Identification of an Erythrocyte Receptor for Plasmodium falciparum Glutamic Acid-rich Protein (Pf-GARP)
Almukadi, Haifa.
2018
-
In the present study,
I investigated the underlying basis of Plasmodium falciparum glutamic acid-rich protein
(Pf-GARP) function in malaria pathogenesis by examining its direct interaction with
human red blood cells (RBCs)/erythrocytes, and its impact on RBC aggregation. We
hypothesized that specific region(s) of P. falciparum proteins bind to human RBCs and
regulate malaria pathogenic effects ... read moremediated by cell adhesion. We identified Pf-GARP as
a novel parasite ligand that binds to the surface of human RBCs. Two overlapping peptide
segments of Pf-GARP, identified by two independent phage display cDNA screens,
specifically interact with human RBCs. RBC-binding assays as well as CHO-K1 (Chinese
Hamster Ovary) cells expressing Pf-GARP confirmed its direct binding to human RBCs. The
overlapping segments are likely to cover the core binding-site of Pf-GARP required for
its interaction with human RBCs. Using recombinant protein expression methods, we
identified and mapped the minimum and stable region of Pf-GARP that binds to human RBCs.
Pretreatment of RBCs by chymotrypsin reduced but did not eliminate Pf-GARP binding to
human RBCs. Glycophorin B, a known chymotrypsin-sensitive receptor, was ruled out as a
host receptor for Pf-GARP using glycophorin B (GYPB)-null (S-s-U-) human RBCs.
Importantly, we identified band 3, also called the anion exchanger-1 (AE1) or solute
carrier family 4 member 1 (SLC4A1), as a host receptor for Pf-GARP. Fusion proteins from
Pf-GARP did not inhibit merozoite invasion in human RBCs under our in vitro conditions.
However, synthetic peptides derived from the RBC-binding domain of Pf-GARP induced
formation of RBC aggregates. Collectively, our results provide evidence that Pf-GARP
plays a role in enhancing the adhesive properties of RBCs. This novel feature of Pf-GARP
is mediated either directly by Pf-GARP binding to RBCs or indirectly by modifying the
conformational state of band 3. Our findings may also provide a molecular rationale for
the well-known phenomenon that P. falciparum infection induces RBC adhesion by exposing
an epitope within the ectoplasmic domain of band 3. We propose that inhibition of
Pf-GARP suppresses the RBC-mediated adhesion events thus unveiling new potential
therapeutic strategies to mitigate lesions in cerebral and pregnancy-associated
malaria.
Thesis (Ph.D.)--Tufts University, 2018.
Submitted to the Dept. of Pharmacology & Experimental Therapeutics.
Advisor: Athar Chishti.
Committee: Mercio Perrin, David Greenblatt, James Baleja, and Carlo Brugnara.
Keyword: Pharmacology.read less - ID:
- jm2151936
- To Cite:
- TARC Citation Guide EndNote
