bims-tubesc 2022-05-01 papers

bims-tubesc

Biomed News

on Molecular mechanisms in tuberous sclerosis

Issue of 2022–05–01
ten papers selected by

Tuberous sclerosis complex: a complex case.
Real-World Evidence Study on the Long-Term Safety of Everolimus in Patients With Tuberous Sclerosis Complex: Final Analysis Results.
Postnatal Cytomegalovirus Infection May Increase the Susceptibility of Tuberous Sclerosis Complex to Autism Spectrum Disorders.
Glutamine, MTOR and autophagy: a multiconnection relationship.
Blocking ribosomal protein S6 phosphorylation inhibits podocyte hypertrophy and focal segmental glomerulosclerosis.
Inhibition of mTOR by temsirolimus overcomes radio-resistance in nasopharyngeal carcinoma.
The TORC1 phosphoproteome in C. elegans reveals roles in transcription and autophagy.
Increased mTORC2 pathway activation in lymph nodes of iMCD-TAFRO.
Neuronal mTOR Outposts: Implications for Translation, Signaling, and Plasticity.
Asteltoxin inhibits extracellular vesicle production through AMPK/mTOR-mediated activation of lysosome function.

Cold Spring Harb Mol Case Stud. 2022 Apr;pii: a006182. [Epub ahead of print]8(3):

Tuberous sclerosis complex: a complex case.

Ryan M Powell, Sharon Pattison, Jiri C Moravec, Basharat Bhat, Nada Guirguis, David Markie, Greg T Jones, Jason Copedo, Cristin G Print, Ian M Morison, Alex Gavryushkin, Bronwyn Gray, Lisa J Wyeth, Mike R Eccles, Erin C Macaulay.

  Tuberous sclerosis complex (TSC) is an inheritable disorder characterized by the formation of benign yet disorganized tumors in multiple organ systems. Germline mutations in the TSC1 (hamartin) or more frequently TSC2 (tuberin) genes are causative for TSC. The malignant manifestations of TSC, pulmonary lymphangioleiomyomatosis (LAM) and renal angiomyolipoma (AML), may also occur as independent sporadic perivascular epithelial cell tumor (PEComa) characterized by somatic TSC2 mutations. Thus, discerning TSC from the copresentation of sporadic LAM and sporadic AML may be obscured in TSC patients lacking additional features. In this report, we present a case study on a single patient initially reported to have sporadic LAM and a mucinous duodenal adenocarcinoma deficient in DNA mismatch repair proteins. Moreover, the patient had a history of Wilms' tumor, which was reclassified as AML following the LAM diagnosis. Therefore, we investigated the origins and relatedness of these tumors. Using germline whole-genome sequencing, we identified a premature truncation in one of the patient's TSC2 alleles. Using immunohistochemistry, loss of tuberin expression was observed in AML and LAM tissue. However, no evidence of a somatic loss of heterozygosity or DNA methylation epimutations was observed at the TSC2 locus, suggesting alternate mechanisms may contribute to loss of the tumor suppressor protein. In the mucinous duodenal adenocarcinoma, no causative mutations were found in the DNA mismatch repair genes MLH1, MSH2, MSH6, or PMS2 Rather, clonal deconvolution analyses were used to identify mutations contributing to pathogenesis. This report highlights both the utility of using multiple sequencing techniques and the complexity of interpreting the data in a clinical context.

Keywords:  duodenal carcinoma; pulmonary lymphangiomyomatosis; renal angiomyolipoma

DOI:  https://doi.org/10.1101/mcs.a006182
Front Pharmacol. 2022 ;13 802334

Real-World Evidence Study on the Long-Term Safety of Everolimus in Patients With Tuberous Sclerosis Complex: Final Analysis Results.

María Luz Ruiz-Falcó Rojas, Martha Feucht, Alfons Macaya, Bernd Wilken, Andreas Hahn, Ricardo Maamari, Yulia Hirschberg, Antonia Ridolfi, John Chris Kingswood.

  The TuberOus SClerosis registry to increase disease Awareness (TOSCA) Post-Authorization Safety Study (PASS) was a non-interventional, multicenter, safety substudy that assessed the long-term safety of everolimus in patients with tuberous sclerosis complex (TSC) receiving everolimus for its licensed indications in the European Union (EU). This substudy also aimed to address TSC-associated neuropsychiatric disorders (TAND), sexual development, and male infertility. Eligible patients were enrolled from 39 sites across 11 countries in the EU. Outcomes of interest included the incidence of adverse events (AEs), serious adverse events (SAEs), treatment-related AEs (TRAEs), AEs leading to everolimus discontinuation, AEs of special interest (AESIs), the observed relationship between everolimus blood levels and incidence of AESIs, TAND, and reproductive clinical features. Herein, we present the final analysis results from this substudy (data cutoff date: 22 January 2020). At data cutoff, 179 patients were enrolled (female, 59.2%; age ≥18 years, 65.9%), of which the majority completed the study (76%). Overall, 121 patients (67.6%) had AEs regardless of causality. The most frequent TRAEs (≥5%) were stomatitis (7.8%), aphthous ulcer (6.7%), and hypercholesterolemia (6.1%). The most common treatment-related SAEs (>1%) were pneumonia (3.4%), influenza, pyelonephritis, aphthous ulcer, stomatitis, dyslipidemia, and hypercholesterolemia (1.1% each). Ten patients (5.6%) reported AEs leading to everolimus discontinuation. The common psychiatric disorders (N = 179) were autism spectrum disorder (21.8%), anxiety disorder (12.8%), "other" psychiatric disorders (8.9%), attention-deficit hyperactivity disorder, and depressive disorder (7.8% each). Of 179 patients, 88 (49.2%) had ≥1 behavioral problem. Of these (n = 88), the most common (>20%) were sleep difficulties (47.7%), anxiety (43.2%), mood swings (37.5%), depression mood (35.2%), impulsivity (30.7%), severe aggression (23.9%), and overactivity (22.7%). Of 179 patients, four (2.2%) reported abnormal puberty onset, and three (1.7%) reported other reproductive disorders. Of 106 females, 23 (21.7%) reported menstrual cycle disorders and 10 (9.4%) reported amenorrhea. Available data did not show delays in sexual maturation or an association between sexual development and infertility. The results demonstrate that everolimus has a manageable long-term safety profile in the TSC treatment setting. No new safety signals emerged. This substudy also contributed to the mapping of TAND and reproductive clinical features in patients with TSC.

Keywords:  TOSCA; everolimus; post-authorization safety study (PASS); real-world evidence (RWE); tuberous sclerosis complex (TSC)

DOI:  https://doi.org/10.3389/fphar.2022.802334
Microbiol Spectr. 2022 Apr 25. e0186421

Postnatal Cytomegalovirus Infection May Increase the Susceptibility of Tuberous Sclerosis Complex to Autism Spectrum Disorders.

Xiao-Yan Yang, Yang-Yang Wang, Yue-Peng Zhou, Jing He, Meng-Jie Mei, Meng-Na Zhang, Bin Wang, Wen-Jing Zhou, Min-Hua Luo, Qiu-Hong Wang, Zhong-Yuan Li, Yong Xu, Qian Lu, Li-Ping Zou.

  Autism spectrum disorder (ASD), a highly hereditary and heterogeneous neurodevelopmental disorder, is influenced by genetic and environmental factors. Tuberous sclerosis complex (TSC) is a common syndrome associated with ASD. Cytomegalovirus (CMV) infection is an environmental risk factor for ASD. The similarities in pathological and mechanistic pathways of TSC and CMV intrigued us to investigate whether CMV and TSC interacted in ASD's occurrence. We detected CMV IgG seroprevalence of 308 TSC patients from our prospective cohort (September 2011 to March 2021) and 93 healthy children by magnetic particle indirect chemiluminescence immunoassay. A total of 206 TSC patients enrolled were divided into ASD and non-ASD groups, and the relationship between ASD and CMV seroprevalence was analyzed. Nested PCR and Western blot were used to detect CMV DNAs and proteins in cortical malformations of seven TSC patients with and without ASD. No difference was found in CMV seroprevalence between TSC patients and healthy children (74.0% versus 72.0%, P = 0.704). Univariate analysis showed the seroprevalence in TSC patients with ASD was higher than that in TSC patients without ASD (89.2% versus 75.1%, P = 0.063), and multifactorial analysis showed that CMV seroprevalence was a risk factor for ASD in TSC patients (OR = 3.976, 95% CI = 1.093 to 14.454). Moreover, CMV was more likely to be detected in the cortical malformations in TSC patients with ASD but not in those without ASD. The findings demonstrated that CMV may increase the susceptibility of TSC to ASD. IMPORTANCE CMV is an environmental risk factor for ASD, but its role in syndromic autism with known genetic etiology has been rarely studied. The pathogenesis of ASD is related to the interaction between environmental and genetic factors. This study demonstrated that CMV can contribute to the occurrence of ASD related to TSC, a common genetic syndrome associated with ASD. Our findings provided support for the theory of gene-environment interaction (G × E) in pathogenesis of ASD and a new perspective for the prevention and therapy for TSC related ASD.

Keywords:  autism spectrum disorder; cytomegalovirus; gene-environment interaction; tuberous sclerosis complex

DOI:  https://doi.org/10.1128/spectrum.01864-21
Autophagy. 2022 Apr 26. 1-2

Glutamine, MTOR and autophagy: a multiconnection relationship.

Clément Bodineau, Mercedes Tomé, Piedad Del Socorro Murdoch, Raúl V Durán.

  Cancer cells metabolize glutamine mostly through glutaminolysis, a metabolic pathway that activates MTORC1. The AMPK-MTORC1 signaling axis is a key regulator of cell growth and proliferation. Our recent investigation identified that the connection between glutamine and AMPK is not restricted to glutaminolysis. Rather, we demonstrated the crucial role of ASNS (asparagine synthetase (glutamine-hydrolyzing)) and the GABA shunt for the metabolic control of the AMPK-MTORC1 axis during glutamine sufficiency. Our results elucidated a metabolic network by which glutamine metabolism regulates the MTORC1-macroautophagy/autophagy pathway through two independent branches involving glutaminolysis and ASNS-GABA shunt.

Keywords:  ASNS; GABA-shunt; MTORC1; glutamine; glutamoptosis

DOI:  https://doi.org/10.1080/15548627.2022.2062875
Kidney Int. 2022 Apr 25. pii: S0085-2538(22)00335-0. [Epub ahead of print]

Blocking ribosomal protein S6 phosphorylation inhibits podocyte hypertrophy and focal segmental glomerulosclerosis.

Fang Li, Yili Fang, Qiyuan Zhuang, Meichu Cheng, Desmond Moronge, Hao Jue, Oded Meyuhas, Xiaoqiang Ding, Zhigang Zhang, Jian-Kang Chen, Huijuan Wu.

  Ribosomal protein S6 (rpS6) phosphorylation mediates the hypertrophic growth of kidney proximal tubule cells. However, the role of rpS6 phosphorylation in podocyte hypertrophy and podocyte loss during the pathogenesis of focal segmental glomerulosclerosis (FSGS) remains undefined. Here, we examined rpS6 phosphorylation levels in kidney biopsy specimens from patients with FSGS and in podocytes from mouse kidneys with adriamycin-induced FSGS. Using genetic and pharmacologic approaches in the mouse model of FSGS, we investigated the role of rpS6 phosphorylation in podocyte hypertrophy and loss during development and progression of FSGS. Phosphorylated rpS6 was found to be markedly increased in the podocytes of patients with FSGS and adriamycin-induced FSGS in mice. Genetic deletion of the Tuberous sclerosis 1 gene in kidney glomerular podocytes activated mammalian target of rapamycin complex 1 signaling to rpS6 phosphorylation, resulting in podocyte hypertrophy and pathologic features similar to those of patients with FSGS including podocyte loss, leading to segmental glomerulosclerosis. Since protein phosphatase 1 is known to negatively regulate rpS6 phosphorylation; treatment with an inhibitor increased phospho-rpS6 levels, promoted podocyte hypertrophy and exacerbated formation of FSGS lesions. Importantly, blocking rpS6 phosphorylation (either by generating congenic rpS6 knock-in mice expressing non-phosphorylatable rpS6 or by inhibiting ribosomal protein S6 kinase 1-mediated rpS6 phosphorylation with an inhibitor) significantly blunted podocyte hypertrophy, inhibited podocyte loss, and attenuated formation of FSGS lesions. Thus, our study provides genetic and pharmacologic evidence indicating that specifically targeting rpS6 phosphorylation can attenuate the development of FSGS lesions by inhibiting podocyte hypertrophy and associated podocyte depletion.

Keywords:  focal segmental glomerulosclerosis (FSGS); podocyte hypertrophy; ribosomal protein S6 (rpS6)

DOI:  https://doi.org/10.1016/j.kint.2022.02.037
Clin Exp Pharmacol Physiol. 2022 Apr 30.

Inhibition of mTOR by temsirolimus overcomes radio-resistance in nasopharyngeal carcinoma.

Shiyong Huang, Ke Du, Zeng Liu, Jiangping Li.

  Radio-resistance is a leading cause of nasopharyngeal carcinoma (NPC) treatment failure and identification of sensitizing therapeutic target is an unmet need to enhance clinical management. Given that the mammalian target of rapamycin (mTOR) signaling confers resistance to cancer therapy, we investigated whether mTOR contributes to radio-resistance in NPC and pharmacological inhibition of mTOR can overcome radio-resistance. We found that mTOR mRNA and protein levels, and phosphorylation of its downstream effector were increased in radio-resistant NPC compared with parental cells. mTOR inhibitor temsirolimus inhibits proliferation and induces apoptosis in a panel of NPC cell lines. Importantly, temsirolimus acts synergistically with radiation and is effective against radio-resistant cells. Using radio-resistant xenograft mouse model, we validated the efficacy of temsirolimus in preventing tumor formation and inhibiting tumor growth. Temsirolimus overcome radio-resistance in NPC via inhibiting mTOR signaling. Our work provides the pre-clinical evidence that the combination of radiation and mTOR inhibitor may be a therapeutic strategy in NPC. Our findings might accelerate the initiation of clinical trials on radio-resistant NPC patients using temsirolimus. This article is protected by copyright. All rights reserved.

Keywords:  NPC; mTOR; radio-resistance; temsirolimus

DOI:  https://doi.org/10.1111/1440-1681.13649
iScience. 2022 May 20. 25(5): 104186

The TORC1 phosphoproteome in C. elegans reveals roles in transcription and autophagy.

Aileen K Sewell, Zachary C Poss, Christopher C Ebmeier, Jeremy R Jacobsen, William M Old, Min Han.

  The protein kinase complex target of rapamycin complex 1 (TORC1) is a critical mediator of nutrient sensing that has been widely studied in cultured cells and yeast, yet our understanding of the regulatory activities of TORC1 in the context of a whole, multi-cellular organism is still very limited. Using Caenorhabditis elegans, we analyzed the DAF-15/Raptor-dependent phosphoproteome by quantitative mass spectrometry and characterized direct kinase targets by in vitro kinase assays. Here, we show new targets of TORC1 that indicate previously unknown regulation of transcription and autophagy. Our results further show that DAF-15/Raptor is differentially expressed during postembryonic development, suggesting a dynamic role for TORC1 signaling throughout the life span. This study provides a comprehensive view of the TORC1 phosphoproteome, reveals more than 100 DAF-15/Raptor-dependent phosphosites that reflect the complex function of TORC1 in a whole, multi-cellular organism, and serves as a rich resource to the field.

Keywords:  Cell biology; Developmental biology; Functional aspects of cell biology; Omics; Proteomics

DOI:  https://doi.org/10.1016/j.isci.2022.104186
J Cell Mol Med. 2022 Apr 30.

Increased mTORC2 pathway activation in lymph nodes of iMCD-TAFRO.

Alexis D Phillips, Joseph J Kakkis, Patricia Y Tsao, Sheila K Pierson, David C Fajgenbaum.

  Idiopathic multicentric Castleman disease (iMCD) is a rare and life-threatening haematologic disorder involving polyclonal lymphoproliferation and organ dysfunction due to excessive cytokine production, including interleukin-6 (IL-6). Clinical trial and real-world data demonstrate that IL-6 inhibition is effective in 34-50% of patients. mTOR, which functions through mTORC1 and mTORC2, is a recently discovered therapeutic target. The mTOR inhibitor sirolimus, which preferentially inhibits mTORC1, has led to sustained remission in a small cohort of anti-IL-6-refractory iMCD patients with thrombocytopenia, anasarca, fever, renal dysfunction and organomegaly (iMCD-TAFRO). However, sirolimus has not shown uniform effect, potentially due to its limited mTORC2 inhibition. To investigate mTORC2 activation in iMCD, we quantified the mTORC2 effector protein pNDRG1 by immunohistochemistry of lymph node tissue from six iMCD-TAFRO and eight iMCD patients who do not meet TAFRO criteria (iMCD-not-otherwise-specified; iMCD-NOS). mTORC2 activation was increased in all regions of iMCD-TAFRO lymph nodes and the interfollicular space of iMCD-NOS compared with control tissue. Immunohistochemistry also revealed increased pNDRG1 expression in iMCD-TAFRO germinal centres compared with autoimmune lymphoproliferative syndrome (ALPS), an mTOR-driven, sirolimus-responsive lymphoproliferative disorder, and comparable staining between iMCD-NOS and ALPS. These results suggest increased mTORC2 activity in iMCD and that dual mTORC1/mTORC2 inhibitors may be a rational therapeutic approach.

Keywords:  Castleman disease; TAFRO; autoimmune lymphoproliferative syndrome; iMCD; idiopathic multicentric Castleman disease; mTOR; mTORC2; pNDRG1

DOI:  https://doi.org/10.1111/jcmm.17251
Front Cell Neurosci. 2022 ;16 853634

Neuronal mTOR Outposts: Implications for Translation, Signaling, and Plasticity.

Bekir Altas, Andrea J Romanowski, Garrett W Bunce, Alexandros Poulopoulos.

  The kinase mTOR is a signaling hub for pathways that regulate cellular growth. In neurons, the subcellular localization of mTOR takes on increased significance. Here, we review findings on the localization of mTOR in axons and offer a perspective on how these may impact our understanding of nervous system development, function, and disease. We propose a model where mTOR accumulates in local foci we term mTOR outposts, which can be found in processes distant from a neuron's cell body. In this model, pathways that funnel through mTOR are gated by local outposts to spatially select and amplify local signaling. The presence or absence of mTOR outposts in a segment of axon or dendrite may determine whether regional mTOR-dependent signals, such as nutrient and growth factor signaling, register toward neuron-wide responses. In this perspective, we present the emerging evidence for mTOR outposts in neurons, their putative roles as spatial gatekeepers of signaling inputs, and the implications of the mTOR outpost model for neuronal protein synthesis, signal transduction, and synaptic plasticity.

Keywords:  axon; axon regeneration; ketamine; local translation; mTOR; ribosome biogenesis; synapse tagging

DOI:  https://doi.org/10.3389/fncel.2022.853634
Sci Rep. 2022 Apr 23. 12(1): 6674

Asteltoxin inhibits extracellular vesicle production through AMPK/mTOR-mediated activation of lysosome function.

Fumie Mitani, Jianyu Lin, Tatsuya Sakamoto, Ryo Uehara, Tomoya Hikita, Takuya Yoshida, Andi Setiawan, Masayoshi Arai, Chitose Oneyama.

Cancer cells secrete aberrantly large amounts of extracellular vesicles (EVs) including exosomes, which originate from multivesicular bodies (MVBs). Because EVs potentially contribute to tumor progression, EV inhibitors are of interest as novel therapeutics. We screened a fungal natural product library. Using cancer cells engineered to secrete luciferase-labeled EVs, we identified asteltoxin, which inhibits mitochondrial ATP synthase, as an EV inhibitor. Low concentrations of asteltoxin inhibited EV secretion without inducing mitochondrial damage. Asteltoxin attenuated cellular ATP levels and induced AMPK-mediated mTORC1 inactivation. Consequently, MiT/TFE transcription factors are translocated into the nucleus, promoting transcription of lysosomal genes and lysosome activation. Electron microscopy analysis revealed that the number of lysosomes increased relative to that of MVBs and the level of EVs decreased after treatment with asteltoxin or rapamycin, an mTORC1 inhibitor. These findings suggest that asteltoxin represents a new type of EV inhibitor that controls MVB fate.

DOI: https://doi.org/10.1038/s41598-022-10692-0