Upregulation of N-acetylglucosaminyltransferase-V by heparin-binding EGF-like growth factor induces keratinocyte proliferation and epidermal hyperplasia.
Oligosaccharide modification by N-acetylglucosaminyltransferase-V (GnT-V), a glycosyltransferase encoded by the Mgat5 gene that catalyses the formation of β1,6 GlcNAc (N-acetylglucosamine) branches on N-glycans, is thought to be associated with cancer growth and metastasis. Overexpression of GnT-V in cancer cells enhances the signalling of growth factors such as epidermal growth factor (EGF) and transforming growth factor-β by increasing galectin-3 binding to polylactosamine structures on receptor N-glycans. We previously demonstrated that transgenic mice overexpressing GnT-V fail to develop spontaneous tumors in any organs, but phenotypes reminiscent of epithelial-to-mesenchymal transition were observed in their skin. However, the biological function of GnT-V in normal skin remained unknown. In this study, we examined the role of GnT-V in keratinocyte proliferation using GnT-V-deficient mice. Proliferation of human keratinocytes was suppressed by treatment with GnT-V siRNA. Mgat5(-/-) mouse keratinocytes also showed impaired cell proliferation through the reduction in EGF receptors on the cell surface. Although the skin of Mgat5(-/-) mice appeared normal, epidermal hyperplasia and proliferation of keratinocytes induced by the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) were downregulated in these mutants. Moreover, a dramatic increase in GnT-V expression was observed by treatment with TPA or heparin-binding EGF-like growth factor (HB-EGF) in normal human epidermal keratinocytes. This increase was inhibited by an EGF receptor inhibitor. These results indicate that a high expression of GnT-V in keratinocytes contributes to HB-EGF-mediated epidermal hyperproliferation by inhibiting endocytosis of EGF receptors bearing β1,6 GlcNAc on their N-glycans. Our findings demonstrate a novel role for GnT-V in epidermal homoeostasis, particularly in hyperproliferative conditions.
Department of Molecular Biochemistry and Clinical Investigation, Osaka University Graduate School of Medicine, Suita, Japan.
Akihiro
A
Kimura
Mika
M
Terao
Arisa
A
Kato
Takaaki
T
Hanafusa
Hiroyuki
H
Murota
Ichiro
I
Katayama
Eiji
E
Miyoshi
D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004817:Epidermis / Q000187:drug effects / Q000473:pathology*; D066246:ErbB Receptors / Q000378:metabolism; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D015603:Keratinocytes / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015854:Up-Regulation
C587883:HBEGF protein, human; C587884:Hbegf protein, mouse; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D017351:N-Acetylglucosaminyltransferases; C052254:alpha-1,6-mannosylglycoprotein beta 1,6-N-acetylglucosaminyltransferase; C541485:EGFR protein, mouse; D066246:ErbB Receptors; D013755:Tetradecanoylphorbol Acetate