Cell adhesion molecule

Overview
Cell Adhesion Molecules (CAMs) are proteins located on the cell surface involved with the binding with other cells or with the extracellular matrix (ECM) in the process called cell adhesion.

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).

Families of CAMs
Most of the CAMs belong to 4 protein families: Ig (immunoglobulin) superfamily (IgSF CAMs), the integrins, the cadherins and the selectins.

IgSF CAMs
Immunoglobulin superfamily CAMs (IgSF CAMs) are either homophilic or heterophilic and bind integrins or different IgSF CAMs. Here is a list of some molecules of this family:


 * NCAMs Neural Cell Adhesion Molecules
 * ICAM-1 Intercellular Cell Adhesion Molecule
 * VCAM-1 Vascular Cell Adhesion Molecule
 * PECAM-1 Platelet-endothelial Cell Adhesion Molecule
 * L1
 * CHL1
 * MAG

Selectins
The selectins are a family of heterophilic CAMs that bind fucosylated carbohydrates, e.g. mucins. They are calcium-dependent. The three family members are E-selectin (endothelial), L-selectin (leukocyte) and P-selectin (platelet). The best-characterized ligand for the three selectins is P-selectin glycoprotein ligand-1 (PSGL-1), which is a mucin-type glycoprotein expressed on all white blood cells.

Neutrophils and eosinophils bind to E-selectin. One of the reported ligands for E-selectin is the sialylated Lewis X Ag (sLe(x)). Eosinophils, like neutrophils, use sialylated, protease-resistant structures to bind to E-selectin, although the eosinophil expresses much lower levels of these structures on its surface. Ligands for P-selectin on eosinophils and neutrophils are similar sialylated, protease-sensitive, endo-beta-galactosidase-resistant structures, clearly different than those reported for E-selectin, and suggest disparate roles for P-selectin and E-selectin during recruitment during inflammatory responses.

Integrins

 * see also main article on Integrins

The integrins are a family of heterophilic CAMs that bind IgSF CAMs or the extracellular matrix. They are heterodimers, consisting in two non-covalently linked subunits, called alpha and beta. 24 different alpha subunits are known that can link in many different combinations with the 9 different beta subunits, however not all combinations are observed.

Some sources (for example, MeSH) don't consider integrins to be cell adhesion molecules.

Cadherins

 * see also main article on Cadherins

The cadherins are a family of homophilic CAMs, Ca2+ dependent. The most important members of this family are E-cadherins (epithelial), P-cadherins (placental) and N-cadherins (neural).

Neurological Diseases Associated With CAM's
Mental retardation and other neurological disorders are attributable in part to disruption of normal cell adhesion

Functions

 * Embyonic development
 * Formation of Nervous System
 * Holding tissues together in adults
 * Inflammation and wound healing
 * Metastasis of tumors
 * Transmits signal into and out of the cell