F-肌动蛋白的协调激活和抑制支持形态发生的运动。了解调节 F-肌动蛋白的蛋白质非常重要，因为这些蛋白质在癌症等疾病中受到错误调节。我们对线虫胚胎表皮形态发生的研究确定了 GTPase CED-10/Rac1 是 F-肌动蛋白的重要激活剂。然而，我们需要确定在胚胎细胞迁移过程中激活 CED-10/Rac1 的 GEF（即鸟嘌呤核苷酸交换因子）。已知双组分 GEF CED-5/CED-12 可激活 CED-10/Rac1 以促进细胞运动，从而导致胚胎发生过程中吞噬垂死细胞，以及随后幼虫远端尖端细胞的细胞迁移。据信，CED-5/CED-12 通过促进 F-肌动蛋白形成来为尸体吞噬和 DTC 迁移的细胞运动提供动力。因此，我们测试了CED-5/CED-12是否参与胚胎迁移，得到了矛盾的结果。 CED-5/CED-12 绝对支持胚胎迁移，因为它们的丢失导致胚胎因表皮细胞迁移失败而死亡。然而，CED-5/CED-12 抑制迁移表皮中的 F-肌动蛋白，这与 CED-10 GEF 的预期相反。为了解决在尸体吞噬和细胞迁移过程中 CED-12/CED-5 如何对 F-肌动蛋白产生两种相反的影响，我们研究了 CED-12 是否具有 GAP（GTP 酶激活蛋白）功能。 CED-12 中的候选 GAP 区域背向 CED-5 GEF 催化区域。 CED-12 GAP 区域 (R537A) 中候选催化精氨酸的突变改变了表皮细胞迁移功能，但没有改变尸体吞噬功能。我们通过干扰 CED-5 结合 Rac1/CED-10 的能力来干扰 GEF 功能。 CED-5/DOCK 中的丝氨酸-精氨酸突变预计会结合并稳定 Rac1 进行催化，导致腹侧外壳和尸体吞噬的损失。遗传和表达研究强烈支持 GAP 功能可能作用于不同的 GTP 酶。因此，我们建议 CED-5/CED-12 通过使用不同的结构域来支持多种 GTPases 的循环，以促进和抑制 F-肌动蛋白成核。版权所有：© 2024 Venkatachalam 等人。这是一篇根据知识共享署名许可条款分发的开放获取文章，允许在任何媒体上不受限制地使用、分发和复制，前提是注明原始作者和来源。

Coordinated activation and inhibition of F-actin supports the movements of morphogenesis. Understanding the proteins that regulate F-actin is important, since these proteins are mis-regulated in diseases like cancer. Our studies of C. elegans embryonic epidermal morphogenesis identified the GTPase CED-10/Rac1 as an essential activator of F-actin. However, we need to identify the GEF, or Guanine-nucleotide Exchange Factor, that activates CED-10/Rac1 during embryonic cell migrations. The two-component GEF, CED-5/CED-12, is known to activate CED-10/Rac1 to promote cell movements that result in the engulfment of dying cells during embryogenesis, and a later cell migration of the larval Distal Tip Cell. It is believed that CED-5/CED-12 powers cellular movements of corpse engulfment and DTC migration by promoting F-actin formation. Therefore, we tested if CED-5/CED-12 was involved in embryonic migrations, and got a contradictory result. CED-5/CED-12 definitely support embryonic migrations, since their loss led to embryos that died due to failed epidermal cell migrations. However, CED-5/CED-12 inhibited F-actin in the migrating epidermis, the opposite of what was expected for a CED-10 GEF. To address how CED-12/CED-5 could have two opposing effects on F-actin, during corpse engulfment and cell migration, we investigated if CED-12 harbors GAP (GTPase Activating Protein) functions. A candidate GAP region in CED-12 faces away from the CED-5 GEF catalytic region. Mutating a candidate catalytic Arginine in the CED-12 GAP region (R537A) altered the epidermal cell migration function, and not the corpse engulfment function. We interfered with GEF function by interfering with CED-5's ability to bind Rac1/CED-10. Mutating Serine-Arginine in CED-5/DOCK predicted to bind and stabilize Rac1 for catalysis, resulted in loss of both ventral enclosure and corpse engulfment. Genetic and expression studies strongly support that the GAP function likely acts on different GTPases. Thus, we propose CED-5/CED-12 support the cycling of multiple GTPases, by using distinct domains, to both promote and inhibit F-actin nucleation.Copyright: © 2024 Venkatachalam et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.