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Cited by 8Trypanosoma species research and implicationsEnzyme Structure and Functionvaccines and immunoinformatics approaches

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Structural similarities between the metacyclic and bloodstream form variant surface glycoproteins of the African trypanosome

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Chandra, Monica, Đaković, Sara, Foti, Konstantina, Zeelen, Johan P., van Straaten, Monique, Aresta-Branco, Francisco, Tihon, Eliane, Lübbehusen, Nicole, Ruppert, Thomas, Glover, Lucy, Papavasiliou, F. Nina, Stebbins, C. Erec·2023·PLOS Neglected Tropical Diseases
DOI 10.1371/journal.pntd.0011093PMC PMC9956791

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Abstract

During infection of mammalian hosts, African trypanosomes thwart immunity using antigenic variation of the dense Variant Surface Glycoprotein (VSG) coat, accessing a large repertoire of several thousand genes and pseudogenes, and switching to antigenically distinct copies. The parasite is transferred to mammalian hosts by the tsetse fly. In the salivary glands of the fly, the pathogen adopts the metacyclic form and expresses a limited repertoire of VSG genes specific to that developmental stage. It has remained unknown whether the metacyclic VSGs possess distinct properties associated with this particular and discrete phase of the parasite life cycle. We present here three novel metacyclic form VSG N-terminal domain crystal structures (mVSG397, mVSG531, and mVSG1954) and show that they mirror closely in architecture, oligomerization, and surface diversity the known classes of bloodstream form VSGs. These data suggest that the mVSGs are unlikely to be a specialized subclass of VSG proteins, and thus could be poor candidates as the major components of prophylactic vaccines against trypanosomiasis.

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Figures

Fig 1 Structural classification of VSG proteins. (A) Two broad superfamily classes of VSGs identified through sequence analysis and defined by structural topology are shown here with representative structures. VSG monomers are shown as ribbon diagrams colored in light blue. Structures reported in this manuscript are denoted in red. The lower, bottom lobe subdomains of the VSGs are outlined with a red box. Structures were drawn with CCP4mg [57]. (B) Sequence and structurally-determined secondary structure of two representative VSGs from Class A (VSG1) and Class B (VSG2). The sequence region that forms the bottom lobe is indicated by red highlighting. Secondary structure was illustrated with PDBSUM [58].
Fig 1 Structural classification of VSG proteins. (A) Two broad superfamily classes of VSGs identified through sequence analysis and defined by structural topology are shown here with representative structures. VSG monomers are shown as ribbon diagrams colored in light blue. Structures reported in this manuscript are denoted in red. The lower, bottom lobe subdomains of the VSGs are outlined with a red box. Structures were drawn with CCP4mg [57]. (B) Sequence and structurally-determined secondary structure of two representative VSGs from Class A (VSG1) and Class B (VSG2). The sequence region that forms the bottom lobe is indicated by red highlighting. Secondary structure was illustrated with PDBSUM [58].CC BY · PubMed Central
Fig 2 Crystal structure of mVSG397. (A) Ribbon diagram of the (crystallographic) dimer of mVSG397, the individual monomers colored gold and light blue. The N-linked glycans are displayed as red space-filling atoms and disulfide bonds are shown in cyan. ‘N’ and ‘C’ indicate the N and C termini of each monomer. Structures drawn with CCP4mg [57] (B) Structural alignment of monomers of VSGsur (orange) and mVSG397 (light blue) with corresponding glycans and disulfides shown in space filling representation, the sugars colored the same as the protein to which they are linked, the disulfides in cyan (mVSG397) and magenta (VSGsur). Structures drawn with CCP4mg [57] (C) 90-degree rotation of the structures in (A) and (B) to view the “top” of the VSGs, rendered as molecular surfaces. Top row shows the surface colored by electrostatic potential (red indicating acidic/negatively charged, blue indicating basic/positively charged, and white neutral, all surfaces scaled identically). The bottom row is colored by the Eisenberg hydrophobicity scale [59], where yellow indicates hydrophobic and white polar. Molecular surfaces are generated by PyMOL [60].
Fig 2 Crystal structure of mVSG397. (A) Ribbon diagram of the (crystallographic) dimer of mVSG397, the individual monomers colored gold and light blue. The N-linked glycans are displayed as red space-filling atoms and disulfide bonds are shown in cyan. ‘N’ and ‘C’ indicate the N and C termini of each monomer. Structures drawn with CCP4mg [57] (B) Structural alignment of monomers of VSGsur (orange) and mVSG397 (light blue) with corresponding glycans and disulfides shown in space filling representation, the sugars colored the same as the protein to which they are linked, the disulfides in cyan (mVSG397) and magenta (VSGsur). Structures drawn with CCP4mg [57] (C) 90-degree rotation of the structures in (A) and (B) to view the “top” of the VSGs, rendered as molecular surfaces. Top row shows the surface colored by electrostatic potential (red indicating acidic/negatively charged, blue indicating basic/positively charged, and white neutral, all surfaces scaled identically). The bottom row is colored by the Eisenberg hydrophobicity scale [59], where yellow indicates hydrophobic and white polar. Molecular surfaces are generated by PyMOL [60].CC BY · PubMed Central
Fig 3 Crystal structure of mVSG531. (A) Superposition of class A2/N2 monomers of mVSG531, VSG1, VSG2, and IlTat1.24 produced using DeepAlign in the RaptorX structure alignment server [48,49]. Images of protein structures were generated and edited using CHIMERA [61]. (B) Side-by-side comparison of different class A VSG dimer highlighting common fold, disulfide placement (cyan spheres), and N-linked glycan (red spheres). Structures drawn with CCP4mg [57]. (C) 90-degree rotation of the structures in (B) to view the “top” surface of the VSG, rendered as a molecular surface. Top row shows the surface colored by contact potential (red indicating acidic/negatively charged, blue indicating basic/positively charged, and white neutral, all surfaces scaled identically). The bottom row is colored by the Eisenberg hydrophobicity scale [59], where yellow indicates hydrophobic and white polar. Molecular surfaces are illustrated with PyMOL [60].
Fig 3 Crystal structure of mVSG531. (A) Superposition of class A2/N2 monomers of mVSG531, VSG1, VSG2, and IlTat1.24 produced using DeepAlign in the RaptorX structure alignment server [48,49]. Images of protein structures were generated and edited using CHIMERA [61]. (B) Side-by-side comparison of different class A VSG dimer highlighting common fold, disulfide placement (cyan spheres), and N-linked glycan (red spheres). Structures drawn with CCP4mg [57]. (C) 90-degree rotation of the structures in (B) to view the “top” surface of the VSG, rendered as a molecular surface. Top row shows the surface colored by contact potential (red indicating acidic/negatively charged, blue indicating basic/positively charged, and white neutral, all surfaces scaled identically). The bottom row is colored by the Eisenberg hydrophobicity scale [59], where yellow indicates hydrophobic and white polar. Molecular surfaces are illustrated with PyMOL [60].CC BY · PubMed Central
Fig 4 Crystal structure of mVSG1954. (A) Superposition of class B mVSG1954 (aquamarine) and BSF VSG3 (grey) monomers by DeepAlign in RaptorX structure alignment server. (B) Structural superposition of the crystallographic trimers of mVSG1954 (yellow) and VSG3 (grey) performed by SSM Superpose function in COOT [37,62]. The O-linked sugar on the top lobe of VSG3 is shown in purple as a space-filling atomic representation, whereas the N-linked glycans are shown in salmon (VSG3) and blue (mVSG1954), respectively. Images of protein structures were generated and edited using CHIMERA [61].
Fig 4 Crystal structure of mVSG1954. (A) Superposition of class B mVSG1954 (aquamarine) and BSF VSG3 (grey) monomers by DeepAlign in RaptorX structure alignment server. (B) Structural superposition of the crystallographic trimers of mVSG1954 (yellow) and VSG3 (grey) performed by SSM Superpose function in COOT [37,62]. The O-linked sugar on the top lobe of VSG3 is shown in purple as a space-filling atomic representation, whereas the N-linked glycans are shown in salmon (VSG3) and blue (mVSG1954), respectively. Images of protein structures were generated and edited using CHIMERA [61].CC BY · PubMed Central

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Metadata

Authors
Chandra, M., Đaković, S., Foti, K., Zeelen, J. P., van Straaten, M., Aresta-Branco, F., Tihon, E., Lübbehusen, N., Ruppert, T., Glover, L., Papavasiliou, F. N., & Stebbins, C. E.
Affiliations
  • German Cancer Research Center (DE)
  • Institut Pasteur (FR)
  • Heidelberg University (DE)
Corresponding author
  • Papavasiliou, F. Nina
  • Stebbins, C. Erec
ORCID
Venue
PLOS Neglected Tropical Diseases
Publisher
Public Library of Science (PLoS)
Published
2023-02-13
Volume
17
Issue
2
Pages
e0011093
ISSN
  • 1935-2727 (ISSN-L)
  • 1935-2735
DOI
10.1371/journal.pntd.0011093
PMC
PMC9956791
OpenAlex
W4320482007
Cited by
8
References
2
Citations by year
2026: 2 · 2024: 4 · 2023: 2
FWCI
1.60
Type
journal article
Language
en
Update notices
new_version (2023-02-24)
Open access
Licence
Locations
  • PLoS neglected tropical diseases (publishedVersion, cc-by)
  • bioRxiv (Cold Spring Harbor Laboratory) (acceptedVersion, cc-by-nc-nd)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • HAL (submittedVersion, cc-by)
  • DORA PSI (Paul Scherrer Institute) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
  • Agence Nationale de la Recherche (ANR-17-CE12-0012 VSGREG)
  • Deutsches Krebsforschungszentrum
Topics
  • Health Sciences › Medicine › Epidemiology › Trypanosoma species research and implications
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Structural Biology › Enzyme Structure and Function
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › vaccines and immunoinformatics approaches
Keywords
African trypanosomes, Trypanosoma brucei, variant surface glycoprotein, metacyclic forms, bloodstream forms, antigenic variation, N-terminal domain, oligomerization, parasite life cycle
MeSH terms
Animals, Mammals, Membrane Glycoproteins, Trypanosoma, Trypanosoma brucei brucei, Trypanosomiasis, African, Tsetse Flies, Variant Surface Glycoproteins, Trypanosoma

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