The amphioxus (Branchiostoma floridae) genome contains a highly diversified set of G protein-coupled receptors

Karl Jv Nordström,Helgi B Schiöth,Robert Fredriksson

doi:10.1186/1471-2148-8-9

Abstract

BackgroundG protein-coupled receptors (GPCRs) are one of the largest families of genes in mammals. Branchiostoma floridae (amphioxus) is one of the species most closely related species to vertebrates.ResultsMining and phylogenetic analysis of the amphioxus genome showed the presence of at least 664 distinct GPCRs distributed among all the main families of GPCRs; Glutamate (18), Rhodopsin (570), Adhesion (37), Frizzled (6) and Secretin (16). Surprisingly, the Adhesion GPCR repertoire in amphioxus includes receptors with many new domains not previously observed in this family. We found many Rhodopsin GPCRs from all main groups including many amine and peptide binding receptors and several previously uncharacterized expansions were also identified. This genome has however no genes coding for bitter taste receptors (TAS2), the sweet and umami (TAS1), pheromone (VR1 or VR2) or mammalian olfactory receptors.ConclusionThe amphioxus genome is remarkably rich in various GPCR subtypes while the main GPCR groups known to sense exogenous substances (such as Taste 2, mammalian olfactory, nematode chemosensory, gustatory, vomeronasal and odorant receptors) in other bilateral species are absent.

Highlights

G protein-coupled receptors (GPCRs) are one of the largest families of genes in mammals
The amphioxus genome is in general terms surprisingly rich in GPCRs, with extensive representation of receptors from all of the main mammalian GPCRs families (See Fig 1)
Amphioxus lacks many of the classical mammalian sensory receptors such as the pheromone receptors that are important for non-primate mammals and the mammalian olfactory receptors

Summary

Introduction

G protein-coupled receptors (GPCRs) are one of the largest families of genes in mammals. The superfamily of G protein-coupled receptors (GPCRs) is one of the largest families of proteins in mammals [1]. The superfamily can be divided according to the GRAFS system into five main families; Glutamate, Rhodopsin, Adhesion, Frizzled and Secretin [3]. These main families arose prior the split of nematodes from the chordate lineage. The Rhodopsin family has been very successful in evolutionary terms, representing about 60% of the GPCRs repertoire of eight bilateria species. The Rhodopsin family can be divided in four main groups (α-, β- γand δ) with 13 main branches and previous studies have shown that members within each of the four main groups seem to be found in most bilaterial species, while the representation of each of the main branches is highly variable [4,6,7,8]

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