E-钙黏蛋白、β-连接素与不明原因不孕症发病机制的探讨

目的探讨E-钙黏蛋白(E-cadherin)和β-连接素(-βcatenin)在人子宫内膜组织中的表达与不明原因不孕症的关系。方法采用免疫组化S-P法,检测35例正常及41例不明原因不孕症子宫内膜E-cadherin和-βcatenin的表达水平。结果正常组各期子宫内膜腺上皮均见二者的表达,且在分泌中期达到高峰;-βcatenin在间质细胞有同样的变化,而E-cadherin增生期未见表达。不孕组增生期腺上皮二者仅有弱表达,分泌期表达增加(P<0.05),分泌中期与早、晚期比较,差异无显著性(P>0.05);间质细胞E-cadherin的表达无统计学意义。结论E-cadherin和-βcatenin在人子宫内膜腺上皮和间质细胞规律性表达,其表达异常,可能是导致不孕的重要原因。     

E-cadherin/catenins与肿瘤发生、侵袭及转移

粘附分子E-cadherin通过catenins与细胞骨架相连介导细胞同质粘附作用。E-cadherin/catenins复合物抑制肿瘤侵袭、转移的作用引起广泛重视。β-catenin除与E-cadherin结合介导细胞同质粘附反应，还参与Wnt信号传导通路与肿瘤发生有关。本文主要就E-cadherin/catenins在肿瘤发生、侵袭及转移中的作用研究进展做一综述。     

Sorting of cadherin–catenin-associated proteins into individual clusters

The cytoplasmic tails of classical cadherins form a multiprotein cadherin–catenin complex (CCC) that constitutes the major structural unit of adherens junctions (AJs). The CCC in AJs forms junctional clusters, “E clusters,” driven by cis and trans interactions in the cadherin ectodomain and stabilized by α-catenin–actin interactions. Additional proteins are known to bind to the cytoplasmic region of the CCC. Here, we analyze how these CCC-associated proteins (CAPs) integrate into cadherin clusters and how they affect the clustering process. Using a cross-linking approach coupled with mass spectrometry, we found that the majority of CAPs, including the force-sensing protein vinculin, interact with CCCs outside of AJs. Accordingly, structural modeling shows that there is not enough space for CAPs the size of vinculin to integrate into E clusters. Using two CAPs, scribble and erbin, as examples, we provide evidence that these proteins form separate clusters, which we term “C clusters.” As proof of principle, we show, by using cadherin ectodomain monoclonal antibodies (mAbs), that mAb-bound E-cadherin forms separate clusters that undergo trans interactions. Taken together, our data suggest that, in addition to its role in cell–cell adhesion, CAP-driven CCC clustering serves to organize cytoplasmic proteins into distinct domains that may synchronize signaling networks of neighboring cells within tissues.

The core structural unit of adherens junctions (AJs), the cadherin–catenin complex (CCC), consists of four proteins—a classical cadherin (E-cadherin in epithelia), β-catenin, α-catenin, and p120-catenin (1–4). In the process of cell–cell adhesion, the CCC forms clusters driven by both extracellular and intracellular binding events (5–8). The clustering of cadherin molecules is essential to reinforce weak individual trans adhesive bonds (9–12). In addition, the continuous and fast reassembly of CCC clusters within AJs renders them both highly adhesive and yet flexible (7, 13). While the importance of CCC clustering in cell–cell adhesion was demonstrated more than two decades ago (14), many of the molecular events associated with clustering are still poorly understood. One critical question, which is the focus of this work, is the role of proteins that associate with the CCC, CCC-associated proteins (CAPs), and, in particular, how these proteins change the properties of CCC clusters.While several mechanisms for CCC clustering have been proposed (12), the best-characterized involves the formation of cis interaction between E-cadherin ectodomains. Cooperative cis and trans interactions arrange cadherin trans dimers into a paracrystalline lattice with a lateral intercadherin (center-to-center) spacing of ∼7 nm (15). The stability of these extracellular clusters is further enhanced by the binding of α-catenin to actin filaments (16–18). Accumulating data suggest that AJs consist of numerous such paracrystalline nanoclusters interspersed with less dense CCC regions (7, 15, 19–21). However, under certain conditions, cadherin clusters can be formed that do not seem to require the formation of ordered ectodomain lattices. For example, clusters are observed in cells expressing a cis interaction–incompetent cadherin mutant although they are less stable than wild-type paracrystalline clusters (20, 22). The underlying clustering mechanism in these cases is unclear.Here we identified CAPs using a cross-linking agent that only detects proteins up to about 1.5 nm from a target. We provide evidence that most of these CAPs interact with the CCCs outside of cadherin clusters. Our results indicate that CCC clusters that integrate CAPs (C clusters) have fundamentally different structures from the “canonical structures” constrained by cadherin cis interactions. We term the latter “E clusters” to indicate that they are driven by extracellular interactions. We found that two CAPs, scribble and erbin, produced a set of CCC clusters that are spatially distinct from E clusters and from one another. It then appears that C clusters have distinct properties that depend on those of the CAPs themselves. To establish proof of principle, we show that anti-cadherin monoclonal antibodies (mAbs), which, similar to CAPs, are too large to be compatible with an E-cluster lattice, generate distinct adhesive clusters. Taken together, our data show that CAPs are both able to spatially separate C from E clusters and form CAP-dependent C clusters that are separate from one another. In addition to their role in cell–cell adhesion, our results thus suggest that CCC clustering serves as a mechanism for organizing cellular proteins into distinct domains within cell–cell contacts.     

Diverse roles of E-cadherin in the morphogenesis of the submandibular gland: insights into the formation of acinar and ductal structures

The formation of acinar and ductal structures during epithelial tissue branching morphogenesis is not well understood. We report that in the mouse submandibular gland (SMG), acinar and ductal cell fates are determined early in embryonic morphogenesis with E-cadherin playing pivotal roles in development. We identified two morphologically distinct cell populations at the single bud stage, destined for different functions. The outer layer of columnar cells with organized E-cadherin junctions expressed the neonatal acinar marker B1 by E13.5, demonstrating their acinar fate. The interior cells initially lacked distinct E-cadherin junctions, but with morphogenesis formed cytokeratin 7 (K7) -positive ductal structures with organized E-cadherin junctions and F-actin filaments. Inhibition of E-cadherin function with either siRNA or function blocking antibody caused extensive apoptosis of ductal cells and aberrantly dilated lumens, providing the first evidence that E-cadherin regulates ductal lumen formation during branching morphogenesis of the salivary gland.     

Integrins,cadherins, and catenins: molecular cross-talk in cancer cells

In the past decade, there have been major advances in the understanding of some of the mechanisms underlying tumour differentiation, invasion, and metastasis, in which cell–cell and cell–matrix adhesion molecules play a critical role. Cadherin/catenin complex and the integrins are the prime mediators of cell adhesion in normal and transformed cells, cadherin/catenin being largely responsible for intercellular adhesion and integrins for cell–extracellular matrix interactions. Intercellular and cell–matrix adhesion mediated by cadherin/catenin and integrins is likely to play a role in the control of both structural morphology and functional differentiation; hence, any loss of this control mechanism may well facilitate the neoplastic process. Indeed, in cancer cells, there is a co-ordinated down-regulation of both integrins and cadherins which correlates with tumour dedifferentiation. However, the expression and cellular localization of catenins do not always correlate with cadherin expression, since the catenins are rather promiscuous molecules which interact not only with E-cadherin, but also with growth regulatory and signalling molecules such as epidermal growth factor receptor and the adenomatous polyposis coli gene product. © 1998 John Wiley & Sons, Ltd.     

离子对高效液相色谱法测定胞磷胆碱钠葡萄糖注射液的有关物质

目的:探讨E-cadherin/catenins复合物在胃癌中的表达及其与组织病理学特征和胃癌侵袭、转移等指标间的关系.方法:用EnVision法检测67例胃癌术后标本及10例正常胃黏膜标本中E-cadherin/catenins复合物的联合表达情况,并比较胃癌不同病理学特征及是否伴侵袭转移的标本间各指标表达率的差异.结果:10例正常胃黏膜标本中E-cadherin和α-,β-,γ-catenin以及P120分子均正常表达;而胃癌组织中上述5种分子的阳性表达率分别为56.6%、61.2%、55.2%、55.2%和59.7%.这5种分子的表达阳性率在胃癌的不同Borrmann分型(Ⅰ～Ⅳ型),不同分化程度(高、中、低),不同组织学类型(肠型和弥漫型,除β-catenin外),以及有无淋巴结转移之间均存在显著性差异(P＜0.05),但在胃癌是否有腹膜播散以及是否有远处转移之间均无显著性差异.E cadherin与α-,β-,γ-catenin和P120的表达趋势一致.结论:E-cadherin,α-,β-,γ-catenin和P120的表达减少与胃癌的发生和发展有关.     

乳腺癌组织VEGF和p120表达及其临床意义的探讨

目的:观察血管内皮生长因子(VEGF)及连环蛋白p120在乳腺腺病和乳腺癌中的表达,探讨两者与乳腺癌临床病理特征的临床意义.方法:采用免疫组化SP法检测62例乳腺癌及26例乳腺腺病组织中VEGF和p120的表达情况.结果:乳腺癌组织中VEGF和p120的异常表达率分别为77.4％(48/62)和80.6％(50/62),与良性组相比差异有统计学意义,P=0.000.两者均与肿瘤病理分级和TNM分期相关,但均与肿瘤大小无相关.VEGF在有腋窝淋巴结转移 的癌组织中阳性率明显高于无淋巴结转移者,P=0.017,p120表达情况和淋巴结转移无关,P=0.072.两者在乳腺癌组织中的表达具有正相关性,P=0.011.结论:VEGF及p120在乳腺癌组织中异常表达,并与乳腺癌浸润转移关系密切,是乳腺癌发生发展的生物学指标之一,联合检测对评估预后及临床治疗有指导意义.     

上皮细胞钙粘素/连环素复合体与肿瘤侵袭转移的关系及其调控机制

上皮细胞钙粘素（E—cadherin）属于钙离子依赖粘附素家族成员，它广泛存在于各类上皮细胞中，以钙离子依赖的形式介导上皮细胞间的同质粘附，主要参与形成紧密连接、粘附连接等；同时它还参与细胞信号转导，对维持上皮细胞的极性和组织结构非常重要。E—cadherin对肿瘤生长和转移具有抑制作用，许多肿瘤的发生及侵袭过程中都发现E—cadhenn的表达下调／缺失或者功能障碍。由于E—cadherin在上皮细胞中和连环素（catenins）结合才能发挥作用，本文将从E—cadherin／catenins复合体的结构出发，着重探讨E—cadhenn／catenins复合体在肿瘤发生及转移过程中的失活机制。