151
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Nayal A, Webb DJ, Brown CM, Schaefer EM, Vicente-Manzanares M, Horwitz AR. Paxillin phosphorylation at Ser273 localizes a GIT1-PIX-PAK complex and regulates adhesion and protrusion dynamics. ACTA ACUST UNITED AC 2006; 173:587-9. [PMID: 16717130 PMCID: PMC2063867 DOI: 10.1083/jcb.200509075] [Citation(s) in RCA: 238] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Continuous adhesion formation and disassembly (adhesion turnover) in the protrusions of migrating cells is regulated by unclear mechanisms. We show that p21-activated kinase (PAK)–induced phosphorylation of serine 273 in paxillin is a critical regulator of this turnover. Paxillin-S273 phosphorylation dramatically increases migration, protrusion, and adhesion turnover by increasing paxillin–GIT1 binding and promoting the localization of a GIT1–PIX–PAK signaling module near the leading edge. Mutants that interfere with the formation of this ternary module abrogate the effects of paxillin-S273 phosphorylation. PAK-dependent paxillin-S273 phosphorylation functions in a positive-feedback loop, as active PAK, active Rac, and myosin II activity are all downstream effectors of this turnover pathway. Finally, our studies led us to identify in highly motile cells a class of small adhesions that reside near the leading edge, turnover in 20–30 s, and resemble those seen with paxillin-S273 phosphorylation. These adhesions appear to be regulated by the GIT1–PIX–PAK module near the leading edge.
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Affiliation(s)
- Anjana Nayal
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
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152
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Gilcrease MZ. Integrin signaling in epithelial cells. Cancer Lett 2006; 247:1-25. [PMID: 16725254 DOI: 10.1016/j.canlet.2006.03.031] [Citation(s) in RCA: 136] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 03/29/2006] [Accepted: 03/29/2006] [Indexed: 02/05/2023]
Abstract
Although most cells of adult mammals express multiple different integrins, particular types of cells have a characteristic repertoire of integrin expression. Benign and malignant epithelial cells use specific integrins to allow the epithelial microenvironment to modulate a wide variety of cell functions, including cell survival, proliferation, morphogenesis, differentiation, motility, invasion and metastasis. An important concept emerging from the data on integrin signal transduction is that integrin signaling impinges on pathways downstream of other receptors, creating elaborate intracellular signaling networks. This review highlights signal transduction functions of epithelial integrins, with particular emphasis on signaling pathways underlying some of the most important functions of epithelium.
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Affiliation(s)
- Michael Z Gilcrease
- Department of Pathology, MD Anderson Cancer Center, University of Texas, Houston, TX 77030, USA.
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153
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Boulter E, Grall D, Cagnol S, Van Obberghen-Schilling E. Regulation of cell-matrix adhesion dynamics and Rac-1 by integrin linked kinase. FASEB J 2006; 20:1489-91. [PMID: 16723384 DOI: 10.1096/fj.05-4579fje] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Extracellular matrix (ECM) receptors of the integrin family initiate changes in cell shape and motility by recruiting signaling components that coordinate these events. Integrin-linked kinase (ILK) is one such partner of beta1 integrins that participates in dynamic rearrangement of cell-matrix adhesions and cell spreading by mechanisms that are not well understood. To further elucidate the role of ILK in these events, we engineered a chimeric molecule comprising ILK fused to a membrane-targeted green fluorescent protein (ILK-GFP-F). ILK-GFP-F is highly enriched in cell-matrix adhesions, and its expression in fibroblasts leads to an accumulation of focal adhesions (2-5 microm) and elongated adhesions (>5 microm). ILK-GFP-F enhances cell spreading on fibronectin and induces a constitutive increase in the levels of GTP-bound Rac-1. Conversely, ILK knock-down by siRNA transfection decreases active Rac-1. Endogenous ILK was found to associate with PKL (paxillin kinase linker) and the Rac/Cdc42 guanine nucleotide exchange factor betaPIX. Further, expression of a dominant negative betaPIX mutant reversed the increase in active Rac-1 levels of ILK-GFP-F-expressing cells, thus placing betaPIX in the pathway leading from ILK to Rac-1 activation. However, expression of constitutively active Rac only partially restores the spreading defects of ILK-depleted cells, suggesting that an additional ILK-dependent signal is required for cell spreading.
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Affiliation(s)
- Etienne Boulter
- Institute of Signaling, Developmental Biology and Cancer Research, CNRS-UMR6543, Centre Antoine Lacassagne, 33 Ave. de Valombrose, Nice 06189, France
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154
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Lakhe-Reddy S, Khan S, Konieczkowski M, Jarad G, Wu KL, Reichardt LF, Takai Y, Bruggeman LA, Wang B, Sedor JR, Schelling JR. Beta8 integrin binds Rho GDP dissociation inhibitor-1 and activates Rac1 to inhibit mesangial cell myofibroblast differentiation. J Biol Chem 2006; 281:19688-99. [PMID: 16690620 PMCID: PMC2711893 DOI: 10.1074/jbc.m601110200] [Citation(s) in RCA: 32] [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
Alpha(v)beta8 integrin expression is restricted primarily to kidney, brain, and placenta. Targeted alpha(v) or beta8 deletion is embryonic lethal due to defective placenta and brain angiogenesis, precluding investigation of kidney alpha(v)beta8 function. We find that kidney beta8 is localized to glomerular mesangial cells, and expression is decreased in mouse models of glomerulosclerosis, suggesting that beta8 regulates normal mesangial cell differentiation. To interrogate beta8 signaling pathways, yeast two-hybrid and co-precipitation studies demonstrated beta8 interaction with Rho guanine nucleotide dissociation inhibitor-1 (GDI). Selective beta8 stimulation enhanced beta8-GDI interaction as well as Rac1 (but not RhoA) activation and lamellipodia formation. Mesangial cells from itgb8-/- mice backcrossed to a genetic background that permitted survival, or gdi-/- mice, which develop glomerulosclerosis, demonstrated RhoA (but not Rac1) activity and alpha-smooth muscle actin assembly, which characterizes mesangial cell myofibroblast transformation in renal disease. To determine whether Rac1 directly modulates RhoA-associated myofibroblast differentiation, mesangial cells were transduced with inhibitory Rac peptide fused to human immunodeficiency virus-Tat, resulting in enhanced alpha-smooth muscle actin organization. We conclude that the beta8 cytosolic tail in mesangial cells organizes a signaling complex that culminates in Rac1 activation to mediate wild-type differentiation, whereas decreased beta8 activation shifts mesangial cells toward a RhoA-dependent myofibroblast phenotype.
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Affiliation(s)
- Sujata Lakhe-Reddy
- Department of Medicine, Case Western Reserve University School of Medicine, Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, Ohio 44109
| | - Shenaz Khan
- Department of Medicine, Case Western Reserve University School of Medicine, Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, Ohio 44109
| | - Martha Konieczkowski
- Department of Medicine, Case Western Reserve University School of Medicine, Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, Ohio 44109
| | - George Jarad
- Department of Medicine, Case Western Reserve University School of Medicine, Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, Ohio 44109
| | - Karen L. Wu
- Department of Medicine, Case Western Reserve University School of Medicine, Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, Ohio 44109
| | - Louis F. Reichardt
- Departments of Physiology and Biochemistry/Biophysics, University of California, San Francisco and Howard Hughes Medical Institute, San Francisco, California 94143
| | - Yoshimi Takai
- Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine, Osaka 565−0871, Japan
| | - Leslie A. Bruggeman
- Department of Medicine, Case Western Reserve University School of Medicine, Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, Ohio 44109
| | - Bingcheng Wang
- Department of Medicine, Case Western Reserve University School of Medicine, Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, Ohio 44109
- Department of Pharmacology, Case Western Reserve University School of Medicine, Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, Ohio 44109
| | - John R. Sedor
- Department of Medicine, Case Western Reserve University School of Medicine, Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, Ohio 44109
- Departments of Physiology and Biophysics, Case Western Reserve University School of Medicine, Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, Ohio 44109
| | - Jeffrey R. Schelling
- Department of Medicine, Case Western Reserve University School of Medicine, Rammelkamp Center for Education and Research, MetroHealth Medical Center, Cleveland, Ohio 44109
- To whom correspondence should be addressed: MetroHealth Medical Center, 2500 MetroHealth Dr., R415, Cleveland, OH. 44109−1998. Tel.: 216−778−4993; E-mail:
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155
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Santy LC, Ravichandran KS, Casanova JE. The DOCK180/Elmo complex couples ARNO-mediated Arf6 activation to the downstream activation of Rac1. Curr Biol 2006; 15:1749-54. [PMID: 16213822 DOI: 10.1016/j.cub.2005.08.052] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2005] [Revised: 08/12/2005] [Accepted: 08/17/2005] [Indexed: 01/27/2023]
Abstract
Cell motility requires extensions of the plasma membrane driven by reorganization of the actin cytoskeleton. Small GTPases, particularly the Rho family, are key regulators of this process. A second class of GTPases, the ADP-ribosylation factors (ARFs), have also been implicated in the regulation of the actin cytoskeleton and motility. ARF6 is intimately involved in the regulation of Rac activity; however, the mechanisms by which ARF activation leads to activation of Rac remain poorly understood. We have previously shown that expression of the ARF-GEF ARNO in MDCK cells induces robust activation of Rac, the formation of large lamellipodia, and the onset of motility. We report here that ARNO-dependent activation of Rac is mediated by a bipartite Rac GEF, the Dock180/Elmo complex. Both DOCK180 and Elmo colocalize extensively with ARNO in migrating MDCK cells. Importantly, both a catalytically inactive Dock180 mutant and an Elmo mutant that fails to couple to Dock180 block ARNO-induced Rac activation and motility. In contrast, a similar mutant of the Rac GEF beta-PIX fails to inhibit ARNO-induced Rac activation or motility. Together, these data suggest that ARNO and ARF6 coordinate with the Dock180/Elmo complex to promote Rac activation at the leading edge of migrating cells.
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Affiliation(s)
- Lorraine C Santy
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22908, USA.
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156
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Frank SR, Adelstein MR, Hansen SH. GIT2 represses Crk- and Rac1-regulated cell spreading and Cdc42-mediated focal adhesion turnover. EMBO J 2006; 25:1848-59. [PMID: 16628223 PMCID: PMC1456948 DOI: 10.1038/sj.emboj.7601092] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2005] [Accepted: 03/21/2006] [Indexed: 11/08/2022] Open
Abstract
G protein-coupled receptor kinase interactors (GITs) regulate focal adhesion (FA) turnover, cell spreading, and motility through direct interaction with paxillin and the Rac-exchange factor Pak-interacting exchange factor beta (betaPIX). However, it is not clear whether GITs function to activate or repress motility or if the predominant GIT forms, GIT1 and GIT2, serve distinct or redundant roles. Here we demonstrate an obligatory role for endogenous GIT2 in repression of lamellipodial extension and FA turnover by Rac1- and Cdc42-dependent signaling pathways, respectively. Moreover, we show that the SH2-SH3 adaptor protein Crk is an essential target of GIT2 inhibition. Unexpectedly, we find that betaPIX is dispensable for the effects elicited by knockdown of GIT2. Finally, we show that loss of GIT2 is sufficient to induce migration of the nontransformed epithelial cell line MCF10A. These results suggest that inactivation of GIT2 function is a required step for induction of cell motility and that GIT2 may be a target of oncogenic signaling pathways that regulate cell migration.
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Affiliation(s)
- Scott R Frank
- Boston Biomedical Research Institute, Watertown, MA, USA
| | | | - Steen H Hansen
- Boston Biomedical Research Institute, Watertown, MA, USA
- GI Cell Biology Laboratory, Harvard Digestive Diseases Center, Enders 730.2, The Children's Hospital, 300 Longwood Avenue, Boston, MA 02115, USA. Tel.: +1 617 919 4544; Fax: +1 617 730 0498; E-mail:
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157
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Kuo JC, Wang WJ, Yao CC, Wu PR, Chen RH. The tumor suppressor DAPK inhibits cell motility by blocking the integrin-mediated polarity pathway. ACTA ACUST UNITED AC 2006; 172:619-31. [PMID: 16476779 PMCID: PMC2063680 DOI: 10.1083/jcb.200505138] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Death-associated protein kinase (DAPK) is a calmodulin-regulated serine/threonine kinase and possesses apoptotic and tumor-suppressive functions. However, it is unclear whether DAPK elicits apoptosis-independent activity to suppress tumor progression. We show that DAPK inhibits random migration by reducing directional persistence and directed migration by blocking cell polarization. These effects are mainly mediated by an inhibitory role of DAPK in talin head domain association with integrin, thereby suppressing the integrin–Cdc42 polarity pathway. We present evidence indicating that the antimigratory effect of DAPK represents a mechanism through which DAPK suppresses tumors. First, DAPK can block migration and invasion in certain tumor cells that are resistant to DAPK-induced apoptosis. Second, using an adenocarcinoma cell line and its highly invasive derivative, we demonstrate DAPK level as a determining factor in tumor invasiveness. Collectively, our study identifies a novel function of DAPK in regulating cell polarity during migration, which may act together with its apoptotic function to suppress tumor progression.
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Affiliation(s)
- Jean-Cheng Kuo
- Institute of Molecular Medicine, National Taiwan University Hospital, National Taiwan University, Taipei 106, Taiwan
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158
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Boulter E, Van Obberghen-Schilling E. Integrin-linked kinase and its partners: A modular platform regulating cell–matrix adhesion dynamics and cytoskeletal organization. Eur J Cell Biol 2006; 85:255-63. [PMID: 16546570 DOI: 10.1016/j.ejcb.2005.09.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Integrin-linked kinase (ILK) represents a key component of integrin signaling complexes that functions in concert with multiple binding partners to transmit cues from the extracellular matrix environment to the actin cytoskeleton. Both gain- and loss-of-function approaches to study ILK have confirmed the essential role of this protein in regulating cell-matrix adhesion dynamics and cytoskeletal organization.
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Affiliation(s)
- Etienne Boulter
- Institute of Signaling, Developmental Biology and Cancer Research, CNRS-UMR6543, Centre Antoine Lacassagne, 33 Avenue de Valombrose, F-06189 Nice, France
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159
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Grazioli A, Alves CS, Konstantopoulos K, Yang JT. Defective blood vessel development and pericyte/pvSMC distribution in alpha 4 integrin-deficient mouse embryos. Dev Biol 2006; 293:165-77. [PMID: 16529735 DOI: 10.1016/j.ydbio.2006.01.026] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2005] [Revised: 01/20/2006] [Accepted: 01/27/2006] [Indexed: 11/16/2022]
Abstract
Blood vessel development is in part regulated by pericytes/presumptive vascular smooth muscle cells (PC/pvSMCs). Here, we demonstrate that interactions between PC/pvSMCs and extracellular matrix play a critical role in this event. We show that the cranial vessels in alpha4 integrin-deficient mouse embryos at the stage of vessel remodeling are increased in diameter. This defect is accompanied by a failure of PC/pvSMCs, which normally express alpha4beta1 integrin, to spread uniformly along the vessels. We also find that fibronectin but not VCAM-1 is localized in the cranial vessels at this stage. Furthermore, cultured alpha4 integrin-null PC/pvSMCs plated on fibronectin display a delay in initiating migration, a reduction in migration speed, and a decrease in directional persistence in response to a polarized force of shear flow. These results suggest that specific motile activities of PC/pvSMCs regulated by mechanical signals imposed by the interstitial extracellular matrix may also be required in vivo for the distribution and function of the PC/pvSMCs during blood vessel development.
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Affiliation(s)
- Alison Grazioli
- Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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160
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Alon R, Feigelson SW, Manevich E, Rose DM, Schmitz J, Overby DR, Winter E, Grabovsky V, Shinder V, Matthews BD, Sokolovsky-Eisenberg M, Ingber DE, Benoit M, Ginsberg MH. Alpha4beta1-dependent adhesion strengthening under mechanical strain is regulated by paxillin association with the alpha4-cytoplasmic domain. ACTA ACUST UNITED AC 2006; 171:1073-84. [PMID: 16365170 PMCID: PMC2171310 DOI: 10.1083/jcb.200503155] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The capacity of integrins to mediate adhesiveness is modulated by their cytoplasmic associations. In this study, we describe a novel mechanism by which α4-integrin adhesiveness is regulated by the cytoskeletal adaptor paxillin. A mutation of the α4 tail that disrupts paxillin binding, α4(Y991A), reduced talin association to the α4β1 heterodimer, impaired integrin anchorage to the cytoskeleton, and suppressed α4β1-dependent capture and adhesion strengthening of Jurkat T cells to VCAM-1 under shear stress. The mutant retained intrinsic avidity to soluble or bead-immobilized VCAM-1, supported normal cell spreading at short-lived contacts, had normal α4-microvillar distribution, and responded to inside-out signals. This is the first demonstration that cytoskeletal anchorage of an integrin enhances the mechanical stability of its adhesive bonds under strain and, thereby, promotes its ability to mediate leukocyte adhesion under physiological shear stress conditions.
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Affiliation(s)
- Ronen Alon
- Department of Immunology, The Weizmann Institute of Science, Rehovot 76100, Israel.
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161
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ten Klooster JP, Jaffer ZM, Chernoff J, Hordijk PL. Targeting and activation of Rac1 are mediated by the exchange factor beta-Pix. ACTA ACUST UNITED AC 2006; 172:759-69. [PMID: 16492808 PMCID: PMC2063707 DOI: 10.1083/jcb.200509096] [Citation(s) in RCA: 212] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Rho guanosine triphosphatases (GTPases) are critical regulators of cytoskeletal dynamics and control complex functions such as cell adhesion, spreading, migration, and cell division. It is generally accepted that localized GTPase activation is required for the proper initiation of downstream signaling events, although the molecular mechanisms that control targeting of Rho GTPases are unknown. In this study, we show that the Rho GTPase Rac1, via a proline stretch in its COOH terminus, binds directly to the SH3 domain of the Cdc42/Rac activator β-Pix (p21-activated kinase [Pak]–interacting exchange factor). The interaction with β-Pix is nucleotide independent and is necessary and sufficient for Rac1 recruitment to membrane ruffles and to focal adhesions. In addition, the Rac1–β-Pix interaction is required for Rac1 activation by β-Pix as well as for Rac1-mediated spreading. Finally, using cells deficient for the β-Pix–binding kinase Pak1, we show that Pak1 regulates the Rac1–β-Pix interaction and controls cell spreading and adhesion-induced Rac1 activation. These data provide a model for the intracellular targeting and localized activation of Rac1 through its exchange factor β-Pix.
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Affiliation(s)
- Jean Paul ten Klooster
- Sanquin Research and Landsteiner Laboratory, Academic Medical Center, University of Amsterdam, 1066 CX Amsterdam, Netherlands
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162
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Barreiro O, de la Fuente H, Mittelbrunn M, Sánchez-Madrid F. Posterolateral approach for open reduction and internal fixation of trimalleolar ankle fractures. Immunol Rev 2006; 218:147-64. [PMID: 17624951 DOI: 10.1111/j.1600-065x.2007.00529.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cell-cell and cell-matrix interactions are of critical importance in immunobiology. Leukocytes make extensive use of a specialized repertoire of receptors to mediate such processes. Among these receptors, integrins are known to be of crucial importance. This review deals with the central role of integrins and their counterreceptors during the establishment of leukocyte-endothelium contacts, interstitial migration, and final encounter with antigen-presenting cells to develop an appropriate immune response. Particularly, we have addressed the molecular events occurring during these sequential processes, leading to the dynamic subcellular redistribution of adhesion receptors and the reorganization of the actin cytoskeleton, which is reflected in changes in cytoarchitecture, including leukocyte polarization, endothelial docking structure formation, or immune synapse organization. The roles of signaling and structural actin cytoskeleton-associated proteins and organized membrane microdomains in the regulation of receptor adhesiveness are also discussed.
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Affiliation(s)
- Olga Barreiro
- Servicio de Inmunología, Hospital de la Princesa, Universidad Autónoma de Madrid, Madrid, Spain
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163
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Hilden TJ, Nurmi SM, Fagerholm SC, Gahmberg CG. Interfering with leukocyte integrin activation--a novel concept in the development of anti-inflammatory drugs. Ann Med 2006; 38:503-11. [PMID: 17101541 DOI: 10.1080/07853890600969130] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Inflammation is a crucial response against invading pathogens, in which immune cells, including neutrophils and T cells, are recruited into tissue from the bloodstream to help clear infection. However, a prevailing inflammatory response where the immune cells attack healthy tissue is associated with many diseases, including asthma, rheumatoid arthritis, atherosclerosis and multiple sclerosis. Integrins are key players in the recruitment of immune cells from the bloodstream into tissues, and are thus therapeutic targets for intervention with inflammatory responses. Thus far, mainly extracellularly acting therapeutics (monoclonal antibodies) have been developed against integrins, targeting ligand binding sites in these heterodimeric adhesion receptors. However, since these therapeutics nonselectively block all integrin functions, some side effects are expected and have been observed. Therefore, novel concepts need to be developed in the therapeutic targeting of integrins. Recently, major advances have been made in the understanding of integrin biology. Integrin structures have been solved by X-ray crystallography, revealing unexpected data about the activation mechanism of integrins in cells. Additionally, several intracellular factors in the integrin activation process have been identified, providing potential specific targets for therapeutic intervention. Here, we present key events and players in leukocyte integrin activation, and discuss potential new drug targets in the prevention of inflammatory disease.
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Affiliation(s)
- Tiina J Hilden
- Division of Biochemistry, Faculty of Biosciences, University of Helsinki, Finland
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164
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Hsia DA, Lim ST, Bernard-Trifilo JA, Mitra SK, Tanaka S, den Hertog J, Streblow DN, Ilic D, Ginsberg MH, Schlaepfer DD. Integrin alpha4beta1 promotes focal adhesion kinase-independent cell motility via alpha4 cytoplasmic domain-specific activation of c-Src. Mol Cell Biol 2005; 25:9700-12. [PMID: 16227616 PMCID: PMC1265817 DOI: 10.1128/mcb.25.21.9700-9712.2005] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The fibronectin binding integrins alpha5beta1 and alpha4beta1 generate signals pivotal for cell migration through distinct yet undefined mechanisms. For alpha5beta1, beta1-mediated activation of focal adhesion kinase (FAK) promotes c-Src recruitment to FAK and the formation of a FAK-Src signaling complex. Herein, we show that FAK expression is essential for alpha5beta1-stimulated cell motility and that exogenous expression of human alpha4 in FAK-null fibroblasts forms a functional alpha4beta1 receptor that promotes robust cell motility equal to the alpha5beta1 stimulation of wild-type and FAK-reconstituted fibroblasts. alpha4beta1-stimulated FAK-null cell spreading and motility were dependent on the integrity of the alpha4 cytoplasmic domain, independent of direct paxillin binding to alpha4, and were not affected by PRNK expression, a dominant-negative inhibitor of Pyk2. alpha4 cytoplasmic domain-initiated signaling led to a approximately 4-fold activation of c-Src which did not require paxillin binding to alpha4. Notably, alpha4-stimulated cell motility was inhibited by catalytically inactive receptor protein-tyrosine phosphatase alpha overexpression and blocked by the p50Csk phosphorylation of c-Src at Tyr-529. alpha4beta1-stimulated cell motility of triple-null Src(-/-), c-Yes(-/-), and Fyn(-/-) fibroblasts was dependent on c-Src reexpression that resulted in p130Cas tyrosine phosphorylation and Rac GTPase loading. As p130Cas phosphorylation and Rac activation are common downstream targets for alpha5beta1-stimulated FAK activation, our results support the existence of a novel alpha4 cytoplasmic domain connection leading to c-Src activation which functions as a FAK-independent linkage to a common motility-promoting signaling pathway.
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Affiliation(s)
- Datsun A Hsia
- The Scripps Research Institute, Department of Immunology, IMM21, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
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165
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Jamieson JS, Tumbarello DA, Hallé M, Brown MC, Tremblay ML, Turner CE. Paxillin is essential for PTP-PEST-dependent regulation of cell spreading and motility: a role for paxillin kinase linker. J Cell Sci 2005; 118:5835-47. [PMID: 16317044 DOI: 10.1242/jcs.02693] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The tyrosine phosphatase PTP-PEST has been implicated in the regulation of cell spreading and migration through dephosphorylation of focal adhesion proteins and inhibition of Rac GTPase activity. The focal adhesion adaptor protein paxillin is also necessary for normal cell migration and binds directly to PTP-PEST. In this study, we have utilized PTP-PEST(-/-) and paxillin(-/-) fibroblasts to demonstrate that paxillin is essential for PTP-PEST inhibition of cell spreading and membrane protrusion as well as inhibition of adhesion-induced Rac activation. Furthermore, we show that paxillin-binding is necessary for PTP-PEST stimulation of cell migration. Mutation analysis indicates that PTP-PEST function involves binding to the paxillin C-terminal LIM domains, and signaling through the tyrosine 31 and 118 phosphorylation sites, as well as the LD4 motif of the paxillin N-terminus. Using 'substrate trapping' approaches and immunoprecipitation, we show that the ARF GAP paxillin kinase linker PKL/GIT2, a paxillin LD4 binding partner, is a substrate for PTP-PEST. Additionally, the PKL-paxillin interaction was necessary for PTP-PEST inhibition of cell spreading. These data provide mechanistic insight into how the paxillin-PTP-PEST interaction contributes to integrin signaling events associated with the spatiotemporal regulation of key modulators of the cytoskeleton and cell motility machinery.
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Affiliation(s)
- Jennifer S Jamieson
- Department of Cell and Developmental Biology, State University of New York, Upstate Medical University, Syracuse, NY 13210, USA
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166
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Pankov R, Endo Y, Even-Ram S, Araki M, Clark K, Cukierman E, Matsumoto K, Yamada KM. A Rac switch regulates random versus directionally persistent cell migration. ACTA ACUST UNITED AC 2005; 170:793-802. [PMID: 16129786 PMCID: PMC2171343 DOI: 10.1083/jcb.200503152] [Citation(s) in RCA: 358] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Directional migration moves cells rapidly between points, whereas random migration allows cells to explore their local environments. We describe a Rac1 mechanism for determining whether cell patterns of migration are intrinsically random or directionally persistent. Rac activity promoted the formation of peripheral lamellae that mediated random migration. Decreasing Rac activity suppressed peripheral lamellae and switched the cell migration patterns of fibroblasts and epithelial cells from random to directionally persistent. In three-dimensional rather than traditional two-dimensional cell culture, cells had a lower level of Rac activity that was associated with rapid, directional migration. In contrast to the directed migration of chemotaxis, this intrinsic directional persistence of migration was not mediated by phosphatidylinositol 3′-kinase lipid signaling. Total Rac1 activity can therefore provide a regulatory switch between patterns of cell migration by a mechanism distinct from chemotaxis.
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Affiliation(s)
- Roumen Pankov
- Craniofacial Developmental Biology and Regeneration Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA
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167
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Howe AK, Baldor LC, Hogan BP. Spatial regulation of the cAMP-dependent protein kinase during chemotactic cell migration. Proc Natl Acad Sci U S A 2005; 102:14320-5. [PMID: 16176981 PMCID: PMC1242330 DOI: 10.1073/pnas.0507072102] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Historically, the cAMP-dependent protein kinase (PKA) has a paradoxical role in cell motility, having been shown to both facilitate and inhibit actin cytoskeletal dynamics and cell migration. In an effort to understand this dichotomy, we show here that PKA is regulated in subcellular space during cell migration. Immunofluorescence microscopy and biochemical enrichment of pseudopodia showed that type II regulatory subunits of PKA and PKA activity are enriched in protrusive cellular structures formed during chemotaxis. This enrichment correlates with increased phosphorylation of key cytoskeletal substrates for PKA, including the vasodilator-stimulated phosphoprotein (VASP) and the protein tyrosine phosphatase containing a PEST motif. Importantly, inhibition of PKA activity or its ability to interact with A kinase anchoring proteins inhibited the activity of the Rac GTPase within pseudopodia. This effect correlated with both decreased guanine nucleotide exchange factor activity and increased GTPase activating protein activity. Finally, inhibition of PKA anchoring, like inhibition of total PKA activity, inhibited pseudopod formation and chemotactic cell migration. These data demonstrate that spatial regulation of PKA via anchoring is an important facet of normal chemotactic cell movement.
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Affiliation(s)
- Alan K Howe
- Department of Pharmacology and the Vermont Cancer Center, The University of Vermont, 149 Beaumont Avenue, HSRF 322, Burlington, VT 05405-0075, USA.
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168
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Abstract
Cell motility depends on the conversion of extracellular cues into intracellular cytoskeletal responses. A recent Keystone meeting on cell migration and adhesion showcased advances in the field.
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Affiliation(s)
- Alissa M Weaver
- Department of Cancer Biology, Vanderbilt University Medical Center, Room 448 Preston Research Building, 23rd Avenue South @ Pierce, Nashville, Tennessee 37232, USA.
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169
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Brown MC, Cary LA, Jamieson JS, Cooper JA, Turner CE. Src and FAK kinases cooperate to phosphorylate paxillin kinase linker, stimulate its focal adhesion localization, and regulate cell spreading and protrusiveness. Mol Biol Cell 2005; 16:4316-28. [PMID: 16000375 PMCID: PMC1196340 DOI: 10.1091/mbc.e05-02-0131] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The ArfGAP paxillin kinase linker (PKL)/G protein-coupled receptor kinase-interacting protein (GIT)2 has been implicated in regulating cell spreading and motility through its transient recruitment of the p21-activated kinase (PAK) to focal adhesions. The Nck-PAK-PIX-PKL protein complex is recruited to focal adhesions by paxillin upon integrin engagement and Rac activation. In this report, we identify tyrosine-phosphorylated PKL as a protein that associates with the SH3-SH2 adaptor Nck, in a Src-dependent manner, after cell adhesion to fibronectin. Both cell adhesion and Rac activation stimulated PKL tyrosine phosphorylation. PKL is phosphorylated on tyrosine residues 286/392/592 by Src and/or FAK and these sites are required for PKL localization to focal adhesions and for paxillin binding. The absence of either FAK or Src-family kinases prevents PKL phosphorylation and suppresses localization of PKL but not GIT1 to focal adhesions after Rac activation. Expression of an activated FAK mutant in the absence of Src-family kinases partially restores PKL localization, suggesting that Src activation of FAK is required for PKL phosphorylation and localization. Overexpression of the nonphosphorylated GFP-PKL Triple YF mutant stimulates cell spreading and protrusiveness, similar to overexpression of a paxillin mutant that does not bind PKL, suggesting that failure to recruit PKL to focal adhesions interferes with normal cell spreading and motility.
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Affiliation(s)
- Michael C Brown
- Department of Cell and Developmental Biology, College of Medicine, State University of New York Upstate Medical University, Syracuse, NY 13210, USA
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170
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