Oxygen Sensing by the AIDS Opportunist Pathogen, Toxoplasma gondii

 描述（由申请人提供）：弓形虫是艾滋病患者和其他免疫缺陷个体以及胎儿的重要机会性感染。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。寄生虫有一个复杂的生命周期，在此期间，它遇到不同的O2环境。这些包括具有低O2张力的组织，例如肠，其是与寄生虫接触的第一个组织，以及外周组织，例如远离脉管系统的脑区域。适应O2可用性的变化是所有呼吸细胞和生物体的关键细胞过程。弓形虫如何感知O2尚不清楚，但我们发表的和额外的初步数据表明，这对寄生虫生长至关重要。细胞质脯氨酰4-羟化酶（PHDs）是后生动物和其他原生生物中的关键细胞O2传感器，其通过催化一个原子从O2转移到蛋白质连接的脯氨酸残基，第二个转移到β-酮戊二酸，产生琥珀酸、CO2和羟基化脯氨酸残基来发挥作用。我们已经确定了两个博士在弓形虫和我们的数据表明，这些TgPhyB是一个必不可少的酶，可以羟基化SKP 1，这是一个亚基的E3 SCF泛素连接酶复合物。该提案的目标是定义TgPhyB的必要性，确定其底物特异性，并鉴定TgPhyB抑制剂。这些目标的成功完成将揭示一种新的信号转导机制在弓形虫和建立如何以及为什么弓形虫O2传感是重要的增长。最重要的是，这项工作可能揭示一个新的药物靶点，以治疗艾滋病患者的这种关键机会性感染。

 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.