Department of Pathology, Oslo University Hospital, Rikshospitalet, Post box 4950 Nydalen, 0424 Oslo, Norway.
Exp Cell Res. 2012 Dec 10;318(20):2578-91. doi: 10.1016/j.yexcr.2012.09.001. Epub 2012 Sep 11.
The monoclonal antibody C225 (Cetuximab) blocks binding of ligand to the epidermal growth factor receptor (EGFR). In addition, it is known that incubation with C225 induces endocytosis of the EGFR. This endocytosis has previously been shown to be increased when C225 is combined with an additional monoclonal anti-EGFR antibody. However, the effects of antibody combinations on EGFR activation, endocytosis, trafficking and degradation have been unclear. By binding a secondary antibody to the C225-EGFR complex, we here demonstrate that a combination of antibodies can efficiently internalize and degrade the EGFR. Although the combination of antibodies activated the EGFR kinase and induced ubiquitination of the EGFR, the kinase activity was not required for internalization of the EGFR. In contrast to EGF-induced EGFR down-regulation, the antibody combination efficiently degraded the EGFR without initiating downstream proliferative signaling. The antibody-induced internalization of EGFR was found not to depend on clathrin and/or dynamin, but depended on actin polymerization, suggesting induction of macropinocytosis. Macropinocytosis may cause internalization of large membrane areas, and this could explain the highly efficient internalization of the EGFR induced by combination of antibodies.
单克隆抗体 C225（西妥昔单抗）阻断配体与表皮生长因子受体（EGFR）的结合。此外，已知与 C225 孵育会诱导 EGFR 的内吞作用。先前已经表明，当 C225 与另一种单克隆抗 EGFR 抗体结合时，内吞作用会增加。然而，抗体组合对 EGFR 激活、内吞作用、运输和降解的影响尚不清楚。通过将二级抗体与 C225-EGFR 复合物结合，我们在此证明抗体组合可以有效地内化和降解 EGFR。尽管抗体组合激活了 EGFR 激酶并诱导 EGFR 的泛素化，但激酶活性对于 EGFR 的内化不是必需的。与 EGF 诱导的 EGFR 下调相反，抗体组合有效地降解了 EGFR，而没有启动下游增殖信号。发现抗体诱导的 EGFR 内化不依赖于网格蛋白和/或发动蛋白，而是依赖于肌动蛋白聚合，提示诱导大胞饮作用。巨胞饮作用可能导致大的膜面积内化，这可以解释抗体组合诱导的 EGFR 高效内化。
