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Abstract
Increased endothelial permeability and reduction of alveolar liquid clearance capacity are two leading pathogenic mechanisms of pulmonary edema, which is a major complication of acute lung injury, severe pneumonia, and acute respiratory distress syndrome, the pathologies characterized by unacceptably high rates of morbidity and mortality. Besides the success in protective ventilation strategies, no efficient pharmacological approaches exist to treat this devastating condition. Understanding of fundamental mechanisms involved in regulation of endothelial permeability is essential for development of barrier protective therapeutic strategies. Ongoing studies characterized specific barrier protective mechanisms and identified intracellular targets directly involved in regulation of endothelial permeability. Growing evidence suggests that, although each protective agonist triggers a unique pattern of signaling pathways, selected common mechanisms contributing to endothelial barrier protection may be shared by different barrier protective agents. Therefore, understanding of basic barrier protective mechanisms in pulmonary endothelium is essential for selection of optimal treatment of pulmonary edema of different etiology. This article focuses on mechanisms of lung vascular permeability, reviews major intracellular signaling cascades involved in endothelial monolayer barrier preservation and summarizes a current knowledge regarding recently identified compounds which either reduce pulmonary endothelial barrier disruption and hyperpermeability, or reverse preexisting lung vascular barrier compromise induced by pathologic insults.
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Affiliation(s)
- Konstantin G Birukov
- Lung Injury Center, Section of Pulmonary and Critical Care, Department of Medicine, University of Chicago, Chicago, Illinois, USA.
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52
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Caldas LA, Seabra SH, Attias M, de Souza W. The effect of kinase, actin, myosin and dynamin inhibitors on host cell egress by Toxoplasma gondii. Parasitol Int 2013; 62:475-82. [DOI: 10.1016/j.parint.2013.04.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 03/26/2013] [Accepted: 04/18/2013] [Indexed: 12/21/2022]
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FilGAP and its close relatives: a mediator of Rho-Rac antagonism that regulates cell morphology and migration. Biochem J 2013; 453:17-25. [PMID: 23763313 DOI: 10.1042/bj20130290] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cell migration, phagocytosis and cytokinesis are mechanically intensive cellular processes that are mediated by the dynamic assembly and contractility of the actin cytoskeleton. GAPs (GTPase-activating proteins) control activities of the Rho family proteins including Cdc42, Rac1 and RhoA, which are prominent upstream regulators of the actin cytoskeleton. The present review concerns a class of Rho GAPs, FilGAP (ARHGAP24 gene product) and its close relatives (ARHGAP22 and AHRGAP25 gene products). FilGAP is a GAP for Rac1 and a binding partner of FLNa (filamin A), a widely expressed F-actin (filamentous actin)-cross-linking protein that binds many different proteins that are important in cell regulation. Phosphorylation of FilGAP serine/threonine residues and binding to FLNa modulate FilGAP's GAP activity and, as a result, its ability to regulate cell protrusion and spreading. FLNa binds to FilGAP at F-actin-enriched sites, such as at the leading edge of the cell where Rac1 activity is controlled to inhibit actin assembly. FilGAP then dissociates from FLNa in actin networks by myosin-dependent mechanical deformation of FLNa's FilGAP-binding site to relocate at the plasma membrane by binding to polyphosphoinositides. Since actomyosin contraction is activated downstream of RhoA-ROCK (Rho-kinase), RhoA activity regulates Rac1 through FilGAP by signalling to the force-generating system. FilGAP and the ARHGAP22 gene product also act as mediators between RhoA and Rac1 pathways, which lead to amoeboid and mesenchymal modes of cell movements respectively. Therefore FilGAP and its close relatives are key regulators that promote the reciprocal inhibitory relationship between RhoA and Rac1 in cell shape changes and the mesenchymal-amoeboid transition in tumour cells.
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Ma Y, McCarty SK, Kapuriya NP, Brendel VJ, Wang C, Zhang X, Jarjoura D, Saji M, Chen CS, Ringel MD. Development of p21 activated kinase-targeted multikinase inhibitors that inhibit thyroid cancer cell migration. J Clin Endocrinol Metab 2013; 98:E1314-22. [PMID: 23709653 PMCID: PMC3733855 DOI: 10.1210/jc.2012-3937] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT The p21 activated kinases (PAKs) are a family of serine/threonine kinases that are downstream effectors of small GTPase Cdc42 and Rac. PAKs regulate cell motility, proliferation, and cytoskeletal rearrangement. PAK isoform expression and activity have been shown to be enhanced in cancer and to function as an oncogene in vivo. PAKs also have been implicated in cancer progression. OBJECTIVE In thyroid cancer, we have previously determined that PAK overactivation is common in the invasive fronts of aggressive tumors and that it is functionally involved in thyroid cancer cell motility using molecular inhibitors. We report the development of two new PAK-inhibiting compounds that were modified from the structure OSU-03012, a previously identified multikinase inhibitor that competitively blocks ATP binding of both phosphoinositide-dependent kinase 1 (PDK1) and PAK1. RESULTS Seventeen compounds were created by combinatorial chemistry predicted to inhibit PAK activity with reduced anti-PDK1 effect. Two lead compounds were identified based on the ability to inhibit PAK1 activity in an ATP-competitive manner without discernible in vivo PDK1 inhibitory activity in thyroid cancer cell lines. Both compounds reduced thyroid cancer cell viability. Although they are not PAK-specific on a multikinase screening assay, the antimigration activity effect of the compounds in thyroid cancer cells was rescued by overexpression of a constitutively active PAK1, suggesting this activity is involved in this biological effect. CONCLUSIONS We have developed 2 new multikinase inhibitors with anti-PAK activity that may serve as scaffolds for further compound development targeting this progression-related thyroid cancer target.
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Affiliation(s)
- Yihui Ma
- Division of Medicinal Chemistry, College of Pharmacy, The Ohio State University College of Medicine and Wexner Medical Center, Columbus, Ohio 43210, USA
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55
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Birukova AA, Tian X, Tian Y, Higginbotham K, Birukov KG. Rap-afadin axis in control of Rho signaling and endothelial barrier recovery. Mol Biol Cell 2013; 24:2678-88. [PMID: 23864716 PMCID: PMC3756920 DOI: 10.1091/mbc.e13-02-0098] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
This study describes the novel role of Rap1 as a molecular switch for down-regulation of the Rho-dependent pathway of agonist-induced endothelial hyperpermeability. The Rho-Rap-Rac autoregulation loop may represent a fundamental mechanism of homeostasis and be critical for reestablishment of cell monolayer integrity in pathological conditions. Activation of the Rho GTPase pathway determines endothelial cell (EC) hyperpermeability after injurious stimuli. To date, feedback mechanisms of Rho down-regulation critical for barrier restoration remain poorly understood. We tested a hypothesis that Rho down-regulation and barrier recovery of agonist-stimulated ECs is mediated by the Ras family GTPase Rap1. Thrombin-induced EC permeability driven by rapid activation of the Rho GTPase pathway was followed by Src kinase–dependent phosphorylation of the Rap1-specific guanine nucleotide exchange factor (GEF) C3G, activation of Rap1, and initiation of EC barrier recovery. Knockdown experiments showed that Rap1 activation was essential for down-regulation of Rho signaling and actin stress fiber dissolution. Rap1 activation also enhanced interaction between adherens junction (AJ) proteins VE-cadherin and p120-catenin and stimulated AJ reannealing mediated by the Rap1 effector afadin. This mechanism also included Rap1-dependent membrane translocation of the Rac1-specific GEF Tiam1 and activation of Rac1-dependent peripheral cytoskeletal dynamics, leading to resealing of intercellular gaps. These data demonstrate that activation of the Rap1-afadin axis is a physiological mechanism driving restoration of barrier integrity in agonist-stimulated EC monolayers via negative-feedback regulation of Rho signaling, stimulation of actin peripheral dynamics, and reestablishment of cell–cell adhesive complexes.
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Affiliation(s)
- Anna A Birukova
- Department of Medicine, Section of Pulmonary and Critical Medicine, Lung Injury Center, University of Chicago, Chicago, IL 60637, USA
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56
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Al-Mulla F, Bitar MS, Taqi Z, Yeung KC. RKIP: much more than Raf kinase inhibitory protein. J Cell Physiol 2013; 228:1688-702. [PMID: 23359513 DOI: 10.1002/jcp.24335] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 01/16/2013] [Indexed: 12/11/2022]
Abstract
From its discovery as a phosphatidylethanolamine-binding protein in bovine brain to its designation as a physiological inhibitor of Raf kinase protein, RKIP has emerged as a critical molecule for maintaining subdued, well-orchestrated cellular responses to stimuli. The disruption of RKIP in a wide range of pathologies, including cancer, Alzheimer's disease, and pancreatitis, makes it an exciting target for individualized therapy and disease-specific interventions. This review attempts to highlight recent advances in the RKIP field underscoring its potential role as a master modulator of many pivotal intracellular signaling cascades that control cellular growth, motility, apoptosis, genomic integrity, and therapeutic resistance. Specific biological and functional niches are highlighted to focus future research towards an enhanced understanding of the multiple roles of RKIP in health and disease.
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Affiliation(s)
- Fahd Al-Mulla
- Faculty of Medicine, Department of Pathology, Kuwait University Health Sciences Centre, Safat, Kuwait.
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57
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Wang XX, Cheng Q, Zhang SN, Qian HY, Wu JX, Tian H, Pei DS, Zheng JN. PAK5-Egr1-MMP2 signaling controls the migration and invasion in breast cancer cell. Tumour Biol 2013; 34:2721-9. [PMID: 23696025 DOI: 10.1007/s13277-013-0824-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 04/26/2013] [Indexed: 12/19/2022] Open
Abstract
p21-activated kinases (PAKs) are activated by various extracellular stimuli and, in turn, activate other kinases by phosphorylating them at specific serine/threonine residues or through protein-protein interaction. As a recently identified member of the group B PAK family, the role of PAK5 in cancer is poorly understood. In this study, we investigated the effect of PAK5 on the malignant phenotype, such as proliferation, cell cycle, apoptosis, migration, and invasion. Cell growth assay and cell cycle analysis consistently showed that knockdown of PAK5 could significantly inhibit the proliferation of breast cancer cells. Wound healing assay. migration assay, and invasion assay showed that PAK5 promoted cell migration. Furthermore, in order to elucidate the underlying mechanism of PAK5 on cellular growth and migration, we examined the protein expressions of cyclin D1, p21, early growth response protein 1 (Egr1), and matrix metalloproteinase 2 (MMP2). Our work further reveals the PAK5-Egr1-MMP2 signaling pathway to be a critical regulator of cell migration and invasion. These results suggest that PAK5 may be a potential therapeutic target for breast cancer.
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Affiliation(s)
- Xiao-Xia Wang
- Jiangsu Key Laboratory of Biological Cancer Therapy, Xuzhou Medical College, 84 West Huai-hai Road, Xuzhou, Jiangsu, 221002, China
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58
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Hammer A, Rider L, Oladimeji P, Cook L, Li Q, Mattingly RR, Diakonova M. Tyrosyl phosphorylated PAK1 regulates breast cancer cell motility in response to prolactin through filamin A. Mol Endocrinol 2013; 27:455-65. [PMID: 23340249 DOI: 10.1210/me.2012-1291] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The p21-activated serine-threonine kinase (PAK1) is activated by small GTPase-dependent and -independent mechanisms and regulates cell motility. Both PAK1 and the hormone prolactin (PRL) have been implicated in breast cancer by numerous studies. We have previously shown that the PRL-activated tyrosine kinase JAK2 (Janus tyrosine kinase 2) phosphorylates PAK1 in vivo and identified tyrosines (Tyr) 153, 201, and 285 in the PAK1 molecule as sites of JAK2 tyrosyl phosphorylation. Here, we have used human breast cancer T47D cells stably overexpressing PAK1 wild type or PAK1 Y3F mutant in which Tyr(s) 153, 201, and 285 were mutated to phenylalanines to demonstrate that phosphorylation of these three tyrosines are required for maximal PRL-dependent ruffling. In addition, phosphorylation of these three tyrosines is required for increased migration of T47D cells in response to PRL as assessed by two independent motility assays. Finally, we show that PAK1 phosphorylates serine (Ser) 2152 of the actin-binding protein filamin A to a greater extent when PAK1 is tyrosyl phosphorylated by JAK2. Down-regulation of PAK1 or filamin A abolishes the effect of PRL on cell migration. Thus, our data presented here bring some insight into the mechanism of PRL-stimulated motility of breast cancer cells.
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Affiliation(s)
- Alan Hammer
- Department of Biological Sciences, University of Toledo, Toledo, OH 43606-3390, USA
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59
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Thrombin stimulation of inflammatory breast cancer cells leads to aggressiveness via the EGFR-PAR1-Pak1 pathway. Int J Biol Markers 2012; 27:e305-13. [PMID: 23280128 DOI: 10.5301/jbm.2012.10437] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/24/2012] [Indexed: 11/20/2022]
Abstract
Inflammatory breast cancer (IBC) accounts for a small fraction but aggressive form of epithelial breast cancer. Although the role of thrombin in cancer is beginning to be unfolded, its impact on the biology of IBC remains unknown. The purpose of this study was to establish the role of thrombin on the invasiveness of IBC cells. The IBC SUM149 cell line was treated with thrombin in the absence or presence of the epidermal growth factor receptor (EGFR) inhibitor erlotinib and protease-activated receptor 1 (PAR1) inhibitor. The effects of pharmacological inhibitors on the ability of thrombin to stimulate the growth rate and invasiveness were examined. We found that the inhibition of putative cellular targets of thrombin action suppresses both the growth and invasiveness of SUM149 cells in a concentration-dependent manner. In addition, thrombin-mediated increased invasion of SUM149 cells was routed through EGFR phosphorylation, and in turn, stimulation of the p21-activated kinase (Pak1) activity in a EGFR-sensitive manner. Interestingly, thrombin-mediated activation of the Pak1 pathway stimulation was blocked by erlotinib and PAR1 inhibitor. For proof-of-principle studies, we found immunohistochemical evidence of Pak1 activation as well as expression of PAR1 in IBC. Thrombin utilizes EGFR to relay signals promoting SUM149 cell growth and invasion via the Pak1 pathway. The study provides the rationale for future therapeutic approaches in mitigating the invasive nature of IBC by targeting Pak1 and/or EGFR.
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Chu J, Pham NT, Olate N, Kislitsyna K, Day MC, LeTourneau PA, Kots A, Stewart RH, Laine GA, Cox CS, Uray K. Biphasic regulation of myosin light chain phosphorylation by p21-activated kinase modulates intestinal smooth muscle contractility. J Biol Chem 2012; 288:1200-13. [PMID: 23161543 DOI: 10.1074/jbc.m112.370718] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Supraphysiological mechanical stretching in smooth muscle results in decreased contractile activity. However, the mechanism is unclear. Previous studies indicated that intestinal motility dysfunction after edema development is associated with increased smooth muscle stress and decreased myosin light chain (MLC) phosphorylation in vivo, providing an ideal model for studying mechanical stress-mediated decrease in smooth muscle contraction. Primary human intestinal smooth muscle cells (hISMCs) were subjected to either control cyclical stretch (CCS) or edema (increasing) cyclical stretch (ECS), mimicking the biophysical forces in non-edematous and edematous intestinal smooth muscle in vivo. ECS induced significant decreases in phosphorylation of MLC and MLC phosphatase targeting subunit (MYPT1) and a significant increase in p21-activated kinase (PAK) activity compared with CCS. PAK regulated MLC phosphorylation in an activity-dependent biphasic manner. PAK activation increased MLC and MYPT1 phosphorylation in CCS but decreased MLC and MYPT1 phosphorylation in hISMCs subjected to ECS. PAK inhibition had the opposite results. siRNA studies showed that PAK1 plays a critical role in regulating MLC phosphorylation in hISMCs. PAK1 enhanced MLC phosphorylation via phosphorylating MYPT1 on Thr-696, whereas PAK1 inhibited MLC phosphorylation via decreasing MYPT1 on both Thr-696 and Thr-853. Importantly, in vivo data indicated that PAK activity increased in edematous tissue, and inhibition of PAK in edematous intestine improved intestinal motility. We conclude that PAK1 positively regulates MLC phosphorylation in intestinal smooth muscle through increasing inhibitory phosphorylation of MYPT1 under physiologic conditions, whereas PAK1 negatively regulates MLC phosphorylation via inhibiting MYPT1 phosphorylation when PAK activity is increased under pathologic conditions.
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Affiliation(s)
- Ji Chu
- Department of Pediatric Surgery, University of Texas Medical School, Houston, Texas 77030, USA
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61
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He H, Baldwin GS. p21-activated kinases and gastrointestinal cancer. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:33-9. [PMID: 23092728 DOI: 10.1016/j.bbamcr.2012.10.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 10/15/2012] [Accepted: 10/15/2012] [Indexed: 12/19/2022]
Abstract
p21-activated kinases (PAKs) were initially identified as effector proteins downstream from GTPases of the Rho family. To date, six members of the PAK family have been discovered in mammalian cells. PAKs play important roles in growth factor signalling, cytoskeletal remodelling, gene transcription, cell proliferation and oncogenic transformation. A large body of research has demonstrated that PAKs are up-regulated in several human cancers, and that their overexpression is linked to tumour progression and resistance to therapy. Structural and biochemical studies have revealed the mechanisms involved in PAK signalling, and opened the way to the development of PAK-targeted therapies for cancer treatment. Here we summarise recent findings from biological and clinical research on the role of PAKs in gastrointestinal cancer, and discuss the current status of PAK-targeted anticancer therapies.
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Affiliation(s)
- Hong He
- Department of Surgery, University of Melbourne, Austin Health, Melbourne, Victoria, Australia
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62
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Staser K, Shew MA, Michels EG, Mwanthi MM, Yang FC, Clapp DW, Park SJ. A Pak1-PP2A-ERM signaling axis mediates F-actin rearrangement and degranulation in mast cells. Exp Hematol 2012; 41:56-66.e2. [PMID: 23063725 DOI: 10.1016/j.exphem.2012.10.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 10/01/2012] [Accepted: 10/06/2012] [Indexed: 01/12/2023]
Abstract
Mast cells coordinate allergy and allergic asthma and are crucial cellular targets in therapeutic approaches to inflammatory disease. Allergens cross-link immunoglobulin E bound at high-affinity receptors on the mast cell's surface, causing release of preformed cytoplasmic granules containing inflammatory molecules, including histamine, a principal effector of fatal septic shock. Both p21 activated kinase 1 (Pak1) and protein phosphatase 2A (PP2A) modulate mast cell degranulation, but the molecular mechanisms underpinning these observations and their potential interactions in common or disparate pathways are unknown. In this study, we use genetic and other approaches to show that Pak1's kinase-dependent interaction with PP2A potentiates PP2A's subunit assembly and activation. PP2A then dephosphorylates threonine 567 of Ezrin/Radixin/Moesin (ERM) molecules that have been shown to couple F-actin to the plasma membrane in other cell systems. In our study, the activity of this Pak1-PP2A-ERM axis correlates with impaired systemic histamine release in Pak1(-/-) mice and defective F-actin rearrangement and impaired degranulation in Ezrin disrupted (Mx1Cre(+)Ezrin(flox/flox)) primary mast cells. This heretofore unknown mechanism of mast cell degranulation provides novel therapeutic targets in allergy and asthma and may inform studies of kinase regulation of cytoskeletal dynamics in other cell lineages.
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Affiliation(s)
- Karl Staser
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
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63
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Pignatelli J, LaLonde SE, LaLonde DP, Clarke D, Turner CE. Actopaxin (α-parvin) phosphorylation is required for matrix degradation and cancer cell invasion. J Biol Chem 2012; 287:37309-20. [PMID: 22955285 DOI: 10.1074/jbc.m112.385229] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Dysregulation of cell adhesion and motility is known to be an important factor in the development of tumor malignancy. Actopaxin (α-parvin) is a paxillin, integrin-linked kinase, and F-actin binding focal adhesion protein with several serine phosphorylation sites in the amino terminus that contribute to the regulation of cell spreading and migration. Here, phosphorylation of actopaxin is shown to contribute to the regulation of matrix degradation and cell invasion. Osteosarcoma cells stably expressing wild type (WT), nonphosphorylatable (Quint), and phosphomimetic (S4D/S8D) actopaxin demonstrate that actopaxin phosphorylation is necessary for efficient Src and matrix metalloproteinase-driven degradation of extracellular matrix. Rac1 was found to be required for actopaxin-induced matrix degradation whereas inhibition of myosin contractility promoted degradation in the phosphomutant-expressing Quint cells, indicating that a balance of Rho GTPase signaling and regulation of cellular tension are important for the process. Furthermore, actopaxin forms a complex with the Rac1/Cdc42 GEF β-PIX and Rac1/Cdc42 effector PAK1, to regulate actopaxin-dependent matrix degradation. Actopaxin phosphorylation is elevated in the invasive breast cancer cell line MDA-MB-231 compared with normal breast epithelial MCF10A cells. Expression of the nonphosphorylatable Quint actopaxin in MDA-MB-231 cells inhibits cell invasion whereas overexpression of WT actopaxin promotes invasion in MCF10A cells. Taken together, this study demonstrates a new role for actopaxin phosphorylation in matrix degradation and cell invasion via regulation of Rho GTPase signaling.
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Affiliation(s)
- Jeanine Pignatelli
- Department of Cell and Developmental Biology, State University of New York, Upstate Medical University, Syracuse, New York 13210, USA
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64
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Gadepalli R, Singh NK, Kundumani-Sridharan V, Heckle MR, Rao GN. Novel role of proline-rich nonreceptor tyrosine kinase 2 in vascular wall remodeling after balloon injury. Arterioscler Thromb Vasc Biol 2012; 32:2652-61. [PMID: 22922962 DOI: 10.1161/atvbaha.112.253112] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
OBJECTIVE To investigate the role of Pyk2, a proline-rich nonreceptor tyrosine kinase, in G protein-coupled receptor agonist, thrombin-induced human aortic smooth muscle cell growth and migration, and injury-induced vascular wall remodeling. METHODS AND RESULTS Thrombin, a G protein-coupled receptor agonist, activated Pyk2 in a time-dependent manner and inhibition of its stimulation attenuated thrombin-induced human aortic smooth muscle cell migration and proliferation. Thrombin also activated Grb2-associated binder protein 1, p115 Rho guanine nucleotide exchange factor, Rac1, RhoA, and p21-activated kinase 1 (Pak1) and interference with stimulation of these molecules attenuated thrombin-induced human aortic smooth muscle cell migration and proliferation. In addition, adenovirus-mediated expression of dominant negative Pyk2 inhibited thrombin-induced Grb2-associated binder protein 1, p115 rho guanine nucleotide exchange factor, Rac1, RhoA and Pak1 stimulation. Balloon injury also caused activation of Pyk2, Grb2-associated binder protein 1, p115 rho guanine nucleotide exchange factor, Rac1, RhoA, and Pak1 in the carotid artery of rat, and these responses were sensitive to inhibition by the dominant negative Pyk2. Furthermore, inhibition of Pyk2 activation resulted in reduced recruitment of smooth muscle cells onto the luminal surface and their proliferation in the intimal region leading to suppression of neointima formation. CONCLUSIONS Together, these results demonstrate for the first time that Pyk2 plays a crucial role in G protein-coupled receptor agonist thrombin-induced human aortic smooth muscle cell growth and migration, as well as balloon injury-induced neointima formation.
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Affiliation(s)
- Ravisekhar Gadepalli
- Department of Physiology, University of Tennessee Health Science Center, 894 Union Avenue, Memphis, TN 38163, USA
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PAK1 kinase promotes cell motility and invasiveness through CRK-II serine phosphorylation in non-small cell lung cancer cells. PLoS One 2012; 7:e42012. [PMID: 22848689 PMCID: PMC3407072 DOI: 10.1371/journal.pone.0042012] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Accepted: 06/29/2012] [Indexed: 12/20/2022] Open
Abstract
The role of c-Crk (CRK) in promoting metastasis is well described however the role of CRK phosphorylation and the corresponding signaling events are not well explained. We have observed CRK-II serine 41 phosphorylation is inversely correlated with p120-catenin and E-cadherin expressions in non-small cell lung cancer (NSCLC) cells. Therefore, we investigated the role of CRK-II serine 41 phosphorylation in the down-regulation of p120-catenin, cell motility and cell invasiveness in NSCLC cells. For this purpose, we expressed phosphomimetic and phosphodeficient CRK-II serine 41 mutants in NSCLC cells. NSCLC cells expressing phosphomimetic CRK-II seine 41 mutant showed lower p120-catenin level while CRK-II seine 41 phosphodeficient mutant expression resulted in higher p120-catenin. In addition, A549 cells expressing CRK-II serine 41 phosphomimetic mutant demonstrated more aggressive behavior in wound healing and invasion assays and, on the contrary, expression of phosphodeficient CRK-II serine 41 mutant in A549 cells resulted in reduced cell motility and invasiveness. We also provide evidence that PAK1 mediates CRK-II serine 41 phosphorylation. RNAi mediated silencing of PAK1 increased p120-catenin level in A549 and H157 cells. Furthermore, PAK1 silencing decreased cell motility and invasiveness in A549 cells. These effects were abrogated in A549 cells expressing phosphomimetic CRK-II serine 41. In summary, these data provide evidence for the role of PAK1 in the promotion of cell motility, cell invasiveness and the down regulation of p120-catenin through CRK serine 41 phosphorylation in NSCLC cells.
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Nie J, Sun C, Faruque O, Ye G, Li J, Liang Q, Chang Z, Yang W, Han X, Shi Y. Synapses of amphids defective (SAD-A) kinase promotes glucose-stimulated insulin secretion through activation of p21-activated kinase (PAK1) in pancreatic β-Cells. J Biol Chem 2012; 287:26435-44. [PMID: 22669945 DOI: 10.1074/jbc.m112.378372] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The p21-activated kinase-1 (PAK1) is implicated in regulation of insulin exocytosis as an effector of Rho GTPases. PAK1 is activated by the onset of glucose-stimulated insulin secretion (GSIS) through phosphorylation of Thr-423, a major activation site by Cdc42 and Rac1. However, the kinase(s) that phosphorylates PAK1 at Thr-423 in islet β-cells remains elusive. The present studies identified SAD-A (synapses of amphids defective), a member of AMP-activated protein kinase-related kinases exclusively expressed in brain and pancreas, as a key regulator of GSIS through activation of PAK1. We show that SAD-A directly binds to PAK1 through its kinase domain. The interaction is mediated by the p21-binding domain (PBD) of PAK1 and requires both kinases in an active conformation. The binding leads to direct phosphorylation of PAK1 at Thr-423 by SAD-A, triggering the onset of GSIS from islet β-cells. Consequently, ablation of PAK1 kinase activity or depletion of PAK1 expression completely abolishes the potentiating effect of SAD-A on GSIS. Consistent with its role in regulating GSIS, overexpression of SAD-A in MIN6 islet β-cells significantly stimulated cytoskeletal remodeling, which is required for insulin exocytosis. Together, the present studies identified a critical role of SAD-A in the activation of PAK1 during the onset of insulin exocytosis.
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Affiliation(s)
- Jia Nie
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing 210029, China
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Eastburn DJ, Zegers MM, Mostov KE. Scrib regulates HGF-mediated epithelial morphogenesis and is stabilized by Sgt1-HSP90. J Cell Sci 2012; 125:4147-57. [PMID: 22623728 DOI: 10.1242/jcs.108670] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Scribble was originally identified as a Drosophila protein that regulates epithelial polarity and formation of the basolateral surface. The mammalian orthologue, Scrib, is evolutionarily conserved, but does not appear to be necessary for apical-basolateral epithelial polarity. Instead, it is implicated in the regulation of cell survival, protein trafficking, adhesion and migration. A key issue is to understand the molecular pathway by which Scrib participates in these processes. We have investigated Scrib using a three-dimensional epithelial cell culture system. We show a novel association between the leucine-rich repeat domain of Scrib and the co-chaperone Sgt1 and demonstrate that these proteins are necessary for epithelial morphogenesis and tubulogenesis following hepatocyte growth factor (HGF) stimulation. The molecular chaperone HSP90 is also required for Sgt1 association with Scrib, and both Sgt1 and HSP90 are needed to ensure proper Scrib protein levels. Furthermore, reduced Scrib stability, following inhibition of Sgt1-HSP90, lowers the cellular abundance of the Scrib-βPix-PAK complex. Inhibition of any member of this complex, Scrib, βPix or PAK, is sufficient to block HGF-mediated epithelial morphogenesis. The identification of Scrib as an Sgt1-HSP90 client protein required for three-dimensional cell migration suggests that chaperone-mediated regulation of polarity protein stability and homeostasis is an unappreciated mechanism underlying dynamic rearrangements during morphogenesis.
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Affiliation(s)
- Dennis J Eastburn
- Department of Anatomy, University of California, San Francisco, CA 94143, USA
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Lai L, Liu J, Zhai D, Lin Q, He L, Dong Y, Zhang J, Lu B, Chen Y, Yi Z, Liu M. Plumbagin inhibits tumour angiogenesis and tumour growth through the Ras signalling pathway following activation of the VEGF receptor-2. Br J Pharmacol 2012; 165:1084-96. [PMID: 21658027 DOI: 10.1111/j.1476-5381.2011.01532.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Angiogenesis-based therapy is an effective anti-tumour strategy and previous reports have shown some beneficial effects of a naturally occurring bioactive compound plumbagin (5-hydroxy-2-methyl-1, 4-naphthoquinone). Here, we sought to determine the biological effects of plumbagin on signalling mechanisms during tumour angiogenesis. EXPERIMENTAL APPROACH The effects of plumbagin were evaluated in various in vitro assays which utilised human umbilical vein endothelial cells (HUVEC) proliferation, migration and tube formation. Plumbagin was also evaluated in vivo using chicken embryo chorioallantoic membrane (CAM) and mouse corneal micropocket models., Human colon carcinoma and prostate cancer xenograft mouse models were used to evaluate the effects of plumbagin on angiogenesis. Immunofluorescence, GST pull-down and Western blotting were employed to explore the underlying mechanisms of VEGF receptor (VEGFR)2-mediated Ras signalling pathways. KEY RESULTS Plumbagin not only inhibited endothelial cell proliferation, migration and tube formation but also suppressed chicken chorioallantoic membrane neovascularzation and VEGF-induced mouse corneal angiogenesis. Moreover, plumbagin suppressed tumour angiogenesis and tumour growth in human colon carcinoma and prostate cancer xenograft mouse models. At a molecular level, plumbagin blocked the Ras/Rac/cofilin and Ras/MEK signalling pathways mediated by VEGFR2 in HUVECs. CONCLUSIONS AND IMPLICATIONS Plumbagin inhibited tumour angiogenesis and tumour growth by interference with the VEGFR2-mediated Ras signalling pathway in endothelial cells. Our findings demonstrate a molecular basis for the effects of plumbagin and suggest that this compound might have therapeutic ant-tumour effects.
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Affiliation(s)
- Li Lai
- Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China
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69
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Bambang IF, Lee YK, Richardson DR, Zhang D. Endoplasmic reticulum protein 29 regulates epithelial cell integrity during the mesenchymal-epithelial transition in breast cancer cells. Oncogene 2012; 32:1240-51. [PMID: 22543584 DOI: 10.1038/onc.2012.149] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The epithelial-mesenchymal transition (EMT) correlates with disruption of cell-cell adhesion, loss of cell polarity and development of epithelial cell malignancy. Identifying novel molecules that inhibit EMT has profound potential for developing mechanism-based therapeutics. We previously demonstrated that the endoplasmic reticulum protein 29 (ERp29) is a novel factor that can drive mesenchymal-epithelial transition (MET) and induce cell growth arrest in MDA-MB-231 cells. Here, we show that ERp29 is an important molecule in establishing epithelial cell integrity during the MET. We demonstrate that ERp29 regulates MET in a cell context-dependent manner. ERp29 overexpression induced a complete MET in mesenchymal MDA-MB-231 cells through downregulating the expression of transcriptional repressors (for example, Slug, Snai1, ZEB2 and Twist) of E-cadherin. In contrast, overexpression of ERp29 induces incomplete MET in basal-like BT549 cells in which the expression of EMT-related markers (for example, vimentin; cytokeratin 19 (CK19) and E-cadherin) and the transcriptional repressors of E-cadherin were not altered. However, ERp29 overexpression in both cell-types resulted in loss of filamentous stress fibers, formation of cortical actin and restoration of an epithelial phenotype. Mechanistic studies revealed that overexpression of ERp29 in both cell-types upregulated the expression of TJ proteins (zonula-occludens-1 (ZO-1) and occludin) and the core apical-basal polarity proteins (Par3 and Scribble) at the membrane to enhance cell-cell contact and cell polarization. Knockdown of ERp29 in the epithelial MCF-7 cells decreased the expression of these proteins, leading to the disruption of cell-cell adhesion. Taken together, ERp29 is a novel molecule that regulates MET and epithelial cell integrity in breast cancer cells.
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Affiliation(s)
- I F Bambang
- Department of Pathology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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70
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Suga N, Sugimura M, Koshiishi T, Yorifuji T, Makino S, Takeda S. Heparin/heparan sulfate/CD44-v3 enhances cell migration in term placenta-derived immortalized human trophoblast cells. Biol Reprod 2012; 86:134, 1-8. [PMID: 22321833 DOI: 10.1095/biolreprod.111.093690] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The function of CD44-v3 and heparin/heparan sulfate (HS) signaling was investigated during trophoblast cell migration to identify their role in the renewal of syncytial layer damage caused by increased hemodynamic turbulence in the intervillous space and maintenance of syncytial integrity in pre-eclampsia. We evaluated the effect of heparin/HS/CD44-v3-mediated processes during scratch wound closure in monolayer immortalized human trophoblast cells derived from term placenta (TCL-1 cells). Western blot analysis showed that these cultured human trophoblast cells express the epidermal growth factor receptor and CD44-v3 but do not express syndecan 4. An in vitro scratch wound healing assay showed enhanced migration of trophoblast cells in a dose-dependent manner in the presence of heparin compared with controls when cultured under serum-free conditions. Conversely, an anti-CD44 function-blocking antibody and CD44 siRNA suppressed the migration of trophoblast cells in the presence of heparin in a similar scratch assay. Furthermore, both heparin treatment and in vitro scratch wounding induced the phosphorylation of p21-activated kinase 1 (PAK1), whereas the anti-CD44-v3 antibody suppressed the heparin-induced phosphorylation of PAK1 in trophoblast cells. These results indicate that heparin/HS/CD44-v3-mediated signaling, in the absence of growth factor networks, enhances the direct repair of the damaged trophoblast layer through the migration of trophoblast cells. This renewed cell coverage may lead to the maintenance of syncytiotrophoblast cell function and an associated reduction in pathogenic soluble factors derived from the damaged trophoblast cells.
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Affiliation(s)
- Naoko Suga
- Department of Obstetrics and Gynecology, School of Medicine, Juntendo University, Tokyo, Japan
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71
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72
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Mizuno T, Sekiguchi Y. Staurosporine induces lamellipodial widening in locomoting fish keratocytes by abolishing the gradient from radial extension of leading edge. Biophysics (Nagoya-shi) 2011; 7:69-75. [PMID: 27857594 PMCID: PMC5036771 DOI: 10.2142/biophysics.7.69] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 09/08/2011] [Indexed: 12/01/2022] Open
Abstract
Fish epidermal keratocytes locomote along surfaces without overall cell size or shape changes, as kinematically described by the graded radial extension (GRE) model. We found that the cell size increased during locomotion after the addition of a low dose of staurosporine or K-252a, broad-spectrum protein-serine/threonine kinase inhibitors. Quantitative shape analysis showed that the cell size increase resulted from an increase in lamellipodial width, the maximal length perpendicular to the direction of the cell locomotion, whereas the lamellipodial length, along the locomotion direction, remained constant. Importantly, the gradient of radial extension in the leading edge disappeared during lamellipodial width increase. These results suggest that a special mechanism for producing graded radial extension of lamellipodia exists to keep cell size constant, and that a protein-serine/threonine kinase plays an important role in regulating this mechanism.
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Affiliation(s)
- Takafumi Mizuno
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8566, Japan
| | - Yuji Sekiguchi
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8566, Japan
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73
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Guilluy C, Garcia-Mata R, Burridge K. Rho protein crosstalk: another social network? Trends Cell Biol 2011; 21:718-26. [PMID: 21924908 DOI: 10.1016/j.tcb.2011.08.002] [Citation(s) in RCA: 239] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 08/02/2011] [Accepted: 08/04/2011] [Indexed: 12/13/2022]
Abstract
Many fundamental processes in cell biology are regulated by Rho GTPases, including cell adhesion, migration and differentiation. While regulating cellular functions, members of the Rho protein family cooperate or antagonize each other. The resulting molecular network exhibits many levels of interaction dynamically regulated in time and space. In the first part of this review we describe the main mechanisms of this crosstalk, which can occur at three different levels of the pathway: (i) through regulation of activity, (ii) through regulation of protein expression and stability, and (iii) through regulation of downstream signaling pathways. In the second part we illustrate the importance of Rho protein crosstalk with two examples: integrin-based adhesion and cell migration.
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Affiliation(s)
- Christophe Guilluy
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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74
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Delorme-Walker VD, Peterson JR, Chernoff J, Waterman CM, Danuser G, DerMardirossian C, Bokoch GM. Pak1 regulates focal adhesion strength, myosin IIA distribution, and actin dynamics to optimize cell migration. ACTA ACUST UNITED AC 2011; 193:1289-303. [PMID: 21708980 PMCID: PMC3216326 DOI: 10.1083/jcb.201010059] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
p21-activated kinases are essential for spatial and temporal coordination of cytoskeletal dynamics with cellular adhesion during cell migration. Cell motility requires the spatial and temporal coordination of forces in the actomyosin cytoskeleton with extracellular adhesion. The biochemical mechanism that coordinates filamentous actin (F-actin) assembly, myosin contractility, adhesion dynamics, and motility to maintain the balance between adhesion and contraction remains unknown. In this paper, we show that p21-activated kinases (Paks), downstream effectors of the small guanosine triphosphatases Rac and Cdc42, biochemically couple leading-edge actin dynamics to focal adhesion (FA) dynamics. Quantitative live cell microscopy assays revealed that the inhibition of Paks abolished F-actin flow in the lamella, displaced myosin IIA from the cell edge, and decreased FA turnover. We show that, by controlling the dynamics of these three systems, Paks regulate the protrusive activity and migration of epithelial cells. Furthermore, we found that expressing Pak1 was sufficient to overcome the inhibitory effects of excess adhesion strength on cell motility. These findings establish Paks as critical molecules coordinating cytoskeletal systems for efficient cell migration.
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Affiliation(s)
- Violaine D Delorme-Walker
- Department of Immunology and Microbial Sciences, The Scripps Research Institute, La Jolla, CA 92037, USA
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75
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Spratley SJ, Bastea LI, Döppler H, Mizuno K, Storz P. Protein kinase D regulates cofilin activity through p21-activated kinase 4. J Biol Chem 2011; 286:34254-61. [PMID: 21832093 DOI: 10.1074/jbc.m111.259424] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dynamic reorganization of the actin cytoskeleton at the leading edge is required for directed cell migration. Cofilin, a small actin-binding protein with F-actin severing activities, is a key enzyme initiating such actin remodeling processes. Cofilin activity is tightly regulated by phosphorylation and dephosphorylation events that are mediated by LIM kinase (LIMK) and the phosphatase slingshot (SSH), respectively. Protein kinase D (PKD) is a serine/threonine kinase that inhibits actin-driven directed cell migration by phosphorylation and inactivation of SSH. Here, we show that PKD can also regulate LIMK through direct phosphorylation and activation of its upstream kinase p21-activated kinase 4 (PAK4). Therefore, active PKD increases the net amount of phosphorylated inactive cofilin in cells through both pathways. The regulation of cofilin activity at multiple levels may explain the inhibitory effects of PKD on barbed end formation as well as on directed cell migration.
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Affiliation(s)
- Samantha J Spratley
- Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic, Jacksonville, Florida 32224, USA
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76
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Singh P, Gan CS, Guo T, Phang HQ, Sze SK, Koh CG. Investigation of POPX2 phosphatase functions by comparative phosphoproteomic analysis. Proteomics 2011; 11:2891-900. [PMID: 21656682 DOI: 10.1002/pmic.201100044] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 04/18/2011] [Accepted: 05/03/2011] [Indexed: 01/13/2023]
Abstract
Identifying the substrates and biochemical pathway regulated by phosphatases has always been more challenging than finding those regulated by kinases. Here, we report the use of phosphoproteomic methods to analyse the pathways regulated by POPX2 (partner of PIX 2) phosphatase. POPX2 is a serine/threonine phosphatase, found in many cancer types. The levels of the POPX2 have been found to be up-regulated in the more invasive breast cancer cells compared with non-invasive ones. Our observations also suggest that POPX2 level is positively correlated with cell motility. Thus, finding substrates or pathways regulated by POPX2 will help to elucidate the regulatory mechanism of cancer cell motility and invasiveness. We have also developed and validated a protocol using electrostatic repulsion-hydrophilic interaction chromatography (ERLIC) to enrich the phosphopeptides followed by LC-MS/MS to allow comparison between the phosphoproteomes of control and POPX2 overexpressing cells. With this approach, we were able to identify a biochemical pathway through which POPX2 exerts its apparent cellular function: the regulation of activity of glycogen synthase kinase-3, which in turn modulates extracellular signal-regulated kinase and cell motility.
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Affiliation(s)
- Pritpal Singh
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore
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77
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Tan I, Lai J, Yong J, Li SFY, Leung T. Chelerythrine perturbs lamellar actomyosin filaments by selective inhibition of myotonic dystrophy kinase-related Cdc42-binding kinase. FEBS Lett 2011; 585:1260-8. [PMID: 21457715 DOI: 10.1016/j.febslet.2011.03.054] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Revised: 03/14/2011] [Accepted: 03/21/2011] [Indexed: 11/25/2022]
Abstract
Cell movement requires forces generated by non-muscle myosin II (NM II) for coordinated protrusion and retraction. The Cdc42/Rac effector MRCK regulates a specific actomyosin network in the lamella essential for cell protrusion and migration. Together with the Rho effector ROK required for cell rear retraction, they cooperatively regulate cell motility and tumour cell invasion. Despite the increasing importance of ROK inhibitors for both experimental and clinical purposes, there is a lack of specific inhibitors for other related kinases such as MRCK. Here, we report the identification of chelerythrine chloride as a specific MRCK inhibitor. Its ability to block cellular activity of MRCK resulted in the specific loss of NM II-associated MLC phosphorylation in the lamella, and the consequential suppression of cell migration.
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Affiliation(s)
- Ivan Tan
- The Neuroscience Research Partnership, A-STAR, Singapore, Singapore
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78
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Clark AG, Paluch E. Mechanics and regulation of cell shape during the cell cycle. Results Probl Cell Differ 2011; 53:31-73. [PMID: 21630140 DOI: 10.1007/978-3-642-19065-0_3] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Many cell types undergo dramatic changes in shape throughout the cell cycle. For individual cells, a tight control of cell shape is crucial during cell division, but also in interphase, for example during cell migration. Moreover, cell cycle-related cell shape changes have been shown to be important for tissue morphogenesis in a number of developmental contexts. Cell shape is the physical result of cellular mechanical properties and of the forces exerted on the cell. An understanding of the causes and repercussions of cell shape changes thus requires knowledge of both the molecular regulation of cellular mechanics and how specific changes in cell mechanics in turn effect global shape changes. In this chapter, we provide an overview of the current knowledge on the control of cell morphology, both in terms of general cell mechanics and specifically during the cell cycle.
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Affiliation(s)
- Andrew G Clark
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
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79
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Zou W, Yang Y, Wu Y, Sun L, Chi Y, Wu W, Yun X, Xie J, Gu J. Negative role of trihydrophobin 1 in breast cancer growth and migration. Cancer Sci 2010; 101:2156-62. [PMID: 20735431 PMCID: PMC11158160 DOI: 10.1111/j.1349-7006.2010.01656.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Trihydrophobin 1 (TH1) is a member of the negative elongation factor complex, which is involved in transcriptional pausing. Although the negative elongation factor complex attenuates the estrogen receptor α-mediated transcription, little is known about the relationship between TH1 and tumor progression. Here, we report that the protein level of TH1 was negatively correlated with the aggressiveness of human breast cancer. Immunohistochemical analysis revealed that TH1 expression in clinical stage III-IV primary breast cancer tissues was statistically significantly lower than that in stage I-II breast tissues (P < 0.01), and especially inversely associated with lymph node metastasis (P < 0.001). Furthermore, we showed that overexpression of TH1 in MDA-MB-231 breast cancer cells inhibited, and knockdown of TH1 in MCF-7 cells enhanced, cell proliferation and migratory ability. Moreover, upregulation of TH1 in MDA-MB-231 cells resulted in the decrease of cyclin D1, β-catenin, and ERK activity, and the increase of p21. In contrast, knockdown of TH1 in MCF-7 cells enhanced the expression of cyclin D1 and β-catenin, increased the activity of ERK, and downregulated the expression of p21. Additionally, overexpression of TH1 in MDA-MB-231 cells prevented. However, knockdown of TH1 in MCF-7 cells induced a number of molecular and cellular alterations associated with epithelial-mesenchymal transition. Taken together, our results suggest that TH1 might play an important role in regulation of proliferation and invasion in human breast cancer, and could be a potential target for human breast cancer treatment.
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Affiliation(s)
- Weiying Zou
- Gene Research Center, Key Laboratory of Glycoconjugate Research, Ministry of Public Health, Shanghai Medical College of Fudan University, Shanghai, China
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80
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Sultana H, Neelakanta G, Kantor FS, Malawista SE, Fish D, Montgomery RR, Fikrig E. Anaplasma phagocytophilum induces actin phosphorylation to selectively regulate gene transcription in Ixodes scapularis ticks. ACTA ACUST UNITED AC 2010; 207:1727-43. [PMID: 20660616 PMCID: PMC2916137 DOI: 10.1084/jem.20100276] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Anaplasma phagocytophilum, the agent of human anaplasmosis, persists in ticks and mammals. We show that A. phagocytophilum induces the phosphorylation of actin in an Ixodes ricinus tick cell line and Ixodes scapularis ticks, to alter the ratio of monomeric/filamentous (G/F) actin. A. phagocytophilum–induced actin phosphorylation was dependent on Ixodes p21-activated kinase (IPAK1)–mediated signaling. A. phagocytophilum stimulated IPAK1 activity via the G protein–coupled receptor Gβγ subunits, which mediated phosphoinositide 3-kinase (PI3K) activation. Disruption of Ixodes gβγ, pi3k, and pak1 reduced actin phosphorylation and bacterial acquisition by ticks. A. phagocytophilum–induced actin phosphorylation resulted in increased nuclear G actin and phosphorylated actin. The latter, in association with RNA polymerase II (RNAPII), enhanced binding of TATA box–binding protein to RNAPII and selectively promoted expression of salp16, a gene crucial for A. phagocytophilum survival. These data define a mechanism that A. phagocytophilum uses to selectively alter arthropod gene expression for its benefit and suggest new strategies to interfere with the life cycle of this intracellular pathogen, and perhaps other Rickettsia-related microbes of medical importance.
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Affiliation(s)
- Hameeda Sultana
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
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81
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p21-activated kinase 5 inhibits camptothecin-induced apoptosis in colorectal carcinoma cells. Tumour Biol 2010; 31:575-82. [PMID: 20567954 DOI: 10.1007/s13277-010-0071-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 06/08/2010] [Indexed: 12/27/2022] Open
Abstract
p21-activated kinase 5 (PAK5) is a recently identified member of the group B PAK family. The PAK proteins are effectors of the small GTPase Cdc42 and Rac1 and are known to regulate cell motility and activate cell-survival signaling pathways. Especially, the mitochondrial localization of PAK5 is vital to its effects on apoptosis and cell survival. Previously, we demonstrated that PAK5 expression increased significantly during the malignant progression of colorectal carcinoma (CRC) and that PAK5 promoted CRC metastasis by regulating CRC cell adhesion and migration. In the present study, we aim to investigate the role of PAK5 in camptothecin-induced apoptosis and its potential mechanism of action. Our results showed that overexpression of PAK5 inhibited camptothecin-induced apoptosis by inhibiting the activity of caspase-8 in CRC cells. Accordingly, knockdown of PAK5 in LoVo cells resulted in increased apoptosis. Mechanistically, we found that PAK5 directly phosphorylated Bad on serine 112 and indirectly led to phosphorylation of serine 136 via the Akt pathway. In conclusion, our study revealed previously unappreciated inhibitory role of PAK5 in camptothecin-induced apoptosis, thus suggesting PAK5 as a novel therapeutic target in CRC.
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82
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Abstract
IMPORTANCE OF THE FIELD Gastric cancer is one of the most common causes of cancer death worldwide. P21-activated kinases (PAKs), regulators of cancer-cell signalling networks, play fundamental roles in a range of cellular processes through their binding partners or kinase substrates. AREAS COVERED IN THIS REVIEW The complex regulation of PAKs through their upstream or downstream effectors in human cancers, especially in gastric cancer, are described and the identified inhibitors of PAKs are summarized. WHAT THE READERS WILL GAIN The structural differences and activation mechanisms between two subgroups of PAK are described. Both groups of PAKs play complicated and important roles in human gastric cancer, which indicated a possible way for us to identify the specific inhibitors targeting PAKs for gastric cancer. TAKE HOME MESSAGE PAKs play important roles in progression of many cancer types, the full mechanisms of PAKs in gastric cancer are still unclear. It seems there are different roles for two groups of PAKs in cancers. Group I PAKs play their functions mostly through their specific substrates, however, many binding partners that are independent of phosphorylation by group II PAKs were identified. Finding specific inhibitors of PAKs will help us discover the roles of PAKs and target these kinases in human gastric cancer.
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Affiliation(s)
- Xiaodong Li
- Department of Cell Biology, China Medical University, Key Laboratory of Cell Biology, Ministry of Public Health, Shenyang, Liaoning 110001, P. R. China.
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83
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Tahirovic S, Hellal F, Neukirchen D, Hindges R, Garvalov BK, Flynn KC, Stradal TE, Chrostek-Grashoff A, Brakebusch C, Bradke F. Rac1 regulates neuronal polarization through the WAVE complex. J Neurosci 2010; 30:6930-43. [PMID: 20484635 PMCID: PMC6632643 DOI: 10.1523/jneurosci.5395-09.2010] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 03/30/2010] [Accepted: 04/03/2010] [Indexed: 11/21/2022] Open
Abstract
Neuronal migration and axon growth, key events during neuronal development, require distinct changes in the cytoskeleton. Although many molecular regulators of polarity have been identified and characterized, relatively little is known about their physiological role in this process. To study the physiological function of Rac1 in neuronal development, we have generated a conditional knock-out mouse, in which Rac1 is ablated in the whole brain. Rac1-deficient cerebellar granule neurons, which do not express other Rac isoforms, showed impaired neuronal migration and axon formation both in vivo and in vitro. In addition, Rac1 ablation disrupts lamellipodia formation in growth cones. The analysis of Rac1 effectors revealed the absence of the Wiskott-Aldrich syndrome protein (WASP) family verprolin-homologous protein (WAVE) complex from the plasma membrane of knock-out growth cones. Loss of WAVE function inhibited axon growth, whereas overexpression of a membrane-tethered WAVE mutant partially rescued axon growth in Rac1-knock-out neurons. In addition, pharmacological inhibition of the WAVE complex effector Arp2/3 also reduced axon growth. We propose that Rac1 recruits the WAVE complex to the plasma membrane to enable actin remodeling necessary for axon growth.
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Affiliation(s)
- Sabina Tahirovic
- Axonal Growth and Regeneration Group, Max Planck Institute of Neurobiology, 82152 Martinsried, Germany
| | - Farida Hellal
- Axonal Growth and Regeneration Group, Max Planck Institute of Neurobiology, 82152 Martinsried, Germany
| | - Dorothee Neukirchen
- Axonal Growth and Regeneration Group, Max Planck Institute of Neurobiology, 82152 Martinsried, Germany
| | - Robert Hindges
- Medical Research Council Centre for Developmental Neurobiology, King's College London, London SE1 1UL, United Kingdom
| | - Boyan K. Garvalov
- Axonal Growth and Regeneration Group, Max Planck Institute of Neurobiology, 82152 Martinsried, Germany
| | - Kevin C. Flynn
- Axonal Growth and Regeneration Group, Max Planck Institute of Neurobiology, 82152 Martinsried, Germany
| | - Theresia E. Stradal
- Signalling and Motility Group, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany
| | - Anna Chrostek-Grashoff
- Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, Virginia 22908, and
| | - Cord Brakebusch
- Biotech Research and Innovation Centre, Biomedical Institute, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Frank Bradke
- Axonal Growth and Regeneration Group, Max Planck Institute of Neurobiology, 82152 Martinsried, Germany
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84
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Hunter MP, Zegers MM. Pak1 regulates branching morphogenesis in 3D MDCK cell culture by a PIX and beta1-integrin-dependent mechanism. Am J Physiol Cell Physiol 2010; 299:C21-32. [PMID: 20457839 DOI: 10.1152/ajpcell.00543.2009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Branching morphogenesis is a fundamental process in the development of the kidney. This process gives rise to a network of ducts, which form the collecting system. Defective branching can lead to a multitude of kidney disorders including agenesis and reduced nephron number. The formation of branching tubules involves changes in cell shape, cell motility, and reorganization of the cytoskeleton. However, the exact intracellular mechanisms involved are far from understood. We have used the three-dimensional (3D) Madin-Darby canine kidney (MDCK) cell culture system to study how p21-activated kinase 1 (Pak1), which is an important regulator of the cytoskeleton, modulates branching. Our data reveal that Pak1 plays a crucial role in regulating branching morphogenesis. Expression of a dominant-negative Pak1 mutant (DN-Pak1) in MDCK cysts resulted in the spontaneous formation of extensions and branching tubules. Cellular contractility and levels of phosphorylated myosin light chain (pMLC) were increased in DN-Pak1 cells in collagen. Expression of a DN-Pak1 mutant that does not bind to PIX (DN-Pak1-DeltaPIX) failed to form extensions in collagen and did not have increased contractility. This shows that the DN-Pak1 mutant requires PIX binding to generate extensions and increased contractility in 3D culture. Furthermore, a beta1-integrin function-blocking antibody (AIIB2) inhibited the formation of branches and blocked the increased contractility in DN-Pak1 cysts. Taken together, our work shows that DN-Pak1-induced branching morphogenesis requires PIX binding and beta1-integrin signaling.
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Affiliation(s)
- Michael P Hunter
- Department of Surgery, University of Chicago, Chicago, IL 60637, USA
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85
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Cadherins and Pak1 control contact inhibition of proliferation by Pak1-betaPIX-GIT complex-dependent regulation of cell-matrix signaling. Mol Cell Biol 2010; 30:1971-83. [PMID: 20154149 DOI: 10.1128/mcb.01247-09] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It is crucial for organ homeostasis that epithelia have effective mechanisms to restrict motility and cell proliferation in order to maintain tissue architecture. On the other hand, epithelial cells need to rapidly and transiently acquire a more mesenchymal phenotype, with high levels of cell motility and proliferation, in order to repair epithelia upon injury. Cross talk between cell-cell and cell-matrix signaling is crucial for regulating these transitions. The Pak1-betaPIX-GIT complex is an effector complex downstream of the small GTPase Rac1. We previously showed that translocation of this complex from cell-matrix to cell-cell adhesion sites was required for the establishment of contact inhibition of proliferation. In this study, we provide evidence that this translocation depends on cadherin function. Cadherins do not recruit the complex by direct interaction. Rather, we found that inhibition of the normal function of cadherin or Pak1 leads to defects in focal adhesion turnover and to increased signaling by phosphatidylinositol 3-kinase. We propose that cadherins are involved in regulation of contact inhibition by controlling the function of the Pak1-betaPIX-GIT complex at focal contacts.
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86
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87
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Guo D, Zhang JJ, Huang XY. A new Rac/PAK/GC/cGMP signaling pathway. Mol Cell Biochem 2009; 334:99-103. [PMID: 19937092 DOI: 10.1007/s11010-009-0327-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 11/04/2009] [Indexed: 10/20/2022]
Abstract
Guanosine 3',5'-cyclic monophosphate (cGMP) and small GTPase Rac are critical regulators of cell functions. Recently, Rac has been shown to use its downstream effector p21-activated kinase (PAK) to directly activate transmembrane guanylyl cyclases (GCs). This novel Rac/PAK/GC/cGMP signaling pathway bridges Rac and cGMP, and provides a general molecular mechanism for diverse receptors to regulate physiological functions such as cell migration through elevating the cellular cGMP level.
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Affiliation(s)
- Dagang Guo
- Department of Physiology, Cornell University Weill Medical College, New York, NY 10065, USA
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88
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Hsu RM, Tsai MH, Hsieh YJ, Lyu PC, Yu JS. Identification of MYO18A as a novel interacting partner of the PAK2/betaPIX/GIT1 complex and its potential function in modulating epithelial cell migration. Mol Biol Cell 2009; 21:287-301. [PMID: 19923322 PMCID: PMC2808764 DOI: 10.1091/mbc.e09-03-0232] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
MYO18A is found as a novel PAK2 binding partner via βPIX/GIT1. MYO18A-depleted cells showed dramatic changes in shape, actin stress fiber and membrane ruffle formation, and displayed increases in the number and size of focal adhesions and a decrease in cell migration, suggesting an important role of MYO18A in regulating epithelial cell migration. The p21-activated kinase (PAK) 2 is known to be involved in numerous biological functions, including the regulation of actin reorganization and cell motility. To better understand the mechanisms underlying this regulation, we herein used a proteomic approach to identify PAK2-interacting proteins in human epidermoid carcinoma A431 cells. We found that MYO18A, an emerging member of the myosin superfamily, is a novel PAK2 binding partner. Using a siRNA knockdown strategy and in vitro binding assay, we discovered that MYO18A binds to PAK2 through the βPIX/GIT1 complex. Under normal conditions, MYO18A and PAK2 colocalized in lamellipodia and membrane ruffles. Interestingly, knockdown of MYO18A in cells did not prevent formation of the PAK2/βPIX/GIT1 complex, but rather apparently changed its localization to focal adhesions. Moreover, MYO18A-depleted cells showed dramatic changes in morphology and actin stress fiber and membrane ruffle formation and displayed increases in the number and size of focal adhesions. Migration assays revealed that MYO18A-depleted cells had decreased cell motility, and reexpression of MYO18A restored their migration ability. Collectively, our findings indicate that MYO18A is a novel binding partner of the PAK2/βPIX/GIT1 complex and suggest that MYO18A may play an important role in regulating epithelial cell migration via affecting multiple cell machineries.
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Affiliation(s)
- Rae-Mann Hsu
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan, Republic of China
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89
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Abstract
There is now increasing evidence that myosin motor proteins, together with the dynamic actin filament machinery and associated adhesion proteins, play crucial roles in the events leading to motility at the leading edge of migrating cells. Myosins exist as a large superfamily of diverse ATP-dependent motors, and in the present review, we focus on the unique minus-end-directed myosin VI, briefly discussing its potential functions in cell motility.
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Affiliation(s)
- Margarita V Chibalina
- Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Hills Road, Cambridge, UK
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90
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Nagel M, Luu O, Bisson N, Macanovic B, Moss T, Winklbauer R. Role of p21-activated kinase in cell polarity and directional mesendoderm migration in the Xenopus gastrula. Dev Dyn 2009; 238:1709-26. [PMID: 19504461 DOI: 10.1002/dvdy.21985] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The p21 activated kinases (Paks) are prominently involved in the regulation of cell motility. Using a kinase-dead mutant of xPak1, we show that during Xenopus gastrulation, the kinase activity of Pak1 is required upstream of Cdc42 for the establishment of cell polarity in the migrating mesendoderm. Overactivation of Pak1 function by the expression of constitutively active xPak1 compromises the maintenance of cell polarity, by indirectly inhibiting RhoA function. Inhibition of cell polarization does not affect the migration of single mesendoderm cells. However, Pak1 inhibition interferes with the guidance of mesendoderm migration by directional cues residing in the extracellular matrix of the blastocoel roof, and with mesendoderm translocation in the embryo.
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Affiliation(s)
- Martina Nagel
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
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91
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Abstract
Angiogenesis recapitulates the growth of blood vessels that progressively expand and remodel into a highly organized and stereotyped vascular network. During adulthood, endothelial cells that formed the vascular wall retain their plasticity and can be engaged in neo-vascularization in response to physiological stimuli, such as hypoxia, wound healing and tissue repair, ovarian cycle and pregnancy. In addition, numerous human diseases and pathological conditions are characterized by an excessive, uncontrolled and aberrant angiogenesis. The signalling pathways involving the small Rho GTPase, Rac and its downstream effector the p21-activated serine/threonine kinase (PAK) had recently emerged as pleiotropic modulators in these processes. Indeed, Rac and PAK were found to modulate endothelial cell biology, such as sprouting, migration, polarity, proliferation, lumen formation, and maturation. Elucidating the Rac/PAK molecular circuitry will provide essential information for the development of new therapeutic agents designed to normalize the blood vasculature in human diseases.
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92
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Ferri N, Corsini A, Bottino P, Clerici F, Contini A. Virtual screening approach for the identification of new Rac1 inhibitors. J Med Chem 2009; 52:4087-90. [PMID: 19527032 DOI: 10.1021/jm8015987] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rac1 protein is implicated in several events of atherosclerotic plaque development and represents a new potential pharmacological target for cardiovascular diseases. In this paper we describe a pharmacophore virtual screening followed by molecular docking calculations leading to the identification of five new Rac1 inhibitors. These compounds were shown to be more effective than the reference compound NSC23766 in reducing the intracellular levels of Rac1-GTP, thus supporting this approach for the development of new Rac1 inhibitors.
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Affiliation(s)
- Nicola Ferri
- Dipartimento di Scienze Farmacologiche, Università degli Studi di Milano, 20133 Milano, Italy.
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93
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Abstract
Some of the characteristics of cancer cells are high rates of cell proliferation, cell survival, and the ability to invade surrounding tissue. The cytoskeleton has an essential role in these processes. Dynamic changes in the cytoskeleton are necessary for cell motility and cancer cells are dependent on motility for invasion and metastasis. The signaling pathways behind the reshaping and migrating properties of the cytoskeleton in cancer cells involve a group of Ras-related small GTPases and their effectors, including the p21-activated kinases (Paks). Paks are a family of serine/threonine protein kinases comprised of six isoforms (Pak 1-6), all of which are direct targets of the small GTPases Rac and Cdc42. Besides their role in cytoskeletal dynamics, Paks have recently been shown to regulate various other cellular activities, including cell survival, mitosis, and transcription. Paks are overexpressed and/or hyperactivated in several human tumors and their role in cell transformation makes them attractive therapeutic targets. Pak-targeted therapeutics may efficiently inhibit certain types of tumors and efforts to identify selective Pak-inhibitors are underway.
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Affiliation(s)
- Bettina Dummler
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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94
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Heckman CA, Demuth JG, Deters D, Malwade SR, Cayer ML, Monfries C, Mamais A. Relationship of p21-activated kinase (PAK) and filopodia to persistence and oncogenic transformation. J Cell Physiol 2009; 220:576-85. [PMID: 19384897 DOI: 10.1002/jcp.21788] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Previously, we found that oncogenically transformed cells had fewer filopodia and more large, p21-activated kinase (PAK)-dependent features than normal cells. These large protrusions (LPs) were increased in cells expressing RhoA(N19) with Cdc42-associated kinase (ACK). Here, we determine how GTPase-mediated mechanisms of focal contact (FC) regulation affect these protrusions. Constructs encoding various proteins were introduced into cells which were then studied by microscopy and computerized image processing and analysis. Constructs that prevented PAK recruitment by PAK-interacting exchange factor (PIX) or restricted PAK residence time on FCs decreased both protrusions. Thus, filopodia were also PAK-dependent. A comparison of FC distribution in cells expressing PAK in the presence or absence of PAK kinase inhibitor domain (KID) suggested that PAK enlarged FCs without affecting the prevalence of either protrusion. KID or Nck expression increased LPs but not filopodia. Nck failed to synergize with KID or ACK and RhoA(N19) in enhancing LPs. Nck and KID synergistically enhanced filopodia, possibly because Nck recruited PAK to FCs while KID prevented their dissociation by PAK-mediated autophosphorylation. Coexpression of Nck, ACK, and RhoA(N19) abrogated filopodia and replicated the transformed phenotype. Since Nck recruitment of PAK is implicated in persistence of directional movement, we studied the PAK-Nck interface. Filopodia were eliminated by the Nck PAK-binding domain and LPs by the PAK Nck-binding domain. The results suggested that filopodia formation has more stringent requirements than LP formation, and Nck and PAK are used differently in the protrusions. Loss of filopodia in transformed cells may reflect defective regulation of GTPase mechanisms.
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Affiliation(s)
- Carol A Heckman
- Department of Biological Sciences, Bowling Green State University, Bowling Green, Ohio 43403-0212, USA.
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95
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Petrie RJ, Doyle AD, Yamada KM. Random versus directionally persistent cell migration. Nat Rev Mol Cell Biol 2009; 10:538-49. [PMID: 19603038 DOI: 10.1038/nrm2729] [Citation(s) in RCA: 688] [Impact Index Per Article: 45.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Directional migration is an important component of cell motility. Although the basic mechanisms of random cell movement are well characterized, no single model explains the complex regulation of directional migration. Multiple factors operate at each step of cell migration to stabilize lamellipodia and maintain directional migration. Factors such as the topography of the extracellular matrix, the cellular polarity machinery, receptor signalling, integrin trafficking, integrin co-receptors and actomyosin contraction converge on regulation of the Rho family of GTPases and the control of lamellipodial protrusions to promote directional migration.
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Affiliation(s)
- Ryan J Petrie
- Laboratory of Cell and Developmental Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892, USA. e-mails:
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96
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Alphaherpesvirus US3-mediated reorganization of the actin cytoskeleton is mediated by group A p21-activated kinases. Proc Natl Acad Sci U S A 2009; 106:8707-12. [PMID: 19435845 DOI: 10.1073/pnas.0900436106] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The US3 protein is a viral serine/threonine kinase that is conserved among all members of the Alphaherpesvirinae. The US3 protein of different alphaherpesviruses causes dramatic alterations in the actin cytoskeleton, such as the disassembly of actin stress fibers and formation of cell projections, which have been associated with increased intercellular virus spread. Here, we find that inhibiting group A p21-activated kinases (PAKs), which are key regulators in Cdc42/Rac1 Rho GTPase signaling pathways, impairs US3-mediated actin alterations. By using PAK1(-/-) and PAK2(-/-) mouse embryo fibroblasts (MEFs), we show that US3-mediated stress fiber disassembly requires PAK2, whereas US3-mediated cell projection formation mainly is mediated by PAK1, also indicating that PAK1 and PAK2 can have different biological effects on the organization of the actin cytoskeleton. In addition, US3 was found to bind and phosphorylate group A PAKs. Lack of group A PAKs in MEFs was correlated with inefficient virus spread. Thus, US3 induces its effect on the actin cytoskeleton via group A PAKs.
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97
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Wang D, Paria BC, Zhang Q, Karpurapu M, Li Q, Gerthoffer WT, Nakaoka Y, Rao GN. A role for Gab1/SHP2 in thrombin activation of PAK1: gene transfer of kinase-dead PAK1 inhibits injury-induced restenosis. Circ Res 2009; 104:1066-75. [PMID: 19359598 DOI: 10.1161/circresaha.109.196691] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
To understand the role of epidermal growth factor receptor (EGFR) transactivation in G protein-coupled receptor (GPCR) agonist-induced signaling events, we have studied the capacity of thrombin in the activation of Gab1-SHP2 in vascular smooth muscle cells (VSMCs). Thrombin activated both Gab1 and SHP2 in EGFR-dependent manner. Similarly, thrombin induced Rac1 and Cdc42 activation, and these responses were suppressed when either Gab1 or SHP2 stimulation is blocked. Thrombin also induced PAK1 activation in a time- and EGFR-Gab1-SHP2-Rac1/Cdc42-dependent manner. Inhibition of activation of EGFR, Gab1, SHP2, Rac1, Cdc42, or PAK1 by pharmacological or genetic approaches attenuated thrombin-induced VSMC stress fiber formation and motility. Thrombin activated RhoA in a time-dependent manner in VSMCs. LARG, a RhoA-specific GEF (guanine nucleotide exchange factor), was found to be associated with Gab1 and siRNA-mediated depletion of its levels suppressed RhoA, Rac1 and PAK1 activation. Dominant negative mutant-mediated interference of RhoA activation inhibited thrombin-induced Rac1 and PAK1 stimulation in VSMCs and their stress fiber formation and migration. Balloon injury induced PAK1 activity and interference with its activation led to attenuation of SMC migration from media to intima, resulting in reduced neointima formation and increased lumen size. Inhibition of thrombin signaling by recombinant hirudin also blocked balloon injury-induced EGFR tyrosine phosphorylation and PAK1 activity. These results show that thrombin-mediated PAK1 activation plays a crucial role in vascular wall remodeling and it could be a potential target for drug development against these vascular lesions.
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MESH Headings
- Angioplasty, Balloon/adverse effects
- Animals
- Carotid Artery Diseases/enzymology
- Carotid Artery Diseases/etiology
- Carotid Artery Diseases/genetics
- Carotid Artery Diseases/therapy
- Carotid Stenosis/enzymology
- Carotid Stenosis/etiology
- Carotid Stenosis/genetics
- Carotid Stenosis/prevention & control
- Cell Movement
- Cells, Cultured
- Disease Models, Animal
- ErbB Receptors/antagonists & inhibitors
- ErbB Receptors/metabolism
- Fibrinolytic Agents/pharmacology
- Gene Transfer Techniques
- Genetic Therapy/methods
- Guanine Nucleotide Exchange Factors/metabolism
- Hirudins/pharmacology
- Humans
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/enzymology
- Muscle, Smooth, Vascular/pathology
- Mutation
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- Phosphorylation
- Protein Kinase Inhibitors/pharmacology
- Protein Tyrosine Phosphatase, Non-Receptor Type 11/genetics
- Protein Tyrosine Phosphatase, Non-Receptor Type 11/metabolism
- Quinazolines
- RNA Interference
- RNA, Small Interfering/metabolism
- Rats
- Rho Guanine Nucleotide Exchange Factors
- Stress Fibers/enzymology
- Thrombin/antagonists & inhibitors
- Thrombin/metabolism
- Time Factors
- Transfection
- Tyrphostins/pharmacology
- cdc42 GTP-Binding Protein/metabolism
- p21-Activated Kinases/genetics
- p21-Activated Kinases/metabolism
- rac1 GTP-Binding Protein/metabolism
- rhoA GTP-Binding Protein/metabolism
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Affiliation(s)
- Dong Wang
- Department of Physiology, University of Tennessee Health Science Center, 894 Union Ave., Memphis, TN 38163, USA
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98
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Heiser LM, Wang NJ, Talcott CL, Laderoute KR, Knapp M, Guan Y, Hu Z, Ziyad S, Weber BL, Laquerre S, Jackson JR, Wooster RF, Kuo WL, Gray JW, Spellman PT. Integrated analysis of breast cancer cell lines reveals unique signaling pathways. Genome Biol 2009; 10:R31. [PMID: 19317917 PMCID: PMC2691002 DOI: 10.1186/gb-2009-10-3-r31] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 01/12/2009] [Accepted: 03/25/2009] [Indexed: 01/21/2023] Open
Abstract
Mapping of sub-networks in the EGFR-MAPK pathway in different breast cancer cell lines reveals that PAK1 may be a marker for sensitivity to MEK inhibitors. Background Cancer is a heterogeneous disease resulting from the accumulation of genetic defects that negatively impact control of cell division, motility, adhesion and apoptosis. Deregulation in signaling along the EgfR-MAPK pathway is common in breast cancer, though the manner in which deregulation occurs varies between both individuals and cancer subtypes. Results We were interested in identifying subnetworks within the EgfR-MAPK pathway that are similarly deregulated across subsets of breast cancers. To that end, we mapped genomic, transcriptional and proteomic profiles for 30 breast cancer cell lines onto a curated Pathway Logic symbolic systems model of EgfR-MAPK signaling. This model was composed of 539 molecular states and 396 rules governing signaling between active states. We analyzed these models and identified several subtype-specific subnetworks, including one that suggested Pak1 is particularly important in regulating the MAPK cascade when it is over-expressed. We hypothesized that Pak1 over-expressing cell lines would have increased sensitivity to Mek inhibitors. We tested this experimentally by measuring quantitative responses of 20 breast cancer cell lines to three Mek inhibitors. We found that Pak1 over-expressing luminal breast cancer cell lines are significantly more sensitive to Mek inhibition compared to those that express Pak1 at low levels. This indicates that Pak1 over-expression may be a useful clinical marker to identify patient populations that may be sensitive to Mek inhibitors. Conclusions All together, our results support the utility of symbolic system biology models for identification of therapeutic approaches that will be effective against breast cancer subsets.
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Affiliation(s)
- Laura M Heiser
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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99
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Ke Y, Lei M, Solaro RJ. Regulation of cardiac excitation and contraction by p21 activated kinase-1. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2009; 98:238-50. [PMID: 19351515 DOI: 10.1016/j.pbiomolbio.2009.01.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cardiac excitation and contraction are regulated by a variety of signaling molecules. Central to the regulatory scheme are protein kinases and phosphatases that carry out reversible phosphorylation of different effectors. The process of beta-adrenergic stimulation mediated by cAMP dependent protein kinase (PKA) forms a well-known pathway considered as the most significant control mechanism in excitation and contraction as well as many other regulatory mechanisms in cardiac function. However, although dephosphorylation pathways are critical to these regulatory processes, signaling to phosphatases is relatively poorly understood. Emerging evidence indicates that regulation of phosphatases, which dampen the effect of beta-adrenergic stimulation, is also important. We review here functional studies of p21 activated kinase-1 (Pak1) and its potential role as an upstream signal for protein phosphatase PP2A in the heart. Pak1 is a serine/threonine protein kinase directly activated by the small GTPases Cdc42 and Rac1. Pak1 is highly expressed in different regions of the heart and modulates the activities of ion channels, sarcomeric proteins, and other phosphoproteins through up-regulation of PP2A activity. Coordination of Pak1 and PP2A activities is not only potentially involved in regulation of normal cardiac function, but is likely to be important in patho-physiological conditions.
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Affiliation(s)
- Yunbo Ke
- The Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, College of Medicine, Room 202, COMRB, 835 South Wolcott Avenue, Chicago, IL 60612, USA
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100
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Cheng C, Kong X, Wang H, Gan H, Hao Y, Zou W, Wu J, Chi Y, Yang J, Hong Y, Chen K, Gu J. Trihydrophobin 1 Interacts with PAK1 and Regulates ERK/MAPK Activation and Cell Migration. J Biol Chem 2009; 284:8786-96. [PMID: 19136554 DOI: 10.1074/jbc.m806144200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The Rac1/Cdc42 effector, p21-activated kinase (PAK), is activated by various signaling cascades, including receptor-tyrosine kinases and integrins, and regulates a number of processes such as cell proliferation and motility. PAK activity has been shown to be required for maximal activation of the canonical RAF-MEK-MAPK signaling cascade, possibly because of PAK co-activation of RAF and MEK. Here we have shown that trihydrophobin 1 (TH1), originally identified as a negative regulator of A-RAF kinase, also interacted with PAK1 in cultured cells. Confocal microscopy assay indicated that TH1 colocalized with PAK1 in both the cytoplasm and nucleus, which is consistent with our previous results. GST pulldown and coimmunoprecipitation experiments demonstrated that TH1 interacted directly with PAK1 and bound selectively to the carboxyl-terminal kinase domain of PAK1, and the ability of the binding was enhanced along with activation of PAK1. The binding pattern of PAK1 implies that this interaction was mediated in part by PAK1 kinase activity. As indicated by in vitro kinase activity assays and Western blot detections, TH1 inhibited PAK1 kinase activity and negatively regulated MAPK signal transduction. Interestingly, TH1 bound with MEK1/ERK in cells and in vitro without directly suppressing their kinase activity. Furthermore, we observed that TH1 localized to focal adhesions and filopodia in the leading edge of cells, where TH1 reduced cell migration through affecting actin and adhesion dynamics. Based on these observations, we propose a model in which TH1 interacts with PAK1 and specifically restricts the activation of MAPK modules through the upstream region of the MAPK pathway, thereby influencing cell migration.
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Affiliation(s)
- Chunming Cheng
- Gene Research Center, Shanghai Medical College, and Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
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