Nanoscale imaging of the adhesion core including integrin β1 on intact living cells using scanning electron-assisted dielectric-impedance microscopy

The integrins are a superfamily of transmembrane proteins composed of α and β subunit dimers involved in cell–cell and cell–extracellular matrix interactions. The largest integrin subgroup is integrin β1, which contributes to several malignant phenotypes. Recently, we have developed a novel imaging technology named scanning electron-assisted dielectric-impedance microscopy (SE-ADM), which visualizes untreated living mammalian cells in aqueous conditions with high contrast. Using the SE-ADM system, we observed 60-nm gold colloids with antibodies directly binding to the focal adhesion core containing integrin β1 on mammalian cancer cells without staining and fixation. The adhesion core contains three or four high-density regions of integrin β1 and connects to the actin filament. An adhesion core with high-density integrin β1 is suggested to contain 10–20 integrin dimers. Our SE-ADM system can also visualize various other membrane proteins in living cells in medium without staining and fixation.整合素（integrins）是一类跨膜蛋白超家族，由α与β亚基二聚体构成，参与细胞-细胞及细胞-细胞外基质的相互作用。其中最大的整合素亚家族为整合素β1（integrin β1），其与多种恶性表型密切相关。近期，我们研发了一种新型成像技术——扫描电子辅助介电阻抗显微镜（scanning electron-assisted dielectric-impedance microscopy, SE-ADM），该技术可在水相环境下对未经处理的活哺乳动物细胞实现高对比度成像。借助该SE-ADM系统，我们观察到：无需染色与固定，即可使携带抗体的60纳米金胶体直接结合在哺乳动物癌细胞表面、包含整合素β1的黏着斑核心区域。黏着斑核心包含3至4个整合素β1的高密度聚集区，并与肌动蛋白丝相连。据推测，带有高密度整合素β1的黏着斑核心可容纳10至20个整合素二聚体。此外，我们的SE-ADM系统还可在无需染色与固定的培养基中，对活细胞内的多种其他膜蛋白实现可视化成像。