Epstein-Barr virus IL-10 engages IL-10R1 by a two-step mechanism leading to altered signaling properties.
Human interleukin-10 (hIL-10) is a pleiotropic cytokine that is able to suppress or activate cellular immune responses to protect the host from invading pathogens. Epstein-Barr virus (EBV) encodes a viral IL-10 (ebvIL-10) in its genome that has retained the immunosuppressive activities of hIL-10 but lost the ability to induce immunostimulatory activities on some cells. These functional differences are at least partially due to the ∼1000-fold difference in hIL-10 and ebvIL-10 binding affinity for the IL-10R1·IL-10R2 cell surface receptors. Despite weaker binding to IL-10R1, ebvIL-10 is more active than hIL-10 in inducing B-cell proliferation. To explore this counterintuitive observation further, a series of monomeric and dimeric ebvIL-10·hIL-10 chimeric proteins were produced and characterized for receptor binding and cellular proliferation on TF-1/hIL-10R1 cells that express high levels of the IL-10R1 chain. On this cell line, monomeric chimeras elicited cell proliferation in accordance with how tightly they bound to the IL-10R1 chain. In contrast, dimeric chimeras exhibiting the highest affinity for IL-10R1 exhibited reduced proliferative activity. These distinct activity profiles are correlated with kinetic analyses that reveal that the ebvIL-10 dimer is impaired in its ability to form a 1:2 ebvIL-10·IL-10R1 complex. As a result, the ebvIL-10 dimer functions like a monomer at low IL-10R1 levels, which prevents efficient signaling. At high IL-10R1 levels, the ebvIL-10 dimer is able to induce signaling responses greater than hIL-10. Thus, the ebvIL-10 dimer scaffold is essential to prevent activation of cells with low IL-10R1 levels but to maintain or enhance activity on cells with high IL-10R1 levels.
Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
Sung Il
SI
Yoon
Brandi C
BC
Jones
Naomi J
NJ
Logsdon
Bethany D
BD
Harris
Srilalitha
S
Kuruganti
Mark R
MR
Walter
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D019281:Dimerization; D004330:Drosophila; D004854:Herpesvirus 4, Human / Q000378:metabolism*; D016753:Interleukin-10 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D053709:Interleukin-10 Receptor alpha Subunit / Q000378:metabolism / Q000502:physiology*; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D020349:Surface Plasmon Resonance
D053709:Interleukin-10 Receptor alpha Subunit; D016753:Interleukin-10