Crystal structures of the human adiponectin receptors

Adiponectin stimulation of its receptors, AdipoR1 and AdipoR2, increases AMPK and PPAR activities, respectively, thereby contributing to healthy longevity as key anti-diabetic molecules. AdipoR1 and AdipoR2 were predicted to contain seven transmembrane helices with the opposite topology to G protein-coupled receptor (GPCR)s. Here we report the crystal structures of human AdipoR1 and AdipoR2 at 2.9- and 2.4-Å resolution, respectively, which represent a novel class of receptor structure. The seven-transmembrane helices, conformationally distinct from those of GPCRs, enclose a large cavity where three conserved histidine residues coordinate a zinc ion. The zinc-binding structure may play a role in the adiponectin-stimulated AMPK phosphorylation and UCP2 upregulation. Adiponectin may broadly interact with the extracellular face, rather than the C-terminal flexible tail, of the receptors. The present information will facilitate the understanding of novel structure-function relationships and the development and optimization of AdipoR agonists for the treatment of obesity-related diseases, such as type 2 diabetes.