对神经系统的偏嗜性是弓形虫感染的显著特征，然而原因尚不清楚。我们前期发现中枢神经组织特异性表达蛋白RTN1-C是弓形虫毒力因子ROP18激酶的直接作用的宿主蛋白；ROP18的激酶活性是神经细胞凋亡的重要因素；鉴于RTN1-C自身可通过线粒体和内质网应激(ERS)相关通路引起细胞凋亡，我们推测弓形虫ROP18激酶磷酸化RTN1-C进而激活线粒体和ERS相关的凋亡通路引起神经损伤，可能是高致病性弓形虫感染致神经损伤的重要原因。本课题拟采用ROP18野生型和激酶失活型转基因虫株感染神经细胞，分析ROP18/RTN1-C靶向的凋亡通路关键蛋白；探究两者之间相互作用机制并鉴定作用功能域和具体磷酸化位点；通过siRNA、点突变和信号通路阻断技术寻找和验证ROP18/RTN1-C对凋亡通路中关键环节的影响。该研究不仅能解释弓形虫对中枢神经系统偏嗜性的原因，也为阻断疾病进程和针对性治疗提供研究基础。

Toxoplasma gondii is a neurotropic parasite, and the central nervous system (CNS) is the most easily damaged of all invaded organs. The ROP18 kinase has been identified as a key virulence molecule conferring a high mortality phenotype characteristic of type I T.gondii strains. Our preliminary data indicated that ROP18 significantly induced the apoptosis of neural cells, and the activity of ROP18 kinase is required for the apoptosis of neural cells. To identify the host targets of ROP18, we employed a yeast two-hybrid assay to screen for ROP18-interacting proteins. To our surprise, we found that RTN1-C, an endoplasmic reticulum (ER) protein preferentially expressing in the CNS, directly interacted with ROP18. Previous study showed that RTN1-C acts as a molecular switch to induce ER stress and mitochondria mediated apoptosis in human neural cells. Therefore, our central hypothesis is that the interaction between ROP18 and the host RTN1-C may be responsible for neuropathogenic action of Toxoplasmosis. Strikingly, our preliminary results also found that ROP18 kinase directly phosphorylated RTN1-C at Ser/Thr sites. According to these results, the present study will analyze the apoptosis of neural cells infected with expressing ROR18 wild type, kinase death and ROR18 knockout transgenic strains. We will uncover the molecular mechanism of ER stress and mitochondria-mediated apoptosis pathway induced by ROP18/RTN1-C interaction. We propose to define the interaction domains of ROP18/RTN1-C and determine the special phosphorylated sites. We will define the related key molecules targeted by the interaction of ROP18/RTN1-C using siRNA, mutation and inhibitors of signal pathway. The systematic studies proposed in this application will be relevant in interpreting reports of neuropathogenesis during T. gondii infection and provide experiment basis of targeted therapy for blocking the progress of Toxoplasmic encephalitis.