Tsujioka Masatsune, Yoshida Kunito, Nagasaki Akira, Yonemura Shigenobu, Müller-Taubenberger Annette, Uyeda Taro Q P
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 4, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562, Japan.
Eukaryot Cell. 2008 May;7(5):906-16. doi: 10.1128/EC.00464-07. Epub 2008 Mar 28.
Talin is a cytoskeletal protein involved in constructing and regulating focal adhesions in animal cells. The cellular slime mold Dictyostelium discoideum has two talin homologues, talA and talB, and earlier studies have characterized the single knockout mutants. talA(-) cells show reduced adhesion to the substrates and slightly impaired cytokinesis leading to a high proportion of multinucleated cells in the vegetative stage, while the development is normal. In contrast, talB(-) cells are characterized by reduced motility in the developmental stage, and they are arrested at the tight-mound stage. Here, we created and analyzed a double mutant with a disruption of both talA and talB. Defects in adhesion to the substrates, cytokinesis, and development were more severe in cells with a disruption of both talA and talB. The talA(-) talB(-) cells failed to attach to the substrates in the vegetative stage, exhibited a higher proportion of multinucleated cells than talA(-) cells, and showed more-reduced motility during the development and an earlier developmental arrest than talB(-) cells at the loose-mound stage. Moreover, overexpression of either talA or talB compensated for the loss of the other talin, respectively. The analysis of talA(-) talB(-) cells also revealed that talin was required for the formation of paxillin-rich adhesion sites and that there was another adhesion mechanism which is independent of talin in the developmental stage. This is the first study demonstrating overlapping functions of two talin homologues, and our data further indicate the importance of talin.
踝蛋白是一种细胞骨架蛋白，参与动物细胞中粘着斑的构建和调节。细胞黏菌盘基网柄菌有两种踝蛋白同源物，talA和talB，早期研究已对单基因敲除突变体进行了表征。talA(-)细胞对底物的粘附能力降低，胞质分裂略有受损，导致营养阶段多核细胞比例较高，而发育正常。相比之下，talB(-)细胞的特征是在发育阶段运动能力降低，并停滞在紧密丘阶段。在这里，我们创建并分析了一个talA和talB均缺失的双突变体。在talA和talB均缺失的细胞中，对底物的粘附、胞质分裂和发育缺陷更为严重。talA(-) talB(-)细胞在营养阶段无法附着于底物，多核细胞比例高于talA(-)细胞，在发育过程中运动能力下降更明显，并且比talB(-)细胞在松散丘阶段更早地停止发育。此外，talA或talB的过表达分别补偿了另一种踝蛋白的缺失。对talA(-) talB(-)细胞的分析还表明，踝蛋白是富含桩蛋白的粘附位点形成所必需的，并且在发育阶段存在另一种独立于踝蛋白的粘附机制。这是第一项证明两种踝蛋白同源物具有重叠功能的研究，我们的数据进一步表明了踝蛋白的重要性。
