title: Direct regulation of gonadotropin release by neurokinin B in tilapia (Oreochromis niloticus).
abstract: Neurokinin B (NKB) was recently identified as a key regulator of reproduction in mammals and fish. Fish were found to possess a specific novel neurokinin termed NKF. To study the role of NKB/NKF in the regulation of fish reproduction and to investigate the role of NKB/NKF and their receptors in the piscine pituitary, we have identified the NKB/tachikinin 3 receptor (tac3r) system in tilapia. Bioinformatics and phylogenetic analyses have demonstrated that the tilapia holds 1 putative tac3 gene and 2 NKB receptor genes (tac3ra and tac3rb) that clustered with other piscine Tac3 and NKB receptor lineages. Furthermore, we found that in African cichlids, NKB peptides differ from other vertebrate NKBs in their C-terminal sequence, possessing isoleucine instead of valine as the X in the NKB FXGLM-NH2-terminal consensus sequence. Signal transduction analysis demonstrated that tilapia NKB (tiNKB), tiNKF, and human NKB activated both CRE-luc and SRE-luc transcriptional activity of both tilapia and human NKB receptors. Two hours after ip injection of tiNKB, the plasma levels of both FSH and LH were increased, whereas tiNKF was more effective in increasing LH levels. However, tiNKB was more effective than tiNKF in increasing both FSH and LH from tilapia pituitary dispersed cells. Using in situ hybridization and fluorescent immunohistochemistry, we have shown that LH cells possess tac3, tac3ra, and tac3rb mRNAs, whereas FSH cells possess mainly tac3rb and tac3ra and tac3 to a much lesser extent. These results suggest that the members of the NKB/tac3r system may serve as paracrine/autocrine regulators of gonadotropin release in fish pituitary.
authors.affiliation: Department of Animal Sciences (J.B., M.G., N.M., B.L.-S.), The Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel; and Brain Research Institute (S.O., I.S.P.), Monash University Sunway Campus, Jalan Lagoon Selatan, Bandar Sunway, Selangor 46150, Malaysia.
authors.forename: Jakob
authors.initials: J
authors.lastname: Biran
authors.forename: Matan
authors.initials: M
authors.lastname: Golan
authors.forename: Naama
authors.initials: N
authors.lastname: Mizrahi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ogawa
authors.forename: Ishwar S
authors.initials: IS
authors.lastname: Parhar
authors.forename: Berta
authors.initials: B
authors.lastname: Levavi-Sivan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005260:Female; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D015287:Neurokinin B / Q000378:metabolism*; D010902:Pituitary Gland / Q000378:metabolism*; D018039:Receptors, Tachykinin / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D015398:Signal Transduction; D017210:Tilapia
chemical_list: D029941:Fish Proteins; D018039:Receptors, Tachykinin; D015287:Neurokinin B; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone