Identification of an osteopontin-derived peptide that binds neuropilin-1 and activates vascular cells

Abstract

Background: The osteopontin-derived peptide FOL-005 has been shown to stimulate hair growth. Using ligand-receptor glycocapture technology we identified neuropilin-1 (NRP-1), a known co-receptor for vascular endothelial growth factor (VEGF) receptors, as the most probable receptor for FOL-005. Considering that induction of perifollicular angiogenesis by VEGF is a critical step in activation of the anagen growth phase of hair follicles, we investigated the effect of the more stable FOL-005 analogue FOL-026 on vascular cells. Methods: X-ray diffraction and microscale thermophoresis analysis were used to determine receptor binding of FOL-peptides. Cultured human arterial smooth muscle cells were used for studies of cell proliferation, migration, intracellular signaling, and apoptosis. A Matrigel plug assay was used to study angiogenesis in vivo. RNA seq. was used to analyze changes in gene expression patterns. Results: FOL-026 was found to share binding site with VEGF in the NRP-1 b1-subdomain. Stimulation of human umbilical vein endothelial cells with FOL-026 resulted in phosphorylation of AKT and ERK1/2, increased cell growth and migration, stimulation of endothelial tube formation and inhibition of apoptosis in vitro, as well as activation of angiogenesis in vivo. Down-regulation of NRP-1 by NRP-1-specific small interfering RNA blocked the stimulatory effects of FOL-026 on endothelial cells. RNA sequencing showed that FOL-026 activated pathways involved in tissue repair. Exposure of human coronary artery smooth muscle cells to FOL-026 stimulated cell proliferation, migration, inhibited apoptosis, and induced VEGF gene expression by an NRP-1-dependent mechanism. Conclusions: These findings identify NRP-1 as the receptor for FOL-026 and show that its biological effects mimic that of growth factors binding to the VEGF receptor family. They also suggest that FOL-026 may have therapeutical potential in conditions that require vascular repair and / or enhanced angiogenesis.