1725-P: Viral Insulins as Agonists and Antagonists on Insulin/IGF-1 Receptors

Abstract

Recently, we identified four insulin/IGF-1 like peptides (VILPs) in the sequence of viruses belonging to the Iridoviridae family. These VILPs show up to 50% homology with the sequence of the human insulin/IGF-1. Moreover, the predicted tertiary structures and major receptor binding residues are conserved between the VILPs and insulin/IGF-1. Although these viruses are known to infect primarily fish, sequences of VILPs have been found in human blood and feces. VILPs can interact with the human and murine insulin and IGF-1 receptors and induce the activation of their downstream signaling. Functionally, VILPs are able to induce glucose uptake and cell proliferation. VILPs can be synthesized as a single-chain (SC) or double-chain (DC) peptides, i.e., more IGF-1 like or more insulin like structures. In the present study, we show that SC and DC forms of lymphocystis disease virus (LCDV-1) VILP interact differently with the human insulin and IGF-1 receptor. Competition binding assay reveals that SC is more potent than DC in binding to the IGF-1 receptor. In vivo, following i.p. injection in mice both LCDV-1 SC and DC produced similar mild decreases in blood glucose compared to insulin, even at a 166-fold excess. In vitro, however, DC LCDV1-VILP acts as a weak agonist to stimulation of IGF1R, whereas SC LCDV-VILP serves as a strong antagonism effect on the IGF-1 receptor. Thus, the activation of the IGF1R by IGF-1 is strongly repressed by the SC LCDV-1 VILP, even at equal concentrations. This antagonistic action of SC VILP is restricted to the IGF1R and does not affect insulin receptor. As a functional consequence of IGF1R blockade, SC LCDV-1 VILP inhibits IGF-1 stimulated migration of a cervical cancer cell line. In summary, we have shown that SC VILP may provide a novel inhibitor of IGF1R signaling and IGF-1 action on tumor cell migration, with minimal effects on glucose metabolism, thus providing a potentially unique reagent for treatment of IGF-1 sensitive tumors. Disclosure F. Moreau: None. B. Brandao: None. C. Cederquist: None. T.M. Batista: None. R. DiMarchi: Employee; Self; Novo Nordisk Inc. E. Altindis: None. C. Kahn: Advisory Panel; Self; ERX Pharmaceuticals, Kaleido Biosciences. Consultant; Self; AntriaBio, Flagship Pioneering, Sana-Cobalt.