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Hepatocyte permissiveness to Plasmodium infection is conveyed by a short and structurally conserved region of the CD81 large extracellular domain.

Yalaoui S, Zougbédé S, Charrin S, Silvie O, Arduise C, Farhati K, Boucheix C, Mazier D, Rubinstein E, Froissard P - PLoS Pathog. (2008)

Bottom Line: Still, the molecular mechanisms underlying sporozoite invasion are largely unknown.By site-directed mutagenesis, we have demonstrated the key role of a solvent-exposed region around residue D137 within this domain.This study has uncovered a new functionally important region of CD81, independent of HCV E2 envelope protein binding domain, and further suggests that CD81 may not interact directly with a parasite ligand during Plasmodium infection, but instead may regulate the function of a yet unknown partner protein.

View Article: PubMed Central - PubMed

Affiliation: Université Pierre et Marie Curie-Paris6, UMR S511, Paris, France.

ABSTRACT
Invasion of hepatocytes by Plasmodium sporozoites is a prerequisite for establishment of a malaria infection, and thus represents an attractive target for anti-malarial interventions. Still, the molecular mechanisms underlying sporozoite invasion are largely unknown. We have previously reported that the tetraspanin CD81, a known receptor for the hepatitis C virus (HCV), is required on hepatocytes for infection by sporozoites of several Plasmodium species. Here we have characterized CD81 molecular determinants required for infection of hepatocytic cells by P. yoelii sporozoites. Using CD9/CD81 chimeras, we have identified in CD81 a 21 amino acid stretch located in a domain structurally conserved in the large extracellular loop of tetraspanins, which is sufficient in an otherwise CD9 background to confer susceptibility to P. yoelii infection. By site-directed mutagenesis, we have demonstrated the key role of a solvent-exposed region around residue D137 within this domain. A mAb that requires this region for optimal binding did not block infection, in contrast to other CD81 mAbs. This study has uncovered a new functionally important region of CD81, independent of HCV E2 envelope protein binding domain, and further suggests that CD81 may not interact directly with a parasite ligand during Plasmodium infection, but instead may regulate the function of a yet unknown partner protein.

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3D structure of CD81 LEL.The drawing of CD81 LEL (PDB #1g8q) was generated in MolMol. Four helices (A, C, D, E) are drawn in red while the B helix, crucial for P. yoelii infection is displayed in blue. The black balls indicate the CCG ubiquitous motif. The crucial D137 as well as D138 and D139 are in purple while V135 and V136 are in royal blue. Residues V146, T149, F150, T153 and L154 putatively involved in contact with the SEL are indicated in dark blue. T163, F186 and D196 residues, in yellow, have been reported to play a role in the HCV E2 glycoprotein binding to CD81-LEL. Residues V135, V136, T163, F186 and D196 projected backward, behind the drawing plane. The two disulfides bridges are colored light coral. Hydrophilic residues K144, K148 and E152 located on the top of the B helix are in green. The SEL, in cyan, is in front of the drawing plane.
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ppat-1000010-g009: 3D structure of CD81 LEL.The drawing of CD81 LEL (PDB #1g8q) was generated in MolMol. Four helices (A, C, D, E) are drawn in red while the B helix, crucial for P. yoelii infection is displayed in blue. The black balls indicate the CCG ubiquitous motif. The crucial D137 as well as D138 and D139 are in purple while V135 and V136 are in royal blue. Residues V146, T149, F150, T153 and L154 putatively involved in contact with the SEL are indicated in dark blue. T163, F186 and D196 residues, in yellow, have been reported to play a role in the HCV E2 glycoprotein binding to CD81-LEL. Residues V135, V136, T163, F186 and D196 projected backward, behind the drawing plane. The two disulfides bridges are colored light coral. Hydrophilic residues K144, K148 and E152 located on the top of the B helix are in green. The SEL, in cyan, is in front of the drawing plane.

Mentions: So far specific tetraspanin functions have been linked to residues in the LEL. Only few studies have investigated whether the A–B region contributes to tetraspanin specific functions. This region was found not to directly contribute to the interaction of CD9 with EWI-2 or CD9P-1 ([25]; S. Charrin and E. Rubinstein, unpublished data) and replacement of most of this region did not prevent the interaction of CD151 with the integrin α3β1 [37]. In contrast, our results indicate that the A–B region of CD81 on a CD9 backbone is sufficient to allow infection of hepatocytic cells by P. yoelii sporozoites. More specifically, a major part of the A helix can be replaced by the corresponding region of CD9 without altering sporozoite infection, and substitution of 21 amino acids of CD9 consisting of the end of the A helix and the B helix with the corresponding residues of CD81 yielded a chimera that supports to some extent infection by P. yoelii sporozoites. The key role of some residues was demonstrated by site-directed mutagenesis. Importantly, these residues were first selected after an analysis of CD81 3D structure [30],[31],[36], looking for residues that were solvent-exposed (Fig. 3A, Fig. 9). Among these solvent-exposed residues, D137 plays a key role since its mutation together with adjacent residues completely abolished the ability of CD81 to support P. yoelii infection, despite normal surface expression and conformation as determined by the recognition by several conformation-dependent mAbs and the ability to interact with CD9P-1 and EWI-2.


Hepatocyte permissiveness to Plasmodium infection is conveyed by a short and structurally conserved region of the CD81 large extracellular domain.

Yalaoui S, Zougbédé S, Charrin S, Silvie O, Arduise C, Farhati K, Boucheix C, Mazier D, Rubinstein E, Froissard P - PLoS Pathog. (2008)

3D structure of CD81 LEL.The drawing of CD81 LEL (PDB #1g8q) was generated in MolMol. Four helices (A, C, D, E) are drawn in red while the B helix, crucial for P. yoelii infection is displayed in blue. The black balls indicate the CCG ubiquitous motif. The crucial D137 as well as D138 and D139 are in purple while V135 and V136 are in royal blue. Residues V146, T149, F150, T153 and L154 putatively involved in contact with the SEL are indicated in dark blue. T163, F186 and D196 residues, in yellow, have been reported to play a role in the HCV E2 glycoprotein binding to CD81-LEL. Residues V135, V136, T163, F186 and D196 projected backward, behind the drawing plane. The two disulfides bridges are colored light coral. Hydrophilic residues K144, K148 and E152 located on the top of the B helix are in green. The SEL, in cyan, is in front of the drawing plane.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2279262&req=5

ppat-1000010-g009: 3D structure of CD81 LEL.The drawing of CD81 LEL (PDB #1g8q) was generated in MolMol. Four helices (A, C, D, E) are drawn in red while the B helix, crucial for P. yoelii infection is displayed in blue. The black balls indicate the CCG ubiquitous motif. The crucial D137 as well as D138 and D139 are in purple while V135 and V136 are in royal blue. Residues V146, T149, F150, T153 and L154 putatively involved in contact with the SEL are indicated in dark blue. T163, F186 and D196 residues, in yellow, have been reported to play a role in the HCV E2 glycoprotein binding to CD81-LEL. Residues V135, V136, T163, F186 and D196 projected backward, behind the drawing plane. The two disulfides bridges are colored light coral. Hydrophilic residues K144, K148 and E152 located on the top of the B helix are in green. The SEL, in cyan, is in front of the drawing plane.
Mentions: So far specific tetraspanin functions have been linked to residues in the LEL. Only few studies have investigated whether the A–B region contributes to tetraspanin specific functions. This region was found not to directly contribute to the interaction of CD9 with EWI-2 or CD9P-1 ([25]; S. Charrin and E. Rubinstein, unpublished data) and replacement of most of this region did not prevent the interaction of CD151 with the integrin α3β1 [37]. In contrast, our results indicate that the A–B region of CD81 on a CD9 backbone is sufficient to allow infection of hepatocytic cells by P. yoelii sporozoites. More specifically, a major part of the A helix can be replaced by the corresponding region of CD9 without altering sporozoite infection, and substitution of 21 amino acids of CD9 consisting of the end of the A helix and the B helix with the corresponding residues of CD81 yielded a chimera that supports to some extent infection by P. yoelii sporozoites. The key role of some residues was demonstrated by site-directed mutagenesis. Importantly, these residues were first selected after an analysis of CD81 3D structure [30],[31],[36], looking for residues that were solvent-exposed (Fig. 3A, Fig. 9). Among these solvent-exposed residues, D137 plays a key role since its mutation together with adjacent residues completely abolished the ability of CD81 to support P. yoelii infection, despite normal surface expression and conformation as determined by the recognition by several conformation-dependent mAbs and the ability to interact with CD9P-1 and EWI-2.

Bottom Line: Still, the molecular mechanisms underlying sporozoite invasion are largely unknown.By site-directed mutagenesis, we have demonstrated the key role of a solvent-exposed region around residue D137 within this domain.This study has uncovered a new functionally important region of CD81, independent of HCV E2 envelope protein binding domain, and further suggests that CD81 may not interact directly with a parasite ligand during Plasmodium infection, but instead may regulate the function of a yet unknown partner protein.

View Article: PubMed Central - PubMed

Affiliation: Université Pierre et Marie Curie-Paris6, UMR S511, Paris, France.

ABSTRACT
Invasion of hepatocytes by Plasmodium sporozoites is a prerequisite for establishment of a malaria infection, and thus represents an attractive target for anti-malarial interventions. Still, the molecular mechanisms underlying sporozoite invasion are largely unknown. We have previously reported that the tetraspanin CD81, a known receptor for the hepatitis C virus (HCV), is required on hepatocytes for infection by sporozoites of several Plasmodium species. Here we have characterized CD81 molecular determinants required for infection of hepatocytic cells by P. yoelii sporozoites. Using CD9/CD81 chimeras, we have identified in CD81 a 21 amino acid stretch located in a domain structurally conserved in the large extracellular loop of tetraspanins, which is sufficient in an otherwise CD9 background to confer susceptibility to P. yoelii infection. By site-directed mutagenesis, we have demonstrated the key role of a solvent-exposed region around residue D137 within this domain. A mAb that requires this region for optimal binding did not block infection, in contrast to other CD81 mAbs. This study has uncovered a new functionally important region of CD81, independent of HCV E2 envelope protein binding domain, and further suggests that CD81 may not interact directly with a parasite ligand during Plasmodium infection, but instead may regulate the function of a yet unknown partner protein.

Show MeSH
Related in: MedlinePlus