Autophagy and ocular toxoplasmosis.

 描述(申请人提供)：专性细胞内原生动物弓形虫是世界上最常见的感染性视网膜脉络膜炎的原因。眼弓形体病是导致视力丧失的重要原因，特别是在先天性心脏病儿童中。 感染以及老年人和免疫抑制者。不幸的是，目前的治疗方案并不理想，因为没有证据表明它们可以改善视觉功能或防止疾病复发。更好地了解促进眼弓形体病的机制有可能导致针对这种疾病的新的和改进的治疗方法。弓形虫存在于宿主细胞内的一个寄生空泡中，该空泡不能与溶酶体融合，这样寄生虫才能存活和复制。自噬是溶酶体降解的一个结构性过程。最近的研究发现了一种新的病原体生存模式，通过这种模式，弓形虫激活宿主细胞中的EGFR信号，从而避免自噬降解。这一发现可能与眼弓形体病有关，因为自噬蛋白缺乏的小鼠对眼弓形体病的易感性增加。这项应用的目的是了解弓形虫如何激活视网膜细胞中的EGFR信号，并确定EGFR信号在眼弓形虫病发生发展中的作用。这项研究的中心假设是，弓形虫通过激活一种特定的宿主细胞蛋白激酶而导致EGFR信号延长，抑制EGFR信号可以增强对眼弓形虫病的保护作用。这一假说将通过阻断特定信号通路的遗传方法、免疫化学研究和转基因小鼠进行验证。在第一个特定的目标中，我们将确定蛋白激酶的激活是否会导致弓形虫感染的视网膜细胞中EGFR的长时间激活。在第二个目标中，我们将确定特定细胞类型的EGFR阻断是否增强了对眼弓形虫病的抵抗力。在第三个目标中，我们将确定抑制EGFR如何预防眼弓形体病。这项拟议的工作可能导致新的策略，以根除弓形虫和治疗基于调制宿主细胞信号的眼弓形虫病。

 DESCRIPTION (provided by applicant): The obligate intracellular protozoan Toxoplasma gondii is the most common cause of infectious retinochoroiditis in the world. Ocular toxoplasmosis is an important cause of loss of visual acuity especially in children with congenital infection as well as the elderly and the immunosuppressed. Unfortunately, current treatment options are not ideal since there is no evidence that they improve visual function or prevent relapses of the disease. A better understanding of the mechanisms that promote ocular toxoplasmosis has the potential to lead to new and improved therapeutic approaches against this disease. T. gondii resides within host cells in a parasitophorous vacuole that must not fuse with lysosomes so that the parasite can survive and replicate. Autophagy is a constitutive process of lysosomal degradation. Recent studies identified a new paradigm of pathogen survival whereby T. gondii activates EGFR signaling in host cells and as a result avoids autophagic degradation. This finding is likely relevant to ocular toxoplasmosis because mice deficient in autophagy proteins have enhanced susceptibility to ocular toxoplasmosis. The objectives of this application are to understand how T. gondii activates EGFR signaling in retinal cells and to determine the role of EGFR signaling in the development of ocular toxoplasmosis. The central hypothesis for the proposed research is that T. gondii causes prolonged EGFR signaling by activating a specific host cell protein kinase and inhibition of EGFR signaling enhances protection against ocular toxoplasmosis. This hypothesis will be tested using genetic approaches that block specific signaling pathways, immunochemical studies and transgenic mice. In the first specific aim we will determine if activation of a protein kinase causes prolonge EGFR activation in T. gondii-infected retinal cells. In the second aim, we will determine if cell type-specific blockade of EGFR enhances resistance to ocular toxoplasmosis. In the third aim, we will determine how inhibition of EGFR protects against ocular toxoplasmosis. The proposed work may lead to new strategies to eradicate T. gondii and treat ocular toxoplasmosis based on modulation host cell signaling.