Abstract
Plasmodium falciparum is the main cause of disease and death from malaria. P. falciparum virulence resides in the ability of infected erythrocytes (IEs) to sequester in various tissues through the interaction between members of the polymorphic P. falciparum erythrocyte membrane protein 1 (PfEMP1) adhesin family to various host receptors. Here, we investigated the effect of phosphorylation of variant surface antigen 2-CSA (VAR2CSA), a member of the PfEMP1 family associated to placental sequestration, on its capacity to adhere to chondroitin sulfate A (CSA) present on the placental syncytium. We showed that phosphatase treatment of IEs impairs cytoadhesion to CSA. MS analysis of recombinant VAR2CSA phosphosites prior to and after phosphatase treatment, as well as of native VAR2CSA expressed on IEs, identified critical phosphoresidues associated with CSA binding. Site-directed mutagenesis on recombinant VAR2CSA of 3 phosphoresidues localised within the CSA-binding region confirmed in vitro their functional importance. Furthermore, using clustered regularly interspaced short palindromic repeats/CRISPR-associated protein-9 nuclease (CRISPR/Cas9), we generated a parasite line in which the phosphoresidue T934 is changed to alanine and showed that this mutation strongly impairs IEs cytoadhesion to CSA. Taken together, these results demonstrate that phosphorylation of the extracellular region of VAR2CSA plays a major role in IEs cytoadhesion to CSA and provide new molecular insights for strategies aiming to reduce the morbidity and mortality of PM.
Highlights
Using static binding assays on immobilised cells from the Human placenta choriocarcinoma cells (BeWo) placental line, we showed that infected erythrocytes (IEs) adhesion of the chondroitin sulfate A (CSA)-selected parasite lines 7G8CSA and FCR3CSA was significantly reduced after treatment with either phosphatase, compared with the untreated IEs (Fig 1A)
Because the central role of variant surface antigen 2-CSA (VAR2CSA) is to mediate IEs cytoadhesion to CSA present on the syncytiotrophoblast layer, we investigated whether phosphatase 1 (PP1) or phosphatase 2a (PP2a) treatment of the 3D7 VAR2CSA full-length extracellular recombinant protein expressed in human embryonic kidney (HEK)293 cells could affect its binding to decorin
In the context of Placental malaria (PM), VAR2CSA exposed on the surface of IEs mediates adhesion to the CSA placental receptor and stands today as the leading vaccine candidate aiming to protect pregnant women living in malaria endemic areas against the severe clinical outcomes of PM [33,34]
Summary
The most severe forms of malaria are caused by the protozoan parasite Plasmodium falciparum [1], whose virulence is associated with an immune evasion strategy based on antigenic. Phosphorylation of VAR2CSA enhances its interaction with CSA. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
