Glucagon-like peptide-1 (GLP-1) releases thyrotropin (TSH): characterization of binding sites for GLP-1 on alpha-TSH cells

Endocrinology. 1996 Oct;137(10):4130-8. doi: 10.1210/endo.137.10.8828468.

Abstract

We have demonstrated specific binding sites for [125I]glucagon-like peptide 1 (GLP-1) on membranes from the rodent thyrotrope cell line, alpha-TSH. Specific [125I]GLP-1 binding was saturable and time dependent. Equilibrium saturation binding analysis was consistent with the presence of a single class of binding site (binding capacity, 85 +/- 7 fmol/mg protein) with a dissociation constant (Kd) of 28 +/- 13 pM. The specific GLP-1 receptor agonists, exendin-4 and exendin-3, and the antagonist, exendin-(9-39), bound to the receptor sites with high affinity (Ki = 190 +/- 70 pM; 130 +/- 50 and 1200 +/- 470 pM, respectively). Chemical cross-linking of [125I]GLP-1-receptor complexes revealed a single band of 64,300 +/- 100 Mr in alpha-TSH membranes. In addition, specific PCR studies demonstrated the presence of GLP-1 receptor messenger RNA. Binding of the peptide to alpha-TSH cell membranes resulted in increased intracellular cAMP concentrations (10 nM GLP-1, 1010 +/- 83 pmol/10(6) cells.h; control, 175 +/- 60 pmol/10(6) cells.h; P < 0.002), indicating that the receptor is linked to stimulation of adenylyl cyclase. GLP-1-mediated increases in cAMP were inhibited by exendin-(9-39) in a dose-dependent manner. Furthermore, GLP-1 stimulates basal TSH release from dispersed anterior pituitary cells in a concentration-dependent manner (100 nM GLP-1, 63 +/- 3 fmol/10(6) cells.h; control, 35 +/- 1 fmol/10(6) cells.h; P < 0.0005), but had no effect on basal PRL, GH, or LH release.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Blotting, Southern
  • Caenorhabditis elegans Proteins*
  • Cell Line
  • Cross-Linking Reagents / pharmacology
  • Cyclic AMP / biosynthesis
  • Male
  • Membrane Glycoproteins / pharmacology
  • Membrane Glycoproteins / physiology*
  • Pituitary Gland, Anterior / cytology
  • Pituitary Gland, Anterior / drug effects
  • Pituitary Gland, Anterior / metabolism*
  • Polymerase Chain Reaction
  • Rats
  • Rats, Wistar
  • Receptors, Notch
  • Thyrotropin / metabolism*

Substances

  • Caenorhabditis elegans Proteins
  • Cross-Linking Reagents
  • Glp-1 protein, C elegans
  • Membrane Glycoproteins
  • Receptors, Notch
  • Thyrotropin
  • Cyclic AMP