The epidermal growth factor receptor (EGFR), a member of ErbB receptor tyrosine kinase (RTK) family, is activated through growth factor-induced reorganization of the actin cytoskeleton and subsequent dimerization. We herein explored the molecular mechanism underlying the suppression of ligand-induced EGFR dimerization by CD99 agonists and its relevance to tumor growth in vivo. Epidermal growth factor (EGF) activated the formation of c-Src/focal adhesion kinase (FAK)-mediated intracellular complex and subsequently induced RhoA-and Rac1-mediated actin remodeling, resulting in EGFR dimerization and endocytosis. In contrast, CD99 agonist facilitated FAK dephosphorylation through the HRAS/ERK/PTPN12 signaling pathway, leading to inhibition of actin cytoskeletal reorganization via inactivation of the RhoA and Rac1 signaling pathways. Moreover, CD99 agonist significantly suppressed tumor growth in a BALB/c mouse model injected with MDA-MB-231 human breast cancer cells. Taken together, these results indicate that CD99-derived agonist ligand inhibits epidermal growth factor (EGF)-induced EGFR dimerization through impairment of cytoskeletal reorganization by PTPN12-dependent c-Src/FAK inactivation, thereby suppressing breast cancer growth.

Melanocytes, located in the epidermis’ basal layer, are responsible for melanin pigment production, crucial for skin coloration and protection against UV radiation-induced damage. Melanin synthesis is intricately regulated by various factors, including the Wnt signaling pathway, particularly mediated by the microphthalmia-associated transcription factor (MITF). While MITF is recognized as a key regulator of pigmentation, its regulation by the Wnt pathway remains poorly understood. This study investigates the role of Sfrp5pepD, a peptide antagonist of the Wnt signaling pathway, in modulating melanogenesis and its potential therapeutic implications for pigmentary disorders. To tackle this issue, we investigated smaller peptides frequently utilized in cosmetics or pharmaceuticals. Nevertheless, there is a significant scarcity of reports on peptides associated with melanin-related signal modulation or inhibiting melanin production. Results indicate that Sfrp5pepD effectively inhibits Wnt signaling by disrupting the interaction between Axin-1 and β-catenin, thus impeding downstream melanogenic processes. Additionally, Sfrp5pepD suppresses the interaction between MITF and β-catenin, inhibiting their nuclear translocation and downregulating melanogenic enzyme expression, ultimately reducing melanin production. These inhibitory effects are validated in cell culture models suggesting potential clinical applications for hyperpigmentation disorders. Overall, this study elucidates the intricate interplay between Wnt signaling and melanogenesis, highlighting Sfrp5pepD as a promising therapeutic agent for pigmentary disorders. Sfrp5pepD, with a molecular weight of less than 500 Da, is anticipated to penetrate the skin unlike SFRPs. This suggests a strong potential for their use as cosmetics or transdermal absorption agents. Additional investigation into its mechanisms and clinical significance is necessary to enhance its effectiveness in addressing melanin-related skin conditions.

Functional analyses of genes are crucial for unveiling biological responses, genetic engineering, and developing new medicines. However, functional analyses have largely been restricted to model organisms, representing a major hurdle for functional studies and industrial applications. To resolve this, comparative genome analyses can be used to provide clues to gene functions as well as their evolutionary history. To this end, we present Prometheus, a web-based omics portal that contains more than 17,215 sequences from prokaryotic and eukaryotic genomes. This portal supports interkingdom comparative analyses via a domain architecture-based gene identification system and Gene Search, and users can easily and rapidly identify single or entire gene sets in specific pathways. Bioinformatics tools for further analyses are provided in Prometheus or through Bio-Express, a cloud-based bioinformatics analysis platform. Prometheus is a new paradigm for comparative analyses of large amounts of genomic information.

The vitamin D receptor (VDR) plays a pivotal role in maintaining epidermal barrier homeostasis and regulating cutaneous inflammatory responses. However, the cosmetic application of vitamin D and its active metabolites is limited by photoinstability, formulation challenges, and regulatory considerations. In this study, we evaluated a synthetic VDR-activating peptide (VDR-Pep) as a potential functional cosmetic ingredient capable of modulating VDR-associated signaling pathways in human keratinocytes. In situ proximity ligation assays (PLAs) demonstrated that VDR-Pep enhanced the heterodimerization of VDR and retinoid X receptor (RXR), indicating activation of canonical VDR signaling. Treatment with VDR-Pep significantly increased the expression of S100A3 and key terminal differentiation markers, including filaggrin, involucrin, and loricrin, in a dose-dependent manner. In addition, VDR-Pep stimulated intracellular calcium mobilization at levels comparable to or exceeding those induced by 1,25-dihydroxyvitamin D₃. Under UVB-induced stress conditions, the peptide attenuated the expression of the pro-inflammatory cytokine interleukin-6 (IL-6) and enhanced NRF2-associated transcriptional engagement, as evidenced by increased interaction between NRF2 and RNA polymerase II. Collectively, these findings suggest that VDR-Pep supports epidermal homeostasis through coordinated modulation of VDR/RXR signaling, calcium-mediated differentiation, barrier-related protein expression, inflammatory responses, and antioxidant-associated pathways. The results indicate that VDR-targeting peptides may represent a promising non-hormonal strategy for cosmetic formulations aimed at reinforcing skin barrier function and improving resilience to environmental stress. Future studies should focus on validating these effects in in vivo human skin models, assessing long-term safety and efficacy, and optimizing formulation stability for practical cosmetic applications.