Activation of the leptin receptor by a ligand-induced conformational change of constitutive receptor dimers.
Binding of leptin to the leptin receptor is crucial for body weight and bone mass regulation in mammals. Leptin receptors were shown to exist as dimers, but the role of dimerization in receptor activation remains unknown. Using a quantitative Bioluminescence Resonance Energy Transfer approach, we show here in living cells that approximately 60% of the leptin receptor exists as constitutive dimers at physiological expression levels in the absence of leptin. No further increase in leptin receptor dimerization was detected in the presence of leptin. Importantly, in cells expressing the short leptin receptor isoform, leptin promoted a robust enhancement of energy transfer signals that reflect specific conformational changes of pre-existing leptin receptor dimers and that may be used as read-out in screening assays for leptin receptor ligands. Both leptin receptor dimerization and the leptin-induced energy transfer were Janus kinase 2-independent. Taken together, our data support a receptor activation model based on ligand-induced conformational changes rather than ligand-induced dimerization.
Couturier
Cyril
C
Department of Cell Biology, Institut Cochin, INSERM U567, CNRS 8104, Université René Descartes, 22 rue Méchain, 75014 Paris, France.
Jockers
Ralf
R
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D019556:COS Cells; D002460:Cell Line; D019281:Dimerization; D004735:Energy Transfer; D006367:HeLa Cells; D006801:Humans; D053614:Janus Kinase 2; D020738:Leptin / Q000378:metabolism; D008024:Ligands; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008163:Luminescent Measurements; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020836:Protein Structure, Quaternary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D054411:Receptors, Leptin; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; C515448:LEPR protein, human; D020738:Leptin; D008024:Ligands; D008164:Luminescent Proteins; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D011993:Recombinant Fusion Proteins; C054562:yellow fluorescent protein, Bacteria; D008156:Luciferases; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2