Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
PLoS One. 2013;8(3):e59755. doi: 10.1371/journal.pone.0059755. Epub 2013 Mar 27.
Mitogen-activated protein kinases (MAPKs) regulate key signaling events in eukaryotic cells. In the genomes of protozoan Plasmodium parasites, the causative agents of malaria, two genes encoding kinases with significant homology to other eukaryotic MAPKs have been identified (mapk1, mapk2). In this work, we show that both genes are transcribed during Plasmodium berghei liver stage development, and analyze expression and subcellular localization of the PbMAPK1 protein in liver stage parasites. Live cell imaging of transgenic parasites expressing GFP-tagged PbMAPK1 revealed a nuclear localization of PbMAPK1 in the early schizont stage mediated by nuclear localization signals in the C-terminal domain. In contrast, a distinct localization of PbMAPK1 in comma/ring-shaped structures in proximity to the parasite's nuclei and the invaginating parasite membrane was observed during the cytomere stage of parasite development as well as in immature blood stage schizonts. The PbMAPK1 localization was found to be independent of integrity of a motif putatively involved in ATP binding, integrity of the putative activation motif and the presence of a predicted coiled-coil domain in the C-terminal domain. Although PbMAPK1 knock out parasites showed normal liver stage development, the kinase may still fulfill a dual function in both schizogony and merogony of liver stage parasites regulated by its dynamic and stage-dependent subcellular localization.
丝裂原活化蛋白激酶（MAPKs）调节真核细胞中的关键信号事件。在疟原虫原生动物寄生虫的基因组中，已经鉴定出两个编码与其他真核 MAPKs 具有显著同源性的激酶的基因（mapk1、mapk2）。在这项工作中，我们表明这两个基因在疟原虫肝期发育过程中都有转录，并分析了 PbMAPK1 蛋白在肝期寄生虫中的表达和亚细胞定位。转染 GFP 标记的 PbMAPK1 的转基因寄生虫的活细胞成像显示，PbMAPK1 的核定位是由 C 端结构域中的核定位信号介导的，这发生在早期裂殖体阶段。相比之下，在寄生虫发育的胞质体阶段以及未成熟的血裂体阶段，观察到 PbMAPK1 定位于靠近寄生虫核和内陷的寄生虫膜的逗号/环形结构中。PbMAPK1 的定位被发现与假定参与 ATP 结合的基序的完整性、假定的激活基序的完整性以及 C 端结构域中预测的卷曲螺旋结构域的存在无关。尽管 PbMAPK1 敲除寄生虫显示出正常的肝期发育，但该激酶可能仍然在裂殖体和肝期寄生虫的配子体发育中发挥双重作用，其亚细胞定位具有动态性和阶段依赖性。
