Lecroisey Claire, Martin Edwige, Mariol Marie-Christine, Granger Laure, Schwab Yannick, Labouesse Michel, Ségalat Laurent, Gieseler Kathrin
Université Lyon 1, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5534, Centre de Génétique Moléculaire et Cellulaire, Bâtiment Mendel, Villeurbanne, F-69622, France.
Mol Biol Cell. 2008 Mar;19(3):785-96. doi: 10.1091/mbc.e07-05-0497. Epub 2007 Dec 19.
In Caenorhabditis elegans, mutations of the dystrophin homologue, dys-1, produce a peculiar behavioral phenotype (hyperactivity and a tendency to hypercontract). In a sensitized genetic background, dys-1 mutations also lead to muscle necrosis. The dyc-1 gene was previously identified in a genetic screen because its mutation leads to the same phenotype as dys-1, suggesting that the two genes are functionally linked. Here, we report the detailed characterization of the dyc-1 gene. dyc-1 encodes two isoforms, which are expressed in neurons and muscles. Isoform-specific RNAi experiments show that the absence of the muscle isoform, and not that of the neuronal isoform, is responsible for the dyc-1 mutant phenotype. In the sarcomere, the DYC-1 protein is localized at the edges of the dense body, the nematode muscle adhesion structure where actin filaments are anchored and linked to the sarcolemma. In yeast two-hybrid assays, DYC-1 interacts with ZYX-1, the homologue of the vertebrate focal adhesion LIM domain protein zyxin. ZYX-1 localizes at dense bodies and M-lines as well as in the nucleus of C. elegans striated muscles. The DYC-1 protein possesses a highly conserved 19 amino acid sequence, which is involved in the interaction with ZYX-1 and which is sufficient for addressing DYC-1 to the dense body. Altogether our findings indicate that DYC-1 may be involved in dense body function and stability. This, taken together with the functional link between the C. elegans DYC-1 and DYS-1 proteins, furthermore suggests a requirement of dystrophin function at this structure. As the dense body shares functional similarity with both the vertebrate Z-disk and the costamere, we therefore postulate that disruption of muscle cell adhesion structures might be the primary event of muscle degeneration occurring in the absence of dystrophin, in C. elegans as well as vertebrates.
在秀丽隐杆线虫中，肌营养不良蛋白同源物dys-1的突变会产生一种特殊的行为表型（多动和过度收缩倾向）。在敏感的遗传背景下，dys-1突变也会导致肌肉坏死。dyc-1基因先前是在一项遗传筛选中被鉴定出来的，因为其突变导致的表型与dys-1相同，这表明这两个基因在功能上是相关联的。在此，我们报告dyc-1基因的详细特征。dyc-1编码两种异构体，它们在神经元和肌肉中表达。异构体特异性RNA干扰实验表明，导致dyc-1突变体表型的原因是肌肉异构体的缺失，而非神经元异构体的缺失。在肌节中，DYC-1蛋白定位于致密体的边缘，致密体是线虫肌肉的粘附结构，肌动蛋白丝在此处锚定并与肌膜相连。在酵母双杂交实验中，DYC-1与ZYX-1相互作用，ZYX-1是脊椎动物粘着斑LIM结构域蛋白zyxin的同源物。ZYX-1定位于秀丽隐杆线虫横纹肌的致密体和M线以及细胞核中。DYC-1蛋白拥有一段高度保守的19个氨基酸序列，该序列参与与ZYX-1的相互作用，并且足以将DYC-1定位于致密体。我们的研究结果总体表明，DYC-1可能参与致密体的功能和稳定性。此外，结合秀丽隐杆线虫DYC-1和DYS-1蛋白之间的功能联系，这表明在该结构处需要肌营养不良蛋白发挥功能。由于致密体与脊椎动物的Z盘和肋膜在功能上具有相似性，因此我们推测，在秀丽隐杆线虫和脊椎动物中，肌肉细胞粘附结构的破坏可能是在缺乏肌营养不良蛋白时发生肌肉退化的主要事件。
