Brain Protein Synthesis Research Articles

The ketamine metabolite (2R,6R)-hydroxynorketamine rescues hippocampal mRNA translation, synaptic plasticity and memory in mouse models of Alzheimer's disease.

Impaired brain protein synthesis, synaptic plasticity, and memory are major hallmarks of Alzheimer's disease (AD). The ketamine metabolite (2R,6R)-hydroxynorketamine (HNK) has been shown to modulate protein synthesis, but its effects on memory in AD models remain elusive. We investigated the effects of HNK on hippocampal protein synthesis, long-term potentiation (LTP), and memory in AD mouse models. HNK activated extracellular signal-regulated kinase 1/2 (ERK1/2), mechanistic target of rapamycin (mTOR), and p70S6 kinase 1 (S6K1)/ribosomal protein S6 signaling pathways. Treatment with HNK rescued hippocampal LTP and memory deficits in amyloid-β oligomers (AβO)-infused mice in an ERK1/2-dependent manner. Treatment with HNK further corrected aberrant transcription, LTP and memory in aged APP/PS1 mice. Our findings demonstrate that HNK induces signaling and transcriptional responses that correct synaptic and memory deficits in AD mice. These results raise the prospect that HNK could serve as a therapeutic approach in AD. The ketamine metabolite HNK activates hippocampal ERK/mTOR/S6 signaling pathways. HNK corrects hippocampal synaptic and memory defects in two mouse models of AD. Rescue of synaptic and memory impairments by HNK depends on ERK signaling. HNK corrects aberrant transcriptional signatures in APP/PS1 mice.

Correction of mTORC1‐mediated brain protein synthesis rescues memory in mouse models of Alzheimer’s disease

AbstractBackgroundAlzheimer’s disease (AD) is a neurodegenerative disorder characterized by synapse failure and cognitive decline. Brain mRNA translation is central to synaptic plasticity and cognition, and converging evidence indicates it is impaired in AD. The mammalian target of rapamycin complex 1 (mTORC1) pathway plays a key role in regulating protein synthesis, and mTORC1 signaling has received considerable attention in AD research. In this current work, we investigated whether stimulating mTORC1‐mediated protein synthesis can alleviate the impairments in synaptic plasticity and memory in AD mice.MethodTo address this question, we used two different approaches: 1. genetic reduction of the translational repressors, Fragile X messenger ribonucleoprotein (FMRP) or eukaryotic initiation factor 4E (eIF4E)‐binding protein 2 (4E‐BP2); and 2. pharmacological treatment with (2R,6R)‐hydroxynorketamine (HNK), an active metabolite of the antidepressant ketamine that stimulates mTORC1 signaling.ResultOur results showed that genetic reduction of FMRP and 4E‐BP2 prevented the inhibition of hippocampal protein synthesis and memory impairment induced by amyloid‐β oligomers (AβOs) in mice. Reduction of 4E‐BP2 further rescued memory deficits in the APPswe/PS1dE9 (APP/PS1) transgenic mouse model of AD. Moreover, HNK treatment prevented deficits in long‐term potentiation (LTP) and fear memory in AbO‐infused and APP/PS1 mice.ConclusionTaken together, our findings indicate that strategies targeting mRNA translation correct hippocampal protein synthesis, synaptic plasticity and memory deficits in AD models, and raise the prospect that HNK could emerge as a therapeutic approach in AD.

Rapid cell type-specific nascent proteome labeling in Drosophila.

Controlled protein synthesis is required to regulate gene expression and is often carried out in a cell type-specific manner. Protein synthesis is commonly measured by labeling the nascent proteome with amino acid analogs or isotope-containing amino acids. These methods have been difficult to implement in vivo as they require lengthy amino acid replacement procedures. O-propargyl-puromycin (OPP) is a puromycin analog that incorporates into nascent polypeptide chains. Through its terminal alkyne, OPP can be conjugated to a fluorophore-azide for directly visualizing nascent protein synthesis, or to a biotin-azide for capture and identification of newly-synthesized proteins. To achieve cell type-specific OPP incorporation, we developed phenylacetyl-OPP (PhAc-OPP), a puromycin analog harboring an enzyme-labile blocking group that can be removed by penicillin G acylase (PGA). Here, we show that cell type-specific PGA expression in Drosophila can be used to achieve OPP labeling of newly-synthesized proteins in targeted cell populations within the brain. Following a brief 2 hr incubation of intact brains with PhAc-OPP, we observe robust imaging and affinity purification of OPP-labeled nascent proteins in PGA-targeted cell populations. We apply this method to show a pronounced age-related decline in neuronal protein synthesis in the fly brain, demonstrating the capability of PhAc-OPP to quantitatively capture in vivo protein synthesis states. This method, which we call POPPi (PGA-dependent OPP incorporation), should be applicable for rapidly visualizing protein synthesis and identifying nascent proteins synthesized under diverse physiological and pathological conditions with cellular specificity in vivo.

Insulin-like growth factor-1 supplementation promotes brain maturation in preterm pigs.

Very preterm infants show low levels of insulin-like growth factor-1 (IGF-1), which is associated with postnatal growth restriction and poor neurological outcomes. It remains unknown whether supplemental IGF-1 may stimulate neurodevelopment in preterm neonates. Using cesarean-delivered preterm pigs as a model of preterm infants, we investigated the effects of supplemental IGF-1 on motor function and regional and cellular brain development. Pigs were treated with 2.25 mg/kg/day of recombinant human IGF-1/IGF binding protein 3 complex from birth until Day 5 or 9 before collection of brain samples for quantitative immunohistochemistry (IHC), RNA-seq and qPCR analyses. Brain protein synthesis was measured using in vivo labeling with [2H5] phenylalanine. We showed that the IGF-1 receptor was widely distributed in the brain and largely coexisted with immature neurons. Region-specific quantification of IHC labeling showed that IGF-1 treatment promoted neuronal differentiation, increased subcortical myelination, and attenuated synaptogenesis in a region- and time-dependent manner. The expression levels of genes involved in neuronal and oligodendrocyte maturation, angiogenic and transport functions were altered, reflecting enhanced brain maturation in response to IGF-1 treatment. Cerebellar protein synthesis was increased by 19% at Day 5 and 14% at Day 9 after IGF-1 treatment. Treatment had no effect on Iba1-positive microglia or regional brain weights and did not affect motor development or the expression of genes related to IGF-1 signaling. In conclusion, the data show that supplemental IGF-1 promotes brain maturation in newborn preterm pigs. The results provide further support for IGF-1 supplementation therapy in the early postnatal period in preterm infants.SIGNIFICANCE STATEMENTDeficiency of systemic insulin-like growth factor-1 (IGF-1) is associated with delayed neurological development in preterm infants. Here, we show that the IGF-1 receptor is primarily expressed in immature neurons in the developing brain of the translational preterm pig model. Supplementation with IGF-1 accelerates neuron differentiation in the hippocampus and promotes myelination in subcortical white matter regions in a time-dependent way. Furthermore, systemic IGF-1 supplementation stimulates cerebral protein synthesis. Our study suggests that IGF-1 therapy in the early postnatal period might be supportive for neurodevelopment in preterm infants.

Insulin Treatment Affects Brain Protein Synthesis Rate in Streptozotocin-Induced Diabetic Rats

The purpose of this study was to determine whether insulin treatment affected the rate of brain protein synthesis in diabetic rats. Experiments were conducted on three groups of rats given streptozotocin without insulin treatment (diabetes), treated with streptozotocin + insulin (diabetes + insulin) or treated with neither streptozotocin nor insulin (control). The fractional rates of protein synthesis in brain, liver and kidney of diabetic rats treated with insulin were significantly greater than in diabetic rats without insulin treatment. In brain, liver and kidney, the RNA activity [g protein synthesized/(g RNA·d)] was significantly correlated with the fractional rate of protein synthesis. The RNA concentration (mg RNA/g protein) was not related to the fractional rate of protein synthesis in any organ. The results suggest that insulin treatment of diabetic rats is likely to increase the rate of protein synthesis in the brain, and that RNA activity is related to the fractional rate of brain protein synthesis.

Increased rates of brain protein synthesis during [N1,N2] sleep: L-[1-11C]leucine PET studies in human subjects

During sleep, reduced brain energy demands provide an opportunity for biosynthetic processes like protein synthesis. Sleep is required for some forms of memory consolidation which requires de novo protein synthesis. We measured regional cerebral protein synthesis rates (rCPS) in human subjects to ascertain how rCPS is affected during sleep. Subjects underwent three consecutive L-[1-11C]leucine PET scans with simultaneous polysomnography: 1. rested awake, 2. sleep-deprived awake, 3. sleep. Measured rCPS were similar across the three conditions. Variations in sleep stage times during sleep scans were used to estimate rCPS in sleep stages under the assumption that measured rCPS is the weighted sum of rCPS in each stage, with weights reflecting time and availability of [11C]leucine in that stage. During sleep scans, subjects spent most of the time in N2, N3, and awake and very little time in N1 and REM; rCPS in N1 and REM could not be reliably estimated. When stages N1 and N2 were combined [N1,N2], estimates of rCPS were more robust. In selective regions, estimated rCPS were statistically significantly higher (30–39%) in [N1,N2] compared with N3; estimated rCPS in N3 were similar to values measured in sleep-deprived awake scans. Results indicate increased rates of protein synthesis linked to [N1,N2] sleep.

Expression of Concern: Potential Risks and Unknown Effects of mRNA Vaccines on Population Health (6th Rev). Damages Are Being Materialized

Several mRNA vaccines are used on the population in the U.S. I started predicting the dangers of mRNA vaccines before March 2021 and update my findings periodically. My prior model study enabled me to identify many flaws in clinical trials, side-effect evaluation methods and mechanism studies, and I also considered consistent failure in predicting drug side effects in the past and systematic failure of FDA in keeping out dangerous drugs from market. I found that the risks of vaccination cannot be determined by experiments alone and must be determined by using a combination of methods. By studying mRNA expression dynamics and kinetics, I predict that vaccination with mRNA vaccines may increase cancer risks, multiple organ failure risks, earlier death risks, genome alteration speeds by one or more mechanisms, alter the normal selection process for viral evolution resulting in more virulent viruses, and aggravate chronic diseases or cause healed diseases to relapse. Two root problems are practical inability to control expression sites and severe adverse reactions from repeated vaccination. Based on mRNA bio-distribution, the mRNA mainly strikes the liver and other vital organs, and poses grave dangers to persons whose vascular functional reserves are relatively small, or whose vascular systems are temporarily burdened by other causes such as viral infections or life activities. If an mRNA vaccine is administered on a pregnant woman by second or booster shots, spike protein synthesis in fetus brain disrupts the highly regulated protein synthesis processes, resulting in potential brain damages. In less than a year, most of my early predicted damages are being materialized or are on the track to hit the population. In this update, I present a benefits-and-risks map to show how the number of deaths caused by mRNA vaccines is grossly underestimated and why claimed benefits like 95% effectiveness rate and 90% death rate reduction are meaningless and misleading.

Tumor burden negatively impacts protein turnover as a proteostatic process in noncancerous liver, heart, and muscle, but not brain.

Cancer survivors are more susceptible to pathologies such as hypertension, liver disease, depression, and coronary artery disease when compared with individuals who have never been diagnosed with cancer. Therefore, it is important to understand how tumor burden negatively impacts nontumor-bearing tissues that may impact future disease susceptibility. We hypothesized that the energetic costs of a tumor would compromise proteostatic maintenance in other tissues. Therefore, the purpose of this study was to determine if tumor burden changes protein synthesis and proliferation rates in heart, brain, and liver. One million Lewis lung carcinoma (LLC) cells or phosphate-buffered saline (PBS, sham) were injected into the hind flank of female mice at ∼4.5 mo of age, and the tumor developed for 3 wk. Rates of proliferation and protein synthesis were measured in heart, brain, liver, and tumor tissue. Compared with sham, rates of protein synthesis (structural/nuclear, cytosolic, mitochondrial, and collagen) relative to proliferation were lower in the heart and liver of LLC mice, but higher in the brain of LLC mice. In the tumor tissue, the ratio of protein synthesis to DNA synthesis was approximately 1.0 showing that protein synthesis in the tumor was used for proliferation with little proteostatic maintenance. We further provide evidence that the differences in tissue responses may be due to energetic stress. We concluded that the decrease in proteostatic maintenance in liver, heart, and muscle might contribute to the increased risk of disease in cancer survivors.NEW & NOTEWORTHY We present data showing that simultaneously measuring protein synthesis and cell proliferation can help in the understanding of protein turnover as a proteostatic process in response to tumor burden. In some tissues, like hepatic, cardiac, and skeletal muscle, there was a decrease in the protein to DNA synthesis ratio indicating less proteostatic maintenance. In contrast, the brain maintained or even increased this protein to DNA synthesis ratio indicating more proteostatic maintenance.

Brain Protein Synthesis and Cell Proliferation in Sulfur Amino Acid Restricted Mice

Protein homeostasis (proteostasis) is the maintenance of the proteome through cellular pathways that are involved in protein synthesis, folding, trafficking, and degradation. Loss of proteostasis is considered one of the hallmarks of aging, and is a driver for age-related neurodegenerative diseases. In order to conserve healthy brain function throughout the lifespan, proteostasis must be maintained. We previously reported that dietary sulfur amino acid restriction (SAAR), a life-/healthspan extending treatment, activates mechanisms that maintain proteostasis in the liver. However, it is unknown if SAAR activates mechanisms promoting proteostatic maintenance in the brain. To address this knowledge gap, wild-type male C57Bl/B6 mice were fed one of four diets: Regular fat control, regular fat SAAR, high fat control, and high fat SAAR. Mice consumed deuterium enriched water, which was used to measure long term rates of newly synthesized proteins and DNA. Brains were collected at days 1, 3, 7, 14, 21, and 35 of treatment. Mitochondrial, cytosolic, and mixed fractions of pulverized frontal cortex were analyzed for rates of protein synthesis and cell proliferation using GC/MS. Data collection is ongoing, however based on preliminary and previous studies analyzing liver and brain, we anticipate that under SAAR, protein synthesis rates will be maintained in select tissue fractions despite slower rates of cell proliferation compared to mice without SAAR.

Correction of eIF2-dependent defects in brain protein synthesis, synaptic plasticity, and memory in mouse models of Alzheimer's disease.

Neuronal protein synthesis is essential for long-term memory consolidation, and its dysregulation is implicated in various neurodegenerative disorders, including Alzheimer's disease (AD). Cellular stress triggers the activation of protein kinases that converge on the phosphorylation of eukaryotic translation initiation factor 2α (eIF2α), which attenuates mRNA translation. This translational inhibition is one aspect of the integrated stress response (ISR). We found that postmortem brain tissue from AD patients showed increased phosphorylation of eIF2α and reduced abundance of eIF2B, another key component of the translation initiation complex. Systemic administration of the small-molecule compound ISRIB (which blocks the ISR downstream of phosphorylated eIF2α) rescued protein synthesis in the hippocampus, measures of synaptic plasticity, and performance on memory-associated behavior tests in wild-type mice cotreated with salubrinal (which inhibits translation by inducing eIF2α phosphorylation) and in both β-amyloid-treated and transgenic AD model mice. Thus, attenuating the ISR downstream of phosphorylated eIF2α may restore hippocampal protein synthesis and delay cognitive decline in AD patients.

Carbendazim exposure during the larval stage suppresses major royal jelly protein expression in nurse bees (Apis mellifera)

Studying the sublethal effects of agrochemical pesticides on nontarget honeybees (Apis mellifera) is important for agricultural development. Carbendazim is a widely used broad-spectrum fungicide that inhibits mitotic microtubule formation and cell division. However, the impact of carbendazim on bee health and development has not been fully elucidated. Here, using proteomics approaches, we assessed in vitro the changes in the expression of functional proteins in the head of newly emerged adults following treatment with field concentration of carbendazim during the larval stage. Treatment with carbendazim severely altered 266 protein expression patterns in the heads of adults and 218 of them showed downregulation after carbendazim exposure. Notably, major royal jelly proteins, a crucial multifunctional protein family with irreplaceable function in sustaining the development of colonies, were significantly suppressed in carbendazim-treated bees. This result was verified in both head and hypopharyngeal gland of nurse bees. Moreover, visual and olfactory loss, immune functions, muscular activity, social behavior, neural and brain development, protein synthesis and modification, and metabolism-related proteins were likely inhibited by carbendazim treatment. Together, these results suggest that carbendazim is an environmental risk factor that likely weakens bee colonies, partially due to reduced expression of major royal jelly proteins, which may be potential causes of colony collapse disorder.

Cognitive function and brain plasticity in a rat model of shift work: role of daily rhythms, sleep and glucocorticoids

Many occupations require operations during the night-time when the internal circadian clock promotes sleep, in many cases resulting in impairments in cognitive performance and brain functioning. Here, we use a rat model to attempt to identify the biological mechanisms underlying such impaired performance. Rats were exposed to forced activity, either in their rest-phase (simulating night-shift work; rest work) or in their active-phase (simulating day-shift work; active work). Sleep, wakefulness and body temperature rhythm were monitored throughout. Following three work shifts, spatial memory performance was tested on the Morris Water Maze task. After 4 weeks washout, the work protocol was repeated, and blood and brain tissue collected. Simulated night-shift work impaired spatial memory and altered biochemical markers of cerebral cortical protein synthesis. Measures of daily rhythm strength were blunted, and sleep drive increased. Individual variation in the data suggested differences in shift work tolerance. Hierarchical regression analyses revealed that type of work, changes in daily rhythmicity and changes in sleep drive predict spatial memory performance and expression of brain protein synthesis regulators. Moreover, serum corticosterone levels predicted expression of brain protein synthesis regulators. These findings open new research avenues into the biological mechanisms that underlie individual variation in shift work tolerance.

Regional rates of brain protein synthesis are unaltered in dexmedetomidine sedated young men with fragile X syndrome: A L-[1-11C]leucine PET study

Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability. Fragile X mental retardation protein (FMRP), a putative translation suppressor, is absent or significantly reduced in FXS. One prevailing hypothesis is that rates of protein synthesis are increased by the absence of this regulatory protein. In accord with this hypothesis, we have previously reported increased rates of cerebral protein synthesis (rCPS) in the Fmr1 knockout mouse model of FXS and others have reported similar effects in hippocampal slices. To address the hypothesis in human subjects, we applied the L[1-11C]leucine PET method to measure rCPS in adults with FXS and healthy controls. All subjects were males between the ages of 18 and 24 years and free of psychotropic medication. As most fragile X participants were not able to undergo the PET study awake, we used dexmedetomidine for sedation during the imaging studies. We found no differences between rCPS measured during dexmedetomidine-sedation and the awake state in ten healthy controls. In the comparison of rCPS in dexmedetomidine-sedated fragile X participants (n = 9) and healthy controls (n = 14) we found no statistically significant differences. Our results from in vivo measurements in human brain do not support the hypothesis that rCPS are elevated due to the absence of FMRP. This hypothesis is based on findings in animal models and in vitro measurements in human peripheral cells. The absence of a translation suppressor may produce a more complex response in pathways regulating translation than previously thought. We may need to revise our working hypotheses regarding FXS and our thinking about potential therapeutics.

Vcp Overexpression and Leucine Supplementation Increase Protein Synthesis and Improve Fear Memory and Social Interaction of Nf1 Mutant Mice

Neurofibromatosis type 1 (NF1) is a dominant genetic disorder manifesting, in part, as cognitive defects. Previous study indicated that neurofibromin (NF1 protein) interacts with valosin-containing protein (VCP)/P97 to control dendritic spine formation, but the mechanism is unknown. Here, using Nf1+/- mice and transgenic mice overexpressing wild-type Vcp/p97, we demonstrate that neurofibromin acts with VCP to control endoplasmic reticulum (ER) formation and consequent protein synthesis and regulates dendritic spine formation, thereby modulating contextual fear memory and social interaction. To validate the role of protein synthesis, we perform leucine supplementation invitro and invivo. Our results suggest that leucine can effectively enter the brain and increase protein synthesis and dendritic spine density of Nf1+/- neurons. Contextual memory and social behavior of Nf1+/- mice are also restored by leucine supplementation. Our study suggests that the "ER-protein synthesis" pathway downstream of neurofibromin and VCP is a critical regulator of dendritic spinogenesis and brain function.

Large-scale cell-type-specific imaging of protein synthesis in a vertebrate brain.

Despite advances in methods to detect protein synthesis, it has not been possible to measure endogenous protein synthesis levels in vivo in an entire vertebrate brain. We developed a transgenic zebrafish line that allows for cell-type-specific labeling and imaging of nascent proteins in the entire animal. By replacing leucine with glycine in the zebrafish MetRS-binding pocket (MetRS-L270G), we enabled the cell-type-specific incorporation of the azide-bearing non-canonical-amino-acid azidonorleucine (ANL) during protein synthesis. Newly synthesized proteins were then labeled via 'click chemistry'. Using a Gal4-UAS-ELAV3 line to express MetRS-L270G in neurons, we measured protein synthesis intensities across the entire nervous system. We visualized endogenous protein synthesis and demonstrated that seizure-induced neural activity results in enhanced translation levels in neurons. This method allows for robust analysis of endogenous protein synthesis in a cell-type-specific manner, in vivo at single-cell resolution.

Effectiveness of Phenylketonuria Diagnosis in The Neonatal Treatment Reference Service

Phenylketonuria is an inborn error of metabolism of autosomal recessive inheritance, with partial or total deficiency of the phenylalanine hydroxylase hepatic enzyme, which converts L-phenylalanine into tyrosine, thus causing accumulation of phenylalanine at the brain and serum level, interfering in the brain protein synthesis and entailing serious deficits. The objective of this study was to analyze the effectiveness of Phenylketonuria Diagnosis in the neonatal treatment reference service. This is a cross-sectional, analytical study with a quantitative approach, documented with retrospective data collection. Sociodemographic data, diagnosis, onset of treatment and the coverage rate analysis were grouped on a quadrennial basis. The sample consisted of 14 patients, from whom 57.1% had records of birth and collection time. In variable days of life, 28.6% were screened within the recommended period, 71.4% were diagnosed up to one month of life and 1 case at 3 years of age, for the onset of treatment (14.3%). The ideal collection would be performed up to 30 days of life. The lowest coverage rate for quadrennial was between 2014-2017 with 84.3%, with an incidence of 1:21,933. In conclusion, we highlight the need to optimize the neonatal screening service in order to make early diagnosis, begin specific treatment and minimize or eradicate irreversible sequelae.

Characterization Of Patients Diagnosed With Phenylketonuria In The Neonatal Treatment Reference Service

Phenylketonuria is an inborn error of autosomal recessive genetic metabolism, with partial or total deficiency of the hepatic enzyme phenylalanine hydroxylase, which converts L-phenylalanine into tyrosine, causing accumulation of phenylalanine at brain and serum levels, interfering with brain protein synthesis causing several damages. This study aimed to characterize patients diagnosed with phenylketonuria at the Neonatal Screening Reference Service from 2008 to 2017. Cross-sectional analytical study with a quantitative approach with retrospective data collection from medical records and databases. Data were grouped as baby gender, date of birth, time of birth and neonatal screening examination collection, type of delivery, gestational age and prenatal status, place of origin, phenylketonuria classification and coverage rate of neonatal screening. The sample consisted of 14 patients, where 64% were male, all mothers had prenatal care and the percentage of cesarean delivery prevailed with 57.2%. Of these 85.7% reside in other states of the country and on the classification of the type of phenylketonuria 64.3% have mild phenylketonuria, as for the coverage rate there was a drop in the number of collections in the reference service. This research contributed to characterize the patient diagnosed with phenylketonuria, which allows greater knowledge about the disease carriers, as well as favoring the reduction of irreversible sequels, expenses and morbidity.

Brain Protein Synthesis Rates in the UM-HET3 Mouse Following Treatment With Rapamycin or Rapamycin With Metformin.

Treatment with the mechanistic target of rapamycin (mTOR) inhibitor, rapamycin (RAP), alone and in combination with the antidiabetic drug, metformin (RAP+MET), extends lifespan in mice. The mechanisms underlying lifespan extension are unclear. One possibility is improved capacity for proteostatic maintenance. We have previously characterized peripheral protein synthesis rates following treatment with RAP. However, it is unknown if RAP+MET elicits similar changes, or if either treatment affects protein synthesis in the brain. We hypothesized that 8 weeks of treatment with RAP and RAP+MET would alter brain protein synthesis rates to reflect proteostatic processes. Using the stable isotopic tracer, deuterium oxide (D2O), we demonstrate in UM-HET3 mice that protein synthesis rates measured in whole brain were unaffected by treatment in young male mice, whereas RAP+MET decreased mitochondrial protein synthesis in young females. Conversely, RAP increased mitochondrial protein synthesis rates in older females. Activity through the AMPK/mTOR pathway was affected in a sex-specific manner in young mice, and minimal changes were observed in the older cohort. Thus, we establish D2O for measurements of biogenesis in the brain. These results provide initial insights into the effects of RAP and RAP+MET on brain protein synthesis. Additionally, these data emphasize that responses to slowed aging treatments vary with sex and age.

Active presynaptic ribosomes in the mammalian brain, and altered transmitter release after protein synthesis inhibition.

Presynaptic neuronal activity requires the localization of thousands of proteins that are typically synthesized in the soma and transported to nerve terminals. Local translation for some dendritic proteins occurs, but local translation in mammalian presynaptic nerve terminals is difficult to demonstrate. Here, we show an essential ribosomal component, 5.8S rRNA, at a glutamatergic nerve terminal in the mammalian brain. We also show active translation in nerve terminals, in situ, in brain slices demonstrating ongoing presynaptic protein synthesis in the mammalian brain. Shortly after inhibiting translation, the presynaptic terminal exhibits increased spontaneous release, an increased paired pulse ratio, an increased vesicle replenishment rate during stimulation trains, and a reduced initial probability of release. The rise and decay rates of postsynaptic responses were not affected. We conclude that ongoing protein synthesis can limit excessive vesicle release which reduces the vesicle replenishment rate, thus conserving the energy required for maintaining synaptic transmission.

Rates of cerebral protein synthesis in primary visual cortex during sleep-dependent memory consolidation, a study in human subjects.

If protein synthesis during sleep is required for sleep-dependent memory consolidation, we might expect rates of cerebral protein synthesis (rCPS) to increase during sleep in the local brain circuits that support performance on a particular task following training on that task. To measure circuit-specific brain protein synthesis during a daytime nap opportunity, we used the L-[1-(11)C]leucine positron emission tomography (PET) method with simultaneous polysomnography. We trained subjects on the visual texture discrimination task (TDT). This was followed by a nap opportunity during the PET scan, and we retested them later in the day after the scan. The TDT is considered retinotopically specific, so we hypothesized that higher rCPS in primary visual cortex would be observed in the trained hemisphere compared to the untrained hemisphere in subjects who were randomized to a sleep condition. Our results indicate that the changes in rCPS in primary visual cortex depended on whether subjects were in the wakefulness or sleep condition but were independent of the side of the visual field trained. That is, only in the subjects randomized to sleep, rCPS in the right primary visual cortex was higher than the left regardless of side trained. Other brain regions examined were not so affected. In the subjects who slept, performance on the TDT improved similarly regardless of the side trained. Results indicate a regionally selective and sleep-dependent effect that occurs with improved performance on the TDT.