Analysis of adhesive domains from the A4VAR Plasmodium falciparum erythrocyte membrane protein-1 identifies a CD36 binding domain.
The A4VAR is a variant antigen expressed by a clonal line that binds CD36 and intercellular adhesion molecule-1, ICAM-1. We have cloned and sequenced the extracellular domain coded by the A4var gene. To probe the relationship between A4var expression and parasite adhesion to ICAM-1, var mRNA and protein expression were analyzed in an enriched population of A4 parasites that displayed higher ICAM-1 binding. By Northern analyses, A4var was the predominant var message and antisera raised against a recombinant A4VAR protein reacted with the majority of infected erythrocytes, reinforcing previous conclusions that A4VAR binds ICAM-1. A4VAR contains five Duffy-binding like (DBL) domains, and two cysteine-rich interdomain regions (CIDR) domains. DBL and CIDR domains from A4VAR were expressed in mammalian cells to determine which regions mediate binding to CD36 and ICAM-1. Using several different binding assays, the A4VAR CIDR1 was the only domain found to bind CD36. In contrast, the same assays were unable to identify the ICAM-1 binding domain in A4VAR. This is the first time that each of the DBL and CIDR domains from a Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) have been systematically expressed and tested for binding. These results confirm that CIDR1 is sufficient to bind CD36 without any apparent contribution from other domains.
Smith
J D
JD
Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
Kyes
S
S
Craig
A G
AG
Fagan
T
T
Hudson-Taylor
D
D
Miller
L H
LH
Baruch
D I
DI
Newbold
C I
CI
D000818:Animals; D000913:Antibodies, Protozoan; D000918:Antibody Specificity; D000953:Antigens, Protozoan / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D018955:CD36 Antigens / Q000737:chemistry*; D016466:CHO Cells; D019556:COS Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D004910:Erythrocyte Membrane / Q000737:chemistry*; D017125:Genes, Protozoan / Q000235:genetics; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D018955:CD36 Antigens; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C085731:erythrocyte membrane protein 1, Plasmodium falciparum; D018799:Intercellular Adhesion Molecule-1