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Updated: May 24, 2026

Reconstitution of Msp1 Extraction Activity with Fully Purified Components
Published on: August 10, 2021
The 18 kDa mitochondrial translocator protein (TSPO) prevents accumulation of protoporphyrin IX. Involvement of
1Department of Molecular Pharmacology, Technion-Israel Institute of Technology, Ephron Street, P.O. Box 9649, Bat-Galim, Haifa 31096, Israel.
Abstract:
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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