TABLE I.
Localizations and major roles of different TJ and AJ proteins at the BBB.31,36–39
| Type of junction | Junction protein | Localization in brain endothelial cells | Role |
|---|---|---|---|
| Tight junctions | Occludin | Membrane | Promote redox-sensitive processes of TJ assembly |
| Claudins | Membrane | Homodimerize with claudins on adjacent endothelial cells | |
| JAMs | Membrane | Facilitate assembly of TJ components and recruit polarity complex | |
| ZOs | Cytoplasm | Bind to claudins and JAMs via PDZ domain and to occluding via other regions to sustain TJ integrity | |
| Cingulin | Cytoplasm | Connect to ZOs, JAMs and myosin to create scaffold between transmembrane proteins and cytoskeleton | |
| 7H6 phosphoprotein | Cytoplasm | Act as barrier to transport of ions and large molecules | |
| Heterotrimeric G-protein | Cytoplasm | Continuously interact with transmembrane proteins to promote TJ integrity | |
| Adherens junction | VE-cadherin | Membrane | Promote actin bundling |
| N-cadherin | Membrane | Regulate angiogenesis | |
| PECAM-1 (CD31) | Membrane | Interact with VE-cadherin to initiate intercellular contacts |