SLC4A4 and Stroke: Since blood-borne proteins, such as albumin, cross the BBB via endothelial caveolae-mediated transcytosis, we further examined the expression of caveolin-1 (Cav-1), a structure protein of caveolae, and its phosphorylated form (pCav-1), an indicator of endothelial transcytosis activity.41 Corresponding to increased albumin leakage in the Slc4a4-icKO brains after stroke (Figures 3D and 3E), we found a 2-fold increase in both endothelial Cav-1 and pCav-1 (Figures 3G, 3H; S3E), suggesting elevated caveolae-mediated transcytosis.