Structural Model of the Oncostatin M (OSM)-OSMRβ-gp130 Ternary Complex Reveals Pathways of Allosteric Communication in OSM Signaling.

Introduction: Human oncostatin M (OSM) is a pleiotropic cytokine that regulates inflammatory and immune responses by binding to the heterodimer receptor complex OSM receptor beta (OSMRβ) and glycoprotein 130 (gp130). The distinct signaling pathways triggered by OSM are involved in multiple chronic inflammatory conditions, such as inflammatory bowel disease (IBD), rheumatoid arthritis (RA), and cancers, making the OSM-bound receptor complex a significant therapeutic target. Currently, no 3D structure of human OSM recognition complex is available, and thus, the molecular mechanisms underlying OSM signaling remain poorly understood.

Methods: In this study, for the first time, we proposed a full-length structural model of the human OSM-OSMRβ-gp130, generated using AlphaFold2 protein structure prediction and all-atom molecular dynamics (MD) simulation (~ 1.12 million atoms with explicit solvent), enabling investigation of the geometric and dynamic profiles of OSM- OSMRβ-gp130 structure at atomic-level.

Results: Analysis of the simulation trajectory demonstrated that the structural rearrangements of the heterodimer receptors (i.e., OSMRβ and gp130) initiated by OSM binding mediated the signal transduction from the extracellular to the intracellular domains. In the representative conformation identified through clustering analysis, two main allosteric pathways contributed were found to mediate signal transduction from the allosteric region of OSM to the active sites of OSMRβ and gp130. Finally, two druggable binding sites located on OSM and gp130 were detected by dynamically monitoring pocket flexibility throughout the simulation. A comprehensive analysis of the OSM-OSMRβ-gp130 model was carried out with respect to OSM signaling.

Conclusion: The findings of this study not only enhance the mechanistic understanding of OSM binding to the heteromeric OSMRβ/gp130 but also identify druggable binding sites for structure-based design of small molecules to inhibit the intracellular signal transduction.