scholarly journals Pathological Consequences of Hepatic mTORC1 Dysregulation

Genes ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 896
Author(s):  
Chun-Seok Cho ◽  
Allison Ho Kowalsky ◽  
Jun Hee Lee
Keyword(s):  
Growth Factors ◽  
Liver Injury ◽  
Liver Function ◽  
Type Ii Diabetes ◽  
Liver Diseases ◽  
Mammalian Target Of Rapamycin ◽  
Type Ii ◽  
Hepatocellular Carcinogenesis ◽  
Stress Signals ◽  
Mtorc1 Activation

The mammalian target of rapamycin complex 1 (mTORC1) is a central regulator of metabolism that integrates environmental inputs, including nutrients, growth factors, and stress signals. mTORC1 activation upregulates anabolism of diverse macromolecules, such as proteins, lipids, and nucleic acids, while downregulating autolysosomal catabolism. mTORC1 dysregulation is often found in various diseases, including cancer, cardiovascular and neurodegenerative diseases, as well as metabolic syndromes involving obesity and type II diabetes. As an essential metabolic organ, the liver requires proper regulation of mTORC1 for maintaining homeostasis and preventing pathologies. For instance, aberrant hyper- or hypoactivation of mTORC1 disrupts hepatocellular homeostasis and damages the structural and functional integrity of the tissue, leading to prominent liver injury and the development of hepatocellular carcinogenesis. Proper regulation of mTORC1 during liver diseases may be beneficial for restoring liver function and ameliorating the detrimental consequences of liver failure.

Rheb and Rags come together at the lysosome to activate mTORC1

2013 ◽  
Vol 41 (4) ◽  
pp. 951-955 ◽  
Author(s):  
Marlous J. Groenewoud ◽  
Fried J.T. Zwartkruis
Keyword(s):  
Amino Acids ◽  
Growth Factors ◽  
Amino Acid ◽  
Cell Growth ◽  
Mammalian Target Of Rapamycin ◽  
Maturation Process ◽  
Phospholipase D1 ◽  
Strict Requirement ◽  
Mtorc1 Activation ◽  
Dependent Interaction

mTORC1 (mammalian target of rampamycin complex 1) is a highly conserved protein complex regulating cell growth and metabolism via its kinase mTOR (mammalian target of rapamycin). The activity of mTOR is under the control of various GTPases, of which Rheb and the Rags play a central role. The presence of amino acids is a strict requirement for mTORC1 activity. The heterodimeric Rag GTPases localize mTORC1 to lysosomes by their amino-acid-dependent interaction with the lysosomal Ragulator complex. Rheb is also thought to reside on lysosomes to activate mTORC1. Rheb is responsive to growth factors, but, in conjunction with PLD1 (phospholipase D1), is also an integral part of the machinery that stimulates mTORC1 in response to amino acids. In the present article, we provide a brief overview of novel mechanisms by which amino acids affect the function of Rags. On the basis of existing literature, we postulate that Rheb is activated at the Golgi from where it will travel to lysosomes. Maturation of endosomes into lysosomes may be required to assure a continuous supply of GTP-bound Rheb for mTORC1 activation, which may help to drive the maturation process.

scholarly journals Si-Wu-Tang ameliorates fibrotic liver injury via modulating intestinal microbiota and bile acid homeostasis

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Xiaoyong Xue ◽  
Jianzhi Wu ◽  
Mingning Ding ◽  
Feng Gao ◽  
Fei Zhou ◽  
...  
Keyword(s):  
Liver Injury ◽  
16S Rrna ◽  
Liver Function ◽  
Inflammatory Response ◽  
Intestinal Microbiota ◽  
Liver Diseases ◽  
Intestinal Barrier ◽  
Therapeutic Effects ◽  
Fibrotic Liver ◽  
Rrna Sequencing

Abstract Background Fibrotic liver injury is a progressive scarring event, which may permanently affect liver function and progress into devastating end-stage liver diseases due to the absence of effective therapies. Si-Wu-Tang (SWT), a traditional Chinese medicine formula used in clinic to treat gynecological disorders for centuries, has been investigated in recent preliminary findings for its role in alleviating chronic liver diseases. Here we aim to elucidate the therapeutic effects and possible mechanisms of SWT against fibrotic liver injury. Methods UHPLC-MS/MS was performed to investigate the chemical characterization of SWT. After intragastrically administered with carbon tetrachloride (CCl4) every 3 days for 1-week, C57BL/6 mice were orally administered with SWT (5.2, 10.4 and 20.8 g/kg) once daily for 3 weeks along with CCl4 challenge. Liver function was determined by the measurement of serum biomarkers, hematoxylin and eosin (H&E) and Masson’s trichrome staining. Intestinal inflammatory infiltration and the disruption of intestinal barrier were examined by H&E and E-cadherin immunohistochemical staining. The microbial composition of intestinal content was determined by 16S rRNA sequencing. Serum bile acids (BAs) profiling was analyzed by LC–MS/MS. Simultaneously, the expression of genes of interest was determined by qPCR and western blot. Results SWT exhibited remarkable therapeutic effects on CCl4-induced liver fibrosis, as indicated by improved collagen accumulation in livers, intestinal barrier injury and hepatic and intestinal inflammatory response. Results of 16S rRNA sequencing revealed that SWT treatment strikingly restructured intestinal microbiota in fibrotic mice by increasing the relative abundances of Bacteroides and Lachnoclostridium and decreasing the relative abundances of Alistipes and Rikenellaceae. UHPLC-MS/MS data suggested that SWT altered the composition of BAs in circulation as evidenced by increased unconjugated BAs like cholic acid and chenodeoxycholic acid but decreased conjugated BAs including taurocholic acid and taurodeoxycholic acid, compared to that in CCl4 mice. Notably, SWT efficiently improved the imbalance of BA homeostasis in livers caused by CCl4 via activating farnesoid X receptor (FXR)-fibroblast growth factor 15 enterohepatic and FXR-small heterodimer partner hepatic pathways. Conclusion SWT decreased inflammatory response, reconstructed gut microbiota-mediated BA homeostasis as well as activated FXR pathways, which eventually protected against CCl4-induced fibrotic liver injury.

scholarly journals Current Models of Mammalian Target of Rapamycin Complex 1 (mTORC1) Activation by Growth Factors and Amino Acids

2014 ◽  
Vol 15 (11) ◽  
pp. 20753-20769 ◽  
Author(s):  
Xu Zheng ◽  
Yan Liang ◽  
Qiburi He ◽  
Ruiyuan Yao ◽  
Wenlei Bao ◽  
...  
Keyword(s):  
Amino Acids ◽  
Growth Factors ◽  
Mammalian Target Of Rapamycin ◽  
Target Of Rapamycin ◽  
Mtorc1 Activation

scholarly journals Amino acid regulation of TOR complex 1

2009 ◽  
Vol 296 (4) ◽  
pp. E592-E602 ◽  
Author(s):  
Joseph Avruch ◽  
Xiaomeng Long ◽  
Sara Ortiz-Vega ◽  
Joseph Rapley ◽  
Angela Papageorgiou ◽  
...  
Keyword(s):  
Amino Acids ◽  
Growth Factors ◽  
Amino Acid ◽  
Mammalian Target Of Rapamycin ◽  
Inhibitory Effect ◽  
Energy Status ◽  
Phospholipase D1 ◽  
Direct Binding ◽  
Charged Form ◽  
Mtorc1 Activation

TOR complex 1 (TORC1), an oligomer of the mTOR (mammalian target of rapamycin) protein kinase, its substrate binding subunit raptor, and the polypeptide Lst8/GβL, controls cell growth in all eukaryotes in response to nutrient availability and in metazoans to insulin and growth factors, energy status, and stress conditions. This review focuses on the biochemical mechanisms that regulate mTORC1 kinase activity, with special emphasis on mTORC1 regulation by amino acids. The dominant positive regulator of mTORC1 is the GTP-charged form of the ras-like GTPase Rheb. Insulin, growth factors, and a variety of cellular stressors regulate mTORC1 by controlling Rheb GTP charging through modulating the activity of the tuberous sclerosis complex, the Rheb GTPase activating protein. In contrast, amino acids, especially leucine, regulate mTORC1 by controlling the ability of Rheb-GTP to activate mTORC1. Rheb binds directly to mTOR, an interaction that appears to be essential for mTORC1 activation. In addition, Rheb-GTP stimulates phospholipase D1 to generate phosphatidic acid, a positive effector of mTORC1 activation, and binds to the mTOR inhibitor FKBP38, to displace it from mTOR. The contribution of Rheb's regulation of PL-D1 and FKBP38 to mTORC1 activation, relative to Rheb's direct binding to mTOR, remains to be fully defined. The rag GTPases, functioning as obligatory heterodimers, are also required for amino acid regulation of mTORC1. As with amino acid deficiency, however, the inhibitory effect of rag depletion on mTORC1 can be overcome by Rheb overexpression, whereas Rheb depletion obviates rag's ability to activate mTORC1. The rag heterodimer interacts directly with mTORC1 and may direct mTORC1 to the Rheb-containing vesicular compartment in response to amino acid sufficiency, enabling Rheb-GTP activation of mTORC1. The type III phosphatidylinositol kinase also participates in amino acid-dependent mTORC1 activation, although the site of action of its product, 3′OH-phosphatidylinositol, in this process is unclear.

scholarly journals Pathophysiological Significance of Hepatic Apoptosis

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Kewei Wang ◽  
Bingliang Lin
Keyword(s):  
Liver Injury ◽  
Liver Function ◽  
Liver Diseases ◽  
Pathological Feature ◽  
Etiological Factors

Apoptosis is a classical pathological feature in liver diseases caused by various etiological factors such as drugs, viruses, alcohol, and cholestasis. Hepatic apoptosis and its deleterious effects exacerbate liver function as well as involvement in fibrosis/cirrhosis and carcinogenesis. An imbalance between apoptotic and antiapoptotic capabilities is a prominent characteristic of liver injury. The regulation of apoptosis and antiapoptosis can be a pivotal step in the treatment of liver diseases.

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