Molecular cloning and pharmacological characterization of a new galanin receptor subtype

Mol Pharmacol. 1997 Sep;52(3):337-43. doi: 10.1124/mol.52.3.337.

Abstract

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.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • COS Cells / metabolism
  • Cloning, Molecular
  • Colforsin / pharmacology
  • Cyclic AMP / biosynthesis
  • DNA, Complementary / genetics
  • Galanin / metabolism
  • Galanin / pharmacology
  • Humans
  • Hypothalamus / chemistry
  • Hypothalamus / metabolism
  • Iodine Radioisotopes
  • Molecular Sequence Data
  • Polymerase Chain Reaction
  • Receptors, Galanin
  • Receptors, Gastrointestinal Hormone / classification*
  • Receptors, Gastrointestinal Hormone / genetics
  • Receptors, Gastrointestinal Hormone / metabolism*
  • Temperature
  • Transfection

Substances

  • DNA, Complementary
  • Iodine Radioisotopes
  • Receptors, Galanin
  • Receptors, Gastrointestinal Hormone
  • Colforsin
  • Galanin
  • Cyclic AMP

Associated data

  • GENBANK/Y15248