DNA-PKcs phosphorylates LAT impacting its localization to the immune synapse and downstream signaling in CD4+ and CD8+ T cells 2409

Abstract Description Formation of the immune synapse (IS) at the interface between the T cell receptor and antigen-presenting cell is pivotal for early T cell activation. One critical event in this process is recruitment of the scaffolding protein Linker for Activation of T cells (LAT). Once at the IS, multiple LAT tyrosines are phosphorylated allowing it to serve as a scaffold for binding of signaling molecules forming the “LAT signalosome” and further driving TCR signal transduction. Here, we provide evidence that the kinase, DNA dependent protein kinase catalytic subunit (DNA-PKcs), impacts LAT IS localization and activity. We show that upon T cell activation, DNA-PKcs physically interacts with LAT and can be found localized to the IS. Inhibition of DNA-PKcs activity diminishes LAT IS localization. Additionally, we identified two serines within LAT that are phosphorylated by DNA-PKcs, S224 and S241, following T cell activation. Phosphorylation of these serines is required for LAT tyrosine phosphorylation, binding of signaling proteins, and IL2 production. Using a unique transgenic mouse model designed to delete DNA-PKcs expression specifically within mature CD4+ or CD8+ T cells, we show that loss of DNA-PKcs expression results in dysfunctional T cells unable to control tumor growth or induce rejection of allogeneic skin grafts. These data bring to the forefront DNA-PKcs as a decisive protein in T cell activation. Funding Sources NIH/NIAID 1R21AI173759-01A1 Topic Categories Immune Response Regulation: Molecular Mechanisms (IRM)