Figure 1.

The Kdelr1–PP1 axis is required for naïve T cell survival. In WT naïve T cells, PP1 associated with Kdelr1 exhibits optimal phosphatase activity to prevent unwanted persistence of ISR. In T-Red naïve T cells, however, Kdelr1 dysfunction results in reduced PP1 activity, leading to prolonged ISR and apoptosis. Endogenous factors that cause ISR in vivo remain unidentified.