scholarly journals Branched actin networks push against each other at adherens junctions to maintain cell–cell adhesion

2018 ◽  
Vol 217 (5) ◽  
pp. 1827-1845 ◽  
Author(s):  
Nadia Efimova ◽  
Tatyana M. Svitkina
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
Mechanical Load ◽  
Adherens Junctions ◽  
Cell Junctions ◽  
Pull System ◽  
Actin Networks ◽  
Pulling Forces ◽  
Intercellular Adhesions ◽  
Cell Cell

Adherens junctions (AJs) are mechanosensitive cadherin-based intercellular adhesions that interact with the actin cytoskeleton and carry most of the mechanical load at cell–cell junctions. Both Arp2/3 complex–dependent actin polymerization generating pushing force and nonmuscle myosin II (NMII)-dependent contraction producing pulling force are necessary for AJ morphogenesis. Which actin system directly interacts with AJs is unknown. Using platinum replica electron microscopy of endothelial cells, we show that vascular endothelial (VE)-cadherin colocalizes with Arp2/3 complex–positive actin networks at different AJ types and is positioned at the interface between two oppositely oriented branched networks from adjacent cells. In contrast, actin–NMII bundles are located more distally from the VE-cadherin–rich zone. After Arp2/3 complex inhibition, linear AJs split, leaving gaps between cells with detergent-insoluble VE-cadherin transiently associated with the gap edges. After NMII inhibition, VE-cadherin is lost from gap edges. We propose that the actin cytoskeleton at AJs acts as a dynamic push–pull system, wherein pushing forces maintain extracellular VE-cadherin transinteraction and pulling forces stabilize intracellular adhesion complexes.

scholarly journals Role of IQGAP1 in endothelial barrier enhancement caused by OxPAPC

2016 ◽  
Vol 311 (4) ◽  
pp. L800-L809 ◽  
Author(s):  
Yufeng Tian ◽  
Xinyong Tian ◽  
Grzegorz Gawlak ◽  
Nicolene Sarich ◽  
David B. Sacks ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
Adherens Junctions ◽  
Adherens Junction ◽  
Cell Junctions ◽  
Endothelial Barrier ◽  
Cell Junction ◽  
Protective Effects ◽  
P120 Catenin

Oxidized 1-palmitoyl-2-arachidonoyl- sn-glycero-3-phosphatidylcholine (OxPAPC) attenuates agonist-induced endothelial cell (EC) permeability and increases pulmonary endothelial barrier function via enhancement of both the peripheral actin cytoskeleton and cell junctions mediated by Rac1 and Cdc42 GTPases. This study evaluated the role for the multifunctional Rac1/Cdc42 effector and regulator, IQ domain containing GTPase-activating protein (IQGAP1), as a molecular transducer of the OxPAPC-mediated EC barrier-enhancing signal. IQGAP1 knockdown in endothelial cells by gene-specific small-interfering RNA abolished OxPAPC-induced enlargement of VE-cadherin-positive adherens junctions, suppressed peripheral accumulation of actin polymerization regulators, namely cortactin, neural Wiskott-Aldrich syndrome protein (N-WASP), and actin-related protein 3, and attenuated remodeling of the peripheral actin cytoskeleton. Inhibition of OxPAPC-induced barrier enhancement by IQGAP1 knockdown was due to suppressed Rac1 and Cdc42 activation. Expression of an IQGAP1 truncated mutant showed that the GTPase regulatory domain of IQGAP1 was essential for the OxPAPC-induced membrane localization of cortactin, adherens junction proteins VE-cadherin and p120-catenin, as well as for EC permeability response. IQGAP1 knockdown attenuated the protective effect of OxPAPC against thrombin-induced cell contraction, cell junction disruption, and EC permeability. These results demonstrate for the first time the role of IQGAP1 as a critical transducer of OxPAPC-induced Rac1/Cdc42 signaling to the actin cytoskeleton and adherens junctions, which promotes cortical cytoskeletal remodeling and EC barrier-protective effects of oxidized phospholipids.

scholarly journals mDia2 formin selectively interacts with catenins and not E-cadherin to regulate Adherens Junction formation

2019 ◽  
Author(s):  
Yuqi Zhang ◽  
Krista M. Pettee ◽  
Kathryn N. Becker ◽  
Kathryn M. Eisenmann
Keyword(s):  
Single Cell ◽  
Actin Polymerization ◽  
Plasma Membranes ◽  
Adherens Junctions ◽  
Single Cells ◽  
Critical Role ◽  
Cell Junctions ◽  
Hek 293 ◽  
E Cadherin ◽  
Cell Cell

AbstractBackgroundEpithelial ovarian cancer (EOC) cells disseminate within the peritoneal cavity, in part, via the peritoneal fluid as single cells, clusters, or spheroids. Initial single cell egress from a tumor can involve disruption of cell-cell adhesions as cells are shed from the primary tumor into the peritoneum. In epithelial cells, Adherens Junctions (AJs) are characterized by homotypic linkage of E-cadherins on the plasma membranes of adjacent cells. AJs are anchored to the intracellular actin cytoskeletal network through a complex involving E-cadherin, p120 catenin, β-catenin, and αE-catenin. However, the specific players involved in the interaction between the junctional E-cadherin complex and the underlying F-actin network remains unclear. Recent evidence indicates that mammalian Diaphanous-related (mDia) formins plays a key role in epithelial cell AJ formation and maintenance through generation of linear actin filaments. Binding of αE-catenin to linear F-actin inhibits association of the branched-actin nucleator Arp2/3, while favoring linear F-actin bundling. We previously demonstrated that loss of mDia2 was associated with invasive single cell egress from EOC spheroids through disruption of junctional F-actin.ResultsIn the current study, we now show that mDia2 has a role at adherens junctions (AJs) in EOC OVCA429 cells and human embryonic kidney (HEK) 293 cells through its association with αE-catenin and β-catenin. mDia2 depletion in EOC cells leads to reduction in actin polymerization and disruption of cell-cell junctions with decreased interaction between β-catenin and E-cadherin.ConclusionsOur results support a necessary role for mDia2 in AJ stability in EOC cell monolayers and indicate a critical role for mDia formins in regulating EOC AJs during invasive transitions.

Plakoglobin expression and localization in zebrafish embryo development

2004 ◽  
Vol 32 (5) ◽  
pp. 797-798 ◽  
Author(s):  
E.D. Martin ◽  
M. Grealy
Keyword(s):  
Confocal Microscopy ◽  
Embryo Development ◽  
Western Blotting ◽  
Protein Level ◽  
Adherens Junctions ◽  
Cell Junctions ◽  
Specific Cell ◽  
Heart Chamber ◽  
Heart Region ◽  
Cell Cell

Plakoglobin (γ-catenin) and β-catenin are major components of the adherens junctions and can be localized to the nucleus by activation of the Wnt signalling pathway. In addition, plakoglobin is also found in desmosomes, a vertebrate-specific cell–cell adhesion structure. Plakoglobin expression and localization were examined at the protein level during zebrafish embryonic development by Western blotting and confocal microscopy. Plakoglobin was expressed throughout embryo development at the protein level. Western blotting revealed that embryonic plakoglobin protein content increased between 12- and 24-h post-fertilization (hpf). Confocal microscopy showed that at stages up to 12 hpf, plakoglobin and β-catenin were co-localized and expressed in both the nucleus and in cell–cell junctions. At 24- and 72-hpf, separate patterns were seen for plakoglobin and β-catenin. These data indicate that plakoglobin localization in the heart region shifts from adherens junctions to desmosomes during heart chamber development.

scholarly journals Spatial and temporal relationships between cadherins and PECAM-1 in cell-cell junctions of human endothelial cells.

1994 ◽  
Vol 126 (1) ◽  
pp. 247-258 ◽  
Author(s):  
O Ayalon ◽  
H Sabanai ◽  
M G Lampugnani ◽  
E Dejana ◽  
B Geiger
Keyword(s):  
Endothelial Cells ◽  
Plasma Membrane ◽  
Vascular System ◽  
Adherens Junctions ◽  
Microscopic Analysis ◽  
Membrane Receptors ◽  
Temporal Organization ◽  
Cell Junctions ◽  
Short Treatment ◽  
Cell Cell

The integrity of the endothelial layer, which lines the entire cavity of the vascular system, depends on tight adhesion of the cells to the underlying basement membrane as well as to each other. It has been previously shown that such interactions occur via membrane receptors that determine the specificity, topology, and mechanical properties of the surface adhesion. Cell-cell junctions between endothelial cells, in culture and in situ, involve both Ca(2+)-dependent and -independent mechanisms that are mediated by distinct adhesion molecules. Ca(2+)-dependent cell-cell adhesion occurs mostly via members of the cadherin family, which locally anchor the microfilament system to the plasma membrane, in adherens junctions. Ca(2+)-independent adhesions were reported to mainly involve members of the Ig superfamily. In this study, we performed three-dimensional microscopic analysis of the relative subcellular distributions of these two endothelial intercellular adhesion systems. We show that cadherins are located at adjacent (usually more apical), yet clearly distinct domains of the lateral plasma membrane, compared to PECAM-1. Moreover, cadherins were first organized in adherens junctions within 2 h after seeding of endothelial cells, forming multiple lateral patches which developed into an extensive belt-like structure over a period of 24 h. PECAM-1 became associated with surface adhesions significantly later and became progressively associated with the cadherin-containing adhesions. Cadherins and PECAM-1 also differed in their detergent extractability, reflecting differences in their mode of association with the cytoskeleton. Moreover, the two adhesion systems could be differentially modulated since short treatment with the Ca2+ chelator EGTA, disrupted the cadherin junctions leaving PECAM-1 apparently intact. These results confirm that endothelial cells possess distinct intercellular contact mechanisms that differ in their spatial and temporal organization as well as in their functional properties.

scholarly journals Cortical Tension Initiates the Positive Feedback Loop Between E-cadherin and F-actin

2021 ◽  
Author(s):  
Qilin Yu ◽  
William R. Holmes ◽  
Jean P. Thiery ◽  
Rodney B. Luwor ◽  
Vijay Rajagopal
Keyword(s):  
Positive Feedback ◽  
Feedback Loop ◽  
Adherens Junctions ◽  
Force Balance ◽  
Intercellular Junction ◽  
Cell Junctions ◽  
Positive Feedback Loop ◽  
Cortical Tension ◽  
E Cadherin ◽  
Cell Cell

AbstractAdherens junctions (AJs) physically link two cells at their contact interface via extracellular homophilic interactions between cadherin molecules and intracellular connections between cadherins and the actomyosin cortex. Both cadherin and actomyosin cytoskeletal dynamics are reciprocally regulated by mechanical and chemical signals, which subsequently determine the strength of cell-cell adhesions and the emergent organization and stiffness of the tissues they form. However, an understanding of the integrated system is lacking. We present a new mechanistic computational model of intercellular junction maturation in a cell doublet to investigate the mechano-chemical crosstalk that regulates AJ formation and homeostasis. The model couples a 2D lattice-based model of cadherin dynamics with a continuum, reaction-diffusion model of the reorganizing actomyosin network through its regulation by Rho signaling at the intercellular junction. We demonstrate that local immobilization of cadherin induces cluster formation in a cis less dependent manner. We further investigate how cadherin and actin regulate and cooperate. By considering the force balance during AJ maturation and the force-sensitive property of the cadherin/F-actin linking molecules, we show that cortical tension applied on the contact rim can explain the ring distribution of cadherin and F-actin on the cell-cell contact of the cell-doublet. Meanwhile, the positive feedback loop between cadherin and F-actin is necessary for maintenance of the ring. Different patterns of cadherin distribution can be observed as an emergent property of disturbances of this feedback loop. We discuss these findings in light of available experimental observations on underlying mechanisms related to cadherin/F-actin binding and the mechanical environment.Significance StatementThe formation, maintenance and disassembly of adherens junctions (AJs) is fundamental to organ development, tissue integrity as well as tissue function. E-cadherins and F-actin are two major players of the adherens junctions (AJs). Although it is well known that cadherins and F-actin affect each other, how these two players work together to maintain the intercellular contact is unclear. Using a novel mechano-chemical model of E-cadherin and F-actin remodeling, we demonstrate that a positive feedback loop between cadherins and F-actin allows them to stabilize each other locally. Mechanical and chemical stimuli applied to the cell adhesion change E-cadherin and F-actin distribution by consolidating or interrupting the feedback loop locally. Our study mechanistically links mechanical force to E-cadherin patterning at cell-cell junctions.

scholarly journals Influence of aminoacyl-tRNA synthetase complex-interacting multifunctional protein 1 on epithelial differentiation and organization during lung development

2020 ◽  
Vol 319 (2) ◽  
pp. L369-L379
Author(s):  
Daniel D. Lee ◽  
Alexandra Hochstetler ◽  
Eric Sah ◽  
Haiming Xu ◽  
Chinn-Woan Lowe ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
Epithelial Cell ◽  
Actin Cytoskeleton ◽  
Cross Talk ◽  
Lung Development ◽  
Trna Synthetase ◽  
Cell Junctions ◽  
Aminoacyl Trna Synthetase ◽  
Multifunctional Protein ◽  
Cell Cell

Proper development of the respiratory bronchiole and alveolar epithelium proceeds through coordinated cross talk between the interface of epithelium and neighboring mesenchyme. Signals that facilitate and coordinate the cross talk as the bronchial forming canalicular stage transitions to construction of air-exchanging capillary-alveoli niche in the alveolar stage are poorly understood. Expressed within this decisive region, levels of aminoacyl-tRNA synthetase complex-interacting multifunctional protein 1 (AIMP1) inversely correlate with the maturation of the lung. The present study addresses the role of AIMP1 in lung development through the generation and characterization of Aimp1−/− mutant mice. Mating of Aimp1+/− produced offspring in expected Mendelian ratios throughout embryonic development. However, newborn Aimp1−/− pups exhibited neonatal lethality with mild cyanosis. Imaging both structure and ultrastructure of Aimp1−/− lungs showed disorganized bronchial epithelium, decreased type I but not type II cell differentiation, increased distal vessels, and disruption of E-cadherin deposition in cell-cell junctions. Supporting the in vivo findings of disrupted epithelial cell-cell junctions, in vitro biochemical experiments show that a portion of AIMP1 binds to phosphoinositides, the lipid anchor of proteins that have a fundamental role in both cellular membrane and actin cytoskeleton organization; a dramatic disruption in F-actin cytoskeleton was observed in Aimp1−/− mouse embryonic fibroblasts. Such observed structural defects may lead to disrupted cell-cell boundaries. Together, these results suggest a requirement of AIMP1 in epithelial cell differentiation in proper lung development.

scholarly journals Flow mechanotransduction regulates traction forces, intercellular forces, and adherens junctions

2012 ◽  
Vol 302 (11) ◽  
pp. H2220-H2229 ◽  
Author(s):  
Lucas H. Ting ◽  
Jessica R. Jahn ◽  
Joon I. Jung ◽  
Benjamin R. Shuman ◽  
Shirin Feghhi ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Laminar Flow ◽  
Adherens Junctions ◽  
Cell Junctions ◽  
Flow Conditions ◽  
Traction Forces ◽  
Disturbed Flow ◽  
Cytoskeletal Tension ◽  
Static Conditions ◽  
Cell Cell

Endothelial cells respond to fluid shear stress through mechanotransduction responses that affect their cytoskeleton and cell-cell contacts. Here, endothelial cells were grown as monolayers on arrays of microposts and exposed to laminar or disturbed flow to examine the relationship among traction forces, intercellular forces, and cell-cell junctions. Cells under laminar flow had traction forces that were higher than those under static conditions, whereas cells under disturbed flow had lower traction forces. The response in adhesion junction assembly matched closely with changes in traction forces since adherens junctions were larger in size for laminar flow and smaller for disturbed flow. Treating the cells with calyculin-A to increase myosin phosphorylation and traction forces caused an increase in adherens junction size, whereas Y-27362 cause a decrease in their size. Since tugging forces across cell-cell junctions can promote junctional assembly, we developed a novel approach to measure intercellular forces and found that these forces were higher for laminar flow than for static or disturbed flow. The size of adherens junctions and tight junctions matched closely with intercellular forces for these flow conditions. These results indicate that laminar flow can increase cytoskeletal tension while disturbed flow decreases cytoskeletal tension. Consequently, we found that changes in cytoskeletal tension in response to shear flow conditions can affect intercellular tension, which in turn regulates the assembly of cell-cell junctions.

WT1-interacting protein and ZO-1 translocate into podocyte nuclei after puromycin aminonucleoside treatment

2005 ◽  
Vol 289 (2) ◽  
pp. F431-F441 ◽  
Author(s):  
Maribel Rico ◽  
Amitava Mukherjee ◽  
Martha Konieczkowski ◽  
Leslie A. Bruggeman ◽  
R. Tyler Miller ◽  
...  
Keyword(s):  
Adherens Junctions ◽  
Slit Diaphragm ◽  
Cell Junctions ◽  
Puromycin Aminonucleoside ◽  
Glomerular Diseases ◽  
Podocyte Injury ◽  
Interacting Protein ◽  
Filtration Barrier ◽  
Cell Cell

Podocyte differentiation is required for normal glomerular filtration barrier function and is regulated by the transcription factor WT1. We identified WT1-interacting protein (WTIP) and hypothesized that it functions as both a scaffold for slit diaphragm proteins and a corepressor of WT1 transcriptional activity by shuttling from cell-cell junctions to the nucleus after injury. Endogenous WTIP colocalizes with zonula occludens-1 (ZO-1) in cultured mouse podocyte adherens junctions. To model podocyte injury in vitro, we incubated differentiated podocytes with puromycin aminonucleoside (PAN; 100 μg/ml) for 24 h, which disassembled cell-cell contacts, rearranged actin cytoskeleton, and caused process retraction. Podocyte synaptopodin expression diminished after PAN treatment, consistent with podocyte dedifferentiation in some human glomerular diseases. To assess podocyte function, we measured albumin flux across differentiated podocytes cultured on collagen-coated Transwell filters. Albumin transit across PAN-treated cells increased to levels observed with undifferentiated podocytes. Consistent with our hypothesis, WTIP, as well as ZO-1, translocated from podocyte adherens junctions to nuclei in PAN-treated cells. Because WTIP is a transcriptional corepressor for WT1, we examined the effect of PAN on expression of retinoblastoma binding protein Rbbp7 (also known as RbAp46), a WT1 target gene expressed in S-shaped bodies during nephrogenesis. Rbbp7 expression in PAN-treated podocytes was reduced compared with untreated cells. In conclusion, WTIP translocates from cell-cell junctions to the nucleus in PAN-treated podocytes. We suggest that WTIP monitors slit diaphragm protein assembly and shuttles into the nucleus after podocyte injury, translating changes in slit diaphragm structure into altered gene expression and a less differentiated phenotype.

Assembly of adherens junctions is required for sphingosine 1-phosphate-induced matriptase accumulation and activation at mammary epithelial cell-cell contacts

2004 ◽  
Vol 286 (5) ◽  
pp. C1159-C1169 ◽  
Author(s):  
Ruei-Jiun Hung ◽  
Ia-Wen J. Hsu ◽  
Jennifer L. Dreiling ◽  
Mon-Juan Lee ◽  
Cicely A. Williams ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Mammary Epithelial Cells ◽  
Adherens Junctions ◽  
Adherens Junction ◽  
Mammary Epithelial ◽  
Cell Junctions ◽  
Cell Contacts ◽  
Cytoskeletal Rearrangement ◽  
Sphingosine 1 Phosphate ◽  
Cell Cell

Sphingosine 1-phosphate (S1P), a bioactive phospholipid, simultaneously induces actin cytoskeletal rearrangements and activation of matriptase, a membrane-associated serine protease in human mammary epithelial cells. In this study, we used a monoclonal antibody selective for activated, two-chain matriptase to examine the functional relationship between these two S1P-induced events. Ten minutes after exposure of 184 A1N4 mammary epithelial cells to S1P, matriptase was observed to accumulate at cell-cell contacts. Activated matriptase first began to appear as small spots at cell-cell contacts, and then its deposits elongated along cell-cell contacts. Concomitantly, S1P induced assembly of adherens junctions and subcortical actin belts. Matriptase localization was observed to be coincident with markers of adherens junctions at cell-cell contacts but likely not to be incorporated into the tightly bound adhesion plaque. Disruption of subcortical actin belt formation and prevention of adherens junction assembly led to prevention of accumulation and activation of the protease at cell-cell contacts. These data suggest that S1P-induced accumulation and activation of matriptase depend on the S1P-induced adherens junction assembly. Although MAb M32, directed against one of the low-density lipoprotein receptor class A domains of matriptase, blocked S1P-induced activation of the enzyme, the antibody had no effect on S1P-induced actin cytoskeletal rearrangement. Together, these data indicate that actin cytoskeletal rearrangement is necessary but not sufficient for S1P-induced activation of matriptase at cell-cell contacts. The coupling of matriptase activation to adherens junction assembly and actin cytoskeletal rearrangement may serve to ensure tight control of matriptase activity, restricted to cell-cell junctions of mammary epithelial cells.

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

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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