Faculty Opinions recommendation of Cadherin puncta are interdigitated dynamic actin protrusions necessary for stable cadherin adhesion.

AbstractMyosin-7a, despite being monomeric in isolation, plays roles in organizing actin-based cell protrusions such as filopodia, microvilli and stereocilia, as well as transporting cargoes within them. Here, we identify a binding protein for Drosophila myosin-7a termed M7BP, and describe how M7BP assembles myosin-7a into a motile complex that enables cargo translocation and actin cytoskeletal remodeling. M7BP binds to the autoinhibitory tail of myosin-7a, extending the molecule and activating its ATPase activity. Single-molecule reconstitution show that M7BP enables robust motility by complexing with myosin-7a as 2:2 translocation dimers in an actin-regulated manner. Meanwhile, M7BP tethers actin, enhancing complex’s processivity and driving actin-filament alignment during processive runs. Finally, we show that myosin-7a-M7BP complex assembles actin bundles and filopodia-like protrusions while migrating along them in living cells. Together, these findings provide insights into the mechanisms by which myosin-7a functions in actin protrusions.

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Rac1-GTPase regulates compression-induced actin protrusions (CAPs) of mesenchymal stem cells in 3D collagen micro-tissues

Biomaterials ◽

10.1016/j.biomaterials.2021.120829 ◽

2021 ◽

Vol 274 ◽

pp. 120829

Author(s):

Vincent Kwok Lim Lam ◽

Johnny Yu Hin Wong ◽

Sing Yian Chew ◽

Barbara Pui Chan

Keyword(s):

Stem Cells ◽

Mesenchymal Stem Cells ◽

Rac1 Gtpase ◽

3D Collagen ◽

Actin Protrusions

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Deafness mutation in the MYO3A motor domain impairs actin protrusion elongation mechanism

Molecular Biology of the Cell ◽

10.1091/mbc.e21-05-0232 ◽

2021 ◽

Author(s):

Laura K. Gunther ◽

Joseph A Cirilo ◽

Rohini Desetty ◽

Christopher M. Yengo

Keyword(s):

Atp Hydrolysis ◽

Kinetic Mechanism ◽

Duty Ratio ◽

Slight Reduction ◽

Average Intensity ◽

Class Iii ◽

Length Regulation ◽

Adp Release ◽

Actin Protrusions

Class III myosins are actin-based motors proposed to transport cargo to the distal tips of stereocilia in the inner ear hairs cells and/or to participate in stereocilia length regulation, which is especially important during development. Mutations in the MYO3A gene are associated with delayed onset deafness. A previous study demonstrated that L697W, a dominant deafness mutation, disrupts MYO3A ATPase and motor properties but does not impair its ability to localize to the tips of actin protrusions. In the current study, we characterized the transient kinetic mechanism of the L697W motor ATPase cycle. Our kinetic analysis demonstrates that the mutation slows the ADP release and ATP hydrolysis steps, which results in a slight reduction in the duty ratio and slows detachment kinetics. Fluorescence recovery after photobleaching (FRAP) of filopodia tip localized L697W and WT MYO3A in COS-7 cells revealed that the mutant does not alter turnover or average intensity at the actin protrusion tips. We demonstrate that the mutation slows filopodia extension velocity in COS-7 cells which correlates with its 2-fold slower in vitro actin gliding velocity. Overall, this work allowed us to propose a model for how the motor properties of MYO3A are crucial for facilitating actin protrusion length regulation.

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Coxiella burnetii Induces Reorganization of the Actin Cytoskeleton in Human Monocytes

Infection and Immunity ◽

10.1128/iai.66.11.5527-5533.1998 ◽

1998 ◽

Vol 66 (11) ◽

pp. 5527-5533 ◽

Cited By ~ 40

Author(s):

Sonia Meconi ◽

Véronique Jacomo ◽

Patrice Boquet ◽

Didier Raoult ◽

Jean-Louis Mege ◽

...

Keyword(s):

Actin Cytoskeleton ◽

Coxiella Burnetii ◽

Actin Polymerization ◽

Q Fever ◽

Morphological Changes ◽

Critical Role ◽

Filamentous Actin ◽

Cytoskeleton Reorganization ◽

Membrane Protrusions ◽

Actin Protrusions

ABSTRACT Coxiella burnetii, an obligate intracellular bacterium which survives in myeloid cells, causes Q fever in humans. We previously demonstrated that virulent C. burnetiiorganisms are poorly internalized by monocytes compared to avirulent variants. We hypothesized that a differential mobilization of the actin cytoskeleton may account for this distinct phagocytic behavior. Scanning electron microscopy demonstrated that virulent C. burnetii stimulated profound and polymorphic changes in the morphology of THP-1 monocytes, consisting of membrane protrusions and polarized projections. These changes were transient, requiring 5 min to reach their maximum extent and vanishing after 60 min of incubation. In contrast, avirulent variants of C. burnetii did not induce any significant changes in cell morphology. The distribution of filamentous actin (F-actin) was then studied with a specific probe, bodipy phallacidin. Virulent C. burnetii induced a profound and transient reorganization of F-actin, accompanied by an increase in the F-actin content of THP-1 cells. F-actin was colocalized with myosin in cell protrusions, suggesting that actin polymerization and the tension of actin-myosin filaments play a role in C. burnetii-induced morphological changes. In addition, contact between the cell and the bacterium seems to be necessary to induce cytoskeleton reorganization. Bacterial supernatants did not stimulate actin remodeling, and virulent C. burnetii organisms were found in close apposition with F-actin protrusions. The manipulation of the actin cytoskeleton by C. burnetiimay therefore play a critical role in the internalization strategy of this bacterium.

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Faculty Opinions recommendation of Actin protrusions push at apical junctions to maintain E-cadherin adhesion.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.737127970.793585955 ◽

2021 ◽

Author(s):

Alpha Yap

Keyword(s):

Apical Junctions ◽

Actin Protrusions ◽

E Cadherin

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The Dictyostelium RasS protein is required for macropinocytosis, phagocytosis and the control of cell movement

Journal of Cell Science ◽

10.1242/jcs.113.4.709 ◽

2000 ◽

Vol 113 (4) ◽

pp. 709-719 ◽

Cited By ~ 4

Author(s):

J.R. Chubb ◽

A. Wilkins ◽

G.M. Thomas ◽

R.H. Insall

Keyword(s):

Cell Migration ◽

Significant Proportion ◽

Cell Movement ◽

Fluid Phase ◽

Small Gtpases ◽

Cell Cortex ◽

Fluid Phase Endocytosis ◽

Ras Family ◽

Actin Protrusions ◽

Mutant Cells

Endocytosis and cell migration both require transient localised remodelling of the cell cortex. Several lines of evidence suggest a key regulatory role in these activities for members of the Ras family of small GTPases. We have generated Dictyostelium cells lacking one member of this family, RasS, and the mutant cells are perturbed in endocytosis and cell migration. Mutant amoebae are defective in phagocytosis and fluid-phase endocytosis and are impaired in growth. Conversely, the rasS(-)cells show an enhanced rate of cell migration, moving three times faster than wild-type controls. The mutant cells display an aberrant morphology, are highly polarised, carry many elongated actin protrusions and show a concomitant decrease in formation of pinocytic crowns on the cell surface. These morphological aberrations are paralleled by changes in the actin cytoskeleton, with a significant proportion of the cortical F-actin relocalised to prominent pseudopodia. Rapid migration and endocytosis appear to be mutually incompatible and it is likely that RasS protein is required to maintain the normal balance between these two actin-dependent processes.

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Compressive Stress Enhances Invasive Phenotype of Breast Cancer Cells via Piezo1 Activation

10.21203/rs.2.18102/v1 ◽

2019 ◽

Author(s):

Mingzhi Luo ◽

Kenneth KY Ho ◽

Zhaowen Tong ◽

Linhong Deng ◽

Allen Liu

Keyword(s):

Breast Cancer ◽

Cancer Cells ◽

Compressive Stress ◽

Breast Cancer Cells ◽

Cancer Metastasis ◽

Calcium Influx ◽

Breast Cancer Metastasis ◽

Matrix Degradation ◽

Apical Side ◽

Actin Protrusions

Abstract Uncontrolled growth in solid tumor generates compressive stress that drives cancer cells into invasive phenotypes, but little is known about how such stress affects the invasion and matrix degradation of cancer cells and the underlying mechanisms. Here we show that compressive stress enhanced invasion and matrix degradation of breast cancer cells. We further identified Piezo1 as the putative mechanosensitive cellular component that transmits compressive stress to induce calcium influx, which in turn activate Src/ERK signaling. Interestingly, we observed actin protrusions with matrix degradation ability on the apical side of the cells. Furthermore, we demonstrate that Piezo1 channels were partially localized in caveolae, and reduction of caveolin-1 expression or disruption of caveolae with methyl-β-cyclodextrin led to not only reduced Piezo1 expression but also attenuation of the invasive phenotypes promoted by compressive stress. Taken together, our data indicate that mechanical compressive stress activates Piezo1 channels to mediate enhanced cancer cell invasion and matrix degradation that may be a critical mechanotransduction pathway during, and potentially a novel therapeutic target for, breast cancer metastasis.

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Actin protrusions push on E-cadherin to maintain epithelial cell-cell adhesion

10.1101/644302 ◽

2019 ◽

Author(s):

John Xiao He Li ◽

Vivian W. Tang ◽

William M. Brieher

Keyword(s):

Cell Adhesion ◽

Actin Polymerization ◽

Mdck Cells ◽

Myosin Ii ◽

Cell Junctions ◽

Apical Junctions ◽

Actin Protrusions ◽

Adhesive Contacts ◽

E Cadherin ◽

Cell Cell

AbstractCadherin mediated cell-cell adhesion is actin dependent, but the precise role of actin in maintaining cell-cell adhesion is not fully understood. Actin polymerization-dependent protrusive activity is required to push distally separated cells close enough together to initiate contact. Whether protrusive activity is required to maintain adhesion in confluent sheets of epithelial cells is not known. By electron microscopy as well as live cell imaging, we have identified a population of protruding actin microspikes that operate continuously near apical junctions of polarized MDCK cells. Live imaging shows that microspikes containing E-cadherin extend into gaps between E-cadherin clusters on neighboring cells while reformation of cadherin clusters across the cell-cell boundary triggers microspike withdrawal. We identify Arp2/3, EVL, and CRMP-1 as three actin assembly factors necessary for microspike formation. Depleting these factors from cells using RNAi results in myosin II-dependent unzipping of cadherin adhesive bonds. Therefore, actin polymerization-dependent protrusive activity operates continuously at cadherin cell-cell junctions to keep them shut and to prevent myosin II-dependent contractility from tearing cadherin adhesive contacts apart.

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