Pharmacological and functional characterization of galanin-like peptide fragments as potent galanin receptor agonists.
The hypothalamic galanin-like peptide (GALP) was isolated by its ability to activate galanin receptors. The mature porcine GALP is a 60-amino acid neuropeptide proteolytically processed from a 120-amino acid precursor protein. It contains a region identical to the N-terminal 13-amino acids of the neuropeptide galanin. Within the sequence of human GALP (1-60) a potential proteolytic cleavage site between two basic amino acids is present at position 33, which might lead to a shorter C-terminally amidated peptide. In addition, the first two amino acids could be potentially removed via the action of dipeptidase IV. Ligand binding assays using the human neuroblastoma cell line SH-SY5Y transfected with the respective galanin receptors revealed that human GALP (1-60) displayed the highest affinity for the galanin receptor subtype GalR3 (IC50 = 10 nM) followed by GalR2 (IC50 = 28 nM) and GalR1 (IC50 = 77 nM). Ligand binding assays and functional studies showed that the human GALP (3-32) fragment was at least as potent as full length GALP (1-60). Other studies have shown that shorter fragments like human GALP (1-21) and GALP (22-60) were not effective on feeding responses in mice as compared to the full length peptide. Taken together these data suggest that the putative fragment GALP (3-32) might represent the strongest mediator of biological GALP activity. Furthermore it might be a useful tool to study the affinity of GALP to galanin receptors and to search for specific GALP receptors.
Lang
Roland
R
Department of Pediatrics, Paracelsus Private Medical University Salzburg, Muellner-Hauptstrasse 48, 5020 Salzburg, Austria.
Berger
Alexandra
A
Santic
Radmila
R
Geisberger
Roland
R
Hermann
Anton
A
Herzog
Herbert
H
Kofler
Barbara
B
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D045744:Cell Line, Tumor; D019004:Galanin / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009447:Neuroblastoma; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology*; D044088:Receptors, Galanin / Q000819:agonists* / Q000378:metabolism
D010446:Peptide Fragments; D044088:Receptors, Galanin; D019004:Galanin