The IGFBP7 homolog Imp-L2 promotes insulin signaling in distinct neurons of the Drosophila brain

Abstract

In Drosophila, the Insulin-like peptide 2 (Dilp-2) is expressed by insulin producing cells (IPCs) in the brain from which it is secreted into the hemolymph to activate insulin signaling (IIS) systemically. Within the brain, however, a more local activation of IIS may be required to couple behavioral and physiological traits to nutritional inputs. We show that a small subset of neurons in the larval brain possesses high Dilp-2 mediated IIS activity. This local IIS activation is accompanied by selective Dilp-2 uptake and depends on the expression of the Imaginal morphogenesis protein-Late 2 (Imp-L2) in the target neurons. We suggest that Imp-L2 acts as a licensing factor for neuronal IIS activation via Dilp-2 to further increase the precision of insulin activity in the brain.