1.17.10 Desmosome Definition

Desmosome Definition is a description of a specialized cell-cell adhesive structure formed at a discrete, spot-like point of contact between two adjacent cells, in which cadherin-family adhesion molecules on each cell surface bind to their counterparts on the neighboring cell and are anchored, through intracellular adaptor proteins, to a dense network of intermediate filaments rather than to the actin cytoskeleton, thereby providing a highly resistant, mechanically robust point of attachment specialized for withstanding substantial mechanical stress.

Conceptual Basis

A Discrete, Spot-Like Adhesive Point

A desmosome is defined by its organization as a discrete, localized point of contact between two adjoining cells, rather than as a continuous band encircling the cell perimeter, and functions as a spot-weld-like reinforcement of the cell-cell contact at that specific location.

Anchorage to Intermediate Filaments

A defining structural feature distinguishing the desmosome from other cell-cell adhesive structures is its anchorage to the intermediate filament network of the cytoskeleton, rather than to the actin cytoskeleton, a distinction that equips the desmosome with particular mechanical properties suited to withstanding sustained tensile stress.

Structural Basis

Cadherin-Family Adhesion Molecules

The extracellular adhesive component of the desmosome is provided by cadherin-family adhesion molecules positioned on the surfaces of the two adjoining cells, which engage in binding interactions with their counterparts on the neighboring cell to form the direct physical connection at the site of the desmosome.

Intracellular Plaque and Intermediate Filament Anchorage

On the cytoplasmic side of the desmosome, a dense structural plaque of adaptor proteins connects the cytoplasmic portion of the desmosomal cadherins to the intermediate filament network of the cell, anchoring the desmosome firmly to this particularly robust category of cytoskeletal filament.

Functional Roles

Providing Resistance to Mechanical Stress

Because desmosomes are anchored to the intermediate filament network, a cytoskeletal component particularly well suited to resisting tensile mechanical forces, desmosomes provide cell-cell contacts with substantial resistance to mechanical stress, contributing to the structural resilience of tissues subjected to significant physical strain.

Distributing Mechanical Forces Across a Tissue

By linking the intermediate filament networks of adjoining cells across the desmosomal junction, desmosomes allow mechanical forces experienced at one point within a tissue to be distributed and shared across the interconnected network of cells, reducing the concentration of stress at any single cell or contact point.

Relationship to Cell-Cell Adhesion and Cancer Cell Biology

A Mechanically Specialized Category of Cell-Cell Adhesion

The desmosome constitutes a mechanically specialized category of cell-cell adhesion, distinguished from the adherens junction by its anchorage to intermediate filaments rather than actin, and providing a particular type of mechanical reinforcement suited to tissues experiencing substantial physical stress.

Consequences of Desmosome Disruption in Cancer Cells

Because desmosomes provide substantial mechanical reinforcement to cell-cell contact, disruption of desmosomal components is closely associated with reduced tissue cohesion and increased capacity for cell detachment, contributing to the weakened cell-cell adhesion and altered tissue integrity characteristic of cancer cell adhesion.