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. 2020 Dec 14;9(12):2685. doi: 10.3390/cells9122685

Figure 2.

Figure 2

Tubulation as a mechanism of transport across the brain endothelium. (a) Transport of transferrin receptor-based brain shuttle constructs that are engineered by fusing a single-chain Fab fragment of an anti-transferrin monoclonal antibody to either one (monovalent, sFab) or both C-terminal ends (bivalent, dFab) across the brain endothelium. (a1) Representative images of mouse brain capillary with brain shuttle platform based on sFab or dFab (green). Arrowheads point to an individual tubule for sFab and short elongated buds for dFab. Star shows vesicles with a dFab signal within the lumen. (a2) Number of lumen-filled vesicles and tubules for sFab and sFab in segments of brain capillaries revealing the differential transport along intracellular tubules in vivo. Permission from [6]. ** represents the statistical significance between sFab and dFab. (b) Tubulation in mouse brain endothelial cells (BECs) mediated by PACSIN-2. (b1) Structure of PACSIN-2. Permission from [121]. (b2) Section of brain capillary stained by lectin (in green) and PACSIN-2 (red) imaged by stimulated energy depletion (STED) microscopy and (b3) corresponding 3D rendering showed as projection and (b4) close-up from top, bottom and side view. Adapted from [7].