TSC2 integrates Wnt and energy signals via a coordinated phosphorylation by AMPK and GSK3 to regulate cell growth

Brain insulin resistance linked Alzheimer's and Parkinson's disease pathology: An undying implication of epigenetic and autophagy modulation

In metabolic syndrome, dysregulated signalling activity of the insulin receptor pathway in the brain due to persistent insulin resistance (IR) condition in the periphery may lead to brain IR (BIR) development. BIR causes an upsurge in the activity of glycogen synthase kinase-3 beta, increased amyloid beta (Aβ) accumulation, hyperphosphorylation of tau, aggravated formation of Aβ oligomers and simultaneously neurofibrillary tangle formation, all of which are believed to be direct contributors in Alzheimer's Disease (AD) pathology. Likewise, for Parkinson's Disease (PD), BIR is associated with alpha-synuclein alterations, dopamine loss in brain areas which ultimately succumbs towards the appearance of classical motor symptoms corresponding to the typical PD phenotype. Modulation of the autophagy process for clearing misfolded proteins and alteration in histone proteins to alleviate disease progression in BIR-linked AD and PD have recently evolved as a research hotspot, as the majority of the autophagy-related proteins are believed to be regulated by histone posttranslational modifications. Hence, this review will provide a timely update on the possible mechanism(s) converging towards BIR induce AD and PD. Further, emphasis on the potential epigenetic regulation of autophagy that can be effectively targeted for devising a complete therapeutic cure for BIR-induced AD and PD will also be reviewed.

Ehrlichia effector SLiM-icry: Artifice of cellular subversion

As an obligately intracellular bacterial pathogen that selectively infects the mononuclear phagocyte, Ehrlichia chaffeensis has evolved sophisticated mechanisms to subvert innate immune defenses. While the bacterium accomplishes this through a variety of mechanisms, a rapidly expanding body of evidence has revealed that E. chaffeensis has evolved survival strategies that are directed by the versatile, intrinsically disordered, 120 kDa tandem repeat protein (TRP120) effector. E. chaffeensis establishes infection by manipulating multiple evolutionarily conserved cellular signaling pathways through effector-host interactions to subvert innate immune defenses. TRP120 activates these pathways using multiple functionally distinct, repetitive, eukaryote-mimicking short linear motifs (SLiMs) located within the tandem repeat domain that have evolved in nihilo. Functionally, the best characterized TRP120 SLiMs mimic eukaryotic ligands (SLiM-icry) to engage pathway-specific host receptors and activate cellular signaling, thereby repurposing these pathways to promote infection. Moreover, E. chaffeensis TRP120 contains SLiMs that are targets of post-translational modifications such as SUMOylation in addition to many other validated SLiMs that are curated in the eukaryotic linear motif (ELM) database. This review will explore the extracellular and intracellular roles TRP120 SLiM-icry plays during infection - mediated through a variety of SLiMs - that enable E. chaffeensis to subvert mononuclear phagocyte innate defenses.

The Metabolic Features of Osteoblasts: Implications for Multiple Myeloma (MM) Bone Disease

The study of osteoblast (OB) metabolism has recently received increased attention due to the considerable amount of energy used during the bone remodeling process. In addition to glucose, the main nutrient for the osteoblast lineages, recent data highlight the importance of amino acid and fatty acid metabolism in providing the fuel necessary for the proper functioning of OBs. Among the amino acids, it has been reported that OBs are largely dependent on glutamine (Gln) for their differentiation and activity. In this review, we describe the main metabolic pathways governing OBs' fate and functions, both in physiological and pathological malignant conditions. In particular, we focus on multiple myeloma (MM) bone disease, which is characterized by a severe imbalance in OB differentiation due to the presence of malignant plasma cells into the bone microenvironment. Here, we describe the most important metabolic alterations involved in the inhibition of OB formation and activity in MM patients.

Trans-gnetin H isolated from the seeds of Paeonia species induces autophagy via inhibiting mTORC1 signalling through AMPK activation

Paeonia is a well-known species of ornamental plants, traditional Chinese medicines, and emerging oilseed crops. Apart from nutritional unsaturated fatty acids, the seeds of peonies are rich in stilbenes characterized by their wide-ranging health-promoting properties. Although the typical stilbene resveratrol has been widely reported for its multiple bioactivities, it remains uncertain whether the trimer of resveratrol trans-gnetin H has properties that regulate cancer cell viability, let alone the underlying mechanism. Autophagy regulated by trans-gnetin H was detected by western blotting, immunofluorescence, and quantitative real-time PCR. The effects of trans-gnetin H on apoptosis and proliferation were examined by flow cytometry, colony formation and Cell Counting Kit-8 assays. Trans-gnetin H significantly inhibits cancer cell viability through autophagy by suppressing the phosphorylation of TFEB and promoting its nuclear transport. Mechanistically, trans-gnetin H inhibits the activation and lysosome translocation of mTORC1 by inhibiting the activation of AMPK, indicating that AMPK is a checkpoint for mTORC1 inactivation induced by trans-gnetin H. Moreover, the binding of TSC2 to Rheb was markedly increased in response to trans-gnetin H stimulation. Similarly, trans-gnetin H inhibited the interaction between Raptor and RagC in an AMPK-dependent manner. More importantly, trans-gnetin H-mediated autophagy highly depends on the AMPK-mTORC1 axis. We propose a regulatory mechanism by which trans-gnetin H inhibits the activation of the mTORC1 pathway to control cell autophagy.

Dissection of the autophagic route in oocytes from atretic follicles

BACKGROUND INFORMATION

Autophagy is a conserved process that functions as a cytoprotective mechanism; it may function as a cell death process called programmed cell death type II. There is considerable evidence for the presence of autophagic cell death during oocyte elimination in prepubertal rats. However, the mechanisms involved in this process have not been deciphered.

RESULTS

Our observations revealed autophagic cell death in oocytes with increased labeling of the autophagic proteins Beclin 1, light chain 3 A (LC3 A), and lysosomal-associated membrane protein 1 (Lamp1). Furthermore, mTOR and phosphorylated (p)-mTOR (S2448) proteins were significantly decreased in oocytes with increased levels of autophagic proteins, indicating autophagic activation. Moreover, phosphorylated protein kinase B (p-AKT) was not expressed by oocytes, but mitogen-activated protein kinase/extracellular signalregulated kinase (MAPK/ERK) signaling was observed. Additionally, selective and elevated mitochondrial degradation was identified in altered oocytes.

CONCLUSIONS

All these results suggest that mTOR downregulation, which promotes autophagy, could be mediated by low energy levels and sustained starvation involving the phosphoinositide 3-kinase (PI3K)/AKT/mTOR and MAPK/ERK pathways.

SIGNIFICANCE

In this work, we analyzed the manner in which autophagy is carried out in oocytes undergoing autophagic cell death by studying the behavior of proteins involved in different steps of the autophagic pathway.

TSC2 regulates tumor susceptibility to TRAIL-mediated T-cell killing by orchestrating mTOR signaling

Resistance to cancer immunotherapy continues to impair common clinical benefit. Here, we use whole-genome CRISPR-Cas9 knockout data to uncover an important role for Tuberous Sclerosis Complex 2 (TSC2) in determining tumor susceptibility to cytotoxic T lymphocyte (CTL) killing in human melanoma cells. TSC2-depleted tumor cells had disrupted mTOR regulation following CTL attack, which was associated with enhanced cell death. Wild-type tumor cells adapted to CTL attack by shifting their mTOR signaling balance toward increased mTORC2 activity, circumventing apoptosis, and necroptosis. TSC2 ablation strongly augmented tumor cell sensitivity to CTL attack in vitro and in vivo, suggesting one of its functions is to critically protect tumor cells. Mechanistically, TSC2 inactivation caused elevation of TRAIL receptor expression, cooperating with mTORC1-S6 signaling to induce tumor cell death. Clinically, we found a negative correlation between TSC2 expression and TRAIL signaling in TCGA patient cohorts. Moreover, a lower TSC2 immune response signature was observed in melanomas from patients responding to immune checkpoint blockade. Our study uncovers a pivotal role for TSC2 in the cancer immune response by governing crosstalk between TSC2-mTOR and TRAIL signaling, aiding future therapeutic exploration of this pathway in immuno-oncology.

The homeostatic regulation of ribosome biogenesis

The continued integrity of biological systems depends on a balance between interdependent elements at the molecular, cellular, and organismal levels. This is particularly true for the generation of ribosomes, which influence almost every aspect of cell and organismal biology. Ribosome biogenesis (RiBi) is an energetically demanding process that involves all three RNA polymerases, numerous RNA processing factors, chaperones, and the coordinated expression of 79-80 ribosomal proteins (r-proteins). Work over the last several decades has revealed that the dynamic regulation of ribosome production represents a major mechanism by which cells maintain homeostasis in response to changing environmental conditions and acute stress. More recent studies suggest that cells and tissues within multicellular organisms exhibit dramatically different levels of ribosome production and protein synthesis, marked by the differential expression of RiBi factors. Thus, distinct bottlenecks in the RiBi process, downstream of rRNA transcription, may exist within different cell populations of multicellular organisms during development and in adulthood. This review will focus on our current understanding of the mechanisms that link the complex molecular process of ribosome biogenesis with cellular and organismal physiology. We will discuss diverse topics including how different steps in the RiBi process are coordinated with one another, how MYC and mTOR impact RiBi, and how RiBi levels change between stem cells and their differentiated progeny. In turn, we will also review how regulated changes in ribosome production itself can feedback to influence cell fate and function.

New Insights into the Regulation of mTOR Signaling via Ca2+-Binding Proteins

Environmental factors are important regulators of cell growth and proliferation. Mechanistic target of rapamycin (mTOR) is a central kinase that maintains cellular homeostasis in response to a variety of extracellular and intracellular inputs. Dysregulation of mTOR signaling is associated with many diseases, including diabetes and cancer. Calcium ion (Ca²⁺) is important as a second messenger in various biological processes, and its intracellular concentration is tightly regulated. Although the involvement of Ca²⁺ mobilization in mTOR signaling has been reported, the detailed molecular mechanisms by which mTOR signaling is regulated are not fully understood. The link between Ca²⁺ homeostasis and mTOR activation in pathological hypertrophy has heightened the importance in understanding Ca²⁺-regulated mTOR signaling as a key mechanism of mTOR regulation. In this review, we introduce recent findings on the molecular mechanisms of regulation of mTOR signaling by Ca²⁺-binding proteins, particularly calmodulin (CaM).

Lymphangioleiomyomatosis: a metastatic lung disease

Lymphangioleiomyomatosis (LAM) is a rare disease affecting women, caused by somatic mutations in the TSC1 or TSC2 genes, and driven by estrogen. Similar to many cancers, it is metastatic, primarily to the lung. Despite its monogenetic nature, like many cancers, LAM is a heterogeneous disease. The cellular constituents of LAM are very diverse, including mesenchymal, epithelial, endothelial, and immune cells. LAM is characterized by dysregulation of many cell signaling pathways, distinct populations of LAM cells, and a rich microenvironment, in which the immune system appears to play an important role. This review delineates the heterogeneity of LAM and focuses on the metastatic features of LAM, the deregulated signaling mechanisms and the tumor microenvironment. Understanding the tumor-host interaction in LAM may provide insights into the development of new therapeutic strategies, which could be combinatorial or superlative to Sirolimus, the current U.S. Food and Drug Administration-approved treatment.

Mitochondrial respiration inhibitor enhances the anti-tumor effect of high-dose ascorbic acid in castration-resistant prostate cancer

Previous evidences have demonstrated that anti-tumor effect of high-dose ascorbic acid is associated with the generation of reactive oxygen species (ROS) via autoxidation. Hypoxia induces therapy resistance in castration-resistant prostate cancer. As a mitochondrial respiration inhibitor, metformin has the potential to improve tumor oxygenation. In this study, we evaluate the anti-tumor effect of ascorbic acid combined with metformin in prostate cancer. We demonstrated that ascorbic acid inhibits prostate cancer cells proliferation by generating ROS, and metformin enhances the anti-tumor effects of ascorbic acid. Mechanistically, metformin reduces oxygen consumption rate and NADP+/NADPH value in prostate cancer cells, thereby increases the ROS content induced by ascorbic acid. In addition, our data demonstrated that ascorbic acid inhibits p-AKT signaling in a ROS-dependent pathway, leading to inhibition of p-mTOR expression. And metformin inhibits the p-mTOR expression by activating the AMPK signaling pathway, exerting a synergistic effect on tumor suppression with ascorbic acid. Furthermore, metformin improves tumor oxygenation, and the combined treatment effect of ascorbic acid and metformin were demonstrated in a xenograft model of prostate cancer. Taken together, our data demonstrate that metformin enhances the anti-tumor proliferation effect of ascorbic acid by increasing ROS content in castration-resistant prostate cancer. This provides a new strategy for the clinical application of high-dose ascorbic acid as an anti-tumor drug. KEY MESSAGES: Ascorbic acid inhibits tumor growth by inducing ROS generation. As a mitochondrial respiration inhibitor, metformin inhibits cellular oxygen consumption rate to improve oxygenation of prostate cancer. Metformin enhances anti-tumor effect of ascorbic acid by increasing ROS content. Ascorbic acid inhibits the mTOR expression via PI3K-AKT pathway, and metformin inhibits the mTOR expression by inhibiting AMPK signaling in prostate cancer cells.

Primary cilia are WNT-transducing organelles whose biogenesis is controlled by a WNT-PP1 axis

WNT signaling is important in development, stem cell maintenance, and disease. WNT ligands typically signal via receptor activation across the plasma membrane to induce β-catenin-dependent gene activation. Here, we show that in mammalian primary cilia, WNT receptors relay a WNT/GSK3 signal that β-catenin-independently promotes ciliogenesis. Characterization of a LRP6 ciliary targeting sequence and monitoring of acute WNT co-receptor activation (phospho-LRP6) support this conclusion. Ciliary WNT signaling inhibits protein phosphatase 1 (PP1) activity, a negative regulator of ciliogenesis, by preventing GSK3-mediated phosphorylation of the PP1 regulatory inhibitor subunit PPP1R2. Concordantly, deficiency of WNT/GSK3 signaling by depletion of cyclin Y and cyclin-Y-like protein 1 induces primary cilia defects in mouse embryonic neuronal precursors, kidney proximal tubules, and adult mice preadipocytes.

Salvianolic Acid B Regulates Oxidative Stress, Autophagy and Apoptosis against Cyclophosphamide-Induced Hepatic Injury in Nile Tilapia (Oreochromis niloticus)

Salvianolic acid B (Sal B), as one of the main water-soluble components of Salvia miltiorrhizae, has significant pharmacological activities, including antioxidant, free radical elimination and biofilm protection actions. However, the protective effect of Sal B on Nile tilapia and the underlying mechanism are rarely reported. Therefore, the aim of this study was to evaluate the effects of Sal B on antioxidant stress, apoptosis and autophagy in Nile tilapia liver. In this experiment, Nile tilapia were fed diets containing sal B (0.25, 0.50 and 0.75 g·kg^-1) for 60 days, and then the oxidative hepatic injury of the tilapia was induced via intrapleural injection of 50 g·kg^-1 cyclophosphamide (CTX) three times. After the final exposure to CTX, the Nile tilapia were weighed and blood and liver samples were collected for the detection of growth and biochemical indicators, pathological observations and TUNEL detection, as well as the determination of mRNA expression levels. The results showed that after the CTX treatment, the liver was severely damaged, the antioxidant capacity of the Nile tilapia was significantly decreased and the hepatocyte autophagy and apoptosis levels were significantly increased. Meanwhile, dietary Sal B can not only significantly improve the growth performance of tilapia and effectively reduce CTX-induced liver morphological lesions, but can also alleviate CTX-induced hepatocyte autophagy and apoptosis. In addition, Sal B also significantly regulated the expression of genes related to antioxidative stress, autophagy and apoptosis pathways. This suggested that the hepatoprotective effect of Sal B may be achieved through various pathways, including scavenging free radicals and inhibiting hepatocyte apoptosis and autophagy.

Look who's TORking: mTOR-mediated integration of cell status and external signals during limb development and endochondral bone growth

The balance of cell proliferation and size is key for the control of organ development and repair. Moreover, this balance has to be coordinated within tissues and between tissues to achieve robustness in the organ's pattern and size. The tetrapod limb has been used to study these topics during development and repair, and several conserved pathways have emerged. Among them, mechanistic target of rapamycin (mTOR) signaling, despite being active in several cell types and developmental stages, is one of the least understood in limb development, perhaps because of its multiple potential roles and interactions with other pathways. In the body of this review, we have collated and integrated what is known about the role of mTOR signaling in three aspects of tetrapod limb development: 1) limb outgrowth; 2) chondrocyte differentiation after mesenchymal condensation and 3) endochondral ossification-driven longitudinal bone growth. We conclude that, given its ability to interact with the most common signaling pathways, its presence in multiple cell types, and its ability to influence cell proliferation, size and differentiation, the mTOR pathway is a critical integrator of external stimuli and internal status, coordinating developmental transitions as complex as those taking place during limb development. This suggests that the study of the signaling pathways and transcription factors involved in limb patterning, morphogenesis and growth could benefit from probing the interaction of these pathways with mTOR components.

Malignant Brain Aging: The Formidable Link Between Dysregulated Signaling Through Mechanistic Target of Rapamycin Pathways and Alzheimer's Disease (Type 3 Diabetes)

Malignant brain aging corresponds to accelerated age-related declines in brain functions eventually derailing the self-sustaining forces that govern independent vitality. Malignant brain aging establishes the path toward dementing neurodegeneration, including Alzheimer's disease (AD). The full spectrum of AD includes progressive dysfunction of neurons, oligodendrocytes, astrocytes, microglia, and the microvascular systems, and is mechanistically driven by insulin and insulin-like growth factor (IGF) deficiencies and resistances with accompanying deficits in energy balance, increased cellular stress, inflammation, and impaired perfusion, mimicking the core features of diabetes mellitus. The underlying pathophysiological derangements result in mitochondrial dysfunction, abnormal protein aggregation, increased oxidative and endoplasmic reticulum stress, aberrant autophagy, and abnormal post-translational modification of proteins, all of which are signature features of both AD and dysregulated insulin/IGF-1-mechanistic target of rapamycin (mTOR) signaling. This article connects the dots from benign to malignant aging to neurodegeneration by reviewing the salient pathologies associated with initially adaptive and later dysfunctional mTOR signaling in the brain. Effective therapeutic and preventive measures must be two-pronged and designed to 1) address complex and shifting impairments in mTOR signaling through the re-purpose of effective anti-diabetes therapeutics that target the brain, and 2) minimize the impact of extrinsic mediators of benign to malignant aging transitions, e.g., inflammatory states, obesity, systemic insulin resistance diseases, and repeated bouts of general anesthesia, by minimizing exposures or implementing neuroprotective measures.

Role of Wnt signaling in the maintenance and regeneration of the intestinal epithelium

The intestinal epithelium plays a key role in digestion and protection against external pathogens. This tissue presents a high cellular turnover with the epithelium being completely renewed every 5days, driven by intestinal stem cells (ISCs) residing in the crypt bases. To sustain this dynamic renewal of the intestinal epithelium, the maintenance, proliferation, and differentiation of ISCs must be precisely controlled. One of the central pathways supporting ISC maintenance and dynamics is the Wnt pathway. In this chapter, we examine the role of Wnt signaling in intestinal epithelial homeostasis and tissue regeneration, including mechanisms regulating ISC identity and fine-tuning of Wnt pathway activation. We extensively discuss the contribution of the stem cell niche in maintaining Wnt signaling in the intestinal crypts that support ISC functions. The integration of these findings highlights the complex interplay of multiple niche signals and cellular components sustaining ISC behavior and maintenance, which together supports the immense plasticity of the intestinal epithelium.

Phosphoproteomic Analysis of the Jejunum Tissue Response to Colostrum and Milk Feeding in Dairy Calves during the Passive Immunity Period

Improvements in the feeding of calves are of increasing importance for the development of the dairy industry. While colostrum is essential for the health of newborn calves, knowledge of protein phosphorylation alterations in neonatal calves that are fed colostrum or mature milk is lacking. Here, mid-jejunum tissue samples were collected from calves that received colostrum or milk. Subsequently, the jejunum phosphoproteome was analyzed using a phosphopeptide enrichment method, i.e., titanium immobilized metal ion affinity chromatography, coupled with liquid chromatography-tandem mass spectrometry. A total of 2093 phosphopeptides carrying unique 1851 phosphorylation sites corresponding to 1180 phosphoproteins were identified. Of the 1180 phosphoproteins, 314 phosphorylation sites on 241 proteins were differentially expressed between the groups. Gene ontology analysis indicated that the phosphoproteins were strongly associated with developmental and macromolecule metabolic processes, signal transduction, and responses to stimuli and insulin. Pathway analysis showed that the spliceosome, Hippo, insulin, and neurotrophin signaling pathways were enriched. These results reveal the expression pattern and changes in the function of phosphoproteins in bovine jejunum tissues under different feeding conditions and provide further insights into the crucial role of colostrum feeding during the early stages of life.

Alcohol, Resistance Exercise, and mTOR Pathway Signaling: An Evidence-Based Narrative Review

Skeletal muscle mass is determined by the balance between muscle protein synthesis (MPS) and degradation. Several intracellular signaling pathways control this balance, including mammalian/mechanistic target of rapamycin (mTOR) complex 1 (C1). Activation of this pathway in skeletal muscle is controlled, in part, by nutrition (e.g., amino acids and alcohol) and exercise (e.g., resistance exercise (RE)). Acute and chronic alcohol use can result in myopathy, and evidence points to altered mTORC1 signaling as a contributing factor. Moreover, individuals who regularly perform RE or vigorous aerobic exercise are more likely to use alcohol frequently and in larger quantities. Therefore, alcohol may antagonize beneficial exercise-induced increases in mTORC1 pathway signaling. The purpose of this review is to synthesize up-to-date evidence regarding mTORC1 pathway signaling and the independent and combined effects of acute alcohol and RE on activation of the mTORC1 pathway. Overall, acute alcohol impairs and RE activates mTORC1 pathway signaling; however, effects vary by model, sex, feeding, training status, quantity, etc., such that anabolic stimuli may partially rescue the alcohol-mediated pathway inhibition. Likewise, the impact of alcohol on RE-induced mTORC1 pathway signaling appears dependent on several factors including nutrition and sex, although many questions remain unanswered. Accordingly, we identify gaps in the literature that remain to be elucidated to fully understand the independent and combined impacts of alcohol and RE on mTORC1 pathway signaling.

Nuclear S6K1 Enhances Oncogenic Wnt Signaling by Inducing Wnt/β-Catenin Transcriptional Complex Formation

Ribosomal protein S6 kinase 1 (S6K1), a key downstream effector of the mammalian target of rapamycin (mTOR), regulates diverse functions, such as cell proliferation, cell growth, and protein synthesis. Because S6K1 was previously known to be localized in the cytoplasm, its function has been mainly studied in the cytoplasm. However, the nuclear localization and function of S6K1 have recently been elucidated and other nuclear functions are expected to exist but remain elusive. Here, we show a novel nuclear role of S6K1 in regulating the expression of the Wnt target genes. Upon activation of the Wnt signaling, S6K1 translocated from the cytosol into the nucleus and subsequently bound to β-catenin and the cofactors of the Wnt/β-catenin transcriptional complex, leading to the upregulation of the Wnt target genes. The depletion or repression of S6K1 downregulated the Wnt target gene expression by inhibiting the formation of the Wnt/β-catenin transcriptional complex. The S6K1-depleted colon cancer cell lines showed lower transcription levels of the Wnt/β-catenin target genes and a decrease in the cell proliferation and invasion compared to the control cell lines. Taken together, these results indicate that nuclear S6K1 positively regulates the expression of the Wnt target genes by inducing the reciprocal interaction of the subunits of the transcriptional complex.

AMPK induces degradation of the transcriptional repressor PROX1 impairing branched amino acid metabolism and tumourigenesis

Tumour cell metabolic plasticity is essential for tumour progression and therapeutic responses, yet the underlying mechanisms remain poorly understood. Here, we identify Prospero-related homeobox 1 (PROX1) as a crucial factor for tumour metabolic plasticity. Notably, PROX1 is reduced by glucose starvation or AMP-activated protein kinase (AMPK) activation and is elevated in liver kinase B1 (LKB1)-deficient tumours. Furthermore, the Ser79 phosphorylation of PROX1 by AMPK enhances the recruitment of CUL4-DDB1 ubiquitin ligase to promote PROX1 degradation. Downregulation of PROX1 activates branched-chain amino acids (BCAA) degradation through mediating epigenetic modifications and inhibits mammalian target-of-rapamycin (mTOR) signalling. Importantly, PROX1 deficiency or Ser79 phosphorylation in liver tumour shows therapeutic resistance to metformin. Clinically, the AMPK-PROX1 axis in human cancers is important for patient clinical outcomes. Collectively, our results demonstrate that deficiency of the LKB1-AMPK axis in cancers reactivates PROX1 to sustain intracellular BCAA pools, resulting in enhanced mTOR signalling, and facilitating tumourigenesis and aggressiveness.

Inhibition of glycogen synthase kinase 3 by lithium, a mechanism in search of specificity

Inhibition of Glycogen synthase kinase 3 (GSK3) is a popular explanation for the effects of lithium ions on mood regulation in bipolar disorder and other mental illnesses, including major depression, cyclothymia, and schizophrenia. Contribution of GSK3 is supported by evidence obtained from animal and patient derived model systems. However, the two GSK3 enzymes, GSK3α and GSK3β, have more than 100 validated substrates. They are thus central hubs for major biological functions, such as dopamine-glutamate neurotransmission, synaptic plasticity (Hebbian and homeostatic), inflammation, circadian regulation, protein synthesis, metabolism, inflammation, and mitochondrial functions. The intricate contributions of GSK3 to several biological processes make it difficult to identify specific mechanisms of mood stabilization for therapeutic development. Identification of GSK3 substrates involved in lithium therapeutic action is thus critical. We provide an overview of GSK3 biological functions and substrates for which there is evidence for a contribution to lithium effects. A particular focus is given to four of these: the transcription factor cAMP response element-binding protein (CREB), the RNA-binding protein FXR1, kinesin subunits, and the cytoskeletal regulator CRMP2. An overview of how co-regulation of these substrates may result in shared outcomes is also presented. Better understanding of how inhibition of GSK3 contributes to the therapeutic effects of lithium should allow for identification of more specific targets for future drug development. It may also provide a framework for the understanding of how lithium effects overlap with those of other drugs such as ketamine and antipsychotics, which also inhibit brain GSK3.

Glycogen Synthase Kinase 3β: A True Foe in Pancreatic Cancer

Glycogen synthase kinase 3 beta (GSK-3β) is a serine/threonine protein kinase involved in multiple normal and pathological cell functions, including cell signalling and metabolism. GSK-3β is highly expressed in the onset and progression of multiple cancers with strong involvement in the regulation of proliferation, apoptosis, and chemoresistance. Multiple studies showed pro- and anti-cancer roles of GSK-3β creating confusion about the benefit of targeting GSK-3β for treating cancer. In this mini-review, we focus on the role of GSK-3β in pancreatic cancer. We demonstrate that the proposed anti-cancer roles of GSK-3β are not relevant to pancreatic cancer, and we argue why GSK-3β is, indeed, a very promising therapeutic target in pancreatic cancer.

Identification of genetic characteristics in pediatric epilepsy with focal cortical dysplasia type 2 using deep whole-exome sequencing

BACKGROUND

Focal cortical dysplasia type 2 (FCD2) is a malformation of cortical development that constitutes a common cause of pediatric focal epilepsy. Germline or somatic variants in the mammalian target of rapamycin (mTOR) signaling pathway genes are the pathogenesis of FCD2.

OBJECTIVE

In this study, whole-exome deep sequencing was performed on dysplastic cortex from focal epilepsy in children to explore genetic characteristics in FCD2.

METHODS

Resected core lesions of FCD2 were confirmed by pathology, and peripheral blood was collected from 11 patients. Deep whole-exome sequencing (>500X) was performed on derived genomic DNA, germline, or somatic variants in brain-specific genes were analyzed and identified.

RESULTS

In 11 patients, a heterozygous likely pathogenic germline variant of DEPDC5 was identified in one case, while somatic variants were found in four brain samples. The frequencies of the somatic variant allele were 2.52%-5.12%. Somatic variants in AKT3, TSC2, and MTOR (mTOR signaling pathway genes) were found in three samples. Besides, one somatic variant was detected in MED12 which has not been reported to associate with FCD2.

CONCLUSION

Our study expanded the variant spectrum in the mTOR-GATOR pathway, and also detected a somatic variant in MED12 which was potentially associated with FCD 2.

Wnt/β-Catenin Signaling as a Driver of Stemness and Metabolic Reprogramming in Hepatocellular Carcinoma

Simple Summary

Aberrant Wnt/β-catenin signaling has been reported to play crucial role in pathogenesis of hepatocellular carcinoma (HCC). In this review, we focus on the regulatory role of Wnt/β-catenin signaling in cancer stemness and metabolic reprogramming, which are two emerging hallmarks of cancer. Understanding the role of Wnt/β-catenin signaling in regulation of the above processes reveals novel therapeutic strategy against this deadly disease.

Abstract

Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide due to its high rates of tumor recurrence and metastasis. Aberrant Wnt/β-catenin signaling has been shown to play a significant role in HCC development, progression and clinical impact on tumor behavior. Accumulating evidence has revealed the critical involvement of Wnt/β-catenin signaling in driving cancer stemness and metabolic reprogramming, which are regarded as emerging cancer hallmarks. In this review, we summarize the regulatory mechanism of Wnt/β-catenin signaling and its role in HCC. Furthermore, we provide an update on the regulatory roles of Wnt/β-catenin signaling in metabolic reprogramming, cancer stemness and drug resistance in HCC. We also provide an update on preclinical and clinical studies targeting Wnt/β-catenin signaling alone or in combination with current therapies for effective cancer therapy. This review provides insights into the current opportunities and challenges of targeting this signaling pathway in HCC.

Angiotensin II Regulates Mitochondrial mTOR Pathway Activity Dependent on Acyl-CoA Synthetase 4 in Adrenocortical Cells

Two well-known protein complexes in mammalian cells, mTOR type 1 and type 2 (mTORC1/2) are involved in several cellular processes such as protein synthesis, cell proliferation, and commonly dysregulated in cancer. An acyl-CoA synthetase type 4 (ACSL4) is one of the most recently mTORC1/2 regulators described, in breast cancer cells. The expression of ACSL4 is hormone-regulated in adrenocortical cells and required for steroid biosynthesis. mTORC1/2 have been reported to be crucial in the proliferation of human adrenocortical tumor cells H295R and interestingly reported at several subcellular locations, which has brought cell biology to the vanguard of the mTOR signaling field. In the present work, we study the regulation of mTORC1/2 activation by angiotensin II (Ang II)-the trophic hormone for adrenocortical cells-the subcellular localization of mTORC1/2 signaling proteins and the role of ACSL4 in the regulation of this pathway, in H295R cells. Ang II promotes activation by phosphorylation of mTORC1/2 pathway proteins in a time-dependent manner. Mitochondrial pools of ribosomal protein S6, protein kinase B (Akt) in threonine 308, and serine 473 and Rictor are phosphorylated and activated. Glycogen synthase kinase type 3 (GSK3) is phosphorylated and inactivated in mitochondria, favoring mTORC1 activation. Epidermal growth factor, a classic mTORC1/2 activator, promoted unique activation kinetics of mTORC1/2 pathway, except for Akt phosphorylation. Here, we demonstrate that ACSL4 is necessary for mTORC1/2 effectors phosphorylation and H295R proliferation, triggered by Ang II. Ang II promotes activation of mitochondrial mTORC1/2 signaling proteins, through ACSL4, with a direct effect on adrenocortical cellular proliferation.

Translational Aspects of the Mammalian Target of Rapamycin Complexes in Diabetic Nephropathy

Significance: Despite the many efforts put into understanding diabetic nephropathy (DN), direct treatments for DN have yet to be discovered. Understanding the mechanisms behind DN is an essential step in the development of novel therapeutic regimens. The mammalian target of rapamycin (mTOR) pathway has emerged as an important candidate in the quest for drug discovery because of its role in regulating growth, proliferation, as well as protein and lipid metabolism. Recent Advances: Kidney cells have been found to rely on basal autophagy for survival and for conserving kidney integrity. Recent studies have shown that diabetes induces renal autophagy deregulation, leading to kidney injury. Hyper-activation of the mTOR pathway and oxidative stress have been suggested to play a role in diabetes-induced autophagy imbalance. Critical Issues: A detailed understanding of the role of mTOR signaling in diabetes-associated complications is of major importance in the search for a cure. In this review, we provide evidence that mTOR is heavily implicated in diabetes-induced kidney injury. We suggest possible mechanisms through which mTOR exerts its negative effects by increasing insulin resistance, upregulating oxidative stress, and inhibiting autophagy. Future Directions: Both increased oxidative stress and autophagy deregulation are deeply embedded in DN. However, the mechanisms controlling oxidative stress and autophagy are not well understood. Although Akt/mTOR signaling seems to play an important role in oxidative stress and autophagy, further investigation is required to uncover the details of this signaling pathway. Antioxid. Redox Signal. 37, 802-819.

GABP couples oncogene signaling to telomere regulation in TERT promoter mutant cancer

Telomerase activation counteracts senescence and telomere erosion caused by uncontrolled proliferation. Epidermal growth factor receptor (EGFR) amplification drives proliferation while telomerase reverse transcriptase promoter (TERTp) mutations underlie telomerase reactivation through recruitment of GA-binding protein (GABP). EGFR amplification and TERTp mutations typically co-occur in glioblastoma, the most common and aggressive primary brain tumor. To determine if these two frequent alterations driving proliferation and immortality are functionally connected, we combine analyses of copy number, mRNA, and protein data from tumor tissue with pharmacologic and genetic perturbations. We demonstrate that proliferation arrest decreases TERT expression in a GABP-dependent manner and elucidate a critical proliferation-to-immortality pathway from EGFR to TERT expression selectively from the mutant TERTp through activation of AMP-mediated kinase (AMPK) and GABP upregulation. EGFR-AMPK signaling promotes telomerase activity and maintains telomere length. These results define how the tumor cell immortality mechanism keeps pace with persistent oncogene signaling and cell cycling.

TERT promoter mutations are common in human cancer and confer cellular immortality. McKinney et al. describe the interaction between TERT promoter mutations, EGFR amplification, and the cell cycle in glioblastoma. The results demonstrate how proliferation drivers cooperate with telomere maintenance mechanisms to counteract telomere shortening caused by unlimited cell division.

GSK3 Is a Central Player in Retinal Degenerative Diseases but a Challenging Therapeutic Target

Glycogen synthase kinase 3 (GSK3) is a key regulator of many cellular signaling processes and performs a wide range of biological functions in the nervous system. Due to its central role in numerous cellular processes involved in cell degeneration, a rising number of studies have highlighted the interest in developing therapeutics targeting GSK3 to treat neurodegenerative diseases. Although recent works strongly suggest that inhibiting GSK3 might also be a promising therapeutic approach for retinal degenerative diseases, its full potential is still under-evaluated. In this review, we summarize the literature on the role of GSK3 on the main cellular functions reported as deregulated during retinal degeneration, such as glucose homeostasis which is critical for photoreceptor survival, or oxidative stress, a major component of retinal degeneration. We also discuss the interest in targeting GSK3 for its beneficial effects on inflammation, for reducing neovascularization that occurs in some retinal dystrophies, or for cell-based therapy by enhancing Müller glia cell proliferation in diseased retina. Together, although GSK3 inhibitors hold promise as therapeutic agents, we highlight the complexity of targeting such a multitasked kinase and the need to increase our knowledge of the impact of reducing GSK3 activity on these multiple cellular pathways and biological processes.

Negative pressure wound therapy improves bone regeneration by promoting osteogenic differentiation via the AMPK-ULK1-autophagy axis

Deficient bone regeneration causes bone defects or nonunion in a substantial proportion of trauma patients that urges for novel therapies. To develop a reliable therapy, we investigated the effect of negative pressure wound therapy (NPWT) on bone regeneration in vivo in a rat calvarial defect model. Negative pressure (NP) treatment in vitro was mimicked to test its effect on osteoblast differentiation in rat mesenchymal stem cells (MSCs) and MC3T3-E1 cells. Transcriptomic analyses, pharmaceutical interventions, and shRNA knockdowns were conducted to explore the underlying mechanism and their clinical relevance was investigated in samples from patients with nonunion. The potential application of a combined therapy of MSCs in hydrogels with negative pressure was tested in the rat critical-size calvarial defect model. We found that NPWT promoted bone regeneration in vivo and NP treatment induced osteoblast differentiation in vitro. NP induced osteogenesis via activating macroautophagy/autophagy by AMPK-ULK1 signaling that was impaired in clinical samples from patients with nonunion. More importantly, the combined therapy involving MSCs in hydrogels with negative pressure significantly improved bone regeneration in rat critical-size calvarial defect model. Thus, our study identifies a novel AMPK-ULK1-autophagy axis by which negative pressure promotes osteoblast differentiation of MSCs and bone regeneration. NPWT treatment can potentially be adopted for therapy of bone defects.Abbreviations: ADP, adenosine diphosphate; AICAR/Aic, acadesine; ALP, alkaline phosphatase; ALPL, alkaline phosphatase, biomineralization associated; AMP, adenosine monophosphate; AMPK, AMP-activated protein kinase; ARS, alizarin red S staining; ATG7, autophagy related 7; ATP, adenosine triphosphate; BA1, bafilomycin A₁; BGLAP/OCN, bone gamma-carboxyglutamate protein; BL, BL-918; BS, bone surface; BS/TV, bone surface per tissue volume; BV/TV, bone volume per tissue volume; C.C, compound C; CCN1, cellular communication network factor 1; COL1A1, collagen type I alpha 1 chain; COL4A3, collagen type IV alpha 3 chain; COL4A4, collagen type IV alpha 4 chain; COL18A1, collagen type XVIII alpha 1 chain; CQ, chloroquine; GelMA, gelatin methacryloyl hydrogel; GO, Gene Ontology; GSEA, gene set enrichment analysis; HIF1A, hypoxia inducible factor 1 subunit alpha; HPLC, high-performance liquid chromatography; ITGAM/CD11B, integrin subunit alpha M; ITGAX/CD11C, integrin subunit alpha X; ITGB1/CdD9, integrin subunit beta 1; KEGG, Kyoto Encyclopedia of Genes and Genomes; MAP1LC3B/LC3B, microtubule associated protein 1 light chain 3 beta; micro-CT, microcomputed tomography; MSCs, mesenchymal stem cells; MTOR, mechanistic target of rapamycin kinase; NP, negative pressure; NPWT, negative pressure wound therapy; PRKAA1/AMPKα1, protein kinase AMP-activated catalytic subunit alpha 1; PRKAA2, protein kinase AMP-activated catalytic subunit alpha 2; PTPRC/CD45, protein tyrosine phosphatase receptor type C; ROS, reactive oxygen species; RUNX2, RUNX family transcription factor 2; SBI, SBI-0206965; SPP1/OPN, secreted phosphoprotein 1; THY1/CD90, Thy-1 cell surface antigen; SQSTM1, sequestosome 1; TGFB3, transforming growth factor beta 3; ULK1/Atg1, unc-51 like autophagy activating kinase 1.

BRAF and MEK Targeted Therapies in Pediatric Central Nervous System Tumors

Simple Summary

This review is divided into two parts. The first analyzes the mechanisms of two important cellular pathways that are involved in tumoral proliferation, differentiation, migration, and angiogenesis: RAS/RAF/MEK/MAPK and PI3K/AKT/mTOR. The second part focuses on the currently available experience regarding targeted therapies against the mitogen-activated protein kinase (MAPK) pathway in pediatric CNS tumors, with the hope of offering a practical guide for consultation.

Abstract

BRAF is a component of the MAPK and PI3K/AKT/mTOR pathways that play a crucial role in cellular proliferation, differentiation, migration, and angiogenesis. Pediatric central nervous system tumors very often show mutations of the MAPK pathway, as demonstrated by next-generation sequencing (NGS), which now has an increasing role in cancer diagnostics. The MAPK mutated pathway in pediatric CNS tumors is the target of numerous drugs, approved or under investigation in ongoing clinical trials. In this review, we describe the main aspects of MAPK and PI3K/AKT/mTOR signaling pathways, with a focus on the alterations commonly involved in tumorigenesis. Furthermore, we reported the main available data about current BRAF and MEK targeted therapies used in pediatric low-grade gliomas (pLLGs), pediatric high-grade gliomas (pHGGs), and other CNS tumors that often present BRAF or MEK mutations. Further molecular stratification and clinical trial design are required for the treatment of pediatric CNS tumors with BRAF and MEK inhibitors.

Molecular Mechanism of Tanshinone against Prostate Cancer

Prostate cancer (PCa) is the most common malignant tumor of the male urinary system in Europe and America. According to the data in the World Cancer Report 2020, the incidence rate of PCa ranks second in the prevalence of male malignant tumors and varies worldwide between regions and population groups. Although early PCa can achieve good therapeutic results after surgical treatment, due to advanced PCa, it can adapt and tolerate androgen castration-related drugs through a variety of mechanisms. For this reason, it is often difficult to achieve effective therapeutic results in the treatment of advanced PCa. Tanshinone is a new fat-soluble phenanthraquinone compound derived from Salvia miltiorrhiza that can play a therapeutic role in different cancers, including PCa. Several studies have shown that Tanshinone can target various molecular pathways of PCa, including the signal transducer and activator of transcription 3 (STAT3) pathway, androgen receptor (AR) pathway, phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway, and mitogen-activated protein kinase (MAPK) pathway, which will affect the release of pro-inflammatory cytokines and affect cell proliferation, apoptosis, tumor metabolism, genomic stability, and tumor drug resistance. Thus, the occurrence and development of PCa cells are inhibited. In this review, we summarized the in vivo and in vitro evidence of Tanshinone against prostate cancer and discussed the effect of Tanshinone on nuclear factor kappa-B (NF-κB), AR, and mTOR. At the same time, we conducted a network pharmacology analysis on the four main components of Tanshinone to further screen the possible targets of Tanshinone against prostate cancer and provide ideas for future research.

Low-Density Lipoprotein Receptor-Related Protein 8 at the Crossroad between Cancer and Neurodegeneration

The low-density-lipoprotein receptors represent a family of pleiotropic cell surface receptors involved in lipid homeostasis, cell migration, proliferation and differentiation. The family shares common structural features but also has significant differences mainly due to tissue-specific interactors and to peculiar proteolytic processing. Among the receptors in the family, recent studies place low-density lipoprotein receptor-related protein 8 (LRP8) at the center of both neurodegenerative and cancer-related pathways. From one side, its overexpression has been highlighted in many types of cancer including breast, gastric, prostate, lung and melanoma; from the other side, LRP8 has a potential role in neurodegeneration as apolipoprotein E (ApoE) and reelin receptor, which are, respectively, the major risk factor for developing Alzheimer’s disease (AD) and the main driver of neuronal migration, and as a γ-secretase substrate, the main enzyme responsible for amyloid formation in AD. The present review analyzes the contributions of LDL receptors, specifically of LRP8, in both cancer and neurodegeneration, pointing out that depending on various interactions and peculiar processing, the receptor can contribute to both proliferative and neurodegenerative processes.

Metalloprotease ADAM9 cleaves ephrin-B ligands and differentially regulates Wnt and mTOR signaling downstream of Akt kinase in colorectal cancer cells

Ephrin-B signaling has been implicated in many normal and pathological processes, including neural crest development and tumor metastasis. We showed previously that proteolysis of ephrin-B ligands by the disintegrin metalloprotease ADAM13 is necessary for canonical Wnt signal activation and neural crest induction in Xenopus, but it was unclear if these mechanisms are conserved in mammals. Here, we report that mammalian ADAM9 cleaves ephrin-B1 and ephrin-B2 and can substitute for Xenopus ADAM13 to induce the neural crest. We found that ADAM9 expression is elevated in human colorectal cancer (CRC) tissues and that knockdown (KD) of ADAM9 inhibits the migration and invasion of SW620 and HCT116 CRC cells by reducing the activity of Akt kinase, which is antagonized by ephrin-Bs. Akt is a signaling node that activates multiple downstream pathways, including the Wnt and mTOR pathways, both of which can promote CRC cell migration/invasion. Surprisingly, we also found that KD of ADAM9 downregulates Wnt signaling but has negligible effects on mTOR signaling in SW620 cells; in contrast, mTOR activity is suppressed while Wnt signaling remains unaffected by ADAM9 KD in HCT116 cells. These results suggest that mammalian ADAM9 cleaves ephrin-Bs to derepress Akt and promote CRC migration and invasion; however, the signaling pathways downstream of Akt are differentially regulated by ADAM9 in different CRC cell lines, reflecting the heterogeneity of CRC cells in responding to manipulations of upstream Akt regulators.

The Regulation of MiTF/TFE Transcription Factors Across Model Organisms: from Brain Physiology to Implication for Neurodegeneration

The microphthalmia/transcription factor E (MiTF/TFE) transcription factors are responsible for the regulation of various key processes for the maintenance of brain function, including autophagy-lysosomal pathway, lipid catabolism, and mitochondrial homeostasis. Among them, autophagy is one of the most relevant pathways in this frame; it is evolutionary conserved and crucial for cellular homeostasis. The dysregulation of MiTF/TFE proteins was shown to be involved in the development and progression of neurodegenerative diseases. Thus, the characterization of their function is key in the understanding of the etiology of these diseases, with the potential to develop novel therapeutics targeted to MiTF/TFE proteins and to the autophagic process. The fact that these proteins are evolutionary conserved suggests that their function and dysfunction can be investigated in model organisms with a simpler nervous system than the mammalian one. Building not only on studies in mammalian models but also in complementary model organisms, in this review we discuss (1) the mechanistic regulation of MiTF/TFE transcription factors; (2) their roles in different regions of the central nervous system, in different cell types, and their involvement in the development of neurodegenerative diseases, including lysosomal storage disorders; (3) the overlap and the compensation that occur among the different members of the family; (4) the importance of the evolutionary conservation of these protein and the process they regulate, which allows their study in different model organisms; and (5) their possible role as therapeutic targets in neurodegeneration.

Beyond controlling cell size: functional analyses of S6K in tumorigenesis

As a substrate and major effector of the mammalian target of rapamycin complex 1 (mTORC1), the biological functions of ribosomal protein S6 kinase (S6K) have been canonically assigned for cell size control by facilitating mRNA transcription, splicing, and protein synthesis. However, accumulating evidence implies that diverse stimuli and upstream regulators modulate S6K kinase activity, leading to the activation of a plethora of downstream substrates for distinct pathobiological functions. Beyond controlling cell size, S6K simultaneously plays crucial roles in directing cell apoptosis, metabolism, and feedback regulation of its upstream signals. Thus, we comprehensively summarize the emerging upstream regulators, downstream substrates, mouse models, clinical relevance, and candidate inhibitors for S6K and shed light on S6K as a potential therapeutic target for cancers.

Medical Aspects of mTOR Inhibition in Kidney Transplantation

The advances in transplant immunosuppression have reduced substantially the incidence of kidney graft rejection. In recent years, the focus has moved from preventing rejection to preventing the long-term consequences of long-standing immunosuppression, including nephrotoxicity induced by calcineurin inhibitors (CNI), as well as infectious and neoplastic complications. Since the appearance in the late 1990s of mTOR inhibitors (mTORi), these unmet needs in immunosuppression management could be addressed thanks to their benefits (reduced rate of viral infections and cancer). However, management of side effects can be troublesome and hands-on experience is needed. Here, we review all the available information about them. Thanks to all the basic, translational and clinical research achieved in the last twenty years, we now use mTORi as de novo immunosuppression in association with CNI. Another possibility is represented by the conversion of either CNI or mycophenolate (MPA) to an mTORi later on after transplantation in low-risk kidney transplant recipients.

Characterization of Genomic Alterations in Colorectal Liver Metastasis and Their Prognostic Value

Colorectal liver metastases (CRLMs) are clinically heterogeneous lesions with poor prognosis. Genetic alterations play a crucial role in their progression. The traditional Fong clinical risk score (Fong-CRS) is commonly used for risk stratification and prognosis prediction. By identifying the genomic alterations of CRLMs, we aimed to develop a mutation-based gene-signature-based clinical score (mut-CS) system to improve clinical prognostication. Tumour tissues from 144 patients with CRLMs were analysed with next-generation sequencing (NGS). A mut-CS scoring system considering the unique mutation-based gene signature, primary site, and Fong-CRS was developed and could identify CRLM patients with poor prognosis. The mean time-dependent receiver operating characteristic curve AUC value of the mut-CS system was greater than that of previously established scoring measures (the Fong-CRS, the e-clinical score, the presence of concomitant RAS and TP53 mutations, and other clinical traits). Taking together, we identified a mutant signature that exhibits a strong prognostic effect for CRLMs. Traditional clinical scoring system characteristics were incorporated into the new mut-CS scoring system to help determine the appropriate treatment for CRLMs.

Decrypting a path based approach for identifying the interplay between PI3K and GSK3 signaling cascade from the perspective of cancer

Cancer is one of those leading diseases worldwide, which takes millions of lives every year. Researchers are continuously looking for specific approaches to eradicate the deadly disease, ensuring minimal adverse effects along with more therapeutic significance. Targeting of different aberrantly regulated signaling pathways, involved in cancer, is surely one of the revolutionary chemotherapeutic approach. In this instance, GSK3 and PI3K signaling cascades are considered as important role player for both the oncogenic activation and inactivation which further leads to cancer proliferation and metastasis. In this review, we have discussed the potential role of GSK3 and PI3K signaling in cancer, and we further established the crosstalk between PI3K and GSK3 signaling, through showcasing their cross activation, cross inhibition and convergence pathways in association with cancer. We also exhibited the effect of GSK3 on the efficacy of PI3K inhibitors to overcome the drug resistance and preventing the cell proliferation, metastasis in a combinatorial way with GSK3 inhibitors for a better treatment strategy in clinical settings.

The central role of mTORC1 in amino acid sensing

The mechanistic target of rapamycin (mTOR) is a master regulator of cell growth that controls cell homeostasis in response to nutrients, growth factors, and other environmental cues. Recent studies have emphasized the importance of lysosomes as a hub for nutrient sensing, especially amino acid sensing by mTORC1. This review highlights recent advances in understanding the amino acid-mTORC1 signaling axis and the role of mTORC1 in cancer.

Pathobiology and Therapeutic Relevance of GSK-3 in Chronic Hematological Malignancies

Glycogen synthase kinase-3 (GSK-3) is an evolutionarily conserved, ubiquitously expressed, multifunctional serine/threonine protein kinase involved in the regulation of a variety of physiological processes. GSK-3 comprises two isoforms (α and β) which were originally discovered in 1980 as enzymes involved in glucose metabolism via inhibitory phosphorylation of glycogen synthase. Differently from other proteins kinases, GSK-3 isoforms are constitutively active in resting cells, and their modulation mainly involves inhibition through upstream regulatory networks. In the early 1990s, GSK-3 isoforms were implicated as key players in cancer cell pathobiology. Active GSK-3 facilitates the destruction of multiple oncogenic proteins which include β-catenin and Master regulator of cell cycle entry and proliferative metabolism (c-Myc). Therefore, GSK-3 was initially considered to be a tumor suppressor. Consistently, GSK-3 is often inactivated in cancer cells through dysregulated upstream signaling pathways. However, over the past 10–15 years, a growing number of studies highlighted that in some cancer settings GSK-3 isoforms inhibit tumor suppressing pathways and therefore act as tumor promoters. In this article, we will discuss the multiple and often enigmatic roles played by GSK-3 isoforms in some chronic hematological malignancies (chronic myelogenous leukemia, chronic lymphocytic leukemia, multiple myeloma, and B-cell non-Hodgkin’s lymphomas) which are among the most common blood cancer cell types. We will also summarize possible novel strategies targeting GSK-3 for innovative therapies of these disorders.

The promoter methylation drives down-regulation mode of HIC1 in gastric cancer, its molecular characteristics and downstream functional pathways

Gastric cancer is a common malignant tumor of the gastrointestinal tract with a high incidence and mortality rate. Previous results have suggested that the HIC1 gene might be a tumor suppressor candidate in gastric cancer. However, several critical points need to be elucidated: (1) The correlation of HIC1 promoter methylation with its specific expression level in gastric cancer; (2) The molecular characterization of HIC1 promoter methylation; (3) The possible mechanism by which HIC1 performs its inhibitory role in gastric cancer. To address these questions, we retrieved data from TCGA database to analyze HIC1 promoter methylation levels and transcript expression data, and performed targeted region bisulfite sequencing on three stable HIC1 down-regulated cell lines and normal control cell lines, and performed whole transcriptome and metabolite assays in HIC1 knockout cell lines by CRISPR-Cas9 technique. Results demonstrated that HIC1 promoter hypermethylation might be a crucial driving force leading to its down-regulation in HIC1 expression in gastric cancer. This implicated that promoter CG methylation of HIC1 might play a major role in the development of gastric carcinogenesis. Besides, HIC1 may suppress gastric cancer progression by maintaining the normal cellular metabolism, and inhibiting the mTOR signaling pathway activity.

Molecular Mechanisms of Isolated Polycystic Liver Diseases

Polycystic liver disease (PLD) is a rare autosomal dominant disorder including two genetically and clinically distinct forms: autosomal dominant polycystic kidney disease (ADPKD) and isolated polycystic liver disease (PCLD). The main manifestation of ADPKD is kidney cysts, while PCLD has predominantly liver presentations with mild or absent kidney cysts. Over the past decade, PRKCSH, SEC63, ALG8, and LRP5 have been candidate genes of PCLD. Recently, more candidate genes such as GANAB, SEC61B, and ALR9 were also reported in PCLD patients. This review focused on all candidate genes of PCLD, including the newly established novel candidate genes. In addition, we also discussed some other genes which might also contribute to the disease.

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

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.

Crosstalk between PI3K/AKT/mTOR and WNT/β-Catenin signaling in GBM - Could combination therapy checkmate the collusion?

Glioblastoma multiforme is one of the calamitous primary glial brain tumors with extensive heterogeneity at cellular and molecular levels. While maximal surgical resection trailed by radio and chemotherapy employing temozolomide remains the gold-standard treatment for malignant glioma patients, the overall prognosis remains dismal and there exists an unmet need for effective therapeutic strategies. In this context, we hypothesize that proper understanding of signaling pathways responsible for glioblastoma multiforme proliferation would be the first trump card while searching for novel targeted therapies. Among the pathways aberrantly activated, PI3K/AKT/mTOR is the most significant pathway, that is clinically implicated in malignancies such as high-grade glioma. Further, the WNT/β-Catenin cascade is well-implicated in several malignancies, while its role in regulating glioma pathogenesis has only emerged recently. Nevertheless, oncogenic activation of both these pathways is a frequent event in malignant glioma that facilitates tumor proliferation, stemness and chemo-resistance. Recently, it has been reported that the cross-talk of PI3K/AKT/mTOR pathway with multiple signaling pathways could promote glioma progression and reduce the sensitivity of glioma cells to the standard therapy. However, very few studies had focused on the relationship between PI3K/AKT/mTOR and WNT/β-Catenin pathways in glioblastoma multiforme. Interestingly, in homeostatic and pathologic circumstances, both these pathways depict fine modulation and are connected at multiple levels by upstream and downstream effectors. Thus, gaining deep insights on the collusion between these pathways would help in discovering unique therapeutic targets for glioblastoma multiforme management. Hence, the current review aims to address, "the importance of inter-play between PI3K/AKT/mTOR and WNT/β-Catenin pathways", and put forward, "the possibility of combinatorially targeting them", for glioblastoma multiforme treatment enhancement.

ROCK ‘n TOR: An Outlook on Keratinocyte Stem Cell Expansion in Regenerative Medicine via Protein Kinase Inhibition

Keratinocyte stem cells play a fundamental role in homeostasis and repair of stratified epithelial tissues. Transplantation of cultured keratinocytes autografts provides a landmark example of successful cellular therapies by restoring durable integrity in stratified epithelia lost to devastating tissue conditions. Despite the overall success of such procedures, failures still occur in case of paucity of cultured stem cells in therapeutic grafts. Strategies aiming at a further amplification of stem cells during keratinocyte ex vivo expansion may thus extend the applicability of these treatments to subjects in which endogenous stem cells pools are depauperated by aging, trauma, or disease. Pharmacological targeting of stem cell signaling pathways is recently emerging as a powerful strategy for improving stem cell maintenance and/or amplification. Recent experimental data indicate that pharmacological inhibition of two prominent keratinocyte signaling pathways governed by apical mTOR and ROCK protein kinases favor stem cell maintenance and/or amplification ex vivo and may improve the effectiveness of stem cell-based therapeutic procedures. In this review, we highlight the pathophysiological roles of mTOR and ROCK in keratinocyte biology and evaluate existing pre-clinical data on the effects of their inhibition in epithelial stem cell expansion for transplantation purposes.

A Pleiotropic Role of Long Non-Coding RNAs in the Modulation of Wnt/β-Catenin and PI3K/Akt/mTOR Signaling Pathways in Esophageal Squamous Cell Carcinoma: Implication in Chemotherapeutic Drug Response

Despite the availability of modern techniques for the treatment of esophageal squamous cell carcinoma (ESCC), tumor recurrence and metastasis are significant challenges in clinical management. Thus, ESCC possesses a poor prognosis and low five-year overall survival rate. Notably, the origin and recurrence of the cancer phenotype are under the control of complex cancer-related signaling pathways. In this review, we provide comprehensive knowledge about long non-coding RNAs (lncRNAs) related to Wnt/β-catenin and phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway in ESCC and its implications in hindering the efficacy of chemotherapeutic drugs. We observed that a pool of lncRNAs, such as HERES, TUG1, and UCA1, associated with ESCC, directly or indirectly targets various molecules of the Wnt/β-catenin pathway and facilitates the manifestation of multiple cancer phenotypes, including proliferation, metastasis, relapse, and resistance to anticancer treatment. Additionally, several lncRNAs, such as HCP5 and PTCSC1, modulate PI3K/Akt/mTOR pathways during the ESCC pathogenesis. Furthermore, a few lncRNAs, such as AFAP1-AS1 and LINC01014, block the efficiency of chemotherapeutic drugs, including cisplatin, 5-fluorouracil, paclitaxel, and gefitinib, used for ESCC treatment. Therefore, this review may help in designing a better therapeutic strategy for ESCC patients.