Department of Physiology and Graduate Group in Biochemistry and Molecular Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
Structure. 2013 Jul 2;21(7):1214-24. doi: 10.1016/j.str.2013.05.008. Epub 2013 Jun 20.
The epidermal growth factor receptor (EGFR) is implicated in human cancers and is the target of several classes of therapeutic agents, including antibody-based drugs. Here, we describe X-ray crystal structures of the extracellular region of EGFR in complex with three inhibitory nanobodies, the variable domains of heavy chain only antibodies (VHH). VHH domains, the smallest natural antigen-binding modules, are readily engineered for diagnostic and therapeutic applications. All three VHH domains prevent ligand-induced EGFR activation, but use two distinct mechanisms. 7D12 sterically blocks ligand binding to EGFR in a manner similar to that of cetuximab. EgA1 and 9G8 bind an epitope near the EGFR domain II/III junction, preventing receptor conformational changes required for high-affinity ligand binding and dimerization. This epitope is accessible to the convex VHH paratope but inaccessible to the flatter paratope of monoclonal antibodies. Appreciating the modes of binding and inhibition of these VHH domains will aid in developing them for tumor imaging and/or cancer therapy.
表皮生长因子受体 (EGFR) 与人类癌症有关，是几类治疗药物的靶点，包括基于抗体的药物。在这里，我们描述了 EGFR 细胞外区域与三种抑制性纳米抗体（仅重链抗体的可变结构域，VHH）复合物的 X 射线晶体结构。VHH 结构域是最小的天然抗原结合模块，易于为诊断和治疗应用进行工程改造。这三种 VHH 结构域都能阻止配体诱导的 EGFR 激活，但使用两种不同的机制。7D12 以类似于西妥昔单抗的方式在空间上阻止配体与 EGFR 的结合。EgA1 和 9G8 结合 EGFR 域 II/III 连接点附近的表位，阻止受体发生高亲和力配体结合和二聚化所需的构象变化。这个表位可被凸面 VHH 互补位接触，但不能被单克隆抗体的平面互补位接触。了解这些 VHH 结构域的结合和抑制模式将有助于将它们开发用于肿瘤成像和/或癌症治疗。
