title: Goldfish spexin: solution structure and novel function as a satiety factor in feeding control.
abstract: Spexin (SPX) is a neuropeptide identified recently by bioinformatic approach. At present not much is known about its biological actions, and comparative studies of SPX in nonmammalian species are still lacking. To examine the structure and function of SPX in fish model, SPX was cloned in goldfish and found to be highly comparable with its mammalian counterparts. As revealed by NMR spectroscopies, goldfish SPX is composed of an α-helix from Gln(5) to Gln(14) with a flexible NH2 terminus from Asn(1) to Pro(4), and its molecular surface is largely hydrophobic except for Lys(11) as the only charged residue in the helical region. In goldfish, SPX transcripts were found to be widely expressed in various tissues, and protein expression of SPX was also detected in the brain. In vivo feeding studies revealed that SPX mRNA levels in the telencephalon, optic tectum, and hypothalamus of goldfish brain could be elevated by food intake. However, brain injection of goldfish SPX inhibited both basal and NPY- or orexin-induced feeding behavior and food consumption. Similar treatment also reduced transcript expression of NPY, AgRP, and apelin, with concurrent rises in CCK, CART, POMC, MCH, and CRH mRNA levels in different brain areas examined. The differential effects of SPX treatment on NPY, CCK, and MCH transcript expression could also be noted in vitro in goldfish brain cell culture. Our studies for the first time unveil the solution structure of SPX and its novel function as a satiety factor through differential modulation of central orexigenic and anorexigenic signals.
authors.affiliation: School of Biological Sciences, University of Hong Kong, Hong Kong, China.
authors.forename: Matthew K H
authors.initials: MK
authors.lastname: Wong
authors.forename: Kong Hung
authors.initials: KH
authors.lastname: Sze
authors.forename: Ting
authors.initials: T
authors.lastname: Chen
authors.forename: Chi Kong
authors.initials: CK
authors.lastname: Cho
authors.forename: Henry C H
authors.initials: HC
authors.lastname: Law
authors.forename: Ivan K
authors.initials: IK
authors.lastname: Chu
authors.forename: Anderson O L
authors.initials: AO
authors.lastname: Wong
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019167:Appetite Stimulants / Q000494:pharmacology; D001921:Brain / Q000166:cytology; D001923:Brain Chemistry / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D002942:Circular Dichroism; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D003627:Data Interpretation, Statistical; D004435:Eating / Q000502:physiology*; D006054:Goldfish / Q000502:physiology*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000378:metabolism / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D019518:Postprandial Period / Q000502:physiology; D012528:Satiety Response / Q000502:physiology*; D014018:Tissue Distribution
chemical_list: D019167:Appetite Stimulants; D017931:DNA Primers; D018076:DNA, Complementary; D009479:Neuropeptides
keywords: appetite control; feeding behavior; goldfish; nuclear magnetic resonance structure; spexin