Intercellular adhesion molecule 2 regulates diapedesis hotspots by allowing neutrophil crawling against the direction of flow.

Intercellular adhesion molecules (ICAMs) are cell surface proteins that play a crucial role in the body's immune response and inflammatory processes. ICAM1 and ICAM2 are two ICAM family members expressed on the surface of various cell types, including endothelial cells. They mediate the interaction between immune cells and endothelial cells, which are critical for the trafficking of leukocytes across the blood vessel wall during inflammation. Although ICAM1 plays a prominent role in the leukocyte extravasation cascade, it is less clear if ICAM2 strengthens ICAM1 function or has a separate function in the cascade. With CRISPR-)Cas9 technology, endothelial cells were depleted for ICAM1,ICAM2, or both, and we found that neutrophils favored ICAM1 over ICAM2 to adhere to. However, the absence of only ICAM2 resulted in neutrophils that were unable to find the transmigration hotspot, i.e. the preferred exit site. Moreover, we found that ICAM2 deficiency prevented neutrophils to migrate against the flow. Due to this deficiency, we concluded that ICAM2 helps neutrophils find the preferred exit sites and thereby contributes to efficient leukocyte extravasation.

A junctional PACSIN2/EHD4/MICAL-L1 complex coordinates VE-cadherin trafficking for endothelial migration and angiogenesis.

Angiogenic sprouting relies on collective migration and coordinated rearrangements of endothelial leader and follower cells. VE-cadherin-based adherens junctions have emerged as key cell-cell contacts that transmit forces between cells and trigger signals during collective cell migration in angiogenesis. However, the underlying molecular mechanisms that govern these processes and their functional importance for vascular development still remain unknown. We previously showed that the F-BAR protein PACSIN2 is recruited to tensile asymmetric adherens junctions between leader and follower cells. Here we report that PACSIN2 mediates the formation of endothelial sprouts during angiogenesis by coordinating collective migration. We show that PACSIN2 recruits the trafficking regulators EHD4 and MICAL-L1 to the rear end of asymmetric adherens junctions to form a recycling endosome-like tubular structure. The junctional PACSIN2/EHD4/MICAL-L1 complex controls local VE-cadherin trafficking and thereby coordinates polarized endothelial migration and angiogenesis. Our findings reveal a molecular event at force-dependent asymmetric adherens junctions that occurs during the tug-of-war between endothelial leader and follower cells, and allows for junction-based guidance during collective migration in angiogenesis.