SummaryOxidative stress is reputed to be a significant contributor to the aging process and a key factor affecting species longevity. The tremendous natural variation in maximum species lifespan may be due to interspecific differences in reactive oxygen species generation, antioxidant defenses and/or levels of accrued oxidative damage to cellular macromolecules (such as DNA, lipids and proteins). The present study tests if the exceptional longevity of the longest living (> 28.3 years) rodent species known, the naked mole-rat (NMR, Heterocephalus glaber ), is associated with attenuated levels of oxidative stress. We compare antioxidant defenses (reduced glutathione, GSH), redox status (GSH/GSSG), as well as lipid (malondialdehyde and isoprostanes), DNA (8-OHdG), and protein (carbonyls) oxidation levels in urine and various tissues from both mole-rats and similar-sized mice. Significantly lower GSH and GSH/GSSG in mole-rats indicate poorer antioxidant capacity and a surprisingly more pro-oxidative cellular environment, manifested by 10-fold higher levels of in vivo lipid peroxidation. Furthermore, mole-rats exhibit greater levels of accrued oxidative damage to lipids (twofold), DNA (~two to eight times) and proteins (1.5 to 2-fold) than physiologically age-matched mice, and equal to that of same-aged mice. Given that NMRs live an order of magnitude longer than predicted based on their body size, our findings strongly suggest that mechanisms other than attenuated oxidative stress explain the impressive longevity of this species.

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Altered structure, and hence function, of cellular macromolecules caused by oxidation can contribute to loss of physiological function with age. Here, we tested whether the lifespan of bats, which generally live far longer than predicted by their size, could be explained by reduced protein damage relative to short-lived mice. We show significantly lower protein oxidation (carbonylation) in Mexican free-tailed bats (Tadarida brasiliensis) relative to mice, and a trend for lower oxidation in samples from cave myotis bats (Myotis velifer) relative to mice. Both species of bat show in vivo and in vitro resistance to protein oxidation under conditions of acute oxidative stress. These bat species also show low levels of protein ubiquitination in total protein lysates along with reduced proteasome activity, suggesting diminished protein damage and removal in bats. Lastly, we show that bat-derived protein fractions are resistant to urea-induced protein unfolding relative to the level of unfolding detected in fractions from mice. Together, these data suggest that long lifespan in some bat species might be regulated by very efficient maintenance of protein homeostasis.

SUMMARY Type 2 diabetes Mellitus (T2DM) and aging are characterized by insulin resistance, lower mitochondrial density and function and increased production of reactive oxygen species (ROS). In lower organisms continuous remodeling critically maintains the function and life cycle of mitochondria, in part by the protease pcp1 (PARL ortholog). We therefore examined whether variation in PARL protein content is associated with mitochondrial abnormalities and insulin resistance. Relative to healthy, young individuals (23±1y), PARL mRNA and mitochondrial mass were both reduced in elderly subjects (64.4±1.2 y; 51% and 44% respectively) and in subjects with T2DM (51.8±3 y; 31% and 41% respectively; all p<0.05). Muscle knock-down of PARL in mice resulted in lower mitochondrial content (−31±3%, p<0.05), lower OPA1 and PGC1α protein levels and impaired insulin signaling. Furthermore, mitochondrial cristae were malformed and resulted in elevated in vivo oxidative stress. Adenoviral suppression of PARL protein in healthy myotubes lowered mitochondrial mass (−33±8%), insulin stimulated glycogen synthesis (−33±9%) and increased ROS production (2-fold) (all p<0.05). We propose that lower PARL expression may contribute to the mitochondrial abnormalities seen in aging and T2DM.

Rapamycin, an inhibitor of target-of-rapamycin, extends lifespan in mice, possibly by delaying aging. We recently showed that rapamycin halts the progression of Alzheimer's (AD)-like deficits, reduces amyloid-beta (Ab) and induces autophagy in the human amyloid precursor protein (PDAPP) mouse model. To delineate the mechanisms by which chronic rapamycin delays AD we determined proteomic signatures in brains of control-and rapamycin-treated PDAPP mice. Proteins with reported chaperone-like activity were overrepresented among proteins up-regulated in rapamycin-fed PDAPP mice and the master regulator of the heatshock response, heat-shock factor 1, was activated. This was accompanied by the up-regulation of classical chaperones/ heat shock proteins (HSPs) in brains of rapamycin-fed PDAPP mice. The abundance of most HSP mRNAs except for alpha B-crystallin, however, was unchanged, and the capdependent translation inhibitor 4E-BP was active, suggesting that increased expression of HSPs and proteins with chaperone activity may result from preferential translation of pre-existing mRNAs as a consequence of inhibition of cap-dependent translation. The effects of rapamycin on the reduction of Ab, up-regulation of chaperones, and amelioration of AD-like cognitive deficits were recapitulated by transgenic over-expression of heat-shock factor 1 in PDAPP mice. These results suggest that, in addition to inducing autophagy, rapamycin preserves proteostasis by increasing chaperones. We propose that the failure of proteostasis associated with aging may be a key event enabling AD, and that chronic inhibition of target-of-rapamycin may delay AD by maintaining proteostasis in brain.

CHO cells are the most prevalent platform for modern bio-therapeutic production. Currently, there are several CHO cell lines used in bioproduction with distinct characteristics and unique genotypes and phenotypes. These differences limit advances in productivity and quality that can be achieved by the most common approaches to bioprocess optimization and cell line engineering. Incorporating omics-based approaches into current bioproduction processes will complement traditional methodologies to maximize gains from CHO engineering and bioprocess improvements. In order to highlight the utility of omics technologies in CHO bioproduction, the authors discuss current applications as well as limitations of genomics, transcriptomics, proteomics, metabolomics, lipidomics, fluxomics, glycomics, and multi-omics approaches and the potential they hold for the future of bioproduction. Multiple omics approaches are currently being used to improve CHO bioprocesses; however, the application of these technologies is still limited. As more CHO-omic datasets become available and integrated into systems models, the authors expect significant gains in product yield and quality. While individual omics technologies provide incremental improvements in bioproduction, the authors will likely see the most significant gains by applying multi-omics and systems biology approaches to individual CHO cell lines.

The naked mole-rat maintains robust proteostasis and high levels of proteasome-mediated proteolysis for most of its exceptional (~31y) life span. Here, we report that the highly active proteasome from the naked mole-rat liver resists attenuation by a diverse suite of proteasome-specific small molecule inhibitors. Moreover, mouse, human, and yeast proteasomes exposed to the proteasome-depleted, naked mole-rat cytosolic fractions, recapitulate the observed inhibition resistance, and mammalian proteasomes also show increased activity. Gel filtration coupled with mass spectrometry and atomic force microscopy indicates that these traits are supported by a protein factor that resides in the cytosol. This factor interacts with the proteasome and modulates its activity. Although HSP72 and HSP40 (Hdj1) are among the constituents of this factor, the observed phenomenon, such as increasing peptidase activity and protecting against inhibition cannot be reconciled with any known chaperone functions. This novel function may contribute to the exceptional protein homeostasis in the naked mole-rat and allow it to successfully defy aging.

It is proposed that conformational changes induced in proteins by oxidation can lead to loss of activity or protein aggregation through exposure of hydrophobic residues and alteration in surface hydrophobicity. Because increased oxidative stress and protein aggregation are consistently observed in amyotrophic lateral sclerosis (ALS), we used a 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid (BisANS) photolabeling approach to monitor changes in protein unfolding in vivo in skeletal muscle proteins in ALS mice. We find two major proteins, creatine kinase (CK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), conformationally affected in the ALS G93A mouse model concordant with a 43% and 41% reduction in enzyme activity, respectively. This correlated with changes in conformation and activity that were detected in CK and GAPDH with in vitro oxidation. Interestingly, we found that GAPDH, but not CK, is conformationally and functionally affected in a longer-lived ALS model (H46R/H48Q), exhibiting a 22% reduction in enzyme activity. We proposed a reaction mechanism for BisANS with nucleophilic amino acids such as lysine, serine, threonine, and tyrosine, and BisANS was found to be primarily incorporated to lysine residues in GAPDH. We identified the specific BisANS incorporation sites on GAPDH in nontransgenic (NTg), G93A, and H46R/H48Q mice using liquid chromatography-tandem mass spectrometry analysis. Four BisANS-containing sites (K52, K104, K212, and K248) were found in NTg GAPDH, while three out of four of these sites were lost in either G93A or H46R/H48Q GAPDH. Conversely, eight new sites (K2, K63, K69, K114, K183, K251, S330, and K331) were found on GAPDH for G93A, including one common site (K114) for H46R/H48Q, which is not found on GAPDH from NTg mice. These data show that GAPDH is differentially affected structurally and functionally in vivo in accordance with the degree of oxidative stress associated with these two models of ALS.