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The Pak1 kinase: an important regulator of neuronal morphology and function in the developing forebrain. Mol Neurobiol 2008; 37:187-202. [PMID: 18649038 DOI: 10.1007/s12035-008-8032-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Accepted: 06/04/2008] [Indexed: 01/07/2023]
Abstract
The mammalian central nervous system (CNS) represents a highly complex unit, the correct function of which relies on the appropriate differentiation and survival of its neurones. It is becoming apparent that the Rho family of small GTPases and their downstream targets have a major function in regulating CNS development. Among the effectors, the role of the Pak family of kinases, especially Pak1, is becoming increasingly evident. Although highest levels of Pak1 expression and activation are detected in the developing nervous system, much remains undiscovered concerning its function in neurones. This review summarises what is currently known regarding the biological and molecular role of Pak1 in the mammalian forebrain. It emphasises the importance of Pak1 in regulating neuronal polarity, morphology, migration and synaptic function. Consequently, there are also strong indications that Pak1 is required for normal cognitive function. Furthermore, loss of Pak1 has been associated with the progression of neurodegenerative disorders, particularly Alzheimer's disease, while up-regulation and de-regulation may be responsible for oncogenic transformation of support cells within the CNS, especially astrocyte progenitors. Together, these new and exciting findings encourage the future exploration into the function of Pak1 in the nervous system, thus, paving the way for novel strategies towards improved diagnosis and therapeutic treatment of diseases that affect the CNS.
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52
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Hake MJ, Choowongkomon K, Kostenko O, Carlin CR, Sönnichsen FD. Specificity determinants of a novel Nck interaction with the juxtamembrane domain of the epidermal growth factor receptor. Biochemistry 2008; 47:3096-108. [PMID: 18269246 DOI: 10.1021/bi701549a] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nck is a ubiquitously expressed adaptor protein containing Src homology 2 (SH2) and Src homology 3 (SH3) domains. It integrates downstream effector proteins with cell membrane receptors, such as the epidermal growth factor receptor (EGFR). EGFR plays a critical role in cellular proliferation and differentiation. The 45-residue juxtamembrane domain of EGFR (JM), located between the transmembrane and kinase domains, regulates receptor activation and trafficking to the basolateral membrane of polarized epithelia through a proline-rich motif that resembles a consensus SH3 domain binding site. We demonstrate here that the JM region can bind to Nck, showing a notable binding preference for the second SH3 domain. To elucidate the structural determinants for this interaction, we have determined the NMR solution structures of both the first and second Nck SH3 domains (Nck1-1 and Nck1-2). These domains adopt a canonical SH3 beta-barrel-like fold, containing five antiparallel strands separated by three loop regions and one 3 10-helical turn. Chemical shift perturbation studies have identified the residues that form the binding cleft of Nck1-2, which are primarily located in the RT and n-Src loops. JM binds to Nck1-2 with an affinity of approximately 80 microM through a positively charged sequence near the N-terminus, as opposed to the polyproline sequence. The two Nck SH3 domains exhibit both steric and electrostatic differences in their RT-Src and n-Src loops, and a model of the Nck1-2 domain complexed with the JM highlights the factors that define the putative binding mode for this ligand.
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Affiliation(s)
- Michael J Hake
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Abstract
Phosphorylation of tyrosine residue (Y1204) of rat nephrin by Fyn kinase allows Nck adaptor protein binding to nephrin motifs, which include the phosphorylated tyrosine. This phosphorylation-dependent switch induces actin polymerization in a cell culture system. Here, we generated an antibody recognizing phosphorylated nephrin at the Nck binding sites pY1204 and pY1228 to determine the phosphorylation status of nephrin using a rat model of puromycin aminonucleoside-induced nephrosis. Changes in globular actin (G-actin) and filamentous actin (F-actin) contents in isolated glomeruli were measured by western blot. Before experimental nephrosis, both Y1204 and Y1228 were phosphorylated, and most of the actin was filamentous. Before the onset of overt proteinuria, however, phosphorylation of both Y1204 and Y1228 rapidly decreased and became almost undetectable. During this period, the amount of F-actin in glomeruli began to decrease, whereas G-actin increased. Phosphorylation of nephrin at Y1228 in glomeruli of patients with minimal change nephrosis was significantly decreased compared with that in normal glomeruli. Our study suggests that tyrosine phosphorylation of nephrin by regulating F-actin formation may be important for the maintenance of normal podocyte morphology and function.
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Zegers M. Roles of P21-activated kinases and associated proteins in epithelial wound healing. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 267:253-98. [PMID: 18544501 DOI: 10.1016/s1937-6448(08)00606-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The primary function of epithelia is to provide a barrier between the extracellular environment and the interior of the body. Efficient epithelial repair mechanisms are therefore crucial for homeostasis. The epithelial wound-healing process involves highly regulated morphogenetic changes of epithelial cells that are driven by dynamic changes of the cytoskeleton. P21-activated kinases are serine/threonine kinases that have emerged as important regulators of the cytoskeleton. These kinases, which are activated downsteam of the Rho GTPases Rac and cd42, were initially mostly implicated in the regulation of cell migration. More recently, however, these kinases were shown to have many additional functions that are relevant to the regulation of epithelial wound healing. Here, we provide an overview of the morphogenetic changes of epithelial cells during wound healing and the many functions of p21-activated kinases in these processes.
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Affiliation(s)
- Mirjam Zegers
- Department of Surgery, University of Chicago, Chicago, IL 60637, USA
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55
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Deacon SW, Peterson JR. Chemical inhibition through conformational stabilization of Rho GTPase effectors. Handb Exp Pharmacol 2008:431-460. [PMID: 18491063 DOI: 10.1007/978-3-540-72843-6_18] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The Rho family of small GTP-binding proteins can activate a large number of downstream effectors and participate in a wide variety of biological processes, including cell motility, membrane trafficking, cell polarity, gene transcription, and mitosis. Specific small-molecule inhibitors of individual effector proteins downstream of Rho GTPases would be powerful tools to elucidate the contributions of particular effectors to these processes. In this chapter we describe the identification of a chemical inhibitor of a Rho effector and scaffolding protein neural-Wiskott-Aldrich syndrome protein (N-WASP), and the discovery of its novel mechanism of action, stabilization of N-WASP's native autoinhibited conformation. Inasmuch as several other Rho GTPase effectors are regulated by autoinhibition, we discuss how this regulatory mechanism could be exploited by small molecules to develop highly specific inhibitors of other Rho GTPase effectors. We illustrate this concept with the Rac/Cdc42 effector p21-activated kinase (Pak1) and the Rho effector mammalian diaphanous-related formin (mDia1).
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Affiliation(s)
- S W Deacon
- Division of Basic Science, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
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56
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Rider L, Shatrova A, Feener EP, Webb L, Diakonova M. JAK2 Tyrosine Kinase Phosphorylates PAK1 and Regulates PAK1 Activity and Functions. J Biol Chem 2007; 282:30985-96. [PMID: 17726028 DOI: 10.1074/jbc.m701794200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The serine-threonine kinase PAK1 is activated by small GTPase-dependent and -independent mechanisms and promotes cell survival. However, the role of tyrosyl phosphorylation in the regulation of PAK1 function is poorly understood. In this study, we have shown that the prolactin-activated tyrosine kinase JAK2 phosphorylates PAK1 in vivo. Wild type, but not kinase-dead, JAK2 directly phosphorylates PAK1 in cells and in an in vitro kinase assay. PAK1 tyrosines 153, 201, and 285 were identified as sites of JAK2 tyrosyl phosphorylation by mass spectrometry and two-dimensional peptide mapping. Mutation of PAK1 tyrosines 153, 201, and 285 to phenylalanines individually or in combination implicated these PAK1 tyrosines in the regulation of PAK1 kinase activity. Tyrosyl phosphorylation by JAK2 significantly increases PAK1 kinase activity, whereas similar phosphorylation of the PAK1 Y153F,Y201F,Y285F mutant has no effect on PAK1 activity. Tyrosyl phosphorylation of wild type PAK1 decreases apoptosis induced by serum deprivation and staurosporine treatment and increases cell motility. In contrast, these parameters are unaltered in the PAK1 Y153F,Y201F,Y285F mutant. Our findings indicate that JAK2 phosphorylates PAK1 at these specific tyrosines and that this phosphorylation plays an important role in cell survival and motility.
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Affiliation(s)
- Leah Rider
- Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606-3390, USA
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57
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Machuy N, Campa F, Thieck O, Rudel T. c-Abl-binding protein interacts with p21-activated kinase 2 (PAK-2) to regulate PDGF-induced membrane ruffles. J Mol Biol 2007; 370:620-32. [PMID: 17543336 DOI: 10.1016/j.jmb.2007.04.080] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2006] [Revised: 03/21/2007] [Accepted: 04/25/2007] [Indexed: 11/25/2022]
Abstract
p21-Activated kinases (PAKs) are serine/threonine kinases involved in multiple cellular functions including cytoskeleton regulation, proliferation and apoptosis. We performed a screen for proteins interacting with PAK-2, a ubiquitously expressed kinase involved in apoptotic signaling. Among the PAK-2 interacting proteins were different members of the Abl-binding protein family. Abl-binding proteins bound to a proline-rich region of PAK-2 located in the regulatory N terminus. Moreover, active PAK-2 phosphorylated Abl-binding proteins in vitro. Interestingly, we show that PAK-2 also interacted with c-Abl but via a different domain than with the Abl-binding proteins. PAK-2 and Abi-1 co-localized in the cytoplasm and to membrane dorsal ruffles induced by PDGF treatment. Expression of mutant PAK-2 deficient in binding to Abl-binding proteins or silencing of PAK-2 expression prevented the formation of membrane dorsal ruffles in response to PDGF. Our findings define a new class of PAK-interacting proteins, which play an important role in actin cytoskeletal reorganization.
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Affiliation(s)
- Nikolaus Machuy
- Max Planck Institute for Infection Biology, Department of Molecular Biology, Charitéplatz 1, D-10117 Berlin, Germany
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58
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Bisson N, Poitras L, Mikryukov A, Tremblay M, Moss T. EphA4 signaling regulates blastomere adhesion in the Xenopus embryo by recruiting Pak1 to suppress Cdc42 function. Mol Biol Cell 2007; 18:1030-43. [PMID: 17215521 PMCID: PMC1805096 DOI: 10.1091/mbc.e06-04-0294] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Revised: 12/04/2006] [Accepted: 12/29/2006] [Indexed: 12/19/2022] Open
Abstract
The control of cell adhesion is an important mechanism by which Eph receptors regulate cell sorting during development. Activation of EphA4 in Xenopus blastulae induces a reversible, cell autonomous loss-of-adhesion and disruption of the blastocoel roof. We show this phenotype is rescued by Nckbeta (Grb4) dependent on its interaction with EphA4. Xenopus p21(Cdc42/Rac)-activated kinase xPAK1 interacts with Nck, is activated in embryo by EphA4 in an Nck-dependent manner, and is required for EphA4-induced loss-of-adhesion. Ectopic expression of xPAK1 phenocopies EphA4 activation. This does not require the catalytic activity of xPAK1, but it does require its GTPase binding domain and is enhanced by membrane targeting. Indeed, membrane targeting of the GTPase binding domain (GBD) of xPAK1 alone is sufficient to phenocopy EphA4 loss-of-adhesion. Both EphA4 and the xPAK1-GBD down-regulate RhoA-GTP levels, and consistent with this, loss-of-adhesion can be rescued by activated Cdc42, Rac, and RhoA and can be epistatically induced by dominant-negative RhoA. Despite this, neither Cdc42 nor Rac activities are down-regulated by EphA4 activation or by the xPAK1-GBD. Together, the data suggest that EphA4 activation sequesters active Cdc42 and in this way down-regulates cell-cell adhesion. This novel signaling pathway suggests a mechanism for EphA4-guided migration.
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Affiliation(s)
- Nicolas Bisson
- Cancer Research Centre and Department of Medical Biology, Laval University, Hôtel-Dieu de Québec, Québec, G1R 2J6 Québec, Canada
| | - Luc Poitras
- Cancer Research Centre and Department of Medical Biology, Laval University, Hôtel-Dieu de Québec, Québec, G1R 2J6 Québec, Canada
| | - Alexander Mikryukov
- Cancer Research Centre and Department of Medical Biology, Laval University, Hôtel-Dieu de Québec, Québec, G1R 2J6 Québec, Canada
| | - Michel Tremblay
- Cancer Research Centre and Department of Medical Biology, Laval University, Hôtel-Dieu de Québec, Québec, G1R 2J6 Québec, Canada
| | - Tom Moss
- Cancer Research Centre and Department of Medical Biology, Laval University, Hôtel-Dieu de Québec, Québec, G1R 2J6 Québec, Canada
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59
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Orr AW, Stockton R, Simmers MB, Sanders JM, Sarembock IJ, Blackman BR, Schwartz MA. Matrix-specific p21-activated kinase activation regulates vascular permeability in atherogenesis. ACTA ACUST UNITED AC 2007; 176:719-27. [PMID: 17312022 PMCID: PMC2064028 DOI: 10.1083/jcb.200609008] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Elevated permeability of the endothelium is thought to be crucial in atherogenesis because it allows circulating lipoproteins to access subendothelial monocytes. Both local hemodynamics and cytokines may govern endothelial permeability in atherosclerotic plaque. We recently found that p21-activated kinase (PAK) regulates endothelial permeability. We now report that onset of fluid flow, atherogenic flow profiles, oxidized LDL, and proatherosclerotic cytokines all stimulate PAK phosphorylation and recruitment to cell-cell junctions. Activation of PAK is higher in cells plated on fibronectin (FN) compared to basement membrane proteins in all cases. In vivo, PAK is activated in atherosclerosis-prone regions of arteries and correlates with FN in the subendothelium. Inhibiting PAK in vivo reduces permeability in atherosclerosis-prone regions. Matrix-specific PAK activation therefore mediates elevated vascular permeability in atherogenesis.
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Affiliation(s)
- A Wayne Orr
- Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA
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60
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Morley S, Wagner J, Kauppinen K, Sherman M, Manor D. Requirement for Akt-mediated survival in cell transformation by the dbl oncogene. Cell Signal 2007; 19:211-8. [PMID: 16916597 DOI: 10.1016/j.cellsig.2006.06.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2006] [Accepted: 06/29/2006] [Indexed: 01/20/2023]
Abstract
The dbl oncogene product is the founding member of a large family of oncogenic proteins that function by activating the small GTP-binding proteins Cdc42, Rac and Rho. Through its substrate GTPases, Dbl transduces proliferative signals from cell-surface receptors to diverse cellular effectors and signaling pathways. The mechanisms by which these multiple signals are integrated, as well as their relative contribution to Dbl-induced cell transformation, are presently poorly understood. We investigated the role of the survival regulators PI3-kinase and Akt in Dbl-induced cell transformation. We found that Dbl induced the phosphorylation of Akt on threonine 308, through the GTPases Rac and Cdc42 and in a PI3-kinase dependent manner. Pharmacological or biochemical interference with this pathway lead to a marked, dose-dependent inhibition of the focus formation activity exhibited by Dbl-expressing cells. Dbl expression stimulated the phosphorylation of the anti-apoptotic Akt substrate Bad, and caused a marked decrease in basal levels of apoptosis. Finally, we found that activated Cdc42 existed in cells in complex with phosphoionositide-dependent kinase-1 (PDK1), the downstream mediator of PI3-kinase action. The data indicate that Dbl signaling stimulate the formation of a novel survival complex, through which anti-apoptotic signals are generated and propagated.
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Affiliation(s)
- S Morley
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
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61
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Zhou GL, Tucker DF, Bae SS, Bhatheja K, Birnbaum MJ, Field J. Opposing roles for Akt1 and Akt2 in Rac/Pak signaling and cell migration. J Biol Chem 2006; 281:36443-53. [PMID: 17012749 DOI: 10.1074/jbc.m600788200] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The Akt/PKB isoforms have different roles in animals, with Akt2 primarily regulating metabolic signaling and Akt1 regulating growth and survival. Here we show distinct roles for Akt1 and Akt2 in mouse embryo fibroblast cell migration and regulation of the cytoskeleton. Akt1-deficient cells responded poorly to platelet-derived growth factor while Akt2-deficient cells had a dramatically enhanced response, resulting in a substantial increase in dorsal ruffling. Swapping domains between Akt1 and Akt2 demonstrated that the N-terminal region containing the pleckstrin homology domain and a linker region distinguishes the two isoforms, while the catalytic domains are interchangeable. Akt2 knock-out cells also migrated faster than wild-type cells, especially through extracellular matrix (ECM), while Akt1 knock-out cells migrated more slowly than wild-type cells. Consistently, Akt2 knock-out cells had elevated Pak1 and Rac activities, suggesting that Akt2 inhibits Rac and Pak1. Both Akt2 and Akt1 associated in complexes with Pak1, but only Akt2 inhibited Pak1 in kinase assays, suggesting an underlying molecular basis for the different cellular phenotypes. Together these data provide evidence for an unexpected functional link between Akt2 and Pak1 that opposes the actions of Akt1 on cell migration.
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Affiliation(s)
- Guo-Lei Zhou
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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62
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Pirruccello M, Sondermann H, Pelton JG, Pellicena P, Hoelz A, Chernoff J, Wemmer DE, Kuriyan J. A dimeric kinase assembly underlying autophosphorylation in the p21 activated kinases. J Mol Biol 2006; 361:312-26. [PMID: 16837009 DOI: 10.1016/j.jmb.2006.06.017] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2006] [Revised: 06/08/2006] [Accepted: 06/09/2006] [Indexed: 12/14/2022]
Abstract
The p21-activated kinases (PAKs) are serine/threonine kinases that are involved in a wide variety of cellular functions including cytoskeletal motility, apoptosis, and cell cycle regulation. PAKs are inactivated by blockage of the active site of the kinase domain by an N-terminal regulatory domain. GTP-bound forms of Cdc42 and Rac bind to the regulatory domain and displace it, thereby allowing phosphorylation of the kinase domain and maximal activation. A key step in the activation process is the phosphorylation of the activation loop of one PAK kinase domain by another, but little is known about the underlying recognition events that make this phosphorylation specific. We show that the phosphorylated kinase domain of PAK2 dimerizes in solution and that this association is prevented by addition of a substrate peptide. We have identified a crystallographic dimer in a previously determined crystal structure of activated PAK1 in which two kinase domains are arranged face to face and interact through a surface on the large lobe of the kinase domain that is exposed upon release of the auto-inhibitory domain. The crystallographic dimer is suggestive of an engagement that mediates trans-autophosphorylation. Mutations at the predicted dimerization interface block dimerization and reduce the rate of autophosphorylation, supporting the role of this interface in PAK activation.
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Affiliation(s)
- Michelle Pirruccello
- Howard Hughes Medical Institute, Department of Molecular and Cell Biology, Department of Chemistry, University of California, Berkeley, CA 94720, USA
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63
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Orth JD, Krueger EW, Weller SG, McNiven MA. A novel endocytic mechanism of epidermal growth factor receptor sequestration and internalization. Cancer Res 2006; 66:3603-10. [PMID: 16585185 DOI: 10.1158/0008-5472.can-05-2916] [Citation(s) in RCA: 170] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cells form transient, circular dorsal ruffles or "waves" in response to stimulation of receptor tyrosine kinases, including epidermal growth factor receptor (EGFR) or platelet-derived growth factor receptor. These dynamic structures progress inward on the dorsal surface and disappear, occurring concomitantly with a marked reorganization of F-actin. The cellular function of these structures is largely unknown. Here we show that EGF-induced waves selectively sequester and internalize approximately 50% of ligand-bound EGFR from the cell surface. This process requires receptor phosphorylation, active phosphatidylinositol 3-kinase, and dynamin 2, although clathrin-coated pits or caveolae are not required. Epithelial and fibroblast cells stimulated with EGF sequestered EGFR rapidly into waves that subsequently generated numerous receptor-positive tubular-vesicular structures. Electron microscopy confirmed that waves formed along the dorsal membrane surface and extended numerous tubules into the cytoplasm. These findings characterize a structure that selectively sequesters large numbers of activated EGFR for their subsequent internalization, independent of traditional endocytic mechanisms such as clathrin pits or caveolae.
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Affiliation(s)
- James D Orth
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
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64
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Koretzky GA, Abtahian F, Silverman MA. SLP76 and SLP65: complex regulation of signalling in lymphocytes and beyond. Nat Rev Immunol 2006; 6:67-78. [PMID: 16493428 DOI: 10.1038/nri1750] [Citation(s) in RCA: 205] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
SLP76 and SLP65 are adaptor proteins that lack intrinsic enzymatic activity but contain multiple protein-binding domains. These proteins are essential for signalling downstream of integrins and receptors that contain immunoreceptor tyrosine-based activation motifs. The absence of these adaptor proteins profoundly affects various lineages in the haematopoietic compartment and severely compromises vascular development, highlighting their importance as regulators of signalling cascades. In this Review, we discuss the role of SLP76 and SLP65 in several signalling pathways in haematopoietic cells, with an emphasis on recent studies that provide insight into their mechanisms of action.
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Affiliation(s)
- Gary A Koretzky
- Department of Pathology and Laboratory Medicine, Abramson Family Cancer Research Institute, University of Pennsylvania, 415 BRBII/III, 421 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA.
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65
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Jones N, Blasutig IM, Eremina V, Ruston JM, Bladt F, Li H, Huang H, Larose L, Li SSC, Takano T, Quaggin SE, Pawson T. Nck adaptor proteins link nephrin to the actin cytoskeleton of kidney podocytes. Nature 2006; 440:818-23. [PMID: 16525419 DOI: 10.1038/nature04662] [Citation(s) in RCA: 364] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2006] [Accepted: 02/21/2006] [Indexed: 12/27/2022]
Abstract
The glomerular filtration barrier in the kidney is formed in part by a specialized intercellular junction known as the slit diaphragm, which connects adjacent actin-based foot processes of kidney epithelial cells (podocytes). Mutations affecting a number of slit diaphragm proteins, including nephrin (encoded by NPHS1), lead to renal disease owing to disruption of the filtration barrier and rearrangement of the actin cytoskeleton, although the molecular basis for this is unclear. Here we show that nephrin selectively binds the Src homology 2 (SH2)/SH3 domain-containing Nck adaptor proteins, which in turn control the podocyte cytoskeleton in vivo. The cytoplasmic tail of nephrin has multiple YDxV sites that form preferred binding motifs for the Nck SH2 domain once phosphorylated by Src-family kinases. We show that this Nck-nephrin interaction is required for nephrin-dependent actin reorganization. Selective deletion of Nck from podocytes of transgenic mice results in defects in the formation of foot processes and in congenital nephrotic syndrome. Together, these findings identify a physiological signalling pathway in which nephrin is linked through phosphotyrosine-based interactions to Nck adaptors, and thus to the underlying actin cytoskeleton in podocytes. Simple and widely expressed SH2/SH3 adaptor proteins can therefore direct the formation of a specialized cellular morphology in vivo.
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Affiliation(s)
- Nina Jones
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada
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66
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Brown MC, Cary LA, Jamieson JS, Cooper JA, Turner CE. Src and FAK kinases cooperate to phosphorylate paxillin kinase linker, stimulate its focal adhesion localization, and regulate cell spreading and protrusiveness. Mol Biol Cell 2005; 16:4316-28. [PMID: 16000375 PMCID: PMC1196340 DOI: 10.1091/mbc.e05-02-0131] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The ArfGAP paxillin kinase linker (PKL)/G protein-coupled receptor kinase-interacting protein (GIT)2 has been implicated in regulating cell spreading and motility through its transient recruitment of the p21-activated kinase (PAK) to focal adhesions. The Nck-PAK-PIX-PKL protein complex is recruited to focal adhesions by paxillin upon integrin engagement and Rac activation. In this report, we identify tyrosine-phosphorylated PKL as a protein that associates with the SH3-SH2 adaptor Nck, in a Src-dependent manner, after cell adhesion to fibronectin. Both cell adhesion and Rac activation stimulated PKL tyrosine phosphorylation. PKL is phosphorylated on tyrosine residues 286/392/592 by Src and/or FAK and these sites are required for PKL localization to focal adhesions and for paxillin binding. The absence of either FAK or Src-family kinases prevents PKL phosphorylation and suppresses localization of PKL but not GIT1 to focal adhesions after Rac activation. Expression of an activated FAK mutant in the absence of Src-family kinases partially restores PKL localization, suggesting that Src activation of FAK is required for PKL phosphorylation and localization. Overexpression of the nonphosphorylated GFP-PKL Triple YF mutant stimulates cell spreading and protrusiveness, similar to overexpression of a paxillin mutant that does not bind PKL, suggesting that failure to recruit PKL to focal adhesions interferes with normal cell spreading and motility.
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Affiliation(s)
- Michael C Brown
- Department of Cell and Developmental Biology, College of Medicine, State University of New York Upstate Medical University, Syracuse, NY 13210, USA
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67
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Gong C, Stoletov KV, Terman BI. VEGF treatment induces signaling pathways that regulate both actin polymerization and depolymerization. Angiogenesis 2005; 7:313-21. [PMID: 15886875 DOI: 10.1007/s10456-004-7960-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2004] [Accepted: 12/10/2004] [Indexed: 10/25/2022]
Abstract
The angiogenic growth factor vascular endothelial growth factor (VEGF) enhances endothelial cell migration through the activation of multiple signaling transduction pathways. Actin reorganization is an important component in VEGF-induced migration, yet the signaling pathways mediating this process remain unclear. Actin reorganization involves both actin polymerization and depolymerization, and in this study we demonstrate that VEGF-treatment regulates both of these activities. With respect to actin polymerization, our results indicate that the actin nucleation promoting factors (NPF) neural Wiskott-Aldrich syndrome protein (N-WASP) binds the SH2- plus SH3-domain containing adaptor protein Nck in both control and VEGF-treated cells. We had previously showed that VEGF treatment leads to the recruitment of Nck to activated receptor, and our current results indicate a VEGF-dependent redistribution of N-WASP to the cell surface. A Nck dominant-negative blocked Nck recruitment to receptor, blocked N-WASP cellular redistribution and attenuated actin stress fiber formation. With respect to actin depolymerization, VEGF-treatment led to the rapid phosphorylation of the actin depolymerization factor cofilin, and its upstream regulator, LIM-kinase (LIMK). Unlike what is observed in certain other cell types, the p21-activated kinase (PAK), a Nck binding protein, does not mediate VEGF-induced LIMK phosphorylation, as a PAK dominant-negative had no effect on this activity. The PAK dominant-negative also did not affect VEGF-induced actin reorganization. Pharmacological inhibitors of phosphoinositide-3 kinase (PI3-K) and the rho-activated kinase (ROCK) attenuated VEGF-induced LIMK phosphorylation, indicating a role for (PI3-K) and ROCK in the signaling pathways leading to regulation of LIMK activity.
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Affiliation(s)
- Chunhong Gong
- Cardiology Division, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, USA
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68
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Abstract
Adapter molecules are multidomain proteins lacking intrinsic catalytic activity, functioning instead by nucleating molecular complexes during signal transduction. The SLP-76 family of adapters includes SH2 domain-containing leukocyte phosphoprotein of 76kDa (SLP-76), B cell linker protein (BLNK), and cytokine-dependent hematopoietic cell linker (Clnk). These proteins are critical for integration of numerous signaling cascades downstream of immunotyrosine-based activation motif (ITAM)-bearing receptors and integrins in diverse hematopoietic cell types. Mutations in genes encoding SLP-76 family adapters result in severe phenotypes, underscoring the critical role these proteins play in cellular development and function by directing formation of signaling complexes in a temporally- and spatially-specific manner.
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Affiliation(s)
- Jennifer N Wu
- Department of Laboratory Medicine and Pathology, School of Medicine, Abramson Family Cancer Research Institute, University of Pennsylvania, 415 BRB II/III, 421 Curie Boulevard, Philadelphia, PA 19104, USA
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69
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Winters MJ, Pryciak PM. Interaction with the SH3 domain protein Bem1 regulates signaling by the Saccharomyces cerevisiae p21-activated kinase Ste20. Mol Cell Biol 2005; 25:2177-90. [PMID: 15743816 PMCID: PMC1061602 DOI: 10.1128/mcb.25.6.2177-2190.2005] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Saccharomyces cerevisiae PAK (p21-activated kinase) family kinase Ste20 functions in several signal transduction pathways, including pheromone response, filamentous growth, and hyperosmotic resistance. The GTPase Cdc42 localizes and activates Ste20 by binding to an autoinhibitory motif within Ste20 called the CRIB domain. Another factor that functions with Ste20 and Cdc42 is the protein Bem1. Bem1 has two SH3 domains, but target ligands for these domains have not been described. Here we identify an evolutionarily conserved binding site for Bem1 between the CRIB and kinase domains of Ste20. Mutation of tandem proline-rich (PxxP) motifs in this region disrupts Bem1 binding, suggesting that it serves as a ligand for a Bem1 SH3 domain. These PxxP motif mutations affect signaling additively with CRIB domain mutations, indicating that Bem1 and Cdc42 make separable contributions to Ste20 function, which cooperate to promote optimal signaling. This PxxP region also binds another SH3 domain protein, Nbp2, but analysis of bem1Delta versus nbp2Delta strains shows that the signaling defects of PxxP mutants result from impaired binding to Bem1 rather than from impaired binding to Nbp2. Finally, the PxxP mutations also reduce signaling by constitutively active Ste20, suggesting that postactivation functions of PAKs can be promoted by SH3 domain proteins, possibly by colocalizing PAKs with their substrates. The overall results also illustrate how the final signaling function of a protein can be governed by combinatorial addition of multiple, independent protein-protein interaction modules.
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Affiliation(s)
- Matthew J Winters
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 377 Plantation St., Four Biotech, Rm. 330, Worcester, MA 01605, USA
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70
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Parsons M, Monypenny J, Ameer-Beg SM, Millard TH, Machesky LM, Peter M, Keppler MD, Schiavo G, Watson R, Chernoff J, Zicha D, Vojnovic B, Ng T. Spatially distinct binding of Cdc42 to PAK1 and N-WASP in breast carcinoma cells. Mol Cell Biol 2005; 25:1680-95. [PMID: 15713627 PMCID: PMC549353 DOI: 10.1128/mcb.25.5.1680-1695.2005] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
While a significant amount is known about the biochemical signaling pathways of the Rho family GTPase Cdc42, a better understanding of how these signaling networks are coordinated in cells is required. In particular, the predominant subcellular sites where GTP-bound Cdc42 binds to its effectors, such as p21-activated kinase 1 (PAK1) and N-WASP, a homolog of the Wiskott-Aldritch syndrome protein, are still undetermined. Recent fluorescence resonance energy transfer (FRET) imaging experiments using activity biosensors show inconsistencies between the site of local activity of PAK1 or N-WASP and the formation of specific membrane protrusion structures in the cell periphery. The data presented here demonstrate the localization of interactions by using multiphoton time-domain fluorescence lifetime imaging microscopy (FLIM). Our data here establish that activated Cdc42 interacts with PAK1 in a nucleotide-dependent manner in the cell periphery, leading to Thr-423 phosphorylation of PAK1, particularly along the lengths of cell protrusion structures. In contrast, the majority of GFP-N-WASP undergoing FRET with Cy3-Cdc42 is localized within a transferrin receptor- and Rab11-positive endosomal compartment in breast carcinoma cells. These data reveal for the first time distinct spatial association patterns between Cdc42 and its key effector proteins controlling cytoskeletal remodeling.
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Affiliation(s)
- Maddy Parsons
- Randall Centre, King's College London, 3rd Floor, New Hunt's House, Guy's Medical School Campus, London SE1 1UL, United Kingdom.
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71
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Zhao ZS, Manser E. PAK and other Rho-associated kinases--effectors with surprisingly diverse mechanisms of regulation. Biochem J 2005; 386:201-14. [PMID: 15548136 PMCID: PMC1134783 DOI: 10.1042/bj20041638] [Citation(s) in RCA: 201] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2004] [Revised: 11/09/2004] [Accepted: 11/17/2004] [Indexed: 11/17/2022]
Abstract
The Rho GTPases are a family of molecular switches that are critical regulators of signal transduction pathways in eukaryotic cells. They are known principally for their role in regulating the cytoskeleton, and do so by recruiting a variety of downstream effector proteins. Kinases form an important class of Rho effector, and part of the biological complexity brought about by switching on a single GTPase results from downstream phosphorylation cascades. Here we focus on our current understanding of the way in which different Rho-associated serine/threonine kinases, denoted PAK (p21-activated kinase), MLK (mixed-lineage kinase), ROK (Rho-kinase), MRCK (myotonin-related Cdc42-binding kinase), CRIK (citron kinase) and PKN (protein kinase novel), interact with and are regulated by their partner GTPases. All of these kinases have in common an ability to dimerize, and in most cases interact with a variety of other proteins that are important for their function. A diversity of known structures underpin the Rho GTPase-kinase interaction, but only in the case of PAK do we have a good molecular understanding of kinase regulation. The ability of Rho GTPases to co-ordinate spatial and temporal phosphorylation events explains in part their prominent role in eukaryotic cell biology.
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Key Words
- cdc42
- mlk (mixed-lineage kinase)
- pak (p21-activated kinase)
- rac
- rho
- rok (rho-kinase)
- acc, anti-parallel coiled-coil
- crib, cdc42 and rac interactive binding
- crik, citron kinase
- crmp, collapsin response mediator protein
- dmpk, myotonic dystrophy kinase
- gef, guanine nucleotide exchange factor
- git1, g-protein-coupled receptor kinase-interacting target 1
- hsp90, heat shock protein 90
- jnk, c-jun n-terminal kinase
- ki, kinase inhibitory
- kim, ki motif
- limk, lim domain kinase
- mapk, mitogen-activated protein kinase
- mbs, myosin-binding subunit
- mekk, mapk/erk (extracellular-signal-regulated kinase) kinase kinase
- mkk, mapk kinase
- mlk, mixed-lineage kinase
- mrck, myotonin-related cdc42-binding kinase
- pak, p21-activated kinase
- pbd, p21-binding domain
- pdk1, 3-phosphoinositide-dependent kinase 1
- ph, pleckstrin homology
- pix, pak-interacting exchange factor
- pkc, protein kinase c
- pkn, protein kinase novel
- pp1, protein phosphatase type 1
- r-mlc, regulatory myosin light chain
- rok, rho-kinase
- sh3, src homology 3
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Affiliation(s)
- Zhou-shen Zhao
- GSK-IMCB Laboratory, Institute of Molecular and Cell Biology, Proteos Building, 61 Biopolis Drive, Singapore 138673
| | - Ed Manser
- GSK-IMCB Laboratory, Institute of Molecular and Cell Biology, Proteos Building, 61 Biopolis Drive, Singapore 138673
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72
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Pulkkinen K, Renkema GH, Kirchhoff F, Saksela K. Nef associates with p21-activated kinase 2 in a p21-GTPase-dependent dynamic activation complex within lipid rafts. J Virol 2004; 78:12773-80. [PMID: 15542629 PMCID: PMC524974 DOI: 10.1128/jvi.78.23.12773-12780.2004] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have previously reported that Nef specifically interacts with a small but highly active subpopulation of p21-activated kinase 2 (PAK2). Here we show that this is due to a transient association of Nef with a PAK2 activation complex within a detergent-insoluble membrane compartment containing the lipid raft marker GM1. The low abundance of this Nef-associated kinase (NAK) complex was found to be due to an autoregulatory mechanism. Although activation of PAK2 was required for assembly of the NAK complex, catalytic activity of PAK2 also promoted dissociation of this complex. Testing different constitutively active PAK2 mutants indicated that the conformation associated with p21-mediated activation rather than kinase activity per se was required for PAK2 to become NAK. Although association with PAK2 is one of the most conserved properties of Nef, we found that the ability to stimulate PAK2 activity differed markedly among divergent Nef alleles, suggesting that PAK2 association and activation are distinct functions of Nef. However, mutations introduced into the p21-binding domain of PAK2 revealed that p21-GTPases are involved in both of these Nef functions and, in addition to promoting PAK2 activation, also help to physically stabilize the NAK complex.
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Affiliation(s)
- Kati Pulkkinen
- Institute of Medical Technology, FIN-33014, University of Tampere, Tampere, Finland
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73
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Wang Y, Li Y, Zeng W, Zhu C, Xiao J, Yuan W, Wang Y, Cai Z, Zhou J, Liu M, Wu X. IXL, a new subunit of the mammalian Mediator complex, functions as a transcriptional suppressor. Biochem Biophys Res Commun 2004; 325:1330-8. [PMID: 15555573 DOI: 10.1016/j.bbrc.2004.10.159] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2004] [Indexed: 10/26/2022]
Abstract
Transcription factors play an essential role in altering gene expression. Much progress about transcription factors has been made toward the understanding of normal physiological processes, embryonic development, and human diseases. In the present study, we report the identification and characterization of a novel human gene, (Drosophila) intersex-like (IXL), from a human embryonic heart cDNA library. IXL encodes a putative protein of 221 amino acids. The protein is conserved across different species during evolution. Northern blot analysis indicates that IXL is expressed in various tissues of human adult and during three different developmental stages of embryo. In COS-7 cells, IXL protein is localized to nucleus and cytoplasm. IXL is a transcription suppressor when fused to Gal-4 DNA-binding domain and cotransfected with VP-16. Overexpression of IXL in COS-7 cells inhibits the transcriptional activities of SRE and AP-1, suggesting that the IXL protein may act as a transcriptional suppressor in mitogen-activated protein kinase signaling pathway to mediate cellular functions.
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Affiliation(s)
- Yuequn Wang
- The Center for Heart Development, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, People's Republic of China
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74
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Sundberg-Smith LJ, Doherty JT, Mack CP, Taylor JM. Adhesion stimulates direct PAK1/ERK2 association and leads to ERK-dependent PAK1 Thr212 phosphorylation. J Biol Chem 2004; 280:2055-64. [PMID: 15542607 DOI: 10.1074/jbc.m406013200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] 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 Ras/Raf/MEK/ERK Map kinase signaling cascade, likely because of PAK co-activation of Raf and MEK. Herein, we found that adhesion signaling also stimulates an association between PAK1 and ERK1/2. PAK1 and ERK1/2 co-immunoprecipitated from rat aortic smooth muscle cells (SMC) plated on fibronectin, and the two proteins co-localized in membrane ruffles and adhesion complexes following PDGF-BB or sphingosine 1-phosphate treatment, respectively. Far Western analysis demonstrated a direct association between the two proteins, and peptide mapping identified an ERK2 binding site within the autoinhibitory domain of PAK1. Interestingly, deletion of a major ERK binding site in PAK attenuates activation of an ERK-dependent serum-responsive element (SRE)-luciferase reporter gene, indicating that association between PAK and ERK is required to facilitate ERK signaling. We also show that ERK2 phosphorylates PAK1 on Thr(212) in vitro and that Thr(212) is phosphorylated in smooth muscle cells following PDGF-BB treatment in an adhesion- and MEK/ERK-dependent fashion. Expression of a phosphomimic variant, PAK-T212E, does not alter ERK association, but markedly attenuates downstream ERK signaling. Taken together, these data suggest that PAK1 may facilitate ERK signaling by serving as a scaffold to recruit Raf, MEK, and ERK to adhesion complexes, and that subsequent growth factor-stimulated phosphorylation of PAK-Thr(212) by ERK may serve to provide a negative feedback signal to control coordinate activation of ERK by growth factor- and matrix-induced signals.
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Affiliation(s)
- Liisa J Sundberg-Smith
- Department of Pathology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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75
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Sitko JC, Guevara CI, Cacalano NA. Tyrosine-phosphorylated SOCS3 Interacts with the Nck and Crk-L Adapter Proteins and Regulates Nck Activation. J Biol Chem 2004; 279:37662-9. [PMID: 15173187 DOI: 10.1074/jbc.m404007200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Suppressors of cytokine signaling (SOCS) are negative feedback inhibitors of cytokine and growth factor signal transduction. Although the affect of SOCS proteins on the Jak-STAT pathway has been well characterized, their role in the regulation of other signaling modules is not well understood. In the present study, we demonstrate that SOCS3 physically interacts with the SH2/SH3-containing adapter proteins Nck and Crk-L, which are known to couple activated receptors to multiple downstream signaling pathways and the actin cytoskeleton. Our data show that the SOCS3/Nck and SOCS3/Crk-L interactions depend on tyrosine phosphorylation of SOCS3 Tyr(221) within the conserved SOCS box motif and intact SH2 domains of Nck and Crk-L. Furthermore, SOCS3 Tyr(221) forms a YXXP motif, which is a consensus binding site for the Nck and Crk-L SH2 domains. Expression of SOCS3 in NIH3T3 cells induces constitutive recruitment of a Nck-GFP fusion protein to the plasma membrane and constitutive tyrosine phosphorylation of endogenous Nck. Our findings suggest that SOCS3 regulates multiple cytokine and growth factor-activated signaling pathways by acting as a recruitment factor for adapter proteins.
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Affiliation(s)
- John C Sitko
- Department of Radiation Oncology, University of California Los Angeles, School of Medicine, Center for Health Sciences, Los Angeles, California 90095, USA
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76
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Miyamoto Y, Yamauchi J, Mizuno N, Itoh H. The Adaptor Protein Nck1 Mediates Endothelin A Receptor-regulated Cell Migration through the Cdc42-dependent c-Jun N-terminal Kinase Pathway. J Biol Chem 2004; 279:34336-42. [PMID: 15187089 DOI: 10.1074/jbc.m402767200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cell migration plays key roles in physiological and pathological phenomena, such as development and oncogenesis. The adaptor proteins Grb2, CrkII, and Nck1 are composed of only a single Src homology 2 domain and some Src homology 3 domains, giving specificity to each signal transduction pathway. However, little is known about the relationships between their adaptor proteins and cell migration, which are regulated by the G protein-coupled receptor. Here we showed that Nck1, but not Grb2 or CrkII, mediated the inhibition of cell migration induced by the endothelin-1 and endothelin A receptor. The small interference RNA and dominant negative mutants of Nck1 diminished the endothelin-1-induced inhibition of cell migration. Although overexpression of wild-type Nck1 was detected in the cytosol and did not affect cell migration, expression of the myristoylation signal sequence-conjugated Nck1 was detected in the membrane and induced activation of Cdc42 and c-Jun N-terminal kinase, inhibiting cell migration. Taken together, these results suggest that the endothelin A receptor transduces the signal of inhibition of cell migration through Cdc42-dependent c-Jun N-terminal kinase activation by using Nck1.
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Affiliation(s)
- Yuki Miyamoto
- Department of Cell Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
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77
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Menard RE, Mattingly RR. Cell surface receptors activate p21-activated kinase 1 via multiple Ras and PI3-kinase-dependent pathways. Cell Signal 2004; 15:1099-109. [PMID: 14575865 DOI: 10.1016/s0898-6568(03)00087-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
p21-activated kinases (PAKs) were the first identified mammalian members of a growing family of Ste20-like serine-threonine protein kinases. In this study, we show that PAK1 can be stimulated by carbachol, lysophosphatidic acid (LPA), epidermal growth factor (EGF), and phorbol 12-myristate 13-acetate (PMA) by multiple independent and overlapping pathways. Dominant-negative Ras, Rac, and Cdc42 inhibited PAK1 activation by all of these agonists, while active Rac1 and Cdc42 were sufficient to maximally activate PAK1 in the absence of any treatment. Active Ras induced only a weak activation of PAK1 that could be potentiated by muscarinic receptor stimulation. Studies using inhibitors of the EGF receptor tyrosine kinase, phosphatidylinositol 3-kinase (PI3-kinase) and protein kinase C (PKC) revealed that all of the cell surface agonists could activate PAK1 through pathways independent of PKC, that EGF stimulated a PI3-kinase dependent pathway to stimulate PAK1, and that muscarinic receptor stimulation of PAK1 was predominantly mediated through this EGF-R-dependent mechanism. Activation of PAK1 by LPA was independent of PI3-kinase and the EGF receptor, but was inhibited by dominant-negative RhoA. These results identify multiple Ras-dependent pathways to activation of PAK1.
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Affiliation(s)
- Raymond E Menard
- Department of Pharmacology, Wayne State University, 540 E. Canfield, Room 6326, Detroit, MI 48201, USA
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78
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Loo TH, Ng YW, Lim L, Manser E. GIT1 activates p21-activated kinase through a mechanism independent of p21 binding. Mol Cell Biol 2004; 24:3849-59. [PMID: 15082779 PMCID: PMC387736 DOI: 10.1128/mcb.24.9.3849-3859.2004] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
p21-activated kinases (PAKs) associate with a guanine nucleotide exchange factor, Pak-interacting exchange factor (PIX), which in turn binds the paxillin-associated adaptor GIT1 that targets the complex to focal adhesions. Here, a detailed structure-function analysis of GIT1 reveals how this multidomain adaptor also participates in activation of PAK. Kinase activation does not occur via Cdc42 or Rac1 GTPase binding to PAK. The ability of GIT1 to stimulate alphaPAK autophosphorylation requires the participation of the GIT N-terminal Arf-GAP domain but not Arf-GAP activity and involves phosphorylation of PAK at residues common to Cdc42-mediated activation. Thus, the activation of PAK at adhesion complexes involves a complex interplay between the kinase, Rho GTPases and protein partners that provide localization cues.
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Affiliation(s)
- Tsui-Han Loo
- GSK-IMCB Group, Institute of Molecular and Cell Biology, Singapore 117609, Singapore
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79
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Heckman CA, Urban JM, Cayer M, Li Y, Boudreau N, Barnes J, Plummer HK, Hall C, Kozma R, Lim L. Novel p21-activated kinase-dependent protrusions characteristically formed at the edge of transformed cells. Exp Cell Res 2004; 295:432-47. [PMID: 15093742 DOI: 10.1016/j.yexcr.2003.12.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2003] [Revised: 12/10/2003] [Indexed: 11/20/2022]
Abstract
During long-term culture, certain lines become neoplastic while accumulating changes in cell shape. Early and late cell populations have characteristic shape phenotypes that have been quantified by computerized assay. Phenotypes are determined from variables describing three-dimensional aspects of the subcellular distribution of mass. The features of cells can be recognized by use of latent factors, which are theoretical variables based on the covariance of the primary variables. Factor #7 represented a cell edge feature different from filopodia. We studied the morphological characteristics and morphogenesis of the feature. Brief exposure of cells from rat tracheal epithelium to phorbol 12-myristate 13-acetate (PMA) enhanced #7 values. The time to reach maximal #7 values was prolonged if PMA was administered with calcium ionophore or lysophosphatidic acid (LPA). Factor #7 was elevated during periods of ruffling suppression and stress fiber reorganization. Cells showing high #7 values were examined by scanning electron microscopy (SEM) and found to exhibit strap-shaped and cupola-shaped projections. Because RhoA regulates stress fiber formation, we sought to perturb #7 features by introducing dominant-acting negative and positive constructs of RhoA, RhoA-N19, and RhoA-V14. Neither affected #7 values. Although overexpression of the kinase inhibitory domain of p21-activated kinase 1 (PAK) had no effect on #7 values, they were affected by overexpression of a domain binding PAK-interacting guanine nucleotide exchange factor (PIX). Because a PAK-PIX complex is implicated in the remodeling of focal complexes (FCs) and recycling of PAK to the cytoplasm, the results implicate a component of FCs in the formation of #7 features. The data suggested that feature formation is driven by activated Cdc42-binding kinase (ACK) and Rac. Moreover, they suggested that the #7 protrusions are neurite-like structures and that their development involves FC regulation.
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Affiliation(s)
- C A Heckman
- Department of Biological Sciences and Center for Microscopy and Microanalysis, Bowling Green State University, Bowling Green, OH 43403, USA.
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80
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Krautkrämer E, Giese SI, Gasteier JE, Muranyi W, Fackler OT. Human immunodeficiency virus type 1 Nef activates p21-activated kinase via recruitment into lipid rafts. J Virol 2004; 78:4085-97. [PMID: 15047825 PMCID: PMC374280 DOI: 10.1128/jvi.78.8.4085-4097.2004] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Nef protein of human immunodeficiency virus type 1 is an important factor in AIDS pathogenesis. In addition to downregulating CD4 and major histocompatibility complex class I molecules from the cell surface, as well as increasing virion infectivity, Nef triggers activation of the T-cell receptor (TCR) cascade to facilitate virus spread. Signaling pathways that are induced by Nef have been identified; however, it is unclear how and in which subcellular compartment Nef triggers signaling. Nef recruits a multiprotein complex to activate the cellular Pak kinase that mediates downstream effector functions. Since a subpopulation of Nef is present in detergent-insoluble microdomains (lipid rafts) from where physiological TCR signaling is initiated, we tested whether lipid rafts are instrumental for Nef-mediated Pak activation. In flotation analysis, Nef-associated Pak activity exclusively fractionated with lipid rafts. Activation of Pak in the presence of Nef coincided with lipid raft recruitment of the kinase, which was otherwise excluded from detergent-insoluble microdomains. Experimental solubilization of lipid rafts interfered with the association of Pak activity with Nef. To analyze the importance of the raft localization for Nef function more rigorously, we generated a palmitoylated Nef (PalmNef). PalmNef was highly enriched in lipid rafts and associated with significantly higher levels of Pak activity than Nef. Notably, activation of Pak by its physiological activators, Cdc42 and Rac, also occurred in lipid rafts and required raft integrity. Together, these data suggest that Nef induces signal transduction via the recruitment of a signaling machinery including Pak into lipid rafts, thereby mimicking a physiological cellular mechanism to initiate the TCR cascade.
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Affiliation(s)
- Ellen Krautkrämer
- Abteilung Virologie, Universitätsklinikum Heidelberg, D-69120 Heidelberg, Germany
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81
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Stofega MR, Sanders LC, Gardiner EM, Bokoch GM. Constitutive p21-activated kinase (PAK) activation in breast cancer cells as a result of mislocalization of PAK to focal adhesions. Mol Biol Cell 2004; 15:2965-77. [PMID: 15047871 PMCID: PMC420118 DOI: 10.1091/mbc.e03-08-0604] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Cytoskeletal remodeling is critical for cell adhesion, spreading, and motility. p21-activated kinase (PAK), an effector molecule of the Rho GTPases Rac and Cdc42, has been implicated in cytoskeletal remodeling and cell motility. PAK kinase activity and subcellular distribution are tightly regulated by rapid and transient localized Rac and Cdc42 activation, and by interactions mediated by adapter proteins. Here, we show that endogenous PAK is constitutively activated in certain breast cancer cell lines and that this active PAK is mislocalized to atypical focal adhesions in the absence of high levels of activated Rho GTPases. PAK localization to focal adhesions in these cells is independent of PAK kinase activity, NCK binding, or GTPase binding, but requires the association of PAK with PIX. Disruption of the PAK-PIX interaction with competitive peptides displaces PAK from focal adhesions and results in a substantial reduction in PAK hyperactivity. Moreover, disruption of the PAK-PIX interaction is associated with a dramatic decrease of PIX and paxillin in focal adhesions, indicating that PAK localization to these structures via PIX is required for the maintenance of paxillin- and PIX-containing focal adhesions. Abnormal regulation of PAK localization and activity may contribute to the tumorigenic properties of certain breast cancer cells.
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Affiliation(s)
- Mary R Stofega
- Department of Immunology, The Scripps Research Institute, San Diego, California 92037, USA
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82
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Abstract
The p21-activated kinases (PAKs) 1-3 are serine/threonine protein kinases whose activity is stimulated by the binding of active Rac and Cdc42 GTPases. Our understanding of the regulation and biology of these important signaling proteins has increased tremendously since their discovery in the mid-1990s. PAKs 1-3 are activated by a variety of GTPase-dependent and -independent mechanisms. This complexity reflects the contributions of PAK function in many cellular signaling pathways and the need to carefully control PAK action in a highly localized manner. PAKs serve as important regulators of cytoskeletal dynamics and cell motility, transcription through MAP kinase cascades, death and survival signaling, and cell-cycle progression. Consequently, PAKs have also been implicated in a number of pathological conditions and in cell transformation. We propose here a key role for PAK action in coordinating the dynamics of the actin and microtubule cytoskeletons during directional motility of cells, as well as in other functions requiring cytoskeletal polarization.
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Affiliation(s)
- Gary M Bokoch
- Departments of Immunology and Cell Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
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83
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Menard RE, Mattingly RR. Gβγ subunits stimulate p21-activated kinase 1 (PAK1) through activation of PI3-kinase and Akt but act independently of Rac1/Cdc42. FEBS Lett 2003; 556:187-92. [PMID: 14706848 DOI: 10.1016/s0014-5793(03)01406-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The p21-activated kinase (PAK) family is homologous to the yeast sterile 20 (Ste20) and regulates a wide variety of cellular responses, including cell morphology, proliferation, and survival. In this study we examined the activation of PAK1 by Gbetagamma subunits. Co-transfection of COS7 cells with Gbeta1gamma2 or Gbeta1gamma5 was sufficient to induce agonist-independent activation of PAK1. Expression of dominant/negative Rac, Cdc42, or Ras did not inhibit this Gbetagamma-dependent activation. Wortmannin, which inhibits phosphoinositide 3-kinase (PI3-kinase) activity, and expression of a dominant/negative form of Akt were sufficient to abrogate the activation of PAK1 that was induced by Gbetagamma. These results reveal that stimulation of PAK1 by Gbetagamma can occur via a PI3-kinase and Akt pathway that does not require Rac1 or Cdc42.
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Affiliation(s)
- Raymond E Menard
- Department of Pharmacology, Wayne State University, 540 East Canfield Avenue, Room 6326, Detroit, MI 48201, USA
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84
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Zhou GL, Zhuo Y, King CC, Fryer BH, Bokoch GM, Field J. Akt phosphorylation of serine 21 on Pak1 modulates Nck binding and cell migration. Mol Cell Biol 2003; 23:8058-69. [PMID: 14585966 PMCID: PMC262366 DOI: 10.1128/mcb.23.22.8058-8069.2003] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2003] [Revised: 05/06/2003] [Accepted: 08/13/2003] [Indexed: 12/30/2022] Open
Abstract
The p21-activated protein kinases (Paks) regulate cellular proliferation, differentiation, transformation, and survival through multiple downstream signals. Paks are activated directly by the small GTPases Rac and Cdc42 and several protein kinases including Akt and PDK-1. We found that Akt phosphorylated and modestly activated Pak1 in vitro. The major site phosphorylated by Akt on Pak1 mapped to serine 21, a site originally shown to be weakly autophosphorylated on Pak1 when Cdc42 or Rac activates it. A peptide derived from the region surrounding serine 21 was a substrate for Akt but not Pak1 in vitro, and Akt stimulated serine 21 phosphorylation on the full-length Pak1 much better than Rac did. The adaptor protein Nck binds Pak near serine 21, and its association is regulated by phosphorylation of this site. We found that either treatment of Pak1 in vitro with Akt or coexpression of constitutively active Akt with Pak1 reduced Nck binding to Pak1. In HeLa cells, green fluorescent protein-tagged Pak1 was concentrated at focal adhesions and was released when Akt was cotransfected. A peptide containing the Nck binding site of Pak1 fused to a portion of human immunodeficiency virus Tat to allow it to enter cells was used to test the functional importance of Nck/Pak binding in Akt-stimulated cell migration. This Tat-Nck peptide reduced Akt-stimulated cell migration. Together, these data suggest that Akt modulates the association of Pak with Nck to regulate cell migration.
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Affiliation(s)
- Guo-Lei Zhou
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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85
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Kissil JL, Wilker EW, Johnson KC, Eckman MS, Yaffe MB, Jacks T. Merlin, the Product of the Nf2 Tumor Suppressor Gene, Is an Inhibitor of the p21-Activated Kinase, Pak1. Mol Cell 2003; 12:841-9. [PMID: 14580336 DOI: 10.1016/s1097-2765(03)00382-4] [Citation(s) in RCA: 187] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The Nf2 tumor suppressor gene codes for merlin, a protein whose function has been elusive. We describe a novel interaction between merlin and p21-activated kinase 1 (Pak1), which is dynamic and facilitated upon increased cellular confluence. Merlin inhibits the activation of Pak1, as the loss of merlin expression results in the inappropriate activation of Pak1 under conditions associated with low basal activity. Conversely, the overexpression of merlin in cells that display a high basal activity of Pak1 resulted in the inhibition of Pak1 activation. This inhibitory function of merlin is mediated through its binding to the Pak1 PBD and by inhibiting Pak1 recruitment to focal adhesions. This link provides a possible mechanism for the effect of loss of merlin expression in tumorigenesis.
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Affiliation(s)
- Joseph L Kissil
- Department of Biology and Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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86
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Li Z, Hannigan M, Mo Z, Liu B, Lu W, Wu Y, Smrcka AV, Wu G, Li L, Liu M, Huang CK, Wu D. Directional sensing requires G beta gamma-mediated PAK1 and PIX alpha-dependent activation of Cdc42. Cell 2003; 114:215-27. [PMID: 12887923 DOI: 10.1016/s0092-8674(03)00559-2] [Citation(s) in RCA: 313] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Efficient chemotaxis requires directional sensing and cell polarization. We describe a signaling mechanism involving G beta gamma, PAK-associated guanine nucleotide exchange factor (PIX alpha), Cdc42, and p21-activated kinase (PAK) 1. This pathway is utilized by chemoattractants to regulate directional sensing and directional migration of myeloid cells. Our results suggest that G beta gamma binds PAK1 and, via PAK-associated PIX alpha, activates Cdc42, which in turn activates PAK1. Thus, in this pathway, PAK1 is not only an effector for Cdc42, but it also functions as a scaffold protein required for Cdc42 activation. This G beta gamma-PAK1/PIX alpha/Cdc42 pathway is essential for the localization of F-actin formation to the leading edge, the exclusion of PTEN from the leading edge, directional sensing, and the persistent directional migration of chemotactic leukocytes. Although ligand-induced production of PIP(3) is not required for activation of this pathway, PIP(3) appears to localize the activation of Cdc42 by the pathway.
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Affiliation(s)
- Zhong Li
- Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, CT 06030, USA
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87
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Bladt F, Aippersbach E, Gelkop S, Strasser GA, Nash P, Tafuri A, Gertler FB, Pawson T. The murine Nck SH2/SH3 adaptors are important for the development of mesoderm-derived embryonic structures and for regulating the cellular actin network. Mol Cell Biol 2003; 23:4586-97. [PMID: 12808099 PMCID: PMC164855 DOI: 10.1128/mcb.23.13.4586-4597.2003] [Citation(s) in RCA: 152] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2002] [Revised: 01/14/2003] [Accepted: 03/24/2003] [Indexed: 01/02/2023] Open
Abstract
Mammalian Nck1 and Nck2 are closely related adaptor proteins that possess three SH3 domains, followed by an SH2 domain, and are implicated in coupling phosphotyrosine signals to polypeptides that regulate the actin cytoskeleton. However, the in vivo functions of Nck1 and Nck2 have not been defined. We have mutated the murine Nck1 and Nck2 genes and incorporated beta-galactosidase reporters into the mutant loci. In mouse embryos, the two Nck genes have broad and overlapping expression patterns. They are functionally redundant in the sense that mice deficient for either Nck1 or Nck2 are viable, whereas inactivation of both Nck1 and Nck2 results in profound defects in mesoderm-derived notochord and embryonic lethality at embryonic day 9.5. Fibroblast cell lines derived from Nck1(-/-) Nck2(-/-) embryos have defects in cell motility and in the organization of the lamellipodial actin network. These data suggest that the Nck SH2/SH3 adaptors have important functions in the development of mesodermal structures during embryogenesis, potentially linked to a role in cell movement and cytoskeletal organization.
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Affiliation(s)
- Friedhelm Bladt
- Programme in Molecular Biology and Cancer, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada
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88
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Poitras L, Jean S, Islam N, Moss T. PAK interacts with NCK and MLK2 to regulate the activation of jun N-terminal kinase. FEBS Lett 2003; 543:129-35. [PMID: 12753919 DOI: 10.1016/s0014-5793(03)00424-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The p21-GTPase activated kinase, PAK1, and the mixed lineage kinase, MLK2, have been implicated in the activation of jun N-terminal kinase (JNK). However, the role of PAK1 in JNK activation is still not understood. Here we show that over-expression of the SH3-SH2 adapter Nck 'squelches' JNK activation but this squelching is relieved by over-expression of PAK1. In turn, PAK1 squelches activation of JNK by MLK2 and these kinases interact via their catalytic domains. The data suggest that PAK1 recruits MLK2 to an activated receptor via the adapter Nck, but cannot itself induce activation of the JNK cascade.
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Affiliation(s)
- Luc Poitras
- Cancer Research Centre and Department of Medical Biology, Laval University, Hôtel-Dieu de Quebec, 9 rue McMahon, G1R 2J6, Québec, QC, Canada
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89
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Huang Z, Ling J, Traugh JA. Localization of p21-activated protein kinase gamma-PAK/Pak2 in the endoplasmic reticulum is required for induction of cytostasis. J Biol Chem 2003; 278:13101-9. [PMID: 12560339 DOI: 10.1074/jbc.m212557200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The intracellular localization and physiological functions of the p21-activated protein kinase gamma-PAK have been examined in human embryonic kidney 293T and COS-7 cells. At 1-4 days post-transfection, cell division is inhibited by the expression of wild type (WT) gamma-PAK and the mutant S490A, whereas cells expressing S490D and the inactive mutants K278R and T402A grow exponentially, indicating a role for gamma-PAK in the induction of cytostasis. WT gamma-PAK and S490A are localized in a region surrounding the nucleus identified as the endoplasmic reticulum (ER), as determined by immunofluorescence, whereas K278R, T402A, and S490D lack localization. As shown by sucrose density gradient centrifugation, WT gamma-PAK, S490A, and endogenous gamma-PAK are distributed among the high density (ER-associated), intermediate density, and low density fractions, whereas the mutants that do not inhibit cell division are present only as soluble enzyme. The amount of endogenous gamma-PAK associated with the particulate fractions is increased 4-fold when cell division is inhibited by ionizing radiation. gamma-PAK in the ER and intermediate density fractions has high specific activity and is active, whereas the soluble form of gamma-PAK has low activity and is activable. The importance of localization of gamma-PAK is supported by data with the C-terminal mutants S490D and Delta 488; these mutants have high levels of protein kinase activity but do not induce cytostasis and are not bound to the ER. A model for the induction of cytostasis by gamma-PAK through targeting of gamma-PAK to the ER is presented in which gamma-PAK activity and Ser-490 are implicated in the regulation of cytostasis.
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Affiliation(s)
- Zhongdong Huang
- Department of Biochemistry, University of California, Riverside, California 92521, USA
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90
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Lu Y, Pan ZZ, Devaux Y, Ray P. p21-activated protein kinase 4 (PAK4) interacts with the keratinocyte growth factor receptor and participates in keratinocyte growth factor-mediated inhibition of oxidant-induced cell death. J Biol Chem 2003; 278:10374-80. [PMID: 12529371 DOI: 10.1074/jbc.m205875200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Keratinocyte growth factor (KGF), a member of the fibroblast growth factor (FGF) family (also known as FGF-7), is an important protective factor for epithelial cells. The receptor for KGF (also called FGFR2-IIIb), which has intrinsic tyrosine kinase activity, is expressed specifically on epithelial cells and in the lung epithelium. Administration of KGF has been shown to protect the lung from various insults, but the mechanism of protection is not well understood. To understand the mechanism by which KGF exerts protective functions on epithelial cells, we used the yeast two-hybrid assay to identify proteins that interact with the KGF receptor (KGFR). Here we show that the cytoplasmic domain of KGFR interacts with p21-activated protein kinase (PAK) 4, which is a new member of the PAK family. The PAKs are regulated by the Rho-family GTPases Rac and Cdc42. PAK4 is the most divergent member of the PAK family of proteins and may have distinct functions. However, stimuli that regulate PAK4 activity are not known. Our data show that PAK4 can associate with the KGFR, which is dependent on KGFR tyrosine kinase activity. We show that a dominant negative mutant of PAK4 blocks KGF-mediated inhibition of caspase-3 activation in epithelial cells subjected to oxidant stress. Our data demonstrate that PAK4 is an important mediator of the anti-apoptotic effects of KGF on epithelial cells.
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Affiliation(s)
- Yunbiao Lu
- Yale University School of Medicine, New Haven, Connecticut 06510, USA
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91
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Puto LA, Pestonjamasp K, King CC, Bokoch GM. p21-activated kinase 1 (PAK1) interacts with the Grb2 adapter protein to couple to growth factor signaling. J Biol Chem 2003; 278:9388-93. [PMID: 12522133 DOI: 10.1074/jbc.m208414200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A variety of intracellular signaling pathways are linked to cell surface receptor signaling through their recruitment by Src homology 2 (SH2)/SH3-containing adapter molecules. p21-activated kinase 1 (PAK1) is an effector of Rac/Cdc42 GTPases that has been implicated in the regulation of cytoskeletal dynamics, proliferation, and cell survival signaling. In this study, we describe the specific interaction of PAK1 with the Grb2 adapter protein both in vitro and in vivo. We identify the site of this interaction as the second proline-rich SH3 binding domain of PAK1. Stimulation of the epidermal growth factor receptor (EGFR) in HaCaT cells enhances the level of EGFR-associated PAK1 and Grb2, although the PAK1-Grb2 association is itself independent of this stimulation. A cell-permeant TAT-tagged peptide encompassing the second proline-rich SH3 binding domain of PAK1 simultaneously blocked Grb2 and activated EGFR association with PAK1, in vitro and in vivo, indicating that Grb2 mediates the interaction of PAK1 with the activated EGFR. Blockade of this interaction decreased the epidermal growth factor-induced extension of membrane lamellae. Thus Grb2 may serve as an important mechanism for linking downstream PAK signaling to various upstream pathways.
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Affiliation(s)
- Lorena A Puto
- Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA
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92
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Gujdár A, Sipeki S, Bander E, Buday L, Faragó A. Phorbol ester-induced migration of HepG2 cells is accompanied by intensive stress fibre formation, enhanced integrin expression and transient down-regulation of p21-activated kinase 1. Cell Signal 2003; 15:307-18. [PMID: 12531429 DOI: 10.1016/s0898-6568(02)00087-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Previously, we observed that phorbol ester induced more intensive scattering of HepG2 human hepatoma cells than hepatocyte growth factor (HGF). Regulatory components accounting for this intensive migration were studied. Phorbol ester-activated protein kinase C induced the early appearance of a great number of actin stress fibres. Whereas in response to HGF, the activation of phosphatidylinositol 3-kinase initiates the rearrangements of the actin cytoskeleton, in phorbol ester-treated cells, the activation of this enzyme was not required to the actin polymerisation. Activation of Erk1/Erk2 MAP kinases that was essential to the migration had a key role in enhancing the adherence of cells to the extracellular matrix via the increased expression of integrins alpha2, alpha6 and beta1. Protein kinase C stimulated the activation of p21-activated kinase (PAK), as well. However, it also stimulated the selective and transient down-regulation of PAK1, which coincided with the formation of stress fibres.
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Affiliation(s)
- Annamária Gujdár
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University of Medicine, PO Box 260, 1444 Budapest, Hungary
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93
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Otsuki Y, Tanaka M, Kamo T, Kitanaka C, Kuchino Y, Sugimura H. Guanine nucleotide exchange factor, Tiam1, directly binds to c-Myc and interferes with c-Myc-mediated apoptosis in rat-1 fibroblasts. J Biol Chem 2003; 278:5132-40. [PMID: 12446731 DOI: 10.1074/jbc.m206733200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transcription factor c-Myc is important for the control of cell growth, cell cycle progression, neoplasia, and apoptotic cell death. Recently, c-Myc-binding proteins, which bind either to the N-terminal domain or the C-terminal domain of c-Myc, have been proposed as the key molecules to realize the mechanisms of these multiple c-Myc functions. We report in the present study on another protein, Tiam1, which is a specific guanine nucleotide exchange factor of Rac1 and which binds to c-Myc and modulates several of its biological functions. We were able to detect the direct binding and in vivo association between c-Myc and Tiam1. The necessary role in this interaction of the Myc box II of c-Myc was revealed in the cell extracts. The additional discovery of the intranuclear localization of Tiam1 in Rat1 cells and in neuronal cells of the mouse brain suggests this interaction may occur in the nucleus. Overexpression of Tiam1 repressed the luciferase activity of c-Myc and also inhibited the c-Myc apoptotic activity through this protein-protein interaction. Taken together, we concluded that Tiam1 is another c-Myc regulator, working in the nuclei to control c-Myc-related apoptosis.
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Affiliation(s)
- Yoshiro Otsuki
- First Department of Pathology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan
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94
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Rousseau V, Goupille O, Morin N, Barnier JV. A new constitutively active brain PAK3 isoform displays modified specificities toward Rac and Cdc42 GTPases. J Biol Chem 2003; 278:3912-20. [PMID: 12464619 DOI: 10.1074/jbc.m207251200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
p21-activated kinases (PAK) are involved in the control of cytoskeleton dynamics and cell cycle progression. Here we report the characterization of a new mammalian PAK3 mRNA that contains a 45-bp alternatively spliced exon. This exon encodes for 15 amino acids that are inserted in the regulatory domain, inside the autoinhibitory domain but outside the Cdc42 and Rac interactive binding domain. The transcript of the 68-kDa new isoform named PAK3b is expressed in various areas of the adult mouse brain. In contrast to PAK3 without the exon b (PAK3a), whose basal kinase activity is weak in resting cells, PAK3b displays a high kinase activity in starved cells that is not further stimulated by active GTPases. Indeed, we demonstrate that the autoinhibitory domain of PAK3b no longer inhibits the kinase activity of PAK3. Moreover, we show that the 15-amino acid insertion within the autoinhibitory domain impedes the ability of PAK3b to bind to the GTPases Rac and Cdc42 and changes its specificity toward the GTPases. Altogether, our results show that the new PAK3b isoform has unique properties and would signal differently from PAK3a in neurons.
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Affiliation(s)
- Veronique Rousseau
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRS, 1 Avenue de la Terrasse, 91198 Gif sur Yvette, France
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95
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Schneeberger D, Raabe T. Mbt, a Drosophila PAK protein, combines with Cdc42 to regulate photoreceptor cell morphogenesis. Development 2003; 130:427-37. [PMID: 12490550 DOI: 10.1242/dev.00248] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The Drosophila gene mushroom bodies tiny (mbt) encodes a putative p21-activated kinase (PAK), a family of proteins that has been implicated in a multitude of cellular processes including regulation of the cytoskeleton, cell polarisation, control of MAPK signalling cascades and apoptosis. The mutant phenotype of mbt is characterised by fewer neurones in the brain and the eye, indicating a role of the protein in cell proliferation, differentiation or survival. We show that mutations in mbt interfere with photoreceptor cell morphogenesis. Mbt specifically localises at adherens junctions of the developing photoreceptor cells. A structure-function analysis of the Mbt protein in vitro and in vivo revealed that the Mbt kinase domain and the GTPase binding domain, which specifically interacts with GTP-loaded Cdc42, are important for Mbt function. Besides regulation of kinase activity, another important function of Cdc42 is to recruit Mbt to adherens junctions. We propose a role for Mbt as a downstream effector of Cdc42 in photoreceptor cell morphogenesis.
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Affiliation(s)
- Daniela Schneeberger
- University of Würzburg, Institut für Medizinische Strahlenkunde und Zellforschung (MSZ), Versbacherstr. 5, 97078 Würzburg, Germany
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96
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Souopgui J, Sölter M, Pieler T. XPak3 promotes cell cycle withdrawal during primary neurogenesis in Xenopus laevis. EMBO J 2002; 21:6429-39. [PMID: 12456650 PMCID: PMC136948 DOI: 10.1093/emboj/cdf644] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We have isolated the Xenopus p21-activated kinase 3 (XPak3) by virtue of its expression in the territory of primary neurogenesis in the developing embryo. XPak3, but not the other Pak variants, responds positively to X-Ngnr-1 and negatively to X-Notch-1. A constitutively active form of XPak3, generated by fusing a myristylation signal to the N-terminus (XPak3-myr), induces early cell cycle arrest at high concentrations, while ectopic expression of low amounts induces premature neuronal differentiation. Conversely, XPak3 loss of function achieved by use of an antisense morpholino oligonucleotide increases cell proliferation and inhibits neuronal differentiation; this phenotype is rescued by co-injection of XPak3-myr. We conclude that XPak3 is a novel member of the proneural pathway, functioning downstream of neurogenin to withdraw neuronally programmed cells from the mitotic cell cycle, thus allowing for their differentiation.
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Affiliation(s)
- Jacob Souopgui
- Institut für Biochemie und Molekulare Zellbiologie, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany and Department of Biochemistry, Faculty of Science, University of Yaoundé I, PO Box 812, Yaoundé, Cameroon Corresponding author e-mail:
| | - Marion Sölter
- Institut für Biochemie und Molekulare Zellbiologie, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany and Department of Biochemistry, Faculty of Science, University of Yaoundé I, PO Box 812, Yaoundé, Cameroon Corresponding author e-mail:
| | - Tomas Pieler
- Institut für Biochemie und Molekulare Zellbiologie, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany and Department of Biochemistry, Faculty of Science, University of Yaoundé I, PO Box 812, Yaoundé, Cameroon Corresponding author e-mail:
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97
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Shin EY, Shin KS, Lee CS, Woo KN, Quan SH, Soung NK, Kim YG, Cha CI, Kim SR, Park D, Bokoch GM, Kim EG. Phosphorylation of p85 beta PIX, a Rac/Cdc42-specific guanine nucleotide exchange factor, via the Ras/ERK/PAK2 pathway is required for basic fibroblast growth factor-induced neurite outgrowth. J Biol Chem 2002; 277:44417-30. [PMID: 12226077 DOI: 10.1074/jbc.m203754200] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Guanine nucleotide exchange factors (GEFs) have been implicated in growth factor-induced neuronal differentiation through the activation of small GTPases. Although phosphorylation of these GEFs is considered an activation mechanism, little is known about the upstream of PAK-interacting exchange factor (PIX), a member of the Dbl family of GEFs. We report here that phosphorylation of p85 betaPIX/Cool/p85SPR is mediated via the Ras/ERK/PAK2 pathway. To understand the role of p85 betaPIX in basic fibroblast growth factor (bFGF)-induced neurite outgrowth, we established PC12 cell lines that overexpress the fibroblast growth factor receptor-1 in a tetracycline-inducible manner. Treatment with bFGF induces the phosphorylation of p85 betaPIX, as determined by metabolic labeling and mobility shift upon gel electrophoresis. Interestingly, phosphorylation of p85 betaPIX is inhibited by PD98059, a specific MEK inhibitor, suggesting the involvement of the ERK cascade. PAK2, a major PAK isoform in PC12 cells as well as a binding partner of p85 betaPIX, also functions upstream of p85 betaPIX phosphorylation. Surprisingly, PAK2 directly binds to ERK, and its activation is dependent on ERK. p85 betaPIX specifically localizes to the lamellipodia at neuronal growth cones in response to bFGF. A mutant form of p85 betaPIX (S525A/T526A), in which the major phosphorylation sites are replaced by alanine, shows significant defect in targeting. Moreover, expression of the mutant p85 betaPIX efficiently blocks PC12 cell neurite outgrowth. Our study defines a novel signaling pathway for bFGF-induced neurite outgrowth that involves activation of the PAK2-p85 betaPIX complex via the ERK cascade and subsequent translocation of this complex.
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Affiliation(s)
- Eun-Young Shin
- Department of Biochemistry, College of Medicine, Chungbuk National University, Cheongju 361-763, Korea
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98
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Wang RA, Mazumdar A, Vadlamudi RK, Kumar R. P21-activated kinase-1 phosphorylates and transactivates estrogen receptor-alpha and promotes hyperplasia in mammary epithelium. EMBO J 2002; 21:5437-47. [PMID: 12374744 PMCID: PMC129075 DOI: 10.1093/emboj/cdf543] [Citation(s) in RCA: 156] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Stimulation of p21-activated kinase-1 (Pak1) induces cytoskeleton reorganization and signaling pathways in mammary cancer cells. Here, we show that inhibition of Pak1 kinase activity by a dominant-negative fragment or by short interference RNA markedly reduced the estrogen receptor-alpha (ER) transactivation functions. To understand the role of Pak1 in mammary glands, we developed a murine model expressing constitutively active Thr423 glutamic acid Pak1 driven by the beta-lactoglobulin promoter. We show that mammary glands from these mice developed widespread hyperplasia associated with apocrine metaplasia and lobuloalveolar hyperdevelopment during lactation. Mammary tissues with active Pak1 also exhibited an increased activation of mitogen-activated protein kinase and stimulated transactivation functions of the ER and expression of endogenous ER target genes. Furthermore, Pak1 directly phosphorylated the activation function-2 domain of the ER at the N-terminal residue Ser305, and its mutation to Ala (S305A) abolished the Pak1-mediated phosphorylation and transactivation functions of the ER, while its mutation to glutamic acid (S305E) promoted transactivation activity of ER. These findings reveal a novel role for the Pak1-ER pathway in promoting hyperplasia in mammary epithelium.
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Affiliation(s)
| | | | | | - Rakesh Kumar
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030-4009, USA
Corresponding author e-mail: R.-A.Wang and A.Mazumdar contributed equally to this work
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99
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Renkema GH, Pulkkinen K, Saksela K. Cdc42/Rac1-mediated activation primes PAK2 for superactivation by tyrosine phosphorylation. Mol Cell Biol 2002; 22:6719-25. [PMID: 12215529 PMCID: PMC134024 DOI: 10.1128/mcb.22.19.6719-6725.2002] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The involvement of p21-activated kinases (PAKs) in important cellular processes such as regulation of the actin skeleton morphology, transduction of signals controlling gene expression, and execution of programmed cell death has directed attention to the regulation of the activity of these kinases. Here we report that activation of PAK2 by p21 GTPases can be strongly potentiated by cellular tyrosine kinases. PAK2 became tyrosine phosphorylated in its N-terminal regulatory domain, where Y130 was identified as the major phosphoacceptor site. Tyrosine phosphorylation-mediated superactivation of PAK2 could be induced by overexpression of different Src kinases or by inhibiting cellular tyrosine phosphatases with pervanadate and could be blocked by the Src kinase inhibitor PP1 or by mutating the Y130 residue. Analysis of PAK2 mutants activated by amino acid changes in the autoinhibitory domain or the catalytic domain indicated that GTPase-induced conformational changes, rather than catalytic activation per se, rendered PAK2 a target for tyrosine phosphorylation. Thus, PAK activation represents a potentially important point of convergence of tyrosine kinase- and p21 GTPase-dependent signaling pathways.
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Affiliation(s)
- G Herma Renkema
- Institute of Medical Technology, FIN-33014 University of Tampere, Finland
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100
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Zhang H, Li Z, Viklund EK, Strömblad S. P21-activated kinase 4 interacts with integrin alpha v beta 5 and regulates alpha v beta 5-mediated cell migration. J Cell Biol 2002; 158:1287-97. [PMID: 12356872 PMCID: PMC2173231 DOI: 10.1083/jcb.200207008] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
p21-activated kinase 1 (PAK1) can affect cell migration (Price et al., 1998; del Pozo et al., 2000) and modulate myosin light chain kinase and LIM kinase, which are components of the cellular motility machinery (Edwards, D.C., L.C. Sanders, G.M. Bokoch, and G.N. Gill. 1999. Nature Cell Biol. 1:253-259; Sanders, L.C., F. Matsumura, G.M. Bokoch, and P. de Lanerolle. 1999. SCIENCE: 283:2083-2085). We here present a novel cell motility pathway by demonstrating that PAK4 directly interacts with an integrin intracellular domain and regulates carcinoma cell motility in an integrin-specific manner. Yeast two-hybrid screening identified PAK4 binding to the cytoplasmic domain of the integrin beta 5 subunit, an association that was also found in mammalian cells between endogenous PAK4 and integrin alpha v beta 5. Furthermore, we mapped the PAK4 binding to the membrane-proximal region of integrin beta 5, and identified an integrin-binding domain at aa 505-530 in the COOH terminus of PAK4. Importantly, engagement of integrin alpha v beta 5 by cell attachment to vitronectin led to a redistribution of PAK4 from the cytosol to dynamic lamellipodial structures where PAK4 colocalized with integrin alpha v beta 5. Functionally, PAK4 induced integrin alpha v beta 5-mediated, but not beta1-mediated, human breast carcinoma cell migration, while no changes in integrin cell surface expression levels were observed. In conclusion, our results demonstrate that PAK4 interacts with integrin alpha v beta 5 and selectively promotes integrin alpha v beta 5-mediated cell migration.
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Affiliation(s)
- Hongquan Zhang
- Karolinska Institutet, Department of Microbiology, Pathology, and Immunology, SE-141 86 Huddinge, Sweden
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