Role of endocytosis in mediating downregulation of G-protein-coupled receptors

Tsao, Patricia; Cao, Tracy T.; Zastrow, Mark von

doi:10.1016/s0165-6147(00)01620-5

Cited by 233 publications

(179 citation statements)

References 60 publications

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“…4C, b) are clearly different. WIN induces an exponential decay of the membrane population of CB1Rs, with a half-time of 4.3 Ϯ 0.6 min, leading to total endocytosis after 30 min, a value that is typical for GPCR endocytosis (26). AM281-induced externalization is slower, with a linear increase of the MFR ratio reaching a plateau after 2 h.…”

Section: Cb1-egfp Is Functional and Displays A Predominantly Intracelmentioning

confidence: 99%

Constitutive Endocytic Cycle of the CB1 Cannabinoid Receptor

Leterrier

Bonnard

Carrel

et al. 2004

Journal of Biological Chemistry

215

234

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The CB1 cannabinoid receptor (CB1R) displays a significant level of ligand-independent (i.e. constitutive) activity, either when heterologously expressed in nonneuronal cells or in neurons where CB1Rs are endogenous. The present study investigates the consequences of constitutive activity on the intracellular trafficking of CB1R. When transfected in HEK-293 cells, CB1R is present at the plasma membrane, but a substantial proportion (ϳ85%) of receptors is localized in intracellular vesicles. Detailed analysis of CB1-EGFP expressed in HEK-293 cells shows that the intracellular CB1R population is mostly of endocytic origin and that treatment with inverse agonist AM281 traps CB1R at the plasma membrane through a monensin-sensitive recycling pathway. Co-transfection with dominant positive or dominant negative mutants of the small GTPases Rab5 and Rab4, but not Rab11, profoundly modifies the steady-state and ligand-induced intracellular distribution of CB1R, indicating that constitutive endocytosis is Rab5-dependent, whereas constitutive recycling is mediated by Rab4. In conclusion, our results indicate that, due to its natural constitutive activity, CB1R permanently and constitutively cycles between plasma membrane and endosomes, leading to a predominantly intracellular localization at steady state.

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Section: Cb1-egfp Is Functional and Displays A Predominantly Intracelmentioning

confidence: 99%

Constitutive Endocytic Cycle of the CB1 Cannabinoid Receptor

Leterrier

Bonnard

Carrel

et al. 2004

Journal of Biological Chemistry

215

234

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“…Most GPCRs are regulated by endocytosis [7][8][9]. The β2-adrenergic receptor (β 2 AR) was the first GPCR found to be regulated by internalization [7].…”

Section: Introductionmentioning

confidence: 99%

Endocytosis of adiponectin receptor 1 through a clathrin- and Rab5-dependent pathway

2008

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In eukaryotic cells, receptor endocytosis is a key event regulating signaling transduction. Adiponectin receptors belong to a new receptor family that is distinct from G-protein-coupled receptors and has critical roles in the pathogenesis of diabetes and metabolic syndrome. Here, we analyzed the endocytosis of adiponectin and adiponectin receptor 1 (AdipoR1) and found that they are both internalized into transferrin-positive compartments that follow similar traffic routes. Blocking clathrin-mediated endocytosis by expressing Eps15 mutants or depleting K + trapped AdipoR1 at the plasma membrane, and K + depletion abolished adiponectin internalization, indicating that the endocytosis of AdipoR1 and adiponectin is clathrin-dependent. Depletion of K + and overexpression of Eps15 mutants enhance adiponectinstimulated AMP-activated protein kinase phosphorylation, suggesting that the endocytosis of AdipoR1 might downregulate adiponectin signaling. In addition, AdipoR1 colocalizes with the small GTPase Rab5, and a dominant negative Rab5 abrogates AdipoR1 endocytosis. These data indicate that AdipoR1 is internalized through a clathrin-and Rab5-dependent pathway and that endocytosis may play a role in the regulation of adiponectin signaling.

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“…For most GPCRs, activation is followed by desensitization and internalization of the receptors, which then are targeted to either recycling or degradation pathways (2,3). Several mechanisms for GPCR internalization have been described, the clathrin-coated pit endocytic pathway being the best understood.…”

mentioning

confidence: 99%

Resistance of the Human β1-Adrenergic Receptor to Agonist-induced Ubiquitination

Liang¹,

Fishman²

2004

Journal of Biological Chemistry

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Down-regulation is a classic response of most G protein-coupled receptors to prolonged agonist stimulation. We recently showed that when expressed in baby hamster kidney cells, the human ␤ 1 -but not the ␤ 2 -adrenergic receptor (AR) is totally resistant to agonistmediated down-regulation, whereas both have similar rates of basal degradation (Liang, W., Austin, S., Hoang, Q., and Fishman, P. H. (2003) J. Biol. Chem. 278, 39773-39781). To identify the underlying mechanism(s) for this resistance, we investigated the role of proteasomes, lysosomes, and ubiquitination in the degradation of ␤ 1 AR expressed in baby hamster kidney and human embryonic kidney 293 cells. Both lysosomal and proteasomal inhibitors reduced ␤ 1 AR degradation in agonist-stimulated cells but were less effective on basal degradation. To determine whether ␤ 1 AR trafficked to lysosomes we used confocal fluorescence microscopy. We observed some colocalization of ␤ 1 AR and lysosomal markers in agonist-treated cells but much less than that of ␤ 2 AR even in cells co-transfected with arrestin-2, which increases ␤ 1 AR internalization. Ubiquitination of ␤ 2 AR readily occurred in agonist-stimulated cells, whereas ubiquitination of ␤ 1 AR was not detectable even under conditions optimal for that of ␤ 2 AR. Moreover, in cells expressing ␤AR chimeras in which the C termini have been switched, the chimeric ␤ 1 AR with ␤ 2 AR C-tail underwent ubiquitination and down-regulation, but the chimeric ␤ 2 AR with ␤ 1 AR C-tail did not. Our results demonstrate for the first time that ␤ 1 AR and ␤ 2 AR differ in the ability to be ubiquitinated. Because ubiquitin serves as a signal for sorting membrane receptors to lysosomes, the lack of agonist-mediated ubiquitination of ␤ 1 AR may prevent its extensive trafficking to lysosomes and, thus, account for its resistance to down-regulation.

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Role of endocytosis in mediating downregulation of G-protein-coupled receptors

Cited by 233 publications

References 60 publications

Constitutive Endocytic Cycle of the CB1 Cannabinoid Receptor

Constitutive Endocytic Cycle of the CB1 Cannabinoid Receptor

Endocytosis of adiponectin receptor 1 through a clathrin- and Rab5-dependent pathway

Resistance of the Human β1-Adrenergic Receptor to Agonist-induced Ubiquitination

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