Vascular Endothelium - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 454

N acetylglucosamine is one of the main components of glycocalyx oligosaccha-
rides. It interacts with endothelial Glc N Ac -recognizing lectins of the luminal surface,
among which some may participate in flow sensing such as glycosylated endothelial
Na + channel (ENaC) [ 851 ]. Connection of hyaluronan to lectin-bearing substance
such as ENaC channel.

9.1.2 Endothelial Cell Adhesions

Endothelial intercellular junctions are necessary for formation and integrity of the
interface between blood and vessel wall. The main junctions between endothelial
cells are adherens and tight junctions that are composed of transmembrane adhe-
sion molecules linked to cytoskeletal-binding proteins and intracellular signaling
partners.
Intercellular junctions not only yield attachment sites, but also transfer signals
for morphogenesis and stabilization of the vessel wall architecture. Vascular home-
ostasis relies also on cellular adhesion with the extracellular matrix. Integrins link
endothelial cells with constituents of the extracellular matrix, such as fibronectin or
vitronectin. Their cytosolic domains are associated with actin cytoskeleton via talin
and vinculin.

9.1.2.1 Junctions between Endothelial Cells

Intercellular junctions include tight, adherens, and gap junctions. Adherens junc-
tions are mainly required for correct vasculo- and angiogenesis and remodeling,
whereas tight junctions essentially control the endothelial barrier. Endothelial cells
do not have desmosomes. In addition, α 2 β 1 -and α 5 β 1 -integrins have also been

identified in endothelial clefts.
In endothelial cells, actomyosin filament contraction can generate forces (up to
120 nN) that pull perpendicularly to the face of intercellular contact, the so-called
tugging forces . Mechanical loading at cell-matrix and -cell adhesions causes focal
adhesion growth. In particular, the size of adherens junctions enlarges when tugging
forces rises and conversely [ 852 ]. Actomyosin-dependent regulation of adherens
junction size is supported by small Rac1 GTPase.

Adherens Junctions

Adherens junctions are mainly composed of cadherins (Vol. 1 - Chap. 7. Plasma
Membrane). Cadherin cytoplasmic tail contains 2 binding sites. The first binding
site associates with β -and γ -catenins in a mutually exclusive manner. The second

links to catenin- δ 1, an inhibitor of Rho GTPases. Cadherin then indirectly connects