Natural killer cell receptor signaling and activation depend on cell cycle stages.

Natural Killer (NK) cells are lymphocytes of the innate immunity and provide key protection against infection and cancer. NK cells express a wide array of inhibitory and activating receptors on the cell surface including the activating receptor NKG2D. Receptor signaling in NK cells leads to rapid post-translational modification (e.g., phosphorylation) of sub-cellular signaling proteins within minutes of receptor stimulation that ultimately give rise to diverse effector functions including cell proliferation. Recent single-cell mass cytometry (i.e., CyTOF) experiments in macrophages showed variations of abundances of phosphorylated signaling proteins across cell cycle stages indicating a dependence of cell signaling kinetics on an order of magnitude slower kinetics (~ several hours) of cell cycle transitions. We investigated cell cycle dependence of NKG2D signaling kinetics in NK cells using longitudinal CyTOF measurements up to 256 minutes post stimulation performed on IL-2-treated NKG2D-stimulated primary human CD56dim NK cells. The CyTOF experiments revealed cell stage specific kinetics of signaling proteins such as pVav1, pErk, and pS6, with the degranulation marker CD107a showing its largest upregulation specifically in the G2 + M stage. We developed stochastic minimal computational models coupling signaling and cell cycle processes to investigate the effect of cell cycle transitions on NK cell receptor induced signaling kinetics. These models suggest that the observed cell stage specific NK cell receptor signaling kinetics arise due to active modulation of the receptor signaling kinetics by cell cycle progression. The framework can be extended to study the interplay between receptor signaling and cell cycle progression in other cell types.