PO.MCB03.03 · 分子与细胞生物学
Septin-9缺失引发癌细胞中桥粒蛋白连接定位缺陷
Defects in junctional localization of desmosomal proteins in cancer cells triggered by loss of Septin-9
作者与单位 Authors & Affiliations
摘要 Abstract
中文摘要
桥粒是一种特化的黏附连接，连接相邻细胞，并在承受显著机械应力的组织（如皮肤和心脏）中提供结构完整性。桥粒黏附复合体的破坏见于一系列不同的皮肤综合征以及肿瘤进展过程中。桥粒蛋白的失调与癌症运动性、侵袭和转移潜能增强相关。已有报道提出破坏桥粒动态的多种机制，但调控桥粒蛋白表达和定位的具体信号通路仍不明确。此前研究表明Septin家族蛋白在黏附连接和紧密连接的维持及功能中发挥重要作用。Septin被称为细胞骨架的第四组分，是一类GTP结合蛋白，可形成与细胞膜相关的寡聚丝状结构，并作为多种不同细胞功能的支架蛋白。特别是，Septin-2被发现邻近含VE-cadherin的细胞间连接，Septin-2缺失会破坏内皮细胞中黏附连接的结构和屏障完整性。Septin-9也被证明可控制极化MDCK细胞中黏附连接的结构、顶-基极性和管腔形成。在本研究中，我们试图通过在鳞状细胞癌9（SCC9）细胞和T47D乳腺癌细胞中开展Septin-9敲低实验，探讨Septin在桥粒细胞间黏附形成中的重要性。我们的实验表明，与表达对照siRNA的细胞相比，表达Septin-9特异性siRNA（siSept9）的两种癌细胞类型中桥粒细胞间连接均显著破坏。特别是，桥粒钙黏蛋白Desmoglein-2（Dsg2）和桥粒斑蛋白Plakophilin-2的边界定位在siSept9细胞中被显著扰乱（通过免疫荧光测定），而其他桥粒蛋白（如Plakoglobin）的定位则不受影响。Dsg2和PKP2边界染色的丧失并未伴随总蛋白表达的变化，提示这些改变主要是蛋白定位的效应。因此，本研究揭示了Sept9在维持癌细胞桥粒结构中的重要作用，为可能在癌症进展过程中扰乱连接结构的机制提供了见解。
查看英文原文 English abstract
Desmosomes are specialized adhesive junctions that link adjacent cells and provide structural integrity in tissues exposed to significant mechanical stress, such as the skin and heart. Disruption of the desmosome adhesion complex is observed in a range of different cutaneous syndromes and during tumor progression. Dysregulation of desmosomal proteins has been associated with enhanced cancer motility, invasion and metastatic potential. Diverse mechanisms for the disruption of desmosome dynamics have been reported, but the specific signaling pathways regulating the expression and localization of desmosome proteins remain elusive. Prior studies have shown that Septin family proteins play an important role in the maintenance and function of adherens junctions and tight junctions. Referred to as the fourth component of the cytoskeleton, Septins are GTP-binding proteins that form oligomeric filamentous structures that associate with cellular membranes and act as scaffolding proteins for a variety of different cellular functions. In particular, Septin-2 has been found adjacent to VE-cadherin containing cell-cell junctions, and loss of Septin-2 disrupts adherens junction structure and barrier integrity in endothelial cells. Septin-9 has also been shown to control adherens junction structure, apico-basal polarity and lumen formation in polarized MDCK cells. In our study, we sought to investigate the importance of Septins in the formation of desmosomal cell-cell adhesions by performing knockdown experiments for Septin-9 in squamous cell carcinoma 9 (SCC9) cells and T47D breast cancer cells. Our experiments show a significant disruption of desmosomal cell-cell junctions in both cancer cell types expressing siRNA specific for Septin-9 (siSept9), in comparison to control siRNA-expressing cells. In particular, border localization of the desmosomal cadherin Desmoglein-2 (Dsg2) and the desmosomal plaque protein Plakophilin-2 were dramatically perturbed in siSept9 cells (determined via immunofluorescence), while the localization of other desmosomal proteins (such as Plakoglobin) remained unaffected. Loss of Dsg2 and PKP2 border staining was not accompanied by changes in total protein expression, suggesting that these changes are predominantly an effect of protein localization. This study has therefore uncovered an important role for Sept9 in maintenance of desmosomal structure in cancer cells, providing insight into mechanisms which may perturb junction structure during cancer progression.
利益披露 Disclosure
C. G. Lyerly, None..
Z. N. Pierce, None..
A. D. Dubash, None.