Regulated activating Thr172 phosphorylation of cyclin-dependent kinase 4(CDK4): Its relationship with cyclins and CDK "inhibitors"
Regulated activating Thr172 phosphorylation of cyclin-dependent kinase 4(CDK4): Its relationship with cyclins and CDK "inhibitors"
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DOI：
10.1128/mcb.02006-05
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发表时间：
2006-07-01
影响因子：
5.3
通讯作者：
Coulonval, Katia
中科院分区：
文献类型：
--
作者：
Bockstaele, Laurence;Kooken, Hugues;Coulonval, Katia
细胞周期蛋白依赖性激酶 4 (CDK4) 是促有丝分裂和抗有丝分裂细胞外信号的主要整合者。它对于许多致癌转化过程也至关重要。 CDK4 激活的各种分子特征仍然鲜为人知或存在争议，包括其与 D 型细胞周期蛋白关联的调节、其激活的 Thr172 磷酸化以及 Cip/Kip CDK“抑制剂”在这些过程中的作用。在各种实验系统中使用二维凝胶电泳重新研究了 CDK4 的 Thr172 磷酸化，包括人成纤维细胞、促甲状腺激素刺激的犬甲状腺上皮细胞以及转染的哺乳动物和昆虫细胞。 CDK4 的 Thr172 磷酸化依赖于先前的 D 型细胞周期蛋白结合，但在 p16 结合的 CDK4 中也发现了 Thr172 磷酸化。在不同系统中观察到的 p27 对细胞周期蛋白 D3-CDK4 活性的相反作用取决于其在该复合物中的化学计量。 Thr172 磷酸化的 CDK4 在含有 p21 或 p27 的复合物中富集，即使 p27 的抑制水平阻止了 CDK4 活性。 p27核定位信号序列的缺失使细胞周期蛋白D3-CDK4重新定位在细胞质中，但不影响CDK4磷酸化。在细胞周期蛋白 D3 复合物中，CDK4（而非 CDK6）的 T 环磷酸化受到直接调节，将其确定为细胞外因子控制细胞周期的决定性靶标。总的来说，这些意想不到的观察结果表明应该重新考虑 CDK4 激活激酶。
Cyclin-dependent kinase 4 (CDK4) is a master integrator of mitogenic and antimitogenic extracellular signals. It is also crucial for many oncogenic transformation processes. Various molecular features of CDK4 activation remain poorly known or debated, including the regulation of its association with D-type cyclins, its activating Thr172 phosphorylation, and the roles of Cip/Kip CDK "inhibitors" in these processes. Thr172 phosphorylation of CDK4 was reinvestigated using two-dimensional gel electrophoresis in various experimental systems, including human fibroblasts, canine thyroid epithelial cells stimulated by thyrotropin, and transfected mammalian and insect cells. Thr172 phosphorylation of CDK4 depended on prior D-type cyclin binding, but Thr172 phosphorylation was also found in p16-bound CDK4. Opposite effects of p27 on cyclin D3-CDK4 activity observed in different systems depended on its stoichiometry in this complex. Thr172-phosphorylated CDK4 was enriched in complexes containing p21 or p27, even at inhibitory levels of p27 that precluded CDK4 activity. Deletion of the p27 nuclear localization signal sequence relocalized cyclin D3-CDK4 in the cytoplasm but did not affect CDK4 phosphorylation. Within cyclin D3 complexes, T-loop phosphorylation of CDK4, but not of CDK6, was directly regulated, identifying it as a determining target for cell cycle control by extracellular factors. Collectively, these unexpected observations indicate that CDK4-activating kinase(s) should be reconsidered.