Tuning cytokine receptor signaling by re-orienting dimer geometry with surrogate ligands
Moraga I., Wernig G., Wilmes S., Gryshkova V., Richter CP., Hong WJ., Sinha R., Guo F., Fabionar H., Wehrman TS., Krutzik P., Demharter S., Plo I., Weissman IL., Minary P., Majeti R., Constantinescu SN., Piehler J., Garcia KC.
© 2015 Elsevier Inc. Most cell-surface receptors for cytokines and growth factors signal as dimers, but it is unclear whether remodeling receptor dimer topology is a viable strategy to "tune" signaling output. We utilized diabodies (DA) as surrogate ligands in a prototypical dimeric receptor-ligand system, the cytokine Erythropoietin (EPO) and its receptor (EpoR), to dimerize EpoR ectodomains in non-native architectures. Diabody-induced signaling amplitudes varied from full to minimal agonism, and structures of these DA/EpoR complexes differed in EpoR dimer orientation and proximity. Diabodies also elicited biased or differential activation of signaling pathways and gene expression profiles compared to EPO. Non-signaling diabodies inhibited proliferation of erythroid precursors from patients with a myeloproliferative neoplasm due to a constitutively active JAK2V617F mutation. Thus, intracellular oncogenic mutations causing ligand-independent receptor activation can be counteracted by extracellular ligands that re-orient receptors into inactive dimer topologies. This approach has broad applications for tuning signaling output for many dimeric receptor systems.