Fish insulin, IGF-I and IGF-II receptors: A phylogenetic approach

Abstract

SYNOPSIS. In fish, the structural and functional characteristics of insulin and IGFI receptors have been well studied. Current evidence indicates that all gnatostome animals, from fish to mammals, contain separate insulin and IGF-I molecules and specific receptors for insulin and IGF-I. However, qualitative differences in the functional aspects of insulin and IGF-I receptors among vertebrate species can account for variations in the biological activity of insulin and IGF-I. In this paper we will focus on the functional evolution of the insulin and IGF-I receptors in vertebrates and on the appearance of the unrelated IGF-II receptors.