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Classical and Novel TSPO Ligands for the Mitochondrial TSPO Can Modulate Nuclear Gene Expression: Implications for
Nasra Yasin1, Leo Veenman2, Sukhdev Singh3
1The Ruth and Bruce Rappaport Faculty of Medicine, Department of Neuroscience, Technion-Israel Institute of Technology, Haifa 32525433, Israel. nasra19@campus.technion.ac.il.
Abstract:
It is known that knockdown of the mitochondrial 18 kDa translocator protein (TSPO) as well as TSPO ligands modulate various functions, including functions related to cancer. To study the ability of TSPO to regulate gene expression regarding such functions, we applied microarray analysis of gene expression to U118MG glioblastoma cells. Within 15 min, the classical TSPO ligand PK 11195 induced changes in expression of immediate early genes and transcription factors. These changes also included gene products that are part of the canonical pathway serving to modulate general gene expression. These changes are in accord with real-time, reverse transcriptase (RT) PCR. At the time points of 15, 30, 45, and 60 min, as well as 3 and 24 h of PK 11195 exposure, the functions associated with the changes in gene expression in these glioblastoma cells covered well known TSPO functions. These functions included cell viability, proliferation, differentiation, adhesion, migration, tumorigenesis, and angiogenesis. This was corroborated microscopically for cell migration, cell accumulation, adhesion, and neuronal differentiation. Changes in gene expression at 24 h of PK 11195 exposure were related to downregulation of tumorigenesis and upregulation of programmed cell death. In the vehicle treated as well as PK 11195 exposed cell cultures, our triple labeling showed intense TSPO labeling in the mitochondria but no TSPO signal in the cell nuclei. Thus, mitochondrial TSPO appears to be part of the mitochondria-to-nucleus signaling pathway for modulation of nuclear gene expression. The novel TSPO ligand 2-Cl-MGV-1 appeared to be very specific regarding modulation of gene expression of immediate early genes and transcription factors.
Insights
Mitochondrial 18 kDa translocator protein (TSPO) ligands rapidly alter gene expression in glioblastoma cells, impacting cancer-related functions like cell viability and tumorigenesis. This suggests a mitochondria-to-nucleus signaling pathway regulating gene expression.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- The mitochondrial 18 kDa translocator protein (TSPO) and its ligands influence cellular functions, including those relevant to cancer.
- Understanding TSPO's role in gene expression modulation is crucial for cancer research.
Purpose of the Study:
- To investigate how TSPO regulates gene expression in glioblastoma cells.
- To identify the functional consequences of TSPO-mediated gene expression changes.
Main Methods:
- Microarray analysis of gene expression in U118MG glioblastoma cells.
- Treatment with the TSPO ligand PK 11195 at various time points.
- Real-time reverse transcriptase (RT) PCR for validation.
- Microscopic corroboration of cellular functions.
- Triple labeling for TSPO localization.
Main Results:
- PK 11195 rapidly altered the expression of immediate early genes and transcription factors within 15 minutes.
- Gene expression changes correlated with known TSPO functions: cell viability, proliferation, differentiation, adhesion, migration, tumorigenesis, and angiogenesis.
- At 24 hours, PK 11195 exposure led to downregulation of tumorigenesis and upregulation of programmed cell death.
- TSPO was localized to mitochondria, not cell nuclei, suggesting a mitochondria-to-nucleus signaling pathway.
- A novel ligand, 2-Cl-MGV-1, showed specificity in modulating immediate early gene and transcription factor expression.
Conclusions:
- Mitochondrial TSPO plays a role in the mitochondria-to-nucleus signaling pathway that modulates nuclear gene expression.
- TSPO ligands can rapidly impact gene expression profiles related to critical cellular functions in glioblastoma.
- The findings highlight TSPO as a potential therapeutic target in glioblastoma.