Epiregulin, a Novel Member of the Epidermal Growth Factor Family, Is an Autocrine Growth Factor in Normal Human Keratinocytes

• Published in: The Journal of biological chemistry 2000-02, Vol.275 (8), p.5748-5753
• Main Authors: Shirakata, Yuji, Komurasaki, Toshi, Toyoda, Hitoshi, Hanakawa, Yasushi, Yamasaki, Kenshi, Tokumaru, Sho, Sayama, Koji, Hashimoto, Koji
• Format: Article
• Language: English
• Subjects: Amphiregulin; Antimetabolites - pharmacokinetics; Autocrine Communication; Blotting, Northern; Bromodeoxyuridine - pharmacokinetics; Cell Division; Dose-Response Relationship, Drug; EGF Family of Proteins; epidermal growth factor; Epidermal Growth Factor - biosynthesis; Epidermal Growth Factor - pharmacology; Epidermal Growth Factor - physiology; Epiregulin; ErbB Receptors - metabolism; Glycoproteins - pharmacology; Growth Substances - pharmacology; Heparin-binding EGF-like Growth Factor; Humans; Intercellular Signaling Peptides and Proteins; Keratinocytes - chemistry; NIH-3T3 cells; Phosphorylation; Protein Binding; Recombinant Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - metabolism; Skin - metabolism; Time Factors; Transforming Growth Factor alpha - biosynthesis; transforming growth factor-a
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.275.8.5748

Epiregulin is a new member of the epidermal growth factor (EGF) family purified from conditioned medium of NIH-3T3 clone T7. Some EGF family growth factors play essential roles in human keratinocytes in an autocrine manner. We show here that epiregulin is another autocrine growth factor for human keratinocytes. Epiregulin stimulated human keratinocyte proliferation under both subconfluent and confluent culture conditions in the absence of exogenous EGF family growth factors. Immunoprecipitation of [35S]methionine-labeled conditioned medium revealed a 5-kDa band corresponding to epiregulin. Northern blot analysis detected a 4.8-kilobase transcript of epiregulin, and the addition of epiregulin up-regulated epiregulin mRNA synthesis. Furthermore, an anti-epiregulin blocking antibody reduced DNA synthesis by 25%. Epiregulin up-regulated the mRNA levels of heparin-binding EGF-like growth factor (HB-EGF), amphiregulin, and TGF-α. In turn, the addition of EGF, HB-EGF, amphiregulin, and TGF-α increased epiregulin mRNA levels. These results demonstrate that epiregulin acts as an autocrine growth factor in human epidermal keratinocytes and is part of auto- and cross-induction mechanisms involving HB-EGF, amphiregulin, and TGF-α. The mRNA expression profile resulting from induction of differentiation with high calcium and fetal calf serum revealed the differential expression of epiregulin, HB-EGF, amphiregulin, and TGF-α in keratinocytes. This indicates that these four growth factors have distinct, non-redundant biological functions.