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Triphenylmethane dye activation of beta-arrestin.

ABSTRACT: ?-Arrestins regulate G protein-coupled receptor signaling as competitive inhibitors and protein adaptors. Low molecular weight biased ligands that bind receptors and discriminate between the G protein dependent arm and ?-arrestin, clathrin-associated arm of receptor signaling are considered therapeutically valuable as a result of this distinctive pharmacological behavior. Other than receptor agonists, compounds that activate ?-arrestins are not available. We show that within minutes of exposure to the cationic triphenylmethane dyes malachite green and brilliant green, tissue culture cells recruit ?-arrestins to clathrin scaffolds in a receptor-activation independent manner. In the presence of these compounds, G protein signaling is inhibited, ERK and GSK3? signaling are preserved, and the recruitment of the beta2-adaptin, AP2 adaptor complex to clathrin as well as transferrin internalization is reduced. Moreover, malachite green binds ?-arrestin2-GFP coated immunotrap beads relative to GFP only coated beads. Triphenylmethane dyes are FDA approved for topical use on newborns as components of triple-dye preparations and are not approved but used effectively as aqueous antibiotics in fish husbandry. As possible carcinogens, their chronic ingestion in food preparations, particularly through farmed fish, is discouraged in the U.S. and Europe. Our results indicate triphenylmethane dyes as a result of novel pharmacology may have additional roles as ?-arrestin/clathrin pathway signaling modulators in both pharmacology research and clinical therapy.

SUBMITTER: Barak LS

PROVIDER: S-EPMC3744129 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature

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Triphenylmethane dye activation of beta-arrestin.

Barak Larry S LS Bai Yushi Y Snyder Joshua C JC Wang Jiangbo J Chen Wei W Caron Marc G MG

Biochemistry 20130801 32

β-Arrestins regulate G protein-coupled receptor signaling as competitive inhibitors and protein adaptors. Low molecular weight biased ligands that bind receptors and discriminate between the G protein dependent arm and β-arrestin, clathrin-associated arm of receptor signaling are considered therapeutically valuable as a result of this distinctive pharmacological behavior. Other than receptor agonists, compounds that activate β-arrestins are not available. We show that within minutes of exposure ...[more]

PMID: 23865508

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Project description:Beta-arrestin2 and its ubiquitination play crucial roles in both internalization and signaling of seven-transmembrane receptors (7TMRs). To understand the connection between ubiquitination and the endocytic and signaling functions of beta-arrestin, we generated a beta-arrestin2 mutant that is defective in ubiquitination (beta-arrestin2(0K)), by mutating all of the ubiquitin acceptor lysines to arginines and compared its properties with the wild type and a stably ubiquitinated beta-arrestin2-ubiquitin (Ub) chimera. In vitro translated beta-arrestin2 and beta-arrestin2(0K) displayed equivalent binding to recombinant beta(2)-adrenergic receptor (beta(2)AR) reconstituted in vesicles, whereas beta-arrestin2-Ub bound approximately 4-fold more. In cellular coimmunoprecipitation assays, beta-arrestin2(0K) bound nonreceptor partners, such as AP-2 and c-Raf and scaffolded phosphorylated ERK robustly but displayed weak binding to clathrin. Moreover, beta-arrestin2(0K) was recruited only transiently to activated receptors at the membrane, did not enhance receptor internalization, and decreased the amount of phosphorylated ERK assimilated into isolated beta(2)AR complexes. Although the wild type beta-arrestin2 formed ERK signaling complexes with the beta(2)AR at the membrane, a stably ubiquitinated beta-arrestin2-Ub chimera not only stabilized the ERK signalosomes but also led to their endosomal targeting. Interestingly, in cellular fractionation assays, the ubiquitination state of beta-arrestin2 favors its distribution in membrane fractions, suggesting that ubiquitination increases the propensity of beta-arrestin for membrane association. Our findings suggest that although beta-arrestin ubiquitination is dispensable for beta-arrestin cytosol to membrane translocation and its "constitutive" interactions with some cytosolic proteins, it nevertheless is a prerequisite both for the formation of tight complexes with 7TMRs in vivo and for membrane compartment interactions that are crucial for downstream endocytic and signaling processes.

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Triphenylmethane dye activation of beta-arrestin.

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Triphenylmethane dye activation of beta-arrestin.

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