scholarly journals Clathrin-independent carriers form a high capacity endocytic sorting system at the leading edge of migrating cells

2010 ◽  
Vol 190 (4) ◽  
pp. 675-691 ◽  
Author(s):  
Mark T. Howes ◽  
Matthew Kirkham ◽  
James Riches ◽  
Katia Cortese ◽  
Piers J. Walser ◽  
...  
Keyword(s):  
High Capacity ◽  
Leading Edge ◽  
Cellular Adhesion ◽  
Endocytic Pathway ◽  
Membrane Turnover ◽  
Major Pathway ◽  
Endocytic Sorting ◽  
And Migration ◽  
Sorting Station ◽  
Migrating Cells

Although the importance of clathrin- and caveolin-independent endocytic pathways has recently emerged, key aspects of these routes remain unknown. Using quantitative ultrastructural approaches, we show that clathrin-independent carriers (CLICs) account for approximately three times the volume internalized by the clathrin-mediated endocytic pathway, forming the major pathway involved in uptake of fluid and bulk membrane in fibroblasts. Electron tomographic analysis of the 3D morphology of the earliest carriers shows that they are multidomain organelles that form a complex sorting station as they mature. Proteomic analysis provides direct links between CLICs, cellular adhesion turnover, and migration. Consistent with this, CLIC-mediated endocytosis of key cargo proteins, CD44 and Thy-1, is polarized at the leading edge of migrating fibroblasts, while transient ablation of CLICs impairs their ability to migrate. These studies provide the first quantitative ultrastructural analysis and molecular characterization of the major endocytic pathway in fibroblasts, a pathway that provides rapid membrane turnover at the leading edge of migrating cells.

scholarly journals The endocytic protein GRAF1 is directed to cell-matrix adhesion sites and regulates cell spreading

2011 ◽  
Vol 22 (22) ◽  
pp. 4380-4389 ◽  
Author(s):  
Gary J. Doherty ◽  
Monika K. Åhlund ◽  
Mark T. Howes ◽  
Björn Morén ◽  
Robert G. Parton ◽  
...  
Keyword(s):  
Rho Gtpase ◽  
Morphological Changes ◽  
Leading Edge ◽  
Cell Spreading ◽  
Endocytic Pathway ◽  
Membrane Microdomains ◽  
Membrane Turnover ◽  
Cell Matrix ◽  
Adhesion Sites ◽  
And Migration

The rho GTPase-activating protein GTPase regulator associated with focal adhesion kinase-1 (GRAF1) remodels membranes into tubulovesicular clathrin-independent carriers (CLICs) mediating lipid-anchored receptor endocytosis. However, the cell biological functions of this highly prevalent endocytic pathway are unclear. In this article, we present biochemical and cell biological evidence that GRAF1 interacted with a network of endocytic and adhesion proteins and was found enriched at podosome-like adhesions and src-induced podosomes. We further demonstrate that these sites comprise microdomains of highly ordered lipid enriched in GRAF1 endocytic cargo. GRAF1 activity was upregulated in spreading cells and uptake via CLICs was concentrated at the leading edge of migrating cells. Depletion of GRAF1, which inhibits CLIC generation, resulted in profound defects in cell spreading and migration. We propose that GRAF1 remodels membrane microdomains at adhesion sites into endocytic carriers, facilitating membrane turnover during cell morphological changes.

scholarly journals Scribble, Lgl1, and myosin II form a complex in vivo to promote directed cell migration

2020 ◽  
Vol 31 (20) ◽  
pp. 2234-2248
Author(s):  
Maha Abedrabbo ◽  
Shoshana Ravid
Keyword(s):  
Cell Migration ◽  
Cell Adhesion ◽  
Myosin Ii ◽  
Leading Edge ◽  
Directed Cell Migration ◽  
Lethal Giant Larvae ◽  
And Migration ◽  
Migrating Cells

Here we show that Scribble (Scrib), Lethal giant larvae 1 (Lgl1), and myosin II form a complex in vivo and colocalize at the cell leading edge of migrating cells, and this colocalization is interdependent. Scrib and Lgl1 are required for proper cell adhesion, polarity, and migration.

scholarly journals Tiam1 interaction with the PAR complex promotes talin-mediated Rac1 activation during polarized cell migration

2012 ◽  
Vol 199 (2) ◽  
pp. 331-345 ◽  
Author(s):  
Shujie Wang ◽  
Takashi Watanabe ◽  
Kenji Matsuzawa ◽  
Akira Katsumi ◽  
Mai Kakeno ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Cell Migration ◽  
Protein Kinase ◽  
Leading Edge ◽  
Cell Spreading ◽  
Kinase C ◽  
Rac1 Activity ◽  
Directional Movement ◽  
And Migration ◽  
Migrating Cells

Migrating cells acquire front-rear polarity with a leading edge and a trailing tail for directional movement. The Rac exchange factor Tiam1 participates in polarized cell migration with the PAR complex of PAR3, PAR6, and atypical protein kinase C. However, it remains largely unknown how Tiam1 is regulated and contributes to the establishment of polarity in migrating cells. We show here that Tiam1 interacts directly with talin, which binds and activates integrins to mediate their signaling. Tiam1 accumulated at adhesions in a manner dependent on talin and the PAR complex. The interactions of talin with Tiam1 and the PAR complex were required for adhesion-induced Rac1 activation, cell spreading, and migration toward integrin substrates. Furthermore, Tiam1 acted with talin to regulate adhesion turnover. Thus, we propose that Tiam1, with the PAR complex, binds to integrins through talin and, together with the PAR complex, thereby regulates Rac1 activity and adhesion turnover for polarized migration.

scholarly journals Paxillin kinase linker (PKL) regulates Vav2 signaling during cell spreading and migration

2013 ◽  
Vol 24 (12) ◽  
pp. 1882-1894 ◽  
Author(s):  
Matthew C. Jones ◽  
Kazuya Machida ◽  
Bruce J. Mayer ◽  
Christopher E. Turner
Keyword(s):  
Cell Migration ◽  
Rho Gtpases ◽  
Focal Adhesions ◽  
Leading Edge ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Gtpase Activating Proteins ◽  
And Migration ◽  
Migrating Cells

The Rho family of GTPases plays an important role in coordinating dynamic changes in the cell migration machinery after integrin engagement with the extracellular matrix. Rho GTPases are activated by guanine nucleotide exchange factors (GEFs) and negatively regulated by GTPase-activating proteins (GAPs). However, the mechanisms by which GEFs and GAPs are spatially and temporally regulated are poorly understood. Here the activity of the proto-oncogene Vav2, a GEF for Rac1, RhoA, and Cdc42, is shown to be regulated by a phosphorylation-dependent interaction with the ArfGAP PKL (GIT2). PKL is required for Vav2 activation downstream of integrin engagement and epidermal growth factor (EGF) stimulation. In turn, Vav2 regulates the subsequent redistribution of PKL and the Rac1 GEF β-PIX to focal adhesions after EGF stimulation, suggesting a feedforward signaling loop that coordinates PKL-dependent Vav2 activation and PKL localization. Of interest, Vav2 is required for the efficient localization of PKL and β-PIX to the leading edge of migrating cells, and knockdown of Vav2 results in a decrease in directional persistence and polarization in migrating cells, suggesting a coordination between PKL/Vav2 signaling and PKL/β-PIX signaling during cell migration.

scholarly journals Actin retrograde flow actively aligns and orients ligand-engaged integrins in focal adhesions

2017 ◽  
Vol 114 (40) ◽  
pp. 10648-10653 ◽  
Author(s):  
Vinay Swaminathan ◽  
Joseph Mathew Kalappurakkal ◽  
Shalin B. Mehta ◽  
Pontus Nordenfelt ◽  
Travis I. Moore ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Focal Adhesions ◽  
Leading Edge ◽  
Retrograde Flow ◽  
Molecular Scaffold ◽  
Cell Adhesion And Migration ◽  
Αvβ3 Integrins ◽  
Mediate Cell ◽  
And Migration ◽  
Migrating Cells

Integrins are transmembrane receptors that, upon activation, bind extracellular ligands and link them to the actin filament (F-actin) cytoskeleton to mediate cell adhesion and migration. Cytoskeletal forces in migrating cells generated by polymerization- or contractility-driven “retrograde flow” of F-actin from the cell leading edge have been hypothesized to mediate integrin activation for ligand binding. This predicts that these forces should align and orient activated, ligand-bound integrins at the leading edge. Here, polarization-sensitive fluorescence microscopy of GFP-αVβ3 integrins in fibroblasts shows that integrins are coaligned in a specific orientation within focal adhesions (FAs) in a manner dependent on binding immobilized ligand and a talin-mediated linkage to the F-actin cytoskeleton. These findings, together with Rosetta modeling, suggest that integrins in FA are coaligned and may be highly tilted by cytoskeletal forces. Thus, the F-actin cytoskeleton sculpts an anisotropic molecular scaffold in FAs, and this feature may underlie the ability of migrating cells to sense directional extracellular cues.

scholarly journals Effects of a New Bioceramic Material on Human Apical Papilla Cells

2018 ◽  
Vol 9 (4) ◽  
pp. 74 ◽  
Author(s):  
Diana Sequeira ◽  
Catarina Seabra ◽  
Paulo Palma ◽  
Ana Cardoso ◽  
João Peça ◽  
...  
Keyword(s):  
Wound Healing ◽  
Mineral Trioxide Aggregate ◽  
Cellular Adhesion ◽  
Cellular Migration ◽  
Cellular Viability ◽  
Migration Rates ◽  
Apical Papilla ◽  
And Migration ◽  
Proliferation And Migration

Background: The development of materials with bioregenerative properties is critically important for vital pulp therapies and regenerative endodontic procedures. The aim of this study was to evaluate the cytocompatibility and cytotoxicity of a new endodontic biomaterial, PulpGuard, in comparison with two other biomaterials widely used in endodontic procedures, ProRoot Mineral Trioxide Aggregate (MTA) and Biodentine. Methods: Apical papilla cells (APCs) were isolated from third molars with incomplete rhizogenesis from patients with orthodontic indication for dental extraction. Cultured APCs were incubated for 24, 48, or 72 h with different dilutions of eluates prepared from the three materials. Cellular viability, mobility, and proliferation were assessed in vitro using the Alamar Blue assay and a wound-healing test. The cells were also cultured in direct contact with the surface of each material. These were then analyzed via Scanning Electron Microscopy (SEM), and the surface chemical composition was determined by Energy-Dispersive Spectroscopy (EDS). Results: Cells incubated in the presence of eluates extracted from ProRoot MTA and PulpGuard presented rates of viability comparable to those of control cells; in contrast, undiluted Biodentine eluates induced a significant reduction of cellular viability. The wound-healing assay revealed that eluates from ProRoot MTA and PulpGuard allowed for unhindered cellular migration and proliferation. Cellular adhesion was observed on the surface of all materials tested. Consistent with their disclosed composition, EDS analysis found high relative abundance of calcium in Biodentine and ProRoot MTA and high abundance of silicon in PulpGuard. Significant amounts of zinc and calcium were also present in PulpGuard discs. Concerning solubility, Biodentine and ProRoot MTA presented mild weight loss after eluate extraction, while PulpGuard discs showed significant water uptake. Conclusions: PulpGuard displayed a good in vitro cytocompatibility profile and did not significantly affect the proliferation and migration rates of APCs. Cells cultured in the presence of PulpGuard eluates displayed a similar profile to those cultured with eluates from the widely used endodontic cement ProRoot MTA.

scholarly journals CaM kinase IIδ2-dependent regulation of vascular smooth muscle cell polarization and migration

2008 ◽  
Vol 294 (6) ◽  
pp. C1465-C1475 ◽  
Author(s):  
Melissa Z. Mercure ◽  
Roman Ginnan ◽  
Harold A. Singer
Keyword(s):  
Smooth Muscle ◽  
Cell Migration ◽  
Vascular Smooth Muscle ◽  
Cell Monolayer ◽  
Leading Edge ◽  
Cell Polarization ◽  
Loss Of Function ◽  
Downstream Signaling ◽  
Transient Activation ◽  
And Migration

Previous studies indicate involvement of the multifunctional Ca2+/calmodulin-dependent protein kinase II (CaMKII) in vascular smooth muscle (VSM) cell migration. In the present study, molecular loss-of-function studies were used specifically to assess the role of the predominant CaMKIIδ2 isoform on VSM cell migration using a scratch wound healing assay. Targeted CaMKIIδ2 knockdown using siRNA or inhibition of activity by overexpressing a kinase-negative mutant resulted in attenuation of VSM cell migration. Temporal and spatial assessments of kinase autophosphorylation indicated rapid and transient activation in response to wounding, in addition to a sustained activation in the leading edge of migrating and spreading cells. Furthermore, siRNA-mediated suppression of CaMKIIδ2 resulted in the inhibition of wound-induced Rac activation and Golgi reorganization, and disruption of leading edge morphology, indicating an important function for CaMKIIδ2 in regulating VSM cell polarization. Numerous previous reports link activation of CaMKII to ERK1/2 signaling in VSM. Wound-induced ERK1/2 activation was also found to be dependent on CaMKII; however, ERK activity did not account for effects of CaMKII in regulating Golgi polarization, indicating alternative mechanisms by which CaMKII affects the complex events involved in cell migration. Wounding a VSM cell monolayer results in CaMKIIδ2 activation, which positively regulates VSM cell polarization and downstream signaling, including Rac and ERK1/2 activation, leading to cell migration.

scholarly journals Molecular Regulation of Actin Turnover at the Leading Edge of Migrating Cells

2015 ◽  
Vol 108 (2) ◽  
pp. 179a-180a
Author(s):  
Brannon R. McCullough ◽  
David J. Odde
Keyword(s):  
Leading Edge ◽  
Molecular Regulation ◽  
Actin Turnover ◽  
Migrating Cells
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