紧密连接蛋白claudins及其在肿瘤发病中的作用

紧密连接分子由occludin,claudins和连接黏附分子(JAMs)3种完整的膜蛋白和闭合小环蛋白(ZO-1,ZO-2和ZO-3)等外周胞浆蛋白组成。Claudin蛋白是构成紧密连接的最主要的功能分子,可维持紧密连接特有的栅栏功能和屏障功能。多种信号分子参与了claudins功能的调节。 Claudins分布于皮肤、脑、神经系统和内脏组织中,其表达有组织特异性,但大多数组织可表达多种claudin蛋白。 Claudin及其结合的蛋白结构改变可导致肿瘤等多种疾病的发生。不同claudins家族成员在不同肿瘤中表达各异,但在恶性肿瘤组织中的表达无论高或低,最终总会引起紧密连接分子的正常结构破坏、生理功能障碍。 claudin蛋白可作?煌琢龅恼锒霞爸瘟频姆肿颖曛尽Ｋ孀欧肿由镅Ъ际醯姆伤俜⒄购投詂laudin更全面的认识,claudin在疾病的检测、诊断、治疗及预后判断方面中会有一个新的应用前景。     

紧密连接蛋白claudins的研究进展

紧密连接蛋白c laud ins是构成紧密连接复合物的主要成分,维持细胞间离子和溶质的选择性渗透,c laud ins的调节主要通过蛋白激酶途径实现。C laud ins基因突变与许多疾病如家族性、伴发高尿钙和肾脏钙质沉着的低镁血症,常染色体隐性耳聋以及新生儿硬化性胆管炎和鱼鳞病有直接关系;C laud ins表达水平的改变与许多肿瘤和神经生殖系统疾病关系密切。研究c laud ins在生理、病理状态下的改变,有助于对相关疾病进行诊断、针对性治疗和判断预后。     

紧密连接蛋白claudins与妇科肿瘤的研究进展

细胞间紧密连接有维持细胞极向排列和屏障功能,claudins是上皮细胞间紧密连接骨架蛋白,参与紧密连接的构成.claudins表达异常与肿瘤的发生、发展关系密切.多种途径可能参与了claudins表达的调节.claudins为肿瘤的诊断和治疗提供了一种新思路.因此,claudins成为肿瘤研究新热点.本文就claudins的基本结构、功能、临床应用前景及其与妇科常见肿瘤关系研究作一综述.     

三细胞紧密连接蛋白tricellulin表达与功能调控的研究进展

<正>紧密连接(tight junction,TJ)是由多个蛋白构成的大分子复合物,广泛分布在所有上皮细胞和内皮细胞的顶侧膜区域。TJ通过调节水、离子和大、小分子物质经旁细胞途径的转运以及限制细胞膜脂质和蛋白的自由流动,发挥着重要的屏障和栅栏功能。狭义的TJ复合物主要包括跨膜蛋白,如密封蛋白(claudin)家族、闭合蛋白(occludin)和连接黏附分子(junctional adhesion molecules,JAMs)等,以及胞浆蛋白,如闭锁小带蛋白(zonula occludens,ZO)和扣带素(cingulin)等^[1];     

高原脑水肿时脑血管通透性改变与紧密连接蛋白的关系

本文概述了高原脑水肿的研究现状与发展趋势,脑血管通透性与紧密连接蛋白的关系以及影响因素,研究脑血管通透性对阐明高原脑水肿的作用及意义.     

缺血再灌注对血脑屏障紧密连接蛋白的影响

紧密连接是血脑屏障的结构功能基础,它是一个复杂的、具有主动调节性的细胞系统.近来的研究表明缺血再灌注通过各种途径影响紧密连接的结构和分布.探讨血脑屏障连接复合体的分子结构、在脑损伤时的变化以及对血脑屏障通透性调节的可能机制为脑损伤的临床防治提供了一个全新的思路.     

siRNA-Tie1下调紧密连接相关蛋白claudin-5、occludin和ZO-1增加血肿瘤屏障通透性

目的研究Tie1 AS和Tie1表达变化对血肿瘤屏障通透性的影响和相关机制。方法建立体外血脑屏障和血肿瘤屏障模型,Real-time PCR检测h CMEC/D3细胞中Tie1 AS和Tie1的表达水平。转染p IRES2-EGFPTie1 AS表达载体上调体外血肿瘤屏障模型h CMEC/D3细胞中Tie1 AS的表达,Western blot检测Tie1的表达变化。将si RNA-Tie1转染人h CMEC/D3细胞并建立体外血肿瘤屏障模型,跨内皮电阻测量系统分析血肿瘤屏障通透性变化;Western blot和免疫荧光法检测h CMEC/D3细胞中紧密连接相关蛋白claudin-5、occludin和ZO-1的表达和分布变化。结果和正常脑微血管内皮细胞相比,体外血肿瘤屏障模型h CMEC/D3细胞中Tie1的表达显著增加,而Tie1 AS的表达显著降低。上调体外血肿瘤屏障模型内皮细胞中Tie1 AS的表达水平,能够显著降低Tie1的表达。下调体外血肿瘤屏障模型内皮细胞中Tie1的表达后屏障通透性显著下降,伴有claudin-5、occludin和ZO-1的表达下调以及在细胞膜上呈不连续分布。结论体外血肿瘤屏障模型内皮细胞中低表达的Tie1 AS能够负性调控Tie1的表达,进而通过调节紧密连接相关蛋白的表达和分布影响屏障的通透性。     

紧密连接对肺通透性影响的研究进展

肺组织受损时,肺泡上皮屏障和肺微血管内皮屏障会随之遭到破坏,从而影响肺的通透性,造成严重的肺水肿.紧密连接是一种上皮与内皮细胞间均存在的蛋白复合物,具有栅栏和屏障功能,对肺通透性的调节至关重要.本文主要就紧密连接(TJs)对肺通透性影响的研究进展进行了综述,以便加深对这一问题的理解,从而为临床治疗提供新的思路.     

缓激肽对脑胶质瘤大鼠紧密连接影响的形态学观察

目的研究缓激肽(BK)对脑胶质瘤大鼠血肿瘤屏障紧密连接的影响。方法采用伊文氏兰(EB)法检测缓激肽作用后血肿瘤屏障(BTB)通透性的变化;应用透射电镜(TEM)观察BK作用后内皮细胞间紧密连接的变化,同时应用硝酸镧[La(NO3)3]和辣根过氧化物酶(HRP)作示踪剂,检测缓激肽作用后,小分子和大分子示踪剂通过紧密连接的情况。结果缓激肽可使血肿瘤屏障对伊文氏兰的通透性增加,在15min时达到高峰,以后逐渐下降。透射电镜显示缓激肽作用15min时,肿瘤组织毛细血管内皮细胞间紧密连接的完整性明显破坏,缝隙指数显著增加,同时可见硝酸镧和辣根过氧化物酶在紧密连接处沉积。结论缓激肽能够通过开放紧密连接选择性增加血肿瘤屏障的通透性。     

锰对大鼠睾丸支持细胞骨架蛋白及紧密连接相关蛋白表达的抑制作用

目的研究染锰诱导的大鼠睾丸超微结构改变及支持细胞(vimentin,VM)和紧密连接Occludins、Claudin-11mRNA表达,探讨锰对支持细胞骨架蛋白和紧密连接蛋白的破坏机制。方法雄性SD大鼠随机分为空白对照组,低剂量(15 mg/kg MnCl_2)和高剂量(30 mg/kg MnCl_2)组,8只/组。实验组分别染锰4周和6周,空白对照组给予等容生理盐水,给药途径均为腹腔注射,电镜观察睾丸支持细胞及血睾屏障超微结构,免疫组织化学(SABC)法检测支持细胞VM表达,实时定量PCR反应检测血睾屏障紧密连接Occludins和Claudin-11 mRNA表达。结果 1与空白对照组比较,各染锰组支持细胞数量及VM阳性细胞率、Occludins mRNA和Claudin-11 mRNA表达均显著降低。2染锰剂量相同,6周与4周组比较,以及染锰时间相同,高剂量组与低剂量组比较,支持细胞数量及VM阳性细胞率、Occludins mRNA和Claudin-11 mRNA表达均显著降低。3各组大鼠睾丸支持细胞数量与VM阳性细胞率及Occludins mRNA和Claudin-11 mRNA表达均成正相关。结论锰可抑制大鼠睾丸支持细胞骨架蛋白及紧密连接相关蛋白表达,破坏血睾屏障,导致生精微环境改变,产生生殖毒性效应。     

Somatostatin regulates tight junction proteins expression in colitis mice

Tight junction plays a critical role in intestinal defence. The alteration and perturbation of tight junction proteins could induce intestine barrier damage, and lead to the malabsorption of electrolytes and water. Previous studies had showed that colonic infection and inflammation could lead to the alteration of tight junction function, and somatostatin could protect intestinal epithelia. Thus, this study could explore that whether somatostatin could regulate tight junction in colitis mice. Colitis mice with diarrhea were induced by Citrobacter rodentium (CR) and Dextran sulfate sodium (DSS). In CR infected model, cladudin-1 and claudin-3 expression significantly decreased compared with the control mice (P < 0.05); after octreotide treatment, claudin-1 and claudin-3 expression significantly increased compared with untreated CR infected mice (P < 0.05). In DSS colitis model, occludin and claudin-3 expression significantly decreased compared with the control mice (P < 0.05); and octreotide treatment could only significantly upregulate claudin-3 expression compared with untreated DSS colitis mice (P < 0.05). To testify our results in vivo, we repeated the models in caco-2 cells by exposed with enteropathogenic Escherichia coli (E. Coli) and Tumor necrosis factor α (TNF-α). The results in vitro were consistent with in vivo study. The results suggested that somatostatin play a role in intestinal barrier protection by modulating tight junction proteins expression.     

The tight junction component Claudin E is required for zebrafish epiboly

Zebrafish epiboly results in the thinning and spreading of the blastoderm to cover the yolk cell and close the blastopore. The extra‐embryonic yolk syncytial layer (YSL) tows the blastoderm vegetally during epiboly by means of its tight junction attachments to the enveloping layer (EVL). Claudins are the major transmembrane protein components of tight junctions. Here, we focus on the function of Claudin E (Cldne), which is expressed specifically in the EVL. Morpholino knock‐down of cldne produced a highly penetrant epiboly delay. Our analysis suggested that the EVL margin, which is attached to the YSL, was under reduced tension in morphant embryos. We propose that local variation in the strength of EVL–YSL attachment in morphant embryos resulted in slow and uneven advancement of the EVL and blastoderm. Our work is the first to demonstrate that Claudins are important for zebrafish epiboly. Developmental Dynamics 239:715–722, 2010. © 2009 Wiley‐Liss, Inc.     

Claudins: unlocking the code to tight junction function during embryogenesis and in disease

Gupta IR, Ryan AK. Claudins: unlocking the code to tight junction function during embryogenesis and in disease. Claudins are the structural and molecular building blocks of tight junctions. Individual cells express more than one claudin family member, which suggests that a combinatorial claudin code that imparts flexibility and dynamic regulation of tight junction function could exist. Although we have learned much from manipulating claudin expression and function in cell lines, loss‐of‐function and gain‐of‐function experiments in animal model systems are essential for understanding how claudin‐based boundaries function in the context of a living embryo and/or tissue. These in vivo manipulations have pointed to roles for claudins in maintaining the epithelial integrity of cell layers, establishing micro‐environments and contributing to the overall shape of an embryo or tissue. In addition, loss‐of‐function mutations in combination with the characterization of mutations in human disease have demonstrated the importance of claudins in regulating paracellular transport of solutes and water during normal physiological states. In this review, we will discuss specific examples of in vivo studies that illustrate the function of claudin family members during development and in disease.     

Immunohistological study of tight junction protein expression in mal de Meleda

Mal de Meleda (MdM, MIM: 248300) is a rare autosomal recessive skin disorder characterized by diffuse palmoplantar keratoderma and transgressive keratosis with onset in early infancy. The gene responsible for MdM, ARS, encodes for Secreted Lys6/Plaur domain-containing protein 1 which is essential for epidermal homeostasis. Tight junctions have been proposed to have two mutually exclusive functions: a fence function which prevents the mixing of membrane proteins between the apical and basolateral membranes; and a gate function which controls the paracellular passage of ions and solutes between cells. In this study we report immunohistochemical investigations of tight junction proteins claudin-1 and occludin in MdM Tunisian families. Nine skin biopsies from patients with MdM were analyzed. The control group was formed by skin biopsies belonging to healthy individuals. Immunohistochemical study was performed on fixed sections from biopsies of four microns with the following polyclonal antibodies: anti-claudin-1 and anti-occludin. In control skin, claudin-1 exhibited membrane expression throughout the epidermis with increasing and upward intensity, whereas occludin was detected in the cell membrane of keratinocytes of the stratum granulosum. In MdM skin, claudin-1 was expressed throughout the thickness of the spinous layers with membrane staining, and occludin had cytoplasmic staining in the granular layer. The immunohistochemical expression of TJ proteins in MdM patients harbors premature expression of occludin and decreased expression of claudin-1, highlighting further evidence for disorders in epidermal homeostasis.     

Disruption of tight junctions during polymicrobial sepsis in vivo

The disruption of intestinal epithelial tight junctions may result in barrier function dysfunction during polymicrobial sepsis. The pathophysiology of sepsis involves breakdown of barrier integrity, which correlates with adverse outcome during sepsis. However, the mechanisms underlying loss of barrier function in sepsis remain unknown. In the present study in mice, tight junction (TJ) structure was analysed by transmission electron microscopy; intestinal permeability was assessed using molecular tracer measurement; and the distribution of TJ proteins was investigated by immunofluorescence microscopy. The membrane microdomains of TJs were isolated using discontinuous sucrose density gradients and the expression of TJ proteins in these was determined by western blot. Immunofluorescence microscopy revealed that claudins 1, 3, 4, 5, and 8 were present predominantly in the microvillous surface of epithelial cells and along the lateral membranes of the cells; in sepsis, however, labelling of these proteins was present diffusely within cells and was no longer focused at the lateral cell boundaries. Moreover, the expression of claudin‐2 was markedly up‐regulated in sepsis. Using western blot analysis, we found that occludin and claudins were displaced from raft fractions to non‐raft fractions in membrane microdomains of TJs in sepsis. In addition, the disruption of TJ structure was accompanied by increased intestinal permeability. Our results demonstrate for the first time that redistribution of TJ proteins in TJ membrane microdomains and redistribution of claudins in epithelial cells of the colon lead to alteration of TJ architecture and TJ barrier dysfunction during the development of polymicrobial sepsis. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

间隙连接研究进展

间隙连接通道是细胞间直接进行物质交流的惟一的膜通道结构。它在细胞间信号传递,物质交流等方面都起着重要的作用。构成间隙连接通道的蛋白亚基为间隙连接蛋白(connexin)。本文就目前已检测到的间隙连接蛋白的种类,间隙连接蛋白的基因突变与疾病的关系,检测间隙连接通讯的常用方法,间隙连接通道的调控机制及间隙连接对肿瘤细胞的影响作一综述。     

Polarized distribution of carcinoembryonic antigen is associated with a tight junction molecule in human colorectal adenocarcinoma

This study we presents a novel anti-occludin monoclonal antibody that can be used for formalin-fixed, paraffin-embedded tissue sections. The relationships between aberrant localization of carcinoembryonic antigen (CEA) and abnormalities of tight junctions were studied in human colorectal cancers by this antibody. Abnormalities in the cell surface expression of CEA have been shown to be characteristic of human colorectal cancer cells. Cancer cells that participated in the formation of glandular structures expressed occludin at the apical cell border and CEA was expressed more apically than occludin. Where cancer cells showed solid nests without glandular structures, occludin was completely lost and CEA was demonstrated in a diffuse pattern throughout the cells. These findings suggest that the polarized apical expression of CEA in neoplastic glandular structures depends on the expression of occludin and the fence function of tight junctions. During tumour progression, loss of occludin may lead to the loss of membrane polarity and the non-polarized expression of CEA. The antibody described provides a powerful tool for the study of tight junctions in surgically resected human tissue.     

Emerging roles of transmembrane-type tight junction proteins in cancers

Tight junctions (TJs) are the most apical components of the cell–cell adhesion machinery in epithelial and endothelial cells and they play essential roles in homeostasis. Recent studies have revealed that aberrant expression of tight junction proteins (TJPs) is frequently observed in various type of cancers. Here we review cancer-associated aberrant expression of TJPs with focus on transmembrane-type TJPs including claudins, junctional adhesion molecule-A (JAM-A), and occludin. Some transmembrane-type TJPs are upregulated at the early neoplastic stage and their expression persists during dedifferentiation. Aberrant expression of TJPs contributes to proliferation, invasion, and dysregulated signaling of cancer cells. In addition to an increase in their expression level, their localization is altered from a TJ-restricted pattern to distribution throughout the whole cell membrane, making them suitable as therapeutic targets. Extracellular domains of transmembrane-type TJPs can be approached by target drugs not only from the lumen side (apical side) but also from the extracellular matrix side (basal side), including blood vessels. Aberrantly expressed TJPs are potential useful diagnostic markers as well as therapeutic targets for cancers.     

Alterations in tight junction molecules of uterine epithelial cells during early pregnancy in the rat

Distribution patterns of the tight junction associated proteins ZO-1, claudin-1 and occludin were investigated in rat uterine epithelial cells during early pregnancy. Light microscopy and immunohistochemical labelling were used to detect these proteins on days 1, 3, 6 and 7 of pregnancy. Intense staining of claudin-1 at the apical region of the lateral plasma membrane accompanied diffuse staining throughout the cytoplasm. ZO-1 was also localised in the apical region, but ZO-1 was not present in the lower two thirds of the lateral plasma membrane or in the cytoplasm. Occludin was present only on days 6 and 7 of pregnancy. Labelling was also localised in the apical region of the lateral plasma membrane where tight junctions are known to be present. Our results show that ZO-1, claudin-1 and occludin are present in the apical region of uterine epithelial cells, and appear to play a role in the very dynamic tight-junctional network of uterine epithelial cells during early pregnancy. In particular, occludin appears only during uterine receptivity for implantation.