β-Arrestin1 mediates nicotinic acid–induced flushing, but not its antilipolytic effect, in mice

Walters, Robert W.; Shukla, Arun K.; Kovacs, Jeffery; Violin, Jonathan D.; DeWire, Scott M.; Lam, Christopher M.; Chen, J. Ruthie; Muehlbauer, Michael J.; Whalen, Erin J.; Lefkowitz, Robert J.

doi:10.1172/jci36806

Cited by 206 publications

(190 citation statements)

References 48 publications

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“…Therefore, together with the observation that treatment with hypertonic sucrose (0.45 M) inhibited GPR109A internalization, we postulate that phosphorylated GPR109A binds arrestin3 after receptor activation, is targeted to clathrin-coated pits, and is then rapidly recycled back to the cell surface from perinuclear early endosomes after internalization (43,44). Walters et al (45) reported that niacin-induced stimulation of GPR109A led to arrestin-dependent signaling to ERK1/2 activation, and this pathway mediated the adverse side effect of cutaneous flushing but not the beneficial antilipolytic effect of niacin. Our results obtained from siRNA experiments demonstrated that knocking down GRK or arrestin expression in HEK-293 cells had no effect on ERK1/2 pathway activation.…”

Section: Discussionsupporting

confidence: 55%

Internalization of the Human Nicotinic Acid Receptor GPR109A Is Regulated by Gi, GRK2, and Arrestin3

Shi

Huang

et al. 2010

Journal of Biological Chemistry

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Nicotinic acid (niacin) has been widely used as a favorable lipid-lowering drug for several decades, and the orphan G protein-coupled receptor GPR109A has been identified to be a receptor for niacin. Mechanistic investigations have shown that as a G i -coupled receptor, GPR109A inhibits adenylate cyclase activity upon niacin activation, thereby inhibiting free fatty acid liberation. However, the underlying molecular mechanisms that regulate signaling and internalization of GPR109A remain largely unknown. To further characterize GPR109A internalization, we made a construct to express GPR109A fused with enhanced green fluorescent protein (EGFP) at its carboxyl-terminal end. In stable GPR109A-EGFP-expressing HEK-293 cells, GPR109A-EGFP was mainly localized at the plasma membrane and was rapidly internalized in a dose-and time-dependent manner upon agonist stimulation. GPR109A internalization was completely blocked by hypertonic sucrose, indicating that GPR109A internalizes via the clathrin-coated pit pathway. Further investigation demonstrated that internalized GPR109A was recycled to the cell surface after the removal of agonist, and recycling of the internalized receptors was not blocked by treatment with acidotropic agents, NH 4 Cl and monensin. Pertussis toxin pretreatment not only inhibited forskolin-induced cAMP accumulation and intracellular Ca 2؉ mobilization; it also significantly attenuated agonist-promoted GPR109A internalization. Moreover, RNA interference experiments showed that knockdown of GRK2 (G protein-coupled receptor kinase 2) and arrestin3 expression significantly impaired receptor internalization. Taken together, these results indicate that the agonist-induced internalization of GPR109A receptors is regulated by GRK2 and arrestin3 in a pertussis toxin-sensitive manner and that internalized receptor recycling is independent of endosomal acidification.

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Section: Discussionsupporting

confidence: 55%

Internalization of the Human Nicotinic Acid Receptor GPR109A Is Regulated by Gi, GRK2, and Arrestin3

Shi

Huang

et al. 2010

Journal of Biological Chemistry

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“…MK-0354 has a beneficial nicotinic acid-like effect on serum lipids but, importantly, does not affect the ␤-arrestin pathway causing the side effect of flushing (17,55). For the ghrelin receptor, development of a biased agonist could have important therapeutic potential, as the receptor is responsible for both growth hormone secretion and induction of hunger and fat accumulation.…”

Section: Discussionmentioning

confidence: 99%

Unique Interaction Pattern for a Functionally Biased Ghrelin Receptor Agonist

Sivertsen

Lang

Frimurer

et al. 2011

Journal of Biological Chemistry

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]substance P, a series of novel, small, peptidemimetic agonists for the ghrelin receptor were generated. By using various simple, ring-constrained spacers connecting the D-Trp-Phe-D-Trp motif with the important C-terminal carboxyamide group, 40 nM agonism potency was obtained and also in one case (wFw-Isn-NH 2 , where Isn is isonipecotic acid) ϳ80% efficacy. However, in contrast to all previously reported ghrelin receptor agonists, the piperidine-constrained wFw-Isn-NH 2 was found to be a functionally biased agonist. Thus, wFw-Isn-NH 2 mediated potent and efficacious signaling through the G␣ q and ERK1/2 signaling pathways, but in contrast to all previous ghrelin receptor agonists it did not signal through the serum response element, conceivably the G␣ 12/13 pathway. The recognition pattern of wFw-Isn-NH 2 with the ghrelin receptor also differed significantly from that of all previously characterized unbiased agonists. Most importantly, wFw-Isn-NH 2 was not dependent on GluIII:09 (Glu3.33), which otherwise is an obligatory TM III anchor point residue for ghrelin agonists. Molecular modeling and docking experiments indicated that wFw-Isn-NH 2 binds in the classical agonist binding site between the extracellular segments of TMs III, VI, and VII, interacting closely with the aromatic cluster between TMs VI and VII, but that it does so in an opposite orientation as compared with, for example, the wFw peptide agonists. It is concluded that the novel peptide-mimetic ligand wFw-Isn-NH 2 is a biased ghrelin receptor agonist and that the selective signaling pattern presumably is due to its unique receptor recognition pattern lacking interaction with key residues especially in TM III.Ghrelin is a neuroendocrine hormone that differs from other peptide hormones by a fatty acid modification, which is crucial for both the binding and activation of its receptor (1). Ghrelin is synthesized mainly in the gastrointestinal tract, where the gene coding for the peptide sequence is expressed together with the enzyme responsible for the acylation of the fatty acid to the ghrelin peptide sequence (2, 3). Multiple functions have been described for ghrelin since it was discovered. Initially it was believed that growth hormone secretion induced by ghrelin receptors in the hypothalamus and the pituitary was the primary function of ghrelin (4). However, the function of ghrelin in the hypothalamus, and in particular in the arcuate nucleus, has become the focus of attention over the last decade. In the arcuate nucleus, ghrelin is responsible for increased activity in the NPY (neuropeptide Y) and AGRP (Agouti-related protein) neurones leading to increased appetite, decreased energy expenditure, and fat accumulation (5, 6). High receptor expression is also observed in the ventromedial nucleus of the hypothalamus, and the function in this area has been proposed to be orexigenic based on the regulation of fatty acid metabolism (7). More recently it has been demonstrated that ghrelin is also involved in reward-seeking behavior such as alcohol and ...

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“…Niacin dose-dependently decreased platelet cyclic AMP, as expected, upon activation of this Gi-linked receptor (ref. 44 and Supplemental Figure 8E).…”

Section: Figurementioning

confidence: 95%