The 18 kDa Mitochondrial Translocator Protein (TSPO) Prevents Accumulation of Protoporphyrin IX. Involvement of Reactive Oxygen Species (ROS)
2012
By exposing cells of the U118MG glioblastoma cell line to protoporphyrin IX (PPIX) in culture, we
found that the 18 kDa mitochondrial translocator protein (TSPO) prevents intracellular accumulation of PPIX.
In particular, TSPO knockdown by stable transfection of TSPO silencing siRNA vectors into U118MG cells
leads to mitochondrial PPIX accumulation. In combination with light exposure, the PPIX accumulation led to
cell death of the TSPO knockdown cells. In the sham control cells (stable transfection of scrambled siRNA
vectors), TSPO expression remained high and no PPIX accumulation was observed. The prevention of PPIX
accumulation by TSPO was not due to conversion of PPIX to heme in the sham control cells. Similar to TSPO
knockdown, the reactive oxygen species (ROS) scavenger glutathione (GSH) also enhanced PPIX
accumulation. This suggests that that ROS generation as modulated by TSPO activation may present a
mechanism to prevent accumulation of PPIX.
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