Department of Biology and Center for Engineering Mechanobiology, Washington University in St. Louis, 1 Brookings Drive, CB 1137, St. Louis, MO 63130, USA.
Department of Biology and Center for Lignocellulose Structure and Formation, The Pennsylvania State University, University Park, PA 16802, USA.
Dev Cell. 2018 Mar 12;44(5):642-651.e5. doi: 10.1016/j.devcel.2018.01.027. Epub 2018 Mar 1.
Spatiotemporal regulation of kinesins is essential for microtubule-dependent intracellular transport. In plants, cell wall deposition depends on the FRA1 kinesin, whose abundance and motility are tightly controlled to match cellular growth rate. Here, we show that an importin-β, IMB4, regulates FRA1 activity in a developmental manner. IMB4 physically interacts with a PY motif in the FRA1 motor domain and inhibits its motility by preventing microtubule binding, while also protecting FRA1 against proteasome-mediated degradation, thus providing a mechanism to couple the motility and stability of FRA1. This regulatory mechanism is likely to be broadly applicable, based on the conservation of the PY motif in the motor domains of plant and animal kinesins and the direct interaction of multiple plant kinesins with IMB4. Together, our data establish IMB4 as a multi-functional regulator of FRA1 and reveal a mechanism for how plants control the magnitude of cargo transport needed for cell wall assembly.
驱动蛋白的时空调节对于微管依赖性的细胞内运输至关重要。在植物中，细胞壁的沉积依赖于 FRA1 驱动蛋白，其丰度和运动性受到严格控制，以匹配细胞的生长速度。在这里，我们表明一种 Importin-β，IMB4，以一种发育的方式调节 FRA1 的活性。IMB4 与 FRA1 运动域中的 PY 基序物理相互作用，并通过防止微管结合来抑制其运动性，同时还保护 FRA1 免受蛋白酶体介导的降解，从而提供了一种将 FRA1 的运动性和稳定性偶联的机制。基于植物和动物驱动蛋白的运动域中 PY 基序的保守性以及多种植物驱动蛋白与 IMB4 的直接相互作用，这种调节机制可能具有广泛的适用性。总之，我们的数据确立了 IMB4 作为 FRA1 的多功能调节剂，并揭示了植物如何控制细胞组装所需的货物运输量的机制。
