Structural plasticity of human leptin binding to its receptor LepR

Leptin receptor (LepR) signaling plays an essential role in balancing food intake and energy expenditure. The architecture of LepR signaling assembly is critical for its function. In this study, we determined the structures of three distinct conformations of human leptin–LepR using cryo-electron microscopy at resolutions of 3.88, 3.77, and 3.58 Å. Both 2:2 and 3:3 stoichiometric assemblies were observed, and the complexes exhibited asymmetric open conformations. Leptin undergoes substantial rearrangement of its flexible regions to accommodate binding to LepR. The assembled leptin–LepR complexes connect through a “hand-in-hand” geometry. The open, interlocked 3:3 trimeric assembly results from the engagement of a third leptin–LepR heterodimer with a 2:2 dimer. The asymmetric geometry of LepR is substantially distinct from that of other gp130 cytokine homologs, and that may be due to the twisted and rigid interface between the D3 and D4 domains. These results highlight the distinct engagement of leptin with LepR and provide important insights into the structural plasticity of LepR-signaling assemblies.