Kim Y Y, Lim C S, Song Y H, Ahnn J, Park D, Song W K
Department of Life Science, Kwangju Institute of Science and Technology, Kwangsangu Sangamdong, Korea.
Cell Adhes Commun. 1999;7(2):85-97. doi: 10.3109/15419069909034393.
The cellular localization of alpha3beta1 integrin isoforms was examined in cultured neonatal myocytes at selected times during development using double immunofluorescence assays. The distribution of alpha3A subunits began as diffuse and patternless, but as the cells matured, the distribution assumed a sarcomeric banding pattern, and alpha3A appeared to be localized in costameres - sarcolemmal regions adjacent to the Z-disks. Alpha-actinin, a component of the Z-disk, was localized in the same intracellular regions. Temporal analysis of the incorporation of the alpha3A subunit and other myofibrillar proteins into sarcomeres revealed that alpha3A was integrated into sarcomeres following incorporation of alpha-actinin and myosin heavy chain (MHC) but prior to that of desmin. This suggests that alpha3A integrins are incorporated into a pre-existing myofibrillar structure, and it is unlikely that alpha3A integrins participate in the initial assembly of myofibrillar proteins. The alpha3B, beta1A and beta1D subunits were also localized in costameres, where they formed alpha3Abeta1A, alpha3Abeta1D and alpha3Bbeta1A heterodimers. The alpha3Bbeta1D heterodimer, however, was not found in cardiac myocytes. The antisera raised against the cytoplasmic domains of alpha3A, alpha3B, beta1A and beta1D caused disruption of sarcomere structure. Thus, the myofibril-extracellular matrix linkages mediated by isoforms of alpha3beta1 integrin may play a crucial role in the stabilization of myofibril assembly and in the maintenance of sarcomere structure. Co-immunoprecipitation experiments revealed that beta1A, but not beta1D, interacts with the Nck signaling protein, suggesting that Nck participates in downstream signaling triggered by beta1A and that the beta1A-mediated signaling pathway is distinct from that of beta1D.
在发育过程中的选定时间，利用双重免疫荧光测定法检测培养的新生心肌细胞中α3β1整合素亚型的细胞定位。α3A亚基的分布最初是弥散且无规律的，但随着细胞成熟，其分布呈现出肌节带状模式，并且α3A似乎定位于肌小节 - 与Z盘相邻的肌膜区域。α - 辅肌动蛋白是Z盘的一个组成部分，定位于相同的细胞内区域。对α3A亚基和其他肌原纤维蛋白掺入肌节的时间分析表明，α3A在α - 辅肌动蛋白和肌球蛋白重链（MHC）掺入之后但在结蛋白掺入之前整合到肌节中。这表明α3A整合素被掺入到预先存在的肌原纤维结构中，并且α3A整合素不太可能参与肌原纤维蛋白的初始组装。α3B、β1A和β1D亚基也定位于肌小节，在那里它们形成α3Aβ1A、α3Aβ1D和α3Bβ1A异二聚体。然而，α3Bβ1D异二聚体在心肌细胞中未被发现。针对α3A、α3B、β1A和β1D的细胞质结构域产生的抗血清导致肌节结构破坏。因此，由α3β1整合素亚型介导的肌原纤维 - 细胞外基质连接可能在肌原纤维组装的稳定和肌节结构的维持中起关键作用。免疫共沉淀实验表明，β1A而非β1D与Nck信号蛋白相互作用，这表明Nck参与由β1A触发的下游信号传导，并且β1A介导的信号通路与β1D的不同。
