Schaefer Antje, van Duijn Trynette J, Majolee Jisca, Burridge Keith, Hordijk Peter L
Department of Molecular Cell Biology, Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, Amsterdam 1066CX, the Netherlands;
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.
J Immunol. 2017 Jun 15;198(12):4823-4836. doi: 10.4049/jimmunol.1601987. Epub 2017 May 8.
Inflammation is driven by excessive transmigration (diapedesis) of leukocytes from the blood to the tissue across the endothelial cell monolayer that lines blood vessels. Leukocyte adhesion, crawling, and transmigration are regulated by clustering of the endothelial mechanosensitive receptor intercellular adhesion molecule-1 (ICAM-1). Whereas several proteins are known to promote ICAM-1 function, the molecular mechanisms that limit ICAM-1-mediated adhesion to prevent excessive leukocyte transmigration remain unknown. We identify the endothelial actin-binding protein CD2-associated protein (CD2AP) as a novel interaction partner of ICAM-1. Loss of CD2AP stimulates the dynamics of ICAM-1 clustering, which facilitates the formation of ICAM-1 complexes on the endothelial cell surface. Consequently, neutrophil adhesion is increased, but crawling is decreased. In turn, this promotes the neutrophil preference for the transcellular over the paracellular transmigration route. Mechanistically, CD2AP is required for mechanosensitive ICAM-1 downstream signaling toward activation of the PI3K, and recruitment of F-actin and of the actin-branching protein cortactin. Moreover, CD2AP is necessary for ICAM-1-induced Rac1 recruitment and activation. Mechanical force applied on ICAM-1 impairs CD2AP binding to ICAM-1, suggesting that a tension-induced negative feedback loop promotes ICAM-1-mediated neutrophil crawling and paracellular transmigration. To our knowledge, these data show for the first time that the mechanoreceptor ICAM-1 is negatively regulated by an actin-binding adaptor protein, i.e., CD2AP, to allow a balanced and spatiotemporal control of its adhesive function. CD2AP is important in kidney dysfunction that is accompanied by inflammation. Our findings provide a mechanistic basis for the role of CD2AP in inflamed vessels, identifying this adaptor protein as a potential therapeutic target.
炎症是由白细胞从血液中通过血管内衬的内皮细胞单层过度迁移（渗出）至组织所驱动的。白细胞的黏附、爬行和迁移受内皮机械敏感受体细胞间黏附分子-1（ICAM-1）的聚集调节。虽然已知几种蛋白质可促进ICAM-1的功能，但限制ICAM-1介导的黏附以防止白细胞过度迁移的分子机制仍不清楚。我们确定内皮肌动蛋白结合蛋白CD2相关蛋白（CD2AP）是ICAM-1的一种新型相互作用伴侣。CD2AP的缺失会刺激ICAM-1聚集的动态变化，这有助于在内皮细胞表面形成ICAM-1复合物。因此，中性粒细胞的黏附增加，但爬行减少。反过来，这促进了中性粒细胞对跨细胞而非旁细胞迁移途径的偏好。从机制上讲，CD2AP是机械敏感的ICAM-1下游信号传导至PI3K激活、F-肌动蛋白和肌动蛋白分支蛋白皮层肌动蛋白募集所必需的。此外，CD2AP是ICAM-1诱导的Rac1募集和激活所必需的。施加在ICAM-1上的机械力会损害CD2AP与ICAM-1的结合，这表明张力诱导的负反馈环促进了ICAM-1介导的中性粒细胞爬行和旁细胞迁移。据我们所知，这些数据首次表明机械感受器ICAM-1受肌动蛋白结合衔接蛋白即CD2AP的负调控，以实现对其黏附功能的平衡和时空控制。CD2AP在伴有炎症的肾功能障碍中很重要。我们的发现为CD2AP在炎症血管中的作用提供了机制基础，确定这种衔接蛋白为潜在的治疗靶点。
