(Section 1, Chapter 9, Part 3) Neuroscience Online: An Electronic Textbook for the Neurosciences | Department of Neurobiology and Anatomy - The University of Texas Medical School at Houston
The cadherins adhesion properties are Ca2+-dependent
CADHERINS: Encoded by multiple genes; 10 have been characterized in
vertebrates. The major N-cadherin in brain is present on most neurons.
Adhesion between individual cadherins is by homophilic binding and is
Ca2+-dependent. N-Cadherin is expressed very early in development
& appears to play an important adhesive role throughout the life of
an organism. Most neurons express both N-CAMs & N-cadherin.
Neuronal cell adhesion molecules or N-CAMs adhesion properties are Ca2+-independent
N-CAMs (neuronal cell adhesion molecule): N-CAMs were first discovered
because of their roles in the development of retina neurons. They are
encoded by one gene; 3 major forms are produced by mRNA splicing. Each
N-CAM is extensively modified by posttranslational glycosylation; in
the developing embryo the N-CAMs have a very high sialic acid content
(30% by weight) which results in a lower affinity between N-CAMs (they
are only 10% by weight sialic acid in the adult). Each N-CAM binds to
another N-CAM, which is called homophilic binding. Also shown is an
example of cell-cell adhesion mediated by heterophilic binding between
TAG-1 and Axonin, two different cell adhesion molecules.
The integrins mediate interactions between the cell-surface and the extracellular
INTEGRINS: Integrins are involved in adhesion between cell-surfaces
and components of the ECM; the adhesive interactions between integrins
and other macromolecules is by heterophilic binding. The integrins are
transmembrane glycoproteins. The expression of different combinations
of integrins on different cells determine which ECM molecules they bind.