结论 TRPC6和podocalyxin在正常肾组织沿肾小球基膜呈连续线状均匀分布;MN患者肾小球内TRPC6表达增加,podocalyxin表达减少,且分布形式亦发生变化,提示TRPC6和podocalyxin等足细胞相关蛋白表达改变及分布异常可能是MN蛋白尿发生的重要病理机制。     

Expression changes of TRPC6 and podocalyxin in human membranous nephropathy

目的 检测膜性肾病(membranous nephropathy,MN)患者肾活检组织中肾小球足细胞瞬时受体电位阳离子通道蛋白6(transient receptor potential cation channel 6,TRPC6)和podocalyxin的表达和分布,探讨足细胞蛋白TRPC6和podocalyxin在MN蛋白尿发生中的作用.方法 采用常规组织病理以及免疫组化检查,并行免疫荧光双套色染色于激光共聚焦显微镜下观察TRPC6、podocalyxin在各组肾组织中表达及分布的改变,以计算机图像分析系统进行半定量分析.结果 对照组肾组织podocalyxin沿肾小球毛细血管壁连续均匀分布,阳性荧光信号表达强,MN组表达减弱,且分布不均或节段性缺失,部分呈点状、短线状不连续分布,肾病综合征组较非肾病综合征组减弱更明显;TRPC6在对照组肾小球有一定的表达,沿肾小球基膜呈均匀连续线型分布,MN组TRPC6荧光强度有不同程度增强,且呈点状、团块状不均匀分布,肾病综合征组较非肾病综合征组更明显.结论 TRPC6和podocalyxin在正常肾组织沿肾小球基膜呈连续线状均匀分布;MN患者肾小球内TRPC6表达增加,podocalyxin表达减少,且分布形式亦发生变化,提示TRPC6和podocalyxin等足细胞相关蛋白表达改变及分布异常可能是MN蛋白尿发生的重要病理机制.     

中枢神经系统内的TRPC6离子通道

<正>TRPC6是TRP(transient receptor potential,TRP)基因超家族C亚家族(canonical)的成员之一,编码钙可通透的非选择性阳离子通道[1,2]。十余年来的研究证明TRPC6分子参与动物体内许多重要的生理和病理调节过程,如血管与气道平滑肌收缩、肾小球滤过膜滤过功能、免疫和血液细胞调节等[3];该分子功能异常会导致高血压和局灶性节段性肾小球硬化[4,5]。     

TRPC6在TGF-β1诱导的体外培养肾小球足细胞损伤中的表达及其高表达对nephrin、desmin表达的影响

目的体外研究经典瞬时受体电位通道6(TRPC6)在TGF-β1诱导的肾小球足细胞损伤中的表达变化及其高表达对足细胞nephrin、desmin表达的影响。方法以肾小球足细胞株(MPC5)为研究对象,以不同质量浓度(0、4、8、12 ng/ml)TGF-β1刺激足细胞,干预72 h后用免疫荧光、Real-time PCR、Wstern blot检测TRPC6的分布及m RNA和蛋白表达。再将MPC5细胞分组,应用12 ng/ml TGF-β1处理各组细胞,分别于0、24、48、72 h应用免疫荧光、Real-time PCR、Western blot检测TRPC6的分布及m RNA和蛋白表达。用脂质体法将小鼠TRPC6真核表达载体p EX-3-TRPC6及对照质粒空载体p EX-3-NC转染足细胞,48 h后应用Western blot检测转染后TRPC6蛋白水平评估传染效率;同时应用免疫荧光、Real time RT-PCR及Western印迹方法检测转染后nephrin、desmin分布及表达的变化。结果与正常对照组相比,倒置显微镜下TGF-β1干预后足细胞足突融合、回缩,当TGF-β1增加至16 ng/ml时足突甚至消失。TGF-β1作用能使足细胞TRPC6表达及分布发生变化,当TGF-β1质量浓度为4 ng/ml,干预72 h后与对照组相比TRPC6 m RNA和蛋白含量即升高,但差异无统计学意义,当TGF-β1质量浓度提高到为8、12 ng/ml时TRPC6 m RNA和蛋白含量明显升高(P0.05),并呈剂量依赖性。应用12 ng/ml干预24 h,与对照组相比,TRPC6m RNA和蛋白含量即升高,但差异无统计学意义,当干预时间延长至48、72 h时TRPC6 m RNA和蛋白含量明显升高(P0.05),并呈时间依赖性。p EX-3-TRPC6转染48 h后足细胞TRPC6蛋白表达水平明显增高(P0.05),nephein分布未发生变化,但表达量在m RNA及蛋白水平分别下降25%及42%左右(P0.05),desmin分布发生改变,表达量在m RNA及蛋白水平分别升高132%及116%左右(P0.05)。结论 TGF-β1可诱导足细胞TRPC6分布变化且表达上调,TRPC6高表达可影响nephrin、desmin表达及desmin的分布,这可能是TRPC6参与足细胞损伤的机制之一。     

TRPC6与肾脏疾病

瞬时受体电位阳离子通道（transient receptor potential channel, TRPC）作为瞬时受体电位（transient receptor potential, TRP）超家族中的一员,是一种非选择性的离子通道,在人体的各种组织、器官和细胞中均有表达。TRPC6基因突变致局灶节段性肾小球硬化(focal segmental glomerulosclerosis, FSGS),从而揭示了TRPC通道,尤其TRPC6与肾脏疾病的密切关系。TRPC6突变可引起细胞内钙离子浓度升高,也可直接影响肌动蛋白细胞支架组织,这些都是导致肾脏疾病的机制。     

Renoprotection: focus on TRPV1, TRPV4, TRPC6 and TRPM2

Members of the transient receptor potential (TRP) cation channel receptor family have unique sites of regulatory function in the kidney which enables them to promote regional vasodilatation and controlled Ca²⁺ influx into podocytes and tubular cells. Activated TRP vanilloid 1 receptor channels (TRPV1) have been found to elicit renoprotection in rodent models of acute kidney injury following ischaemia/reperfusion. Transient receptor potential cation channel, subfamily C, member 6 (TRPC6) in podocytes is involved in chronic proteinuric kidney disease, particularly in focal segmental glomerulosclerosis (FSGS). TRP vanilloid 4 receptor channels (TRPV4) are highly expressed in the kidney, where they induce Ca²⁺ influx into endothelial and tubular cells. TRP melastatin (TRPM2) non‐selective cation channels are expressed in the cytoplasm and intracellular organelles, where their inhibition ameliorates ischaemic renal pathology. Although some of their basic properties have been recently identified, the renovascular role of TRPV1, TRPV4, TRPC6 and TRPM2 channels in disease states such as obesity, hypertension and diabetes is largely unknown. In this review, we discuss recent evidence for TRPV1, TRPV4, TRPC6 and TRPM2 serving as potential targets for acute and chronic renoprotection in chronic vascular and metabolic disease.     

Angiotensin II contributes to podocyte injury by increasing TRPC6 expression via an NFAT-mediated positive feedback signaling pathway

The transient receptor potential channel C6 (TRPC6) is a slit diaphragm-associated protein in podocytes involved in regulating glomerular filter function. Gain-of-function mutations in TRPC6 cause hereditary focal segmental glomerulosclerosis (FSGS), and several human acquired proteinuric diseases show increased glomerular TRPC6 expression. Angiotensin II (AngII) is a key contributor to glomerular disease and may regulate TRPC6 expression in nonrenal cells. We demonstrate that AngII regulates TRPC6 mRNA and protein levels in cultured podocytes and that AngII infusion enhances glomerular TRPC6 expression in vivo. In animal models for human FSGS (doxorubicin nephropathy) and increased renin-angiotensin system activity (Ren2 transgenic rats), glomerular TRPC6 expression was increased in an AngII-dependent manner. TRPC6 expression correlated with glomerular damage markers and glomerulosclerosis. We show that the regulation of TRPC6 expression by AngII and doxorubicin requires TRPC6-mediated Ca(2+) influx and the activation of the Ca(2+)-dependent protein phosphatase calcineurin and its substrate nuclear factor of activated T cells (NFAT). Accordingly, calcineurin inhibition by cyclosporine decreased TRPC6 expression and reduced proteinuria in doxorubicin nephropathy, whereas podocyte-specific inducible expression of a constitutively active NFAT mutant increased TRPC6 expression and induced severe proteinuria. Our findings demonstrate that the deleterious effects of AngII on podocytes and its pathogenic role in glomerular disease involve enhanced TRPC6 expression via a calcineurin/NFAT positive feedback signaling pathway.     

Functional role of TRPC proteins in native systems: implications from knockout and knock-down studies

Available data on transient receptor potential channel (TRPC) protein functions indicate that these proteins represent essential constituents of agonist-activated and phospholipase C-dependent cation entry pathways in primary cells which contribute to the elevation of cytosolic Ca²⁺. In addition, a striking number of biological functions have already been assigned to the various TRPC proteins, including mechanosensing activity (TRPC1), chemotropic axon guidance (TRPC1 and TRPC3), pheromone sensing and the regulation of sexual and social behaviour (TRPC2), endothelial-dependent regulation of vascular tone, endothelial permeability and neurotransmitter release (TRPC4), axonal growth (TRPC5), modulation of smooth muscle tone in blood vessels and lung and regulation of podocyte structure and function in the kidney (TRPC6). The lack of compounds which specifically block or activate TRPC proteins impairs the analysis of TRPC function in primary cells. We therefore concentrate in this contribution on (i) studies of TRPC-deficient mouse lines, (ii) data obtained by gene-silencing approaches using antisense oligonucleotides or RNA interference, (iii) expression experiments employing dominant negative TRPC constructs, and (iv) recent data correlating mutations of TRPC genes associated with human disease.     

Proteomic analysis of TRPC5- and TRPC6-binding partners reveals interaction with the plasmalemmal Na+/K+-ATPase

Mammalian transient receptor potential canonical (TRPC) genes encode a family of nonselective cation channels that are activated following stimulation of G-protein-coupled membrane receptors linked to phospholipase C. In Drosophila photoreceptor cells, TRP channels are found in large, multimolecular signaling complexes in association with the PDZ-containing scaffolding protein, INAD. A similar mammalian TRPC signalplex has been proposed, but has yet to be defined. In the present study, affinity-purified polyclonal antibodies against TRPC5 and TRPC6 were used to immunoprecipitate signalplex components from rat brain lysates. Immunoprecipitated proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, digested with trypsin, and sequenced by mass spectrometry. Proteins identified in the immunoprecipitates included cytoskeletal proteins spectrin, myosin, actin, drebrin, tubulin, and neurabin; endocytic vesicle-associated proteins clathrin, dynamin and AP-2; and the plasmalemmal Na⁺/K⁺-ATPase (NKA) pump. Several of these interactions were confirmed by reciprocal immunoprecipitation followed by Western blot analysis. In lysates from rat kidney, TRPC6, but not TRPC3, was found to coimmunoprecipitate with the NKA pump. Likewise, TRPC6, stably expressed in human embryonic kidney (HEK) cells, coimmunoprecipitated with endogenous NKA and colocalized with the pump to the plasmalemma when examined by immunofluorescence microscopy. Cell surface biotinylation experiments in intact HEK cells, confirmed that both the Na⁺ pump and TRPC6 were present in the surface membrane and appeared to interact. Lastly, TRPC6 coimmunoprecipitated with the NKA pump when the proteins were coexpressed in Spodoptera frugiperda insect cells using recombinant baculoviruses. These observations suggest that TRPC6 and the Na⁺ pump are part of a functional complex that may be involved in ion transport and homeostasis in both the brain and kidney.     

Regulation of podocyte structure during the development of nephrotic syndrome

 Nephrotic syndrome is a common kidney disease seen in both children and adults. The clinical syndrome includes massive proteinuria, hypoalbuminemia, edema, and usually hypercholesterolemia. Development of these clinical changes is closely correlated with profound structural changes in glomerular epithelial cells, or podocytes, which together with the glomerular basement membrane and endothelium comprise the kidney’s blood filtration barrier. Although relatively little is known about the cellular or molecular changes which occur within podocytes during the development of nephrotic syndrome, cytoskeletal proteins very likely play a central role in these changes since they are primarily responsible for the maintenance of cell structure in almost all cells. This review focuses on: (a) the structure and function of podocytes in both the normal state and during nephrotic syndrome and (b) the potential roles of several cytoskeleton-associated proteins identified in podocytes in the development of and/or recovery from the pathophysiological cytoskeletal changes which occur in podocytes during nephrotic syndrome. Received: 18 April 1997 / Accepted: 18 July 1997     

CD2AP在足细胞中的生理功能研究

CD2相关蛋白(CD2 associated protein,CD2AP)是新近发现的足细胞裂孔隔膜(slit diaphragm,SD)分子。近年来的研究发现,CD2AP在足细胞内与多种结构蛋白相互作用,参与了足细胞多种重要的生理过程,并在蛋白尿的发生、发展中发挥着重要作用。文章综述了CD2AP的分子结构及其在肾脏足细胞中的表达分布,深入探讨CD2AP的生理功能及作用机制。     

Revisiting TRPC1 and TRPC6 mechanosensitivity

This article addresses whether TRPC1 or TRPC6 is an essential component of a mammalian stretch-activated mechano-sensitive Ca²⁺ permeable cation channel (MscCa). We have transiently expressed TRPC1 and TRPC6 in African green monkey kidney (COS) or Chinese hamster ovary (CHO) cells and monitored the activity of the stretch-activated channels using a fast pressure clamp system. Although both TRPC1 and TRPC6 are highly expressed at the protein level, the amplitude of the mechano-sensitive current is not significantly altered by overexpression of these subunits. In conclusion, although several TRPC channel members, including TRPC1 and TRPC6, have been recently proposed to form MscCa in vertebrate cells, the functional expression of these TRPC subunits in heterologous systems remains problematic. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Co-first authors: Philip Gottlieb, Joost Folgering, and Rosario Maroto.     

Nitric oxide lacks direct effect on TRPC5 channels but suppresses endogenous TRPC5-containing channels in endothelial cells

TRPC5 is a member of the canonical transient receptor potential (TRPC) family of proteins that forms cationic channels either through homomultimeric assembly or heteromultimeric coordination with other TRPC proteins. It is expressed in a variety of cells including central neurones and endothelial cells and has susceptibility to stimulation by multiple factors. Here we investigated if TRPC5 is sensitive to nitric oxide. Mouse TRPC5 or human TRPC5 was over-expressed in HEK293 cells, and TRPC5 activity was determined by measuring the cytosolic Ca²⁺ concentration with an indicator dye or by recording membrane current under voltage clamp. TRPC5 activity could be evoked by carbachol acting at muscarinic receptors, lanthanum, or a reducing agent. However, S-nitroso-N-acetylpenicillamine (SNAP) and diethylamine NONOate (DEA-NONOate) failed to stimulate or inhibit TRPC5 at concentrations that generated nitric oxide, caused vasorelaxation, or suppressed activity of TRPC6 via protein kinase G. At high concentrations, SNAP (but not DEA-NONOate) occasionally stimulated TRPC5 but the effect was confounded by background TRPC5-independent Ca²⁺ signals. Endogenous Ca²⁺-entry in bovine aortic endothelial cells (BAECs) was suppressed by SNAP; TRPC5 blocking antibody or dominant-negative mutant TRPC5 suppressed this Ca²⁺ entry and occluded the effect of SNAP. The data suggest that nitric oxide is not a direct modulator of homomeric TRPC5 channels but may inhibit endogenous BAEC channels that contain TRPC5.