51
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Webb BA, Eves R, Mak AS. Cortactin regulates podosome formation: roles of the protein interaction domains. Exp Cell Res 2006; 312:760-9. [PMID: 16434035 DOI: 10.1016/j.yexcr.2005.11.032] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2005] [Revised: 10/26/2005] [Accepted: 11/21/2005] [Indexed: 01/27/2023]
Abstract
Cortactin, a multi-domain scaffolding protein involved in actin polymerization, is enriched in podosomes induced by phorbol ester in vascular smooth muscle cells. We generated several functional and truncation mutants of cortactin to probe the roles of various protein interaction domains in the regulation of the dynamics of podosome formation. At the onset of podosome genesis, cortactin clustered near the ends of stress fibers that appeared to act as nucleation platforms onto which the actin polymerization machinery assembled. Translocation of cortactin to these pre-podosome clusters required the intact N-WASp-binding SH3 domain. Overexpression of the C-terminal third of cortactin containing the intact SH3 domain inhibited podosome formation presumably by sequestering of N-WASp and prevented cortactin clustering. Subsequent assembly of the actin-rich core of podosomes required translocation of additional cortactin to the actin core, a process that required the actin-binding repeats, but not the Arp2/3-binding N-terminal acidic region nor the SH3 domain. These results suggest that the SH3 domain and the actin-binding repeat region are involved, respectively, in the early and late stages of podosome formation process.
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Affiliation(s)
- Bradley A Webb
- Department of Biochemistry and Protein Function Discovery Program, Queen's University, Kingston, ON, Canada K7L 3N6
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52
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Hao JJ, Zhu J, Zhou K, Smith N, Zhan X. The coiled-coil domain is required for HS1 to bind to F-actin and activate Arp2/3 complex. J Biol Chem 2005; 280:37988-94. [PMID: 16157603 DOI: 10.1074/jbc.m504552200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
HS1 (hematopoietic lineage cell-specific protein 1), a substrate of protein tyrosine kinases in lymphocytes, binds to F-actin, and promotes Arp2/3 complex-mediated actin polymerization. However, the mechanism for the interaction between HS1 and F-actin has not yet been fully characterized. HS1 contains 3.5 tandem repeats, a coiled-coil region, and an SH3 domain at the C terminus. Unlike cortactin, which is closely related to HS1 and requires absolutely the repeat domain for F-actin binding, an HS1 mutant with deletion of the repeat domain maintains a significant F-actin binding activity. On the other hand, deletion of the coiled-coil region abolished the ability of HS1 to bind to actin filaments and to activate the Arp2/3 complex for actin nucleation and actin branching. Furthermore, a peptide containing the coiled-coil sequence only was sufficient for F-actin binding. Within cells overexpressing green fluorescent protein-tagged HS1 proteins, wild type HS1 co-localizes with cortical F-actin at the cell leading edge, whereas mutants with deletion of either the coiled-coil region or the repeat domain diffuse in the cytoplasm. Immunoprecipitation analysis reveals that the coiled-coil deletion mutant binds poorly to F-actin, whereas the mutant without the repeat domain fails to bind to both Arp2/3 complex and F-actin. These data suggest that the HS1 coiled-coil region acts synergistically with the repeat domain in the modulation of the Arp2/3 complex-mediated actin polymerization.
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Affiliation(s)
- Jian-Jiang Hao
- Department of Pathology, Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, 20855, USA
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53
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D'Agostino JL, Goode BL. Dissection of Arp2/3 complex actin nucleation mechanism and distinct roles for its nucleation-promoting factors in Saccharomyces cerevisiae. Genetics 2005; 171:35-47. [PMID: 16183906 PMCID: PMC1456526 DOI: 10.1534/genetics.105.040634] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2005] [Accepted: 05/31/2005] [Indexed: 11/18/2022] Open
Abstract
Actin nucleation by the Arp2/3 complex is under tight control, remaining inactive until stimulation by nucleation-promoting factors (NPFs). Although multiple NPFs are expressed in most cell types, little is known about how they are coordinated and whether they perform similar or distinct functions. We examined genetic relationships among the four S. cerevisiae NPFs. Combining las17delta with pan1-101 or myo3delta myo5delta was lethal at all temperatures, whereas combining pan1-101 with myo3delta myo5delta showed no genetic interaction and abp1delta partially suppressed las17delta. These data suggest that NPFs have distinct and overlapping functions in vivo. We also tested genetic interactions between each NPF mutant and seven different temperature-sensitive arp2 alleles and purified mutant Arp2/3 complexes to compare their activities. Two arp2 alleles with mutations at the barbed end were severely impaired in nucleation, providing the first experimental evidence that Arp2 nucleates actin at its barbed end in vitro and in vivo. Another arp2 allele caused partially unregulated ("leaky") nucleation in the absence of NPFs. Combining this mutant with a partially unregulated allele in a different subunit of Arp2/3 complex was lethal, suggesting that cells cannot tolerate high levels of unregulated activity. Genetic interactions between arp2 alleles and NPF mutants point to Abp1 having an antagonistic role with respect to other NPFs, possibly serving to attenuate their stronger activities. In support of this model, Abp1 binds strongly to Arp2/3 complex, yet has notably weak nucleation-promoting activity and inhibits Las17 activity on Arp2/3 complex in a dose-responsive manner.
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54
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Selbach M, Backert S. Cortactin: an Achilles' heel of the actin cytoskeleton targeted by pathogens. Trends Microbiol 2005; 13:181-9. [PMID: 15817388 DOI: 10.1016/j.tim.2005.02.007] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Cortactin is an actin-binding protein and a central regulator of the actin cytoskeleton. Importantly, cortactin is also a common target exploited by microbes during infection. Its involvement in disease development is exemplified by a variety of pathogenic processes, such as pedestal formation [enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC and EHEC)], invasion (Shigella, Neisseria, Rickettsia, Chlamydia, Staphylococcus and Cryptosporidium), actin-based motility (Listeria, Shigella and vaccinia virus) and cell scattering (Helicobacter). Recent progress turns our attention to how cortactin function can be regulated by serine and tyrosine phosphorylation. This has an important impact on how pathogens abuse cortactin to modulate the architecture of the host actin cytoskeleton.
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Affiliation(s)
- Matthias Selbach
- University of Southern Denmark, Center for Experimental BioInformatics, Department of Biochemistry and Molecular Biology, Campusvej 55, DK-5230 Odense M, Denmark.
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55
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Abstract
Spines may undergo rapid, activity-dependent changes in shape and size, reflecting reorganization of the actin cytoskeleton. This remodeling is implicated in development and also in the late phase of long-term potentiation. However, the cellular mechanisms that convert activity into morphological change remain poorly understood, and little is known about the anatomical distribution of the actin-regulating proteins that mediate this remodeling. Using immunocytochemistry, we demonstrate here that cortactin (a protein implicated in actin filament nucleation, branching, and stabilization) is concentrated in hippocampal spines, where it colocalizes with F-actin. Cortactin has a Shank-binding domain; recent studies report that synaptic activity may trigger actin remodeling via this interaction with Shank. However, our immunogold electron microscopic data show that cortactin concentrates within the spine core, 100-150 nm away from the postsynaptic density (PSD); only a small fraction of the cortactin in spines lies adjacent to the PSD. These data suggest that the adult dendritic spine contains two functional pools of cortactin: a large pool in the spine core that may help to mediates changes in spine shape and a small synaptic pool that may modify the PSD in response to synaptic activity.
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Affiliation(s)
- Bence Racz
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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56
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Zhang W, Wu Y, Du L, Tang DD, Gunst SJ. Activation of the Arp2/3 complex by N-WASp is required for actin polymerization and contraction in smooth muscle. Am J Physiol Cell Physiol 2005; 288:C1145-60. [PMID: 15625304 DOI: 10.1152/ajpcell.00387.2004] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Contractile stimulation has been shown to initiate actin polymerization in smooth muscle tissues, and this actin polymerization is required for active tension development. We evaluated whether neuronal Wiskott-Aldrich syndrome protein (N-WASp)-mediated activation of the actin-related proteins 2 and 3 (Arp2/3) complex regulates actin polymerization and tension development initiated by muscarinic stimulation in canine tracheal smooth muscle tissues. In vitro, the COOH-terminal CA domain of N-WASp acts as an inhibitor of N-WASp-mediated actin polymerization; whereas the COOH-terminal VCA domain of N-WASp is constitutively active and is sufficient by itself to catalyze actin polymerization. Plasmids encoding EGFP-tagged wild-type N-WASp, the N-WASp VCA and CA domains, or enhanced green fluorescent protein (EGFP) were introduced into tracheal smooth muscle strips by reversible permeabilization, and the tissues were incubated for 2 days to allow for expression of the proteins. Expression of the CA domain inhibited actin polymerization and tension development in response to ACh, whereas expression of the wild-type N-WASp, the VCA domain, or EGFP did not. The increase in myosin light-chain (MLC) phosphorylation in response to contractile stimulation was not affected by expression of either the CA or VCA domain of N-WASp. Stimulation of the tissues with ACh increased the association of the Arp2/3 complex with N-WASp, and this association was inhibited by expression of the CA domain. The results demonstrate that 1) N-WASp-mediated activation of the Arp2/3 complex is necessary for actin polymerization and tension development in response to muscarinic stimulation in tracheal smooth muscle and 2) these effects are independent of the regulation of MLC phosphorylation.
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Affiliation(s)
- Wenwu Zhang
- Dept. of Cellular and Integrative Physiology, Indiana Univ. School of Medicine, 635 Barnhill Drive, MS374, Indianapolis, IN 46202, USA
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57
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Lin J, Liu J, Wang Y, Zhu J, Zhou K, Smith N, Zhan X. Differential regulation of cortactin and N-WASP-mediated actin polymerization by missing in metastasis (MIM) protein. Oncogene 2005; 24:2059-66. [PMID: 15688017 DOI: 10.1038/sj.onc.1208412] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Missing in metastasis (MIM) gene encodes an actin binding protein that is expressed at low levels in a subset of malignant cell lines. MIM protein tagged by green fluorescent protein (GFP) colocalizes with cortactin, an Arp2/3 complex activator, and interacts directly with the SH3 domain of cortactin. Recombinant full-length MIM promotes markedly cortactin and Arp2/3 complex-mediated actin polymerization in an SH3 dependent manner. In contrast, MIM-CT, a short splicing variant of MIM, binds poorly to cortactin in vitro and is unable to enhance actin polymerization. Full-length MIM binds to G-actin with a similar affinity as N-WASP-VCA, a constitutively active form of N-WASP, and inhibits N-WASP-VCA-mediated actin polymerization as analysed in vitro. The significance of the association of MIM with cortactin and G-actin was evaluated in NIH3T3 cells expressing several MIM constructs. Overexpression of full-length wild-type MIM-GFP inhibited markedly the motility of NIH3T3 cells induced by PDGF and that of human vein umbilical endothelial cells induced by sphingosine 1 phosphate. However, an MIM mutant with deletion of the WH2 domain, which is responsible for G-actin binding, enhanced cell motility. The motility inhibition imposed by MIM was compromised in the cells overexpressing N-WASP. In contrast, deletion of an MIM proline-rich domain, which is required for an optimal binding to cortactin, substantiated the MIM-mediated inhibition of cell motility. These data imply that MIM regulates cell motility by modulating different Arp2/3 activators in a distinguished manner.
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Affiliation(s)
- Jinxiu Lin
- Holland Laboratory, American Red Cross, 15601 Crabbs Branch Way, Rockville, MD 20855, USA
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58
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Lua BL, Low BC. Cortactin phosphorylation as a switch for actin cytoskeletal network and cell dynamics control. FEBS Lett 2005; 579:577-85. [PMID: 15670811 DOI: 10.1016/j.febslet.2004.12.055] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2004] [Revised: 12/01/2004] [Accepted: 12/06/2004] [Indexed: 12/27/2022]
Abstract
Cortactin is an important molecular scaffold for actin assembly and organization. Novel mechanistic functions of cortactin have emerged with more interacting partners identified, revealing its multifaceted roles in regulating actin cytoskeletal networks that are necessary for endocytosis, cell migration and invasion, adhesion, synaptic organization and cell morphogenesis. These processes are mediated by its multi-domains binding to F-actin and Arp2/3 complex and various SH3 targets. Furthermore, its role in actin remodeling is subjected to regulation by tyrosine and serine/threonine kinases. Elucidating the mechanisms underlying cortactin phosphorylation and its functional consequences would provide new insights to various aspects of cell dynamics control.
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Affiliation(s)
- Bee Leng Lua
- Cell Signaling and Developmental Biology Laboratory, Department of Biological Sciences, The National University of Singapore, 14 Science Drive 4, Singapore 117543, The Republic of Singapore
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59
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Ethell IM, Pasquale EB. Molecular mechanisms of dendritic spine development and remodeling. Prog Neurobiol 2005; 75:161-205. [PMID: 15882774 DOI: 10.1016/j.pneurobio.2005.02.003] [Citation(s) in RCA: 264] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2004] [Revised: 01/28/2005] [Accepted: 02/22/2005] [Indexed: 12/19/2022]
Abstract
Dendritic spines are small protrusions that cover the surface of dendrites and bear the postsynaptic component of excitatory synapses. Having an enlarged head connected to the dendrite by a narrow neck, dendritic spines provide a postsynaptic biochemical compartment that separates the synaptic space from the dendritic shaft and allows each spine to function as a partially independent unit. Spines develop around the time of synaptogenesis and are dynamic structures that continue to undergo remodeling over time. Changes in spine morphology and density influence the properties of neural circuits. Our knowledge of the structure and function of dendritic spines has progressed significantly since their discovery over a century ago, but many uncertainties still remain. For example, several different models have been put forth outlining the sequence of events that lead to the genesis of a spine. Although spines are small and apparently simple organelles with a cytoskeleton mainly composed of actin filaments, regulation of their morphology and physiology appears to be quite sophisticated. A multitude of molecules have been implicated in dendritic spine development and remodeling, suggesting that intricate networks of interconnected signaling pathways converge to regulate actin dynamics in spines. This complexity is not surprising, given the likely importance of dendritic spines in higher brain functions. In this review, we discuss the molecules that are currently known to mediate the exquisite sensitivity of spines to perturbations in their environment and we outline how these molecules interface with each other to mediate cascades of signals flowing from the spine surface to the actin cytoskeleton.
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Affiliation(s)
- Iryna M Ethell
- Division of Biomedical Sciences, University of California Riverside, Riverside, CA 92521, USA
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60
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Daly RJ. Cortactin signalling and dynamic actin networks. Biochem J 2005; 382:13-25. [PMID: 15186216 PMCID: PMC1133910 DOI: 10.1042/bj20040737] [Citation(s) in RCA: 239] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Revised: 06/08/2004] [Accepted: 06/09/2004] [Indexed: 12/29/2022]
Abstract
Cortactin was first identified over a decade ago, and its initial characterization as both an F-actin binding protein and v-Src substrate suggested that it was likely to be a key regulator of actin rearrangements in response to tyrosine kinase signalling. The recent discovery that cortactin binds and activates the actin related protein (Arp)2/3 complex, and thus regulates the formation of branched actin networks, together with the identification of multiple protein targets of the cortactin SH3 domain, have revealed diverse cellular roles for this protein. This article reviews current knowledge regarding the role of cortactin in signalling to the actin cytoskeleton in the context of these developments.
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Affiliation(s)
- Roger J Daly
- Cancer Research Program, Garvan Institute of Medical Research, 384 Victoria St, Sydney, NSW 2010, Australia.
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61
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Abstract
Endocytosis is characterized by movement and precisely controlled changes in membrane geometry during vesicle formation. Recent developments in live-cell imaging have enabled such movements to be monitored in vivo and correlated with the recruitment and dismissal of fluorescently labeled proteins. This experimental strategy has revealed the sequential recruitment of proteins that are involved in actin polymerization, and actin to single sites of endocytosis in both yeast and mammalian cells. Actin polymerization is correlated with the inward movements of endocytic organelles, which suggests that actin polymerization has a conserved role in this process. In this article, I will discuss three models for the role of actin polymerization in endocytosis.
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62
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Zhu J, Zhou K, Hao JJ, Liu J, Smith N, Zhan X. Regulation of cortactin/dynamin interaction by actin polymerization during the fission of clathrin-coated pits. J Cell Sci 2005; 118:807-17. [PMID: 15671060 DOI: 10.1242/jcs.01668] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Separation of clathrin-coated pits from the plasma membrane, a key event during endocytosis, is thought to be driven by dynamin and the actin cytoskeleton. However, the mechanism for the actin-mediated endocytosis remains elusive. RNA interference-mediated suppression of cortactin, an F-actin binding protein that promotes Arp2/3 complex-mediated actin polymerization, effectively blocked transferrin uptake. Depletion of cortactin in brain cytosol inhibited formation of clathrin-coated vesicles by 70% as analyzed in a cell-free system. Interestingly, the interaction between cortactin and dynamin 2 in cells was dependent on actin polymerization and was attenuated upon cell exposure to cytochalasin D as analyzed by immunofluorescence and immunoprecipitation. Moreover, a cortactin mutant deficient in Arp2/3 binding colocalized less efficiently with dynamin 2 and inhibited the uptake of transferrin. The effect of actin polymerization on the interaction between cortactin and the dynamin proline-rich domain (PRD) was further evaluated under a condition for actin polymerization in vitro. Cortactin binds to the dynamin PRD with an equilibrium dissociation constant of 81 nM in the presence of the Arp2/3 complex and actin, and 617 nM in the absence of actin polymerization. Taken together, these data demonstrate that Arp2/3-mediated actin polymerization regulates the accessibility of cortactin to dynamin 2 and imply a novel mechanism by which cortactin and dynamin drive the fission of clathrin-coated pits in an actin polymerization dependent manner.
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Affiliation(s)
- Jianwei Zhu
- Department of Pathology, Greenebaum Cancer Center, University of Maryland School of Medicine, 15601 Crabbs Branch Way, Rockville, MD 20855, USA
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63
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Kowalski JR, Egile C, Gil S, Snapper SB, Li R, Thomas SM. Cortactin regulates cell migration through activation of N-WASP. J Cell Sci 2005; 118:79-87. [PMID: 15585574 DOI: 10.1242/jcs.01586] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cortactin is an actin-associated scaffolding protein that regulates cell migration. Amplification of the human gene, EMS1, has been detected in breast, head and neck tumors, where it correlates with increased invasiveness. Cortactin can regulate actin dynamics directly via its N-terminal half, which can bind and activate the Arp2/3 complex. The C-terminal portion of cortactin, however, is thought to have limited function in its regulation of the actin polymerization machinery. In this report, we identify a role for the cortactin C-terminus in regulating cell migration and, more specifically, actin dynamics. Overexpression of either full-length cortactin or cortactin C-terminus is sufficient to enhance migration of mammary epithelial cells. In vitro, cortactin binds to and activates, via its SH3 domain, a regulator of the Arp2/3 complex, neural Wiskott Aldrich Syndrome protein (N-WASP). This in vitro activation of N-WASP is likely to be important in vivo, as cortactin-enhanced migration is dependent upon N-WASP. Thus, our results suggest that cortactin has multiple mechanisms by which it can recruit and modulate the actin machinery and ultimately regulate cell migration.
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Affiliation(s)
- Jennifer R Kowalski
- Biological and Biomedical Sciences Program, Harvard Medical School, Boston, MA 02215, USA
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64
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Kempiak SJ, Yamaguchi H, Sarmiento C, Sidani M, Ghosh M, Eddy RJ, Desmarais V, Way M, Condeelis J, Segall JE. A neural Wiskott-Aldrich Syndrome protein-mediated pathway for localized activation of actin polymerization that is regulated by cortactin. J Biol Chem 2004; 280:5836-42. [PMID: 15579908 DOI: 10.1074/jbc.m410713200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of the epidermal growth factor (EGF) receptor can stimulate actin polymerization via the Arp2/3 complex using a number of signaling pathways, and specific stimulation conditions may control which pathways are activated. We have previously shown that localized stimulation of EGF receptor with EGF bound to beads results in localized actin polymerization and protrusion. Here we show that the actin polymerization is dependent upon activation of the Arp2/3 complex by neural Wiskott-Aldrich Syndrome protein (N-WASP) via Grb2 and Nck2. Suppression of Grb2 or Nck2 results in loss of localization of N-WASP at the activation site and reduced actin polymerization. Although cortactin has been found to synergize with N-WASP for Arp2/3-dependent actin polymerization in vitro, we find that cortactin can restrict N-WASP localization around EGF-bead-induced protrusions. In addition, cortactin-deficient cells have increased lamellipod dynamics but show reduced net translocation, suggesting that cortactin can contribute to cell polarity by controlling the extent of Arp2/3 activation by WASP family members and the stability of the F-actin network.
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Affiliation(s)
- Stephan J Kempiak
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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65
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Unsworth KE, Way M, McNiven M, Machesky L, Holden DW. Analysis of the mechanisms of Salmonella-induced actin assembly during invasion of host cells and intracellular replication. Cell Microbiol 2004; 6:1041-55. [PMID: 15469433 DOI: 10.1111/j.1462-5822.2004.00417.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Salmonella enterica serovar Typhimurium (S. typhimurium) induces actin assembly both during invasion of host cells and during the course of intracellular bacterial replication. In this study, we investigated the involvement in these processes of host cell signalling pathways that are frequently utilized by bacterial pathogens to manipulate the eukaryotic actin cytoskeleton. We confirmed that Cdc42, Rac, and Arp3 are involved in S. typhimurium invasion of HeLa cells, and found that N-WASP and Scar/WAVE also play a role in this process. However, we found no evidence for the involvement of these proteins in actin assembly during intracellular replication. Cortactin was recruited by Salmonella during both invasion and intracellular replication. However, RNA interference directed against cortactin did not inhibit either invasion or intracellular actin assembly, although it resulted in increased cell spreading and a greater number of lamellipodia. We also found no role for either the GTPase dynamin or the formin family member mDia1 in actin assembly by intracellular bacteria. Collectively, these data provide evidence that signalling pathways leading to Arp2/3-dependent actin nucleation play an important role in S. typhimurium invasion, but are not involved in intracellular Salmonella-induced actin assembly, and suggest that actin assembly by intracellular S. typhimurium may proceed by a novel mechanism.
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Affiliation(s)
- Kate E Unsworth
- Centre for Molecular Microbiology and Infection, Department of Infectious Diseases, Imperial College London, Armstrong Road, London SW7 2AZ, UK
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66
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Millard TH, Sharp SJ, Machesky LM. Signalling to actin assembly via the WASP (Wiskott-Aldrich syndrome protein)-family proteins and the Arp2/3 complex. Biochem J 2004; 380:1-17. [PMID: 15040784 PMCID: PMC1224166 DOI: 10.1042/bj20040176] [Citation(s) in RCA: 211] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Revised: 02/18/2004] [Accepted: 03/25/2004] [Indexed: 01/15/2023]
Abstract
The assembly of a branched network of actin filaments provides the mechanical propulsion that drives a range of dynamic cellular processes, including cell motility. The Arp2/3 complex is a crucial component of such filament networks. Arp2/3 nucleates new actin filaments while bound to existing filaments, thus creating a branched network. In recent years, a number of proteins that activate the filament nucleation activity of Arp2/3 have been identified, most notably the WASP (Wiskott-Aldrich syndrome protein) family. WASP-family proteins activate the Arp2/3 complex, and consequently stimulate actin assembly, in response to extracellular signals. Structural studies have provided a significant refinement in our understanding of the molecular detail of how the Arp2/3 complex nucleates actin filaments. There has also been much progress towards an understanding of the complicated signalling processes that regulate WASP-family proteins. In addition, the use of gene disruption in a number of organisms has led to new insights into the specific functions of individual WASP-family members. The present review will discuss the Arp2/3 complex and its regulators, in particular the WASP-family proteins. Emphasis will be placed on recent developments in the field that have furthered our understanding of actin dynamics and cell motility.
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Affiliation(s)
- Thomas H Millard
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
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67
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Merrifield CJ, Qualmann B, Kessels MM, Almers W. Neural Wiskott Aldrich Syndrome Protein (N-WASP) and the Arp2/3 complex are recruited to sites of clathrin-mediated endocytosis in cultured fibroblasts. Eur J Cell Biol 2004; 83:13-8. [PMID: 15085951 DOI: 10.1078/0171-9335-00356] [Citation(s) in RCA: 176] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Several findings suggest that actin-mediated motility can play a role in clathrin-mediated endocytosis but it remains unclear whether and when key proteins required for this process are recruited to endocytic sites. Here we investigate this question in live Swiss 3T3 cells using two-colour evanescent field (EF) microscopy. We find that Arp3, a component of the Arp2/3 complex, appears transiently while single clathrin-coated pits internalize. There is also additional recruitment of Neural-Wiskott Aldrich Syndrome Protein (N-WASP), a known activator of the Arp2/3 complex. Both proteins appear at about the same time as actin. We suggest that N-WASP and the Arp2/3 complex trigger actin polymerization during a late step in clathrin-mediated endocytosis, and propel clathrin-coated pits or vesicles from the plasma membrane into the cytoplasm.
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Affiliation(s)
- Christien J Merrifield
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, USA
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68
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Bougnères L, Girardin SE, Weed SA, Karginov AV, Olivo-Marin JC, Parsons JT, Sansonetti PJ, Van Nhieu GT. Cortactin and Crk cooperate to trigger actin polymerization during Shigella invasion of epithelial cells. ACTA ACUST UNITED AC 2004; 166:225-35. [PMID: 15263018 PMCID: PMC2172305 DOI: 10.1083/jcb.200402073] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Shigella, the causative agent of bacillary dysentery, invades epithelial cells in a process involving Src tyrosine kinase signaling. Cortactin, a ubiquitous actin-binding protein present in structures of dynamic actin assembly, is the major protein tyrosine phosphorylated during Shigella invasion. Here, we report that RNA interference silencing of cortactin expression, as does Src inhibition in cells expressing kinase-inactive Src, interferes with actin polymerization required for the formation of cellular extensions engulfing the bacteria. Shigella invasion induced the recruitment of cortactin at plasma membranes in a tyrosine phosphorylation–dependent manner. Overexpression of wild-type forms of cortactin or the adaptor protein Crk favored Shigella uptake, and Arp2/3 binding–deficient cortactin derivatives or an Src homology 2 domain Crk mutant interfered with bacterial-induced actin foci formation. Crk was shown to directly interact with tyrosine-phosphorylated cortactin and to condition cortactin-dependent actin polymerization required for Shigella uptake. These results point at a major role for a Crk–cortactin complex in actin polymerization downstream of tyrosine kinase signaling.
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Affiliation(s)
- Laurence Bougnères
- Unité de Pathogénie Microbienne Moléculaire, INSERM U389, Institut Pasteur, 28 rue du Dr. Roux, 75724 Paris Cedex 15, France.
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Li Y, Uruno T, Haudenschild C, Dudek SM, Garcia JGN, Zhan X. Interaction of cortactin and Arp2/3 complex is required for sphingosine-1-phosphate-induced endothelial cell remodeling. Exp Cell Res 2004; 298:107-21. [PMID: 15242766 DOI: 10.1016/j.yexcr.2004.03.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2004] [Revised: 03/06/2004] [Indexed: 11/26/2022]
Abstract
Sphingosine-1-phosphate (S1P) induces capillary formation of endothelial cells on Matrigel in accompany with actin assembly and accumulation of cortactin and Arp2/3 complex at the cell-leading edge. Suppression of cortactin expression with a cortactin antisense oligo significantly impaired S1P-induced capillary formation, migration of endothelial cells, and actin assembly at the cell periphery. Overexpression of wild-type cortactin tagged by green fluorescent protein (GFP) increased the S1P-induced tube formation and cell motility, whereas the cells overexpressing the mutant formed poorly capillary network and became less motile in response to S1P. Analysis of distribution in Triton X-100 insoluble fractions demonstrated that the cortactin mutant inhibited the association of wild-type cortactin and Arp2/3 complex with the actin-enriched complex. Furthermore, actin polymerization at and distribution of Arp2/3 complex as well as endogenous cortactin into the cell-leading edge mediated by S1P was disturbed. These data suggest that the interaction between cortactin and Arp2/3 complex plays an important role in S1P-mediated remodeling of endothelial cells.
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Affiliation(s)
- Yansong Li
- Department of Experimental Pathology, Jerome H. Holland Laboratory for the Biomedical Sciences, American Red Cross, Rockville, MD 20855, USA
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Hao JJ, Carey GB, Zhan X. Syk-mediated tyrosine phosphorylation is required for the association of hematopoietic lineage cell-specific protein 1 with lipid rafts and B cell antigen receptor signalosome complex. J Biol Chem 2004; 279:33413-20. [PMID: 15166239 DOI: 10.1074/jbc.m313564200] [Citation(s) in RCA: 39] [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
Hematopoietic lineage cell-specific protein 1 (HS1) is an F-actin- and actin-related proteins 2 and 3 (Arp2/3)-binding protein that undergoes a rapid tyrosine phosphorylation upon B cell antigen receptor (BCR) activation. Density gradient centrifugation of Triton X-100 lysates from B lymphocytes demonstrated that HS1 was translocated in response to BCR cross-linking into lipid raft microdomain along with Arp2/3 complex and Wiskott-Aldrich syndrome protein. HS1-green fluorescent protein was localized in membrane patches enriched with GM1 gangliosides and BCR in the cells treated with anti-IgM antibody. Colocalization of HS1-green fluorescent protein with BCR was also correlated with tyrosine phosphorylation of HS1. Interestingly a murine HS1 mutant at the tyrosine residues Tyr388 and Tyr405 targeted by Syk failed to respond to BCR cross-linking for either translocation into lipid rafts or colocalization with BCR within cells. Furthermore HS1 was unable to translocate into lipid rafts in a chicken B cell line deficient in Syk. Reintroducing a Syk construct into the Syk knock-out cells recovered effectively both tyrosine phosphorylation and translocation of HS1 into lipid rafts. In contrast, translocation of HS1 into rafts was normal in a Lyn knock-out B cell line, and an HS1 mutant at the tyrosine residue Tyr222 targeted by Lyn maintained the ability to partition into rafts upon BCR cross-linking. These data indicate that Syk plays an important role in the translocation of HS1 into lipid rafts and may be responsible for actin assembly recruitment to rafts and subsequent antigen presentations.
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Affiliation(s)
- Jian-Jiang Hao
- Departments of Experimental Pathology and Immunology, Holland Laboratory, American Red Cross, Rockville, Maryland 20855, USA
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72
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Kaksonen M, Sun Y, Drubin DG. A pathway for association of receptors, adaptors, and actin during endocytic internalization. Cell 2004; 115:475-87. [PMID: 14622601 DOI: 10.1016/s0092-8674(03)00883-3] [Citation(s) in RCA: 541] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In budding yeast, many proteins involved in endocytic internalization, including adaptors and actin cytoskeletal proteins, are localized to cortical patches of differing protein composition. Using multicolor real-time fluorescence microscopy and particle tracking algorithms, we define an early endocytic pathway wherein an invariant sequence of changes in cortical patch protein composition correlates with changes in patch motility. Three Arp2/3 activators each showed a distinct behavior, suggesting distinct patch-related endocytic functions. Actin polymerization occurs late in the endocytic pathway and is required both for endocytic internalization and for patch disassembly. In cells lacking the highly conserved endocytic protein Sla2p, patch motility was arrested and actin comet tails associated with endocytic patch complexes. Fluorescence recovery after photobleaching of the actin comet tails revealed that endocytic complexes are nucleation sites for rapid actin polymerization. Attention is now focused on the mechanisms by which the order and timing of events in this endocytic pathway are achieved.
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Affiliation(s)
- Marko Kaksonen
- Department of Molecular and Cell Biology, 16 Barker Hall, University of California, Berkeley, Berkeley, CA 94720, USA
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73
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Abstract
Dynamic actin filaments contribute to cell migration, organelle movements, memory, and gene regulation. These dynamic processes are often regulated by extracellular and?or cell cycle signals. Regulation targets, not actin itself, but the factors that determine it's dynamic properties. Thus, filament nucleation, rate and duration of elongation, and depolymerization are each controlled with regard to time and?or space. Two mechanisms exist for nucleating filaments de novo, the Arp23 complex and the formins; multiple pathways regulate each. A new filament elongates rapidly but transiently before its barbed end is capped. Rapid capping allows the cell to maintain fine temporal and spatial control over F-actin distribution. Modulation of capping protein activity and its access to barbed ends is emerging as a site of local regulation. Finally, to maintain a steady state filaments must depolymerize. Depolymerization can limit the rate of new filament nucleation and elongation. The activity of ADF?cofilin, which facilitates depolymerization, is also regulated by multiple inputs. This chapter describes (1) mechanism and regulation of new filament formation, (2) mechanism of enhancing elongation at barbed ends, (3) capping proteins and their regulators, and (4) recycling of actin monomers from filamentous actin (F-actin) back to globular actin (G-actin).
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Affiliation(s)
- Sally H Zigmond
- Biology Department, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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van Rossum AGSH, de Graaf JH, Schuuring-Scholtes E, Kluin PM, Fan YX, Zhan X, Moolenaar WH, Schuuring E. Alternative splicing of the actin binding domain of human cortactin affects cell migration. J Biol Chem 2003; 278:45672-9. [PMID: 12952985 DOI: 10.1074/jbc.m306688200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cortactin is a filamentous actin (F-actin)-binding protein that regulates cytoskeletal dynamics by activating the Arp2/3 complex; it binds to F-actin by means of six N-terminal "cortactin repeats". Gene amplification of 11q13 and consequent overexpression of cortactin in several human cancers is associated with lymph node metastasis. Overexpression as well as tyrosine phosphorylation of cortactin has been reported to enhance cell migration, invasion, and metastasis. Here we report the identification of two alternative splice variants (SV1 and SV2) that affect the cortactin repeats: SV1-cortactin lacks the 6th repeat (exon 11), whereas SV2-cortactin lacks the 5th and 6th repeats (exons 10 and 11). SV-1 cortactin is found co-expressed with wild type (wt)-cortactin in all tissues and cell lines examined, whereas the SV2 isoform is much less abundant. SV1-cortactin binds F-actin and promotes Arp2/3-mediated actin polymerization equally well as wt-cortactin, whereas SV2-cortactin shows reduced F-actin binding and polymerization. Alternative splicing of cortactin does not affect its subcellular localization or growth factor-induced tyrosine phosphorylation. However, cells that overexpress SV1- or SV2-cortactin show significantly reduced cell migration when compared with wt-cortactin-overexpressing cells. Thus, in addition to overexpression and tyrosine phosphorylation, alternative splicing of the F-actin binding domain of cortactin is a new mechanism by which cortactin influences cell migration.
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Affiliation(s)
- Agnes G S H van Rossum
- Department of Pathology, Leiden University Medical Center, 2300 RC, Leiden, The Netherlands
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