Comparative structural requirements of thirty GRF analogs for interaction with GRF- and VIP receptors and coupling to adenylate cyclase in rat adenopituitary, liver and pancreas.
Robberecht. P P; Waelbroeck. M M; Coy. D D; De Neef. P P; Camus. J C JC; Christophe. J J
Key Findings
- The C‑terminal region of GRF‑1‑29 is essential for recognizing GRF receptors, while the N‑terminal region drives enzyme activation.
- Specific modifications (e.g., N‑Ac‑Tyr1, D‑Arg2) created peptides that act as antagonists of GRF‑stimulated pituitary activity.
- Other analogs (e.g., N‑Ac‑Tyr1, D‑Phe2) became selective antagonists of VIP receptors in pancreatic tissue.
- Free NH2 at position 1 is required for pancreatic adenylate cyclase activation, and iodination of Tyr1 reduces activity.
Practical Outcomes
- For biohackers, the study mainly shows which parts of the GRF‑1‑29 molecule are important for receptor binding and activation, but it does not provide a clear dosing or usage protocol for humans. The identified antagonist variants could be useful for researchers designing experiments to block GRF or VIP pathways, though they have limited immediate application for everyday longevity or performance supplementation.
Summary
Scientists tested 30 modified versions of the short peptide GRF‑1‑29 to see how changes affect its ability to turn on an enzyme called adenylate cyclase in rat pituitary, liver and pancreas cells. They found that the tail end of the peptide is needed to bind the classic GRF receptor, while the front part of the molecule is crucial for actually activating the enzyme. Some modifications turned the peptide into blockers (antagonists) of either GRF or VIP receptors.
Abstract
The ability of 30 synthetic GRF(1-29)-NH2 analogs to stimulate adenylate cyclase activity was investigated in membranes from rat adenopituitary, rat liver and rat pancreas. In adenopituitary membranes, GRF and GRF analogs interacted with specific GRF receptors, whereas in liver and pancreatic membranes, they interacted with VIP receptors. The C-terminal moiety of GRF was responsible for GRF receptor recognition as the hybrid analog (His1, D-Ala2)-GRF(1-9), VIP(10-28) stimulated pituitary adenylate cyclase through the occupancy of VIP receptors only. When GRF or VIP receptors were occupied by GRF analogs, the N-terminal part of the ligand appeared critical for adenylate cyclase activation. This was established by testing 30 GRF analogs mono-, bi- or tri-substituted in positions 1 to 10. Major observations included: (a) the characterization of (N-Ac-Tyr1, D-Arg2)-GRF(1-29)-NH2 as an antagonist of GRF-stimulated pituitary adenylate cyclase; (b) the discovery of the (N-Ac-Tyr1, D-Phe2)-, (His1, D-Ala2, D-Ser3, NLeu27)-, and (His1, D-Ala2, D-Thr7, NLeu27)-derivatives of GRF(1-29)-NH2 as specific antagonists of VIP receptors in rat pancreatic membranes; (c) the importance of the free NH2 function of amino acid residue 1 for pancreatic adenylate cyclase activation, and (d) the decreased efficiency of iodinated (Tyr1)-GRF(1-29)-NH2 as opposed to the non iodinated form, in all systems tested.
Study Information
pubmed
1986
1986-12-31T00:00:00.000Z
10.1016/0196-9781(86)90164-6
22
26