Shirakata Y, Komurasaki T, Toyoda H, Hanakawa Y, Yamasaki K, Tokumaru S, Sayama K, Hashimoto K
Department of Dermatology, Ehime University School of Medicine, Shitsukawa, Shigenobu-cho, Onsen-gun, Ehime 791-0295, Japan.
J Biol Chem. 2000 Feb 25;275(8):5748-53. 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 [(35)S]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-alpha. In turn, the addition of EGF, HB-EGF, amphiregulin, and TGF-alpha 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-alpha. 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-alpha in keratinocytes. This indicates that these four growth factors have distinct, non-redundant biological functions.
表皮调节素是从NIH-3T3克隆T7的条件培养基中纯化得到的表皮生长因子（EGF）家族的新成员。一些EGF家族生长因子以自分泌方式在人角质形成细胞中发挥重要作用。我们在此表明，表皮调节素是另一种人角质形成细胞的自分泌生长因子。在不存在外源性EGF家族生长因子的情况下，表皮调节素在亚汇合和汇合培养条件下均刺激人角质形成细胞增殖。对[（35）S]甲硫氨酸标记的条件培养基进行免疫沉淀，显示出一条与表皮调节素相对应的5 kDa条带。Northern印迹分析检测到表皮调节素的4.8千碱基转录本，添加表皮调节素可上调表皮调节素mRNA的合成。此外，抗表皮调节素阻断抗体使DNA合成减少25%。表皮调节素上调了肝素结合表皮生长因子样生长因子（HB-EGF）、双调蛋白和转化生长因子-α（TGF-α）的mRNA水平。反过来，添加EGF、HB-EGF、双调蛋白和TGF-α可增加表皮调节素mRNA水平。这些结果表明，表皮调节素在人表皮角质形成细胞中作为自分泌生长因子发挥作用，并且是涉及HB-EGF、双调蛋白和TGF-α的自诱导和交叉诱导机制的一部分。用高钙和胎牛血清诱导分化所产生的mRNA表达谱揭示了角质形成细胞中表皮调节素、HB-EGF、双调蛋白和TGF-α的差异表达。这表明这四种生长因子具有独特的、非冗余的生物学功能。
