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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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Related in: MedlinePlus

Erythrocyte-binding activity of rRH5.A 0.6 µmoles of rRH5 were used in binding assays with untreated RBCs and RBCs treated with neuraminidase- (N), low-trypsin- (LT), medium-trypsin- (MT), high-trypsin- (HT) and chymotrypsin, followed by elution and immunoprecipitation with anti-RH5 antibodies. Gels containing the immuno-precipitates were blotted and probed with anti-RH5 antibodies. B Antibodies to rRH5 block the erythrocyte binding of the recombinant protein. Total IgG from rabbits immunized with rRH5, blocks erythrocyte binding of the RH5 recombinant protein. 0.6 µmoles of rRH5 was incubated with normal erythrocytes in the presence of purified IgG from rabbit sera at final concentrations of 0–10 µg/100 µl.
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pone-0003300-g004: Erythrocyte-binding activity of rRH5.A 0.6 µmoles of rRH5 were used in binding assays with untreated RBCs and RBCs treated with neuraminidase- (N), low-trypsin- (LT), medium-trypsin- (MT), high-trypsin- (HT) and chymotrypsin, followed by elution and immunoprecipitation with anti-RH5 antibodies. Gels containing the immuno-precipitates were blotted and probed with anti-RH5 antibodies. B Antibodies to rRH5 block the erythrocyte binding of the recombinant protein. Total IgG from rabbits immunized with rRH5, blocks erythrocyte binding of the RH5 recombinant protein. 0.6 µmoles of rRH5 was incubated with normal erythrocytes in the presence of purified IgG from rabbit sera at final concentrations of 0–10 µg/100 µl.

Mentions: The binding of rRH5 to wild type and various surface-modified erythrocytes was compared with the binding of the native PfRH5: as can be seen in Fig. 4 A the binding profile of rRH5 simulates that of native RH5, in that it binds to a receptor that is non-sialylated but sensitive to high concentrations of trypsin. Low concentrations of trypsin (0.5 mg/ml) had no inhibitory effect on the binding, while moderate (1.5 mg/ml) trypsin concentrations visibly decreased the binding. Thus rRH5 appears to bind with the same specificity as the native PfRH5, indicating that rRH5 contains an intact receptor-binding domain, as in the native protein. This result permits the use of rRH5 in place of the native parasite supernatant for further analysis of its interaction with the RBC.


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)

Erythrocyte-binding activity of rRH5.A 0.6 µmoles of rRH5 were used in binding assays with untreated RBCs and RBCs treated with neuraminidase- (N), low-trypsin- (LT), medium-trypsin- (MT), high-trypsin- (HT) and chymotrypsin, followed by elution and immunoprecipitation with anti-RH5 antibodies. Gels containing the immuno-precipitates were blotted and probed with anti-RH5 antibodies. B Antibodies to rRH5 block the erythrocyte binding of the recombinant protein. Total IgG from rabbits immunized with rRH5, blocks erythrocyte binding of the RH5 recombinant protein. 0.6 µmoles of rRH5 was incubated with normal erythrocytes in the presence of purified IgG from rabbit sera at final concentrations of 0–10 µg/100 µl.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0003300-g004: Erythrocyte-binding activity of rRH5.A 0.6 µmoles of rRH5 were used in binding assays with untreated RBCs and RBCs treated with neuraminidase- (N), low-trypsin- (LT), medium-trypsin- (MT), high-trypsin- (HT) and chymotrypsin, followed by elution and immunoprecipitation with anti-RH5 antibodies. Gels containing the immuno-precipitates were blotted and probed with anti-RH5 antibodies. B Antibodies to rRH5 block the erythrocyte binding of the recombinant protein. Total IgG from rabbits immunized with rRH5, blocks erythrocyte binding of the RH5 recombinant protein. 0.6 µmoles of rRH5 was incubated with normal erythrocytes in the presence of purified IgG from rabbit sera at final concentrations of 0–10 µg/100 µl.
Mentions: The binding of rRH5 to wild type and various surface-modified erythrocytes was compared with the binding of the native PfRH5: as can be seen in Fig. 4 A the binding profile of rRH5 simulates that of native RH5, in that it binds to a receptor that is non-sialylated but sensitive to high concentrations of trypsin. Low concentrations of trypsin (0.5 mg/ml) had no inhibitory effect on the binding, while moderate (1.5 mg/ml) trypsin concentrations visibly decreased the binding. Thus rRH5 appears to bind with the same specificity as the native PfRH5, indicating that rRH5 contains an intact receptor-binding domain, as in the native protein. This result permits the use of rRH5 in place of the native parasite supernatant for further analysis of its interaction with the RBC.

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
Related in: MedlinePlus