School of Life Sciences, Immune Synapse Research Center and Cell Dynamics Research Center, Gwangju Institute of Science and Technology, Gwangju, Korea.
PLoS One. 2013 Aug 15;8(8):e71626. doi: 10.1371/journal.pone.0071626. eCollection 2013.
Protein functions are often revealed by their localization to specialized cellular sites. Recent reports demonstrated that swiprosin-1 is found together with actin and actin-binding proteins in the cytoskeleton fraction of human mast cells and NK-like cells. However, direct evidence of whether swiprosin-1 regulates actin dynamics is currently lacking. We found that swiprosin-1 localizes to microvilli-like membrane protrusions and lamellipodia and exhibits actin-binding activity. Overexpression of swiprosin-1 enhanced lamellipodia formation and cell spreading. In contrast, swiprosin-1 knockdown showed reduced cell spreading and migration. Swiprosin-1 induced actin bundling in the presence of Ca(2+), and deletion of the EF-hand motifs partially reduced bundling activity. Swiprosin-1 dimerized in the presence of Ca(2+) via its coiled-coil domain, and a lysine (Lys)-rich region in the coiled-coil domain was essential for regulation of actin bundling. Consistent with these observations, mutations of the EF-hand motifs and coiled-coil region significantly reduced cell spreading and lamellipodia formation. We provide new evidence of how swiprosin-1 influences cytoskeleton reorganization and cell spreading.
蛋白质的功能通常通过其在特定细胞位置的定位来揭示。最近的报告表明，swiprosin-1 与人肥大细胞和 NK 样细胞的细胞骨架部分中的肌动蛋白和肌动蛋白结合蛋白一起存在。然而，目前缺乏 swiprosin-1 是否调节肌动蛋白动力学的直接证据。我们发现 swiprosin-1 定位于微绒毛样膜突和片状伪足，并表现出肌动蛋白结合活性。swiprosin-1 的过表达增强了片状伪足的形成和细胞扩展。相比之下，swiprosin-1 的敲低显示出细胞扩展和迁移减少。swiprosin-1 在 Ca(2+)存在下诱导肌动蛋白成束，EF 手模体的缺失部分降低了成束活性。swiprosin-1 在 Ca(2+)存在下通过其卷曲螺旋结构域二聚化，卷曲螺旋结构域中的富含赖氨酸（Lys）区域对于调节肌动蛋白成束是必需的。与这些观察结果一致，EF 手模体和卷曲螺旋结构域的突变显著减少了细胞扩展和片状伪足的形成。我们提供了 swiprosin-1 如何影响细胞骨架重组和细胞扩展的新证据。
