Galactose-1-phosphate inhibits cytochrome c oxidase and causes mitochondrial dysfunction in classic galactosemia.

Classic galactosemia is an inborn error of metabolism caused by mutations in the GALT gene resulting in the diminished activity of the galactose-1-phosphate uridyltransferase enzyme. This reduced GALT activity leads to the buildup of the toxic intermediate galactose-1-phosphate and a decrease in ATP levels upon exposure to galactose. In this work, we focused our attention on mitochondrial oxidative phosphorylation in the context of this metabolic disorder.

Apoptotic stress causes mtDNA release during senescence and drives the SASP.

Senescent cells drive age-related tissue dysfunction partially through the induction of a chronic senescence-associated secretory phenotype (SASP). Mitochondria are major regulators of the SASP; however, the underlying mechanisms have not been elucidated. Mitochondria are often essential for apoptosis, a cell fate distinct from cellular senescence.

Sphingolipid depletion suppresses UPR activation and promotes galactose hypersensitivity in yeast models of classic galactosemia.

Classic galactosemia is an inborn error of metabolism caused by deleterious mutations on the GALT gene, which encodes the Leloir pathway enzyme galactose-1-phosphate uridyltransferase. Previous studies have shown that the endoplasmic reticulum unfolded protein response (UPR) is relevant to galactosemia, but the molecular mechanism behind the endoplasmic reticulum stress that triggers this response remains elusive. In the present work, we show that the activation of the UPR in yeast models of galactosemia does not depend on the binding of unfolded proteins to the ER stress sensor protein Ire1p since the protein domain responsible for unfolded protein binding to Ire1p is not necessary for UPR activation.

Regulation of sphingolipid synthesis by the G1/S transcription factor Swi4.

SBF (Swi4/Swi6 Binding Factor) complex is a crucial regulator of G1/S transition in Saccharomyces cerevisiae. Here, we show that SBF complex is required for myriocin resistance, an inhibitor of sphingolipid synthesis. This phenotype was not shared with MBF complex mutants nor with deletion of the Swi4p downstream targets, CLN1/CLN2.

Rqc1 and other yeast proteins containing highly positively charged sequences are not targets of the RQC complex.

Previous work has suggested that highly positively charged protein segments coded by rare codons or poly (A) stretches induce ribosome stalling and translational arrest through electrostatic interactions with the negatively charged ribosome exit tunnel, leading to inefficient elongation. This arrest leads to the activation of the Ribosome Quality Control (RQC) pathway and results in low expression of these reporter proteins. However, the only endogenous yeast proteins known to activate the RQC are Rqc1, a protein essential for RQC function, and Sdd1, a protein with unknown function, both of which contain polybasic sequences.

Neutrophils induce paracrine telomere dysfunction and senescence in ROS-dependent manner.

Cellular senescence is characterized by an irreversible cell cycle arrest as well as a pro-inflammatory phenotype, thought to contribute to aging and age-related diseases. Neutrophils have essential roles in inflammatory responses; however, in certain contexts their abundance is associated with a number of age-related diseases, including liver disease. The relationship between neutrophils and cellular senescence is not well understood.

The yeast protein Ubx4p contributes to mitochondrial respiration and lithium-galactose-mediated activation of the unfolded protein response.

In the presence of galactose, lithium ions activate the unfolded protein response (UPR) by inhibiting phosphoglucomutase activity and causing the accumulation of galactose-related metabolites, including galactose-1-phosphate. These metabolites also accumulate in humans who have the disease classic galactosemia. Here, we demonstrate that yeast strains harboring a deletion of , a gene encoding a partner of Cdc48p in the endoplasmic reticulum-associated degradation (ERAD) pathway, exhibit delayed UPR activation after lithium and galactose exposure because the deletion decreases galactose-1-phosphate levels.

Methyl and Ethylmercury elicit oxidative stress and unbalance the antioxidant system in Saccharomyces cerevisiae.

Methylmercury (MeHg) and Ethylmercury (EtHg) are toxic to the central nervous system. Human exposure to MeHg and EtHg results mainly from the consumption of contaminated fish and thimerosal-containing vaccines, respectively. The mechanisms underlying the toxicity of MeHg and EtHg are still elusive.

Induction of triacylglycerol synthesis in yeast by cell cycle arrest.

In this study, we found that cell cycle arrest induced by alpha-factor mating pheromone (G1), hydroxyurea (S) or nocodazole (G2/M) was associated to increased lipid droplet (LD) content. To identify novel cell cycle genes involved in LD homeostasis, we screened a deletion library for strains with altered LD levels. Among the mutants related to mitotic cell cycle, we found 24 hits that displayed a significantly higher LD content.

The galactose-induced decrease in phosphate levels leads to toxicity in yeast models of galactosemia.

Classic galactosemia is an inborn error of metabolism caused by deleterious mutations in the GALT gene. A number of evidences indicate that the galactose-1-phosphate accumulation observed in patient cells is a cause of toxicity in this disease. Nevertheless, the consequent molecular events caused by the galactose-1-phosphate accumulation remain elusive.

A Chemogenomic Screen Reveals Novel Snf1p/AMPK Independent Regulators of Acetyl-CoA Carboxylase.

Acetyl-CoA carboxylase (Acc1p) is a key enzyme in fatty acid biosynthesis and is essential for cell viability. To discover new regulators of its activity, we screened a Saccharomyces cerevisiae deletion library for increased sensitivity to soraphen A, a potent Acc1p inhibitor. The hits identified in the screen (118 hits) were filtered using a chemical-phenotype map to exclude those associated with pleiotropic drug resistance.

The ACBP gene family in Rhodnius prolixus: Expression, characterization and function of RpACBP-1.

The acyl-CoA-binding proteins (ACBP) constitute a family of conserved proteins that bind acyl-CoA with high affinity and protect it from hydrolysis. Thus, ACBPs may have essential roles in basal cellular lipid metabolism. The genome of the insect Rhodnius prolixus encodes five ACBP genes similar to those described for other insect species.

TORC1 inhibition induces lipid droplet replenishment in yeast.

Lipid droplets (LDs) are intracellular structures that regulate neutral lipid homeostasis. In mammals, LD synthesis is inhibited by rapamycin, a known inhibitor of the mTORC1 pathway. In Saccharomyces cerevisiae, LD dynamics are modulated by the growth phase; however, the regulatory pathways involved are unknown.

The unfolded protein response has a protective role in yeast models of classic galactosemia.

Classic galactosemia is a human autosomal recessive disorder caused by mutations in the GALT gene (GAL7 in yeast), which encodes the enzyme galactose-1-phosphate uridyltransferase. Here we show that the unfolded protein response pathway is triggered by galactose in two yeast models of galactosemia: lithium-treated cells and the gal7Δ mutant. The synthesis of galactose-1-phosphate is essential to trigger the unfolded protein response under these conditions because the deletion of the galactokinase-encoding gene GAL1 completely abolishes unfolded protein response activation and galactose toxicity.

Pyruvate decarboxylase activity is regulated by the Ser/Thr protein phosphatase Sit4p in the yeast Saccharomyces cerevisiae.

Deletion of SIT4 phosphatase decreased the pyruvate decarboxylase activity, which is essential for directing the glucose flux to ethanol production. Concomitantly, a reduction in the fermentative capacity was observed. As pyruvate decarboxylase expression was not altered, its post-translational phosphorylation was studied.

High hydrostatic pressure activates gene expression that leads to ethanol production enhancement in a Saccharomyces cerevisiae distillery strain.

High hydrostatic pressure (HHP) is a stress that exerts broad effects on microorganisms with characteristics similar to those of common environmental stresses. In this study, we aimed to identify genetic mechanisms that can enhance alcoholic fermentation of wild Saccharomyces cerevisiae isolated from Brazilian spirit fermentation vats. Accordingly, we performed a time course microarray analysis on a S.

Expression of the glucose transporter HXT1 involves the Ser-Thr protein phosphatase Sit4 in Saccharomyces cerevisiae.

We studied the effect of the loss of the Ser-Thr protein phosphatase Sit4, an important post-translational regulator, on the steady-state levels of the low-affinity glucose transporter Hxt1p and observed a delay in its appearance after high glucose induction, slow growth, and diminished glucose consumption. By analyzing the known essential pathway necessary to induce Hxt1p, we observed a partial inhibition of casein kinase I activity. In both WT and sit4Δ strains, the transcript was induced with no significant difference at 15 min of glucose induction; however, after 45 min, a clear difference in the level of expression was observed being 45% higher in WT than in sit4Δ strain.

Heme-induced ROS in Trypanosoma cruzi activates CaMKII-like that triggers epimastigote proliferation. One helpful effect of ROS.

Heme is a ubiquitous molecule that has a number of physiological roles. The toxic effects of this molecule have been demonstrated in various models, based on both its pro-oxidant nature and through a detergent mechanism. It is estimated that about 10 mM of heme is released during blood digestion in the blood-sucking bug's midgut.

A new fluorescence-based method identifies protein phosphatases regulating lipid droplet metabolism.

In virtually every cell, neutral lipids are stored in cytoplasmic structures called lipid droplets (LDs) and also referred to as lipid bodies or lipid particles. We developed a rapid high-throughput assay based on the recovery of quenched BODIPY-fluorescence that allows to quantify lipid droplets. The method was validated by monitoring lipid droplet turnover during growth of a yeast culture and by screening a group of strains deleted in genes known to be involved in lipid metabolism.

The serine/threonine protein phosphatase Sit4p activates multidrug resistance in Saccharomyces cerevisiae.

Multidrug resistance in Saccharomyces cerevisiae is frequently associated with gain-of-function mutations in zinc finger-containing transcription factors Pdr1p and Pdr3p. These regulatory proteins activate the expression of several ATP-binding cassette transporter genes, leading to elevated drug resistance. Here, we report that loss of the type 2A-related serine/threonine protein phosphatase Sit4p renders yeast cells sensitive to cycloheximide, azoles, daunorubicin and rhodamine 6G.

Structural and functional study of YER067W, a new protein involved in yeast metabolism control and drug resistance.

The genome of Saccharomyces cerevisiae is arguably the best studied eukaryotic genome, and yet, it contains approximately 1000 genes that are still relatively uncharacterized. As the majority of these ORFs have no homologs with characterized sequence or protein structure, traditional sequence-based approaches cannot be applied to deduce their biological function. Here, we characterize YER067W, a conserved gene of unknown function that is strongly induced in response to many stress conditions and repressed in drug resistant yeast strains.

A fluorescent mutant of the NM domain of the yeast prion Sup35 provides insight into fibril formation and stability.

The Sup35 protein of Saccharomyces cerevisiae forms a prion that generates the [PSI(+)] phenotype. Its NM region governs prion status, forming self-seeding amyloid fibers in vivo and in vitro. A tryptophan mutant of Sup35 (NM(F117W)) was used to probe its aggregation.

A mouse forward genetics screen identifies LISTERIN as an E3 ubiquitin ligase involved in neurodegeneration.

A mouse neurological mutant, lister, was identified through a genome-wide N-ethyl-N-nitrosourea (ENU) mutagenesis screen. Homozygous lister mice exhibit profound early-onset and progressive neurological and motor dysfunction. lister encodes a RING finger protein, LISTERIN, which functions as an E3 ubiquitin ligase in vitro.

Overexpression of the aldose reductase GRE3 suppresses lithium-induced galactose toxicity in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, lithium induces a 'galactosemia-like' phenotype as a consequence of inhibition of phosphoglucomutase, a key enzyme in galactose metabolism. Induced galactose toxicity is prevented by deletion of GAL4, which inhibits the transcriptional activation of genes involved in galactose metabolism and by deletion of the galactokinase (GAL1), indicating that galactose-1-phosphate, a phosphorylated intermediate of the Leloir pathway, is the toxic compound. As an alternative to inhibiting entry and metabolism of galactose, we investigated whether deviation of galactose metabolism from the Leloir pathway would also overcome the galactosemic effect of lithium.