Constitutive LcK activity drives sensitivity differences between CD8+ memory T cell subsets

Abstract

Abstract CD8+ T cells develop increased sensitivity following antigen experience, and differences in sensitivity exist between T cell memory subsets. How differential T cell receptor (TCR) signaling between memory subsets contributes to sensitivity differences is unclear. We show that constitutive activity of lymphocyte-specific protein tyrosine kinase (Lck) is greater in effector memory T cells (TEM) compared with central memory T cells (TCM), leading to enhanced activation signaling, including Zeta-chain-associated protein kinase 70 (Zap-70) phosphorylation and intracellular calcium influx, and resulting in increased cytotoxic effector function in TEM. We provide evidence that the differences in Lck activity between CD8+ TCM and TEM are due to differential regulation by SH2 domain-containing phosphatase-1 (Shp-1) and C-terminal Src kinase (Csk). Together, this work demonstrates a role for constitutive Lck activity in controlling antigen sensitivity, and suggests that differential activities of TCR-proximal signaling components may contribute to establishing the divergent effector properties of TCM and TEM.