Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden.
Mol Biol Cell. 2011 Dec;22(23):4588-601. doi: 10.1091/mbc.E11-09-0754. Epub 2011 Oct 12.
Septin family proteins oligomerize through guanosine 5'-triphosphate-binding domains into core heteromers, which in turn polymerize at the cleavage furrow of dividing fungal and animal cells. Septin assemblies during the interphase of animal cells remain poorly defined and are the topic of this report. In this study, we developed protocols for visualization of authentic higher-order assemblies using tagged septins to effectively replace the endogenous gene product within septin core heteromers in human cells. Our analysis revealed that septins assemble into microtubule-supported, disk-like structures at the plasma membrane. In the absence of cell substrate adhesion, this is the predominant higher-order arrangement in interphase cells and each of the seven to eight septin family members expressed by the two analyzed cell types appears equally represented. However, studies of myeloid and lymphoid cell model systems revealed cell type-specific alterations of higher-order septin arrangements in response to substrate adhesion. Live-cell observations suggested that all higher-order septin assemblies are mutually exclusive with plasma membrane regions undergoing remodeling. The combined data point to a mechanism by which densely arranged cortical microtubules, which are typical for nonadhered spherical cells, support plasma membrane-bound, disk-like septin assemblies.
septin 家族蛋白通过鸟苷 5'-三磷酸结合结构域形成核心异源三聚体，进而在真菌和动物细胞的分裂沟处聚合。动物细胞间期的 septin 组装仍然定义不明确，这是本报告的主题。在这项研究中，我们开发了使用标记 septin 可视化真实的高级组装的方案，以有效地在人细胞的 septin 核心异源三聚体中替代内源性基因产物。我们的分析表明，septin 组装成微管支持的盘状结构在质膜上。在没有细胞基质附着的情况下，这是间期细胞中的主要高级排列，并且两种分析的细胞类型表达的七个到八个 septin 家族成员中的每一个都表现出相同的表达。然而，对髓样和淋巴样细胞模型系统的研究表明，对基质附着的反应会导致高级 septin 排列发生细胞类型特异性改变。活细胞观察表明，所有高级 septin 组装都与正在进行重塑的质膜区域相互排斥。综合数据表明了一种机制，即密集排列的皮质微管（非附着的球形细胞的典型特征）支持质膜结合的盘状 septin 组装。
