title: Structural and mechanistic paradigm of leptin receptor activation revealed by complexes with wild-type and antagonist leptins.
abstract: Leptin activates its cognate receptor (LR) to regulate body weight and metabolically costly processes, such as reproduction and immune responses. Despite such benevolent pleiotropy, leptin-mediated signaling has been implicated in autoimmune diseases and breast cancer, thereby rejuvenating interest in leptin antagonism. We present comparative biochemical and structural studies of the LR ectodomain (LRecto) in complex with wild-type and antagonist leptin variants. We show that high-affinity binding of leptin to the cytokine receptor homology 2 domain of LRecto primes interactions with the Ig-domain (LRIg) of another leptin-bound LRecto to establish a quaternary assembly. In contrast, antagonist leptin variants carrying mutations at the LRIg binding site only enable binary complexes with LRecto. Acetylation of free cysteines in LRecto also abrogates quaternary complexes, suggesting a functional role for intrareceptor disulfides. We propose a revised conceptual framework for LR activation whereby leptin activates predimerized LR at the cell surface to seed higher order complexes with 4:4 stoichiometry.
authors.affiliation: Unit for Structural Biology, Laboratory for Protein Biochemistry and Biomolecular Engineering (L-ProBE), Ghent University, 9000 Ghent, Belgium.
authors.forename: Kedar
authors.initials: K
authors.lastname: Moharana
authors.affiliation: Flanders Institute for Biotechnology (VIB) and Department of Medical Protein Research, Ghent University, 9000 Ghent, Belgium.
authors.forename: Lennart
authors.initials: L
authors.lastname: Zabeau
authors.affiliation: Flanders Institute for Biotechnology (VIB) and Department of Medical Protein Research, Ghent University, 9000 Ghent, Belgium.
authors.forename: Frank
authors.initials: F
authors.lastname: Peelman
authors.affiliation: Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, 4003 Basel, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Ringler
authors.affiliation: Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, 4003 Basel, Switzerland.
authors.forename: Henning
authors.initials: H
authors.lastname: Stahlberg
authors.affiliation: Flanders Institute for Biotechnology (VIB) and Department of Medical Protein Research, Ghent University, 9000 Ghent, Belgium. Electronic address: jan.tavernier@vib-ugent.be.
authors.forename: Jan
authors.initials: J
authors.lastname: Tavernier
authors.affiliation: Unit for Structural Biology, Laboratory for Protein Biochemistry and Biomolecular Engineering (L-ProBE), Ghent University, 9000 Ghent, Belgium. Electronic address: savvas.savvides@ugent.be.
authors.forename: Savvas N
authors.initials: SN
authors.lastname: Savvides
mesh_terms: D055592:Biophysical Phenomena; D003545:Cysteine / Q000737:chemistry; D006801:Humans; D020738:Leptin / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D054411:Receptors, Leptin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: C515448:LEPR protein, human; D020738:Leptin; D046912:Multiprotein Complexes; D054411:Receptors, Leptin; D011994:Recombinant Proteins; D003545:Cysteine