Transduction of translationally controlled tumor protein employing TCTP-derived protein transduction domain

Protein transduction domains (PTDs), which are cell-penetrating peptides, have been employed for delivery of various cargos. We previously showed that the N-terminal fragment of translationally controlled tumor protein functions as a PTD (TCTP-PTD) by as yet poorly understood mechanisms. In this study, we generated several green fluorescent protein (GFP)-tagged TCTP fusion proteins by conjugating a single PTD or tandem PTDs at the N-terminus, the C-terminus, and both termini and compared their transduction efficiencies in human lung adenocarcinoma A549 cells to determine whether the protein transducing function of TCTP depends on the location or the number of PTD moieties in the TCTP molecule. Fluorimetric analysis and Western blotting assays revealed that TCTP-GFP fusion protein containing one or two TCTP-PTDs at its N-terminus showed more efficient cellular entry than either the C-terminal TCTP-PTD or TCTP-PTD with PTDs located at both the N- and C-terminals. This study demonstrates the feasibility of transduction of TCTP target cells employing its TCTP-PTD by simple co-incubation with purified proteins.