Program in Cancer Biology, Stanford University, Stanford, CA 94305, USA.
Science. 2011 Mar 11;331(6022):1336-9. doi: 10.1126/science.1199633.
A fundamental characteristic of metazoans is the formation of a simple, polarized epithelium. In higher animals, the structural integrity and functional polarization of simple epithelia require a cell-cell adhesion complex that contains a classical cadherin, the Wnt-signaling protein β-catenin and the actin-binding protein α-catenin. We show that the non-metazoan Dictyostelium discoideum forms a polarized epithelium that is essential for multicellular development. Although D. discoideum lacks a cadherin homolog, we identify an α-catenin ortholog that binds a β-catenin-related protein. Both proteins are essential for formation of the epithelium, polarized protein secretion, and proper multicellular morphogenesis. Thus, the organizational principles of metazoan multicellularity may be more ancient than previously recognized, and the role of the catenins in cell polarity predates the evolution of Wnt signaling and classical cadherins.
后生动物的一个基本特征是形成简单的极化上皮细胞。在高等动物中，简单上皮细胞的结构完整性和功能极化需要一个细胞-细胞粘附复合物，该复合物包含一个经典的钙粘蛋白、Wnt 信号蛋白β-连环蛋白和肌动蛋白结合蛋白α-连环蛋白。我们表明，非后生动物盘基网柄菌形成了一个极化的上皮细胞，这对多细胞发育是必不可少的。尽管盘基网柄菌缺乏钙粘蛋白同源物，但我们鉴定出一个α-连环蛋白同源物，它与β-连环蛋白相关蛋白结合。这两种蛋白质对于上皮细胞的形成、极化蛋白的分泌以及适当的多细胞形态发生都是必不可少的。因此，后生动物多细胞性的组织原则可能比以前认识的更为古老，而且连环蛋白在细胞极性中的作用先于 Wnt 信号和经典钙粘蛋白的进化。
