Department of Thoracic Surgery, Provincial Hospital Affiliated to Shandong University, Shandong University, Jinan 250021, China.
FEBS Open Bio. 2011 Dec 27;2:1-5. doi: 10.1016/j.fob.2011.12.001. Print 2012.
The insulin like growth factor receptor subtype 1(IGF-1R) plays an important role in cancers transformation and progression. The aim is to investigate the effects of sunitinib on IGF-1R cell signaling transduction, especially on receptor phosphorylation and ubiquitination. In HEK293 cells, IGF-1R signaling pathways are activated in response to IGF-1, which induces obvious phosphorylations of receptor tyrosine and Akt, ERK. However, the phosphorylations of receptor tyrosine, Akt and ERK were significant inhibited by sunitinib. We found that both IGF-1 and sunitinib obviously down regulated the IGF-1R expression. For analysis the ubiquitination, HEK293 cells were simulated with 100 ng/ml IGF-1 or 10 nM sunitinib for 10 min after serum starvation for 24 h. Both IGF-1 and sunitinib could obviously induce the IGF-1R ubiquitination at 10 min compared with control (only serum free, no stimulation), indicating IGF-1 and sunitinib down-regulate the IGF-1R by increasing the receptor degradation through ubiquitination dependent proteasome pathway. We also found that MDM2 combined to IGF-1R in response to sunitinib stimulation. To confirm it, HEK293 cells were transfected with human HA-MDM2 (+MDM2) or siRNA to MDM2 (-MDM2). Following 24 h serum starvation, cells were stimulated with 10 nM sunitinib for 10 min. In over-expressed MDM2 cells, IGF-1R was more ubiquitinated than that in mock-transfected cells (control), and no ubiquitination in -MDM2 cells. These results mean that sunitinib mediates ubiquitination of IGF-1R dependent on MDM2. In summary, sunitinib could block signaling transduction and mediate degradation of IGF-1R.
胰岛素样生长因子受体亚型 1（IGF-1R）在癌症的转化和进展中起着重要作用。本研究旨在探讨舒尼替尼对 IGF-1R 细胞信号转导的影响，特别是对受体磷酸化和泛素化的影响。在 HEK293 细胞中，IGF-1 激活 IGF-1R 信号通路，导致受体酪氨酸和 Akt、ERK 的明显磷酸化。然而，舒尼替尼显著抑制受体酪氨酸、Akt 和 ERK 的磷酸化。我们发现 IGF-1 和舒尼替尼均明显下调 IGF-1R 的表达。为了分析泛素化，在血清饥饿 24 小时后，用 100ng/ml IGF-1 或 10nM 舒尼替尼刺激 HEK293 细胞 10 分钟。与对照组（仅无血清，无刺激）相比，IGF-1 和舒尼替尼均能明显诱导 10 分钟时 IGF-1R 的泛素化，表明 IGF-1 和舒尼替尼通过增加受体降解来下调 IGF-1R，从而通过泛素化依赖的蛋白酶体途径。我们还发现 MDM2 在舒尼替尼刺激下与 IGF-1R 结合。为了证实这一点，用 HA-MDM2（+MDM2）或 MDM2 小干扰 RNA（-MDM2）转染 HEK293 细胞。血清饥饿 24 小时后，用 10nM 舒尼替尼刺激细胞 10 分钟。在过表达 MDM2 的细胞中，IGF-1R 的泛素化程度高于 mock 转染细胞（对照组），而 -MDM2 细胞中没有泛素化。这些结果表明，舒尼替尼介导 IGF-1R 的泛素化依赖于 MDM2。总之，舒尼替尼可阻断 IGF-1R 的信号转导并介导其降解。
