Research ArticleBiochemistry

Oxygen-Regulated β2-Adrenergic Receptor Hydroxylation by EGLN3 and Ubiquitylation by pVHL

Science Signaling  07 Jul 2009:
Vol. 2, Issue 78, pp. ra33
DOI: 10.1126/scisignal.2000444

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Abstract

Agonist-induced ubiquitylation and degradation of heterotrimeric guanine nucleotide–binding protein (G protein)–coupled receptors (GPCRs) play an essential role in surface receptor homeostasis, thereby tuning many physiological processes. Although β-arrestin and affiliated E3 ligases mediate agonist-stimulated lysosomal degradation of the β2-adrenergic receptor (β2AR), a prototypic GPCR, the molecular cues that mark receptors for ubiquitylation and the regulation of receptor degradation by the proteasome remain poorly understood. We show that the von Hippel–Lindau tumor suppressor protein (pVHL)–E3 ligase complex, known for its regulation of hypoxia-inducible factor (HIF) proteins, interacts with and ubiquitylates the β2AR, thereby decreasing receptor abundance. We further show that the interaction of pVHL with β2AR is dependent on proline hydroxylation (proline-382 and -395) and that the dioxygenase EGLN3 interacts directly with the β2AR to serve as an endogenous β2AR prolyl hydroxylase. Under hypoxic conditions, receptor hydroxylation and subsequent ubiquitylation decrease dramatically, thus attenuating receptor degradation and down-regulation. Notably, in both cells and tissue, the abundance of endogenous β2AR is shown to reflect constitutive turnover by EGLN3 and pVHL. Our findings provide insight into GPCR regulation, broaden the functional scope of prolyl hydroxylation, and expand our understanding of the cellular response to hypoxia.

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