Role of the F-box protein Skp2 in adhesion-dependent cell cycle progression.
Role of the F-box protein Skp2 in adhesion-dependent cell cycle progression.
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DOI：
10.1083/jcb.153.7.1381
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发表时间：
2001-06-25
期刊：
影响因子：
--
通讯作者：
Pagano M
中科院分区：
文献类型：
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作者：
Carrano AC;Pagano M
细胞与细胞外基质（ECM）的粘附是增殖的必要条件，而恶性细胞通常会丧失这种能力。在没有粘附的情况下，随着细胞周期蛋白依赖性激酶抑制剂 p27 水平的增加，非转化细胞停滞在 G1 期。我们之前曾报道过，p27 的降解需要其 Thr-187 上的磷酸化，并由 Skp2 介导，Skp2 是一种 F-box 蛋白，与 Skp1、Cul1 和 Roc1/Rbx1 结合形成 SCFSkp2 泛素连接酶复合物。在这里，我们表明 Skp2 蛋白的积累依赖于细胞粘附和生长因子，但 Skp2 mRNA 的诱导完全依赖于细胞与 ECM 的粘附。相反，SCFSkp2 复合物的其他三个亚基的表达与细胞锚定无关。 p27 在 Thr-187 上的磷酸化也不会受到细胞粘附丧失的显着影响，这表明 p27 稳定性的增加并不依赖于 p27 去磷酸化。值得注意的是，非贴壁 G1 细胞中 Skp2 的异位表达导致 p27 下调、进入 S 期和细胞分裂。通过将 Skp2 与细胞周期蛋白 D1 共表达，但不与细胞周期蛋白 E 共表达，可以增强诱导粘附非依赖性细胞周期进程的能力，这表明 Skp2 和细胞周期蛋白 D1 合作拯救悬浮细胞的增殖。我们的研究表明 Skp2 是控制细胞增殖的 ECM 信号传导的关键靶标。
Cell adhesion to the extracellular matrix (ECM) is a requirement for proliferation that is typically lost in malignant cells. In the absence of adhesion, nontransformed cells arrest in G1 with increased levels of the cyclin-dependent kinase inhibitor p27. We have reported previously that the degradation of p27 requires its phosphorylation on Thr-187 and is mediated by Skp2, an F-box protein that associates with Skp1, Cul1, and Roc1/Rbx1 to form the SCFSkp2 ubiquitin ligase complex. Here, we show that the accumulation of Skp2 protein is dependent on both cell adhesion and growth factors but that the induction of Skp2 mRNA is exclusively dependent on cell adhesion to the ECM. Conversely, the expression of the other three subunits of the SCFSkp2 complex is independent of cell anchorage. Phosphorylation of p27 on Thr-187 is also not affected significantly by the loss of cell adhesion, demonstrating that increased p27 stability is not dependent on p27 dephosphorylation. Significantly, ectopic expression of Skp2 in nonadherent G1 cells resulted in p27 downregulation, entry into S phase, and cell division. The ability to induce adhesion-independent cell cycle progression was potentiated by coexpressing Skp2 with cyclin D1 but not with cyclin E, indicating that Skp2 and cyclin D1 cooperate to rescue proliferation in suspension cells. Our study shows that Skp2 is a key target of ECM signaling that controls cell proliferation.