Structural basis for murine norovirus engagement of bile acids and the CD300lf receptor

Murine norovirus (MNoV) is closely related to human norovirus (HNoV), an infectious agent responsible for acute gastroenteritis worldwide. Here we report the X-ray crystal structure of the dimeric MNoV VP1 protruding (P) domain in complex with its cellular receptor CD300lf. CD300lf binds the P domain with a 2:2 stoichiometry, engaging a cleft between the AB and DE loops of the P2 subdomain at a site that overlaps the epitopes of neutralizing antibodies. We also identify that bile acids are cofactors enhancing MNoV cell-binding and infectivity. Structures of CD300lf–P domain in complex with glycochenodeoxycholic acid (GCDCA) and lithocholic acid (LCA) reveal two bile acid binding sites at the P domain dimer interface distant from receptor binding sites. The structural determinants for receptor and bile acid binding are supported by numerous biophysical assays utilizing interface residue mutations. We find that the monomeric affinity of CD300lf for the P domain is low and is divalent cation dependent. We have also determined the crystal structure of CD300lf in complex with phosphocholine, revealing that MNoV engages its receptor in a manner mimicking host ligands including similar metal coordination. Docking of the cocomplex structures onto a cryo-EM–derived model of MNoV suggests that each virion can make multiple CD300lf engagements, and thus, infection may be driven by the avidity of cell surface clustered CD300lf. These studies identify multiple potential modulators of norovirus infection that may act to regulate the interaction between the viral capsid P domain and its cognate cellular receptor.

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Structural Basis for Human Norovirus Capsid Binding to Bile Acids

Journal of Virology ◽

10.1128/jvi.01581-18 ◽

2018 ◽

Vol 93 (2) ◽

Cited By ~ 23

Author(s):

Turgay Kilic ◽

Anna Koromyslova ◽

Grant S. Hansman

Keyword(s):

Bile Acid ◽

Amino Acid ◽

Bile Acids ◽

Natural Infection ◽

Structural Basis ◽

Amino Acid Side Chain ◽

Blood Group Antigens ◽

Human Norovirus ◽

Bile Acid Binding ◽

P Domain

ABSTRACT A recently developed human norovirus cell culture system revealed that the presence of bile enhanced or was an essential requirement for the growth of certain genotypes. Before this discovery, histo-blood group antigens (HBGAs) were the only well-studied cofactor known for human noroviruses, and there was evidence that several genotypes poorly bound HBGAs. Therefore, the purpose of this study was to investigate how human norovirus capsids interact with bile acids. We found that bile acids had low-micromolar affinities for GII.1, GII.10, and GII.19 capsids but did not bind GI.1, GII.3, GII.4, or GII.17. We showed that bile acid bound at a partially conserved pocket on the norovirus capsid-protruding (P) domain using X-ray crystallography. Amino acid sequence alignment and structural analysis delivered an explanation of selective bile acid binding. Intriguingly, we discovered that binding of the bile acid was the critical step to stabilize several P domain loops that optimally placed an essential amino acid side chain (Asp375) to bind HBGAs in an otherwise HBGA nonbinder (GII.1). Furthermore, bile acid enhanced HBGA binding for a known HBGA binder (GII.10). Altogether, these new data suggest that bile acid functions as a loop-stabilizing regulator and enhancer of HBGA binding for certain norovirus genotypes. IMPORTANCE Given that human norovirus virions likely interact with bile acid during a natural infection, our evidence that an HBGA nonbinder (GII.1) can be converted to an HBGA binder after bile acid binding is of major significance. Our data provide direct evidence that, like HBGAs, bile acid interaction on the capsid is an important cofactor for certain genotypes. However, more unanswered questions seem to arise from these new discoveries. For example, is there an association between the bile acid requirement and the prevalence of certain genotypes? That is, the GII.1 and GII.10 (bile acid binders) genotypes rarely caused outbreaks, whereas the GII.4 and GII.17 genotypes (bile acid nonbinders) were responsible for large epidemics. Therefore, it seems plausible that certain genotypes require bile acids, whereas others have modified their bile acid requirements on the capsid.

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Faculty Opinions recommendation of Structural basis for bile acid binding and activation of the nuclear receptor FXR.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1014043.192544 ◽

2003 ◽

Author(s):

Matt Redinbo

Keyword(s):

Bile Acid ◽

Nuclear Receptor ◽

Structural Basis ◽

Bile Acid Binding

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Validation of Recombinant Chicken Liver Bile Acid Binding Protein as a Tool for Cholic Acid Hosting

Biomolecules ◽

10.3390/biom11050645 ◽

2021 ◽

Vol 11 (5) ◽

pp. 645

Author(s):

Giusy Tassone ◽

Maurizio Orlandini ◽

Massimo Olivucci ◽

Cecilia Pozzi

Keyword(s):

Bile Acid ◽

High Resolution ◽

Affinity Chromatography ◽

Bile Acids ◽

Drug Carriers ◽

Chicken Liver ◽

Purification Procedure ◽

Acid Binding Protein ◽

Bile Acid Binding ◽

Exogenous Substances

Bile acids (BAs) are hydroxylated steroids derived from cholesterol that act at the intestinal level to facilitate the absorption of several nutrients and also play a role as signaling molecules. In the liver of various vertebrates, the trafficking of BAs is mediated by bile acid-binding proteins (L-BABPs). The ability to host hydrophobic or amphipathic molecules makes BABPs suitable for the distribution of a variety of physiological and exogenous substances. Thus, BABPs have been proposed as drug carriers, and more recently, they have also been employed to develop innovative nanotechnology and biotechnology systems. Here, we report an efficient protocol for the production, purification, and crystallization of chicken liver BABP (cL-BABP). By means of target expression as His6-tag cL-BABP, we obtained a large amount of pure and homogeneous proteins through a simple purification procedure relying on affinity chromatography. The recombinant cL-BABP showed a raised propensity to crystallize, allowing us to obtain its structure at high resolution and, in turn, assess the structural conservation of the recombinant cL-BABP with respect to the liver-extracted protein. The results support the use of recombinant cL-BABP for the development of drug carriers, nanotechnologies, and innovative synthetic photoswitch systems.

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Effect of Bile Acids and Other Factors on Cholesterol Uptake by Inverted Intestinal Sacs

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1958.195.3.773 ◽

1958 ◽

Vol 195 (3) ◽

pp. 773-778 ◽

Cited By ~ 6

Author(s):

Archie L. Smith ◽

C. R. Treadwell

Keyword(s):

Small Intestine ◽

Bile Acid ◽

Bile Acids ◽

Binding Sites ◽

Cellular Protein ◽

Rat Small Intestine ◽

Cholesterol Uptake ◽

Quantitative Studies ◽

Mucosal Cells ◽

Intestinal Mucosal Cells

Conditions for the use of inverted sacs of rat small intestine for quantitative studies of cholesterol uptake are described. The uptake of cholesterol by sacs did not require glucose in the incubation medium. Albumin aided cholesterol uptake but was not obligatory for this process. A binding of cholesterol to a cellular protein is proposed as the mechanism for the entrance of cholesterol into intestinal mucosal cells. Both conjugated and unconjugated bile acids inhibited cholesterol uptake possibly by blocking the binding sites of the protein responsible for cholesterol uptake. Commercial taurocholate and glycocholate contain an inhibitor of cholesterol uptake other than the bile acid.

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