Azapeptide Analogues of the Growth Hormone Releasing Peptide 6 as Cluster of Differentiation 36 Receptor Ligands with Reduced Affinity for the Growth Hormone Secretagogue Receptor 1a
摘要:
The synthetic hexapeptide growth hormone releasing peptide-6 (GHRP-6) exhibits dual affinity for the growth hormone secretagogue receptor la (GHS-R1a) and the cluster of differentiation 36 (CD36) receptor. Azapeptide GHRP-6 analogues have been synthesized, exhibiting micromolar affinity to the CD36 receptor with reduced affinity toward the GHS-R1a. A combinatorial split-and-mix approach furnished aza-GHRP-6 leads, which were further examined by alanine scanning. Incorporation of an aza-amino acid residue respectively at the D-Trp(2) Ala(3), or Trp(4) position gave aza-GHRP-6 analogues with reduced affinity toward the GHS-R1a by at least a factor of 100 and in certain cases retained affinity for the CD36 receptor. In the latter cases, the D-Trp2 residue proved important for CD36 receptor affinity; however, His' could be replaced by Ala' without considerable loss of binding. In a microvascular sprouting assay using a choroid explant, [azaTyr(4)]-GHRP-6 (15), [Ala(1), azaPhe(2)]-GHRP-6 (16), and [azaLeu(3), Ala(6)]-GHRP-6 (33) all exhibited antiangiogenic activity.
Exploring Side-Chain Diversity by Submonomer Solid-Phase Aza-Peptide Synthesis
作者:David Sabatino、Caroline Proulx、Sophie Klocek、Carine B. Bourguet、Damien Boeglin、Huy Ong、William D. Lubell
DOI:10.1021/ol901423c
日期:2009.8.20
Submonomer synthesis of aza-peptides featuring regioselective alkylation of peptide-bound aza-Gly residues provided ten aza-analogues of the Growth Hormone Releasing Peptide-6 (GHRP-6) in 15−42% yield and purity generally ≥90%. Circular dichroism demonstrated that azaPhe-peptide 7a induced a β-turn conformation which may be responsible for its 1000-fold improvement in GHRP-6 selectivity for the CD36