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PfRH5: a novel reticulocyte-binding family homolog of plasmodium falciparum that binds to the erythrocyte, and an investigation of its receptor.

Rodriguez M, Lustigman S, Montero E, Oksov Y, Lobo CA - PLoS ONE (2008)

Bottom Line: Attachment is inhibited if the target cells are exposed to high concentrations of trypsin, but not to lower concentrations or to chymotrypsin or neuraminidase.We have determined the affinity, copy number and apparent molecular mass of the receptor protein.Thus, we have shown that PfRH5 is a novel erythrocyte-binding ligand and the identification and partial characterization of the new RBC receptor may indicate the existence of an unrecognized P. falciparum invasion pathway.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Blood-Borne Parasites, Lindsley Kimball Research Institute, The New York Blood Center, New York, New York, USA.

ABSTRACT
Multiple interactions between parasite ligands and their receptors on the human erythrocyte are a condition of successful Plasmodium falciparum invasion. The identification and characterization of these receptors presents a major challenge in the effort to understand the mechanism of invasion and to develop the means to prevent it. We describe here a novel member of the reticulocyte-binding family homolog (RH) of P. falciparum, PfRH5, and show that it binds to a previously unrecognized receptor on the RBC. PfRH5 is expressed as a 63 kDa protein and localized at the apical end of the invasive merozoite. We have expressed a fragment of PfRH5 which contains the RBC-binding domain and exhibits the same pattern of interactions with the RBC as the parent protein. Attachment is inhibited if the target cells are exposed to high concentrations of trypsin, but not to lower concentrations or to chymotrypsin or neuraminidase. We have determined the affinity, copy number and apparent molecular mass of the receptor protein. Thus, we have shown that PfRH5 is a novel erythrocyte-binding ligand and the identification and partial characterization of the new RBC receptor may indicate the existence of an unrecognized P. falciparum invasion pathway.

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Cartoon of PfRH ligands and characterization in the parasite.A. Schematic depiction of different members of the PfRH family, showing location of the signal peptide, region of homology among the various RH ligands and the trans-membrane region at the C-termini of the proteins. The bar at the bottom of PfRH5 marks the region of PfRH5 that was expressed in E. coli. B. Expression of a recombinant 43-kDa protein of PfRH5 (rRH5), chosen on the basis of homology with putative binding domains of P. vivax reticulocyte-binding protein 1 (PvRBP1) and PfRH4. Arrow indicates rRH5 after purification on GST-agarose column. C. Western Blot and immunoprecipitation analysis of asynchronous Dd2 parasite lysates with anti-rRH5 antibodies (IM). Pre-immune serum (PI) was used as a negative control. Arrow indicates specific 63 kDA RH5 protein seen in lysates.
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pone-0003300-g001: Cartoon of PfRH ligands and characterization in the parasite.A. Schematic depiction of different members of the PfRH family, showing location of the signal peptide, region of homology among the various RH ligands and the trans-membrane region at the C-termini of the proteins. The bar at the bottom of PfRH5 marks the region of PfRH5 that was expressed in E. coli. B. Expression of a recombinant 43-kDa protein of PfRH5 (rRH5), chosen on the basis of homology with putative binding domains of P. vivax reticulocyte-binding protein 1 (PvRBP1) and PfRH4. Arrow indicates rRH5 after purification on GST-agarose column. C. Western Blot and immunoprecipitation analysis of asynchronous Dd2 parasite lysates with anti-rRH5 antibodies (IM). Pre-immune serum (PI) was used as a negative control. Arrow indicates specific 63 kDA RH5 protein seen in lysates.

Mentions: Ligands belonging to the reticulocyte-binding protein family, found in different Plasmodium species, are high MW proteins that share a low level of amino acid homology and structural features, notably a short exon 1 encoding a signal sequence, followed by a large exon 2 encoding the bulk of the protein, and a single predicted transmembrane domain (TMD) close to the cytoplasmic COOH terminus (Fig. 1 A) [25]. The gene (PFD1145c) encoding the ligand PfRH5, described in this paper, is not a typical member of this family, being relatively small and lacking the transmembrane and cytoplasmic domains (Fig. 1A). The cDNA is composed of only 1581 bp and encodes a putative polypeptide of 526 amino acids with a calculated molecular mass of 63 kDa. CLUSTAL W alignments of the predicted PfRH5 amino acid sequence with the other RH members support a familial relationship, with an overall level of similarity of 15–30% (identity plus conservative substitutions) to the different RH members [http://plasmodb.org].


PfRH5: a novel reticulocyte-binding family homolog of plasmodium falciparum that binds to the erythrocyte, and an investigation of its receptor.

Rodriguez M, Lustigman S, Montero E, Oksov Y, Lobo CA - PLoS ONE (2008)

Cartoon of PfRH ligands and characterization in the parasite.A. Schematic depiction of different members of the PfRH family, showing location of the signal peptide, region of homology among the various RH ligands and the trans-membrane region at the C-termini of the proteins. The bar at the bottom of PfRH5 marks the region of PfRH5 that was expressed in E. coli. B. Expression of a recombinant 43-kDa protein of PfRH5 (rRH5), chosen on the basis of homology with putative binding domains of P. vivax reticulocyte-binding protein 1 (PvRBP1) and PfRH4. Arrow indicates rRH5 after purification on GST-agarose column. C. Western Blot and immunoprecipitation analysis of asynchronous Dd2 parasite lysates with anti-rRH5 antibodies (IM). Pre-immune serum (PI) was used as a negative control. Arrow indicates specific 63 kDA RH5 protein seen in lysates.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2553180&req=5

pone-0003300-g001: Cartoon of PfRH ligands and characterization in the parasite.A. Schematic depiction of different members of the PfRH family, showing location of the signal peptide, region of homology among the various RH ligands and the trans-membrane region at the C-termini of the proteins. The bar at the bottom of PfRH5 marks the region of PfRH5 that was expressed in E. coli. B. Expression of a recombinant 43-kDa protein of PfRH5 (rRH5), chosen on the basis of homology with putative binding domains of P. vivax reticulocyte-binding protein 1 (PvRBP1) and PfRH4. Arrow indicates rRH5 after purification on GST-agarose column. C. Western Blot and immunoprecipitation analysis of asynchronous Dd2 parasite lysates with anti-rRH5 antibodies (IM). Pre-immune serum (PI) was used as a negative control. Arrow indicates specific 63 kDA RH5 protein seen in lysates.
Mentions: Ligands belonging to the reticulocyte-binding protein family, found in different Plasmodium species, are high MW proteins that share a low level of amino acid homology and structural features, notably a short exon 1 encoding a signal sequence, followed by a large exon 2 encoding the bulk of the protein, and a single predicted transmembrane domain (TMD) close to the cytoplasmic COOH terminus (Fig. 1 A) [25]. The gene (PFD1145c) encoding the ligand PfRH5, described in this paper, is not a typical member of this family, being relatively small and lacking the transmembrane and cytoplasmic domains (Fig. 1A). The cDNA is composed of only 1581 bp and encodes a putative polypeptide of 526 amino acids with a calculated molecular mass of 63 kDa. CLUSTAL W alignments of the predicted PfRH5 amino acid sequence with the other RH members support a familial relationship, with an overall level of similarity of 15–30% (identity plus conservative substitutions) to the different RH members [http://plasmodb.org].

Bottom Line: Attachment is inhibited if the target cells are exposed to high concentrations of trypsin, but not to lower concentrations or to chymotrypsin or neuraminidase.We have determined the affinity, copy number and apparent molecular mass of the receptor protein.Thus, we have shown that PfRH5 is a novel erythrocyte-binding ligand and the identification and partial characterization of the new RBC receptor may indicate the existence of an unrecognized P. falciparum invasion pathway.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Blood-Borne Parasites, Lindsley Kimball Research Institute, The New York Blood Center, New York, New York, USA.

ABSTRACT
Multiple interactions between parasite ligands and their receptors on the human erythrocyte are a condition of successful Plasmodium falciparum invasion. The identification and characterization of these receptors presents a major challenge in the effort to understand the mechanism of invasion and to develop the means to prevent it. We describe here a novel member of the reticulocyte-binding family homolog (RH) of P. falciparum, PfRH5, and show that it binds to a previously unrecognized receptor on the RBC. PfRH5 is expressed as a 63 kDa protein and localized at the apical end of the invasive merozoite. We have expressed a fragment of PfRH5 which contains the RBC-binding domain and exhibits the same pattern of interactions with the RBC as the parent protein. Attachment is inhibited if the target cells are exposed to high concentrations of trypsin, but not to lower concentrations or to chymotrypsin or neuraminidase. We have determined the affinity, copy number and apparent molecular mass of the receptor protein. Thus, we have shown that PfRH5 is a novel erythrocyte-binding ligand and the identification and partial characterization of the new RBC receptor may indicate the existence of an unrecognized P. falciparum invasion pathway.

Show MeSH