Zeng T, Yamamoto H, Bowen E, Broverman R L, Nguyen K H, Humphreys-Beher M G
Department of Oral Biology, University of Florida, Gainesville 32601, USA.
Comp Biochem Physiol C Pharmacol Toxicol Endocrinol. 1996 Nov;115(3):271-9. doi: 10.1016/s0742-8413(96)00140-5.
The eukaryotic cell cycle is a summary of a complex network of signal transduction pathways resulting in both DNA replication and cell division. Cyclin-dependent kinases (CDKs) control the cell cycle in all eukaryotes, whereas other proteins, known as cyclins, act as their regulatory subunits. Chronic injection with isoproterenol (ISO) can induce acinar cell proliferation in rodent salivary glands. Cyclins and CDK proteins from control and ISO-treated murine parotid acinar cells were detected by using Western blotting techniques. By comparing the expression of these cell cycle regulatory kinases in the parotid acinar cell transition from a quiescent state to a hypertrophic state, we found rapid increases in the protein levels of all CDKs, cyclin D and proliferating cell nuclear antigen (PCNA). The highest protein levels for CDKs and cyclins appeared at about 72 hr of ISO stimulation and were coincident with the highest rate of increase in gland wet weight. After 72 hr, the increase of both cell cycle protein and gland wet weight began to subside. By using a co-immunoprecipitation method, the following cell cycle regulators (CDK-cyclin complexes) were detected, CDK4-cyclin D, CDK2-cyclin E, CDK2-cyclin A, and cdc2-cyclin B, along with an increase in kinase activity over control untreated animals. Additionally, we detected significant decreases in the newly isolated CDK inhibitor (CKI) p27kip but not Wee 1 kinase. The increased levels of CKI correlated with a decrease in kinase activity of CDK/cyclin complexes by 144 hr of chronic isoproterenol treatment. Our data suggest that the holoenzymes for cell cycle control (cyclin-CDK complexes) function as a final regulatory mechanism leading to salivary gland acinar cell proliferation. The gradual decline in protein levels of the CDKs and cyclins after 3 days of chronic treatment further indicates that ISO-induced proliferation of parotid acinar cells is self-limiting and non-tumorigenic.
真核细胞周期是一个复杂的信号转导通路网络的总结，该网络导致DNA复制和细胞分裂。细胞周期蛋白依赖性激酶（CDK）控制所有真核生物的细胞周期，而其他蛋白质，即细胞周期蛋白，作为其调节亚基发挥作用。长期注射异丙肾上腺素（ISO）可诱导啮齿动物唾液腺腺泡细胞增殖。通过蛋白质印迹技术检测对照和ISO处理的小鼠腮腺腺泡细胞中的细胞周期蛋白和CDK蛋白。通过比较这些细胞周期调节激酶在腮腺腺泡细胞从静止状态转变为肥大状态时的表达，我们发现所有CDK、细胞周期蛋白D和增殖细胞核抗原（PCNA）的蛋白质水平迅速增加。CDK和细胞周期蛋白的最高蛋白质水平出现在ISO刺激约72小时时，与腺体湿重的最高增加率一致。72小时后，细胞周期蛋白和腺体湿重的增加开始消退。通过共免疫沉淀法，检测到以下细胞周期调节因子（CDK-细胞周期蛋白复合物）：CDK4-细胞周期蛋白D、CDK2-细胞周期蛋白E、CDK2-细胞周期蛋白A和cdc2-细胞周期蛋白B，同时激酶活性相对于未处理的对照动物有所增加。此外，我们检测到新分离的CDK抑制剂（CKI）p27kip显著降低，但Wee 1激酶没有降低。慢性异丙肾上腺素处理144小时后，CKI水平的升高与CDK/细胞周期蛋白复合物激酶活性的降低相关。我们的数据表明，细胞周期控制的全酶（细胞周期蛋白-CDK复合物）作为导致唾液腺腺泡细胞增殖的最终调节机制发挥作用。慢性处理3天后CDK和细胞周期蛋白蛋白质水平的逐渐下降进一步表明，ISO诱导的腮腺腺泡细胞增殖是自我限制的且非致瘤性的。
