188. Internalization of Novel Delivery Vector TAT-Streptavidin into Human Cells

The cell penetrating peptide derived from the Human immunodeficiency virus-1 Tat protein possesses the capacity to promote the effective uptake of various cargo molecules across the cellular plasma membrane in vitro and in vivo. The objective of this study was to characterize the uptake and delivery mechanisms of a novel TAT-streptavidin (TAT-SA) construct in human cells. By confocal and immunoelectron microscopy the majority of internalized TAT-SA was shown to accumulate in perinuclear vesicles. The uptake studies in living cells with various fluorescent endocytic markers or inhibitors of cellular entry pathways suggested that TAT-SA internalized cells efficiently using both clathrin-mediated endocytosis and lipid-raft mediated macropinocytosis. When endosomal release of TAT-SA was enhanced through the incorporation of a biotinylated, pH-responsive polymer poly(propylacrylic acid) (PPAA), nuclear localization of TAT-SA was markedly improved. Additionally, no cytotoxicity of TAT-SA construct was detected. In conclusion, the non-viral vector TAT-SA may be utilized in protein therapeutics to deliver a wide range of biotinylated molecules into mammalian cells.