In addition to the membrane activity, researchers discovered that the HIV TAT peptide also creates its own binding site out of the membrane. This means the peptide can actually go through the membrane and induce the cytoskeleton directly to have an endocytotic event.
"We found that there are two channels of activity," Wong said. "Because of the peculiar sequence of HIV TAT, it's very good at being able to interact with membranes. Further, with the high-density packing of charged amino acids in the peptide, it can also interact very strongly with the cell's cytoskeleton, as well as its receptors."
In addition, the researchers noticed that small cargoes can be transferred directly, while cargoes larger than a few nanometers needed to be anchored to the membrane by the TAT peptide.
Deming, who specializes in synthetic methods, prepared the polypeptide samples for use in the experiments. Kamei, an expert in cellular trafficking, performed cell-based endocytosis experiments using inhibitor drugs and confocal microscopy to identify dominant mechanisms of endocytosis.
"This research is exciting because cell-penetrating peptides have been used in the area of drug delivery for some time," Kamei said. "Gaining any additional understanding of these delivery agents will help in future drug-carrier designs."
It is the group's hope that the new understanding gained from their study will be used to engineer new molecules that are more effective in delivering therapeutic agents.
"This collaboration was important because it combined expertise in the areas of synthesis, characterization and cellular trafficking to address a very relevant problem," Kamei said. "I definitely see more opportunity for combining these areas to tackle other problems in the growing field of biomate
|Contact: Wileen Wong Kromhout|
University of California - Los Angeles