TAT-mediated protein transduction into mammalian cells

Manipulation of mammalian cells has been achieved by the transfection of expression vectors, microinjection, or diffusion of peptidyl mimetics. While these approaches have been somewhat successful, the classic manipulation methods are not easily regulated and can be laborious. One approach to circumvent these problems is the use of HIV TAT-mediated protein transduction. Although this technology was originally described in 1988, few improvements were reported in the subsequent 10 years. In the last few years, significant steps have been taken to advance this technology into a broadly applicable method that allows for the rapid introduction of full-length proteins into primary and transformed cells. The technology requires the synthesis of a fusion protein, linking the TAT transduction domain to the molecule of interest using a bacterial expression vector, followed by the purification of this fusion protein under either soluble or denaturing conditions. The purified fusion protein can be directly added to mammalian cell culture or injected in vivo into mice. Protein transduction occurs in a concentration-dependent manner, achieving maximum intracellular concentrations in less than 5 min, with nearly equal intracellular concentrations between all cells in the transduced population. Full-length TAT fusion proteins have been used to address a number of biological questions, relating to cell cycle progression, apoptosis, and cellular architecture. Described here are the fundamental requirements for the creation, isolation, and utilization of TAT-fusion proteins to affect mammalian cells. A detailed protocol for production and transduction of TAT-Cdc42 into primary cells is given to illustrate the technique.