... Liebner S., Andbjer B., Kalbacher H., Wolburg H., Haller H., and Fuxe K. Organization of choroid plexus epithe-lial and endothelial cell tight junctions and regulation of claudin-1, -2 and -5 expression ... analysis, these transfectants demonstrate the presence of claudin-1 protein in the cytoplasm, with small amounts in the nucleus. When cells are transfected with CLDN1 under the control of a nuclear ... signal (CLDN1-NLS), there is increased expression of claudin-1 in the nucleus, but there are still large amounts of claudin-1 in the cytoplasm as well. B) All of the claudin-1 in the nucleus can...