Interaction Between Lck Kinase And Vav1 In The Initial Adhesion Of Leukocytes

Leukocyte recruitment from the bloodstream to a site of inflammation entails a cascade of cellular adhesive events, including tethering, rolling, adhesion and transmigration. L-selectin constitutively expresses on the top of microvilli and appears to be the first receptor for the early kinetics of leukocyte-endothelial cell interaction. Besides, L-selectin contributes in leukocyte adhesion through its signaling properties. L-selectin engagement with antibody cross-linking could trigger actin cytoskeleton rearrangement, cell shape change, superoxide generation, increased gene expression of cytokine TNF-αand IL-8, and so on. But in initial adhesion of leukocytes, we still do not know what role L-selectin plays in actin cytoskeleton rearrangement.Lck kinase is a member of the Src family of non-receptor protein tyrosine kinases, which is expressed primarily in T lymphocytes and plays an important role in T cell activation and development. Lck contains an N-terminal membrane-targeting domain, a unique region, single Src SH3 and SH2 domains, and a tyrosine kinase domain followed by a C-terminal-negative regulatory domain. In our previous study, we have demonstrated that Lck was the first kinase activated in L-selectin signaling.Vav1 is a 95-kD protein expressed in all hemopoietic cells and it is activated following tyrosine phosphorylation.Vav1 acts as the guanine nucleotide exchange factor(GEF)for Rho-family GTPases and can mediate several cytoskeletal-associated cellular processes. Vav1 contains a proline-rich(PR) domain and an array of SH3, SH2 and SH3 domains, suggesting that Vav1 may have adapter functions.In this study, we focus on the function of Lck kinase and Vav1 in actin cytoskeleton rearrangement induced by L-selectin ligation. Our results demonstrated that Lck kinase could interact with Vav1 after the cross-linking of L-selectin in Jurkat T cells, and they were phosphorylated induced by L-selectin engagement. And then, we find that Lck can associate with Vav1 through its SH2 and SH3 domains. Finally, we suggested SH2 and both of SH3 domains in Vav1 could interact with Lck kinase. These results indicate that Lck kinase and Vav1 are all key signal transducers downstream of the L-selectin.