Identification of F-Box Proteins in Toxoplasma

E3泛素连接酶的Skp1/cullin/F-box(SCF)类在进化上是一种 保守的酶家族，调节包括细胞在内的关键细胞过程 周期、膜运输和信号转导。SCF-E3由四个核心组成 组分-Rbx1、Cullin1、Skp1和一个F-box蛋白。F-box蛋白是 招募底物蛋白的亚基被SCF-E3多泛素化，它们 也可以直接被多泛素化。依赖SCF-E3的多聚泛素作为一种 靶向26S-蛋白酶体并被其降解的信号。每一种真核生物 表达一系列F-box蛋白，其中大多数具有不同的亲和力 对于不同的底物蛋白质。因此，F-box蛋白是至关重要的，因为它们决定了 特定的蛋白质将被SCF-E3泛素化。此外，F-box蛋白可以 功能独立于SCF-E3。因此，识别和表征F-box 蛋白质是了解SCF-E3的功能和细胞重塑的核心 蛋白质组作为细胞承担新的功能。这一点很重要，因为蛋白质会降解 在定义细胞蛋白质组方面与基因转录一样重要。在这里，我们将确定 必需的SCF-E3依赖的F-box蛋白，确定它们为什么是必需的，以及 确定作为其泛素化底物的蛋白质。这些研究将揭示 泛素如何支持一种主要人类寄生虫的生长和毒力。此外, 这些发现将与相关病原体相关，因为SCF- E3和许多F-box蛋白存在于弓形虫和其他顶端复合体寄生虫之间。

The SKP1/Cullin/F-box (SCF) class of E3 Ubiquitin Ligases is an evolutionarily conserved family of enzymes that regulate key cellular processes including the cell cycle, membrane trafficking, and signaling. The SCF-E3 is composed of four core components - Rbx1, Cullin1, SKP1, and a F-box protein. F-box proteins are the subunits that recruit substrate proteins to be poly-ubiquitinated by the SCF-E3, and they can also be directly poly-ubiquitinated. SCF-E3 dependent polyubiquitin serves as a signal for targeting to and degradation by the 26S-proteasome. Every eukaryote expresses a repertoire of F-box proteins, the majority of which have different affinities for different substrate proteins. Thus, F-box proteins are critical since they dictate which specific proteins will be ubiquitinated by the SCF-E3. In addition, F-box proteins can function independently of the SCF-E3. Thus, identifying and characterizing F-box proteins is central to understanding the functions of the SCF-E3 and remodeling of the proteome as cells engage new functions. This is important because protein degradation is as important as gene transcription in defining a cell's proteome. Here, we will identify essential SCF-E3 dependent F-box proteins, determine why they are essential, and identify the proteins that are their ubiquitination substrates. These studies will reveal how ubiquitin supports growth and virulence of a major human parasite. In addition, these findings will be relevant to related pathogens given the conservation of the SCF- E3 and many F-box proteins between Toxoplasma and other apicomplexan parasites.