p66shc is highly expressed in fibroblasts from centenarians

The Role of p66Shc in Diabetes: A Comprehensive Review from Bench to Bedside

It is well-documented that diabetes is an inflammatory and oxidative disease, with an escalating global burden. Still, there is no definite treatment for diabetes or even prevention of its harmful complications. Therefore, understanding the molecular pathways associated with diabetes might help in finding a solution. p66Shc is a member of Shc family proteins, and it is considered as an oxidative stress sensor and regulator in cells. There are inconsistent data about the role of p66Shc in inducing diabetes, but accumulating evidence supports its role in the pathogenesis of diabetes-related complications, including macro and microangiopathies. There is growing hope that by understanding and targeting molecular pathways involved in this network, prevention of diabetes or its complications would be achievable. This review provides an overview about the role of p66Shc in the development of diabetes and its complications.

Interrelation between ROS and Ca2+ in aging and age-related diseases

Calcium (Ca2+) and reactive oxygen species (ROS) are versatile signaling molecules coordinating physiological and pathophysiological processes. While channels and pumps shuttle Ca2+ ions between extracellular space, cytosol and cellular compartments, short-lived and highly reactive ROS are constantly generated by various production sites within the cell. Ca2+ controls membrane potential, modulates mitochondrial adenosine triphosphate (ATP) production and affects proteins like calcineurin (CaN) or calmodulin (CaM), which, in turn, have a wide area of action. Overwhelming Ca2+ levels within mitochondria efficiently induce and trigger cell death. In contrast, ROS comprise a diverse group of relatively unstable molecules with an odd number of electrons that abstract electrons from other molecules to gain stability. Depending on the type and produced amount, ROS act either as signaling molecules by affecting target proteins or as harmful oxidative stressors by damaging cellular components. Due to their wide range of actions, it is little wonder that Ca2+ and ROS signaling pathways overlap and impact one another. Growing evidence suggests a crucial implication of this mutual interplay on the development and enhancement of age-related disorders, including cardiovascular and neurodegenerative diseases as well as cancer.

The Mitochondria-Endoplasmic Reticulum Contacts and Their Critical Role in Aging and Age-Associated Diseases

The recent discovery of interconnections between the endoplasmic reticulum (ER) membrane and those of almost all the cell compartments is providing novel perspectives for the understanding of the molecular events underlying cellular mechanisms in both physiological and pathological conditions. In particular, growing evidence strongly supports the idea that the molecular interactions occurring between ER and mitochondrial membranes, referred as the mitochondria (MT)-ER contacts (MERCs), may play a crucial role in aging and in the development of age-associated diseases. As emerged in the last decade, MERCs behave as signaling hubs composed by structural components that act as critical players in different age-associated disorders, such as neurodegenerative diseases and motor disorders, cancer, metabolic syndrome, as well as cardiovascular diseases. Age-associated disorders often derive from mitochondrial or ER dysfunction as consequences of oxidative stress, mitochondrial DNA mutations, accumulation of misfolded proteins, and defective organelle turnover. In this review, we discuss the recent advances associating MERCs to aging in the context of ER-MT crosstalk regulating redox signaling, ER-to MT lipid transfer, mitochondrial dynamics, and autophagy.

Modulation of Obesity and Insulin Resistance by the Redox Enzyme and Adaptor Protein p66Shc

Initially reported as a longevity-related protein, the 66 kDa isoform of the mammalian Shc1 locus has been implicated in several metabolic pathways, being able to act both as an adaptor protein and as a redox enzyme capable of generating reactive oxygen species (ROS) when it localizes to the mitochondrion. Ablation of p66^Shc has been shown to be protective against obesity and the insurgence of insulin resistance, but not all the studies available in the literature agree on these points. This review will focus in particular on the role of p66^Shc in the modulation of glucose homeostasis, obesity, body temperature, and respiration/energy expenditure. In view of the obesity and diabetes epidemic, p66^Shc may represent a promising therapeutic target with enormous implications for human health.

Mitochondria-associated membranes in aging and senescence: structure, function, and dynamics

Sites of close contact between mitochondria and the endoplasmic reticulum (ER) are known as mitochondria-associated membranes (MAM) or mitochondria-ER contacts (MERCs), and play an important role in both cell physiology and pathology. A growing body of evidence indicates that changes observed in the molecular composition of MAM and in the number of MERCs predisposes MAM to be considered a dynamic structure. Its involvement in processes such as lipid biosynthesis and trafficking, calcium homeostasis, reactive oxygen species production, and autophagy has been experimentally confirmed. Recently, MAM have also been studied in the context of different pathologies, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, type 2 diabetes mellitus and GM1-gangliosidosis. An underappreciated amount of data links MAM with aging or senescence processes. In the present review, we summarize the current knowledge of basic MAM biology, composition and action, and discuss the potential connections supporting the idea that MAM are significant players in longevity.

Resveratrol Pretreatment Attenuates Concanavalin A-induced Hepatitis through Reverse of Aberration in the Immune Response and Regenerative Capacity in Aged Mice

Loss of regenerative capacity plays a critical role in age-related autoimmune hepatitis. Evidence implicates SIRT1 and p66^shc in cell senescence, apoptosis, oxidative stress, and proliferation. This study investigated the effect of resveratrol on concanavalin A (Con A)-induced hepatitis in aged mice and the roles of SIRT1 and p66^shc. Aged mice were administrated resveratrol (30 mg/kg orally) seven times at an interval of 12 h before a single intravenous injection of Con A (20 mg/kg). Results showed that the cytokines, TNF-α, IL-6, IFN-γ, and MCP-1, as well as infiltration of macrophages, neutrophils, and T lymphocytes in liver were dramatically enhanced in the mice given only Con A. The aged mouse livers showed markedly raised oxidative stress and cell apoptosis. This oxidative stress further aggravated regenerative dysfunction as indicated by the decreased levels of Ki67, PCNA, Cyclin D1, and Cdk2. Conversely, these phenomena were attenuated by pretreatment with resveratrol. Moreover, resveratrol suppressed the elevation of p66^shc in the liver by reversing Con-A-mediated downregulation of SIRT1. The findings suggest that resveratrol protected against Con A-induced hepatitis in aged mice by attenuating an aberration of immune response and liver regeneration, partially via the mechanism of SIRT1-mediated repression of p66^shc expression.

Ageing, metabolism and cardiovascular disease

Age is one of the major risk factors associated with cardiovascular disease (CVD). About one-fifth of the world population will be aged 65 or older by 2030, with an exponential increase in CVD prevalence. It is well established that environmental factors (overnutrition, smoking, pollution, sedentary lifestyles) may lead to premature defects in mitochondrial functionality, insulin signalling, endothelial homeostasis and redox balance, fostering early senescent features. Over the last few years, molecular investigations have unveiled common signalling networks which may link the ageing process with deterioration of cardiovascular homeostasis and metabolic disturbances, namely insulin resistance. These different processes seem to be highly interconnected and their interplay may favour adverse vascular and cardiac phenotypes responsible for myocardial infarction, stroke and heart failure. In the present review, we carefully describe novel molecular cues underpinning ageing, metabolism and CVD. In particular, we describe a dynamic interplay between emerging pathways such as FOXOs, AMPK, SIRT1, p66(Shc) , JunD and NF-kB. This overview will provide the background for attractive molecular targets to prevent age-driven pathology in the vasculature and the heart.

Molecular pathways of arterial aging

The incidence of stroke and myocardial infarction increases in aged patients and it is associated with an adverse outcome. Considering the aging population and the increasing incidence of cardiovascular disease, the prediction for population well-being and health economics is daunting. Accordingly, there is an unmet need to focus on fundamental processes underlying vascular aging. A better understanding of the pathways leading to arterial aging may contribute to design mechanism-based therapeutic approaches to prevent or attenuate features of vascular senescence. In the present review, we discuss advances in the pathophysiology of age-related vascular dysfunction including nitric oxide signalling, dysregulation of oxidant/inflammatory genes, epigenetic modifications and mechanisms of vascular calcification as well as insights into vascular repair. Such an overview highlights attractive molecular targets for the prevention of age-driven vascular disease.

The influence of Shc proteins on life span in mice

The signaling molecule p66Shc is often described as a longevity protein. This conclusion is based on a single life span study that used a small number of mice. The purpose of the present studies was to measure life span in a sufficient number of mice to determine if longevity is altered in mice with decreased Shc levels (ShcKO). Studies were completed at UC Davis and the European Institute of Oncology (EIO). At UC Davis, male C57BL/6J WT and ShcKO mice were fed 5% or 40% calorie-restricted (CR) diets. In the 5% CR group, there was no difference in survival curves between genotypes. There was also no difference between genotypes in prevalence of neoplasms or other measures of end-of-life pathology. At 40% calorie restriction group, 70th percentile survival was increased in ShcKO, while there were no differences between genotypes in median or subsequent life span measures. At EIO, there was no increase in life span in ShcKO male or female mice on C57BL/6J, 129Sv, or hybrid C57BL/6J-129Sv backgrounds. These studies indicate that p66Shc is not a longevity protein. However, additional studies are needed to determine the extent to which Shc proteins may influence the onset and severity of specific age-related diseases.

Oxidative stress and vascular inflammation in aging

Vascular aging, a determinant factor for cardiovascular disease and health status in the elderly, is now viewed as a modifiable risk factor. Impaired endothelial vasodilation is a early hallmark of arterial aging that precedes the clinical manifestations of vascular dysfunction, the first step to cardiovascular disease and influencing vascular outcomes in the elderly. Accordingly, the preservation of endothelial function is thought to be an essential determinant of healthy aging. With special attention on the effects of aging on the endothelial function, this review is focused on the two main mechanisms of aging-related endothelial dysfunction: oxidative stress and inflammation. Aging vasculature generates an excess of the reactive oxygen species (ROS), superoxide and hydrogen peroxide, that compromise the vasodilatory activity of nitric oxide (NO) and facilitate the formation of the deleterious radical, peroxynitrite. Main sources of ROS are mitochondrial respiratory chain and NADPH oxidases, although NOS uncoupling could also account for ROS generation. In addition, reduced antioxidant response mediated by erythroid-2-related factor-2 (Nrf2) and downregulation of mitochondrial manganese superoxide dismutase (SOD2) contributes to the establishment of chronic oxidative stress in aged vessels. This is accompanied by a chronic low-grade inflammatory phenotype that participates in defective endothelial vasodilation. The redox-sensitive transcription factor, nuclear factor-κB (NF-κB), is upregulated in vascular cells from old subjects and drives a proinflammatory shift that feedbacks oxidative stress. This chronic NF-κB activation is contributed by increased angiotensin-II signaling and downregulated sirtuins and precludes adequate cellular response to acute ROS generation. Interventions targeted to recover endogenous antioxidant capacity and cellular stress response rather than exogenous antioxidants could reverse oxidative stress-inflammation vicious cycle in vascular aging. Lifestyle attitudes such as caloric restriction and exercise training appear as effective ways to overcome defective antioxidant response and inflammation, favoring successful vascular aging and decreasing the risk for cardiovascular disease.

Redox modification of proteins as essential mediators of CNS autophagy and mitophagy

Production of cellular reactive oxygen species (ROS) is typically associated with protein and DNA damage, toxicity, and death. However, ROS are also essential regulators of signaling and work in concert with redox-sensitive proteins to regulate cell homeostasis during stress. In this review, we focus on the redox regulation of mitophagy, a process that contributes to energetic tone as well as mitochondrial form and function. Mitophagy has been increasingly implicated in diseases including Parkinson's, Amyotrophic Lateral Sclerosis, and cancer. Although these disease states employ different genetic mutations, they share the common factors of redox dysregulation and autophagic signaling. This review highlights key redox sensitive signaling molecules which can enhance neuronal survival by promoting temporally and spatially controlled autophagic signaling and mitophagy.

P66Shc-rac1 pathway-mediated ROS production and cell migration is downregulated by ascorbic acid

The oxidative role(s) of p66Shc protein has been increasingly expanded over the last decade. However, its relation with the most potent antioxidant molecule, i.e. ascorbic acid has never been studied. We have previously shown that p66Shc mediates rac1 activation, reactive oxygen species (ROS) production and cell death. Here we studied the effect of ascorbic acid on the pathway involving p66Shc and rac1. Our results indicate a decrease in the expression of p66Shc in a dose- and time-dependent manner. We studied the effect of ascorbic acid on rac1 expression and its activity. Ascorbic acid has no effect on total rac1 expression; however, rac1 activation was inhibited in a dose-dependent manner. Results suggest that the decrease in rac1 activity is mediated through ascorbic acid-modulated p66Shc expression. The decrease in rac1 activity was evident in cells transfected with the p66shc mutant (proline motif mutant, at residues P47 to P50). Our studies indicate that p66Shc-mediated ROS upregulation is significantly decreased in the presence of ascorbic acid. Cell migration experiments point towards the inhibition of p66Shc-rac1-mediated migration in the presence of ascorbic acid. Finally, results are suggestive that ascorbic acid-mediated decrease in Shc expression occurs through an increased Shc ubiquitination. Overall, the study brings out the novel role of ascorbic acid in antioxidant signal transduction.

Reactive oxygen species induced by p66Shc longevity protein mediate nongenomic androgen action via tyrosine phosphorylation signaling to enhance tumorigenicity of prostate cancer cells

Steroid hormones exhibit diverse biological activities. Despite intensive studies on steroid function at the genomic level, their nongenomic actions remain an enigma. In this study, we investigated the role of reactive oxygen species (ROS) in androgen-stimulated prostate cancer (PCa) cell proliferation. In androgen-treated PCa cells, increased cell growth and ROS production correlated with elevated p66Shc protein, an authentic oxidase. This growth stimulation was blocked by antioxidants. Further, elevated expression of p66Shc protein by cDNA transfection encoding wild-type protein, but not a redox-deficient (W134F) mutant, was associated with increased PCa cell proliferation. Conversely, knockdown of p66Shc expression by shRNA resulted in diminished cell growth. Increased p66Shc expression in PCa cells enhanced their tumorigenicity in xenograft animals. Importantly, p66Shc protein level is higher in clinical prostate adenocarcinomas than in adjacent noncancerous cells. Expression of redox-deficient p66Shc mutant protein abolished androgen-stimulated cell growth. In androgen-treated, H(2)O(2)-treated, and p66Shc cDNA-transfected PCa cells, cellular prostatic acid phosphatase, an authentic tyrosine phosphatase, was inactivated by reversible oxidation; subsequently, ErbB-2 was activated by phosphorylation at tyrosine-1221/1222. These results together support the notion that androgens induce ROS production through the elevation of p66Shc protein, which inactivates tyrosine phosphatase activity for the activation of interacting tyrosine kinase, leading to increased cell proliferation and enhanced tumorigenicity. Our results thus suggest that p66Shc protein functions at the critical junction point between androgens and tyrosine phosphorylation signaling in human PCa cells.

Ischemic preconditioning: the role of mitochondria and aging

Aging represents a triple threat for myocardial infarction (MI). Not only does the incidence of MI increase with age, but the heart becomes more susceptible to MI induced damage and protective interventions such as ischemic preconditioning (IPC) become less effective. Therefore, any rational therapeutic strategy must be built around the ability to combat the detrimental effects of ischemia in aged individuals. To accomplish this, we need to develop a better understanding of how ischemic damage, protection, and aging are linked. In this regard, mitochondria have emerged as a common theme. First, mitochondria contribute to cell damage during ischemia-reperfusion (IR) and are central to cell death. Second, the protective signaling pathways activated by IPC converge on mitochondria, and the opening of mitochondrial ion channels alone is sufficient to elicit protection. Finally, mitochondria clearly influence the aging process, and specific defects in mitochondrial activity are associated with age-related functional decline. This review will summarize the effects of aging on myocardial IR injury and discuss relevant and emerging strategies to protect against MI with an emphasis on mitochondrial function.

p66Shc aging protein in control of fibroblasts cell fate

Reactive oxygen species (ROS) are wieldy accepted as one of the main factors of the aging process. These highly reactive compounds modify nucleic acids, proteins and lipids and affect the functionality of mitochondria in the first case and ultimately of the cell. Any agent or genetic modification that affects ROS production and detoxification can be expected to influence longevity. On the other hand, genetic manipulations leading to increased longevity can be expected to involve cellular changes that affect ROS metabolism. The 66-kDa isoform of the growth factor adaptor Shc (p66Shc) has been recognized as a relevant factor to the oxygen radical theory of aging. The most recent data indicate that p66Shc protein regulates life span in mammals and its phosphorylation on serine 36 is important for the initiation of cell death upon oxidative stress. Moreover, there is strong evidence that apart from aging, p66Shc may be implicated in many oxidative stress-associated pathologies, such as diabetes, mitochondrial and neurodegenerative disorders and tumorigenesis. This article summarizes recent knowledge about the role of p66Shc in aging and senescence and how this protein can influence ROS production and detoxification, focusing on studies performed on skin and skin fibroblasts.

Hemodialysis induces p66(shc) gene expression in nondiabetic humans: correlations with oxidative stress and systemic inflammation

OBJECTIVE

Oxidative stress and inflammation characterize hemodialysis (HD) and are associated with malnutrition, cardiovascular disease, and poor clinical outcome. p66(shc) stimulates oxidative stress and atherogenesis. The objective of the present study was to assess p66(shc) expression levels in HD and their associations with inflammatory and oxidative stress markers.

DESIGN

p66(shc) messenger ribonucleic acid (mRNA) was compared with systemic oxidative stress and inflammation markers in control subjects and patients on HD before and after a single HD session in a cross-sectional analysis.

SETTING

Outpatient hemodialysis unit.

PATIENTS

The study included stable HD patients (n = 21, men/women: 18/3) who were on HD 3 times per week for a minimum of 8 weeks; age-matched control subjects (n = 22, men/women:17/5).

MAIN OUTCOME MEASURE

mRNA levels of p66(shc), tumor necrosis factor α (TNF-α), and pentraxin 3 (PTX3), p66(shc) protein levels in white blood cells, lipid peroxidation (in the form of plasma thiobarbituric acid-reactive substance [TBARS]) and serum C-reactive protein.

RESULTS

In patients on dialysis, of the p66(shc), TNF-α, and PTX3 mRNAs, p66(shc) protein levels were higher (P < .05) than in control subjects, as well as plasma TBARS and C-reactive protein (P < .05). p66(shc) mRNA directly correlated with TBARS (r = 0.69, P = .0005) and with TNF-α mRNA (r = 0.63, P = .003). These associations were confirmed in the whole study population (TBARS: r = 0.541, P = .0003; TNF-α: r = 0.581, P < .0001), whereas in the control group only the positive association between p66(shc) and TNF-α was detected. TNF-α was directly correlated with PTX3 both in HD patients (r = 0.72, P = .0005) and in the whole study group (r = 0.678, P < .0001). The dialysis session affected neither p66(shc) and TNF-α mRNA nor p66(shc) protein expression, whereas it further increased (P = .002) PTX3 mRNA. As compared with predialysis levels, TBARS were reduced (P < .05) after dialysis. In these conditions, p66(shc) remained directly correlated with TNF-α (r = 0.901, P < .0001).

CONCLUSIONS

Increased p66(shc) gene expression correlates with TNF-α mRNA and with levels of markers of oxidative stress in HD. We suggest a novel link between HD-associated inflammation and p66(shc) gene expression contributing to systemic oxidative stress.

IP(3) Receptors, Mitochondria, and Ca Signaling: Implications for Aging

The tight interplay between endoplasmic-reticulum-(ER-) and mitochondria-mediated Ca(2+) signaling is a key determinant of cellular health and cellular fate through the control of apoptosis and autophagy. Proteins that prevent or promote apoptosis and autophagy can affect intracellular Ca(2+) dynamics and homeostasis through binding and modulation of the intracellular Ca(2+)-release and Ca(2+)-uptake mechanisms. During aging, oxidative stress becomes an additional factor that affects ER and mitochondrial function and thus their role in Ca(2+) signaling. Importantly, mitochondrial dysfunction and sustained mitochondrial damage are likely to underlie part of the aging process. In this paper, we will discuss the different mechanisms that control intracellular Ca(2+) signaling with respect to apoptosis and autophagy and review how these processes are affected during aging through accumulation of reactive oxygen species.

The Lifespan-regulator p66Shc in mitochondria: redox enzyme or redox sensor?

Mitochondria contribute to various diseases and aging phenotypes. Reactive oxygen species (ROS), mainly formed by the respiratory chain, were long thought to cause these effects by damaging proteins, DNA, and lipids. The emerging understanding that ROS act not only destructively but also as dedicated signaling molecules, and that aging processes are regulated by specific signaling networks has stimulated research on mitochondrial signaling systems and the regulation of mitochondrial ROS metabolism. p66Shc is a lifespan-regulating protein contributing to mitochondrial ROS metabolism and regulating the mitochondrial apoptosis pathway. It was found to participate in aging processes and has been implicated in several pathologies. Considerable progress has been made recently concerning the molecular function of p66Shc. It appears that p66Shc responds to a variety of proapoptotic stimuli by increasing ROS levels in the mitochondrial intermembrane space through an inherent ROS-producing activity, and that this ROS formation might trigger initiation of the mitochondrial apoptosis pathway. In this review, we will discuss the current knowledge on the molecular architecture of the p66Shc protein, its role in ROS metabolism and apoptosis regulation in the mitochondrial intermembrane space, the regulation of its mitochondrial transport, and the molecular mechanisms and interactions involved in these processes.

Chromium III histidinate exposure modulates gene expression in HaCaT human keratinocytes exposed to oxidative stress

While the toxicity of hexavalent chromium is well established, trivalent chromium is an essential nutrient involved in insulin and glucose homeostasis. To study the antioxidant effects of Cr(III)His, cDNA arrays were used to investigate the modulation of gene expression by trivalent chromium histidinate (Cr(III)His) in HaCaT human keratinocytes submitted to hydrogen peroxide (H2O2). Array was composed by a set of 81 expressed sequences tags (ESTs) essentially represented by antioxidant and DNA repair genes. HaCaT were preincubated for 24 h with 50 microM Cr(III)His and were treated with 50 muM H2O2. Total RNAs were isolated immediately or 6 h after the stress. In Cr(III)His preincubated cells, transcripts related to antioxidant family were upregulated (glutathione synthetase, heme oxygenase 2, peroxiredoxin 4). In Cr(III)His preincubated cells and exposed to H2O2, increased expressions of polymerase delta 2 and antioxidant transcripts were observed. Biochemical methods performed in parallel to measure oxidative stress in cells showed that Cr(III)His supplementation before H2O2 stress protected HaCaT from thiol groups decrease and thiobarbituric acid reactive substances increase. In summary, these results give evidence of antioxidant gene expression and antioxidant protection in HaCaT preincubated with Cr(III)His and help to explain the lack of toxicity reported for Cr(III)His.

Emerging mitochondrial signaling mechanisms in physiology, aging processes, and as drug targets

Advances in research on mitochondria have elucidated their importance in cell survival and cell death regulation in addition to their function in energy production. Mitochondria are further implicated in various metabolic and aging-related diseases, which are now assumed to be caused by misregulation of physiological systems rather than pure accumulation of oxidative damage. Thus, the signaling mechanisms within mitochondria and between the organelle and its environment have gained interest as potential drug targets. Emerging mitochondrial signaling systems with potential for exploiting them for therapeutic intervention include, among others, the NAD(+)-dependent protein deacetylases of the Sirtuin family, the redox enzyme p66(Shc), and enzymes of the cyclic adenosine monophosphate (cAMP) signaling pathways. Here, we discuss functions of these signaling systems in mitochondria, their roles in aging processes and disease, and their potential to serve as therapeutic targets.

Epigenetic enhancement of p66Shc during cellular replicative or premature senescence

The cytoplasmic protein p66Shc is expressed in a wide range of cell types, initially believed to be involved in signaling pathways that regulate cell growth and oxidative stress. Here the epigenetic alterations in the promoter of p66Shc were investigated in replicative senescence and in premature senescence induced by hydrogen peroxide in human embryonic pulmonary fibroblast cells. In both cases p66Shc expression was elevated compared to that seen in growing cultures. However, methylation-specific PCR and bisulfite sequencing revealed that the CpG sites were hypermethylated in all cultures. In addition, quantitative chromatin immunoprecipitation showed increased histone H4 acetylation and histone H3 Lys-4 methylation during replicative senescence, while the increased acetylation of histone H3 and H4, as well as increased H3 Lys-4 methylation, was seen in premature senescence persistence. These findings suggest that histone modifications of p66Shc might be the molecular event in cellular senescence. Taken together, the epigenetic enhancement of p66Shc is associated with the specifically increased histone acetylation and methylation, which may contribute to cellular replicative senescence or premature senescence.

p66Shc--a longevity redox protein in human prostate cancer progression and metastasis : p66Shc in cancer progression and metastasis

p66Shc, a 66 kDa proto-oncogene Src homologous-collagen homologue (Shc) adaptor protein, is classically known in mediating receptor tyrosine kinase signaling and recently identified as a sensor to oxidative stress-induced apoptosis and as a longevity protein in mammals. The expression of p66Shc is decreased in mice and increased in human fibroblasts upon aging and in aging-related diseases, including prostate cancer. p66Shc protein level correlates with the proliferation of several carcinoma cells and can be regulated by steroid hormones. Recent advances point that p66Shc protein plays a role in mediating cross-talk between steroid hormones and redox signals by serving as a common convergence point in signaling pathways on cell proliferation and apoptosis. This article first reviews the unique function of p66Shc protein in regulating oxidative stress-induced apoptosis. Subsequently, we discuss its novel role in androgen-regulated prostate cancer cell proliferation and metastasis and the mechanism by which it mediates androgen action via the redox signaling pathway. The data together indicate that p66Shc might be a useful biomarker for the prognosis of prostate cancer and serve as an effective target for its cancer treatment.

The Pro/Pro genotype of the p53 codon 72 polymorphism modulates PAI-1 plasma levels in ageing

Plasminogen activator inhibitor 1 (PAI-1) is over-expressed during ageing and it has been linked to cellular senescence. Recently, PAI-1 has been also identified in vitro as a critical downstream target of p53. TP53, the p53 gene, has a common functional polymorphism at codon 72 which influences the capability to modulate both apoptosis and cell senescence. In the attempt to demonstrate an in vivo role of p53 in the relationship between PAI-1 and age, we studied PAI-1 on 570 healthy subjects (aged from 18 to 92yrs.). PAI-1 showed significant relationship with age (r=0.12, p=0.02). Stratifying by genotype, it became evident that the association between PAI-1 and age was mainly due to Pro/Pro subjects (partial r=0.75, p<0.01). These results have been confirmed by a validation study on an independent sample population of 496 subjects (aged from 18 to 94yrs.). This is the first demonstration of an in vivo role of TP53 polymorphism in PAI-1 regulation, supporting the hypothesis that the effects of this polymorphism are age-dependent. In particular, our results indicate that Pro/Pro genotype plays a pivotal role in determining PAI-1 levels in aged subjects, while in Arg carriers PAI-1 levels are associated to the known insulin related determinants.

A novel role of Shc adaptor proteins in steroid hormone-regulated cancers

Tyrosine phosphorylation plays a critical role in growth regulation, and its aberrant regulation can be involved in carcinogenesis. The association of Shc (Src homolog and collagen homolog) adaptor protein family members in tyrosine phosphorylation signaling pathway is well recognized. Shc adaptor proteins transmit activated tyrosine phosphorylation signaling that suggest their plausible role in growth regulation including carcinogenesis and metastasis. In parallel, by sharing a similar mechanism of carcinogenesis, the steroids are involved in the early stage of carcinogenesis as well as the regulation of cancer progression and metastatic processes. Recent evidence indicates a cross-talk between tyrosine phosphorylation signaling and steroid hormone action in epithelial cells, including prostate and breast cancer cells. Therefore, the members of Shc proteins may function as mediators between tyrosine phosphorylation and steroid signaling in steroid-regulated cell proliferation and carcinogenesis. In this communication, we discuss the novel roles of Shc proteins, specifically p52(Shc) and p66(Shc), in steroid hormone-regulated cancers and a novel molecular mechanism by which redox signaling induced by p66(Shc) mediates steroid action via a non-genomic pathway. The p66(Shc) protein may serve as an effective biomarker for predicting cancer prognosis as well as a useful target for treatment.

The role of p66Shc deletion in age-associated arterial dysfunction and disease states

Accumulation of oxidative stress with age is hypothesized to be the primary causative mediator of age-associated diseases. Among different tissues, aging vessels are known to accumulate oxidative damage and undergo functional impairment. Oxidative stress affects the availability and/or balance of key regulators of vascular homeostasis and favors the development of cardiovascular disease. Reactive oxygen species are generated by different intracellular molecular pathways principally located in the cytoplasm and in the mitochondria. The mitochondrial enzyme p66Shc is an adaptor protein and plays an important role as a redox enzyme implicated in mitochondrial eactive oxygen species generation and translation of oxidative signals into apoptosis. Mice lacking p66Shc−/− gene display reduced production of intracellular oxidants and a 30% prolonged life span. For this reasons, a series of studies conceived to elucidate the function of p66Shc and its possible implication in age-associated cardiovascular diseases have been carried out. Indeed, p66Shc−/− mice have been shown to be protected from age-dependent endothelial dysfunction as well as age-related risk factors such as diabetes and hypercholesterolemia. This review focuses on delineating the role of the p66Shc adaptor protein and its potential implication in the pathophysiology of aging and age-related cardiovascular disease.

Mitochondrial redox signaling by p66Shc is involved in regulating androgenic growth stimulation of human prostate cancer cells

p66Shc is shown to negatively regulate the life span in mice through reactive oxygen species (ROS) production. Recent reports, however, revealed that p66Shc protein level is significantly elevated in several human cancer tissues and growth-stimulated carcinoma cells, suggesting a mitogenic and carcinogenic role for p66Shc. In this communication, we demonstrate for the first time that p66Shc mediates androgenic growth signals in androgen-sensitive human prostate cancer cells through mitochondrial ROS production. Growth stimulation of prostate cancer cells with 5alpha-dihydrotestosterone (DHT) is accompanied by increased p66Shc level and ROS production, which is abolished by antioxidant treatments. However, antioxidant treatments do not affect the transcriptional activity of androgen receptor (AR) as observed by its inability to block DHT-induced prostate-specific antigen expression, an AR-dependent correlate of prostate cancer progression. Elevated expression of p66Shc by cDNA transfection increases the basal cell proliferation and, thus, reduces additional DHT-induced cell proliferation. Furthermore, DHT increases the translocation of p66Shc into mitochondria and its interaction with cytochrome c. Conversely, both redox-negative p66Shc mutant (W134F), which is deficient in cytochrome c interaction, and p66Shc small interfering RNA decrease DHT-induced cell proliferation. These results collectively reveal a novel role for p66Shc-ROS pathway in androgen-induced prostate cancer cell proliferation and, thus, may play a role in early prostate carcinogenesis.

Permanent embryo arrest: molecular and cellular concepts

Developmental arrest is one of the mechanisms responsible for the elevated levels of embryo demise during the first week of in vitro development. Approximately 10-15% of IVF embryos permanently arrest in mitosis at the 2- to 4-cell cleavage stage showing no indication of apoptosis. Reactive oxygen species (ROS) are implicated in this process and must be controlled in order to optimize embryo production. A stress sensor that can provide a key understanding of permanent cell cycle arrest and link ROS with cellular signaling pathway(s) is p66Shc, an adaptor protein for apoptotic-response to oxidative stress. Deletion of the p66Shc gene in mice results in extended lifespan, which is linked to their enhanced resistance to oxidative stress and reduced levels of apoptosis. p66Shc has been shown to generate mitochondrial H(2)O(2) to trigger apoptosis, but may also serve as an integration point for many signaling pathways that affect mitochondrial function. We have detected elevated levels of p66Shc and ROS within arrested embryos and believe that p66Shc plays a central role in regulating permanent embryo arrest. In this paper, we review the cellular and molecular aspects of permanent embryo arrest and speculate on the mechanism(s) and etiology of this method of embryo demise.

Human longevity within an evolutionary perspective: The peculiar paradigm of a post-reproductive genetics

The data we collected on the genetics of human longevity, mostly resulting from studies on centenarians, indicate that: (1) centenarians and long-living sib-pairs are a good choice for the study of human longevity, because they represent an extreme phenotype, i.e., the survival tail of the population who escaped neonatal mortality, pre-antibiotic era illnesses, and fatal outcomes of age-related complex diseases. (2) The model of centenarians is not simply an additional model with respect to well-studied organisms, and the study of humans has revealed characteristics of ageing and longevity (geographical and sex differences, role of antigenic load and inflammation, role of mtDNA variants) which did not emerge from studies in laboratory model systems and organisms. (3) All the phenotypic characteristics of nonagenarians and centenarians fit the hypothesis that ageing is a remodelling process where the body of survivors progressively adapts to internal and external damaging agents they are exposed to during several decades, largely unpredicted by evolution. (4) Such a remodelling process, which can be considered a Darwinian process occurring at the somatic level within the framework of the evolutionary constraints, established by evolution for Homo sapiens as a species, may explain why the same gene polymorphism can have different (beneficial or detrimental) effects at different ages. (5) Geographic and demographic evidence suggest that longevity can be achieved by different combinations of genes, environment, and chance quantitatively and qualitatively different in many geographic areas, and that population-specific genetic factors, play a role on the longevity trait. (6) The concomitant and integrated use of new in silico and high throughput strategies will greatly accelerate the identification of new longevity genes in humans.

AGE-receptor-1 counteracts cellular oxidant stress induced by AGEs via negative regulation of p66shc-dependent FKHRL1 phosphorylation

Advanced glycation end products (AGEs) promote reactive oxygen species (ROS) formation and oxidant stress (OS) in diabetes and aging-related diseases. AGE-induced OS is suppressed by AGER1, an AGE-receptor that counteracts receptor for advanced glycation end products (RAGE) and epidermal growth factor receptor (EGFR)-mediated Shc/Ras signal activation, resulting in decreased OS. Akt, FKHRL1, and antioxidants; e.g., MnSOD, regulate OS. Serine phosphorylation of p66 shc also promotes OS. We examined the effects of two defined AGEs Nε-carboxy-methyl-lysine (CML) and methyl-glyoxal derivatives (MG) on these cellular pathways and their functional relationship to AGER1 in human embryonic kidney cells (HEK293). Stimulation of HEK293 cells with either AGE compound increased phosphorylation of Akt and FKHRL1 by approximately threefold in a redox-dependent manner. The use of p66 shc mutants showed that the AGE-induced effects required Ser-36 phosphorylation of p66 shc. AGE-induced phosphorylation of FKHRL1 led to a 70% downregulation of MnSOD, an effect partially blocked by a phosphatidylinositol 3-kinase inhibitor (LY-294002) and strongly inhibited by an antioxidant ( N-acetylcysteine). These pro-oxidant responses were suppressed in AGER1 overexpressing cells and reappeared when AGER1 expression was reduced by small interfering RNA (siRNA). These studies point to a new pathway for the induction of OS by AGEs involving FKHRL1 inactivation and MnSOD suppression via Ser-36 phosphorylation of p66 shc in human kidney cells. This represents a key mechanism by which AGER1 maintains cellular resistance against OS. Thus the decrease of AGER1 noted in aging and diabetes may further enhance OS and reduce innate antioxidant defenses.

Final common molecular pathways of aging and cardiovascular disease: role of the p66Shc protein

Oxidative stress affects the availability of key-regulators of vascular homeostasis and controls a number of signaling pathways relevant to myocardial and vascular disease. Reactive oxygen species are generated by different intracellular molecular pathways principally located in mitochondria. The notion that mice carrying a targeted mutation of the p66(Shc) gene display prolonged lifespan, reduced production of intracellular oxidants, and increased resistance to oxidative stress-induced apoptosis prompted a series of studies aimed at defining the biochemical function of p66(Shc) and its possible implication in cardiovascular diseases. Indeed, p66(Shc-/-) mice are protected against vascular, cardiac, and renal impairment attributable to hypercholesterolemia, aging, diabetes, and ischemia/reperfusion. The present review focuses on the biochemical and physiological function of the p66(Shc) adaptor protein as well as on the mechanisms linking p66(Shc)-associated generation of free radicals to the pathophysiology of aging and cardiovascular disease. On the whole, the evidence so far reported and here discussed supports the concept that pharmacological modulation of p66(Shc) expression and activity may be a novel and effective target for the treatment of atherosclerotic vascular disease as well as myocardial adaptation to hypertrophic, inflammatory and neuro-hormonal stimuli in the overloaded heart.

p66Shc, oxidative stress and aging: importing a lifespan determinant into mitochondria

The 66 KDa isoform of Shc and its signalling properties have attracted in the past years major interest in aging research. Here, we summarize p66Shc functions and outline a specific signalling route leading to mitochondrial import, that accounts for its pro-apoptotic activity upon oxidative stress. This model, that could explain the alterations of mitochondrial Ca2+ homeostasis observed after oxidative stress, highlights novel pharmacological targets in age-related disorders.

The Genetics of Human Longevity

Aging is due to a complex interaction of genetic, epigenetic, and environmental factors, but a strong genetic component appears to have an impact on survival to extreme ages. In order to identify "longevity genes" in humans, different strategies are now available. In our laboratory, we performed association studies on a variety of "candidate" polymorphisms in Italian centenarians. Many genes/polymorphisms gave negative results, while others showed a positive association with human longevity and a sometimes-positive association with unsuccessful aging (myocardial infarction, Alzheimer's disease, and type 2 diabetes). Results regarding genes involved in inflammation (IL-1 cluster, IL-6, IL-10, TNF-alpha, TGF-beta, TLR-4, PPARgamma), insulin/IGF-1 signaling pathway and lipid metabolism (apolipoproteins, CETP, PON1), and oxidative stress (p53, p66(shc)) will be described. In addition, a strong role of the interaction between nuclear and mitochondrial genomes (mtDNA haplogroups and the C150T mutation) emerged from our findings. Thus, the genetics of human longevity appears to be quite peculiar in a context where antagonistic pleiotropy can play a major role and genes can have a different biological role at different ages.

p66(Shc) gene has a pro-apoptotic role in human cell lines and it is activated by a p53-independent pathway

p66(Shc) protein has been proposed to be an indispensable factor for p53-dependent, mitochondria-mediated apoptosis in mice. Here, we show that p66(Shc) plays a pro-apoptotic role also in cell lines of human origin such as SaOs-2 and HeLa, where p53 is either absent or inactivated, thus, suggesting that p66(Shc) pro-apoptotic role is independent from the presence of a functional form of p53. The active form of p66(Shc) is phosphorylated in Serine 36. We confirm the importance of Serine 36 phosphorylation for p66(Shc) pro-apoptotic role, and our results suggest that the kinase involved in this process is activated independently from p53.