Introduction: Cell Adhesion Molecules

Cell adhesion molecules (CAMs) are specialized proteins that mediate binding between cells or between cells and the extracellular matrix. These molecules are essential for the development and maintenance of tissues, cell signaling, and immune responses. Four main CAM families dominate biological discussions: integrins, cadherins, selectins, and Ig-superfamily CAMs.​

Integrins: ECM and Cell Interaction

Integrins are heterodimeric proteins made of α and β subunits, providing essential connections between cells and the extracellular matrix. They influence cell migration, survival, and differentiation, acting both as anchors and as signal transmitters. Integrins are recognized as classic cell adhesion molecules due to their direct role in mediating cell-ECM interactions.​

Cadherins: Cell-Cell Adhesion

Cadherins primarily mediate calcium-dependent binding between cells, building strong and stable cell-cell junctions. They are integral for tissue integrity, found in adherens junctions and desmosomes—vital for embryonic development and maintaining epithelial layers.​

Selectins: Transient Interactions

Selectins are a group of three proteins—E-selectin, P-selectin, and L-selectin—each participating in transient, calcium-dependent adhesions within the circulatory and immune systems. They initiate specific cell migration events, such as leukocyte recruitment during inflammation.​​

Immunoglobulin: Not a Classic CAM

Immunoglobulin molecules are generally known as antibodies, signaling proteins within the immune system. However, some cell adhesion molecules do belong to the immunoglobulin superfamily (IgSF CAMs). Still, the term “immunoglobulin” in typical biology refers to antibodies, which do not serve as classical cell adhesion molecules. Their main role is in immune defense.​

• While Ig-superfamily cell adhesion molecules exist, generic immunoglobulins (e.g., IgG, IgA, IgM, IgE, IgD) do not mediate cell adhesion in tissue architecture.​

• Cadherins, integrins, and selectins are all direct cell adhesion molecules committed to mediating physical cell-cell or cell-matrix contacts.​

Table: Classification

Conclusion

• Cadherin, integrin, and selectin are all true cell adhesion molecules, integral to tissue development and immune function.​

• Immunoglobulin, in the context of classical antibodies, is not a cell adhesion molecule, though some Ig-superfamily proteins do exhibit adhesion properties as part of the CAM family.​

• Understanding this distinction highlights the complex family networks within cell biology and how communication and structure are maintained.​