Ali M Yusuf, Lu Hailong, Fagnant Patricia M, Macfarlane Jill E, Trybus Kathleen M
Department of Molecular Physiology & Biophysics, University of Vermont, Burlington, Vermont, USA.
Traffic. 2025 Apr-Jun;26(4-6):e70008. doi: 10.1111/tra.70008.
The folded auto-inhibited state of kinesin-1 is stabilized by multiple weak interactions and binds poorly to microtubules. Here we investigate the extent to which homodimeric Drosophila kinesin-1 lacking light chains is activated by the dynein activating adaptor Drosophila BicD. We show that one or two kinesins can bind to the central region of BicD (CC2), a region distinct from that which binds dynein-dynactin (CC1) and cargo-adaptor proteins (CC3). Kinesin light chain significantly reduces the amount of kinesin bound to BicD and thus regulates this interaction. Binding of BicD to kinesin enhances processive motion, suggesting that the adaptor relieves kinesin auto-inhibition. In contrast, the kinesin-binding domain of microtubule-associated protein 7 (MAP7) has minimal impact on the fraction of motors moving processively while full-length MAP7 enhances kinesin-1 recruitment to the microtubule and run length because of its microtubule-binding domain. BicD thus relieves auto-inhibition of kinesin, while MAP7 enhances motor engagement with the microtubules. When BicD and MAP7 are combined, the most robust activation of kinesin-1 occurs, highlighting the crosstalk between adaptors and microtubule-associated proteins in regulating transport.
驱动蛋白-1的折叠自抑制状态通过多种弱相互作用得以稳定，且与微管的结合能力较差。在此，我们研究了缺乏轻链的同型二聚体果蝇驱动蛋白-1被动力蛋白激活适配体果蝇BicD激活的程度。我们发现，一个或两个驱动蛋白可与BicD的中央区域（CC2）结合，该区域与结合动力蛋白-动力蛋白激活蛋白复合物（CC1）和货物适配体蛋白（CC3）的区域不同。驱动蛋白轻链显著减少了与BicD结合的驱动蛋白数量，从而调节这种相互作用。BicD与驱动蛋白的结合增强了持续性运动，这表明该适配体缓解了驱动蛋白的自抑制。相比之下，微管相关蛋白7（MAP7）的驱动蛋白结合结构域对进行持续性运动的驱动蛋白比例影响极小，而全长MAP7由于其微管结合结构域，增强了驱动蛋白-1在微管上的募集和运行长度。因此，BicD缓解了驱动蛋白的自抑制，而MAP7增强了驱动蛋白与微管的结合。当BicD和MAP7结合时，会发生对驱动蛋白-1最有力的激活，突出了适配体与微管相关蛋白在调节运输过程中的相互作用。
