Molecular basis for the dichotomy in Plasmodium falciparum adhesion to CD36 and chondroitin sulfate A

Plasmodium falciparum-infected erythrocytes adhere dichotomously to the host receptors CD36 and chondroitin sulfate A (CSA). This dichotomy is associated with parasite sequestration to microvasculature beds (CD36) or placenta (CSA), leading to site-specific pathogenesis. Both properties are mediated by members of the variant A falciparum erythrocyte membrane protein 1 (PfEMP-1) family and reside on nonoverlapping domains of the molecule. To identify the molecular basis for the apparent dichotomy, we expressed various domains of PfEMP-1 individually or in combination and tested their binding properties. We found that the CD36-binding mode of the cysteine-rich interdomain region-1 (CIDR1) ablates the ability of the Duffy binding-like gamma domain to bind CSA. In contrast, neither a non-CD36-binding CIDR1 nor an intercellular adhesion molecule 1 binding domain had any affect on CSA binding. Our findings point out that interactions between different domains of PfEMP-1 can alter the adhesion phenotype of infected erythrocytes and provide a molecular basis for the apparent dichotomy in adhesion. We suggest that the basis for the dichotomy is structural and that mutually exclusive conformations of PfEMP-1 are involved in binding to CD36 or CSA. Furthermore, we propose a model explaining the requirement for structural dichotomy between placental and nonplacental isolates.