501
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Verma A, Mohindru M, Deb DK, Sassano A, Kambhampati S, Ravandi F, Minucci S, Kalvakolanu DV, Platanias LC. Activation of Rac1 and the p38 mitogen-activated protein kinase pathway in response to arsenic trioxide. J Biol Chem 2002; 277:44988-95. [PMID: 12239215 DOI: 10.1074/jbc.m207176200] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Arsenic trioxide induces differentiation and apoptosis of malignant cells in vitro and in vivo, but the mechanisms by which such effects occur have not been elucidated. In the present study we provide evidence that arsenic trioxide induces activation of the small G-protein Rac1 and the alpha and beta isoforms of the p38 mitogen-activated protein (MAP) kinase in several leukemia cell lines. Such activation of Rac1 and p38-isoforms results in downstream engagement of the MAP kinase-activated protein kinase-2 and is enhanced by pre-treatment of cells with ascorbic acid. Interestingly, pharmacological inhibition of p38 potentiates arsenic-dependent apoptosis and suppression of growth of leukemia cell lines, suggesting that this signaling cascade negatively regulates induction of antileukemic responses by arsenic trioxide. Consistent with this, overexpression of a dominant-negative p38 mutant (p38betaAGF) enhances the antiproliferative effects of arsenic trioxide on target cells. To further define the relevance of activation of the Rac1/p38 MAP kinase pathway in the induction of arsenic-dependent antileukemic effects, studies were performed using bone marrows from patients with chronic myelogenous leukemia. Arsenic trioxide suppressed the growth of leukemic myeloid (CFU-GM) progenitors from such patients, whereas concomitant pharmacological inhibition of the p38 pathway enhanced its growth-suppressive effects. Altogether, these data provide evidence for a novel function of the p38 MAP kinase pathway, acting as a negative regulator of arsenic trioxide-induced apoptosis and inhibition of malignant cell growth.
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Affiliation(s)
- Amit Verma
- Robert H. Lurie Comprehensive Cancer Center and Section of Hematology-Oncology, Northwestern University Medical School, Chicago, Illinois 60611, USA
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502
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Pearce AC, Wilde JI, Doody GM, Best D, Inoue O, Vigorito E, Tybulewicz VLJ, Turner M, Watson SP. Vav1, but not Vav2, contributes to platelet aggregation by CRP and thrombin, but neither is required for regulation of phospholipase C. Blood 2002; 100:3561-9. [PMID: 12411320 DOI: 10.1182/blood.v100.10.3561] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We have investigated the role of the Rho and Rac family small guanine triphosphate (GTP) exchange factors (RhoGEFs), Vav1 and Vav2, in the activation of platelets by the immunoreceptor tyrosine-based activation motif (ITAM)-coupled collagen receptor GPVI and by the G protein-coupled receptor agonist thrombin. The glycoprotein VI (GPVI)-specific agonist collagen-related peptide (CRP) and thrombin stimulated tyrosine phosphorylation of Vav1 but not Vav2 in human platelets. Surprisingly, however, CRP did not activate the low-molecular-weight G protein Rac and stimulated only a small increase in activity of p21-associated kinase 2 (PAK2), despite the fact that both proteins are regulated downstream of Vav1 in other cells. Further, activation of Rac and PAK2 by thrombin was maintained in platelets from mice deficient in Vav1. Activation of phospholipase C (PLC) by GPVI and thrombin was unaltered in Vav1-, Vav2-, and Vav1/Vav2-deficient platelets. A weak inhibition of late-stage aggregation to CRP and thrombin was observed in platelets deficient in Vav1 but not Vav2, whereas spreading on fibrinogen was not changed. The present results demonstrate that neither Vav1 nor Vav2 lie upstream of PLC or Rac in platelets, highlighting an important difference in their role in signaling by ITAM-coupled receptors in other cell types. The present study has provided evidence for a possible role of Vav1 but not Vav2 in the later stages of platelet aggregation.
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Affiliation(s)
- Andrew C Pearce
- Department of Pharmacology, University of Oxford, United Kingdom.
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503
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Berrier AL, Martinez R, Bokoch GM, LaFlamme SE. The integrin beta tail is required and sufficient to regulate adhesion signaling to Rac1. J Cell Sci 2002; 115:4285-91. [PMID: 12376560 DOI: 10.1242/jcs.00109] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Rac1 is a small Rho family GTPase that regulates changes in cell morphology associated with cell spreading and migration. Integrin-mediated adhesion is known to activate Rac1 and to regulate the interaction of Rac1 with downstream effectors. Currently, it is not clear how integrins signal Rac1 activation following cell adhesion. Integrin beta cytoplasmic domains (beta-tails) are known to be required for integrin-mediated cell spreading, and isolated beta tails expressed as tac-beta tail chimeras can inhibit cell spreading indicating that protein interactions with beta tails can regulate this process. Our recent studies demonstrated that the expression of constitutively activated Rac1 can restore cell spreading inhibited by tac beta tail chimeras, suggesting a role for Rac1 in the regulation of cell spreading by beta tails. Hence, we examined the role of beta tails in integrin activation of Rac1. By using recombinant wild-type and mutant integrin heterodimers, we demonstrate that integrin beta tails are required for adhesion to increase Rac1-GTP loading. We demonstrate that clustering tac-beta tail chimeras, on the surface of cells in suspension, activates Rac1. Thus, beta tails are not only required, but also sufficient for integrin-triggered Rac1 activation. Our findings indicate that integrin beta-tails are an important link between integrin engagement and Rac1 signaling, and that protein interactions initiated at beta tails are sufficient for integrins to regulate Rac1 activity.
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Affiliation(s)
- Allison L Berrier
- The Center for Cell Biology and Cancer Research, Albany Medical College, Albany, NY 12208, USA
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504
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Harris C, Maroney AC, Johnson EM. Identification of JNK-dependent and -independent components of cerebellar granule neuron apoptosis. J Neurochem 2002; 83:992-1001. [PMID: 12421372 DOI: 10.1046/j.1471-4159.2002.01219.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cerebellar granule neurons grown in high potassium undergo rapid apoptosis when switched to medium containing 5 mm potassium, a stimulus mimicking deafferentation. This cell death can be blocked by genetic deletion of Bax, a member of the pro-apoptotic Bcl-2 family, cycloheximide an inhibitor of macromolecular synthesis or expression of dominant-negative c-jun. These observations suggest that Bax activation is the result of c-jun target gene(s) up-regulation following trophic withdrawal. Candidate genes include the BH3-only Bcl-2 family members Dp5 and Bim. The molecular mechanisms underlying granule cell neuronal apoptosis in response to low potassium were investigated using CEP-1347 (KT7515), an inhibitor of the MLK family of JNKKK. CEP-1347 provided protection of potassium-serum-deprived granule cells, but such neuroprotection was not long term. The incomplete protection was not due to incomplete blockade of the JNK signaling pathway because c-jun phosphorylation as well as induction of c-jun RNA and protein were completely blocked by CEP-1347. Following potassium-serum deprivation the JNKK MKK4 becomes phosphorylated, an event blocked by CEP-1347. Cells that die in the presence of CEP-1347 activate caspases; and dual inhibition of caspases and MLKs has additive, not synergistic, effects on survival. A lack of synergism was also seen with the p38 inhibitor SB203580, indicating that the neuroprotective effect of the JNK pathway inhibitor cannot be explained by p38 activation. Activation of the JNK signaling pathway seems to be a key event in granule cell apoptosis, but these neurons cannot survive long term in the absence of sustained PI3 kinase signaling.
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Affiliation(s)
- Charles Harris
- Department of Molecular Biology, Washington University School of Medicine, St Louis, Missouri 63110, USA
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505
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Tsukamoto K, Hirano KI, Yamashita S, Sakai N, Ikegami C, Zhang Z, Matsuura F, Hiraoka H, Matsuyama A, Ishigami M, Matsuzawa Y. Retarded intracellular lipid transport associated with reduced expression of Cdc42, a member of Rho-GTPases, in human aged skin fibroblasts: a possible function of Cdc42 in mediating intracellular lipid transport. Arterioscler Thromb Vasc Biol 2002; 22:1899-904. [PMID: 12426222 DOI: 10.1161/01.atv.0000036080.42391.33] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Many cell types in atherosclerotic lesions are thought to have various biological abnormalities, such as impaired lipid homeostasis and slow cell proliferation, which may be related to senescence at cellular and individual levels. One of the common characteristics of senescent cells in vitro is the alteration of actin cytoskeletons, which have been reported to be involved in the intracellular transport of lipids. Recently, we raised the hypothesis that Cdc42, which is a member of the Rho-GTPase family and is known to play an important role in actin dynamics, might be important in cellular lipid transport. METHODS AND RESULTS In the present study, we found that the protein expression levels and GTP-binding activities of Cdc42 were decreased in aged human skin fibroblasts. Moreover, we found the intracellular kinetics of Golgi-associated lipids to be retarded in these cells, which was demonstrated by the fluorescence recovery after photobleaching (FRAP) technique and the use of N-[7-(4-nitrobenzo-2-oxa-1,3-diazole)]-6-aminohexanoyl-D-erythro-sphingosine as a tracer. To correlate the decreased expression of Cdc42 with the retarded FRAP, we complemented the amount of wild-type c-myc-tagged Cdc42Hs (myc-Cdc42Hs-WT) by adenovirus-mediated gene transfer. We further tested the effect of the dominant-active form (myc-Cdc42Hs-DA, V12Cdc42Hs) or dominant-negative form (myc-Cdc42Hs-DN, N17Cdc42Hs) of Cdc42Hs on FRAP. Introduction of myc-Cdc42Hs-WT or myc-Cdc42Hs-DA recovered the retarded FRAP in the aged fibroblasts. Conversely, control fibroblasts infected with myc-Cdc42Hs-DN exhibited significantly retarded FRAP. CONCLUSIONS These data clearly indicate that the expression of Cdc42, a small G protein, is decreased in the aged cells in close association with the retarded intracellular lipid transport. The present study demonstrates a possible function of Cdc42 in the mediation of intracellular lipid transport.
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Affiliation(s)
- Kosuke Tsukamoto
- Department of Internal Medicine and Molecular Science, Graduate School of Medicine, Osaka University, Osaka, Japan
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506
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Gu Y, Byrne MC, Paranavitana NC, Aronow B, Siefring JE, D'Souza M, Horton HF, Quilliam LA, Williams DA. Rac2, a hematopoiesis-specific Rho GTPase, specifically regulates mast cell protease gene expression in bone marrow-derived mast cells. Mol Cell Biol 2002; 22:7645-57. [PMID: 12370311 PMCID: PMC135684 DOI: 10.1128/mcb.22.21.7645-7657.2002] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2001] [Revised: 07/01/2002] [Accepted: 08/08/2002] [Indexed: 11/20/2022] Open
Abstract
Rho family GTPases activate intracellular kinase cascades to modulate transcription of multiple genes. Previous studies have examined the roles of the ubiquitously expressed Rho GTPase, Rac1, in regulation of gene expression in cell lines and implicated NF-kappaB, serum response factor, and kinase signaling pathways in this regulation. To understand the role of the closely related but hematopoiesis-specific Rho GTPase, Rac2, in regulation of gene transcription, we compared the gene expression profiles between wild-type and Rac2(-/-) bone marrow-derived mast cells. Our data demonstrate remarkable specificity in the regulation of gene expression by Rac2 versus Rac1. Microarray analysis demonstrated that expression of 38 known genes was significantly altered in Rac2(-/-) mast cells after cytokine stimulation compared with those in wild-type cells. Of these, the expression of the mouse mast cell protease 7 (MMCP-7) gene in wild-type cells was highly induced at the transcriptional level after stimulation with stem cell factor (SCF). In spite of compensatorily increased expression of Rac1 in Rac2-deficient cells, SCF-induced MMCP-7 transcription did not occur. Surprisingly, the loss of MMCP-7 induction was not due to decreased activation of NF-kappaB, a transcription factor postulated to lie downstream of Rac1 and known to play a critical role in hematopoietic cell differentiation and proliferation. However, the activities of c-Jun N-terminal kinases (JNKs) were markedly decreased in Rac2(-/-) mast cells. Our results suggest that cytokine-stimulated activation of MMCP-7 gene transcription is selectively regulated by a Rac2-dependent JNK signaling pathway in primary mast cells and imply a remarkable specificity in the regulation of transcriptional activity by these two highly related Rho GTPases.
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Affiliation(s)
- Yi Gu
- Division of Experimental Hematology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA
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507
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Lopes NHM, Vasudevan SS, Gregg D, Selvakumar B, Pagano PJ, Kovacic H, Goldschmidt-Clermont PJ. Rac-dependent monocyte chemoattractant protein-1 production is induced by nutrient deprivation. Circ Res 2002; 91:798-805. [PMID: 12411394 DOI: 10.1161/01.res.0000040421.54108.81] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Under ischemic conditions, the vessel wall recruits inflammatory cells. Human aortic endothelial cells (HAECs) exposed to hypoxia followed by reoxygenation produce monocyte chemoattractant protein-1 (MCP-1); however, most experiments have been performed in the presence of nutrient deprivation (ND). We hypothesized that ND rather than hypoxia mediates endothelial MCP-1 production during ischemia, and that the small GTP-binding protein Rac1 and reactive oxygen species (ROS) are involved in this process. ND was generated by shifting HAECs from 10% to 1% FBS. Superoxide production by HAECs was increased 6 to 24 hours after ND, peaking at 18 hours. MCP-1 production was increased over a similar time frame, but peaked later at 24 hours. These effects were blocked by treatment with antioxidants such as superoxide dismutase mimetic and N-acetylcysteine (NAC), or NADPH oxidase inhibitors, DPI and gp91ds-tat. Superoxide and MCP-1 production were enhanced by RacV12 (constitutively active) in the absence of ND, and were inhibited by RacN17 (dominant-negative) adenoviral transduction under ND, suggesting that the small G-protein Rac1 is required. In conclusion, ND, an important component of ischemia, is sufficient to induce MCP-1 production by HAECs, and such production requires a functional Rac1, redox-dependent pathway.
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Affiliation(s)
- Neuza H M Lopes
- Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA
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508
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Li S, Yamauchi A, Marchal CC, Molitoris JK, Quilliam LA, Dinauer MC. Chemoattractant-stimulated Rac activation in wild-type and Rac2-deficient murine neutrophils: preferential activation of Rac2 and Rac2 gene dosage effect on neutrophil functions. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 169:5043-51. [PMID: 12391220 DOI: 10.4049/jimmunol.169.9.5043] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The hemopoietic-specific Rho family GTPase Rac2 shares 92% amino acid identity with ubiquitously expressed Rac1. Neutrophils from rac2(-/-) mice have multiple defects, including chemoattractant-stimulated NADPH oxidase activity and chemotaxis, which may result from an overall reduction in cellular Rac or mechanisms that discriminate Rac1 and Rac2. We show that murine neutrophils have similar amounts of Rac1 and Rac2, unlike human neutrophils, which express predominantly Rac2. An affinity precipitation assay for Rac-GTP showed that although FMLP-induced activation of both isoforms in wild-type neutrophils, approximately 4-fold more Rac2-GTP was detected than Rac1-GTP. Wild-type and Rac2-deficient neutrophils have similar levels of total Rac1. FMLP-induced Rac1-GTP in rac2(-/-) neutrophils was approximately 3-fold greater than in wild-type cells, which have similar levels of total Rac1, yet FMLP-stimulated F-actin, chemotaxis, and superoxide production are markedly impaired in rac2(-/-) neutrophils. Heterozygous rac2(+/-) neutrophils, which had intermediate levels of total and FMLP-induced activated Rac2, exhibited intermediate functional responses to FMLP, suggesting that Rac2 was rate limiting for these functions. Thus, phenotypic defects in FMLP-stimulated Rac2-deficient neutrophils appear to reflect distinct activation and signaling profiles of Rac1 and Rac2, rather than a reduction in the total cellular level of Rac.
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Affiliation(s)
- Shijun Li
- Herman B Wells Center for Pediatric Research and Department of Pediatrics (Hematology/Oncology), Indiana University Medical School, Indianapolis 46202, USA
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509
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Grill B, Schrader JW. Activation of Rac-1, Rac-2, and Cdc42 by hemopoietic growth factors or cross-linking of the B-lymphocyte receptor for antigen. Blood 2002; 100:3183-92. [PMID: 12384416 DOI: 10.1182/blood-2002-01-0154] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Interleukin-3 (IL-3)-induced activation of endogenous Rac-1, Rac-2, and Cdc42. Rac-1 was also activated by colony-stimulating factor-1 (CSF-1), Steel locus factor (SLF), granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-5 or by cross-linking the B-lymphocyte receptor for antigen (BCR). The activation of Rac-1 induced by cross-linking the BCR or by IL-3 stimulation was blocked only partially by Ly294002, with about 25% to 30% of Rac-1 activation still occurring in the absence of detectable increases in phosphatidyl-inositol-3 kinase (PI-3K) activity. Overexpression of constitutively active mutants of H-Ras, N-Ras, or M-Ras resulted in activation of coexpressed Rac-1 through an Ly29402-resistant, PI-3K-independent mechanism. Overexpression of constitutively active mutants of p21 Ras, or Rac-1, but not of PI-3K, was sufficient for activation of p38 mitogen-activated protein kinase (MAPK) in cells of hemopoietic origin. Inhibition of increases in PI-3K activity by Ly294002 had no effect on the IL-3-induced activation of p38 MAPK. In contrast, Ly294002 partially inhibited the activation of p38 MAPK induced by cross-linking of the BCR, although some p38 MAPK activation occurred in the absence of increases in the activity of Rac-1 or PI-3K. The activation of Rac-1, Rac-2, and Cdc42 by IL-3 and other hemopoietic growth factors is likely to be an important component of their actions in promoting growth, survival, and function.
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Affiliation(s)
- Brock Grill
- The Biomedical Research Centre, University of British Columbia, 2222 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
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510
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Shalom-Barak T, Knaus UG. A p21-activated kinase-controlled metabolic switch up-regulates phagocyte NADPH oxidase. J Biol Chem 2002; 277:40659-65. [PMID: 12189148 DOI: 10.1074/jbc.m206650200] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chemoattractant-stimulated phagocytes increase their glucose uptake and divert energy production from glycolysis to the pentose phosphate pathway to generate NADPH. NADPH is a required cofactor for the NADPH oxidase to produce reactive oxygen metabolites, an important microbicidal tool in host defense. p21-Activated kinases (Paks) are regulated by the GTPases Rac and Cdc42 and control actin dynamics and phosphorylation of the oxidase component p47(phox). Here we report the interaction of Pak with phosphoglycerate mutase (PGAM)-B, an enzyme of the glycolytic pathway. Activated Pak1 inhibits glycolysis by association of its catalytic domain with PGAM-B and subsequent phosphorylation of the enzyme on serine residues 23 and 118, thereby abolishing PGAM activity. Leukocyte activation through chemoattractant receptors leads to Pak activation and transient inhibition of endogenous PGAM-B activity. Consistent with these observations, treatment of neutrophils with phosphoglycolic acid, a competitive PGAM-B inhibitor, increases upstream intermediates, thereby amplifying the respiratory burst. These results demonstrate that Rho GTPases regulate the glycolytic pathway through Pak and suggest a link between chemoattractant signaling and metabolic responses to enhance host defense.
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Affiliation(s)
- Tali Shalom-Barak
- Department of Immunology IMM28, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
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511
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Cicchetti G, Allen PG, Glogauer M. Chemotactic signaling pathways in neutrophils: from receptor to actin assembly. CRITICAL REVIEWS IN ORAL BIOLOGY AND MEDICINE : AN OFFICIAL PUBLICATION OF THE AMERICAN ASSOCIATION OF ORAL BIOLOGISTS 2002; 13:220-8. [PMID: 12090462 DOI: 10.1177/154411130201300302] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In this review, we present an overview of the signaling elements between neutrophil chemotactic receptors and the actin cytoskeleton that drives cell motility. From receptor-ligand interactions, activation of heterotrimeric G-proteins, their downstream effectors PLC and PI-3 kinase, the activation of small GTPases of the Rho family, and their regulation of particular cytoskeletal regulatory proteins, we describe pathways specific to the chemotaxing neutrophil and elements documented to be important for neutrophil function.
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Affiliation(s)
- Gregor Cicchetti
- Hematology Division, Harvard Medical School, Brigham and Women's Hospital, LMRC 301, Boston, MA 02115, USA
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512
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Allen MP, Xu M, Linseman DA, Pawlowski JE, Bokoch GM, Heidenreich KA, Wierman ME. Adhesion-related kinase repression of gonadotropin-releasing hormone gene expression requires Rac activation of the extracellular signal-regulated kinase pathway. J Biol Chem 2002; 277:38133-40. [PMID: 12138087 DOI: 10.1074/jbc.m200826200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Recent studies suggest that adhesion-related kinase (Ark) plays a role in gonadotropin-releasing hormone (GnRH) neuronal physiology. Ark promotes migration of GnRH neurons via Rac GTPase and concomitantly suppresses GnRH gene expression via homeodomain and myocyte enhancer factor-2 (MEF2) transcription factors. Here, we investigated the signaling cascade required for Ark inhibition of the GnRH promoter in GT1-7 GnRH neuronal cells. Ark repression was blocked by the MEK/ERK pathway inhibitor, PD98059, and dominant negative MEK1 but was unaffected by dominant negative Ras. Inhibitors of the Rho family GTPases, Clostridium difficile toxin B (Rho/Rac/Cdc42 inhibitor) and Clostridium sordellii lethal toxin (Rac/Cdc42 inhibitor), blocked Ark inhibition of GnRH transcription. Moreover, dominant negative Rac blunted both Ark activation of ERK and repression of the GnRH promoter, demonstrating an essential role for Rac in coupling Ark to ERK activation. Like Ark, a constitutively active mutant of Rac suppressed GnRH transcription in an ERK-dependent manner. Finally, Ark-mediated repression was significantly attenuated by a dominant negative MEF2C, whereas repression induced by constitutively active Rac was unaffected, indicating that MEF2 proteins are not targets of the Ark --> Rac --> MEK --> ERK cascade. The data suggest that Ark suppresses GnRH gene expression via the coordinated activation of a Rac --> ERK signaling pathway and a distinct MEF2- dependent mechanism.
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Affiliation(s)
- Melissa P Allen
- Department of Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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513
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Chang L, Adams RD, Saltiel AR. The TC10-interacting protein CIP4/2 is required for insulin-stimulated Glut4 translocation in 3T3L1 adipocytes. Proc Natl Acad Sci U S A 2002; 99:12835-40. [PMID: 12242347 PMCID: PMC130546 DOI: 10.1073/pnas.202495599] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The GTPase TC10 plays a critical role in insulin-stimulated glucose transport. We report here the identification of the TC10-interacting protein CIP4/2 (Cdc42-interacting protein 4/2) as an effector in this pathway. CIP4/2 localizes to an intracellular compartment under basal conditions and translocates to the plasma membrane on insulin stimulation. Overexpression of constitutively active TC10 brings CIP4/2 to the plasma membrane, whereas overexpression of an inhibitory form of TC10 blocks the translocation of CIP4/2 produced by insulin. Overexpression of mutant forms of CIP4/2 containing an N-terminal deletion or with diminished TC10 binding inhibits insulin-stimulated Glut4 translocation. These data suggest that CIP4/2 may play an important role in insulin-stimulated glucose transport as a downstream effector of TC10.
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Affiliation(s)
- Louise Chang
- Departments of Internal Medicine and Physiology, Life Sciences Institute, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
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514
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Caviston JP, Tcheperegine SE, Bi E. Singularity in budding: a role for the evolutionarily conserved small GTPase Cdc42p. Proc Natl Acad Sci U S A 2002; 99:12185-90. [PMID: 12218170 PMCID: PMC129419 DOI: 10.1073/pnas.182370299] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2001] [Indexed: 11/18/2022] Open
Abstract
The budding yeast Saccharomyces cerevisiae initiates polarized growth or budding once per cell cycle at a specific time of the cell cycle and at a specific location on the cell surface. Little is known about the molecular nature of the temporal and spatial regulatory mechanisms. It is also unclear what factors, if any, among the numerous proteins required to make a bud are involved in the determination of budding frequency. Here we describe a class of cdc42 mutants that produce multiple buds at random locations on the cell surface within one nuclear cycle. The critical mutation responsible for this phenotype affects amino acid residue 60, which is located in a domain required for GTP binding and hydrolysis. This mutation bypasses the requirement for the essential guanine-nucleotide-exchange factor Cdc24p, suggesting that the alteration at residue 60 makes Cdc42p hyperactive, which was confirmed biochemically. This result also suggests that the only essential function of Cdc24p is to activate Cdc42p. Together, these data suggest that the temporal and spatial regulation of polarized growth converges at the level of Cdc42p and that the activity of Cdc42p determines the budding frequency.
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Affiliation(s)
- Juliane P Caviston
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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515
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Yamauchi J, Miyamoto Y, Kokubu H, Nishii H, Okamoto M, Sugawara Y, Hirasawa A, Tsujimoto G, Itoh H. Endothelin suppresses cell migration via the JNK signaling pathway in a manner dependent upon Src kinase, Rac1, and Cdc42. FEBS Lett 2002; 527:284-8. [PMID: 12220675 DOI: 10.1016/s0014-5793(02)03231-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Cell migration is a complex phenomenon that is stimulated by chemoattractive factors such as chemokines, a family of ligands for G protein-coupled receptors (GPCRs). In contrast, factors that suppress cell migration, and the mechanism of their action, remain largely unknown. In this study, we show that endothelin, a GPCR ligand, inhibits cell motility in a manner dependent upon signaling through the c-Jun N-terminal kinase (JNK) pathway. We further demonstrate that this effect is dependent upon Src kinase and small GTPases Rac1 and Cdc42. These findings provide new insight into GPCR-mediated regulation of cell migration.
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Affiliation(s)
- Junji Yamauchi
- Department of Cell Biology, Graduate School of Biological Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, 630-0101, Nara, Japan.
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516
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Ruiz-Velasco R, Lanning CC, Williams CL. The activation of Rac1 by M3 muscarinic acetylcholine receptors involves the translocation of Rac1 and IQGAP1 to cell junctions and changes in the composition of protein complexes containing Rac1, IQGAP1, and actin. J Biol Chem 2002; 277:33081-91. [PMID: 12070151 DOI: 10.1074/jbc.m202664200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The abilities of the M(3) muscarinic acetylcholine receptor (mAChR) and Rac1 to regulate similar cellular responses, including cadherin-mediated adhesion, prompted us to investigate Rac1 regulation by M(3) mAChR. We characterized changes in Rac1 induced by stimulating transfected M(3) mAChR in Chinese hamster ovary cells stably expressing hemagglutinin (HA)-tagged wild-type or mutant Rac1. mAChR activation converts endogenous Rac1 to the GTP-bound form in cells expressing HA-Rac1 but not in cells expressing dominant negative HA-Rac1(Asn-17) or constitutively active HA-Rac1(Val-12). The competitive binding of endogenous IQGAP1 by HA-Rac1(Val-12) may diminish the mAChR-mediated activation of endogenous Rac1. HA-Rac1 and HA-Rac1(Val-12), but not HA-Rac1(Asn-17), accumulate with IQGAP1 at cell junctions during mAChR-induced cell-cell compaction. Co-localization studies suggest that Rac1 can accumulate at junctions without IQGAP1, but IQGAP1 cannot accumulate at junctions without Rac1. mAChR activation also induces GTP-independent changes in Rac1 because mAChR activation redistributes HA-Rac1(Asn-17), which does not bind GTP. Actin associates with complexes containing HA-Rac1 or HA-Rac1(Val-12) after prolonged mAChR activation. We also demonstrate that Rac1 participates in mAChR-induced cell-cell compaction and c-Jun phosphorylation. These results indicate that M(3) mAChR activation converts Rac1 to the GTP-bound form, alters interactions between Rac1, IQGAP1, and actin, and causes the junctional accumulation of Rac1 and IQGAP1.
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Affiliation(s)
- Rebecca Ruiz-Velasco
- Molecular Pharmacology Laboratory, Guthrie Research Institute, One Guthrie Square, Sayre, Pennsylvania 18840, USA
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517
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Seshiah PN, Weber DS, Rocic P, Valppu L, Taniyama Y, Griendling KK. Angiotensin II stimulation of NAD(P)H oxidase activity: upstream mediators. Circ Res 2002; 91:406-13. [PMID: 12215489 DOI: 10.1161/01.res.0000033523.08033.16] [Citation(s) in RCA: 550] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Angiotensin II (Ang II)-stimulated hypertrophy of vascular smooth muscle cells is mediated by reactive oxygen species (ROS) derived from NAD(P)H oxidases. The upstream signaling mechanisms by which Ang II activates these oxidases are unclear but may include protein kinase C, tyrosine kinases, phosphatidylinositol-3-kinase, and Rac, a small molecular weight G protein. We found that Ang II-stimulated ROS production is biphasic. The first phase occurs rapidly (peak at 30 seconds) and is dependent on protein kinase C activation. The larger second phase of ROS generation (peak at 30 minutes) requires Rac activation, because inhibition of Rac by either Clostridium difficile toxin A or dominant-negative Rac significantly inhibits Ang II-induced ROS production. Phosphatidylinositol-3-kinase inhibitors (wortmannin or LY294002) and the epidermal growth factor (EGF) receptor kinase blocker AG1478 attenuate both Rac activation and ROS generation. The upstream activator of EGF receptor transactivation, c-Src, is also required for ROS generation, because PP1, an Src kinase inhibitor, abrogates the Ang II stimulation of both responses. These results suggest that c-Src, EGF receptor transactivation, phosphatidylinositol-3-kinase, and Rac play important roles in the sustained Ang II-mediated activation of vascular smooth muscle cell NAD(P)H oxidases and provide insight into the integrated signaling mechanisms whereby Ang II stimulation leads to activation of the growth-related NAD(P)H oxidases.
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MESH Headings
- Androstadienes/pharmacology
- Angiotensin II/pharmacology
- Animals
- Cells, Cultured
- Chromones/pharmacology
- Enzyme Inhibitors/pharmacology
- ErbB Receptors/metabolism
- Flow Cytometry
- Hydrogen Peroxide/metabolism
- Indoles/pharmacology
- Male
- Maleimides/pharmacology
- Morpholines/pharmacology
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- NADH, NADPH Oxidoreductases/drug effects
- NADH, NADPH Oxidoreductases/metabolism
- NADPH Oxidases
- Phosphatidylinositol 3-Kinases/metabolism
- Phosphoinositide-3 Kinase Inhibitors
- Protein Kinase C/antagonists & inhibitors
- Protein Kinase C/metabolism
- Pyrazoles/pharmacology
- Pyrimidines/pharmacology
- Rats
- Rats, Sprague-Dawley
- Reactive Oxygen Species/metabolism
- Signal Transduction/drug effects
- Time Factors
- Wortmannin
- rac GTP-Binding Proteins/metabolism
- src-Family Kinases/antagonists & inhibitors
- src-Family Kinases/metabolism
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Affiliation(s)
- Puvi N Seshiah
- Division of Cardiology, Emory University, Atlanta, Ga 30322, USA
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518
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Abassi YA, Vuori K. Tyrosine 221 in Crk regulates adhesion-dependent membrane localization of Crk and Rac and activation of Rac signaling. EMBO J 2002; 21:4571-82. [PMID: 12198159 PMCID: PMC126186 DOI: 10.1093/emboj/cdf446] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The adaptor protein CrkII plays a central role in signal transduction cascades downstream of a number of different stimuli. We and others have previously shown that CrkII mediates attachment-induced JNK activation, membrane ruffling and cell motility in a Rac-dependent manner. We report here that cell attachment leads to tyrosine phosphorylation of CrkII on Y221, and that CrkII-Y221F mutant demonstrates enhanced association with the Crk-binding partners C3G and paxillin. Despite this enhanced signaling complex formation, CrkII-Y221F fails to induce JNK and PAK activation, membrane ruffling and cell migration, suggesting that it is defective in activating Rac signaling. Wild-type CrkII has no effect on adhesion-induced GTP loading of Rac, but its expression results in enhanced membrane localization of Rac, which is known to be required for Rac signaling. In contrast, CrkII-Y221F is deficient in enhancing membrane localization of Rac. Mutations in Rac and CrkII-Y221F that force membrane targeting of these molecules restore Rac signaling in adherent cells. Together, these results indicate that the Y221 site in CrkII regulates Rac membrane translocation upon cell adhesion, which is necessary for activation of downstream Rac signaling pathways.
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Affiliation(s)
| | - Kristiina Vuori
- Cancer Research Center, The Burnham Institute, 10901 N. Torrey Pines Road, La Jolla, CA 92037, USA
Corresponding author e-mail:
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519
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Verma A, Ihler GM. Activation of Rac, Cdc42 and other downstream signalling molecules by Bartonella bacilliformis during entry into human endothelial cells. Cell Microbiol 2002; 4:557-69. [PMID: 12390349 DOI: 10.1046/j.1462-5822.2002.00217.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Bartonella bacilliformis is an intracellular bacterial pathogen of human endothelial cells. In vitro incubation of B. bacilliformis with human endothelial cells leads to the formation of filamentous actin extensions (filopodia) within 30 min, followed by formation of membrane rufflings or lamellipodia within 1 h of incubation. By immunofluorescence, F-actin phalloidin staining and anti-Rac antibodies were shown to co-localize in the membrane rufflings, indicating the recruitment of activated Rac at lamellipodia. Preincubation of endothelial cells with the Clostridial toxin, TcdB-10463, which inactivates the Rho-family GTPases, Rho, Rac and Cdc42, inhibited the entry of B. bacilliformis by 50-90%. Preincubation of endothelial cells with the Clostridial toxin, TcsL-1522, which specifically inactivates Rac and, to a lesser extent, Cdc42, but not Rho, inhibited entry by 30-40%. A 3.4-5.0-fold increase in activated (GTP-bound) -intracellular Rac and Cdc42 was observed in affinity precipitation assays. Increased kinase activity of p21-activated kinase (PAK), a specific downstream effector of activated Rac/Cdc42 was also observed during the time course of infection. Activation of SAPK/JNK-1 and 2, and p38 MAPKs in signalling pathways, was also detected during infection with Bartonella, as was increased binding activity of AP-1 transcription factor.
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Affiliation(s)
- Anita Verma
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of Health Sciences, Bethesda, MD 20814-4799, USA
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520
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Rabiet MJ, Tardif M, Braun L, Boulay F. Inhibitory effects of a dominant-interfering form of the Rho-GTPase Cdc42 in the chemoattractant-elicited signaling pathways leading to NADPH oxidase activation in differentiated HL-60 cells. Blood 2002; 100:1835-44. [PMID: 12176907 DOI: 10.1182/blood-2001-12-0193] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A tetracycline-controlled expression system was adapted to the human promyelocytic HL-60 cell line by placement of the transactivator (tTA-off) sequence under the control of the human EF-1alpha promoter region. Constitutively active and dominant-inhibitory forms of Cdc42 (Cdc42V12 and Cdc42N17, respectively) were conditionally expressed in this system. The expression of Cdc42V12 had no marked effect on chemoattractant-mediated superoxide production, corroborating previous results indicating that the guanosine 5'-triphosphate (GTP)-bound form of Cdc42 is ineffective in directly activating nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in a cell-free system. However, the N17 mutant potently inhibited chemoattractant-induced superoxide production. The expression of Cdc42N17 interfered with the GTP-loading of Rac and Ras and with the activation of the MAP-kinase pathway. A drastic reduction of chemoattractant-induced inositol-1,4,5-trisphosphate formation and calcium mobilization was observed, corroborating previous in vitro study results identifying PLCbeta2 as a Rac/Cdc42 effector. Cdc42N17 was also found to inhibit the translocation of Ras-GRF2, a guanine nucleotide exchange factor for Ras and Rac but not for Cdc42. Thus, the dominant-inhibitory mutant Cdc42N17 was found to interfere at multiple levels in the signaling pathways. The pleiotropic inhibitory effects of Cdc42N17 illustrate the potential pitfalls of using dominant-inhibitory proteins to study the function of Ras-family GTPases. In this regard, a number of conclusions drawn from the use of dominant-inhibitory mutants in myeloid cells might have to be reconsidered.
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Affiliation(s)
- Marie-Josèphe Rabiet
- Département Réponse et Dynamique Cellulaires/Biochimie et Biophysique des Systèmes Intégrés, Grenoble, France.
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521
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Di Ciano C, Nie Z, Szászi K, Lewis A, Uruno T, Zhan X, Rotstein OD, Mak A, Kapus A. Osmotic stress-induced remodeling of the cortical cytoskeleton. Am J Physiol Cell Physiol 2002; 283:C850-65. [PMID: 12176742 DOI: 10.1152/ajpcell.00018.2002] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Osmotic stress is known to affect the cytoskeleton; however, this adaptive response has remained poorly characterized, and the underlying signaling pathways are unexplored. Here we show that hypertonicity induces submembranous de novo F-actin assembly concomitant with the peripheral translocation and colocalization of cortactin and the actin-related protein 2/3 (Arp2/3) complex, which are key components of the actin nucleation machinery. Additionally, hyperosmolarity promotes the association of cortactin with Arp2/3 as revealed by coimmunoprecipitation. Using various truncation or phosphorylation-incompetent mutants, we show that cortactin translocation requires the Arp2/3- or the F-actin binding domain, but the process is independent of the shrinkage-induced tyrosine phosphorylation of cortactin. Looking for an alternative signaling mechanism, we found that hypertonicity stimulates Rac and Cdc42. This appears to be a key event in the osmotically triggered cytoskeletal reorganization, because 1) constitutively active small GTPases translocate cortactin, 2) Rac and cortactin colocalize at the periphery of hypertonically challenged cells, and 3) dominant-negative Rac and Cdc42 inhibit the hypertonicity-provoked cortactin and Arp3 translocation. The Rho family-dependent cytoskeleton remodeling may be an important osmoprotective response that reinforces the cell cortex.
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Affiliation(s)
- Caterina Di Ciano
- Department of Surgery, Toronto General Hospital, University Health Network and University of Toronto, Ontario, Canada
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522
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Buchan AMJ, Lin CY, Choi J, Barber DL. Somatostatin, acting at receptor subtype 1, inhibits Rho activity, the assembly of actin stress fibers, and cell migration. J Biol Chem 2002; 277:28431-8. [PMID: 12045195 DOI: 10.1074/jbc.m201261200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Somatostatin regulates multiple biological functions by acting through a family of five G protein-coupled receptors, somatostatin receptors (SSTRs) 1-5. Although all five receptor subtypes inhibit adenylate cyclase activity and decrease intracellular cAMP levels, specific receptor subtypes also couple to additional signaling pathways. In CCL39 fibroblasts expressing either human SSTR1 or SSTR2, we demonstrate that activation of SSTR1 (but not SSTR2) attenuated both thrombin- and integrin-stimulated Rho-GTP complex formation. The reduction in Rho-GTP formation in the presence of somatostatin was associated with decreased translocation of Rho and LIM kinase to the plasma membrane and fewer focal contacts. Activation of Rho resulted in the formation of intracellular actin stress fibers and cell migration. In CCL39-R1 cells, somatostatin treatment prevented actin stress fiber assembly and attenuated thrombin-stimulated cell migration through Transwell membranes to basal levels. To show that native SSTR1 shares the ability to inhibit Rho activation, we demonstrated that somatostatin treatment of human umbilical vein endothelial cells attenuated thrombin-stimulated Rho-GTP accumulation. These data show for the first time that a G protein-coupled receptor, SSTR1, inhibits the activation of Rho, the assembly of focal adhesions and actin stress fibers, and cell migration.
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Affiliation(s)
- Alison M J Buchan
- Department of Physiology, University of British Columbia, Vancouver V6T 1Z3, Canada.
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523
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Abstract
Negative guidance molecules are important for guiding the growth of axons and ultimately for determining the wiring pattern in the developing nervous system. In tissue culture, growth cones at the tips of growing axons collapse in response to negative guidance molecules, such as ephrin-A2 and semaphorin 3A. The small GTPase Rac1 is involved in growth cone collapse, but the nature of its role is not clear. Rac1 activity assays showed that Rac1 is transiently inactivated after treatment with ephrin-A2. Ephrin-induced growth cone collapse, however, correlated with resumption of Rac1 activity. We demonstrate that Rac1 is required for endocytosis of the growth cone plasma membrane and reorganization of F-actin but not for the depolymerization of F-actin during growth cone collapse in response to ephrin-A2 and semaphorin 3A. Rac1, however, does not regulate constitutive endocytosis in growth cones. These findings show that in response to negative guidance molecules, the function of Rac1 changes from promoting actin polymerization associated with axon growth to driving endocytosis of the plasma membrane, resulting in growth cone collapse. Furthermore, Rac1 antisense injected into the embryonic chick eye in vivo caused the retinotectal projection to develop without normal topography in a manner consistent with Rac1 having an obligatory role in mediating ephrin signaling.
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524
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Papakonstanti EA, Stournaras C. Association of PI-3 kinase with PAK1 leads to actin phosphorylation and cytoskeletal reorganization. Mol Biol Cell 2002; 13:2946-62. [PMID: 12181358 PMCID: PMC117954 DOI: 10.1091/mbc.02-01-0599] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The family of p21-activated kinases (PAKs) have been implicated in the rearrangement of actin cytoskeleton by acting downstream of the small GTPases Rac and Cdc42. Here we report that even though Cdc42/Rac1 or Akt are not activated, phosphatidylinositol-3 (PI-3) kinase activation induces PAK1 kinase activity. Indeed, we demonstrate that PI-3 kinase associates with the N-terminal regulatory domain of PAK1 (amino acids 67-150) leading to PAK1 activation. The association of the PI-3 kinase with the Cdc42/Rac1 binding-deficient PAK1(H83,86L) confirms that the small GTPases are not involved in the PI-3 kinase-PAK1 interaction. Furthermore, PAK1 was activated in cells expressing the dominant-negative forms of Cdc42 or Rac1. Additionally, we show that PAK1 phosphorylates actin, resulting in the dissolution of stress fibers and redistribution of microfilaments. The phosphorylation of actin was inhibited by the kinase-dead PAK1(K299R) or the PAK1 autoinhibitory domain (PAK1(83-149)), indicating that PAK1 was responsible for actin phosphorylation. We conclude that the association of PI-3 kinase with PAK1 regulates PAK1 kinase activity through a Cdc42/Rac1-independent mechanism leading to actin phosphorylation and cytoskeletal reorganization.
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525
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Chockalingam PS, Cholera R, Oak SA, Zheng Y, Jarrett HW, Thomason DB. Dystrophin-glycoprotein complex and Ras and Rho GTPase signaling are altered in muscle atrophy. Am J Physiol Cell Physiol 2002; 283:C500-11. [PMID: 12107060 DOI: 10.1152/ajpcell.00529.2001] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The dystrophin-glycoprotein complex (DGC) is a sarcolemmal complex whose defects cause muscular dystrophies. The normal function of this complex is not clear. We have proposed that this is a signal transduction complex, signaling normal interactions with matrix laminin, and that the response is normal growth and homeostasis. If so, the complex and its signaling should be altered in other physiological states such as atrophy. The amount of some of the DGC proteins, including dystrophin, beta-dystroglycan, and alpha-sarcoglycan, is reduced significantly in rat skeletal muscle atrophy induced by tenotomy. Furthermore, H-Ras, RhoA, and Cdc42 decrease in expression levels and activities in muscle atrophy. When the small GTPases were assayed after laminin or beta-dystroglycan depletion, H-Ras, Rac1, and Cdc42 activities were reduced, suggesting a physical linkage between the DGC and the GTPases. Dominant-negative Cdc42, introduced with a retroviral vector, resulted in fibers that appeared atrophic. These data support a putative role for the DGC in transduction of mechanical signals in muscle.
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Affiliation(s)
- Priya Sethu Chockalingam
- Department of Molecular Sciences, University of Tennessee Health Sciences Center, Memphis, Tennessee 38163, USA
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526
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Bakin AV, Rinehart C, Tomlinson AK, Arteaga CL. p38 mitogen-activated protein kinase is required for TGFβ-mediated fibroblastic transdifferentiation and cell migration. J Cell Sci 2002; 115:3193-206. [PMID: 12118074 DOI: 10.1242/jcs.115.15.3193] [Citation(s) in RCA: 325] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Transforming growth factor β (TGFβ) contributes to tumor progression by inducing an epithelial to mesenchymal transdifferentiation(EMT) and cell migration. We found that TGFβ-induced EMT was blocked by inhibiting activation of p38 mitogen-activated protein kinase (MAPK) with H-7,a protein kinase C inhibitor, and with SB202190, a direct inhibitor of p38MAPK. Inhibition of the p38MAPK pathway affected TGFβ-mediated phosphorylation of ATF2, but did not inhibit phosphorylation of Smad2. SB202190 impaired TGFβ-mediated changes in cell shape and reorganization of the actin cytoskeleton. Forced expression of dominant-negative (DN) MAPK kinase 3 (MKK3) inhibited TGFβ-mediated activation of p38MAPK and EMT. Expression of DN-p38α impaired TGFβ-induced EMT. Inhibition of p38MAPK blocked TGFβ-induced migration of non-tumor and tumor mammary epithelial cells. TGFβ induced activation of the p38MAPK pathway within 15 minutes. Expression of TGFβ type II (TβRII) and type I(TβRI/Alk5) kinase-inactive receptors blocked EMT and activation of p38MAPK, whereas expression of constitutively active Alk5-T204D resulted in EMT and phosphorylation of MKK3/6 and p38MAPK. Finally, dominant-negative Rac1N17 blocked TGFβ-induced activation of the p38MAPK pathway and EMT,suggesting that Rac1 mediates activation of the p38MAPK pathway. These studies suggest that the p38MAPK pathway is required for TGFβ-mediated EMT and cell migration.
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Affiliation(s)
- Andrei V Bakin
- Department of Medicine, Vanderbilt University School of Medicine, 777 Preston Research Building, Nashville, TN 37232, USA
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527
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McLeod SJ, Li AHY, Lee RL, Burgess AE, Gold MR. The Rap GTPases regulate B cell migration toward the chemokine stromal cell-derived factor-1 (CXCL12): potential role for Rap2 in promoting B cell migration. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 169:1365-71. [PMID: 12133960 DOI: 10.4049/jimmunol.169.3.1365] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Stromal cell-derived factor-1 (SDF-1) is a potent chemoattractant for B cells and B cell progenitors. Although the binding of SDF-1 to its receptor, CXCR4, activates multiple signaling pathways, the mechanism by which SDF-1 regulates cell migration is not completely understood. In this report we show that activation of the Rap GTPases is important for B cells to migrate toward SDF-1. We found that treating B cells with SDF-1 resulted in the rapid activation of both Rap1 and Rap2. Moreover, blocking the activation of Rap1 and Rap2 via the expression of a Rap-specific GTPase-activating protein significantly reduced the ability of B cells to migrate toward SDF-1. Conversely, expressing a constitutively active form of Rap2 increased SDF-1-induced B cell migration. Thus, the Rap GTPases control cellular processes that are important for B cells to migrate toward SDF-1.
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Affiliation(s)
- Sarah J McLeod
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
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528
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Werner E, Werb Z. Integrins engage mitochondrial function for signal transduction by a mechanism dependent on Rho GTPases. J Cell Biol 2002; 158:357-68. [PMID: 12119354 PMCID: PMC2173123 DOI: 10.1083/jcb.200111028] [Citation(s) in RCA: 207] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
We show here the transient activation of the small GTPase Rac, followed by a rise in reactive oxygen species (ROS), as necessary early steps in a signal transduction cascade that lead to NFkappaB activation and collagenase-1 (CL-1)/matrix metalloproteinase-1 production after integrin-mediated cell shape changes. We show evidence indicating that this constitutes a new mechanism for ROS production mediated by small GTPases. Activated RhoA also induced ROS production and up-regulated CL-1 expression. A Rac mutant (L37) that prevents reorganization of the actin cytoskeleton prevented integrin-induced CL-1 expression, whereas mutations that abrogate Rac binding to the neutrophil NADPH membrane oxidase in vitro (H26 and N130) did not. Instead, ROS were produced by integrin-induced changes in mitochondrial function, which were inhibited by Bcl-2 and involved transient membrane potential loss. The cells showing this transient decrease in mitochondrial membrane potential were already committed to CL-1 expression. These results unveil a new molecular mechanism of signal transduction triggered by integrin engagement where a global mitochondrial metabolic response leads to gene expression rather than apoptosis.
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Affiliation(s)
- Erica Werner
- Department of Anatomy, University of California, San Francisco, CA 94143.
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529
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Swiercz JM, Kuner R, Behrens J, Offermanns S. Plexin-B1 directly interacts with PDZ-RhoGEF/LARG to regulate RhoA and growth cone morphology. Neuron 2002; 35:51-63. [PMID: 12123608 DOI: 10.1016/s0896-6273(02)00750-x] [Citation(s) in RCA: 289] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Plexins are widely expressed transmembrane proteins that, in the nervous system, mediate repulsive signals of semaphorins. However, the molecular nature of plexin-mediated signal transduction remains poorly understood. Here, we demonstrate that plexin-B family members associate through their C termini with the Rho guanine nucleotide exchange factors PDZ-RhoGEF and LARG. Activation of plexin-B1 by semaphorin 4D regulates PDZ-RhoGEF/LARG activity leading to RhoA activation. In addition, a dominant-negative form of PDZ-RhoGEF blocks semaphorin 4D-induced growth cone collapse in primary hippocampal neurons. Our study indicates that the interaction of mammalian plexin-B family members with the multidomain proteins PDZ-RhoGEF and LARG represents an essential molecular link between plexin-B and localized, Rho-mediated downstream signaling events which underly various plexin-mediated cellular phenomena including axonal growth cone collapse.
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Affiliation(s)
- Jakub M Swiercz
- Institute of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, Germany
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530
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Paris S, Za L, Sporchia B, de Curtis I. Analysis of the subcellular distribution of avian p95-APP2, an ARF-GAP orthologous to mammalian paxillin kinase linker. Int J Biochem Cell Biol 2002; 34:826-37. [PMID: 11950598 DOI: 10.1016/s1357-2725(02)00008-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We describe here the identification and characterization of avian p95-APP2, a multi-domain protein of a recently identified family of ADP-ribosylation factor (ARF)-GTPase-activating proteins (GAPs) including mammalian G protein-coupled receptor kinases (GRK)-interactor 1 (GIT1), paxillin kinase linker (PKL), and GIT2, as well as avian p95-APP1. The p95-APP2 is eluted from Rac-GTP-gamma-S, but not from Rac-GDP-beta-S columns. As other members of the family, p95-APP2 has binding regions for the focal adhesion protein paxillin, and for the Rac exchanging factor PIX. Sequence comparison indicates that p95-APP2 is the avian orthologue of mammalian PKL. Expression studies showed a largely diffuse distribution of the full length p95-APP2, without evident effects on cell morphology. We observed a dramatic difference between the localization of the amino-terminal portion of the protein, including the ARF-GAP domain and the three ankyrin repeats, and the carboxy-terminal portion including the paxillin-binding site. Moreover, the expression of truncated carboxy-terminal polypeptides including both the PIX- and paxillin-binding regions leads to a marked localization of the protein together with paxillin at large vesicles. Comparison of the expression of corresponding ARF-GAP-deficient constructs from p95-APP2 and p95-APP1 shows their distribution at distinct endocytic compartments. Altogether, these data support a role of distinct members of this family of ARF-GAPs in the regulation of different steps of membrane traffic during cell motility, and suggest that p95-APP2 may shuttle between an intracellular compartment and the cell periphery, although, further work will be needed to address this point.
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Affiliation(s)
- Simona Paris
- Cell Adhesion Unit, DIBIT, S. Raffaele Scientific Institute, Via Olgettina 58, 20132 Milan, Italy
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531
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Weiner OD, Neilsen PO, Prestwich GD, Kirschner MW, Cantley LC, Bourne HR. A PtdInsP(3)- and Rho GTPase-mediated positive feedback loop regulates neutrophil polarity. Nat Cell Biol 2002; 4:509-13. [PMID: 12080346 PMCID: PMC2823287 DOI: 10.1038/ncb811] [Citation(s) in RCA: 433] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
When presented with a gradient of chemoattractant, many eukaryotic cells respond with polarized accumulation of the phospholipid PtdIns(3,4,5)P(3). This lipid asymmetry is one of the earliest readouts of polarity in neutrophils, Dictyostelium discoideum and fibroblasts. However, the mechanisms that regulate PtdInsP(3) polarization are not well understood. Using a cationic lipid shuttling system, we have delivered exogenous PtdInsP(3) to neutrophils. Exogenous PtdInsP(3) elicits accumulation of endogenous PtdInsP(3) in a positive feedback loop that requires endogenous phosphatidylinositol-3-OH kinases (PI(3)Ks) and Rho family GTPases. This feedback loop is important for establishing PtdInsP(3) polarity in response to both chemoattractant and to exogenous PtdInsP(3); it may function through a self-organizing pattern formation system. Emergent properties of positive and negative regulatory links between PtdInsP(3) and Rho family GTPases may constitute a broadly conserved module for the establishment of cell polarity during eukaryotic chemotaxis.
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Affiliation(s)
- Orion D Weiner
- Department of Cell Biology, Harvard Medical School and Beth Israel Deaconess Medical Center, 240 Longwood Ave/ C-1, Boston, MA 02115, USA
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532
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Abstract
P-Rex1, a novel Rac activator, has been identified in the first biochemical purification of a guanine nucleotide exchange factor for GTPases of the Rho family. P-Rex1 is synergistically activated by PIP(3) and Gbetagamma and may act as a coincidence detector for these signaling molecules.
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Affiliation(s)
- Orion D Weiner
- Department of Cell Biology, Harvard Medical School, 240 Longwood Ave/ C-1, 502, Boston, Massachusetts 02115, USA.
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533
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Brandt D, Gimona M, Hillmann M, Haller H, Mischak H. Protein kinase C induces actin reorganization via a Src- and Rho-dependent pathway. J Biol Chem 2002; 277:20903-10. [PMID: 11925438 DOI: 10.1074/jbc.m200946200] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We have investigated the mechanism of PKC-induced actin reorganization in A7r5 vascular smooth muscle cells. PKC activation by 12-O-tetradecanoylphorbol-13-acetate induces the disassembly of actin stress fibers concomitant with the appearance of membrane ruffles. PKC also induces rapid tyrosine phosphorylation in these cells. As we could show, utilizing the Src-specific inhibitor PP2 and a kinase-deficient c-Src mutant, actin reorganization is dependent on PKC-induced Src activation. Subsequently, the activity of the small G-protein RhoA is decreased, whereas Rac and Cdc42 activities remain unchanged. Disassembly of actin stress fibers could also be observed using the Rho kinase-specific inhibitor Y-27632, indicating that the decrease in RhoA activity on its own is responsible for actin reorganization. In addition, we show that tyrosine phosphorylation of p190RhoGAP is increased upon 12-O-tetradecanoylphorbol-13-acetate stimulation, directly linking Src activation to a decrease in RhoA activity. Our data provide substantial evidence for a model elucidating the molecular mechanisms of PKC-induced actin rearrangements.
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Affiliation(s)
- Dominique Brandt
- Medizinische Hochschule Hannover, Department of Nephrology, 30625 Hannover, Germany
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534
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Wang D, Sai J, Carter G, Sachpatzidis A, Lolis E, Richmond A. PAK1 kinase is required for CXCL1-induced chemotaxis. Biochemistry 2002; 41:7100-7. [PMID: 12033944 PMCID: PMC2668253 DOI: 10.1021/bi025902m] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The CXC subfamily of chemokines plays an important role in diverse processes, including inflammation, wound healing, growth regulation, angiogenesis, and tumorigenesis. The CXC chemokine CXCL1, or MGSA/GROalpha, is traditionally considered to be responsible for attracting leukocytes into sites of inflammation. To better understand the molecular mechanisms by which CXCL1 induces CXCR2-mediated chemotaxis, the signal transduction components involved in CXCL1-induced chemotaxis were examined. It is shown here that CXCL1 induces cdc42 and PAK1 activation in CXCR2-expressing HEK293 cells. Activation of the cdc42-PAK1 cascade is required for CXCL1-induced chemotaxis but not for CXCL1-induced intracellular Ca2+ mobilization. Moreover, CXCL1 activation of PAK1 is independent of ERK1/2 activation, a conclusion based on the observations that the inhibition of MEK-ERK activation by expression of dominant negative ERK or by the MEK inhibitor, PD98059, has no effect on CXCL1-induced PAK1 activation or CXCL1-induced chemotaxis.
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Affiliation(s)
| | | | | | | | | | - Ann Richmond
- Author to whom correspondence should be addressed [telephone (615) 343-7777; fax (615) 343-4539; e-mail ]
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535
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Kanazawa H, Ohsawa K, Sasaki Y, Kohsaka S, Imai Y. Macrophage/microglia-specific protein Iba1 enhances membrane ruffling and Rac activation via phospholipase C-gamma -dependent pathway. J Biol Chem 2002; 277:20026-32. [PMID: 11916959 DOI: 10.1074/jbc.m109218200] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Iba1 is a macrophage/microglia-specific calcium-binding protein that is involved in RacGTPase-dependent membrane ruffling and phagocytosis. In this study, we introduced Iba1 into Swiss 3T3 fibroblasts and demonstrated the enhancement of platelet-derived growth factor (PDGF)-induced membrane ruffling and chemotaxis. Wortmannin treatment did not completely suppressed this enhanced membrane ruffling in Iba1-expressing cells, whereas it did in Iba1-nonexpressing cells, suggesting that the enhancement is mediated through a phosphatidylinositol 3-kinase (PI3K)-independent signaling pathway. Porcine aorta endothelial cells transfected with expression constructs of Iba1 and PDGF receptor add-back mutants were used to analyze the signaling pathway responsible for the Iba1-induced enhancement of membrane ruffling. In the absence of Iba1 expression, PDGF did not induced membrane ruffling in cells expressing the Tyr-1021 receptor mutant, which is capable of activating phospholipase C-gamma (PLC-gamma) but not PI3K. In contrast, in the presence of Iba1 expression, membrane ruffling was formed in cells expressing the Tyr-1021 mutant. In addition, Rac was shown to be activated during membrane ruffling in cells expressing Iba1 and the Tyr-1021 mutant. Furthermore, dominant negative forms of PLC-gamma completely suppressed PDGF-induced Iba1-dependent membrane ruffling and Rac activation. These results indicate the existence of a novel signaling pathway where PLC-gamma activates Rac in a manner dependent on Iba1.
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Affiliation(s)
- Hiroko Kanazawa
- Department of Neurochemistry, National Institute of Neuroscience, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan
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536
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Fong AM, Premont RT, Richardson RM, Yu YRA, Lefkowitz RJ, Patel DD. Defective lymphocyte chemotaxis in beta-arrestin2- and GRK6-deficient mice. Proc Natl Acad Sci U S A 2002; 99:7478-83. [PMID: 12032308 PMCID: PMC124256 DOI: 10.1073/pnas.112198299] [Citation(s) in RCA: 250] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Lymphocyte chemotaxis is a complex process by which cells move within tissues and across barriers such as vascular endothelium and is usually stimulated by chemokines such as stromal cell-derived factor-1 (CXCL12) acting via G protein-coupled receptors. Because members of this receptor family are regulated ("desensitized") by G protein-coupled receptor kinase (GRK)-mediated receptor phosphorylation and beta-arrestin binding, we examined signaling and chemotactic responses in splenocytes derived from knockout mice deficient in various beta-arrestins and GRKs, with the expectation that these responses might be enhanced. Knockouts of beta-arrestin2, GRK5, and GRK6 were examined because all three proteins are expressed at high levels in purified mouse CD3+ T and B220+ B splenocytes. CXCL12 stimulation of membrane GTPase activity was unaffected in splenocytes derived from GRK5-deficient mice but was increased in splenocytes from the beta-arrestin2- and GRK6-deficient animals. Surprisingly, however, both T and B cells from beta-arrestin2-deficient animals and T cells from GRK6-deficient animals were strikingly impaired in their ability to respond to CXCL12 both in transwell migration assays and in transendothelial migration assays. Chemotactic responses of lymphocytes from GRK5-deficient mice were unaffected. Thus, these results indicate that beta-arrestin2 and GRK6 actually play positive regulatory roles in mediating the chemotactic responses of T and B lymphocytes to CXCL12.
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Affiliation(s)
- Alan M Fong
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA
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537
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Yamamori T, Inanami O, Sumimoto H, Akasaki T, Nagahata H, Kuwabara M. Relationship between p38 mitogen-activated protein kinase and small GTPase Rac for the activation of NADPH oxidase in bovine neutrophils. Biochem Biophys Res Commun 2002; 293:1571-8. [PMID: 12054696 DOI: 10.1016/s0006-291x(02)00418-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Superoxide production by NADPH oxidase is essential for bactericidal properties of neutrophils. However, molecular mechanisms underlying the activation of this enzyme remain largely unknown. Here, using bovine neutrophils we examined the role of p38 mitogen-activated protein kinase (p38 MAPK) in the signaling pathways of the NADPH oxidase activation. Superoxide production was induced by stimulation with serum-opsonized zymosan (OZ) and attenuated by p38 MAPK inhibitor, SB203580. OZ stimulation induced the translocation of p47(phox) and Rac to the plasma membrane and SB203580 completely blocked the translocation of Rac, but only partially blocked that of p47(phox). Furthermore, SB203580 abolished the OZ-elicited activation of Rac, which was assessed by detecting the GTP-bound form of this protein. Phosphatidylinositol 3-kinase (PI3K) inhibitors, wortmannin and LY294002, blocked not only p38 MAPK activation but also Rac activation. However, SB203580 showed no effect on the PI3K activity. These results suggested that PI3K/p38 MAPK/Rac pathway was present in the activation of NADPH oxidase in bovine neutrophils.
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Affiliation(s)
- Tohru Yamamori
- Laboratory of Radiation Biology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
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538
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Price MO, Atkinson SJ, Knaus UG, Dinauer MC. Rac activation induces NADPH oxidase activity in transgenic COSphox cells, and the level of superoxide production is exchange factor-dependent. J Biol Chem 2002; 277:19220-8. [PMID: 11896053 DOI: 10.1074/jbc.m200061200] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transient expression of constitutively active Rac1 derivatives, (G12V) or (Q61L), was sufficient to induce phagocyte NADPH oxidase activity in a COS-7 cell model in which human cDNAs for essential oxidase components, gp91(phox), p22(phox), p47(phox), and p67(phox), were expressed as stable transgenes. Expression of constitutively active Rac1 in "COS(phox)" cells induced translocation of p47(phox) and p67(phox) to the membrane. Furthermore, translocation of p47(phox) was induced in the absence of p67(phox) expression, even though Rac does not directly bind p47(phox). Rac effector domain point substitutions (A27K, G30S, D38A, Y40C), which can selectively eliminate interaction with different effector proteins, impaired Rac1V12-induced superoxide production. Activation of endogenous Rac1 by expression of constitutively active Rac-guanine nucleotide exchange factor (GEF) derivatives was sufficient to induce high level NADPH oxidase activity in COS(phox) cells. The constitutively active form of the hematopoietic-specific GEF, Vav1, was the most effective at activating superoxide production, despite detection of higher levels of Rac1-GTP upon expression of constitutively active Vav2 or Tiam1 derivatives. These data suggest that Rac can play a dual role in NADPH oxidase activation, both by directly participating in the oxidase complex and by activating signaling events leading to oxidase assembly, and that Vav1 may be the physiologically relevant GEF responsible for activating this Rac-regulated complex.
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Affiliation(s)
- Marianne O Price
- Herman B Wells Center for Pediatric Research, Department of Pediatrics (Hematology/Oncology), James Whitcomb Riley Hospital for Children, Indiana University Medical Center, Indianapolis, Indiana 46202, USA
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539
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Fukuda T, Kiuchi K, Takahashi M. Novel mechanism of regulation of Rac activity and lamellipodia formation by RET tyrosine kinase. J Biol Chem 2002; 277:19114-21. [PMID: 11886862 DOI: 10.1074/jbc.m200643200] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rac activation in neuronal cells plays an important role in lamellipodia formation that is a critical event for neuritogenesis. It is well known that the Rac activity is regulated via activation of phosphatidylinositol 3-kinase (PI3K) by a variety of receptor tyrosine kinases. Here we show that increased serine phosphorylation on RET receptor tyrosine kinase following cAMP elevation promotes lamellipodia formation of neuronal cells induced by glial cell line-derived neurotrophic factor (GDNF). We identified serine 696 in RET as a putative phosphorylation site by protein kinase A and found that mutation of this serine almost completely inhibited lamellipodia formation by GDNF without affecting activation of the PI3K/AKT signaling pathway. Mutation of tyrosine 1062 in RET, whose phosphorylation is crucial for activation of PI3K, also inhibited lamellipodia formation by GDNF. Inhibition of lamellipodia formation by mutation of either serine 696 or tyrosine 1062 was associated with decrease of the Rac1-guanine nucleotide exchange factor (GEF) activity, suggesting that this activity is regulated by two different signaling pathways via serine 696 and tyrosine 1062 in RET. Moreover, in the presence of serine 696 mutation, lamellipodia formation was rescued by replacing tyrosine 687 with phenylalanine. These findings propose a novel mechanism that receptor tyrosine kinase modulates actin dynamics in neuronal cells via its cAMP-dependent phosphorylation.
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Affiliation(s)
- Toshifumi Fukuda
- Department of Pathology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Japan
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540
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Nisimoto Y, Ogawa H. Interaction between p21-activated protein kinase and Rac during differentiation of HL-60 human promyelocytic leukemia cell induced by all-trans-retinoic acid. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:2622-9. [PMID: 12027902 DOI: 10.1046/j.1432-1033.2002.02939.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Undifferentiated human promyelocytic leukemia HL-60 cells show little or no superoxide production, but generate a very low O(2)(-) concentration upon incubation with all-trans-retinoic acid (ATRA). Its production reaches a maximum within 20 h, and thereafter is maintained at an almost constant level. The differentiated cells show phorbol 12-myristate 13-acetate (PMA)-stimulated NADPH oxidase activity consistent with the amount of gp91phox (phagocytic oxidase) expressed in the plasma membrane. Three isoforms of p21-activated serine/threonine kinases, PAK68, PAK65 and PAK62, were found in both cytosolic and membrane fractions, and their contents were significantly increased during induced differentiation. The amount of Rac identified in the two fractions was also markedly enhanced by ATRA- induced differentiation. In contrast, neither PAK nor Rac was seen in the plasma membrane of undifferentiated HL-60 or human neutrophil, but they were abundant in the cytoplasmic fraction. Binding of Rac with PAK isoforms was shown in the membrane upon induced differentiation of HL-60 cells. Direct binding of purified Rac1 to PAK68 was quantified using a fluorescent analog of GTP (methylanthraniloyl guanosine-5'-[beta,gamma-imido]triphosphate) bound to Rac as a reporter group. Rac1 bound to PAK68 with a 1 : 1 stoichiometry and with a K(d) value of 6.7 nm.
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Affiliation(s)
- Yukio Nisimoto
- Department of Biochemistry, Aichi Medical University, School of Medicine, Nagakute, Aichi, Japan.
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541
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Chiang SH, Hou JC, Hwang J, Pessin JE, Saltiel AR. Cloning and functional characterization of related TC10 isoforms, a subfamily of Rho proteins involved in insulin-stimulated glucose transport. J Biol Chem 2002; 277:13067-73. [PMID: 11821390 DOI: 10.1074/jbc.m109471200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Insulin stimulates glucose transport via phosphatidylinositol 3-kinase-dependent and -independent pathways. The phosphatidylinositol 3-kinase-independent pathway involves activation of the G protein TC10. A cDNA encoding the mouse homolog of TC10 was cloned, and its gene was mapped at the distal end of chromosome 17. Additionally, a second gene was discovered with approximately 70% sequence identity to TC10. We refer to this gene as TC10beta. Both isoforms of TC10 were activated by insulin upon transfection in 3T3L1 adipocytes. Cotransfection of cells with TC10alpha or beta plus a dominant negative form of the c-cbl-associated protein CAP prevented the activation by insulin, implicating the CAP/Cbl pathway. Interestingly, both forms of TC10 were also localized in lipid raft fractions in transfected adipocytes. However, although overexpression of TC10alpha completely blocked glucose transport, TC10beta only partially inhibited this process. Furthermore, TC10alpha overexpression disrupted adipocyte cortical actin, whereas TC10beta had little if any effect. Thus, there are two isoforms of this key signaling intermediate, both of which are activated by insulin, but they may play different roles in initiating downstream effectors that influence glucose transport.
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Affiliation(s)
- Shian-Huey Chiang
- Department of Medicine, Life Sciences Institute, University of Michigan School of Medicine, Ann Arbor, MI 48109-0650, USA
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542
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Affiliation(s)
- Kendall D Carey
- Vollum Institute L-474, Department of Cell and Developmental Biology, Oregon Health and Sciences University, Portland, Oregon 97201, USA
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543
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544
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Bassermann F, Jahn T, Miething C, Seipel P, Bai RY, Coutinho S, Tybulewicz VL, Peschel C, Duyster J. Association of Bcr-Abl with the proto-oncogene Vav is implicated in activation of the Rac-1 pathway. J Biol Chem 2002; 277:12437-45. [PMID: 11790798 DOI: 10.1074/jbc.m112397200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vav is a guanine nucleotide exchange factor for the Rho/Rac family predominantly expressed in hematopoietic cells and implicated in cell proliferation and cytoskeletal organization. The oncogenic tyrosine kinase Bcr-Abl has been shown to activate Rac-1, which is important for Bcr-Abl induced leukemogenesis. Previous studies by Matsuguchi et al. (Matsuguchi, T., Inhorn, R. C., Carlesso, N., Xu, G., Druker, B., and Griffin, J. D. (1995) EMBO J. 14, 257-265) describe enhanced phosphorylation of Vav in Bcr-Abl-expressing Mo7e cells yet fail to demonstrate association of the two proteins. Here, we report the identification of a direct complex between Vav and Bcr-Abl in yeast, in vitro and in vivo. Furthermore, we show tyrosine phosphorylation of Vav by Bcr-Abl. Mutational analysis revealed that the SH2 domain and the C-terminal SH3 domain as well as a tetraproline motif directly adjacent to the N-terminal SH3 domain of Vav are important for establishing this phosphotyrosine dependent interaction. Activation of Rac-1 by Bcr-Abl was abrogated by co-expression of the Vav C terminus encoding the SH3-SH2-SH3 domains as a dominant negative construct. Bcr-Abl transduced primary bone marrow from Vav knock-out mice showed reduced proliferation in a culture cell transformation assay compared with wild-type bone marrow. These results suggest, that Bcr-Abl utilizes Vav as a guanine nucleotide exchange factor to activate Rac-1 in a process that involves a folding mechanism of the Vav C terminus. Given the importance of Rac-1 activation for Bcr-Abl-mediated leukemogenesis, this mechanism may be crucial for the molecular pathogenesis of chronic myeloid leukemia and of importance for other signal transduction pathways leading to the activation of Rac-1.
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Affiliation(s)
- Florian Bassermann
- Department of Internal Medicine III, Laboratory of Leukemogenesis, Technical University of Munich, 81675, Germany
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545
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Krendel M, Zenke FT, Bokoch GM. Nucleotide exchange factor GEF-H1 mediates cross-talk between microtubules and the actin cytoskeleton. Nat Cell Biol 2002; 4:294-301. [PMID: 11912491 DOI: 10.1038/ncb773] [Citation(s) in RCA: 501] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Regulation of the actin cytoskeleton by microtubules is mediated by the Rho family GTPases. However, the molecular mechanisms that link microtubule dynamics to Rho GTPases have not, as yet, been identified. Here we show that the Rho guanine nucleotide exchange factor (GEF)-H1 is regulated by an interaction with microtubules. GEF-H1 mutants that are deficient in microtubule binding have higher activity levels than microtubule-bound forms. These mutants also induce Rho-dependent changes in cell morphology and actin organization. Furthermore, drug-induced microtubule depolymerization induces changes in cell morphology and gene expression that are similar to the changes induced by the expression of active forms of GEF-H1. Furthermore, these effects are inhibited by dominant-negative versions of GEF-H1. Thus, GEF-H1 links changes in microtubule integrity to Rho-dependent regulation of the actin cytoskeleton.
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Affiliation(s)
- Mira Krendel
- Department of Immunology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
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546
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Abstract
The Syk tyrosine kinase plays a critical role in the signaling machinery of various receptors of the adaptive immune system. Here we show that Syk is also an essential component of integrin signaling in neutrophils. syk(-/-) neutrophils failed to undergo respiratory burst, degranulation, or spreading in response to proinflammatory stimuli while adherent to immobilized integrin ligands or when stimulated by direct crosslinking of integrins. Signaling from the beta(1), beta(2), or beta(3) integrins was defective in syk(-/-) cells. Syk colocalized with CD18 during cell spreading and initiated downstream signaling events leading to actin polymerization. Surprisingly, these defects in integrin-mediated activation did not impair the integrin-dependent in vitro or in vivo migration of syk(-/-) neutrophils or of cells deficient in Src-family kinases. Thus, integrins use different signaling mechanisms to support migration and adherent activation.
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Affiliation(s)
- Attila Mócsai
- Department of Laboratory Medicine, University of California, San Francisco, CA 94143, USA
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547
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Abstract
Phosphatidylinositol 3-kinase lipid products and the Rho GTPases play a central role in transmitting information from chemotactic receptors to the effectors of cell polarity, and recent advances in the field have allowed us to understand these roles more clearly. Emergent properties of positive and negative regulation of these molecules may account for the establishment of cell polarity during chemotaxis for a wide range of cells from Dictyostelium to fibroblasts to neutrophils.
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Affiliation(s)
- Orion D Weiner
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue/C-1, 502, Boston, MA 02115, USA.
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548
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Kuo MT, Liu Z, Wei Y, Lin-Lee YC, Tatebe S, Mills GB, Unate H. Induction of human MDR1 gene expression by 2-acetylaminofluorene is mediated by effectors of the phosphoinositide 3-kinase pathway that activate NF-kappaB signaling. Oncogene 2002; 21:1945-54. [PMID: 11960367 DOI: 10.1038/sj.onc.1205117] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2001] [Revised: 10/22/2001] [Accepted: 10/30/2001] [Indexed: 01/30/2023]
Abstract
The expression of P-glycoprotein encoded by the multidrug resistance (MDR1) gene is associated with the emergence of the MDR phenotype in cancer cells. Human MDR1 and its rodent homolog mdr1a and mdr1b are frequently overexpressed in liver cancers. However, the underlying mechanisms are largely unknown. The hepatocarcinogen 2-acetylaminofluorene (2-AAF) efficiently activates rat mdr1b expression in cultured cells and in Fisher 344 rats. We recently reported that activation of rat mdr1b in cultured cells by 2-AAF involves a cis-activating element containing a NF-kappaB binding site located -167 to -158 of the rat mdr1b promoter. 2-AAF activates IkappaB kinase (IKK), resulting in degradation of IkappaBbeta and activation of NF-kappaB. In this study, we report that 2-AAF could also activate the human MDR1 gene in human hepatoma and embryonic fibroblast 293 cells. Induction of MDR1 by AAF was mediated by DNA sequence located at -6092 which contains a NF-kappaB binding site. Treating hepatoma cells with 2-AAF activated phosphoinositide 3-kinase (PI3K) and its downstream effectors Rac1, and NAD(P)H oxidase. Transient transfection assays demonstrated that constitutively activated PI3K and Rac1 enhanced the activation of the MDR1 promoter by 2-AAF. Treatment of hepatoma cells with 2-AAF also activated another PI3K downstream effector Akt. Transfection of recombinant encoding a dominant activated Akt also enhanced the activation of MDR1 promoter activation by 2-AAF. These results demonstrated that 2-AAF up-regulates MDR1 expression is mediated by the multiple effectors of the PI3K signaling pathway.
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Affiliation(s)
- Macus Tien Kuo
- Department of Molecular Pathology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, TX 77030, USA.
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549
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Diakonova M, Gunter DR, Herrington J, Carter-Su C. SH2-Bbeta is a Rac-binding protein that regulates cell motility. J Biol Chem 2002; 277:10669-77. [PMID: 11786545 DOI: 10.1074/jbc.m111138200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The Src homology 2 (SH2) domain-containing protein SH2-Bbeta binds to and is a substrate of the growth hormone (GH) and cytokine receptor-associated tyrosine kinase JAK2. SH2-Bbeta also binds, via its SH2 domain, to multiple activated growth factor receptor tyrosine kinases. We have previously implicated SH2-Bbeta in GH and platelet-derived growth factor regulation of the actin cytoskeleton. We extend these findings by establishing a potentiating effect of SH2-Bbeta on GH-dependent cell motility and defining regions of SH2-Bbeta required for this potentiation. Time-lapse video microscopy, phagokinetic, and/or wounding assays demonstrate reduced movement of cells overexpressing SH2-Bbeta lacking an intact SH2 domain because of a point mutation or a C-terminal truncation. An N-terminal proline-rich domain (amino acids 85-106) of SH2-Bbeta is required for inhibition of cellular motility by SH2 domain-deficient mutants. Co-immunoprecipitation experiments indicate that Rac binds to this domain. GH is shown to activate endogenous Rac, and dominant negative mutants of SH2-Bbeta are shown to inhibit membrane ruffling induced by constitutively active Rac. These findings suggest that SH2-Bbeta is an adapter protein that facilitates actin rearrangement and cellular motility by recruiting Rac and potentially Rac-regulating, Rac effector, or other actin-regulating proteins to activated cytokine (e.g. GH) and growth factor receptors.
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Affiliation(s)
- Maria Diakonova
- Department of Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0622, USA
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550
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Welch HCE, Coadwell WJ, Ellson CD, Ferguson GJ, Andrews SR, Erdjument-Bromage H, Tempst P, Hawkins PT, Stephens LR. P-Rex1, a PtdIns(3,4,5)P3- and Gbetagamma-regulated guanine-nucleotide exchange factor for Rac. Cell 2002; 108:809-21. [PMID: 11955434 DOI: 10.1016/s0092-8674(02)00663-3] [Citation(s) in RCA: 419] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Rac, a member of the Rho family of monomeric GTPases, is an integrator of intracellular signaling in a wide range of cellular processes. We have purified a PtdIns(3,4,5)P3-sensitive activator of Rac from neutrophil cytosol. It is an abundant, 185 kDa guanine-nucleotide exchange factor (GEF), which we cloned and named P-Rex1. The recombinant enzyme has Rac-GEF activity that is directly, substantially, and synergistically activated by PtdIns(3,4,5)P3 and Gbetagammas both in vitro and in vivo. P-Rex1 antisense oligonucleotides reduced endogenous P-Rex1 expression and C5a-stimulated reactive oxygen species formation in a neutrophil-like cell line. P-Rex1 appears to be a coincidence detector in PtdIns(3,4,5)P3 and Gbetagamma signaling pathways that is particularly adapted to function downstream of heterotrimeric G proteins in neutrophils.
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