Queen Mary University of London, Barts and The London School of Medicine and Dentistry, Centre for Clinical and Diagnostic Oral Sciences, Institute of Dentistry, London, UK.
Exp Cell Res. 2012 Nov 1;318(18):2269-83. doi: 10.1016/j.yexcr.2012.07.002. Epub 2012 Jul 13.
Desmoglein 3 (Dsg3), a member of the desmoglein sub-family, serves as an adhesion molecule in desmosomes. Our previous study showed that overexpression of human Dsg3 in several epithelial lines induces formation of membrane protrusions, a phenotype suggestive of Rho GTPase activation. Here we examined the interaction between Dsg3 and actin in detail and showed that endogenous Dsg3 colocalises and interacts with actin, particularly the junctional actin in a Rac1-dependent manner. Ablation of Rac1 activity by dominant negative Rac1 mutant (N17Rac1) or the Rac1 specific inhibitor (NSC23766) directly disrupts the interaction between Dsg3 and actin. Assembly of the junctional actin at the cell borders is accompanied with enhanced levels of Dsg3, while inhibition of Dsg3 by RNAi results in profound changes in the organisation of actin cytoskeleton. In accordance, overexpression of Dsg3 results in a remarkable increase of Rac1 and Cdc42 activities and to a lesser extent, RhoA. The enhancements in Rho GTPases are accompanied by the pronounced actin-based membrane structures such as lamellipodia and filopodia, enhanced rate of actin turnover and cell polarisation. Together, our results reveal an important novel function for Dsg3 in promoting actin dynamics through regulating Rac1 and Cdc42 activation in epithelial cells.
桥粒糖蛋白 3（Dsg3）是桥粒蛋白亚家族的成员，作为桥粒中的黏附分子。我们之前的研究表明，在几种上皮细胞系中过表达人 Dsg3 会诱导膜突起的形成，这是 Rho GTPase 激活的表型。在这里，我们详细研究了 Dsg3 与肌动蛋白之间的相互作用，并表明内源性 Dsg3 与肌动蛋白共定位，并与肌动蛋白相互作用，特别是与 Rac1 依赖性的连接肌动蛋白相互作用。通过显性负性 Rac1 突变体（N17Rac1）或 Rac1 特异性抑制剂（NSC23766）阻断 Rac1 活性可直接破坏 Dsg3 与肌动蛋白之间的相互作用。细胞边界处连接肌动蛋白的组装伴随着 Dsg3 水平的增强，而通过 RNAi 抑制 Dsg3 会导致肌动蛋白细胞骨架的组织发生深刻变化。相应地，Dsg3 的过表达导致 Rac1 和 Cdc42 活性的显著增加，以及 RhoA 的较小程度增加。Rho GTPases 的增强伴随着明显的基于肌动蛋白的膜结构，如片状伪足和丝状伪足、肌动蛋白周转率的增加和细胞极化。总之，我们的结果揭示了 Dsg3 在促进上皮细胞中肌动蛋白动力学方面的一个新的重要功能，通过调节 Rac1 和 Cdc42 的激活。
