Abstract
The major regulators of melanogenesis are glycoproteins, however no role for glycosylation in the pathway has yet been described. We stained skin biopsies and melanocyte-keratinocyte co-cultures with a panel of 20 lectins as oligosaccharide markers. Notably, the Elderberry Bark Lectin (EBL/SNA) stained melanocytes in both systems. EBL binds the sequence Neu5Ac(α(2-6)Gal/GalNAc)- at the termini of some oligosaccharide antennae. We used inhibitors of synthesis and/or binding of this sequence to assess effects on pigmentation. METHODS. Cell culture, lectin histochemistry, siRNA transfection, and assays for dopa oxidase and melanin were carried out by standard techniques. RESULTS. 6′-sialyllactose, a short homolog of the sequence in question, anti-sialyltransferase 6 (ST6) siRNA, and cytidine, a sialyltransferase (ST) inhibitor, each inhibited EBL binding, melanogenesis and melanosome transfer. Unexpectedly, 3′-sialyllactose and siRNA for ST3, chosen as a negative controls, also inhibited these processes. Though strong inhibitors of melanization, none of the agents affected tyrosinase/dopa oxidase activity, indicating previously unrecognized post-tyrosinase regulation of melanization. CONCLUSIONS. We report for the first time that Neu5Ac (α(2-6)Gal/GalNAc)- and possibly Neu5Ac(α(2–3)Gal/GalNAc)-terminated oligosaccharides play multiple roles in melanin synthesis and transfer.
Highlights
Melanosome transfer from melanocytes to keratinocytes is a unique biological process involving organelle donation from one cell to another and a crucial step in skin pigmentation
Histological sections of skin biopsies were stained with Elderberry Bark lectin (EBL) and as a control the MAAII lectin (Maackia amurensis L.) that had shown little or no staining of melanocytes in the 20-lectin survey above
These findings demonstrated the specificity of the EBL lectin and the Neu5Ac(α2-6)Gal/ GalNAc- sequence for melanocytes
Summary
Melanosome transfer from melanocytes to keratinocytes is a unique biological process involving organelle donation from one cell to another and a crucial step in skin pigmentation. Melanosome transfer begins with attachment of melanocyte dendrites to keratinocytes followed by transfer of melanosomes through the melanocyte dendrites into the keratinocytes and trafficking of the melanin within keratinocytes to the supra-nuclear area of the cell. While the major protein regulators are glycoproteins, little is known about the roles of glycosylation in the process. We assembled a panel of 20 biotinylated lectins as markers for specific glycosylation structures and used lectin histochemistry to analyze staining patterns in biopsies of human skin and co-cultures of human melanocytes and keratinocytes. The Elderberry Bark lectin (EBL) showed specific staining of melanocytes and highlighted melanocyte dendrites. We report on the EBL binding site and its roles in melanin synthesis and transfer
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
