Department of Biological Sciences, University of Denver, Denver, CO, USA.
Nat Commun. 2022 Sep 8;13(1):5276. doi: 10.1038/s41467-022-32853-5.
In early blood vessel development, trafficking programs, such as those using Rab GTPases, are tasked with delivering vesicular cargo with high spatiotemporal accuracy. However, the function of many Rab trafficking proteins remain ill-defined in endothelial tissue; therefore, their relevance to blood vessel development is unknown. Rab35 has been shown to play an enigmatic role in cellular behaviors which differs greatly between tissue-type and organism. Importantly, Rab35 has never been characterized for its potential contribution in sprouting angiogenesis; thus, our goal was to map Rab35's primary function in angiogenesis. Our results demonstrate that Rab35 is critical for sprout formation; in its absence, apicobasal polarity is entirely lost in vitro and in vivo. To determine mechanism, we systematically explored established Rab35 effectors and show that none are operative in endothelial cells. However, we find that Rab35 partners with DENNd1c, an evolutionarily divergent guanine exchange factor, to localize to actin. Here, Rab35 regulates actin polymerization through limiting Rac1 and RhoA activity, which is required to set up proper apicobasal polarity during sprout formation. Our findings establish that Rab35 is a potent brake of actin remodeling during blood vessel development.
在早期血管发育过程中，运输程序（如使用 Rab GTPases 的程序）的任务是利用高时空准确性来输送囊泡货物。然而，许多 Rab 运输蛋白在血管内皮组织中的功能仍然不明确；因此，它们与血管发育的相关性尚不清楚。Rab35 在细胞行为中发挥着神秘的作用，其在组织类型和生物体之间存在很大差异。重要的是，Rab35 从未因其在发芽血管生成中的潜在贡献而被描述过；因此，我们的目标是确定 Rab35 在血管生成中的主要功能。我们的研究结果表明，Rab35 对芽的形成至关重要；在其不存在的情况下，体外和体内的顶底极性完全丧失。为了确定机制，我们系统地探索了已建立的 Rab35 效应物，发现没有一个在血管内皮细胞中起作用。然而，我们发现 Rab35 与 DENNd1c 结合，DENNd1c 是一种进化上不同的鸟嘌呤交换因子，将 Rab35 定位到肌动蛋白上。在这里，Rab35 通过限制 Rac1 和 RhoA 的活性来调节肌动蛋白聚合，这是在芽的形成过程中建立适当的顶底极性所必需的。我们的研究结果表明，Rab35 是血管发育过程中肌动蛋白重塑的有效制动器。
