February 15-18, 2009 Washington State Convention Center Seattle ...

C-TERMINAL MODIFICATION MEDIATES BIOLOGICAL ACTIVITY OF GHRELIN IN
CHANNEL CATFISH
Brian C. Small
USDA/ARS Catfish Genetics Research Unit
Thad Cochran National Warmwater Aquaculture Center
P.O. Box 38
Stoneville, MS 38776 USA
Brian.Small@ars.usda.gov
Ghrelin is a multifunctional peptide hormone secreted by the stomach and originally identified as the endogenous ligand for
the growth hormone secretagogue receptor (GHS-R). In vertebrates, ghrelin functions primarily as a growth hormone (GH)releasing
hormone and an appetite-stimulatory (orexigenic) hormone. Ghrelin has been isolated and partially characterized in
several mammalian and non-mammalian species, including fish. Ghrelin mature peptide has been identified in goldfish, eel,
Mozambique tilapia, Nile tilapia, rainbow trout, seabream, European sea bass, zebrafish, and channel catfish. Fish ghrelins are
typically 19-23 amino acids and exhibit GH-, prolactin (PRL)-, or luteinizing hormone (LH)-releasing activity.
Channel catfish ghrelin peptide and cDNA encoding precursor protein were isolated from the stomach of a channel catfish. In
addition to the amidated 22-amino acid ghrelin peptide, a Gly-extended, non-amidated 23-amino acid ghrelin (ghrelin-gly) was
isolated. Characterization of the two forms of channel catfish ghrelin indicates differential actions on GH-releasing activity,
receptor regulation, and tissue specificity. These results demonstrate C-terminal modification mediates biological activity in
channel catfish. Such an effect of C-terminal modification has not been previously described for any other vertebrate ghrelin.
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