WPI Research Initiative for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
National Institute of Animal Health, National Agriculture and Food Research Organization (NARO), 3-1-5 Kannondai, Tsukuba, Ibaraki 305-0856, Japan.
Acta Biomater. 2019 Apr 1;88:383-391. doi: 10.1016/j.actbio.2019.02.026. Epub 2019 Feb 19.
The proliferation epidermal growth factor (EGF) is known to acquire contradictory apoptotic activities upon conjugation with gold nanoparticles (GNPs) through hitherto unknown mechanisms. Here, we identified an essential role of membrane rafts in the drastic activity switching of EGF-GNPs through the following intracellular signaling. (1) In contrast to the rapid diffusion of activated EGF receptor after the soluble EGF stimulation, the receptor is confined within membrane rafts upon binding to the EGF-GNPs. (2) This initial receptor confinements switch its endocytosis process from normal clathrin-mediated endocytosis to caveolin-mediated one, changing the phosphorylation dynamics of essential downstream kinases, i.e., extracellular signal-regulated kinase and AKT. Importantly, the destruction of membrane rafts by β-cyclodextrin reversed this trafficking and signaling, restoring EGF-GNPs to lost anti-apoptotic property. These results reveal the importance of GNP-mediated signal condensation at membrane rafts in conferring the unique apoptotic activity on EGF-nanoparticle conjugates. STATEMENT OF SIGNIFICANCE: Epidermal growth factor (EGF) is a small secretory protein that induces cell proliferation upon binding to its receptor existed on cellular plasma membranes. One interesting feature of the protein in the nanobiology field is, its acquisition of apoptosis-inducing (cellular suicide) activity rather than proliferative one upon conjugation to gold nanoparticles through hitherto unknown mechanisms. Here, we identified the involvement of membrane rafts, plasma membrane nanodomains enriched with cholesterol, in the apoptosis processes by changing the receptor trafficking and downstream signal transduction pathways. Moreover, the destruction of lipid rafts restored the EGF-nanoparticle conjugates with lost anti-apoptotic activity. These finding highlight potential applications of EGF-nanoparticle conjugates to cancer therapy, as the EGF receptor are highly expressed in cancer cells.
表皮生长因子（EGF）的增殖作用众所周知，通过目前尚不清楚的机制与金纳米粒子（GNPs）结合后会获得相反的凋亡活性。在这里，我们通过以下细胞内信号通路确定了质膜筏在 EGF-GNPs 剧烈活性转换中的重要作用。（1）与可溶性 EGF 刺激后激活的 EGF 受体的快速扩散相反，当受体与 EGF-GNPs 结合时，它被局限在质膜筏内。（2）这种初始受体的限制将其内化过程从正常的网格蛋白介导的内化转变为小窝蛋白介导的内化，改变了关键下游激酶，即细胞外信号调节激酶和 AKT 的磷酸化动力学。重要的是，β-环糊精破坏质膜筏可逆转这种运输和信号转导，使 EGF-GNPs 恢复失去的抗凋亡特性。这些结果表明，在赋予 EGF-纳米粒子缀合物独特的凋亡活性方面，GNPs 介导的信号浓缩在质膜筏中的重要性。
表皮生长因子（EGF）是一种小分泌蛋白，它在与存在于细胞膜质膜上的受体结合后诱导细胞增殖。该蛋白在纳米生物学领域的一个有趣特征是，通过目前尚不清楚的机制与金纳米粒子结合后，它获得了诱导细胞凋亡（细胞自杀）的活性，而不是增殖的活性。在这里，我们通过改变受体运输和下游信号转导途径，确定了富含胆固醇的质膜纳米域（质膜筏）在凋亡过程中的参与。此外，破坏脂质筏可使 EGF-纳米粒子缀合物恢复失去的抗凋亡活性。这些发现强调了 EGF-纳米粒子缀合物在癌症治疗中的潜在应用，因为 EGF 受体在癌细胞中高度表达。
