Biomedical Engineering Reference
In-Depth Information
7.2 ADHESION RECEPTORS IN NATIVE TISSUE
Cells form connections with the ECM as well as with each other through adhesion
receptors that are present on the surface of the cell. There are three major classes of
adhesion receptors: integrins, cadherins, and members of the immunoglobulin (Ig)
family. Although the exact functions of each class of receptor may vary, many
adhesion receptors share some common properties, including the formation of
receptor clusters after binding with an extracellular ligand and the formation
of connections to the underlying cytoskeleton.
7.2.1 Integrins
Integrins are a superfamily of cell adhesion receptors that exist as 24 distinct
transmembrane
heterodimers,
1
which can be found in Table 7.1. Currently,
ab
there are 18
subunits identified, which associate through noncovalent
interactions.
2
The term integrin originates from the importance of such receptors at
maintaining the “integrity” of the cytoskeleton. Integrins primarily interact with
a
and 8
b
TABLE 7.1 Integrin Heterodimers and Their Extracellular Matrix Binding Sites
b
Subunit
a
Subunit
ECM Binding Site
b
1
a
1
Laminin, collagen (GFOGER)
a
2
Collagen (GFOGER), laminin, E-cadherin
a
3
Laminin
a
4
VCAM-1, ICAM-4, fibronectin
a
5
Fibronectin (RGD)
a
6
Laminin
a
7
Laminin
a
8
Fibronectin (RGD)
a
9
VCAM-1
a
10
Collagen (GFOGER), laminin
a
11
Collagen (GFOGER)
a
v
Fibronectin (RGD)
b
2
a
D
ICAM, VCAM-1, fibronectin, fibrinogen
a
L
ICAM, ICAM-2, ICAM-4
a
M
ICAM, ICAM-4, fibrinogen
a
X
ICAM, ICAM-4, fibrinogen, collagen
b
3
a
v
Fibrinogen, fibronectin (RGD), ICAM-4
a
IIb
Fibrinogen, fibronectin (RGD)
b
4
a
6
Laminin
b
5
a
v
Vitronectin (RGD)
b
6
a
v
Fibronectin (RGD)
b
7
a
4
VCAM-1, fibronectin
a
E
E-cadherin
b
8
a
v
Vitronectin (RGD)
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