Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093.
Howard Hughes Medical Institute, Chevy Chase, MD 20815.
Mol Biol Cell. 2021 Mar 15;32(6):492-503. doi: 10.1091/mbc.E20-08-0559. Epub 2021 Jan 21.
In canonical microtubule-based transport, adaptor proteins link cargoes to dynein and kinesin motors. Recently, an alternative mode of transport known as "hitchhiking" was discovered, where cargoes achieve motility by hitching a ride on already-motile cargoes, rather than attaching to a motor protein. Hitchhiking has been best studied in two filamentous fungi, and In ribonucleoprotein complexes, peroxisomes, lipid droplets (LDs), and endoplasmic reticulum hitchhike on early endosomes (EEs). In , peroxisomes hitchhike using a putative molecular linker, peroxisome distribution mutant A (PxdA), which associates with EEs. However, whether other organelles use PxdA to hitchhike on EEs is unclear, as are the molecular mechanisms that regulate hitchhiking. Here we find that the proper distribution of LDs, mitochondria, and preautophagosomes do not require PxdA, suggesting that PxdA is a peroxisome-specific molecular linker. We identify two new alleles, including a point mutation (R2044P) that disrupts PxdA's ability to associate with EEs and reduces peroxisome movement. We also identify a novel regulator of peroxisome hitchhiking, the phosphatase DipA. DipA colocalizes with EEs and its association with EEs relies on PxdA. Together, our data suggest that PxdA and the DipA phosphatase are specific regulators of peroxisome hitchhiking on EEs.
在经典的基于微管的运输中,衔接蛋白将货物与动力蛋白和驱动蛋白连接起来。最近,发现了一种被称为“搭便车”的替代运输方式,其中货物通过搭乘已经运动的货物来实现运动,而不是附着在运动蛋白上。搭便车在两种丝状真菌中得到了最好的研究, 和 在核糖核蛋白复合物、过氧化物酶体、脂滴(LDs)和内质网中,早期内体(EEs)上搭便车。在 中,过氧化物酶体使用假定的分子接头过氧化物酶体分布突变体 A(PxdA)进行搭便车,该分子与 EEs 相关联。然而,其他细胞器是否使用 PxdA 在 EEs 上搭便车以及调节搭便车的分子机制尚不清楚。在这里,我们发现 LDs、线粒体和前自噬体的正常分布不依赖于 PxdA,这表明 PxdA 是一种过氧化物酶体特异性的分子接头。我们鉴定了两个新的 等位基因,包括一个点突变(R2044P),该突变破坏了 PxdA 与 EEs 结合的能力并降低了过氧化物酶体的运动能力。我们还鉴定了一种新的过氧化物酶体搭便车调节剂 DipA。DipA 与 EEs 共定位,其与 EEs 的结合依赖于 PxdA。总之,我们的数据表明 PxdA 和 DipA 磷酸酶是过氧化物酶体在 EEs 上搭便车的特异性调节剂。