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Structure of reovirus sigma1 in complex with its receptor junctional adhesion molecule-A.

ABSTRACT: Viral attachment to specific host receptors is the first step in viral infection and serves an essential function in the selection of target cells. Mammalian reoviruses are highly useful experimental models for studies of viral pathogenesis and show promise as vectors for oncolytics and vaccines. Reoviruses engage cells by binding to carbohydrates and the immunoglobulin superfamily member, junctional adhesion molecule-A (JAM-A). JAM-A exists at the cell surface as a homodimer formed by extensive contacts between its N-terminal immunoglobulin-like domains. We report the crystal structure of reovirus attachment protein sigma1 in complex with a soluble form of JAM-A. The sigma1 protein disrupts the JAM-A dimer, engaging a single JAM-A molecule via virtually the same interface that is used for JAM-A homodimerization. Thus, reovirus takes advantage of the adhesive nature of an immunoglobulin-superfamily receptor by usurping the ligand-binding site of this molecule to attach to the cell surface. The dissociation constant (K(D)) of the interaction between sigma1 and JAM-A is 1,000-fold lower than that of the homophilic interaction between JAM-A molecules, indicating that JAM-A strongly prefers sigma1 as a ligand. Analysis of reovirus mutants engineered by plasmid-based reverse genetics revealed residues in sigma1 required for binding to JAM-A and infectivity of cultured cells. These studies define biophysical mechanisms of reovirus cell attachment and provide a platform for manipulating reovirus tropism to enhance vector targeting.

SUBMITTER: Kirchner E

PROVIDER: S-EPMC2588538 | biostudies-literature | 2008 Dec

REPOSITORIES: biostudies-literature

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Structure of reovirus sigma1 in complex with its receptor junctional adhesion molecule-A.

Kirchner Eva E Guglielmi Kristen M KM Strauss Holger M HM Dermody Terence S TS Stehle Thilo T

PLoS pathogens 20081212 12

Viral attachment to specific host receptors is the first step in viral infection and serves an essential function in the selection of target cells. Mammalian reoviruses are highly useful experimental models for studies of viral pathogenesis and show promise as vectors for oncolytics and vaccines. Reoviruses engage cells by binding to carbohydrates and the immunoglobulin superfamily member, junctional adhesion molecule-A (JAM-A). JAM-A exists at the cell surface as a homodimer formed by extensive ...[more]

PMID: 19079583

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Project description:Molecular dynamics simulations were performed using the recently determined crystal structure of the reovirus attachment protein, sigma1. These studies were conducted to improve an understanding of two unique features of sigma1 structure: the protonation state of Asp(345), which is buried in the sigma1 trimer interface, and the flexibility of the protein at a defined region below the receptor-binding head domain. Three copies of aspartic acids Asp(345) and Asp(346) cluster in a solvent-inaccessible and hydrophobic region at the sigma1 trimer interface. These residues are hypothesized to mediate conformational changes in sigma1 during viral attachment or cell entry. Our results indicate that protonation of Asp(345) is essential to the integrity of the trimeric structure seen by x-ray crystallography, whereas deprotonation induces structural changes that destabilize the trimer interface. This finding was confirmed by electrostatic calculations using the finite difference Poisson-Boltzmann method. Earlier studies show that sigma1 can exist in retracted and extended conformations on the viral surface. Since protonated Asp(345) is necessary to form a stable, extended trimer, our results suggest that protonation of Asp(345) may allow for a structural transition from a partially detrimerized molecule to the fully formed trimer seen in the crystal structure. Additional studies were conducted to quantify the previously observed flexibility of sigma1 at a defined region below the receptor-binding head domain. Increased mobility was observed for three polar residues (Ser(291), Thr(292), and Ser(293)) located within an insertion between the second and third beta-spiral repeats of the crystallized portion of the sigma1 tail. These amino acids interact with water molecules of the solvent bulk and are responsible for oscillating movement of the head of approximately 50 degrees during 5 ns of simulations. This flexibility may facilitate viral attachment and also function in cell entry and disassembly. These findings provide new insights about the conformational dynamics of sigma1 that likely underlie the initiation of the reovirus infectious cycle.

Dataset Information

Structure of reovirus sigma1 in complex with its receptor junctional adhesion molecule-A.

Publications

Structure of reovirus sigma1 in complex with its receptor junctional adhesion molecule-A.

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