Role of Plasmodium falciparum thrombospondin-related anonymous protein in host-cell interactions.
BACKGROUND
Thrombospondin-related anonymous protein (TRAP) is essential for sporozoite motility and for liver cell invasion. TRAP is a type 1 membrane protein that possesses multiple adhesive domains in its extracellular region.


METHODS
Plasmodium falciparum TRAP (PfTRAP) and its subdomains were expressed in a mammalian expression system, and eleven different mutants generated to study interaction of PfTRAP with liver cells. Binding studies between HepG2 cell extracts and PfTRAP were performed using co-immunoprecipitation protocols.


RESULTS
Five different amino acid residues of PfTRAP that are involved in liver cell binding have been identified. These PfTRAP mutants bound to heparin like the wild type PfTRAP thereby suggesting a non-heparin mediated binding of PfTRAP to liver cells. Three Src family proteins -Lyn, Lck and CrkL which interact with PfTRAP are also identified. Liver cell extracts and immunoprecipitated Src family kinases phosphorylated PfTRAP at multiple sites. An analysis of multiple TRAP sequences revealed Src homology 3 domain (SH3) binding motifs.


CONCLUSIONS
Binding of PfTRAP to SH3-domain containing proteins like Src-family kinases and their ability to phosphorylate PfTRAP suggests a novel role for PfTRAP in cell signaling during sporozoite invasion and homing inside the liver cells. These data shed new light on TRAP-liver cell interactions.
Akhouri
Reetesh Raj
RR
Structural and Computational Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India. rrakhouri@gmail.com
Sharma
Ashwani
A
Malhotra
Pawan
P
Sharma
Amit
A
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D045744:Cell Line, Tumor; D002474:Cell-Free System / Q000378:metabolism; D022781:Hepatocytes / Q000201:enzymology / Q000469:parasitology / Q000502:physiology; D006790:Host-Parasite Interactions; D006801:Humans; D047468:Immunoprecipitation; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D010963:Plasmodium falciparum / Q000502:physiology*; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D018909:src Homology Domains
D015800:Protozoan Proteins; C069428:thrombospondin-related adhesive protein, protozoan; D011505:Protein-Tyrosine Kinases