Dissecting the molecular mechanisms of intraflagellar transport in Chlamydomonas
Dissecting the molecular mechanisms of intraflagellar transport in Chlamydomonas
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DOI：
10.1016/j.cub.2006.02.020
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发表时间：
2006-03-07
期刊：
影响因子：
9.2
通讯作者：
Rosenbaum, JL
中科院分区：
文献类型：
--
作者：
Pedersen, LB;Gelmer, S;Rosenbaum, JL
背景：真核生物纤毛和鞭毛的组装和维持是由鞭毛内转运(IFT)介导的，IFT是一种基于微管(MT)的双向运输系统。IFT系统由顺行(kinesin-2)和逆行(CDynein1b)运动复合体和IFT颗粒组成，其中包括两个复合体A和B。在目前的IFT模型中，kinesin-2携带cDynein1b、ift颗粒和轴丝前体从鞭毛底部到顶端，cDynein1b将kinesin-2、ift颗粒和轴丝周转产物从顶端输送回底端。目前已鉴定和表征了IFT系统的大部分成分，但这些不同成分在鞭毛底部和鞭毛顶端的协调和调节机制尚不清楚。结果：利用多种衣藻突变体，我们证实了cDynein1b需要Kinesin-2才能向鞭毛末端运输，并表明在逆行IFT过程中，Kinesin-2可以独立于cDynein1b轻中间链(LIC)和IFT颗粒离开鞭毛。此外，利用生化方法，我们发现IFT络合物B可以与cDynein1b结合，而不依赖于络合物A和cDynein1b LIC。结论：我们的结果支持IFT尖端翻转的模型，即(1)IFT复合体A和B的解离和非活性cDynein1b从复合体B中释放，(2)复合体A与活性cDynein1b结合，以及(3)复合体B在逆行IFT之前与A重新结合。
Background: The assembly and maintenance of eukaryotic cilia and flagella are mediated by intraflagellar transport (IFT), a bidirectional microtubule (MT)-based transport system. The IFT system consists of anterograde (kinesin-2) and retrograde (cDynein1b) motor complexes and IFT particles comprising two complexes, A and B. In the current model for IFT, kinesin-2 carries cDynein1b, IFT particles, and axonemal precursors from the flagellar base to the tip, and cDynein1b transports kinesin-2, IFT particles, and axonemal turnover products from the tip back to the base. Most of the components of the IFT system have been identified and characterized, but the mechanisms by which these different components are coordinated and regulated at the flagellar base and tip are unclear.Results: Using a variety of Chlamydomonas mutants, we confirm that cDynein1b requires kinesin-2 for transport toward the tip and show that during retrograde IFT, kinesin-2 can exit the flagella independent of the cDynein1b light intermediate chain (LIC) and IFT particles. Furthermore, using biochemical approaches, we find that I FT complex B can associate with cDynein1b independent of complex A and cDynein1b LIC. Finally, using electron microscopy, we show that the IFT tip turnaround point most likely is localized distal to the plus end of the outer-doublet B MTs.Conclusion: Our results support a model for IFT in which tip turnaround involves (1) dissociation of IFT complexes A and B and release of inactive cDynein1b from complex B, (2) binding of complex A to active cDynein1b, and (3) reassociation of complex B with A prior to retrograde IFT.