Insights into the Role of Cell–Cell Junctions in Physiology and Disease

Angiogenic sprouting is a critical process involved in vascular network formation within tissues. During sprouting, tip cells and ensuing stalk cells migrate collectively into the extracellular matrix while preserving cell–cell junctions, forming patent structures that support blood flow. Although several signaling pathways have been identified as controlling sprouting, it remains unclear to what extent this process is mechanoregulated. To address this question, we investigated the role of cellular contractility in sprout morphogenesis, using a biomimetic model of angiogenesis. Three-dimensional maps of mechanical deformations generated by sprouts revealed that mainly leader cells, not stalk cells, exert contractile forces on the surrounding matrix. Surprisingly, inhibiting cellular contractility with blebbistatin did not affect the extent of cellular invasion but resulted in cell–cell dissociation primarily between tip and stalk cells. Closer examination of cell–cell junctions revealed that blebbistatin impaired adherens-junction organization, particularly between tip and stalk cells. Using CRISPR/Cas9-mediated gene editing, we further identified NMIIA as the major isoform responsible for regulating multicellularity and cell contractility during sprouting. Together, these studies reveal a critical role for NMIIA-mediated contractile forces in maintaining multicellularity during sprouting and highlight the central role of forces in regulating cell–cell adhesions during collective motility.

Download Full-text

Cytokinesis and the establishment of early embryonic cell polarity

Biochemical Society Transactions ◽

10.1042/bst0360384 ◽

2008 ◽

Vol 36 (3) ◽

pp. 384-386 ◽

Cited By ~ 3

Author(s):

David R. Burgess

Keyword(s):

Epithelial Cells ◽

Cell Polarity ◽

Primary Cilia ◽

Embryonic Cell ◽

Cell Junctions ◽

Cell Contact ◽

Apical Surface ◽

Integral Role ◽

Cell Cell

Cleavage divisions in many animals form a blastula made up of a simple polarized epithelium. This simple embryonic epithelium possesses an apical surface covered with microvilli and primary cilia separated from the basolateral surfaces by cell–cell junctions. The apical membrane proteins and lipids differ from those of the basolateral on these embryonic epithelial cells, as is found in adult epithelial cells. Formation of cell polarity in embryos at fertilization, including those from both protostomes and deuterostomes, uses the same molecules and signalling machinery as do polarizing epithelial cells that polarize upon cell–cell contact. In addition, the actin–myosin cytoskeleton plays an integral role in establishment and maintenance of this early cell polarity. However, early cleaving blastomeres from higher organisms including echinoderms and vertebrates have not been considered to exhibit cell polarity until formation of junctions at the third through to the fifth cleavage divisions. The role of new membrane addition into the late cleavage furrow during the early rounds of cytokinesis may play a key role in the early establishment of cell polarity in all animal embryos.

Download Full-text

Regulation of vascular endothelial barrier function

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1994.267.3.l223 ◽

1994 ◽

Vol 267 (3) ◽

pp. L223-L241 ◽

Cited By ~ 96

Author(s):

H. Lum ◽

A. B. Malik

Keyword(s):

Endothelial Cells ◽

Inflammatory Mediators ◽

Barrier Function ◽

Cell Junctions ◽

Paracellular Transport ◽

Endothelial Barrier ◽

Endothelial Barrier Function ◽

Cell Rounding ◽

Cell Cell

The increase in endothelial permeability in response to inflammatory mediators such as alpha-thrombin and histamine is accompanied by cell rounding and interendothelial gap formation, implicating that the predominant transport pathway is a diffusive one [i.e., via cellular junctions (paracellular transport)]. However, the possible contribution by vesicle-mediated transport (i.e., via albumin binding protein gp60) to the overall permeability increase needs investigation. Regulation of paracellular transport in endothelial cells is associated with modulation of actin-based systems which anchor the cell to its neighbor or extracellular matrix, thus maintaining endothelial integrity. At the cell-cell junctions, actin is linked indirectly to the plasma membrane by linking proteins (e.g., vinculin, catenins, alpha-actinin) to cadherins, which function in homophilic intercellular adhesion. Cadherins may also play a role in regulating the formation of tight junctions, which also may be associated with actin. At endothelial focal contacts, the transmembrane receptors (integrins) for matrix proteins are linked to actin via linking proteins (i.e., vinculin, talin, alpha-actinin). In response to inflammatory mediators, second messengers signal two regulatory pathways which modulate the actin-based systems, which may lead to impairment of the endothelial barrier integrity. One pathway is based on protein kinase C (PKC) isozyme-specific phosphorylation of linking proteins at the cell-cell and cell-matrix junctions. The increased phosphorylation is associated with actin reorganization, cell rounding, and increased paracellular transport. The other is the activation of myosin light-chain kinase, (MLCK), which causes an actin-myosin-based contraction that may lead to a centripetal retraction of endothelial cells. Current research is in the identification of protein substrates of PKC isozymes, the specific role of their phosphorylation in barrier function, and determining the precise role of MLCK in modulation of endothelial barrier function.

Download Full-text

Golgi-associated cPLA2α Regulates Endothelial Cell–Cell Junction Integrity by Controlling the Trafficking of Transmembrane Junction Proteins

Molecular Biology of the Cell ◽

10.1091/mbc.e08-02-0210 ◽

2009 ◽

Vol 20 (19) ◽

pp. 4225-4234 ◽

Cited By ~ 25

Author(s):

Elsa Regan-Klapisz ◽

Vincent Krouwer ◽

Miriam Langelaar-Makkinje ◽

Laxman Nallan ◽

Michael Gelb ◽

...

Keyword(s):

Endothelial Cell ◽

Intracellular Trafficking ◽

Adherens Junction ◽

Cell Junctions ◽

Cell Junction ◽

Tight Junction Formation ◽

Junction Formation ◽

Junction Proteins ◽

Cell Cell

In endothelial cells specifically, cPLA2α translocates from the cytoplasm to the Golgi complex in response to cell confluence. Considering the link between confluence and cell–cell junction formation, and the emerging role of cPLA2α in intracellular trafficking, we tested whether Golgi-associated cPLA2α is involved in the trafficking of junction proteins. Here, we show that the redistribution of cPLA2α from the cytoplasm to the Golgi correlates with adherens junction maturation and occurs before tight junction formation. Disruption of adherens junctions using a blocking anti-VE-cadherin antibody reverses the association of cPLA2α with the Golgi. Silencing of cPLA2α and inhibition of cPLA2α enzymatic activity using various inhibitors result in the diminished presence of the transmembrane junction proteins VE-cadherin, occludin, and claudin-5 at cell–cell contacts, and in their accumulation at the Golgi. Altogether, our data support the idea that VE-cadherin triggers the relocation of cPLA2α to the Golgi and that in turn, Golgi-associated cPLA2α regulates the transport of transmembrane junction proteins through or from the Golgi, thereby controlling the integrity of endothelial cell–cell junctions.

Download Full-text

Cooperative contractility: The role of stress fibres in the regulation of cell-cell junctions

Journal of Biomechanics ◽

10.1016/j.jbiomech.2014.11.025 ◽

2015 ◽

Vol 48 (3) ◽

pp. 520-528 ◽

Cited By ~ 8

Author(s):

William Ronan ◽

Robert M. McMeeking ◽

Christopher S. Chen ◽

J. Patrick McGarry ◽

Vikram S. Deshpande

Keyword(s):

Cell Junctions ◽

Cell Cell

Download Full-text