bims-tubesc 2022-04-24 papers

bims-tubesc

Biomed News

on Molecular mechanisms in tuberous sclerosis

Issue of 2022‒04‒24
seventeen papers selected by
Marti Cadena Sandoval
metabolic-signalling.eu

Efficacy and Safety of Topical Mechanistic Target of Rapamycin Inhibitors for Facial Angiofibromas in Patients with Tuberous Sclerosis Complex: A Systematic Review and Network Meta-Analysis.
The association of neurodevelopmental abnormalities, congenital heart and renal defects in a tuberous sclerosis complex patient cohort.
DEPDC5-related epilepsy: A comprehensive review.
SOD1 mediates lysosome-to-mitochondria communication and its dysregulation by amyloid-β oligomers.
Kidney Transplantation in a Patient With Tuberous Sclerosis Complex: A Case Report.
mTORC1 Regulates High Levels of Protein Synthesis in Retinal Ganglion Cells of Adult Mice.
Unique presentation of retroperitoneal malignant perivascular epithelioid cell tumor (PEComa) in a young male.
Exploratory Analysis of Selected Components of the mTOR Pathway Reveals Potentially Crucial Associations with Childhood Malnutrition.
Electrophysiological and Behavioral Evidence for Hyper- and Hyposensitivity in Rare Genetic Syndromes Associated with Autism.
Application of mTORC1 Inhibitors for Tissue-Agnostic Management of Standard-Therapy-Refractory Solid Tumors.
Downregulation of CASTOR1 Inhibits Heat-Stress-Induced Apoptosis and Promotes Casein and Lipid Synthesis in Mammary Epithelial Cells.
FKBP5/FKBP51 on weight watch: central FKBP5 links regulatory WIPI protein networks to autophagy and metabolic control.
SLC38A10 Regulate Glutamate Homeostasis and Modulate the AKT/TSC2/mTOR Pathway in Mouse Primary Cortex Cells.
mTOR deletion ameliorates CD4 + T cell apoptosis during sepsis by improving autophagosome-lysosome fusion.
Translational control by heme-regulated elF2α kinase during erythropoiesis.
Rapamycin improves the quality and developmental competence of mice oocytes by promoting DNA damage repair during in vitro maturation.
Enhanced Activation of mTOR Signaling Pathway Was Found in the Hypertrophic and Nodular Lesions of Port Wine Stains.

Biomedicines. 2022 Mar 31. pii: 826. [Epub ahead of print]10(4):

Efficacy and Safety of Topical Mechanistic Target of Rapamycin Inhibitors for Facial Angiofibromas in Patients with Tuberous Sclerosis Complex: A Systematic Review and Network Meta-Analysis.

Yu-Ting Lin, Chia-Ling Yu, Yu-Kang Tu, Ching-Chi Chi.

  Previous studies have suggested that the topical mechanistic target of rapamycin (mTOR) inhibitors may be effective in treating facial angiofibromas in patients with tuberous sclerosis complex (TSC). Various concentrations of topical sirolimus for TSC have been tested, but their comparative efficacy and safety remained unclear. To assess the effects of topical mTOR inhibitors in treating facial angiofibromas, we conducted a systematic review and network meta-analysis (NMA) and searched MEDLINE, Embase, and Cochrane Library for relevant randomized controlled trials on 14 February 2022. The Cochrane Collaboration tool was used to assess the risk of bias of included trials. Our outcomes were clinical improvement and severe adverse events leading to withdrawal. We included three trials on 261 TSC patients with facial angiofibromas. The NMA found when compared with placebo, facial angiofibromas significantly improved following the application of various concentrations of topical sirolimus (risk ratio being 3.87, 2.70, 4.43, and 3.34 for 0.05%, 0.1%, 0.2%, and 1%, respectively). When compared with placebo, all concentrations of topical sirolimus did not differ in severe adverse events leading to withdrawal. The ranking analysis suggested topical sirolimus 0.2% as the most effective drug. In conclusion, topical sirolimus 0.05-1% are effective and safe in treating facial angiofibromas in patients with TSC, with topical sirolimus 0.2% being the most effective.

Keywords:  angiofibroma; mechanistic target of rapamycin (mTOR); network meta-analysis; sirolimus; systematic review; tuberous sclerosis complex

DOI:  https://doi.org/10.3390/biomedicines10040826
BMC Med. 2022 Apr 20. 20(1): 123

The association of neurodevelopmental abnormalities, congenital heart and renal defects in a tuberous sclerosis complex patient cohort.

Jessica Robinson, Orhan Uzun, Ne Ron Loh, Isabelle Rose Harris, Thomas E Woolley, Adrian J Harwood, Jennifer Frances Gardner, Yasir Ahmed Syed.

  BACKGROUND: Tuberous sclerosis complex (TSC) is a rare multi-system genetic disorder characterised by the presence of benign tumours throughout multiple organs including the brain, kidneys, heart, liver, eyes, lungs and skin, in addition to neurological and neuropsychiatric complications. Intracardiac tumour (rhabdomyoma), neurodevelopmental disorders (NDDs) and kidney disorders (KD) are common manifestations of TSC and have been linked with TSC1 and TSC2 loss-of-function mutations independently, but the dynamic relationship between these organ manifestations remains unexplored. Therefore, this study aims to characterise the nature of the relationship specifically between these three organs' manifestations in TSC1 and TSC2 mutation patients.METHODS: Clinical data gathered from TSC patients across South Wales registered with Cardiff and Vale University Health Board (CAV UHB) between 1990 and 2020 were analysed retrospectively to evaluate abnormalities in the heart, brain and kidney development. TSC-related abnormalities such as tumour prevalence, location and size were analysed for each organ in addition to neuropsychiatric involvement and were compared between TSC1 and TSC2 mutant genotypes. Lastly, statistical co-occurrence between organ manifestations co-morbidity was quantified, and trajectories of disease progression throughout organs were modelled.
RESULTS: This study found a significantly greater mutational frequency at the TSC2 locus in the cohort in comparison to TSC1. An equal proportion of male and female patients were observed in this group and by meta-analysis of previous studies. No significant difference in characterisation of heart involvement was observed between TSC1 and TSC2 patients. Brain involvement was seen with increased severity in TSC2 patients, characterised by a greater prevalence of cortical tubers and communication disorders. Renal pathology was further enhanced in TSC2 patients, marked by increased bilateral angiomyolipoma prevalence. Furthermore, co-occurrence of NDDs and KDs was the most positively correlated out of investigated manifestations, regardless of genotype. Analysis of disease trajectories revealed a more diverse clinical outcome for TSC2 patients: however, a chronological association of rhabdomyoma, NDD and KD was most frequently observed for TSC1 patients.
CONCLUSIONS: This study marks the first empirical investigation of the co-morbidity between congenital heart defects (CHD), NDDs, and KDs in TSC1 and TSC2 patients. This remains a unique first step towards the characterisation of the dynamic role between genetics, heart function, brain function and kidney function during the early development in the context of TSC.

Keywords:  Kidney lesions; Neurodevelopmental disorders; Rhabdomyoma; TAND; TSC1; TSC2

DOI:  https://doi.org/10.1186/s12916-022-02325-0
Epilepsy Behav. 2022 Apr 13. pii: S1525-5050(22)00127-5. [Epub ahead of print]130 108678

DEPDC5-related epilepsy: A comprehensive review.

Debopam Samanta.

  DEPDC5-related epilepsy, caused by pathogenic germline variants(with or without additional somatic variants in the brain) of DEPDC5 (Dishevelled, Egl-10 and Pleckstrin domain-containing protein 5) gene, is a newly discovered predominantly focal epilepsy linked to enhanced mTORC1 pathway. DEPDC5-related epilepsy includes several familial epilepsy syndromes, including familial focal epilepsy with variable foci (FFEVF) and rare sporadic nonlesional focal epilepsy. DEPDC5 has been identified as one of the more common epilepsy genes linked to infantile spasms and sudden unexpected death (SUDEP). Although intelligence usually is unaffected in DEPDC5-related epilepsy, some people have been diagnosed with intellectual disabilities, autism spectrum disorder, and other psychiatric problems. DEPDC5 variants have also been found in 20% of individuals with various brain abnormalities, challenging the traditional distinction between lesional and nonlesional epilepsies. The most exciting development of DEPDC5 variants is the possibility of precision therapeutics using mTOR inhibitors, as evidenced with phenotypic rescue in many animal models. However, more research is needed to better understand the functional impact of diverse (particularly missense or splice-region) variants, the specific involvement of DEPDC5 in epileptogenesis, and the creation and utilization of precision therapies in humans. Precision treatments for DEPDC5-related epilepsy will benefit not only a small number of people with the condition, but they will also pave the way for new therapeutic approaches in epilepsy (including acquired epilepsies in which mTORC1 activation occurs, for example, post-traumatic epilepsy) and other neurological disorders involving a dysfunctional mTOR pathway.

Keywords:  Children; Everolimus; Gene; Genomic; Mechanistic target of rapamycin; Seizure

DOI:  https://doi.org/10.1016/j.yebeh.2022.108678
Neurobiol Dis. 2022 Apr 19. pii: S0969-9961(22)00129-2. [Epub ahead of print] 105737

SOD1 mediates lysosome-to-mitochondria communication and its dysregulation by amyloid-β oligomers.

Andrés Norambuena, Xuehan Sun, Horst Wallrabe, Ruofan Cao, Naidi Sun, Evelyn Pardo, Nutan Shivange, Dora Bigler Wang, Lisa A Post, Heather A Ferris, Song Hu, Ammasi Periasamy, George S Bloom.

  Altered mitochondrial DNA (mtDNA) occurs in neurodegenerative disorders like Alzheimer's disease (AD); how mtDNA synthesis is linked to neurodegeneration is poorly understood. We previously discovered Nutrient-induced Mitochondrial Activity (NiMA), an inter-organelle signaling pathway where nutrient-stimulated lysosomal mTORC1 activity regulates mtDNA replication in neurons by a mechanism sensitive to amyloid-β oligomers (AβOs), a primary factor in AD pathogenesis (Norambuena et al., 2018). Using 5-ethynyl-2'-deoxyuridine (EdU) incorporation into mtDNA of cultured neurons, along with photoacoustic and mitochondrial metabolic imaging of cultured neurons and mouse brains, we show these effects being mediated by mTORC1-catalyzed T40 phosphorylation of superoxide dismutase 1 (SOD1). Mechanistically, tau, another key factor in AD pathogenesis and other tauopathies, reduced the lysosomal content of the tuberous sclerosis complex (TSC), thereby increasing NiMA and suppressing SOD1 activity and mtDNA synthesis. AβOs inhibited these actions. Dysregulation of mtDNA synthesis was observed in fibroblasts derived from tuberous sclerosis (TS) patients, who lack functional TSC and elevated SOD1 activity was also observed in human AD brain. Together, these findings imply that tau and SOD1 couple nutrient availability to mtDNA replication, linking mitochondrial dysfunction to AD.

Keywords:  Alzheimer's disease; Amino acids; Insulin; Tau; mTOR

DOI:  https://doi.org/10.1016/j.nbd.2022.105737
Transplant Proc. 2022 Apr 13. pii: S0041-1345(22)00211-1. [Epub ahead of print]

Kidney Transplantation in a Patient With Tuberous Sclerosis Complex: A Case Report.

Agnieszka Kluz, Jolanta Gozdowska, Piotr Domagała, Magdalena Durlik.

BACKGROUND: Tuberous sclerosis complex (TSC) is a rare autosomal dominant genetic disease caused by mutations of either of 2 genes, TSC1 and TSC2. Renal manifestations include angiomyolipomas (AMLs), multiple cysts, and renal cell carcinoma. AMLs increase bleeding tendency and the risk of renal insufficiency which end-stage develops in 1% of affected patients.CASE REPORT: A 38-year-old woman suffering from TSC since early childhood has developed multiple complications associated with this disease. The patient was diagnosed with brain tumor-giant cell astrocytoma-which was removed in 1992. In 2006, right nephrectomy was performed due to the unsuccessful right renal artery embolization after the massive hemorrhage into the AML. Moreover, the right idiopathic pneumothorax occurred twice. Therefore, the video-assisted thoracoscopic surgery and pleurodesis were conducted (2006, 2013). The patient is intellectually disabled and unable to make decisions on her own. Her legal guardians (parents) make all decisions associated with her treatment. Diagnostic and therapeutic procedures demanding cooperation were conducted under anesthesia. Because of end-stage renal failure, the patient required the renal replacement therapy (RRT). Preemptive kidney transplantation (KTx) was the best solution for this patient. Procedures such as hemodialysis and peritoneal dialysis were infeasible to perform due to the intellectual disability that inhibits essential cooperation. During KTx qualification tests, the expanding AML with risk of hemorrhage was noticed. The patient was qualified for simultaneous left nephrectomy and KTx from the living donor (her father). The surgery was performed on the 2nd of June 2020. The patient is looked after by her parents, stays in good general condition. The patient's creatinine level is maintained at 0.6 to 0.8 mg/dL.
CONCLUSION: Patients with significant intellectual disability that prevents maintaining conscious cooperation who require RRT must have individually adjusted therapy. In the case of the presented patient, it was decided to perform the preemptive kidney transplantation from her determined father.

DOI: https://doi.org/10.1016/j.transproceed.2022.02.055
J Biol Chem. 2022 Apr 18. pii: S0021-9258(22)00384-2. [Epub ahead of print] 101944

mTORC1 Regulates High Levels of Protein Synthesis in Retinal Ganglion Cells of Adult Mice.

Patrice E Fort, Mandy K Losiewicz, Lynda Elghazi, Dejuan Kong, Corentin Cras-Méneur, Diane C Fingar, Scot R Kimball, Raju V S Rajala, Alexander J Smith, Robin R Ali, Steven F Abcouwer, Thomas W Gardner.

  Mechanistic target of rapamycin (mTOR) and members of mTOR complex 1 (mTORC1), a linchpin of the nutrient sensing and protein synthesis pathways, are present at relatively high levels in the ganglion cell layer (GCL) and retinal ganglion cells (RGC) of rodent and human retinas. However, the role of mTOR complexes in the control of protein synthesis in RGC is unknown. Here we applied the SUnSET method of nascent protein labeling to localize and quantify protein synthesis in the retinas of adult mice. We also used intravitreal injection of an AAV2 vector encoding Cre recombinase in the eyes of mtor- or rptor-floxed mice to conditionally knockout either both mTOR complexes or only mTORC1, respectively, in cells within the GCL. A novel vector encoding an inactive Cre mutant (CreΔC) served as control. We found that retinal protein synthesis was highest in the GCL, particularly in RGC. Negation of both complexes or only mTORC1 significantly reduced protein synthesis in RGC. In addition, loss of mTORC1 function caused a significant reduction in the pan-RGC marker, RNA binding protein with multiple splicing (RBPMS), with little decrease of the total number of cells in the RGC layer, even at 25 weeks after AAV-Cre injection. These findings reveal that mTORC1 signaling is necessary for maintaining the high rate of protein synthesis in RGCs of adult rodents, but it may not be essential to maintain RGC viability. These findings may also be relevant to understanding the pathophysiology of RGC disorders, including glaucoma, diabetic retinopathy, and optic neuropathies.

Keywords:  eye; gene knockout; mRNA translation; mTOR complex (mTORC); mTORC1; mechanistic target of rapamycin (mTOR); protein synthesis; puromycin; retina; retinal ganglion cell

DOI:  https://doi.org/10.1016/j.jbc.2022.101944
Urol Case Rep. 2022 Jul;43 102077

Unique presentation of retroperitoneal malignant perivascular epithelioid cell tumor (PEComa) in a young male.

Ryan Freeman, Erin Kelley.

  Perivascular Epithelioid Cell tumors (PEComas) are rare mesenchymal tumors composed of epithelioid and spindle cells that can be found almost anywhere in the body with predominance for abdominopelvic locations. They are usually diagnosed in middle-aged females and are associated with tuberous sclerosis complex. This report describes an unusual presentation of a malignant retroperitoneal PEComa in an otherwise healthy, young male. Treatment included radical nephrectomy and adrenalectomy followed by medical oncology evaluation.

Keywords:  Angiomyolipoma; HMB-45; Malignant PEComa; Perivascular epithelioid cell tumor (PEComa)

DOI:  https://doi.org/10.1016/j.eucr.2022.102077
Nutrients. 2022 Apr 12. pii: 1612. [Epub ahead of print]14(8):

Exploratory Analysis of Selected Components of the mTOR Pathway Reveals Potentially Crucial Associations with Childhood Malnutrition.

Parag Palit, Md Amran Gazi, Subhasish Das, Md Mehedi Hasan, Zannatun Noor, Jafrin Ferdous, Md Ashraful Alam, Sharika Nuzhat, Md Ridwan Islam, Mustafa Mahfuz, Rashidul Haque, Tahmeed Ahmed.

  Dysregulations in the mammalian target of rapamycin (mTOR) pathway are associated with several human anomalies. We aimed to elucidate possible implications for potential aberrations in the mTOR pathway with childhood malnutrition. We analyzed the activity of phospho-mTORC1 and the expressions of several mTOR pathway genes, namely: MTOR, TSC1, LAMTOR2, RPS6K1 and RICTOR from peripheral blood mononuclear cells isolated from venous blood of children suffering from different forms of malnutrition and compared them with those from healthy children. Significant reduction in the phosphorylation of mTORC1 was noted, as well as a decrease in expression of LAMTOR2 gene and increase in TSC1 gene expression were observed between malnourished children in comparison to the healthy children. The deregulation in the activity of the TSC1 and LAMTOR2 gene was significantly associated with all forms of childhood malnutrition. Our findings provide key insights into possible down-modulation in the overall activity of the mTOR pathway in childhood malnutrition. Further studies focusing on the analysis of a multitude of components involved in the mTOR pathway both at the gene and protein expression levels are required for conclusive evidence for the aforementioned proposition.

Keywords:  childhood malnutrition; gene expression; mTOR pathway

DOI:  https://doi.org/10.3390/nu14081612
Genes (Basel). 2022 Apr 11. pii: 671. [Epub ahead of print]13(4):

Electrophysiological and Behavioral Evidence for Hyper- and Hyposensitivity in Rare Genetic Syndromes Associated with Autism.

Anastasia Neklyudova, Kirill Smirnov, Anna Rebreikina, Olga Martynova, Olga Sysoeva.

  Our study reviewed abnormalities in spontaneous, as well as event-related, brain activity in syndromes with a known genetic underpinning that are associated with autistic symptomatology. Based on behavioral and neurophysiological evidence, we tentatively subdivided the syndromes on primarily hyper-sensitive (Fragile X, Angelman) and hypo-sensitive (Phelan-McDermid, Rett, Tuberous Sclerosis, Neurofibromatosis 1), pointing to the way of segregation of heterogeneous idiopathic ASD, that includes both hyper-sensitive and hypo-sensitive individuals. This segmentation links abnormalities in different genes, such as FMR1, UBE3A, GABRB3, GABRA5, GABRG3, SHANK3, MECP2, TSC1, TSC2, and NF1, that are causative to the above-mentioned syndromes and associated with synaptic transmission and cell growth, as well as with translational and transcriptional regulation and with sensory sensitivity. Excitation/inhibition imbalance related to GABAergic signaling, and the interplay of tonic and phasic inhibition in different brain regions might underlie this relationship. However, more research is needed. As most genetic syndromes are very rare, future investigations in this field will benefit from multi-site collaboration with a common protocol for electrophysiological and event-related potential (EEG/ERP) research that should include an investigation into all modalities and stages of sensory processing, as well as potential biomarkers of GABAergic signaling (such as 40-Hz ASSR).

Keywords:  Angelman syndrome; Fragile X syndrome; Phelan–McDermid syndrome; Rett syndrome; autism spectrum disorder (ASD); biomarkers; electroencephalogram (EEG); event-related potentials (ERP); neurofibromatosis type 1; sensory deficits; tuberous sclerosis

DOI:  https://doi.org/10.3390/genes13040671
Cancers (Basel). 2022 Apr 12. pii: 1936. [Epub ahead of print]14(8):

Application of mTORC1 Inhibitors for Tissue-Agnostic Management of Standard-Therapy-Refractory Solid Tumors.

Hossein Taghizadeh, Agnieszka Maj-Hes, Gerald W Prager, Leonhard Müllauer, Robert M Mader.

  In this analysis, we examined the efficacy, feasibility, and limitations of the application of mTOR inhibitors based on the individual molecular profiles of pretreated cancer patients after the failure of all standard treatments in the palliative setting. In this single-center, real-world analysis of our platform for precision medicine, we analyzed the molecular characteristics of 71 cancer patients. The tumor samples of the patients were analyzed using next-generation sequencing panels of mutation hotspots, microsatellite stability testing, and immunohistochemistry. All profiles were reviewed by a multidisciplinary team to provide a targeted treatment recommendation after a consensus discussion. Seventy-one cancer patients with activation of the mTOR pathway were offered an mTORC1-inhibitor-based targeted therapy, and twenty-three (32.4%) of them eventually received the targeted therapy. Only three patients (4.2%) achieved stable disease, of whom one experienced progressive disease again after 9.1 months. The median time to treatment failure was 2.8 months. In total, 110 mutations were detected in 60 patients (84.5%). The three most frequent mutations were found in TP53, PTEN, and KRAS, which accounted for over 50% (56.4%) of all mutations. In sum, in selected patients with heavily pretreated solid tumors with activation of the mTOR pathway, the antitumoral activity of mTORC1 inhibition was weak.

Keywords:  mTOR; molecular oncology; targeted therapy; tissue-agnostic

DOI:  https://doi.org/10.3390/cancers14081936
J Agric Food Chem. 2022 Apr 20.

Downregulation of CASTOR1 Inhibits Heat-Stress-Induced Apoptosis and Promotes Casein and Lipid Synthesis in Mammary Epithelial Cells.

Zhongchao Gai, Yujiao Wang, Jie Wang, Jiapeng Fu, Lu Tian, Xue Li, Jieqiong Zhao, Guoli Gong.

  Heat stress is one of the most important factors limiting the milk yields of dairy animals. This decline can be attributed to the heat-stress-induced apoptosis of mammary epithelial cells (MECs). The cytosolic arginine sensor for mTORC1 subunit 1 (CASTOR1) is a crucial upstream regulator of the mechanistic target of rapamycin complex 1 (mTORC1) signaling, which has close connections with apoptosis. However, the specific roles of CASTOR1 in regulating the apoptosis and lactation of MECs are still obscure. In the present study, we found that heat stress promotes apoptosis and CASTOR1's expression in HC11 cells. Downregulation of CASTOR1 inhibits heat-stress-induced apoptosis through a ROS-independent pathway. In addition, silencing of CASTOR1 promotes cell proliferation, cell cycle progression, and milk component synthesis, and overexpressing of CASTOR1 reverses these observations. Furthermore, we found that silencing of CASTOR1 contributes to the nuclear transport of SREBP1 and promotes lipid synthesis. This study demonstrates the pivotal roles of CASTOR1 in heat-stress-induced apoptosis and milk component synthesis in MECs.

Keywords:  CASTOR1; MECs; apoptosis; heat stress; lactation; mTOR

DOI:  https://doi.org/10.1021/acs.jafc.2c00877
Autophagy. 2022 Apr 19. 1-3

FKBP5/FKBP51 on weight watch: central FKBP5 links regulatory WIPI protein networks to autophagy and metabolic control.

Thomas Bajaj, Alexander S Häusl, Mathias V Schmidt, Nils C Gassen.

  Stress and changes in energy stores are perceived by hormone- and nutrient-sensing nuclei of the hypothalamus, which orchestrate an adaptive physiological body response to maintain homeostasis. Macroautophagy/autophagy is a fundamental lysosomal degradation system contributing to preservation of proteome balance and metabolic homeostasis. Its dysregulation is linked to diverse human pathologies, including neuropsychiatric and metabolic disorders. Autophagy is coordinated by cellular nutrient sensors, including AMPK and MTORC1 that interact with WIPI proteins. Studies suggest that WDR45/WIPI4 interacts with the stress-sensitive co-chaperone FKBP5/FKBP51, which has emerged as a key autophagy scaffold. However, the impact of FKBP5 on autophagy signaling in response to metabolic challenges, such as a high-fat diet, is elusive. Therefore, we manipulated FKBP5 in the mediobasal hypothalamus (MBH) and studied autophagy signaling and protein interactions in their physiological context. We identified FKBP5 as a scaffold of the STK11/LKB1-AMPK complex with WDR45/WIPI4 and TSC2 with WDR45B/WIPI3 in response to metabolic challenges, positioning FKBP5 in major nutrient-sensing and autophagy-regulating networks. Intriguingly, we could demonstrate that FKBP5 deletion in the MBH strongly induces obesity, whereas its overexpression protects against high-fat diet-induced obesity. Our findings suggest a crucial regulatory and adaptive function of FKBP5-regulated autophagy within the MBH in response to metabolic challenges.Abbreviations: AKT: thymoma viral proto-oncogene; AMPK: AMP-activated protein kinase; BECN1: beclin 1, autophagy related; eWAT: epididymal white adipose tissue; FKBP5/FKBP51: FK506 binding protein 5; KO, knockout; MBH, mediobasal hypothalamus; MTORC1, mechanistic target of rapamycin kinase complex 1; p: phosphorylated; PHLPP: PH domain and leucine rich repeat protein phosphatase; RPS6KB/p70S6K: ribosomal protein S6 kinase; SKP2: S-phase kinase-associated protein 2; SM: soleus muscle; SQSTM1/p62, sequestosome 1; STK11/LKB1: serine/threonine kinase 11; TSC: TSC complex; ULK1: unc-51 like kinase 1; WIPI: WD repeat domain, phosphoinositide interacting; WT: wild type.

Keywords:  AMPK; FKBP5/FKBP51; WIPI; autophagy; metabolic stress

DOI:  https://doi.org/10.1080/15548627.2022.2063006
Front Cell Dev Biol. 2022 ;10 854397

SLC38A10 Regulate Glutamate Homeostasis and Modulate the AKT/TSC2/mTOR Pathway in Mouse Primary Cortex Cells.

Rekha Tripathi, Tanya Aggarwal, Frida A Lindberg, Anna H Klemm, Robert Fredriksson.

  Glutamate acts as a critical regulator of neurotransmitter balance, recycling, synaptic function and homeostasis in the brain and glutamate transporters control glutamate levels in the brain. SLC38A10 is a member of the SLC38 family and regulates protein synthesis and cellular stress responses. Here, we uncover the role of SLC38A10 as a transceptor involved in glutamate-sensing signaling pathways that control both the glutamate homeostasis and mTOR-signaling. The culture of primary cortex cells from SLC38A10 knockout mice had increased intracellular glutamate. In addition, under nutrient starvation, KO cells had an impaired response in amino acid-dependent mTORC1 signaling. Combined studies from transcriptomics, protein arrays and metabolomics established that SLC38A10 is involved in mTOR signaling and that SLC38A10 deficient primary cortex cells have increased protein synthesis. Metabolomic data showed decreased cholesterol levels, changed fatty acid synthesis, and altered levels of fumaric acid, citrate, 2-oxoglutarate and succinate in the TCA cycle. These data suggests that SLC38A10 may act as a modulator of glutamate homeostasis, and mTOR-sensing and loss of this transceptor result in lower cholesterol, which could have implications in neurodegenerative diseases.

Keywords:  SLC38A10; mTOR; primary cortex cultures; solute carriers transporter; starvation

DOI:  https://doi.org/10.3389/fcell.2022.854397
Apoptosis. 2022 Apr 18.

mTOR deletion ameliorates CD4 + T cell apoptosis during sepsis by improving autophagosome-lysosome fusion.

Hao Wang, Guangxu Bai, Jianwei Chen, Wen Han, Ran Guo, Na Cui.

  Autophagy dysfunction contributes to CD4 + T cell apoptosis during sepsis leading to impairment of adaptive immunity. However, the underlying mechanism is unclear. The mammalian target of rapamycin (mTOR) pathway modulates CD4 + T cell survival during sepsis through mechanisms that are not fully understood. We developed a mouse model of sepsis through cecal ligation and puncture (CLP) to investigate dynamic changes in autophagy in CD4 + T cells. We used T cell specific-mTOR/tuberous sclerosis complex 1 (TSC1)-knockout mice to explore the roles of the mTOR pathway in modulating autophagy during sepsis. We observed reduced fusion of autophagosomes with lysosomes in the CD4 + T cells of CLP mice, which may represent a characteristic feature of autophagy dysfunction. Deletion of mTOR relieved autophagosome-lysosome fusion dysfunction and ameliorated apoptosis of CD4 + T cells in CLP mice, but this rescued phenotype was abolished by treatment with bafilomycin A1, a specific A-L fusion inhibitor. We further explored the underlying molecular mechanism and found that phosphorylation levels of transcription factor EB were significant higher in CLP mice and that expression of A-L fusion protein SNAREs were restricted, both of which were ameliorated by mTOR deletion. Taken together, these results suggest that the mTOR pathway plays a critical role in regulation of CD4 + T-cell apoptosis during sepsis, partly through regulation of A-L fusion-related protein transcription.

Keywords:  Autophagosome-lysosome fusion; Sepsis; mTOR

DOI:  https://doi.org/10.1007/s10495-022-01719-y
Curr Opin Hematol. 2022 May 01. 29(3): 103-111

Translational control by heme-regulated elF2α kinase during erythropoiesis.

Jane-Jane Chen, Shuping Zhang.

PURPOSE OF REVIEW: HRI is the heme-regulated elF2α kinase that phosphorylates the α-subunit of elF2. Although the role of HRI in inhibiting globin synthesis in erythroid cells is well established, broader roles of HRI in translation have been uncovered recently. This review is to summarize the new discoveries of HRI in stress erythropoiesis and in fetal γ-globin expression.RECENT FINDINGS: HRI and activating transcription factor 4 (ATF4) mRNAs are highly expressed in early erythroblasts. Inhibition of protein synthesis by HRI-phosphorylated elF2α (elF2αP) is necessary to maintain protein homeostasis in both the cytoplasm and mitochondria. In addition, HRI-elF2αP specifically enhances translation of ATF4 mRNA leading to the repression of mechanistic target of rapamycin complex 1 (mTORC1) signaling. ATF4-target genes are most highly activated during iron deficiency to maintain mitochondrial function, redox homeostasis, and to enable erythroid differentiation. HRI is therefore a master translation regulator of erythropoiesis sensing intracellular heme concentrations and oxidative stress for effective erythropoiesis. Intriguingly, HRI-elF2αP-ATF4 signaling also inhibits fetal hemoglobin production in human erythroid cells.
SUMMARY: The primary function of HRI is to maintain protein homeostasis accompanied by the induction of ATF4 to mitigate stress. Role of HRI-ATF4 in γ-globin expression raises the potential of HRI as a therapeutic target for hemoglobinopathy.

DOI: https://doi.org/10.1097/MOH.0000000000000704
Reprod Biol Endocrinol. 2022 Apr 18. 20(1): 67

Rapamycin improves the quality and developmental competence of mice oocytes by promoting DNA damage repair during in vitro maturation.

Qiyu Yang, Qingsong Xi, Meng Wang, Rui Long, Juan Hu, Zhou Li, Xinling Ren, Lixia Zhu, Lei Jin.

  BACKGROUND: Increasing evidence has shown that the mammalian target of rapamycin (mTOR) pathway plays a critical role in oocyte meiosis and embryonic development, however, previous studies reporting the effects of rapamycin on oocyte IVM showed different or even opposite results, and the specific mechanisms were not clear.METHODS: The immature oocytes from female mice underwent IVM with rapamycin at different concentrations to select an optimal dose. The maturation rate, activation rate, subsequent cleavage and blastocyst formation rates, spindle assembly, chromosome alignment, mitochondrial membrane potential (MMP), ROS levels, and DNA damage levels were evaluated and compared in oocytes matured with or without rapamycin. In addition, the expression levels of genes associated with mTORC1 pathway, spindle assembly, antioxidant function, and DNA damage repair (DDR) were also assessed and compared.
RESULTS: Rapamycin at 10 nM was selected as an optimal concentration based on the higher maturation and activation rate of IVM oocytes. Following subsequent culture, cleavage and blastocyst formation rates were elevated in activated embryos from the rapamycin group. Additionally, oocytes cultured with 10 nM rapamycin presented decreased ROS levels, reduced chromosome aberration, and attenuated levels of γ-H2AX. No significant effects on the percentages of abnormal spindle were observed. Correspondingly, the expressions of Nrf2, Atm, Atr, and Prkdc in IVM oocytes were markedly increased, following the inhibition of mTORC1 pathway by 10 nM rapamycin.
CONCLUSION: Rapamycin at 10 nM could ameliorate the developmental competence and quality of IVM oocytes of mice, mainly by improving the chromosome alignments. The inhibition of mTORC1 pathway, which involved in activating DDR-associated genes may act as a potential mechanism for oocyte quality improvement by rapamycin.

Keywords:  DNA damage; In vitro maturation; Oocyte quality; Rapamycin; mTOR

DOI:  https://doi.org/10.1186/s12958-022-00943-0
Clin Cosmet Investig Dermatol. 2022 ;15 643-651

Enhanced Activation of mTOR Signaling Pathway Was Found in the Hypertrophic and Nodular Lesions of Port Wine Stains.

Meng-Nan Xu, Qian Wang, Min Wang, Yuan Xu, Si-Ming Yuan.

  Background: Port wine stain (PWS) is a congenital skin lesion involving capillary malformations. Most PWS lesions will gradually become hypertrophic and appear nodular in contour. Current research shows that rapamycin, an mTOR inhibitor, is probably a promising adjunctive therapy for PWS, which suggests that the mTOR signaling pathway may play an important role in its pathological process.Methods: From January 2013 to January 2019, 13 samples were obtained during the surgical excision. Each sample was divided into 3 parts according to the type of lesion, namely, the flat, hypertrophic and nodular lesions. Pathologic structures of each type were observed under the microscope after HE staining. The expression of mTORC1, p70S6, p-p70S6, eIF4EBP1 and p-eIF4EBP1 was examined by immunohistochemical staining and western blotting. The location of the expression of mTORC1, p-p70S6 and p-elF4EBP1 was further detected by immunofluorescence staining.
Results: Large amounts of dilated and malformed vessels were observed in all types of PWS lesions. Abundant hyperplastic hair follicles/glands were shown in the hypertrophic or nodular lesions. Phosphorylation level of p70S6 and elF4EBP1 in PWS was significantly higher than those in normal skin and increased accordingly in the progression of PWS. Activated molecules in mTOR signaling pathway were mostly located in the endothelium of malformed vessels. They were also located in the hyperplastic hair follicles/glands of hypertrophic and nodular lesions.
Conclusion: The mTOR signaling pathway was increasingly activated during the progression of PWS. Enhanced activation of mTOR signaling pathway may contribute to the hypertrophy and nodularity of PWS. The results provide preliminary evidence for treating PWS and related syndromes by inhibiting mTOR signaling pathway.

Keywords:  mTOR signaling pathway; port wine stain

DOI:  https://doi.org/10.2147/CCID.S358612