CELL PENETRATION BY TRANSPORTAN

Transportan is a 27 amino acid-long peptide containing 12 functional a mino acids from the amino terminus of the neuropeptide galanin and mas toparan in the carboxyl terminus, connected via a lysine. Transportan is a cell-penetrating peptide as judged by indirect immunofluorescence using N-epsilon 13-biotinyl-transportan. The internalization of bioti nyl-transportan is energy independent and takes place efficiently at 3 7 degrees, 4 degrees, and 0 degrees C, Cellular uptake of transportan is probably not mediated by endocytosis, since it cannot be blocked by treating the cells with phenylarsine oxide or hyperosmolar sucrose so lution and is nonsaturable, The kinetics of internalization was studie d with the aid of the I-125-labeled peptide. At 37 degrees C, the maxi mal intracellular concentration is reached in about 20 min, The intern alized transportan is protected from trypsin. The cell-penetrating abi lity of transportan is not restricted by cell type, but seems to be a general feature of this peptide, In Bowes' melanoma cells, transportan first localizes in the outer membrane and cytoplasmatic membrane stru ctures, This is followed by a redistribution into the nuclear membrane and uptake into the nuclei where transportan concentrates in distinct substructures, probably the nucleoli.