Martin MaryAnn, Ahern-Djamali Shawn M, Hoffmann F Michael, Saxton William M
Department of Biology, Indiana University, Bloomington, IN 47405, USA.
Mol Biol Cell. 2005 Sep;16(9):4225-30. doi: 10.1091/mbc.e05-02-0116. Epub 2005 Jun 22.
Relatively little is known about how microtubule motors are controlled or about how the functions of different cytoskeletal systems are integrated. A yeast two-hybrid screen for proteins that bind to Drosophila Enabled (Ena), an actin polymerization factor that is negatively regulated by Abl tyrosine kinase, identified kinesin heavy chain (Khc), a member of the kinesin-1 subfamily of microtubule motors. Coimmunoprecipitation from Drosophila cytosol confirmed a physical interaction between Khc and Ena. Kinesin-1 motors can carry organelles and other macromolecular cargoes from neuronal cell bodies toward terminals in fast-axonal-transport. Ena distribution in larval axons was not affected by mutations in the Khc gene, suggesting that Ena is not itself a fast transport cargo of Drosophila kinesin-1. Genetic interaction tests showed that in a background sensitized by reduced Khc gene dosage, a reduction in Abl gene dosage caused distal paralysis and axonal swellings. A concomitant reduction in ena dosage rescued those defects. These results suggest that Ena/VASP, when not inhibited by the Abl pathway, can bind Khc and reduce its transport activity in axons.
关于微管马达蛋白是如何被调控的，以及不同细胞骨架系统的功能是如何整合的，我们所知甚少。通过酵母双杂交筛选与果蝇 Enabled（Ena）相互作用的蛋白质，Ena是一种肌动蛋白聚合因子，受Abl酪氨酸激酶负调控，筛选出了驱动蛋白重链（Khc），它是微管马达蛋白驱动蛋白-1亚家族的成员。从果蝇胞质溶胶中进行的免疫共沉淀证实了Khc与Ena之间存在物理相互作用。驱动蛋白-1马达蛋白可以在快速轴突运输中，将细胞器和其他大分子货物从神经元细胞体运往轴突末端。幼虫轴突中的Ena分布不受Khc基因突变的影响，这表明Ena本身不是果蝇驱动蛋白-1的快速运输货物。遗传相互作用测试表明，在Khc基因剂量降低导致的敏感背景下，Abl基因剂量的降低会导致远端麻痹和轴突肿胀。同时降低ena剂量可挽救这些缺陷。这些结果表明，当不受Abl途径抑制时，Ena/VASP可以结合Khc并降低其在轴突中的运输活性。
