A rapid and sensitive binding assay for growth hormone releasing factor

Area of Science:

• Biochemistry
• Pharmacology
• Molecular Biology

Background:

• Growth hormone releasing factor (GRF) plays a crucial role in endocrine regulation.
• Accurate binding assays are essential for understanding GRF receptor interactions and developing therapeutics.
• Existing methods for measuring GRF binding can be time-consuming and labor-intensive.

Purpose of the Study:

• To develop and validate a novel scintillation proximity assay (SPA) for measuring growth hormone releasing factor (GRF) binding.
• To characterize the binding kinetics and pharmacology of GRF and related peptides using the SPA.
• To adapt the SPA format for high-throughput screening of G-protein linked receptor ligands.

Main Methods:

• Development of a SPA using HEK293 and GH4C1 cells expressing the porcine GRF receptor.
• Validation of binding conditions, including equilibrium and saturation binding studies.
• Competition binding assays to determine the rank order of potency for various peptides.

Main Results:

• Equilibrium binding was achieved within 3 hours at 22°C.
• Saturation isotherms yielded a KD of 296 pM and Bmax of 4.7 pmols/mg in 293-P2 cells.
• GRF analogs showed high potency (IC50 ~1 nM), significantly greater than PACAP, secretin, and VIP.

Conclusions:

• The developed SPA is a sensitive and efficient method for GRF binding assays.
• This assay enables real-time, detailed pharmacological evaluations of G-protein linked receptor ligands.
• The 96-well format is suitable for high-throughput screening, advancing drug discovery efforts.