Increasing the activity of cell adherent cyclic NGR peptides by optimizing the peptide length and amino acid character

Discovery of fibroblast growth factor 2-derived peptides for enhancing mice skeletal muscle satellite cell proliferation

Skeletal muscle satellite cells (SCs) are essential for muscle regeneration. Their proliferation and differentiation are influenced by fibroblast growth factor (FGF)-2. In this study, we screened for FGF-2-derived peptides that promote SC proliferation. Utilizing photocleavable peptide array technology, a library of 7-residue peptides was synthesized, and its effect on SC proliferation was examined using a mixture of five peptides. The results showed that peptides 1-5 (136%), 21-25 (136%), 26-30 (141%), 31-35 (159%), 71-75 (135%), 76-80 (144%), and 126-130 (137%) significantly increased SC proliferation. Further experiments revealed that peptide 33, CKNGGFF, enhanced SC proliferation. Furthermore, its extended form, peptide 33-13, CKNGGFFLRIHPD, promoted SC proliferation and increased the percentage of Pax7-positive cells, indicating that SCs were maintained in an undifferentiated state. The addition of FGF-2 and peptide 33-13 further induced cell proliferation but did not increase the percentage of Pax7-positive cells. A proliferation assay using an FGF receptor (FGFR) inhibitor suggested that peptide 33-13 acts through the FGFR-mediated and other pathways. Although further research is necessary to explore the mechanisms of action of these peptides and their potential for in vivo and in vitro use, the high sequence conservation of peptides 33 and 33-13 in FGF-2 across multiple species suggests their broad application prospects in biomedical engineering and biotechnology.

Agonist/Antagonist Activity of Oxytocin Variants Obtained from Free Cyclic Peptide Libraries Generated via Amino Acid Substitution

We established a method for synthesizing a free cyclic peptide library via peptide array synthesis to demonstrate the sequence activity of cyclic peptides. Variants of the cyclic nonapeptide oxytocin (OXT) were synthesized via residue substitution. Natural amino acids (AAs) were classified into eight groups based on their physical properties and the size of their side chains, and a representative AA from each group was selected for residue substitution. All OXT variants were systematically evaluated for agonist/antagonist activity. Consequently, no improvement in agonist activity was observed, although substitution of the P4 and P8 residues resulted in decreased activity due to AA substitution. A few OXT variants exhibited antagonistic activity. In particular, the variants with P2 Leu residue substitution (Y2L) and Phe substitutions at residues 4 (Q4F), 5 (N5F), and 7 (P7F) showed high antagonistic activity. Variant Y2W was found to have the highest inhibitory effect, with a dissociation constant of 44 nM, which was comparable to that of the commercial antagonist atosiban (21 nM). Therefore, a free cyclic peptide library constructed via substitution with a natural AA residue was confirmed to be a powerful tool for bioactive peptide screening.