Abstract: WANG Nan, SONG Zhi-qi. Department of Dermatology, First Affiliated Hospital, Dalian Medical University, Dalian 116021, China Corresponding author: SONG Zhi-qi, Email: szqdalian@yahoo.com 【Abstract】 Objective To investigate the regulatory effect of glutamate signaling pathway on filopodia formation in epidermal cells and on melanosome transfer. Methods Epidermal melanocytes and keratinocytes were isolated from human foreskin and subjected to subculture. After two to three passages of subculture, the melanocytes and keratinocytes were cultured alone or in combination with or without the presence of MK801 （an antagonist of N-methyl-D-aspartic acid （NMDA） receptor） of 100 μmol/L, or NMDA （the activator of NMDA receptor） of 100 μmol/L, for 24 hours. The melanocytes irradiated with UVB at 311 nm served as the control. Scanning electron microscopy was used to observe the appearance of filopodia and dendrites of melanocytes and keratinocytes. Melanosome transfer was visualized under confocal laser scanning microscopy after double immunofluorescent staining. Results Although no obvious changes were observed in the number of dendrites in monocultured melanocytes after treatment with MK801 or NMDA for 24 hours, dendrites became thinner at the terminus and longer with a decrease in the number and length of filopodia after MK801 treatment, but thicker and shorter with an increase in the number and length of filopodia after NMDA treatment compared with untreated monocultured melanocytes. In the coculture system, filopodia were observed between the untreated melanocytes and keratinocytes, and the number of filopodia in melanocytes was larger in the side adjacent to keratinocytes than in the opposite side. Compared with the untreated coculture system, the number of both filopodia connecting melanocytes and keratinocytes and filopodia extending from melanocytes to keratinocytes decreased in the coculture system after treatment with MK801 of 100 μmol/L, but increased after treatment with NMDA of 100 μmol/L, for 24 hours. Melanosomes were found in keratinocytes cocultured with melanocytes without treatment, which were decreased in number after 24-hour treatment with MK801 of 100 μmol/L, but increased in number and even present in keratinocytes nonadjacent to melanocytes after 24-hour treatment with NMDA of 100 μmol/L. Conclusion Glutamate signaling pathway may modulate the transfer of melanosomes from melanocytes to keratinocytes via modulating the appearance of melanocyte dendrites and formation of filopodia. 【Key words】 Keratinocytes; Melanocytes; Glutamic acid; Pseudopodia; Melanosomes; Dendrites

Key words: melanosome