Structural insights into adiponectin receptors suggest ceramidase activity.
Adiponectin receptors (ADIPORs) are integral membrane proteins that control glucose and lipid metabolism by mediating, at least in part, a cellular ceramidase activity that catalyses the hydrolysis of ceramide to produce sphingosine and a free fatty acid (FFA). The crystal structures of the two receptor subtypes, ADIPOR1 and ADIPOR2, show a similar overall seven-transmembrane-domain architecture with large unoccupied cavities and a zinc binding site within the seven transmembrane domain. However, the molecular mechanisms by which ADIPORs function are not known. Here we describe the crystal structure of ADIPOR2 bound to a FFA molecule and show that ADIPOR2 possesses intrinsic basal ceramidase activity that is enhanced by adiponectin. We also identify a ceramide binding pose and propose a possible mechanism for the hydrolytic activity of ADIPOR2 using computational approaches. In molecular dynamics simulations, the side chains of residues coordinating the zinc rearrange quickly to promote the nucleophilic attack of a zinc-bound hydroxide ion onto the ceramide amide carbonyl. Furthermore, we present a revised ADIPOR1 crystal structure exhibiting a seven-transmembrane-domain architecture that is clearly distinct from that of ADIPOR2. In this structure, no FFA is observed and the ceramide binding pocket and putative zinc catalytic site are exposed to the inner membrane leaflet. ADIPOR1 also possesses intrinsic ceramidase activity, so we suspect that the two distinct structures may represent key steps in the enzymatic activity of ADIPORs. The ceramidase activity is low, however, and further studies will be required to characterize fully the enzymatic parameters and substrate specificity of ADIPORs. These insights into ADIPOR function will enable the structure-based design of potent modulators of these clinically relevant enzymes.
Institut de Génomique Fonctionnelle, CNRS UMR-5203 INSERM U1191, University of Montpellier, 34094 Montpellier, France.
Ieva
I
Vasiliauskaité-Brooks
Institut de Génomique Fonctionnelle, CNRS UMR-5203 INSERM U1191, University of Montpellier, 34094 Montpellier, France.
Remy
R
Sounier
Institut de Génomique Fonctionnelle, CNRS UMR-5203 INSERM U1191, University of Montpellier, 34094 Montpellier, France.
Pascal
P
Rochaix
Institut de Génomique Fonctionnelle, CNRS UMR-5203 INSERM U1191, University of Montpellier, 34094 Montpellier, France.
Gaëtan
G
Bellot
Institut de Génomique Fonctionnelle, CNRS UMR-5203 INSERM U1191, University of Montpellier, 34094 Montpellier, France.
Mathieu
M
Fortier
Centre de Biochimie Structurale, CNRS UMR 5048-INSERM 1054 University of Montpellier, 29 rue de Navacelles, 34090 Montpellier Cedex, France.
François
F
Hoh
Division of Structural Biology, University of Oxford, Oxford, UK.
Luigi
L
De Colibus
Dynamique des Interactions Membranaires Normales et Pathologiques, CNRS UMR5235, University of Montpellier, 34095 Montpellier, France.
Chérine
C
Bechara
Institute for chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany.|Chemistry Department, Faculty of Science, Suez Canal University, 41522 Ismailia, Egypt.
Essa M
EM
Saied
Institute for chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany.
Christoph
C
Arenz
Institut de Génomique Fonctionnelle, CNRS UMR-5203 INSERM U1191, University of Montpellier, 34094 Montpellier, France.
Cédric
C
Leyrat
Institut de Génomique Fonctionnelle, CNRS UMR-5203 INSERM U1191, University of Montpellier, 34094 Montpellier, France.
Sébastien
S
Granier
D052242:Adiponectin / Q000378:metabolism / Q000494:pharmacology; D001665:Binding Sites; D020134:Catalytic Domain; D002518:Ceramides / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D005230:Fatty Acids, Nonesterified / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis / Q000187:drug effects; D006878:Hydroxides / Q000378:metabolism; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D000072417:Protein Domains; D054419:Receptors, Adiponectin / Q000737:chemistry* / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism
C475418:ADIPOR1 protein, human; C475420:ADIPOR2 protein, human; D052242:Adiponectin; D002518:Ceramides; D005230:Fatty Acids, Nonesterified; D006878:Hydroxides; D054419:Receptors, Adiponectin; C031356:hydroxide ion; D015032:Zinc