bims-tubesc Biomed News
on Molecular mechanisms in tuberous sclerosis
Issue of 2021‒01‒31
ten papers selected by
Marti Cadena Sandoval

  1. Cell. 2021 Jan 18. pii: S0092-8674(20)31694-9. [Epub ahead of print]
      Ras GTPase-activating protein-binding proteins 1 and 2 (G3BP1 and G3BP2, respectively) are widely recognized as core components of stress granules (SGs). We report that G3BPs reside at the cytoplasmic surface of lysosomes. They act in a non-redundant manner to anchor the tuberous sclerosis complex (TSC) protein complex to lysosomes and suppress activation of the metabolic master regulator mechanistic target of rapamycin complex 1 (mTORC1) by amino acids and insulin. Like the TSC complex, G3BP1 deficiency elicits phenotypes related to mTORC1 hyperactivity. In the context of tumors, low G3BP1 levels enhance mTORC1-driven breast cancer cell motility and correlate with adverse outcomes in patients. Furthermore, G3bp1 inhibition in zebrafish disturbs neuronal development and function, leading to white matter heterotopia and neuronal hyperactivity. Thus, G3BPs are not only core components of SGs but also a key element of lysosomal TSC-mTORC1 signaling.
    Keywords:  G3BP1; G3BP2; TSC complex; cancer; lysosome; mTORC1; metabolism; neuronal function; stress granule
  2. Front Mol Neurosci. 2020 ;13 604158
      Epilepsies are chronic neurological diseases that affect approximately 2% of the world population. In addition to being one of the most frequent neurological disorders, treatment for patients with epilepsy remains a challenge, because a proportion of patients do not respond to the antiseizure medications that are currently available. This results in a severe economic and social burden for patients, families, and the healthcare system. A characteristic common to all forms of epilepsy is the occurrence of epileptic seizures that are caused by abnormal neuronal discharges, leading to a clinical manifestation that is dependent on the affected brain region. It is generally accepted that an imbalance between neuronal excitation and inhibition generates the synchronic electrical activity leading to seizures. However, it is still unclear how a normal neural circuit becomes susceptible to the generation of seizures or how epileptogenesis is induced. Herein, we review the results of recent proteomic studies applied to investigate the underlying mechanisms leading to epilepsies and how these findings may impact research and treatment for these disorders.
    Keywords:  epileptogenesis; hippocampal sclerosis; malformations of cortical development; mesial temporal lobe epilepsy; proteomics; seizures
  3. Acad Radiol. 2021 Jan 21. pii: S1076-6332(21)00005-2. [Epub ahead of print]
      Tuberous sclerosis complex is a multiorgan syndrome manifesting with several benign and malignant tumors. Complications arising from renal abnormalities are a leading cause of death in patients with tuberous sclerosis complex. Renal cell carcinoma is relatively uncommon, occurring in 2%-4% of patients with tuberous sclerosis complex syndrome, but nonetheless can significantly contribute to morbidity and mortality. Extrarenal manifestations of tuberous sclerosis complex, including within the chest, abdomen and central nervous system, aid in diagnosis. Pathogenesis and management are also discussed, including the importance of the types of renal masses found in these patients.
    Keywords:  kidney; renal cell carcinoma; targeted therapy; tuberous sclerosis complex
  4. Cardiovasc Res. 2021 Jan 29. pii: cvab033. [Epub ahead of print]
      The mechanistic target of rapamycin (mTOR) integrates several intracellular and extracellular signals involved in the regulation of anabolic and catabolic processes. mTOR assembles into two macromolecular complexes, named mTORC1 and mTORC2, which have different regulators, substrates and functions. Studies of gain- and loss-of-function animal models of mTOR signaling revealed that mTORC1/2 elicit both adaptive and maladaptive functions in the cardiovascular system. Both mTORC1 and mTORC2 are indispensable for driving cardiac development and cardiac adaption to stress, such as pressure overload. However, persistent and deregulated mTORC1 activation in the heart is detrimental during stress and contributes to the development and progression of cardiac remodeling and genetic and metabolic cardiomyopathies. In this review, we discuss the latest findings regarding the role of mTOR in the cardiovascular system, both under basal conditions and during stress, such as pressure overload, ischemia and metabolic stress. Current data suggest that mTOR modulation may represent a potential therapeutic strategy for the treatment of cardiac diseases.
    Keywords:  heart disease; mTOR; mTORC1; mTORC2; rapamycin
  5. Clin Exp Dermatol. 2021 Jan 28.
      A 19-year-old-male, previously diagnosed case of tuberous sclerosis complex, presented to us with gradually progressive thickening of the fourth finger of his right hand that was first noticed at seven years of age. There was no pain or difficulty in moving the finger. On examination, the distal aspect of the fourth digit of right hand appeared thicker than other fingers. The overlying skin was loose, hyperpigmented with a thickened velvety appearance, and a doughy consistency.
  6. FASEB J. 2021 Feb;35(2): e21325
      The objectives of our study were to investigate the roles of mTORC1 in odontoblast proliferation and mineralization and to determine the mechanism by which mTORC1 regulates odontoblast mineralization. In vitro, MDPC23 cells were treated with rapamycin (10 nmol/L) and transfected with a lentivirus for short hairpin (shRNA)-mediated silencing of the tuberous sclerosis complex (shTSC1) to inhibit and activate mTORC1, respectively. CCK8 assays, flow cytometry, Alizarin red S staining, ALP staining, qRT-PCR, and western blot analysis were performed. TSC1-conditional knockout (DMP1-Cre+ ; TSC1f/f , hereafter CKO) mice and littermate control (DMP1-Cre- ; TSC1f/f , hereafter WT) mice were generated. H&E staining, immunofluorescence, and micro-CT analysis were performed. Transcriptome sequencing analysis was used to screen the mechanism of this process. mTORC1 inactivation decreased the cell proliferation. The qRT-PCR and western blot results showed that mineralization-related genes and proteins were downregulated in mTORC1-inactivated cells. Moreover, mTORC1 overactivation promoted cell proliferation and mineralization-related gene and protein expression. In vivo, the micro-CT results showed that DV/TV and dentin thickness were higher in CKO mice than in controls and H&E staining showed the same results. Mineralization-related proteins expression was upregulated. Transcriptome sequencing analysis revealed that p53 pathway-associated genes were differentially expressed in TSC1-deficient cells. By inhibiting p53 alone or both mTORC1 and p53 with rapamycin and a p53 inhibitor, we elucidated that p53 acts downstream of mTORC1 and that mTORC1 thereby promotes odontoblast mineralization. Taken together, our findings demonstrate that the role of mTORC1 in odontoblast proliferation and mineralization, and confirm that mTORC1 upregulates odontoblast mineralization via the p53 pathway.
    Keywords:  cell signaling; dentinogenesis; mTORC1; molecular biology; odontoblast; tooth development
  7. Epilepsia. 2021 Jan 25.
      Loss of myelin and altered oligodendrocyte distribution in the cerebral cortex are commonly observed both in postsurgical tissue derived from different focal epilepsies (such as focal cortical dysplasias and tuberous sclerosis) and in animal models of focal epilepsy. Moreover, seizures are a frequent symptom in demyelinating diseases, such as multiple sclerosis, and in animal models of demyelination and oligodendrocyte dysfunction. Finally, the excessive activity reported in demyelinated axons may promote hyperexcitability. We hypothesize that the extracellular potassium rise generated during epileptiform activity may be amplified by the presence of axons without appropriate myelin coating and by alterations in oligodendrocyte function. This process could facilitate the triggering of recurrent spontaneous seizures in areas of altered myelination and could result in further demyelination, thus promoting epileptogenesis.
    Keywords:  ictogenesis; myelin; oligodendrocyte; potassium; seizures
  8. Respir Med. 2021 Jan 05. pii: S0954-6111(20)30434-0. [Epub ahead of print]177 106294
      INTRODUCTION: Sarcoidosis is a systemic granulomatous disease with a variable clinical presentation and disease course. There is still no reliable biomarker available, which assists in the diagnosis or prediction of the clinical course. According to a murine model, the expression level of the metabolic checkpoint kinase mechanistic target of Rapamycin complex 1 (mTORC1) in granulomas of sarcoidosis patients may be used as a clinical biomarker.MATERIAL AND METHODS: This is a retrospective analysis of 58 patients with histologically confirmed sarcoidosis. Immunohistochemical staining of granulomas from tissue samples was evaluated for the expression of activated mTORC1 signaling, including phosphorylated mTOR, its downstream effectors S6K1, 4EBP1 and the proliferation marker Ki-67. Patients were categorized according to different clinical phenotypes, serum biomarkers, and immunomodulatory therapy.
    RESULTS: All patients showed activated mTORC1 signaling in granulomas, which correlated with its downstream effectors S6K1 and 4EBP1 but was not related to Ki-67 expression. The mTORC1 activity revealed an association neither to disease severity nor the necessity of treatment; however, p-mTOR inversely correlated with cumulative corticosteroid dosage.
    CONCLUSION: Our data confirm activation of the mTORC1 pathway in sarcoidosis, supporting the hypothesis that mTOR is a significant driver in granuloma formation. However, we could not find a relationship between the degree of mTOR activation and disease severity or the need for therapy.
    Keywords:  Biomarker; Clinical study; Prognosis; Sarcoidosis; mTOR
  9. J Biochem Mol Toxicol. 2021 Jan 24. e22726
      The role of ROR1-AS1 in non-small-cell lung cancer (NSCLC) remains unclear. Therefore, we aimed to investigate the functional role of ROR1-AS1 in NSCLC and to explore the underlying mechanisms. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay was performed to detect cell proliferation. Transwell assay was performed to evaluate cell invasive ability. Cell apoptotic rates and caspase-3/7 activity were determined to evaluate apoptosis. The expression levels of PI3K/Akt/mTOR pathway-related proteins were measured using Western blot analysis. Results showed that ROR1-AS1 expression was upregulated in NSCLC samples. Knockdown of ROR1-AS1 inhibited the viability and invasive ability of NSCLC cells. Knockdown of ROR1-AS1 induced apoptotic rate and caspase-3/7 activity and suppressed xenograft NSCLC tumor growth. In addition, ROR1-AS1 knockdown inhibited the activation of the PI3K/Akt/mTOR pathway in NSCLC cells. However, treatment with 740Y-P prevented the effects of si-ROR1-AS1 on viability, invasive ability, and apoptosis of NSCLC cells. These findings implied that ROR1-AS1 played an oncogenic role in NSCLC via regulating the PI3K/Akt/mTOR pathway.
    Keywords:  NSCLC; PI3K/Akt/mTOR pathway; ROR1-AS1; oncogene
  10. Epigenetics. 2021 Jan 24.
      Neural tube defects (NTDs) are a group of common and severe congenital malformations. The PI3K-AKT signaling pathway plays a crucial role in the neural tube development. There is limited evidence concerning any possible association between aberrant methylation in genes of the PI3K-AKT signaling pathway and NTDs. Therefore, we aimed to investigate potential associations between aberrant methylation of PI3K-AKT pathway genes and NTDs. Methylation studies of PI3K-AKT pathway genes utilizing microarray genome-methylation data derived from neural tissues of ten NTD cases and eight non-malformed controls were performed. Targeted DNA methylation analysis was subsequently performed in an independent cohort of 73 NTD cases and 32 controls to validate the methylation levels of identified genes. siRNAs were used to pull-down the target genes in human embryonic stem cells (hESCs) to examine the effects of the aberrant expression of target genes on neural cells. As a result, 321 differentially hypermethylated CpG sites in the promoter regions of 30 PI3K-AKT pathway genes were identified in the microarray data. In subsequent target methylation analysis, CHRM1, FGF19, and ITGA7 were confirmed to be significantly hypermethylated in NTD cases and were associated with increased risk for NTDs. The down-regulation of FGF19, CHRM1, and ITGA7 impaired the formation of rosette-like cell aggregates. Besides, the down-regulation of those three genes affected the expression of PAX6, SOX2 and MAP2, implying their influence on the differentiation of neural cells. This study for the first time reported that hypermethylation of PI3K-AKT pathway genes such as CHRM1, FGF19, and ITGA7 is associated with human NTDs.Keywords: Neural tube defects, PI3K-AKT signaling pathway, methylation.