[The molecular bases for copper uptake and distribution: lessons from yeast]

High-affinity iron and calcium transport pathways are involved in U(VI) uptake in the budding yeast Saccharomyces cerevisiae

Uranium (U) is a naturally-occurring radionuclide that is toxic for all living organisms. To date, the mechanisms of U uptake are far from being understood. Here we provide a direct characterization of the transport machineries capable of transporting U, using the yeast Saccharomyces cerevisiae as a unicellular eukaryote model. First, we evidenced a metabolism-dependent U transport in yeast. Then, competition experiments with essential metals allowed us to identify calcium, iron and copper entry pathways as potential routes for U uptake. The analysis of various metal transport mutants revealed that mutant affected in calcium (mid1Δ and cch1Δ) and Fe(III) (ftr1Δ) transport, exhibited highly reduced U uptake rates and accumulation, demonstrating the implication of the calcium channel Mid1/Cch1 and the iron permease Ftr1 in U uptake. Finally, expression of the Mid1 gene into the mid1Δ mutant restored U uptake levels of the wild type strain, underscoring the central role of the Mid1/Cch1 calcium channel in U absorption process in yeast. Our results also open up the opportunity for rapid screening of U-transporter candidates by functional expression in yeast, before their validation in more complex higher eukaryote model systems.

She Has The Blues: An Unusual Case of Copper Sulphate Intoxication

BACKGROUND

Copper is an essential trace element of the human body. However, it is related to many diseases. Copper intoxication is not common in Western countries, but needs to be rapidly recognised because of its high lethality.

CASE PRESENTATION

We report the case of a 40-year-old woman who presented to the emergency department after performing intrarectal administration of a blue powder sent from Cameroon by her family, in the belief that this would help her to get pregnant. Her evolution was complicated by multiorgan failure and the unusual circumstances. The diagnosis was suspected on the basis of the clinical presentation and the colour of the powder, and confirmed by blood dosage and toxicological analysis of the powder. She underwent symptomatic treatment, and the outcome was progressively favourable, apart from persistent chronic renal failure with dependence on dialysis.

CONCLUSION

Copper intoxications are rare but severe. Laboratory diagnosis of the condition is not an issue; the difficulty is suspecting it and quickly initiating chelation treatment associated with symptomatic treatments.

LEARNING POINTS

Copper sulphate is a rare but severe condition that must be promptly diagnosed. Diagnosis may be based on clinical presentation, characterised by multiple organ failure, and suspected in the case of ingestion of a blue chemical product.In the presence of saturation gap on pulse oximetry, the clinician must consider the possibility of methemoglobinaemia, and look for toxic causes.Treatment of copper sulphate poisoning requires mainly symptomatic treatment and chelation of copper by oral or IV drugs.

Membrane lipid peroxidation in copper alloy-mediated contact killing of Escherichia coli

Copper alloy surfaces are passive antimicrobial sanitizing agents that kill bacteria, fungi, and some viruses. Studies of the mechanism of contact killing in Escherichia coli implicate the membrane as the target, yet the specific component and underlying biochemistry remain unknown. This study explores the hypothesis that nonenzymatic peroxidation of membrane phospholipids is responsible for copper alloy-mediated surface killing. Lipid peroxidation was monitored with the thiobarbituric acid-reactive substances (TBARS) assay. Survival, TBARS levels, and DNA degradation were followed in cells exposed to copper alloy surfaces containing 60 to 99.90% copper or in medium containing CuSO(4). In all cases, TBARS levels increased with copper exposure levels. Cells exposed to the highest copper content alloys, C11000 and C24000, exhibited novel characteristics. TBARS increased immediately at a very rapid rate but peaked at about 30 min. This peak was associated with the period of most rapid killing, loss in membrane integrity, and DNA degradation. DNA degradation is not the primary cause of copper-mediated surface killing. Cells exposed to the 60% copper alloy for 60 min had fully intact genomic DNA but no viable cells. In a fabR mutant strain with increased levels of unsaturated fatty acids, sensitivity to copper alloy surface-mediated killing increased, TBARS levels peaked earlier, and genomic DNA degradation occurred sooner than in the isogenic parental strain. Taken together, these results suggest that copper alloy surface-mediated killing of E. coli is triggered by nonenzymatic oxidative damage of membrane phospholipids that ultimately results in the loss of membrane integrity and cell death.