Morphological changes and spatial regulation of diacylglycerol kinase-ζ, syntrophins, and Rac1 during myoblast fusion
Morphological changes and spatial regulation of diacylglycerol kinase-ζ, syntrophins, and Rac1 during myoblast fusion
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DOI：
10.1002/cm.20204
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发表时间：
2007-07-01
影响因子：
--
通讯作者：
Gee, Stephen H.
中科院分区：
文献类型：
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作者：
Abramovici, Hanan;Gee, Stephen H.
单核成肌细胞融合成多核肌纤维是骨骼肌形成和生长所必需的。成肌细胞融合遵循一系列明确的细胞事件，从最初的识别和粘附，到对齐，最后是质膜融合。这些过程依赖于肌动蛋白细胞骨架的协调重塑。我们最近的研究表明，二酰甘油激酶-ζ（DGK-xi），代谢二酰甘油产生磷脂酸的酶，在肌动蛋白重组中起着重要作用。在这里，我们研究了DGK-xi是否在培养的C2 C12成肌细胞的融合中起作用。我们表明，DGK-XI和突触营养蛋白，支架蛋白的肌营养不良蛋白糖蛋白复合物，直接结合DGK-XI，在融合过程中的空间调节。这两种蛋白质积累的GTCRac 1在网站上细丝状伪足调解成肌细胞之间的初始接触。此外，DGK-XI与钙依赖性细胞粘附分子N-钙粘蛋白在新生时共分布，而不是先前建立的细胞接触。我们提供的证据表明，C2细胞被拉在一起，在细胞-细胞交界处的N-钙粘蛋白含有filepodia让人想起上皮粘附拉链，这引导的进步，从并列细胞的板状伪足。在以后的时间，囊泡与大胞饮体的性质形成接近细胞-细胞连接。共聚焦光学切片的重建显示，这些形式的圆顶状突起从接触细胞的背表面。总的来说，这些结果表明DGK-xi和突触营养蛋白在融合过程的多个阶段发挥作用。此外，我们的研究结果提供了一个潜在的联系，在成肌细胞融合过程中的膜双层和肌动蛋白细胞骨架的重组的脂质含量的变化。
The fusion of mononuclear myoblasts into multinucleated myofibers is essential for the formation and growth of skeletal muscle. Myoblast fusion follows a well-defined sequence of cellular events, from initial recognition and adhesion, to alignment, and finally plasma membrane fusion. These processes depend upon coordinated remodeling of the actin cytoskeleton. Our recent studies suggest diacylglycerol kinase-zeta (DGK-xi), an enzyme that metabolizes diacylglycerol to yield phosphatidic acid, plays an important role in actin reorganization. Here, we investigated whether DGK-xi has a role in the fusion of cultured C2C12 myoblasts. We show that DGK-xi and syntrophins, scaffold proteins of the dystrophin glycoprotein complex that bind directly to DGK-xi, are spatially regulated during fusion. Both proteins accumulated with the GTPase Rac1 at sites where fine filopodia mediate the initial contact between myoblasts. In addition, DGK-xi codistributed with the Ca2+-dependent cell adhesion molecule N-cadherin at nascent, but not previously established cell contacts. We provide evidence that C2 cells are pulled together at cell-cell junctions by N-cadherin-containing filopodia reminiscent of epithelial adhesion zippers, which guide the advance of lamellipodia from apposing cells. At later times, vesicles with properties of macropinosomes formed close to cell-cell junctions. Reconstruction of confocal optical sections showed these form dome-like protrusions from the dorsal surface of contacting cells. Collectively, these results suggest DGK-xi and syntrophins play a role at multiple stages of the fusion process. Moreover, our findings provide a potential link between changes in the lipid content of the membrane bilayer and reorganization of the actin cytoskeleton during myoblast fusion.