Protein 4.1R is Involved in the Transport of 5-Aminolevulinic Acid by Interaction with GATs in MEF Cells.

5-aminolevulinic acid (5-ALA)-based photodynamic therapy (PDT) has been successfully used in the treatment of cancers. However, the mechanism of 5-ALA transportation into cancer cells is still not fully elucidated. Previous studies have confirmed that the efficiency of 5-ALA-PDT could be affected by the membrane skeleton protein 4.1R. In this study, we investigated the role of 4.1R in the transport of 5-ALA into cells. Wild-type (4.1R+/+ ) and 4.1R gene knockout (4.1R-/- ) mouse embryonic fibroblast (MEF) cells were incubated with 1 mm 5-ALA and different concentrations of specific inhibitors of GABA transporters GAT (1-3). Our results showed that the inhibition of GAT1 and GAT2 in particular markedly attenuated the intracellular PpIX production, reactive oxygen species (ROS) level and 5-ALA-induced photodamage. However, the inhibition of GAT3 did not show such effects. Further research showed that 4.1R-/- MEF cells had a lower expression of GAT1 and GAT2 than 4.1R+/+ MEF cells. Additionally, 4.1R directly bound to GAT1 and GAT2. Taken together, GAT1 and GAT2 transporters are involved in the uptake of 5-ALA in MEF cells. 4.1R plays an important role in transporting 5-ALA into cells via at least partly interaction with GAT1 and GAT2 transporters in 5-ALA-PDT.