title: The Receptor-Binding Domain in the VP1u Region of Parvovirus B19.
abstract: Parvovirus B19 (B19V) is known as the human pathogen causing the mild childhood disease erythema infectiosum. B19V shows an extraordinary narrow tissue tropism for erythroid progenitor cells in the bone marrow, which is determined by a highly restricted uptake. We have previously shown that the specific internalization is mediated by the interaction of the viral protein 1 unique region (VP1u) with a yet unknown cellular receptor. To locate the receptor-binding domain (RBD) within the VP1u, we analyzed the effect of truncations and mutations on the internalization capacity of the recombinant protein into UT7/Epo cells. Here we report that the N-terminal amino acids 5-80 of the VP1u are necessary and sufficient for cellular binding and internalization; thus, this N-terminal region represents the RBD required for B19V uptake. Using site-directed mutagenesis, we further identified a cluster of important amino acids playing a critical role in VP1u internalization. In silico predictions and experimental results suggest that the RBD is structured as a rigid fold of three α-helices. Finally, we found that dimerization of the VP1u leads to a considerably enhanced cellular binding and internalization. Taken together, we identified the RBD that mediates B19V uptake and mapped functional and structural motifs within this sequence. The findings reveal insights into the uptake process of B19V, which contribute to understand the pathogenesis of the infection and the neutralization of the virus by the immune system.
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland. remo.leisi@dcb.unibe.ch.
authors.forename: Remo
authors.initials: R
authors.lastname: Leisi
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland. chiarina.ditommaso@hotmail.com.
authors.forename: Chiarina
authors.initials: C
authors.lastname: Di Tommaso
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland. christoph.kempf@dcb.unibe.ch.|CSL Behring AG, Bern 3014, Switzerland. christoph.kempf@dcb.unibe.ch.
authors.forename: Christoph
authors.initials: C
authors.lastname: Kempf
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland. carlos.ros@dcb.unibe.ch.|CSL Behring AG, Bern 3014, Switzerland. carlos.ros@dcb.unibe.ch.
authors.forename: Carlos
authors.initials: C
authors.lastname: Ros
mesh_terms: D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004252:DNA Mutational Analysis; D006801:Humans; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D016732:Parvovirus B19, Human / Q000235:genetics / Q000502:physiology*; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D011991:Receptors, Virus / Q000378:metabolism*; D017384:Sequence Deletion; D053586:Virus Internalization
chemical_list: D036022:Capsid Proteins; D050505:Mutant Proteins; D011991:Receptors, Virus; C095547:capsid protein VP1, parvovirus B19
keywords: VP1u; immunodominant region; parvovirus B19; receptor-binding domain; virus entry