Fig 9.

Model for Atf3 function in maintaining basal metabolic and immune system homeostasis in Drosophila larvae. Atf3 ensures the normal digestive and immune function of the gut by controlling appropriate expression of genes involved in PM composition. At the same time, Atf3 prevents the epithelial immune system from overreacting, at least partly through regulating Relish. Loss of Atf3 function causes chronic inflammation accompanied by stress and starvation responses that are mediated by JNK and FOXO signaling. Elevated activity of lipases in the gut may cause imbalance in nutrient utilization. The fat body takes up superfluous DAG and FFA and stores extra fat. An increase in the gut microbiota may further exacerbate defects in digestion, nutrient absorption, and immune system activity.