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

J Med Chem. 2012 Jul 26;55(14):6502-11. doi: 10.1021/jm300557t. Epub 2012 Jul 9.

Abstract

The synthetic hexapeptide growth hormone releasing peptide-6 (GHRP-6) exhibits dual affinity for the growth hormone secretagogue receptor 1a (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-Trp(2) residue proved important for CD36 receptor affinity; however, His(1) could be replaced by Ala(1) 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Angiogenesis Inhibitors / chemistry
  • Angiogenesis Inhibitors / metabolism
  • Animals
  • Aza Compounds / chemistry*
  • CD36 Antigens / metabolism*
  • Cell Line
  • Inhibitory Concentration 50
  • Ligands
  • Oligopeptides / chemistry*
  • Oligopeptides / metabolism*
  • Protein Binding
  • Rats
  • Receptors, Ghrelin / metabolism*

Substances

  • Angiogenesis Inhibitors
  • Aza Compounds
  • CD36 Antigens
  • Ligands
  • Oligopeptides
  • Receptors, Ghrelin
  • growth hormone releasing hexapeptide