Protein Homoeostasis Research Articles

ARD1-mediated Hsp70 acetylation balances stress-induced protein refolding and degradation.

Heat shock protein (Hsp)70 is a molecular chaperone that maintains protein homoeostasis during cellular stress through two opposing mechanisms: protein refolding and degradation. However, the mechanisms by which Hsp70 balances these opposing functions under stress conditions remain unknown. Here, we demonstrate that Hsp70 preferentially facilitates protein refolding after stress, gradually switching to protein degradation via a mechanism dependent on ARD1-mediated Hsp70 acetylation. During the early stress response, Hsp70 is immediately acetylated by ARD1 at K77, and the acetylated Hsp70 binds to the co-chaperone Hop to allow protein refolding. Thereafter, Hsp70 is deacetylated and binds to the ubiquitin ligase protein CHIP to complete protein degradation during later stages. This switch is required for the maintenance of protein homoeostasis and ultimately rescues cells from stress-induced cell death in vitro and in vivo. Therefore, ARD1-mediated Hsp70 acetylation is a regulatory mechanism that temporally balances protein refolding/degradation in response to stress.

N-3 Fatty acids preserve muscle mass and insulin sensitivity in a rat model of energy restriction.

In obese subjects, the loss of fat mass during energy restriction is often accompanied by a loss of muscle mass. The hypothesis that n-3 PUFA, which modulate protein homoeostasis via effects on insulin sensitivity, could contribute to maintain muscle mass during energy restriction was tested in rats fed a high-fat diet (4 weeks) rich in 18 : 1 n-9 (oleic acid, OLE-R), 18 : 3 n-3 (α-linolenic acid, ALA-R) or n-3 long-chain (LC-R) fatty acid and then energy restricted (8 weeks). A control group (OLE-ad libitum (AL)) was maintained with AL diet throughout the study. Rats were killed 10 min after an i.v. insulin injection. All energy-restricted rats lost weight and fat mass, but only the OLE-R group showed a significant muscle loss. The Gastrocnemius muscle was enriched with ALA in the ALA-R group and with LC-PUFA in the ALA-R and LC-R groups. The proteolytic ubiquitin-proteasome system was differentially affected by energy restriction, with MAFbx and muscle ring finger-1 mRNA levels being decreased in the LC-R group (-30 and -20 %, respectively). RAC-α serine/threonine-protein kinase and insulin receptor substrate 1 phosphorylation levels increased in the LC-R group (+70 %), together with insulin receptor mRNA (+50 %). The ALA-R group showed the same overall activation pattern as the LC-R group, although to a lesser extent. In conclusion, dietary n-3 PUFA prevent the loss of muscle mass associated with energy restriction, probably by an improvement in the insulin-signalling pathway activation, in relation to enrichment of plasma membranes in n-3 LC-PUFA.

Using the Ubiquitin-modified Proteome to Monitor Distinct and Spatially Restricted Protein Homeostasis Dysfunction

Protein homeostasis dysfunction has been implicated in the development and progression of aging related human pathologies. There is a need for the establishment of quantitative methods to evaluate global protein homoeostasis function. As the ubiquitin (ub) proteasome system plays a key role in regulating protein homeostasis, we applied quantitative proteomic methods to evaluate the sensitivity of site-specific ubiquitylation events as markers for protein homeostasis dysfunction. Here, we demonstrate that the ub-modified proteome can exceed the sensitivity of engineered fluorescent reporters as a marker for proteasome dysfunction and can provide unique signatures for distinct proteome challenges which is not possible with engineered reporters. We demonstrate that combining ub-proteomics with subcellular fractionation can effectively separate degradative and regulatory ubiquitylation events on distinct protein populations. Using a recently developed potent inhibitor of the critical protein homeostasis factor p97/VCP, we demonstrate that distinct insults to protein homeostasis function can elicit robust and largely unique alterations to the ub-modified proteome. Taken together, we demonstrate that proteomic approaches to monitor the ub-modified proteome can be used to evaluate global protein homeostasis and can be used to monitor distinct functional outcomes for spatially separated protein populations.

Dopamine helps worms deal with stress.

To maintain protein homoeostasis, animals have developed stress response pathways such as the ubiquitin proteasome system (UPS). Joshi and colleagues have demonstrated that in Caenorhabditis elegans, dopamine release from neurons acts on receptors in the epithelia to modulate protein turnover, by controlling the expression of regulators of the xenobiotic stress response. Dopamine receptor mutants challenged with pathogenic bacteria were defective in protein turnover and were also more sensitive to infection thus highlighting a role for monoamine signalling in innate immunity and stress responses.

Vacuolin-1 inhibits autophagy by impairing lysosomal maturation via PIKfyve inhibition.

Lysosomal protein degradation via autophagy strictly regulates cellular protein homoeostasis. Herein we performed high-content screening to identify compounds that inhibit autophagy pathways. We obtained 11 hit compounds and performed cluster analysis using cellular morphological information. Vacuolin-1, which induces the formation of giant vacuoles and is a target unknown compound, clustered with the known PIKfyve inhibitor YM201636. We further confirmed that vacuolin-1 is a potent PIKfyve inhibitor, and we finally concluded that PIKfyve inhibitors are novel chemical tools for regulating autophagy.

Uncommon functional properties of the first piscine 26S proteasome from the Antarctic notothenioid Trematomus bernacchii.

Protein homoeostasis is a fundamental process allowing the preservation of functional proteins and it has a great impact on the life of the Antarctic organisms. However, the effect of low temperatures on protein turnover is poorly understood and the cold-adaptation of the degradation machinery remains an unresolved issue. As the 26S proteasome represents the main proteolytic system devoted to the controlled degradation of intracellular proteins, the purpose of the present study was to investigate the functions of this complex in the notothenioid Trematomus bernacchii, in order to better understand its role in the physiology of Antarctic fish. To this aim, we purified and characterized the 26S proteasome from T. bernacchii and isolated the cDNAs codifying seven of the 14 subunits belonging to the proteasome 20S core particle. Results provided evidences of the high resistance of the piscine 26S proteasome to oxidative agents and of its 'uncommon' ability to efficiently hydrolyse oxidized bovine serum albumin (BSA), suggesting that this enzymatic complex could play a key role in the antioxidant defense systems in fish inhabiting permanently cold marine environments. These unique properties were also reflected by the 3D model analysis, which revealed a higher structural stability of the piscine complex respect to the murine template. Finally, a comparative analysis, performed in a variety of tissues collected from T. bernacchii and the temperate fish Dicentrarchus labrax, showed a lower protein retention in the cold-adapted fish, possibly due to a better efficiency of its degradation machinery.

The Hsp90 Chaperone Machinery: An Important Hub in Protein Interaction Networks

Heat shock protein 90 (Hsp90) represents one of the most conserved proteins in living organisms and is present in all kingdoms of life except for Archaea. HSP90 proteins define a widespread family of molecular chaperones that play a fundamental role in protein homoeostasis and viability. HSP90s mediate folding and maturation of a broad spectrum of client proteins including steroid hormone receptors, transcription factors, and protein kinases. HSP90s primarily exist as homodimers whose activity is regulated by ATP. Hsp90 can adopt different ATP-triggered conformations, ranging from an open V-shaped unliganded to a closed ATP-bound state. HSP90 chaperones can be found not only in the cytosol, ER, chloroplasts, mitochondria, and the nucleus but also in the extracellular milieu where they act as potent stimulators of immune responses. The activity of Hsp90 is regulated by post-translational modifications and its association with numerous co-chaperones and client proteins involved in signal transduction and transcriptional regulation. Elevated levels of HSP90s can be found in a broad spectrum of cancers where they enhance cell growth, suppress senescence, and confer resistance to stress-induced apoptosis, including protection against cytostatic drugs and radiation therapy. Since numerous oncoproteins are clients of Hsp90, targeting Hsp90 represents a useful anti-cancer approach. In this review, the current knowledge on the Hsp90 chaperone machinery and its role in disease and therapy is compiled.

Redox proteomics analysis to decipher the neurobiology of Alzheimer-like neurodegeneration: overlaps in Down's syndrome and Alzheimer's disease brain.

Accumulation of oxidative damage is a common feature of neurodegeneration that, together with mitochondrial dysfunction, point to the fact that reactive oxygen species are major contributors to loss of neuronal homoeostasis and cell death. Among several targets of oxidative stress, free-radical-mediated damage to proteins is particularly important in aging and age-related neurodegenerative diseases. In the majority of cases, oxidative-stress-mediated post-translational modifications cause non-reversible modifications of protein structure that consistently lead to impaired function. Redox proteomics methods are powerful tools to unravel the complexity of neurodegeneration, by identifying brain proteins with oxidative post-translational modifications that are detrimental for protein function. The present review discusses the current literature showing evidence of impaired pathways linked to oxidative stress possibly involved in the neurodegenerative process leading to the development of Alzheimer-like dementia. In particular, we focus attention on dysregulated pathways that underlie neurodegeneration in both aging adults with DS (Down's syndrome) and AD (Alzheimer's disease). Since AD pathology is age-dependent in DS and shows similarities with AD, identification of common oxidized proteins by redox proteomics in both DS and AD can improve our understanding of the overlapping mechanisms that lead from normal aging to development of AD. The most relevant proteomics findings highlight that disturbance of protein homoeostasis and energy production are central mechanisms of neurodegeneration and overlap in aging DS and AD. Protein oxidation affects crucial intracellular functions and may be considered a 'leitmotif' of degenerating neurons. Therapeutic strategies aimed at preventing/reducing multiple components of processes leading to accumulation of oxidative damage will be critical in future studies.

Protein folding, misfolding and quality control: the role of molecular chaperones.

Cells have to cope with stressful conditions and adapt to changing environments. Heat stress, heavy metal ions or UV stress induce damage to cellular proteins and disturb the balanced status of the proteome. The adjusted balance between folded and folding proteins, called protein homoeostasis, is required for every aspect of cellular functionality. Protective proteins called chaperones are expressed under extreme conditions in order to prevent aggregation of cellular proteins and safeguard protein quality. These chaperones co-operate during de novo folding, refolding and disaggregation of damaged proteins and in many cases refold them to their functional state. Even under physiological conditions these machines support protein homoeostasis and maintain the balance between de novo folding and degradation. Mutations generating unstable proteins, which are observed in numerous human diseases such as Alzheimer's disease, Huntington's disease, amyotrophic lateral sclerosis and cystic fibrosis, also challenge the protein quality control system. A better knowledge of how the protein homoeostasis system is regulated will lead to an improved understanding of these diseases and provide potential targets for therapy.

Plasmodial Hsp40 and Hsp70 chaperones: current and future perspectives

Plasmodium falciparum displays a large and remarkable variety of heat shock protein 40 family members (PfHsp40s). The majority of the PfHsp40s are poorly characterized, and although the functions of some of them have been suggested, their exact mechanism of action is still elusive and their interacting partners and client proteins are unknown. The P. falciparum heat shock protein 70 family members (PfHsp70s) have been more extensively characterized than the PfHsp40s, with certain members shown to function as molecular chaperones. However, little is known about the PfHsp70-PfHsp40 chaperone partnerships. There is mounting evidence that these chaperones are important not only in protein homoeostasis and cytoprotection, but also in protein trafficking across the parasitophorous vacuole (PV) and into the infected erythrocyte. We propose that certain members of these chaperone families work together to maintain exported proteins in an unfolded state until they reach their final destination. In this review, we critically evaluate what is known and not known about PfHsp40s and PfHsp70s.

Glycative stress and glyoxalase in kidney disease and aging

Glycation is one of the important reactions regulating physiological state, and glycative stress, namely an overwhelming and unfavourable glycation state, is established as a pathological factor. Glycative stress is closely associated with not only various kidney diseases, but also kidney aging. Accumulating evidence, including studies in my laboratory, demonstrates that progression of renal tubular damage and its aging is correlated with the decrease in the activity of anti-glycative stress enzyme Glo1 (glyoxalase I) in the kidney. The reduction of glycative and oxidative stresses by Glo1 overexpression is beneficial for prevention of kidney disease and treatment, suggesting the novel therapeutic approaches targeting Glo1. The present review is focused on the impact of glycative stress and Glo1 on protein homoeostasis and discusses further the cross-talk between glycative stress and UPR (unfolded protein response), which controls the protein homoeostasis state.

The effect of L-thyroxine substitution on lipid profile, glucose homeostasis, inflammation and coagulation in patients with subclinical hypothyroidism

Subclinical hypothyroidism (SH) is associated with increased risk for atherosclerosis, mainly attributable to dyslipidaemia and hypercoagulability. However, conflicting data exist regarding the effect of L-thyroxine substitution on these parameters. The purpose of this study was to assess the effect of L-thyroxine therapy on lipidaemic profile, coagulation markers, high-sensitivity C-reactive protein (hsCRP) and glucose homoeostasis in SH patients. It was a prospective open-label study. The following parameters were measured before and 6 months after intervention: anthropometric data, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), apolipoproteins B (apoB) and A1 (apoA1), lipoprotein (a) [Lp(a)], fasting plasma glucose and insulin, homoeostasis model assessment-insulin resistance (HOMA-IR), hsCRP, antithrombin III (AT-III), protein C (PC), protein S (PS), fibrinogen and homocysteine. Thirty-two patients (30 women) aged 52.1 ± 13.9 years with SH completed the study. Baseline mean TSH levels were 6.79 ± 2.58 mIU/ml. Achievement of euthyroidism significantly reduced systolic blood pressure (BP) in patients with SH (from 135.2 ± 18.5 to 129.7 ± 15.8 mmHg, p = 0.03) and diastolic BP only in those with baseline TSH levels > 7 mIU/ml (from 79.5 ± 9.8 to 72.1 ± 7.3 mmHg, p = 0.03). No significant changes in body weight, TC, LDL-C, HDL-C, TG, apoB, glucose, insulin, HOMA-IR, hsCRP, AT-III, PC, PS, fibrinogen or homocysteine levels were noticed after restoration of euthyroidism, except for a decrease in apoA1 (p = 0.04) and an increase in Lp(a) levels (p = 0.02). Except for a reduction in systolic and diastolic BP, thyroid substitution therapy does not affect lipidaemic profile, systematic inflammation, glucose homoeostasis or coagulation in patients with SH.

Decreased Thioredoxin-1 and Increased HSP90 Expression in Skeletal Muscle in Subjects with Type 2 Diabetes or Impaired Glucose Tolerance

In diabetes, the endogenous defence systems are overwhelmed, causing various types of stress in tissues. In this study, newly diagnosed or diet-treated type 2 diabetics (T2D) (n = 10) were compared with subjects with impaired glucose tolerance (IGT) (n = 8). In both groups, at resting conditions, blood samples were drawn for assessing metabolic indices and skeletal muscle samples (m. vastus lateralis) were taken for the measurements of cellular defence markers: thioredoxin-1 (TRX-1) and stress proteins HSP72, HSP90. The protein level of TRX-1 was 36.1% lower (P = 0.031) and HSP90 was 380% higher (P < 0.001) in the T2D than in the IGT subjects, with no significant changes in HSP72. However, after the adjustment of both analyses with HOMA-IR only HSP90 difference remained significant. In conclusion, level of TRX-1 in skeletal muscle tissue was lower while that of HSP90 was higher in T2D than in IGT subjects. This may impair antioxidant defence and lead to disruptions of protein homoeostasis and redox regulation of cellular defences. Because HSP90 may be involved in sustaining functional insulin signalling pathway in type 2 diabetic muscles and higher HSP90 levels can be a consequence of type 2 diabetes, our results are potentially important for the diabetes research.

Signal-peptide-mediated translocation is regulated by a p97–AIRAPL complex

Protein homoeostasis is a fundamental requirement for all living cells in order to survive in a dynamic surrounding. Proper levels of AIRAPL (arsenite-inducible RNA-associated protein-like protein) (ZFAND2B) are required in order to maintain cellular folding capacity in metazoans, and functional impairment of AIRAPL results in acceleration of aging and protein aggregation. However, the cellular roles of AIRAPL in this process are not known. In the present paper, we report that AIRAPL binds and forms a complex with p97 [VCP (valosin-containing protein)/Cdc48], Ubxd8 (ubiquitin regulatory X domain 8), Npl4-Ufd1, Derlin-1 and Bag6 on the ER (endoplasmic reticulum) membrane. In spite of the fact that AIRAPL complex partners are involved in the ERAD (ER-associated degradation) process, AIRAPL knockdown does not show any impairment in ERAD substrate degradation. However, translocation into the ER of a subset of ERAD- and non-ERAD-secreted proteins are regulated by AIRAPL. The ability to regulate translocation by the p97-AIRAPL complex is entirely dependent on the proteins' signal peptide. Our results demonstrate a p97 complex regulating translocation into the ER in a signal-peptide-dependent manner.

Molecular alterations in proteasomes of rat liver during aging result in altered proteolytic activities.

Aging induces alterations of tissue protein homoeostasis. To investigate one of the major systems catalysing intracellular protein degradation we have purified 20S proteasomes from rat liver of young (2 months) and aged (23 months) animals and separated them into three subpopulations containing different types of intermediate proteasomes with standard- and immuno-subunits. The smallest subpopulation ΙΙΙ and the major subpopulation Ι comprised proteasomes containing immuno-subunits β1i and β5i beside small amounts of standard-subunits, whereas proteasomes of subpopulation ΙΙ contained only β5i beside standard-subunits. In favour of a relative increase of the major subpopulation Ι, subpopulation ΙΙ and ΙΙΙ were reduced for about 55 % and 80 %, respectively, in aged rats. Furthermore, in all three 20S proteasome subpopulations from aged animals standard-active site subunits were replaced by immuno-subunits. Overall, this transformation resulted in a relative increase of immuno-subunit-containing proteasomes, paralleled by reduced activity towards short fluorogenic peptide substrates. However, depending on the substrate their hydrolysing activity of long polypeptide substrates was significantly higher or unchanged. Furthermore, our data revealed an altered MHC class I antigen-processing efficiency of 20S proteasomes from liver of aged rats. We therefore suggest that the age-related intramolecular alteration of hepatic proteasomes modifies its cleavage preferences without a general decrease of its activity. Such modifications could have implications on protein homeostasis as well as on MHC class I antigen presentation as part of the immunosenescence process.

Calpains in the cardiovascular system

This editorial refers to the following review articles in the issue which make up this Review Focus on Calpains in the Cardiovascular System: H. Sorimachi and Y. Ono, pp. 11–22; J. Inserte et al. pp. 23–31; M.A. Smith and R.G. Schnellmann, pp. 32–37; E. Letavernier et al. , pp. 38–45; O. Yamaguchi et al. , pp. 46–52. Although proteolytic systems have received much less attention than the processes controlling protein synthesis, their importance for maintaining cellular function is becoming increasingly recognized. Among them are the calpains, a large family of non-lysosomal calcium-dependent cysteine proteases. In contrast with other major proteolytic systems such as the proteasome and the lysosomal proteases that are degradative, calpains produce a limited proteolysis of specific substrates. Owing to their dependence on Ca2+, calpains have attracted much attention as modulators implicated in a wide variety of biological phenomena including proliferation, cell migration, differentiation, protein homoeostasis, and cell signalling.1–5 The genetic alterations in tissue-specific calpains are responsible for various diseases, providing solid evidence of the physiological importance of these enzymes.5,6 However, many reports have demonstrated that exaggerated calpain activation exacerbates those pathologies that are associated with the loss of …

Insulin and IGF-1 signalling: longevity, protein homoeostasis and Alzheimer's disease

The quality control of protein homoeostasis deteriorates with aging, causing the accumulation of misfolded proteins and neurodegeneration. Thus, in AD (Alzheimer's disease), soluble oligomers, protofibrils and fibrils of the Aβ (amyloid β-peptide) and tau protein accumulate in specific brain regions. This is associated with the progressive destruction of synaptic circuits controlling memory and higher mental function. The primary signalling mechanisms that (i) become defective in AD to alter the normal proteostasis of Aβ and tau, and (ii) initiate a pathophysiological response to cause cognitive decline, are unclear. The IIS [insulin/IGF-1 (insulin-like growth factor 1)-like signalling] pathway is mechanistically linked to longevity, protein homoeostasis, learning and memory, and is emerging to be central to both (i) and (ii). This pathway is aberrantly overactivated in AD brain at the level of increased activation of the serine/threonine kinase Akt and the phosphorylation of its downstream targets, including mTOR (mammalian target of rapamycin). Feedback inhibition of normal insulin/IGF activation of the pathway also occurs in AD due to inactivation of IRS-1 (insulin receptor substrate 1) and decreased IRS-1/2 levels. Pathogenic forms of Aβ may induce aberrant sustained activation of the PI3K (phosphoinositide 3-kinase)/Akt signal in AD, also causing non-responsive insulin and IGF-1 receptor, and altered tau phosphorylation, conformation and function. Reducing IIS activity in animal models by decreasing IGF-1R levels or inhibiting mTOR activity alters Aβ and tau protein homoeostasis towards less toxic protein conformations, improves cognitive function and extends healthy lifespan. Thus normalizing IIS dysfunction may be therapeutically relevant in abrogating Aβ and tau proteotoxicity, synaptic dysfunction and cognitive decline in AD.

EGF signalling activates the ubiquitin proteasome system to modulate C. elegans lifespan.

Epidermal growth factor (EGF) signalling regulates growth and differentiation. Here, we examine the function of EGF signalling in Caenorhabditis elegans lifespan. We find that EGF signalling regulates lifespan via the Ras-MAPK pathway and the PLZF transcription factors EOR-1 and EOR-2. As animals enter adulthood, EGF signalling upregulates the expression of genes involved in the ubiquitin proteasome system (UPS), including the Skp1-like protein SKR-5, while downregulating the expression of HSP16-type chaperones. Using reporters for global UPS activity, protein aggregation, and oxidative stress, we find that EGF signalling alters protein homoeostasis in adults by increasing UPS activity and polyubiquitination, while decreasing protein aggregation. We show that SKR-5 and the E3/E4 ligases that comprise the ubiquitin fusion degradation (UFD) complex are required for the increase in UPS activity observed in adults, and that animals that lack SKR-5 or the UFD have reduced lifespans and indications of oxidative stress. We propose that as animals enter fertile adulthood, EGF signalling switches the mechanism for maintaining protein homoeostasis from a chaperone-based approach to an approach involving protein elimination via augmented UPS activity.

K48‐ and K63‐linked polyubiquitination of deubiquitinating enzyme USP44

Ubiquitination and deubiquitination have a critical role in protein homoeostasis in the cell. Here, we have characterized a novel USP44 (ubiquitin-specific protease 44), which has a ZnF-UBP (zinc-finger ubiquitin-specific protease) domain and conserved cysteine, histidine and asparagine/aspartic acid residues characteristic of deubiquitinating enzymes. The biochemical assay revealed that USP44 can cleave ubiquitin from ubiquitinated substrates both in vitro and in vivo. Further, USP44 undergoes both lysine 48- and lysine 63-linked polyubiquitination. In situ hybridization using mouse tissues showed a basal detection level in all organs tested, with strong detection in lung, pancreas, skin, liver, stomach and intestine. RT-PCR (reverse-transcription PCR) analysis showed high levels of detection of USP44 mRNA in testis, spleen, lung, stomach and ovary. Furthermore, we raised a polyclonal antibody against USP44 and checked its endogenous protein expression in different cell lines. A localization study of USP44 showed its predominant expression in the nucleus.

Maternal protein restriction affects gene expression profiles in the kidney at weaning with implications for the regulation of renal function and lifespan

Nutritionally induced alterations in early growth can influence health and disease in later adult life. We have demonstrated previously that low birthweight resulting from maternal protein restriction during pregnancy followed by accelerated growth in rodents was associated with shortened lifespan, whereas protein restriction and slow growth during lactation increased lifespan. Thus early life events can also have a long lasting impact on longevity. In the present study, we show that long-lived PLP (postnatal low protein) mice were protected from developing albuminuria, whereas short-lived recuperated mice demonstrated an age-dependent increase in albuminuria in old age. Microarray analysis of kidneys from 21-day-old mice revealed that gene expression profiles were differentially affected depending on whether protein restriction was imposed during pregnancy or lactation. The differentially expressed genes were involved in diverse biological functions such as cytoprotective functions, vitamin D synthesis, protein homoeostasis, regulation of antioxidant enzymes and cellular senescence. Significantly, up-regulation of Hmox1 (haem oxygenase 1) in kidneys from PLP mice suggests that tissues of long-lived mice are equipped with a better cytoprotective function. In contrast, up-regulation of Nuak2 (NUAK family, SNF1-like kinase 2) and down-regulation of Lonp2 (Lon peptidase 2), Foxo3a (forkhead box O3a), Sod1 (copper/zinc superoxide dismutase) and Sesn1 (sestrin 1) in the kidneys of recuperated offspring suggest that protein homoeostasis and resistance to oxidative stress are compromised, leading to accelerated cellular senescence in these shorter-lived mice.