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Int J Clin Exp Med. 2008; 1(1): 32–41.
Published online 2008 January 20.
PMCID: PMC2596334

β-Arrestin 2: a Negative Regulator of Inflammatory Responses in Polymorphonuclear Leukocytes


Heterotrimeric Gi proteins have been previously implicated in signaling leading to inflammatory mediator production induced by bacterial lipopolysaccharide (LPS). β-arrestins are ubiquitously expressed proteins that alter G-protein-coupled receptors signaling. β-arrestin 2 plays a multifaceted role as a scaffold protein in regulating cellular inflammatory responses. Polymorphonuclear leukocytes (PMNs) activated by LPS induce inflammatory responses resulting in organ injury during sepsis. We hypothesized that β-arrestin 2 is a critical modulator of inflammatory responses in PMNs. To examine the potential role of β-arrestin 2 in LPS-induced cellular activation, we studied homozygous β-arrestin 2 (-/-), heterozygous (+/-), and wildtype (+/+) mice. PMNs were stimulated with LPS for 16h. There was increased basal TNFα and IL-6 production in the β-arrestin 2 (-/-) compared to both β-arrestin 2 (+/-) and (+/+) cells. LPS failed to stimulate TNFα production in the β-arrestin 2 (-/-) PMNs. However, LPS stimulated IL-6 production was increased in the β-arrestin 2 (-/-) cells compared to (+/+) cells. In subsequent studies, peritoneal PMN recruitment was increased 81% in the β-arrestin 2 (-/-) mice compared to (+/+) mice (p<0.05). β-arrestin 2 deficiency resulted in an augmented expression of CD18 and CD62L (p<0.05). In subsequent studies, β-arrestin 2 (-/-) and (+/+) mice were subjected to cecal ligation and puncture (CLP) and lung was collected and analyzed for myeloperoxidase activity (MPO) as index of PMNs infiltrate. CLP-induced MPO activity was significantly increased (p<0.05) in the β-arrestin 2 (-/-) compared to (+/+) mice. These studies demonstrate that β-arrestin 2 is a negative regulator of PMN activation and pulmomary leukosequestration in response to polymicrobial sepsis.

Keywords: Polymorphonuclear leukocytes (PMN), lipopolysaccharide (LPS), β-arrestin 2, adhesion receptors


Polymorphonuclear leukocytes (PMNs) are critical cells involved in process of innate immunity [1, 2]. Activation of toll-like receptor (TLR)s on granulocytes result in induction of signaling pathways that produce chemokines, cytokines and other inflammatory mediators [3, 4]. Lipopolysaccharide (LPS) binds to TLR4 and leads to the secretion of pro-inflammatory molecules including TNF-α, IL-6 and chemokines. Fluorescence resonance energy transfer analysis has demonstrated that LPS binds initially to the membrane-bound CD14 and is transferred not only to TLR4 but to a cluster of receptors in lipid rafts which elicit the associated immune response [5]. Among these clustered receptors are G-protein coupled receptors (GPCRs). Previous studies have elucidated the involvement of post receptor heterotrimeric guanine nucleotide binding regulatory (Gi) proteins in LPS signal transduction [6-10]. In vitro kinase assays performed on human CD14 co-immunoprecipitated proteins demonstrated the presence of Gαi2 and Gαi3 proteins [7]. Our studies and others suggest that TLR4 signaling is, in part, Gi protein regulated [6, 9]. The importance of Gi proteins in regulating TLR activation also has been underscored by findings in Gαi2 KO mice. Although there are phenotype differences of inflammatory cell responses to TLR activation in Gαi2 KO mice, the in vivo pro-inflammatory response to endotoxin is augmented suggesting that Gi2 KO mice signaling pathways predominantly down-regulate TLR activation [8].

β-Arrestins 1 and 2 are adaptor proteins that regulate Gi protein function by forming complexes with most GPCRs. This occurs following agonist binding and phosphorylation of receptors by G protein-coupled receptor kinases. β-arrestins play a central role in the processes of homologous desensitization and GPCR sequestration that leads to termination of G protein activation by endocytosis in clathrin-coated pits [11-14]. It has also been shown that β-arrestins 1 and 2 function as multifunctional scaffold/adaptor proteins for GPCR activation of signaling cascades [15-19]. Our studies and others have recently demonstrated that β-arrestins 1 and 2 also regulate TLR activation in specific cell lines and bone marrow macrophages from β-arrestins 2 KO mice [20-23].

PMNs are the most numerous type of white blood cell involved in the innate immune response. PMNs have a very short life span (hours), have phagocytic functions, and produce cytokines and chemokines that are critical in the innate immune response [1, 2]. However, the role of β-arrestins in the regulation of PMN innate immune activation has not been previously investigated. The availability of β-arrestin 2 KO mice provides an approach to evaluate the role of this β-arrestins isoform in innate immunity [24]. Therefore, we hypothesized that β-arrestins 2 regulates the inflammatory response in PMNs upon activation of TLR4 and chemotactic responses to an inflammation stimulus. Specifically, we examined the effect of β-arrestins 2 deficiency on: 1) oyster glycogen-induced recruitment of PMNs to the peritoneal cavity, 2) LPS-induced PMN pro-inflammatory mediator production, 3) LPS binding/uptake by PMNs, 4) the expression of specific surface adhesion receptors of PMNs, and 5) In a clinically relevant murine model, we examined the effect of β-arrestins 2 deficiency on pulmonary myeloperoxidase activity at 18h after cecal ligation and puncture (CLP) induced polymicrobial sepsis.

Materials and Methods


Male WT (+/+), heterozygous (+/-), and β-arrestin 2 knockout (-/-) C57BL/6 mice, 6-9 weeks of age, housed at the Medical University of South Carolina were used in this study. Mice were allowed access to food and water ad libitum and maintained on a 12-hr light/12-hr dark cycle. The investigations conformed to the Guide for the Care and Use of Laboratory Animals published by the National Institutes of Health and commenced with the approval of the Institutional Animal Care and Use Committee.


Protein-free S. minnesota R595 LPS was provided by Dr. Ernst Reitschel, Borstel, Germany. Oyster glycogen, type II, was purchased from Sigma (St. Louis, MO). RPMI 1640 media was purchased from Gibco Invitrogen Corporation (Carlsbad, CA). DPBS, fetal bovine serum, and penicillin/streptomycin were purchased from Cellgro Mediatech Inc. (Herndon, VA). TNF-α and IL-6 ELISA kits, flow cytometry staining buffer, and as anti-mouse FITC-labeled antibodies to CD45, CD11b, F4/80, CD18, and CD62L for flow cytometry were purchased from eBioscience (San Diego, CA).

Experimental methods

Mice were injected with 10 ml of 2% oyster glycogen in sterile DPBS to recruit PMNs to the peritoneal cavity, as previously described [25]. After 5 h, the peritoneal cells were lavaged and harvested using 10 ml per mouse of RPMI 1640 supplemented with 1% fetal bovine serum and 1% penicillin/streptomycin. The peritoneal exudate cells were counted and centrifuged in a Beckman GPR Centrifuge at 1500 rpm for 30 minutes. The supernatant was removed and the cells resuspended in 3 ml of media. Based upon CD45 expression and morphologic criteria, the cell population was >95% PMNs. The cells were counted and plated in a 24-well plate such that each well contained 1 ml of medium with 5 × 105 cells/ml. The samples in each well were treated with increasing concentrations of LPS (0, 10, 100, or 500 ng/mL) and allowed to incubate for 16 hr. The incubation time was selected based on previous studies that the cells produce measurable amounts of cytokines after 12-24h. Viability was greater than 90% after 16hs of LPS stimulation as determined by Trypan Blue. After incubation, the plate was centrifuged at 1500 rpm for 5 minutes. The supernatant was collected for ELISAs to measure TNF-α and IL-6 levels.

Flow cytometry

To study expression of surface molecules, specifically activation markers and adhesion molecules, cells were plated in a 96-well plate such that each well contained 5 × 105 cells. Antibodies used for flow cytometry were diluted 1:50, and 50 μL was added to each well, after which the samples were allowed to incubate at 4°C for at least 20 minutes. Samples were washed twice and then resuspended in flow cytometry staining buffer, after which the samples underwent analysis with a Becton Dickinson FACSCalibur analytical flow cytometer housed at the Analytical Flow Cytometry Facility at the Medical University of South Carolina.

To study LPS uptake, PMNs were plated in 6-well plates containing 5 × 106 cells. The cells were incubated with FITC-LPS (10 μg/ml) for various times. Cells were scraped into flow cytometry staining buffer and washed twice, after which the samples underwent flow cytometry analysis. Since LPS binding to the cell surface receptors and LPS uptaking into the cells were not differentiated, we refer to the response as binding/uptake.

Cecal ligation and puncture

Sepsis was induced by cecal ligation and puncture (CLP) as described previously [26]. Specifically, a midline incision was made below the diaphragm to expose the cecum. The cecum was ligated at the colon juncture with a 6-0 silk ligature suture without interrupting intestinal continuity and punctured twice with a 22-guage needle. The cecum was returned to the abdomen, and the incision was closed in layer with a 6-0 silk ligature suture. With this procedure, WT mice exhibit considerably prolonged survival times beyond 24 hs. Less than 10% mortality within 8 hours of CLP.

Measurement of myeloperoxidase activity

Myeloperoxidase activity was determined in lung as an index of neutrophil accumulation as previously described [27]. Tissues were homogenized in a solution containing 0.5% hexa-decyl-trimethylammonium bromide disolved in 10mM potassium phosphate buffer (pH 7.0) and were centrifuged for 30 min at 20,000×g 4°C. An aliquot of the supernatant was allowed to react with a solution of tera-methyl-benzidine (1.6mM) and 0.1 mM H2O2. The rate of change in absorbance was measured by spectrophotometry at 650 nm. Myeloperoxidase activity was defined as the quantity of enzyme degrading 1 μmol hydrogen peroxide/min at 37°C and was expressed in units per 100 mg of tissue.

Statistics analysis

Data are expressed as mean ± SE. Statistical significance was determined using ANOVA with Fisher's probable least-squares difference test using Microsoft Excel and Statview software (SAS Institute, Cary, NC). Nonparametric statistical analysis was performed using the Mann-Whitney Test for two-group comparisons with Statview software. P < 0.05 was considered significant.


β-Arrestin 2 deficiency augments proinflammatory mediator production by PMNs

PMNs harvested from β-arrestin (-/-), (+/-) and (+/+) mice were stimulated with LPS. TNF-α and IL-6 production was determined. In the β-arrestin (-/-) there was a significant (p<0.05) increase in basal and stimulated TNF-α production compared to (+/-) or (+/+) extent at the lowest LPS concentration (10 ng/mL, Figure 1). Thus, oyster glycogen alone appeared to have maximally stimulated TNF-α production in the (-/-) cells.

Figure 1
TNFα production by oyster glycogen elicited peritoneal cells. Murine PMNs were stimulated with LPS (0, 10, 100, or 500 ng/ml) for 16 hours. The supernatant was collected to test for TNF-α production using ELISA. Wildtype n=7; heterozygous ...

There were significantly greater increases in IL-6 production in (-/-) cells in basal and at all concentrations of LPS compared to (+/-) or (+/+) PMNs (Figure 2). As with TNF-α oyster glycogen obscured further stimulation with LPS except at the highest LPS concentration. When compared to (+/+) mice, the (-/-) mice exhibited a 85±1% (376pg/ml) increase in IL-6 production when stimulated with LPS (500 ng/mL) (p<0.05).

Figure 2
IL-6 production by oyster glycogen elicited peritoneal cells. Murine PMNs were stimulated with LPS (0, 10, 100, or 500 ng/mL) for 16 hours. The supernatant was collected to test for IL-6 production using ELISA. Wildtype n=7; heterozygous n=11; knockout ...

β-Arrestin 2 deficiency does not affect LPS binding/uptake to PMNs

To determine if β-arrestin 2 deficiency alters the binding/uptake of LPS to PMNs, the uptake of FITC-labeled LPS by flow cytometry was examined at 30, 60, and 120 min in β-arrestin2 (-/-) PMNs and (+/+) cells. FITC-labeled LPS was significantly increased in β-arrestin 2 KO and WT PMNs at 30 minutes but no further increase occurred at 60 and 120 min of incubation (Figure 3). There were no significant differences between β-arrestin 2 (-/-) and (+/+) cells. Additionally, flow cytometry expression of TLR4 was not altered between βarrestin 2 (-/-) and (+/+) cells (data not shown).

Figure 3
LPS uptake by oyster glycogen elicited peritoneal cells. Murine peritoneal exudate cells were incubated with FITC-labeled LPS, after which cells were washed and analyzed using flow cytometry to determine the percentage of labeled cells.

β-Arrestin 2 deficiency augments PMN chemotaxis

To analyze the chemotaxic response of PMNs after administration of oyster glycogen, peritoneal recruitment of PMNs was quantitaed increase (81±1 % 4.2E+6 cells, p<0.05) PMN recruitment was observed in the (-/-) mice as compared to both (+/+) and (+/-) mice (Figure 4).

Figure 4
Absolute peritoneal cell counts. Murine peritoneal exudate cells were counted after harvesting using hemacytometer. Wildtype n=6; heterozygous n=9; knockout n=6.* = p<0.05 compared to wildtype.

β-Arrestin 2 deficiency augments expression of CD18 and CD62L by PMNS

The expression of selected activation markers and adhesion molecules known to be expressed on the surface of PMNs were examined. Flow cytometry was used to determine expression of CD45, a granulocyte/leukocyte marker used to confirm the purity of the harvested cells. In addition, expression of F4/80, a pan-macrophage marker; CD11b and CD18, adhesion receptors and CD62L, also known as L-selectin were determined. In β-arrestin 2 (-/-) cells, CD18 expression was elevated by 22% (p<0.05), and CD62L expression was elevated in the KO mice by 4.9 fold (p<0.05) compared to (+/+) cells (Figure 5).

Figure 5
Adhesion molecular expression by oyster glycogen elicited peritoneal cells Murine peritoneal exudate cells were incubated with FITC-labeled antibodies to CD45, F4/80, CD11b, CD18, and CD62L, after which cells were washed and analyzed using flow cytometry ...

β-Arrestin 2 deficiency augments cecal ligation and puncture-induced myeloperoxidase activity in lung

β-Arrestin 2 (-/-) and (+/+) mice were subjected to CLP. 18h after CLP lung was collected and myeloperoxidase activity (MPO) as index of PMNs infiltrate into lung were examined. CLP-induced MPO activity was significantly increased (2.8 fold, p<0.05) in the β-arrestin 2 (-/-) compared to (+/+) (Figure 6).

Figure 6
Cecal ligation and puncture-induced myeloperoxidase activity β-arrestin 2 (+/+) and (-/-) mice were subjected to CLP. 18h after CLP lung MPO were examined. *, p<0.05 compared to control. #, p<0.05 compared to (+/+) underwent CLP. ...


Our studies demonstrate that LPS-induced IL-6 production was significantly increased in PMNs harvested from β-arrestin 2 (-/-) mice compared to (+/+) mice. Thus, β-arrestin 2 is a negative regulator of pro-inflammatory mediator production in PMNs. β-arrestin 2 deficiency had no effect on LPS binding/uptake to PMNs or TLR4 expression on the surface of PMNs. However, we found that PMN chemotaxis was greatly augmented in β-arrestin 2-deficient mice, suggesting that it may play a significant role in the mediation of PMN recruitment and activity at the site of inflammation. Expression of adhesion receptors CD18 and particularly CD62L were also found to be increased in β-arrestin 2-deficient mice, suggesting a role for the β-arrestin 2 in expression of these receptors at the cell surface. In our study with β-arrestin 2 we demonstrated a marked increase in pulmonary MPO activity relative to WT mice. These findings suggest that β-arrestin 2 negatively regulates PMN tissue infiltration during sepsis.

The measured basal +LPS stimulated production of TNFα and IL-6 in oyster glycogen recruited PMNs from β-arrestin 2-deficient mice suggest a predominant anti-inflammatory function of β-arrestin 2 in PMNs. Our recent studies showed that both β-arrestin 1 and 2 negatively regulate NFκB activation [20]. In HEK293 cells rendered LPS-responsive by stable transfections with CD14 and TLR4, we demonstrated by siRNA depletion of β-arrestin 1 and 2 augmented NFκB activation in response to LPS [20]. On the other hand, over-expression of WT β-arrestins 1 and 2 in these cells suppressed LPS-induced NFκB activation [20]. These findings agree with studies that β-arrestin 2 directly interacts with, IκBα thus preventing the phosphorylation and degradation of IκBα [21, 28]. Recent studies have demonstrated that β-arrestins 1 and 2 directly interact with TRAF6 following TLR or IL-6 activation [29]. The complexes of β-arrestins and TRAF6 prevented its autouitination and activation of NFκB [29]. These studies further support an inhibitory role for β-arrestins in the regulation of LPS signaling. Since cytokine production was also increased in oyster glycogen recruited PMNs, it is probable that β-arrestin 2 may negatively regulate other inflammatory stimuli through similar mechanisms.

In addition to studying the effect of β-arrestin 2 on the production of pro-inflammatory cytokines, we demonstrated an increase in chemotaxis of PMNs induced by oyster glycogen in the peritoneal cavity of β-arrestin 2 deficient mice as compared to (+/+) mice. These findings are in accordance with other studies implicating β-arrestins as negative regulators of chemotaxis. The interactions between β-arrestins and Gi protein-coupled receptors involved in regulation of PMN chemotaxis, specifically in neutrophils, are pronounced in the CXC subfamily of receptors, including CXCR1 and CXCR2 [29]. Exposure to increased concentrations of chemokines, e.g. IL-8 can cause neutrophils to become unresponsive to further stimulation by other inflammatory cytokines; therefore, desensitization and internalization of CXC receptors is necessary for proper neutrophil functioning during inflammation. Barlic et al. showed that CXCR1 internalization is decreased in HEK293 cells with low β-arrestin 2 expression, and that such internalization is increased with additional expression of β-arrestin 1 or 2 [30, 31]. Su et al. showed that neutrophil recruitment with the binding of the chemokine CXCR1 to the CXCR2 receptor was increased in β-arrestin 2 deficient mice, and that although increased neutrophil activity in the form of calcium mobilization and superoxide anion production were increased in KO mice, receptor internalization was markedly decreased [32]. These two studies suggest that β-arrestin 2 may be negatively regulate chemotaxic activity of neutrophils by mediating chemokine receptor internalization and ultimately terminating chemokine signaling. However, such an interpretation may be an over simplification of the response.

One concept of chemotaxis is that desensitization and recycling of chemotactic receptors are essential for maintaining cellular polarity that promotes chemotaxis [29]. This concept is, in part, based upon in vitro studies where β-arrestin 2 deficiency actually suppresses chemotaxis [29, 32]. Thus, β-arrestin regulation of PMN recruitment in vivo likely reflects responses to other signals at the site of inflammation that are not present in transwell filter assays. Also, in contrast to CRCR1 and CXCR2, β-arrestin 2 appears to positively regulate CXCR4 in vivo lymphocyte chemotaxis [33]. Therefore, the effect of β-arrestins in regulation of chemotaxis in vivo depends upon the chemotactic receptor activation.

We also observed an increase in CD18 and CD62L (L-selectin) expression in the KO mice as compared to WT, in the recruited PMNs. This suggests that β-arrestin 2 is involved in the inhibition of signaling by these two integrins in PMNs. Mulligan et al. [25] examined the role of adhesion molecule expression in recruitment of neutrophils and found that blocking the selectins reduced the accumulation of neutrophils in the peritoneal cavity after oyster glycogen-induced peritonitis. A similar trend was seen after the use of blocking antibodies for CD11a, CD11b, and CD18 [32], indicating that these adhesion molecules are involved in the recruitment of neutrophils and the subsequent release of cytokines. β-arrestin may thus reduce the relative expression of these adhesion molecules and thus reduce PMNs to endothelial surfaces.

The CLP model is accepted as a clinically relevant sepsis model. CLP-induced pulmonary MPO activity was significantly increased in β-arresin 2 KO compared to WT mice demonstrating that β-arrestin 2 negatively regulates pulmonary leukosequestration. In WT mice, CLP-induced small but statistically significant increase of pulmonary MPO activity suggesting that the strain of mice has low response to sepsis induced inflammation. However, the β-arrestin 2 (-/-) mice with same background exhibited a more severe response suggesting that β-arrestin 2 negatively regulates tissue PMN infiltration in sepsis. Whether this is a result of altered PMN or endothelial adhesion receptor expression and/or altered chemokine production is currently under investigation. However this finding highlights the translational significance of β-arrestin 2 in polymicrobial sepsis.

Our studies demonstrate an effect of β-arrestin 2 on PMN inflammatory responses as reflected by altered cytokine production, PMN recruitment, adhesion molecule expression, and pulmonary leukosequtration in response to CLP. The extent that such responses may affect other pathogenesic events of sepsis remains to be determined.


This work was supported in part by NIH grants GM27673 and GM67202.


1. Faurschou M, Borregaard N. Neutrophil granules and secretory vesicles in inflammation. Microbes Infect. 2003;5:1317–1327. [PubMed]
2. Mizgerd JP. Molecular mechanisms of neutrophil recruitment elicited by bacteria in the lungs. Semin Immunol. 2002;14:123–132. [PubMed]
3. Akira S, Takeda K. Toll-like receptor signalling. Nat Rev Immunol. 2004;4:499–511. [PubMed]
4. Akira S, Uematsu S, Takeuchi O. Pathogen recognition and innate immunity. Cell. 2006;124:783–801. [PubMed]
5. Triantafilou M, Triantafilou K. Lipopolysaccharide recognition: CD14, TLRs and the LPS-activation cluster. Trends Immunol. 2002;23:301–304. [PubMed]
6. Fan H, Peck OM, Tempel GE, Halushka PV, Cook JA. Toll-like receptor 4 coupled Gl protein signaling pathways regulate extracellular signal-regulated kinase phosphorylation and AP-1 activation independent of NFkappaB activation. Shock. 2004;22:57–62. [PubMed]
7. Fan H, Teti G, Ashton S, Guyton K, Tempel GE, Halushka PV, Cook JA. Involvement of G(i) proteins and Src tyrosine kinase in TNFalpha production induced by lipopolysaccharide, group B Streptococci and Staphylococcus aureus. Cytokine. 2003;22:126–133. [PubMed]
8. Fan H, Zingarelli B, Peck OM, Teti G, Tempel GE, Halushka PV, Spicher K, Boulay G, Birnbaumer L, Cook JA. Lipopolysaccharide and gram-positive bacteria-induced cellular inflammatory responses: role of heterotrimeric Galpha(i) proteins. Am J Physiol Cell Physiol. 2005;289:C293–301. [erratum appears in Am J Physiol Cell Physiol. 2005 Nov;289(5):C1360 Note: Spicher, Karsten [added]; Boulay, Guylain [added]; Birnbaumer, Lutz [added]] [PubMed]
9. Lentschat A, Karahashi H, Michelsen KS, Thomas LS, Zhang W, Vogel SN, Arditi M. Mastoparan, a G protein agonist peptide, differentially modulates TLR4- and TLR2- mediated signaling in human endothelial cells and murine macrophages. J Immunol. 2005;174:4252–4261. [PubMed]
10. Solomon KR, Kurt-Jones EA, Saladino RA, Stack AM, Dunn IF, Ferretti M, Golenbock D, Fleisher GR, Finberg RW. Heterotrimeric G proteins physically associated with the lipopolysaccharide receptor CD14 modulate both in vivo and in vitro responses to lipopolysaccharide. J Clin Invest. 1998;102:2019–2027. [PMC free article] [PubMed]
11. Goodman OB, Jr., Krupnick JG, Santini F, Gurevich W, Penn RB, Gagnon AW, Keen JH, Benovic JL. Beta-arrestin acts as a clathrin adaptor in endocytosis of the beta2-adrenergic receptor. Nature. 1996;383:447–450. [PubMed]
12. Luttrell LM, Lefkowitz RJ. The role of beta-arrestins in the termination and transduction of G-protein-coupled receptor signals. J Cell Sci. 2002;115:455–465. [PubMed]
13. Miller WE, Lefkowitz RJ. Expanding roles for beta-arrestins as scaffolds and adapters in GPCR signaling and trafficking. Curr Opin Cell Biol. 2001;13:139–145. [PubMed]
14. Pitcher JA, Freedman NJ, Lefkowitz RJ. G protein-coupled receptor kinases. Annu Rev Biochem. 1998;67:653–692. [PubMed]
15. DeFea KA, Vaughn ZD, O'Bryan EM, Nishijima D, Dery O, Bunnett NW. The proliferative and antiapoptotic effects of substance P are facilitated by formation of a beta -arrestin- dependent scaffolding complex. Proc Natl Acad Sci U S A. 2000;97:11086–11091. [PubMed]
16. DeFea KA, Zalevsky J, Thoma MS, Dery O, Mullins RD, Bunnett NW. beta-arrestin- dependent endocytosis of proteinase-activated receptor 2 is required for intracellular targeting of activated ERK1/2. J Cell Biol. 2000;148:1267–1281. [PMC free article] [PubMed]
17. Luttrell LM, Roudabush FL, Choy EW, Miller WE, Field ME, Pierce KL, Lefkowitz RJ. Activation and targeting of extracellular signal-regulated kinases by beta-arrestin scaffolds. Proc Natl Acad Sci U S A. 2001;98:2449–2454. [PubMed]
18. McDonald PH, Chow CW, Miller WE, Laporte SA, Field ME, Lin FT, Davis RJ, Lefkowitz RJ. Beta-arrestin 2: a receptor-regulated MAPK scaffold for the activation of JNK3. Science. 2000;290:1574–1577. [PubMed]
19. Sun Y, Cheng Z, Ma L, Pel G. Beta-arrestin2 is critically involved in CXCR4-mediated chemotaxis, and this is mediated by its enhancement of p38 MAPK activation. J Biol Chem. 2002;277:49212–49219. [PubMed]
20. Fan H, Luttrell LM, Tempel GE, Senn JJ, Halushka PV, Cook JA. Beta-arrestins 1 and 2 differentially regulate LPS-induced signaling and pro-inflammatory gene expression. Mol Immunol. 2007;44:3092–3099. [PMC free article] [PubMed]
21. Gao H, Sun Y, Wu Y, Luan B, Wang Y, Qu B, Pel G. Identification of beta-arrestin2 as a G protein-coupled receptor-stimulated regulator of NF-kappaB pathways. Mol Cell. 2004;14:303–317. [PubMed]
22. Parameswaran N, Pao CS, Leonhard KS, Kang DS, Kratz M, Ley SC, Benovic JL. Arrestin-2 and G protein-coupled receptor kinase 5 interact with NFkappaB1 p105 and negatively regulate lipopolysaccharide-stimulated ERK1/2 activation in macrophages. J Biol Chem. 2006;281:34159–34170. [PubMed]
23. Wang Y, Tang Y, Teng L, Wu Y, Zhao X, Pel G. Association of beta-arrestin and TRAF6 negatively regulates Toll-like receptor-interleukin 1 receptor signaling. Nat Immunol. 2006;7:139–147. [PubMed]
24. Lefkowitz RJ, Shenoy SK. Transduction of receptor signals by beta-arrestins. Science. 2005;308:512–517. [PubMed]
25. Mulligan MS, Lentsch AB, Miyasaka M, Ward PA. Cytokine and adhesion molecule requirements for neutrophil recruitment during glycogen-induced peritonitis. Inflamm Res. 1998;47:251–255. [PubMed]
26. Vromen A, Arkovitz MS, Zingarelli B, Salzman AL, Garcia VF, Szabo C. Low-level expression and limited role for the inducible isoform of nitric oxide synthase in the vascular hyporeactivity and mortality associated with cecal ligation and puncture in the rat. Shock. 1996;6:248–253. [PubMed]
27. Zingarelli B, Hake PW, Yang Z, O'Connor M, Denenberg A, Wong HR. Absence of inducible nitric oxide synthase modulates early reperfusion-induced NF-kappaB and AP-1 activation and enhances myocardial damage. FASEB J. 2002;16:327–342. [PubMed]
28. Witherow DS, Garrison TR, Miller WE, Lefkowitz RJ. beta-Arrestin inhibits NF-kappaB activity by means of its interaction with the NF-kappaB inhibitor IkappaBalpha. Proc Natl Acad Sci U S A. 2004;101:8603–8607. [PubMed]
29. DeFea KA. Stop that cell! Beta-arrestin-dependent chemotaxis: a tale of localized actin assembly and receptor desensitization. Annu Rev Physiol. 2007;69:535–560. [PubMed]
30. Barlic J, Andrews JD, Kelvin AA, Bosinger SE, DeVries ME, Xu L, Dobransky T, Feldman RD, Ferguson SS, Kelvin DJ. Regulation of tyrosine kinase activation and granule release through beta-arrestin by CXCRI. Nat Immunol. 2000;1:227–233. [PubMed]
31. Barlic J, Khandaker MH, Mahon E, Andrews J, DeVries ME, Mitchell GB, Rahimpour R, Tan CM, Ferguson SS, Kelvin DJ. beta-arrestins regulate interleukin-8-induced CXCRI internalization. J Biol Chem. 1999;274:16287–16294. [PubMed]
32. Su Y, Raghuwanshi SK, Yu Y, Nanney LB, Richardson RM, Richmond A. Altered CXCR2 signaling in beta-arrestin-2-deficient mouse models. J Immunol. 2005;175:5396–5402. [PMC free article] [PubMed]
33. Cheng ZJ, Zhao J, Sun Y, Hu W, Wu YL, Cen B, Wu GX, Pel G. beta-arrestin differentially regulates the chemokine receptor CXCR4-mediated signaling and receptor internalization, and this implicates multiple interaction sites between beta-arrestin and CXCR4. J Biol Chem. 2000;275:2479–2485. [PubMed]

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