The overlapping roles of manganese and Cu/Zn SOD in oxidative stress protection

Abstract

In various organisms, high intracellular manganese provides protection against oxidative damage through unknown pathways. Herein we use a genetic approach in S. cerevisiae to analyze factors that promote manganese as an anti-oxidant in cells lacking Cu/Zn superoxide dismutase (sod1Δ). Unlike certain bacterial systems [1], oxygen resistance in yeast correlates with high intracellular manganese without a lowering of iron. This manganese for anti-oxidant protection is provided by the Nramp transporters Smf1p and Smf2p, with Smf1p playing a major role. In fact, loss of manganese transport by Smf1p together with loss of the Pmr1p manganese pump is lethal to sod1Δ cells in spite of normal manganese SOD2 activity. Manganese-phosphate complexes are excellent superoxide dimustase mimics in vitro [2], yet through genetic disruption of phosphate transport and storage, we observed no requirement for phosphate in manganese suppression of oxidative damage. If anything, elevated phosphate correlated with profound oxidative stress in sod1Δ mutants. The efficacy of manganese as an anti-oxidant was drastically reduced in cells that hyper-accumulate phosphate without effects on MnSOD activity. Non-SOD manganese can provide a critical backup for Cu/Zn SOD1, but only under appropriate physiologic conditions.

Probing in vivo Mn2+speciation and oxidative stress resistance in yeast cells with electron-nuclear double resonance spectroscopy

“…To alter phosphate levels specifically, we targeted the Vph1p subunit of the vacuolar ATPase, needed for phosphate accumulation (4,25), and the Pho85p kinase, which negatively controls phosphate uptake and storage (25)(26)(27). As shown in Table 1, the resulting vph1 and pho85 strains respectively exhibit a fourfold decrease and an eightfold increase in cellular Pi, polyphosphate (pP), and total phosphates concentrations, with negligible changes in manganese concentrations.…”

“…For instance, the sod1 pmr1 mutant has the greatest [Mn-Pi] concentration and is most resistant to oxygen stress, whereas the sod1 smf2 and sod1 pho85 mutants have the smallest [Mn-Pi] and are most sensitive to oxygen. It is important to note that without the application of ENDOR spectroscopy, one might have reached the opposite conclusion based on the analytical results, namely, that in vivo manganesePi interactions do not correlate with oxidative stress resistance (4). The present use of ENDOR to probe whole-cell Mn 2þ speciation, which allows us to distinguish between Mn 2þ -Pi and Mn 2þ -pP, thus reveals the potential hazard of assuming a transition metal speciation based on altered total cellular concentrations of a given ligand, thereby highlighting the importance of in situ biophysical techniques to probe metal speciation.…”

Superoxide Dismutase Mimics: Chemistry, Pharmacology, and Therapeutic Potential

“…We also showed that 1 mM Mn 2þ offers some radioprotection to ataxia telangiectasia cells, but is significantly less efficient than 1 mM of a more potent SOD mimic, Mn porphyrin MnTnHex-2-PyP 5þ (255 (193). The role of Mn transporters also was addressed, and carboxylates rather than phosphates were suggested as possible ligand carriers for Mn 2þ (267). Data by Reddi et al (267) are in agreement with our study, in which Mn oxo=hydroxo=acetato complexes, present as a non-innocent impurity in ill-purified MnTBAP 3À preparations, are responsible for the SOD-like activity (264 , and particularly when mechanistic purposes are the goal of the study, it is important to have Mn-based antioxidants very pure and devoid of ''free'', residual Mn 2þ in any form.…”

Endogeous sulfur dioxide protects against oleic acid-induced acute lung injury in association with inhibition of oxidative stress in rats

“…31 In most tissues, the first line of defense against oxidative stress is the endogenous antioxidant defense system such as SODs: SOD1 in the cytoplasm, SOD2 in mitochondria, and SOD3 in the extracellular space. 32 Furthermore, free radical insult might activate PARP and culminate in an apoptotic cascade. 33 Caspase-3 is a potent, terminal caspase that executes apoptosis.…”