细胞器和囊泡货物由驱动蛋白和动力蛋白马达团队沿着微管运输。我们从不同成熟阶段的细胞中分离了内吞细胞器,并在体外重建了它们沿微管的运动性。我们询问运输货物的电动机组如何确定其运动性和对微管相关蛋白tau的反应。这里,我们发现吞噬体沿着微管向两个方向移动,但是方向偏差在成熟过程中会发生变化。早期吞噬体表现出逆行偏向的运输,而晚期吞噬体在方向上无偏。相应地,早期和晚期吞噬体被驱动蛋白-1、-2、-3和动力蛋白的不同数量和组合结合。Tau稳定微管并指导神经元内的运输。虽然单分子研究表明,tau在体外差异调节驱动蛋白和动力蛋白的运动,人们对其在调节本国汽车团队运输的内源性货物贩运中的作用知之甚少。以前的研究表明,tau优先抑制驱动蛋白马达,这将晚期吞噬体运输偏向微管负端。这里,我们发现tau强烈抑制远程,动力蛋白介导的早期吞噬体的运动性。Tau减少了动力蛋白马达团队对早期吞噬体产生的力,并在负载下加速动力蛋白的脱离。因此,货物对tau的不同反应,其中,早期吞噬体上的动力蛋白复合物对tau抑制比晚期吞噬体上的动力蛋白复合物更敏感。数学建模进一步解释了货物上驱动蛋白和动力蛋白数量的微小变化如何影响净方向性,以及具有不同组电机的货物对tau的反应不同。
Organelles and vesicular cargoes are transported by teams of kinesin and dynein motors along microtubules. We isolated endocytic organelles from cells at different stages of maturation and reconstituted their motility along microtubules in vitro. We asked how the sets of motors transporting a cargo determine its motility and response to the microtubule-associated protein tau. Here, we find that
phagosomes move in both directions along microtubules, but the directional bias changes during maturation. Early
phagosomes exhibit retrograde-biased transport while late
phagosomes are directionally unbiased. Correspondingly, early and late
phagosomes are bound by different numbers and combinations of kinesins-1, -2, -3, and dynein. Tau stabilizes microtubules and directs transport within neurons. While single-molecule studies show that tau differentially regulates the motility of kinesins and dynein in vitro, less is known about its role in modulating the trafficking of endogenous cargoes transported by their native teams of motors. Previous studies showed that tau preferentially inhibits kinesin motors, which biases late phagosome transport towards the microtubule minus-end. Here, we show that tau strongly inhibits long-range, dynein-mediated motility of early
phagosomes. Tau reduces forces generated by teams of dynein motors on early phagosomes and accelerates dynein unbinding under load. Thus, cargoes differentially respond to tau, where dynein complexes on early phagosomes are more sensitive to tau inhibition than those on late
phagosomes. Mathematical modeling further explains how small changes in the number of kinesins and dynein on cargoes impact the net directionality but also that cargoes with different sets of motors respond differently to tau.