Nakamura N, Yamamoto A, Wada Y, Futai M
Division of Biological Sciences, Institute of Scientific and Industrial Research, Osaka University, Japan.
J Biol Chem. 2000 Mar 3;275(9):6523-9. doi: 10.1074/jbc.275.9.6523.
The lysosome functions are ensured by accurate membrane trafficking in the cell. We found that mouse syntaxin 7 could complement yeast vam3 and pep12 mutants defective in docking/fusion to vacuolar and prevacuolar membranes, respectively. Immunohistochemical studies showed that syntaxin 7 is localized to late endosomes, but not to early endosomes. Induced expression of mutant syntaxin 7 blocked endocytic transport from early to late endosomes but did not block the transport of cathepsin D and lamp-2 from the trans-Golgi network to lysosomes. Thus, syntaxin 7 mediates the endocytic trafficking from early endosomes to late endosomes and lysosomes. These results also suggest that the biosynthetic pathway utilizes a different machinery from that of the endocytic pathway in the docking/fusion to late endosomes.
溶酶体的功能通过细胞内精确的膜运输得以保证。我们发现小鼠 syntaxin 7 可以分别弥补酵母中在对接/融合到液泡膜和前液泡膜方面存在缺陷的 vam3 和 pep12 突变体。免疫组织化学研究表明，syntaxin 7 定位于晚期内体，而非早期内体。突变型 syntaxin 7 的诱导表达阻断了从早期内体到晚期内体的内吞运输，但未阻断组织蛋白酶 D 和 lamp-2 从反式高尔基体网络到溶酶体的运输。因此，syntaxin 7 介导了从早期内体到晚期内体及溶酶体的内吞运输。这些结果还表明，在对接/融合到晚期内体的过程中，生物合成途径利用了与内吞途径不同的机制。
