Dorin-Semblat Dominique, Semblat Jean-Philippe, Hamelin Romain, Srivastava Anand, Tetard Marilou, Matesic Graziella, Doerig Christian, Gamain Benoit
Sorbonne Université, CNRS, Inserm, Centre d'Immunologie et des Maladies Infectieuses, CIMI, Paris, France.
Proteomics Core Facility, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
PLoS Pathog. 2025 Jan 13;21(1):e1012861. doi: 10.1371/journal.ppat.1012861. eCollection 2025 Jan.
Placental malaria is characterized by the massive accumulation and sequestration of infected erythrocytes in the placental intervillous blood spaces, causing severe birth outcomes. The variant surface antigen VAR2CSA is associated with Plasmodium falciparum sequestration in the placenta via its capacity to adhere to chondroitin sulfate A. We have previously shown that the extracellular region of VAR2CSA is phosphorylated on several residues and that the phosphorylation enhances the adhesive properties of CSA-binding infected erythrocytes. Here, we aimed to identify the kinases mediating this phosphorylation. We report that Human and Plasmodium falciparum Casein Kinase 2α are involved in the phosphorylation of the extracellular region of VAR2CSA. We notably show that both CK2α can phosphorylate the extracellular region of recombinant and immunoprecipitated VAR2CSA. Mass spectrometry analysis of recombinant VAR2CSA phosphorylated by recombinant Human and P. falciparum CK2α combined with site-directed mutagenesis led to the identification of residue S1068 in VAR2CSA, which is phosphorylated by both enzymes and is associated with CSA binding. Furthermore, using CRISPR/Cas9 we generated a parasite line in which phosphoresidue S1068 was changed to alanine. This mutation strongly impairs infected erythrocytes adhesion by abolishing VAR2CSA translocation to the surface of infected erythrocytes. We also report that two specific CK2 inhibitors reduce infected erythrocytes adhesion to CSA and decrease the phosphorylation of the recombinant extracellular region of VAR2CSA using either infected erythrocytes lysates as a source of kinases or recombinant Human and P. falciparum casein kinase 2. Taken together, these results undoubtedly demonstrate that host and P. falciparum CK2α phosphorylate the extracellular region of VAR2CSA and that this post-translational modification is important for VAR2CSA trafficking and for infected erythrocytes adhesion to CSA.
胎盘疟疾的特征是受感染的红细胞在胎盘绒毛间隙血腔中大量聚集和滞留,从而导致严重的分娩结局。变异表面抗原VAR2CSA通过其与硫酸软骨素A的黏附能力,与恶性疟原虫在胎盘中的滞留有关。我们之前已经表明,VAR2CSA的细胞外区域在几个残基上发生磷酸化,并且这种磷酸化增强了结合硫酸软骨素A的受感染红细胞的黏附特性。在此,我们旨在鉴定介导这种磷酸化的激酶。我们报告称,人和恶性疟原虫酪蛋白激酶2α参与了VAR2CSA细胞外区域的磷酸化。我们特别表明,两种CK2α都可以使重组的和免疫沉淀的VAR2CSA的细胞外区域发生磷酸化。对由重组人CK2α和恶性疟原虫CK2α磷酸化的重组VAR2CSA进行质谱分析,并结合定点诱变,从而鉴定出VAR2CSA中的S1068残基,这两种酶都会使其磷酸化,并且与硫酸软骨素A的结合有关。此外,我们使用CRISPR/Cas9技术构建了一个寄生虫株系,其中磷酸化残基S1068被替换为丙氨酸。这种突变通过消除VAR2CSA向受感染红细胞表面的转运,强烈损害了受感染红细胞的黏附。我们还报告称,两种特异性CK2抑制剂可降低受感染红细胞与硫酸软骨素A的黏附,并减少VAR2CSA重组细胞外区域的磷酸化,所用的激酶来源要么是受感染红细胞裂解物,要么是重组人酪蛋白激酶2和恶性疟原虫酪蛋白激酶2。综上所述,这些结果无疑表明,宿主和恶性疟原虫CK2α使VAR2CSA的细胞外区域发生磷酸化,并且这种翻译后修饰对于VAR2CSA的转运以及受感染红细胞与硫酸软骨素A的黏附很重要。