PRAS40 alleviates neurotoxic prion peptide-induced apoptosis via mTOR-AKT signaling

Purine metabolism in bone marrow microenvironment inhibits hematopoietic stem cell differentiation under microgravity

BACKGROUND

Spaceflight and microgravity environments have been shown to cause significant health impairments, including bone loss, immune dysfunction, and hematopoietic disorders. Hematopoietic stem cells (HSCs), as progenitors of the hematopoietic system, are critical for the continuous renewal and regulation of immune cells. Therefore, elucidating the regulatory mechanisms governing HSC fate and differentiation in microgravity environments is of paramount importance.

METHODS

In this study, hindlimb unloading (HU) was employed in mice to simulate microgravity conditions. After 28 days of HU, cells were isolated for analysis. Flow cytometry and colony-forming assays were utilized to assess changes in HSC proliferation and differentiation. Additionally, transcriptomic and untargeted metabolomic sequencing were performed to elucidate alterations in the metabolic pathways of the bone marrow microenvironment and their molecular regulatory effects on HSCs fate.

RESULTS

Our findings revealed that 28 days of HU impaired hematopoietic function, leading to multi-organ damage and hematological disorders. The simulated microgravity environment significantly increased the HSCs population in the bone marrow, particularly within the long-term and short-term subtypes, while severely compromising the differentiation capacity of hematopoietic stem/progenitor cells. Transcriptomic analysis of HSCs, combined with metabolomic profiling of bone marrow supernatants, identified 1,631 differentially expressed genes and 58 metabolites with altered abundance. Gene set enrichment analysis indicated that HU suppressed key pathways, including hematopoietic cell lineage and MAPK signaling. Furthermore, integrated analyses revealed that metabolites affected by HU, particularly hypoxanthine enriched in the purine metabolism pathway, were closely associated with hematopoietic cell lineage and MAPK signaling pathways. Molecular docking simulations and in vitro experiments confirmed that hypoxanthine interacts directly with core molecules within these pathways, influencing their expression.

CONCLUSIONS

These findings demonstrate that hypoxanthine in the bone marrow supernatant acts as a signaling mediator under microgravity, influencing HSCs fate by modulating hematopoietic cell lineage and MAPK signaling pathways. This study offers novel insights into the impact of microgravity on HSC fate and gene expression, underscoring the pivotal role of bone marrow microenvironmental metabolic changes in regulating key signaling pathways that determine hematopoietic destiny.

Hyperuricemia and its related diseases: mechanisms and advances in therapy

Hyperuricemia, characterized by elevated levels of serum uric acid (SUA), is linked to a spectrum of commodities such as gout, cardiovascular diseases, renal disorders, metabolic syndrome, and diabetes, etc. Significantly impairing the quality of life for those affected, the prevalence of hyperuricemia is an upward trend globally, especially in most developed countries. UA possesses a multifaceted role, such as antioxidant, pro-oxidative, pro-inflammatory, nitric oxide modulating, anti-aging, and immune effects, which are significant in both physiological and pathological contexts. The equilibrium of circulating urate levels hinges on the interplay between production and excretion, a delicate balance orchestrated by urate transporter functions across various epithelial tissues and cell types. While existing research has identified hyperuricemia involvement in numerous biological processes and signaling pathways, the precise mechanisms connecting elevated UA levels to disease etiology remain to be fully elucidated. In addition, the influence of genetic susceptibilities and environmental determinants on hyperuricemia calls for a detailed and nuanced examination. This review compiles data from global epidemiological studies and clinical practices, exploring the physiological processes and the genetic foundations of urate transporters in depth. Furthermore, we uncover the complex mechanisms by which the UA induced inflammation influences metabolic processes in individuals with hyperuricemia and the association with its relative disease, offering a foundation for innovative therapeutic approaches and advanced pharmacological strategies.

PHB2 Alleviates Neurotoxicity of Prion Peptide PrP106-126 via PINK1/Parkin-Dependent Mitophagy

Prion diseases are a group of neurodegenerative diseases characterized by mitochondrial dysfunction and neuronal death. Mitophagy is a selective form of macroautophagy that clears injured mitochondria. Prohibitin 2 (PHB2) has been identified as a novel inner membrane mitophagy receptor that mediates mitophagy. However, the role of PHB2 in prion diseases remains unclear. In this study, we isolated primary cortical neurons from rats and used the neurotoxic prion peptide PrP106-126 as a cell model for prion diseases. We examined the role of PHB2 in PrP106-126-induced mitophagy using Western blotting and immunofluorescence microscopy and assessed the function of PHB2 in PrP106-126-induced neuronal death using the cell viability assay and the TUNEL assay. The results showed that PrP106-126 induced mitochondrial morphological abnormalities and mitophagy in primary cortical neurons. PHB2 was found to be indispensable for PrP106-126-induced mitophagy and was involved in the accumulation of PINK1 and recruitment of Parkin to mitochondria in primary neurons. Additionally, PHB2 depletion exacerbated neuronal cell death induced by PrP106-126, whereas the overexpression of PHB2 alleviated PrP106-126 neuronal toxicity. Taken together, this study demonstrated that PHB2 is indispensable for PINK1/Parkin-mediated mitophagy in PrP106-126-treated neurons and protects neurons against the neurotoxicity of the prion peptide.

mTOR signaling as a molecular target for the alleviation of Alzheimer's disease pathogenesis

Mechanistic/mammalian target of rapamycin (mTOR) belongs to the phosphatidylinositol kinase-related kinase (PIKK) family. mTOR signaling is required for the commencement of essential cell functions including autophagy. mTOR primarily governs cell growth in response to favourable nutrients and other growth stimuli. However, it also influences aging and other aspects of nutrient-related physiology such as protein synthesis, ribosome biogenesis, and cell proliferation in adults with very limited growth. The major processes for survival such as synaptic plasticity, memory storage and neuronal recovery involve a significant mTOR activity. mTOR dysregulation is becoming a prevalent motif in a variety of human diseases, including cancer, neurological disorders, and other metabolic syndromes. The use of rapamycin to prolong life in different animal models may be attributable to the multiple roles played by mTOR signaling in various processes involved in ageing, protein translation, autophagy, stem cell pool turnover, inflammation, and cellular senescence. mTOR activity was found to be altered in AD brains and rodent models, supporting the notion that aberrant mTOR activity is one of the key events contributing to the onset and progression of AD hallmarks This review assesses the molecular association between the mTOR signaling pathway and pathogenesis of Alzheimer's disease. The research data supporting this theme are also reviewed.

Targeting PRAS40: a novel therapeutic strategy for human diseases

Proline-rich Akt substrate of 40 kD (PRAS40) is not only the substrate of protein kinase B (PKB/Akt), but also the binding protein of 14-3-3 protein. PRAS40 is expressed in a variety of tissues in vivo and has multiple phosphorylation sites, which its activity is closely related to phosphorylation. Studies have shown that PRAS40 is involved in regulating cell growth, cell apoptosis, oxidative stress, autophagy and angiogenesis, as well as various of signalling pathways such as mammalian target of mammalian target rapamycin (mTOR), protein kinase B (PKB/Akt), nuclear factor kappa-B(NF-κB), proto-oncogene serine/threonine-protein kinase PIM-1(PIM1) and pyruvate kinase M2 (PKM2). The interactive roles between PRAS40 and these signal proteins were analysed by bioinformatics in this paper. Moreover, it is of great necessity for analyse the important roles of PRAS40 in some human diseases including cardiovascular disease, ischaemia-reperfusion injury, neurodegenerative disease, cancer, diabetes and other metabolic diseases. Finally, the effects of miRNA on the regulation of PRAS40 function and the occurrence and development of PRAS40-related diseases are also discussed. Overall, PRAS40 is expected to be a drug target and provide a new treatment strategy for human diseases.

Montelukast Induces Apoptosis-Inducing Factor-Mediated Cell Death of Lung Cancer Cells

Developing novel chemo-prevention techniques and advancing treatment are key elements to beating lung cancer, the most common cause of cancer mortality worldwide. Our previous cohort study showed that cysteinyl leukotriene receptor antagonists, mainly montelukast, decreased the lung cancer risk in asthma patients. In the current study, we conducted in vivo and in vitro experiments to demonstrate the inhibiting effect of montelukast on lung cancer and to investigate the underlying mechanisms. Using Lewis lung carcinoma-bearing mice, we showed that feeding montelukast significantly delayed the tumor growth in mice (p < 0.0001). Montelukast inhibited cell proliferation and colony formation and induced the cell death of lung cancer cells. Further investigation showed the down-regulation of B-cell lymphoma 2 (Bcl-2), up-regulation of Bcl-2 homologous antagonist/killer (Bak), and nuclear translocation of apoptosis-inducing factor (AIF) in montelukast-treated lung cancer cells. Montelukast also markedly decreased the phosphorylation of several proteins, such as with no lysine 1 (WNK1), protein kinase B (Akt), extracellular signal-regulated kinase 1/2 (Erk1/2), MAPK/Erk kinase (MEK), and proline-rich Akt substrate of 40-kDa (PRAS40), which might contribute to cell death. In conclusion, montelukast induced lung cancer cell death via the nuclear translocation of AIF. This study confirmed the chemo-preventive effect of montelukast shown in our previous cohort study. The utility of montelukast in cancer prevention and treatment thus deserves further studies.

Downregulation of the Repressor Element 1-Silencing Transcription Factor (REST) Is Associated with Akt-mTOR and Wnt-β-Catenin Signaling in Prion Diseases Models

Prion diseases are a group of infectious diseases characterized by multiple neuropathological changes, yet the mechanisms that preserve function and protect against prion-associated neurodegeneration are still unclear. We previously reported that the repressor element 1-silencing transcription factor (REST) alleviates neurotoxic prion peptide (PrP106-126)-induced toxicity in primary neurons. Here we confirmed the findings of the in vitro model in 263K infected hamsters, an in vivo model of prion diseases and further showed the relationships between REST and related signaling pathways. REST was depleted from the nucleus in prion infected brains and taken up by autophagosomes in the cytoplasm, co-localizing with LC3-II. Importantly, downregulation of the Akt–mTOR and at least partially inactivation of LRP6-Wnt-β-catenin signaling pathways correlated with the decreased levels of REST in vivo in the brain of 263K-infected hamsters and in vitro in PrP106-126-treated primary neurons. Overexpression of REST in primary cortical neurons alleviated PrP106-126 peptide-induced neuronal oxidative stress, mitochondrial damage and partly inhibition of the LRP6-Wnt-β-catenin and Akt–mTOR signaling. Based on our findings, a model of REST-mediated neuroprotection in prion infected animals is proposed, with Akt–mTOR and Wnt-β-catenin signaling as the key pathways. REST-mediated neuronal survival signaling could be explored as a viable therapeutic target for prion diseases and related neurodegenerative diseases.

PRAS40 alleviates neurotoxic prion peptide-induced apoptosis via mTOR-AKT signaling

AIMS

The proline-rich Akt substrate of 40-kDa (PRAS40) protein is a direct inhibitor of mTORC1 and an interactive linker between the Akt and mTOR pathways. The mammalian target of rapamycin (mTOR) is considered to be a central regulator of cell growth and metabolism. Several investigations have demonstrated that abnormal mTOR activity may contribute to the pathogenesis of several neurodegenerative disorders and lead to cognitive deficits.

METHODS

Here, we used the PrP peptide 106-126 (PrP^106-126 ) in a cell model of prion diseases (also known as transmissible spongiform encephalopathies, TSEs) to investigate the mechanisms of mTOR-mediated cell death in prion diseases.

RESULTS

We have shown that, upon stress caused by PrP^106-126 , the mTOR pathway activates and contributes to cellular apoptosis. Moreover, we demonstrated that PRAS40 down-regulates mTOR hyperactivity under stress conditions and alleviates neurotoxic prion peptide-induced apoptosis. The effect of PRAS40 on apoptosis is likely due to an mTOR/Akt signaling.

CONCLUSION

PRAS40 inhibits mTORC1 hyperactivation and plays a key role in protecting cells against neurotoxic prion peptide-induced apoptosis. Thus, PRAS40 is a potential therapeutic target for prion disease.