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?-Arrestin-mediated receptor trafficking and signal transduction.

ABSTRACT: ?-Arrestins function as endocytic adaptors and mediate trafficking of a variety of cell-surface receptors, including seven-transmembrane receptors (7TMRs). In the case of 7TMRs, ?-arrestins carry out these tasks while simultaneously inhibiting upstream G-protein-dependent signaling and promoting alternate downstream signaling pathways. The mechanisms by which ?-arrestins interact with a continuously expanding ensemble of protein partners and perform their multiple functions including trafficking and signaling are currently being uncovered. Molecular changes at the level of protein conformation as well as post-translational modifications of ?-arrestins probably form the basis for their dynamic interactions during receptor trafficking and signaling. It is becoming increasingly evident that ?-arrestins, originally discovered as 7TMR adaptor proteins, indeed have much broader and more versatile roles in maintaining cellular homeostasis. In this review paper, we assess the traditional and novel functions of ?-arrestins and discuss the molecular attributes that might facilitate multiple interactions in regulating cell signaling and receptor trafficking.

SUBMITTER: Shenoy SK

PROVIDER: S-EPMC3159699 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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β-Arrestin-mediated receptor trafficking and signal transduction.

Shenoy Sudha K SK Lefkowitz Robert J RJ

Trends in pharmacological sciences 20110615 9

β-Arrestins function as endocytic adaptors and mediate trafficking of a variety of cell-surface receptors, including seven-transmembrane receptors (7TMRs). In the case of 7TMRs, β-arrestins carry out these tasks while simultaneously inhibiting upstream G-protein-dependent signaling and promoting alternate downstream signaling pathways. The mechanisms by which β-arrestins interact with a continuously expanding ensemble of protein partners and perform their multiple functions including trafficking ...[more]

PMID: 21680031

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Project description:G protein-coupled receptors (GPCRs) are involved in essentially all physiological processes in mammals. The classical GPCR signal transduction mechanism occurs by coupling to G protein, but it has recently been demonstrated that interaction with ?-arrestins leads to activation of pathways that are independent of the G protein pathway. Also, it has been reported that some ligands can preferentially activate one of these signaling pathways; being therefore called biased agonists for G protein or ?-arrestin pathways. The angiotensin II (AngII) AT1 receptor is a prototype GPCR in the study of biased agonism due to the existence of well-known ?-arrestin-biased agonists, such as [Sar(1), Ile(4), Ile(8)]-AngII (SII), and [Sar(1), D-Ala(8)]-AngII (TRV027). The aim of this study was to comparatively analyze the two above mentioned ?-arrestin-biased agonists on downstream phosphorylation events and gene expression profiles. Our data reveal that activation of AT1 receptor by each ligand led to a diversity of activation profiles that is far broader than that expected from a simple dichotomy between "G protein-dependent" and "?-arrestin-dependent" signaling. We observed clusters of activation profiles common to AngII, SII, and TRV027, as well as downstream effector activation that are unique to AngII, SII, or TRV027. Analyses of ?-arrestin conformational changes after AT1 receptor stimulation with SII or TRV027 suggests that the observed differences could account, at least partially, for the diversity of modulated targets observed. Our data reveal that, although the categorization "G protein-dependent" vs. "?-arrestin-dependent" signaling can be of pharmacological relevance, broader analyses of signaling pathways and downstream targets are necessary to generate an accurate activation profile for a given ligand. This may bring relevant information for drug development, as it may allow more refined comparison of drugs with similar mechanism of action and effects, but with distinct side effects.

Project description:Formyl-methionine-containing peptides (e.g. fMet-Leu-Phe) stimulate a variety of neutrophil functions by interacting with specific cell surface receptors which are coupled via G-proteins to stimulation of phospholipase C. Two markedly distinct cDNAs coding for formyl peptide receptors have recently been isolated from a rabbit and a human cDNA library respectively. To examine the hitherto unknown signal transduction properties of the formyl peptide receptor encoded by the human cDNA, we have used the PCR to clone this cDNA from poly(A)+ RNA of myeloid differentiated human leukaemia (HL-60) cells, and have injected the cDNA-derived receptor cRNA into Xenopus laevis oocytes. Receptor activity was determined electrophysiologically by measuring the agonist-dependent opening of intracellular Ca2+ concentration ([Ca2+]i)-independent Cl- channels. Injection of pure formyl peptide receptor cRNA did not lead to peptide-dependent changes in membrane current. In contrast, marked alterations of membrane current were observed in response to formyl peptides when the receptor cRNA was supplemented with poly(A)+ RNA isolated from undifferentiated HL-60 cells. Injection of the latter RNA did not lead to formyl-peptide-dependent alterations of membrane current. Binding studies using a radioiodinated formyl peptide revealed that injection of formyl peptide receptor cRNA alone led to expression of the formyl peptide receptor on the oocyte surface, and that co-injection of poly(A)+ RNA from undifferentiated HL-60 cells did not alter the level of receptor expression. Size fractionation of poly(A)+ RNA from undifferentiated HL-60 cells showed that the mRNA required to complement formyl-peptide-dependent signal transduction in oocytes had a size of approx. 3-3.5 kb. These results strongly suggest that the human formyl peptide receptor requires a specific cofactor(s), which is lacking in Xenopus oocytes but is present in undifferentiated HL-60 cells, to activate the second messenger pathway in oocytes. Identification of this factor will provide important information about the molecular mechanisms by which G-protein-coupled granulocyte-activating receptors stimulate phospholipase C.

Dataset Information

?-Arrestin-mediated receptor trafficking and signal transduction.

Publications

β-Arrestin-mediated receptor trafficking and signal transduction.

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