Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy.
mBio. 2019 Aug 6;10(4):e01324-19. doi: 10.1128/mBio.01324-19.
is a ubiquitous pathogen that can cause encephalitis, congenital defects, and ocular disease. has also been implicated as a risk factor for mental illness in humans. The parasite persists in the brain as slow-growing bradyzoites contained within intracellular cysts. No treatments exist to eliminate this form of parasite. Although proteolytic degradation within the parasite lysosome-like vacuolar compartment (VAC) is critical for bradyzoite viability, whether other aspects of the VAC are important for parasite persistence remains unknown. An ortholog of chloroquine resistance transporter (CRT), TgCRT, has previously been identified in To interrogate the function of TgCRT in chronic-stage bradyzoites and its role in persistence, we knocked out TgCRT in a cystogenic strain and assessed VAC size, VAC digestion of host-derived proteins and parasite autophagosomes, and the viability of and bradyzoites. We found that whereas parasites deficient in TgCRT exhibit normal digestion within the VAC, they display a markedly distended VAC and their viability is compromised both and Interestingly, impairing VAC proteolysis in TgCRT-deficient bradyzoites restored VAC size, consistent with a role for TgCRT as a transporter of products of digestion from the VAC. In conjunction with earlier studies, our current findings suggest a functional link between TgCRT and VAC proteolysis. This study provides further evidence of a crucial role for the VAC in bradyzoite persistence and a new potential VAC target to abate chronic infection. Individuals chronically infected with the intracellular parasite are at risk of experiencing reactivated disease that can result in progressive loss of vision. No effective treatments exist for chronic toxoplasmosis due in part to a poor understanding of the biology underlying chronic infection and a lack of well-validated potential targets. We show here that a transporter is functionally linked to protein digestion within the parasite lysosome-like organelle and that this transporter is necessary to sustain chronic infection in culture and in experimentally infected mice. Ablating the transporter results in severe bloating of the lysosome-like organelle. Together with earlier work, this study suggests the parasite's lysosome-like organelle is vital for parasite survival, thus rendering it a potential target for diminishing infection and reducing the risk of reactivated disease.
刚地弓形虫是一种普遍存在的病原体，可导致脑炎、先天缺陷和眼部疾病。刚地弓形虫也被认为是人类精神疾病的一个风险因素。寄生虫作为缓慢生长的缓殖子存在于细胞内囊泡中，在大脑中持续存在。目前尚无消除这种寄生虫形式的治疗方法。尽管寄生虫溶酶体样空泡腔（VAC）内的蛋白水解降解对于缓殖子的存活至关重要，但其他方面的 VAC 是否对寄生虫的持续存在很重要仍不清楚。在 中，已先前鉴定出氯喹耐药转运蛋白（CRT）的同源物 TgCRT。为了研究 TgCRT 在慢性期缓殖子中的功能及其在持续感染中的作用，我们敲除了致囊虫株中的 TgCRT，并评估了 VAC 大小、VAC 对宿主来源蛋白和寄生虫自噬体的消化以及 和 缓殖子的活力。我们发现，尽管 TgCRT 缺陷型寄生虫在 VAC 内表现出正常的消化，但它们显示出明显肿胀的 VAC，其活力受到损害，无论是在 和 有趣的是，在 TgCRT 缺陷型缓殖子中抑制 VAC 蛋白水解恢复了 VAC 大小，这与 TgCRT 作为 VAC 中消化产物的转运蛋白的作用一致。结合早期研究，我们目前的发现表明 TgCRT 与 VAC 蛋白水解之间存在功能联系。这项研究为 VAC 在缓殖子持续感染中的关键作用提供了进一步证据，并为减轻慢性 感染提供了一个新的潜在 VAC 靶点。慢性感染细胞内寄生虫 的个体有经历再激活疾病的风险，这可能导致视力逐渐丧失。由于对慢性感染的生物学基础缺乏深入了解以及缺乏经过充分验证的潜在靶点，因此目前尚无有效的治疗方法。我们在这里表明，一种 转运蛋白与寄生虫溶酶体样细胞器内的蛋白消化功能相关，并且该转运蛋白对于在培养中和实验感染的小鼠中维持慢性感染是必需的。消除该转运蛋白会导致溶酶体样细胞器严重肿胀。结合早期的工作，这项研究表明寄生虫的溶酶体样细胞器对于寄生虫的存活至关重要，因此它是一个潜在的靶点，可以减少感染并降低再激活疾病的风险。
