Laboratory of Molecular Basis of Cell Motility, Department of Biochemistry, Nencki Institute of Experimental Biology, 3 Pasteur St, 02-093 Warsaw, Poland.
Biochem Cell Biol. 2012 Aug;90(4):565-74. doi: 10.1139/o2012-009. Epub 2012 Apr 4.
Myosin VI (MVI), the only known myosin that walks towards the minus end of actin filaments, is involved in several processes such as endocytosis, cell migration, and cytokinesis. It may act as a transporting motor or a protein engaged in actin cytoskeleton remodelling via its binding partners, interacting with its C-terminal globular tail domain. By means of pull-down technique and mass spectrometry, we identified Dock7 (dedicator of cytokinesis 7) as a potential novel MVI-binding partner in neurosecretory PC12 cells. Dock7, expressed mainly in neuronal cells, is a guanine nucleotide exchange factor (GEF) for small GTPases, Rac1 and Cdc42, which are the major regulators of actin cytoskeleton. MVI-Dock7 interaction was further confirmed by co-immunoprecipitation of endogenous MVI complexed with Dock7. In addition, MVI and Dock7 colocalized in interphase and dividing cells. We conclude that in PC12 cells MVI-Dock7 complexes may function at different cellular locations during the entire cell cycle. Of note, MVI and Dock7 colocalized in primary culture hippocampal neurons also, predominantly in the outgrowths. We hypothesize that this newly identified interaction between MVI and Dock7 may help explain a mechanism for MVI-dependent regulation of actin cytoskeleton organization.
肌球蛋白 VI（MVI）是唯一已知的向肌动蛋白丝负端行走的肌球蛋白，参与多种过程，如内吞作用、细胞迁移和胞质分裂。它可能作为一种运输马达，或通过与其 C 端球状尾部结构域结合的伴侣蛋白，参与肌动蛋白细胞骨架重塑。通过下拉技术和质谱分析，我们在神经分泌 PC12 细胞中鉴定出 Dock7（胞质分裂 7 蛋白）为肌球蛋白 VI 的一个潜在新的结合伴侣。Dock7 主要在神经元细胞中表达，是小 GTP 酶 Rac1 和 Cdc42 的鸟嘌呤核苷酸交换因子（GEF），它们是肌动蛋白细胞骨架的主要调节因子。通过共免疫沉淀内源性肌球蛋白复合物与 Dock7，进一步证实了 MVI-Dock7 相互作用。此外，MVI 和 Dock7 在有丝分裂和分裂细胞中均共定位。我们的结论是，在 PC12 细胞中，MVI-Dock7 复合物可能在整个细胞周期的不同细胞位置发挥作用。值得注意的是，MVI 和 Dock7 也在原代培养海马神经元中共定位，主要在突起中。我们假设，MVI 和 Dock7 之间新鉴定的相互作用可能有助于解释 MVI 依赖的肌动蛋白细胞骨架组织调节的机制。
