Expression of claudins in murine tooth development.

Claudins belong to a family of transmembrane proteins that were identified as components of tight junction strands. We carried out comparative in situ hybridization analysis of 11 claudin genes (claudin1 - claudin11) during murine odontogenesis from the formation of the epithelial thickening to the cytodifferentiation stage. We identify dynamic spatiotemporal expression of 9 of the 11 claudins. At the early bell stage, two claudins (claudin1 and 4) are specifically expressed in stratum intemedium, whereas only one claudin is expressed in each of the preameloblasts (claudin2) and preodontoblasts (claudin10). At the bud stage, when the first epithelial differentiation pathways are being established, localized expression of six claudins (claudin1, 3, 4, 6, 7, and 10) identify spatial specific interactions, suggesting a hitherto unobserved complexity of epithelial organization, within the early tooth primordium.     

Claudins: control of barrier function and regulation in response to oxidant stress

Claudins are a family of nearly two dozen transmembrane proteins that are a key part of the tight junction barrier that regulates solute movement across polarized epithelia. Claudin family members interact with each other, as well as with other transmembrane tight junction proteins (such as occludin) and cytosolic scaffolding proteins (such as zonula occludens-1 (ZO-1)). Although the interplay between all of these different classes of proteins is critical for tight junction formation and function, claudin family proteins are directly responsible for forming the equivalent of paracellular ion selective channels (or pores) with specific permeability and thus are essential for barrier function. In this review, we summarize current progress in identifying structural elements of claudins that regulate their transport, assembly, and function. The effects of oxidant stress on claudins are also examined, with particular emphasis on lung epithelial barrier function and oxidant stress induced by chronic alcohol abuse.     

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Claudin与肾脏

Claudin属于紧密连接蛋白家族,哺乳动物细胞的claudin有24个蛋白亚型,具有四个跨膜区,分别为细胞内的-NH2末端和-COOH末端,以及细胞外的初级大环和次级小环。Claudin广泛分布于肾脏的多种组织结构,如肾小管、血管、肾小体等。不同亚型在不同的肾单位节段表达,同一肾单位节段表达不同亚型。此外,claudin-16和-19基因突变与高尿钙和低血镁性肾钙质沉着病(FHHNC)的发生有密切联系,而多囊肾的发生可能与claudin-7基因突变有关。     

紧密连接蛋白claudins与肿瘤的研究进展

Claudins是新近发现的构成细胞紧密连接的一类完整的跨膜蛋白,维持紧密连接特有的栅栏功能和屏障功能。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。     

Claudins 1, 2, 3, 4, 5 and 7 in solar keratosis and squamocellular carcinoma of the skin

Claudins are tight junction proteins regulating the paracellular permeability of cell layers. We investigated the expression of claudins 1, 2, 3, 4, 5 and 7 in a sample set consisting of a total of 93 cases representing normal skin, actinic keratoses and squamous cell carcinomas of the skin. There were several changes found in claudin expression. Claudin 1 appeared to be progressively decreased in solar keratosis and skin squamous cell carcinomas compared to normal skin while expression of claudin 2 was increased. With claudins 3 and 5 occasional immunoreactivity was found in squamous cell carcinomas. Claudins 4 and 7 were variably expressed in skin neoplasia compared to normal skin. According to the results expression of claudins 1 and 2 change in parallel with the severity of the epidermal preneoplastic and neoplastic lesions thus probably influencing the disturbed epithelial polarity characteristic of these lesions. Claudin 1 under- and claudin 2 overexpression also lead to a leakier epithelial barrier function of the skin with a resulting damage to skin epithelial resistance. Other claudins investigated in this study did not show progressive changes even though occasional overexpression of them was found in skin squamous cell carcinoma.     

Diagnostic utility of expression of claudins in non-small cell lung cancer: Different expression profiles in squamous cell carcinomas and adenocarcinomas

The claudins, members of a large family of adherent junction proteins, regulate the integrity and function of tight junctions. At present, at least 23 different claudins are known to exist in humans, and claudin gene expression is frequently altered in several human cancers. However, few studies have examined the expression of claudins in lung cancer. This study examined the expression of claudin-1, claudin-3, claudin-4, and claudin-5 proteins using immunohistochemical analysis in 14 normal lung tissue samples and 171 NSCLC samples. All of the claudin proteins examined were expressed in normal bronchial epithelial cells. In the normal peripheral parenchyma, only claudin-5 strongly stained most of the pneumocytes. Claudin-1 expression was stronger in squamous cell carcinomas than in adenocarcinomas, whereas claudin-4 and claudin-5 expression was stronger in adenocarcinomas. Clinically, expression of claudin proteins was not found to be associated with patient survival. These data suggest that the disruption of tight junction protein might be involved in the development of these tumors. Immunohistochemical evaluation of the different expression patterns of claudins in NSCLC suggests that claudin-4, in addition to 1 and 5, might be a useful differential diagnostic marker in Korean people.     

claudin蛋白在卵巢癌中的研究进展

claudin蛋白是构成细胞间紧密连接的骨架蛋白,是紧密连接最重要的组成部分。许多恶性肿瘤中都存在claudin蛋白的异常表达,与肿瘤细胞粘附、增殖、侵袭等密切相关。近年来,研究者们将claudin蛋白作为肿瘤治疗研究中的新靶点,探讨了靶向claudin治疗的可行性及潜在应用价值。同时,由于claudin蛋白在肿瘤组织中表达的差异性,其可能成为肿瘤诊断及预后的分子标志。claudin蛋白已成为肿瘤研究的新热点。本文就claudin蛋白在卵巢癌中的研究进展作一综述。     

Heterogeneity in expression and subcellular localization of tight junction proteins, claudin-10 and -15, examined by RT-PCR and immunofluorescence microscopy

Tight junctions regulate paracellular permeability, create the luminal fluid microenvironment of blood vessels and the digestive tract, and also form the protective barrier in the stratified epithelium including the epidermis. Claudins are the integral membrane proteins at tight junctions and form a multigene family composed of at least 24 members, but knowledge of the subcellular localization of each claudin is still fragmentary. We performed RT-PCR for fifteen claudin species to examine the mRNA expression in various mouse tissues, and focused on investigating the subcellular localization of claudin-10 and -15 by immunofluorescence microscopy in various rat tissues. Neither claudin-10 nor -15 was detected in vascular endothelial cells in most tissues, and these claudins were restricted to the vasa recta in the kidney medulla. Both claudins were also detected at apical tight junctions in the epithelium of the jejunum with no intensity gradients along the crypt-to-villus axis. However, both claudins were expressed only in the basal half of the crypt epithelium in the colon, showing obvious gradients along crypt-to-surface axis. Moreover, claudin-10 showed the ectopic subcellular localization where tight junction strands do not exist. Claudin-10 was detected along the entire lateral membranes of acinar cells in addition to the apical tight junctions in exocrine glands, and in the cytoplasm of basal cells in the stratified epithelium including the dorsal skin and cutaneous stomach. These heterogeneous distributions of claudin-10 and -15 in tissues may be related to the differences in paracellular permeability among tissues.     

Expression of claudins 1, 2, 3, 4, 5 and 7 in various types of tumours

AIMS: Claudins are adhesion molecules present in tight junctions. To evaluate their usefulness as differentiation markers claudins 1, 2, 3, 4, 5 and 7 were studied in 116 epithelial and 92 non-epithelial tumours. METHODS AND RESULTS: Immunoreactivity for all claudins could be seen in different carcinomas. There were, however, tumour type-specific differences in their expression. Lower expression of claudin 2 was seen in breast and prostatic carcinomas, while hepatocellular and renal carcinomas expressed lower levels of claudins 4 and 5. In contrast to epithelial tumours, lymphomas did not express claudins and most soft tissue tumours and naevocytic lesions were negative or showed weaker, mainly cytoplasmic positivity for some claudins. Of non-epithelial tumours, claudin 5 was found only in angiosarcomas and benign vascular tumours, which also showed reactivity for claudins 2, 3 and 7, but was not expressed in any other soft tissue lesions or lymphomas. CONCLUSIONS: The results show that claudins 1, 2, 3, 4, 5 and 7 can be used as markers for epithelial differentiation and to distinguish epithelial neoplasms from lymphomas and selectively also from soft tissue and naevocytic lesions. Since these claudins show type-specific differential expression in epithelial tumours, they may also be of some value in distinguishing different epithelial tumours from each other. Additionally, claudin 5 shows promise as a marker for endothelial lesions compared with other soft tissue lesions.     

Claudins and tricellulin in fibrolamellar hepatocellular carcinoma

Fibrolamellar hepatocellular carcinoma is a subtype of hepatocellular carcinoma occurring in non-cirrhotic liver at a younger age. The tumor expresses both hepatocellular and cholangiocellular markers. Previously, our group described overexpression of tight junction protein claudin 4 in cholangiocellular carcinoma in contrast to hepatocellular carcinoma. In the present study, tight junction protein expressions were studied to possibly clarify bipotential lineage of fibrolamellar hepatocellular carcinoma. Eleven fibrolamellar hepatocellular carcinomas were compared with seven “conventional” hepatocellular carcinomas, seven cholangiocellular carcinomas, and five normal liver samples. By immunohistochemistry, all fibrolamellar hepatocellular carcinomas were positive for HepPar1 and cytokeratins 7, 8, and 18, but negative for cytokeratin 19. Glypican-3 gave weak staining in two cases. Expression of claudin 1 was lower, while that of claudin 2 was higher in fibrolamellar hepatocellular carcinomas than in other tumors. Claudins 3, 4, and 7 were not detectable in fibrolamellar hepatocellular carcinomas as in the majority of “conventional” hepatocellular carcinomas, contrary to high expression observed in cholangiocellular carcinomas. Focal or diffuse claudin 5 expression was detected in nine of 11 fibrolamellar hepatocellular carcinomas contrary to other tumors. Tricellulin was significantly downregulated in all tumors compared with normal liver. Our findings showed claudins to exhibit specific expression patterns in fibrolamellar hepatocellular carcinomas not observed in other primary liver tumors, with unique claudin 5 expression and pattern features similar to common hepatocellular carcinoma, but different from cholangiocellular carcinoma. This is the first report describing the loss of tricellulin expression in human hepatic tumors.     

Claudins 2, 3, 4, and 5 in Paget's disease and breast carcinoma

Claudins are involved in the formation of tight junctions in epithelial and endothelial cells. The present study evaluated the expression of claudin 2, 3, 4, and 5 in 20 cases of Paget's disease (13 mammary and 7 extramammary cases), and compared the results with those of other neoplastic skin lesions, including actinic keratoses, basal cell carcinomas, and malignant melanomas. To compare claudin expression in Paget's disease and breast neoplasia, it was also studied in a large set of breast carcinomas. Membrane-bound claudin 3 and 4 expression was seen in all cases of Paget's disease, whereas claudin 5 was seen in 50% of cases and claudin 2 was seen in 32% of cases. In contrast, claudins 3, 4, and 5 were not seen in the other skin lesions, and claudin 2 was seen in most of them, suggesting an inverse expression of these claudins between Paget's disease and epidermal and nevocytic lesions. Claudin expression in breast carcinomas was claudin 2 in 52%, claudin 3 in 93%, claudin 4 in 92%, and claudin 5 in 47%. Claudins 2 and 5 were found more often in ductal carcinomas than in lobular carcinomas. Expression of claudins were frequently associated with each other. They were not associated with estrogen or progesterone receptor status or with tumor grade. No significant differences were found between claudin expression in Paget's disease and breast carcinomas. The results demonstrate that claudins could be useful in diagnosing Paget's disease and in differentiating these lesions from other epidermal lesions, such as actinic keratoses, basal cell carcinomas, and nevocytic lesions. The lack of difference in claudin expression between Paget's disease and breast tumors suggests that changes in the phenotype of claudins 2, 3, 4, and 5 are not necessary for epidermal invasion.     

Enhancing epithelial engraftment of rat mesenchymal stem cells restores epithelial barrier integrity

The cellular origin, in vivo function and fate of donor bone marrow‐derived cells residing in the recipient intestinal epithelial cells, pericryptal myofibroblasts or endothelial cells remain obscure. Although ‘immunoprivileged’ mesenchymal stem cells (MSCs) are prime candidates for cell‐ and gene‐based therapy, their precise role in colitis remains largely undetermined. Using a dextran sulphate sodium (DSS) colitis with busulphan (BU)‐induced hypoplastic marrow model, we examined the therapeutic effects of MSC transplantation, focusing on the role of MSCs as both cell providers and immunomodulators. Donor‐derived MSCs were detected by eGFP immunofluorescence and fluorescence in situ hybridization for Y‐chromosome (Y‐FISH) analysis. Western blot analysis of apical‐most tight junction proteins was performed with antibodies against claudin‐2, ‐7, ‐8, ‐12, ‐13, ‐15 and ZO‐1. Cytokine and cell cycle profiles were analysed by semi‐quantitative RT‐PCR and flow cytometry. Susceptibility to DSS colitis was significantly increased by co‐existing BU‐induced bone marrow hypoplasia and this increase was significantly reduced by enhancing epithelial engraftment of MSCs, an effect depending on restoring epithelial barrier integrity rather than inhibiting host immune responses. We provide evidence that implicates MSCs in maintaining epithelial barrier function by reassembling apical‐most tight junction proteins, claudins. The therapeutic efficacy of extrinsic MSCs depends on enhancing epithelial engraftment in damaged crypts by busulphan conditioning. Such a role for the MSC‐derived intestinal cells in colitis therapy merits further examination and may offer a promising new treatment for inflammatory bowel disease (IBD). Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Loss of claudins-1 and -7 and expression of claudins-3 and -4 correlate with prognostic variables in prostatic adenocarcinomas

Claudins, members of a large family of adherent junction proteins, regulate the integrity and function of tight junctions and influence tumorigenesis. Recent studies have shown that altered levels of the different claudins may be related to invasion and progression of carcinoma cells in several primary neoplasms. However, there is no reported study documenting the pattern of claudin expression in prostatic adenocarcinomas (PACs). Formalin-fixed paraffin-embedded sections from 141 PACs were immunostained by manual and automated methods on the Xmatrx (BioGenex, San Ramon, CA) using antihuman claudin-1, -3, -4, -5, and -7 antibodies (Zymed, San Francisco, CA). Membranous immunoreactivity for each protein was semiquantitatively scored in both the tumor and adjacent benign epithelium in each case. Results were correlated with clinicopathologic variables. Variable membranous positivity was noted in the adjacent benign glands for all 5 proteins in all cases. PACs showed variable membranous positivity ranging from decreased, similar to, and increased in relation to the adjacent benign epithelium for all claudins. Decreased expression of claudin-1 correlated with high tumor grade (P = .001) and biochemical disease recurrence (P = .01), whereas decreased claudin-7 correlated with high tumor grade (P < .0001). In contrast, expression of claudin-3 correlated with advanced stage tumors (P = .03) and recurrence (P = .02), and expression of claudin-4 correlated with advanced stage (P = .02). On multivariate analysis, advanced stage (P = .026) and decreased claudin-1 protein expression (P = .005) independently predicted disease recurrence. Immunohistochemical expression and prognostic significance of claudins are variable in PACs, with decreased expression of claudin-1 emerging as an independent prognostic variable warranting further study.     

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.     

Vertebrate Claudin/PMP22/EMP22/MP20 family protein TMEM47 regulates epithelial cell junction maturation and morphogenesis

Background: TMEM47 is the vertebrate orthologue of C. elegans VAB‐9, a tetraspan adherens junction protein in the PMP22/EMP/Claudin family of proteins. VAB‐9 regulates cell morphology and adhesion in C. elegans and TMEM47 is expressed during kidney development and regulates the activity of Fyn. The conserved functions of VAB‐9 and TMEM47 are not well understood. Results: expression of TMEM47 in C. elegans functionally rescues vab‐9 mutations. Unlike Claudins, expression of TMEM47 in L fibroblasts does not generate tight junction strands; instead, membrane localization requires E‐cadherin expression. Temporally, TMEM47 localizes at cell junctions first with E‐cadherin before ZO‐1 colocalization and in polarized epithelia, TMEM47 colocalizes with adherens junction proteins. By immunoprecipitation, TMEM47 associates with classical adherens junction proteins, but also with tight junction proteins Par6B and aPKCλ. Over‐expression of TMEM47 in MDCK cells decreases apical surface area, increases activated myosin light chain at cell–cell contacts, disrupts cell polarity and morphology, delays cell junction reassembly following calcium switch, and selectively interferes with tight junction assembly. Reduced TMEM47 expression results in opposite phenotypes. Conclusions: TMEM47 regulates the localization of a subset of tight junction proteins, associated actomyosin structures, cell morphology, and participates in developmental transitions from adherens to tight junctions. Developmental Dynamics 245:653–666, 2016. © 2016 Wiley Periodicals, Inc.     

Expression of claudins 1, 4, 5, and 7 and occludin, and relationship with prognosis in squamous cell carcinoma of the tongue

Claudins and occludin are tight junctional proteins known to play a role in normal tissues and epithelial tumors. We analyzed the distribution patterns of claudins 1, 4, 5, and 7 and occludin in the superficial and invasive front of squamous cell carcinoma of the tongue of 97 patients and their relationship to cause-specific (squamous cell carcinoma of the tongue) patient survival (median follow-up period of 33.5 months; range, 1-234 months). Claudins 1 and 7 were strongly expressed, claudin 4 had moderate expression, whereas claudin 5 was least expressed. Occludin staining was mostly negative or very weak. Western blot analysis of tongue carcinoma (HSC-3) cells showed that all these proteins are also expressed in vitro. In cause-specific survival analysis, strong and low immunoreactivity of claudin 7 tended to be associated with decreased survival compared with medium immunoreactivity. We suggest that analyzing the immunohistologic staining levels of claudin 7 could be used for the prognostic purposes in patients with tongue squamous cell carcinoma.