New insights into the assembly of extracellular microfibrils from the analysis of the fibrillin 1 mutation in the Tight skin mouse
New insights into the assembly of extracellular microfibrils from the analysis of the fibrillin 1 mutation in the Tight skin mouse
复制标题
DOI：
10.1083/jcb.150.3.667
复制
发表时间：
2000-08-07
影响因子：
7.8
通讯作者：
Ramirez, F
中科院分区：
文献类型：
--
作者：
Gayraud, B;Keene, DR;Ramirez, F
紧皮肤（Tsk）突变是小鼠原纤维蛋白1 （Fbn1）基因的重复，导致比正常（350kd）更大的蛋白（418kd）；Tsk/+小鼠显示结缔组织增加、骨过度生长和肺气肿。肺肺气肿、骨过度生长和血管并发症是Fbn1基因表达降低的小鼠和杂合纤维蛋白1突变的马凡综合征（MFS）患者的显著特征。虽然Tsk/+小鼠产生等量的418-和350-kD蛋白，但它们表现出相对温和的表型，没有与MFS患者和原纤维蛋白缺失小鼠相关的血管并发症。我们使用遗传杂交、细胞培养测定和Tsk特异性抗体来调和这种差异，并获得对微纤维组装的新见解。Tsk突变和次胚型Fbn1等位基因复合杂合的小鼠同时表现出Tsk和MFS性状。利用tsk和物种特异性抗体对免疫反应性原纤维1微原纤维进行分析，发现突变细胞培养比对照细胞更少，并且在形态上不同。Tsk/Tsk成纤维细胞与不能组装原纤维1微原纤维的人类WISH细胞共培养，表明Tsk原纤维蛋白1与野生型原纤维蛋白1共聚，此外，Tsk原纤维蛋白1与野生型原纤维蛋白1共聚可以恢复Tsk/Tsk聚集体的异常形态。因此，研究表明，Tsk/+小鼠的骨骼和肺部异常是由于突变型和野生型分子共聚成功能缺陷的微原纤维。然而，这些动物没有出现血管并发症，因为功能性微原纤维的水平没有低于临界阈值。间接的体外证据表明，将Tsk原纤维蛋白1掺入微原纤维的主要负面作用的潜在机制是通过重复的Tsk区域增加蛋白水解敏感性。
The Tight skin (Tsk) mutation is a duplication of the mouse fibrillin 1 (Fbn1) gene that results in a larger (418 kD) than normal (350 kD) protein; Tsk/+ mice display increased connective tissue, bone overgrowth, and lung emphysema. Lung emphysema, bone overgrowth, and vascular complications are the distinctive traits of mice with reduced Fbn1 gene expression and of Marfan syndrome (MFS) patients with heterozygous fibrillin 1 mutations. Although Tsk/+ mice produce equal amounts of the 418- and 350-kD proteins, they exhibit a relatively mild phenotype without the vascular complications that are associated with MFS patients and fibrillin l-deficient mice, We have used genetic crosses, cell culture assays and Tsk-specific antibodies to reconcile this discrepancy and gain new insights into microfibril assembly. Mice compound heterozygous for the Tsk mutation and hypomorphic Fbn1 alleles displayed both Tsk and MFS traits. Analyses of immunoreactive fibrillin 1 microfibrils using Tsk-and species-specific antibodies revealed that the mutant cell cultures elaborate a less abundant and morphologically different meshwork than control cells. Cocultures of Tsk/Tsk fibroblasts and human WISH cells that do not assemble fibrillin 1 microfibrils, demonstrated that Tsk fibrillin 1 copolymerizes with wild-type fibrillin 1, Additionally, copolymerization of Tsk fibrillin 1 with wild-type fibrillin 1 rescues the abnormal morphology of the Tsk/Tsk aggregates. Therefore, the studies suggest that bone and lung abnormalities of Tsk/+ mice are due to copolymerization of mutant and wild-type molecules into functionally deficient microfibrils. However, vascular complications are not present in these animals because the level of functional microfibrils does not drop below the critical threshold. Indirect in vitro evidence suggests that a potential mechanism for the dominant negative effects of incorporating Tsk fibrillin 1 into microfibrils is increased proteolytic susceptibility conferred by the duplicated Tsk region.