Whole organism snRNA-seq reveals systemic peripheral changes in Alzheimer's Disease fly models

Peripheral tissues become disrupted in Alzheimer's Disease (AD). However, a comprehensive understanding of how the expression of AD-associated toxic proteins, Aβ42 and Tau, in neurons impacts the periphery is lacking. Using Drosophila, a prime model organism for studying aging and neurodegeneration, we generated the Alzheimer's Disease Fly Cell Atlas (AD-FCA): whole-organism single-nucleus transcriptomes of 219 cell types from adult flies neuronally expressing human Aβ42 or Tau. In-depth analyses and functional data reveal impacts on peripheral sensory neurons by Aβ42 and on various non-neuronal peripheral tissues by Tau, including the gut, fat body, and reproductive system. This novel AD atlas provides valuable insights into potential biomarkers and the intricate interplay between the nervous system and peripheral tissues in response to AD-associated proteins.

Distinct sets of lysosomal genes define synucleinopathy and tauopathy

Neurodegenerative diseases are characterized by distinct protein aggregates, such as those of α-synuclein and tau. Lysosomal defect is a key contributor to the accumulation and propagation of aberrant protein aggregates in these diseases. The discoveries of common proteinopathies in multiple forms of lysosomal storage diseases (LSDs) and the identification of some LSD genes as susceptible genes for those proteinopathies suggest causative links between LSDs and the proteinopathies. The present study hypothesized that defects in lysosomal genes will differentially affect the propagation of α-synuclein and tau proteins, thereby determining the progression of a specific proteinopathy. We established an imaging-based high-contents screening (HCS) system in Caenorhabditis elegans (C. elegans) model, by which the propagation of α-synuclein or tau is measured by fluorescence intensity. Using this system, we performed RNA interference (RNAi) screening to induce a wide range of lysosomal malfunction through knock down of 79 LSD genes, and to obtain the candidate genes with significant change in protein propagation. While some LSD genes commonly affected both α-synuclein and tau propagation, our study identified the distinct sets of LSD genes that differentially regulate the propagation of either α-synuclein or tau. The specificity and efficacy of these LSD genes were retained in the disease-related phenotypes, such as pharyngeal pumping behavior and life span. This study suggests that distinct lysosomal genes differentially regulate the propagation of α-synuclein and tau, and offer a steppingstone to understanding disease specificity. [BMB Reports 2023; 56(12): 657-662].

Activation of eIF4E-binding-protein-1 rescues mTORC1-induced sarcopenia by expanding lysosomal degradation capacity

BACKGROUND

Chronic mTORC1 activation in skeletal muscle is linked with age-associated loss of muscle mass and strength, known as sarcopenia. Genetic activation of mTORC1 by conditionally ablating mTORC1 upstream inhibitor TSC1 in skeletal muscle accelerates sarcopenia development in adult mice. Conversely, genetic suppression of mTORC1 downstream effectors of protein synthesis delays sarcopenia in natural aging mice. mTORC1 promotes protein synthesis by activating ribosomal protein S6 kinases (S6Ks) and inhibiting eIF4E-binding proteins (4EBPs). Whole-body knockout of S6K1 or muscle-specific over-expression of a 4EBP1 mutant transgene (4EBP1mt), which is resistant to mTORC1-mediated inhibition, ameliorates muscle loss with age and preserves muscle function by enhancing mitochondria activities, despite both transgenic mice showing retarded muscle growth at a young age. Why repression of mTORC1-mediated protein synthesis can mitigate progressive muscle atrophy and dysfunction with age remains unclear.

METHODS

Mice with myofiber-specific knockout of TSC1 (TSC1mKO), in which mTORC1 is hyperactivated in fully differentiated myofibers, were used as a mouse model of sarcopenia. To elucidate the role of mTORC1-mediated protein synthesis in regulating muscle mass and physiology, we bred the 4EBP1mt transgene or S6k1 floxed mice into the TSC1mKO mouse background to generate 4EBP1mt-TSC1mKO or S6K1-TSC1mKO mice, respectively. Functional and molecular analyses were performed to assess their role in sarcopenia development.

RESULTS

Here, we show that 4EBP1mt-TSC1mKO, but not S6K1-TSC1mKO, preserved muscle mass (36.7% increase compared with TSC1mKO, P < 0.001) and strength (36.8% increase compared with TSC1mKO, P < 0.01) at the level of control mice. Mechanistically, 4EBP1 activation suppressed aberrant protein synthesis (two-fold reduction compared with TSC1mKO, P < 0.05) and restored autophagy flux without relieving mTORC1-mediated inhibition of ULK1, an upstream activator of autophagosome initiation. We discovered a previously unidentified phenotype of lysosomal failure in TSC1mKO mouse muscle, in which the lysosomal defect was also conserved in the naturally aged mouse muscle, whereas 4EBP1 activation enhanced lysosomal protease activities to compensate for impaired autophagy induced by mTORC1 hyperactivity. Consequently, 4EBP1 activation relieved oxidative stress to prevent toxic aggregate accumulation (0.5-fold reduction compared with TSC1mKO, P < 0.05) in muscle and restored mitochondrial homeostasis and function.

CONCLUSIONS

We identify 4EBP1 as a communication hub coordinating protein synthesis and degradation to protect proteostasis, revealing therapeutic potential for activating lysosomal degradation to mitigate sarcopenia.

SAMS-1 coordinates HLH-30/TFEB and PHA-4/FOXA activities through histone methylation to mediate dietary restriction-induced autophagy and longevity

Dietary restriction (DR) is known to promote autophagy to exert its longevity effect. While SAMS-1 (S-adenosyl methionine synthetase-1) has been shown to be a key mediator of the DR response, little is known about the roles of S-adenosyl methionine (SAM) and SAM-dependent methyltransferase in autophagy and DR-induced longevity. In this study, we show that DR and SAMS-1 repress the activity of SET-2, a histone H3K4 methyltransferase, by limiting the availability of SAM. Consequently, the reduced H3K4me3 levels promote the expression and activity of two transcription factors, HLH-30/TFEB and PHA-4/FOXA, which both regulate the transcription of autophagy-related genes. We then find that HLH-30/TFEB and PHA-4/FOXA act collaboratively on their common target genes to mediate the transcriptional response of autophagy-related genes and consequently the lifespan of the animals. Our study thus shows that the SAMS-1-SET-2 axis serves as a nutrient-sensing module to epigenetically coordinate the activation of HLH-30/TFEB and PHA-4/FOXA transcription factors to control macroautophagy/autophagy and longevity in response to DR.Abbreviations: ChIP: chromatin immunoprecipitation; ChIP-seq: chromatin immuno precipitation-sequencing; COMPASS: complex of proteins associated with Set1; DR: dietary restriction; GO: gene ontology; SAM: S-adenosyl methionine; SAMS-1: S-adenosyl methionine synthetase-1; TSS: transcription start site; WT: wild-type.

Development of a traditional Chinese medicine-based agent for the treatment of cancer cachexia

BACKGROUND

Despite recent advances in understanding the pathophysiology of cancer cachexia, prevention/treatment of this debilitating disease remains an unmet medical need.

METHODS

We developed an integrated, multi-tiered strategy involving both in vitro and in vivo muscle atrophy platforms to identify traditional Chinese medicine (TCM)-based anti-cachectic agents. In the initial screening, we used inflammatory cytokine-induced atrophy of C2C12 myotubes as a phenotypic screening platform to assess the protective effects of TCMs. The selected TCMs were then evaluated for their abilities to protect Caenorhabditis elegans from age-related reduction of mobility and contractility, followed by the C-26 colon adenocarcinoma mouse model of cachexia to confirm the anti-muscle atrophy effects (body/skeletal muscle weights, fibre size distribution, grip strengths, and serum IL-6). Transcriptome analysis, quantitative real-time polymerase chain reaction, and immunoblotting were performed to gain understanding of the potential mechanism(s) by which effective TCM protected against C26 tumour-induced muscle atrophy.

RESULTS

Of 29 widely used TCMs, Dioscorea radix (DR) and Mu Dan Pi (MDP) showed a complete protection (all P values, 0.0002) vis-à-vis C26 conditioned medium control in the myotube atrophy platform. MDP exhibited a unique ability to ameliorate age-associated decreases in worm mobility, accompanied by improved total body contractions, relative to control (P < 0.0001 and <0.01, respectively), which, however, was not noted with DR. This differential in vivo protective effect between MDP and DR was also confirmed in the C-26 mouse model. MDP at 1000 mg/kg (MDP-H) was effective in protecting body weight loss (P < 0.05) in C-26 tumour-bearing mice without changing food or water intake, accompanied by the restoration of the fibre size distribution of hindleg skeletal muscles (P < 0.0001) and the forelimb grip strength (P < 0.05). MDP-treated C-26-tumour-bearing mice were alert, showed normal posture and better body conditions, and exhibited lower serum IL-6 levels (P = 0.06) relative to vehicle control. This decreased serum IL-6 was associated with the in vitro suppressive effect of MDP (25 and 50 μg/mL) on IL-6 secretion into culture medium by C26 cells. RNA-seq analysis, followed by quantitative real-time polymerase chain reaction and/or immunoblotting, shows that MDP's anti-cachectic effect was attributable to its ability to reverse the C-26 tumour-induced re-programming of muscle homoeostasis-associated gene expression, including that of two cachexia drivers (MuRF1 and Atrogin-1), in skeletal muscles.

CONCLUSIONS

All these findings suggest the translational potential of MDP to foster new strategies for the prevention and/or treatment of cachexia. The protective effect of MDP on other types of muscle atrophy such as sarcopenia might warrant investigations.

A maze platform for the assessment of Caenorhabditis elegans behavior and learning

Mazes are broadly used to investigate animal decision-making and spatial learning. However, they have been sparsely employed to explore C. elegans behavior and training-improved performance. This protocol describes a highly reproducible, low-cost maze platform, made of the standard, agar-based, nematode culturing material. It can be used to reliably assess C. elegans' maze behavior, and we have recently applied this protocol to establish multisensory learning. Limitations include challenges in locomotion tracking and in distinguishing learning formation versus retrieval.

For complete details on the use and execution of this protocol, please refer to Gourgou et al. (2021).

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Design and 3D-print the maze mold and fabricate the maze plates

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Bait the mazes and insert C. elegans nematodes

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Record nematode behavior and analyze data

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Tips on steps that require extra caution

Using Convolutional Neural Networks to Measure the Physiological Age of Caenorhabditis elegans

Caenorhabditis elegans (C. elegans) is a popular and excellent model for studies of aging due to its short lifespan. Methods for precisely measuring the physiological age of C. elegans are critically needed, especially for antiaging drug screening and genetic screening studies. The effects of various antiaging interventions on the rate of aging in the early stage of the aging process can be determined based on the quantification of physiological age. However, in general, the age of C. elegans is evaluated via human visual inspection of morphological changes based on personal experience and subjective judgment. For example, the rate of motor activity decay has been used to predict lifespan in early- to mid-stage aging. Using image processing, the physiological age of C. elegans can be measured and then classified into periods or classes from childhood to elderhood (e.g., 3 periods comprising days 0-2, 4-6 and 10-12) by using texture entropy (Shamir, L. et al., 2009). Our dataset consists of 913 microscopic images of C. elegans, with approximately 60 images per day from day 1 to day 14 of adulthood. We present quantitative methods to measure the physiological age of C. elegans with convolution neural networks (CNNs), which can measure age with a granularity of days rather than periods. The methods achieved a mean absolute error (MAE) of less than 1 day for the measured age of C. elegans. In our experiments, we found that after training and testing our dataset, 5 popular CNN models, 50-layer residual network (ResNet50), InceptionV3, InceptionResNetV2, 16-layer Visual Geometry Group network (VGG16) and MobileNet, measured the physiological age of C. elegans with an average testing MAE of 1.58 days. Furthermore, based on the results, we propose two models, one model for linear regression analysis and the other model for logistic regression, that combine a CNN model and a new attribute: curved_or_straight. The linear regression analysis model achieved a test MAE of 0.94 days; the logistic regression model achieved an accuracy of 84.78 percent with an error tolerance of 1 day.

Caenorhabditis elegans learning in a structured maze is a multisensory behavior

We show that C. elegans nematodes learn to associate food with a combination of proprioceptive cues and information on the structure of their surroundings (maze), perceived through mechanosensation. By using the custom-made Worm-Maze platform, we demonstrate that C. elegans young adults can locate food in T-shaped mazes and, following that experience, learn to reach a specific maze arm. C. elegans learning inside the maze is possible after a single training session, it resembles working memory, and it prevails over conflicting environmental cues. We provide evidence that the observed learning is a food-triggered multisensory behavior, which requires mechanosensory and proprioceptive input, and utilizes cues about the structural features of nematodes' environment and their body actions. The CREB-like transcription factor and dopamine signaling are also involved in maze performance. Lastly, we show that the observed aging-driven decline of C. elegans learning ability in the maze can be reversed by starvation.

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C. elegans can be trained to reach a target arm in a T-shaped maze

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Learning requires the contribution of tactile and proprioceptive cues

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C. elegans follow a kind of response learning strategy in the maze environment

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Learning is short-term and sensitive to distraction

HSB-1/HSF-1 pathway modulates histone H4 in mitochondria to control mtDNA transcription and longevity

Heat shock factor-1 (HSF-1) is a master regulator of stress responses across taxa. Overexpression of HSF-1 or genetic ablation of its conserved negative regulator, heat shock factor binding protein 1 (HSB-1), results in robust life-span extension in Caenorhabditis elegans Here, we found that increased HSF-1 activity elevates histone H4 levels in somatic tissues during development, while knockdown of H4 completely suppresses HSF-1-mediated longevity. Moreover, overexpression of H4 is sufficient to extend life span. Ablation of HSB-1 induces an H4-dependent increase in micrococcal nuclease protection of both nuclear chromatin and mitochondrial DNA (mtDNA), which consequently results in reduced transcription of mtDNA-encoded complex IV genes, decreased respiratory capacity, and a mitochondrial unfolded protein response-dependent life-span extension. Collectively, our findings reveal a previously unknown role of HSB-1/HSF-1 signaling in modulation of mitochondrial function via mediating histone H4-dependent regulation of mtDNA gene expression and concomitantly acting as a determinant of organismal longevity.

High-throughput small molecule screening reveals Nrf2-dependent and -independent pathways of cellular stress resistance

Aging is the dominant risk factor for most chronic diseases. Development of antiaging interventions offers the promise of preventing many such illnesses simultaneously. Cellular stress resistance is an evolutionarily conserved feature of longevity. Here, we identify compounds that induced resistance to the superoxide generator paraquat (PQ), the heavy metal cadmium (Cd), and the DNA alkylator methyl methanesulfonate (MMS). Some rescue compounds conferred resistance to a single stressor, while others provoked multiplex resistance. Induction of stress resistance in fibroblasts was predictive of longevity extension in a published large-scale longevity screen in Caenorhabditis elegans, although not in testing performed in worms and flies with a more restricted set of compounds. Transcriptomic analysis and genetic studies implicated Nrf2/SKN-1 signaling in stress resistance provided by two protective compounds, cardamonin and AEG 3482. Small molecules identified in this work may represent attractive tools to elucidate mechanisms of stress resistance in mammalian cells.

Short-term enhancement of motor neuron synaptic exocytosis during early aging extends lifespan in Caenorhabditis elegans

IMPACT STATEMENT

The functional decline of motor activity is a common feature in almost all aging animals that leads to frailty, loss of independence, injury, and even death in the elderly population. Thus, understanding the molecular mechanism that drives the initial stage of this functional decline and developing strategies to increase human healthspan and even lifespan by targeting this process would be of great interests to the field. In this study, we found that by precisely targeting the motor neurons to potentiate its synaptic releases either genetically or pharmacologically, we can not only delay the functional aging at NMJs but also slow the rate of aging at the organismal level. Most importantly, we have demonstrated that a critical window of time, that is the early stage of NMJs functional decline, is required for the beneficial effects. A short-term treatment within this time period is sufficient to extend the animals' lifespan.

Genetic and pharmacological interventions in the aging motor nervous system slow motor aging and extend life span in C. elegans

As animals and humans age, the motor system undergoes a progressive functional decline, leading to frailty. Age-dependent functional deteriorations at neuromuscular junctions (NMJs) contribute to this motor aging. However, it is unclear whether one can intervene in this process to slow motor aging. The Caenorhabditis elegans BK channel SLO-1 dampens synaptic transmission at NMJs by repressing synaptic release from motor neurons. Here, we show that genetic ablation of SLO-1 not only reduces the rate of age-dependent motor activity decline to slow motor aging but also surprisingly extends life span. SLO-1 acts in motor neurons to mediate both functions. Genetic knockdown or pharmacological inhibition of SLO-1 in aged, but not young, worms can slow motor aging and prolong longevity. Our results demonstrate that genetic and pharmacological interventions in the aging motor nervous system can promote both health span and life span.

Prefoldin 6 mediates longevity response from heat shock factor 1 to FOXO in C. elegans

Heat shock factor 1 (HSF-1) and forkhead box O (FOXO) are key transcription factors that protect cells from various stresses. In Caenorhabditis elegans, HSF-1 and FOXO together promote a long life span when insulin/IGF-1 signaling (IIS) is reduced. However, it remains poorly understood how HSF-1 and FOXO cooperate to confer IIS-mediated longevity. Here, we show that prefoldin 6 (PFD-6), a component of the molecular chaperone prefoldin-like complex, relays longevity response from HSF-1 to FOXO under reduced IIS. We found that PFD-6 was specifically required for reduced IIS-mediated longevity by acting in the intestine and hypodermis. We showed that HSF-1 increased the levels of PFD-6 proteins, which in turn directly bound FOXO and enhanced its transcriptional activity. Our work suggests that the prefoldin-like chaperone complex mediates longevity response from HSF-1 to FOXO to increase the life span in animals with reduced IIS.

Reciprocal Changes in Phosphoenolpyruvate Carboxykinase and Pyruvate Kinase with Age Are a Determinant of Aging in Caenorhabditis elegans

Aging involves progressive loss of cellular function and integrity, presumably caused by accumulated stochastic damage to cells. Alterations in energy metabolism contribute to aging, but how energy metabolism changes with age, how these changes affect aging, and whether they can be modified to modulate aging remain unclear. In locomotory muscle of post-fertile Caenorhabditis elegans, we identified a progressive decrease in cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C), a longevity-associated metabolic enzyme, and a reciprocal increase in glycolytic pyruvate kinase (PK) that were necessary and sufficient to limit lifespan. Decline in PEPCK-C with age also led to loss of cellular function and integrity including muscle activity, and cellular senescence. Genetic and pharmacologic interventions of PEPCK-C, muscle activity, and AMPK signaling demonstrate that declines in PEPCK-C and muscle function with age interacted to limit reproductive life and lifespan via disrupted energy homeostasis. Quantifications of metabolic flux show that reciprocal changes in PEPCK-C and PK with age shunted energy metabolism toward glycolysis, reducing mitochondrial bioenergetics. Last, calorie restriction countered changes in PEPCK-C and PK with age to elicit anti-aging effects via TOR inhibition. Thus, a programmed metabolic event involving PEPCK-C and PK is a determinant of aging that can be modified to modulate aging.

Environmental Temperature Differentially Modulates C. elegans Longevity through a Thermosensitive TRP Channel

Temperature profoundly affects aging in both poikilotherms and homeotherms. A general belief is that lower temperatures extend lifespan, whereas higher temperatures shorten it. Although this "temperature law" is widely accepted, it has not been extensively tested. Here, we systematically evaluated the role of temperature in lifespan regulation in C. elegans. We found that, although exposure to low temperatures at the adult stage prolongs lifespan, low-temperature treatment at the larval stage surprisingly reduces lifespan. Interestingly, this differential effect of temperature on longevity in larvae and adults is mediated by the same thermosensitive TRP channel TRPA-1 that signals to the transcription factor DAF-16/FOXO. DAF-16/FOXO and TRPA-1 act in larva to shorten lifespan but extend lifespan in adulthood. DAF-16/FOXO differentially regulates gene expression in larva and adult in a temperature-dependent manner. Our results uncover complexity underlying temperature modulation of longevity, demonstrating that temperature differentially regulates lifespan at different stages of life.

Analysis of lifespan-promoting effect of garlic extract by an integrated metabolo-proteomics approach

The beneficial effects of garlic (Allium sativum) consumption in treating human diseases have been reported worldwide over a long period of human history. The strong antioxidant effect of garlic extract (GE) has also recently been claimed to prevent cancer, thrombus formation, cardiovascular disease and some age-related maladies. Using Caenorhabditis elegans as a model organism, aqueous GE was herein shown to increase the expression of longevity-related FOXO transcription factor daf-16 and extend lifespan by 20%. By employing microarray and proteomics analysis on C. elegans treated with aqueous GE, we have systematically mapped 229 genes and 46 proteins with differential expression profiles, which included many metabolic enzymes and yolky egg vitellogenins. To investigate the garlic components functionally involved in longevity, an integrated metabolo-proteomics approach was employed to identify metabolites and protein components associated with treatment of aqueous GE. Among potential lifespan-promoting substances, mannose-binding lectin and N-acetylcysteine were found to increase daf-16 expression. Our study points to the fact that the lifespan-promoting effect of aqueous GE may entail the DAF-16-mediated signaling pathway. The result also highlights the utility of metabolo-proteomics for unraveling the complexity and intricacy involved in the metabolism of natural products in vivo.

Co-chaperone p23 regulates C. elegans Lifespan in Response to Temperature

Temperature potently modulates various physiologic processes including organismal motility, growth rate, reproduction, and ageing. In ectotherms, longevity varies inversely with temperature, with animals living shorter at higher temperatures. Thermal effects on lifespan and other processes are ascribed to passive changes in metabolic rate, but recent evidence also suggests a regulated process. Here, we demonstrate that in response to temperature, daf-41/ZC395.10, the C. elegans homolog of p23 co-chaperone/prostaglandin E synthase-3, governs entry into the long-lived dauer diapause and regulates adult lifespan. daf-41 deletion triggers constitutive entry into the dauer diapause at elevated temperature dependent on neurosensory machinery (daf-10/IFT122), insulin/IGF-1 signaling (daf-16/FOXO), and steroidal signaling (daf-12/FXR). Surprisingly, daf-41 mutation alters the longevity response to temperature, living longer than wild-type at 25°C but shorter than wild-type at 15°C. Longevity phenotypes at 25°C work through daf-16/FOXO and heat shock factor hsf-1, while short lived phenotypes converge on daf-16/FOXO and depend on the daf-12/FXR steroid receptor. Correlatively daf-41 affected expression of DAF-16 and HSF-1 target genes at high temperature, and nuclear extracts from daf-41 animals showed increased occupancy of the heat shock response element. Our studies suggest that daf-41/p23 modulates key transcriptional changes in longevity pathways in response to temperature.

Monitoring newly synthesized proteins over the adult life span of Caenorhabditis elegans

Little is known regarding how the synthesis and degradation of individual proteins change during the life of an organism. Such knowledge is vital to understanding the aging process. To fill this knowledge gap, we monitored newly synthesized proteins on a proteome scale in Caenorhabditis elegans over time during adulthood using a stable-isotope labeling by amino acids in cell culture (SILAC)-based label-chase approach. For most proteins, the rate of appearance of newly synthesized protein was high during the first 5 days of adulthood, slowed down between the fifth and the 11th days, and then increased again after the 11th day. However, the magnitude of appearance rate differed significantly from protein to protein. For example, the appearance of newly synthesized protein was fast for proteins involved in embryonic development, transcription regulation, and lipid binding/transport, with >70% of these proteins newly synthesized by day 5 of adulthood, whereas it was slow for proteins involved in cellular assembly and motility, such as actin and myosin, with <70% of these proteins newly synthesized even on day 16. The late-life increase of newly synthesized protein was especially high for ribosomal proteins and ATP synthases. We also investigated the effect of RNAi-mediated knockdown of the rpl-9 (ribosomal protein), atp-3 (ATP synthase), and ril-1 (RNAi-induced longevity-1) genes and found that inhibiting the expression of atp-3 and ril-1 beginning in late adulthood is still effective to extend the life span of C. elegans.

Integrin-linked kinase modulates longevity and thermotolerance in C. elegans through neuronal control of HSF-1

Integrin-signaling complexes play important roles in cytoskeletal organization and cell adhesion in many species. Components of the integrin-signaling complex have been linked to aging in both Caenorhabditis elegans and Drosophila melanogaster, but the mechanism underlying this function is unknown. Here, we investigated the role of integrin-linked kinase (ILK), a key component of the integrin-signaling complex, in lifespan determination. We report that genetic reduction of ILK in both C. elegans and Drosophila increased resistance to heat stress, and led to lifespan extension in C. elegans without majorly affecting cytoskeletal integrity. In C. elegans, longevity and thermotolerance induced by ILK depletion was mediated by heat-shock factor-1 (HSF-1), a major transcriptional regulator of the heat-shock response (HSR). Reduction in ILK levels increased hsf-1 transcription and activation, and led to enhanced expression of a subset of genes with roles in the HSR. Moreover, induction of HSR-related genes, longevity and thermotolerance caused by ILK reduction required the thermosensory neurons AFD and interneurons AIY, which are known to play a critical role in the canonical HSR. Notably, ILK was expressed in neighboring neurons, but not in AFD or AIY, implying that ILK reduction initiates cell nonautonomous signaling through thermosensory neurons to elicit a noncanonical HSR. Our results thus identify HSF-1 as a novel effector of the organismal response to reduced ILK levels and show that ILK inhibition regulates HSF-1 in a cell nonautonomous fashion to enhance stress resistance and lifespan in C. elegans.

Functional aging in the nervous system contributes to age-dependent motor activity decline in C. elegans

Aging is characterized by a progressive decline in multiple physiological functions (i.e., functional aging). As animals age, they exhibit a gradual loss in motor activity, but the underlying mechanisms remain unclear. Here we approach this question in C. elegans by functionally characterizing its aging nervous system and muscles. We find that motor neurons exhibit a progressive functional decline, beginning in early life. Surprisingly, body-wall muscles, which were previously thought to undergo functional aging, do not manifest such a decline until mid-late life. Notably, motor neurons first develop a deficit in synaptic vesicle fusion followed by that in quantal size and vesicle docking/priming, revealing specific functional deteriorations in synaptic transmission. Pharmacological stimulation of synaptic transmission can improve motor activity in aged animals. These results uncover a critical role for the nervous system in age-dependent motor activity decline in C. elegans and provide insights into how functional aging occurs in this organism.

Critical airway obstruction by mediastinal masses in the intensive care unit

Critical airway obstruction is a dreaded complication of a mediastinal mass. The acute management is difficult and catastrophic outcomes have been reported. A total of 19 patients, aged between 13 and 69 years, who had critical major airway obstruction due to mediastinal mass requiring mechanical ventilation were reviewed. Three patients had benign pathologies (retrosternal goitre, bronchogenic cyst, giant left atrium) and three had lymphoma. The remaining patients had advanced malignancies: metastatic mediastinal lymphadenopathy (n=6), thyroid carcinoma (n=1) and oesophageal carcinoma (n=6). Three patients underwent surgery, three received chemotherapy and 15 had airway stenting under deep intravenous sedation. Apart from one patient who had brain haemorrhage and nosocomial infection after cardiac surgery, all other patients were successfully weaned off ventilation within five days after the interventions to alleviate the major airway obstruction without major complications. All patients were discharged from hospital without supplemental oxygen. Patients who had benign pathologies and lymphoma (n=6, 32%) were still alive after a mean follow-up period of six years (range 3 to 10) and those with metastatic disease died after a mean survival period of 3.3 months (range 1 to 9). In summary, critical major airway obstruction is caused by a heterogeneous group of mediastinal pathologies, and the definitive treatment and long-term prognosis of these patients are highly dependent on the underlying aetiology. Combining various therapeutic modalities can lead to successful separation of these patients from mechanical ventilation within a short period of time.

C. elegans SIRT6/7 homolog SIR-2.4 promotes DAF-16 relocalization and function during stress

FoxO transcription factors and sirtuin family deacetylases regulate diverse biological processes, including stress responses and longevity. Here we show that the Caenorhabditis elegans sirtuin SIR-2.4—homolog of mammalian SIRT6 and SIRT7 proteins—promotes DAF-16–dependent transcription and stress-induced DAF-16 nuclear localization. SIR-2.4 is required for resistance to multiple stressors: heat shock, oxidative insult, and proteotoxicity. By contrast, SIR-2.4 is largely dispensable for DAF-16 nuclear localization and function in response to reduced insulin/IGF-1-like signaling. Although acetylation is known to regulate localization and activity of mammalian FoxO proteins, this modification has not been previously described on DAF-16. We find that DAF-16 is hyperacetylated in sir-2.4 mutants. Conversely, DAF-16 is acetylated by the acetyltransferase CBP-1, and DAF-16 is hypoacetylated and constitutively nuclear in response to cbp-1 inhibition. Surprisingly, a SIR-2.4 catalytic mutant efficiently rescues the DAF-16 localization defect in sir-2.4 null animals. Acetylation of DAF-16 by CBP-1 in vitro is inhibited by either wild-type or mutant SIR-2.4, suggesting that SIR-2.4 regulates DAF-16 acetylation indirectly, by preventing CBP-1-mediated acetylation under stress conditions. Taken together, our results identify SIR-2.4 as a critical regulator of DAF-16 specifically in the context of stress responses. Furthermore, they reveal a novel role for acetylation, modulated by the antagonistic activities of CBP-1 and SIR-2.4, in modulating DAF-16 localization and function.

Sensing and responding appropriately to environmental insults is a challenge facing all organisms. In the roundworm C. elegans, the FoxO protein DAF-16 moves to the nucleus in response to stress, where it regulates gene expression and plays a key role in ensuring organismal survival. In this manuscript, we characterize SIR-2.4 as a novel factor that promotes DAF-16 function during stress. SIR-2.4 is a member of a family of proteins called sirtuins, some of which promote increased lifespan in model organisms. Worms lacking SIR-2.4 show impaired DAF-16 nuclear recruitment, DAF-16–dependent gene expression, and survival in response to a variety of stressors. SIR-2.4 regulates DAF-16 by indirectly affecting levels of a modification called acetylation on DAF-16. Overall, our work has revealed SIR-2.4 to be a key new factor in stress resistance and DAF-16 regulation in C. elegans. Future studies will address whether mammalian SIR-2.4 homologs SIRT6 and SIRT7 act similarly towards mammalian FoxO proteins.

Enhanced energy metabolism contributes to the extended life span of calorie-restricted Caenorhabditis elegans

Caloric restriction (CR) markedly extends life span and improves the health of a broad number of species. Energy metabolism fundamentally contributes to the beneficial effects of CR, but the underlying mechanisms that are responsible for this effect remain enigmatic. A multidisciplinary approach that involves quantitative proteomics, immunochemistry, metabolic quantification, and life span analysis was used to determine how CR, which occurs in the Caenorhabditis elegans eat-2 mutants, modifies energy metabolism of the worm, and whether the observed modifications contribute to the CR-mediated physiological responses. A switch to fatty acid metabolism as an energy source and an enhanced rate of energy metabolism by eat-2 mutant nematodes were detected. Life span analyses validated the important role of these previously unknown alterations of energy metabolism in the CR-mediated longevity of nematodes. As observed in mice, the overexpression of the gene for the nematode analog of the cytosolic form of phosphoenolpyruvate carboxykinase caused a marked extension of the life span in C. elegans, presumably by enhancing energy metabolism via an altered rate of cataplerosis of tricarboxylic acid cycle anions. We conclude that an increase, not a decrease in fuel consumption, via an accelerated oxidation of fuels in the TCA cycle is involved in life span regulation; this mechanism may be conserved across phylogeny.

HSF-1 regulators DDL-1/2 link insulin-like signaling to heat-shock responses and modulation of longevity

Extended longevity is often correlated with increased resistance against various stressors. Insulin/IGF-1-like signaling (IIS) is known to have a conserved role in aging and cellular mechanisms against stress. In C. elegans, genetic studies suggest that heat-shock transcription factor HSF-1 is required for IIS to modulate longevity. Here, we report that the activity of HSF-1 is regulated by IIS. This regulation occurs at an early step of HSF-1 activation via two HSF-1 regulators, DDL-1 and DDL-2. Inhibition of DDL-1/2 increases longevity and thermotolerance in an hsf-1-dependent manner. Furthermore, biochemical analyses suggest that DDL-1/2 negatively regulate HSF-1 activity by forming a protein complex with HSF-1. The formation of this complex (DHIC) is affected by the phosphorylation status of DDL-1. Both the formation of DHIC and the phosphorylation of DDL-1 are controlled by IIS. Our findings point to DDL-1/2 as a link between IIS and the HSF-1 pathway.

Celecoxib extends C. elegans lifespan via inhibition of insulin-like signaling but not cyclooxygenase-2 activity

One goal of aging research is to develop interventions that combat age-related illnesses and slow aging. Although numerous mutations have been shown to achieve this in various model organisms, only a handful of chemicals have been identified to slow aging. Here, we report that celecoxib, a nonsteroidal anti-inflammatory drug widely used to treat pain and inflammation, extends Caenorhabditis elegans lifespan and delays the age-associated physiological changes, such as motor activity decline. Celecoxib also delays the progression of age-related proteotoxicity as well as tumor growth in C. elegans. Celecoxib was originally developed as a potent cyclooxygenase-2 (COX-2) inhibitor. However, the result from a structural-activity analysis demonstrated that the antiaging effect of celecoxib might be independent of its COX-2 inhibitory activity, as analogs of celecoxib that lack COX-2 inhibitory activity produce a similar effect on lifespan. Furthermore, we found that celecoxib acts directly on 3'-phosphoinositide-dependent kinase-1, a component of the insulin/IGF-1 signaling cascade to increase lifespan.

Solid plate-based dietary restriction in Caenorhabditis elegans

Reduction of food intake without malnutrition or starvation is known to increase lifespan and delay the onset of various age-related diseases in a wide range of species, including mammals. It also causes a decrease in body weight and fertility, as well as lower levels of plasma glucose, insulin, and IGF-1 in these animals. This treatment is often referred to as dietary restriction (DR) or caloric restriction (CR). The nematode Caenorhabditis elegans has emerged as an important model organism for studying the biology of aging. Both environmental and genetic manipulations have been used to model DR and have shown to extend lifespan in C. elegans. However, many of the reported DR studies in C. elegans were done by propagating animals in liquid media, while most of the genetic studies in the aging field were done on the standard solid agar in petri plates. Here we present a DR protocol using standard solid NGM agar-based plate with killed bacteria.

drr-2 encodes an eIF4H that acts downstream of TOR in diet-restriction-induced longevity of C. elegans

Dietary restriction (DR) results in a robust increase in lifespan while maintaining the physiology of much younger animals in a wide range of species. Here, we examine the role of drr-2, a DR-responsive gene recently identified, in determining the longevity of Caenorhabditis elegans. Inhibition of drr-2 has been shown to increase longevity. However, the molecular mechanisms by which drr-2 influences longevity remain unknown. We report here that drr-2 encodes an ortholog of human eukaryotic translation initiation factor 4H (eIF4H), whose function is to mediate the initiation step of mRNA translation. The molecular function of DRR-2 is validated by the association of DRR-2 with polysomes and by the decreased rate of protein synthesis observed in drr-2 knockdown animals. Previous studies have also suggested that DR might trigger a regulated reduction in drr-2 expression to initiate its longevity response. By examining the effect of increasing drr-2 expression on DR animals, we find that drr-2 is essential for a large portion of the longevity response to DR. The nutrient-sensing target of rapamycin (TOR) pathway has been shown to mediate the longevity effects of DR in C. elegans. Results from our genetic analyses suggest that eIF4H/DRR-2 functions downstream of TOR, but in parallel to the S6K/PHA-4 pathway to mediate the lifespan effects of DR. Together, our findings reveal an important role for eIF4H/drr-2 in the TOR-mediated longevity responses to DR.

Identification by machine vision of the rate of motor activity decline as a lifespan predictor in C. elegans

One challenge in aging research concerns identifying physiological parameters or biomarkers that can reflect the physical health of an animal and predict its lifespan. In C. elegans, a model organism widely used in aging research, motor deficits develop in old worms. Here we employed machine vision to quantify worm locomotion behavior throughout lifespan. We confirm that aging worms undergo a progressive decline in motor activity, beginning in early life. Importantly, the rate of motor activity decline rather than the absolute motor activity in the early-to-mid life of individual worms in an isogenic population inversely correlates with their lifespan, and thus may serve as a lifespan predictor. Long-lived mutant strains with deficits in insulin/IGF-1 signaling or food intake display a reduction in the rate of motor activity decline, suggesting that this parameter might also be used for across-strain comparison of healthspan. Our work identifies an endogenous physiological parameter for lifespan prediction and healthspan comparison.

Effects of supplemental vitamin E during the mature period on the reproduction performance of Taiwan Native Chicken cockerels

One-day-old Taiwan native male chicks were fed with maize-soybean rearing diets without supplemental vitamin E to 23 weeks of age. From 23 to 52 weeks of age, the cockerels (n = 90) were assigned at random to 5 dietary treatments and fed with maize-soybean diets supplemented with 0, 20, 40, 80 and 160 mg/kg of vitamin E (dl-alpha-tocopherol acetate). Pullets (225) of the same age were fed with standard diets throughout. They were artificially inseminated with one dose of 0.04 ml/bird intact and 5-fold diluted pooled semen at 31 to 43 weeks of age and at 49 weeks of age, respectively. The criteria evaluated included: semen quality, fertility and maximum and effective duration of fertility, blood characteristics, body and testes weight. Supplemental vitamin E did not affect cockerels' effective duration of fertility and percentage of fertility. However, when pullets were inseminated with diluted semen, supplementing 160 mg/kg vitamin E increased the maximum duration of fertility at 49 weeks of age. Cockerels receiving 40 to 160mg/kg supplements had higher sperm viability and motility after 39 weeks of age and those fed 80 mg/kg had higher sperm concentration at 39 weeks of age. Cockerels receiving supplements of more than 40 mg/kg vitamin E had higher body weight gain. Plasma cholesterol and testosterone were not affected by supplemental vitamin E. However, plasma luteinising hormone (LH) concentration was lower in cockerels fed 160 mg/kg. Lack of supplemental vitamin E over 39 weeks was associated with lower semen quality but did not reduce the proportion of fertile eggs laid by inseminated hens, perhaps because the insemination dose compensated for low sperm quality. We found that the maximum duration of fertility might be improved by supplementing 160 mg/kg vitamin E at 49 weeks of age.

New genes tied to endocrine, metabolic, and dietary regulation of lifespan from a Caenorhabditis elegans genomic RNAi screen

Most of our knowledge about the regulation of aging comes from mutants originally isolated for other phenotypes. To ask whether our current view of aging has been affected by selection bias, and to deepen our understanding of known longevity pathways, we screened a genomic Caenorhabditis elegans RNAi library for clones that extend lifespan. We identified 23 new longevity genes affecting signal transduction, the stress response, gene expression, and metabolism and assigned these genes to specific longevity pathways. Our most important findings are (i) that dietary restriction extends C. elegans' lifespan by down-regulating expression of key genes, including a gene required for methylation of many macromolecules, (ii) that integrin signaling is likely to play a general, evolutionarily conserved role in lifespan regulation, and (iii) that specific lipophilic hormones may influence lifespan in a DAF-16/FOXO-dependent fashion. Surprisingly, of the new genes that have conserved sequence domains, only one could not be associated with a known longevity pathway. Thus, our current view of the genetics of aging has probably not been distorted substantially by selection bias.

Effects of supplemental vitamin E during the laying period on the reproductive performance of Taiwan native chickens

1. One-day-old Taiwan Native Breeder female chicks were fed on maize/soybean growing diets without supplemental vitamin E from hatch to 17 weeks of age. After 17 weeks the birds (n = 300) were randomly assigned to 5 dietary treatments and fed on maize/soybean laying diets supplemented with 0, 40, 80, 120 and 160 mg/kg of vitamin E (dl-alpha-tocopherol acetate), respectively, until 46 weeks of age. The variates measured included: age at first egg, feed consumption (FC), feed efficiency (FE), egg production (EP), egg weight (EW), egg specific gravity (ESG), eggshell strength (ESS), fertility and hatchability. 2. The addition of 120mg/kg of vitamin E lowered the first EW (P<0.05); however, there was no significant difference in the age or body weight (BW) of pullets at first egg or mortality rate to 46 weeks of age among the treatments. FE and egg mass were improved (P<0.05) in pullets fed 80 mg/kg of supplemental vitamin E. A significant increase in EP was observed after peak EP in pullets given 80 mg/kg of supplemental vitamin E. However, this favourable effect decreased as supplemental vitamin E exceeded 80 mg/kg. 3. From 17 to 46 weeks of age, egg quality (ESG and ESS) decreased with age. However, there was no correlation between age and fertility or hatchability during the experimental period, suggesting that egg quality is more age-sensitive than reproductive performance for breeder pullets. 4. Compared with the control, fertility and hatchability of all eggs set for the treatment with 80 mg/kg supplemental vitamin E increased by 7.7 and 13.4%, respectively. There was no difference in the hatchability of fertile eggs. 5. These results suggest that using supplemental vitamin E during the laying period can improve the reproductive performance of breeder pullets. The addition of 80 mg/kg of vitamin E obtained the best performance in EP, egg mass, FE (feed/egg), hatchability and fertility.

Regulation of aging and age-related disease by DAF-16 and heat-shock factor

The Caenorhabditis elegans transcription factor HSF-1, which regulates the heat-shock response, also influences aging. Reducing hsf-1 activity accelerates tissue aging and shortens life-span, and we show that hsf-1 overexpression extends lifespan. We find that HSF-1, like the transcription factor DAF-16, is required for daf-2-insulin/IGF-1 receptor mutations to extend life-span. Our findings suggest this is because HSF-1 and DAF-16 together activate expression of specific genes, including genes encoding small heat-shock proteins, which in turn promote longevity. The small heat-shock proteins also delay the onset of polyglutamine-expansion protein aggregation, suggesting that these proteins couple the normal aging process to this type of age-related disease.

Rates of behavior and aging specified by mitochondrial function during development

To explore the role of mitochondrial activity in the aging process, we have lowered the activity of the electron transport chain and adenosine 5'-triphosphate (ATP) synthase with RNA interference (RNAi) in Caenorhabditis elegans. These perturbations reduced body size and behavioral rates and extended adult life-span. Restoring messenger RNA to near-normal levels during adulthood did not elevate ATP levels and did not correct any of these phenotypes. Conversely, inhibiting respiratory-chain components during adulthood only did not reset behavioral rates and did not affect life-span. Thus, the developing animal appears to contain a regulatory system that monitors mitochondrial activity early in life and, in response, establishes rates of respiration, behavior, and aging that persist during adulthood.

The cyclo-oxygenase-2 inhibitor celecoxib perturbs intracellular calcium by inhibiting endoplasmic reticulum Ca2+-ATPases: a plausible link with its anti-tumour effect and cardiovascular risks

Substantial evidence indicates that the cyclo-oxygenase-2 (COX-2) inhibitor celecoxib, a widely prescribed anti-inflammatory agent, displays anti-tumour effect by sensitizing cancer cells to apoptosis. As part of our effort to understand the mechanism by which celecoxib mediates apoptosis in androgen-independent prostate cancer cells, we investigated its effect on intracellular calcium concentration ([Ca(2+)](i)). Digital ratiometric imaging analysis indicates that exposure of PC-3 cells to celecoxib stimulates an immediate [Ca(2+)](i) rise in a dose- and time-dependent manner. Kinetic data show that this Ca(2+) signal arises from internal Ca(2+) release in conjunction with external Ca(2+) influx. Examinations of the biochemical mechanism responsible for this Ca(2+) mobilization indicate that celecoxib blocks endoplasmic reticulum (ER) Ca(2+)-ATPases. Consequently, inhibition of this Ca(2+) reuptake mechanism results in Ca(2+) mobilization from ER stores followed by capacitative calcium entry, leading to [Ca(2+)](i) elevation. In view of the important role of Ca(2+) in apoptosis regulation, this Ca(2+) perturbation may represent part of the signalling mechanism that celecoxib uses to trigger rapid apoptotic death in cancer cells. This Ca(2+)-ATPase inhibitory activity is highly specific for celecoxib, and is not noted with other COX inhibitors tested, including aspirin, ibuprofen, naproxen, rofecoxib (Vioxx), DuP697 and NS398. Moreover, it is noteworthy that this activity is also observed in many other cell lines examined, including A7r5 smooth muscle cells, NIH 3T3 fibroblast cells and Jurkat T cells. Consequently, this Ca(2+)-perturbing effect may provide a plausible link with the reported toxicities of celecoxib such as increased cardiovascular risks in long-term anti-inflammatory therapy.

Genetic analysis of tissue aging in Caenorhabditis elegans: a role for heat-shock factor and bacterial proliferation

The genetic analysis of life span has revealed many interesting genes and pathways; however, our understanding of aging has been limited by the lack of a way to assay the aging process itself. Here we show that the tissues of aging worms have a characteristic appearance that is easy to recognize and quantify using Nomarski optics. We have used this assay to determine whether life-span mutations affect the rate of aging, to identify animals that age more rapidly than normal, and to infer the cause of death in C. elegans. Mutations that reduce insulin/IGF-1 signaling double the life span of C. elegans, and we find that tissue decline is slowed in these mutants. Thus this endocrine system appears to influence the rate at which tissues age. This effect extends even to the germline, which is the only mitotically active tissue in the adult. We find that Nomarski microscopy also allows a ready distinction between short-lived mutants that age more rapidly than normal and those that are simply sick, and we have identified an RNAi clone that confers a dramatic rapid-aging phenotype. This clone encodes the C. elegans heat-shock factor (HSF), a transcription factor that regulates the response to heat and oxidative stress. This suggests that heat-shock proteins, many of which act as chaperones, may function in normal animals to slow the rate of aging. Finally, we have identified a cause of death of C. elegans: namely, proliferating bacteria. This suggests that increased susceptibility to bacterial infections contributes to mortality in these animals, just as it does in humans.

Phosphoinositide 3-kinase facilitates antigen-stimulated Ca(2+) influx in RBL-2H3 mast cells via a phosphatidylinositol 3,4,5-trisphosphate-sensitive Ca(2+) entry mechanism

This study presents evidence that phosphoinositide 3-kinase (PI3K) plays a concerted role with phospholipase Cgamma in initiating antigen-mediated Ca(2+) signaling in mast cells via a phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P(3))-sensitive Ca(2+) entry pathway. Exogenous PI(3,4,5)P(3) at concentrations close to its physiological level induces instantaneous Ca(2+) influx into RBL-2H3 cells. This PI(3,4,5)P(3)-induced intracellular Ca(2+) increase is independent of phospholipase C activity or the depletion of internal stores. Moreover, inhibition of PI3K by LY294002 or by overexpression of the dominant negative inhibitor Deltap85 suppresses the Ca(2+) response to the cross-linking of the high affinity receptor for IgE (FcepsilonRI). Concomitant treatment of RBL-2H3 cells with LY294002 or Deltap85 and 2-aminoethyl diphenylborate, a cell-permeant antagonist of D-myo-inositol 1,4,5-trisphosphate receptors, abrogates antigen-induced Ca(2+) signals, whereas either treatment alone gives rise to partial inhibition. Conceivably, PI(3,4,5)P(3)-sensitive Ca(2+) entry and capacitative Ca(2+) entry represent major Ca(2+) influx pathways that sustain elevated [Ca(2+)]i to achieve optimal physiological responses. This study also refutes the second messenger role of D-myo-inositol 1,3,4,5-tetrakisphosphate in regulating FcepsilonRI-mediated Ca(2+) response. Considering the underlying mechanism, our data suggest that PI(3,4,5)P(3) directly stimulates a Ca(2+) transport system in plasma membranes. Together, these data provide a molecular basis to account for the role of PI3K in the regulation of FcepsilonRI-mediated degranulation in mast cells.

A phosphatidylinositol 3,4,5-trisphosphate analogue with low serum protein-binding affinity

Phosphatidylinositol 3,4,5-trisphosphate (PIP3) plays an important role in the regulation of diverse physiological functions. Recent evidence indicates that PIP3 is cell permeant, and can be added exogenously to modulate cellular responses. However, like many other phospholipids, PIP3 binds serum proteins with high affinity, resulting in rapid deactivation of this lipid second messenger. Our study indicates that bovine serum albumin (BSA) at concentrations as low as 10 microg/mL abrogated the biological activity of dipalmitoyl-PIP3. This nonspecific interaction with serum proteins hampers the use of PIP3 in biological studies where serum is needed. We report here an ether-linked PIP3 analogue, 1-O-(1-O-hexadecyl-2-O-methyl-sn-glycero-3-phosphoryl)-myo-inositol 3,4,5-trisphosphate (C16Me-PIP3). which displays low serum protein-binding affinity while retaining the biological function of PIP3. The affinity of C16Me-PIP3 with BSA was two orders of magnitude lower than that of its dipalmitoyl-counterpart. Biochemical data indicate that C16Me-PIP3 was able to stimulate Ca2+ influx in T cells in the presence of moderate levels (up to 1 mg/mL) of BSA. Thus. C16Me-PIP3 may provide a useful tool to study the physiological function of phosphoinositide (PI) 3-kinase in vivo.

Novel function of phosphoinositide 3-kinase in T cell Ca2+ signaling. A phosphatidylinositol 3,4,5-trisphosphate-mediated Ca2+ entry mechanism

This study presents evidence that phosphoinositide (PI) 3-kinase is involved in T cell Ca(2+) signaling via a phosphatidylinositol 3,4, 5-trisphosphate PI(3,4,5)P(3)-sensitive Ca(2+) entry pathway. First, exogenous PI(3,4,5)P(3) at concentrations close to its physiological levels induces Ca(2+) influx in T cells, whereas PI(3,4)P(2), PI(4, 5)P(2), and PI(3)P have no effect on [Ca(2+)](i). This Ca(2+) entry mechanism is cell type-specific as B cells and a number of cell lines examined do not respond to PI(3,4,5)P(3) stimulation. Second, inhibition of PI 3-kinase by wortmannin and by overexpression of the dominant negative inhibitor Deltap85 suppresses anti-CD3-induced Ca(2+) response, which could be reversed by subsequent exposure to PI(3,4,5)P(3). Third, PI(3,4,5)P(3) is capable of stimulating Ca(2+) efflux from Ca(2+)-loaded plasma membrane vesicles prepared from Jurkat T cells, suggesting that PI(3,4,5)P(3) interacts with a Ca(2+) entry system directly or via a membrane-bound protein. Fourth, although D-myo-inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4, 5)P(4)) mimics PI(3,4,5)P(3) in many aspects of biochemical functions such as membrane binding and Ca(2+) transport, we raise evidence that Ins(1,3,4,5)P(4) does not play a role in anti-CD3- or PI(3,4,5)P(3)-mediated Ca(2+) entry. This PI(3,4,5)P(3)-stimulated Ca(2+) influx connotes physiological significance, considering the pivotal role of PI 3-kinase in the regulation of T cell function. Given that PI 3-kinase and phospholipase C-gamma form multifunctional complexes downstream of many receptor signaling pathways, we hypothesize that PI(3,4,5)P(3)-induced Ca(2+) entry acts concertedly with Ins(1,4,5)P(3)-induced Ca(2+) release in initiating T cell Ca(2+) signaling. By using a biotinylated analog of PI(3,4,5)P(3) as the affinity probe, we have detected several putative PI(3,4,5)P(3)-binding proteins in T cell plasma membranes.

The cyclooxygenase-2 inhibitor celecoxib induces apoptosis by blocking Akt activation in human prostate cancer cells independently of Bcl-2

This study investigates the apoptotic activity of the cyclooxygenase-2 (COX-2) inhibitor celecoxib in prostate carcinoma cells. COX-2 is constitutively expressed in androgen-responsive LNCaP and androgen-nonresponsive PC-3 cells. Exposure of these cells to celecoxib induces characteristic features of apoptosis, including morphological changes, DNA laddering, and caspase-3 activation, whereas piroxicam, a COX-1-specific inhibitor, displays no appreciable effect on either cancer cell line even after prolonged exposure. Moreover, the potency of celecoxib in apoptosis induction is significantly higher than that of other COX-2 inhibitors examined despite the observation that these inhibitors exhibit similar IC(50) in COX-2 inhibition. It is noteworthy that normal human prostate epithelial cells, expressing a marginally detectable level of COX-2, are insensitive to the induction of apoptosis by celecoxib. These data suggest a correlation between COX-2 expression and sensitivity to the apoptotic effect of the COX-2 inhibitor. In an effort to delineate the underlying mechanism, we examined the effect of celecoxib on the expression of Bcl-2 as well as the activation of the key anti-apoptotic kinase Akt. In contrast to an earlier report that attributed the apoptotic activity of NS398 in LNCaP cells to Bcl-2 down-regulation, we provide evidence that the induction of apoptosis by celecoxib in LNCaP and PC-3 cells is independent of Bcl-2. First, treatment with celecoxib does not alter the cellular Bcl-2 level in both cell lines. Second, enforced Bcl-2 expression in PC-3 cells does not confer protection against the induction of apoptosis by celecoxib. Our data show that celecoxib treatment blocks the phosphorylation of Akt. This correlation is supported by studies showing that overexpression of constitutively active Akt protects PC-3 cells from celecoxib-induced apoptosis. Nevertheless, how celecoxib down-regulates Akt is not clear because the drug does not adversely affect phosphoinositide 3-kinase activity in vivo and okadaic acid, a protein phosphatase 2A inhibitor, cannot rescue the inhibition. In summary, our data demonstrate that inhibition of Akt activation may play a crucial role in the induction of apoptosis by celecoxib.

Identification of multiple phosphoinositide-specific phospholipases D as new regulatory enzymes for phosphatidylinositol 3,4, 5-trisphosphate

In the course of delineating the regulatory mechanism underlying phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3) metabolism, we have discovered three distinct phosphoinositide-specific phospholipase D (PI-PLD) isozymes from rat brain, tentatively designated as PI-PLDa, PI-PLDb, and PI-PLDc. These enzymes convert [3H]PI(3,4,5)P3 to generate a novel inositol phosphate, D-myo-[3H]inositol 3,4,5-trisphosphate ([3H]Ins(3,4,5)P3) and phosphatidic acid. These isozymes are predominantly associated with the cytosol, a notable difference from phosphatidylcholine PLDs. They are partially purified by a three-step procedure consisting of DEAE, heparin, and Sephacryl S-200 chromatography. PI-PLDa and PI-PLDb display a high degree of substrate specificity for PI(3,4, 5)P3, with a relative potency of PI(3,4,5)P3 >> phosphatidylinositol 3-phosphate (PI(3)P) or phosphatidylinositol 4-phosphate (PI(4)P) > phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) > phosphatidylinositol 3,4-bisphosphate (PI(3,4)P2). In contrast, PI-PLDc preferentially utilizes PI(3)P as substrate, followed by, in sequence, PI(3,4,5)P3, PI(4)P, PI(3,4)P2, and PI(4,5)P2. Both PI(3, 4)P2 and PI(4,5)P2 are poor substrates for all three isozymes, indicating that the regulatory mechanisms underlying these phosphoinositides are different from that of PI(3,4,5)P3. None of these enzymes reacts with phosphatidylcholine, phosphatidylserine, or phosphatidylethanolamine. All three PI-PLDs are Ca2+-dependent. Among them, PI-PLDb and PI-PLDc show maximum activities within a sub-microM range (0.3 and 0.9 microM Ca2+, respectively), whereas PI-PLDa exhibits an optimal [Ca2+] at 20 microM. In contrast to PC-PLD, Mg2+ has no significant effect on the enzyme activity. All three enzymes require sodium deoxycholate for optimal activities; other detergents examined including Triton X-100 and Nonidet P-40 are, however, inhibitory. In addition, PI(4,5)P2 stimulates these isozymes in a dose-dependent manner. Enhancement in the enzyme activity is noted only when the molar ratio of PI(4,5)P2 to PI(3,4, 5)P3 is between 1:1 and 2:1.

14-3-3 proteins are required for maintenance of Raf-1 phosphorylation and kinase activity

By binding to serine-phosphorylated proteins, 14-3-3 proteins function as effectors of serine phosphorylation. The exact mechanism of their action is, however, still largely unknown. Here we demonstrate a requirement for 14-3-3 for Raf-1 kinase activity and phosphorylation. Expression of dominant negative forms of 14-3-3 resulted in the loss of a critical Raf-1 phosphorylation, while overexpression of 14-3-3 resulted in enhanced phosphorylation of this site. 14-3-3 levels, therefore, regulate the stoichiometry of Raf-1 phosphorylation and its potential activity in the cell. Phosphorylation of Raf-1, however, was insufficient by itself for kinase activity. Removal of 14-3-3 from phosphorylated Raf abrogated kinase activity, whereas addition of 14-3-3 restored it. This supports a paradigm in which the effects of phosphorylation on serine as well as tyrosine residues are mediated by inducible protein-protein interactions.

Phosphatidylinositol 3,4,5-trisphosphate triggers platelet aggregation by activating Ca2+ influx

Exogenous phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P3] stimulates the aggregation of washed rabbit platelets in a Ca2+- and dose-dependent manner. This aggregation is reversible at low PtdIns(3,4,5)P3 levels, but becomes irreversible when the concentration exceeds a threshold of about 20 microM. Other D-3 and D-4 phosphoinositides examined, including phosphatidylinositol 3, 4-bisphosphate [PtdIns(3,4)P2], phosphatidylinositol 4, 5-bisphosphate [PtdIns(4,5)P2], and phosphatidylinositol 3-monophosphate [PtdIns(3)P], fail to exert appreciable platelet activation at comparable concentrations. In addition, PtdIns(3,4, 5)P3 can reverse the inhibitory effect of wortmannin on thrombin-induced platelet aggregation. Taken together with the observation that PtdIns(3,4,5)P3 is readily incorporated into cell membranes, these findings reaffirm the second messenger role of PtdIns(3,4,5)P3 in thrombin receptor activation. The existence of a PtdIns(3,4,5)P3-dependent Ca2+ entry system on platelet membranes is supported by the partial inhibition of thrombin-induced Ca2+ influx by wortmannin. Evidence suggests that this system differs from receptor-operated nonselective Ca2+ channels. However, the mechanism by which PtdIns(3,4,5)P3 facilitates Ca2+ entry remains unclear. Although PtdIns(3,4,5)P3 has been known to stimulate phospholipase C-gamma (PLC-gamma), internal Ca2+ mobilization does not play a significant role in the cytosolic Ca2+ increase in response to PtdIns(3,4,5)P3 stimulation. Collectively, these data provide a putative link between PtdIns(3,4,5)P3 and Ca2+ signaling, which may, in part, account for the regulatory function of PtdIns(3,4,5)P3 during platelet aggregation. Moreover, this study bears out the notion that individual PI 3-kinase lipid products play distinct roles in the regulation of cellular functions.

Phosphoinositide 3-kinase in rat liver nuclei

Biochemical and immunochemical data from the present investigation reveal the existence of a p85/p110 phosphoinositide 3-kinase (PI 3-kinase) in rat liver nuclei. 32P-Labeling of membrane phosphoinositides by incubating intact nuclei with [gamma-32P]ATP results in the formation of [32P]phosphatidyl-inositol 3,4, 5-trisphosphate [PtdIns(3,4,5)P3], accompanied by small quantities of [32P]phosphatidylinositol 3-phosphate [PtdIns(3)P]. Studies with subnuclear fractions indicate that the PI 3-kinase is not confined to nuclear membranes. The nuclear soluble fraction also contains PI 3-kinase and an array of inositide-metabolizing enzymes, including phospholipase C (PLC), phosphoinositide phosphatase, and diacylglycerol (DAG) kinase. As a result, exposure of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] to the nuclear extract in the presence of [gamma-32P]ATP generates a series of 32P-labeled D-3 phosphoinositides and phosphatidic acid (PA) in an interdependent manner. On the basis of the immunological reactivity and kinetic behavior, the nuclear PI 3-kinase is analogous, if not identical, to PI 3-kinase alpha, and constitutes about 5% of the total PI 3-kinase in the cell. Moreover, we test the premise that nuclear PI 3-kinase may, in part, be regulated through the control of substrate availability by PtdIns(4,5)P2-binding proteins. Effect of CapG, a nuclear actin-regulatory protein, on PI 3-kinase activity is examined in view of its unique Ca2+-dependent PtdIns(4, 5)P2-binding capability. In vitro data show that the CapG-mediated inhibition of nuclear PI 3-kinase is prompted by PKC phosphorylation of CapG and elevated [Ca2+]. This CapG-dependent regulation provides a plausible link between nuclear PLC and PI 3-kinase pathways for cross-communications. Taken together, these findings provide definite data concerning the presence of an autonomous PI 3-kinase cycle in rat liver nuclei. The nuclear location of PI 3-kinase may lead to a better understanding regarding its functional role in transducing signals from the plasma membrane to the nucleus in response to diverse physiological stimuli.

Regulation of nuclear calcium uptake by inositol phosphates and external calcium

Factors affecting Ins(1,3,4,5)P4-mediated nuclear Ca2+ uptake are investigated, which include Ins(1,3,4,5)P4 receptor ligand specificity and free external Ca2+ concentrations. Among various inositol phosphates examined, Ins(1,3,4,5)P4, Ins(3,4,5,6)P4, and Ins(1,3,4,5,6)P5 can also stimulate 45Ca2+ influx into isolated rat liver nuclei by activating the Ins(1,3,4,5)P4 receptor-mediated Ca2+ uptake into the nucleus. The EC50 values of these polyphosphates range between 200 and 300 nM, which are 3-4 folds higher than that of Ins(1,3,4,5)P4. It is plausible that these polyphosphates in conjunction with Ins(1,3,4,5)P4 take part in the regulation of nuclear Ca2+ uptake in view of their intracellular levels during cell activation. Moreover, the inositol phosphate-induced Ca2+ uptake is facilitated by increasing Ca2+ levels in the uptake milieu, suggesting a possible link between cytosolic and nuclear Ca2+ signals through the Ins(1,3,4,5)P4 receptor.

Myelin basic protein-specific T helper 2 (Th2) cells cause experimental autoimmune encephalomyelitis in immunodeficient hosts rather than protect them from the disease

Chronic inflammatory autoimmune diseases such as multiple sclerosis, diabetes, and rheumatoid arthritis are caused by CD4(+) Th1 cells. Because Th2 cells antagonize Th1 cell functions in several ways, it is believed that immune deviation towards Th2 can prevent or cure autoimmune diseases. Experimental autoimmune encephalomyelitis (EAE) is a demyelinating disease used as a model for multiple sclerosis. Using an adoptive transfer system we assessed the role of Th1 and Th2 cells in EAE. In vitro generated Th1 and Th2 cells from myelin basic protein (MBP)-specific TCR transgenic mice were transferred into normal and immunodeficient mice. Th1 cells caused EAE in all recipients after a brief preclinical phase. Surprisingly, Th2 cells also caused EAE in RAG-1 KO mice and in alphabeta T cell-deficient mice, albeit after a longer preclinical phase. Normal or gammadelta T cell-deficient mice were resistant to EAE induced by Th2 cells. The histopathological features of this disease resembled those of an allergic process. In addition, disease induction by Th1 cells was not altered by coadmininstration of Th2 cells in any of the recipients. These findings indicate that MBP-specific Th2 cells have the potential to induce EAE and that the disease induced by previously activated Th1 cells cannot be prevented by normal lymphocytes nor by previously activated Th2 cells.

Sequence analysis of one major basic beta-crystallin (beta Bp) of amphibian lenses: evolutionary comparison and phylogenetic relatedness between beta- and gamma-crystallins

beta Bp-Crystallin, a major basic beta-crystallin of vertebrate eye lens, is developmentally regulated during the process of amphibian metamorphosis. In order to facilitate the determination of the primary sequence of this ubiquitous crystallin present in all vertebrate species, cDNA mixture was synthesized from the poly(A)+ mRNA isolated from bullfrog eye lenses. A protocol of Rapid Amplification of cDNA Ends (RACE) was used to amplify cDNAs encoding beta Bp-crystallin by polymerase chain reaction (PCR). PCR-amplified product corresponding to beta Bp-crystallin was then ligated into pGEM-T vector and then transformed into E. coli strain JM109. One complete full-length reading frame of 615 base pairs, which covers a deduced protein sequence of 205 amino acids, including the universal initiating methionine, was revealed by automatic nucleotide sequencing with a fluorescence-based dideoxynucleotide chain-termination method. It shows 83, 74, 78 and 80 percent sequence similarity to the homologous beta 2 crystallins of chicken, rat, bovine, and human species, respectively, revealing the close structural relationship among beta Bp-crystallins even from remotely related species. In this study phylogenetic trees based on nucleotide and protein sequences of various beta- and gamma-crystallins from different vertebrate classes are constructed using a combination of distance matrix and approximate parsimony methods, which corroborate the previous supposition that beta- and gamma-crystallins form a superfamily with a common ancestry.

Characterization of gamma-crystallin from a catfish: structural characterization of one major isoform with high methionine by cDNA sequencing

gamma-Crystallin is the major and most abundant lens protein present in the eye lens of most teleostean fishes. To facilitate structural characterization of gamma-crystallins isolated from the lens of the catfishes (Clarias fuscus), a cDNA mixture was synthesized from the poly(A)+mRNA isolated from fresh eye lenses, and amplification by polymerase chain reaction (PCR) was adopted to obtain cDNAs encoding various gamma-crystallins. Plasmids of transformed E. coli strain JM109 containing amplified gamma-crystallin cDNAs were purified and prepared for nucleotide sequencing by the dideoxynucleotide chain-termination method. Sequencing more than five clones containing DNA inserts of 0.52 kb revealed the presence of one major isoform with a complete reading frame of 534 base pairs, covering a gamma-crystallin (gamma M1) with a deduced protein sequence of 177 amino acids excluding the initiating methionine. It was of interest to find that this crystallin of pI 9.1 contains a high-methionine content of 15.3% in contrast to those gamma-crystallins of low-methionine content from most mammalian lenses. Sequence comparisons of catfish gamma M1-crystallin with those published sequences of gamma-crystallins from carp, bovine and mouse lenses indicate that there is approx. an 82% sequence homology between the catfish and the carp species of piscine class whereas only 51-58% homology is found between mammals and the catfish. Moreover the differences in the hydropathy profiles for these two groups of gamma-crystallins, i.e. one with a high-methionine content from teleostean fishes and the other with a low-methionine content from mammalian species, reflect a distinct variance in the polarity distributions of surface amino acids in these crystallins.(ABSTRACT TRUNCATED AT 250 WORDS)