Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia Research Institute, Philadelphia, PA, USA.
Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
Sci Signal. 2018 Dec 11;11(560):eaat3178. doi: 10.1126/scisignal.aat3178.
T cell entry into inflamed tissue involves firm adhesion, spreading, and migration of the T cells across endothelial barriers. These events depend on "outside-in" signals through which engaged integrins direct cytoskeletal reorganization. We investigated the molecular events that mediate this process and found that T cells from mice lacking expression of the adaptor protein Crk exhibited defects in phenotypes induced by the integrin lymphocyte function-associated antigen 1 (LFA-1), namely, actin polymerization, leading edge formation, and two-dimensional cell migration. Crk protein was an essential mediator of LFA-1 signaling-induced phosphorylation of the E3 ubiquitin ligase c-Cbl and its subsequent interaction with the phosphatidylinositol 3-kinase (PI3K) subunit p85, thus promoting PI3K activity and cytoskeletal remodeling. In addition, we found that Crk proteins were required for T cells to respond to changes in substrate stiffness, as measured by alterations in cell spreading and differential phosphorylation of the force-sensitive protein CasL. These findings identify Crk proteins as key intermediates coupling LFA-1 signals to actin remodeling and provide mechanistic insights into how T cells sense and respond to substrate stiffness.
T 细胞进入炎症组织涉及 T 细胞与内皮屏障牢固黏附、铺展和迁移。这些事件依赖于“外向内”信号，通过这些信号，整合素引导细胞骨架重组。我们研究了介导这一过程的分子事件，发现缺乏衔接蛋白 Crk 表达的小鼠 T 细胞在整合素淋巴细胞功能相关抗原 1（LFA-1）诱导的表型中表现出缺陷，即肌动蛋白聚合、前缘形成和二维细胞迁移。Crk 蛋白是 LFA-1 信号诱导的 E3 泛素连接酶 c-Cbl 磷酸化及其随后与磷脂酰肌醇 3-激酶（PI3K）亚基 p85 相互作用的必需介质，从而促进 PI3K 活性和细胞骨架重塑。此外，我们发现 Crk 蛋白对于 T 细胞响应底物刚度的变化是必需的，这可以通过细胞铺展的变化和力敏感蛋白 CasL 的差异磷酸化来衡量。这些发现将 Crk 蛋白鉴定为将 LFA-1 信号偶联到肌动蛋白重塑的关键中介，并提供了关于 T 细胞如何感知和响应底物刚度的机制见解。
