Departments of Biochemistry & Molecular Biophysics and Cell Biology & Physiology, Washington University, St. Louis, MO 63110.
Mol Biol Cell. 2018 Jul 15;29(13):1693-1703. doi: 10.1091/mbc.E18-02-0136. Epub 2018 May 17.
Junctional integrity of endothelial monolayers is crucial to control movement of molecules and cells across the endothelium. Examining the structure and dynamics of cell junctions in endothelial monolayers, we discovered a role for septins. Contacts between adjacent endothelial cells were dynamic, with protrusions extending above or below neighboring cells. Vascular endothelial cadherin (VE-cadherin) was present at cell junctions, with a membrane-associated layer of F-actin. Septins localized at cell-junction membranes, in patterns distinct from VE-cadherin and F-actin. Septins assumed curved and scallop-shaped patterns at junctions, especially in regions of positive membrane curvature associated with actin-rich membrane protrusions. Depletion of septins led to disrupted morphology of VE-cadherin junctions and increased expression of VE-cadherin. In videos, septin-depleted cells displayed remodeling at cell junctions; regions with VE-cadherin were broader, and areas with membrane ruffling were wider. Septin depletion and junction disruption led to functional loss of junctional integrity, revealed by decreased transendothelial electric resistance and increased transmigration of immune cells. We conclude that septins, as cytoskeletal elements associated with the plasma membrane, are important for cell junctions and junctional integrity of endothelial monolayers, functioning at regions of positive curvature in support of actin-rich protrusions to promote cadherin-based cell junctions.
内皮细胞单层的连接完整性对于控制分子和细胞穿过内皮的运动至关重要。在研究内皮细胞单层中细胞连接的结构和动态时，我们发现了 septin 的作用。相邻内皮细胞之间的接触是动态的，突起延伸到相邻细胞的上方或下方。血管内皮钙黏蛋白 (VE-cadherin) 存在于细胞连接处，有一层与膜相关的 F-肌动蛋白。septin 定位于细胞连接的膜上，其模式与 VE-cadherin 和 F-actin 不同。septin 在连接处呈弯曲和扇贝状模式，特别是在与富含肌动蛋白的膜突起相关的正膜曲率区域。septin 的耗竭导致 VE-cadherin 连接的形态破坏和 VE-cadherin 的表达增加。在视频中，septin 耗竭的细胞在细胞连接处发生重塑；具有 VE-cadherin 的区域变宽，膜皱襞的区域变宽。septin 耗竭和连接破坏导致连接完整性的功能丧失，表现为跨内皮电阻降低和免疫细胞的迁移增加。我们的结论是，作为与质膜相关的细胞骨架成分，septin 对于内皮细胞单层的细胞连接和连接完整性很重要，在支持富含肌动蛋白的突起的正曲率区域发挥作用，以促进基于钙黏蛋白的细胞连接。
