Simiczyjew Aleksandra, Mazur Antonina Joanna, Ampe Christophe, Malicka-Błaszkiewicz Maria, van Troys Marleen, Nowak Dorota
Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, 50-383 Wroclaw, Poland.
Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, 50-383 Wroclaw, Poland.
Exp Cell Res. 2015 Dec 10;339(2):206-19. doi: 10.1016/j.yexcr.2015.11.003. Epub 2015 Nov 5.
Invadopodia are actin-rich protrusions formed by mesenchymally migrating cancer cells. They are mainly composed of actin, actin-associated proteins, integrins and proteins of signaling machineries. These protrusions display focalized proteolytic activity towards the extracellular matrix. It is well known that polymerized (F-)actin is present in these structures, but the nature of the actin isoform has not been studied before. We here show that both cytoplasmic actin isoforms, β- and γ-actin, are present in the invadopodia of MDA-MB-231 breast cancer cells cultured on a 2D-surface, where they colocalize with the invadopodial marker cortactin. Invadopodial structures formed by the cells in a 3D-collagen matrix also contain β- and γ-actin. We demonstrate this using isoform-specific antibodies and expression of fluorescently-tagged actin isoforms. Additionally, using simultaneous expression of differentially tagged β- and γ-actin in cells, we show that the actin isoforms are present together in a single invadopodium. Cells with an increased level of β- or γ-actin, display a similar increase in the number and size of invadopodia in comparison to control cells. Moreover, increasing the level of either actin isoforms also increases invasion velocity.
侵袭伪足是间充质迁移癌细胞形成的富含肌动蛋白的突起。它们主要由肌动蛋白、肌动蛋白相关蛋白、整合素和信号传导机制的蛋白组成。这些突起对细胞外基质表现出局部蛋白水解活性。众所周知，聚合的（F-）肌动蛋白存在于这些结构中，但肌动蛋白异构体的性质此前尚未研究过。我们在此表明，在二维表面培养的MDA-MB-231乳腺癌细胞的侵袭伪足中同时存在细胞质肌动蛋白异构体β-肌动蛋白和γ-肌动蛋白，它们与侵袭伪足标记物皮层肌动蛋白共定位。细胞在三维胶原基质中形成的侵袭伪足结构也含有β-肌动蛋白和γ-肌动蛋白。我们使用异构体特异性抗体和荧光标记的肌动蛋白异构体表达来证明这一点。此外，通过在细胞中同时表达差异标记的β-肌动蛋白和γ-肌动蛋白，我们表明肌动蛋白异构体共同存在于单个侵袭伪足中。与对照细胞相比，β-肌动蛋白或γ-肌动蛋白水平升高的细胞，其侵袭伪足的数量和大小也有类似增加。此外，增加任何一种肌动蛋白异构体的水平也会提高侵袭速度。
