Faculty of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel.
Biochem Biophys Res Commun. 2011 Apr 29;408(1):71-7. doi: 10.1016/j.bbrc.2011.03.118. Epub 2011 Mar 30.
Our knowledge concerning the mechanisms of cell cycle regulation in organisms belonging to the Trypanosometidae family is limited. Leishmania donovani are parasitic protozoa that cause kala azar, a fatal form of visceral leishmaniasis in humans. Here we provide evidence that the L. donovani genome contains a Cdc20 homologue. Cdc20 is a regulator of the Anaphase Promoting Complex/Cyclosome (APC/C) that mediates ubiquitin-dependent proteasomal degradation of key cell cycle regulators in eukaryotes. We show that L. donovani Cdc20 protein (LdCdc20p) can complement a lack of yeast Cdc20 protein in Saccharomyces cerevisiae cells, validating the functionality of LdCdc20p. Furthermore, we demonstrate cyclic expression of LdCdc20p and that it contains an active RXXL destruction motif, a distinctive feature of proteins targeted for proteasomal degradation by APC/C. Finally, in line with the proteasome mediating LdCdc20p degradation, promastigotes exposed to proteasome inhibitor display elevated LdCdc20p levels. Taken together our data indicate that Leishmania regulate their cell cycle by ubiquitin-dependent proteasomal degradation mediated by the APC/C.
我们对属于锥虫科的生物的细胞周期调控机制的了解是有限的。利什曼原虫是寄生性原生动物，会导致黑热病，这是一种致命的内脏利什曼病。在这里，我们提供的证据表明，利什曼原虫基因组包含一个 Cdc20 同源物。Cdc20 是一种有丝分裂促进复合物/环体（APC/C）的调节因子，介导真核生物中关键细胞周期调节剂的泛素依赖性蛋白酶体降解。我们表明，利什曼原虫 Cdc20 蛋白（LdCdc20p）可以在酿酒酵母细胞中补充酵母 Cdc20 蛋白的缺乏，验证了 LdCdc20p 的功能。此外，我们证明了 LdCdc20p 的周期性表达，并且它包含一个活性 RXXL 破坏基序，这是 APC/C 靶向的蛋白质进行蛋白酶体降解的独特特征。最后，与蛋白酶体介导的 LdCdc20p 降解一致，暴露于蛋白酶体抑制剂的前鞭毛体显示出升高的 LdCdc20p 水平。综上所述，我们的数据表明，利什曼原虫通过 APC/C 介导的泛素依赖性蛋白酶体降解来调节它们的细胞周期。
