Interactions Between HEP Peptide and EGFR Involved in the Osteoblast Differentiation

The epidermal growth factor receptor (EGFR), as an important target protein for inhibiting and intervening in osteoporosis, is associated with cell migration, proliferation, and apoptosis. Peptides derived from food have been shown to have a strong affinity for EGFR, thereby regulating downstream cellular-signaling pathways and participating in stimulating bone formation. However, it is still a "black box" as to how active peptides affect the conformational changes in the EGFR-binding domain when interacting with its ligand EGF. To shed light on the roles, peptides in EGFR binding, which is involved in the osteoblast differentiation, a high EGFR affinity soybean peptide (HEP) was isolated and purified from soy yogurt. Firstly, the osteogenic activity of HEP was identified through cellular alkaline-phosphatase (ALP) and calcium influx. HEP promoted ALP activity from 0.01897 ± 0.00165 to 0.04051 ± 0.00402 U/mg after 100 μM of peptide treatment, and free intracellular calcium ions and calcium deposition both increased in a dose-dependent manner at 1-100 μg/mL. Secondly, the interaction between HEP and EGFR was detected by bioinformatics, spectroscopy analysis, and Western blot. The Molecular docking results showed that HEP (VVELLKAFEEKF) exhibited high affinity among all the peptides, with -CDOCKER energy values of 184.077 kcal/mol on one EGFR. Moreover, a different loop conformation has been detected in HEP, comparing it to that of EGF, which influences HEP interactions with EGFR. GlU3, LEU4, and LEU5 (HEP) match GLU40, LEU26, and GLU40 (EGF). Moreover, the CD data showed that HEP could interact with extracellular domain protein of EGFR, but the secondary structure did not change after HEP was mixed with Mutant extracellular domain protein. Furthermore, treatment with HEP increased the expression of EGFR and the activation of the PI3K-RUNX2-signaling pathway. These results suggested that HEP may have the function of promoting bone remodeling, which could promote the binding between EGF and EGFR and may be used as a potential active factor for functional food development to prevent osteoporosis.