title: Ghrelin-like peptide with fatty acid modification and O-glycosylation in the red stingray, Dasyatis akajei.
abstract: BACKGROUND
  Ghrelin (GRLN) is now known to be an appetite-stimulating and growth hormone (GH)-releasing peptide that is predominantly synthesized and secreted from the stomachs of various vertebrate species from fish to mammals. Here, we report a GRLN-like peptide (GRLN-LP) in a cartilaginous fish, the red stingray, Dasyatis akajei.
  
  
  RESULTS
  The purified peptide contains 16 amino acids (GVSFHPQPRS10TSKPSA), and the serine residue at position 3 is modified by n-octanoic acid. The modification is the characteristic of GRLN. The six N-terminal amino acid residues (GVSFHP) were identical to another elasmobranch shark GRLN-LP that was recently identified although it had low identity with other GRLN peptides. Therefore, we designated this peptide stingray GRLN-LP. Uniquely, stingray GRLN-LP was O-glycosylated with mucin-type glycan chains [N-acetyl hexosamine (HexNAc)3 hexose(Hex)2] at threonine at position 11 (Thr-11) or both serine at position 10 (Ser-10) and Thr-11. Removal of the glycan structure by O-glycanase made the in vitro activity of stingray GRLN-LP decreased when it was evaluated by the increase in intracellular Ca2+ concentrations using a rat GHS-R1a-expressing cell line, suggesting that the glycan structure plays an important role for maintaining the activity of stingray GRLN-LP.
  
  
  CONCLUSIONS
  This study reveals the structural diversity of GRLN and GRLN-LP in vertebrates.
authors.affiliation: Department of Biochemistry, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan. kaiya@ri.ncvc.go.jp
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kaiya
authors.forename: Shiho
authors.initials: S
authors.lastname: Kodama
authors.forename: Koutaro
authors.initials: K
authors.lastname: Ishiguro
authors.forename: Kouhei
authors.initials: K
authors.lastname: Matsuda
authors.forename: Minoru
authors.initials: M
authors.lastname: Uchiyama
authors.forename: Mikiya
authors.initials: M
authors.lastname: Miyazato
authors.forename: Kenji
authors.initials: K
authors.lastname: Kangawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002240:Carbohydrate Sequence; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism*; D054439:Ghrelin / Q000737:chemistry* / Q000145:classification / Q000302:isolation & purification; D006031:Glycosylation; D008969:Molecular Sequence Data; D010802:Phylogeny; D054440:Receptors, Ghrelin / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012754:Sharks / Q000378:metabolism; D012860:Skates, Fish / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D005227:Fatty Acids; D054439:Ghrelin; D054440:Receptors, Ghrelin