Adhesion molecule

Cell adhesion molecules (CAMs) are proteins located on the cell surface involved in binding with other cells or with the extracellular matrix (ECM) in the process called cell adhesion. In essence, cell adhesion molecules help cells stick to each other and to their surroundings.

These proteins are typically transmembrane receptors and are composed of three domains: an intracellular domain that interacts with the cytoskeleton, a transmembrane domain, and an extracellular domain that interacts either with other CAMs of the same kind (homophilic binding) or with other CAMs or the extracellular matrix (heterophilic binding).

Most of the CAMs belong to four protein families: Ig (immunoglobulin) superfamily (IgSF CAMs), the integrins, the cadherins, and the selectins.

One classification system involves the distinction between calcium-independent CAMs and calcium-dependent CAMs.

Integrins and the Ig-superfamily CAMs do not depend on Ca²⁺ while cadherins and selectins depend on Ca²⁺. In addition, integrins participate in cell-matrix interactions, while other CAM families participate in cell-cell interactions.

Integrins, one of the major classes of receptors within the ECM, mediates cell-ECM interactions with collagen, fibrinogen, fibronectin, and vitronectin. Integrins provide essential links between the extracellular environment and the intracellular signalling pathways, which can play roles in cell behaviours such as apoptosis, differentiation, survival, and transcription.

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