Two Rab7 isotypes, EhRab7A and EhRab7B, play distinct roles in biogenesis of lysosomes and phagosomes in the enteric protozoan parasite Entamoeba histolytica
Two Rab7 isotypes, EhRab7A and EhRab7B, play distinct roles in biogenesis of lysosomes and phagosomes in the enteric protozoan parasite Entamoeba histolytica
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DOI：
10.1111/j.1462-5822.2007.00915.x
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发表时间：
2007-07-01
影响因子：
3.4
通讯作者：
Nozaki, Tomoyoshi
中科院分区：
文献类型：
--
作者：
Saito-Nakano, Yumiko;Mitra, Biswa Nath;Nozaki, Tomoyoshi
Rab 7小GTP酶在运输到晚期内体、溶酶体和吞噬体的调节中起关键作用。虽然大多数真核生物编码一个Rab 7，但寄生原生生物溶组织内阿米巴（Entamoeba histolytica）拥有9个Rab 7。在这项研究中，为了理解多种Rab 7同种型存在的意义，研究了两种代表性Rab 7同种型EhRab 7A和EhRab 7 B的作用。EhRab 7 B仅定位于含有溶酶体蛋白（例如阿米巴孔-A和半胱氨酸蛋白酶）的酸性空泡。EhRab 7 B的这种溶酶体定位与EhRab 7A形成良好对比，在稳态下定位于非酸性隔室，并且仅部分与溶酶体蛋白共定位。EhRab 7 B的过表达导致晚期内体/溶酶体酸化的增强，类似于EhRab 7A的过表达。EhRab 7 B-GTP突变体的表达引起显性负性表型，包括晚期内体/溶酶体酸化和溶酶体蛋白的误分泌减少，而EhRab 7A-GTP增强酸化，但不影响细胞内或分泌的半胱氨酸蛋白酶活性。EhRab 7 B或EhRab 7 B-GTP突变体的表达引起吞噬功能的缺陷，伴随着前吞噬体空泡的干扰形成和解体，该隔室先前被证明与有效的摄取有关。总之，这些数据表明，这两个Rab 7同种型发挥独特的，但协调的作用，在溶酶体和吞噬体的生物发生。
Rab7 small GTPase plays a crucial role in the regulation of trafficking to late endosomes, lysosomes and phagosomes. While most eukaryotes encode a single Rab7, the parasitic protist Entamoeba histolytica possesses nine Rab7. In this study, to understand the significance of the presence of multiple Rab7 isotypes, a role of two representative Rab7 isotypes, EhRab7A and EhRab7B, was investigated. EhRab7B was exclusively localized to acidic vacuoles containing lysosomal proteins, e.g. amoebapore-A and cysteine protease. This lysosome localization of EhRab7B was in good contrast to EhRab7A, localized to a non-acidic compartment in steady state, and only partially colocalized with lysosomal proteins. Overexpression of EhRab7B resulted in augmentation of late endosome/lysosome acidification, similar to the EhRab7A overexpression. Expression of EhRab7B-GTP mutant caused dominant-negative phenotypes including decrease in late endosome/lysosome acidification and missecretion of lysosomal proteins, while EhRab7A-GTP enhanced acidification but did not affect either intracellular or secreted cysteine protease activity. Expression of either EhRab7B or EhRab7B-GTP mutant caused defect in phagocytosis, concomitant with the disturbed formation and disassembly of prephagosomal vacuoles, the compartment previously shown to be linked to efficient ingestion. Altogether, these data indicate that the two Rab7 isotypes play distinct but co-ordinated roles in lysosome and phagosome biogenesis.