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Mechanisms of epithelial cell-cell adhesion and cell compaction revealed by high-resolution tracking of E-cadherin-green fluorescent protein.

Adams CL, Chen YT, Smith SJ, Nelson WJ - J. Cell Biol. (1998)

Bottom Line: This reorganization results in the formation of a circumferential actin cable that circumscribes both cells, and is embedded into each E-cadherin plaque at the contact margin.The reorganization of E-cadherin and actin results in the condensation of cells into colonies.We propose a model to explain how, through strengthening and compaction, E-cadherin and actin cables coordinate to remodel initial cell-cell contacts to the final condensation of cells into colonies.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305-5345, USA.

ABSTRACT
Cadherin-mediated adhesion initiates cell reorganization into tissues, but the mechanisms and dynamics of such adhesion are poorly understood. Using time-lapse imaging and photobleach recovery analyses of a fully functional E-cadherin/GFP fusion protein, we define three sequential stages in cell-cell adhesion and provide evidence for mechanisms involving E-cadherin and the actin cytoskeleton in transitions between these stages. In the first stage, membrane contacts between two cells initiate coalescence of a highly mobile, diffuse pool of cell surface E-cadherin into immobile punctate aggregates along contacting membranes. These E-cadherin aggregates are spatially coincident with membrane attachment sites for actin filaments branching off from circumferential actin cables that circumscribe each cell. In the second stage, circumferential actin cables near cell-cell contact sites separate, and the resulting two ends of the cable swing outwards to the perimeter of the contact. Concomitantly, subsets of E-cadherin puncta are also swept to the margins of the contact where they coalesce into large E-cadherin plaques. This reorganization results in the formation of a circumferential actin cable that circumscribes both cells, and is embedded into each E-cadherin plaque at the contact margin. At this stage, the two cells achieve maximum contact, a process referred to as compaction. These changes in E-cadherin and actin distributions are repeated when additional single cells adhere to large groups of cells. The third stage of adhesion occurs as additional cells are added to groups of >3 cells; circumferential actin cables linked to E-cadherin plaques on adjacent cells appear to constrict in a purse-string action, resulting in the further coalescence of individual plaques into the vertices of multicell contacts. The reorganization of E-cadherin and actin results in the condensation of cells into colonies. We propose a model to explain how, through strengthening and compaction, E-cadherin and actin cables coordinate to remodel initial cell-cell contacts to the final condensation of cells into colonies.

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A three-stage model for cell–cell adhesion and colony  formation. Stage I: multiple E-cadherin puncta form along the  developing contact and loosly hold contacting cells together. A  circumferential actin cable (thick red line) surrounds isolated  cells. As cells adhere, E-cadherin clusters into puncta within the  cell–cell contact interface (blue circle) and rapidly associates with  thin actin bundles and filaments (thin red lines). As the contact  lengthens, puncta continue to develop along the length of the  contact at a constant average density during the first 2 h. Stage II:  E-cadherin plaques develop at the edges of the contact which  compact and strengthen cell–cell interactions. Stabilization of actin filaments by E-cadherin puncta within the cell–cell contact results in gradual dissolution of the circumferential actin cable behind the developing contact and insertion of the circumferential  actin cables into the cell–cell contact accompanied by additional  clustering of E-cadherin puncta into E-cadherin plaques (green  ovals). Between cell plaques, E-cadherin is more diffusely distributed (green line) and associates with actin filaments oriented  along the axis of the cell–cell contact (red line). Stage III: E-cadherin plaques cinch together to form multicellular vertices, further condensing cell colonies. In multicellular colonies, contractility within the circumferential actin cable brings E-cadherin  plaques from adjacent cells together. Dynamics within the cytoskeleton result in continual rearrangement.
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Figure 10: A three-stage model for cell–cell adhesion and colony formation. Stage I: multiple E-cadherin puncta form along the developing contact and loosly hold contacting cells together. A circumferential actin cable (thick red line) surrounds isolated cells. As cells adhere, E-cadherin clusters into puncta within the cell–cell contact interface (blue circle) and rapidly associates with thin actin bundles and filaments (thin red lines). As the contact lengthens, puncta continue to develop along the length of the contact at a constant average density during the first 2 h. Stage II: E-cadherin plaques develop at the edges of the contact which compact and strengthen cell–cell interactions. Stabilization of actin filaments by E-cadherin puncta within the cell–cell contact results in gradual dissolution of the circumferential actin cable behind the developing contact and insertion of the circumferential actin cables into the cell–cell contact accompanied by additional clustering of E-cadherin puncta into E-cadherin plaques (green ovals). Between cell plaques, E-cadherin is more diffusely distributed (green line) and associates with actin filaments oriented along the axis of the cell–cell contact (red line). Stage III: E-cadherin plaques cinch together to form multicellular vertices, further condensing cell colonies. In multicellular colonies, contractility within the circumferential actin cable brings E-cadherin plaques from adjacent cells together. Dynamics within the cytoskeleton result in continual rearrangement.

Mentions: In summary, we suggest a model for how contacts between cells are initiated, strengthened, compacted, and condensed as cells transform from the migratory phenotype of a single cell to a sedentary phenotype of one cell in a multicell monolayer. Cell–cell adhesion is initiated by weak binding between extracellular domains of E-cadherin that are present in a highly mobile pool at the plasma membrane. At or near the same time, E-cadherin/catenin complexes attach to actin filaments that branch from actin cables that circumscribe the perimeter of migratory cells. These two processes act synergistically to assemble puncta, which, as a group, are sufficiently adhesive to hold the nascent cell–cell contact together (Fig. 10, stage I). Subsequently, there is a change in actin dynamics as actin treadmilling ceases in areas of cell–cell contact, perhaps due to sequestration of the barbed ends of actin filaments into E-cadherin puncta. We hypothesize that reduced actin treadmilling causes the dissolution of the circumferential actin cables immediately adjacent to the developing contact. It is also possible that a signaling event at the cell surface induced by cell–cell adhesion causes a change in the organization or polymerized state of the circumferential actin cables adjacent to the contact site. We suggest that stabilization of actin via the clustered cadherin/catenin complex engages the myosin II clutch (Suter et al., 1998), thereby inducing translocation of circumferential actin cables and the rest of the cell body to the cell–cell contact interface and the rapid movement of associated E-cadherin puncta into large plaques. This coordinated reorganization of E-cadherin and the actin cytoskeleton results in the establishment of strong compacted cell–cell contacts and the generation of an actin cable that circumscribes the free edges of the newly contacting cells and is embedded into either side of a E-cadherin plaque at the margins of the contact (Fig. 10, stage II).


Mechanisms of epithelial cell-cell adhesion and cell compaction revealed by high-resolution tracking of E-cadherin-green fluorescent protein.

Adams CL, Chen YT, Smith SJ, Nelson WJ - J. Cell Biol. (1998)

A three-stage model for cell–cell adhesion and colony  formation. Stage I: multiple E-cadherin puncta form along the  developing contact and loosly hold contacting cells together. A  circumferential actin cable (thick red line) surrounds isolated  cells. As cells adhere, E-cadherin clusters into puncta within the  cell–cell contact interface (blue circle) and rapidly associates with  thin actin bundles and filaments (thin red lines). As the contact  lengthens, puncta continue to develop along the length of the  contact at a constant average density during the first 2 h. Stage II:  E-cadherin plaques develop at the edges of the contact which  compact and strengthen cell–cell interactions. Stabilization of actin filaments by E-cadherin puncta within the cell–cell contact results in gradual dissolution of the circumferential actin cable behind the developing contact and insertion of the circumferential  actin cables into the cell–cell contact accompanied by additional  clustering of E-cadherin puncta into E-cadherin plaques (green  ovals). Between cell plaques, E-cadherin is more diffusely distributed (green line) and associates with actin filaments oriented  along the axis of the cell–cell contact (red line). Stage III: E-cadherin plaques cinch together to form multicellular vertices, further condensing cell colonies. In multicellular colonies, contractility within the circumferential actin cable brings E-cadherin  plaques from adjacent cells together. Dynamics within the cytoskeleton result in continual rearrangement.
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Related In: Results  -  Collection

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Figure 10: A three-stage model for cell–cell adhesion and colony formation. Stage I: multiple E-cadherin puncta form along the developing contact and loosly hold contacting cells together. A circumferential actin cable (thick red line) surrounds isolated cells. As cells adhere, E-cadherin clusters into puncta within the cell–cell contact interface (blue circle) and rapidly associates with thin actin bundles and filaments (thin red lines). As the contact lengthens, puncta continue to develop along the length of the contact at a constant average density during the first 2 h. Stage II: E-cadherin plaques develop at the edges of the contact which compact and strengthen cell–cell interactions. Stabilization of actin filaments by E-cadherin puncta within the cell–cell contact results in gradual dissolution of the circumferential actin cable behind the developing contact and insertion of the circumferential actin cables into the cell–cell contact accompanied by additional clustering of E-cadherin puncta into E-cadherin plaques (green ovals). Between cell plaques, E-cadherin is more diffusely distributed (green line) and associates with actin filaments oriented along the axis of the cell–cell contact (red line). Stage III: E-cadherin plaques cinch together to form multicellular vertices, further condensing cell colonies. In multicellular colonies, contractility within the circumferential actin cable brings E-cadherin plaques from adjacent cells together. Dynamics within the cytoskeleton result in continual rearrangement.
Mentions: In summary, we suggest a model for how contacts between cells are initiated, strengthened, compacted, and condensed as cells transform from the migratory phenotype of a single cell to a sedentary phenotype of one cell in a multicell monolayer. Cell–cell adhesion is initiated by weak binding between extracellular domains of E-cadherin that are present in a highly mobile pool at the plasma membrane. At or near the same time, E-cadherin/catenin complexes attach to actin filaments that branch from actin cables that circumscribe the perimeter of migratory cells. These two processes act synergistically to assemble puncta, which, as a group, are sufficiently adhesive to hold the nascent cell–cell contact together (Fig. 10, stage I). Subsequently, there is a change in actin dynamics as actin treadmilling ceases in areas of cell–cell contact, perhaps due to sequestration of the barbed ends of actin filaments into E-cadherin puncta. We hypothesize that reduced actin treadmilling causes the dissolution of the circumferential actin cables immediately adjacent to the developing contact. It is also possible that a signaling event at the cell surface induced by cell–cell adhesion causes a change in the organization or polymerized state of the circumferential actin cables adjacent to the contact site. We suggest that stabilization of actin via the clustered cadherin/catenin complex engages the myosin II clutch (Suter et al., 1998), thereby inducing translocation of circumferential actin cables and the rest of the cell body to the cell–cell contact interface and the rapid movement of associated E-cadherin puncta into large plaques. This coordinated reorganization of E-cadherin and the actin cytoskeleton results in the establishment of strong compacted cell–cell contacts and the generation of an actin cable that circumscribes the free edges of the newly contacting cells and is embedded into either side of a E-cadherin plaque at the margins of the contact (Fig. 10, stage II).

Bottom Line: This reorganization results in the formation of a circumferential actin cable that circumscribes both cells, and is embedded into each E-cadherin plaque at the contact margin.The reorganization of E-cadherin and actin results in the condensation of cells into colonies.We propose a model to explain how, through strengthening and compaction, E-cadherin and actin cables coordinate to remodel initial cell-cell contacts to the final condensation of cells into colonies.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305-5345, USA.

ABSTRACT
Cadherin-mediated adhesion initiates cell reorganization into tissues, but the mechanisms and dynamics of such adhesion are poorly understood. Using time-lapse imaging and photobleach recovery analyses of a fully functional E-cadherin/GFP fusion protein, we define three sequential stages in cell-cell adhesion and provide evidence for mechanisms involving E-cadherin and the actin cytoskeleton in transitions between these stages. In the first stage, membrane contacts between two cells initiate coalescence of a highly mobile, diffuse pool of cell surface E-cadherin into immobile punctate aggregates along contacting membranes. These E-cadherin aggregates are spatially coincident with membrane attachment sites for actin filaments branching off from circumferential actin cables that circumscribe each cell. In the second stage, circumferential actin cables near cell-cell contact sites separate, and the resulting two ends of the cable swing outwards to the perimeter of the contact. Concomitantly, subsets of E-cadherin puncta are also swept to the margins of the contact where they coalesce into large E-cadherin plaques. This reorganization results in the formation of a circumferential actin cable that circumscribes both cells, and is embedded into each E-cadherin plaque at the contact margin. At this stage, the two cells achieve maximum contact, a process referred to as compaction. These changes in E-cadherin and actin distributions are repeated when additional single cells adhere to large groups of cells. The third stage of adhesion occurs as additional cells are added to groups of >3 cells; circumferential actin cables linked to E-cadherin plaques on adjacent cells appear to constrict in a purse-string action, resulting in the further coalescence of individual plaques into the vertices of multicell contacts. The reorganization of E-cadherin and actin results in the condensation of cells into colonies. We propose a model to explain how, through strengthening and compaction, E-cadherin and actin cables coordinate to remodel initial cell-cell contacts to the final condensation of cells into colonies.

Show MeSH
Related in: MedlinePlus