The laminin α2 expressed by dystrophic dy2J mice is defective in its ability to form polymers
The laminin α2 expressed by dystrophic dy2J mice is defective in its ability to form polymers
复制标题
DOI：
10.1016/s0960-9822(00)80056-1
复制
发表时间：
1999-11-18
期刊：
影响因子：
9.2
通讯作者：
Yurchenco, PD
中科院分区：
文献类型：
--
作者：
Colognato, H;Yurchenco, PD
LAMA 2突变导致严重的先天性肌营养不良症，伴有神经系统缺陷[1]。LAMAS的dy（2 J）等位基因纯合小鼠表达氨基末端结构域VI缺失的层粘连蛋白α 2亚基，为研究先天性肌营养不良的分子基础提供了动物模型[2，3]。预测结构域VI与来自层粘连蛋白β和γ链的氨基末端结构域一起沿着参与层粘连蛋白聚合[4]。在溶液聚合测定中，我们发现纯化的dy（2 J）层粘连蛋白组装不良并且形成很少的聚合物，与野生型肌层粘连蛋白相反。此外，胶原IV网络的溶解导致dy（2 J）层粘连蛋白释放到溶液中，表明骨骼肌基底膜内的层粘连蛋白聚合物是有缺陷的。除了聚合损失之外，dy（2 J）层粘连蛋白对肝素的亲和力降低。最后，用dy（2 J）缺失工程化的重组层粘连蛋白对蛋白水解更敏感，并且在结构域V和VI的连接处附近容易被切割。因此，dy（2 J）缺失选择性地破坏聚合物形成，降低对肝素的亲和力，并使结构域VI不稳定。这些是在肌营养不良层粘连蛋白中鉴定的第一个特定功能缺陷，并且这些缺陷可能导致dy（2 J）/dy（2 J）肌肉和神经中观察到的异常。
Mutations in LAMA2 cause severe congenital muscular dystrophy accompanied by nervous system defects [1]. Mice homozygous for the dy(2J) allele of LAMAS express a laminin alpha 2 subunit that has a deletion in the amino-terminal domain VI, providing an animal model for study of the molecular basis of congenital muscular dystrophy [2,3]. Domain VI is predicted to be involved in laminin polymerization, along with amino-terminal domains from laminin beta and gamma chains [4], In a solution-polymerization assay, we found that purified dy(2J) laminin assembled poorly and formed little polymer, in contrast to wild-type muscle laminin. Furthermore, dissolution of the collagen IV network caused dy(2J) laminin to be released into solution, indicating that laminin polymers within the skeletal muscle basement membrane were defective, In addition to loss of polymerization, dy(2J) laminin had a reduced affinity for heparin. Finally, recombinant laminin engineered with the dy(2J) deletion was more sensitive to proteolysis and was readily cleaved near the junction of domains V and VI. Thus, the dy(2J) deletion selectively disrupts polymer formation, reduces affinity for heparin, and destabilizes domain VI. These are the first specific functional defects to be identified in a muscular dystrophy laminin, and it is likely that these defects contribute to the abnormalities seen in dy(2J)/dy(2J) muscle and nerve.