Anaysis of vesicular trafficking in Entamoeba histolytica

囊泡转运参与了致病因子的分泌和吞噬作用，是溶组织内阿米巴致病的关键。我们在红细胞吞噬过程中发现了一个新的细胞室(吞噬前空泡，PPV)。两个Rab小GTP酶Rab5和Rab7A在PPV的形成和水解酶通过PPV向吞噬小体的运输中是必不可少的。我们推测PPV在消化物质降解所需的水解酶的加工、激活、储存和运输中起作用。我们还发现了一个与Rab7A相关的新的逆转录体样复合体。该复合体由Vps26、Vps29和VPS35组成，参与调节水解酶对吞噬小体的分选。我们对内阿米巴基因组数据库的基因组调查显示，该原生生物至少有9个Rab7亚型。至少有4个亚型Rab7A、B、D和E显示出不同的细胞分布，推测具有非冗余功能。这些关于毒力因子囊泡运输调控的发现将有助于我们理解这种重要的肠道原虫的毒力机制。

Vesicular trafficking involved in secretion of pathogenic factors and in phagocytosis is essential for virulence of Entamoeba histolytica. We identified a novel cellular compartment (prephagosomal vacuole;PPV) during erythrophagocytosis. Two Rab small GTPases Rab5 and Rab7A were shown to be essential for the formation of PPV and the transport of hydrolytic enzymes to phagosomes via PPVs. We presumed that PPV plays a role inprocessing, activation, storage, and transport of hydrolases necessary for degradation of ingested materials. We also identified a novel retromer-like complex associated with Rab7A. This complex, consisted of Vps26, Vps29, and Vps35, was shown to be involved in the regulation of the sorting of hydrolases to phagosomes. Our genomic survey of the Entamoeba genome database showed that this protist possesses at least 9 Rab7 isotypes. At least 4 isotypes Rab7A,B,D,and E showed distinct cellular distribution and were presumed to have non-redundant function. These findings on the regulation of vesicular trafficking of virulence factors should facilitate our understanding of virulence mechanisms of this important enteric protozoan parasite.