Proteomic analysis of Rac1 signaling regulation by guanine nucleotide exchange factors

The small GTPase Rac1 is implicated in various cellular processes that are essential for normal cell function. Deregulation of Rac1 signaling has also been linked to a number of diseases, including cancer. The diversity of Rac1 functioning in cells is mainly attributed to its ability to bind to a multitude of downstream effectors following activation by Guanine nucleotide Exchange Factors (GEFs). Despite the identification of a large number of Rac1 binding partners, factors influencing downstream specificity are poorly defined, thus hindering the detailed understanding of both Rac1's normal and pathological functions. In a recent study, we demonstrated a role for 2 Rac-specific GEFs, Tiam1 and P-Rex1, in mediating Rac1 anti- versus pro-migratory effects, respectively. Importantly, via conducting a quantitative proteomic screen, we identified distinct changes in the Rac1 interactome following activation by either GEF, indicating that these opposing effects are mediated through GEF modulation of the Rac1 interactome. Here, we present the full list of identified Rac1 interactors together with functional annotation of the differentially regulated Rac1 binding partners. In light of this data, we also provide additional insights into known and novel signaling cascades that might account for the GEF-mediated Rac1-driven cellular effects.

小GTP酶Rac1（small GTPase Rac1）参与诸多维持细胞正常功能不可或缺的细胞进程。Rac1信号通路的异常调控还与包括癌症在内的多种疾病密切相关。细胞内Rac1功能的多样性，主要源于其在被鸟苷酸交换因子（Guanine nucleotide Exchange Factors，GEFs）激活后，可结合大量下游效应蛋白的特性。尽管已鉴定出大量Rac1结合蛋白，但调控其下游信号特异性的分子机制仍未明确，这极大阻碍了学界对Rac1生理与病理功能的深入解析。在近期的一项研究中，我们证实了两种Rac特异性GEFs——Tiam1与P-Rex1——分别介导Rac1的抗迁移与促迁移效应。尤为关键的是，通过定量蛋白质组筛选，我们发现两种GEFs分别激活Rac1后，其相互作用组（Rac1 interactome）会发生显著差异变化，这表明上述相反的生物学效应，是通过GEFs对Rac1相互作用组的调控实现的。本数据集提供了本次研究中鉴定出的全部Rac1相互作用蛋白列表，以及差异调控的Rac1结合伴侣的功能注释信息。基于上述数据集，我们还补充了针对已知及全新信号级联反应的相关见解，这些信号通路或可解释GEFs介导的、由Rac1驱动的细胞效应。