Hashizume Toshihiro, Fukuda Takayuki, Nagaoka Tadahiro, Tada Hiroko, Yamada Hidenori, Watanabe Kazuhide, Salomon David S, Seno Masaharu
Department of Medical Bioengineering, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-Naka, Okayama 700-8530, Japan.
Cell Biol Int. 2008 Jul;32(7):814-26. doi: 10.1016/j.cellbi.2008.03.012. Epub 2008 Mar 29.
ErbB2, which is a member of the epidermal growth factor (erbB) receptor family, is frequently overexpressed in breast and ovarian cancers. Antibody and small molecule anti-tyrosine kinase inhibitors have been developed for targeted therapies for cancers overexpressing erbB2. Internalization and downregulation of erbB2, which is induced by a ligand, may be important for efficacious therapeutic effects. However, ligand-dependent erbB2 internalization has not been well characterized. Here we investigated the internalization of erbB2 in SKBr3 and SKOv3 cells, both overexpressing erbB2, using an EC-1 peptide fused to eGFP (EC-eGFP), which specifically binds to erbB2. ErbB2 was internalized in SKOv3 cells when the cells were treated with EC-eGFP. The accumulation of endosomal erbB2 was EC-eGFP dependent, which colocalized with transferrin implying endocytosis via clathrin-coated pits. In contrast, internalization of erbB2 was not observed in SKBr3 cells. As a result, two different mechanisms, which are cell type dependent for the internalization of erbB2, are proposed.
ErbB2是表皮生长因子（erbB）受体家族的成员之一，在乳腺癌和卵巢癌中经常过度表达。已经开发出抗体和小分子抗酪氨酸激酶抑制剂用于对erbB2过度表达的癌症进行靶向治疗。由配体诱导的erbB2的内化和下调可能对有效的治疗效果很重要。然而，配体依赖性erbB2内化尚未得到很好的表征。在这里，我们使用与eGFP融合的EC-1肽（EC-eGFP）研究了erbB2在均过度表达erbB2的SKBr3和SKOv3细胞中的内化，该肽特异性结合erbB2。当用EC-eGFP处理细胞时，erbB2在SKOv3细胞中被内化。内体erbB2的积累是EC-eGFP依赖性的，它与转铁蛋白共定位，这意味着通过网格蛋白包被小窝的内吞作用。相比之下，在SKBr3细胞中未观察到erbB2的内化。因此，提出了两种不同的机制，它们对erbB2内化是细胞类型依赖性的。
