Modifications in the CD36 binding domain of the Plasmodium falciparum variant antigen are responsible for the inability of chondroitin sulfate A adherent parasites to bind CD36.
Adhesion of mature Plasmodium falciparum parasitized erythrocytes to microvascular endothelial cells or to placenta contributes directly to the virulence and severe pathology of P falciparum malaria. Whereas CD36 is the major endothelial receptor for microvasculature sequestration, infected erythrocytes adhering in the placenta bind chondroitin sulfate A (CSA) but not CD36. Binding to both receptors is mediated by different members of the large and diverse protein family P falciparum erythrocyte membrane protein-1 (PfEMP-1) and involves different regions of the molecule. The PfEMP-1-binding domain for CD36 resides in the cysteine-rich interdomain region 1 (CIDR-1). To explore why CSA-binding parasites do not bind CD36, CIDR-1 domains from CD36- or CSA-binding parasites were expressed in mammalian cells and tested for adhesion. Although CIDR-1 domains from CD36-adherent strains strongly bound CD36, those from CSA-adherent parasites did not. The CIDR-1 domain has also been reported to bind CSA. However, none of the CIDR-1 domains tested bound CSA. Chimeric proteins between CIDR-1 domains that bind or do not bind CD36 and mutagenesis experiments revealed that modifications in the minimal CD36-binding region (M2 region) are responsible for the inability of CSA-selected parasites to bind CD36. One of these modifications, mapped to a 3-amino acid substitution in the M2 region, ablated binding in one variant and largely reduced binding of another. These findings provide a molecular explanation for the inability of placental sequestered parasites to bind CD36 and provide additional insight into critical residues for the CIDR-1/CD36 interaction.
Gamain
B
B
Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
Smith
J D
JD
Miller
L H
LH
Baruch
D I
DI
D000595:Amino Acid Sequence; D000818:Animals; D000953:Antigens, Protozoan / Q000737:chemistry / Q000235:genetics; D001665:Binding Sites; D018955:CD36 Antigens / Q000378:metabolism*; D016466:CHO Cells; D002460:Cell Line; D002809:Chondroitin Sulfates / Q000378:metabolism*; D017124:Conserved Sequence; D006224:Cricetinae; D003545:Cysteine / Q000032:analysis; D004910:Erythrocyte Membrane; D004912:Erythrocytes / Q000469:parasitology / Q000502:physiology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010963:Plasmodium falciparum / Q000276:immunology* / Q000378:metabolism*; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D014162:Transfection
D000953:Antigens, Protozoan; D018955:CD36 Antigens; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; C085731:erythrocyte membrane protein 1, Plasmodium falciparum; D002809:Chondroitin Sulfates; D003545:Cysteine