Cell Adhesion Molecules (CAMs)

Cell adhesion molecules (CAMs) are the cell-surface proteins that mediate binding between cells and between cells and the extracellular matrix. Grouped into several families—cadherins, integrins, selectins, and immunoglobulin-superfamily proteins—they are the molecular components that build junctions, guide morphogenesis, and let cells recognise and respond to their neighbours and surroundings.

Definition

Cell adhesion molecules are transmembrane or membrane-associated proteins whose extracellular domains bind ligands on other cells or in the extracellular matrix, mediating adhesion and often transmitting signals across the membrane; the principal families are the cadherins, integrins, selectins, and immunoglobulin-superfamily CAMs.

Scope

This topic surveys the major CAM families, the distinction between calcium-dependent and calcium-independent adhesion, the difference between homophilic and heterophilic binding, the contrast between cell-cell and cell-matrix adhesion, and the role of CAMs as signalling receptors. It is treated as a reference and educational entry, not clinical guidance.

Key concepts

• Cadherins (calcium-dependent cell-cell adhesion)
• Integrins (cell-matrix adhesion)
• Selectins (carbohydrate-binding adhesion)
• Immunoglobulin-superfamily CAMs
• Homophilic versus heterophilic binding
• Cell-cell versus cell-matrix adhesion
• Adhesion-dependent signalling and mechanosensing

Mechanisms

Each CAM family uses a characteristic binding strategy. Cadherins mediate calcium-dependent, largely homophilic cell-cell adhesion and are the adhesive core of adherens junctions and desmosomes; calcium binding between their extracellular repeats is required for adhesion. Integrins are heterodimeric receptors that bind extracellular-matrix ligands and connect the matrix to the actin cytoskeleton, mediating cell-matrix adhesion. Selectins bind specific carbohydrate ligands and support transient adhesion, notably the rolling of leukocytes on endothelium. Immunoglobulin-superfamily CAMs use immunoglobulin-like domains for calcium-independent homophilic or heterophilic binding. Beyond holding cells in place, adhesion molecules act as receptors: engagement transmits signals inward and allows cells to sense the mechanical properties of their environment, so adhesion and signalling are coupled.

Clinical relevance

CAMs govern processes such as tissue assembly, leukocyte trafficking, and cell migration, and altered adhesion is a recurring theme in studies of inflammation, development, and cancer. This entry describes the molecules and their mechanisms for reference and education and is not a basis for diagnosis or treatment.

History

The recognition that distinct protein families mediate cell adhesion emerged in the 1980s, when cadherins, integrins, and other adhesion receptors were biochemically defined. Gumbiner's synthesis (1996) framed cell adhesion as the molecular basis of tissue architecture and morphogenesis, and later structural work clarified how cadherins and catenins assemble and how adhesion couples to signalling and mechanosensing.

Key figures

• Barry Gumbiner
• Masatoshi Takeichi
• Richard Hynes
• Benjamin Geiger

Seminal works

• gumbiner-1996
• gumbiner-2005
• shapiro-weis-2009

Frequently asked questions

What are the main families of cell adhesion molecules?

The principal families are cadherins, integrins, selectins, and immunoglobulin-superfamily CAMs, each with a distinct binding mechanism and typical role in cell-cell or cell-matrix adhesion.

Do cell adhesion molecules only hold cells together?

No. In addition to mediating adhesion, many CAMs act as signalling receptors: binding their ligands transmits information into the cell and allows cells to sense the mechanical properties of their surroundings.