The role of ion homeostasis imbalance due to citrate accumulation in fluoroacetic acid (FAA) toxicity in Neurospora crassa.

Fluoroacetic acid (FAA) is a poison commonly used for the lethal control of invasive species in Australia and New Zealand. Despite its widespread use and long history as a pesticide, no effective treatment for accidental poisoning exists. Although it is known to inhibit the tricarboxylic acid (TCA) cycle, specific details of FAA toxicology have remained elusive, with hypocalcemia suggested to be involved in the neurological symptoms prior to death.

Evolution of TOP1 and TOP1MT Topoisomerases in Chordata.

Type IB topoisomerases relax the torsional stress associated with DNA metabolism in the nucleus and mitochondria and constitute important molecular targets of anticancer drugs. Vertebrates stand out among eukaryotes by having two Type IB topoisomerases acting specifically in the nucleus (TOP1) and mitochondria (TOP1MT). Despite their major importance, the origin and evolution of these paralogues remain unknown.

Evolutionary History of TOPIIA Topoisomerases in Animals.

TOPIIA topoisomerases are required for the regulation of DNA topology by DNA cleavage and re-ligation and are important targets of antibiotic and anticancer agents. Humans possess two TOPIIA paralogue genes (TOP2A and TOP2B) with high sequence and structural similarity but distinct cellular functions. Despite their functional and clinical relevance, the evolutionary history of TOPIIA is still poorly understood.

Molecular Evolution of DNA Topoisomerase III Beta (TOP3B) in Metazoa.

DNA topoisomerase III beta (TOP3B) is unique by operating on both DNA and RNA substrates to regulate gene expression and genomic stability. Mutations in human TOP3B are linked to neurodevelopmental and cognitive disorders, highlighting its relevance for human health. Despite the emerging importance of TOP3B, its precise cellular functions and evolutionary history remain poorly understood.

The Fungal Cell Death Regulator Is Allelic to .

Fungal infections have far-reaching implications that range from severe human disease to a panoply of disruptive agricultural and ecological effects, making it imperative to identify and understand the molecular pathways governing the response to antifungal compounds. In this context, CZT-1 (cell death-activated zinc cluster transcription factor) functions as a master regulator of cell death and drug susceptibility in . Here we provide evidence indicating that is allelic to , a previously described locus that we now found to harbor a point mutation in its coding sequence.

Changes in the Biophysical Properties of the Cell Membrane Are Involved in the Response of to Staurosporine.

is a non-pathogenic filamentous fungus widely used as a multicellular eukaryotic model. Recently, the biophysical properties of the plasma membrane of conidia were thoroughly characterized. They evolve during conidial germination at a speed that depends on culture conditions, suggesting an important association between membrane remodeling and the intense membrane biogenesis that takes place during the germinative process.

Regulated Forms of Cell Death in Fungi.

Cell death occurs in all domains of life. While some cells die in an uncontrolled way due to exposure to external cues, other cells die in a regulated manner as part of a genetically encoded developmental program. Like other eukaryotic species, fungi undergo programmed cell death (PCD) in response to various triggers.

Reorganization of plasma membrane lipid domains during conidial germination.

Neurospora crassa, a filamentous fungus, in the unicellular conidial stage has ideal features to study sphingolipid (SL)-enriched domains, which are implicated in fundamental cellular processes ranging from antifungal resistance to apoptosis. Several changes in lipid metabolism and in the membrane composition of N. crassa occur during spore germination.

Transcription profiling of the Neurospora crassa response to a group of synthetic (thio)xanthones and a natural acetophenone.

Xanthones are a class of heterocyclic compounds characterized by a dibenzo-γ-pyrone nucleus. Analysis of their mode of action in cells, namely uncovering alterations in gene expression, is important because these compounds have potential therapeutic applications. Thus, we studied the transcriptional response of the filamentous fungus Neurospora crassa to a group of synthetic (thio)xanthone derivatives with antitumor activity using high throughput RNA sequencing.

Involvement of mitochondrial proteins in calcium signaling and cell death induced by staurosporine in Neurospora crassa.

Staurosporine-induced cell death in Neurospora crassa includes a well defined sequence of alterations in cytosolic calcium levels, comprising extracellular Ca(2+) influx and mobilization of Ca(2+) from internal stores. Here, we show that cells undergoing respiratory stress due to the lack of certain components of the mitochondrial complex I (like the 51kDa and 14kDa subunits) or the Ca(2+)-binding alternative NADPH dehydrogenase NDE-1 are hypersensitive to staurosporine and incapable of setting up a proper intracellular Ca(2+) response. Cells expressing mutant forms of NUO51 that mimic human metabolic diseases also presented Ca(2+) signaling deficiencies.

Mitochondrial type II NAD(P)H dehydrogenases in fungal cell death.

During aerobic respiration, cells produce energy through oxidative phosphorylation, which includes a specialized group of multi-subunit complexes in the inner mitochondrial membrane known as the electron transport chain. However, this canonical pathway is branched into single polypeptide alternative routes in some fungi, plants, protists and bacteria. They confer metabolic plasticity, allowing cells to adapt to different environmental conditions and stresses.

Extracellular calcium triggers unique transcriptional programs and modulates staurosporine-induced cell death in .

Alterations in the intracellular levels of calcium are a common response to cell death stimuli in animals and fungi and, particularly, in the response to staurosporine. We highlight the importance of the extracellular availability of Ca for this response. Limitation of the ion in the culture medium further sensitizes cells to the drug and results in increased accumulation of reactive oxygen species (ROS).

Activation of a TRP-like channel and intracellular Ca2+ dynamics during phospholipase-C-mediated cell death.

The model organism Neurospora crassa undergoes programmed cell death when exposed to staurosporine. Here, we show that staurosporine causes defined changes in cytosolic free Ca(2+) ([Ca(2+)]c) dynamics and a distinct Ca(2+) signature that involves Ca(2+) influx from the external medium and internal Ca(2+) stores. We investigated the molecular basis of this Ca(2+) response by using [Ca(2+)]c measurements combined with pharmacological and genetic approaches.

CZT-1 is a novel transcription factor controlling cell death and natural drug resistance in Neurospora crassa.

We pinpoint CZT-1 (cell death-activated zinc cluster transcription factor) as a novel transcription factor involved in tolerance to cell death induced by the protein kinase inhibitor staurosporine in Neurospora crassa. Transcriptional profiling of staurosporine-treated wild-type cells by RNA-sequencing showed that genes encoding the machinery for protein synthesis are enriched among the genes repressed by the drug. Functional category enrichment analyses also show that genes encoding components of the mitochondrial respiratory chain are downregulated by staurosporine, whereas genes involved in endoplasmic reticulum activities are upregulated.

Syndromes associated with mitochondrial DNA depletion.

Mitochondrial dysfunction accounts for a large group of inherited metabolic disorders most of which are due to a dysfunctional mitochondrial respiratory chain (MRC) and, consequently, deficient energy production. MRC function depends on the coordinated expression of both nuclear (nDNA) and mitochondrial (mtDNA) genomes. Thus, mitochondrial diseases can be caused by genetic defects in either the mitochondrial or the nuclear genome, or in the cross-talk between the two.

A novel SUCLA2 mutation in a Portuguese child associated with "mild" methylmalonic aciduria.

Succinyl-coenzyme A synthase is a mitochondrial matrix enzyme that catalyzes the reversible synthesis of succinate and adenosine triphosphate (ATP) from succinyl-coenzyme A and adenosine diphosphate (ADP) in the tricarboxylic acid cycle. This enzyme is made up of α and β subunits encoded by SUCLG1 and SUCLA2, respectively. We present a child with severe muscular hypotonia, dystonia, failure to thrive, sensorineural deafness, and dysmorphism.

Reduced glutathione export during programmed cell death of Neurospora crassa.

In a previous study, we demonstrated that staurosporine (STS) induces programmed cell death (PCD) in the fungus Neurospora crassa and that glutathione has the capability of inhibiting both STS-induced reactive oxygen species (ROS) formation and cell death. Here, we further investigated the role of glutathione in STS-induced PCD in N. crassa and observed an efflux of reduced glutathione (GSH) together with a change in the cell internal redox state to a more oxidative environment.

Novel insights into the role of Neurospora crassa NDUFAF2, an evolutionarily conserved mitochondrial complex I assembly factor.

Complex I deficiency is commonly associated with mitochondrial oxidative phosphorylation diseases. Mutations in nuclear genes encoding structural subunits or assembly factors of complex I have been increasingly identified as the cause of the diseases. One such factor, NDUFAF2, is a paralog of the NDUFA12 structural subunit of the enzyme, but the mechanism by which it exerts its function remains unknown.

Defective valyl-tRNA synthetase hampers the mitochondrial respiratory chain in Neurospora crassa.

Respiratory chain deficiency can result from alterations in mitochondrial and/or cytosolic protein synthesis due to the dual genetic origin of mitochondrial oxidative phosphorylation. In the present paper we report a point mutation (D750G) in the bifunctional VARS (valyl-tRNA synthetase) of the fungus Neurospora crassa, associated with a temperature-sensitive phenotype. Analysis of the mutant strain revealed decreased steady-state levels of VARS and a clear reduction in the rate of mitochondrial protein synthesis.

Characterization of apoptosis-related oxidoreductases from Neurospora crassa.

The genome from Neurospora crassa presented three open reading frames homologous to the genes coding for human AIF and AMID proteins, which are flavoproteins with oxidoreductase activities implicated in caspase-independent apoptosis. To investigate the role of these proteins, namely within the mitochondrial respiratory chain, we studied their cellular localization and characterized the respective null mutant strains. Efficiency of the respiratory chain was analyzed by oxygen consumption studies and supramolecular organization of the OXPHOS system was assessed through BN-PAGE analysis in the respective null mutant strains.

Disruption of alternative NAD(P)H dehydrogenases leads to decreased mitochondrial ROS in Neurospora crassa.

Mitochondria are a main providers of high levels of energy, but also a major source of reactive oxygen species (ROS) during normal oxidative metabolism. The involvement of Neurospora crassa alternative NAD(P)H dehydrogenases in mitochondrial ROS production was evaluated. The growth responses of a series of respiratory mutants to several stress conditions revealed that disrupting alternative dehydrogenases leads to an increased tolerance to the redox cycler paraquat, with a mutant devoid of the external NDE1 and NDE2 enzymes being significantly more resistant.

Modulation of fungal sensitivity to staurosporine by targeting proteins identified by transcriptional profiling.

An analysis of the time-dependent genetic response to the death-inducer staurosporine was performed in Neurospora crassa by transcriptional profiling. Staurosporine induced two major genes encoding an ABC transporter and a protein with similarity to regulatory subunits of potassium channels. The transcriptional response is dependent on the activity of a novel transcription factor.

Synergistic growth inhibition of cancer cells harboring the RET/PTC1 oncogene by staurosporine and rotenone involves enhanced cell death.

TPC-1 is a highly proliferative thyroid papillary carcinoma-derived cell line. These cells express the RET/PTC1 fusion protein, whose isoforms are characterized in this work. The bacterial alkaloid staurosporine and the plant extract rotenone are death-inducing drugs that have an inhibitory synergistic effect on the growth of TPC-1 cells.

Orthovanadate-induced cell death in RET/PTC1-harboring cancer cells involves the activation of caspases and altered signaling through PI3K/Akt/mTOR.

Aims: Oncogenic RET/PTC1 chromosomal rearrangements are hallmarks of thyroid papillary carcinoma. The resulting protein, mainly through tyrosine 451, is responsible for the activation of pathways controlling cell survival, including the PI3K/Akt/mTOR cascade. Vanadium compounds were shown to have anti-neoplastic potential.

Involvement of p53 in cell death following cell cycle arrest and mitotic catastrophe induced by rotenone.

In order to investigate the cell death-inducing effects of rotenone, a plant extract commonly used as a mitochondrial complex I inhibitor, we studied cancer cell lines with different genetic backgrounds. Rotenone inhibits cell growth through the induction of cell death and cell cycle arrest, associated with the development of mitotic catastrophe. The cell death inducer staurosporine potentiates the inhibition of cell growth by rotenone in a dose-dependent synergistic manner.