Rab 7: an important regulator of late endocytic membrane traffic.
Rab 7: an important regulator of late endocytic membrane traffic.
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DOI：
10.1083/jcb.131.6.1435
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发表时间：
1995-12
期刊：
影响因子：
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通讯作者：
Wandinger-Ness A
中科院分区：
文献类型：
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作者：
Feng Y;Press B;Wandinger-Ness A
Rab5和Rab7蛋白属于已知的小分子GTP酶超家族，分别与早期和晚期内含体相关。Rab5蛋白在早期的内吞作用中起着重要的调节作用，但其功能尚不清楚。通过比较水疱性口炎病毒(VSV)G蛋白在过量表达Rab7蛋白的野生型或显性负突变形式(Rab7N125I和Rab7T22N)的幼鼠肾细胞中的内化动力学来解决这个问题。野生型Rab7蛋白的过度表达使VSV G蛋白能够正常转运到晚期(甘露糖6-磷酸受体阳性)的内吞体内，而Rab7N125I突变体导致VSV G蛋白在早期(转铁蛋白受体阳性)内特异积聚。辣根过氧化物酶和副粘病毒SV5血凝素神经氨酸酶(HN)用于定量生化分析，进一步证明Rab7功能在早期内化事件中不是必需的，但在下游降解事件中起关键作用。SV5 HN在晚期内吞体内的特有裂解区别于内吞途径从运输到后期的内化。突变的Rab7N125I和Rab7T22N蛋白对辣根过氧化物酶和SV5 HN蛋白的内化均无影响。相反，突变蛋白明显抑制了SV5HN蛋白随后的切割。综上所述，这些数据支持了Rab5下游的Rab7在调节从早期到晚期的内小体的膜运输中发挥的关键作用。我们将我们的发现与酵母同系物Ypt51p、Ypt52p、Ypt53p和Ypt7p的研究结果进行了比较。
Rab5 and rab7 proteins belong to a superfamily of small molecular weight GTPases known to be associated with early and late endosomes, respectively. The rab5 protein plays an important regulatory role in early endocytosis, yet the function of rab7 protein was previously uncharacterized. This question was addressed by comparing the kinetics of vesicular stomatitis virus (VSV) G protein internalization in baby hamster kidney cells overexpressing wild-type or dominant negative mutant forms of the rab7 protein (rab7N125I and rab7T22N). Overexpression of wild-type rab7 protein allowed normal transport to late endosomes (mannose 6-phosphate receptor positive), while the rab7N125I mutant caused the VSV G protein to accumulate specifically in early (transferrin receptor positive) endosomes. Horseradish peroxidase and paramyxovirus SV5 hemagglutinin-neuraminidase (HN) were used in quantitative biochemical assays to further demonstrate that rab7 function was not required for early internalization events, but was crucial in downstream degradative events. The characteristic cleavage of SV5 HN in the late endosome distinguishes internalization from transport to later stages of the endocytic pathway. Mutant rab7N125I or rab7T22N proteins had no effect on the internalization of either horseradish peroxidase or SV5 HN protein. In contrast, the mutant proteins markedly inhibited the subsequent cleavage of the SV5 HN protein. Taken together, these data support a key role for rab7, downstream of rab5, in regulating membrane transport leading from early to late endosomes. We compare our findings to those obtained for the yeast homologues Ypt51p, Ypt52p, Ypt53p, and Ypt7p.