Junctional adherence molecules

Gap junctions (nexus) are broad areas of closely opposed plasma membranes, but there is no fusion of the plasma membranes and a narrow gap, of about 2 to 3 nm wide, remains. The gap is crossed by cytoplasmic filaments, which allow intracellular cytoplasm to transfer between cells. This type of cell junction not only functions as an adherent zone, but also permits the passage of ions and other small molecules (sugars, amino acids, nucleotides and vitamins). Thus the gap junctions are sites of intercellular information exchange. 

VE)-cadherin and platelet endothelial cell adhesion molecule-1 (PECAM-1). VE-cadherin is an endothelial-specific Ca " -regulated protein that is linked to the cytoskeleton via catenins (Fig. 1). PECAM-1, also known as CD31, is a key participant in the migration of blood-borne cells across the BBB. Changes in the adherent junction proteins can lead to increased paracellular permeability (Abbruscato and Davis, 1999) and leukocyte trafficking in the CNS (Newman, 1994 Garrido-Urbani et al., 2008). 

Epithelial cadherin (E-cadherin) has a molecular weight of 130 kDa and is found in PNS myelin. E-cadherin is a protein of the superfamily of calcium-dependent cell adhesion molecules that can usually form adherent junctions. This protein has an N-terminal extracellular domain, a short transmembrane domain and a C-terminal intracellular domain. 

The assembly of distinct tissues and their organization into organs are determined by molecular interactions at the cellular level and would not be possible without the temporally and spatially regulated expression of a wide array of adhesive molecules. Cells In tissues can adhere directly to one another (cell-cell adhesion) through specialized integral membrane proteins called cell-adhesion molecules (CAMs) that often cluster Into specialized cell junctions (Figure 6-1). Cells in animal tissues also adhere Indirectly (cell-matrix... 

Fig. la shows spherical particles adhering to each other in more or less linear arrangement, Fig. lb rodlet shaped particles building up a similar continuous framework. In Fig. Ic the case of linear macro-molecules forming a framework consisting of molecular chains with junction points of a crystalline nature is represented. Fig. Id shows a typical case of gel formation by chemical cross-linking of dissolved linear macromolecules. Such a case can, e. g., be reali2 ed if a rubber solution is vulcanised... 

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