The motor function of Drosophila melanogaster myosin-5 is activated by calcium and cargo-binding protein dRab11
The motor function of Drosophila melanogaster myosin-5 is activated by calcium and cargo-binding protein dRab11
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果蝇 myosin-5 的运动功能由钙和货物结合蛋白 dRab11 激活。
DOI：
10.1042/bj20141330
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发表时间：
2015-07-01
影响因子：
4.1
通讯作者：
Li, Xiang-dong
中科院分区：
文献类型：
--
作者：
Ji, Huan-Hong;Zhang, Hai-Man;Li, Xiang-dong
在果蝇复眼中，肌球蛋白 5 (DmM5) 在响应光刺激时发挥两个不同的作用：将色素颗粒转运至横纹肌基底以减少光照，以及将携带视紫红质的囊泡转运至横纹肌基底以补偿光照期间视紫红质的损失。然而，人们对 DmM5 的运动功能如何在分子水平上进行调节知之甚少。在本研究中，我们在 Sf9 昆虫细胞中过度表达 DmM5，并使用纯化的蛋白质研究其调节。我们发现DmM5的肌动蛋白激活的ATP酶活性显着低于C端球状尾结构域(GTD)删除的截短DmM5，表明GTD是抑制结构域。 DmM5 的肌动蛋白激活的 ATP 酶活性被微摩尔水平的钙显着激活。 DmM5 分别通过货物结合蛋白 Lightoid (Ltd) 和 dRab11 与色素颗粒和携带视紫红质的囊泡结合。我们发现 GTP 结合的 dRab11（而非 Ltd）显着激活 DmM5 肌动蛋白激活的 ATP 酶活性。此外，我们确定 GTD 中的 Gln(1689) 是与 dRab11 相互作用以及 dRab11 激活 DmM5 运动功能的关键残基。基于这些结果，我们提出，光诱导的钙内流直接激活色素颗粒的 DmM5 依赖性运输，而视紫红质囊泡的 DmM5 依赖性运输则由活性 GTP 结合的 dRab11 激活，而光诱导的钙内流会刺激其形成。
In the Drosophila melanogaster compound eye, myosin-5 (DmM5) plays two distinct roles in response to light stimulation: transport of pigment granules to the rhabdomere base to decrease light exposure and transport of rhodopsin-bearing vesicles to the rhabdomere base to compensate for the rhodopsin loss during light exposure. However, little is known of how the motor function of DmM5 is regulated at the molecular level. In the present study, we overexpressed DmM5 in Sf9 insect cells and investigated its regulation using purified proteins. We found that the actin-activated ATPase activity of DmM5 is significantly lower than that of the truncated DmM5 having the C-terminal globular tail domain (GTD) deleted, indicating that the GTD is the inhibitory domain. The actin-activated ATPase activity of DmM5 is significantly activated by micromolar levels of calcium. DmM5 associates with pigment granules and rhodopsin-bearing vesicles through cargo-binding proteins Lightoid (Ltd) and dRab11 respectively. We found that GTP-bound dRab11, but not Ltd, significantly activates DmM5 actin-activated ATPase activity. Moreover, we identified Gln(1689) in the GTD as the critical residue for the interaction with dRab11 and activation of DmM5 motor function by dRab11. Based on those results, we propose that DmM5-dependent transport of pigment granules is directly activated by light-induced calcium influx and the DmM5-dependent transport of rhodopsin-bearing vesicle is activated by active GTP-bound dRab11, whose formation is stimulated by light-induced calcium influx.