title: Identification, expression of a glycoprotein hormone receptor homolog in the amphioxus Branchiostoma belcheri with implications for origin of vertebrate GpHRs.
abstract: Amphioxus is phylogenetically located at the most primitive position of the chordate clade. Its endocrine system has been extensively studied; however, key information about the glycoprotein hormone (GpH) and its receptor (GpHR) in the endocrine system remained to be elucidated. In this study, a GpHR homologous gene, BbGpHR-like, has been identified in the amphioxus Branchiostoma belcheri. It contains a 1377bp open reading frame that corresponds to a deduced protein of 458 amino acid residues with a predicted molecular mass of approximately 50kDa. Phylogenetic analysis shows that BbGpHR-like is located at the position between vertebrate and invertebrate, indicating amphioxus B. belcheri is in an evolutionary transitional state between vertebrate and invertebrate in the GpHR lineage. BbGpHR-like has been successfully expressed in Pichia pastoris. Western blot analysis confirmed that the receptor produced a cross-immunoreactivity with human thyrotropin receptor (TSHR), the luteinizing hormone receptor (LHR) and the follicle-stimulating hormone receptor (FSHR). In situ hybridization and immunohistochemical analyses revealed that the BbGpHR-like transcripts and proteins were strongly distributed in the ovaries, testes and/or endostyle. These findings suggest that BbGpHR-like possibly plays an ancient and fundamental role in the control of thyroid hormone synthesis and gametogenesis in chordates. Presumably, the amphioxus BbGpHR-like represents the ancestral form of the GpHR gene prior to its split to the vertebrate paralogs gonadotropin receptor and thyrotropin receptor.
authors.affiliation: Laboratory of Developmental and Evolutionary Biology, School of Life Sciences, Shandong University of Technology, Zibo 255049, PR China.
authors.forename: Juan
authors.initials: J
authors.lastname: Dong
authors.forename: Ming
authors.initials: M
authors.lastname: Xin
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.forename: Meng
authors.initials: M
authors.lastname: Zhang
authors.forename: Qiuxiang
authors.initials: Q
authors.lastname: Pang
authors.forename: Lingling
authors.initials: L
authors.lastname: Chen
authors.forename: Bosheng
authors.initials: B
authors.lastname: Zhao
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D043344:Chordata / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D011962:Receptors, FSH / Q000378:metabolism; D011974:Receptors, LH / Q000378:metabolism
chemical_list: D006023:Glycoproteins; D011962:Receptors, FSH; D011974:Receptors, LH