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First Isolation of the Growth Hormone Secretagogue Receptor from Pituitary Tissue

RPEP-003791996Pomés, A; Pong, S S; Schaeffer, J M
In VitroModerate evidence
The takeaway

The receptor responsible for GHRP-6, MK-677, and related GH secretagogues was solubilized and characterized for the first time, revealing a ~255 kDa G-protein-coupled complex.

~255 kDa receptor complex

The GH secretagogue receptor was solubilized as a large complex including receptor, ligand, and G-protein

What the researchers found

The GH secretagogue receptor was solubilized as a ~255 kDa receptor-ligand-G-protein complex from porcine pituitary, confirming it is distinct from the GHRH receptor.

Why it matters

Isolating the GH secretagogue receptor was essential for understanding how GHRPs and MK-677 work and for the eventual cloning of the ghrelin receptor (GHS-R).

How the study worked

Porcine anterior pituitary membranes were solubilized with digitonin detergent, and the GH secretagogue receptor complex was characterized by size and binding properties.

What this study cannot tell us

In vitro biochemistry using solubilized membranes. Molecular mass estimate may include detergent-associated artifacts. Porcine receptor may differ from human.

How to read the evidence

Moderate biochemical evidence from a technically demanding receptor solubilization. Important milestone in receptor characterization.

When this study was published

Published in 1996, this was a key step toward the cloning of GHS-R1a and the discovery of ghrelin (1999).

The bigger picture

This biochemical characterization paved the way for the molecular cloning of the GHS receptor and the subsequent discovery of ghrelin as its natural ligand — transforming our understanding of growth hormone regulation.

Questions still open

  • What is the molecular identity of this receptor?
  • Is this the same receptor through which the body naturally regulates GH secretion?

Common questions

What is the GH secretagogue receptor?
It's the receptor (now called GHS-R1a) that GHRP-6, hexarelin, MK-677, and the natural hormone ghrelin all bind to in order to stimulate growth hormone release. It's different from the GHRH receptor, which is why these compounds can be combined synergistically.
Why was isolating this receptor important?
Physically isolating the receptor proved it was a real, distinct protein — not just a variation of known receptors. This enabled its molecular cloning and led directly to the discovery of ghrelin, its natural ligand.

Read the original research

Solubilization and characterization of a growth hormone secretagogue receptor from porcine anterior pituitary membranes.

Biochemical and biophysical research communications, 225(3), 939-45

View on PubMed ↗

Citation

Pomés, A; Pong, S S; Schaeffer, J M. (1996). Solubilization and characterization of a growth hormone secretagogue receptor from porcine anterior pituitary membranes.. Biochemical and biophysical research communications, 225(3), 939-45.