Regulation of microtubule-based transport by MAP4.
Regulation of microtubule-based transport by MAP4.
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DOI：
10.1091/mbc.e14-01-0022
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发表时间：
2014-10-15
影响因子：
3.3
通讯作者：
Rodionov V
中科院分区：
文献类型：
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作者：
Semenova I;Ikeda K;Resaul K;Kraikivski P;Aguiar M;Gygi S;Zaliapin I;Cowan A;Rodionov V
非洲爪蟾微管相关蛋白4（XMAP 4）与微管的结合负调节膜细胞器的动力蛋白依赖性运动，正调节基于驱动蛋白2的运动。磷酸化减少XMAP 4与微管的结合，因此调节基于微管的运输方向。微管（MT）为基础的细胞器的运输由相反的MT马达驱动蛋白和动力蛋白在细胞中受到严格调控，但基本的分子机制仍然在很大程度上未知。在这里，我们测试的MT运输的普遍存在的蛋白质MAP 4使用非洲爪蟾作为实验系统的调节。在这些细胞中，色素颗粒（黑素体）分别通过细胞质动力蛋白和驱动蛋白-2沿着沿着MT移动到细胞中心（聚集）或周边（分散）。我们发现，聚集信号诱导磷酸化的苏氨酸残基的MT结合结构域的非洲爪蟾MAP 4（XMAP 4），从而减少这种蛋白质的结合MT。过表达XMAP 4通过缩短动力蛋白依赖的黑素体MT运行来抑制色素聚集，而从MT中去除XMAP 4减少了驱动蛋白2依赖的运行的长度并抑制色素分散。我们假设，结合XMAP 4 MT负调控动力蛋白依赖的黑素体运动和积极调节驱动蛋白-2为基础的运动。色素聚集过程中的磷酸化降低了XMAP 4与MT的结合，从而增加了动力蛋白依赖性并降低了黑素体的驱动蛋白-2依赖性运动，这刺激了它们在细胞中心的积累，而分散过程中XMAP 4的去磷酸化具有相反的效果。
Binding to microtubules of Xenopus microtubule-associated protein 4 (XMAP4) negatively regulates dynein-dependent movement of membrane organelles and positively regulates kinesin-2–based movement. Phosphorylation reduces binding of XMAP4 to microtubules and therefore regulates the direction of microtubule-based transport. Microtubule (MT)-based transport of organelles driven by the opposing MT motors kinesins and dynein is tightly regulated in cells, but the underlying molecular mechanisms remain largely unknown. Here we tested the regulation of MT transport by the ubiquitous protein MAP4 using Xenopus melanophores as an experimental system. In these cells, pigment granules (melanosomes) move along MTs to the cell center (aggregation) or to the periphery (dispersion) by means of cytoplasmic dynein and kinesin-2, respectively. We found that aggregation signals induced phosphorylation of threonine residues in the MT-binding domain of the Xenopus MAP4 (XMAP4), thus decreasing binding of this protein to MTs. Overexpression of XMAP4 inhibited pigment aggregation by shortening dynein-dependent MT runs of melanosomes, whereas removal of XMAP4 from MTs reduced the length of kinesin-2–dependent runs and suppressed pigment dispersion. We hypothesize that binding of XMAP4 to MTs negatively regulates dynein-dependent movement of melanosomes and positively regulates kinesin-2–based movement. Phosphorylation during pigment aggregation reduces binding of XMAP4 to MTs, thus increasing dynein-dependent and decreasing kinesin-2–dependent motility of melanosomes, which stimulates their accumulation in the cell center, whereas dephosphorylation of XMAP4 during dispersion has an opposite effect.