Protein homeostasis and molecular chaperones in aging

Protection against Aβ-induced neuronal damage by KU-32: PDHK1 inhibition as important target

A feature of most neurodegenerative diseases is the presence of "mis-folded proteins" that form aggregates, suggesting suboptimal activity of neuronal molecular chaperones. Heat shock protein 90 (Hsp90) is the master regulator of cell responses to "proteotoxic" stresses. Some Hsp90 modulators activate cascades leading to upregulation of additional chaperones. Novobiocin is a modulator at the C-terminal ATP-binding site of Hsp90. Of several novobiocin analogs synthesized and tested for protection against amyloid beta (Aβ)-induced neuronal death, "KU-32" was the most potent in protecting primary neurons, but did not increase expression of other chaperones believed to help clear misfolded proteins. However, KU-32 reversed Aβ-induced superoxide formation, activated Complex I of the electron transfer chain in mitochondria, and blocked the Aβ-induced inhibition of Complex I in neuroblastoma cells. A mechanism for these effects of KU-32 on mitochondrial metabolism appeared to be the inhibition of pyruvate dehydrogenase kinase (PDHK), both in isolated brain mitochondria and in SH-SY5Y cells. PDHK inhibition by the classic enzyme inhibitor, dichloroacetate, led to neuroprotection from Aβ25-35-induced cell injury similarly to KU-32. Inhibition of PDHK in neurons would lead to activation of the PDH complex, increased acetyl-CoA generation, stimulation of the tricarboxylic acid cycle and Complex I in the electron transfer chain, and enhanced oxidative phosphorylation. A focus of future studies may be on the potential value of PDHK as a target in AD therapy.

Contribution of Extracellular Vesicles and Molecular Chaperones in Age-Related Neurodegenerative Disorders of the CNS

Many neurodegenerative disorders are characterized by the abnormal aggregation of misfolded proteins that form amyloid deposits which possess prion-like behavior such as self-replication, intercellular transmission, and consequent induction of native forms of the same protein in surrounding cells. The distribution of the accumulated proteins and their correlated toxicity seem to be involved in the progression of nervous system degeneration. Molecular chaperones are known to maintain proteostasis, contribute to protein refolding to protect their function, and eliminate fatally misfolded proteins, prohibiting harmful effects. However, chaperone network efficiency declines during aging, prompting the onset and the development of neurological disorders. Extracellular vesicles (EVs) are tiny membranous structures produced by a wide range of cells under physiological and pathological conditions, suggesting their significant role in fundamental processes particularly in cellular communication. They modulate the behavior of nearby and distant cells through their biological cargo. In the pathological context, EVs transport disease-causing entities, including prions, α-syn, and tau, helping to spread damage to non-affected areas and accelerating the progression of neurodegeneration. However, EVs are considered effective for delivering therapeutic factors to the nervous system, since they are capable of crossing the blood-brain barrier (BBB) and are involved in the transportation of a variety of cellular entities. Here, we review the neurodegeneration process caused mainly by the inefficiency of chaperone systems as well as EV performance in neuropathies, their potential as diagnostic biomarkers and a promising EV-based therapeutic approach.

Protein homeostasis in aging and cancer

Aging is a major risk factor for cancer development. As dysfunction in protein homeostasis, or proteostasis, is a universal hallmark of both the aging process and cancer, a comprehensive understanding of the proteostasis system and its roles in aging and cancer will shed new light on how we can improve health and quality of life for older individuals. In this review, we summarize the regulatory mechanisms of proteostasis and discuss the relationship between proteostasis and aging and age-related diseases, including cancer. Furthermore, we highlight the clinical application value of proteostasis maintenance in delaying the aging process and promoting long-term health.

Natural compounds in the regulation of proteostatic pathways: An invincible artillery against stress, ageing, and diseases

Cells have different sets of molecules for performing an array of physiological functions. Nucleic acids have stored and carried the information throughout evolution, whereas proteins have been attributed to performing most of the cellular functions. To perform these functions, proteins need to have a unique conformation and a definite lifespan. These attributes are achieved by a highly coordinated protein quality control (PQC) system comprising chaperones to fold the proteins in a proper three-dimensional structure, ubiquitin-proteasome system for selective degradation of proteins, and autophagy for bulk clearance of cell debris. Many kinds of stresses and perturbations may lead to the weakening of these protective cellular machinery, leading to the unfolding and aggregation of cellular proteins and the occurrence of numerous pathological conditions. However, modulating the expression and functional efficiency of molecular chaperones, E3 ubiquitin ligases, and autophagic proteins may diminish cellular proteotoxic load and mitigate various pathological effects. Natural medicine and small molecule-based therapies have been well-documented for their effectiveness in modulating these pathways and reestablishing the lost proteostasis inside the cells to combat disease conditions. The present article summarizes various similar reports and highlights the importance of the molecules obtained from natural sources in disease therapeutics.

Post-translational modifications: Regulators of neurodegenerative proteinopathies

One of the hallmark features in the neurodegenerative disorders (NDDs) is the accumulation of aggregated and/or non-functional protein in the cellular milieu. Post-translational modifications (PTMs) are an essential regulator of non-functional protein aggregation in the pathogenesis of NDDs. Any alteration in the post-translational mechanism and the protein quality control system, for instance, molecular chaperone, ubiquitin-proteasome system, autophagy-lysosomal degradation pathway, enhances the accumulation of misfolded protein, which causes neuronal dysfunction. Post-translational modification plays many roles in protein turnover rate, accumulation of aggregate and can also help in the degradation of disease-causing toxic metabolites. PTMs such as acetylation, glycosylation, phosphorylation, ubiquitination, palmitoylation, SUMOylation, nitration, oxidation, and many others regulate protein homeostasis, which includes protein structure, functions and aggregation propensity. Different studies demonstrated the involvement of PTMs in the regulation of signaling cascades such as PI3K/Akt/GSK3β, MAPK cascade, AMPK pathway, and Wnt signaling pathway in the pathogenesis of NDDs. Further, mounting evidence suggests that targeting different PTMs with small chemical molecules, which acts as an inhibitor or activator, reverse misfolded protein accumulation and thus enhances the neuroprotection. Herein, we briefly discuss the protein aggregation and various domain structures of different proteins involved in the NDDs, indicating critical amino acid residues where PTMs occur. We also describe the implementation and involvement of various PTMs on signaling cascade and cellular processes in NDDs. Lastly, we implement our current understanding of the therapeutic importance of PTMs in neurodegeneration, along with emerging techniques targeting various PTMs.

Voluntary aerobic exercise increases arterial resilience and mitochondrial health with aging in mice

Mitochondrial dysregulation and associated excessive reactive oxygen species (mtROS) production is a key source of oxidative stress in aging arteries that reduces baseline function and may influence resilience (ability to withstand stress). We hypothesized that voluntary aerobic exercise would increase arterial resilience in old mice. An acute mitochondrial stressor (rotenone) caused greater (further) impairment in peak carotid EDD in old (~27 mo., OC, n=12; -32.5±-10.5%) versus young (~7 mo., YC n=11; -5.4±- 3.7%) control male mice, whereas arteries from young and old exercising (YVR n=10 and OVR n=11, 10-wk voluntary running; -0.8±-2.1% and -8.0±4.9%, respectively) mice were protected. Ex-vivo simulated Western diet (WD, high glucose and palmitate) caused greater impairment in EDD in OC (-28.5±8.6%) versus YC (-16.9±5.2%) and YVR (-15.3±2.3%), whereas OVR (-8.9±3.9%) were more resilient (not different versus YC). Simultaneous ex-vivo treatment with mitochondria-specific antioxidant MitoQ attenuated WD-induced impairments in YC and OC, but not YVR or OVR, suggesting that exercise improved resilience to mtROS-mediated stress. Exercise normalized age-related alterations in aortic mitochondrial protein markers PGC-1α, SIRT-3 and Fis1 and augmented cellular antioxidant and stress response proteins. Our results indicate that arterial aging is accompanied by reduced resilience and mitochondrial health, which are restored by voluntary aerobic exercise.

Zinc nanoparticles potentiates thermal tolerance and cellular stress protection of Pangasius hypophthalmus reared under multiple stressors

A preliminary study was conducted to delineate the ameliorating effect of dietary zinc nanoparticles (Zn-NPs) against thermal stress in Pangasius hypophthalmus reared under concurrent exposure to lead (Pb) and elevated temperature (34°C). Three diets were formulated such as control (no Zn-NPs), Zn-NPs 10 and 20mg/kg diet. Two hundred and thirty four fish were randomly distributed in to six treatments groups in triplicates; such as control group (no Zn-NPs in diet and unexposed to Pb and temperature, Ctr/Ctr), control diet with concurrent exposure to Pb and temperature (Pb-T/Ctr), Zn-NPs 10 and 20mg/kg without stressors (Zn-NPs 10mg/kg, Zn-NPs 20mg/kg), Zn-NPs 10 and 20mg/kg diet with concurrent exposure to Pb and temperature (Pb-T/Zn-NPs 10mg/kg, Pb-T/Zn-NPs 20mg/kg). The Pb in treated water was maintained at the level of 1/21th of LC₅₀ (4ppm) at 34 °C temperature in stressors groups. Post 60 days feeding trial, critical thermal minimum (CTmin), lethal thermal minimum (LTmin), and critical thermal maximum (CTmax), lethal thermal maximum (LTmax) and biochemical attributes on P. hypophthalmus were evaluated. The results indicated that, dietary supplementation of Zn-NPs increased the CTmin, LTmin and CTmax, LTmax in P. hypophthalmus. Positive correlations were observed between CTmin LTmin (Y = - 0.495 + 10.08x, R², 0.896) and CTmax LTmax (Y = - 0.872 + 4.43x, R², 0.940). At the end of the thermal tolerance study, oxidative stress and lipid peroxidation (LPO) were significantly reduced and neurotransmitter enzyme was significantly increased in the groups fed with Zn-NPs @ 10mg and 20mg/kg diet. Overall results indicated that dietary Zn-NPs can confer protection against thermal stress in P. hypophthalmus.

Expression of cellular protective proteins SIRT1, HSP70 and SOD2 correlates with age and is significantly higher in NK cells of the oldest seniors

Background

NK cells are key effector lymphocytes of innate immunity provided with constitutive cytolytic activity, however, their role in human ageing is not entirely understood. The study aimed to analyze the expression of proteins involved in cellular stress response sirtuin 1 (SIRT1), heat shock protein 70 (HSP70) and manganese superoxide dismutase (SOD2) in non-stimulated NK cells of the oldest seniors (n = 25; aged over 85; mean age 88 years) and compare with NK cells of the old (n = 30; aged under 85; mean age 76 years) and the young (n = 32; mean age 21 years) to find potential relationships between the level of expression of these proteins in NK cells and longevity. The concentration of carbonyl groups and 8-isoprostanes in NK cell lysates reflecting the level of oxidative stress was also measured.

Results

The group of the oldest seniors differed from the other age groups by significantly higher percentage of NK cells expressing SIRT1, HSP70 and SOD2. The concentration of both carbonyl groups and 8-isoprostanes in NK cell extracts remained within the normal range in all age groups. The percentage of NK cells with the expression of, respectively, SIRT1, HSP70 and SOD2 correlated positively with age. Some correlations between expression levels of particular protective proteins SIRT1, HSP70 and SOD2 were observed in the study population.

Conclusions

The increased expression of cellular protective proteins SIRT1, HSP70 and SOD2 in NK cells of the oldest seniors seems to correspond to longevity and the observed correlations may suggest the involvement of these proteins in establishing NK cell homeostasis specific for healthy ageing process.

Specific protein homeostatic functions of small heat-shock proteins increase lifespan

During aging, oxidized, misfolded, and aggregated proteins accumulate in cells, while the capacity to deal with protein damage declines severely. To cope with the toxicity of damaged proteins, cells rely on protein quality control networks, in particular proteins belonging to the family of heat‐shock proteins (HSPs). As safeguards of the cellular proteome, HSPs assist in protein folding and prevent accumulation of damaged, misfolded proteins. Here, we compared the capacity of all Drosophila melanogaster small HSP family members for their ability to assist in refolding stress‐denatured substrates and/or to prevent aggregation of disease‐associated misfolded proteins. We identified CG14207 as a novel and potent small HSP member that exclusively assisted in HSP70‐dependent refolding of stress‐denatured proteins. Furthermore, we report that HSP67BC, which has no role in protein refolding, was the most effective small HSP preventing toxic protein aggregation in an HSP70‐independent manner. Importantly, overexpression of both CG14207 and HSP67BC in Drosophila leads to a mild increase in lifespan, demonstrating that increased levels of functionally diverse small HSPs can promote longevity in vivo.

Naked mole-rat has increased translational fidelity compared with the mouse, as well as a unique 28S ribosomal RNA cleavage

The naked mole-rat (Heterocephalus glaber) is a subterranean eusocial rodent with a markedly long lifespan and resistance to tumorigenesis. Multiple data implicate modulation of protein translation in longevity. Here we report that 28S ribosomal RNA (rRNA) of the naked mole-rat is processed into two smaller fragments of unequal size. The two breakpoints are located in the 28S rRNA divergent region 6 and excise a fragment of 263 nt. The excised fragment is unique to the naked mole-rat rRNA and does not show homology to other genomic regions. Because this hidden break site could alter ribosome structure, we investigated whether translation rate and amino acid incorporation fidelity were altered. We report that naked mole-rat fibroblasts have significantly increased translational fidelity despite having comparable translation rates with mouse fibroblasts. Although we cannot directly test whether the unique 28S rRNA structure contributes to the increased fidelity of translation, we speculate that it may change the folding or dynamics of the large ribosomal subunit, altering the rate of GTP hydrolysis and/or interaction of the large subunit with tRNA during accommodation, thus affecting the fidelity of protein synthesis. In summary, our results show that naked mole-rat cells produce fewer aberrant proteins, supporting the hypothesis that the more stable proteome of the naked mole-rat contributes to its longevity.

Aging and diets regulate the rat anterior pituitary and hypothalamic transcriptome

Dietary interventions involving caloric restriction represent a powerful strategy to prevent or delay age-related deteriorations and diseases. Their beneficial effects have been observed in several tissues and species. This microarray study investigated the effects of aging, long-term moderate caloric restriction (LTMCR) and long-term dietary soy on the regulation of gene expression in the anterior pituitary and hypothalamus of 20-month-old Sprague-Dawley rats. In both tissues, aging regulated genes mainly involved in cell defense and repair mechanisms related to apoptosis, DNA repair, cellular stress, inflammatory and immune response. In the aging pituitary, the highest upregulated gene was the regenerating islet-derived 3β (5.77-fold), coding for a secretory protein involved in acute stress and inflammation. A protective effect of LTMCR on age-related change of gene expression was observed for 35 pituitary genes. In addition, beneficial effects of LTMCR in the pituitary were observed on new regulated genes mainly involved in cell death and cell stress response. In the hypothalamus, the effects of LTMCR on age-related changes were modest. Finally, changing the quality of dietary protein (20% casein for soy) had a low impact on the regulation of mRNA levels in both tissues. Genes associated with the somatotroph function were also differentially expressed in the aging pituitary. Interestingly, LTMCR prevented the effect of aging on insulin-like growth factor-binding protein-3 gene. Altogether, this study proposes novel pituitary and hypothalamic molecular targets and signaling pathways to help in understanding the mechanisms involved in aging processes and LTMCR.

The role of stress and anxiety in the onset of familial Creutzfeldt-Jakob Disease (CJD): review

Creutzfeldt-Jakob Disease (CJD) is considered to be a sudden and fatal degenerative brain disorder that leads to death within a few months. In the last decade, we have studied the course of familial CJD (fCJD) among Jews of Libyan descent, one of the largest clusters of fCJD in the world. Recently, we published results that included the identification of abnormal anxiety levels in healthy CJD E200K mutation carriers that were significantly different from those of healthy non-carriers from the same families. All participants were first-degree relatives of patients known to have been carriers of the E200K mutation and had died from CJD, and none of the participants was aware of his/her genetic make-up. In the current review, it is suggested that an abnormality in anxiety levels among the healthy fCJD mutation carriers may reflect the clinical presentation of the disease onset especially during and after any stressful experience. This hypothesis is supported by a summary of relevant literature, dealing with psychological, physiological, and cellular aspects.

Endocrine regulation of heat shock protein mRNA levels in long-lived dwarf mice

Heat shock proteins (HSPs) maintain proteostasis and may protect against age-associated pathology caused by protein malfolding. In Caenorhabditis elegans, the lifespan extension and thermotolerance in mutants with impaired insulin/IGF signals depend partly on HSP elevation. Less is known about the role of HSPs in the increased lifespan of mice with defects in GH/IGF-I pathways. We measured HSP mRNAs in liver, kidney, heart, lung, muscle and cerebral cortex from long-lived Pit1(dw/dw) Snell dwarf mice. We found many significant differences in HSP mRNA levels between dwarf and control mice, but these effects were complex and organ-specific. We noted 15 instances where HSP mRNAs were lower in Pit1(dw/dw) liver, kidney, or heart tissues, and 14/15 of these were also seen in Ghr(-/-) mice, which lack GH receptor. In contrast, of 12 examples where HSP mRNAs were higher in Snell liver, kidney, or heart, none were altered in Ghr(-/-) mice. Four liver mRNAs were depressed in both Pit1(dw/dw) and Ghr(-/-) mice, and each of these was elevated by GH injection in Ames (Prop1(df/df)) dwarf mice, consistent with the hypothesis that these declines depended on GH and/or IGF-I. Contributions of chaperones to longevity in mice may be more complex than those inferred from C. elegans.

Resveratrol induces the heat-shock response and protects human cells from severe heat stress

Molecular chaperones play key roles in protein quality control, signal transduction, proliferation, and cell death, and confer cytoprotection and assure survival after environmental stress. The heat-shock response is implicated in a variety of conditions including ischemic diseases, infection and immunity, neurodegeneration, and aging. Physiologic and pharmacologic chaperone inducers were shown to be an efficient therapeutic approach in different acute and chronic diseases. Here we characterize resveratrol, a polyphenol from red wine, as an inducer of the heat-shock response. Resveratrol activated the heat-shock promoter and the expression of the major chaperone Hsp70 in cell lines and in human peripheral lymphocytes, comparable to moderate heat stress. This effect was not due to its antioxidant property, because 5 mM N-acetylcysteine was unable to activate the heat-shock response. Moreover, resveratrol failed to upregulate Grp78, and tunicamycin was unable to induce Hsp70, suggesting that the resveratrol-induced heat-shock response was not mediated by canonic endoplasmic reticulum stress. Resveratrol synergized with mild to moderate heat shock and conferred cytoprotection against severe heat stress. Our results reveal resveratrol as a chaperone inducer that may contribute to its pleiotropic effects in ameliorating stress and promoting longevity.

Protein microchips in biomedicine and biomarker discovery

Protein microarray technology is of high recent interest, especially for generating confirmatory and complementary information for transcriptomic studies. In this paper, the advantages, technical limitations, main application fields, and some early results of protein microarrays are reviewed. Today protein microchip technology is mostly available in the form of printed glass slides, bioaffinity surfaces, and tissue microarray (TMA)-based techniques. The advantages of glass slide-based microchips are the simplicity of their application and their relatively low cost. Affinity surface-based protein chip techniques are applicable to minute amounts of starting material (< 1 microg), but interrogation of these chips requires expensive instrumentation, such as mass spectrometers. TMAs are useful for parallel testing of antibody specificities on a broad range of histological specimens in a single slide. Protein microarrays have been successfully implemented for serum tumor marker profiling, cell physiology studies, and mRNA expression study verification. Some of the bottlenecks of the technology are protein instability, problems with nonspecific interactions, and the lack of amplification techniques to generate sufficient amounts of the lower abundance proteins. In spite of the current difficulties, protein microchips are envisioned to be available for routine biomedical and diagnostic applications provided that the ongoing technological developments are successful in improving sensitivity, specificity, and reducing costs.

Protein stress and stress proteins: implications in aging and disease

Environmental stress induces damage that activates an adaptive response in any organism. The cellular stress response is based on the induction of cytoprotective proteins,the so called stress or heat shock proteins. The stress response as well as stress proteins are ubiquitous,highly conserved mechanism, and genes, respectively, already present in prokaryotes. Chaperones protect the proteome against conformational damage, promoting the function of protein networks. Protein damage takes place during aging and in several degenerative diseases, and presents a threat to overload the cellular defense mechanisms. The preservation of a robust stress response and protein disposal is indispensable for health and longevity. This review summarizes the present knowledge of protein damage, turnover, and the stress response in aging and degenerative diseases.

Low-level caloric restriction rescues proteasome activity and Hsc70 level in liver of aged rats

Proteasome activity is known to decrease with aging in ad libitum (AL) fed rats. Severe caloric restriction (CR) significantly extends the maximum life-span of rats, and counteracts the age-associated decrease in liver proteasome activities. Since few investigations have explored whether lower CR diets might positively counteract the age associated decrease in proteasome activity, we then investigated the effects of a mild CR regimen on animal life-span, proteasome content and function. In addition, we addressed the question whether both CR regimens might also affect the expression of Hsc70 protein, a constitutive chaperone reported to share a role in the function of proteasome complex and in the repair of proteotoxic damage, and whose level decreased during aging. In contrast to severe CR, mild CR had a poor effect on life-span; however, it better counteracted the decrease of proteasome activities. Both regimens, however, maintain Hsc70 in liver of old rats at level comparable to that of young rats. Interestingly, the effects of aging and CRs on liver proteasome enzyme activities did not appear to be associated with parallel changes in the amount of proteasome proteins suggesting that the quality (molecular activity of the enzymes) rather than the quantity are likely to be modified with age. In conclusion, the results presented in this work show that a mild CR can have beneficial effects on liver function of aging rats because is adequate to counteract the decrease of proteasome function and Hsc70 chaperone level.

[Theoretical foundations of protein chips and their possible use in medical research and diagnostics]

The confirmation of mRNA expression studies by protein chips is of high recent interest due to the widespread application of expression arrays. In this review the advantages, technical limitations, application fields and the first results of the protein arrays is described. The bottlenecks of the increasing protein array applications are the fast decomposition of proteins, the problem with aspecific binding and the lack of amplification techniques. Today glass slide based printed, SELDI (MS) based, electrophoresis based and tissue microarray based technologies are available. The advantage of the glass slide based chips are the simplicity of their application, and relatively low cost. The SELDI based protein chip technique is applicable to minute amounts of starting material (<1 microg) but it is the most expensive one. The electrophoresis based techniques are still under intensive development. The tissue microarrays can be used for the parallel testing of the sensitivity and specificity of single antibodies on a broad range of histological specimens on a single slide. Protein chips were successfully used for serum tumor marker detection, cancer research, cell physiology studies and for the verification of mRNA expression studies. Protein chips are envisioned to be available for routine diagnostic applications if the ongoing technology development will be successful in increase in sensitivity, specificity, costs reduction and for the reduction of the necessary sample volume.

Chaperonopathies and chaperonotherapy

The study of molecular chaperones (genetics, structure, location, physiology, pathology, and therapeutics) has developed into a science with specific objectives, methods, and hypotheses, a discipline we called chaperonology. Subdisciplines of chaperonology include the study of pathological chaperones (chaperonopathies) and the analysis of their genes in sequenced genomes (chaperonomics). Chaperonopathies are pathological conditions in which one type of chaperone is deficient due to a genetic or acquired defect that modifies the chaperone's structure and/or makes the chaperone unavailable for functioning when needed. Experimental and clinical data show that chaperones and their genes can be used for treating various pathological conditions, thus justifying the development of chaperonotherapy. We discuss recent work showing that chaperonotherapy is on solid foundations: the data demonstrate that molecular chaperones counteract pathogenetic mechanisms in disease and during stress.

Molecular Chaperones and the Epigenetics of Longevity and Cancer Resistance

The inherent immortality of embryonic stem cells demonstrates that replicative senescence as possibly the aging of species are epigenetic phenomena. The cellular level of expression of the housekeeping molecular chaperones correlates with longevity and cancer resistance of species. The chaperones are cancer antagonists by acting as genetic buffers, stabilizing the normal phenotype. Probably the progressive age-related silencing of the housekeeping genes contributes to the phenotype of aging, with the associated increase in cancer incidence. The present review concerns epigenetic chemical, immunological, and hormonal mechanisms, activating chaperone- and immune-response genes, which have proved effective in increasing longevity and cancer resistance. The relation of steroid hormone levels to species longevity, the anticarcinogenic activity of pregnancy hormones, and the influence of hormones on the longevity of social insects, illustrates the importance of hormonal mechanisms for the activation of longevity genes.

On why decreasing protein synthesis can increase lifespan

An explanation is offered for the increased lifespan of Caenorhabditis elegans when mRNA translation is inhibited due to loss of the initiation factor IFE-2 [Hansen, M., Taubert, T., Crawford, D., Libina, N., Lee, S.-J., Kenyon, C., 2007. Lifespan extension by conditions that inhibit translation in Caenorhabditis elegans. Ageing Cell 6, 95-110; Pan, K.Z., Palter, J.E., Rogers, A.N., Olsen, A., Chen, D., Lithgow, G.J., Kapahi, P., 2007. Inhibition of mRNA translation extends lifespan in Caenorhabditis elegans. Ageing Cell 6, 111-119; Syntichaki, P., Troulinaki, K., Tavernarakis, N., 2007. eIF4E function in somatic cells modulates ageing in Caenorhabditis elegans. Nature 445, 922-926]. It is suggested that the general reduction of protein synthesis, due to the decreased frequency of mRNA translation, also lowers the cellular load of erroneously synthesized polypeptides which the constitutive protein homeostatic apparatus (proteases and chaperones proteins) normally eliminates. This situation results in "spare" proteolytic and chaperone function which can then deal with those proteins modified post-synthetically, e.g. by oxidation and/or glycation, which are thought to contribute to the senescent phenotype. This increased availability of proteolytic and chaperone functions may thereby contribute to the observed increase in organism stress resistance and lifespan.