Coxiella secreted proteins mediating inter-organelle membrane contact sites

项目总结/摘要 贝氏柯克斯体是一种专性胞内细菌，是Q热的病原体。在宿主细胞内， 该细菌存活于被称为Coxiella Containing cervicole（CCV）的吞噬溶酶体样空泡中。斯体 是唯一敏感的宿主胆固醇水平，其中胆固醇升高，特别是在CCV和 内溶酶体系统，导致细菌死亡。而柯克斯体直接调节宿主胆固醇稳态 通过柯克斯体4 B型分泌系统（T4 BSS）分泌的效应蛋白，T4 BSS效应子 负责操纵宿主细胞胆固醇的蛋白质尚未被鉴定出来。使用生物信息学 方法，我们确定了一个新的家庭柯克斯体T4 BSS效应蛋白，其中包含一个真核FFAT基序。 在真核细胞中，FFAT蛋白与内质网（ER）上的VAP蛋白家族结合，并介导VAP蛋白家族的表达。 细胞器和ER之间的膜接触位点（MCS）。这些细胞器间的多组分复合物在 在调节脂质体内平衡方面。所提出的实验将验证我们的假设，即含有Coxiella FFAT的 T4 BSS效应蛋白介导ER和其他宿主细胞器之间的MCS，以操纵宿主细胞。 胆固醇代谢目的1将确定哪些Coxiella FFAT蛋白家族成员与VAP结合 蛋白质，并确定这些蛋白质定位在宿主细胞中的位置。目标2将测试这些蛋白质是否 对于Coxiella感染是必需的，以及它们是否在调节宿主胆固醇中起作用。完成 这些研究不仅揭示了柯克斯体调节宿主脂质代谢的新策略， 显著地增加了我们关于病原体分泌的蛋白质如何操纵宿主细胞的知识。

PROJECT SUMMARY/ABSTRACT Coxiella burnetii is an obligate intracellular bacterium and the etiological agent of Q fever. Inside the host cell, the bacterium survives in a phagolysosome-like vacuole called the Coxiella Containing Vacuole (CCV). Coxiella is uniquely sensitive to host cholesterol levels, where elevated cholesterol, especially in the CCV and endolysosomal system, leads to bacterial death. While Coxiella directly regulates host cholesterol homeostasis through effector proteins secreted by the Coxiella Type 4B Secretory System (T4BSS), the T4BSS effector proteins responsible for manipulating host cell cholesterol have not yet been identified. Using a bioinformatic approach, we identified a new family of Coxiella T4BSS effector proteins which contain a eukaryotic FFAT motif. In eukaryotic cells, FFAT proteins bind to the VAP protein family on the endoplasmic reticulum (ER) and mediate membrane contact sites (MCS) between cell organelles and ER. These inter-organelle MCS play a critical role in regulating lipid homeostasis. The proposed experiments will test our hypothesis that Coxiella FFAT-containing T4BSS effector proteins mediate MCS between the ER and other host organelles in order to manipulate host cholesterol metabolism. Aim 1 will establish which members of the Coxiella FFAT protein family bind to VAP proteins, and determine where these proteins localize in the host cell. Aim 2 will test whether these proteins are essential for Coxiella infection, as well as whether they function in modulating host cholesterol. Completion of these studies will not only reveal a new strategy utilized by Coxiella to modulate host lipid metabolism, but significantly add to our knowledge on how pathogen-secreted proteins manipulate the host cell.