Translocator Protein Is Involved in the Induction and Regulation of Mitochondrial Permeability Transition Pore Opening in C6 Glioma Cells.

Translocator protein (TSPO), formerly known as the peripheral-type benzodiazepine receptor (PBR), is a 18-kDa protein localized in the outer mitochondrial membrane and involved in cell proliferation and apoptosis. In the present work, we found TSPO as a monomer and dimer in rat C6 glioma cells. We have shown that a reduced TSPO expression in cells affects the induction of a mitochondrial permeability transition pore (mPTP). It also stimulated the Ca²⁺-induced opening of mPTP. The natural endogenous TSPO ligand protoporphyrin IX (PPIX) accelerated the opening of mPTP. The stimulatory effect of PPIX was higher in the mitochondria of wild-type C6 glioma cells than in TSPO knockdown C6 glioma cells. Phosphorylation of membrane receptors, ion channels, and transcription factors is an important intracellular signaling event responsible for the regulation of various enzymes and many cellular functions. In the present study, PPIX modulated protein phosphorylation. We hypothesized that TSPO is an important protein in the regulation of cell survival and may be involved in mPTP functioning. [ABSTRACT FROM AUTHOR]