Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
Structure. 2017 Nov 7;25(11):1732-1739.e5. doi: 10.1016/j.str.2017.09.007. Epub 2017 Oct 12.
The LM609 antibody specifically recognizes αβ integrin and inhibits angiogenesis, bone resorption, and viral infections in an arginine-glycine-aspartate-independent manner. LM609 entered phase II clinical trials for the treatment of several cancers and was also used for αβ-targeted radioimmunotherapy. To elucidate the mechanisms of recognition and inhibition of αβ integrin, we solved the structure of the LM609 antigen-binding fragment by X-ray crystallography and determined its binding affinity for αβ. Using single-particle electron microscopy, we show that LM609 binds at the interface between the β-propeller domain of the α chain and the βI domain of the β chain, near the RGD-binding site, of all observed integrin conformational states. Integrating these data with fluorescence size-exclusion chromatography, we demonstrate that LM609 sterically hinders access of large ligands to the RGD-binding pocket, without obstructing it. This work provides a structural framework to expedite future efforts utilizing LM609 as a diagnostic or therapeutic tool.
LM609 抗体特异性识别 αβ 整合素，并以精氨酸-甘氨酸-天冬氨酸非依赖性方式抑制血管生成、骨质吸收和病毒感染。LM609 进入治疗多种癌症的 II 期临床试验，也用于 αβ 靶向放射免疫治疗。为了阐明识别和抑制 αβ 整合素的机制，我们通过 X 射线晶体学解析了 LM609 抗原结合片段的结构，并确定了其与 αβ 的结合亲和力。通过单颗粒电子显微镜，我们表明 LM609 结合在 α 链的 β 三叶桨结构域和 β 链的 βI 结构域之间，靠近 RGD 结合位点，处于所有观察到的整合素构象状态。将这些数据与荧光大小排阻色谱法相结合，我们证明 LM609 阻碍了大配体进入 RGD 结合口袋的通道，而不会阻塞它。这项工作提供了一个结构框架，以加速未来利用 LM609 作为诊断或治疗工具的努力。
