Mitochondrial TSPO Deficiency Triggers Retrograde Signaling in MA-10 Mouse Tumor Leydig Cells

Abstract

The mitochondrial translocator protein (TSPO) has been shown to bind cholesterol with high affinity and is involved in mediating its availability for steroidogenesis. We recently reported that targeted Tspo gene deletion in MA-10 mouse tumor Leydig cells resulted in reduced cAMP-stimulated steroid formation and significant reduction in the mitochondrial membrane potential (ΔΨm) compared to control cells. We hypothesized that ΔΨm reduction in the absence of TSPO probably reflects the dysregulation and/or maintenance failure of some basic mitochondrial function(s). To explore the consequences of TSPO depletion via CRISPR-Cas9-mediated deletion (indel) mutation in MA-10 cells, we assessed the transcriptome changes in TSPO-mutant versus wild-type (Wt) cells using RNA-seq. Gene expression profiles were validated using real-time PCR. We report herein that there are significant changes in nuclear gene expression in Tspo mutant versus Wt cells. The identified transcriptome changes were mapped to several signaling pathways including the regulation of membrane potential, calcium signaling, extracellular matrix, and phagocytosis. This is a retrograde signaling pathway from the mitochondria to the nucleus and is probably the result of changes in expression of several transcription factors, including key members of the NF-κB pathway. In conclusion, TSPO regulates nuclear gene expression through intracellular signaling. This is the first evidence of a compensatory response to the loss of TSPO with transcriptome changes at the cellular level.

Deletion of Mitochondrial Translocator Protein (TSPO) Gene Decreases Oxidative Retinal Pigment Epithelial Cell Death via Modulation of TRPM2 Channel

“…Accumulating evince indicates that the presence of TSPO participated the modulations of Ca 2+ homeostasis and mitochondrial fROS generation [10,11]. The deletion of TSPO gene provides to study the action of TSPO on the levels of apoptosis, ADPR, Mito-fROS and apoptosis via the stimulation of Ca 2+ permeable channels in the models of cell culture [40][41][42][43]. The stimulations of oxidative stress and ADPR induce the activation of TRPM2 in the ARPE19 [21,23].…”

“…The influxes of Ca 2+ also action as a direct stimulus to cause TRPM2 stimulation-induced fROS in the ARPE19 [21,23]. The deletions of TSPO regulate mPTP activity via the inhibition of VDCC activation by decreasing the mitochondrial fROS generation, Ca 2+ influx and mitochondrial Ca 2+ accumulation in several cells [14,40]. PARP-1 can be overstimulated by fROS and PARP-1.…”

Exploring Translocator Protein (TSPO) Medicinal Chemistry: An Approach for Targeting Radionuclides and Boron Atoms to Mitochondria

“…The results demonstrated that derivatives 33 and 34, acting in vitro as good boron carriers, were able to concentrate boron atoms into tumor cells better than BPA. Despite its lower potency in comparison with 33, the fluoromethyl derivative 34 was selected for further in vivo studies owing to its lower cytotoxicity, the suitable boron uptake, and its potential as a 19 F magnetic resonance imaging (MRI) agent.…”

“…It also regulates the mitochondrial membrane potential, the respiratory chain, the immune response, the glial activation linked to brain damage, and finally it controls cell growth, differentiation , and programmed cell death . It was recently reported how TSPO controls nuclear gene expression by controlling intracellular signaling from the mitochondria to the nucleus, acting on the expression of several transcription factors . The programmed cell death control exerted by TSPO includes changes in TSPO expression levels and typically gives rise to reactive oxygen species (ROS) generation in mitochondria .…”

“…18 It was recently reported how TSPO controls nuclear gene expression by controlling intracellular signaling from the mitochondria to the nucleus, acting on the expression of several transcription factors. 19 The programmed cell death control exerted by TSPO includes changes in TSPO expression levels and typically gives rise to reactive oxygen species (ROS) generation in mitochondria. 9 TSPO plays a pivotal role in the regulation of ROS level not only in apoptosis.…”