Adherens junctions

Definition

Adherens junctions are specialized cell-cell adhesion structures that connect adjacent cells, primarily through cadherin proteins. These junctions play a critical role in maintaining tissue architecture and facilitating cellular communication by linking the cytoskeleton of one cell to another. This connection is vital for processes such as tissue morphogenesis, wound healing, and cellular differentiation.

5 Must Know Facts For Your Next Test

1. Adherens junctions are primarily composed of cadherins, which require calcium ions for their adhesive function.
2. These junctions help maintain the structure of tissues by providing mechanical strength through connections with the actin cytoskeleton.
3. In embryonic development, adherens junctions are essential for processes like epithelial-to-mesenchymal transition (EMT), which is critical for organ formation.
4. Disruption of adherens junctions can lead to pathological conditions, including cancer metastasis, where cells lose their adhesion properties and invade other tissues.
5. Adherens junctions also participate in signaling pathways that regulate cell behavior, including growth, differentiation, and apoptosis.

Review Questions

• How do adherens junctions contribute to tissue integrity and cellular communication?
  • Adherens junctions maintain tissue integrity by providing strong adhesion between adjacent cells through cadherin proteins. They connect the actin cytoskeleton of each cell, allowing for mechanical support and stability within tissues. Furthermore, these junctions facilitate cellular communication by allowing signaling molecules to pass between cells, influencing processes such as growth and differentiation.
• Discuss the role of cadherins and catenins in the structure and function of adherens junctions.
  • Cadherins are transmembrane proteins that form homophilic interactions with cadherins on neighboring cells, establishing the adhesive properties of adherens junctions. Catenins bind to the cytoplasmic domain of cadherins and connect them to the actin cytoskeleton. This binding not only stabilizes the junction but also facilitates intracellular signaling pathways that regulate cellular functions and contribute to maintaining tissue architecture.
• Evaluate the implications of disrupted adherens junctions in disease states such as cancer and how this affects cellular differentiation.
  • Disruption of adherens junctions can lead to a loss of cell adhesion, which is a key characteristic of cancer metastasis. When these junctions fail, cancerous cells can detach from their original tissue and invade surrounding areas, contributing to tumor progression. This disruption also affects cellular differentiation because loss of adhesion signals can alter the gene expression patterns necessary for maintaining differentiated states, resulting in more aggressive cellular behaviors.

Related terms

Cadherins:

A family of transmembrane proteins that mediate cell-cell adhesion by forming homophilic bonds between adjacent cells.

Catenins: Proteins that bind to cadherins and link them to the actin cytoskeleton, playing a crucial role in the stability and signaling of adherens junctions.

Tight Junctions:

Another type of cell-cell junction that creates a barrier to prevent the passage of molecules between cells, maintaining the integrity of epithelial layers.