Comparative genomics of leucine-rich repeats containing G protein-coupled receptors and their ligands.

Leucine-rich repeats containing G protein-coupled receptors (LGRs) constitute a unique cluster of transmembrane proteins sharing a large leucine-rich extracellular domain for hormone binding. In mammals, LGRs steer important developmental, metabolic and reproductive processes as receptors for glycoprotein hormones and insulin/relaxin-related proteins. In insects, a receptor structurally related to human LGRs mediates the activity of the neurohormone bursicon thereby regulating wing expansion behaviour and remodelling of the newly synthesized exoskeleton. In the past decade, novel insights into the molecular evolution of LGR encoding genes accumulated rapidly due to comparative genome analyses indicating that the endocrine LGR signalling system likely emerged before the radiation of metazoan phyla and expanded throughout evolution. Here, we present a short survey on the evolution of LGRs and the hormones they interact with.