Import of mitochondrial transcription factor A (TFAM) into rat liver mitochondria stimulates transcription of mitochondrial DNA.
Garstka Heike L,Schmitt Wolfgang E,Schultz Jeanette,Sogl Bettina,Silakowski Barbara,Pérez-Martos Acisclo,Montoya Julio,Wiesner Rudolf J
Nucleic acids research
Mitochondrial transcription factor A (TFAM) has been shown to stimulate transcription from mitochondrial DNA promoters in vitro. In order to determine whether changes in TFAM levels also regulate RNA synthesis in situ, recombinant human precursor proteins were imported into the matrix of rat liver mitochondria. After uptake of wt-TFAM, incorporation of [alpha-32P]UTP into mitochondrial mRNAs as well as rRNAs was increased 2-fold (P < 0.05), whereas import of truncated TFAM lacking 25 amino acids at the C-terminus had no effect. Import of wt-TFAM into liver mitochondria from hypothyroid rats stimulated RNA synthesis up to 4-fold. We conclude that the rate of transcription is submaximal in freshly isolated rat liver mitochondria and that increasing intra-mitochondrial TFAM levels is sufficient for stimulation. The low transcription rate associated with the hypothyroid state observed in vivo as well as in organello seems to be a result of low TFAM levels, which can be recovered by treating animals with T3 in vivo or by importing TFAM in organello. Thus, this protein meets the criteria for being a key factor in regulating mitochondrial gene expression in vivo.
10.1093/nar/gkg717
PDX1 deficiency causes mitochondrial dysfunction and defective insulin secretion through TFAM suppression.
Gauthier Benoit R,Wiederkehr Andreas,Baquié Mathurin,Dai Chunhua,Powers Alvin C,Kerr-Conte Julie,Pattou François,MacDonald Raymond J,Ferrer Jorge,Wollheim Claes B
Cell metabolism
Mutations in the transcription factor Pdx1 cause maturity-onset diabetes of the young 4 (MODY4). Islet transduction with dominant-negative Pdx1 (RIPDN79PDX1) impairs mitochondrial metabolism and glucose-stimulated insulin secretion (GSIS). Transcript profiling revealed suppression of nuclear-encoded mitochondrial factor A (TFAM). Herein, we show that Pdx1 suppression in adult mice reduces islet TFAM expression coinciding with hyperglycemia. We define TFAM as a direct target of Pdx1 both in rat INS1 cells and human islets. Adenoviral overexpression of TFAM along with RIPDN79PDX1 in isolated rat islets rescued mitochondrial DNA (mtDNA) copy number and restored respiratory chain activity as well as glucose-induced ATP synthesis and insulin secretion. CGP37157, which blocks the mitochondrial Na(+)/Ca(2+) exchanger, restored ATP generation and GSIS in RIPDN79PDX1 islets, thereby bypassing the transcriptional defect. Thus, the genetic control by the beta cell-specific factor Pdx1 of the ubiquitous gene TFAM maintains beta cell mtDNA vital for ATP production and normal GSIS.
10.1016/j.cmet.2009.07.002
Overexpression of TFAM or twinkle increases mtDNA copy number and facilitates cardioprotection associated with limited mitochondrial oxidative stress.
Ikeda Masataka,Ide Tomomi,Fujino Takeo,Arai Shinobu,Saku Keita,Kakino Takamori,Tyynismaa Henna,Yamasaki Toshihide,Yamada Ken-Ichi,Kang Dongchon,Suomalainen Anu,Sunagawa Kenji
PloS one
BACKGROUND:Mitochondrial DNA (mtDNA) copy number decreases in animal and human heart failure (HF), yet its role in cardiomyocytes remains to be elucidated. Thus, we investigated the cardioprotective function of increased mtDNA copy number resulting from the overexpression of human transcription factor A of mitochondria (TFAM) or Twinkle helicase in volume overload (VO)-induced HF. METHODS AND RESULTS:Two strains of transgenic (TG) mice, one overexpressing TFAM and the other overexpressing Twinkle helicase, exhibit an approximately 2-fold equivalent increase in mtDNA copy number in heart. These TG mice display similar attenuations in eccentric hypertrophy and improved cardiac function compared to wild-type (WT) mice without any deterioration of mitochondrial enzymatic activities in response to VO, which was accompanied by a reduction in matrix-metalloproteinase (MMP) activity and reactive oxygen species after 8 weeks of VO. Moreover, acute VO-induced MMP-2 and MMP-9 upregulation was also suppressed at 24 h in both TG mice. In isolated rat cardiomyocytes, mitochondrial reactive oxygen species (mitoROS) upregulated MMP-2 and MMP-9 expression, and human TFAM (hTFAM) overexpression suppressed mitoROS and their upregulation. Additionally, mitoROS were equally suppressed in H9c2 rat cardiomyoblasts that overexpress hTFAM or rat Twinkle, both of which exhibit increased mtDNA copy number. Furthermore, mitoROS and mitochondrial protein oxidation from both TG mice were suppressed compared to WT mice. CONCLUSIONS:The overexpression of TFAM or Twinkle results in increased mtDNA copy number and facilitates cardioprotection associated with limited mitochondrial oxidative stress. Our findings suggest that increasing mtDNA copy number could be a useful therapeutic strategy to target mitoROS in HF.
10.1371/journal.pone.0119687
Mitochondrial transcription factors TFAM and TFB2M regulate Serca2 gene transcription.
Watanabe Atai,Arai Masashi,Koitabashi Norimichi,Niwano Kazuo,Ohyama Yoshiaki,Yamada Yoshihumi,Kato Noriko,Kurabayashi Masahiko
Cardiovascular research
AIMS:Sarco(endo)plasmic reticulum Ca²(+)-ATPase 2a (SERCA2a) transports Ca²(+) by consuming ATP produced by mitochondrial respiratory chain enzymes. Messenger RNA (mRNA) for these enzymes is transcribed by mitochondrial transcription factors A (TFAM) and B2 (TFB2M). This study examined whether TFAM and TFB2M coordinately regulate the transcription of the Serca2 gene and mitochondrial genes. METHODS AND RESULTS:Nuclear localization of TFAM and TFB2M was demonstrated by immunostaining in rat neonatal cardiac myocytes. Chromatin immunoprecipitation assay and fluorescence correlation spectroscopy revealed that TFAM and TFB2M bind to the -122 to -114 nt and -122 to -117 nt regions of the rat Serca2 gene promoter, respectively. Mutation of these sites resulted in decreased Serca2 gene transcription. In a rat myocardial infarction model, Serca2a mRNA levels significantly correlated with those of Tfam (r = 0.54, P < 0.001) and Tfb2m (r = 0.73, P < 0.001). Overexpression of TFAM and TFB2M blocked hydrogen peroxide- and norepinephrine-induced decreases in Serca2a mRNA levels. In addition, overexpression of TFAM and TFB2M increased the mitochondrial DNA (mtDNA) copy number and mRNA levels of mitochondrial enzymes. CONCLUSION:Although TFAM and TFB2M are recognized as mtDNA-specific transcription factors, they also regulate transcription of nuclear DNA, i.e. the Serca2 gene. Our findings suggest a novel paradigm in which the transcription of genes for mitochondrial enzymes that produce ATP and the gene for SERCA2a that consumes ATP is coordinately regulated by the same transcription factors. This mechanism may contribute to maintaining proper cardiac function.
10.1093/cvr/cvq374
Pattern recognition receptors mediate pro-inflammatory effects of extracellular mitochondrial transcription factor A (TFAM).
Schindler Stephanie M,Frank Matthew G,Annis Jessica L,Maier Steven F,Klegeris Andis
Molecular and cellular neurosciences
Neuroinflammation is a common pathogenic mechanism for a number of neurodegenerative disorders including Alzheimer's and Parkinson's diseases. Microglia, the immune cells of the brain, contribute to the onset and progression of the neuroinflammation observed in these diseases. Microglia become activated and initiate an inflammatory response by interacting with a diverse set of molecules, including the group of endogenous proteins released upon cell damage, termed damage-associated molecular patterns (DAMPs). One of these molecules, mitochondrial transcription factor A (TFAM), has been shown to induce pro-inflammatory and cytotoxic responses of microglia in vitro. Here, we demonstrate that TFAM injected into the cisterna magna of male Sprague-Dawley rats upregulates (i) the expression of monocyte chemotactic protein (MCP)-1, interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and nuclear factor-kappa B inhibitor alpha (NF-κBIA) in the hippocampus; (ii) the expression of MCP-1, IL-1β and TNF-α in the frontal cortex; and (iii) IL-1β protein concentration in both these brain regions. These same inflammatory mediators are upregulated in isolated rat microglia following their in vitro exposure to extracellular TFAM. Blocking the receptor for advanced glycation endproducts (RAGE) and the macrophage antigen complex (Mac)-1 by specific antibodies inhibited the TFAM-induced secretion of MCP-1 by THP-1 monocytic cells, which were used to model human microglia. Our data support the hypothesis that extracellular TFAM can interact with RAGE and Mac-1 to function as a DAMP that causes pro-inflammatory microglial activation. Blocking this interaction may represent a potential target for attenuating the neuroinflammation observed in neurodegenerative diseases.
10.1016/j.mcn.2018.04.005
The neuroprotective effect of NeuroAid on morphine-induced amnesia with respect to the expression of TFAM, PGC-1α, ΔfosB and CART genes in the hippocampus of male Wistar rats.
Malboosi Nasrin,Nasehi Mohammad,Hashemi Mehrdad,Vaseghi Salar,Zarrindast Mohammad-Reza
Gene
Morphine is a natural alkaloid which derived from the opium poppy Papaver somniferum. Many studies have reported the effect of morphine on learning, memory and gene expression. CART (cocaine-amphetamine regulated transcript)is an important neuropeptide which has a critical role in physiological processes including drug dependence and antioxidant activity. ΔfosB is a transcription factor which modulates synaptic plasticity and affects learning and memory. TFAM (the mitochondrial transcription factor A) and PGC-1α (Peroxisome proliferator-activated receptor γ coactivator-1α) are critically involved in mitochondrial biogenesis and antioxidant pathways. NeuroAid is a Chinese medicine that induces neuroprotective and anti-apoptotic effects. In this research, we aimed to investigate the effect of NeuroAid on morphine-induced amnesia with respect to the expression of TFAM, PGC-1α, ΔfosB and CART in the rat's hippocampus. In this study, Morphine sulfate (at increasing doses), Naloxone hydrochloride (2.5 mg/kg) and NeuroAid (2.5 mg/kg) were administered intraperitoneal and real-time PCR reactions were done to assess gene expression. The results showed, morphine impaired memory of step-through passive avoidance, while NeuroAid had no effect. NeuroAid attenuated (but not reversed) morphine-induced memory impairment in morphine-addicted rats. Morphine increased the expression of PGC-1α and decreased the expression of CART. However, NeuroAid increased the expression of TFAM, PGC-1α, ΔfosB and CART. NeuroAid restored the effect of morphine on the expression of CART and PGC-1α. In conclusion, morphine impaired memory of step-through passive avoidance and NeuroAid attenuated this effect. The effect of NeuroAid on morphine-induced memory impairment/gene expression may be related to its anti-apoptotic and neuroprotective effects.
10.1016/j.gene.2020.144601