Yao Xuanli, Wang Xiangfeng, Xiang Xin
Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences-F. Edward Hébert School of Medicine, Bethesda, MD 20814.
School of Plant Sciences, University of Arizona, Tucson, AZ 85721.
Mol Biol Cell. 2014 Jul 15;25(14):2181-9. doi: 10.1091/mbc.E14-04-0873. Epub 2014 May 28.
The minus end-directed microtubule motor cytoplasmic dynein transports various cellular cargoes, including early endosomes, but how dynein binds to its cargo remains unclear. Recently fungal Hook homologues were found to link dynein to early endosomes for their transport. Here we identified FhipA in Aspergillus nidulans as a key player for HookA (A. nidulans Hook) function via a genome-wide screen for mutants defective in early-endosome distribution. The human homologue of FhipA, FHIP, is a protein in the previously discovered FTS/Hook/FHIP (FHF) complex, which contains, besides FHIP and Hook proteins, Fused Toes (FTS). Although this complex was not previously shown to be involved in dynein-mediated transport, we show here that loss of either FhipA or FtsA (A. nidulans FTS homologue) disrupts HookA-early endosome association and inhibits early endosome movement. Both FhipA and FtsA associate with early endosomes, and interestingly, while FtsA-early endosome association requires FhipA and HookA, FhipA-early endosome association is independent of HookA and FtsA. Thus FhipA is more directly linked to early endosomes than HookA and FtsA. However, in the absence of HookA or FtsA, FhipA protein level is significantly reduced. Our results indicate that all three proteins in the FtsA/HookA/FhipA complex are important for dynein-mediated early endosome movement.
负端定向微管马达胞质动力蛋白可运输包括早期内体在内的多种细胞货物，但动力蛋白如何与其货物结合仍不清楚。最近发现真菌的Hook同源物可将动力蛋白与早期内体连接起来以便运输。在这里，我们通过对早期内体分布有缺陷的突变体进行全基因组筛选，确定了构巢曲霉中的FhipA是HookA（构巢曲霉Hook）功能的关键参与者。FhipA的人类同源物FHIP是先前发现的FTS/Hook/FHIP（FHF）复合物中的一种蛋白质，该复合物除了包含FHIP和Hook蛋白外，还包含融合脚趾（FTS）。尽管此前未表明该复合物参与动力蛋白介导的运输，但我们在此表明，FhipA或FtsA（构巢曲霉FTS同源物）的缺失会破坏HookA与早期内体的结合，并抑制早期内体的移动。FhipA和FtsA都与早期内体相关联，有趣的是，虽然FtsA与早期内体的关联需要FhipA和HookA，但FhipA与早期内体的关联独立于HookA和FtsA。因此，FhipA比HookA和FtsA更直接地与早期内体相连。然而，在没有HookA或FtsA的情况下，FhipA蛋白水平会显著降低。我们的结果表明，FtsA/HookA/FhipA复合物中的所有三种蛋白质对于动力蛋白介导的早期内体移动都很重要。
