The folding interactome of GPCRs

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    The folding interactome of GPCRsChristian Bergmayr, Christian Nanoff, Oliver Kudlacek, Michael Freissmuth, Christian W Gruber*

    From 17th Scientific Symposium of the Austrian Pharmacological Society (APHAR). Joint meeting with theHungarian Society of Experimental and Clinical Pharmacology (MFT)Innsbruck, Austria. 29-30 September 2011

    BackgroundThe A2A adenosine receptor is a prototypical G protein-coupled receptor. It is expressed in a wide variety of cellsincluding as different types as neurons, platelets, cells ofthe immune system and muscle. The A2A receptor has anunusually long C-terminus (of >120 residues), whichfor the most part is dispensable for coupling to Gs. ThisC-terminus turned out to be the docking site for otherproteins. Using a yeast-2-hybrid screen we have previouslyidentified proteins interacting with the C-terminus includ-ing ARNO/cytohesin2, SAP102 and USP4.

    MethodsTo verify these interactions in vivo and to identify newinteracting proteins of the A2A adenosine receptor wechose a two-step proteomics approach: we first expressedtagged receptors in HEK293 fibroblasts using various TAP(tandem affinity purification)-tag variants; the differentlytagged receptors were analyzed for expression, localizationand their pharmacological properties (ligand binding andcAMP accumulation) to identify tags suitable to furtheranalyze the receptors interactome. These tagged receptorswere then used to optimize the purification and to makethe first initial screens using 2D-nano-LC-MS/MSapproach. To prove the interaction of the A2A receptorwith promising targets found in our screens, biochemicalapproaches, e.g. co-immunoprecipitation and whole-cellbinding, were performed.

    Results and conclusionsWe could identify two tags suitable for further analysisof the A2A adenosine receptor interactome. Pharmacolo-gical properties of the tagged receptors were comparableto the native receptor. However, the tags seemed to

    retain the receptor to a large extent in the endoplasmicreticulum (ER) and hence we used this system to studythe ER/folding interactome of the receptor. LC-MS/MSanalysis of the purified ER-trapped version of the recep-tor revealed proteins putatively involved in the foldingof the receptor, such as chaperones. We are currentlygenerating a transgenic mouse-model expressing theTAP-tagged version of the A2A adenosine receptorunder the control of its endogenous promotors (homo-logous knock-in). This will allow us to examine tissue-and development-specific interaction partners of theA2A adenosine receptor utilizing the optimized proteo-mics approach.

    Published: 5 September 2011

    doi:10.1186/1471-2210-11-S2-A41Cite this article as: Bergmayr et al.: The folding interactome of GPCRs.BMC Pharmacology 2011 11(Suppl 2):A41.

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    * Correspondence: of Pharmacology, Center of Physiology and Pharmacology, MedicalUniversity of Vienna, 1090 Vienna, Austria

    Bergmayr et al. BMC Pharmacology 2011, 11(Suppl 2):A41

    2011 Bergmayr et al; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the CreativeCommons Attribution License (, which permits unrestricted use, distribution, andreproduction in any medium, provided the original work is properly cited.

    BackgroundMethodsResults and conclusions