A Co-ligand Complex Anchors Plasmodium falciparum Merozoites to the Erythrocyte Invasion Receptor Band 3

Abstract

In Plasmodium falciparum malaria, erythrocyte invasion by circulating merozoites may occur via two distinct pathways involving either a sialic acid-dependent or -independent mechanism. Earlier, we identified two nonglycosylated exofacial regions of erythrocyte band 3 termed 5ABC and 6A as an important host receptor in the sialic acid-independent invasion pathway. 5ABC, a major segment of this receptor, interacts with the 42-kDa processing product of merozoite surface protein 1 (MSP142) through its 19-kDa C-terminal domain. Here, we show that two regions of merozoite surface protein 9 (MSP9), also known as acidic basic repeat antigen, interact directly with 5ABC during erythrocyte invasion by P. falciparum. Native MSP9 as well as recombinant polypeptides derived from two regions of MSP9 (MSP9/Δ1 and MSP9/Δ2) interacted with both 5ABC and intact erythrocytes. Soluble 5ABC added to the assay mixture drastically diminished the binding of MSP9 to erythrocytes. Recombinant MSP9/Δ1 and MSP9/Δ2 present in the culture medium blocked P. falciparum reinvasion into erythrocytes in vitro. Native MSP9 and MSP142, the two ligands binding to the 5ABC receptor, existed as a stable complex. Our results establish a novel concept wherein the merozoite exploits a specific complex of co-ligands on its surface to target a single erythrocyte receptor during invasion. This new paradigm poses a new challenge in the development of a vaccine for blood stage malaria. In Plasmodium falciparum malaria, erythrocyte invasion by circulating merozoites may occur via two distinct pathways involving either a sialic acid-dependent or -independent mechanism. Earlier, we identified two nonglycosylated exofacial regions of erythrocyte band 3 termed 5ABC and 6A as an important host receptor in the sialic acid-independent invasion pathway. 5ABC, a major segment of this receptor, interacts with the 42-kDa processing product of merozoite surface protein 1 (MSP142) through its 19-kDa C-terminal domain. Here, we show that two regions of merozoite surface protein 9 (MSP9), also known as acidic basic repeat antigen, interact directly with 5ABC during erythrocyte invasion by P. falciparum. Native MSP9 as well as recombinant polypeptides derived from two regions of MSP9 (MSP9/Δ1 and MSP9/Δ2) interacted with both 5ABC and intact erythrocytes. Soluble 5ABC added to the assay mixture drastically diminished the binding of MSP9 to erythrocytes. Recombinant MSP9/Δ1 and MSP9/Δ2 present in the culture medium blocked P. falciparum reinvasion into erythrocytes in vitro. Native MSP9 and MSP142, the two ligands binding to the 5ABC receptor, existed as a stable complex. Our results establish a novel concept wherein the merozoite exploits a specific complex of co-ligands on its surface to target a single erythrocyte receptor during invasion. This new paradigm poses a new challenge in the development of a vaccine for blood stage malaria. Erythrocyte invasion by circulating malaria merozoites occurs through a multi-step process requiring specific host-parasite interactions at the molecular level. In human malaria Plasmodium falciparum, erythrocyte invasion is thought to proceed via two distinctive pathways involving either a sialic acid-dependent or -independent mechanism (1Mitchell G.H. Hadley T.J. McGinniss M.H. Klotz F.W. Miller L.H. Blood. 1986; 67: 1519-1521Crossref PubMed Google Scholar, 2Dolan S.A. Miller L.H. Wellems T.E. J. Clin. Invest. 1990; 86: 618-624Crossref PubMed Scopus (176) Google Scholar). In the sialic acid-dependent invasion pathway, the sialic acid moiety on erythrocyte glycophorin A was identified as a major invasion receptor binding the merozoite ligand, erythrocyte-binding antigen 175 (EBA-175) 1The abbreviations used are: EBAerythrocyte-binding antigenADGal4 activation domainBDGal4 DNA-binding domainMSPmerozoite surface proteinRAPrhoptry-associated proteinTrxthioredoxinY2Hyeast two-hybridGSTglutathione S-transferasepAbpolyclonal antibodyPBSphosphate-buffered salineHRPhorseradish peroxidaseELISAenzyme-linked immunosorbent assaymAbmonoclonal antibody. (3Camus D. Hadley T.J. Science. 1985; 230: 553-556Crossref PubMed Scopus (294) Google Scholar, 4Orlandi P.A. Klotz F.W. Haynes J.D. J. Cell Biol. 1992; 116: 901-909Crossref PubMed Scopus (203) Google Scholar, 5Sim B.K. Chitnis C.E. Wasniowska K. Hadley T.J. Miller L.H. Science. 1994; 264: 1941-1944Crossref PubMed Scopus (490) Google Scholar). The C terminus (F2 domain) of the N-terminal cysteine-rich region (region II) of EBA-175 was shown as the glycophorin A-binding site (5Sim B.K. Chitnis C.E. Wasniowska K. Hadley T.J. Miller L.H. Science. 1994; 264: 1941-1944Crossref PubMed Scopus (490) Google Scholar). Another sialic acid-dependent invasion mechanism utilizing erythrocyte glycophorin C and P. falciparum BABEL (also known as EBP-2 and EBA-140) has also been reported (6Maier A.G. Duraisingh M.T. Reeder J.C. Patel S.S. Kazura J.W. Zimmerman P.A. Cowman A.F. Nat. Med. 2003; 9: 87-92Crossref PubMed Scopus (261) Google Scholar, 7Lobo C.A. Rodriguez M. Reid M. Lustigman S. Blood. 2003; 101: 4628-4631Crossref PubMed Scopus (130) Google Scholar, 8Mayer D.C. Kaneko O. Hudson-Taylor D.E. Reid M.E. Miller L.H. Proc. Natl. Acad. Sci. U. S. A. 2001; 98: 5222-5227Crossref PubMed Scopus (152) Google Scholar). The BABEL-binding site in glycophorin C was mapped to amino acid residues 14–22 within exon 2 (7Lobo C.A. Rodriguez M. Reid M. Lustigman S. Blood. 2003; 101: 4628-4631Crossref PubMed Scopus (130) Google Scholar). Antibodies against the region II/F2 domain of BABEL inhibited P. falciparum invasion into erythrocytes (6Maier A.G. Duraisingh M.T. Reeder J.C. Patel S.S. Kazura J.W. Zimmerman P.A. Cowman A.F. Nat. Med. 2003; 9: 87-92Crossref PubMed Scopus (261) Google Scholar), implicating a common erythrocyte receptor-binding feature in sialic acid-dependent invasion mechanisms. Recently, it has been suggested that P. falciparum reticulocyte-binding homologue protein 1 (PfRh1, also known as PfNBP-1) binds to erythrocytes via a distinct sialic acid-dependent trypsin-resistant host receptor (9Rayner J.C. Vargas-Serrato E. Huber C.S. Galinski M.R. Barnwell J.W. J. Exp. Med. 2001; 194: 1571-1581Crossref PubMed Scopus (169) Google Scholar). P. falciparum JESEBL (also known as EBA-181) is an invasion ligand binding to an unidentified erythrocyte sialoglycoprotein resistant to trypsin and sensitive to chymotrypsin (10Gilberger T.W. Thompson J.K. Triglia T. Good R.T. Duraisingh M.T. Cowman A.F. J. Biol. Chem. 2003; 278: 14480-14486Abstract Full Text Full Text PDF PubMed Scopus (158) Google Scholar). erythrocyte-binding antigen Gal4 activation domain Gal4 DNA-binding domain merozoite surface protein rhoptry-associated protein thioredoxin yeast two-hybrid glutathione S-transferase polyclonal antibody phosphate-buffered saline horseradish peroxidase enzyme-linked immunosorbent assay monoclonal antibody. Mounting evidence nonetheless suggests that the sialic acid-dependent invasion pathway is dispensable in P. falciparum malaria. When the Dd2 line favoring a sialic acid-dependent invasion mechanism was propagated in neuraminidase-treated erythrocytes where sialic acid residues were removed from the erythrocyte surface, the parasite switched to a sialic acid-independent invasion phenotype (Dd2/Nm) (2Dolan S.A. Miller L.H. Wellems T.E. J. Clin. Invest. 1990; 86: 618-624Crossref PubMed Scopus (176) Google Scholar). Disrupting the C-terminal region of EBA-175 in the Dd2/Nm clone by gene targeting had no effect on erythrocyte invasion (11Kaneko O. Fidock D.A. Schwartz O.M. Miller L.H. Mol. Biochem. Parasitol. 2000; 110: 135-146Crossref PubMed Scopus (45) Google Scholar). A similar truncation of EBA-175 switched the sialic acid-dependent W2-mef strain to a sialic acid-independent line (12Reed M.B. Caruana S.R. Batchelor A.H. Thompson J.K. Crabb B.S. Cowman A.F. Proc. Natl. Acad. Sci. U. S. A. 2000; 97: 7509-7514Crossref PubMed Scopus (170) Google Scholar). Furthermore, lacking the expression of either EBA-175 (13Duraisingh M.T. Maier A.G. Triglia T. Cowman A.F. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 4796-4801Crossref PubMed Scopus (187) Google Scholar) or BABEL (6Maier A.G. Duraisingh M.T. Reeder J.C. Patel S.S. Kazura J.W. Zimmerman P.A. Cowman A.F. Nat. Med. 2003; 9: 87-92Crossref PubMed Scopus (261) Google Scholar) had little effect on erythrocyte invasion in both W2-mef (sialic acid-dependent) and 3D7 (sialic acid-independent) strains. Interestingly, disrupting JESEBL expression by gene targeting did not affect the erythrocyte invasion of the W2-mef strain but appeared to be deleterious in the 3D7 strain (10Gilberger T.W. Thompson J.K. Triglia T. Good R.T. Duraisingh M.T. Cowman A.F. J. Biol. Chem. 2003; 278: 14480-14486Abstract Full Text Full Text PDF PubMed Scopus (158) Google Scholar). In fact, P. falciparum field isolates commonly use the sialic acid-independent invasion pathway (14Okoyeh J.N. Pillai C.R. Chitnis C.E. Infect. Immun. 1999; 67: 5784-5791Crossref PubMed Google Scholar). Despite its importance in malaria pathogenesis, the latter invasion pathway remains unclear at the molecular level. For example, a chymotrypsin-sensitive, trypsin-resistant, sialic acid-independent erythrocyte invasion receptor binding the P. falciparum PfRh2b ligand is yet to be identified (15Duraisingh M.T. Triglia T. Ralph S.A. Rayner J.C. Barnwell J.W. McFadden G.I. Cowman A.F. EMBO J. 2003; 22: 1047-1057Crossref PubMed Scopus (224) Google Scholar). Recently, we identified two exofacial regions of human band 3 termed 5ABC and 6A that function as a crucial erythrocyte receptor in the P. falciparum sialic acid-independent invasion pathway (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar). 5ABC, a major segment of this receptor, interacted with MSP142 through its conserved 19-kDa C-terminal domain (MSP119) and blocked the binding of MSP142 to intact erythrocytes (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar). We also reported that the band 3 receptor interacts directly with a number of unidentified merozoite proteins (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar). An earlier study has suggested that band 3 could interact with the N-terminal cysteine-rich region of P. falciparum MSP9, also known as acidic basic repeat antigen and p101 (17Kushwaha A. Perween A. Mukund S. Majumdar S. Bhardwaj D. Chowdhury N.R. Chauhan V.S. Mol. Biochem. Parasitol. 2002; 122: 45-54Crossref PubMed Scopus (23) Google Scholar). In this study, we provide compelling evidence that two regions encoded by amino acids 77–183 and 364–528 of MSP9 interact directly with the 5ABC segment of band 3 during P. falciparum invasion into erythrocytes and that native MSP9 and MSP142 form a co-ligand complex that binds to the invasion receptor 5ABC on the erythrocyte surface. Based on these findings, we propose a model illustrating a novel concept in host-parasite interaction during erythrocyte invasion by P. falciparum. Yeast P. falciparum was as C.A. Mol. Biochem. Parasitol. 2001; PubMed Scopus Google Scholar) from a of parasite Yeast was with the The of was The (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar) into yeast activation of the The was two-hybrid 3 on yeast with the medium lacking and and and and and were in Yeast and were by from P. falciparum and into The gene was into by as (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar). The and The expression of as proteins in yeast was in MSP9/Δ1 and MSP9/Δ2 were into from and was (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar). proteins were in and For was in The 5ABC gene was into from and was in E. and a encoded the two were with of in were with the of protein in The were with the from E. to recombinant The to the MSP9/Δ2 but not domain in not and were termed Recombinant and were as (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar), and the domain was removed to was with MSP9/Δ1 or MSP9/Δ2 in binding A 1 The were by and with to were used as proteins with the were by and from were a The were blocked with for 2 the two was added to the in and in with with 3 The were with and was with and The were with and with a of The was by 2 and the was at binding from the domain was for The binding were for binding and the binding of to and was and was not The were from Recombinant MSP9 to the binding or from was with human erythrocytes in binding A for 2 at The erythrocytes were with and in The erythrocyte were in and to by was used as In the binding was with or in binding at erythrocytes were added to this mixture and The erythrocytes were and as by was used as Native MSP9 and P. falciparum culture as (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar) was with or to at the were with with and the proteins with the were by by or against P. falciparum and were used as erythrocytes were with the P. falciparum culture at in the recombinant MSP9 binding the erythrocytes were and by erythrocytes in the culture medium were used as P. falciparum culture and merozoite protein as (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar), were with protein at for The or protein was with at by protein at for 3 the were with with complex polypeptides with the were by by and from the and The was used as P. falciparum malaria merozoite proteins directly with the erythrocyte invasion receptor band we a of a P. falciparum the 5ABC segment acids of human band 3 as The was to of with to was on the expression of the the yeast from were from yeast and into E. the recombinant were on The P. falciparum in the were to the the at and (MSP9/Δ1 and of the P. falciparum MSP9 acidic basic repeat gene T. G.H. J.D. J. Biol. Chem. Full Text PDF PubMed Google Scholar, Mol. Biol. Med. 1986; Google Scholar) were identified in the were P. falciparum by Yeast on the we to the in the MSP9 the MSP9 gene and were into as a to the Gal4 activation domain Recombinant of the MSP9 as well as MSP9/Δ1 and MSP9/Δ2 from the were into yeast Recombinant of human band 3 gene to the 5ABC, acids and acids were as a to Gal4 DNA-binding domain and into as (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar). The expression of MSP9 and band 3 was by monoclonal against the and of the MSP9/Δ1 were in yeast as of was as two molecular with at the C terminus of the protein recombinant and we by a in as (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar). and did not interact with and the both MSP9/Δ1 and MSP9/Δ2 interacted with 5ABC but not with and assay results by the yeast and that two distinct in MSP9/Δ2 and the terminus of 3 interactions in yeast two-hybrid in a new of 3 in the interaction of 5ABC with MSP9/Δ1 and MSP9/Δ2 identified in the we an binding MSP9/Δ1 and MSP9/Δ2 were in and as proteins to expression in MSP9/Δ1 was as two proteins 3 and and two proteins had at the C terminus as shown by the and of the domain from the mixture of and in the could not be by of its molecular of the of The N-terminal of this that the domain is intact not that the and C of and the of a of that the C terminus of is and of 1 and by a of MSP9/Δ2 Our to MSP9 as a protein in was not as by A. V.S. P. Chauhan V.S. Mol. Biochem. Parasitol. 2000; PubMed Scopus Google Scholar). a binding we a mixture of and and with and removed the domain by and MSP9/Δ2 to but not to in the binding the and specific interaction of 5ABC with and MSP9/Δ2 binding were for both MSP9 of and a of the binding assay these interactions we an of 5ABC as a protein and a mixture with and on the for the interaction of with as a mixture with and MSP9/Δ2 were and of MSP9 to a mixture of and or was with human erythrocytes in and to erythrocytes but not in an did not interact with erythrocytes that the interactions were specific to the and MSP9/Δ2 When was added to the binding assay the erythrocyte interaction with both and MSP9/Δ2 was drastically The domain added to the assay mixture did not affect the binding and results that the binding of and MSP9/Δ2 to erythrocytes is by the 5ABC evidence this we a against the MSP9/Δ2 domain in The MSP9/Δ2 to native MSP9 present in the P. falciparum culture in native MSP9 in the culture to the 5ABC domain 3 and as well as intact human erythrocytes and that MSP9 interacts directly with erythrocytes through its and utilizing the 5ABC region of band 3 as the receptor, during P. falciparum merozoite invasion of erythrocytes. of P. falciparum Recombinant MSP9 the of and MSP9/Δ2 binding to the host band 3 5ABC during erythrocyte we an erythrocyte reinvasion assay in P. falciparum culture as (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar) and as with the both and drastically reinvasion in as well as reinvasion for MSP9 were similar at both and reinvasion the for the was as for were and at a effect and at a effect on reinvasion to the not We did not an of and in culture during the of the reinvasion that the added to the culture at the stage did not affect and of the results that and MSP9/Δ2 P. falciparum invasion into erythrocytes by binding to the 5ABC domain of band 3 on the erythrocyte surface. Our that the 3 interaction as in this study a in the erythrocyte invasion MSP9 and a we that native MSP142 in the P. falciparum culture directly with the 5ABC domain of band 3 (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar). the results of this study that native MSP9 in the culture also interacts directly with 5ABC we the of MSP9 and as a complex of co-ligands binding the 5ABC In the binding both a mixture of and and native MSP142 from the P. falciparum culture did not We native MSP9 from the P. falciparum culture of the complex against in the domain (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar) that MSP142 with MSP9 Our not with MSP142 or parasite proteins on When was for the in the MSP142 was not by the that the merozoite or its the parasite culture could be we used a parasite protein to repeat the The protein was from a mixture of and merozoites by a and the by as (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar). MSP142 with the from the parasite protein of the assay a against P. falciparum rhoptry-associated protein 1 Mol. Biochem. Parasitol. 1986; PubMed Scopus Google Scholar), that is not of the complex This that the protein complex has a specific protein that at MSP9 and MSP142 but not from its in parasite C.A. Mol. Biochem. Parasitol. PubMed Scopus Google Scholar), we were to in the parasite protein but not in the culture In MSP142 was not in the protein C and results that native MSP9 and MSP142 form a specific complex as co-ligands binding the host invasion receptor P. falciparum MSP9 is a conserved antigen that an C-terminal repeat an N-terminal repeat and residues in the terminus J.D. Haynes J.D. M. J. Google Scholar). MSP9 is in the within and at the surface of merozoites T. G.H. J.D. J. Biol. Chem. Full Text PDF PubMed Google Scholar, Mol. Biol. Med. 1986; Google Scholar, J.D. Haynes J.D. M. J. Google Scholar). suggests that MSP9 to the is to the of to the Crabb B.S. Cowman A.F. Mol. 2002; PubMed Scopus Google Scholar). MSP9 in the culture medium a of in the of J.D. Haynes J.D. M. J. Google Scholar). The function of MSP9 during erythrocyte invasion by merozoites has a has been reported for MSP9 A. V.S. P. Chauhan V.S. Mol. Biochem. Parasitol. 2000; PubMed Scopus Google Scholar, M. Haynes J.D. P.A. J.D. Exp. Parasitol. 1992; PubMed Scopus Google Scholar) with the of M. Haynes J.D. P.A. J.D. Exp. Parasitol. 1992; PubMed Scopus Google Scholar), for MSP9 is yet to be Interestingly, the for P. falciparum MSP9 and on 3D7 is not in Plasmodium Plasmodium and Plasmodium E. Barnwell J.W. P. Galinski M.R. Mol. Biochem. Parasitol. 2002; PubMed Scopus Google Scholar), against the of the MSP9 in malaria parasite Recently, H. M. Rodriguez M. A. M. M.E. 2001; PubMed Scopus Google Scholar) that regions of P. falciparum MSP9 to intact erythrocytes in a and a sialic acid-independent with this (17Kushwaha A. Perween A. Mukund S. Majumdar S. Bhardwaj D. Chowdhury N.R. Chauhan V.S. Mol. Biochem. Parasitol. 2002; 122: 45-54Crossref PubMed Scopus (23) Google Scholar) suggested that P. falciparum MSP9 interacts with erythrocyte band The latter study, used a mixture of erythrocyte proteins with a as the of band the of is that band 3 a complex with its erythrocyte proteins the complex J. Blood. 2003; 101: PubMed Scopus Google Scholar). (17Kushwaha A. Perween A. Mukund S. Majumdar S. Bhardwaj D. Chowdhury N.R. Chauhan V.S. Mol. Biochem. Parasitol. 2002; 122: 45-54Crossref PubMed Scopus (23) Google Scholar) reported that the band 3 interaction site in the N-terminal cysteine-rich region of MSP9 acids Our from the P. falciparum in binding assay the and binding A and a interaction MSP9 and the 5ABC domain of band Soluble 5ABC with the binding of and MSP9/Δ2 to intact erythrocytes implicating that the 5ABC domain of band 3 the interaction of MSP9 with erythrocytes. of the site in MSP9 and C-terminal by acids and MSP9/Δ2 acids acids did not interact with 5ABC, the N-terminal binding site could be within amino acids the conserved two repeat regions directly in the MSP9 did not interact with and two of band 3 the of the interaction with we that the interaction of 5ABC with is with MSP9/Δ2 with the of these and MSP9/Δ2 present in the culture medium at blocked the P. falciparum reinvasion of erythrocytes by and as with is that the two binding in MSP9 could form a single in the native In for the that native MSP9 binds to intact erythrocytes as well as the 5ABC segment of band 3 results that MSP9 interacts directly with the erythrocyte surface during P. falciparum and the interaction is through the 5ABC domain of band 3 and two specific regions of We reported earlier that the 5ABC segment of band 3 interacts with P. falciparum (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar). Our and a specific merozoite protein complex that MSP9 and This co-ligand complex to a in binding merozoites to the host band 3 receptor during erythrocyte invasion. is not at MSP9 binds directly to MSP142, native MSP142 in the culture with recombinant and MSP9/Δ2 MSP9 and Crabb B.S. Cowman A.F. Mol. 2002; PubMed Scopus Google Scholar, H. H. E. T. M. A. P. Blood. 1994; PubMed Google Scholar, A. M. Thompson J.K. Mol. Biochem. Parasitol. 1994; PubMed Scopus Google Scholar) could be a of the identified merozoite protein complex D. S. T.J. M. S.A. Mol. Biochem. Parasitol. 2001; PubMed Scopus Google Scholar) and A. Mol. Biochem. Parasitol. PubMed Scopus Google Scholar, M. S. D. Mol. Biochem. Parasitol. 2001; PubMed Scopus Google Scholar), to be to the merozoite surface through the interaction with Based on and in the earlier study (16Goel V.K. Li X. Chen H. Liu S.C. Chishti A.H. Oh S.S. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 5164-5169Crossref PubMed Scopus (179) Google Scholar), we propose two for the interaction in the band invasion pathway MSP142 and MSP9, the two band co-ligands to the merozoite surface could to two of a single 5ABC segment of the two co-ligands to a single 5ABC domain but through co-ligand in the co-ligand complex interact at the with an 5ABC domain In of well evidence that native band 3 as and in the erythrocyte J. J. Biol. Chem. Full Text PDF PubMed Google Scholar, J. Biol. Chem. Full Text PDF PubMed Google Scholar, J.W. PubMed Scopus Google Scholar, H. A. J. PubMed Scopus Google Scholar, D. A. Blood. 2000; PubMed Google Scholar), we is in the latter model that the merozoite an to the erythrocyte surface through either 3 or 3 interaction and into a stable host-parasite interaction by both to two 5ABC in the band 3 or Furthermore, this process could be by of the merozoite on the erythrocyte surface. the it is that of the co-ligands may interact with band 3 at a and the of co-ligands is to provide in the 3 binding The of a complex of merozoite surface proteins and processing of has been reported D. S. T.J. M. S.A. Mol. Biochem. Parasitol. 2001; PubMed Scopus Google Scholar, A. Mol. Biochem. Parasitol. PubMed Scopus Google Scholar, M. S. D. Mol. Biochem. Parasitol. 2001; PubMed Scopus Google Scholar, Mol. Biochem. Parasitol. PubMed Scopus Google Scholar). evidence that proteins in the as Crabb B.S. Cowman A.F. Mol. 2002; PubMed Scopus Google Scholar, H. H. E. T. M. A. P. Blood. 1994; PubMed Google Scholar), MSP9 basic repeat T. G.H. J.D. J. Biol. Chem. Full Text PDF PubMed Google Scholar, Crabb B.S. Cowman A.F. Mol. 2002; PubMed Scopus Google Scholar), and M.E. Exp. Parasitol. 1990; PubMed Scopus Google Scholar, J. 1990; PubMed Scopus Google Scholar) also with the merozoite surface by a or complex with a merozoite surface Our two a novel concept in erythrocyte invasion by malaria wherein the merozoite exploits a specific complex of co-ligands on its surface to target a single erythrocyte This new paradigm of the molecular mechanism by malaria erythrocytes and poses a new challenge in to and an vaccine for blood stage malaria. We to the and of for the from and from We of for and N-terminal and for the