The scaffold protein CasL regulates T cell migration by restricting membrane blebbing

T cell migration into inflamed tissue is a key control point in the inflammatory response and relies on integrin interactions with their endothelial ligands. Here, we identify the signaling scaffold CasL (Hef1, NEDD9) as a central regulator of integrin-dependent migration in primary T cells. We found CasL is specifically needed for efficient migration on ICAM-1, but not VCAM-1 coated surfaces. While WT T cells migrating on ICAM-1 form an actin-rich cell front and move smoothly, T cells lacking CasL instead form numerous, aberrant membrane blebs. The abnormal blebbing observed in CasL KO T cells likely stems from diminished F-actin in the cell front coupled with increased contractile forces behind the nucleus, suggesting CasL regulates the cytoskeletal architecture in migrating T cells. Importantly, using an in vivo allogeneic hematopoietic transplant model we found that CasL promotes T cell migration into inflamed peripheral tissue, but was dispensable for trafficking to secondary lymphoid organs. Together, these results indicate CasL functions to control the balance of cytoskeletal components during integrin-dependent migration and highlight the importance of integrin signaling for proper migration into inflamed tissue.