Dnase1L3 trafficking is redirected from secretion to the nucleus in lupus-prone mice

Abstract

Abstract Pediatric-onset Systemic Lupus Erythematosus (SLE) is linked to a deficiency of the endonuclease Dnase1L3. Dnase1L3 can function extracellularly as a barrier to transfection or localize to the nucleus of macrophages to cleave DNA during apoptosis, though the mechanism by which Dnase1L3 protects from pediatric-onset SLE is unknown. Two polygenic lupus murine models, MRL-lpr and NZB/W F1, bear the activity-reducing T89I mutation in Dnase1L3. Dnase1L3 T89I has an eight-fold decrease in barrier-to-transfection activity, while the endonuclease activity is only decreased two-fold compared to the wildtype, providing a tool with which to dissect Dnase1L3 trafficking in SLE. We hypothesized that Dnase1L3 T89I localizes to the nucleus, which decreases barrier-to-transfection activity and enhances SLE onset. We transfected HEK cells with wild type or T89I Dnase1L3, and determined the subcellular localization of Dnase1L3. We found that the majority of wild type Dnase1L3 is secreted from the cell, while Dnase1L3 T89I showed increased nuclear localization. Since Dnase1L3 alters inflammasome function, we tested whether inflammatory stimuli alter Dnase1L3 trafficking. LPS treatment of cells transfected with Dnase1L3 T89I reduced its nuclear localization. Altered Dnase1L3 trafficking may impair inflammasome function, since macrophages from NZB/W F1 mice secreted less IL-1β than wild type mice. Overall, the increase in nuclear localization of Dnase1L3 T89I suggests that barrier to transfection or extracellular nuclease activity may promote IL-1β release and protect against pediatric-onset SLE.