First functional insulin-binding protein in invertebrates
Insulin-like growth factor (IGF) signalling that helps to regulate mammals' growth, metabolism, reproduction and longevity is well documented…
Now, however, research published in the open access journal Journal of Biology describes the genetic identification of the first functional insulin-like growth factor binding protein (IGFBP) ortholog in invertebrates.
Insulin and insulin-like growth factors (IGFs) signal through a highly conserved pathway and control growth and metabolism in both vertebrates and invertebrates. The well-studied mammalian IGF binding proteins (IGFBPs) do not, however, have obvious sequence homologs in the fruit fly Drosophila. The discovery of a functional ortholog transforms Drosophila into a powerful model system in which to explore metabolic regulation and presents a significant advance in our understanding of the mechanisms by which the actions of insulin-like peptides are regulated.
A research team led by Ernst Hafen from the Institute of Molecular Systems Biology at the ETH in Zurich, Switzerland, employed a genetic strategy to search for negative insulin/insulin-like growth factor signalling (IIS) regulators in Drosophila. The team identified a new functional insulin-binding protein that acts as an IIS antagonist. Dubbed imaginal morphogenesis protein-late 2 (Imp-L2), the new antagonist binds the Drosophila insulin-like peptide 2 (Dilp2), inhibiting its growth-promoting function. Imp-L2 not only has a role in growth regulation - it is also essential for the dampening of insulin signalling under adverse conditions.
The authors hope that better understanding of Imp-L2's role in growth control and insulin signalling in Drosophila will ultimately influence our understanding of the human ortholog IGFBP-7. This has a regulatory role in pathways that impact upon diabetes and cancer. IGFBP-7 acts as a tumour suppressor in a variety of human organs and differs in the C-terminus from the other IGFBPs.
"Since Imp-L2 and the human tumour suppressor IGFBP-7 display sequence homology in their C-terminal immunoglobulin-like domains, we suggest that their common precursor represents an ancestral insulin-binding protein," says Hafen
