Fig. 1
From: The CLDN5 gene at the blood-brain barrier in health and disease
The schematic illustration of the BBB.
(a) The BBB is composed of microvascular endothelial cells, pericytes and surrounded end-feet of astrocytes. One of the key features in brain microvascular endothelial cells is its well-developed tight junctions in their cellular clefts. Tight junctions can be observed as the mesh-like strands composed of intramembrane particles. At the membrane particles, the two plasma membranes are almost fused (also called kissing-points). (b) The junctional proteins in brain endothelial cells. VE-cadherin is a component of adherens junctions, but the subcellular localization of tight junctions and adherens junctions are almost same in brain endothelial cells. These proteins are interacted with ZO-1/-2 using different binding domain of ZO-1/-2. ZO-1 and -2 are also oligomerized by themselves. Paracingulin is a recruiter of guanidine exchange factors (GEFs) to junctional areas and GEFs are necessary to activate small GTPases Rac1 or RhoA. Rac1 strengthens the tight junctions while RhoA destabilizes the tight junctions and they inhibit each other