Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON, Canada.
J Cell Biochem. 2012 Mar;113(3):868-76. doi: 10.1002/jcb.23417.
Roscovitine, a cyclin-dependent kinase (Cdk) inhibitor, inhibited kinase activity and the axenic growth of Dictyostelium discoideum at micromolar concentrations. Growth was almost fully rescued in 50 µM and ≈ 50% rescued in 100 µM roscovitine-treated cultures by the over-expression of Cdk5-GFP. This supports the importance of Cdk5 function during cell proliferation in Dictyostelium and indicates that Cdk5 is a primary target of the drug. Roscovitine did not affect the expression of Cdk5 protein during axenic growth but did inhibit its nuclear translocation. This novel result suggests that the effects of roscovitine could be due in part to altering Cdk5 translocation in other systems as well. Kinase activity was inhibited by roscovitine in assays using AX3 whole cell lysates, but not in assays using lysates from Cdk5-GFP over-expressing cells. At higher concentrations, roscovitine impaired slug and fruiting body formation. Fruiting bodies that did form were small and produced relatively fewer spores many of which were round. However, roscovitine did not affect stalk cell differentiation. Together with previous findings, these data reveal that roscovitine inhibits Cdk5 during growth and as yet undefined Cdks during mid-late development.
罗斯考维丁是一种细胞周期蛋白依赖性激酶（Cdk）抑制剂，能在微摩尔浓度下抑制纤毛海鞘的激酶活性和无基质生长。在 50μM 的罗斯考维丁处理的培养物中，通过过表达 Cdk5-GFP，生长几乎完全得到挽救，而在 100μM 的罗斯考维丁处理的培养物中，生长约有 50%得到挽救。这支持了 Cdk5 在细胞增殖过程中在纤毛海鞘中的重要功能，并表明 Cdk5 是该药物的主要靶标。罗斯考维丁在无基质生长过程中并不影响 Cdk5 蛋白的表达，但确实抑制了其核易位。这一新颖的结果表明，罗斯考维丁的作用部分可能是由于改变了其他系统中的 Cdk5 易位。激酶活性在使用 AX3 全细胞裂解物的测定中被罗斯考维丁抑制，但在使用 Cdk5-GFP 过表达细胞裂解物的测定中没有被抑制。在较高浓度下，罗斯考维丁会损害变形体和生殖体的形成。形成的生殖体较小，产生的孢子相对较少，其中许多是圆形的。然而，罗斯考维丁并不影响柄细胞的分化。结合先前的发现，这些数据表明，罗斯考维丁在生长过程中抑制 Cdk5，在中期到晚期发育过程中还抑制了其他尚未确定的 Cdk。
