cell-cell adhesion via plasma-membrane adhesion molecules

Definition

Target type: biologicalprocess

The attachment of one cell to another cell via adhesion molecules that are at least partially embedded in the plasma membrane. [GOC:dos]

Cell-cell adhesion is a fundamental process in multicellular organisms, enabling cells to interact and form tissues, organs, and ultimately, the entire organism. This intricate process is mediated by specialized molecules embedded within the plasma membrane, collectively known as cell adhesion molecules (CAMs). These molecules exhibit remarkable diversity in their structure and function, allowing for a wide range of adhesive interactions, from transient interactions between immune cells to the long-lasting connections between epithelial cells.

There are several key classes of CAMs, each with distinct properties and mechanisms of action:

**1. Cadherins:** These calcium-dependent transmembrane proteins are responsible for strong, stable cell-cell adhesion, particularly in epithelial tissues. Cadherins form homophilic interactions, meaning they bind to identical molecules on adjacent cells. This binding is mediated by their extracellular domains, which contain repeating units called cadherin repeats. The cytoplasmic domain of cadherins interacts with the cytoskeleton, providing structural support and transmitting signals to regulate cell behavior.

**2. Integrins:** Integrins are heterodimeric transmembrane proteins that link the extracellular matrix (ECM) to the intracellular cytoskeleton. They play a crucial role in cell adhesion, migration, and signaling. Integrins bind to a wide range of ECM components, including collagen, fibronectin, and laminin, through their extracellular domains. Their cytoplasmic domains connect to the cytoskeleton, allowing for communication between the cell and its environment.

**3. Immunoglobulin superfamily (IgSF) CAMs:** These molecules share a common structural motif called the immunoglobulin domain, which is also found in antibodies. IgSF CAMs exhibit diverse adhesive properties, mediating both homophilic and heterophilic interactions. They are involved in a variety of cellular processes, including immune cell adhesion, neuronal development, and cell-cell signaling.

**4. Selectins:** Selectins are transmembrane proteins that mediate transient cell-cell interactions, particularly between leukocytes and endothelial cells. They play a critical role in immune responses, allowing leukocytes to adhere to blood vessel walls and migrate to sites of inflammation. Selectins bind to specific carbohydrate ligands on the surface of target cells, and their expression is often regulated by inflammatory signals.

**5. Other CAMs:** In addition to these major classes, there are several other CAMs involved in specialized adhesive interactions. These include:
- **Neural cell adhesion molecules (NCAMs):** These IgSF CAMs play a crucial role in neuronal development and synapse formation.
- **Platelet endothelial cell adhesion molecule (PECAM-1):** This IgSF CAM is expressed on endothelial cells and platelets and is involved in vascular permeability and angiogenesis.
- **Junctional adhesion molecules (JAMs):** These IgSF CAMs are involved in tight junction formation and cell-cell signaling.

The process of cell-cell adhesion via CAMs is a complex and highly regulated process that involves multiple steps:

**1. Recognition and binding:** The initial step involves recognition and binding between CAMs on opposing cell surfaces. This binding can be homophilic or heterophilic, depending on the specific CAMs involved.

**2. Adhesion strengthening:** Once the initial binding occurs, the adhesion is strengthened through the clustering of CAMs and the formation of larger complexes.

**3. Signal transduction:** CAMs are not simply passive anchors; they also play a crucial role in signal transduction. When CAMs bind to their ligands, they activate intracellular signaling pathways that regulate a variety of cellular responses, including gene expression, cytoskeletal organization, and cell proliferation.

**4. Cell-cell communication:** Cell-cell adhesion via CAMs is not only important for structural integrity, but it also facilitates communication between cells. This communication can be direct, through the interaction of CAMs on adjacent cells, or indirect, through the activation of signaling pathways.

**5. Dynamic regulation:** Cell-cell adhesion is a highly dynamic process that is constantly regulated in response to changing cellular needs. CAM expression levels, affinity, and organization can all be modulated by factors such as developmental cues, growth factors, and environmental stimuli.

In conclusion, cell-cell adhesion via plasma-membrane adhesion molecules is a fundamental process that plays a critical role in the development, function, and survival of multicellular organisms. These molecules exhibit remarkable diversity in their structure and function, allowing for a wide range of adhesive interactions that contribute to tissue organization, cell signaling, and immune responses.'
"

Proteins (2)

Compounds (12)