bims-tubesc 2023-02-19 papers

bims-tubesc

Biomed News

on Molecular mechanisms in tuberous sclerosis

Issue of 2023–02–19
eight papers selected by

Spectrum of germline and somatic mitochondrial DNA variants in Tuberous Sclerosis Complex.
Mechanistic Target of Rapamycin Complex 1: From a Nutrient Sensor to a Key Regulator of Metabolism and Health.
The role of the mechanistic target of rapamycin complex 1 in the regulation of mitochondrial adaptation during skeletal muscle atrophy under denervation or calorie restriction in mice.
Tuberous Sclerosis: Unusual Findings in the Setting of a Rare Disease.
Pharmacological vitamin C inhibits mTOR signaling and tumor growth by degrading Rictor and inducing HMOX1 expression.
Nuclear receptor subfamily 1 group D member 1 suppresses the proliferation, migration of adventitial fibroblasts, and vascular intimal hyperplasia via mammalian target of rapamycin complex 1/β-catenin pathway.
Structural basis for mTORC1-dependent regulation of the lysosomal and autophagic transcription factor EB.
In vivo Assessment of Lysosomal Stress in the Drosophila Brain Using Confocal Fluorescence Microscopy.

Front Genet. 2022 ;13 917993

Spectrum of germline and somatic mitochondrial DNA variants in Tuberous Sclerosis Complex.

Krinio Giannikou, Katie R Martin, Ahmad G Abdel-Azim, Kaila J Pamir, Thomas R Hougard, Shefali Bagwe, Yan Tang, Jeffrey P MacKeigan, David J Kwiatkowski, Elizabeth P Henske, Hilaire C Lam.

  Tuberous Sclerosis Complex (TSC) is caused by loss of function variants in either TSC1 or TSC2 and is characterized by broad phenotypic heterogeneity. Currently, there is limited knowledge regarding the role of the mitochondrial genome (mtDNA) in TSC pathogenesis. In this study, we aimed to determine the prevalence and spectrum of germline and somatic mtDNA variants in TSC and identify potential disease modifiers. Analysis of mtDNA amplicon massively parallel sequencing (aMPS) data, off-target mtDNA from whole-exome sequencing (WES), and/or qPCR, revealed mtDNA alterations in 270 diverse tissues (139 TSC-associated tumors and 131 normal tissue samples) from 199 patients and six healthy individuals. Correlation of clinical features to mtDNA variants and haplogroup analysis was done in 102 buccal swabs (age: 20-71 years). No correlation was found between clinical features and either mtDNA variants or haplogroups. No pathogenic variants were identified in the buccal swab samples. Using in silico analysis, we identified three predicted pathogenic variants in tumor samples: MT-ND4 (m.11742G>A, p. Cys328Tyr, VAF: 43%, kidney angiomyolipoma), MT-CYB (m.14775T>C, p. Leu10Pro, VAF: 43%, LAM abdominal tumor) and MT-CYB (m.15555C>T, p. Pro270Leu, VAF: 7%, renal cell carcinoma). Large deletions of the mitochondrial genome were not detected. Analysis of tumors from 23 patients with corresponding normal tissue did not reveal any recurrent tumor-associated somatic variants. The mtDNA/gDNA ratio between tumors and corresponding normal tissue was also unchanged. Overall, our findings demonstrate that the mitochondrial genome is highly stable across tissues and within TSC-associated tumors.

Keywords:  angiomyolipoma; buccal swab; lymphangioleiomyomatosis; mTORC1; renal cell carcinoma

DOI:  https://doi.org/10.3389/fgene.2022.917993
Adv Nutr. 2022 Sep;pii: S2161-8313(23)00046-7. [Epub ahead of print]13(5): 1882-1900

Mechanistic Target of Rapamycin Complex 1: From a Nutrient Sensor to a Key Regulator of Metabolism and Health.

Guoyan Wang, Lei Chen, Senlin Qin, Tingting Zhang, Junhu Yao, Yanglei Yi, Lu Deng.

  Mechanistic target of rapamycin complex 1 (mTORC1) is a multi-protein complex widely found in eukaryotes. It serves as a central signaling node to coordinate cell growth and metabolism by sensing diverse extracellular and intracellular inputs, including amino acid-, growth factor-, glucose-, and nucleotide-related signals. It is well documented that mTORC1 is recruited to the lysosomal surface, where it is activated and, accordingly, modulates downstream effectors involved in regulating protein, lipid, and glucose metabolism. mTORC1 is thus the central node for coordinating the storage and mobilization of nutrients and energy across various tissues. However, emerging evidence indicated that the overactivation of mTORC1 induced by nutritional disorders leads to the occurrence of a variety of metabolic diseases, including obesity and type 2 diabetes, as well as cancer, neurodegenerative disorders, and aging. That the mTORC1 pathway plays a crucial role in regulating the occurrence of metabolic diseases renders it a prime target for the development of effective therapeutic strategies. Here, we focus on recent advances in our understanding of the regulatory mechanisms underlying how mTORC1 integrates metabolic inputs as well as the role of mTORC1 in the regulation of nutritional and metabolic diseases.

Keywords:  mTORC1; metabolic diseases; metabolism; nutrient; signal transduction

DOI:  https://doi.org/10.1093/advances/nmac055
Appl Physiol Nutr Metab. 2023 Feb 14.

The role of the mechanistic target of rapamycin complex 1 in the regulation of mitochondrial adaptation during skeletal muscle atrophy under denervation or calorie restriction in mice.

Kazuki Uemichi, Takanaga Shirai, Ryunosuke Matsuno, Tomohiro Iwata, Riku Tanimura, Tohru Takemasa.

  Mechanistic target of rapamycin complex 1 (mTORC1) is a protein complex that regulates skeletal muscle protein synthesis and hypertrophy. mTORC1-mediated signaling activities are activated during denervation-induced skeletal muscle atrophy and suppressed during calorie restriction-induced atrophy. Mitochondria control the qualitative plasticity of skeletal muscles primarily through biogenesis, fusion, and fission. We recently showed that mTORC1 activation contributes toward mitochondrial homeostasis. In this study, we examined the role of mTORC1 in mitochondrial adaptation during denervation- or calorie restriction-induced skeletal muscle atrophy. Seven-week-old Institute of Cancer Research mice were subjected to 14 days of denervation or calorie restriction combined with the administration of the mTORC1 inhibitor-"rapamycin". Our results showed that although mTORC1 inhibition did not alter mitochondrial biogenesis, content and enzyme activity, it suppressed the activation of dynamin-related protein 1 (DRP1), a mitochondrial fission-related protein in denervated muscle, and reduced DRP1 expression in calorie-restricted muscle. Furthermore, calorie restriction-induced mitochondrial fragmentation was partially suppressed by mTORC1 inhibition. Taken together, our results indicate that mTORC1 activation upon denervation and inhibition upon calorie restriction contributes to qualitative changes in muscle plasticity by at least partially regulating the mitochondrial fission response.

Keywords:  mTORC1; mitochondrial dynamics; skeletal muscle atrophy

DOI:  https://doi.org/10.1139/apnm-2022-0336
Arq Bras Cardiol. 2023 Jan;pii: S0066-782X2023000101001. [Epub ahead of print]120(1): e20220147

Tuberous Sclerosis: Unusual Findings in the Setting of a Rare Disease.

Ines Oliveira, Rafaela Lopes, Isabel Cruz, Bruno Bragança, João Azevedo, Aurora Andrade.

DOI: https://doi.org/10.36660/abc.20220147
PLoS Genet. 2023 Feb;19(2): e1010629

Pharmacological vitamin C inhibits mTOR signaling and tumor growth by degrading Rictor and inducing HMOX1 expression.

Senlin Qin, Guoyan Wang, Lei Chen, Huijun Geng, Yining Zheng, Chao Xia, Shengru Wu, Junhu Yao, Lu Deng.

Pharmacological vitamin C (VC) is a potential natural compound for cancer treatment. However, the mechanism underlying its antitumor effects remains unclear. In this study, we found that pharmacological VC significantly inhibits the mTOR (including mTORC1 and mTORC2) pathway activation and promotes GSK3-FBXW7-mediated Rictor ubiquitination and degradation by increasing the cellular ROS. Moreover, we identified that HMOX1 is a checkpoint for pharmacological-VC-mediated mTOR inactivation, and the deletion of FBXW7 or HMOX1 suppresses the regulation of pharmacological VC on mTOR activation, cell size, cell viability, and autophagy. More importantly, it was observed that the inhibition of mTOR by pharmacological VC supplementation in vivo produces positive therapeutic responses in tumor growth, while HMOX1 deficiency rescues the inhibitory effect of pharmacological VC on tumor growth. These results demonstrate that VC influences cellular activities and tumor growth by inhibiting the mTOR pathway through Rictor and HMOX1, which may have therapeutic potential for cancer treatment.

DOI: https://doi.org/10.1371/journal.pgen.1010629
Clin Exp Hypertens. 2023 Dec 31. 45(1): 2178659

Nuclear receptor subfamily 1 group D member 1 suppresses the proliferation, migration of adventitial fibroblasts, and vascular intimal hyperplasia via mammalian target of rapamycin complex 1/β-catenin pathway.

Ke Peng, Mingliang Wang, Jun Wang, Qiang Wang, De Li, Xiongshan Sun, Yongjian Yang, Dachun Yang.

   BACKGROUND: In-stent restenosis hardly limits the therapeutic effect of the percutaneous vascular intervention. Although the restenosis is significantly ameliorated after the application of new drug-eluting stents, the incidence of restenosis remains at a high level.
OBJECTIVE: Vascular adventitial fibroblasts (AFs) play an important role in intimal hyperplasia and subsequent restenosis. The current study was aimed to investigate the role of nuclear receptor subfamily 1, group D, member 1 (NR1D1) in the vascular intimal hyperplasia.
METHODS AND RESULTS: We observed increased expression of NR1D1 after the transduction of adenovirus carrying Nr1d1 gene (Ad-Nr1d1) in AFs. Ad-Nr1d1 transduction significantly reduced the numbers of total AFs, Ki-67-positive AFs, and the migration rate of AFs. NR1D1 overexpression decreased the expression level of β-catenin and attenuated the phosphorylation of the effectors of mammalian target of rapamycin complex 1 (mTORC1), including mammalian target of rapamycin (mTOR) and 4E binding protein 1 (4EBP1). Restoration of β-catenin by SKL2001 abolished the inhibitory effects of NR1D1 overexpression on the proliferation and migration of AFs. Surprisingly, the restoration of mTORC1 activity by insulin could also reverse the decreased expression of β-catenin, attenuated proliferation, and migration in AFs induced by NR1D1 overexpression. In vivo, we found that SR9009 (an agonist of NR1D1) ameliorated the intimal hyperplasia at days 28 after injury of carotid artery. We further observed that SR9009 attenuated the increased Ki-67-positive AFs, an essential part of vascular restenosis at days 7 after injury to the carotid artery.
CONCLUSION: These data suggest that NR1D1 inhibits intimal hyperplasia by suppressing the proliferation and migration of AFs in a mTORC1/β-catenin-dependent manner.

Keywords:  AFs; NR1D1; mTORC1; neointimal hyperplasia; β-catenin

DOI:  https://doi.org/10.1080/10641963.2023.2178659
Biophys J. 2023 Feb 10. pii: S0006-3495(22)02651-0. [Epub ahead of print]122(3S1): 308a

Structural basis for mTORC1-dependent regulation of the lysosomal and autophagic transcription factor EB.

Zhicheng Cui, James H Hurley.

DOI: https://doi.org/10.1016/j.bpj.2022.11.1735
Bio Protoc. 2023 Jan 20. 13(2): e4599

In vivo Assessment of Lysosomal Stress in the Drosophila Brain Using Confocal Fluorescence Microscopy.

Felipe Martelli.

  Lysosomes play a central role in signaling, nutrient sensing, response to stress, and the degradation and recycling of cellular content. Defects in lysosomal digestive enzymes or structural components can impair lysosomal function with dire consequences to the cell, such as neurodegeneration. A number of methods exist to assess lysosomal stress in the model Drosophila, such as specific driver and reporter strains, transmission electron microscopy, and the investigation of gene expression. These methods, however, can be time consuming and, in some cases, costly. The procedure described here provides a quick, reliable, and low-cost approach to measure lysosomal stress in the Drosophila brain. Using fluorescence confocal microscopy and the LysoTracker staining, this protocol allows for the direct measurement of lysosome size and number. This method can be used to assess lysosomal stress under a number of different genetic and environmental scenarios in the Drosophila brain.

Keywords:  Brain; Fluorescence microscopy; Fruit fly; Insecticide; LysoTracker; Lysosomal stress; Lysosome

DOI:  https://doi.org/10.21769/BioProtoc.4599