Nuclear mTOR Signaling Orchestrates Transcriptional Programs Underlying Cellular Growth and Metabolism.

mTOR is a central regulator of cell growth and metabolism in response to mitogenic and nutrient signals. Notably, mTOR is not only found in the cytoplasm but also in the nucleus. This review highlights direct involvement of nuclear mTOR in regulating transcription factors, orchestrating epigenetic modifications, and facilitating chromatin remodeling. These effects intricately modulate gene expression programs associated with growth and metabolic processes. Furthermore, the review underscores the importance of nuclear mTOR in mediating the interplay between metabolism and epigenetic modifications. By integrating its functions in nutrient signaling and gene expression related to growth and metabolism, nuclear mTOR emerges as a central hub governing cellular homeostasis, malignant transformation, and cancer progression. Better understanding of nuclear mTOR signaling has the potential to lead to novel therapies against cancer and other growth-related diseases.

[Mid-term outcome of deep layer repair with the long head of the biceps autograft bridging for Kim classification type â A delaminiated rotator cuff tear].

Objective: To investigate the mid-term clinical outcome of deep layer repair with the long head of the biceps autograft bridging for Kim classification type ⅠA delaminated rotator cuff tear. Methods: A follow-up study. The clinical data of 42 consecutive patients with Kim classification type ⅠA delaminated rotator cuff tear admitted to the First Affiliated Hospital of Jinan University from January 2018 to June 2019 were retrospectively included. All patients underwent shoulder arthroscopic surgery. During the operation, the autogenous long head of the biceps tendon was transferred to repair the deep layer of delaminated rotator cuff tear. The preoperative and postoperative (last follow-up) visual analogue scale (VAS) for pain, University of California Los Angeles (UCLA) score, Constant-Murley shoulder score, range of motion (ROM) of the shoulder and radiographic results were statistically analyzed. Results: A total of 42 patients were included in this study. There were 18 males and 24 females, with an average age of (64.5±15.2) years and a mean follow-up of (43.9±7.1) months. At the last follow-up, ROM of abduction increased from 80.8°±26.5° to 154.2°±14.3°, and ROM of external rotation increased from 18.2°±13.6° to 31.8°±7.8°; the VAS score of pain decreased from (5.5±1.3) points to (0.7±0.7) points, the UCLA score increased from (21.3±3.7) points to (29.9±2.1) points, and the Constant-Murley score increased from (45.4±10.0) points to (87.2±4.8) points; the differences were all statistically significant (all P<0.001). The X-ray films showed that there were no upward of the humeral head in all the patients. MRI results indicated that rotator cuff re-teared in one case (Sugaya classification type Ⅲ), and healed in other cases (Sugaya classification type Ⅰ-Ⅱ). No complications such as upper limb nerve injury was found in all cases. Conclusion: Deep layer repair with the long head of the biceps autograft bridging can significantly alleviate the pain and improve the function of patients with Kim classification type ⅠA delaminated rotator cuff tear, and the incidence of retear is low.

mTOR regulates aerobic glycolysis through NEAT1 and nuclear paraspeckle-mediated mechanism in hepatocellular carcinoma.

Background: Hepatocellular Carcinoma (HCC) is a major form of liver cancer and a leading cause of cancer-related death worldwide. New insights into HCC pathobiology and mechanism of drug actions are urgently needed to improve patient outcomes. HCC undergoes metabolic reprogramming of glucose metabolism from respiration to aerobic glycolysis, a phenomenon known as the 'Warburg Effect' that supports rapid cancer cell growth, survival, and invasion. mTOR is known to promote Warburg Effect, but the underlying mechanism(s) remains poorly defined. The aim of this study is to understand the mechanism(s) and significance of mTOR regulation of aerobic glycolysis in HCC. Methods: We profiled mTORC1-dependent long non-coding RNAs (lncRNAs) by RNA-seq of HCC cells treated with rapamycin. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays were used to explore the transcriptional regulation of NEAT1 by mTORC1. [U-13C]-glucose labeling and metabolomic analysis, extracellular acidification Rate (ECAR) by Seahorse XF Analyzer, and glucose uptake assay were used to investigate the role of mTOR-NEAT1-NONO signaling in the regulation of aerobic glycolysis. RNA immunoprecipitation (RIP) and NONO-binding motif scanning were performed to identify the regulatory mechanism of pre-mRNA splicing by mTOR-NEAT1. Myristoylated AKT1 (mAKT1)/NRASV12-driven HCC model developed by hydrodynamic transfection (HDT) was employed to explore the significance of mTOR-NEAT1 signaling in HCC tumorigenesis and mTOR-targeted therapy. Results: mTOR regulates lncRNA transcriptome in HCC and that NEAT1 is a major mTOR transcriptional target. Interestingly, although both NEAT1_1 and NEAT1_2 are down-regulated in HCC, only NEAT1_2 is significantly correlated with poor overall survival of HCC patients. NEAT1_2 is the organizer of nuclear paraspeckles that sequester the RNA-binding proteins NONO and SFPQ. We show that upon oncogenic activation, mTORC1 suppresses NEAT1_2 expression and paraspeckle biogenesis, liberating NONO/SFPQ, which in turn, binds to U5 within the spliceosome, stimulating mRNA splicing and expression of key glycolytic enzymes. This series of actions lead to enhanced glucose transport, aerobic glycolytic flux, lactate production, and HCC growth both in vitro and in vivo. Furthermore, the paraspeckle-mediated mechanism is important for the anticancer action of US FDA-approved drugs rapamycin/temsirolimus. Conclusions: These findings reveal a molecular mechanism by which mTOR promotes the 'Warburg Effect', which is important for the metabolism and development of HCC, and anticancer response of mTOR-targeted therapy.

Amino acids control blood glucose levels through mTOR signaling.

Amino Acids are not only major nutrient sources, but also serve as chemical signals to control cellular growth. Rab1A recently emerged as a key component in amino acid sensing and signaling to activate the mTOR complex1 (mTORC1). In a recently published study [1], we generated tamoxifen-inducible, conditional whole-body Rab1A knockout in adult mice. These mice are viable but develop hyperglycemia and glucose intolerance. Interestingly, Rab1A ablation selectively reduces insulin expression and pancreatic beta-cell population. Mechanistically, branched chain amino acids (BCAA), through the Rab1A-mTORC1 complex, promote the stability and nuclear localization of Pdx1, a master transcription factor that controls growth, function and identity of pancreatic beta-cells. These findings reveal a role and underlying mechanism by which amino acids control body's glucose level through a beta-cell specific function by the Rab1A-mTORC1-Pdx1 signaling axis, which has implications in both diabetes and cancer.

Nuclear SOD1 in Growth Control, Oxidative Stress Response, Amyotrophic Lateral Sclerosis, and Cancer.

SOD1 is the major superoxide dismutase responsible for catalyzing dismutation of superoxide to hydrogen peroxide and molecular oxygen. It is well known as an essential antioxidant enzyme for maintaining cellular redox homeostasis. SOD1 dysregulation has been associated with many diseases, including amyotrophic lateral sclerosis (ALS), cancer, accelerated aging, and age-related diseases. Recent studies also revealed that SOD1 can serve as a regulatory protein in cell signaling, transcription, and ribosome biogenesis. Notably, SOD1 is localized in the nucleus under both normal and pathological conditions, contributing to oxidative stress response and growth control. Moreover, increasing evidence points to the importance of nuclear SOD1 in the pathogenesis of ALS and cancer.

Phosphorylation of androgen receptor by mTORC1 promotes liver steatosis and tumorigenesis.

BACKGROUND AND AIMS: Androgen receptor (AR) has been reported to play an important role in the development and progression of man's prostate cancer. Hepatocellular carcinoma (HCC) is also male-dominant, but the role of AR in HCC remains poorly understood. Mechanistic target of rapamycin complex 1 (mTORC1) also has been reported to be highly activated in HCC. In this study, we aimed to explore the role of AR phosphorylation and its relationship with mTORC1 in hepatocarcinogenesis. APPROACH AND RESULTS: In vitro experiment, we observed that mTORC1 interacts with hepatic AR and phosphorylates it at S96 in response to nutrient and mitogenic stimuli in HCC cells. S96 phosphorylation promotes the stability, nuclear localization, and transcriptional activity of AR, which enhances de novo lipogenesis and proliferation in hepatocytes and induces liver steatosis and hepatocarcinogenesis in mice independently and cooperatively with androgen. Furthermore, high ARS96 phosphorylation is observed in human liver steatotic and HCC tissues and is associated with overall survival and disease-free survival, which has been proven as an independent survival predictor for patients with HCC. CONCLUSIONS: AR S96 phosphorylation by mTORC1 drives liver steatosis and HCC development and progression independently and cooperatively with androgen, which not only explains why HCC is man-biased but also provides a target molecule for prevention and treatment of HCC and a potential survival predictor in patients with HCC.

mTORC1 Promotes ARID1A Degradation and Oncogenic Chromatin Remodeling in Hepatocellular Carcinoma.

The SWI/SNF chromatin remodeling complexes control accessibility of chromatin to transcriptional and coregulatory machineries. Chromatin remodeling plays important roles in normal physiology and diseases, particularly cancer. The ARID1A-containing SWI/SNF complex is commonly mutated and thought to be a key tumor suppressor in hepatocellular carcinoma (HCC), but its regulation in response to oncogenic signals remains poorly understood. mTOR is a conserved central controller of cell growth and an oncogenic driver of HCC. Remarkably, cancer mutations in mTOR and SWI/SNF complex are mutually exclusive in human HCC tumors, suggesting that they share a common oncogenic function. Here, we report that mTOR complex 1 (mTORC1) interact with ARID1A and regulates ubiquitination and proteasomal degradation of ARID1A protein. The mTORC1-ARID1A axis promoted oncogenic chromatin remodeling and YAP-dependent transcription, thereby enhancing liver cancer cell growth in vitro and tumor development in vivo. Conversely, excessive ARID1A expression counteracted AKT-driven liver tumorigenesis in vivo. Moreover, dysregulation of this axis conferred resistance to mTOR-targeted therapies. These findings demonstrate that the ARID1A-SWI/SNF complex is a regulatory target for oncogenic mTOR signaling, which is important for mTORC1-driven hepatocarcinogenesis, with implications for therapeutic interventions in HCC. SIGNIFICANCE: mTOR promotes oncogenic chromatin remodeling by controlling ARID1A degradation, which is important for liver tumorigenesis and response to mTOR- and YAP-targeted therapies in hepatocellular carcinoma.See related commentary by Pease and Fernandez-Zapico, p. 5608.

SOD1 regulates ribosome biogenesis in KRAS mutant non-small cell lung cancer.

SOD1 is known as the major cytoplasmic superoxide dismutase and an anticancer target. However, the role of SOD1 in cancer is not fully understood. Herein we describe the generation of an inducible Sod1 knockout in KRAS-driven NSCLC mouse model. Sod1 knockout markedly reduces tumor burden in vivo and blocks growth of KRAS mutant NSCLC cells in vitro. Intriguingly, SOD1 is enriched in the nucleus and notably in the nucleolus of NSCLC cells. The nuclear and nucleolar, not cytoplasmic, form of SOD1 is essential for lung cancer cell proliferation. Moreover, SOD1 interacts with PeBoW complex and controls its assembly necessary for pre-60S ribosomal subunit maturation. Mechanistically, SOD1 regulates co-localization of PeBoW with and processing of pre-rRNA, and maturation of cytoplasmic 60S ribosomal subunits in KRAS mutant lung cancer cells. Collectively, our study unravels a nuclear SOD1 function essential for ribosome biogenesis and proliferation in KRAS-driven lung cancer.

Amino acids-Rab1A-mTORC1 signaling controls whole-body glucose homeostasis.

Rab1A is a small GTPase known for its role in vesicular trafficking. Recent evidence indicates that Rab1A is essential for amino acids (aas) sensing and signaling to regulate mTORC1 in normal and cancer cells. However, Rab1A's in vivo function in mammals is not known. Here, we report the generation of tamoxifen (TAM)-induced whole body Rab1A knockout (Rab1A-/-) in adult mice. Rab1A-/- mice are viable but become hyperglycemic and glucose intolerant due to impaired insulin transcription and ß-cell proliferation and maintenance. Mechanistically, Rab1A mediates AA-mTORC1 signaling, particularly branched chain amino acids (BCAA), to regulate the stability and localization of the insulin transcription factor Pdx1. Collectively, these results reveal a physiological role of aa-Rab1A-mTORC1 signaling in the control of whole-body glucose homeostasis in mammals. Intriguingly, Rab1A expression is reduced in ß-cells of type 2 diabetes (T2D) patients, which is correlated with loss of insulin expression, suggesting that Rab1A downregulation contributes to T2D progression.

Toward improving androgen receptor-targeted therapies in male-dominant hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the predominant form of liver cancer and a leading cause of cancer deaths worldwide. HCC is a male-dominant cancer with a male:female ratio of up to 7:1. The androgen receptor (AR) is the male hormone receptor known as a major oncogenic driver of prostate cancer. Although AR has been linked to the sexual dimorphism of HCC, clinical trials with AR-targeted agents failed to generate survival benefits. Recent studies provide new insights into the role of AR in liver tumorigenesis and therapeutic responses. Herein, we review current understanding of AR signaling in HCC and feedback mechanisms that limit response to AR blockade. New AR-targeting strategies that might improve outcomes in HCC therapies are also discussed.

TGFß1I1 suppressed cell migration and invasion in colorectal cancer by inhibiting the TGF-ß pathway and EMT progress.

OBJECTIVE: Colorectal cancer (CRC) is the fourth leading cause of death worldwide and there is a need for more specific therapeutic targets and biomarkers for the disease. Transforming growth factor ß1-induced transcript 1 (TGFΒ1I1) was reported to be downregulated in CRC tissues; however, the precise roles of TGFΒ1I1 in CRC remain unclear. PATIENTS AND METHODS: The expression of TGFΒ1I1 in CRC cell lines and tissues was assessed by quantitative Polymerase Chain Reaction (qPCR). TGFΒ1I1 was overexpressed in SW620 and RKO cells. Cell viability was analyzed by a CCK-8 assay. The proportion of apoptotic cells was analyzed by flow cytometry. The EdU cell proliferation assay of SW620 and RKO cells after transfection was performed via flow cytometry. The migration potency of SW620 and RKO cells was analyzed using a cell migration assay. A wound healing assay was performed to assess the migration potency of SW620 and RKO cells. The invasion potency of SW620 and RKO cells after TGFΒ1I1 overexpression was analyzed. The protein levels of VEGF, TGF-ß, MMP9, p-Smad2/3, N-cadherin, and E-cadherin were analyzed by Western blot. RESULTS: Decreased expression of TGFΒ1I1 was found in CRC tissues and cell lines. Overexpression of TGFΒ1I1 inhibited the proliferation and induced the apoptosis of CRC cells. The overexpression of TGFΒ1I1 inhibited the migration and invasion of CRC cells. We also found that the overexpression of TGFΒ1I1 in CRC cells inhibited the TGF-ß pathway and epithelial-mesenchymal transition (EMT) progress. CONCLUSIONS: TGFΒ1I1 suppressed cell migration and invasion in CRC by inhibiting the TGF-ß pathway and EMT progress.

[Establishment and clinical testing of pancreatic cancer Faster R-CNN AI system based on fast regional convolutional neural network].

Objective: To investigate the effectiveness of an enhanced CT automatic recognition system based on Faster R-CNN for pancreatic cancer and its clinical value. Methods: In this study, 4 024 enhanced CT imaging sequences of 315 patients with pancreatic cancer from January 2013 to May 2016 at the Affiliated Hospital of Qingdao University were collected retrospectively, and 2 614 imaging sequences were input into the faster R-CNN system as training dataset to create an automatic image recognition model, which was then validated by reading 1 410 enhanced CT images of 135 cases of pancreatic cancer.In order to identify its effectiveness, 3 750 CT images of 150 patients with pancreatic lesions were read and a followed-up was carried out.The accuracy and recall rate in detecting nodules were recorded and regression curves were generated.In addition, the accuracy, sensitivity and specificity of Faster R-CNN diagnosis were analyzed, the ROC curves were generated and the area under the curves were calculated. Results: Based on the enhanced CT images of 135 cases, the area under the ROC curve was 0.927 calculated by Faster R-CNN. The accuracy, specificity and sensitivity were 0.902, 0.913 and 0.801 respectively.After the data of 150 patients with pancreatic cancer were verified, 893 CT images showed positive and 2 857 negative.Ninety-eight patients with pancreatic cancer were diagnosed by Faster R-CNN.After the follow-up, it was found that 53 cases were post-operatively proved to be pancreatic ductal carcinoma, 21 cases of pancreatic cystadenocarcinoma, 12 cases of pancreatic cystadenoma, 5 cases of pancreatic cyst, and 7 cases were untreated.During 5 to 17 months after operation, 6 patients died of abdominal tumor infiltration, liver and lung metastasis.Of the 52 patients who were diagnosed negative by Faster R-CNN, 9 were post-operatively proved to be pancreatic ductal carcinoma. Conclusion: Faster R-CNN system has clinical value in helping imaging physicians to diagnose pancreatic cancer.

[Application of convolutional neural network to risk evaluation of positive circumferential resection margin of rectal cancer by magnetic resonance imaging].

Objective: To explore the feasibility of using faster regional convolutional neural network (Faster R-CNN) to evaluate the status of circumferential resection margin (CRM) of rectal cancer in the magnetic resonance imaging (MRI). Methods: This study was registered in the Chinese Clinical Trial Registry (ChiCTR-1800017410). Case inclusion criteria: (1) the positive area of CRM was located between the plane of the levator ani, anal canal and peritoneal reflection; (2) rectal malignancy was confirmed by electronic colonoscopy and histopathological examination; (3) positive CRM was confirmed by postoperative pathology or preoperative high-resolution MRI. Exclusion criteria: patients after neoadjuvant therapy, recurrent cancer after surgery, poor quality images, giant tumor with extensive necrosis and tissue degeneration, and rectal tissue construction changes in previous pelvic surgery. According to the above criteria, MRI plain scan images of 350 patients with rectal cancer and positive CRM in The Affiliated Hospital of Qingdao University from July 2016 to June 2019 were collected. The patients were classified by gender and tumor position, and randomly assigned to the training group (300 cases) and the validation group (50 cases) at a ratio of 6:1 by computer random number method. The CRM positive region was identified on the T2WI image using the LabelImg software. The identified training group images were used to iteratively train and optimize parameters of the Faster R-CNN model until the network converged to obtain the best deep learning model. The test set data were used to evaluate the recognition performance of the artificial intelligence platform. The selected indicators included accuracy, sensitivity, positive predictive value, receiver operating characteristic (ROC) curves, areas under the ROC curves (AUC), and the time taken to identify a single image. Results: The accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of the CRM status determined by the trained Faster R-CNN artificial intelligence approach were 0.884, 0.857, 0.898, 0.807, and 0.926, respectively; the AUC was 0.934 (95% CI: 91.3% to 95.4%). The Faster R-CNN model's automatic recognition time for a single image was 0.2 s. Conclusion: The artificial intelligence model based on Faster R-CNN for the identification and segmentation of CRM-positive MRI images of rectal cancer is established, which can complete the risk assessment of CRM-positive areas caused by in-situ tumor invasion and has the application value of preliminary screening.

Research on the correlation of changes in plasma lncRNA MEG3 with change in inflammatory factors and prognosis in patients with traumatic brain injury.

OBJECTIVE: To study the correlation between the plasma long non-coding RNA (lncRNA) maternally expressed gene 3 (MEG3) and the levels of inflammatory cytokines in patients with traumatic brain injury (TBI) and to evaluate its prognosis to screen new biological targets for the diagnosis and treatment of TBI. PATIENTS AND METHODS: 40 patients with TBI (TBI group) and 40 healthy people (control group) were collected and venous blood was drawn. The plasma MEG3 in subjects was quantitatively analyzed via quantitative Polymerase Chain Reaction (qPCR). Moreover, the levels of inflammatory cytokines [tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), IL-6, and IL-8] in plasma in each group were detected via enzyme-linked immunosorbent assay (ELISA). Finally, the correlation analysis was performed for the MEG3 expression level and inflammatory cytokine levels in patients with TBI. Patients were divided into high-expression MEG3 group and low-expression MEG3 group, high-level inflammatory cytokine group and low-level inflammatory cytokine group according to the median, followed by prognosis evaluation. The MEG3 expression level in TBI group was significantly decreased compared to that in control group, and the levels of inflammatory cytokines in plasma, including TNF-α, IL-1ß, IL-6, and IL-8, were significantly higher than in control group. RESULTS: The results of the correlation analysis showed that the expression level of plasma MEG3 had a significantly negative correlation with the level of each inflammatory cytokine. The prognostic analysis revealed that the prognosis of patients with high MEG3 expression level and low inflammatory cytokine levels was good, while it was poor in patients with low MEG3 expression level and high inflammatory cytokine levels; the difference was significant. In patients with TBI, the expression level of plasma MEG3 is decreased, while the inflammatory cytokine levels are increased, and there is a significantly negative correlation between the two items. CONCLUSIONS: The prognosis of patients with high MEG3 expression level and low inflammatory cytokine levels is good so MEG3 and inflammatory cytokines can be used as biomarkers for diagnosis and treatment of TBI, improving the prognosis of patients.

A balancing act: mTOR integrates nutrient signals to regulate redox-dependent growth and survival through SOD1.

Maintaining cellular redox is critical for growth, metabolism and survival in response to changing environments. How nutrients regulate this process is a long-standing fundamental question in cell biology. Our recent study revealed a conserved mechanism by which eukaryotes, particularly cancer cells, couple nutrient signaling to dynamically regulate redox homeostasis. Abbreviations: ATP: adenosine triphosphate; Ala: alanine; C6H12O6: glucose; OH-: hydroxyl radical; Glu: glutamate; mRNA: messenger RNA; mTOR: mechanistic/mammalian target of rapamycin; OXYPHOS: oxidative phosphorylation; Ser: serine; ROS: reactive oxygen species; O2 -: superoxide; SOD1: superoxide dismutase 1; Thr: threonine.

Sorafenib and Carfilzomib Synergistically Inhibit the Proliferation, Survival, and Metastasis of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is one of the most common and deadly human cancers. The 5-year survival rate is very low. Unfortunately, there are few efficacious therapeutic options. Until recently, Sorafenib has been the only available systemic drug for advanced HCC. However, it has very limited survival benefits, and new therapies are urgently needed. In this study, we investigated the anti-HCC activity of carfilzomib, a second-generation, irreversible proteasome inhibitor, as a single agent and in combination with sorafenib. In vitro, we found that carfilzomib has moderate anticancer activity toward liver cancer cells, but strongly enhances the ability of sorafenib to suppress HCC cell growth, proliferation, migration, invasion, and survival. Remarkably, the drug combination exhibits even more potent antitumor activity when tested in animal tumor models. Mechanistically, the combined treatment activates caspase-dependent and endoplasmic reticulum stress/CHOP-mediated apoptotic pathways, and suppresses epithelial-mesenchymal transition. In conclusion, our results demonstrate that the combination of carfilzomib and sorafenib has synergistic antitumor activities against HCC, providing a potential therapeutic strategy to improve the mortality and morbidity of HCC patients.

MicroRNA­342­3p suppresses proliferation and invasion of nasopharyngeal carcinoma cells by directly targeting Cdc42.

Deregulated microRNAs play an important role in the development and progression of various types of cancer. In our previous study, we observed that microRNA­342­3p (miR­342­3p) was one of the most markedly downregulated microRNAs in two nasopharyngeal carcinoma (NPC) cell lines compared to non­neoplastic cells by using whole genome small RNA sequencing. In the present study, we confirmed that the expression of miR­342­3p was significantly reduced in NPC tissues compared with normal nasopharyngeal epithelial tissues. Overexpression of miR­342­3p inhibited proliferation, epithelial­mesenchymal transition (EMT), migration and invasiveness of NPC cells. In addition, we observed that Cdc42, a Rho GTPase family member involved in cell proliferation and metastasis, is a direct target of miR­342­3p. Additionally, ML141, a small­molecule inhibitor of Cdc42, efficiently suppressed the invasion of NPC cells compared with the control cells. Finally, we analyzed NPC tissues derived from 10 NPC patients and subjected them to quantitative RT­PCR and immunohistochemistry assays for concomitant determination of the expression levels of miR­342­3p and Cdc42. Our results revealed that miR­342­3p levels were significantly inversely correlated with the protein levels of its target Cdc42. The results of the present study indicated that miR­342­3p inhibited NPC tumor growth and invasion by directly targeting the Cdc42 pathway.

SOD1 Phosphorylation by mTORC1 Couples Nutrient Sensing and Redox Regulation.

Nutrients are not only organic compounds fueling bioenergetics and biosynthesis, but also key chemical signals controlling growth and metabolism. Nutrients enormously impact the production of reactive oxygen species (ROS), which play essential roles in normal physiology and diseases. How nutrient signaling is integrated with redox regulation is an interesting, but not fully understood, question. Herein, we report that superoxide dismutase 1 (SOD1) is a conserved component of the mechanistic target of rapamycin complex 1 (mTORC1) nutrient signaling. mTORC1 regulates SOD1 activity through reversible phosphorylation at S39 in yeast and T40 in humans in response to nutrients, which moderates ROS level and prevents oxidative DNA damage. We further show that SOD1 activation enhances cancer cell survival and tumor formation in the ischemic tumor microenvironment and protects against the chemotherapeutic agent cisplatin. Collectively, these findings identify a conserved mechanism by which eukaryotes dynamically regulate redox homeostasis in response to changing nutrient conditions.

Beyond regulation of pol III: Role of MAF1 in growth, metabolism, aging and cancer.

MAF1 was discovered as a master repressor of Pol III-dependent transcription in response to diverse extracellular signals, including growth factor, nutrient and stress. It is regulated through posttranslational mechanisms such as phosphorylation. A prominent upstream regulator of MAF1 is the mechanistic target of rapamycin (mTOR) pathway. mTOR kinase directly phosphorylates MAF1, controlling its localization and transcriptional activity. In mammals, MAF1 has also been shown to regulate Pol I- and Pol II-dependent transcription. Interestingly, MAF1 modulates Pol II activity both as a repressor and activator, depending on specific target genes, to impact on cellular growth and metabolism. While MAF1 represses genes such as TATA-binding protein (TBP) and fatty acid synthase (FASN), it activates the expression of PTEN, a major tumor suppressor and an inhibitor of the mTOR signaling. Increasing evidence indicates that MAF1 plays an important role in different aspects of normal physiology, lifespan and oncogenesis. Here we will review the current knowledge on MAF1 in growth, metabolism, aging and cancer. This article is part of a Special Issue entitled: SI: Regulation of tRNA synthesis and modification in physiological conditions and disease edited by Dr. Boguta Magdalena.