The Ubiquitin-Specific Protease Usp4 Regulates the Cell Surface Level of the A2a Receptor

␤-Arrestins are multifunctional adaptors that mediate the desensitization, internalization, and some signaling functions of seventransmembrane receptors (7TMRs). Agonist-stimulated ubiquitination of ␤-arrestin2 mediated by the E3 ubiquitin ligase Mdm2 is critical for rapid ␤2-adrenergic receptor (␤2AR) internalization. We now report the discovery that the deubiquitinating enzyme ubiquitin-specific protease 33 (USP33) binds ␤-arrestin2 and leads to the deubiquitination of ␤-arrestins. USP33 and Mdm2 function reciprocally and favor respectively the stability or lability of the receptor ␤-arrestin complex, thus regulating the longevity and subcellular localization of receptor signalosomes. Receptors such as the ␤2AR, previously shown to form loose complexes with ␤-arrestin (''class A'') promote a ␤-arrestin conformation conducive for binding to the deubiquitinase, whereas the vasopressin V2R, which forms tight ␤-arrestin complexes (''class B''), promotes a distinct ␤-arrestin conformation that favors dissociation of the enzyme. Thus, USP33-␤-arrestin interaction is a key regulatory step in 7TMR trafficking and signal transmission from the activated receptors to downstream effectors.endocytosis ͉ G protein-coupled receptors ͉ ubiquitination ͉ phosphorylation ͉ ERK1/2

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“…S3B). Additionally, ␤-arrestin2-V2R trafficking is unaffected when another DUB, GFP-USP4 (12), is coexpressed (Fig. S4).…”

Section: Resultsmentioning

confidence: 99%

β-Arrestin-dependent signaling and trafficking of 7-transmembrane receptors is reciprocally regulated by the deubiquitinase USP33 and the E3 ligase Mdm2

Shenoy¹,

Modi²,

Shukla

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

145

133

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“…Upregulation of astrocytic A 2A receptors may be a compensatory reaction to reduced adenosine basal tone. Increased sensitivity to extracellular adenosine may also result from recruitment of latent intracellular receptors to the plasma membrane [64]. While previous studies associate internalization of A 2A receptors to abnormal increases in extracellular adenosine (see, e.g., [65]), more recent data ague against this by showing that A 2A receptors may be mobilized to the plasma membrane under anoxic conditions coinciding with high extracellular adenosine concentrations [66].…”

Section: Discussionmentioning

confidence: 99%

Adenosine A2A receptor and ecto-5′-nucleotidase/CD73 are upregulated in hippocampal astrocytes of human patients with mesial temporal lobe epilepsy (MTLE)

Barros‐Barbosa

Ferreirinha

Oliveira

et al. 2016

Purinergic Signalling

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Refractoriness to existing medications of up to 80 % of the patients with mesial temporal lobe epilepsy (MTLE) prompts for finding new antiepileptic drug targets. The adenosine A 2A receptor emerges as an interesting pharmacological target since its excitatory nature partially counteracts the dominant antiepileptic role of endogenous adenosine acting via inhibitory A 1 receptors. Gain of function of the excitatory A 2A receptor has been implicated in a significant number of brain pathologies commonly characterized by neuronal excitotoxicity. Here, we investigated changes in the expression and cellular localization of the A 2A receptor and of the adenosine-generating enzyme, ecto-5′-nucleotidase/ CD73, in the hippocampus of control individuals and MTLE human patients. Western blot analysis indicates that the A 2A receptor is more abundant in the hippocampus of MTLE patients compared to control individuals. Immunoreactivity against the A 2A receptor predominates in astrocytes staining positively for the glial fibrillary acidic protein (GFAP). No colocalization was observed between the A 2A receptor and neuronal cell markers, like synaptotagmin 1/2 (nerve terminals) and neurofilament 200 (axon fibers). Hippocampal astrogliosis observed in MTLE patients was accompanied by a proportionate increase in A 2A receptor and ecto-5′-nucleotidase/CD73 immunoreactivities. Given our data, we hypothesize that selective blockade of excessive activation of astrocytic A 2A receptors and/or inhibition of surplus adenosine formation by membrane-bound ecto-5′-nucleotidase/CD73 may reduce neuronal excitability, thus providing a novel therapeutic target for drug-refractory seizures in MTLE patients. • Ecto-5′-nucleotidase/CD73 localizes in close proximity with adenosine A 2A receptors in astrocytes of the human hippocampus. Keywords Mesial temporal lobe epilepsy (MTLE• Up-regulation of A 2A receptors and ecto-5′-nucleotidase/CD73 associates with astrogliosis of the hippocampus of MTLE patients.• Targeting astrocytic A 2A activation and/or adenosine formation via ecto-5′-nucleotidase/CD73 may control neuronal excitability.• Inhibitors of astrocytic A 2A receptors and ecto-5′-nucleotidase/CD73 may be a novel therapeutic strategy to control drug-refractory MTLE.

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“…USP4, which was among the most up-regulated genes is an enzyme of yet unclear function, however, its deregulation has previously been linked to cancer and USP4 has been ascribed oncogenic (32,33) as well as having tumour suppressor functions (34) indicating that it may be a multifunctional protein. USP4 has previously been reported to interact with the retinoblastoma tumour suppressor, pRb, the pocket proteins, p107 and p130 (35,36), the ubiquitin ligase Ro52 (37) and the transmembrane G-coupled adenosine 2A receptor for which it has been suggested to function to relax the endoplasmic reticulum quality control mechanisms, resulting in increased cell surface expression of the receptor (38). The role of USP4 in adrenocortical carcinomas is however, still unexplored.…”

Section: Discussionmentioning

confidence: 99%

Transcriptional profiling enables molecular classification of adrenocortical tumours

Laurell

Velázquez-Fernández

Lindsten

et al. 2009

European Journal of Endocrinology

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Objective: Tumours in the adrenocortex are common human tumours. Malignancy is however, rare, the yearly incidence being 0.5-2 per million inhabitants, but associated with a very aggressive behaviour. Adrenocortical tumours are often associated with altered hormone production with a variety of clinical symptoms. The aggressiveness of carcinomas together with the high frequency of adenomas calls for a deeper understanding of the underlying biological mechanisms and an improvement of the diagnostic possibilities. Methods: Microarray gene expression analysis was performed in tumours of adrenocortex with emphasis on malignancy as well as hormonal activity. The sample set consisted of 17 adenomas, 11 carcinomas and 4 histological normal adrenocortexes. RNA from these was hybridised according to a reference design on microarrays harbouring 29 760 human cDNA clones. Confirmation was performed with quantitative real time-PCR and western blot analysis. Results: Unsupervised clustering to reveal relationships between samples based on the entire gene expression profile resulted in two subclusters; carcinomas and non-cancer specimens. A large number of genes were accordingly found to be differentially expressed comparing carcinomas to adenomas. Among these were IGF2, FGFR1 and FGFR4 in growth factor signalling the most predominant and also the USP4, UBE2C and UFD1L in the ubiquitin-proteasome pathway. Moreover, two subgroups of carcinomas were identified with different survival outcome, suggesting that survival prediction can be made on the basis of gene expression profiles. Regarding adenomas with aldosterone overproduction, OSBP and VEGFB were among the most up-regulated genes compared with the other samples. Conclusions: Adrenocortical carcinomas are associated with a distinct molecular signature apparent in their gene expression profiles. Differentially expressed genes were identified associated with malignancy, survival as well as hormonal activity providing a resource of candidate genes for an exploration of possible drug targets and diagnostic and prognostic markers.

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The Ubiquitin-Specific Protease Usp4 Regulates the Cell Surface Level of the A2a Receptor

Cited by 117 publications

References 42 publications

β-Arrestin-dependent signaling and trafficking of 7-transmembrane receptors is reciprocally regulated by the deubiquitinase USP33 and the E3 ligase Mdm2

β-Arrestin-dependent signaling and trafficking of 7-transmembrane receptors is reciprocally regulated by the deubiquitinase USP33 and the E3 ligase Mdm2

Adenosine A2A receptor and ecto-5′-nucleotidase/CD73 are upregulated in hippocampal astrocytes of human patients with mesial temporal lobe epilepsy (MTLE)

Transcriptional profiling enables molecular classification of adrenocortical tumours

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