Constitutive Lck Activity Drives Sensitivity Differences between CD8+ Memory T Cell Subsets

Abstract

CD8+ T cells develop increased sensitivity following antigen experience, and differences in sensitivity exist between T cell memory subsets. How differential TCR signaling between memory subsets contributes to sensitivity differences is unclear. We show in mouse effector memory T cells (TEM) that more than 50% of lymphocyte-specific protein tyrosine kinase (Lck) exists in a constitutively active conformation, compared with less than 20% in central memory T cells (TCM). Immediately proximal to Lck signaling, we observed enhanced Zap-70 phosphorylation in TEM following TCR ligation compared with TCM. Further, we observed superior cytotoxic effector function in TEM compared with TCM, and provide evidence that this results from a lower probability of TCM reaching threshold signaling due to the decreased magnitude of TCR-proximal signaling. We provide evidence that the differences in Lck constitutive 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), and use modeling of early TCR signaling to reveal the significance of these differences. We show that inhibition of Shp-1 results in increased constitutive Lck activity in TCM to levels similar to TEM, as well as increased cytotoxic effector function in TCM. 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. This work also identifies Shp-1 as a potential target to improve the cytotoxic effector functions of TCM for adoptive cell therapy applications.

Conformational states control Lck switching between free and confined diffusion modes in T cells

“…Another study, based on measurements of fluorescence resonance energy transfer (FRET) between fluorescent proteins fused to the N- and C-terminals of Lck, concluded there was no significant change in open versus closed populations of Lck even after T cell stimulation 24 . While different papers report different percentages of open Lck in pre-stimulated cells, constitutively active Lck were also found in CD8 + memory T cells and may account for the enhanced sensitivity to antigen in these cells 25 . A pool of active Lck existing prior to T cell stimulation led to the idea that rapid TCR triggering post receptor engagement may be caused by changes in Lck spatial rearrangements as opposed to, or in addition to conformational changes.…”

A Phosphosite within the SH2 Domain of Lck Regulates Its Activation by CD45

“…Moreover, using small molecule inhibitors of Csk to increase active Lck abundance strikingly sensitizes the TCR to less abundant and lower affinity antigens (Manz et al, 2015). CD8 + T cell subsets also appear to differ in their amounts of active Lck and capacity to signal through the TCR (Moogk et al, 2016). These observations together indicate that the amount of active Lck in a T cell sets an important threshold for TCR signaling.…”

A evolução do diagnóstico da doença mista do tecido conjuntivo

“…A proteína Tirosina Quinase (CSK) desempenha um papel importante na resposta imune. Resíduos de fosforilização de tirosina estão localizados na proteína Tirosina Quinase específica para Linfócitos, p56 (LCK) resultando em uma interação que resulta na inibição de uma destas duas proteínas 29 . Foi observado que as proteínas CSK e LCK podem estar ligadas, devido a relação entre estas proteínas.…”