bims-tubesc 2023-04-02 papers

bims-tubesc

Biomed News

on Molecular mechanisms in tuberous sclerosis

Issue of 2023–04–02
eight papers selected by

Bcat1 is controlled by Tsc2/mTORC1 pathway at expression levels and its deficiency together with Bcat2 inactivation suppresses the growth of a Tsc2-/- tumor cell line.
Persistent mTORC1 activation due to loss of liver tuberous sclerosis complex 1 promotes liver injury in alcoholic hepatitis.
An affinity tool for the isolation of endogenous active mTORC1 from various cellular sources.
CDK5-PRMT1-WDR24 signaling cascade promotes mTORC1 signaling and tumor growth.
Mammalian Target of Rapamycin (mTOR) Signalling Pathway a Potential Target for Cancer Intervention: a Short Overview.
Kinase Inhibitors in Genetic Diseases.
TFEB and TFE3 drive kidney cystogenesis and tumorigenesis.
A multi-organ analysis of the role of mTOR in fetal alcohol spectrum disorders.

Genes Cells. 2023 Mar 25.

Bcat1 is controlled by Tsc2/mTORC1 pathway at expression levels and its deficiency together with Bcat2 inactivation suppresses the growth of a Tsc2-/- tumor cell line.

Keiko Nishikawa, Yoshihiro Mezawa, Toshiyuki Kobayashi.

  The tuberous sclerosis complex (TSC) gene products (TSC1/TSC2) negatively regulate mTORC1. Although mTORC1 inhibitors are used for the treatment of TSC, incomplete tumor elimination and the adverse effects from long-term administration are problems that need to be solved. Branched-chain amino acid (BCAA) metabolism is involved in the growth of many tumor cells via the mTORC1 pathway. However, it remains unclear how BCAA metabolism affects the growth of mTORC1-dysregulated tumors. We show here that the expression of branched-chain amino transferase1 (Bcat1) was suppressed in Tsc2-deficient murine renal tumor cells either by treatment with rapamycin or restoration of Tsc2 expression suggesting that Bcat1 is located downstream of Tsc2-mTORC1 pathway. We also found that gabapentin, a Bcat1 inhibitor suppressed the growth of Tsc2-deficient tumor cells and increased efficacy when combined with rapamycin. We investigate the functional importance of Bcat1 and the mitochondrial isoform Bcat2 by inhibiting each enzyme separately or both together by genome editing and shRNA in Tsc2-deficient cells. We found that deficiency of both enzymes, but not either alone, inhibited cell growth, indicating that BCAA-metabolic reactions support Tsc2-deficient cell proliferation. Our results indicate that inhibition of Bcat1 and Bcat2 by specific drugs should be a useful method for TSC treatment.

Keywords:  BCAA; Bcat1; Bcat2; Tuberous sclerosis complex; mTORC1

DOI:  https://doi.org/10.1111/gtc.13027
Hepatology. 2023 Apr 03.

Persistent mTORC1 activation due to loss of liver tuberous sclerosis complex 1 promotes liver injury in alcoholic hepatitis.

Xiaojuan Chao, Shaogui Wang, Xiaowen Ma, Chen Zhang, Hui Qian, Sha Neisha Williams, Zhaoli Sun, Zheyun Peng, Wanqing Liu, Feng Li, Namratha Sheshadri, Wei-Xing Zong, Hong-Min Ni, Wen-Xing Ding.

OBJECTIVE: The aim of the study is to investigate the role and mechanisms of tuberous sclerosis complex 1 (TSC1) and mechanistic target of rapamycin complex 1 (mTORC1) in alcohol associated liver disease.
DESIGN: Liver-specific Tsc1 knockout (L-Tsc1 KO) mice and their matched wild type ( WT) mice were subjected to Gao-binge alcohol. Human alcoholic hepatitis (AH) samples were also used for immunohistochemical (IHC) staining, western blot and q-PCR analysis.
RESULTS: Human AH and Gao-binge alcohol-fed mice had decreased hepatic TSC1 and increased mTORC1 activation. Gao-binge alcohol markedly increased liver/body weight ratio and serum alanine aminotransferase (ALT) levels in L-Tsc1 KO mice compared to Gao-binge alcohol-fed WT mice. Results from IHC staining, western blot and q-PCR analysis revealed that human AH and Gao-binge alcohol-fed L-Tsc1 KO mouse livers significantly increased hepatic progenitor cells, macrophages and neutrophils but decreased HNF4α positive cells. Gao-binge alcohol-fed L-Tsc1 KO mice also developed severe inflammation and liver fibrosis. Deleting Tsc1 in cholangiocytes but not in hepatocytes promoted cholangiocyte proliferation and aggravated alcohol-induced ductular reactions (DR), fibrosis, inflammation and liver injury. Pharmacological inhibition of mTORC1 partially reversed hepatomegaly, DR, fibrosis, inflammatory cell infiltration and liver injury in alcohol-fed L-Tsc1 KO mice.
CONCLUSION: Our findings indicate that persistent activation of mTORC1 due to the loss of cholangiocyte TSC1 promotes hepatomegaly, liver cell repopulation, DR, inflammation, fibrosis and liver injury in Gao-binge alcohol fed L-Tsc1 KO mice, which phenocopy the pathogenesis of human AH.

DOI: https://doi.org/10.1097/HEP.0000000000000373
J Biol Chem. 2023 Mar 23. pii: S0021-9258(23)00286-7. [Epub ahead of print] 104644

An affinity tool for the isolation of endogenous active mTORC1 from various cellular sources.

Yasir H Ibrahim, Spyridon Pantelios, Anders P Mutvei.

The mechanistic target of rapamycin complex 1 (mTORC1) is a central regulator of mammalian cell growth that is dysregulated in a number of human diseases, including metabolic syndromes, aging and cancer. Structural, biochemical and pharmacological studies that have increased our understanding of how mTORC1 executes growth control often relied upon purified mTORC1 protein. However, current immunoaffinity-based purification methods are expensive, inefficient, and do not necessarily isolate endogenous mTORC1, hampering their overall utility in research. Here we present a simple tool to isolate endogenous mTORC1 from various cellular sources. By recombinantly expressing and isolating mTORC1-binding Rag GTPases from E. Coli and using them as affinity probes, we demonstrate that mTORC1 can be isolated from mouse, bovine and human sources. Our results indicate that mTORC1 isolated by this relatively inexpensive method is catalytically active and amenable to scaling. Collectively, this tool may be utilized to isolate mTORC1 from various cellular sources, organs, and disease contexts, aiding mTORC1-related research.

DOI: https://doi.org/10.1016/j.jbc.2023.104644
Cell Rep. 2023 Mar 29. pii: S2211-1247(23)00327-3. [Epub ahead of print]42(4): 112316

CDK5-PRMT1-WDR24 signaling cascade promotes mTORC1 signaling and tumor growth.

Shasha Yin, Liu Liu, Lauren E Ball, Yalong Wang, Mark T Bedford, Stephen A Duncan, Haizhen Wang, Wenjian Gan.

  The mammalian target of rapamycin complex1 (mTORC1) is a central regulator of metabolism and cell growth by sensing diverse environmental signals, including amino acids. The GATOR2 complex is a key component linking amino acid signals to mTORC1. Here, we identify protein arginine methyltransferase 1 (PRMT1) as a critical regulator of GATOR2. In response to amino acids, cyclin-dependent kinase 5 (CDK5) phosphorylates PRMT1 at S307 to promote PRMT1 translocation from nucleus to cytoplasm and lysosome, which in turn methylates WDR24, an essential component of GATOR2, to activate the mTORC1 pathway. Disruption of the CDK5-PRMT1-WDR24 axis suppresses hepatocellular carcinoma (HCC) cell proliferation and xenograft tumor growth. High PRMT1 protein expression is associated with elevated mTORC1 signaling in patients with HCC. Thus, our study dissects a phosphorylation- and arginine methylation-dependent regulatory mechanism of mTORC1 activation and tumor growth and provides a molecular basis to target this pathway for cancer therapy.

Keywords:  CDK5; CP: Cancer; CP: Molecular biology; GATOR2; HCC; PRMT1; WDR24; amino acids; arginine methylation; mTORC1

DOI:  https://doi.org/10.1016/j.celrep.2023.112316
Curr Mol Pharmacol. 2023 Mar 31.

Mammalian Target of Rapamycin (mTOR) Signalling Pathway a Potential Target for Cancer Intervention: a Short Overview.

Rajesh Basnet, Buddha Bahadur Basnet, Radheshyam Gupta, TilBahadur Basnet, Sandhya Khadka, Md Shan Alam.

   BACKGROUND: The mammalian role of the rapamycin (mTOR) pathway is the practical nutrient-sensitive regulation of animal growth and plays a central role in physiology, metabolism, and common diseases. The mTOR is activated in response to nutrients, growth factors, and cellular energy. The mTOR pathway activates in various cellular processes and human cancer diseases. Dysfunction of mTOR signal transduction is associated with metabolic disorders, cancer for instance.
OBJECTIVE: In recent years, significant achievements envisaged in developing targeted drugs for cancer. The global impact of cancer continues to grow. However, the focus of disease-modifying therapies remains elusive. The mTOR is a significant target in cancer to be considered for mTOR inhibitors, even though the costs are high. Despite many mTOR inhibitors, potent, selective inhibitors for mTOR are still limited. Therefore, in this review, the mTOR structure and protein-ligand interactions of utmost importance to provide the basis for molecular modelling and structure-based drug design are discussed.
CONCLUSION: This review introduces the mTOR, its crystal structure, and the latest research on mTOR.Besides, the role of mTOR in cancer, its function, and its regulation are reviewed. In addition, the mechanistic role of mTOR signalling networks in cancer and interaction with drugs that inhibit the development of mTOR and crystal structures of mTOR and its complexes are explored. Finally, the current status and prospects of mTOR-targeted therapy are addressed.

Keywords:  Cancer; Cell growth; Crystal structure; PIK3; mTOR; mTOR 2; mTOR1

DOI:  https://doi.org/10.2174/1874467217666230331081959
Int J Mol Sci. 2023 Mar 09. pii: 5276. [Epub ahead of print]24(6):

Kinase Inhibitors in Genetic Diseases.

Lucia D'Antona, Rosario Amato, Carolina Brescia, Valentina Rocca, Emma Colao, Rodolfo Iuliano, Bonnie L Blazer-Yost, Nicola Perrotti.

  Over the years, several studies have shown that kinase-regulated signaling pathways are involved in the development of rare genetic diseases. The study of the mechanisms underlying the onset of these diseases has opened a possible way for the development of targeted therapies using particular kinase inhibitors. Some of these are currently used to treat other diseases, such as cancer. This review aims to describe the possibilities of using kinase inhibitors in genetic pathologies such as tuberous sclerosis, RASopathies, and ciliopathies, describing the various pathways involved and the possible targets already identified or currently under study.

Keywords:  RAS pathway; Wnt pathway; genetics; kinase inhibitors; mTOR pathway

DOI:  https://doi.org/10.3390/ijms24065276
EMBO Mol Med. 2023 Mar 29. e16877

TFEB and TFE3 drive kidney cystogenesis and tumorigenesis.

Chiara Di Malta, Angela Zampelli, Letizia Granieri, Claudia Vilardo, Rossella De Cegli, Laura Cinque, Edoardo Nusco, Salvatore Pece, Daniela Tosoni, Francesca Sanguedolce, Nicolina Cristina Sorrentino, Maria J Merino, Deborah Nielsen, Ramaprasad Srinivasan, Mark W Ball, Christopher J Ricketts, Cathy D Vocke, Martin Lang, Baktiar Karim, Luisa Lanfrancone, Laura S Schmidt, W Marston Linehan, Andrea Ballabio.

  Birt-Hogg-Dubé (BHD) syndrome is an inherited familial cancer syndrome characterized by the development of cutaneous lesions, pulmonary cysts, renal tumors and cysts and caused by loss-of-function pathogenic variants in the gene encoding the tumor-suppressor protein folliculin (FLCN). FLCN acts as a negative regulator of TFEB and TFE3 transcription factors, master controllers of lysosomal biogenesis and autophagy, by enabling their phosphorylation by the mechanistic Target Of Rapamycin Complex 1 (mTORC1). We have previously shown that deletion of Tfeb rescued the renal cystic phenotype of kidney-specific Flcn KO mice. Using Flcn/Tfeb/Tfe3 double and triple KO mice, we now show that both Tfeb and Tfe3 contribute, in a differential and cooperative manner, to kidney cystogenesis. Remarkably, the analysis of BHD patient-derived tumor samples revealed increased activation of TFEB/TFE3-mediated transcriptional program and silencing either of the two genes rescued tumorigenesis in human BHD renal tumor cell line-derived xenografts (CDXs). Our findings demonstrate in disease-relevant models that both TFEB and TFE3 are key drivers of renal tumorigenesis and suggest novel therapeutic strategies based on the inhibition of these transcription factors.

Keywords:  BHD; TFE3; TFEB; cysts; kidney cancer

DOI:  https://doi.org/10.15252/emmm.202216877
FASEB J. 2023 May;37(5): e22897

A multi-organ analysis of the role of mTOR in fetal alcohol spectrum disorders.

Alexander L Carabulea, Joseph D Janeski, Vishal D Naik, Kang Chen, Gil Mor, Jayanth Ramadoss.

  Alcohol exposure during gestation can lead to fetal alcohol spectrum disorders (FASD), an array of cognitive and physical developmental impairments. Over the past two and a half decades, Mammalian Target of Rapamycin (mTOR) has emerged at the nexus of many fields of study, and has recently been implicated in FASD etiology. mTOR plays an integral role in modulating anabolic and catabolic activities, including protein synthesis and autophagy. These processes are vital for proper development and can have long lasting effects following alcohol exposure, such as impaired hippocampal and synapse formation, reduced brain size, as well as cognitive, behavioral, and memory impairments. We highlight recent advances in the field of FASD, primarily with regard to animal model discoveries and discuss the interaction between alcohol and mTOR in the context of various tissues, including brain, placenta, bone, and muscle, with respect to developmental alcohol exposure paradigms. The current review focuses on novel FASD research within the context of the mTOR signaling and sheds light on mechanistic etiologies at various biological levels including molecular, cellular, and functional, across multiple stages of development and illuminates the dichotomy between the different mTOR complexes and their unique signaling roles.

Keywords:  alcohol; autophagy; development; fetal; mTOR; pregnancy

DOI:  https://doi.org/10.1096/fj.202201865R