Biology Reference
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25 different integrin receptors.
1,2
Many integrins require the presence of
divalent cations for binding, such as Mg
2+
and Mn
2+
. Some force measurements
on integrins are described in section 11.4.
Figure 11.1.
Major families of cell adhesion molecules with ligands. (1)
Selectins.
P-selectins are expressed in activated platelets and endothelial cells and their
major ligand is P-selectin glycoprotein ligand-1 (section 11.4 describes published
force measurements on selectins). (2)
Immunoglobulin superfamily (IgSF).
NCAM is
expressed in neural cells and mediate cell-cell homotypic adhesion. Other members
of the IgSF are intercellular adhesion molecules (ICAMs), which are known ligands
of some integrins, such as
α
L
β
2
(depicted). (3)
Cadherins.
Cadherins' subtypes are
mainly found in speciic tissues, e.g. VE-cadherin in the vascular endothelium, N-
cadherin in neuronal cells or E-cadherin in the epithelium.
2
(4)
Integrins
(
α
1
β
5
/
ibronectin, top;
α
L
β
2
/ICAM-1, bottom). Certain leukocytic intregrins allow irm
adhesion and migration to the vascular endothelium, such as
α
L
β
2
that binds to ICAM-
1 (depicted). Integrins expressed in tissues, such as
α
5
β
1
, mediate irm adhesion to
extracellular matrix proteins, including ibronectin and collagen, by forming focal
adhesion complexes, in which integrins cluster and link their cytoplasmic domains
to the actin cytoskeleton via other proteins, such as talin and
α
-actinin. Integrins
mediate inside-out and outside-in communication and are primary candidates for
cell mechanotransduction. Major conformational changes have been observed on
integrins (shaded cartoon).
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