Galanin (2-29) (rat)

Cloning and expressional characterization of a novel galanin receptor. Identification of different pharmacophores within galanin for the three galanin receptor subtypes.[Pubmed:9405385]

J Biol Chem. 1997 Dec 19;272(51):31949-52.

Galanin, a 29-30 amino acid neuropeptide, is found in the central and peripheral nervous systems and displays several important physiological activities. The actions are believed to be mediated through distinct G protein-coupled receptors. To date, two galanin receptor subtypes have been cloned. In this report, we describe the cloning and expression of a cDNA encoding a novel galanin receptor (GalR3). The receptor has 370 amino acids and shares 36 and 54% homology with the rat GalR1 and GalR2 receptors. 125I-Porcine galanin binds the rat GalR3 receptor expressed in COS-7 cells with high affinity (Kd = 0.6 nM) and could be displaced by galanin and galanin fragments and galanin-chimeric peptides. The pharmacological profile of this novel receptor is distinct from those of GalR1 and GalR2, revealing different pharmacophores within galanin for the three galanin receptor subtypes. Northern blot analysis showed expression in heart, spleen, and testis. Unlike GalR1 and GalR2, no expression of GalR3 was detectable in the brain, suggesting that GalR3 may mediate some of the peripheral functions of galanin.

Molecular cloning and pharmacological characterization of a new galanin receptor subtype.[Pubmed:9281594]

Mol Pharmacol. 1997 Sep;52(3):337-43.

Galanin, a 29-30-amino acid neuropeptide, is widely distributed in central and peripheral systems and mediates a variety of physiological functions. Pharmacological studies have suggested the existence of multiple receptor subtypes but only the type I (GalR1) galanin receptor has been cloned. Now we report the cloning by a combination of sib selection and rapid amplification of cDNA ends of a cDNA encoding a new galanin receptor (GalR2) from rat hypothalamus. The receptor is 372 amino acids in length and shares only 40% homology with the rat GalR1 receptor. It contains seven putative transmembrane domains with the amino and carboxyl termini being least identical to GalR1. Northern blot analyses revealed a 2-kilobase pair mRNA species distributed in several tissues, suggesting a broader functional spectrum than GalR1. 125I-Labeled human galanin binding to rat GalR2 receptor expressed in COS-1 cells was saturable (Kd = 0.59 nM) and could be displaced by galanin, several galanin fragments, and chimeric peptides. The pharmacological profiles of GalR1 and GalR2 receptors were distinguishable by galanin fragment(2-29), which bound the cloned GalR2 receptor with markedly higher affinity than the GalR1 receptor. Activation of the cloned receptor by galanin led to inhibition of forskolin-stimulated intracellular cAMP production. The cloning of this new receptor subtype should provide further insights into the mechanisms by which galanin mediates its diverse physiological functions. The identification of galanin(2-29) as a receptor-specific ligand should enhance the understanding of specificity of galanin-receptor interactions.

Structural requirement for galanin action in the pancreatic beta cell line Rin m 5F.[Pubmed:2472967]

Eur J Pharmacol. 1989 Apr 12;163(1):205-7.

Galanin fragments were tested for their ability to alter forskolin-stimulated cyclic AMP production and insulin release from Rin m 5F cells. Galanin and its fragments inhibited both events with the following potencies: Gal-(1-29) greater than N-AcGal-(2-29) greater than Gal-(2-29) greater than Gal-(1-15). In contrast, Gal-(3-29), Gal-(10-29) and [Ile2]Gal were inactive. [Phe2]- and [Tyr2]Gal were moderately effective. We conclude that the N-terminal portion of galanin (in particular the aromatic amino acid in position 2) is crucial for activity.