Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Biol Chem. 2012 Nov 9;287(46):38637-46. doi: 10.1074/jbc.M112.373969. Epub 2012 Sep 19.
The actin-based molecular motor myosin VI functions in the endocytic uptake pathway, both during the early stages of clathrin-mediated uptake and in later transport to/from early endosomes. This study uses fluorescence recovery after photobleaching (FRAP) to examine the turnover rate of myosin VI during endocytosis. The results demonstrate that myosin VI turns over dynamically on endocytic structures with a characteristic half-life common to both the large insert isoform of myosin VI on clathrin-coated structures and the no-insert isoform on early endosomes. This half-life is shared by the myosin VI-binding partner Dab2 and is identical for full-length myosin VI and the cargo-binding tail region. The 4-fold slower half-life of an artificially dimerized construct of myosin VI on clathrin-coated structures suggests that wild type myosin VI does not function as a stable dimer, but either as a monomer or in a monomer/dimer equilibrium. Taken together, these FRAP results offer insight into both the basic turnover dynamics and the monomer/dimer nature of myosin VI.
肌球蛋白 VI 是一种基于肌动蛋白的分子马达，在网格蛋白介导的内吞作用的早期阶段和随后向/从早期内体的运输中都发挥作用。本研究使用光漂白后荧光恢复（FRAP）来研究肌球蛋白 VI 在胞吞作用过程中的周转率。结果表明，肌球蛋白 VI 在胞吞结构上动态周转，半衰期特征与网格蛋白包被结构上的肌球蛋白 VI 大插入异构体和早期内体上的无插入异构体相同。肌球蛋白 VI 结合伴侣 Dab2 共享此半衰期，全长肌球蛋白 VI 和货物结合尾部区域也是如此。肌球蛋白 VI 在网格蛋白包被结构上的人工二聚化构建体的半衰期慢 4 倍，表明野生型肌球蛋白 VI 不作为稳定的二聚体发挥作用，而是作为单体或以单体/二聚体平衡发挥作用。总之，这些 FRAP 结果提供了对肌球蛋白 VI 的基本周转率动态和单体/二聚体性质的深入了解。
