Diaphanous regulates myosin and adherens junctions to control cell contractility and protrusive behavior during morphogenesis

Cell-substrate adhesion is crucial at various stages of development and for the maintenance of normal tissues. Little is known about the regulation of these adhesive interactions. To investigate the role of GTPases in the control of cell morphology and cell-substrate adhesion we have injected guanine nucleotide analogs into Xenopus XTC fibroblasts. Injection of GTP gamma S inhibited ruffling and increased spreading, suggesting an increase in adhesion. To further investigate this, we made use of GRGDSP, a peptide which inhibits binding of integrins to vitronectin and fibronectin. XTC fibroblasts injected with non-hydrolyzable analogs of GTP took much more time to round up than mock-injected cells in response to treatment with GRGDSP, while GDP beta S-injected cells rounded up in less time than controls. Injection with GTP gamma S did not inhibit cell rounding induced by trypsin however, showing that cell contractility is not significantly affected by the activation of GTPases. These data provide evidence for the existence of a GTPase which can control cell-substrate adhesion from the cytoplasm. Treatment of XTC fibroblasts with the phorbol ester 12-o-tetradecanoylphorbol-13-acetate reduced cell spreading and accelerated cell rounding in response to GRGDSP, which is essentially opposite to the effect exerted by non-hydrolyzable GTP analogs. These results suggest the existence of at least two distinct pathways controlling cell-substrate adhesion in XTC fibroblasts, one depending on a GTPase and another one involving protein kinase C.

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Cdc42 antagonizes Rho1 activity at adherens junctions to limit epithelial cell apical tension

The Journal of Cell Biology ◽

10.1083/jcb.200906047 ◽

2009 ◽

Vol 187 (1) ◽

pp. 119-133 ◽

Cited By ~ 41

Author(s):

Stephen J. Warner ◽

Gregory D. Longmore

Keyword(s):

Epithelial Cell ◽

Adherens Junctions ◽

Apical Cell ◽

Cell Junction ◽

Cell Contractility ◽

Kinase C ◽

P21 Activated Kinase ◽

And Function ◽

Syndrome Protein ◽

Actomyosin Cytoskeleton

In epithelia, cells are arranged in an orderly pattern with a defined orientation and shape. Cadherin containing apical adherens junctions (AJs) and the associated actomyosin cytoskeleton likely contribute to epithelial cell shape by providing apical tension. The Rho guanosine triphosphatases are well known regulators of cell junction formation, maintenance, and function. Specifically, Rho promotes actomyosin activity and cell contractility; however, what controls and localizes this Rho activity as epithelia remodel is unresolved. Using mosaic clonal analysis in the Drosophila melanogaster pupal eye, we find that Cdc42 is critical for limiting apical cell tension by antagonizing Rho activity at AJs. Cdc42 localizes Par6–atypical protein kinase C (aPKC) to AJs, where this complex limits Rho1 activity and thus actomyosin contractility, independent of its effects on Wiskott-Aldrich syndrome protein and p21-activated kinase. Thus, in addition to its role in the establishment and maintenance of apical–basal polarity in forming epithelia, the Cdc42–Par6–aPKC polarity complex is required to limit Rho activity at AJs and thus modulate apical tension so as to shape the final epithelium.

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Abstract 337: VE-Cadherin Mechanotransduction Regulates Lung Endothelial Contractility and Barrier Integrity

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.34.suppl_1.337 ◽

2014 ◽

Vol 34 (suppl_1) ◽

Author(s):

Adrienne K Barry ◽

Ning Wang ◽

Deborah E Leckband

Keyword(s):

Shear Stress ◽

Cell Surface ◽

Adherens Junctions ◽

Cell Monolayer ◽

Adherens Junction ◽

Indirect Evidence ◽

Cell Junctions ◽

Specific Cell ◽

Structural Protein ◽

Cell Contractility

Dysfunctional regulation of endothelial adherens junctions is the direct underlying cause of vascular leak and pulmonary edema in acute lung injury. Indirect evidence suggests that cytoskeletal rearrangements are linked to adherens junction remodeling, but there is no clear demonstration that adherens junction proteins play an active role in the regulation of intracellular or extracellular mechanical tension. Here I investigate mechanotransduction (response to applied force) of VE-cadherin, the main structural protein at adherens junctions, and how this regulates global cell contractility and actin remodeling both locally and globally. Mechanical responses in human pulmonary artery endothelial cells were studied using magnetic twisting cytometry (MTC) experiments, in which shear stress was exerted on specific cell surface receptors by twisting magnetized beads bound to the cell surface. Remodeling of adherens junctions and F-actin in response to mechanical force was visualized by immunofluorescence. Confocal microscopy revealed force-actuated changes in both local and global cytoskeletal organization, as well as local rearrangements at both bead-cell and cell-cell junctions. This force-dependent remodeling correlated directly with the stiffening of VE-cadherin junctions with increasing applied stress. Treatment with cytoskeletal inhibitors significantly diminished this response. When a constant magnitude of shear stress was applied continuously over time, VE-cadherin junctions increased stiffness, suggesting active junction reinforcement. These data provide direct evidence that VE-cadherin complexes are tension sensors, and that associated mechanotransduction regulates global cell mechanics. Moreover, I present data showing that cadherin adhesions across the cell monolayer form a mechanically coupled network that regulates the endothelial barrier in response to force. This suggests a new mechanism regulating endothelial monolayer integrity.

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Traction forces control cell-edge dynamics and mediate distance-sensitivity during cell polarization

10.1101/745687 ◽

2019 ◽

Author(s):

Zeno Messi ◽

Alicia Bornert ◽

Franck Raynaud ◽

Alexander Verkhovsky

Keyword(s):

Control Cell ◽

Focal Adhesions ◽

Cell Polarization ◽

Matrix Remodeling ◽

Traction Forces ◽

Cell Edge ◽

Cell Parameters ◽

Cell Contractility ◽

Edge Behavior ◽

Shape Changes

SUMMARYTraction forces are generated by cellular actin-myosin system and transmitted to the environment through adhesions. They are believed to drive cell motion, shape changes, and extracellular matrix remodeling [1–3]. However, most of the traction force analysis has been performed on stationary cells, investigating forces at the level of individual focal adhesions or linking them to static cell parameters such as area and edge curvature [4–10]. It is not well understood how traction forces are related to shape changes and motion, e.g. forces were reported to either increase or drop prior to cell retraction [11–15]. Here, we analyze the dynamics of traction forces during the protrusion-retraction cycle of polarizing fish epidermal keratocytes and find that forces fluctuate in concert with the cycle, increasing during the protrusion phase and reaching maximum at the beginning of retraction. We relate force dynamics to the recently discovered phenomenological rule [16] that governs cell edge behavior during keratocyte polarization: both traction forces and the probability of switch from protrusion to retraction increase with the distance from the cell center. Diminishing traction forces with cell contractility inhibitor leads to decreased edge fluctuations and abnormal polarization, while externally applied force can induce protrusion-retraction switch. These results suggest that forces mediate distance-sensitivity of the edge dynamics and ultimately organize cell-edge behavior leading to spontaneous polarization. Actin flow rate did not exhibit the same distance-dependence as traction stress, arguing against its role in organizing edge dynamics. Finally, using a simple model of actin-myosin network, we show that force-distance relationship may be an emergent feature of such networks.

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