Cell adhesion molecule

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Families of CAMs[edit]

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.[2]


IgSF CAMs[edit]

Main article: IgSF CAM


Lymphocyte homing receptors[edit]

These are also known as addressins. Two well-known examples are CD34 and GLYCAM-1.



Main article: Integrin

Integrins, one of the major classes of receptors within the ECM,[3] mediates cell-ECM interactions with collagen, fibrinogen, fibronectin, and vitronectin.[4] 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.[5]

Integrins are heterodimeric, as they consist of an alpha and beta subunit.[6] There are currently 18 alpha subunits and 8 beta subunits, which combine to make up 24 different integrin combinations.[4] Within each of the alpha and beta subunits there is a large extracellular domain, a transmembrane domain and a short cytoplasmic domain.[7] The extracellular domain is where the ligand binds through the use of divalent cations. In general, Mn2+
increases affinity, Mg2+
promotes adhesion to cells, and Ca2+
decreases cell adhesion.[5] Integrins regulate their activity within the body by changing conformation. Most exist at rest in a low affinity state, which can be altered to high affinity through an external agonist which causes a conformational change within the integrin, increasing their affinity.[5]

An example of this is the aggregation of platelets;[5] Agonists such as thrombin or collagen trigger the integrin into its high affinity state, which causes increased fibrinogen binding, causing platelet aggregation.

Calcium dependent


Main article: Cadherin

The cadherins are homophilic Ca2+
-dependent glycoproteins.[8] The classic cadherins (E-, N- and P-) are concentrated at the intermediate cell junctions, which link to the actin filament network through specific linking proteins called catenins.[8]

Each cadherin exhibits a unique pattern of tissue distribution, such as epithelial (E-cadherins), placental (P-cadherins), neural (N-cadherins), retinal (R-cadherins), brain (B-cadherins and T-cadherins), and muscle (M-cadherins).[8] Many cell types express combinations of cadherin types.

The extracellular domain has major repeats called extracellular cadherin domains (ECD). Sequences involved in Ca2+
binding between the ECDs are necessary for cell adhesion. The cytoplasmic domain has specific regions where catenin proteins bind.[9]


Main article: Selectin

The selectins are a family of heterophilic CAMs that bind fucosylated carbohydrates, e.g., mucins. 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.

See also[edit]


  1. ^ Cell Adhesion Molecules at the US National Library of Medicine Medical Subject Headings (MeSH)
  2. ^ Brackenbury R, Rutishauser U, Edelman GM (January 1981). "Distinct calcium-independent and calcium-dependent adhesion systems of chicken embryo cells". Proc. Natl. Acad. Sci. U.S.A. 78 (1): 387–91. doi:10.1073/pnas.78.1.387. PMC 319058. PMID 6165990. 
  3. ^ Brown, K; Yamada, K (1995), "The Role of Integrins during Vertebrae Development", Developmental Biology 6: 69–77, doi:10.1016/s1044-5781(06)80016-2 
  4. ^ a b Humphries JD, Byron A, Humphries MJ (October 2006). "Integrin ligands at a glance". J. Cell. Sci. 119 (Pt 19): 3901–3. doi:10.1242/jcs.03098. PMC 3380273. PMID 16988024. 
  5. ^ a b c d Schnapp, L (2006). Integrin, Adhesion/cell-matrix. Seattle: Elsevier. 
  6. ^ García AJ (December 2005). "Get a grip: integrins in cell-biomaterial interactions". Biomaterials 26 (36): 7525–9. doi:10.1016/j.biomaterials.2005.05.029. PMID 16002137. 
  7. ^ Vinatier D (March 1995). "Integrins and reproduction". Eur J Obstet Gynecol Reprod Biol 59 (1): 71–81. doi:10.1016/0028-2243(94)01987-I. 
  8. ^ a b c Buxton RS, Magee AI (June 1992). "Structure and interactions of desmosomal and other cadherins". Semin. Cell Biol. 3 (3): 157–67. doi:10.1016/s1043-4682(10)80012-1. PMID 1623205. 
  9. ^ Soncin, F.; Ward, M.C. (2011). "The Function of E-Cadherin in Stem Cell Pluripotency and Self-Renewal". Genes 2 (1): 229–259. doi:10.3390/genes2010229.