Late endosomal Rab7 regulates lysosomal trafficking of endocytic but not biosynthetic cargo in Trypanosoma brucei.
Late endosomal Rab7 regulates lysosomal trafficking of endocytic but not biosynthetic cargo in Trypanosoma brucei.
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DOI：
10.1111/j.1365-2958.2011.07842.x
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发表时间：
2011-11
影响因子：
3.6
通讯作者：
Bangs JD
中科院分区：
文献类型：
--
作者：
Silverman JS;Schwartz KJ;Hajduk SL;Bangs JD
我们提出了第一个功能分析的小GTb 7，TbRab 7，在布氏锥虫。TbRab 7定义了与末端p67+溶酶体紧密并列的离散晚期内体。RNAi表明TbRab 7在血流锥虫中是必需的。内吞作用的初始速率不受影响，但溶酶体递送货物，包括番茄凝集素（TL）和锥虫溶解因子（TLF）被阻断。这些聚集在pH升高的分散的内部隔室中，可能来源于晚期内体。TL而不是TLF的表面结合减少，表明鞭毛口袋受体的细胞分布受到TbRab 7的差异调节。TLF活性降低约三倍，证实溶酶体递送对于锥虫毒性至关重要。出乎意料的是，内源性蛋白质p67和TbCatL的递送不受影响，表明TbRab 7不调节生物合成溶酶体运输。因此，与哺乳动物细胞和酵母不同，内吞蛋白和内源蛋白的溶酶体运输通过不同的途径发生和/或受到差异调节。TbRab 7沉默对通向溶酶体的隐蔽默认途径没有影响，这表明默认的溶酶体报告基因p67ΔTM、p67ΔCD和VSGΔGPI不利用先前提出的内吞途径。令人惊讶的是，条件性敲除表明TbRab 7在前环昆虫形式的锥虫中可能是非必需的。
We present the first functional analysis of the small GTPase, TbRab7, in Trypanosoma brucei. TbRab7 defines discrete late endosomes closely juxtaposed to the terminal p67+ lysosome. RNAi indicates that TbRab7 is essential in bloodstream trypanosomes. Initial rates of endocytosis were unaffected, but lysosomal delivery of cargo, including tomato lectin (TL) and trypanolytic factor (TLF) were blocked. These accumulate in a dispersed internal compartment of elevated pH, likely derived from the late endosome. Surface binding of TL but not TLF was reduced, suggesting that cellular distribution of flagellar pocket receptors is differentially regulated by TbRab7. TLF activity was reduced approximately threefold confirming that lysosomal delivery is critical for trypanotoxicity. Unexpectedly, delivery of endogenous proteins, p67 and TbCatL, were unaffected indicating that TbRab7 does not regulate biosynthetic lysosomal trafficking. Thus, unlike mammalian cells and yeast, lysosomal trafficking of endocytosed and endogenous proteins occur via different routes and/or are regulated differentially. TbRab7 silencing had no effect on a cryptic default pathway to the lysosome, suggesting that the default lysosomal reporters p67ΔTM, p67ΔCD and VSGΔGPI do not utilize the endocytic pathway as previously proposed. Surprisingly, conditional knockout indicates that TbRab7 may be non-essential in procyclic insect form trypanosomes.
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影响因子：
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