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Recruitment of a cytoplasmic chaperone relay by the A2A adenosine receptor.

ABSTRACT: The adenosine A2A receptor is a prototypical rhodopsin-like G protein-coupled receptor but has several unique structural features, in particular a long C terminus (of >120 residues) devoid of a palmitoylation site. It is known to interact with several accessory proteins other than those canonically involved in signaling. However, it is evident that many more proteins must interact with the A2A receptor, if the trafficking trajectory of the receptor is taken into account from its site of synthesis in the endoplasmic reticulum (ER) to its disposal by the lysosome. Affinity-tagged versions of the A2A receptor were expressed in HEK293 cells to identify interacting partners residing in the ER by a proteomics approach based on tandem affinity purification. The receptor-protein complexes were purified in quantities sufficient for analysis by mass spectrometry. We identified molecular chaperones (heat-shock proteins HSP90? and HSP70-1A) that interact with and retain partially folded A2A receptor prior to ER exit. Complex formation between the A2A receptor and HSP90? (but not HSP90?) and HSP70-1A was confirmed by co-affinity precipitation. HSP90 inhibitors also enhanced surface expression of the receptor in PC12 cells, which endogenously express the A2A receptor. Finally, proteins of the HSP relay machinery (e.g. HOP/HSC70-HSP90 organizing protein and P23/HSP90 co-chaperone) were recovered in complexes with the A2A receptor. These observations are consistent with the proposed chaperone/coat protein complex II exchange model. This posits that cytosolic HSP proteins are sequentially recruited to folding intermediates of the A2A receptor. Release of HSP90 is required prior to recruitment of coat protein complex II components. This prevents premature ER export of partially folded receptors.

SUBMITTER: Bergmayr C

PROVIDER: S-EPMC3789979 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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Recruitment of a cytoplasmic chaperone relay by the A2A adenosine receptor.

Bergmayr Christian C Thurner Patrick P Keuerleber Simon S Kudlacek Oliver O Nanoff Christian C Freissmuth Michael M Gruber Christian W CW

The Journal of biological chemistry 20130821 40

The adenosine A2A receptor is a prototypical rhodopsin-like G protein-coupled receptor but has several unique structural features, in particular a long C terminus (of >120 residues) devoid of a palmitoylation site. It is known to interact with several accessory proteins other than those canonically involved in signaling. However, it is evident that many more proteins must interact with the A2A receptor, if the trafficking trajectory of the receptor is taken into account from its site of synthesi ...[more]

PMID: 23965991

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Project description:ObjectivePharmacological activation of adenosine signaling has been shown to increase ?-cell proliferation and thereby ?-cell regeneration in zebrafish and rodent models of diabetes. However, whether adenosine has an endogenous role in regulating ?-cell proliferation is unknown. The objective of this study was to determine whether endogenous adenosine regulates ?-cell proliferation-either in the basal state or states of increased demand for insulin-and to delineate the mechanisms involved.MethodsWe analyzed the effect of pharmacological adenosine agonists on ?-cell proliferation in in vitro cultures of mouse islets and in zebrafish models with ?- or ?-cell ablation. In addition, we performed physiological and histological characterization of wild-type mice and mutant mice with pancreas- or ?-cell-specific deficiency in Adora2a (the gene encoding adenosine receptor A2a). The mutant mice were used for in vivo studies on the role of adenosine in the basal state and during pregnancy (a state of increased demand for insulin), as well as for in vitro studies of cultured islets.ResultsPharmacological adenosine signaling in zebrafish had a stronger effect on ?-cell proliferation during ?-cell regeneration than in the basal state, an effect that was independent of the apoptotic microenvironment of the regeneration model. In mice, deficiency in Adora2a impaired glucose control and diminished compensatory ?-cell proliferation during pregnancy but did not have any overt phenotype in the basal state. Islets isolated from Adora2a-deficient mice had a reduced baseline level of ?-cell proliferation in vitro, consistent with our finding that UK432097, an A2a-specific agonist, promotes the proliferation of mouse ?-cells in vitro.ConclusionsThis is the first study linking endogenously produced adenosine to ?-cell proliferation. Moreover, we show that adenosine signaling via the A2a receptor has an important role in compensatory ?-cell proliferation, a feature that could be harnessed pharmacologically for ?-cell expansion and future therapeutic development for diabetes.

Dataset Information

Recruitment of a cytoplasmic chaperone relay by the A2A adenosine receptor.

Publications

Recruitment of a cytoplasmic chaperone relay by the A2A adenosine receptor.

Similar Datasets

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