Oxygen Sensing by the AIDS Opportunist Pathogen, Toxoplasma gondii

 描述(申请人提供)：弓形虫是一种重要的机会性感染艾滋病患者和其他免疫功能受损的个人以及胎儿。这种寄生虫在包括大脑和视网膜在内的各种组织中引起广泛的疾病。这种寄生虫有一个复杂的生命周期，在此期间它会遇到不同的氧气环境。这些组织包括氧气压力低的组织，如肠道，这是第一个接触寄生虫的组织，以及外围组织，如远离血管系统的大脑区域。对所有呼吸细胞和生物体来说，适应氧气供应的变化是一个关键的细胞过程。弓形虫如何感知O2尚不清楚，但我们公布的和更多的初步数据表明，这对寄生虫的生长至关重要。细胞质中的脯氨基4-羟基酶(PhDS)是后生动物和其他原生动物细胞内关键的O2感受器，其功能是通过催化一个原子从O2转移到蛋白质连接的Pro残基和第二个原子转移到-酮戊二酸，产生琥珀酸、二氧化碳和羟基化的Pro残基。我们已经在弓形虫中发现了两个PhD，我们的数据表明其中一个TgPhyB是一种能够羟化Skp1的重要酶，Skp1是E3SCF泛素连接酶复合体的一个亚单位。该提案的目的是定义TgPhyB的重要性，确定其底物特异性，并确定TgPhyB抑制剂。这些目标的成功完成将揭开弓形虫中一种新的信号机制的面纱，并确定弓形虫O2感知对生长的重要性的方式和原因。最重要的是，这项工作可能会揭示一种治疗艾滋病患者这种严重机会性感染的新药物靶点。

 DESCRIPTION (provided by applicant): Toxoplasma gondii is an important opportunistic infection in AIDS patients and other immune- compromised individuals as well as fetuses. The parasite causes a broad spectrum of disorders in a variety of tissues including the brain and retina. The parasite has a complex life cycle during which it encounters diverse O2 environments. These include tissues with low O2 tensions such as the intestine, which is the first tissue that comes in contact with the parasite, and peripheral tissues such as regions of the brain that are distant from the vasculature. Adapting to changes in O2 availability is a critical cellular process for all respiring cells and organisms. How Toxoplasma senses O2 is unknown but our published and additional preliminary data indicate that this is critical for parasite growt. Cytoplasmic prolyl 4-hydroxylases (PHDs) are key cellular O2 sensors in metazoans and other protists that function by catalyzing the transfer of one atom from O2 to a protein-linked proline residue and the second one to -ketoglutarate yielding succinate, CO2 and a hydroxylated proline residue. We have identified two PHDs in Toxoplasma and our data suggests that one of these TgPhyB is an essential enzyme that can hydroxylate SKP1, which is a subunit of the E3SCF ubiquitin ligase complex. The goal of this proposal is to define the essentiality of TgPhyB, determine its substrate specificity, and identify TgPhyB inhibitors. Successful completion of these aims will unveil a novel signaling mechanism in Toxoplasma and establish how and why Toxoplasma O2 sensing is important for growth. Most importantly, this work could potentially reveal a new drug target to treat this critical opportunistic infection of AIDS patients.