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Cell adhesion molecule

Abbreviation: CAM
German: Adhäsionsmolekül

1 Definition

Cell adhesion molecules are membrane proteins that are located on the surface of membranes. They enable the interaction of cells among each other or with the extracellular matrix through receptor-ligand bonds.

2 Occurrence

Adhesion molecules allow cells to receive important transmembrane signals for migration, growth and differentiation. They are especially important for the following cell types:

3 Function

Adhesion molecules are responsible for the mediation of migration and cell adhesion processes during inflammatory and immunological reactions. This includes for example the interaction of antigen presenting cells with the T cell, or the attachment of leukocytes to endothelial cells of the vascular wall.

Moreover, adhesion molecules have tissue- and cell-specific properties in order to enable the emigration of specific cells to specific areas through adhesion. This means that their complementary ligands are located on endothelial cells, antigen-presenting cells, or in tissues.

4 Classification

Adhesion molecules can be classified into four groups, according to their different structures:

4.1 Integrins

Integrins consist of two peptide chains (α and β chains) that are anchored into a membrane and can bind to each other. Several families of integrins can be distinguished:

4.1.1 β1 Integrins

β1 integrins are present in many tissue cells but also on hematopoietic cells. Cells bind through β1 integrins to proteins of the extracellular matrix, like collagen, fibronectin and elastin.

4.1.2 β2 integrins

β2 integrins are responsible for the constitution of tissues, embryogenesis and cell adhesion. They allow very strong connections of cells to the endothelium and enable the transmigration of leukocytes to inflamed tissue. The gene expression of β2 integrins can be rapidly adjusted to meet increased demand.

4.2 Selectins

Selectins are also referred to as "leukocyte endothelial cell-cell adhesion molecules". They are transmembrane glycoproteins that have oligosaccharide ligands which contain sialin (SLC17A5). Selectins are responsible for leukocyte-endothelial interaction, but in contrast to integrins only with low affinity. This slows down the transmigration along the endothelium. This process is referred to as "rolling".

4.3 Proteins of the immunoglobulin superfamily

ICAM-1 and VCAM-1 are proteins of the immunoglobulin superfamily. They are surface proteins that interact with integrins and are present on endothelial cells, leukocytes and other cells. One of their functions is the so-called "rolling" of monocytes along the endothelium into the intima of the vascular wall during atherogenesis.

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