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Single-molecule characterization of subtype-specific β1 integrin mechanics. Nat Commun 2022; 13:7471. [PMID: 36463259 PMCID: PMC9719539 DOI: 10.1038/s41467-022-35173-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 11/17/2022] [Indexed: 12/05/2022] Open
Abstract
Although integrins are known to be mechanosensitive and to possess many subtypes that have distinct physiological roles, single molecule studies of force exertion have thus far been limited to RGD-binding integrins. Here, we show that integrin α4β1 and RGD-binding integrins (αVβ1 and α5β1) require markedly different tension thresholds to support cell spreading. Furthermore, actin assembled downstream of α4β1 forms cross-linked networks in circularly spread cells, is in rapid retrograde flow, and exerts low forces from actin polymerization. In contrast, actin assembled downstream of αVβ1 forms stress fibers linking focal adhesions in elongated cells, is in slow retrograde flow, and matures to exert high forces (>54-pN) via myosin II. Conformational activation of both integrins occurs below 12-pN, suggesting that post-activation subtype-specific cytoskeletal remodeling imposes the higher threshold for spreading on RGD substrates. Multiple layers of single integrin mechanics for activation, mechanotransduction and cytoskeleton remodeling revealed here may underlie subtype-dependence of diverse processes such as somite formation and durotaxis.
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2
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Faralli JA, Filla MS, Peters DM. Integrin Crosstalk and Its Effect on the Biological Functions of the Trabecular Meshwork/Schlemm’s Canal. Front Cell Dev Biol 2022; 10:886702. [PMID: 35573686 PMCID: PMC9099149 DOI: 10.3389/fcell.2022.886702] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 04/05/2022] [Indexed: 11/20/2022] Open
Abstract
Integrins are a family of heterodimeric receptors composed of an α- and β-subunit that mediate cell-adhesion to a number of extracellular matrix (ECM) proteins in the Trabecular Meshwork/Schlemm’s canal (TM/SC) of the eye. Upon binding an ECM ligand, integrins transmit signals that activate a number of signaling pathways responsible for regulating actin-mediated processes (i.e phagocytosis, cell contractility, and fibronectin fibrillogenesis) that play an important role in regulating intraocular pressure (IOP) and may be involved in glaucoma. An important function of integrin-mediated signaling events is that the activity of one integrin can affect the activity of other integrins in the same cell. This creates a crosstalk that allows TM/SC cells to respond to changes in the ECM presumably induced by the mechanical forces on the TM/SC, aging and disease. In this review, we discuss how integrin crosstalk influences the function of the human TM/SC pathway. In particular, we will discuss how different crosstalk pathways mediated by either the αvβ3 or α4β1 integrins can play opposing roles in the TM when active and therefore act as on/off switches to modulate the cytoskeleton-mediated processes that regulate the outflow of aqueous humor through the TM/SC.
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Affiliation(s)
- Jennifer A. Faralli
- Department of Pathology and Laboratory Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Mark S. Filla
- Department of Pathology and Laboratory Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| | - Donna M. Peters
- Department of Pathology and Laboratory Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
- *Correspondence: Donna M. Peters,
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3
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Eldawud R, Wagner A, Dong C, Gupta N, Rojanasakul Y, O'Doherty G, Stueckle TA, Dinu CZ. Potential antitumor activity of digitoxin and user-designed analog administered to human lung cancer cells. Biochim Biophys Acta Gen Subj 2020; 1864:129683. [PMID: 32679249 DOI: 10.1016/j.bbagen.2020.129683] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 06/19/2020] [Accepted: 07/09/2020] [Indexed: 12/15/2022]
Abstract
BACKGROUND Cardiac glycosides (CGs), such as digitoxin, are traditionally used for treatment of congestive heart failure; recently they also gained attention for their anticancer properties. Previous studies showed that digitoxin and a synthetic L-sugar monosaccharide analog treatment decreases cancer cell proliferation, increases apoptosis, and pro-adhesion abilities; however, no reports are available on their potential to alter lung cancer cell cytoskeleton structure and reduce migratory ability. Herein, we investigated the anticancer effects of digitoxin and its analog, digitoxigenin-α-L-rhamnoside (D6MA), to establish whether cytoskeleton reorganization and reduced motility are drug-induced cellular outcomes. METHODS We treated non-small cell lung carcinoma cells (NSCLCs) with sub-therapeutic, therapeutic, and toxic concentrations of digitoxin and D6MA respectively, followed by both single point and real-time assays to evaluate changes in cellular gene and protein expression, adhesion, elasticity, and migration. RESULTS Digitoxin and D6MA induced a decrease in matrix metalloproteinases expression via altered focal adhesion signaling and a suppression of the phosphoinositide 3-kinases / protein kinase B pathway which lead to enhanced adhesion, altered elasticity, and reduced motility of NSCLCs. Global gene expression analysis identified dose-dependent changes to nuclear factor kappa-light-chain-enhancer, epithelial tumor, and microtubule dynamics signaling. CONCLUSIONS Our study demonstrates that digitoxin and D6MA can target antitumor signaling pathways to alter NSCLC cytoskeleton and migratory ability to thus potentially reduce their tumorigenicity. SIGNIFICANCE Discovering signaling pathways that control cancer's cell phenotype and how such pathways are affected by CG treatment will potentially allow for active usage of synthetic CG analogs as therapeutic agents in advanced lung conditions.
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Affiliation(s)
- Reem Eldawud
- Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV 26506, USA
| | - Alixandra Wagner
- Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV 26506, USA
| | - Chenbo Dong
- Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV 26506, USA
| | - Neha Gupta
- Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV 26506, USA
| | - Yon Rojanasakul
- Department of Basic Pharmaceutical Sciences, West Virginia University, Morgantown, WV 26506, USA
| | - George O'Doherty
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115, USA
| | - Todd A Stueckle
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA
| | - Cerasela Zoica Dinu
- Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV 26506, USA
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4
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Regulation of cell migration by α4 and α9 integrins. Biochem J 2019; 476:705-718. [PMID: 30819933 DOI: 10.1042/bcj20180415] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 02/09/2019] [Accepted: 02/12/2019] [Indexed: 12/15/2022]
Abstract
Integrins are heterodimeric transmembrane receptors that play an essential role in enabling cells to sense and bind to extracellular ligands. Activation and clustering of integrins leads to the formation of focal adhesions at the plasma membrane that subsequently initiate signalling pathways to control a broad range of functional endpoints including cell migration, proliferation and survival. The α4 and α9 integrins form a small sub-family of receptors that share some specific ligands and binding partners. Although relatively poorly studied compared with other integrin family members, emerging evidence suggests that despite restricted cell and tissue expression profiles, these integrins play a key role in the regulation of signalling pathways controlling cytoskeletal remodelling and migration in both adherent and non-adherent cell types. This review summarises the known shared and specific roles for α4 and α9 integrins and highlights the importance of these receptors in controlling cell migration within both homeostatic and disease settings.
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5
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Jahan F, Madhavan S, Rolova T, Viazmina L, Grönholm M, Gahmberg CG. Phosphorylation of the α-chain in the integrin LFA-1 enables β2-chain phosphorylation and α-actinin binding required for cell adhesion. J Biol Chem 2018; 293:12318-12330. [PMID: 29903913 DOI: 10.1074/jbc.ra118.004318] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 06/11/2018] [Indexed: 11/06/2022] Open
Abstract
The integrin leukocyte function-associated antigen-1 (LFA-1) plays a pivotal role in leukocyte adhesion and migration, but the mechanism(s) by which this integrin is regulated has remained incompletely understood. LFA-1 integrin activity requires phosphorylation of its β2-chain and interactions of its cytoplasmic tail with various cellular proteins. The α-chain is constitutively phosphorylated and necessary for cellular adhesion, but how the α-chain regulates adhesion has remained enigmatic. We now show that substitution of the α-chain phosphorylation site (S1140A) in T cells inhibits the phosphorylation of the functionally important Thr-758 in the β2-chain, binding of α-actinin and 14-3-3 protein, and expression of an integrin-activating epitope after treatment with the stromal cell-derived factor-1α. The presence of this substitution resulted in a loss of cell adhesion and directional cell migration. Moreover, LFA-1 activation through the T-cell receptor in cells expressing the S1140A LFA-1 variant resulted in less Thr-758 phosphorylation, α-actinin and talin binding, and cell adhesion. The finding that the LFA-1 α-chain regulates adhesion through the β-chain via specific phosphorylation at Ser-1140 in the α-chain has not been previously reported and emphasizes that both chains are involved in the regulation of LFA-1 integrin activity.
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Affiliation(s)
- Farhana Jahan
- From the Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki 00014 UH, Finland
| | - Sudarrshan Madhavan
- From the Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki 00014 UH, Finland
| | - Taisia Rolova
- From the Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki 00014 UH, Finland
| | - Larisa Viazmina
- From the Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki 00014 UH, Finland
| | - Mikaela Grönholm
- From the Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki 00014 UH, Finland
| | - Carl G Gahmberg
- From the Faculty of Biological and Environmental Sciences, Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki 00014 UH, Finland
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6
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Amschler K, Kossmann E, Erpenbeck L, Kruss S, Schill T, Schön M, Möckel SMC, Spatz JP, Schön MP. Nanoscale Tuning of VCAM-1 Determines VLA-4-Dependent Melanoma Cell Plasticity on RGD Motifs. Mol Cancer Res 2017; 16:528-542. [PMID: 29222169 DOI: 10.1158/1541-7786.mcr-17-0272] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 08/08/2017] [Accepted: 11/09/2017] [Indexed: 11/16/2022]
Abstract
The biophysical fine-tuning of cancer cell plasticity is crucial for tumor progression but remains largely enigmatic. Although vascular cell adhesion molecule-1 (VCAM-1/CD106) has been implicated in melanoma progression, here its presentation on endothelial cells was associated with diminished melanoma cell spreading. Using a specific nanoscale modulation of VCAM-1 (tunable from 70 to 670 ligands/μm²) next to integrin ligands (RGD motifs) in a bifunctional system, reciprocal regulation of integrin α4 (ITGA4/VLA-4/CD49d)-dependent adhesion and spreading of melanoma cells was found. As the VCAM-1/VLA-4 receptor pair facilitated adhesion, while at the same time antagonizing RGD-mediated spreading, melanoma cell morphogenesis on these bifunctional matrices was directly regulated by VCAM-1 in a dichotomic and density-dependent fashion. This was accompanied by concordant regulation of F-actin cytoskeleton remodeling, Rac1-expression, and paxillin-related adhesion formation. The novel function of VCAM-1 was corroborated in vivo using two murine models of pulmonary metastasis. The regulation of melanoma cell plasticity by VCAM-1 highlights the complex regulation of tumor-matrix interactions.Implications: Nanotechnology has revealed a novel dichotomic function of the VCAM-1/VLA-4 interaction on melanoma cell plasticity, as nanoscale tuning of this interaction reciprocally determines adhesion and spreading in a ligand density-dependent manner. Mol Cancer Res; 16(3); 528-42. ©2017 AACR.
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Affiliation(s)
- Katharina Amschler
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen, Germany
| | - Eugen Kossmann
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen, Germany
| | - Luise Erpenbeck
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen, Germany
| | - Sebastian Kruss
- Department of Physical Chemistry, Georg August University, Göttingen, Germany
| | - Tillmann Schill
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen, Germany
| | - Margarete Schön
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen, Germany
| | - Sigrid M C Möckel
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen, Germany
| | - Joachim P Spatz
- Department of Cellular Biophysics, Max Planck Institute for Medical Research, Heidelberg and Laboratory of Biophysical Chemistry, University of Heidelberg, Heidelberg, Germany
| | - Michael P Schön
- Department of Dermatology, Venereology and Allergology, University Medical Center, Göttingen, Germany.
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7
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Li J, Springer TA. Energy landscape differences among integrins establish the framework for understanding activation. J Cell Biol 2017; 217:397-412. [PMID: 29122968 PMCID: PMC5748972 DOI: 10.1083/jcb.201701169] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 09/15/2017] [Accepted: 10/04/2017] [Indexed: 11/22/2022] Open
Abstract
Li and Springer demonstrate differences between integrins α4β1 and α5β1 in intrinsic affinities and relative free energies of three conformational states. Integrin conformational equilibria are both subunit and cell type specific. The energy landscapes of intact receptors on the cell surface provide a framework for understanding regulation of integrin adhesiveness. Why do integrins differ in basal activity, and how does affinity for soluble ligand correlate with cellular adhesiveness? We show that basal conformational equilibrium set points for integrin α4β1 are cell type specific and differ from integrin α5β1 when the two integrins are coexpressed on the same cell. Although α4β1 is easier to activate, its high-affinity state binds vascular cell adhesion molecule and fibronectin 100- to 1,000-fold more weakly than α5β1 binds fibronectin. Furthermore, the difference in affinity between the high- and low-affinity states is more compressed in α4β1 (600- to 800-fold) than in α5β1 (4,000- to 6,000-fold). α4β1 basal conformational equilibria differ among three cell types, define affinity for soluble ligand and readiness for priming, and may reflect differences in interactions with intracellular adaptors but do not predict cellular adhesiveness for immobilized ligand. The measurements here provide a necessary framework for understanding integrin activation in intact cells, including activation of integrin adhesiveness by application of tensile force by the cytoskeleton, across ligand–integrin–adaptor complexes.
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Affiliation(s)
- Jing Li
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA
| | - Timothy A Springer
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA .,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA
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8
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Young SA, McCabe KE, Bartakova A, Delaney J, Pizzo DP, Newbury RO, Varner JA, Schlaepfer DD, Stupack DG. Integrin α4 Enhances Metastasis and May Be Associated with Poor Prognosis in MYCN-low Neuroblastoma. PLoS One 2015; 10:e0120815. [PMID: 25973900 PMCID: PMC4431816 DOI: 10.1371/journal.pone.0120815] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 02/08/2015] [Indexed: 12/11/2022] Open
Abstract
High-risk neuroblastoma is associated with an overall survival rate of 30–50%. Neuroblastoma-expressed cell adhesion receptors of the integrin family impact cell adhesion, migration, proliferation and survival. Integrin α4 is essential for neural crest cell motility during development, is highly expressed on leukocytes, and is critical for transendothelial migration. Thus, cancer cells that express this receptor may exhibit increased metastatic potential. We show that α4 expression in human and murine neuroblastoma cell lines selectively enhances in vitro interaction with the alternatively spliced connecting segment 1 of fibronectin, as well as vascular cell adhesion molecule-1 and increases migration. Integrin α4 expression enhanced experimental metastasis in a syngeneic tumor model, reconstituting a pattern of organ involvement similar to that seen in patients. Accordingly, antagonism of integrin α4 blocked metastasis, suggesting adhesive function of the integrin is required. However, adhesive function was not sufficient, as mutants of integrin α4 that conserved the matrix-adhesive and promigratory function in vitro were compromised in their metastatic capacity in vivo. Clinically, integrin α4 is more frequently expressed in non-MYNC amplified tumors, and is selectively associated with poor prognosis in this subset of disease. These results reveal an unexpected role for integrin α4 in neuroblastoma dissemination and identify α4 as a potential prognostic indicator and therapeutic target.
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Affiliation(s)
- Shanique A. Young
- Division of Gynecologic Oncology, Department of Reproductive Medicine, UCSD School of Medicine, 9500 Gilman Drive, La Jolla, California, 92093, United States of America
- University of California San Diego Moores Cancer Center, 3855 Health Sciences Drive, La Jolla, California, 92093, United States of America
| | - Katelyn E. McCabe
- Division of Gynecologic Oncology, Department of Reproductive Medicine, UCSD School of Medicine, 9500 Gilman Drive, La Jolla, California, 92093, United States of America
- University of California San Diego Moores Cancer Center, 3855 Health Sciences Drive, La Jolla, California, 92093, United States of America
| | - Alena Bartakova
- Division of Gynecologic Oncology, Department of Reproductive Medicine, UCSD School of Medicine, 9500 Gilman Drive, La Jolla, California, 92093, United States of America
| | - Joe Delaney
- Division of Gynecologic Oncology, Department of Reproductive Medicine, UCSD School of Medicine, 9500 Gilman Drive, La Jolla, California, 92093, United States of America
- University of California San Diego Moores Cancer Center, 3855 Health Sciences Drive, La Jolla, California, 92093, United States of America
| | - Donald P. Pizzo
- University of California San Diego Center for Advanced Laboratory Medicine, 10300 Campus Point Drive, MC7210, Room 1253, San Diego, CA, 92121, United States of America
- Department of Pathology, UCSD School of Medicine, 9500 Gilman Drive, La Jolla, California, 92093, United States of America
| | - Robert O. Newbury
- Department of Pathology, UCSD School of Medicine, 9500 Gilman Drive, La Jolla, California, 92093, United States of America
| | - Judith A. Varner
- University of California San Diego Moores Cancer Center, 3855 Health Sciences Drive, La Jolla, California, 92093, United States of America
- Department of Pathology, UCSD School of Medicine, 9500 Gilman Drive, La Jolla, California, 92093, United States of America
| | - David D. Schlaepfer
- Division of Gynecologic Oncology, Department of Reproductive Medicine, UCSD School of Medicine, 9500 Gilman Drive, La Jolla, California, 92093, United States of America
- University of California San Diego Moores Cancer Center, 3855 Health Sciences Drive, La Jolla, California, 92093, United States of America
| | - Dwayne G. Stupack
- Division of Gynecologic Oncology, Department of Reproductive Medicine, UCSD School of Medicine, 9500 Gilman Drive, La Jolla, California, 92093, United States of America
- University of California San Diego Moores Cancer Center, 3855 Health Sciences Drive, La Jolla, California, 92093, United States of America
- * E-mail:
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9
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Wang W, Guo L, Yu Y, Chen Z, Zhou R, Yuan Z. Peptide REDV-modified polysaccharide hydrogel with endothelial cell selectivity for the promotion of angiogenesis. J Biomed Mater Res A 2014; 103:1703-12. [PMID: 25103847 DOI: 10.1002/jbm.a.35306] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 07/28/2014] [Indexed: 11/06/2022]
Abstract
Rapid and controlled vascularization of engineered tissues remains one of the key limitations in thick tissue engineering. Although many studies have focused on improving the rapid vascularization through the immobilization of bioactive molecules, the competition in growth between endothelial cells (ECs) and other cell types is to some extent neglected. In this study, we developed a peptide GREDV-modified scaffold for selective adhesion of human umbilical vein endothelial cells (HUVECs) through the specific recognition of the REDV peptide and integrin α4 β1 . In vitro studies showed that GREDV-conjugated alginate (ALG-GREDV) improved HUVEC adhesion, migration and proliferation when compared with a non-modified group. Furthermore, ALG-GREDV exhibited a superior capability for promoting the proliferation and selective adhesion of HUVEC over that of other peptide (RGD and YIGSR) modified groups (ALG-Pep). In vivo angiogenic assays demonstrated that the ALG-GREDV scaffold induced an angiogenic potential by stimulating new vessel formation and showed the highest blood vessel density among all samples after 21 days of implanting (83.7 vessels/mm(2) ). More importantly, the blood vessel density in cambium fibrous tissue of ALG-GREDV was about 1.5 times greater than other ALG-Pep groups, indicating facilitation of ALG-GREDV on selective angiogenesis in vivo. These results demonstrated that REDV-conjugated alginate could be a useful scaffold for stimulating and inducing angiogenesis in tissue-engineered applications.
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Affiliation(s)
- Wei Wang
- Key Laboratory of Functional Polymer Materials of Ministry of Education, Institute of Polymer Chemistry, Nankai University, and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, 300071, China
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10
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Schlesinger M, Bendas G. Vascular cell adhesion molecule-1 (VCAM-1)--an increasing insight into its role in tumorigenicity and metastasis. Int J Cancer 2014; 136:2504-14. [PMID: 24771582 DOI: 10.1002/ijc.28927] [Citation(s) in RCA: 161] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Accepted: 04/16/2014] [Indexed: 12/14/2022]
Abstract
Vascular cell adhesion molecule-1 (VCAM-1) first attracted attention more than two decades ago as endothelial adhesion receptor with key function for leukocyte recruitment in term of cellular immune response. The early finding of VCAM-1 binding to melanoma cells, and thus a suggested mechanistic contribution to metastatic spread, was the first and for a long time the only link of VCAM-1 to cancer sciences. In the last few years, hallmarked by a growing insight into the molecular understanding of tumorigenicity and metastasis, an impressive variety of VCAM-1 functionalities in cancer have been elucidated. The present review aims to provide a current overview of VCAM-1 relevance for tumor growth, metastasis, angiogenesis, and related processes. By illustrating the intriguing role of VCAM-1 in cancer disease, VCAM-1 is suggested as a new and up to now underestimated target in cancer treatment and in clinical diagnosis of malignancies.
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Affiliation(s)
- Martin Schlesinger
- Department of Pharmacy, Rheinische Friedrich-Wilhelms-University Bonn, 53121, Bonn, Germany
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11
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Chua GL, Patra AT, Tan SM, Bhattacharjya S. NMR structure of integrin α4 cytosolic tail and its interactions with paxillin. PLoS One 2013; 8:e55184. [PMID: 23383101 PMCID: PMC3561355 DOI: 10.1371/journal.pone.0055184] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2012] [Accepted: 12/19/2012] [Indexed: 12/24/2022] Open
Abstract
Background Integrins are a group of transmembrane signaling proteins that are important in biological processes such as cell adhesion, proliferation and migration. Integrins are α/β hetero-dimers and there are 24 different integrins formed by specific combinations of 18 α and 8 β subunits in humans. Generally, each of these subunits has a large extracellular domain, a single pass transmembrane segment and a cytosolic tail (CT). CTs of integrins are important in bidirectional signal transduction and they associate with a large number of intracellular proteins. Principal Findings Using NMR spectroscopy, we determined the 3-D structure of the full-length α4 CT (Lys968-Asp999) and characterize its interactions with the adaptor protein paxillin. The α4 CT assumes an overall helical structure with a kink in its membrane proximal region. Residues Gln981-Asn997 formed a continuous helical conformation that may be sustained by potential ionic and/or hydrogen bond interactions and packing of aromatic-aliphatic side-chains. 15N-1H HSQC NMR experiments reveal interactions of the α4 CT C-terminal region with a fragment of paxillin (residues G139-K277) that encompassed LD2-LD4 repeats. Residues of these LD repeats including their adjoining linkers showed α4 CT binding-induced chemical shift changes. Furthermore, NMR studies using LD-containing peptides showed predominant interactions between LD3 and LD4 of paxillin and α4 CT. Docked structures of the α4 CT with these LD repeats suggest possible polar and/or salt-bridge and non-polar packing interactions. Significance The current study provides molecular insights into the structural diversity of α CTs of integrins and interactions of integrin α4 CT with the adaptor protein paxillin.
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Affiliation(s)
- Geok-Lin Chua
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Alok Tanala Patra
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Suet-Mien Tan
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- * E-mail: (SB); (SMT)
| | - Surajit Bhattacharjya
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- * E-mail: (SB); (SMT)
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12
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Byron A, Humphries JD, Craig SE, Knight D, Humphries MJ. Proteomic analysis of α4β1 integrin adhesion complexes reveals α-subunit-dependent protein recruitment. Proteomics 2012; 12:2107-14. [PMID: 22623428 PMCID: PMC3472074 DOI: 10.1002/pmic.201100487] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Integrin adhesion receptors mediate cell-cell and cell-extracellular matrix interactions, which control cell morphology and migration, differentiation, and tissue integrity. Integrins recruit multimolecular adhesion complexes to their cytoplasmic domains, which provide structural and mechanosensitive signaling connections between the extracellular and intracellular milieux. The different functions of specific integrin heterodimers, such as α4β1 and α5β1, have been attributed to distinct signal transduction mechanisms that are initiated by selective recruitment of adhesion complex components to integrin cytoplasmic tails. Here, we report the isolation of ligand-induced adhesion complexes associated with wild-type α4β1 integrin, an activated α4β1 variant in the absence of the α cytoplasmic domain (X4C0), and a chimeric α4β1 variant with α5 leg and cytoplasmic domains (α4Pα5L), and the cataloguing of their proteomes by MS. Using hierarchical clustering and interaction network analyses, we detail the differential recruitment of proteins and highlight enrichment patterns of proteins to distinct adhesion complexes. We identify previously unreported components of integrin adhesion complexes and observe receptor-specific enrichment of molecules with previously reported links to cell migration and cell signaling processes. Furthermore, we demonstrate colocalization of MYO18A with active integrin in migrating cells. These datasets provide a resource for future studies of integrin receptor-specific signaling events.
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Affiliation(s)
- Adam Byron
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, UK
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13
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Byron A, Humphries JD, Bass MD, Knight D, Humphries MJ. Proteomic analysis of integrin adhesion complexes. Sci Signal 2011; 4:pt2. [PMID: 21467297 DOI: 10.1126/scisignal.2001827] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Integrin receptors regulate cell fate by coupling the binding of extracellular adhesion proteins to the assembly of intracellular cytoskeletal and signaling complexes. A detailed, integrative view of adhesion complexes will provide insight into the molecular mechanisms that control cell morphology, survival, movement, and differentiation. To date, membrane receptor-associated signaling complexes have been refractory to proteomic analysis because of their inherent lability and inaccessibility. We developed a methodology to isolate ligand-induced integrin adhesion complexes, and we used this technique to analyze the composition of complexes associated with multiple receptor-ligand pairs and define core and receptor-specific subnetworks. In particular, we identified regulator of chromosome condensation-2 (RCC2) as a component of fibronectin-activated signaling pathways that regulate directional cell movement. The development of this proteomics pipeline provides the means to investigate the molecular composition and function of various adhesion complexes.
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Affiliation(s)
- Adam Byron
- Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, UK
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Faralli JA, Newman JR, Sheibani N, Dedhar S, Peters DM. Integrin-linked kinase regulates integrin signaling in human trabecular meshwork cells. Invest Ophthalmol Vis Sci 2011; 52:1684-92. [PMID: 21071740 DOI: 10.1167/iovs.10-6397] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To determine whether integrin-linked kinase (ILK) controls the organization of the actin cytoskeleton in the trabecular meshwork (TM) by regulating integrin co-signaling. METHODS The cell binding domain and the Heparin II (Hep II) domain of fibronectin were used to activate α5β1 and α4β1 integrin signaling, respectively, in differentiated human TM (HTM) cells. The role of ILK was determined using either ILK small interfering RNA (siRNA) to knockout ILK expression or the ILK inhibitors, KP392 and QLT0267. The knockdown of ILK expression was verified by Western blot analysis. The presence of actin stress fibers and focal adhesions was determined by labeling cultures with phalloidin and anti-talin or ILK antibodies, respectively. RESULTS Cell spreading in differentiated HTM cells required ILK, since ILK siRNA and the ILK inhibitors significantly reduced cell spreading, actin polymerization, and the localization of talin and ILK in focal adhesions (FAs). Both cell spreading and the localization of talin and ILK to FAs in differentiated HTM cells could be rescued by inducing α4β1 integrin signaling with a recombinant Hep II domain of fibronectin, even though α4β1 integrins were not found in FAs. In the absence of ILK inhibition, the Hep II domain had minimal effect on α5β1 integrin-mediated spreading. CONCLUSIONS This study suggests that cooperative α5β1/α4β1 integrin signaling may be regulated by ILK trans-dominantly and that alterations in ILK activity may affect actin cytoskeleton organization and contractility in the TM.
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Affiliation(s)
- Jennifer A Faralli
- Department of Pathology and Laboratory Medicine, University of Wisconsin, Madison, Wisconsin, USA
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15
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Humphries JD, Byron A, Bass MD, Craig SE, Pinney JW, Knight D, Humphries MJ. Proteomic analysis of integrin-associated complexes identifies RCC2 as a dual regulator of Rac1 and Arf6. Sci Signal 2009; 2:ra51. [PMID: 19738201 PMCID: PMC2857963 DOI: 10.1126/scisignal.2000396] [Citation(s) in RCA: 189] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The binding of integrin adhesion receptors to their extracellular matrix ligands controls cell morphology, movement, survival, and differentiation in various developmental, homeostatic, and disease processes. Here, we report a methodology to isolate complexes associated with integrin adhesion receptors, which, like other receptor-associated signaling complexes, have been refractory to proteomic analysis. Quantitative, comparative analyses of the proteomes of two receptor-ligand pairs, alpha(4)beta(1)-vascular cell adhesion molecule-1 and alpha(5)beta(1)-fibronectin, defined both core and receptor-specific components. Regulator of chromosome condensation-2 (RCC2) was detected in the alpha(5)beta(1)-fibronectin signaling network at an intersection between the Rac1 and adenosine 5'-diphosphate ribosylation factor 6 (Arf6) subnetworks. RCC2 knockdown enhanced fibronectin-induced activation of both Rac1 and Arf6 and accelerated cell spreading, suggesting that RCC2 limits the signaling required for membrane protrusion and delivery. Dysregulation of Rac1 and Arf6 function by RCC2 knockdown also abolished persistent migration along fibronectin fibers, indicating a functional role for RCC2 in directional cell movement. This proteomics workflow now opens the way to further dissection and systems-level analyses of adhesion signaling.
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Affiliation(s)
- Jonathan D. Humphries
- Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, Manchester M13 9PT, UK
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
| | - Adam Byron
- Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, Manchester M13 9PT, UK
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
| | - Mark D. Bass
- Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, Manchester M13 9PT, UK
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
| | - Sue E. Craig
- Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, Manchester M13 9PT, UK
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
| | - John W. Pinney
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
| | - David Knight
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
| | - Martin J. Humphries
- Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, Manchester M13 9PT, UK
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
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16
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Kucik DF. Measurement of adhesion under flow conditions. CURRENT PROTOCOLS IN CELL BIOLOGY 2009; Chapter 9:Unit 9.6. [PMID: 19499509 DOI: 10.1002/0471143030.cb0906s43] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
This unit describes the analysis of dynamic cell adhesion using a flow chamber assay. The flow chamber enables the researcher to reconstruct cell systems in the presence of shear stress to assay adhesion under well&defined forces. These assays are most commonly used to study leukocyte adhesion, either to cultured endothelial cell monolayers or to purified substrates, simulating physiological interactions of leukocytes with endothelial cells. This assay can be also be used to characterize transient adhesive events or adhesion strengthening even for cells that do not normally experience shear stress, because contact time between cells and substrates and anti&adhesive forces can be closely regulated by stopping and starting the flow. Flow chamber assays are also useful for measuring bacterial adhesion under flow.
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Affiliation(s)
- Dennis F Kucik
- University of Alabama at Birmingham, Birmingham, Alabama, USA
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17
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Cooperation between integrin alpha5 and tetraspan TM4SF5 regulates VEGF-mediated angiogenic activity. Blood 2008; 113:1845-55. [PMID: 19036703 DOI: 10.1182/blood-2008-05-160671] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tetraspan TM4SF5 is highly expressed in a diverse number of tumor types. Here we explore the mechanistic roles of TM4SF5 in angiogenesis. We found that TM4SF5 overexpression correlates with vascular endothelial growth factor (VEGF) expression in SNU449 hepatocytes and with vessel formation in clinical hepatocarcinoma samples. Conditioned media from TM4SF5-expressing cells enhanced viability and tube formation of primary human umbilical vein endothelial cells, and outgrowth of endothelial cells from aorta ring segments, which was abolished by treatment with an anti-VEGF antibody. TM4SF5 retained integrin alpha(5) on the cell surface for VEGF induction, and preincubation with anti-integrin alpha(5) antibody abolished TM4SF5-mediated VEGF expression and secretion. TM4SF5-mediated effects required integrin alpha(5), c-Src, and signal transducer and activator of transcription 3 (STAT3). In addition, tumors from nude mice injected with TM4SF5-expressing cells and from clinical human hepatocarcinoma tissues showed enhanced integrin alpha(5) expression, vessel formation, and signaling activity, which were inhibited by administration of anti-integrin alpha(5) or -VEGF antibody. This study suggests that TM4SF5 facilitates angiogenesis of neighboring endothelial cells through VEGF induction, mediated by cooperation between TM4SF5 and integrin alpha(5) of epithelial cells.
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18
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Weinländer K, Naschberger E, Lehmann MH, Tripal P, Paster W, Stockinger H, Hohenadl C, Stürzl M. Guanylate binding protein-1 inhibits spreading and migration of endothelial cells through induction of integrin alpha4 expression. FASEB J 2008; 22:4168-78. [PMID: 18697840 DOI: 10.1096/fj.08-107524] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Human guanylate binding protein-1 (GBP-1) is a large GTPase that is induced by inflammatory cytokines and acts antiangiogenically through the inhibition of endothelial cell proliferation and migration. In this study, we detected that GBP-1-expressing cells show a significantly reduced spreading and migration on fibronectin matrices. Investigating possible mechanisms of these effects, we found that integrin alpha(4) (ITGA4) was consistently up-regulated at both the RNA and protein level in GBP-1-expressing cell cultures. Inhibition of cell spreading and migration by GBP-1 was dependent on the binding of ITGA4 to fibronectin. The inflammatory cytokines IL-1beta and TNF-alpha induced ITGA4 expression in HUVECs and inhibited spreading and migration. Knockdown of GBP-1 by shRNA abrogated inflammatory cytokine induced ITGA4 expression and restored spreading and migration capabilities of the cells. These results show that inhibition of endothelial cell spreading and migration by inflammatory cytokines is mediated by GBP-1 through induction of ITGA4 expression. Endothelial cell migration is a key process during angiogenesis. Therefore, ITGA4 may be a novel molecular target to modulate angiogenesis in human disease.
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Affiliation(s)
- Kristina Weinländer
- Division of Molecular and Experimental Surgery, Department of Surgery, University of Erlangen-Nuremberg, Schwabachanlage 10, 91054 Erlangen, Germany
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19
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Abstract
This unit describes the analysis of dynamic cell adhesion using a flow chamber assay. The flow chamber enables the researcher to reconstruct cell systems in the presence of shear stress to assay adhesion under well&defined forces. These assays are most commonly used to study leukocyte adhesion, either to cultured endothelial cell monolayers or to purified substrates, simulating physiological interactions of leukocytes with endothelial cells. This assay can be also be used to characterize transient adhesive events or adhesion strengthening even for cells that do not normally experience shear stress, because contact time between cells and substrates and anti&adhesive forces can be closely regulated by stopping and starting the flow. Flow chamber assays are also useful for measuring bacterial adhesion under flow.
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Affiliation(s)
- Dennis F Kucik
- University of Alabama at Birmingham, Birmingham, Alabama, USA
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20
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Manevich E, Grabovsky V, Feigelson SW, Alon R. Talin 1 and Paxillin Facilitate Distinct Steps in Rapid VLA-4-mediated Adhesion Strengthening to Vascular Cell Adhesion Molecule 1. J Biol Chem 2007; 282:25338-48. [PMID: 17597073 DOI: 10.1074/jbc.m700089200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
VLA-4 (alpha4beta1) is a key integrin in lymphocytes, interacting with endothelial vascular cell adhesion molecule 1 (VCAM-1) on blood vessels and stroma. To dissect the contribution of the two cytoskeletal VLA-4 adaptor partners paxillin and talin to VLA-4 adhesiveness, we transiently knocked them down in Jurkat T cells and primary resting human T cells by small interfering RNA silencing. Paxillin was required for VLA-4 adhesiveness to low density VCAM-1 under shear stress conditions and was found to control mechanical stability of bonds mediated by the alpha4 subunit but did not affect the integrin affinity or avidity to VCAM-1 in shear-free conditions. Talin 1 maintained VLA-4 in a high affinity conformation, thereby promoting rapid VLA-4 adhesion strengthening to VCAM-1 under both shear stress and shear-free conditions. Talin 1, but not paxillin, was required for VLA-4 to undergo optimal stimulation by the prototypic chemokine, CXCL12, under shear stress conditions. Interestingly, talin 1 and paxillin played the same distinct roles in VLA-4 adhesions of primary T lymphocytes, although VLA-4 affinity to VCAM-1 was at least 200-fold lower in these cells than in Jurkat cells. Collectively, our results suggest that whereas paxillin is a mechanical regulator of VLA-4 bonds generated in the absence of chemokine signals and low VCAM-1 occupancy, talin 1 is a versatile VLA-4 affinity regulator implicated in both spontaneous and chemokine-triggered rapid adhesions to VCAM-1.
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Affiliation(s)
- Eugenia Manevich
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
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21
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Neurite outgrowth on a fibronectin isoform expressed during peripheral nerve regeneration is mediated by the interaction of paxillin with alpha4beta1 integrins. BMC Neurosci 2007; 8:44. [PMID: 17603879 PMCID: PMC1940015 DOI: 10.1186/1471-2202-8-44] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Accepted: 06/29/2007] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND The regeneration of peripheral nerve is associated with a change in the alternative splicing of the fibronectin primary gene transcript to re-express embryonic isoforms containing a binding site for alpha4beta1 integrins that promote neurite outgrowth. Here we use PC12 cells to examine the role of the interaction between paxillin and the alpha4 integrin cytoplasmic domain in neurite outgrowth. RESULTS Expression of alpha4 with mutations in the paxillin-binding domain reduced neurite outgrowth on recombinant embryonic fibronectin fragments relative to wild type alpha4. Over-expression of paxillin promoted neurite outgrowth while a mutant isoform lacking the LD4 domain implicated in the regulation of ARF and Rac GTPases was less effective. Optimal alpha4-mediated migration in leucocytes requires spatial regulation of alpha4 phosphorylation at Ser988, a post-translational modification that blocks paxillin binding to the integrin cytoplasmic domain. In keeping with this alpha4(S988D), which mimics phosphorylated alpha4, did not promote neurite outgrowth. However, alpha4 was not phosphorylated in the PC12 cells, and a non-phosphorylatable alpha4(S988A) mutant promoted neurite outgrowth indistinguishably from the wild type integrin. CONCLUSION We establish the importance of the alpha4 integrin-paxillin interaction in a model of axonal regeneration and highlight differing dependence on phosphorylation of alpha4 for extension of neuronal growth cones and migration of non-neural cells.
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22
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Lin KY, Lu D, Hung CF, Peng S, Huang L, Jie C, Murillo F, Rowley J, Tsai YC, He L, Kim DJ, Jaffee E, Pardoll D, Wu TC. Ectopic expression of vascular cell adhesion molecule-1 as a new mechanism for tumor immune evasion. Cancer Res 2007; 67:1832-41. [PMID: 17308126 PMCID: PMC3172051 DOI: 10.1158/0008-5472.can-06-3014] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Immune escape is an important reason why the immune system cannot control tumor growth, but how escape variants emerge during immunotherapy remains poorly understood. Here, we identify a new mechanism of tumor immune escape using an in vivo selection strategy. We generated a highly immune-resistant cancer cell line (P3) by subjecting a susceptible cancer cell line (P0/TC-1) to multiple rounds of in vivo immune selection. Microarray analysis of P0 and P3 revealed that vascular cell adhesion molecule-1 (VCAM-1) is up-regulated in the P3-resistant variant. Retroviral transfer of VCAM-1 into P0 significantly increased its resistance against a vaccine-induced immune response. Analysis of tumors showed a dramatic decrease in the number of tumor-infiltrating cluster of differentiation 8(+) (CD8(+)) T cells in the tumors expressing VCAM-1. In vitro transwell migration assays showed that VCAM-1 can promote the migration of CD8(+) T cells through its interaction with the alpha(4)beta(1) integrin. Site-directed mutagenesis of VCAM-1 at amino acid residues required for interaction with alpha(4)beta(1) integrin completely abolished the immune resistance conferred by VCAM-1 in vivo. Surface staining showed that most renal cell carcinomas (RCC) express VCAM-1, whereas an RCC that responded to vaccination was VCAM-1 negative. These data provide evidence that tumor expression of VCAM-1 represents a new mechanism of immune evasion and has important implications for the development of immunotherapy for human RCC.
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Affiliation(s)
- Ken-Yu Lin
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland
- Department of Oncology, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Dan Lu
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Chien-Fu Hung
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Shiwen Peng
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Lanqing Huang
- Department of Oncology, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Chunfa Jie
- Institute of Genetic Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Francisco Murillo
- Institute of Genetic Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Jesse Rowley
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Ya-Chea Tsai
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Liangmei He
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Dae-Jin Kim
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Elizabeth Jaffee
- Department of Oncology, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Drew Pardoll
- Department of Oncology, Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - T.-C. Wu
- Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland
- Department of Obstetrics and Gynecology, Johns Hopkins Medical Institutions, Baltimore, Maryland
- Department of Molecular Microbiology and Immunology, Johns Hopkins Medical Institutions, Baltimore, Maryland
- Department of Oncology, Johns Hopkins Medical Institutions, Baltimore, Maryland
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23
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Kummer C, Ginsberg MH. New approaches to blockade of alpha4-integrins, proven therapeutic targets in chronic inflammation. Biochem Pharmacol 2006; 72:1460-8. [PMID: 16870156 DOI: 10.1016/j.bcp.2006.06.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2006] [Revised: 06/09/2006] [Accepted: 06/12/2006] [Indexed: 10/24/2022]
Abstract
The recruitment of leukocytes into tissue is a pivotal step in inflammation. alpha4-Integrins are adhesion receptors on circulating leukocytes that mediate attachment to the endothelium and facilitate their migration into the inflamed tissue. This multistep process is mediated by the interaction of alpha4-integrins with their counter receptors VCAM-1 and MadCAM-1 that are expressed on endothelial cells. alpha4-Integrins act as both adhesive and signaling receptors. Paxillin, a signaling adaptor molecule, binds directly to the alpha4 cytoplasmic tail and its binding is important for cell migration. Blocking the adhesive functions of alpha4-integrins has been shown to be an effective therapeutic approach in the treatment of autoimmune diseases, but also carries the risk of defects in development, hematopoiesis and immune surveillance. Interfering with alpha4 signaling by inhibiting the alpha4-paxillin interaction decreases alpha4-mediated cell migration and adhesion to VCAM-1 and MadCAM under shear flow. These in vitro effects are accompanied by a selective impairment of leukocyte migration into inflammatory sites when the alpha4-paxillin interaction is blocked in vivo. Thus, blockade of alpha4-integrin signaling may offer a novel strategy for interfering with the functions of these receptors in pathological events while sparing important physiological functions.
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Affiliation(s)
- Christiane Kummer
- Department of Medicine, University of California-San Diego, 9500 Gilman Drive 0726, La Jolla, CA 92093, USA.
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24
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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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25
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Valenick LV, Schwarzbauer JE. Ligand density and integrin repertoire regulate cellular response to LPA. Matrix Biol 2006; 25:223-31. [PMID: 16503403 DOI: 10.1016/j.matbio.2006.01.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Revised: 12/06/2005] [Accepted: 01/04/2006] [Indexed: 01/24/2023]
Abstract
Engagement of integrin receptors by the extracellular matrix (ECM) protein fibronectin (FN) activates intracellular signaling, cytoskeletal reorganization and cellular tension. The soluble factor lysophosphatidic acid (LPA) acts through Rho GTPase and its effector Rho kinase (ROCK) to enhance alpha5beta1 integrin-mediated cell spreading on the Arg-Gly-Asp (RGD) cell-binding domain of FN. A second cell-binding site for alpha4 integrins resides in the CS1 segment of the alternatively spliced V region of FN. We show here that LPA treatment of alpha4beta1-expressing CHOalpha4 cells on FN induced a significant decrease in spread cell area. LPA also decreased apoptosis induced by serum-deprivation in CHOalpha4 and human A375 melanoma cells in an alpha4beta1-dependent manner. Improvement in cell viability and changes in cell morphology were dependent on ROCK and on the number of substrate binding sites for alpha4beta1. LPA signaling combined with alpha4beta1-mediated adhesion appears to sustain cell viability in situations where FN matrix is limiting. Such cooperation may impact dynamic cellular events such as wound healing, fibrosis, and metastasis.
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Affiliation(s)
- Leyla V Valenick
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544-1014, USA
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26
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Humphries JD, Schofield NR, Mostafavi-Pour Z, Green LJ, Garratt AN, Mould AP, Humphries MJ. Dual functionality of the anti-beta1 integrin antibody, 12G10, exemplifies agonistic signalling from the ligand binding pocket of integrin adhesion receptors. J Biol Chem 2005; 280:10234-43. [PMID: 15632175 PMCID: PMC3327468 DOI: 10.1074/jbc.m411102200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although integrins are known to mediate connections between extracellular adhesion molecules and the intracellular actin cytoskeleton, the mechanisms that are responsible for coupling ligand binding to intracellular signaling, for generating diversity in signaling, and for determining the efficacy of integrin signaling in response to ligand engagement are largely unknown. By characterizing the class of anti-integrin monoclonal antibodies (mAbs) that stimulate integrin activation and ligand binding, we have identified integrin-ligand-mAb complexes that exhibit differential signaling properties. Specifically, addition of 12G10 mAb to cells adhering via integrin alpha4beta1 was found to trigger disruption of the actin cytoskeleton and prevent cell attachment and spreading, whereas mAb addition to cells adhering via alpha5beta1 stimulated all of these processes. In contrast, soluble ligand binding to either alpha4beta1 or alpha5beta1 was augmented or unaffected by 12G10. The regions of the integrin responsible for differential signaling were then mapped using chimeras. Surprisingly, a chimeric alpha5 integrin containing the beta-propeller domain from the ligand binding pocket of alpha4 exhibited the same signaling properties as the full-length alpha4 integrin, whereas exchanging or removing cytoplasmic domains had no effect. Thus the mAb 12G10 demonstrates dual functionality, inhibiting cell adhesion and spreading while augmenting soluble ligand binding, via a mechanism that is determined by the extracellular beta-propeller domain of the associating alpha-subunit. These findings therefore demonstrate a direct and variable agonistic link between the ligand binding pocket of integrins and the cell interior that is independent of the alpha cytoplasmic domains. We propose that either ligand-specific transmembrane conformational changes or ligand-specific differences in the kinetics of transmembrane domain separation underlie integrin agonism.
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Affiliation(s)
- Jonathan D. Humphries
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, United Kingdom
| | - Neil R. Schofield
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, United Kingdom
| | | | - Linda J. Green
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, United Kingdom
| | | | - A. Paul Mould
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, United Kingdom
| | - Martin J. Humphries
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, United Kingdom
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27
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Chen C, Young BA, Coleman CS, Pegg AE, Sheppard D. Spermidine/spermine N1-acetyltransferase specifically binds to the integrin alpha9 subunit cytoplasmic domain and enhances cell migration. ACTA ACUST UNITED AC 2004; 167:161-70. [PMID: 15479742 PMCID: PMC2172529 DOI: 10.1083/jcb.200312166] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The integrin α9β1 is expressed on migrating cells, such as leukocytes, and binds to multiple ligands that are present at sites of tissue injury and inflammation. α9β1, like the structurally related integrin α4β1, mediates accelerated cell migration, an effect that depends on the α9 cytoplasmic domain. α4β1 enhances migration through reversible binding to the adapter protein, paxillin, but α9β1-dependent migration is paxillin independent. Using yeast two-hybrid screening, we identified the polyamine catabolizing enzyme spermidine/spermine N1-acetyltransferase (SSAT) as a specific binding partner of the α9 cytoplasmic domain. Overexpression of SSAT increased α9β1-mediated migration, and small interfering RNA knockdown of SSAT inhibited this migration without affecting cell adhesion or migration that was mediated by other integrin cytoplasmic domains. The enzyme activity of SSAT is critical for this effect, because a catalytically inactive version did not enhance migration. We conclude that SSAT directly binds to the α9 cytoplasmic domain and mediates α9-dependent enhancement of cell migration, presumably by localized effects on acetylation of polyamines or of unidentified substrates.
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Affiliation(s)
- Chun Chen
- Lung Biology Center, Department of Medicine, University of California-San Francisco, San Francisco, CA 94110, USA
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28
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Paxillin selectively associates with constitutive and chemoattractant-induced high-affinity α4β1 integrins: implications for integrin signaling. Blood 2004; 104:2818-24. [DOI: 10.1182/blood-2003-12-4402] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractLeukocyte α4β1 integrins regulate hematopoietic and lymphoid development, as well as the emigration of circulating cells to sites of inflammation. Because vascular cell adhesion molecule-1 (VCAM-1) binding to high-affinity α4β1 is stable, these integrins can be detected and selectively precipitated from cell lysates using VCAM-1/Fc. With this approach, high-affinity α4β1 integrin expression was demonstrated on lymphocytes in the bone marrow, thymus, spleen, and the peritoneal cavity of normal mice, but not in peripheral lymph nodes. Immature lymphocytes preferentially expressed high-affinity α4β1 in the bone marrow and thymus. Paxillin is a cytoplasmic adaptor molecule that can bind to the α4 tail and initiate signaling. Paxillin was associated selectively with high-affinity integrins that were isolated from human Jurkat T cells or from murine tissues, and blotting with a phospho-specific antibody demonstrated that Ser988 in the α4 cytoplasmic tail was dephosphorylated in high-affinity but not low-affinity integrins. A rapid and transient α4β1 affinity up-regulation in formyl peptide receptor-transfected U937 cells stimulated with N-formyl-methyonyl-leucyl-phenylalanine (fMLP) correlated temporally with induced paxillin binding to α4 integrins. These data suggest that ligand binding to high-affinity α4β1 integrins may initiate outside-in signaling cascades through paxillin that regulate leukocyte maturation and emigration. (Blood. 2004;104:2818-2824)
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Johansson MW, Lye MH, Barthel SR, Duffy AK, Annis DS, Mosher DF. Eosinophils adhere to vascular cell adhesion molecule-1 via podosomes. Am J Respir Cell Mol Biol 2004; 31:413-22. [PMID: 15220135 DOI: 10.1165/rcmb.2004-0099oc] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Vascular cell adhesion molecule (VCAM)-1 supports specific eosinophil adhesion via alpha4beta1 integrin. We tested the hypothesis that adhesive contacts formed by eosinophils on VCAM-1 are different from focal adhesions formed by adherent fibroblasts. Eosinophils adherent on VCAM-1 formed punctate adhesions that fit the criteria for podosomes, highly dynamic structures found in adherent transformed fibroblasts, osteoclasts, and macrophages. The structures contained beta1 integrin subunit, phosphotyrosine-containing proteins, punctate filamentous actin, and gelsolin, a podosome marker. In contrast, nontransformed fibroblasts on VCAM-1 formed peripheral focal adhesions that were positive for alpha4, beta1, phosphotyrosine, vinculin, talin, and paxillin; negative for gelsolin; and associated with microfilaments. Phorbol myristate acetate or tumor necrosis factor-alpha and interleukin-5 stimulated podosome formation in adherent eosinophils. Because podosomes in tumor cells are associated with extracellular matrix degradation, we analyzed the VCAM-1 layer. VCAM-1 was lost under adherent eosinophils but not under adherent fibroblasts. This loss was inhibited by the metalloproteinase inhibitor ortho-phenanthroline and correlated with expression and podosome localization of a membrane-tethered metalloproteinase, a disintegrin and metalloproteinase domain 8. Podosome-mediated VCAM-1 clearance may be a mechanism to regulate eosinophil arrest and extravasation in allergic conditions such as asthma.
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Affiliation(s)
- Mats W Johansson
- Department of Medicine, University of Wisconsin, 4285A, Medical Sciences Center, 1300 University Avenue, Madison, WI 53706-1532, USA.
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Liu JC, Heilshorn SC, Tirrell DA. Comparative Cell Response to Artificial Extracellular Matrix Proteins Containing the RGD and CS5 Cell-Binding Domains. Biomacromolecules 2004; 5:497-504. [PMID: 15003012 DOI: 10.1021/bm034340z] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This study addresses endothelial cell adhesion and spreading on a family of artificial extracellular matrix (aECM) proteins designed for application in small-diameter vascular grafts. The aECM proteins contain domains derived from elastin and from fibronectin. aECM 1 contains the RGD sequence from the tenth type III domain of fibronectin; aECM 3 contains the fibronectin CS5 cell-binding domain. Negative control proteins aECM 2 and 4 are scrambled versions of aECM 1 and 3, respectively. Competitive peptide inhibition studies and comparisons of positive and negative control proteins confirm that adhesion of HUVECs to aECM proteins 1 and 3 is sequence specific. When subjected to a normal detachment force of 780 pN, 3-fold more HUVECs remained adherent to aECM 1 than to aECM 3. HUVECs also spread more rapidly on aECM 1 than on aECM 3. These results (i) indicate that cellular responses to aECM proteins can be modulated through choice of cell-binding domain and (ii) recommend the RGD sequence for applications that require rapid endothelial cell spreading and matrix adhesion.
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Affiliation(s)
- Julie C Liu
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Mail Code 210-41, Pasadena, California 91125, USA
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31
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Alon R, Etzioni A. LAD-III, a novel group of leukocyte integrin activation deficiencies. Trends Immunol 2004; 24:561-6. [PMID: 14552841 DOI: 10.1016/j.it.2003.08.001] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
To extravasate the bloodstream at specific targets, circulating immune cells must activate their integrins to undergo rapid in situ modulation of affinity or avidity for their endothelial ligands. This activation involves specialized sub-second G-protein signal transduction triggered by endothelium-displayed chemoattractants--primarily chemokines--and their cognate leukocyte-expressed G-protein-coupled receptors (GPCRs). Recently, we reported a rare autosomal-recessive leukocyte adhesion deficiency (LAD) syndrome associated with a defective ability of integrins to undergo GPCR-mediated stimulation at endothelial contacts. This LAD shows significant similarities to a group of integrin-activation syndromes reported in leukocytes and platelets. Here, the mechanisms by which GPCRs might regulate leukocyte and platelet integrins are outlined with respect to this new family of LAD cases. We propose to term this the LAD-III family.
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Affiliation(s)
- Ronen Alon
- Department of Immunology, The Weizmann Institute of Science, 76100 Rehovot, Israel.
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Luong JH, Xiao C, Lachance B, Leabu Š, Li X, Uniyal S, Chan BM. Extended applications of electric cell-substrate impedance sensing for assessment of the structure–function of α2β1 integrin. Anal Chim Acta 2004. [DOI: 10.1016/j.aca.2003.09.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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33
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Leabu M, Uniyal S, Xie J, Xu YQ, Vladau C, Morris VL, Chan BMC. Integrin ?2?1 modulates EGF stimulation of Rho GTPase-dependent morphological changes in adherent human rhabdomyosarcoma RD cells. J Cell Physiol 2004; 202:754-66. [PMID: 15481063 DOI: 10.1002/jcp.20163] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The ability of cells to undergo shape changes is essential for diverse cellular functions including cell growth, differentiation, and movement. The present study examines how an integration of the function of alpha2beta1 integrin with that of the receptor for epidermal growth factor (EGFR) modulates EGF-stimulated morphological changes in human rhabdomyosarcoma RD transfectant cells. Upon EGF stimulation, RD transfectant cells that lacked alpha2beta1 integrin expression (RDpF) underwent contraction; in contrast, expression of alpha2beta1 on RD cells (RDX2C2) resulted in transient cell spreading. Integrin alpha2 cytoplasmic domain played a critical role in the observed alpha2beta1-mediated conversion from a cell rounding to a cell spreading phenotype. Thus, the expression of an alpha2 cytoplasmic domain deletion variant (X2C0) or a chimeric alpha2beta1 containing the cytoplasmic domain of alpha4 (X2C4) or alpha5 (X2C5), instead of alpha2, failed to mediate spreading upon EGF stimulation. Using dominant negative (DN) mutants of RhoGTPases, results revealed that RhoA activation was required for both EGF-stimulated responses of cell rounding and spreading, Cdc42 functioned in the re-spreading of cells after undergoing EGF-stimulated contraction, and Rac1 was required in alpha2beta1-mediated RD cell spreading. Therefore, alpha2beta1 integrin function can switch the Rho GTPase-dependent cell shape changes in RD cells from an EGF-stimulated cell contraction to a spreading morphology. Together, results show that integrin alpha2 cytoplasmic domain plays an indispensable role in the ability of integrin alpha2beta1 to modulate EGF stimulation of Rho-GTPase-dependent morphological changes in RD cells.
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Affiliation(s)
- M Leabu
- Department of Cellular and Molecular Medicine, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
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Feigelson SW, Grabovsky V, Shamri R, Levy S, Alon R. The CD81 Tetraspanin Facilitates Instantaneous Leukocyte VLA-4 Adhesion Strengthening to Vascular Cell Adhesion Molecule 1 (VCAM-1) under Shear Flow. J Biol Chem 2003; 278:51203-12. [PMID: 14532283 DOI: 10.1074/jbc.m303601200] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Leukocyte integrins must rapidly strengthen their binding to target endothelial sites to arrest rolling adhesions under physiological shear flow. We demonstrate that the integrin-associated tetraspanin, CD81, regulates VLA-4 and VLA-5 adhesion strengthening in monocytes and primary murine B cells. CD81 strengthens multivalent VLA-4 contacts within subsecond integrin occupancy without altering intrinsic adhesive properties to low density ligand. CD81 facilitates both VLA-4-mediated leukocyte rolling and arrest on VCAM-1 under shear flow as well as VLA-5-dependent adhesion to fibronectin during short stationary contacts. CD81 also augments VLA-4 avidity enhancement induced by either chemokine-stimulated Gi proteins or by protein kinase C activation, although it is not required for Gi protein or protein kinase C signaling activities. In contrast to other proadhesive integrin-associated proteins, CD81-promoted integrin adhesiveness does not require its own ligand occupancy or ligation. These results provide the first demonstration of an integrin-associated transmembranal protein that facilitates instantaneous multivalent integrin occupancy events that promote leukocyte adhesion to an endothelial ligand under shear flow.
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Affiliation(s)
- Sara W Feigelson
- Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel 76100
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35
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Boyd ND, Chan BMC, Petersen NO. β1integrins are distributed in adhesion structures with fibronectin and caveolin and in coated pits. Biochem Cell Biol 2003; 81:335-48. [PMID: 14569297 DOI: 10.1139/o03-063] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Integrins are found in adhesion structures, which link the extracelullar matrix to cytoskeletal proteins. Here, we attempt to further define the distribution of β1integrins in the context of their association with matrix proteins and other cell surface molecules relevant to the endocytic process. We find that β1integrins colocalize with fibronectin in fibrillar adhesion structures. A fraction of caveolin is also organized along these adhesion structures. The extracellular matrix protein laminin is not concentrated in these structures. The α4β1integrin exhibits a distinct distribution from other β1integrins after cells have adhered for 1 h to extracellular matrix proteins but is localized in adhesion structures after 24 h of adhesion. There are differences between the fibronectin receptors: α5β1integrins colocalize with adaptor protein-2 in coated pits, while α4β1integrins do not. This parallels our earlier observation that of the two laminin receptors, α1β1and α6β1, only αaβ1integrins colocalize with adaptor protein-2 in coated pits. Calcium chelation or inhibition of mitogen-activated protein kinase kinase, protein kinase C, or src did not affect localization of α1β1and α5β1integrins in coated pits. Likewise, the integrity of coated-pit structures or adhesion structures is not required for integrin and adaptor protein-2 colocalization. This suggests a robust and possibly constitutive interaction between these integrins and coated pits.Key words: adhesion, endocytosis, extracellular matrix, microscopy, confocal, signalling.
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Affiliation(s)
- Nikhat D Boyd
- Department of Biochemistry, The University of Western Ontario, London, Canada
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Han J, Rose DM, Woodside DG, Goldfinger LE, Ginsberg MH. Integrin alpha 4 beta 1-dependent T cell migration requires both phosphorylation and dephosphorylation of the alpha 4 cytoplasmic domain to regulate the reversible binding of paxillin. J Biol Chem 2003; 278:34845-53. [PMID: 12837751 DOI: 10.1074/jbc.m304691200] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
alpha 4 integrins mediate increased cell migration and decreased cell spreading because the alpha 4 cytoplasmic domain (tail) binds tightly to paxillin, a signaling adaptor protein. Paxillin binding to the alpha 4 tail is blocked by alpha 4 phosphorylation at Ser988. To establish the biological role of alpha 4 phosphorylation, we reconstituted alpha 4-deficient Jurkat T cells with phosphorylation-mimicking (alpha 4(S988D)) or non-phosphorylatable (alpha 4(S988A)) mutants. alpha 4(S988D) disrupted paxillin binding and also inhibited cell migration and promoted cell spreading. In contrast, the non-phosphorylatable alpha 4(S988A) resulted in a further reduction in cell spreading; however, this mutation led to an unexpected suppression of cell migration. The suppression of cell migration by alpha 4(S988A) was ascribable to enhanced alpha 4-paxillin association, because enforced association by an alpha 4-paxillin fusion led to a phenotype similar to that of the non-phosphorylatable alpha 4(S988A) mutant. These data establish that optimal alpha 4-mediated cell migration requires both phosphorylation and dephosphorylation of the alpha 4 cytoplasmic domain to regulate the reversible binding of paxillin.
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Affiliation(s)
- Jaewon Han
- Department of Cell Biology, Division of Vascular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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37
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Goldfinger LE, Han J, Kiosses WB, Howe AK, Ginsberg MH. Spatial restriction of alpha4 integrin phosphorylation regulates lamellipodial stability and alpha4beta1-dependent cell migration. J Cell Biol 2003; 162:731-41. [PMID: 12913113 PMCID: PMC2173787 DOI: 10.1083/jcb.200304031] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Integrins coordinate spatial signaling events essential for cell polarity and directed migration. Such signals from alpha4 integrins regulate cell migration in development and in leukocyte trafficking. Here, we report that efficient alpha4-mediated migration requires spatial control of alpha4 phosphorylation by protein kinase A, and hence localized inhibition of binding of the signaling adaptor, paxillin, to the integrin. In migrating cells, phosphorylated alpha4 accumulated along the leading edge. Blocking alpha4 phosphorylation by mutagenesis or by inhibition of protein kinase A drastically reduced alpha4-dependent migration and lamellipodial stability. alpha4 phosphorylation blocks paxillin binding in vitro; we now find that paxillin and phospho-alpha4 were in distinct clusters at the leading edge of migrating cells, whereas unphosphorylated alpha4 and paxillin colocalized along the lateral edges of those cells. Furthermore, enforced paxillin association with alpha4 inhibits migration and reduced lamellipodial stability. These results show that topographically specific integrin phosphorylation can control cell migration and polarization by spatial segregation of adaptor protein binding.
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Affiliation(s)
- Lawrence E Goldfinger
- Department of Cell Biology, Division of Vascular Biology, The Scripps Research Institute, 10550 N. Torrey Pines Road, VB-2 La Jolla, CA 92037, USA
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Chan BMC, Morris VL, Hangan-Steinman D, Jarvie B, Cialacu M, Laansoo J, Hunter G, Wan W, Uniyal S. Integrin alpha2beta1 on rat myeloma cells modulates interaction of alpha4beta1 integrin with vascular cell adhesion molecule-1 but not fibronectin. JOURNAL OF BIOMATERIALS SCIENCE. POLYMER EDITION 2003; 13:429-46. [PMID: 12160302 DOI: 10.1163/156856202320253947] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
It is well established that alpha2beta1 integrin functions as a receptor for collagen and laminin; whereas alpha4beta1 integrin binds fibronectin and vascular cell adhesion molecule-1 (VCAM-1). In the present study, we showed that rat myeloma YB2/0 cells constitutively expressed alpha4beta1 but not alpha2beta1 integrin. Transfection of cDNA of mouse a2 integrin subunit resulted in the expression of heterologous alpha2beta1 integrin on YB2/0 cells (YBmalpha2). The expression of alpha2beta1 conferred YBmalpha2 cells the ability to interact with collagen and laminin. In comparison with mock transfected YB2/0 cells (YBpF), YBmalpha2 cells exhibited increases in the binding and migration on VCAM-1; in contrast, both YBpF and YBmalpha2 were similar in their interactions with fibronectin or fibronectin fragment FN-40 that contains the binding site for alpha4beta1 integrin. The interaction of alpha4beta1 with VCAM-1 was further stimulated upon ligation with alpha2beta1-specific mAb. The use of specific inhibitory mAb demonstrated the role of alpha4beta1 in mediating the observed interactions with fibronectin and VCAM-1. Therefore, results show that expression of alpha2beta1 differentially regulated alpha4alpha1 integrin function by stimulating its interactions with VCAM-1 but not fibronectin. The in vivo significance of alpha2beta1 integrin expression was demonstrated by intravital videomicroscopy showing that ligation of alpha2beta1 enhanced alpha4beta1-mediated extravasation of YBmalpha2 cells in the liver.
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Affiliation(s)
- Bosco M C Chan
- Biotherapeutic Research Group, The John P. Robarts Research Institute, London, Ontario, Canada
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39
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Dettman RW, Pae SH, Morabito C, Bristow J. Inhibition of alpha4-integrin stimulates epicardial-mesenchymal transformation and alters migration and cell fate of epicardially derived mesenchyme. Dev Biol 2003; 257:315-28. [PMID: 12729561 DOI: 10.1016/s0012-1606(03)00064-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Epithelial-mesenchymal transformation of the embryonic epicardium produces the subepicardial mesenchyme that is essential for normal coronary vascular development. Gene targeting experiments in mice have demonstrated an essential role for alpha4-integrin in normal epicardial development, but the precise cellular consequences of alpha4-integrin loss remain uncertain. To better understand the function of alpha4-integrin in epicardial development, we constructed a replication-incompetent adenovirus (AdlacZalpha4AS) that expresses antisense chicken alpha4-integrin as the 3' untranslated region of a lacZ reporter gene. This construct effectively labeled cells while greatly reducing levels of alpha4-integrin mRNA and protein. In quail chick chimeras, transplanted epicardial cells infected with AdlacZalpha4AS adhered to the heart and were incorporated into the epicardium, but 4 days after grafting, were largely absent from the epicardial epithelium, recapitulating the defect in alpha4-null mice. This did not result from epicardial cell apoptosis or anomalous migration of epicardial cells to extracardiac sites. Rather, AdlacZalpha4AS-infected epicardial cells were particularly invasive, being three to four times more likely to migrate to the interstitium of the myocardium than AdlacZ-infected epicardial cells. Accelerated epicardial-mesenchymal transformation and migration of alpha4-negative epicardium was observed in an organ culture system that does not require prior culture of epicardial cells. Remarkably, AdlacZalpha4AS infection also prevented targeting of epicardially derived mesenchyme to the media of developing coronary vasculature in the myocardial interstitium. This study provides evidence that epicardial alpha4-integrin normally restrains epicardial-mesenchymal transformation, invasion, and migration and is essential for correct targeting of epicardially derived mesenchyme to the developing coronary vasculature.
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Affiliation(s)
- Robert W Dettman
- Department of Pediatrics, Northwestern University, Neonatology Research Laboratory, 303 E. Chicago Avenue, Chicago, IL 60611, USA.
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40
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Mostafavi-Pour Z, Askari JA, Parkinson SJ, Parker PJ, Ng TTC, Humphries MJ. Integrin-specific signaling pathways controlling focal adhesion formation and cell migration. J Cell Biol 2003; 161:155-67. [PMID: 12695503 PMCID: PMC2172880 DOI: 10.1083/jcb.200210176] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.3] [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
The fibronectin (FN)-binding integrins alpha4beta1 and alpha5beta1 confer different cell adhesive properties, particularly with respect to focal adhesion formation and migration. After analyses of alpha4+/alpha5+ A375-SM melanoma cell adhesion to fragments of FN that interact selectively with alpha4beta1 and alpha5beta1, we now report two differences in the signals transduced by each receptor that underpin their specific adhesive properties. First, alpha5beta1 and alpha4beta1 have a differential requirement for cell surface proteoglycan engagement for focal adhesion formation and migration; alpha5beta1 requires a proteoglycan coreceptor (syndecan-4), and alpha4beta1 does not. Second, adhesion via alpha5beta1 caused an eightfold increase in protein kinase Calpha (PKCalpha) activation, but only basal PKCalpha activity was observed after adhesion via alpha4beta1. Pharmacological inhibition of PKCalpha and transient expression of dominant-negative PKCalpha, but not dominant-negative PKCdelta or PKCzeta constructs, suppressed focal adhesion formation and cell migration mediated by alpha5beta1, but had no effect on alpha4beta1. These findings demonstrate that different integrins can signal to induce focal adhesion formation and migration by different mechanisms, and they identify PKCalpha signaling as central to the functional differences between alpha4beta1 and alpha5beta1.
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Spessotto P, Cervi M, Mucignat MT, Mungiguerra G, Sartoretto I, Doliana R, Colombatti A. beta 1 Integrin-dependent cell adhesion to EMILIN-1 is mediated by the gC1q domain. J Biol Chem 2003; 278:6160-7. [PMID: 12456677 DOI: 10.1074/jbc.m208322200] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
EMILIN-1 (Elastin Microfibril Interface Located ProteIN), the prototype of the EMILIN family, consists of a cysteine-rich domain (EMI domain) at the N terminus, an extended region with a high potential coiled-coil structure, a short collagenous stalk, and a self-interacting globular gC1q-l domain. EMILIN-1 is an adhesive extracellular matrix constituent associated with elastic fibers, detected also in the proximity of cell surfaces. To localize the cell attachment site(s), monoclonal antibodies (mAbs) against EMILIN-1 or the gC1q-1 domain were used to inhibit cell attachment to EMILIN-1. Thus, one mAb mapping to the gC1q-1 domain caused complete inhibition of cell attachment. EMILIN-1 and gC1q-1 displayed a comparable dose-dependent ability to promote cell adhesion. Adhesion kinetics was similar to that of fibronectin (FN), reaching the maximum level of attachment at 20 min, but in the absence of cations adhesion was negligible. The relative adhesion strength to detach 50% of the cells was similar for EMILIN-1 and gC1q-1 (250-270 x g) but lower than that for FN (>>500). Cell adhesion to EMILIN-1 or gC1q-1 was completely blocked by a function-blocking beta(1) integrin subunit mAb. In contrast, adhesion to the complement C1q component was totally unaffected. Among the various function-blocking mAbs against the alpha integrin subunits only the anti-alpha(4) fully abrogated cell adhesion to gC1q-1 and up to 70% to EMILIN-1. Furthermore, only K562 cells transfected with the alpha(4) integrin chain, but not wild type K562, were able to adhere to EMILIN-1 and were specifically inhibited by anti-alpha(4) function-blocking mAb. Finally, cells attached to EMILIN-1 or gC1q-1, compared with cells plated on FN or vitronectin, which appeared well spread out on the substrate with prominent stress fibers and focal contacts, were much smaller with wide ruffles and a different organization status of the actin cytoskeleton along the cell periphery. This pattern was in accord with the ability of EMILIN-1 to promote cell movement.
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Affiliation(s)
- Paola Spessotto
- Divisione di Oncologia Sperimentale 2, Centro di Riferimento Oncologico, Aviano, Italy
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Pinco KA, He W, Yang JT. alpha4beta1 integrin regulates lamellipodia protrusion via a focal complex/focal adhesion-independent mechanism. Mol Biol Cell 2002; 13:3203-17. [PMID: 12221126 PMCID: PMC124153 DOI: 10.1091/mbc.02-05-0086] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
alpha4beta1 integrin plays an important role in cell migration. We show that when ectopically expressed in Chinese hamster ovary cells, alpha4beta1 is sufficient and required for promoting protrusion of broad lamellipodia in response to scratch-wounding, whereas alpha5beta1 does not have this effect. By time-lapse microscopy of cells expressing an alpha4/green fluorescent protein fusion protein, we show that alpha4beta1 forms transient puncta at the leading edge of cells that begin to protrude lamellipodia in response to scratch-wounding. The cells expressing a mutant alpha4/green fluorescent protein that binds paxillin at a reduced level had a faster response to scratch-wounding, forming alpha4-positive puncta and protruding lamellipodia much earlier. While enhancing lamellipodia protrusion, this mutation reduces random motility of the cells in Transwell assays, indicating that lamellipodia protrusion and random motility are distinct types of motile activities that are differentially regulated by interactions between alpha4beta1 and paxillin. Finally, we show that, at the leading edge, alpha4-positive puncta and paxillin-positive focal complexes/adhesions do not colocalize, but alpha4beta1 and paxillin colocalize partially in ruffles. These findings provide evidence for a specific role of alpha4beta1 in lamellipodia protrusion that is distinct from the motility-promoting functions of alpha5beta1 and other integrins that mediate cell adhesion and signaling events through focal complexes and focal adhesions.
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Affiliation(s)
- Karen A Pinco
- Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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Cunningham SA, Rodriguez JM, Arrate MP, Tran TM, Brock TA. JAM2 interacts with alpha4beta1. Facilitation by JAM3. J Biol Chem 2002; 277:27589-92. [PMID: 12070135 DOI: 10.1074/jbc.c200331200] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have previously reported that junctional adhesion molecule 2 (JAM2) adheres to T cells through heterotypic interactions with JAM3. An examination of the cation dependence of JAM2 adhesion to HSB cells revealed a Mn(2+)-enhanced binding component indicative of integrin involvement. Using neutralizing integrin antibodies, we have defined an interaction between JAM2 and alpha(4)beta(1) in T cells. The interaction is readily amenable to drug intervention as demonstrated by the ability of TBC 772, an alpha(4)-specific inhibitor, to attenuate the Mn(2+)-enhanced component. Intriguingly, the engagement of alpha(4)beta(1) by JAM2 is only enabled following prior adhesion of JAM2 with JAM3 and is not detectable in cells where JAM3 expression is absent. Supporting this observation, we show that neutralizing JAM3 serum and soluble JAM3 ectodomain inhibit not only JAM2 binding to JAM3 but also prevent JAM2/alpha(4)beta(1) interactions in T cells. We further define the first Ig-like fold of JAM2 as being competent in binding both JAM3 and alpha(4)beta(1) counter-receptors. Mutagenesis of the only acidic residue in the C-D loop of this Ig fold, namely Asp-82, has no bearing on alpha(4)beta(1) interactions, and thus JAM2 deviates somewhat from the mechanism used by other immunoglobulin superfamily cell adhesion molecules to engage integrin.
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Affiliation(s)
- Sonia A Cunningham
- Department of Pharmacology, Texas Biotechnology Corporation, Houston, Texas 77030, USA.
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Abstract
The alpha4 integrins (alpha4beta1 and alpha4beta7) play multiple roles in the immune system. Alpha4 integrins impact hematopoiesis, leukocyte trafficking in immune surveillance and inflammation, and leukocyte activation and survival. To perform these functions, alpha4 integrins act as both adhesive and signaling receptors. Paxillin, a signaling adapter molecule, binds directly to the alpha4 subunit cytoplasmic domain, and its binding is regulated by serine phosphorylation of the alpha4 subunit. This regulated interaction of paxillin with the alpha4 subunit is likely to regulate the diverse functions of alpha4 integrins in the immune system. Furthermore, this protein-protein interaction may provide novel targets for the modulation of the immune response.
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Affiliation(s)
- David M Rose
- Division of Rheumatology, Allergy, and Immunology, Department of Medicine, The University of California, San Diego, California, USA
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Liu S, Kiosses WB, Rose DM, Slepak M, Salgia R, Griffin JD, Turner CE, Schwartz MA, Ginsberg MH. A fragment of paxillin binds the alpha 4 integrin cytoplasmic domain (tail) and selectively inhibits alpha 4-mediated cell migration. J Biol Chem 2002; 277:20887-94. [PMID: 11919182 DOI: 10.1074/jbc.m110928200] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The alpha(4) integrins play important roles in embryogenesis, hematopoiesis, cardiac development, and the immune responses. The alpha(4) integrin subunit is indispensable for these biological processes, possibly because the alpha(4) subunit regulates cellular functions differently from other integrin alpha subunits. We have previously reported that the alpha(4) cytoplasmic domain directly and tightly binds paxillin, an intracellular signaling adaptor molecule, and this interaction accounts for some of the unusual functional responses to alpha(4) integrin-mediated cell adhesion. We also have identified a conserved 9-amino acid region (Glu(983)-Tyr(991)) in the alpha(4) cytoplasmic domain that is sufficient for paxillin binding, and an alanine substitution at either Glu(983) or Tyr(991) within this region disrupted the alpha(4)-paxillin interaction and reversed the effects of the alpha(4) cytoplasmic domain on cell spreading and migration. In the current study, we have mapped the alpha(4)-binding site within paxillin using mutational analysis, and examined its effects on the alpha(4) tail-mediated functional responses. Here we report that sequences between residues Ala(176) and Asp(275) of paxillin are sufficient for binding to the alpha(4) tail. We found that the alpha(4) tail, paxillin, and FAT, the focal adhesion targeting domain of pp125(FAK), could form a ternary complex and that the alpha(4)-binding paxillin fragment, P(Ala(176)-Asp(275)), specifically blocked paxillin binding to the alpha(4) tail more efficiently than it blocked binding to FAT. Furthermore, when expressed in cells, this alpha(4)-binding paxillin fragment specifically inhibited the alpha(4) tail-stimulated cell migration. Thus, paxillin binding to the alpha(4) tail leads to enhanced cell migration and inhibition of the alpha(4)-paxillin interaction selectively blocks the alpha4-dependent cellular responses.
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Affiliation(s)
- Shouchun Liu
- Department of Vascular Biology and Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
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Sengbusch JK, He W, Pinco KA, Yang JT. Dual functions of [alpha]4[beta]1 integrin in epicardial development: initial migration and long-term attachment. J Cell Biol 2002; 157:873-82. [PMID: 12021259 PMCID: PMC2173412 DOI: 10.1083/jcb.200203075] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The epicardium of the mammalian heart arises from progenitor cells outside the developing heart. The epicardial progenitor (EPP) cells migrate onto the heart through a cyst-mediated mechanism in which the progenitors are released from the tissue of origin as cysts; the cysts float in the fluid of the pericardial cavity and attach to the naked myocardial surface of the heart, and cells in the cysts then migrate out to form an epithelial sheet. In this paper, we show that the gene encoding the alpha4 subunit of alpha4beta1 integrin (alpha4beta1) is essential for this migratory process. We have generated a knockin mutation in mice replacing the alpha4 integrin gene with the lacZ reporter gene, placing lacZ under the control of the alpha4 integrin promoter. We show that in homozygous mutant embryos, the migration of EPP progenitor cells is impaired due to inefficient budding of the cysts and a failure of the cells in the cysts to migrate on the heart. This study provides direct genetic evidence for essential roles for alpha4beta1 integrin-mediated cell adhesion in the migration of progenitor cells to form the epicardium, in addition to a previous finding that alpha4beta1 is essential for maintaining the epicardium (Yang, J.T., H. Rayburn, and R.O. Hynes. 1995. Development. 121:549-560).
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Affiliation(s)
- Jennifer K Sengbusch
- Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Liu S, Slepak M, Ginsberg MH. Binding of Paxillin to the alpha 9 Integrin Cytoplasmic Domain Inhibits Cell Spreading. J Biol Chem 2001; 276:37086-92. [PMID: 11477105 DOI: 10.1074/jbc.m105114200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
alpha(9)beta(1) integrin is a member of the beta(1) integrin family, plays an important role in extravasation of neutrophils at sites of acute inflammation, and is required for the normal development of the lymphatic system. The alpha(9) and alpha(4) integrin subunits are most closely related and form a subfamily of integrin alpha subunits. Previously, we have reported that the alpha(4) cytoplasmic domain directly and tightly binds paxillin, an intracellular signaling adaptor molecule. This interaction accounts for some of the unusual functional responses to alpha(4) integrin-mediated cell adhesion, including stimulation of cell migration and inhibition of cell spreading and focal adhesion formation. In the current studies, we have examined the interaction between the alpha(9) cytoplasmic domain and paxillin. Here we report that the alpha(9) cytoplasmic domain binds paxillin directly and tightly and that the alpha(9)-paxillin association inhibits cell spreading. We have identified amino acid residues in the alpha(9) cytoplasmic domain, Trp(999) and Trp(1001), that are critical for paxillin binding, and alanine substitution of either Trp(999) or Trp(1001) blocks paxillin binding. Furthermore, these mutations also reverse the effect of the alpha(9) cytoplasmic domain on cell spreading. Thus, the alpha(9) and alpha(4) integrin subunits form a paxillin-binding subfamily of integrin alpha subunits, and direct binding of paxillin to the alpha(9) cytoplasmic domain mediates some of the biological activities of the alpha(9)beta(1) integrin.
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Affiliation(s)
- S Liu
- Department of Vascular Biology, The Scripps Research Institute, La Jolla, California 92037
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Testaz S, Duband JL. Central role of the alpha4beta1 integrin in the coordination of avian truncal neural crest cell adhesion, migration, and survival. Dev Dyn 2001; 222:127-40. [PMID: 11668592 DOI: 10.1002/dvdy.1181] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Based on functional and histological studies, the fibronectin receptor of the integrin family alpha4beta1 has been ascribed a critical role during neural crest cell migration in the vertebrate embryo. In the present study, because integrins have been shown to participate in multiple basic cellular processes, including cell adhesion, migration, survival, proliferation, and differentiation, we have reexamined in detail the role of alpha4beta1 during avian truncal neural crest cell migration. RT-PCR and immunocytochemical studies revealed that migrating neural crest cells but not premigratory cells explanted in vitro expressed detectable levels of alpha4 messengers and proteins suggesting that alpha4beta1 expression was induced at the time of the initiation of the migration phase. In agreement with this observation, antibody inhibition of alpha4beta1 activity in vitro resulted in a strong, immediate and sustained reduction of neural crest cell motion on fibronectin, as judged on videomicroscopy analyses, but apparently did not prevent their delamination from the neural tube. However, alpha4beta1 appeared to exhibit a broader role in the control of cell migration on a variety of extracellular matrix molecules, presumably by regulating cellular events downstream from integrins. Moreover, blocking alpha4beta1 function caused a severe increase in apoptotic cell death among the neural crest population without influencing notably cell proliferation. Collectively, these results indicate that, notwithstanding its critical implication in cell motion, alpha4beta1 integrin could play a central role in neural crest cell development by coordinating multiple cellular events, such as cell adhesion, locomotion, and survival.
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Affiliation(s)
- S Testaz
- Laboratoire de Biologie du Développement, CNRS UMR 7622, Université Pierre et Marie Curie, 9 quai Saint Bernard, 7éme etage, 75005 Paris, France
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Lin SJ, Wang JY, Klickstein LB, Chuang KP, Chen JY, Lee JF, Shieh CC. Lack of age-associated LFA-1 up-regulation and impaired ICAM-1 binding in lymphocytes from patients with Down syndrome. Clin Exp Immunol 2001; 126:54-63. [PMID: 11678899 PMCID: PMC1906165 DOI: 10.1046/j.1365-2249.2001.01660.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/09/2001] [Indexed: 01/30/2023] Open
Abstract
To investigate the role of LFA-1 in the immune defects in DS patients, we analysed lymphocytes from DS patients in LFA-1 expression and LFA-1 mediated cell adhesion. DS patients less than 2 years of age expressed a higher level of LFA-1 when compared with age-matched controls. The difference in LFA-1 expression was much less significant in older DS patients when compared with age-matched children. Although older children (2-15-year-old groups) without DS tend to increase their expression of lymphocyte LFA-1 when compared with younger normal children (0-2 years old), DS patients showed no age-associated increase in lymphocyte LFA-1 expression. Two-colour analysis with CD4/CD8 and LFA-1 in patients and controls showed that proportions of CD4 + lymphocytes were comparable in DS patients and controls, while the proportion of CD8 + lymphocytes was higher in older DS patients. Expression levels of LFA-1 on both CD4 + and CD8 + lymphocytes in younger DS patients were higher when compared with age-matched controls and close to the expression levels in the older DS group. Proportions of memory lymphocytes expressing the CD45RO isoform were higher in both younger and older DS patients when compared with age-matched control groups. Noticeably, the LFA-1 expression levels on CD45RO lymphocytes from younger DS patients were higher than the levels of the controls and declined in the older DS group. We tested lymphocytes (EBV transformed B cells, resting and anti-CD3 stimulated T cells) for cellular adhesion to recombinant ICAM-1 and found that lymphocytes from DS patients were less adhesive, even though their beta2 integrin expression was comparable with that of normal controls. These results suggest that more generalized pathological processes, such as early senescence of the immune system or ineffective lymphocyte activation, and subsequent integrin dysfunction may underlie the immune defects in DS patients.
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Affiliation(s)
- S J Lin
- Department of Paediatrics, National Cheng Kung University Medical College, Tainan, Taiwan
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Young BA, Taooka Y, Liu S, Askins KJ, Yokosaki Y, Thomas SM, Sheppard D. The cytoplasmic domain of the integrin alpha9 subunit requires the adaptor protein paxillin to inhibit cell spreading but promotes cell migration in a paxillin-independent manner. Mol Biol Cell 2001; 12:3214-25. [PMID: 11598204 PMCID: PMC60168 DOI: 10.1091/mbc.12.10.3214] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2001] [Revised: 07/12/2001] [Accepted: 08/03/2001] [Indexed: 12/22/2022] Open
Abstract
The integrin alpha9 subunit forms a single heterodimer, alpha9beta1. The alpha9 subunit is most closely related to the alpha4 subunit, and like alpha4 integrins, alpha9beta1 plays an important role in leukocyte migration. The alpha4 cytoplasmic domain preferentially enhances cell migration and inhibits cell spreading, effects that depend on interaction with the adaptor protein, paxillin. To determine whether the alpha9 cytoplasmic domain has similar effects, a series of chimeric and deleted alpha9 constructs were expressed in Chinese hamster ovary cells and tested for their effects on migration and spreading on an alpha9beta1-specific ligand. Like alpha4, the alpha9 cytoplasmic domain enhanced cell migration and inhibited cell spreading. Paxillin also specifically bound the alpha9 cytoplasmic domain and to a similar level as alpha4. In paxillin(-/-) cells, alpha9 failed to inhibit cell spreading as expected but surprisingly still enhanced cell migration. Further, mutations that abolished the alpha9-paxillin interaction prevented alpha9 from inhibiting cell spreading but had no effect on alpha9-dependent cell migration. These findings suggest that the mechanisms by which the cytoplasmic domains of integrin alpha subunits enhance migration and inhibit cell spreading are distinct and that the alpha9 and alpha4 cytoplasmic domains, despite sequence and functional similarities, enhance cell migration by different intracellular signaling pathways.
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Affiliation(s)
- B A Young
- Lung Biology Center, Department of Medicine, University of California, San Francisco, 94110, USA
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