bims-tubesc 2022-02-20 papers

bims-tubesc

Biomed News

on Molecular mechanisms in tuberous sclerosis

Issue of 2022–02–20
twenty-one papers selected by

ETV2 regulates PARP-1 binding protein to induce ER stress-mediated death in tuberin-deficient cells.
A scoping review on cannabidiol therapy in tuberous sclerosis: Current evidence and perspectives for future development.
Managing Headache Disorders Associated with Tuberous Sclerosis and Neurofibromatosis.
[Subependymal Giant Cell Astrocytoma with Tuberous Sclerosis Complex(TSC-SEGA)].
Time to Onset of Cannabidiol (CBD) Treatment Effect and Resolution of Adverse Events in Tuberous Sclerosis Complex: Post Hoc Analysis of Randomized Controlled Phase 3 Trial GWPCARE6.
[Clinical manifestation of odontogenic fibroma associated with tuberous sclerosis complex: a case report].
Lung-selective mRNA delivery of synthetic lipid nanoparticles for the treatment of pulmonary lymphangioleiomyomatosis.
Cerebellar demyelination and neurodegeneration associated with mTORC1 hyperactivity may contribute to the developmental onset of autism-like neurobehavioral phenotype in a rat model.
Low-grade oncocytic tumor (LOT) - a new renal entity ready for a prime time: An updated review.
The research landscape of tuberous sclerosis complex-associated neuropsychiatric disorders (TAND)-a comprehensive scoping review.
Biomarker-Based Phase II Study of Sapanisertib (TAK-228): An mTORC1/2 Inhibitor in Patients With Refractory Metastatic Renal Cell Carcinoma.
Postoperative pneumothorax after nephrectomy in a patient with tuberous sclerosis and undiagnosed lymphangioleiomyomatosis.
NPRL2 Inhibition of mTORC1 Controls Sodium Channel Expression and Brain Amino Acid Homeostasis.
Role of mTOR Complex 1 Signaling Pathway in the Pathogenesis of Diabetes Complications; A Mini Review.
Exosomal miR-673-5p from fibroblasts promotes Schwann cell-mediated peripheral neuron myelination by targeting the TSC2/mTORC1/SREBP2 axis.
Predominant Role of mTOR Signaling in Skin Diseases with Therapeutic Potential.
Cortical Dysplasia and the mTOR Pathway: How the Study of Human Brain Tissue Has Led to Insights into Epileptogenesis.
mTOR Signaling Components in Tumor Mechanobiology.
Bur1 functions with TORC1 for vacuole-mediated cell cycle progression.
An AMPKα2-specific phospho-switch controls lysosomal targeting for activation.
PTEN loss confers sensitivity to rapalogs in clear cell renal cell carcinoma.

Life Sci Alliance. 2022 May;pii: e202201369. [Epub ahead of print]5(5):

ETV2 regulates PARP-1 binding protein to induce ER stress-mediated death in tuberin-deficient cells.

Shikshya Shrestha, Anthony Lamattina, Gustavo Pacheco-Rodriguez, Julie Ng, Xiaoli Liu, Abhijeet Sonawane, Jewel Imani, Weiliang Qiu, Kosmas Kosmas, Pierce Louis, Anne Hentschel, Wendy K Steagall, Rieko Onishi, Helen Christou, Elizabeth P Henske, Kimberly Glass, Mark A Perrella, Joel Moss, Kelan Tantisira, Souheil El-Chemaly.

Lymphangioleiomyomatosis (LAM) is a rare progressive disease, characterized by mutations in the tuberous sclerosis complex genes (TSC1 or TSC2) and hyperactivation of mechanistic target of rapamycin complex 1 (mTORC1). Here, we report that E26 transformation-specific (ETS) variant transcription factor 2 (ETV2) is a critical regulator of Tsc2-deficient cell survival. ETV2 nuclear localization in Tsc2-deficient cells is mTORC1-independent and is enhanced by spleen tyrosine kinase (Syk) inhibition. In the nucleus, ETV2 transcriptionally regulates poly(ADP-ribose) polymerase 1 binding protein (PARPBP) mRNA and protein expression, partially reversing the observed down-regulation of PARPBP expression induced by mTORC1 blockade during treatment with both Syk and mTORC1 inhibitors. In addition, silencing Etv2 or Parpbp in Tsc2-deficient cells induced ER stress and increased cell death in vitro and in vivo. We also found ETV2 expression in human cells with loss of heterozygosity for TSC2, lending support to the translational relevance of our findings. In conclusion, we report a novel ETV2 signaling axis unique to Syk inhibition that promotes a cytocidal response in Tsc2-deficient cells and therefore maybe a potential alternative therapeutic target in LAM.

DOI: https://doi.org/10.26508/lsa.202201369
Epilepsy Behav. 2022 Feb 09. pii: S1525-5050(22)00026-9. [Epub ahead of print]128 108577

A scoping review on cannabidiol therapy in tuberous sclerosis: Current evidence and perspectives for future development.

Debopam Samanta.

  Cannabidiol (CBD) has recently been approved as an add-on therapy by various regulatory agencies for tuberous sclerosis complex (TSC)-associated seizures based on its short-term efficacy and safety in a pivotal randomized controlled trial. However, critical information about which patients with TSC and seizure types respond best to CBD (clinical, electrophysiological, and genetic predictors of responsiveness), when to use CBD in the treatment algorithm, and how CBD can be combined with other antiseizure medications (ASMs) in the form of a rational polypharmacy therapy is still lacking. In general, there is a limited in-depth critical review of CBD for the treatment of TSC to facilitate its optimal use in a clinical context. Here, we utilized a scoping review approach to report the current evidence of efficacy and safety of pharmaceutical-grade CBD in patients with TSC, including relevant mechanism of action and drug-drug interactions with other ASMs. We also discussed emerging information about CBD's long-term efficacy and safety data in patients with TSC. Finally, we discussed some critical unanswered questions in several domains related to effective clinical management of TSC using CBD, including barriers to early and aggressive treatment in infants, difficulty with universal access to CBD, a lack of studies to understand CBD's impact on seizure severity and specific seizure types, insufficient exploration of CBD in TSC-related cognitive and behavioral issues, and the need for more research into CBD's effects on various biomarkers.

Keywords:  CBD; Cannabis; Epilepsy; Vigabatrin; mTOR

DOI:  https://doi.org/10.1016/j.yebeh.2022.108577
Curr Pain Headache Rep. 2022 Feb 18.

Managing Headache Disorders Associated with Tuberous Sclerosis and Neurofibromatosis.

Irene Patniyot, William Qubty.

   PURPOSE OF REVIEW: Tuberous sclerosis complex (TSC) and neurofibromatosis (NF) are neurocutaneous disorders often encountered by neurologists in clinical practice. This article aims to familiarize adult and pediatric neurologists with common features of these disorders and headache specific evaluation and management.
RECENT FINDINGS: Non-malignant intracranial tumors in TSC include cortical tubers (glioneuronal hamartomas), subependymal nodules or subependymal giant-cell astrocytomas (SEGA). Headache disorders in TSC are largely secondary and can cause headaches due to increased intracranial pressure, mass effect, obstructive hydrocephalus, or hemorrhage. Neurosurgical intervention is typically required for management of large SEGAs; however, in patients with increased surgical risk, newer treatment modalities may be offered such as neoadjuvant therapy with an mTOR inhibitor (mTORi). Newer studies indicate headache disorders are more prevalent in neurofibromatosis type 1 (NF1). Primary headache disorders can include migraine and tension-type headache, while secondary headache disorders can be due to associated neoplasms such as optic pathway gliomas or brainstem gliomas, or less commonly vasculopathies such as moyamoya syndrome. Selumetinib is an oral, small molecule mitogen-activated protein kinase (MEK) agent with antineoplastic activity which is in ongoing trials for treatment of NF1-associated pediatric low-grade gliomas. NF1 stands out as having a higher association with primary headache disorders such as migraine. This association may be related to effects of mutation of the neurofibromin gene on pathways involved in pain and migraine genesis, however, warrants future study. Care should be taken when formulating a headache treatment plan to address comorbidities and avoid medications that may be contraindicated.

Keywords:  Neurocutaneous disorders; Neurofibromatosis 1; Neurofibromatosis 2; Tuberous sclerosis

DOI:  https://doi.org/10.1007/s11916-022-01032-y
No Shinkei Geka. 2022 Jan;50(1): 111-121

[Subependymal Giant Cell Astrocytoma with Tuberous Sclerosis Complex(TSC-SEGA)].

Tomotsugu Ichikawa, Yo Niida.

Subependymal giant cell astrocytoma(SEGA)is a low-grade brain tumor occurring specifically in patients with tuberous sclerosis complex(TSC). TSC is an autosomal dominant genetic disease affecting multiple body systems and with wide variability in presentation. SEGA usually arises around the caudothalamic groove near the foramen of Monro, and can therefore cause life-threatening complications due to hydrocephalus. SEGA develops due to complete loss of function of the TSC1/TSC2 complex through a two-hit mechanism of biallelic inactivation of the TSC1 or TSC2 gene, leading to activation of mammalian target of rapamycin(mTOR). Identification of a pathogenic variant in TSC1 or TSC2 is sufficient for the diagnosis of TSC. Individuals with SEGAs presenting with acute deterioration due to obstructive hydrocephalus should undergo urgent surgical treatment. mTOR inhibitors have been shown to prevent SEGA growth in patients with TSC. Treatment with mTOR inhibitors is primarily recommended for individuals with non-acute symptomatic or asymptomatic growing or large SEGAs and those who are not surgical candidates or prefer medical treatment over surgery. Long-term treatment with mTOR inhibitors efficiently reduced SEGAs and prevented hydrocephalus. The surgical risks, potential side effects of mTOR inhibitors, and effect on other TSC manifestations should be considered so that the best treatment option is selected.

DOI: https://doi.org/10.11477/mf.1436204536
Epilepsia. 2022 Feb 17.

Time to Onset of Cannabidiol (CBD) Treatment Effect and Resolution of Adverse Events in Tuberous Sclerosis Complex: Post Hoc Analysis of Randomized Controlled Phase 3 Trial GWPCARE6.

Joyce Y Wu, Hannah R Cock, Orrin Devinsky, Charuta Joshi, Ian Miller, Colin M Roberts, Rocio Sanchez-Carpintero, Daniel Checketts, Farhad Sahebkar.

   OBJECTIVE: To estimate the timing of cannabidiol (CBD) treatment effect (seizure reduction and adverse events [AEs]) onset, we conducted a post hoc analysis of GWPCARE6 (NCT02544763), a randomized, placebo-controlled, phase 3 trial in patients with drug-resistant epilepsy associated with tuberous sclerosis complex (TSC).
METHODS: Patients received plant-derived pharmaceutical formulation of highly purified CBD (Epidiolex® ; 100 mg/mL oral solution) at 25 mg/kg/day (CBD25) or 50 mg/kg/day (CBD50) or placebo for 16 weeks (4-week titration, 12-week maintenance). Treatment started at 5 mg/kg/day for all groups and reached 25 mg/kg/day on Day 9 and 50 mg/kg/day on Day 29. Percentage change from baseline in TSC-associated seizure (countable focal or generalized) count was calculated by cumulative day (i.e., including all previous days). Time to onset and resolution of AEs were evaluated.
RESULTS: Of 224 patients, 75 were randomized to CBD25, 73 to CBD50, and 76 to placebo. Median (range) age was 11.3 (1.1-56.8) years. Patients had discontinued a median (range) of 4 (0-15) antiseizure medications and were currently taking 3 (0-5). Difference in seizure reduction between CBD and placebo emerged on Day 6 (titrated dose, 15 mg/kg/day) and became nominally significant (p<0.049) by Day 10. Separation between placebo and CBD in ≥50% responder rate also emerged by Day 10. Onset of AEs occurred during the first 2 weeks of the titration period in 61% of patients (CBD25, 61%; CBD50, 67%; placebo, 54%). In patients with an AE, resolution occurred within 4 weeks of onset in 42% of placebo and 27% of CBD patients and by end of trial in 78% of placebo and 51% of CBD patients.
SIGNIFICANCE: Onset of treatment effect occurred within 6-10 days. AEs lasted longer for CBD than placebo but the most common (diarrhea, decreased appetite, and somnolence) resolved during the 16-week trial in most patients.

Keywords:  antiseizure medication; cannabidiol; epilepsy; focal seizures; medication-resistant seizures; tuberous sclerosis complex

DOI:  https://doi.org/10.1111/epi.17199
Zhonghua Kou Qiang Yi Xue Za Zhi. 2022 Feb 09. 57(2): 186-188

[Clinical manifestation of odontogenic fibroma associated with tuberous sclerosis complex: a case report].

D Shang, S M Liu.

DOI: https://doi.org/10.3760/cma.j.cn112144-20210524-00262
Proc Natl Acad Sci U S A. 2022 Feb 22. pii: e2116271119. [Epub ahead of print]119(8):

Lung-selective mRNA delivery of synthetic lipid nanoparticles for the treatment of pulmonary lymphangioleiomyomatosis.

Min Qiu, Yan Tang, Jinjin Chen, Rachel Muriph, Zhongfeng Ye, Changfeng Huang, Jason Evans, Elizabeth P Henske, Qiaobing Xu.

  Safe and efficacious systemic delivery of messenger RNA (mRNA) to specific organs and cells in vivo remains the major challenge in the development of mRNA-based therapeutics. Targeting of systemically administered lipid nanoparticles (LNPs) coformulated with mRNA has largely been confined to the liver and spleen. Using a library screening approach, we identified that N-series LNPs (containing an amide bond in the tail) are capable of selectively delivering mRNA to the mouse lung, in contrast to our previous discovery that O-series LNPs (containing an ester bond in the tail) that tend to deliver mRNA to the liver. We analyzed the protein corona on the liver- and lung-targeted LNPs using liquid chromatography-mass spectrometry and identified a group of unique plasma proteins specifically absorbed onto the surface that may contribute to the targetability of these LNPs. Different pulmonary cell types can also be targeted by simply tuning the headgroup structure of N-series LNPs. Importantly, we demonstrate here the success of LNP-based RNA therapy in a preclinical model of lymphangioleiomyomatosis (LAM), a destructive lung disease caused by loss-of-function mutations in the Tsc2 gene. Our lung-targeting LNP exhibited highly efficient delivery of the mouse tuberous sclerosis complex 2 (Tsc2) mRNA for the restoration of TSC2 tumor suppressor in tumor and achieved remarkable therapeutic effect in reducing tumor burden. This research establishes mRNA LNPs as a promising therapeutic intervention for the treatment of LAM.

Keywords:  lipid nanoparticles; lung-targeted delivery; lymphangioleiomyomatosis; mRNA; tuberous sclerosis complex

DOI:  https://doi.org/10.1073/pnas.2116271119
Autism Res. 2022 Feb 18.

Cerebellar demyelination and neurodegeneration associated with mTORC1 hyperactivity may contribute to the developmental onset of autism-like neurobehavioral phenotype in a rat model.

Viera Kútna, Valerie Bríd O'Leary, Cyril Hoschl, Saak V Ovsepian.

  The cerebellum hosts more than half of all neurons of the human brain, with their organized activity playing a key role in coordinating motor functions. Cerebellar activity has also been implicated in the control of speech, communication, and social behavior, which are compromised in autism spectrum disorders (ASD). Despite major research advances, there is a shortage of mechanistic data relating cellular and molecular changes in the cerebellum to autistic behavior. We studied the impact of tuberous sclerosis complex 2 haploinsufficiency (Tsc2+/-) with downstream mTORC1 hyperactivity on cerebellar morphology and cellular organization in 1, 9, and 18 m.o. Eker rats, to determine possible structural correlates of an autism-like behavioural phenotype in this model. We report a greater developmental expansion of the cerebellar vermis, owing to enlarged white matter and thickened molecular layer. Histochemical and immunofluorescence data suggest age-related demyelination of central tract of the vermis, as evident from reduced level of myelin-basic protein in the arbora vitae. We also observed a higher number of astrocytes in Tsc2+/- rats of older age while the number of Purkinje cells (PCs) in these animals was lower than in wild-type controls. Unlike astrocytes and PCs, Bergmann glia remained unaltered at all ages in both genotypes, while the number of microglia was higher in Tsc2+/- rats of older age. The convergent evidence for a variety of age-dependent cellular changes in the cerebellum of rats associated with mTORC1 hyperactivity, thus, predicts an array of functional impairments, which may contribute to the developmental onset of an autism-like behavioral phenotype in this model. LAY SUMMARY: This study elucidates the impact of constitutive mTORC1 hyperactivity on cerebellar morphology and cellular organization in a rat model of autism and epilepsy. It describes age-dependent degeneration of Purkinje neurons, with demyelination of central tract as well as activation of microglia, and discusses the implications of these changes for neuro-behavioral phenotypes. The described changes provide new indications for the putative mechanisms underlying cerebellar impairments with their age-related onset, which may contribute to the pathobiology of autism, epilepsy, and related disorders.

Keywords:  Purkinje neurons; autism spectrum disorder; cerebellum; demyelination; mTORC1 signaling; microglia activation; synaptophysin

DOI:  https://doi.org/10.1002/aur.2688
Histol Histopathol. 2022 Feb 14. 18435

Low-grade oncocytic tumor (LOT) - a new renal entity ready for a prime time: An updated review.

Mehdi Mansoor, Farshid Siadat, Kiril Trpkov.

Low-grade oncocytic tumor (LOT) of kidney has been recently proposed as a new renal entity. LOT was identified in the spectrum of oncocytic renal tumors with overlapping features between oncocytoma and eosinophilic chromophobe renal cell carcinoma, or it has been labelled as one of those entities in prior studies and in practice. LOT is often a single, relatively small tumor, found in a non-syndromic setting, but rare examples of multiple LOTs or admixed with other tumors have been found in patients with tuberous sclerosis complex. LOT typically has solid architecture, and it is composed of eosinophilic cells, with round to oval 'low-grade' nuclei, lacking irregularities and showing focal perinuclear halos. Sharp transition into edematous stromal areas, with scattered or loosely arranged cells are frequently found. LOT has a consistent immunohistochemical profile with diffuse reactivity for cytokeratin 7 and absent (or rarely weak) expression for CD117, a profile different from oncocytoma and eosinophilic chromophobe renal cell carcinoma. Similarly, in contrast to those entities, it also lacks or shows only weak expression for FOXI1. Recent studies have shown that LOT has a molecular/genetic profile different from other renal tumors, with frequent alterations affecting the MTOR/TSC pathway genes. LOT demonstrates either disomic pattern or deletions of 19p13, 19q13 and 1p36, and lacks complete chromosomal losses or gains. In all published studies to date, LOT has shown benign behavior. In this review, we summarize the evidence from recently published studies, which strongly supports the conclusion that LOT is a distinct and unique renal entity.

DOI: https://doi.org/10.14670/HH-18-435
J Neurodev Disord. 2022 Feb 13. 14(1): 13

The research landscape of tuberous sclerosis complex-associated neuropsychiatric disorders (TAND)-a comprehensive scoping review.

Stephanie Vanclooster, Stacey Bissell, Agnies M van Eeghen, Nola Chambers, Liesbeth De Waele, Anna W Byars, Jamie K Capal, Sebastián Cukier, Peter Davis, Jennifer Flinn, Sugnet Gardner-Lubbe, Tanjala Gipson, Tosca-Marie Heunis, Dena Hook, J Christopher Kingswood, Darcy A Krueger, Aubrey J Kumm, Mustafa Sahin, Eva Schoeters, Catherine Smith, Shoba Srivastava, Megumi Takei, Robert Waltereit, Anna C Jansen, Petrus J de Vries.

   BACKGROUND: Tuberous sclerosis complex (TSC)-associated neuropsychiatric disorders (TAND) is an umbrella term for the behavioural, psychiatric, intellectual, academic, neuropsychological and psychosocial manifestations of TSC. Although TAND affects 90% of individuals with TSC during their lifetime, these manifestations are relatively under-assessed, under-treated and under-researched. We performed a comprehensive scoping review of all TAND research to date (a) to describe the existing TAND research landscape and (b) to identify knowledge gaps to guide future TAND research.
METHODS: The study was conducted in accordance with stages outlined within the Arksey and O'Malley scoping review framework. Ten research questions relating to study characteristics, research design and research content of TAND levels and clusters were examined.
RESULTS: Of the 2841 returned searches, 230 articles published between 1987 and 2020 were included (animal studies = 30, case studies = 47, cohort studies = 153), with more than half published since the term TAND was coined in 2012 (118/230; 51%). Cohort studies largely involved children and/or adolescents (63%) as opposed to older adults (16%). Studies were represented across 341 individual research sites from 45 countries, the majority from the USA (89/341; 26%) and the UK (50/341; 15%). Only 48 research sites (14%) were within low-middle income countries (LMICs). Animal studies and case studies were of relatively high/high quality, but cohort studies showed significant variability. Of the 153 cohort studies, only 16 (10%) included interventions. None of these were non-pharmacological, and only 13 employed remote methodologies (e.g. telephone interviews, online surveys). Of all TAND clusters, the autism spectrum disorder-like cluster was the most widely researched (138/230; 60%) and the scholastic cluster the least (53/200; 27%).
CONCLUSIONS: Despite the recent increase in TAND research, studies that represent participants across the lifespan, LMIC research sites and non-pharmacological interventions were identified as future priorities. The quality of cohort studies requires improvement, to which the use of standardised direct behavioural assessments may contribute. In human studies, the academic level in particular warrants further investigation. Remote technologies could help to address many of the TAND knowledge gaps identified.

Keywords:  Autism; Behaviour; Intellectual; Neuropsychological; Psychiatric; Psychosocial; Scholastic; Scoping review; TSC-associated neuropsychiatric disorders; Tuberous sclerosis complex

DOI:  https://doi.org/10.1186/s11689-022-09423-3
JCO Precis Oncol. 2022 Feb;6 e2100448

Biomarker-Based Phase II Study of Sapanisertib (TAK-228): An mTORC1/2 Inhibitor in Patients With Refractory Metastatic Renal Cell Carcinoma.

Bradley A McGregor, Wanling Xie, Elio Adib, Walter M Stadler, Yousef Zakharia, Aijai Alva, M Dror Michaelson, Shilpa Gupta, Elaine T Lam, Subrina Farah, Amin H Nassar, Xiao X Wei, Kerry L Kilbridge, Lauren Harshman, Sabina Signoretti, Lynette Sholl, David J Kwiatkowski, Rana R McKay, Toni K Choueiri.

PURPOSE: Sapanisertib is a kinase inhibitor that inhibits both mammalian target of rapamycin complex 1 (mTORC1) and mTORC2. In this multicenter, single-arm phase II trial, we evaluated the efficacy of sapanisertib in patients with treatment-refractory metastatic renal cell carcinoma (mRCC; NCT03097328).
METHODS: Patients with mRCC of any histology progressing through standard therapy (including prior mTOR inhibitors) had baseline biopsy and received sapanisertib 30 mg by mouth once weekly until unacceptable toxicity or disease progression. The primary end point was objective response rate by RECIST 1.1. Tissue biomarkers of mTOR pathway activation were explored.
RESULTS: We enrolled 38 patients with mRCC (clear cell = 28; variant histology = 10) between August 2017 and November 2019. Twenty-four (63%) had received ≥ 3 prior lines of therapy; 17 (45%) had received prior rapalog therapy. The median follow-up was 10.4 (range 1-27.4) months. Objective response rate was two of 38 (5.3%; 90% CI, 1 to 15.6); the median progression-free survival (PFS) was 2.5 months (95% CI, 1.8 to 3.7). Twelve patients (32%) developed treatment-related grade 3 adverse events, with no grade 4 or 5 toxicities. Alterations in the mTOR pathway genes were seen in 5 of 29 evaluable patients (MTOR n = 1, PTEN n = 3, and TSC1 n = 1) with no association with response or PFS. Diminished or loss of PTEN expression by immunohistochemistry was seen in 8 of 21 patients and trended toward shorter PFS compared with intact PTEN (median 1.9 v 3.7 months; hazard ratio 2.5; 95% CI, 0.9 to 6.7; P = .055).
CONCLUSION: Sapanisertib had minimal activity in treatment-refractory mRCC independent of mTOR pathway alterations. Additional therapeutic strategies are needed for patients with refractory mRCC.

DOI: https://doi.org/10.1200/PO.21.00448
J Clin Anesth. 2022 Feb 12. pii: S0952-8180(22)00011-3. [Epub ahead of print]78 110655

Postoperative pneumothorax after nephrectomy in a patient with tuberous sclerosis and undiagnosed lymphangioleiomyomatosis.

Kamelia Habchi, Antonia Blanié, Nejla Essafi, Christine Fessenmeyer, Paul Zetlaoui, Dan Benhamou.



Keywords:  General anesthesia; Lymphangioleiomyomatosis; Pneumothorax; Protective ventilation; Tuberous sclerosis

DOI:  https://doi.org/10.1016/j.jclinane.2022.110655
eNeuro. 2022 Feb 11. pii: ENEURO.0317-21.2022. [Epub ahead of print]

NPRL2 Inhibition of mTORC1 Controls Sodium Channel Expression and Brain Amino Acid Homeostasis.

Jeremy B Hui, Jose Cesar Hernandez Silva, Mari Carmen Pelaez, Myriam Sévigny, Janani Priya Venkatasubramani, Quentin Plumereau, Mohamed Chahine, Christophe D Proulx, Chantelle F Sephton, Paul A Dutchak.

  Genetic mutations in nitrogen permease regulator-like 2 (NPRL2) are associated with a wide spectrum of familial focal epilepsies, autism, and sudden unexpected death of epileptics (SUDEP), but the mechanisms by which NPRL2 contributes to these effects are not well known. NPRL2 is a requisite subunit of the Gap Activity TOward Rags 1 (GATOR1) complex, which functions as a negative regulator of mammalian Target Of Rapamycin Complex 1 (mTORC1) kinase when intracellular amino acids are low. Here we show that loss of NPRL2 expression in mouse excitatory glutamatergic neurons causes seizures prior to death, consistent with SUDEP in humans with epilepsy. Additionally, the absence of NPRL2 expression increases mTORC1-dependent signal transduction and significantly alters amino acid homeostasis in the brain. Loss of NPRL2 reduces dendritic branching and increases the strength of electrically stimulated action potentials in neurons. The increased action potential strength is consistent with elevated expression of epilepsy-linked, voltage-gated sodium channels in the NPRL2-deficient brain. Targeted deletion of NPRL2 in primary neurons increases the expression of sodium channel Scn1A, whereas treatment with the pharmacological mTORC1 inhibitor called rapamycin prevents Scn1A upregulation. These studies demonstrate a novel role of NPRL2 and mTORC1 signaling in the regulation of sodium channels, which can contribute to seizures and early lethality.Significance StatementNPRL2 is a requisite subunit of the epilepsy-linked GATOR1 complex that functions as a negative regulator of mTORC1 kinase when intracellular amino acids are limited. Here we report the generation and characterization of a new neurological model of GATOR1-dependent mTORopathy, caused by the loss of NPRL2 function in glutamatergic neurons. Loss of NPRL2 increases mTORC1 signal transduction, significantly alters amino acid homeostasis in the brain, and causes SUDEP. In addition, loss of NPRL2 increases the strength of electrically stimulated action potentials and the expression of epilepsy-linked sodium channels. These data reveal an unanticipated link between intracellular amino acid signaling by NPRL2 and a novel mTORC1-dependent regulation of sodium-channel expression in epilepsy.

Keywords:  GATOR1; NPRL2; epilepsy; mTORC1; neurometabolism; sodium channels

DOI:  https://doi.org/10.1523/ENEURO.0317-21.2022
Int J Mol Cell Med. 2021 ;10(3): 181-189

Role of mTOR Complex 1 Signaling Pathway in the Pathogenesis of Diabetes Complications; A Mini Review.

Amir Yarahmadi, Negar Azarpira, Zohreh Mostafavi-Pour.

  The mammalian target of rapamycin (mTOR) is an evolutionarily conserved serine/threonine-protein kinase that senses and combines various environmental signals to regulate the growth and homeostasis of human cells. This signaling pathway synchronizes many critical cellular processes and is involved in an increasing number of pathological conditions such as diabetes, cancer, obesity, and metabolic syndrome. Here, we review different complications of diabetes that are associated with mTOR complex 1 imbalance. We further discuss pharmacological approaches to treat diabetes complications linked to mTOR deregulation.

Keywords:  Diabetes; complications; mTOR; mTOR complex 1; signaling

DOI:  https://doi.org/10.22088/IJMCM.BUMS.10.3.181
J Biol Chem. 2022 Feb 10. pii: S0021-9258(22)00158-2. [Epub ahead of print] 101718

Exosomal miR-673-5p from fibroblasts promotes Schwann cell-mediated peripheral neuron myelination by targeting the TSC2/mTORC1/SREBP2 axis.

Yahong Zhao, Yunyun Liang, Zhixin Xu, Jina Liu, Xiaoyu Liu, Jinyu Ma, Cheng Sun, Yumin Yang.

  Peripheral myelination is a complicated process, wherein Schwann cells (SCs) promote the formation of the myelin sheath around the axons of peripheral neurons. Fibroblasts are the second resident cells in the peripheral nerves; however, the precise function of fibroblasts in SC-mediated myelination has rarely been examined. Here, we show that exosomes derived from fibroblasts boost myelination-related gene expression in SCs. We used exosome sequencing, together with bioinformatic analysis, to demonstrate that exosomal microRNA miR-673-5p is capable of stimulating myelin gene expression in SCs. Subsequent functional studies revealed that miR-673-5p targets the regulator of mTOR complex 1 (mTORC1) TSC2 in SCs, leading to the activation of downstream signaling pathways including mTORC1 and SREBP2. In vivo experiments further confirmed that miR-673-5p activates the TSC2/mTORC1/SREBP2 axis, thus promoting the synthesis of cholesterol and related lipids and subsequently accelerating myelin sheath maturation in peripheral nerves. Overall, our findings revealed exosome-mediated crosstalk between fibroblasts and SCs that plays a pivotal role in peripheral myelination. We propose that exosomes derived from fibroblasts and miR-673-5p might be useful for promoting peripheral myelination in translational medicine.

Keywords:  Exosomes; Fibroblasts; Lipid synthesis; Myelination; Peripheral nerve regeneration; Schwann cells

DOI:  https://doi.org/10.1016/j.jbc.2022.101718
Int J Mol Sci. 2022 Feb 01. pii: 1693. [Epub ahead of print]23(3):

Predominant Role of mTOR Signaling in Skin Diseases with Therapeutic Potential.

Fani Karagianni, Antreas Pavlidis, Lina S Malakou, Christina Piperi, Evangelia Papadavid.

  The serine/threonine kinase mechanistic target of rapamycin (mTOR) plays a pivotal role in the regulation of cell proliferation, survival, and motility in response to availability of energy and nutrients as well as mitogens. The mTOR signaling axis regulates important biological processes, including cellular growth, metabolism, and survival in many tissues. In the skin, dysregulation of PI3K/AKT/mTOR pathway may lead to severe pathological conditions characterized by uncontrolled proliferation and inflammation, including skin hyperproliferative as well as malignant diseases. Herein, we provide an update on the current knowledge regarding the pathogenic implication of the mTOR pathway in skin diseases with inflammatory features (such as psoriasis, atopic dermatitis, pemphigus, and acne) and malignant characteristics (such as cutaneous T cell lymphoma and melanoma) while we critically discuss current and future perspectives for therapeutic targeting of mTOR axis in clinical practice.

Keywords:  acne; atopic dermatitis; cutaneous T cell lymphoma; inhibitors; mTOR signaling pathway; melanoma; pemphigus; psoriasis; therapy

DOI:  https://doi.org/10.3390/ijms23031693
Int J Mol Sci. 2022 Jan 25. pii: 1344. [Epub ahead of print]23(3):

Cortical Dysplasia and the mTOR Pathway: How the Study of Human Brain Tissue Has Led to Insights into Epileptogenesis.

Wei Shern Lee, Sara Baldassari, Sarah E M Stephenson, Paul J Lockhart, Stéphanie Baulac, Richard J Leventer.

  Type II focal cortical dysplasia (FCD) is a neuropathological entity characterised by cortical dyslamination with the presence of dysmorphic neurons only (FCDIIA) or the presence of both dysmorphic neurons and balloon cells (FCDIIB). The year 2021 marks the 50th anniversary of the recognition of FCD as a cause of drug resistant epilepsy, and it is now the most common reason for epilepsy surgery. The causes of FCD remained unknown until relatively recently. The study of resected human FCD tissue using novel genomic technologies has led to remarkable advances in understanding the genetic basis of FCD. Mechanistic parallels have emerged between these non-neoplastic lesions and neoplastic disorders of cell growth and differentiation, especially through perturbations of the mammalian target of rapamycin (mTOR) signalling pathway. This narrative review presents the advances through which the aetiology of FCDII has been elucidated in chronological order, from recognition of an association between FCD and the mTOR pathway to the identification of somatic mosaicism within FCD tissue. We discuss the role of a two-hit mechanism, highlight current challenges and future directions in detecting somatic mosaicism in brain and discuss how knowledge of FCD may inform novel precision treatments of these focal epileptogenic malformations of human cortical development.

Keywords:  epilepsy; focal cortical dysplasia; genetics; hemimegalencephaly; mTOR signalling

DOI:  https://doi.org/10.3390/ijms23031344
Int J Mol Sci. 2022 Feb 05. pii: 1825. [Epub ahead of print]23(3):

mTOR Signaling Components in Tumor Mechanobiology.

Antonios N Gargalionis, Kostas A Papavassiliou, Efthimia K Basdra, Athanasios G Papavassiliou.

  Mechanistic target of rapamycin (mTOR) is a central signaling hub that integrates networks of nutrient availability, cellular metabolism, and autophagy in eukaryotic cells. mTOR kinase, along with its upstream regulators and downstream substrates, is upregulated in most human malignancies. At the same time, mechanical forces from the tumor microenvironment and mechanotransduction promote cancer cells' proliferation, motility, and invasion. mTOR signaling pathway has been recently found on the crossroads of mechanoresponsive-induced signaling cascades to regulate cell growth, invasion, and metastasis in cancer cells. In this review, we examine the emerging association of mTOR signaling components with certain protein tools of tumor mechanobiology. Thereby, we highlight novel mechanisms of mechanotransduction, which regulate tumor progression and invasion, as well as mechanisms related to the therapeutic efficacy of antitumor drugs.

Keywords:  Akt; PI3K; extracellular matrix; integrin; mTOR; matrix stiffness; mechanotransduction; tumor mechanobiology

DOI:  https://doi.org/10.3390/ijms23031825
EMBO Rep. 2022 Feb 15. e53477

Bur1 functions with TORC1 for vacuole-mediated cell cycle progression.

Yui Jin, Natsuko Jin, Yu Oikawa, Ron Benyair, Michiko Koizumi, Thomas E Wilson, Yoshinori Ohsumi, Lois S Weisman.

  The vacuole/lysosome plays essential roles in the growth and proliferation of many eukaryotic cells via the activation of target of rapamycin complex 1 (TORC1). Moreover, the yeast vacuole/lysosome is necessary for progression of the cell division cycle, in part via signaling through the TORC1 pathway. Here, we show that an essential cyclin-dependent kinase, Bur1, plays a critical role in cell cycle progression in cooperation with TORC1. A mutation in BUR1 combined with a defect in vacuole inheritance shows a synthetic growth defect. Importantly, the double mutant, as well as a bur1-267 mutant on its own, has a severe defect in cell cycle progression from G1 phase. In further support that BUR1 functions with TORC1, mutation of bur1 alone results in high sensitivity to rapamycin, a TORC1 inhibitor. Mechanistic insight for Bur1 function comes from the findings that Bur1 directly phosphorylates Sch9, a target of TORC1, and that both Bur1 and TORC1 are required for the activation of Sch9. Together, these discoveries suggest that multiple signals converge on Sch9 to promote cell cycle progression.

Keywords:   SCH9 ; SGV1 ; lysosome; rapamycin; yeast

DOI:  https://doi.org/10.15252/embr.202153477
Cell Rep. 2022 02 15. pii: S2211-1247(22)00086-9. [Epub ahead of print]38(7): 110365

An AMPKα2-specific phospho-switch controls lysosomal targeting for activation.

Kaitlin R Morrison, William J Smiles, Naomi X Y Ling, Ashfaqul Hoque, Gabrielle Shea, Kevin R W Ngoei, Dingyi Yu, Lisa Murray-Segal, John W Scott, Sandra Galic, Bruce E Kemp, Janni Petersen, Jonathan S Oakhill.

  AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin complex 1 (mTORC1) are metabolic kinases that co-ordinate nutrient supply with cell growth. AMPK negatively regulates mTORC1, and mTORC1 reciprocally phosphorylates S345/7 in both AMPK α-isoforms. We report that genetic or torin1-induced loss of α2-S345 phosphorylation relieves suppression of AMPK signaling; however, the regulatory effect does not translate to α1-S347 in HEK293T or MEF cells. Dephosphorylation of α2-S345, but not α1-S347, transiently targets AMPK to lysosomes, a cellular site for activation by LKB1. By mass spectrometry, we find that α2-S345 is basally phosphorylated at 2.5-fold higher stoichiometry than α1-S347 in HEK293T cells and, unlike α1, phosphorylation is partially retained after prolonged mTORC1 inhibition. Loss of α2-S345 phosphorylation in endogenous AMPK fails to sustain growth of MEFs under amino acid starvation conditions. These findings uncover an α2-specific mechanism by which AMPK can be activated at lysosomes in the absence of changes in cellular energy.

Keywords:  AMPK; energy homeostasis; kinase; lysosome; mTORC1; metabolic signaling; phosphorylation

DOI:  https://doi.org/10.1016/j.celrep.2022.110365
Acta Pharmacol Sin. 2022 Feb 14.

PTEN loss confers sensitivity to rapalogs in clear cell renal cell carcinoma.

Xiao-Lian Liu, Gui-Ming Zhang, Si-Si Huang, Wen-Hui Shi, Lin-Xuan Ye, Zhong-Lu Ren, Jia-Jie Zhang, Shu-Wen Liu, Le Yu, Yi-Lei Li.

  Rapalogs (everolimus and temsirolimus) are allosteric mTORC1 inhibitors and approved agents for advanced clear cell renal cell carcinoma (ccRCC), although only a subset of patients derive clinical benefit. Progress in genomic characterization has made it possible to generate comprehensive profiles of genetic alterations in ccRCC; however, the correlations between recurrent somatic mutations and rapalog efficacy remain unclear. Here, we demonstrate by using multiple patient-derived ccRCC cell lines that compared to PTEN-proficient cells, PTEN-deficient cells exhibit hypersensitivity to rapalogs. Rapalogs inhibit cell proliferation by inducing G0/G1 arrest without inducing apoptosis in PTEN-deficient ccRCC cell lines. Using isogenic cell lines generated by CRISPR/Cas9, we validate the correlation between PTEN loss and rapalog hypersensitivity. In contrast, deletion of VHL or chromatin-modifying genes (PBRM1, SETD2, BAP1, or KDM5C) fails to influence the cellular response to rapalogs. Our mechanistic study shows that ectopic expression of an activating mTOR mutant (C1483F) antagonizes PTEN-induced cell growth inhibition, while introduction of a resistant mTOR mutant (A2034V) enables PTEN-deficient ccRCC cells to escape the growth inhibitory effect of rapalogs, suggesting that PTEN loss generates vulnerability to mTOR inhibition. PTEN-deficient ccRCC cells are more sensitive to the inhibitory effects of temsirolimus on cell migration and tumor growth in zebrafish and xenograft mice, respectively. Of note, PTEN protein loss as detected by immunohistochemistry is much more frequent than mutations in the PTEN gene in ccRCC patients. Our study suggests that PTEN loss correlates with rapalog sensitivity and could be used as a marker for ccRCC patient selection for rapalog therapy.

Keywords:  PTEN; clear cell renal cell carcinoma; mTOR; rapalogs; recurrent mutations; sensitivity

DOI:  https://doi.org/10.1038/s41401-022-00862-1