Driscoll Bellana, Fountain Madison B, Gates Isabella N, Abdollahi Reihane, Langley Allison M, Owens Matthew B, Christensen Jenna R, Salogiannis John
Department of Molecular Physiology and Biophysics, University of Vermont Larner College of Medicine, Burlington, VT 05405.
Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208.
Mol Biol Cell. 2025 Sep 3:mbcE25040186. doi: 10.1091/mbc.E25-04-0186.
Motor-driven transport on microtubules is critical for distributing organelles throughout the cell. Most commonly, organelle movement is mediated by cargo adaptors, proteins on the surface of an organelle that directly recruit microtubule-based motors. An alternative mechanism called hitchhiking was recently discovered: some organelles move, not by recruiting the motors directly, but instead by using membrane contact sites to attach to motor-driven vesicles and hitchhike along microtubules. Organelle hitchhiking is observed across fungi and animals. In filamentous fungi, nearly all peroxisomes move by hitchhiking on early endosomes (EEs). In the fungus , EE-associated linker proteins PxdA and DipA are critical for establishing EE-peroxisome membrane contact sites required for peroxisome movement. Whether peroxisome-membrane proteins exist that regulate peroxisome hitchhiking on EEs is not known. Through a forward mutagenesis screen, we discovered an acyl-coA binding (ACB) domain-containing protein AcbdA/AN1062 that localizes to peroxisomes via its tail-anchored transmembrane domain (TMD). Deleting the AcbdA gene or only its N-terminal ACB domain perturbs the movement and distribution of peroxisomes. Importantly, AcbdA is not required for the movement of EEs or for the recruitment of PxdA and DipA on EEs. Fatty acid (FA)-induced increases in peroxisome movement require AcbdA, suggesting that peroxisome hitchhiking on EEs is coupled to FA metabolism. Mutating a conserved FFAT motif, predicted to interact with the endoplasmic reticulum (ER), has no effect on peroxisome movement. Taken together, our data indicate that AcbdA is a peroxisome-membrane protein required for peroxisome hitchhiking on EEs. AcbdA's involvement in peroxisome hitchhiking represents a divergence from known functions of Acbd4/5 proteins and adds layers to our understanding of the functionality of the Acbd4/5 family of proteins. [Media: see text] [Media: see text] [Media: see text].
微管上由马达驱动的运输对于细胞器在整个细胞中的分布至关重要。最常见的是，细胞器的运动由货物衔接蛋白介导，这些蛋白位于细胞器表面，直接招募基于微管的马达。最近发现了一种称为搭便车的替代机制：一些细胞器不是直接招募马达来移动，而是利用膜接触位点附着在由马达驱动的囊泡上，并沿着微管搭便车移动。在真菌和动物中都观察到了细胞器搭便车现象。在丝状真菌中，几乎所有过氧化物酶体都是通过搭早期内体（EEs）的便车来移动的。在这种真菌中，与EE相关的连接蛋白PxdA和DipA对于建立过氧化物酶体移动所需的EE - 过氧化物酶体膜接触位点至关重要。目前尚不清楚是否存在调节过氧化物酶体在EEs上搭便车的过氧化物酶体膜蛋白。通过正向诱变筛选，我们发现了一种含有酰基辅酶A结合（ACB）结构域的蛋白AcbdA/AN1062，它通过其尾锚定跨膜结构域（TMD）定位于过氧化物酶体。删除AcbdA基因或仅其N端ACB结构域会扰乱过氧化物酶体的移动和分布。重要的是，EEs的移动或EEs上PxdA和DipA的招募不需要AcbdA。脂肪酸（FA）诱导的过氧化物酶体移动增加需要AcbdA，这表明过氧化物酶体在EEs上搭便车与FA代谢相关。突变一个预测与内质网（ER）相互作用的保守FFAT基序，对过氧化物酶体移动没有影响。综上所述，我们的数据表明AcbdA是过氧化物酶体在EEs上搭便车所需的过氧化物酶体膜蛋白。AcbdA参与过氧化物酶体搭便车代表了与Acbd4/5蛋白已知功能的差异，并加深了我们对Acbd4/5蛋白家族功能的理解。
