Regulation Of Protein Synthesis Research Articles

MicroRNA-29-mediated cross-talk between metabolic organs in the pathogenesis of diabetes mellitus and its complications: A narrative review.

Diabetes mellitus (DM) is a heterogeneous group of disorders characterized by hyperglycemia. Microribonucleic acids (microRNAs) are noncoding RNA molecules synthesized in the nucleus, modified, and exported to the extracellular environment to bind to their complementary target sequences. It regulates protein synthesis in the targeted cells by inhibiting translation or triggering the degradation of the target messenger. MicroRNA-29 is one of noncoding RNA that can be secreted by adipose tissue, hepatocytes, islet cells, and brain cells. The expression level of the microRNA-29 family in several metabolic organs is regulated by body weight, blood concentrations of inflammatory mediators, serum glucose levels, and smoking habits. Several experimental studies have demonstrated the effect of microRNA-29 on the expression of target genes involved in glucose metabolism, insulin synthesis and secretion, islet cell survival, and proliferation. These findings shed new light on the role of microRNA-29 in the pathogenesis of diabetes and its complications, which plays a vital role in developing appropriate therapies. Different molecular pathways have been proposed to explain how microRNA-29 promotes the development of diabetes and its complications. However, to the best of our knowledge, no published review article has summarized the molecular mechanism of microRNA-29-mediated initiation of DM and its complications. Therefore, this narrative review aims to summarize the role of microRNA-29-mediated cross-talk between metabolic organs in the pathogenesis of diabetes and its complications.

ATP1A3 regulates protein synthesis for mitochondrial stability under heat stress.

Pathogenic variants in ATP1A3, the α3 subunit of the Na+/K+-ATPase-encoding gene, cause alternating hemiplegia of childhood (AHC) and related disorders. Impairments in Na+/K+-ATPase activity are associated with the clinical phenotype. However, it remains unclear whether additional mechanisms are involved in the exaggerating symptoms under stressed conditions in patients with AHC. We herein report that the intracellular loop (ICL) of ATP1A3 interacted with RNA-binding proteins, such as EIF4G, PABPC1 and FMRP. Both the siRNA-mediated depletion of Atp1a3 and ectopic expression of the p.R756C-variant ATP1A3-ICL in Neuro2a cells resulted in excessive phosphorylation of ribosomal protein S6 and increased susceptibility to heat stress. In agreement with these findings, iPSCs from a patient with the p.R756C variant were more vulnerable to heat stress than control iPSCs. Neurons established from the patient's iPSCs showed lower calcium influxes in responses to stimulation with ATP than controls. These data indicated that inefficient protein synthesis contributes to the progressive and deteriorating phenotypes of patients with the p.R756C variant among a variety of ATP1A3-related disorders.

Homeostasis and evolution in relation to regeneration and repair.

Homeostasis constitutes a key concept in physiology and refers to self-regulating processes that maintain internal stability when adjusting to changing external conditions. It diminishes internal entropy constituting a driving force behind evolution. Natural selection might act on homeostatic regulatory mechanisms and control mechanisms including homeodynamics, allostasis, hormesis and homeorhesis, where different stable stationary states are reached. Regeneration is under homeostatic control through hormesis. Damage to tissues initiates a response to restore the impaired equilibrium caused by mild stress using cell proliferation, cell differentiation and cell death to recover structure and function. Repair is a homeorhetic change leading to a new stable stationary state with decreased functionality and fibrotic scarring without reconstruction of the 3-D pattern. Mechanisms determining entrance of the tissue or organ to regeneration or repair include the balance between innate and adaptive immune cells in relation to cell plasticity and stromal stem cell responses, and redox balance. The regenerative and reparative capacities vary in different species, distinct tissues and organs, and at different stages of development including ageing. Many cell signals and pathways play crucial roles determining regeneration or repair by regulating protein synthesis, cellular growth, inflammation, proliferation, autophagy, lysosomal function, metabolism and metalloproteinase cell signalling. Attempts to favour the entrance of damaged tissues to regeneration in those with low proliferative rates have been made; however, there are evolutionary constraint mechanisms leading to poor proliferation of stem cells in unfavourable environments or tumour development. More research is required to better understand the regulatory processes of these mechanisms.

MTORC1 and BMP-Smad1/5 Regulation of Serum-Stimulated Myotube Hypertrophy: A Role for Autophagy.

Protein synthesis regulation is critical for skeletal muscle hypertrophy; yet, other established cellular processes are necessary for growth-related cellular remodeling. Autophagy has a well-acknowledged role in muscle quality control, but evidence for its role in myofiber hypertrophy remains equivocal. Both mTORC1 and BMP-Smad1/5 signaling are reported regulators of myofiber hypertrophy; however, gaps remain in our understanding of how this regulation is integrated with the growth processes and autophagy regulation. Therefore, we investigated the mTORC1 and Smad1/5 regulation of protein synthesis and autophagy flux during serum-stimulated myotube growth. Chronic serum stimulation experiments were performed on day-5 differentiated C2C12 myotubes incubated in differentiation media (2%HS) or growth media (5%FBS) for 48 hours. Rapamycin or LDN193189 were dosed for 48 hours to inhibit mTORC1 and BMP-Smad1/5 signaling, respectively. Acute serum stimulation was examined in day-7 differentiated myotubes. Protein synthesis was measured by puromycin incorporation. Bafilomycin A1 and immunoblotting for LC3B were used to assess autophagy flux. Chronic serum stimulation increased myotube diameter 22%, total protein 21%, total RNA 100%, Smad1/5 phosphorylation 404%, and suppressed autophagy flux. Rapamycin, but not LDN193189, blocked serum-induced myotube hypertrophy and the increase in total RNA. Acute serum stimulation increased protein synthesis 111%, Smad1/5 phosphorylation 559%, rpS6 phosphorylation 117%, and suppressed autophagy flux. Rapamycin increased autophagy flux during acute serum stimulation. These results provide evidence for mTORC1, but not BMP-Smad1/5 signaling, being required for serum-induced myotube hypertrophy and autophagy flux by measuring LC3BII/I expression. Further investigation is warranted to examine the role of autophagy flux in myotube hypertrophy.

Dietary glycine supplementation activates mTOR signaling pathway in tissues of pigs with intrauterine growth restriction.

The mechanistic target of rapamycin (mTOR) cell signaling pathway serves as the central mechanism for the regulation of tissue protein synthesis and growth. We recently reported that supplementing 1% glycine to corn- and soybean meal-based diets enhanced growth performance between weaning and market weights in pigs with intrauterine growth restriction (IUGR). Results of recent studies have revealed an important role for glycine in activating mTOR and protein synthesis in C2C12 muscle cells. Therefore, the present study tested the hypothesis that dietary glycine supplementation enhanced the mTOR cell signaling pathway in skeletal muscle and other tissues of IUGR pigs. At weaning (21 d of age), IUGR pigs and litter mates with normal birth weights (NBW) were assigned randomly to one of two groups: supplementation with either 1% glycine or 1.19% L-alanine (isonitrogenous control) to a corn- and soybean meal-based diet. Tissues were obtained from the pigs within 1wk after the feeding trial ended at 188 d of age to determine the abundances of total and phosphorylated forms of mTOR and its two major downstream proteins: eukaryotic initiation factor 4E-binding protein-1 (4EBP1) and ribosomal protein S6 kinase-1 (p70S6K). Results showed that IUGR decreased (P < 0.05) the abundances of both total and phosphorylated mTOR, 4EBP1, and p70S6K in the gastrocnemius muscle and jejunum. In the longissimus lumborum muscle of IUGR pigs, the abundances of total mTOR did not differ (P > 0.05) but those for phosphorylated mTOR and both total and phosphorylated 4EBP1 and p70S6K were down-regulated (P < 0.05), when compared to NBW pigs. These adverse effects of IUGR in the gastrocnemius muscle, longissimus lumborum muscle, and jejunum were prevented (P < 0.05) by dietary glycine supplementation. Interestingly, the abundances of total or phosphorylated mTOR, 4EBP1, and p70S6K in liver were not affected (P > 0.05) by IUGR or glycine supplementation. Collectively, our findings indicate that IUGR impaired the mTOR cell signaling pathway in tissues of pigs and that adequate glycine intake was crucial for maintaining active mTOR-dependent protein synthesis for the growth and development of skeletal muscle.

Maximizing ISRIB Potential Requires Addressing Specificity, Long-Term Safety, and Disease-Specific Considerations.

Integrated Stress Response Inhibitor (ISRIB) works by inhibiting the integrated stress response, a cellular pathway involved in the regulation of protein synthesis during stress conditions. Conditions that have been studied or suggested as potential candidates for treatment with ISRIB include neurological and metabolic disorders, cognitive impairment, viral infections, and cancer. The study aimed to discuss the challenges related to specificity, long-term safety, and disease-specific considerations crucial for realizing the full potential of ISRIB. A narrative review of the literature has been conducted to delve into ISRIB's chemistry, mechanisms of action, disease-specific considerations, and long-term safety implications. While ISRIB has shown promising results in preclinical studies, more research is needed to determine its safety and effectiveness in human patients. Clinical trials are required to validate its therapeutic potential for various conditions. Despite having been proposed a decade ago, news of its clinical trials has been circulated only recently, without any published information yet and with rumors that its efficacy vs. safety profile may be compromised by side effects. While ISRIB offers exciting prospects for a range of biomedical applications, addressing challenges related to specificity, disease-specific considerations, and importantly long-term safety, is crucial for realizing its full potential.

MTORC1/S6K1 signaling promotes sustained oncogenic translation through modulating CRL3IBTK-mediated ubiquitination of eIF4A1 in cancer cells.

Enhanced protein synthesis is a crucial molecular mechanism that allows cancer cells to survive, proliferate, metastasize, and develop resistance to anti-cancer treatments, and often arises as a consequence of increased signaling flux channeled to mRNA-bearing eukaryotic initiation factor 4F (eIF4F). However, the post-translational regulation of eIF4A1, an ATP-dependent RNA helicase and subunit of the eIF4F complex, is still poorly understood. Here, we demonstrate that IBTK, a substrate-binding adaptor of the Cullin 3-RING ubiquitin ligase (CRL3) complex, interacts with eIF4A1. The non-degradative ubiquitination of eIF4A1 catalyzed by the CRL3IBTK complex promotes cap-dependent translational initiation, nascent protein synthesis, oncogene expression, and cervical tumor cell growth both in vivo and in vitro. Moreover, we show that mTORC1 and S6K1, two key regulators of protein synthesis, directly phosphorylate IBTK to augment eIF4A1 ubiquitination and sustained oncogenic translation. This link between the CRL3IBTK complex and the mTORC1/S6K1 signaling pathway, which is frequently dysregulated in cancer, represents a promising target for anti-cancer therapies.

MTORC1/S6K1 signaling promotes sustained oncogenic translation through modulating CRL3IBTK-mediated ubiquitination of eIF4A1 in cancer cells

Enhanced protein synthesis is a crucial molecular mechanism that allows cancer cells to survive, proliferate, metastasize, and develop resistance to anti-cancer treatments, and often arises as a consequence of increased signaling flux channeled to mRNA-bearing eukaryotic initiation factor 4F (eIF4F). However, the post-translational regulation of eIF4A1, an ATP-dependent RNA helicase and subunit of the eIF4F complex, is still poorly understood. Here, we demonstrate that IBTK, a substrate-binding adaptor of the Cullin 3-RING ubiquitin ligase (CRL3) complex, interacts with eIF4A1. The non-degradative ubiquitination of eIF4A1 catalyzed by the CRL3IBTK complex promotes cap-dependent translational initiation, nascent protein synthesis, oncogene expression, and cervical tumor cell growth both in vivo and in vitro. Moreover, we show that mTORC1 and S6K1, two key regulators of protein synthesis, directly phosphorylate IBTK to augment eIF4A1 ubiquitination and sustained oncogenic translation. This link between the CRL3IBTK complex and the mTORC1/S6K1 signaling pathway, which is frequently dysregulated in cancer, represents a promising target for anti-cancer therapies.

Impacts of protein quantity and distribution on body composition.

The importance of meal distribution of dietary protein to optimize muscle mass and body remains unclear, and the findings are intertwined with age, physical activity, and the total quantity and quality of protein consumed. The concept of meal distribution evolved from multiple discoveries about regulating protein synthesis in skeletal muscle. The most significant was the discovery of the role of the branched-chain amino acid leucine as a metabolic signal to initiate a post-meal anabolic period of muscle protein synthesis (MPS) in older adults. Aging is often characterized by loss of muscle mass and function associated with a decline in protein synthesis. The age-related changes in protein synthesis and subsequent muscle atrophy were generally considered inevitable until the discovery of the unique role of leucine for the activation of the mTOR signal complex for the initiation of MPS. Clinical studies demonstrated that older adults (>60 years) require meals with at least 2.8 g of leucine (~30 g of protein) to stimulate MPS. This meal requirement for leucine is not observed in younger adults (<30 years), who produce a nearly linear response of MPS in proportion to the protein content of a meal. These findings suggest that while the efficiency of dietary protein to stimulate MPS declines with aging, the capacity for MPS to respond is maintained if a meal provides adequate protein. While the meal response of MPS to total protein and leucine is established, the long-term impact on muscle mass and body composition remains less clear, at least in part, because the rate of change in muscle mass with aging is small. Because direct diet studies for meal distribution during aging are impractical, research groups have applied meal distribution and the leucine threshold to protein-sparing concepts during acute catabolic conditions such as weight loss. These studies demonstrate enhanced MPS at the first meal after an overnight fast and net sparing of lean body mass during weight loss. While the anabolic benefits of increased protein at the first meal to stimulate MPS are clear, the benefits to long-term changes in muscle mass and body composition in aging adults remain speculative.

Cloning of cDNA-gene of Arabidopsis thaliana ribosomal protein S6, its expression in Escherichia coli and purification of AtRPS6B1 recombinant protein

Ribosomal protein S6 is a component of the 40S small ribosomal subunit and plays an important role in protein biosynthesis. Its main function is related to the regulation of mechanisms that control cell growth and division. The RPS6 can be phosphorylated on defined serine and threonine residues by kinases such as S6K1 and S6K2, which in turn are activated by signaling pathways associated with the activation of the mTORC1 molecular complex. The phosphorylation process of protein RPS6 plays a key role in the regulation of cell growth and protein synthesis. Activated RPS6 protein influences translation initiation, which means start the process of protein synthesis on the ribosome. Thus, RPS6 is associated with the regulation of cell size and their ability to divide. In addition, the RPS6 protein can be associated with other proteins and participate in various molecular interactions, which may vary depending on the context of cellular activity. In this study, cloning and site-directed cDNA mutagenesis of the second isoform of the AtRPS6 protein (AtRPS6B) was performed. Further, the obtained phosphomimetic and nonphosphorylated forms of this protein were expressed in E.coli ArcticExpress (DE3) cells, the proteins were purified by metal chelate chromatography (IMAC) and the presence and purity of the obtained proteins was confirmed by immunoblotting

The E3 ubiquitin-protein ligase synoviolin (Syvn1/Hrd1) promotes adaptive decreases in cardiac myocyte protein synthesis via eIF2α/ATF4 pathway activation

As the heart undergoes pathologic hypertrophy in response to many disease conditions, an imbalance between protein synthesis and degradation in cardiac myocytes, due to the increases in protein synthesis relative to protein degradation, happens, which challenges protein folding and endoplasmic reticulum (ER) proteostasis. This leads to ER stress and the activation of the ER stress response. Synoviolin (Syvn1), also known as HMG-CoA reductase degradation protein 1 (Hrd1), is an ER-localized protein that is upregulated in cardiac myocytes during ER stress. We previously found that Syvn1 mediates the ubiquitylation and consequent degradation of toxic misfolded proteins and preserved cardiac function in a model of pressure overload-induced cardiac pathology. The objective of this study was to examine whether Syvn1 is involved in regulating protein synthesis, and if so, what its function is during hypertrophic growth of cardiac myocytes. Given that cardiac hypertrophy is caused by increases in protein synthesis, we hypothesized that Syvn1 provides an adaptive response in part through regulation of protein synthesis and consequent decrease in cardiac hypertrophic response. We examined the effects of Syvn1 on ventricular myocyte growth in vitro and found that overexpression of Syvn1 decreased cardiac myocyte surface area as well as protein synthesis when treated with phenylephrine (PE), a treatment which normally leads to increased protein synthesis and increased cardiac myocyte size, mimicking pathological cardiac hypertrophy. We next focused on identifying the mechanism of Syvn1-mediated growth inhibition and found that increases in Syvn1 lead to activation of the PERK (protein kinase RNA (PKR)-like ER kinase) branch of the ER stress response, which leads to increased phosphorylation of the α-subunit of translation initiation factor 2 (eIF2α) at Ser51, thereby inhibiting global translational initiation. PERK activation also results in selective translation of a subset of mRNAs, including activating transcription factor 4 (ATF4), which activates the transcription of a wide range of genes involved in adaptation to stress conditions. We found increased ATF4 levels and increased ATF4 target gene expression with Syvn1 overexpression during PE treatment, compared to control PE treatment. Inhibition of the PERK pathway blocked Syvn1-mediated decrease in cardiac myocyte size and protein synthesis as well as PERK activation and ATF4 target gene induction. Additionally, we found that an adeno-associated virus encoding Syvn1, administered in a therapeutically-relevant manner after the onset of pathological cardiac hypertrophy induced by transverse-aortic constriction in mice, blunted pathological remodeling and preserved cardiac function. We posit that the Syvn1/eIF2α/ATF4 pathway constitutes a newly-discovered mechanism for balancing the proteome in cardiac myocytes. Here we found that Syvn1 upregulation blunts maladaptive increase in cardiac myocyte size during pathologic hypertrophy. In conclusion, these findings suggest that Syvn1 is a critical regulator of cardiac myocyte protein synthesis and subsequent growth and that increases in Syvn1 lead to the activation of the PERK branch of the ER stress response, which results in inhibition of global protein synthesis, and activation of ATF4. This work was supported by the National Institutes of Health (R01HL157027) and the University of Arizona Health Sciences Career Development Award. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Wheat seedlings extract ameliorates sarcopenia in aged mice by regulating protein synthesis and degradation with anti-inflammatory and mitochondrial biogenesis effects

Wheat seedlings extract ameliorates sarcopenia in aged mice by regulating protein synthesis and degradation with anti-inflammatory and mitochondrial biogenesis effects

Investigating ZMP Accumulation in C2C12 Myotubes with AICAR and Prodrug-39

5’Adenosine monophosphate (AMP) is a signaling molecule and a known regulator of enzymes in glycolysis, glycogen breakdown, and may play a role in regulating protein synthesis. It is also a known activator of AMP-dependent protein kinase (AMPK), a key energy sensor within the cell. Activation of AMPK has been linked to the regulation of mitochondrial biogenesis, upregulation of BCAA catabolism, and increased skeletal muscle glucose uptake and fatty acid oxidation. AMPK can be activated pharmacologically with 5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR), an adenosine analogue. AICAR enters the cell through adenosine transporters and undergoes phosphorylation by Adenosine Kinase forming AICAR monophosphate (ZMP). Unfortunately, the poor bioavailability of AICAR limits its use pharmacologically. Prodrug-39 (P39) is comprised of ZMP with a 4-nitrophenol group to allow membrane permeability and subsequent ZMP formation without the need of membrane transporters. We investigated the ZMP accumulation in C2C12 myotubes following exposure to different concentrations of P39 or AICAR. Based on preliminary data, we hypothesized that AICAR treatments would be more effective at producing ZMP over short periods of time and when treatment concentrations were high, but that P39 treatments would result in greater and more consistent ZMP accumulation over longer periods of time when treatment concentrations were low. We first measured the absorbance of 4-nitrophenol (4NP) within the cell media to determine phosphodiesterase cleavage of P39. Nitrophenol absorbance was 3.9 times higher at 1000 μM compared to 100 μM treatment of P39 after 15 minute incubation, and 13.3 times higher at 11 hours. The nitrophenol absorbance per hour increased linearly between 250 μM to 1000 μM of P39. Adenine nucleotide content and ZMP accumulation in treated cells was determined following organic protein extraction and UV-Vis ultra-performance liquid chromatography (UPLC). After 13 hours of treatment with 500 μM AICAR or P39, ZMP accumulation was 14 fold higher following AICAR treatment compared to P39 (59.7±5.0 vs 4.2±0.1 μmol/g protein). Interestingly, ZMP accumulation was not different between 100 μM treatments (5.6±1.3 vs. 5.7±1.5 μmol/g protein). This suggests that phosphodiesterase cleavage of P39 is likely the limiting factor for ZMP accumulation. Interestingly, while ZMP accumulation following 13 hour incubation with 100 μM AICAR or P39 was not different, ATP content was approximately 50% higher in P39 treated cells (33.7±5.8 vs. 51.0±5.8 μmol/g protein). While the measurement of ZMP accumulation at very low treatment concentrations (10 μM) is very diffcult, P39 exposure for 1 to 1.5 hours resulted in a 3 to 8 fold increase in ZMP content compared to AICAR. This data illustrates the potential for P39 as a drug capable of accumulating greater ZMP than AICAR at very low treatment concentrations, however the capacity of phosphodiesterase activity may limit the application of this drug. This work was funded by a grant from Skylark Biosciences. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Reconsidering the pre-eminence of dietary leucine and plasma leucinemia for predicting the stimulation of postprandial muscle protein synthesis rates

The regulation of postprandial muscle protein synthesis (MPS) with or without physical activity has been an intensely studied area within nutrition and physiology. The leucine content of dietary protein and the subsequent plasma leucinemia it elicits postingestion is often considered the primary drivers of the postprandial MPS response. This concept, generally known as the leucine “trigger” hypothesis, has also been adopted within more applied aspects of nutrition. Our view is that recent evidence is driving a more nuanced picture of the regulation of postprandial MPS by revealing a compelling dissociation between ingested leucine or plasma leucinemia and the magnitude of the postprandial MPS response. Much of this lack of coherence has arisen as experimental progress has demanded relevant studies move beyond reliance on isolated amino acids and proteins to use increasingly complex protein-rich meals, whole foods, and mixed meals. Our overreliance on the centrality of leucine in this field has been reflected in 2 recent systematic reviews. In this perspective, we propose a re-evaluation of the pre-eminent role of these leucine variables in the stimulation of postprandial MPS. We view the development of a more complex intellectual framework now a priority if we are to see continued progress concerning the mechanistic regulation of postprandial muscle protein turnover, but also consequential from an applied perspective when evaluating the value of novel dietary protein sources.

Investigating the Effect of Rapamycin on Impaired Proteostasis in Aged Skeletal Muscle After Disuse Atrophy

Older individuals undergo loss of muscle mass and strength, which can be compounded during bed rest and extended hospital stays. Adult and aged individuals lose muscle mass at similar rates during periods of disuse; however, only aged skeletal muscle fails to fully recover once activity resumes. Current efforts to facilitate skeletal muscle recovery are aimed at increasing myofibrillar protein synthesis by stimulating mTORC1(mammalian target of rapamycin complex 1), a major regulator of protein synthesis. However, we showed that skeletal muscle in aged rats already has higher rates of myofibrillar protein synthesis and mTORC1 activity than adult rats. We also showed that aged skeletal muscle has an accumulation of insoluble ubiquitinated proteins compared to adult muscle, indicating impaired proteostasis and possibly impaired autophagy degradation. We hypothesized that mTORC1 inhibition via rapamycin administration would reduce protein synthesis and the accumulation of p62 aggregates, facilitating recovery in aged skeletal muscle after disuse. Methods: Adult (10 months) and old (26 months) OKC HET rats were hindlimb unloaded (HU) for 14-days to induce atrophy, followed by subsequent 14 days of reloading (RE) through normal ambulation. Animals were fed either a control or rapamycin-supplemented (42 ppm) diet. To determine bulk protein synthesis, rats were labeled with deuterium oxide (D2O) during weight bearing (WB), HU, and RE, (n=4-6 per time point per group). Finally, to assess the presence of autophagy related protein aggregates we immuno stained for Sequestosome 1/p62, an autophagy cargo receptor protein. Results: Our data showed that myofibrillar protein synthesis rates were elevated in the old muscle compared to the adult ( k = 0.029 1/day ±0.002 vs. 0.039 1/day ±0.002, p&lt;0.0001), and that protein synthesis rates were lower in the old rapamycin cohort (k = 1/day ±0.002 vs. 1/day ±0.003, p&lt;0.0001). Furthermore, p62 puncta was three-fold more abundant (p&lt;0.01) in aged skeletal muscle, compared to the adult muscle. Although the sample size is small, when comparing p62 puncta in the old rapamycin group to the old controls, there was no difference between the cohorts. Conclusion: We show that mTORC1 inhibition reduces protein synthesis in aged skeletal muscle. We also show that aged muscle has more p62 aggregates compared to adult skeletal muscle, indicating that autophagy related targets are not being degraded effciently with age. Further analyses will assess the effects of mTORC1 inhibition on other proteostatic mechanisms in atrophied skeletal muscle of aged rats. NIA Training Grant: 5T32AG052363-04VA I01 BX005592 APS SURF. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The phosphorylation of carboxyl-terminal eIF2α by SPA kinases contributes to enhanced translation efficiency during photomorphogenesis

Light triggers an enhancement of global translation during photomorphogenesis in Arabidopsis, but little is known about the underlying mechanisms. The phosphorylation of the α-subunit of eukaryotic initiation factor 2 (eIF2α) at a conserved serine residue in the N-terminus has been shown as an important mechanism for the regulation of protein synthesis in mammalian and yeast cells. However, whether the phosphorylation of this residue in plant eIF2α plays a role in regulation of translation remains elusive. Here, we show that the quadruple mutant of SUPPRESSOR OF PHYA-105 family members (SPA1-SPA4) display repressed translation efficiency after light illumination. Moreover, SPA1 directly phosphorylates the eIF2α C-terminus under light conditions. The C-term-phosphorylated eIF2α promotes translation efficiency and photomorphogenesis, whereas the C-term-unphosphorylated eIF2α results in a decreased translation efficiency. We also demonstrate that the phosphorylated eIF2α enhances ternary complex assembly by promoting its affinity to eIF2β and eIF2γ. This study reveals a unique mechanism by which light promotes translation via SPA1-mediated phosphorylation of the C-terminus of eIF2α in plants.

Repeated sprint training in hypoxia induces specific skeletal muscle adaptations through S100A protein signaling.

Athletes increasingly engage in repeated sprint training consisting in repeated short all-out efforts interspersed by short recoveries. When performed in hypoxia (RSH), it may lead to greater training effects than in normoxia (RSN); however, the underlying molecular mechanisms remain unclear. This study aimed at elucidating the effects of RSH on skeletal muscle metabolic adaptations as compared to RSN. Sixteen healthy young men performed nine repeated sprint training sessions in either normoxia (FIO2 = 0.209, RSN, n = 7) or normobaric hypoxia (FIO2 = 0.136, RSH, n = 9). Before and after the training period, exercise performance was assessed by using repeated sprint ability (RSA) and Wingate tests. Vastus lateralis muscle biopsies were performed to investigate muscle metabolic adaptations using proteomics combined with western blot analysis. Similar improvements were observed in RSA and Wingate tests in both RSN and RSH groups. At the muscle level, RSN and RSH reduced oxidative phosphorylation protein content but triggered an increase in mitochondrial biogenesis proteins. Proteomics showed an increase in several S100A family proteins in the RSH group, among which S100A13 most strongly. We confirmed a significant increase in S100A13 protein by western blot in RSH, which was associated with increased Akt phosphorylation and its downstream targets regulating protein synthesis. Altogether our data indicate that RSH may activate an S100A/Akt pathway to trigger specific adaptations as compared to RSN.

Single-Nucleus Transcriptome Profiling from the Hippocampus of a PTSD Mouse Model and CBD-Treated Cohorts.

Post-traumatic stress disorder (PTSD) is the most common psychiatric disorder after a catastrophic event; however, the efficacious treatment options remain insufficient. Increasing evidence suggests that cannabidiol (CBD) exhibits optimal therapeutic effects for treating PTSD. To elucidate the cell-type-specific transcriptomic pathology of PTSD and the mechanisms of CBD against this disease, we conducted single-nucleus RNA sequencing (snRNA-seq) in the hippocampus of PTSD-modeled mice and CBD-treated cohorts. We constructed a mouse model by adding electric foot shocks following exposure to single prolonged stress (SPS+S) and tested the freezing time, anxiety-like behavior, and cognitive behavior. CBD was administrated before every behavioral test. The PTSD-modeled mice displayed behaviors resembling those of PTSD in all behavioral tests, and CBD treatment alleviated all of these PTSD-like behaviors (n = 8/group). Three mice with representative behavioral phenotypes were selected from each group for snRNA-seq 15 days after the SPS+S. We primarily focused on the excitatory neurons (ExNs) and inhibitory neurons (InNs), which accounted for 68.4% of the total cell annotations. A total of 88 differentially upregulated genes and 305 differentially downregulated genes were found in the PTSD mice, which were found to exhibit significant alterations in pathways and biological processes associated with fear response, synaptic communication, protein synthesis, oxidative phosphorylation, and oxidative stress response. A total of 63 overlapping genes in InNs were identified as key genes for CBD in the treatment of PTSD. Subsequent Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the anti-PTSD effect of CBD was related to the regulation of protein synthesis, oxidative phosphorylation, oxidative stress response, and fear response. Furthermore, gene set enrichment analysis (GSEA) revealed that CBD also enhanced retrograde endocannabinoid signaling in ExNs, which was found to be suppressed in the PTSD group. Our research may provide a potential explanation for the pathogenesis of PTSD and facilitate the discovery of novel therapeutic targets for drug development. Moreover, it may shed light on the therapeutic mechanisms of CBD.

Applications of L-Arginine in Pregnancy and Beyond: An Emerging Pharmacogenomic Approach.

L-arginine is a semi-essential amino acid that plays a critical role in various physiological processes, such as protein synthesis, wound healing, immune function, and cardiovascular regulation. The use of L-arginine in pregnancy has been an emerging topic in the field of pharmacogenomics. L-arginine, an amino acid, plays a crucial role in the production of nitric oxide, which is necessary for proper placental development and fetal growth. Studies have shown that L-arginine supplementation during pregnancy can have positive effects on fetal growth, maternal blood pressure, and the prevention of preeclampsia. This emerging pharmacogenomic approach involves using genetic information to personalize L-arginine dosages for pregnant women based on their specific genetic makeup. By doing so, it may be possible to optimize the benefits of L-arginine supplementation during pregnancy and improve pregnancy outcomes. This paper emphasizes the potential applications of L-arginine in pregnancy and the use of pharmacogenomic approaches to enhance its effectiveness. Nonetheless, the emerging pharmacogenomic approach to the application of L-arginine offers exciting prospects for the development of novel therapies for a wide range of diseases.

KDM5-mediated transcriptional activation of ribosomal protein genes alters translation efficiency to regulate mitochondrial metabolism in neurons.

Genes encoding the KDM5 family of transcriptional regulators are disrupted in individuals with intellectual disability (ID). To understand the link between KDM5 and ID, we characterized five Drosophila strains harboring missense alleles analogous to those observed in patients. These alleles disrupted neuroanatomical development, cognition and other behaviors, and displayed a transcriptional signature characterized by the downregulation of many ribosomal protein genes. A similar transcriptional profile was observed in KDM5C knockout iPSC-induced human glutamatergic neurons, suggesting an evolutionarily conserved role for KDM5 proteins in regulating this class of gene. In Drosophila, reducing KDM5 changed neuronal ribosome composition, lowered the translation efficiency of mRNAs required for mitochondrial function, and altered mitochondrial metabolism. These data highlight the cellular consequences of altered KDM5-regulated transcriptional programs that could contribute to cognitive and behavioral phenotypes. Moreover, they suggest that KDM5 may be part of a broader network of proteins that influence cognition by regulating protein synthesis.