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Structural and Functional Analysis of Murine Polyomavirus Capsid Proteins Establish the Determinants of Ligand Recognition and Pathogenicity.

Buch MH, Liaci AM, O'Hara SD, Garcea RL, Neu U, Stehle T - PLoS Pathog. (2015)

Bottom Line: By comparing electron density of the oligosaccharides within the binding pockets at various concentrations, we show that the [α-2,8]-linked sialic acid increases the strength of binding.Moreover, the amino acid exchanges have subtle effects on their affinity for the validated receptor GD1a.Our results indicate that both receptor specificity and affinity influence MuPyV pathogenesis.

View Article: PubMed Central - PubMed

Affiliation: Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany.

ABSTRACT
Murine polyomavirus (MuPyV) causes tumors of various origins in newborn mice and hamsters. Infection is initiated by attachment of the virus to ganglioside receptors at the cell surface. Single amino acid exchanges in the receptor-binding pocket of the major capsid protein VP1 are known to drastically alter tumorigenicity and spread in closely related MuPyV strains. The virus represents a rare example of differential receptor recognition directly influencing viral pathogenicity, although the factors underlying these differences remain unclear. We performed structural and functional analyses of three MuPyV strains with strikingly different pathogenicities: the low-tumorigenicity strain RA, the high-pathogenicity strain PTA, and the rapidly growing, lethal laboratory isolate strain LID. Using ganglioside deficient mouse embryo fibroblasts, we show that addition of specific gangliosides restores infectability for all strains, and we uncover a complex relationship between virus attachment and infection. We identify a new infectious ganglioside receptor that carries an additional linear [α-2,8]-linked sialic acid. Crystal structures of all three strains complexed with representative oligosaccharides from the three main pathways of ganglioside biosynthesis provide the molecular basis of receptor recognition. All strains bind to a range of sialylated glycans featuring the central [α-2,3]-linked sialic acid present in the established receptors GD1a and GT1b, but the presence of additional sialic acids modulates binding. An extra [α-2,8]-linked sialic acid engages a protein pocket that is conserved among the three strains, while another, [α-2,6]-linked branching sialic acid lies near the strain-defining amino acids but can be accommodated by all strains. By comparing electron density of the oligosaccharides within the binding pockets at various concentrations, we show that the [α-2,8]-linked sialic acid increases the strength of binding. Moreover, the amino acid exchanges have subtle effects on their affinity for the validated receptor GD1a. Our results indicate that both receptor specificity and affinity influence MuPyV pathogenesis.

No MeSH data available.


Related in: MedlinePlus

Overview and biosynthetic pathway of the four most prominent ganglioside series.The glycan parts of important members are shown for each series. The downstream biosynthetic steps are identical for all members of a row, although they may vary in linkage orientation. The six-membered pyranose rings are numbered counterclockwise, starting from the bottom (C1, except for C2 in Neu5Ac), and the ring oxygen is symbolized with a black dot. Neu5Ac moieties are rearranged for clarity, and all linkages are mediated by O2 or O8. Most of the gangliosides (e.g. LM1) can be further modified, e.g. by fucosylation. Linkages involving Neu5Ac are present in the α conformation, all other linkages are in the β conformation. Boxes represent three distinguishable sialoglycotopes that contain linkages found in GT1a (blue, representative for [α-2,8]), GD1a (green, [α-2,3]), and 3’-6’-iso-LD1 (also referred to as DSLNT, orange, [α-2,6]). The naming is according to the corresponding gangliosides; if possible, the Svennerholm shorthand is used [64–66] All biosynthetic routes were verified using the KEGG metabolic pathway database [67]. A prototype glycan that exemplifies the different positions of Gal and Neu5Ac moieties is depicted on the lower right. The glycan portions investigated in this study are highlighted by purple boxes.
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ppat.1005104.g001: Overview and biosynthetic pathway of the four most prominent ganglioside series.The glycan parts of important members are shown for each series. The downstream biosynthetic steps are identical for all members of a row, although they may vary in linkage orientation. The six-membered pyranose rings are numbered counterclockwise, starting from the bottom (C1, except for C2 in Neu5Ac), and the ring oxygen is symbolized with a black dot. Neu5Ac moieties are rearranged for clarity, and all linkages are mediated by O2 or O8. Most of the gangliosides (e.g. LM1) can be further modified, e.g. by fucosylation. Linkages involving Neu5Ac are present in the α conformation, all other linkages are in the β conformation. Boxes represent three distinguishable sialoglycotopes that contain linkages found in GT1a (blue, representative for [α-2,8]), GD1a (green, [α-2,3]), and 3’-6’-iso-LD1 (also referred to as DSLNT, orange, [α-2,6]). The naming is according to the corresponding gangliosides; if possible, the Svennerholm shorthand is used [64–66] All biosynthetic routes were verified using the KEGG metabolic pathway database [67]. A prototype glycan that exemplifies the different positions of Gal and Neu5Ac moieties is depicted on the lower right. The glycan portions investigated in this study are highlighted by purple boxes.

Mentions: The engagement of one or several host cell receptors is the first step in the infectious cycle of a virus. A large number of viruses, including many human pathogens, depend on carbohydrate recognition for initial attachment to the cell surface. Viral tropism and the internalization pathway are usually determined by the specificity and affinity of the receptor interaction as well as the glycan distribution on different cell surfaces (reviewed in [1]). Many viruses use glycoproteins, glycolipids, or both as receptors for cell entry [2]. Gangliosides are ubiquitous glycolipids on the outer leaflet of mammalian cell membranes that serve as receptors for a number of viruses. They are composed of a membrane-embedded ceramide moiety linked to a complex carbohydrate structure that projects away from the cell. Gangliosides almost always contain α-5-N-acetyl-neuraminic acid (sialic acid, Neu5Ac) that can be attached to the core of the molecule with [α-2,3], [α-2,6], or [α-2,8] linkages (Fig 1). Gangliosides exist on cell surfaces in complex and poorly understood patterns that are cell type-, age-, and tissue-dependent ([3,4], reviewed in [5]).


Structural and Functional Analysis of Murine Polyomavirus Capsid Proteins Establish the Determinants of Ligand Recognition and Pathogenicity.

Buch MH, Liaci AM, O'Hara SD, Garcea RL, Neu U, Stehle T - PLoS Pathog. (2015)

Overview and biosynthetic pathway of the four most prominent ganglioside series.The glycan parts of important members are shown for each series. The downstream biosynthetic steps are identical for all members of a row, although they may vary in linkage orientation. The six-membered pyranose rings are numbered counterclockwise, starting from the bottom (C1, except for C2 in Neu5Ac), and the ring oxygen is symbolized with a black dot. Neu5Ac moieties are rearranged for clarity, and all linkages are mediated by O2 or O8. Most of the gangliosides (e.g. LM1) can be further modified, e.g. by fucosylation. Linkages involving Neu5Ac are present in the α conformation, all other linkages are in the β conformation. Boxes represent three distinguishable sialoglycotopes that contain linkages found in GT1a (blue, representative for [α-2,8]), GD1a (green, [α-2,3]), and 3’-6’-iso-LD1 (also referred to as DSLNT, orange, [α-2,6]). The naming is according to the corresponding gangliosides; if possible, the Svennerholm shorthand is used [64–66] All biosynthetic routes were verified using the KEGG metabolic pathway database [67]. A prototype glycan that exemplifies the different positions of Gal and Neu5Ac moieties is depicted on the lower right. The glycan portions investigated in this study are highlighted by purple boxes.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4608799&req=5

ppat.1005104.g001: Overview and biosynthetic pathway of the four most prominent ganglioside series.The glycan parts of important members are shown for each series. The downstream biosynthetic steps are identical for all members of a row, although they may vary in linkage orientation. The six-membered pyranose rings are numbered counterclockwise, starting from the bottom (C1, except for C2 in Neu5Ac), and the ring oxygen is symbolized with a black dot. Neu5Ac moieties are rearranged for clarity, and all linkages are mediated by O2 or O8. Most of the gangliosides (e.g. LM1) can be further modified, e.g. by fucosylation. Linkages involving Neu5Ac are present in the α conformation, all other linkages are in the β conformation. Boxes represent three distinguishable sialoglycotopes that contain linkages found in GT1a (blue, representative for [α-2,8]), GD1a (green, [α-2,3]), and 3’-6’-iso-LD1 (also referred to as DSLNT, orange, [α-2,6]). The naming is according to the corresponding gangliosides; if possible, the Svennerholm shorthand is used [64–66] All biosynthetic routes were verified using the KEGG metabolic pathway database [67]. A prototype glycan that exemplifies the different positions of Gal and Neu5Ac moieties is depicted on the lower right. The glycan portions investigated in this study are highlighted by purple boxes.
Mentions: The engagement of one or several host cell receptors is the first step in the infectious cycle of a virus. A large number of viruses, including many human pathogens, depend on carbohydrate recognition for initial attachment to the cell surface. Viral tropism and the internalization pathway are usually determined by the specificity and affinity of the receptor interaction as well as the glycan distribution on different cell surfaces (reviewed in [1]). Many viruses use glycoproteins, glycolipids, or both as receptors for cell entry [2]. Gangliosides are ubiquitous glycolipids on the outer leaflet of mammalian cell membranes that serve as receptors for a number of viruses. They are composed of a membrane-embedded ceramide moiety linked to a complex carbohydrate structure that projects away from the cell. Gangliosides almost always contain α-5-N-acetyl-neuraminic acid (sialic acid, Neu5Ac) that can be attached to the core of the molecule with [α-2,3], [α-2,6], or [α-2,8] linkages (Fig 1). Gangliosides exist on cell surfaces in complex and poorly understood patterns that are cell type-, age-, and tissue-dependent ([3,4], reviewed in [5]).

Bottom Line: By comparing electron density of the oligosaccharides within the binding pockets at various concentrations, we show that the [α-2,8]-linked sialic acid increases the strength of binding.Moreover, the amino acid exchanges have subtle effects on their affinity for the validated receptor GD1a.Our results indicate that both receptor specificity and affinity influence MuPyV pathogenesis.

View Article: PubMed Central - PubMed

Affiliation: Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany.

ABSTRACT
Murine polyomavirus (MuPyV) causes tumors of various origins in newborn mice and hamsters. Infection is initiated by attachment of the virus to ganglioside receptors at the cell surface. Single amino acid exchanges in the receptor-binding pocket of the major capsid protein VP1 are known to drastically alter tumorigenicity and spread in closely related MuPyV strains. The virus represents a rare example of differential receptor recognition directly influencing viral pathogenicity, although the factors underlying these differences remain unclear. We performed structural and functional analyses of three MuPyV strains with strikingly different pathogenicities: the low-tumorigenicity strain RA, the high-pathogenicity strain PTA, and the rapidly growing, lethal laboratory isolate strain LID. Using ganglioside deficient mouse embryo fibroblasts, we show that addition of specific gangliosides restores infectability for all strains, and we uncover a complex relationship between virus attachment and infection. We identify a new infectious ganglioside receptor that carries an additional linear [α-2,8]-linked sialic acid. Crystal structures of all three strains complexed with representative oligosaccharides from the three main pathways of ganglioside biosynthesis provide the molecular basis of receptor recognition. All strains bind to a range of sialylated glycans featuring the central [α-2,3]-linked sialic acid present in the established receptors GD1a and GT1b, but the presence of additional sialic acids modulates binding. An extra [α-2,8]-linked sialic acid engages a protein pocket that is conserved among the three strains, while another, [α-2,6]-linked branching sialic acid lies near the strain-defining amino acids but can be accommodated by all strains. By comparing electron density of the oligosaccharides within the binding pockets at various concentrations, we show that the [α-2,8]-linked sialic acid increases the strength of binding. Moreover, the amino acid exchanges have subtle effects on their affinity for the validated receptor GD1a. Our results indicate that both receptor specificity and affinity influence MuPyV pathogenesis.

No MeSH data available.


Related in: MedlinePlus