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Consortium Updates

Welcome to the Cell Migration Consortium's updates page, where we highlight major additions of data and information, and outline some of the publications appearing as a result of the Consortium's activities.

Archive

  1. 2002
  2. 2003
  3. 2004
  4. 2005
  5. 2006
  6. 2007
  7. 2008
  8. 2009
  9. 2010

  • September 2010

    1. Cell spreading: RhoA-induced oscillations
    2. Consortium Data Additions & Site Updates
    3. Other CMC Publications
    4. Upcoming Conferences & Workshops

    • Cell spreading: RhoA-induced oscillations

      Periodic morphological oscillations are observed in the cellular cortex of spreading cells after microtubule (MT) depolymerization. Timothy Elston, Ken Jacobson and colleagues previously used a coarse-grained computational model called causal mapping (CMAP) and demonstrated that both calcium and RhoA could have a role during oscillatory behavior. In their report in Biophysical Journal, they now use fluorescence and electron microscopy imaging and reveal the structural and biochemical factors underlying the oscillatory behavior in spreading cells. In contrast to their earlier findings, in the present study calcium flux did not affect the propagation of cortical oscillations. Importantly, short-interfering (si)RNA inhibition of RhoA dramatically reduced the number of oscillating cells, whereas global activation of RhoA through pathways other than MT depolymerization could not induce oscillations. This indicated that RhoA needs to be activated downstream of MT depolymerization to regulate oscillatory behavior. Next, they investigated the dynamic cell structure during oscillations and demonstrated that the oscillating cells are dynamically polarized in terms of their morphology, acto-myosin cortex and nuclear positioning. This study shows that experimental data is needed to support computational models, and presents important findings for Rho-mediated cellular contractility.

      • Costigliola N, Kapustina MT, Weinreb GE, Monteith A, Rajfur Z, Elston TC, Jacobson K. RhoA regulates calcium-independent periodic contractions of the cell cortex. Biophys J 2010; 99 (4):1053-63. PubMed

    • Consortium Data Additions & Site Updates

      • Interactive Pathway Viewer integrated into Knowledgebase pages

        The Cell Migration Knowledgebase pages provide a wealth of information on migration-related proteins and has now been expanded to include an interactive pathway viewer for the Adhesome. With it, you can quickly see what other proteins your favorite protein interacts with, as well as the type of, and evidence for, the interaction. Search your favorite protein here, or take a look at a few of our favorites: paxillin; FAK; vinculin

    • Other CMC Publications

      • One of this month's featured articles in the Cell Migration Update section of the Gateway, highlights a publication generated through a collaboration with the Consortium's structure efforts. Using cryo-electron tomography to study the three-dimensional structural reconstruction of focal adhesions, particles have been identified that mediate the membrane–cytoskeleton interaction." Click here to read the article review on this publication.

        Patla I, Volberg T, Elad N, Hirschfeld-Warneken V, Grashoff C, Fassler R, Spatz JP, Geiger B, Medalia O. Dissecting the molecular architecture of integrin adhesion sites by cryo-electron tomography. Nat Cell Biol 2010 [Epub ahead of print] PubMed

      • Srikrishna G, Nayak J, Weigle B, Temme A, Foell D, Hazelwood L, Olsson A, Volkmann N, Hanein D, Freeze HH. Carboxylated N-glycans on RAGE promote S100A12 binding and signaling. J Cell Biochem. 2010;110(3):645-59. PubMed

      • Parsons JT, Horwitz AR, Schwartz MA. Cell adhesion: integrating cytoskeletal dynamics and cellular tension. Nat Rev Mol Cell Biol. 2010;11(9):633-43. PubMed

      • Moens PD, Gratton E, Salvemini IL. Fluorescence correlation spectroscopy, raster image correlation spectroscopy, and number and brightness on a commercial confocal laser scanning microscope with analog detectors (Nikon C1). Microsc Res Tech. 2010 Aug 23. [Epub ahead of print] PubMed

    • Upcoming Conferences & Workshops

      • 5th LFD Workshop in Advanced Fluorescence Imaging and Dynamics October 25–29, 2010:

        Registration for this workshop at the LFD, UC-Irvine, CA is now open and a limited number of student awards are available. The deadline for submitting student award applications is September 24, 2010. For more details and to register visit the web site at www.lfd.uci.edu/workshop.

      • ASCB 50th Annual Meeting - December 11 - 15, 2010, Philadelphia, PA:

        Registration for this meeting is now open and applications for travel awards must be received by September 1: For more details and to register visit the meeting web site at http://www.ascb.org/meetings/.

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  • August 2010

    1. Modeling FRAP and CALI: insights into actin dynamics
    2. PEAK performance: pseudopodial kinase regulates the cytoskeleton
    3. Consortium Data Additions & Site Updates
    4. Other CMC Publications
    5. Upcoming Conferences & Workshops

    • Modeling FRAP and CALI: insights into actin dynamics

      Control of actin polymerization is important for cell motility. Among various regulators of this process are capping proteins (CPs), which bind to the barbed end of the actin filament and inhibit further elongation, thereby maintaining a short and highly branched actin network. In contrast, anticapping proteins, such as the vasodilator-stimulated phosphoprotein (VASP), disable the capping of the barbed ends and facilitate elongation of the filaments. Following on from recent studies using fluorescence recovery after photobleaching (FRAP) and chromophore-assisted laser inactivation (CALI) to investigate actin polymerization, Ken Jacobson and colleagues now take a mathematical approach and use the Virtual Cell modeling and simulation software to analyze the dendritic nucleation model for actin polymerization. In Cytoskeleton, they show simulations of FRAP and CALI experiments on a CP bound to enhanced green fluorescent protein (EGFP, a CALI chromophore) and make comparisons with previous data. Modeling the FRAP kinetics demonstrates that CP dissociates from actin filaments at a faster rate in vivo than in vitro. In addition, the CALI simulations show that anticapping proteins are required to induce sustainable changes in cell morphology after CP inactivation. To further investigate this, the authors include VASP in their modeling platform and find that VASP affinity is increased by local concentration of VASP–barbed-end complexes. This positive feedback mechanism stabilizes VASP and enables sustainable growth of actin filaments. Finally, they analyze the range of laser intensities and demonstrate that FRAP experiments are safe, with no effect on cell morphologies. This study provides insights into the mechanisms of VASP and CP activity and the regulation of actin polymerization.

      • Kapustina M, Vitriol E, Elston TC, Loew LM, Jacobson K. Modeling capping protein FRAP and CALI experiments reveals in vivo regulation of actin dynamics. Cytoskeleton 2010;67, 519–34. PubMed

    • PEAK performance: pseudopodial kinase regulates the cytoskeleton

      Pseudopodia are highly specialized, actin-rich cellular protrusions that are essential for cell migration. Wang et al. report on the identification of pseudopodium-enriched atypical kinase 1 (PEAK1), a pseudopodial-enriched phosphotyrosine protein, using phosphotyrosine immunoaffinity purification followed by multidimensional protein identification technology. PEAK1 contains numerous protein–protein interaction sites and is predicted to be phosphorylated by several proteins that regulate the cytoskeleton. Many putative phosphorylation sites are present within residues 338–727; the researchers found that this region was responsible for mediating the localization of PEAK1 to the actin cytoskeleton and focal adhesions. Tyrosine phosphorylation of PEAK1 was induced in a Src-dependent manner in response to growth factor stimulation or integrin engagement. When expressed exogenously, PEAK1 coprecipitated with Crk and p130Cas, and increased the phosphorylation of paxillin, p130Cas and extracellular signal-regulated protein (ERK) on residues known to influence the cytoskeleton and cell migration, indicating a potential role in spreading and migration. Knockdown of PEAK1 delayed the initial stages of cell spreading and reduced migration, although the cells did eventually spread and cell attachment was not affected. Depletion of PEAK1 also abrogated the anchorage-independent growth in vitro and increase in ERK activity that were seen when PEAK1 was overexpressed in cancer cells. These cells also formed larger and heavier tumors than control cells when injected into nude mice. Finally, human colon tumors and liver metastases showed elevated PEAK1 expression. These findings indicate that PEAK1, through Src–p130Cas–Crk–paxillin and ERK signaling pathways, mediates cell spreading, migration and cancer progression.

      • Wang Y, Kelber JA, Tran Cao HS, Cantin GT, Lin R, Wang W, Kaushal S, Bristow JM, Edgington TS, Hoffman RM, Bouvet M, Yates JR 3rd, Klemke RL. Pseudopodium-enriched atypical kinase 1 regulates the cytoskeleton and cancer progression. Proc Natl Acad Sci U S A. 2010; 107 (24):10920–10925. PubMed

    • Consortium Data Additions & Site Updates

      • Correlative Analysis software packages available through the Structure Initiative

        Provided are a collection of command-line executables, each of which performs a relatively simple task, that can be strung together to allow; segmentation, denoising, or docking of atomic models into a density. For more details visit the structure initiative software page.

    • Other CMC Publications

      • One of this month's featured articles in the Cell Migration Update section of the Gateway highlights the use of a new tension sensor developed by the Biosensors initiative of the Consortium. Using this new sensor the Schwartz laboratory has demonstrated that stabilization of focal adhesions under tension requires the recruitment of vinculin and transmission of force across this molecule - processes that are regulated separately." Click here to read the article review on this publication.

        Grashoff C, Hoffman BD, Brenner MD, Zhou R, Parsons M, Yang MT, McLean MA, Sligar SG, Chen CS, Ha T, Schwartz MA. Measuring mechanical tension across vinculin reveals regulation of focal adhesion dynamics. Nature. 2010 Jul 8;466(7303):263-6. PubMed

      • van der Flier A, Badu-Nkansah K, Whittaker CA, Crowley D, Bronson RT, Lacy-Hulbert A, Hynes RO. Endothelial alpha5 and alphav integrins cooperate in remodeling of the vasculature during development. Development. 2010;137(14):2439-49. PubMed

      • Hertzog M, Milanesi F, Hazelwood L, Disanza A, Liu H, Perlade E, Malabarba MG, Pasqualato S, Maiolica A, Confalonieri S, Le Clainche C, Offenhauser N, Block J, Rottner K, Di Fiore PP, Carlier MF, Volkmann N, Hanein D, Scita G. Molecular basis for the dual function of Eps8 on actin dynamics: bundling and capping. PLoS Biol 2010; 8 (6):e1000387. PubMed

    • Upcoming Conferences & Workshops

      • 5th LFD Workshop in Advanced Fluorescence Imaging & Dynamics October 25 – 29, 2010, Irvine, CA:

        Registration for this workshop at the LFD, UC-Irvine, CA is now open and a limited number of student awards are available. The deadline for submitting student award applications is September 24, 2010. For more details and to register visit the web site at www.lfd.uci.edu/workshop.

      • ASCB 50th Annual Meeting - December 11 - 15, 2010, Philadelphia, PA:

        Registration for this meeting is now open and applications for travel awards must be received by September 1: For more details and to register visit the meeting web site at http://www.ascb.org/meetings/.

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  • July 2010

    1. New kinase activation method reveals FAK control of ruffling
    2. Consortium technology gets traction in other fields
    3. Other CMC Publications
    4. Upcoming Conferences & Workshops

    • New kinase activation method reveals FAK control of ruffling

      A newly developed and broadly applicable approach to precisely controlling kinase activity within living cells has successfully uncovered a previously unknown function of focal adhesion kinase (FAK) in regulating membrane dynamics, as reported in Nature Biotechnology by Karginov et al. Based on previous reports that the conformational rigidity of FKBP12 increases considerably on ligand binding, the notion arose that inserting this small protein near the catalytic site of kinases could be used to regulate the conformation mobility of their active site. Karginov et al. used this approach to create a form of FAK that could be regulated by rapamycin — RapR-FAK. Introducing an optimally-truncated form of FKBP12 into FAK allowed FAK’s catalytic activity to be robustly and specifically stimulated in living cells in response to rapamycin (within 2 minutes) without altering its other features. The FKBP12 insertion confers inactivity by increasing the flexibility of the kinase domain, and rapamycin restores rigidity, thereby rescuing activity; this approach could therefore potentially be applied to a whole range of other kinases, and was validated for both tyrosine and ser/thr kinases in this publication. Using a mutant form of RapR-FAK — Y180A/M183A (RapR-FAK-YM) — to ensure RapR-FAK activation only in response to rapamycin and not by endogenous factors, Karginov et al. induced activation in HeLa cells and observed dorsal membrane ruffling. The use of RapR-FAK-YM as well as Src inhibitors demonstrated that FAK catalysis activates Src to induce dorsal membrane protrusions. These cellular structures are involved in invasive migration, consistent with FAK overexpression in invasive tumour cells.

      • Karginov AV, Ding F, Kota P, Dokholyan NV, Hahn KM. Engineered allosteric activation of kinases in living cells. Nat Biotech. 2010; Jun 27.[Epub ahead of print] PubMed

    • Consortium technology gets traction in other fields

      Neurodegenerative disease: inclusion formation: Aggregation of proteins containing expanded polyglutamine (polyQ) repeats (stretches of over 40 glutamines) is hypothesized to initiate Huntington’s disease. Ossato et al. propose a two-step pathway leading to the formation of inclusions (monomers→oligomers→inclusions) on the basis of results using the number and brightness (N&B) method. N&B shows protein aggregation in real-time by measuring intensity fluctuations at each pixel in an image. The researchers transiently expressed processed N-terminal fragments of human Huntingtin exon 1 (Httex1p) containing different polyQ lengths, tagged with enhanced green fluorescent protein (EGFP). Unexpanded Httex1p-25QP-EGFP mostly remained monomeric following transfection in COS-7 cells. Constructs encoding proteins with longer polyQ tracts (Httex1p-46Q-EGFP) created higher-order complexes, although monomers and oligomers were in a rapid equilibrium. Further expanding the polyQ repeats (Httex1p-97QP-EGFP) generated immobile cytoplasmic inclusions after the aggregation of monomers into oligomers. Almost all the Httex1p-97QP-EGFP in the cell was recruited to the inclusions, and was derived from the nucleus as well as the cytoplasm. The three constructs overall showed the same behaviour when expressed in neuronal precursor cells, although the rates of inclusion formation and the number of inclusions formed differed. Ossato et al. propose a four-phase model for inclusion formation: initially, only monomers are present, at a concentration below 1 μM; when the monomers accumulate to a concentration above 1 μM, and if the polyQ stretches exceed 40 glutamines, small oligomers (5–15 proteins) form; in the nucleation phase, inclusions begin to form at cytoplasmic nucleation sites; finally, the growing inclusions sequester most of the remainder of the protein.

      • Ossato G, Digman MA, Aiken C, Lukacsovich T, Marsh JL, Gratton E. A two-step path to inclusion formation of Huntingtin peptides revealed by number and brightness analysis. Biophys J. 2010;98(12):3078–3085. PubMed

    • Other CMC Publications

      •

        Wang Y, Kelber JA, Tran Cao HS, Cantin GT, Lin R, Wang W, Kaushal S, Bristow JM, Edgington TS, Hoffman RM, Bouvet M, Yates JR 3rd, Klemke RL. Pseudopodium-enriched atypical kinase 1 regulates the cytoskeleton and cancer progession. Proc Natl Acad Sci U S A. 2010 Jun 1. [Epub ahead of print] PubMed

      • Mogilner A, Rubinstein B. Actin disassembly 'clock' and membrane tension determine cell shape and turning: a mathematical model. J Phys Condens Matter 2010; 22 (19):194118. PubMed

    • Upcoming Conferences & Workshops

      • First Annual Montreal Light Microscopy Course: July 5 - 16, 2010:

        This exciting new course comprises two weeks of training to include beginners session (week 1), covering the basics of light microscopy, followed by a second week directed at more advanced microscopy techniques. Participants may register for one or both sessions and more details can be found at the web site www.mlmc.ca

      • Gordon Research Conferences: Signaling By Adhesion Receptors July 11 - 16, 2010:

        This meeting will take place at Colby College, Waterville, ME as part of the Gordon Research Conference series. Applications for the meeting must be submitted by June 20, 2010. For more details Visit the web site at www.grc.org/programs.

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  • June 2010

    1. Cell migration: Protrusion versus adhesion maturation
    2. Neuronal migration: Role of integrin α5β1
    3. Other CMC Publications
    4. Upcoming Conferences & Workshops

    • Cell migration: Protrusion versus adhesion maturation

      Computational modeling is often used to study adhesion and cytoskeletal dynamics during cell migration, but mainly to investigate the mechanical aspects of the process. In their report in Cellular and Molecular Bioengineering, Erik Welf and Jason Haugh have instead applied modeling to analyze the regulation of cell motility by signaling pathways. Protrusion of the cell membrane is driven by Rac-mediated actin polymerization in the lamellipodium, promoting adhesion between integrins and the extracellular matrix (ECM). Through a feedback mechanism termed the 'core protrusion cycle' by Welf and Haugh, nascent adhesions, in turn, mediate Rac activation (and subsequent protrusion and adhesion formation) through at least two pathways, one of which involves recruitment of the Rac guanine nucleotide-exchange factor DOCK180 to a multiprotein complex. Myosin-dependent maturation of nascent adhesions forms stable adhesions, which antagonize membrane protrusion. They used stochastic modeling to show that, at lower densities of ECM, the full array of protrusion–adhesion dynamics could be generated by the core protrusion cycle and its inhibition by stable adhesion, but that higher ECM densities promote stable adhesion. However, if adhesion maturation was inhibited by Src-dependent signaling to the GTPase-activating protein p190RhoGAP, which opposes myosin-based contractility, transient protrusion could then occur at these higher ECM densities through a mechanism described as 'buffering of inhibition'. A balance between Src-mediated feed-forward inhibition of adhesion maturation and adhesion-mediated inhibition of protrusion determines the outcome, in terms of protrusion or adhesion, depending on the ECM density and levels of myosin activity.

      • Welf ES, Haugh JM. Stochastic dynamics of membrane protrusion mediated by the DOCK180/Rac pathway in migrating cells. Cell Mol Bioeng. 2010; 3(1):30-39 PubMed

    • Neuronal migration: Role of integrin α5β1

      Adhesive interactions between the extracellular matrix, neurons and radial glia mediate neuronal migration during cortical development. Elisabeth Georges-Labouesse, Richard Hynes and colleagues now report in European Journal of Neuroscience that radial migration of cortical neurons is regulated by integrin α5β1. In developing murine neocortex cells, they showed that integrin α5 is localized to the ventricular and sub-ventricular zones, in contrast to more widespread expression of integrin β1. Deletion of integrin α5 with short-hairpin (sh)RNA introduced via in utero electroporation inhibited cell migration, without affecting cell proliferation or apoptosis, suggesting that α5 is required for proper neuronal migration. Next, the authors used Cre-mediated recombination to delete the integrin α5 gene from neural progenitors and showed that radial migration was impaired. Interestingly, integrin α5 deficiency resulted in morphological defects in migrating neurons, whereas the morphology of radial glia was not affected. Furthermore, neuronal differentiation was not affected by lack of integrin α5. As integrin β1 deletion was previously shown to inhibit migration of neuronal progenitors in vivo, the results presented here elucidate an important role of integrin α5β1 in regulation of neural morphology and migration, independently of differentiation, during cortical development.

      • Marchetti G, Escuin S, van der Flier A, De Arcangelis A, Hynes RO, Georges-Labouesse E. Integrin α5β1 is necessary for regulation of radial migration of cortical neurons during mouse brain development. Eur J Neurosci.2010; 31(3):399-409 PubMed

    • Other CMC Publications

      • One of this month's featured articles in the Cell Migration Update section of the Gateway highlights the in vivo use of novel photo-activatable proteins with new FRET designs. Click here to read the article review

        Wang X, He L, Wu YI, Hahn KM, Montell DJ. Light-mediated activation reveals a key role for Rac in collective guidance of cell movement in vivo. Nat Cell Biol. 2010 May 16. [Epub ahead of print] PubMed

    • Upcoming Conferences & Workshops

      • First Annual Montreal Light Microscopy Course: July 5 - 16, 2010:

        This exciting new course comprises two weeks of training to include beginners session (week 1), covering the basics of light microscopy, followed by a second week directed at more advanced microscopy techniques. Participants may register for one or both sessions and more details can be found at the web site www.mlmc.ca

      • Gordon Research Conferences: Signaling By Adhesion Receptors July 11 - 16, 2010:

        This meeting will take place at Colby College, Waterville, ME as part of the Gordon Research Conference series. Applications for the meeting must be submitted by June 20, 2010. For more details Visit the web site at www.grc.org/programs.

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  • May 2010

    1. New protocols: Biosensor designs for RhoGTPases
    2. Osteoclast adhesion: Sense and stability
    3. Consortium Data Additions & Site Updates
    4. Other CMC Publications
    5. Upcoming Conferences & Workshops

    • New protocols: Biosensor designs for RhoGTPases

      Biosensors are analytical devices that convert a biological event into a measurable signal. Although recent advances in software development and microscopy have enhanced their accessibility and ease of use, there are still limitations for their application in cell biology. Klaus Hahn and colleagues now report in Current Protocols in Cell Biology three new biosensor designs for characterizing the dynamics of RhoGTPases in living cells. They present step-by-step protocols for the production and use of meroCBD biosensor for Cdc42 (a dye-based sensor that involves binding of a fragment of Wiskott-Aldrich Syndrome protein to activated Cdc42), a single-chain FRET biosensor for RhoA and a dual-chain FRET biosensor for Rac1 (named Rac1 FLAIR). They test the new designs and report their improvements over the original ones and further discuss the critical factors affecting the imaging procedure in living cells. For example, meroCBD produces a brighter signal than the previous FRET biosensor for Cdc42 and does not require expression of exogenous Cdc42. The new RhoA sensor is an intramolecular FRET biosensor, which detects the physical attachment of RhoA to its effector Rhotekin with the fluorescent proteins undergoing FRET built in the chain connecting the RhoA–Rhotekin fragment; this is an improvement over the original design as it leaves the RhoA protein intact. As regards the Rac1 FLAIR sensor, the fluorescent dyes used in the original design are replaced with fluorescent proteins to detect Rac1 and p21-activated kinase 1 separately; this provides a fully genetically encoded sensor, which has a higher sensitivity than the original system. The authors also provide a detailed description of the imaging procedures in living cells for each biosensor and present the critical parameters affecting efficiency and image analysis. Proper application of the new designs as described here will help the investigation of previously invisible RhoGTPase dynamics and further elucidate their role in cell migration.

      • Hodgson L, Shen F, Hahn K. Biosensors for characterizing the dynamics of Rho family GTPases in living cells. Curr Protoc Cell Biol. 2010:14(14):11.1-26 PubMed

    • Osteoclast adhesion: Sense and stability

      Osteoclasts are large multinucleated cells that adhere to the bone via actin-rich adhesive ‘sealing zone’ and mediate bone resorption. Earlier studies showed that surface topography regulates the activity of adherent cells through their integrin-mediated ‘sensors’. Benjamin Geiger and colleagues now report in the Journal of Cell Science that the structure and dynamics of osteoclast adhesion is controlled by the nano-topography of the surface to which they are bound. By culturing osteoclasts on large single crystals of calcite, they visualize the changes in sealing zone formation on smooth and rough surfaces. Scanning electron microscopy images show that osteoclasts adhering to rough surfaces develop large and stable sealing zone rings, whereas on smooth surfaces only small and unstable rings are formed. Consistently, fluorescence intensity of actin is increased on rough surfaces, which is in support of the formation of stable actin-rich sealing zones. Surprisingly, prolonged incubation of cells on smooth surface results in roughening of the surface that leads to stable ring formation, suggesting that adherent osteoclasts not only respond to surface topography, but also modify it. Experiments on rough and smooth glass surfaces were consistent with the findings on calcite crystals, which supports the notion that topographical changes affect the formation and dynamics of osteoclast sealing zones. Further investigation is necessary to clarify the cellular components and adhesive proteins that control the mechanism whereby osteoclasts sense the topography of a bone surface, and this will help our understanding of bone remodeling.

      • Geblinger D, Addadi L, Geiger B. Nano-topography sensing by osteoclasts. J Cell Sci. 2010:123(Pt 9):1503-10 PubMed

    • Consortium Data Additions & Site Updates

      • ImageJ plug-ins available for photomicrograph analysis

        The Machesky group showcases two new plug-ins for photomicrograph analysis in their recent Current Biology publication entitled “The actin-bundling protein fascin stabilizes actin in invadopodia and potentiates protrusive invasion”, Li A, Dawson JC, Forero-Vargas M, Spence HJ, Yu X, Konig I, Anderson K, Machesky LM. Curr Biol; 20 (4):339-45. The plug-ins are being made available by the Machesky group via the Cell Migration Gateway's Imaging & Photomanipulation Initiative software page and provide a useful tool for the analysis of stacks of photomicrographs taken of cancer cells degrading fluorescently labeled extracellular matrix (ECM). Visit the site for more details.

      • Phosphoproteomics data for Myosin Light Chain/MLY9 now available

        Data showing the phosphorylation sites present on the myosin light chain/MLY9 can be accessed through the proteomics initiative activity table.

    • Other CMC Publications

      •

        Goult BT, Gingras AR, Bate N, Barsukov IL, Critchley DR, Roberts GC. The domain structure of talin: Residues 1815-1973 form a five-helix bundle containing a cryptic vinculin-binding site. FEBS Lett 2010; Apr 20. [Epub ahead of print] PubMed

      • Lim JI, Sabouri-Ghomi M, Machacek M, Waterman CM, Danuser G. Protrusion and actin assembly are coupled to the organization of lamellar contractile structures. Exp Cell Res 2010; [Epub ahead of print] PubMed

    • Upcoming Conferences & Workshops

      • First Annual Montreal Light Microscopy Course: July 5 - 16, 2010:

        This exciting new course comprises two weeks of training to include beginners session (week 1), covering the basics of light microscopy, followed by a second week directed at more advanced microscopy techniques. Participants may register for one or both sessions and more details can be found at the web site www.mlmc.ca.

      • Gordon Research Conferences: Signaling By Adhesion Receptors July 11 - 16, 2010:

        This meeting will take place at Colby College, Waterville, ME as part of the Gordon Research Conference series. Applications for the meeting must be submitted by June 20, 2010. For more details visit the web site at: www.grc.org/programs.

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  • April 2010

    1. Cell motility: PI(3)K-mediated regulation
    2. Modeling: Leading edge protrusion
    3. Consortium Data Additions & Site Updates
    4. Upcoming Conferences & Workshops

    • Cell motility: PI(3)K-mediated regulation

      Cell polarity and protrusion are prerequisites for directional migration. Although several molecular events in leading edge dynamics have been reported, the exact mechanism coordinating these processes is not clear. Anna Huttenlocher, Klaus Hahn and colleagues have now developed an in vivo system to study cell signalling and polarity during cell migration. In Developmental Cell, they report that phosphoinositide 3-kinase (PI(3)K) regulates neutrophil migration in zebrafish, by modulating Rac-mediated protrusion and F-actin polarization in a pathway that is separable from Rac activation. By using a wound-induced chemotaxis system based on live imaging, they first showed that PI(3)K is necessary for directed cell migration. To investigate the spatiotemporal dynamics of PI(3K) activity, they used in vivo high-resolution ratiometric imaging and demonstrated that PI(3)K activity is polarized to the leading edge and is involved in both forward and reverse migration. Furthermore, inhibition of PI(3)K activity impaired random motility in vivo, supporting a role for PI(3)K in cell migration. To elaborate the role of PI(3)K in migration, and as PI(3)K is known to regulate migration through activating Rac, they expressed a photoactivatable Rac protein specifically in neutrophils. Surprisingly, Rac activation was unable to restore migration in PI(3)K-inhibited cells, whereas localized photoactivation of Rac in normal cells was sufficient to induce protrusion and direct migration in vivo. Interestingly, analyses of F-actin dynamics showed that PI(3)K inhibition impairs anteroposterior polarity of F-actin. Taken together, this study demonstrates a two-tiered role for PI(3)K during cell motility: Rac-dependent protrusion of the leading edge and polarization of F-actin dynamics.

      • Yoo SK, Deng Q, Cavnar PJ, Wu YI, Hahn KM, Huttenlocher A. Differential regulation of protrusion and polarity by PI(3)K during neutrophil motility in live zebrafish. Dev. Cell. 2010:18, 226-236. PubMed

    • Modeling: Leading edge protrusion

      Coordination of cell adhesion, protrusion and actomyosin contraction is important during cell migration. Integrins are critical molecules for coordinating these processes; their interaction with extracellular matrix (ECM) proteins not only links the actin cytoskeleton to the substrate, but also activates downstream signaling involved in membrane protrusion and cell spreading. Jason Haugh and colleagues have developed a computational model that describes the stochastic mechanisms involved in the coupling between cell protrusion and integrin-mediated adhesion. Their work, published in PLoS Computational Biology, suggests that newer (nascent) adhesions, and not stable ones, promote protrusion through a positive feedback mechanism involving the small GTPase Rac. This pathway can propagate spatially across the leading edge and is optimized at intermediate ECM density in their model. Although high ECM density promotes nascent adhesion formation for a given protrusion rate, a higher fraction of those adhesions mature to form stable adhesions that promote additional adhesion maturation through recruitment of myosin. In accord with the model, myosin-depleted cells showed enhanced protrusion, especially at higher ECM density. This study presents a new model and insights regarding how cell migration and protrusion are governed by the availability of ECM.

      • Cirit M, Krajcovic M, Choi CK, Welf ES, Horwitz AF, Haugh JM. Stochastic model of integrin-mediated signaling and adhesion dynamics at the leading edges of migrating cells. PLoS Comput Biol. 2010:6, e1000688. PubMed

    • Consortium Data Additions & Site Updates

      • Cell Migration ventures onto the Facebook & Twitter scene

        The Cell Migration Gateway now has a Twitter feed and a Facebook page. Both sites will have the monthly update content and provide a venue for interaction amongst interested researchers. We are looking for your feedback so please share any suggestions for additional ways we could use social or other media tools.

    • Upcoming Conferences & Workshops

      • Gordon Research Conferences: Signaling By Adhesion Receptors July 11 - 16, 2010:

        This meeting will take place at Colby College, Waterville, ME as part of the Gordon Research Conference series. Applications for the meeting must be submitted by June 20, 2010. For more details Visit the web site at: www.grc.org/programs.aspx?year=2010&program=sigadhes

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  • March 2010

    1. Dendritic cell protrusions: The fungipod
    2. Structure: Domains in the talin head
    3. Consortium Data Additions & Site Updates
    4. Other CMC Publications
    5. Upcoming Conferences & Workshops

    • Dendritic cell protrusions: The fungipod

      Monocyte-derived dendritic cells (DCs) and their C-type lectin receptors (CLR) are important for generating an innate immune response against fungal pathogens and for recognition of non-self ligands. A recent study in PLoS Pathogens by Ken Jacobson and Aaron Neumann reports that a novel actin-based protrusive structure, the fungipod, mediates the interaction between immature DCs and yeast, including pathogenic Candida species. The authors show that fungipod formation is triggered by binding of yeast cell wall carbohydrates mannan and chitin to CD206, a CLR that recognizes both ligands. They also demonstrate that the fungipods contain a dense F-actin network and express cortactin — the actin nucleation factor that maintains the structure of actin cytoskeleton in lamellipodial protrusions. This indicates that actin cytoskeletal remodelling is important for formation of fungipodial protrusions in DCs, and highlights a dynamic actin-driven cellular structure that mediates innate immune response against fungal pathogens.

      • Neumann AC, Jacobson K. A novel pseudopodial component of the dendritic cell anti-fungal response: The fungipod. PLoS Pathog. 6, e1000760 (2010). PubMed

    • Structure: Domains in the talin head

      Integrin activation and interaction with the actin cytoskeleton is mediated by the adaptor protein talin. Talin contains an N-terminal FERM domain comprised of F1, F2 and F3 domains, and F1 contains an atypical large insert and is preceded by an extra domain F0. Although F3 was previously shown to bind to β integrin tails and to activate integrins, F0 and F1 are also required for efficient integrin activation. In The EMBO Journal, Ben Goult, Dave Critchley, Igor Barsukov and colleagues now report the solution structures of the F0 and F1 domains. Using NMR spectroscopy, they show that both F0 and F1 have ubiquitin-like folds joined in a novel fixed orientation, which has not previously been seen in other tandem ubiquitin-like domains. The large loop in F1 is unstructured, but binding to acidic phospholipids induces formation of a helix with basic residues aligned along one face. Charge reversal mutations compromise the phospholipid binding and the ability of the talin head to activate integrins. The authors propose a so-called “fly-casting model” in which the contact between the F1 loop and PIP2-rich membrane microdomains induces helix formation, and this in turn shortens the loop, pulling the talin head close to the membrane. Interestingly, in a related study in the Journal of Molecular Biology, the authors show that kindlins, which are required for talin-mediated integrin activation, have the same domain architecture as the talin FERM domain.

      • Goult BT, Bouaouina M, Harburger DS, Bate N, Patel B, Anthis NJ, Campbell ID, Calderwood DA, Barsukov IL, Roberts GC, Critchley DR. The structure of the N-terminus of Kindlin-1: A domain important for αIIbβ3 integrin activation. J. Mol Biol. 394, 944-956 (2009) PubMed

      • Goult BT, Bouaouina M, Elliott PR, Bate N, Patel B, Gingras AR, Grossmann JG, Roberts GC, Calderwood DA, Critchley DR, Barsukov IL. Structure of a double ubiquitin-like domain in the talin head: a role in integrin activation. EMBO J. 2010 Feb 11. [Epub ahead of print] PubMed

    • Consortium Data Additions & Site Updates

      • Cell Migration ventures onto the Facebook & Twitter scene

        The Cell Migration Gateway now has a Twitter feed and a Facebook page. Both sites will have the monthly update content and provide a venue for interaction amongst interested researchers. We are looking for your feedback so please share any suggestions for additional ways we could use social or other media tools.

    • Other CMC Publications

      •

        Koivusalo M, Welch C, Hayashi H, Scott CC, Kim M, Alexander T, Touret N, Hahn KM, Grinstein S. Amiloride inhibits macropinocytosis by lowering submembranous pH and preventing Rac1 and Cdc42 signaling. J Cell Biol 2010; Feb 15. [Epub ahead of print] PubMed

      • Premkumar L, Bobkov AA, Patel M, Jaroszewski L, Bankston LA, Stec B, Vuori K, Cote JF, Liddington RC. Structural basis of membrane-targeting by the Dock180 family of Rho-family guanine exchange factors (RhoGEFs). J Biol Chem 2010; Feb 18. [Epub ahead of print] PubMed

      • Yoo SK, Deng Q, Cavnar PJ, Wu YI, Hahn KM, Huttenlocher A. Differential Regulation of Protrusion and Polarity by PI(3)K during Neutrophil Motility in Live Zebrafish. Dev Cell 2010; 18 (2):226-36. PubMed

    • Upcoming Conferences & Workshops

      • Gordon Research Conferences: Signaling By Adhesion Receptors July 11 - 16, 2010:

        This meeting will take place at Colby College, Waterville, ME as part of the Gordon Research Conference series. Applications for the meeting must be submitted by June 20, 2010. For more details Visit the web site at: www.grc.org/programs.

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  • February 2010

    1. Cell migration: Signaling for persistence
    2. Consortium Data Additions & Site Updates
    3. Upcoming Conferences & Workshops

    • Cell migration: Signaling for persistence

      Several intracellular signaling pathways regulate cell protrusion, adhesion and motility; however, the mechanism of how the signaling molecules coordinate and control the dynamics of cell migration is not known. Jason Haugh and colleagues previously reported that ‘hot spots’ of phosphoinositide 3-kinase (PI3K) signaling are localized in the membrane protrusions of randomly migrating fibroblasts. In their latest report in Biophysical Journal, the authors now present a new computational framework called ‘signaling vector analysis’ (SVA), which allows researchers to identify and track signaling ‘hot spots’ in migrating cells. They quantified images of fluorescent signaling biosensors alongside the corresponding paths of cell movement to demonstrate that the persistence of the direction of cell migration correlates with the intracellular pattern and duration of PI3K activity. Tracking individual PI3K hot spots revealed that the spots with higher PI3K activity were more stable and therefore more likely to correlate with productive cell movement. This study offers a conceptual model of cell orientation during random migration based on the dynamic fluctuations of intracellular signaling.

      • Weiger MC, Ahmed S, Welf ES, Haugh JM. Directional persistence of cell migration coincides with stability of asymmetric intracellular signaling. Biophys J. 2010 Jan 98; 67-75. PubMed

    • Consortium Data Additions & Site Updates

      • Cell Migration ventures onto the Facebook & Twitter scene

        The Cell Migration Gateway now has a Twitter feed and a Facebook page. Both sites will have the monthly update content and provide a venue for interaction amongst interested researchers. We are looking for your feedback so please share any suggestions for additional ways we could use social or other media tools.

    • Upcoming Conferences & Workshops

      • Biophysical Society 54th Annual Meeting February 20-24, 2010:

        This meeting will take place in San Francisco, CA later this month. Visit the web site for more details of the program and late registration information: www.biophysics.org/2010meeting.

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  • January 2010

    1. Holding on to the cytoskeleton: CBP-mediated Thy-1 anchorage
    2. Integrin activation: All we need is talin
    3. Consortium Data Additions & Site Updates
    4. Other CMC Publications
    5. Upcoming Conferences & Workshops

    • Holding on to the cytoskeleton: CBP-mediated Thy-1 anchorage

      Glycosylphosphatidylinositol (GPI)-anchored proteins (GPIAPs) can drive signal transduction through association with cytoplasmic proteins. Ken Jacobson and colleagues previously showed that GPIAPs are transiently anchored at the cell surface through association with the actin cytoskeleton. They carried out this earlier study using single-particle tracking with gold particles, which clustered GPIAPs, and showed that transient anchorage of GPIAPs is regulated by Src-family kinases and cholesterol. In the Journal of Cell Science, the authors now demonstrate that, Csk-binding protein (CBP) — a transmembrane protein —regulates transient anchorage of Thy-1 — a GPIAP located on lymphoid cells, neurons and fibroblasts — via an Ezrin/Radixin/Moesin (ERM)-binding protein 50 (EBP50)-mediated linkage to the cytoskeleton. In this study, they use quantum-dot-based single-particle tracking to induce transient anchorage of Thy-1 molecules. By transfecting murine fibroblasts with short hairpin RNA (shRNA) for CBP, they found that CBP is required for transient anchorage of Thy-1 clusters with the actin cytoskeleton. Furthermore, pharmacological inhibition of CBP dephosphorylation resulted in preservation of anchorage, suggesting that release of transiently anchored Thy-1 requires dephosphorylation of CBP. Finally, transient anchorage of Thy-1 was inhibited in cells expressing a dominant-negative mutant of EBP50, which indicates that CBP mediates anchorage to the cytoskeleton via EBP50.

      • Chen Y, Veracini L, Benistant C, Jacobson K. The transmembrane protein CBP plays a role in transiently anchoring small clusters of Thy-1, a GPI-anchored protein, to the cytoskeleton. J Cell Sci. 2009 Nov 15; 122(22): 3966-72. PubMed

    • Integrin activation: All we need is talin

      Integrins regulate cell migration and cell-matrix adhesion, which are important processes for development and disease. Genetic studies investigating mechanisms involved in integrin activation indicated that both talin and kindlins are involved by binding the integrin beta subunit cytoplasmic domain. Nevertheless, it is uncertain whether these molecules are sufficient for integrin activation. By developing a purified system to recreate the final events in integrin activation, Mark Ginsberg, Kenneth Taylor and colleagues now report in the Journal of Cell Biology that talin binding to the beta3 tail is sufficient for activation of integrin alphaIIb beta3. The authors incorporated alphaIIb beta3 into liposomes and used cryo-electron tomography to establish the incorporation of the integrin and its orientation. When talin head domain was present, the integrin was activated showing that talin is sufficient for integrin activation. Supporting this, talin also activated a beta3 mutant that is impaired for kindlin binding. The authors went on to demonstrate that for activation by talin, the integrin is required to be embedded in a phospholipid bilayer, and the talin is required to bind the phospholipid. Lastly, quantitative electron microscopy analysis of phospholipid nanodiscs with single integrins embedded in them revealed that talin activates un-clustered integrins, changing their conformation to an extended form. This study resolves the uncertainty as to whether talin is sufficient to activate and extend un-clustered integrins, and paves the way for understanding the physiological events involved in inside-out integrin signalling.

      • Ye F, Hu G, Taylor D, Ratnikov B, Bobkov AA, McLean MA, Sligar SG, Taylor KA, Ginsberg MH. Recreation of the Terminal Events in Physiological Integrin Activation. J Cell Biol. 2010 Jan 4 [Epub ahead of print]. PubMed

    • Consortium Data Additions & Site Updates

      • Migration 101 Reviews Updated

        The Reviews section of Migration 101 has been updated with recent publications. Migration 101 Reviews

    • Other CMC Publications

      •

        Goult BT, Bouaouina M, Harburger DS, Bate N, Patel B, Anthis NJ, Campbell ID, Calderwood DA, Barsukov IL, Roberts GC, Critchley DR. The structure of the N-terminus of kindlin-1: a domain important for alphaiibbeta3 integrin activation. J Mol Biol 2009; 394 (5):944-56. PubMed

      • Loving GS, Sainlos M, Imperiali B. Monitoring protein interactions and dynamics with solvatochromic fluorophores. Trends Biotechnol. 2009 Dec 3. [Epub ahead of print] PubMed

    • Upcoming Conferences & Workshops

      • Biophysical Society 54th Annual Meeting February 20-24, 2010:

        This meeting will be held in San Francisco, CA and is now accepting papers. Visit the web site for more details: www.biophysics.org/2010meeting.

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2010