The actin-binding domain of Slac2-a/melanophilin is required for melanosome distribution in melanocytes
The actin-binding domain of Slac2-a/melanophilin is required for melanosome distribution in melanocytes
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DOI：
10.1128/mcb.23.15.5245-5255.2003
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发表时间：
2003-08-01
影响因子：
5.3
通讯作者：
Fukuda, M
中科院分区：
文献类型：
--
作者：
Kuroda, TS;Ariga, H;Fukuda, M
含有黑色素的黑素体通过微管和肌动蛋白依赖性机制的组合从黑素细胞的细胞体运输到其树突的尖端。已知三种蛋白质Rab 27 A、肌球蛋白Va和Slac 2-a/亲黑素蛋白（Rab 27 A和肌球蛋白Va之间的接头蛋白）对于黑素细胞中适当的基于肌动蛋白的黑素体转运是必需的。尽管Slac 2-a分别通过其N-末端区域（氨基酸1至146）和中间区域（氨基酸241至405）与Rab 27 A和肌球蛋白Va直接相互作用，但Slac 2-a C末端（氨基酸401至590）的推定肌动蛋白结合结构域在黑素体转运中的功能重要性从未被阐明。在这项研究中，我们发现，Rab 27 A，Slac 2-a，和肌球蛋白Va单独之间的三方蛋白复合物的形成是不够的黑素细胞中的黑素体的外周分布和C-末端肌动蛋白结合结构域的Slac 2-a也需要适当的黑素体运输。当缺乏肌动蛋白结合能力的Slac 2-a缺失突变体（AABD）或点突变体（KA）在黑素细胞中表达时，Slac 2-a突变体诱导黑素体在核周区域中积累，可能是通过显性负效应，与Slac 2-a的Rab 27 A结合缺陷突变体或肌球蛋白Va结合缺陷突变体相同。我们的研究结果表明，Slac 2-a组织肌动蛋白为基础的黑素体运输与Rab 27 A，肌球蛋白Va，肌动蛋白合作。
Melanosomes containing melanin pigments are transported from the cell body of melanocytes to the tips of their dendrites by a combination of microtubule- and actin-dependent machinery. Three proteins, Rab27A, myosin Va, and Slac2-a/melanophilin (a linker protein between Rab27A and myosin Va), are known to be essential for proper actin-based melanosome transport in melanocytes. Although Slac2-a directly interacts with Rab27A and myosin Va via its N-terminal region (amino acids 1 to 146) and the middle region (amino acids 241 to 405), respectively, the functional importance of the putative actin-binding domain of the Slac2-a C terminus (amino acids 401 to 590) in melanosome transport has never been elucidated. In this study we showed that formation of a tripartite protein complex between Rab27A, Slac2-a, and myosin Va alone is insufficient for peripheral distribution of melanosomes in melanocytes and that the C-terminal actin-binding domain of Slac2-a is also required for proper melanosome transport. When a Slac2-a deletion mutant (AABD) or point mutant (KA) that lacks actin-binding ability was expressed in melanocytes, the Slac2-a mutants induced melanosome accumulation in the perinuclear region, possibly by a dominant negative effect, the same as the Rab27A-binding-defective mutant of Slac2-a or the myosin Va-binding-defective mutant. Our findings indicate that Slac2-a organizes actin-based melanosome transport in cooperation with Rab27A, myosin Va, and actin.