ABSTRACT

There are three Rap proteins in Dictyostelium. RapA is a key regulator of cell adhesion and cytoskeletal rearrangement. Recently, RapC has been reported to be involved in cytokinesis, cell migration, and multicellular development. Here, we compare the functions of RapA and RapC using cells expressing or lacking Rap proteins, and confirm that RapA and RapC have opposite functions in cell spreading, adhesion, and migration. On the other hand, RapC has a unique function in cytokinesis and multicellular development. Activated RapA appears to stimulate spreading and adhesion of the cells to the substrate, possibly resulting in a decrease in the migration speed of the cells during chemotaxis without affecting the directionality, whereas RapC suppresses cell spreading and adhesion, thereby increasing the migration speed. Cells lacking RapC were defective in cytokinesis and multicellular development and showed multinucleation and formation of multiple tips from a mound during development. At the C-terminus, RapC has an additional stretch of amino acids, which is not found in RapA. The mechanism through which RapA and RapC perform their opposite functions in diverse cellular processes should be characterized further to understand the Rap signaling pathways in detail.

摘要

盘基柄菌中有 3 种 Rap 蛋白. RapA 是细胞粘附和细胞骨架重排的关键调节剂。最近，据报道 RapC 参与胞质分裂、细胞迁移和多细胞发育。在这里，我们使用表达或缺乏 Rap 蛋白的细胞比较了 RapA 和 RapC 的功能，并确认 RapA 和 RapC 在细胞扩散、粘附和迁移方面具有相反的功能。另一方面，RapC 在胞质分裂和多细胞发育中具有独特的功能。活化的 RapA 似乎会刺激细胞向基质的扩散和粘附，可能导致趋化过程中细胞迁移速度降低而不影响方向性，而 RapC 抑制细胞扩散和粘附，从而提高迁移速度。缺乏 RapC 的细胞在胞质分裂和多细胞发育方面存在缺陷，并在发育过程中显示出多核化和多个尖端的形成。在 C 端，RapC 有一段额外的氨基酸，这在 RapA 中没有。应该进一步表征 RapA 和 RapC 在不同细胞过程中执行其相反功能的机制，以详细了解 Rap 信号通路。