Purification, cDNA cloning, and characterization of ghrelin in channel catfish, Ictalurus punctatus.
The ghrelin peptide and cDNA encoding precursor protein were isolated from the stomach of a channel catfish, Ictalurus punctatus. Catfish ghrelin is a 22-amino acid peptide with a sequence of GSSFLSPTQKPQNRGDRKPPRV. The third serine residue has been modified by n-decanoic acid and unsaturated fatty acids; however, an octanoylated form could not be identified. The carboxyl end of the peptide possessed an amide structure. A Gly-extended, non-amidated 23-amino acid ghrelin (ghrelin-Gly) was also isolated. Real-time quantitative PCR analysis revealed high levels of gene expression in the stomach and moderate levels in the pancreas and gall bladder. Intraperitoneal (IP) injection of ghrelin increased plasma GH levels in the catfish, but the effect of ghrelin-Gly was more potent than that of amidated ghrelin. Furthermore, IP injection with both amidated ghrelin and ghrelin-Gly caused a significant increase in pituitary GH mRNA expression over a 3-h period. These results indicate that ghrelin is present in catfish and stimulates GH gene expression and GH release in channel catfish.
Kaiya
Hiroyuki
H
Department of Biochemistry, National Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka 565-8565, Japan. kaiya@ri.ncvc.go.jp
Small
Brian C
BC
Bilodeau
A Lelania
AL
Shepherd
Brian S
BS
Kojima
Masayasu
M
Hosoda
Hiroshi
H
Kangawa
Kenji
K
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D020869:Gene Expression Profiling; D054439:Ghrelin; D013006:Growth Hormone / Q000378:metabolism; D007059:Ictaluridae / Q000502:physiology*; D008969:Molecular Sequence Data; D036361:Peptide Hormones / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification* / Q000502:physiology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D014018:Tissue Distribution
D018076:DNA, Complementary; D054439:Ghrelin; D036361:Peptide Hormones; D012333:RNA, Messenger; D013006:Growth Hormone