Discovery of a junctional epitope antibody that stabilizes IL-6 and gp80 protein:protein interaction and modulates its downstream signaling

• Published in: Scientific reports Vol. 7; no. 1; p. 37716
• Main Authors: Adams, Ralph, Burnley, Rebecca J., Valenzano, Chiara R., Qureshi, Omar, Doyle, Carl, Lumb, Simon, del Carmen Lopez, Maria, Griffin, Robert, McMillan, David, Taylor, Richard D., Meier, Chris, Mori, Prashant, Griffin, Laura M., Wernery, Ulrich, Kinne, Jörg, Rapecki, Stephen, Baker, Terry S., Lawson, Alastair D. G., Wright, Michael, Ettorre, Anna
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 30.01.2017; Nature Publishing Group
• Subjects: 101/1; 101/58; 38/47; 45/77; 631/154/51; 631/535/1266; 631/61/24; 96; 96/21; 96/63; Animals; Antibodies; Antibodies - chemistry; Antibodies - immunology; Camelus - immunology; CHO Cells; Cricetulus; Crystallography; Endothelial cells; Epitope Mapping; Epitopes; Gene Expression Profiling; HEK293 Cells; Homeostasis; Humanities and Social Sciences; Humans; Inflammation; Interleukin 6; Interleukin-6 - immunology; multidisciplinary; Nanobodies; Phosphorylation; Protein interaction; Protein Structure, Tertiary; Proteins; Receptors, Interleukin-6 - immunology; Science; Science (multidisciplinary); Signal Transduction; Stat3 protein; STAT3 Transcription Factor - metabolism; X-ray crystallography
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep37716

Protein:protein interactions are fundamental in living organism homeostasis. Here we introduce VHH6, a junctional epitope antibody capable of specifically recognizing a neo-epitope when two proteins interact, albeit transiently, to form a complex. Orthogonal biophysical techniques have been used to prove the “junctional epitope” nature of VHH6, a camelid single domain antibody recognizing the IL-6–gp80 complex but not the individual components alone. X-ray crystallography, HDX-MS and SPR analysis confirmed that the CDR regions of VHH6 interact simultaneously with IL-6 and gp80, locking the two proteins together. At the cellular level, VHH6 was able to alter the response of endothelial cells to exogenous IL-6, promoting a sustained STAT3 phosphorylation signal, an accumulation of IL-6 in vesicles and an overall pro-inflammatory phenotype supported further by transcriptomic analysis. Junctional epitope antibodies, like VHH6, not only offer new opportunities in screening and structure-aided drug discovery, but could also be exploited as therapeutics to modulate complex protein:protein interactions.