Lack of robustness of life extension associated with several single-gene P element mutations in Drosophila melanogaster

The Neuronal Overexpression of Gclc in Drosophila melanogaster Induces Life Extension With Longevity-Associated Transcriptomic Changes in the Thorax

Some effects of aging in animals are tissue-specific. In D. melanogaster neuronal overexpression of Gclc increases lifespan and improves certain physiological parameters associated with health benefits such as locomotor activity, circadian rhythmicity, and stress resistance. Our previous transcriptomic analyses of Drosophila heads, primarily composed of neuronal tissue, revealed significant changes in expression levels of genes involved in aging-related signaling pathways (Jak-STAT, MAPK, FOXO, Notch, mTOR, TGF-beta), translation, protein processing in endoplasmic reticulum, proteasomal degradation, glycolysis, oxidative phosphorylation, apoptosis, regulation of circadian rhythms, differentiation of neurons, synaptic plasticity, and transmission. Considering that various tissues age differently and age-related gene expression changes are tissue-specific, we investigated the effects of neuronal Gclc overexpression on gene expression levels in the imago thorax, which is primarily composed of muscles. A total of 58 genes were found to be differentially expressed between thoraces of control and Gclc overexpressing flies. The Gclc level demonstrated associations with expression of genes involved in the circadian rhythmicity, the genes in categories related to the muscle system process and the downregulation of genes involved in proteolysis. Most of the functional categories altered by Gclc overexpression related to metabolism including Drug metabolism, Metabolism of xenobiotics by cytochrome P450, Glutathione metabolism, Starch and sucrose metabolism, Citrate cycle (TCA cycle), One carbon pool by folate. Thus, the transcriptomic changes caused by neuron-specific Gclc overexpression in the thorax were less pronounced than in the head and affected pathways also differed from previous results. Although these pathways don't belong to the canonical longevity pathways, we suggest that they could participate in the delay of aging of Gclc overexpressing flies.

Regulation of protein function by reversible methionine oxidation and the role of selenoprotein MsrB1

SIGNIFICANCE

Protein structure and function can be regulated via post-translational modifications by numerous enzymatic and nonenzymatic mechanisms. Regulation involving oxidation of sulfur-containing residues emerged as a key mechanism of redox control. Unraveling the participants and principles of such regulation is necessary for understanding the biological significance of redox control of cellular processes.

RECENT ADVANCES

Reversible oxidation of methionine residues by monooxygenases of the Mical family and subsequent reduction of methionine sulfoxides by a selenocysteine-containing methionine sulfoxide reductase B1 (MsrB1) was found to control the assembly and disassembly of actin in mammals, and the Mical/MsrB pair similarly regulates actin in fruit flies. This finding has opened up new avenues for understanding the use of stereospecific methionine oxidation in regulating cellular processes and the roles of MsrB1 and Micals in regulation of actin dynamics.

CRITICAL ISSUES

So far, Micals have been the only known partners of MsrB1, and actin is the only target. It is important to identify additional substrates of Micals and characterize other Mical-like enzymes.

FUTURE DIRECTIONS

Oxidation of methionine, reviewed here, is an emerging but not well-established mechanism. Studies suggest that methionine oxidation is a form of oxidative damage of proteins, a modification that alters protein structure or function, a tool in redox signaling, and a mechanism that controls protein function. Understanding the functional impact of reversible oxidation of methionine will require identification of targets, substrates, and regulators of Micals and Msrs. Linking the biological processes, in which these proteins participate, might also lead to insights into disease conditions, which involve regulation of actin by Micals and Msrs.

Herbal supplement extends life span under some environmental conditions and boosts stress resistance

Genetic studies indicate that aging is modulated by a great number of genetic pathways. We have used Drosophila longevity and stress assays to test a multipath intervention strategy. To carry out this strategy, we supplemented the flies with herbal extracts (SC100) that are predicted to modulate the expression of many genes involved in aging and stress resistance, such as mTOR, NOS, NF-KappaB, and VEGF. When flies were housed in large cages with SC100 added, daily mortality rates of both male and female flies were greatly diminished in mid to late life. Surprisingly, SC100 also stabilized midlife mortality rate increases so as to extend the maximum life span substantially beyond the limits previously reported for D. melanogaster. Under these conditions, SC100 also promoted robust resistance to partial starvation stress and to heat stress. Fertility was the same initially in both treated and control flies, but it became significantly higher in treated flies at older ages as the fertility of control flies declined. Mean and maximum life spans of flies in vials at the same test site were also extended by SC100, but the life spans were short in absolute terms. In contrast, at an independent test site where stress was minimized, the flies exhibited much longer mean life spans, but the survival curves became highly rectangular and the effects of SC100 on both mean and maximum life spans declined greatly or were abolished. The data indicate that SC100 is a novel herbal mix with striking effects on enhancing Drosophila stress resistance and life span in some environments, while minimizing mid to late life mortality rates. They also show that the environment and other factors can have transformative effects on both the length and distribution of survivorship, and on the ability of SC100 to extend the life span.