Structural determinants for activity of glucagon-like peptide-2

Area of Science:

• Biochemistry
• Molecular Biology
• Endocrinology

Background:

• Glucagon-like peptide-2 (GLP-2) is a crucial gastrointestinal hormone regulating intestinal epithelial growth.
• Dipeptidylpeptidase IV inactivates GLP-2 by cleaving it at alanine position 2, limiting its therapeutic potential.

Purpose of the Study:

• To elucidate the structural basis of GLP-2 action by examining receptor binding and activation.
• To identify specific amino acid residues critical for GLP-2 receptor (GLP-2R) interaction.

Main Methods:

• Synthesized and analyzed 56 GLP-2 analogues with substitutions at position 2 or alanine replacements elsewhere.
• Assessed GLP-2R binding affinity and receptor activation efficacy for each analogue.
• Utilized circular dichroism to evaluate the secondary structure of active analogues.

Main Results:

• Position 2 substitutions generally maintained or enhanced GLP-2R binding, but only specific substitutions (Gly, Ile, Pro, α-aminobutyric acid, D-Ala, nor-Val) improved receptor activation.
• Alanine replacements at multiple positions (e.g., 5, 6, 17, 20-26, 30, 31) significantly reduced GLP-2R binding.
• Certain position 2 and alanine substitutions enhanced GLP-2R activation, with D-Ala(2), Pro(2), and Gly(2)/Ala(16) showing significantly lower EC50 values than native GLP-2.

Conclusions:

• Single amino acid substitutions can alter the GLP-2-GLP-2R interface, impacting both binding and activation.
• Identified specific residues crucial for GLP-2R binding and activation, providing insights for designing improved GLP-2 analogues.
• Enhanced GLP-2R activity in analogues was independent of changes in alpha-helical content.