RESUMEN
The cytokine interferon-γ (IFNγ) is a central coordinator of innate and adaptive immunity, but its highly pleiotropic actions have diminished its prospects for use as an immunotherapeutic agent. Here, we took a structure-based approach to decoupling IFNγ pleiotropy. We engineered an affinity-enhanced variant of the ligand-binding chain of the IFNγ receptor IFNγR1, which enabled us to determine the crystal structure of the complete hexameric (2:2:2) IFNγ-IFNγR1-IFNγR2 signalling complex at 3.25 Šresolution. The structure reveals the mechanism underlying deficits in IFNγ responsiveness in mycobacterial disease syndrome resulting from a T168N mutation in IFNγR2, which impairs assembly of the full signalling complex. The topology of the hexameric complex offers a blueprint for engineering IFNγ variants to tune IFNγ receptor signalling output. Unexpectedly, we found that several partial IFNγ agonists exhibited biased gene-expression profiles. These biased agonists retained the ability to induce upregulation of major histocompatibility complex class I antigen expression, but exhibited impaired induction of programmed death-ligand 1 expression in a wide range of human cancer cell lines, offering a route to decoupling immunostimulatory and immunosuppressive functions of IFNγ for therapeutic applications.
Asunto(s)
Diseño de Fármacos , Interferón gamma/agonistas , Interferón gamma/inmunología , Receptores de Interferón/química , Receptores de Interferón/metabolismo , Antígeno B7-H1/biosíntesis , Antígeno B7-H1/genética , Línea Celular Tumoral , Agonismo Parcial de Drogas , Perfilación de la Expresión Génica , Regulación de la Expresión Génica/efectos de los fármacos , Antígenos de Histocompatibilidad Clase I/biosíntesis , Antígenos de Histocompatibilidad Clase I/genética , Humanos , Interferón gamma/química , Interferón gamma/genética , Ligandos , Modelos Moleculares , Mutación , Infecciones por Mycobacterium/genética , Infecciones por Mycobacterium/inmunología , Estabilidad Proteica , Receptores de Interferón/genética , Transducción de Señal , Relación Estructura-Actividad , Receptor de Interferón gammaRESUMEN
Type III interferons (IFN-λs) signal through a heterodimeric receptor complex composed of the IFN-λR1 subunit, specific for IFN-λs, and interleukin-10Rß (IL-10Rß), which is shared by multiple cytokines in the IL-10 superfamily. Low affinity of IL-10Rß for cytokines has impeded efforts aimed at crystallizing cytokine-receptor complexes. We used yeast surface display to engineer a higher-affinity IFN-λ variant, H11, which enabled crystallization of the ternary complex. The structure revealed that IL-10Rß uses a network of tyrosine residues as hydrophobic anchor points to engage IL-10 family cytokines that present complementary hydrophobic binding patches, explaining its role as both a cross-reactive but cytokine-specific receptor. H11 elicited increased anti-proliferative and antiviral activities in vitro and in vivo. In contrast, engineered higher-affinity type I IFNs did not increase antiviral potency over wild-type type I IFNs. Our findings provide insight into cytokine recognition by the IL-10R family and highlight the plasticity of type III interferon signaling and its therapeutic potential.