Malaria is responsible for hundreds of thousands of deaths every year. The lack of an effective vaccine and the global spread of multi-drug resistant parasites hampers the fight against the disease and underlines the need for new antimalarial drugs. Central to the pathogenesis of malaria is the proliferation of Plasmodium parasites within human erythrocytes. Parasites invade erythrocytes via a coordinated sequence of receptor-ligand interactions between the parasite and the host cell. Post-translational modifications such as protein phosphorylation are known to be key regulators in this process and are mediated by protein kinases. For several parasite kinases, including the Plasmodium falciparum Glycogen Synthase Kinase 3 (PfGSK3), inhibitors have been shown to block erythrocyte invasion. Here, we provide an assessment of PfGSK3 function by reverse genetics. Using targeted gene disruption, we show the active gene copy, PfGSK3β, is not essential for asexual blood stage proliferation, although it modulates efficient erythrocyte invasion. We found functional inactivation leads to a 69% decreased growth rate and confirmed this growth defect by rescue experiments with wild-type and catalytically inactive mutants. Functional knock-out of PfGSK3β does not lead to transcriptional up-regulation of the second copy of PfGSK3. We further analyze expression, localization, and function of PfGSK3β during gametocytogenesis using a parasite line allowing conditional induction of sexual commitment. We demonstrate PfGSK3β-deficient gametocytes show a strikingly malformed morphology leading to the death of parasites in later stages of gametocyte development. Taken together, these findings are important for our understanding and the development of PfGSK3 as an anti-malarial target.

疟疾每年造成数十万人死亡。缺乏有效的疫苗和多重耐药寄生虫的全球传播阻碍了与该疾病的斗争，并强调了对新的抗疟疾药物的需求。疟疾发病机制的核心是人红细胞内疟原虫寄生虫的增殖。寄生虫通过寄生虫和宿主细胞之间的受体-配体相互作用的协调序列侵入红细胞。已知翻译后修饰（例如蛋白质磷酸化）是该过程中的关键调节因子，并由蛋白激酶介导。对于几种寄生虫激酶，包括恶性疟原虫糖原合成酶激酶 3 (PfGSK3) 抑制剂已被证明可阻止红细胞侵袭。在这里，我们通过反向遗传学提供了对 PfGSK3 功能的评估。使用靶向基因破坏，我们显示活性基因拷贝 PfGSK3β 对无性血期增殖不是必需的，尽管它调节有效的红细胞侵袭。我们发现功能失活导致生长速率降低 69%，并通过对野生型和催化失活突变体的拯救实验证实了这种生长缺陷。PfGSK3β 的功能性敲除不会导致 PfGSK3 第二个拷贝的转录上调。我们使用允许有条件地诱导性承诺的寄生虫系进一步分析 PfGSK3β 在配子细胞发生过程中的表达、定位和功能。我们证明 PfGSK3β 缺陷的配子体表现出明显畸形的形态，导致寄生虫在配子体发育的后期死亡。总之，这些发现对于我们理解和开发 PfGSK3 作为抗疟疾靶点非常重要。