Purpose: To examine the applicability of TAT (the protein transduction domain of transactivating transcription polypeptide)-mediated protein-transduction technology, in introducing proteins of interest into trabecular meshwork (TM) cells in various culture systems.
Methods: Normal human TM cell cultures, human tissues in organ cultures, and bovine eyes in perfusion organ cultures were incubated or perfused for various lengths of time with TAT- and hemagglutinin (HA)-tagged fusion proteins, TAT-HA-beta-galactosidase (TAT-HA-beta-gal), TAT-HA-myocilin, and TAT-HA-myocilin-EGFP. Transduction of TAT-HA-beta-gal was detected by X-gal staining. Transduction of myocilin or myocilin-EGFP was evaluated by immunostaining or fluorescence. beta-Gal and EGFP proteins were used as the negative control.
Results: Blue X-gal staining, signifying beta-gal activity resulting from transduction, was observed in cultured TM cells in a concentration- and time-dependent manner. TAT-HA-beta-gal was also transduced into cells in all regions of TM tissues in organ cultures. TM cell cultures, after TAT-HA-myocilin incubation, showed an enhanced myocilin staining compared with the control cultures. Stronger myocilin or HA staining was also noted in TM tissues of TAT-HA-myocilin-incubated or -perfused eyes. Myocilin transduction resulted in a loss of actin stress fibers and focal adhesions in TM cells in culture. The level of phosphorylated myosin light chain was reduced. Human and bovine TM tissues after TAT-myocilin transduction also exhibited a diminished actin and paxillin-vinculin staining.
Conclusions: TAT fusion proteins can be efficiently transduced into TM cells and tissues. The TAT-mediated protein transduction technology may be valuable in studies of proteins such as myocilin in the TM.