A Patatin-Like Protein Protects Toxoplasma gondii from Degradation in a Nitric Oxide-Dependent Manner
A Patatin-Like Protein Protects Toxoplasma gondii from Degradation in a Nitric Oxide-Dependent Manner
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DOI：
10.1128/iai.05543-11
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发表时间：
2012-01-01
影响因子：
3.1
通讯作者：
Knoll, Laura J.
中科院分区：
文献类型：
--
作者：
Tobin, Crystal M.;Knoll, Laura J.
弓形虫是一种专性细胞内寄生虫，利用免疫细胞在宿主体内传播。通过降低一氧化氮 (NO) 等分子的抗菌作用，弓形虫可以在活化的宿主巨噬细胞中持续存在，甚至缓慢复制。一种名为 TgPL1 的弓形虫 patatin 样蛋白先前已被证明对于激活的巨噬细胞的生存很重要。在这里，我们展示了 TgPL1 基因缺失 (Delta TgPL1) 的刚地弓形虫突变体在激活的巨噬细胞中被降解。使用诱导型 NO 合酶 (iNOS) 抑制剂或 iNOS 缺陷型巨噬细胞去除 NO，可以消除这种降解表型。向巨噬细胞外源添加 NO 会导致寄生虫生长减少，但不会导致 Delta TgPL1 寄生虫降解。这些结果表明，NO 对于活化巨噬细胞中 Delta TgPL1 寄生虫的降解是必要的，但还不够。虽然一些 patatin 样蛋白具有磷脂酶 A(2) (PLA(2)) 活性，但从大肠杆菌中纯化的重组 TgPL1 不具有磷脂酶活性。这一结果并不令人意外，因为 TgPL1 在预测的催化丝氨酸残基处包含 G 到 S 的变化。 TgPL1 的表位标记版本与寄生液泡空间中的致密颗粒蛋白部分共定位。这些结果可能表明 TgPL1 移动到寄生液泡，通过未确定的机制保护寄生虫免受一氧化氮的侵害。
Toxoplasma gondii is an obligate intracellular parasite that uses immune cells to disseminate throughout its host. T. gondii can persist and even slowly replicate in activated host macrophages by reducing the antimicrobial effects of molecules such as nitric oxide (NO). A T. gondii patatin-like protein called TgPL1 was previously shown to be important for survival in activated macrophages. Here we show that a T. gondii mutant with a deletion of the TgPL1 gene (Delta TgPL1) is degraded in activated macrophages. This degradation phenotype is abolished by the removal of NO by the use of an inducible NO synthase (iNOS) inhibitor or iNOS-deficient macrophages. The exogenous addition of NO to macrophages results in reduced parasite growth but not the degradation of Delta TgPL1 parasites. These results suggest that NO is necessary but not sufficient for the degradation of Delta TgPL1 parasites in activated macrophages. While some patatin-like proteins have phospholipase A(2) (PLA(2)) activity, recombinant TgPL1 purified from Escherichia coli does not have phospholipase activity. This result was not surprising, as TgPL1 contains a G-to-S change at the predicted catalytic serine residue. An epitope-tagged version of TgPL1 partially colocalized with a dense granule protein in the parasitophorous vacuole space. These results may suggest that TgPL1 moves to the parasitophorous vacuole to protect parasites from nitric oxide by an undetermined mechanism.