Phosphorylation and regulation of Raf by Akt (protein kinase B)

IGF-1R inhibition induces MEK phosphorylation to promote survival in colon carcinomas

The insulin-like growth factor 1 receptor (IGF-1R) governs several signaling pathways for cell proliferation, survival, and anti-apoptosis. Thus, targeting IGF-1R appears as a reasonable rationale for tumor treatment. However, clinical studies showed that inhibition of IGF-1R has very limited efficacy due to the development of resistance to IGF-1R blockade in tumor cells. Here, we discovered that prolonged treatment of colon cancer cells with IGF-1R inhibitors (BMS-754807 and GSK1838705A) stimulates p70 KDa ribosomal protein S6 kinase 1 (p70S6K1) activation, a well-known kinase signaling for cell survival. We also found that p70S6K1 activation by IGF-1R inhibition is independent of K-Ras and PIK3CA mutations that frequently occur in colon cancer. Besides the increased p70S6K1 phosphorylation, the phosphorylation of mitogen-activated protein kinase kinase 1 and 2 (MEK1/2) was elevated in the cells treated with BMS-754807. Interestingly, the increases in MEK1/2 and p70S6K1 phosphorylation were also observed when cells were subjected to the treatment of AKT inhibitor or genetic knockdown of AKT2 but not AKT1, suggesting that AKT2 inhibition stimulates MEK1/2 phosphorylation to activate p70S6K1. Conversely, inhibition of MEK1/2 by MEK1/2 inhibitor (U0126) or knockdown of MEK1 and MEK2 by corresponding mek1 and mek2 siRNA enhanced AKT phosphorylation, indicating mutual inhibition between AKT and MEK. Furthermore, the combination of BMS-754807 and U0126 efficiently decreased the cell viability and increased cleaved caspase 3 and apoptosis in vitro and in vivo. Our data suggest that the treatment of colon tumor cells with IGF-1R inhibitors stimulates p70S6K1 activity via MEK1/2 to promote survival, providing a new strategy for colorectal cancer therapeutics.

Protective Effects of Active Compounds from Salviae miltiorrhizae Radix against Glutamate-Induced HT-22 Hippocampal Neuronal Cell Death

Oxidative stress is considered one of the factors that cause dysfunction and damage of neurons, causing diseases such as amyotrophic lateral sclerosis (ALS), Alzheimer’s disease (AD), and Parkinson’s disease (PD).Recently, natural antioxidant sources have emerged as one of the main research areas for the discovery of potential neuroprotectants that can be used to treat neurological diseases. In this research, we assessed the neuroprotective effect of a 70% ethanol Salvia miltiorrhiza Radix (SMR) extract and five of its constituent compounds (tanshinone IIA, caffeic acid, salvianolic acid B, rosmarinic acid, and salvianic acid A) in HT-22 hippocampal cells. The experimental data showed that most samples were effective in attenuating the cytotoxicity caused by glutamate in HT-22 cells, except for rosmarinic acid and salvianolic acid B. Of the compounds tested, tanshinone IIA (TS-IIA) exerted the strongest effect in protecting HT-22 cells against glutamate neurotoxin. Treatment with 400 nM TS-IIA restored HT-22 cell viability almost completely. TS-IIA prevented glutamate-induced oxytosis by abating the accumulation of calcium influx, reactive oxygen species, and phosphorylation of mitogen-activated protein kinases. Moreover, TS-IIA inhibited glutamate-induced cytotoxicity by reducing the activation and phosphorylation of p53, as well as by stimulating Akt expression. This research suggested that TS-IIA is a potential neuroprotective component of SMR, with the ability to protect against neuronal cell death induced by excessive amounts of glutamate.

P21-Activated Kinase 1: Emerging biological functions and potential therapeutic targets in Cancer

The p21-Activated kinase 1 (PAK1), a member of serine-threonine kinases family, was initially identified as an interactor of the Rho GTPases RAC1 and CDC42, which affect a wide range of processes associated with cell motility, survival, metabolism, cell cycle, proliferation, transformation, stress, inflammation, and gene expression. Recently, the PAK1 has emerged as a potential therapeutic target in cancer due to its role in many oncogenic signaling pathways. Many PAK1 inhibitors have been developed as potential preclinical agents for cancer therapy. Here, we provide an overview of essential roles that PAK1 plays in cancer, including its structure and autoactivation mechanism, its crucial function from onset to progression to metastasis, metabolism, immune escape and even drug resistance in cancer; endogenous regulators; and cancer-related pathways. We also summarize the reported PAK1 small-molecule inhibitors based on their structure types and their potential application in cancer. In addition, we provide overviews on current progress and future challenges of PAK1 in cancer, hoping to provide new ideas for the diagnosis and treatment of cancer.

ERK and Akt exhibit distinct signaling responses following stimulation by pro-angiogenic factors

Background

Angiogenesis plays an important role in the survival of tissues, as blood vessels provide oxygen and nutrients required by the resident cells. Thus, targeting angiogenesis is a prominent strategy in many different settings, including both tissue engineering and cancer treatment. However, not all of the approaches that modulate angiogenesis lead to successful outcomes. Angiogenesis-based therapies primarily target pro-angiogenic factors such as vascular endothelial growth factor-A (VEGF) or fibroblast growth factor (FGF) in isolation, and there is a limited understanding of how these promoters combine together to stimulate angiogenesis. Targeting one pathway could be insufficient, as alternative pathways may compensate, diminishing the overall effect of the treatment strategy.

Methods

To gain mechanistic insight and identify novel therapeutic strategies, we have developed a detailed mathematical model to quantitatively characterize the crosstalk of FGF and VEGF intracellular signaling. The model focuses on FGF- and VEGF-induced mitogen-activated protein kinase (MAPK) signaling to promote cell proliferation and the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway, which promotes cell survival and migration. We fit the model to published experimental datasets that measure phosphorylated extracellular regulated kinase (pERK) and Akt (pAkt) upon FGF or VEGF stimulation. We validate the model with separate sets of data.

Results

We apply the trained and validated mathematical model to characterize the dynamics of pERK and pAkt in response to the mono- and co-stimulation by FGF and VEGF. The model predicts that for certain ranges of ligand concentrations, the maximum pERK level is more responsive to changes in ligand concentration compared to the maximum pAkt level. Also, the combination of FGF and VEGF indicates a greater effect in increasing the maximum pERK compared to the summation of individual effects, which is not seen for maximum pAkt levels. In addition, our model identifies the influential species and kinetic parameters that specifically modulate the pERK and pAkt responses, which represent potential targets for angiogenesis-based therapies.

Conclusions

Overall, the model predicts the combination effects of FGF and VEGF stimulation on ERK and Akt quantitatively and provides a framework to mechanistically explain experimental results and guide experimental design. Thus, this model can be utilized to study the effects of pro- and anti-angiogenic therapies that particularly target ERK and/or Akt activation upon stimulation with FGF and VEGF.

The PI3K-AKT-mTOR Pathway and Prostate Cancer: At the Crossroads of AR, MAPK, and WNT Signaling

Oncogenic activation of the phosphatidylinositol-3-kinase (PI3K), protein kinase B (PKB/AKT), and mammalian target of rapamycin (mTOR) pathway is a frequent event in prostate cancer that facilitates tumor formation, disease progression and therapeutic resistance. Recent discoveries indicate that the complex crosstalk between the PI3K-AKT-mTOR pathway and multiple interacting cell signaling cascades can further promote prostate cancer progression and influence the sensitivity of prostate cancer cells to PI3K-AKT-mTOR-targeted therapies being explored in the clinic, as well as standard treatment approaches such as androgen-deprivation therapy (ADT). However, the full extent of the PI3K-AKT-mTOR signaling network during prostate tumorigenesis, invasive progression and disease recurrence remains to be determined. In this review, we outline the emerging diversity of the genetic alterations that lead to activated PI3K-AKT-mTOR signaling in prostate cancer, and discuss new mechanistic insights into the interplay between the PI3K-AKT-mTOR pathway and several key interacting oncogenic signaling cascades that can cooperate to facilitate prostate cancer growth and drug-resistance, specifically the androgen receptor (AR), mitogen-activated protein kinase (MAPK), and WNT signaling cascades. Ultimately, deepening our understanding of the broader PI3K-AKT-mTOR signaling network is crucial to aid patient stratification for PI3K-AKT-mTOR pathway-directed therapies, and to discover new therapeutic approaches for prostate cancer that improve patient outcome.

Zinc-mediated Neurotransmission in Alzheimer's Disease: A Potential Role of the GPR39 in Dementia

With more people reaching an advanced age in modern society, there is a growing need for strategies to slow down age-related neuropathology and loss of cognitive functions, which are a hallmark of Alzheimer's disease. Neuroprotective drugs and candidate drug compounds target one or more processes involved in the neurodegenerative cascade, such as excitotoxicity, oxidative stress, misfolded protein aggregation and/or ion dyshomeostasis. A growing body of research shows that a G-protein coupled zinc (Zn²⁺) receptor (GPR39) can modulate the abovementioned processes.

Zn²⁺ itself has a diverse activity profile at the synapse, and by binding to numerous receptors, it plays an important role in neurotransmission. However, Zn²⁺ is also necessary for the formation of toxic oligomeric forms of amyloid beta, which underlie the pathology of Alzheimer’s disease. Furthermore, the binding of Zn²⁺ by amyloid beta causes a disruption of zincergic signaling, and recent studies point to GPR39 and its intracellular targets being affected by amyloid pathology.

In this review, we present neurobiological findings related to Zn²⁺ and GPR39, focusing on its signaling pathways, neural plasticity, interactions with other neurotransmission systems, as well as on the effects of pathophysiological changes observed in Alzheimer's disease on GPR39 function.

Direct targeting of the GPR39 might be a promising strategy for the pharmacotherapy of zincergic dyshomeostasis observed in Alzheimer’s disease. The information presented in this article will hopefully fuel further research into the role of GPR39 in neurodegeneration and help in identifying novel therapeutic targets for dementia.

Differential responses to kinase inhibition in FGFR2-addicted triple negative breast cancer cells: a quantitative phosphoproteomics study

Fibroblast Growth Factor (FGF) dependent signalling is frequently activated in cancer by a variety of different mechanisms. However, the downstream signal transduction pathways involved are poorly characterised. Here a quantitative differential phosphoproteomics approach, SILAC, is applied to identify FGF-regulated phosphorylation events in two triple- negative breast tumour cell lines, MFM223 and SUM52, that exhibit amplified expression of FGF receptor 2 (FGFR2) and are dependent on continued FGFR2 signalling for cell viability. Comparative Gene Ontology proteome analysis revealed that SUM52 cells were enriched in proteins associated with cell metabolism and MFM223 cells enriched in proteins associated with cell adhesion and migration. FGFR2 inhibition by SU5402 impacts a significant fraction of the observed phosphoproteome of these cells. This study expands the known landscape of FGF signalling and identifies many new targets for functional investigation. FGF signalling pathways are found to be flexible in architecture as both shared, and divergent, responses to inhibition of FGFR2 kinase activity in the canonical RAF/MAPK/ERK/RSK and PI3K/AKT/PDK/mTOR/S6K pathways are identified. Inhibition of phosphorylation-dependent negative-feedback pathways is observed, defining mechanisms of intrinsic resistance to FGFR2 inhibition. These findings have implications for the therapeutic application of FGFR inhibitors as they identify both common and divergent responses in cells harbouring the same genetic lesion and pathways of drug resistance.

A phase I dose-escalation study of enzalutamide in combination with the AKT inhibitor AZD5363 (capivasertib) in patients with metastatic castration-resistant prostate cancer

BACKGROUND

Activation of the PI3K/AKT/mTOR pathway through loss of phosphatase and tensin homolog (PTEN) occurs in approximately 50% of patients with metastatic castration-resistant prostate cancer (mCRPC). Recent evidence suggests that combined inhibition of the androgen receptor (AR) and AKT may be beneficial in mCRPC with PTEN loss.

PATIENTS AND METHODS

mCRPC patients who previously failed abiraterone and/or enzalutamide, received escalating doses of AZD5363 (capivasertib) starting at 320 mg twice daily (b.i.d.) given 4 days on and 3 days off, in combination with enzalutamide 160 mg daily. The co-primary endpoints were safety/tolerability and determining the maximum tolerated dose and recommended phase II dose; pharmacokinetics, antitumour activity, and exploratory biomarker analysis were also evaluated.

RESULTS

Sixteen patients were enrolled, 15 received study treatment and 13 were assessable for dose-limiting toxicities (DLTs). Patients were treated at 320, 400, and 480 mg b.i.d. dose levels of capivasertib. The recommended phase II dose identified for capivasertib was 400 mg b.i.d. with 1/6 patients experiencing a DLT (maculopapular rash) at this level. The most common grade ≥3 adverse events were hyperglycemia (26.7%) and rash (20%). Concomitant administration of enzalutamide significantly decreased plasma exposure of capivasertib, though this did not appear to impact pharmacodynamics. Three patients met the criteria for response (defined as prostate-specific antigen decline ≥50%, circulating tumour cell conversion, and/or radiological response). Responses were seen in patients with PTEN loss or activating mutations in AKT, low or absent AR-V7 expression, as well as those with an increase in phosphorylated extracellular signal-regulated kinase (pERK) in post-exposure samples.

CONCLUSIONS

The combination of capivasertib and enzalutamide is tolerable and has antitumour activity, with all responding patients harbouring aberrations in the PI3K/AKT/mTOR pathway.

CLINICAL TRIAL NUMBER

NCT02525068.

Human vtRNA1-1 Levels Modulate Signaling Pathways and Regulate Apoptosis in Human Cancer Cells

Regulatory non-protein coding RNAs perform a remarkable variety of complex biological functions. Previously, we demonstrated a role of the human non-coding vault RNA1-1 (vtRNA1-1) in inhibiting intrinsic and extrinsic apoptosis in several cancer cell lines. Yet on the molecular level, the function of the vtRNA1-1 is still not fully clear. Here, we created HeLa knock-out cell lines revealing that prolonged starvation triggers elevated levels of apoptosis in the absence of vtRNA1-1 but not in vtRNA1-3 knock-out cells. Next-generation deep sequencing of the mRNome identified the PI3K/Akt pathway and the ERK1/2 MAPK cascade, two prominent signaling axes, to be misregulated in the absence of vtRNA1-1 during starvation-mediated cell death conditions. Expression of vtRNA1-1 mutants identified a short stretch of 24 nucleotides of the vtRNA1-1 central domain as being essential for successful maintenance of apoptosis resistance. This study describes a cell signaling-dependent contribution of the human vtRNA1-1 to starvation-induced programmed cell death.

Expressions of ezrin, ERK, STAT3, and AKT in tongue cancer and association with tumor characteristics and patient survival

Background

Ezrin, ERK, STAT3, and AKT are proteins that are overexpressed in various types of cancer, although their expressions in tongue cancer has received less focus. This study aimed to address associations between the expression levels of these proteins and with characteristics of the tumor and patient survival.

Methods

We performed immunohistochemical staining of ezrin, ERK, STAT3, and AKT in tumors from patients with tongue carcinoma in situ (CIS, n = 17) and tongue squamous cell carcinoma (SCC, n = 46). Statistical differences between the SCC versus the CIS cohorts were estimated by calculations of bivariate odds ratios of low versus high expression of the proteins. Fisher's exact tests were used to appraise interassociations between the proteins, as well as expression levels versus patient and tumor characteristics. Survival based on Kaplan–Meier statistics in combination log‐rank tests were used to address potential effects of the patient and tumor characteristics versus 5‐year survival rate.

Results

The relative high: low expression of all four proteins in the two cohorts differed, and particularly ERK was markedly overexpressed in the SCC versus the CIS cohort (odds ratio = 45.3, p < .01). The relative high: low expression each protein versus patient and tumor characteristics; showed associations between AKT expression and T stage (p = .002) plus node metastases (p = .12), and between ERK expression and drinking (p = .01) and smoking history (p = .01). There was no significant difference observed between ERK and the three other molecules, nor any significant difference between the degree of expression of each protein and the 5‐year disease‐specific survival rate.

Conclusion

Ezrin, ERK, STAT3, and AKT appear to be involved in the progress from carcinoma in situ in the tongue into squamous cell carcinoma. ERK in particular is overexpressed, suggesting that ERK may be a novel therapeutic target for preventing tongue cancer.

Dual-specificity phosphatase 6 plays a critical role in the maintenance of a cancer stem-like cell phenotype in human endometrial cancer

The prognosis of patients with high‐grade or advanced‐stage endometrial cancer remains poor. As cancer stem‐like cells (CSCs) are thought to be associated with endometrial cancers, it is essential to investigate the molecular mechanisms that regulate endometrial CSCs. Dual‐specificity phosphatase 6 (DUSP6) functions as a negative‐feedback regulator of MAPK–ERK1/2 signaling, but its role in endometrial cancer remains unknown. We investigated whether DUSP6 is involved in cancer cell stemness using endometrial cancer cell lines and specimens from endometrial cancer patients. DUSP6 induced the expression of CSC‐related genes including ALDH1, Nanog, SOX2 and Oct4A, increased the population of cells in the G0/G1 phase, and promoted sphere formation ability. DUSP6 knockdown resulted in reduced cell invasion and metastasis, whereas DUSP6 overexpression inhibited apoptosis under serum‐free conditions. Moreover, DUSP6 decreased phosphorylated ERK1/2 and increased phosphorylated Akt levels, which potentially induces CSC features. In patients with endometrial cancers, DUSP6 expression was determined using immunohistochemistry, and based on the results, the patients were dichotomized into high‐ and low‐DUSP6‐expression groups. Progression‐free survival and overall survival were significantly shorter in the high‐DUSP6‐expression group. These results suggest that DUSP6 has potential value as a biomarker of CSCs and as a target of therapies designed to eliminate CSCs in endometrial cancer.

What's new?

Although cancer stem‐like cells (CSCs) are involved in human endometrial cancers, the underlying molecular mechanisms and biomarkers for CSCs in endometrial cancers remain elusive. Here, the authors found that DUSP6 plays an important role in regulating endometrial CSC phenotypes by increasing self‐renewal ability and starvation resistance. DUSP6 expression was required for inducing invasion and metastasis and resulted in ERK1/2 dephosphorylation and Akt phosphorylation, which potentially contribute to the promotion of CSC phenotypes. As DUSP6 expression was also positively associated with worse progression‐free and overall survival, DUSP6 represents a potential biomarker for endometrial CSCs and a therapeutic target in endometrial cancers.

Akt1-Mediated Phosphorylation of RBP-Jk Controls Notch1 Signaling

The Notch1 signaling pathway plays a crucial role in determining cell fate, including cell growth and differentiation. In this study, we demonstrated that the antagonistic action of RTK (receptor tyrosine kinase) signaling pathway on the Notch1 signaling pathway is mediated via Ras-PI3K-Akt1. The PI3K-Akt1 signaling pathway was shown to inhibit Notch1 signaling via phosphorylation of RBP-Jk. We observed not only reduced association between Notch1 and RBP-Jk, but also suppression of the Notch1 transcriptional activity. Our results demonstrated that Akt1 functions as a natural inhibitor of the Notch1 signaling pathway via phosphorylation of RBP-Jk.

Ivermectin-induced programmed cell death and disruption of mitochondrial membrane potential in bovine mammary gland epithelial cells

Ivermectin (IVM) is a commercially well-known antiparasitic agent derived from the natural fermentation product avermectin. Originally used as a veterinary drug, IVM has been studied for its pharmacokinetic advantages, such as anticancer, antimigration, and antiproliferative effects, using several cell types. In the present study, we verified that IVM suppressed bovine mammary gland epithelial cell proliferation and induced the arrest of the cell cycle from the sub-G1 to the G2/M phase in these cells. Due to IVM treatment, the homeostasis of calcium ions, which play a crucial role in intracellular metabolism, deteriorated, leading to the loss of the mitochondrial membrane potential (MMP). To underpin these results, further studies using inhibitors of Ca²⁺ signaling were performed; combination treatment with IVM and these factors, including 2-APB, BAPTA-AM, or ruthenium red, inhibited the IVM-induced MMP disruption. Furthermore, following IVM treatment, the relationships among various cell signaling mediators were altered, and the balance between diverse cellular processes associated with cell survival or death was disturbed. In conclusion, we assessed the anti-survival effects of IVM on mammary gland epithelial cells; IVM may impede normal lactation in dairy cows.

Simultaneous Knockdown of Sprouty2 and PTEN Promotes Axon Elongation of Adult Sensory Neurons

Sprouty2 (Spry2) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) are both well-established regulators of receptor tyrosine kinase (RTK) signaling, and knockdown of Spry2 or PTEN enhances axon regeneration of dorsal root ganglia (DRG) neurons. The major role of Spry2 is the inhibition of the rat sarcoma RAS/extracellular signal-regulated kinase (ERK) pathway, whereas PTEN acts mainly as an inhibitor of the phosphoinositide 3-kinase (PI3K)/Akt pathway. In non-neuronal cells, Spry2 increases the expression and activity of PTEN, and PTEN enhances the amount of Spry2 by the inhibition of the microRNA-21 (miR-21) that downregulates Spry2. Applying dissociated DRG neuron cultures from wild-type (WT) or Spry2 deficient mice, we demonstrate that PTEN protein was reduced after 72 h during rapid axonal outgrowth on the laminin substrate. Furthermore, PTEN protein was decreased in DRG cultures obtained from homozygous Spry2−/− knockout mice. Vice versa, Spry2 protein was reduced by PTEN siRNA in WT and heterozygous Spry2+/− neurons. Knockdown of PTEN in DRG cultures obtained from homozygous Spry2−/− knockout mice promoted axon elongation without increasing axonal branching. Activation of Akt, but not ERK, was stronger in response to PTEN knockdown in homozygous Spry2−/− DRG neurons than in WT neurons. Together, our study confirms the important role of the signaling modulators Spry2 and PTEN in axon growth of adult DRG neurons. Both function as endogenous inhibitors of neuronal growth factor signaling and their simultaneous knockdown promotes axon elongation more efficiently than the single knockdown of each inhibitor. Furthermore, Spry2 and PTEN are reciprocally downregulated in adult DRG neuron cultures. Axon growth is influenced by multiple factors and our results demonstrate that the endogenous inhibitors of axon growth, Spry2 and PTEN, are co-regulated in adult DRG neuron cultures. Together, our data demonstrate that combined approaches may be more useful to improve nerve regeneration than targeting one single inhibitor of axon growth.

The ubiquitin system: orchestrating cellular signals in non-small-cell lung cancer

The ubiquitin system, known as a common feature in eukaryotes, participates in multiple cellular processes, such as signal transduction, cell-cycle progression, receptor trafficking and endocytosis, and even the immune response. In lung cancer, evidence has revealed that aberrant events in ubiquitin-mediated processes can cause a variety of pathological outcomes including tumorigenesis and metastasis. Likewise, ubiquitination on the core components contributing to the activity of cell signaling controls bio-signal turnover and cell final destination. Given this, inhibitors targeting the ubiquitin system have been developed for lung cancer therapies and have shown great prospects for clinical application. However, the exact biological effects and physiological role of the drugs used in lung cancer therapies are still not clearly elucidated, which might seriously impede the progress of treatment. In this work, we summarize current research advances in cell signal regulation processes mediated through the ubiquitin system during the development of lung cancer, with the hope of improving the therapeutic effects by means of aiming at efficient targets.

Targeting Aberrant RAS/RAF/MEK/ERK Signaling for Cancer Therapy

The RAS/RAF/MEK/ERK (MAPK) signaling cascade is essential for cell inter- and intra-cellular communication, which regulates fundamental cell functions such as growth, survival, and differentiation. The MAPK pathway also integrates signals from complex intracellular networks in performing cellular functions. Despite the initial discovery of the core elements of the MAPK pathways nearly four decades ago, additional findings continue to make a thorough understanding of the molecular mechanisms involved in the regulation of this pathway challenging. Considerable effort has been focused on the regulation of RAF, especially after the discovery of drug resistance and paradoxical activation upon inhibitor binding to the kinase. RAF activity is regulated by phosphorylation and conformation-dependent regulation, including auto-inhibition and dimerization. In this review, we summarize the recent major findings in the study of the RAS/RAF/MEK/ERK signaling cascade, particularly with respect to the impact on clinical cancer therapy.

Mitochondrial fission regulates germ cell differentiation by suppressing ROS-mediated activation of Epidermal Growth Factor Signaling in the Drosophila larval testis

Mitochondria are essential organelles that have recently emerged as hubs for several metabolic and signaling pathways in the cell. Mitochondrial morphology is regulated by constant fusion and fission events to maintain a functional mitochondrial network and to remodel the mitochondrial network in response to external stimuli. Although the role of mitochondria in later stages of spermatogenesis has been investigated in depth, the role of mitochondrial dynamics in regulating early germ cell behavior is relatively less-well understood. We previously demonstrated that mitochondrial fusion is required for germline stem cell (GSC) maintenance in the Drosophila testis. Here, we show that mitochondrial fission is also important for regulating the maintenance of early germ cells in larval testes. Inhibition of Drp1 in early germ cells resulted in the loss of GSCs and spermatogonia due to the accumulation of reactive oxygen species (ROS) and activation of the EGFR pathway in adjacent somatic cyst cells. EGFR activation contributed to premature germ cell differentiation. Our data provide insights into how mitochondrial dynamics can impact germ cell maintenance and differentiation via distinct mechanisms throughout development.

Ferulin C triggers potent PAK1 and p21-mediated anti-tumor effects in breast cancer by inhibiting Tubulin polymerization in vitro and in vivo

Ferulin C, a natural sesquiterpene coumarin, isolated from the roots of Ferula ferulaeoides (Steud.) Korov, displaying potent antiproliferatory activity against breast cancer cells. This study aimed to elucidate the underlying molecular mechanisms of Ferulin C-induced breast cancer cells death in vitro and in vivo. Ferulin C presented potent antiproliferatory activity against MCF-7 and MDA-MB-231 cells and remarkable tubulin polymerization inhibitory activity (IC₅₀ = 9.2 μM). Meanwhile, we predicted Ferulin C bind to the Colchicine site of tubulin through CETSA assay, molecular docking and molecular dynamics (MD) simulations. In immunofluorescence assay, Ferulin C disturbed the microtubule integrity and structure. Furthermore, Ferulin C stimulated significant cell cycle arrest in the G1/S period via p21^Cip1/Waf1 - CDK2 signaling, induced classic cell apoptosis, impaired metastasis via down-regulating Ras-Raf-ERK and AKT-mTOR signaling. Intriguingly, Ferulin C treatment induced autophagy by ULK1 signaling to synergize with the inhibition of proliferation and metastasis. Based upon the RNAseq analysis, PAK1, as a novel essential modulator, was involved in the signaling regulated by Ferulin C -induced α/β-tubulin depolymerization. Additionally, Ferulin C displayed an acceptable antiproliferatory activity in an MCF-7 xenograft model without inducing obvious weight loss in the Ferulin C treated mice. Summarily, our findings substantiated that Ferulin C was a potent, colchicine site binding microtubule-destabilizing agent with anti-proliferation and anti-metastasis activity via PAK1 and p21-mediated signaling in breast cancer cells.

The Upstream Pathway of mTOR-Mediated Autophagy in Liver Diseases

Autophagy, originally found in liver experiments, is a cellular process that degrades damaged organelle or protein aggregation. This process frees cells from various stress states is a cell survival mechanism under stress stimulation. It is now known that dysregulation of autophagy can cause many liver diseases. Therefore, how to properly regulate autophagy is the key to the treatment of liver injury. mechanistic target of rapamycin (mTOR)is the core hub regulating autophagy, which is subject to different upstream signaling pathways to regulate autophagy. This review summarizes three upstream pathways of mTOR: the phosphoinositide 3-kinase (PI3K)/protein kinase (AKT) signaling pathway, the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway, and the rat sarcoma (Ras)/rapidly accelerated fibrosarcoma (Raf)/mitogen-extracellular activated protein kinase kinase (MEK)/ extracellular-signal-regulated kinase (ERK) signaling pathway, specifically explored their role in liver fibrosis, hepatitis B, non-alcoholic fatty liver, liver cancer, hepatic ischemia reperfusion and other liver diseases through the regulation of mTOR-mediated autophagy. Moreover, we also analyzed the crosstalk between these three pathways, aiming to find new targets for the treatment of human liver disease based on autophagy.

Conditional expression of a dominant-negative form of Epstein-Barr virus (EBV) nuclear antigen EBNALP inhibits EBV-positive lymphoblastoid cell growth

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus that transforms primary B lymphocytes, yielding lymphoblastoid cell lines (LCLs). EBV-encoded nuclear antigen 2 (EBNA2) and EBV-encoded nuclear antigen leader protein (EBNALP) are the first viral products expressed after EBV infection of primary B lymphocytes and are essential for EBV-induced B-lymphocyte growth transformation. EBNA2 functions as a transcriptional activator of viral and cellular genes, with EBNALP as a coactivator for EBNA2-mediated transcriptional activation. We previously reported that mutant EBNALP with a C-terminal 10-amino-acid truncation loses the ability to coactivate, and has a dominant-negative effect on wild-type-EBNALP-mediated coactivation. However, the functional relevance of EBNALP in maintenance of LCL cell growth has not been investigated. To address this, we have constructed LCL-derived cell clones in which this dominant-negative form of EBNALP (DNLP) is conditionally expressed by the Cre-loxP system. We used these cells to evaluate the effect of DNLP expression on EBV-induced cell proliferation. After drug treatment, the DNLP-expressing LCL clones showed reduced cell proliferation and viability. These results indicate that EBNALP is critical for maintaining LCL growth and EBV-induced cell proliferation.

Does Ras Activate Raf and PI3K Allosterically?

The mechanism through which oncogenic Ras activates its effectors is vastly important to resolve. If allostery is at play, then targeting allosteric pathways could help in quelling activation of MAPK (Raf/MEK/ERK) and PI3K (PI3K/Akt/mTOR) cell proliferation pathways. On the face of it, allosteric activation is reasonable: Ras binding perturbs the conformational ensembles of its effectors. Here, however, we suggest that at least for Raf, PI3K, and NORE1A (RASSF5), that is unlikely. Raf's long disordered linker dampens effective allosteric activation. Instead, we suggest that the high-affinity Ras–Raf binding relieves Raf's autoinhibition, shifting Raf's ensemble from the inactive to the nanocluster-mediated dimerized active state, as Ras also does for NORE1A. PI3K is recruited and allosterically activated by RTK (e.g., EGFR) at the membrane. Ras restrains PI3K's distribution and active site orientation. It stabilizes and facilitates PIP₂ binding at the active site and increases the PI3K residence time at the membrane. Thus, RTKs allosterically activate PI3Kα; however, merging their action with Ras accomplishes full activation. Here we review their activation mechanisms in this light and draw attention to implications for their pharmacology.

d-a-Tocopheryl Polyethylene Glycol 1000 Succinate and a small-molecule Survivin suppressant synergistically induce apoptosis in SKBR3 breast cancer cells

Breast cancer is the second in mortality rate malignancy among women. Despite the many advances in breast cancer treatment, there is still a need to improve drug efficacy and reduce non-specific effects. D-alpha-tocopheryl polyethylene glycol succinate (TPGS) is frequently used in the development of drug delivery systems to improve the pharmacokinetics of anti-cancer drugs and reduce multi-drug resistance. We have previously shown that TPGS not only acts as a carrier molecule but also exerts anti-cancer effects. As part of this study, we investigated the effect of TPGS with YM155, a small molecule suppressant of Survivin, in various breast cancer cell lines representing different subtypes of the disease. We aimed to evaluate the presumed synergistic effect of the TPGS-YM155 combination and reveal its mechanism of action. Our results show that the TPGS-YM155 combination acts synergistically to reduce specifically the viability of SKBR3 cells. The combination of these agents reduced activation of the AKT pathway, decreased Survivin and Bcl-2 levels, and induced caspase-dependent and independent apoptosis via the mitochondrial pathway. Importantly, the TPGS-YM155 combination did not significantly affect the viability of MCF-10A normal immortalized cells. In conclusion, the combination of YM155 and TPGS could be a promising approach against SKBR3-type breast cancer.

Putative Mechanisms of Action and Clinical Use of Lithium in Children and Adolescents: A Critical Review

Background:

Lithium is a first-line treatment for bipolar disorder in adults, but its mechanism of action is still far from clear. Furthermore, evidences of its use in pediatric populations are sparse, not only for bipolar disorders, but also for other possible indications.

Objectives:

To provide a synthesis of published data on the possible mechanisms of action of lithium, as well as on its use in pediatric samples, including pharmacokinetics, efficacy, and safety data.

Methods:

Clinical trials in pediatric samples with at least one standardized measure of efficacy/effectiveness were included in this review. We considered: i) randomized and open label trials, ii) combination studies iii) augmentation studies iv) case series including at least 5 patients.

Results:

Different and non-alternative mechanisms of action can explain the clinical efficacy of lithium. Clinical studies in pediatric samples suggest that lithium is effective in managing manic symptoms/episodes of bipolar disorder, both in the acute phase and as maintenance strategy. Efficacy on depressive symptoms/phases of bipolar disorder is much less clear, while studies do not support its use in unipolar depression and severe mood dysregulation. Conversely, it may be effective on aggression in the context of conduct disorder. Other possible indications, with limited published evidence, are the acute attacks in Kleine-Levin syndrome, behavioral symptoms of X-fragile syndrome, and the management of clozapine- or chemotherapy- induced neutropenia. Generally, lithium resulted relatively safe.

Conclusions:

Lithium seems an effective and well-tolerated medication in pediatric bipolar disorder and aggression, while further evidences are needed for other clinical indications.

Effect of the Large and Small T-Antigens of Human Polyomaviruses on Signaling Pathways

Viruses are intracellular parasites that require a permissive host cell to express the viral genome and to produce new progeny virus particles. However, not all viral infections are productive and some viruses can induce carcinogenesis. Irrespective of the type of infection (productive or neoplastic), viruses hijack the host cell machinery to permit optimal viral replication or to transform the infected cell into a tumor cell. One mechanism viruses employ to reprogram the host cell is through interference with signaling pathways. Polyomaviruses are naked, double-stranded DNA viruses whose genome encodes the regulatory proteins large T-antigen and small t-antigen, and structural proteins that form the capsid. The large T-antigens and small t-antigens can interfere with several host signaling pathways. In this case, we review the interplay between the large T-antigens and small t-antigens with host signaling pathways and the biological consequences of these interactions.

Inhibition of Phosphoinositide-3-Kinase Signaling Promotes the Stem Cell State of Trophoblast

Trophoblast stem cells (TSCs) are a heterogeneous cell population despite the presence of fibroblast growth factor (FGF) and transforming growth factor β (TGFB) as key growth factors in standard culture conditions. To understand what other signaling cascades control the stem cell state of mouse TSCs, we performed a kinase inhibitor screen and identified several novel pathways that cause TSC differentiation. Surprisingly, inhibition of phosphoinositide-3-kinase (PI3K) signaling increased the mRNA and protein expression of stem cell markers instead, and resulted in a tighter epithelial colony morphology and fewer differentiated cells. PI3K inhibition could not substitute for FGF or TGFB and did not affect phosphorylation of extracellular signal-regulated kinase, and thus acts independently of these pathways. Upon removal of PI3K inhibition, TSC transcription factor levels reverted to normal TSC levels, indicating that murine TSCs can reversibly switch between these two states. In summary, PI3K inhibition reduces the heterogeneity and seemingly heightens the stem cell state of TSCs as indicated by the simultaneous upregulation of multiple key marker genes and cell morphology. Stem Cells 2019;37:1307-1318.

Mechanosensitive ion channel Piezo1 promotes prostate cancer development through the activation of the Akt/mTOR pathway and acceleration of cell cycle

Prostate cancer is one of the most common types of cancer affecting men worldwide; however, its etiology and pathological mechanisms remain poorly understood. Mechanical stimulation plays a key role in prostate cancer development. Piezo type mechanosensitive ion channel component 1 (Piezo1), which functions as a cell sensor and transducer of mechanical stimuli, may have a crucial role in the development of prostate cancer. In the present study, the expression of the Piezo1 channel was demonstrated to be significantly elevated in prostate cancer cell lines and in human prostate malignant tumor tissues. Downregulation of Piezo1 significantly suppressed the viability, proliferation and migration of prostate cancer cells in vitro, and inhibited prostate tumor growth in vivo. The activation of the Akt/mTOR pathway or acceleration of cell cycle progression from G₀/G₁ to S phase may downstream consequences of Piezo 1 signal pathway activation. Downregulation of Piezo1 considerably suppressed Ca²⁺ signal increments, inhibited the phosphorylation of Akt and mTOR and arrested the cell cycle of prostate cancer cells at G₀/G₁ phase in while inhibiting the activation of CDK4 and cyclin D1. Taken together, these findings suggest that Piezo1 channels have a crucial role in prostate cancer development and may, therefore, be a novel therapeutic target in the treatment of prostate cancer.

Akt in cancer: Mediator and more

Akt is a serine/threonine kinase and it participates in the key role of the PI3K signaling pathway. The Akt can be activated by a wide range of growth signals and the biochemical mechanisms leading to Akt activation are well defined. Once activated, Akt modulates the function of many downstream proteins involved in cellular survival, proliferation, migration, metabolism, and angiogenesis. The Akt is a central node of many signaling pathways and it is frequently deregulated in many types of human cancers. In this review, we provide an overview of Akt function and its role in the hallmarks of human cancer. We also discussed various mechanisms of Akt dysregulation in cancers, including epigenetic modifications like methylation, post-transcriptional non-coding RNAs-mediated regulation, and the overexpression and mutation.

Salvinorin A attenuates early brain injury through PI3K/Akt pathway after subarachnoid hemorrhage in rat

Early brain injury (EBI) refers to the direct injury to the brain during the first 72 h after subarachnoid hemorrhage (SAH), which is one of the major causes for the poor clinical outcome after SAH. In this study, we investigated the effect and the related mechanism of Salvinorin A (SA), a selective kappa opioid receptor agonist, on EBI after SAH. SA was administered by intraperitoneal injection at 24 h, 48 h and 72 h after SAH. The volume of lateral ventricle was measured by magnetic resonance imaging (MRI). The neuronal morphological changes and the apoptotic level in CA1 area of hippocampus were observed by Nissl and TUNEL staining respectively. Protein expression of p-PI3K, p-Akt, p-IKKα/β, p-NF-κB, FoxO1, Bim, Bax and Cleaved-caspase-3 was measured to explore the potential mechanism. We found that SA alleviated the neuronal morphological changes and apoptosis in CA1 area of hippocampus. The mechanism might be related to the increased protein expression of p-PI3K/p-Akt, which accompanied by decreased expression of p-IKKα/β, p-NF-κB, FoxO1, Bim, Bax and Cleaved-caspase-3 in the hippocampus. Thus, therapeutic interventions of SA targeting the PI3K/Akt pathway might be a novel approach to ameliorate EBI via reducing the apoptosis and inflammation after SAH.

Sex Differences in Neuroplasticity- and Stress-Related Gene Expression and Protein Levels in the Rat Hippocampus Following Oxycodone Conditioned Place Preference

Prescription opioid abuse is a serious public health issue. Recently, we showed that female and male Sprague-Dawley rats acquire conditioned place preference (CPP) to the mu opioid receptor agonist oxycodone. Anatomical analysis of the hippocampus from these rats unveiled sex differences in the opioid system in a way that would support excitation and opiate associative learning processes especially in females. In this study, we examined the expression and protein densities of opioid, plasticity, stress and related kinase and signaling molecules in the hippocampus of female and male rats following oxycodone CPP. Oxycodone CPP females have: a) increases in ARC (activity regulated cytoskeletal-associated protein)-immunoreactivity (ir) in CA3 pyramidal cells; b) decreases in Npy (neuropeptide Y) gene expression in the medial hippocampus but higher numbers of NPY-containing hilar interneurons compared to males; c) increases in Crhr2 (corticotropin releasing factor receptor 2) expression in CA2/3; d) increases in Akt1 (AKT serine/threonine kinase 1) expression in medial hippocampus; and e) decreases in phosphorylated MAPK (mitogen activated protein kinase)-ir in CA1 and dentate gyrus. Oxycodone CPP males have: a) increases in Bdnf (brain derived-neurotrophic factor) expression, which is known to be produced in granule cells, relative to females; b) elevated Mapk1 expression and pMAPK-ir in the dentate hilus which harbors newly generated granule cells; and c) increases in CRHR1-ir in CA3 pyramidal cell soma. These sex-specific changes in plasticity, stress and kinase markers in hippocampal circuitry parallel previously observed sex differences in the opioid system after oxycodone CPP.

A microfluidic assay for the quantification of the metastatic propensity of breast cancer specimens

The challenge of predicting which patients with breast cancer will develop metastases leads to the overtreatment of patients with benign disease and to the inadequate treatment of the aggressive cancers. Here, we report the development and testing of a microfluidic assay that quantifies the abundance and proliferative index of migratory cells in breast-cancer specimens, for the assessment of their metastatic propensity and for the rapid screening of potential antimetastatic therapeutics. On the basis of the key roles of cell motility and proliferation in cancer metastasis, the device accurately predicts the metastatic potential of breast-cancer cell lines and of patient-derived xenografts. Compared to unsorted cancer cells, highly motile cells isolated by the device exhibited similar tumourigenic potential but markedly increased metastatic propensity in vivo. RNA sequencing of the highly motile cells revealed an enrichment of motility-related and survival-related genes. The approach might be developed into a companion assay for the prediction of metastasis in patients and for the selection of effective therapeutic regimens.

Blocking TBK1 alleviated radiation-induced pulmonary fibrosis and epithelial-mesenchymal transition through Akt-Erk inactivation

As a common serious complication of thoracic radiotherapy, radiation-induced pulmonary fibrosis (RIPF) severely limits radiation therapy approaches. Epithelial–mesenchymal transition (EMT) is a direct contributor to the fibroblast pool during fibrogenesis, and prevention of EMT is considered an effective strategy to inhibit tissue fibrosis. Our previous study revealed that TANK-binding kinase 1 (TBK1) regulates EMT in lung cancer cells. In the present study, we aimed to investigate the therapeutic potential of targeting TBK1 to prevent RIPF and EMT progression. We found radiation-induced EMT and pulmonary fibrosis in normal alveolar epithelial cells and lung tissues. TBK1 knockdown or inhibition significantly reversed EMT in vivo and in vitro and attenuated pulmonary fibrosis and collagen deposition. Moreover, we observed that TBK1 was elevated in a time- and dose-dependent manner by radiation. Meanwhile, radiation also induced time- and dose-dependent activation of AKT and ERK, each of whose inhibitors suppressed radiation-induced EMT. Intriguingly, silencing of TBK1 with shRNA also blocked the radiation-induced activation of AKT and ERK signaling. The ERK inhibitor did not obviously affect the expression of TBK1 or phosphorylated AKT, while AKT inhibition suppressed activation of ERK without changing the expression of TBK1. Finally, we found that a TBK1 inhibitor inhibited inflammatory cytokine expression in a RIPF model and Amlexanox protected normal cells and mice from ionizing radiation. In conclusion, our results indicate that the TBK1–AKT–ERK signaling pathway regulates radiation-induced EMT in normal alveolar epithelial cells, suggesting that TBK1 is a potential target for pulmonary fibrosis prevention during cancer radiotherapy.

The risk of scarred tissues and respiratory distress during radiation treatment of lung cancer could be reduced by targeting an enzyme that alters healthy cells. Lung cancer radiotherapy often causes pulmonary fibrosis, excessive growth of fibrous tissues in the lungs, involving the transition of normal epithelial cells into an invasive form of multipotent stem cells. The development of pulmonary fibrosis limits the clinical application of radiotherapy. Hongjin Qu and co-workers at the Second Military University in Shanghai, China, previously demonstrated that the TANK-binding kinase 1 (TBK1) enzyme regulates this transition. Now, the team have shown that levels of TBK1 itself increased during radiation treatment, together with two proteins that would normally suppress alterations in healthy cells. Inhibiting TBK1, both in cell cultures and mouse models, reversed the cell transitions and prevented pulmonary fibrosis.

The Expression of Key Guidance Genes at a Forebrain Axon Turning Point Is Maintained by Distinct Fgfr Isoforms but a Common Downstream Signal Transduction Mechanism

During development the axons of neurons grow toward and locate their synaptic partners to form functional neural circuits. Axons do so by reading a map of guidance cues expressed by surrounding tissues. Guidance cues are expressed at a precise space and time, but how guidance cue expression is regulated, and in a coordinated manner, is poorly understood. Semaphorins (Semas) and Slits are families of molecular ligands that guide axons. We showed previously that fibroblast growth factor (Fgf) signaling maintains sema3a and slit1 forebrain expression in Xenopus laevis, and these two repellents cooperate to guide retinal ganglion cell (RGC) axons away from the mid-diencephalon and on towards the optic tectum. Here, we investigate whether there are common features of the regulatory pathways that control the expression of these two guidance cues at this single axon guidance decision point. We isolated the sema3a proximal promoter and confirmed its responsiveness to Fgf signaling. Through misexpression of truncated Fgf receptors (Fgfrs), we found that sema3a forebrain expression is dependent on Fgfr2-4 but not Fgfr1. This is in contrast to slit1, whose expression we showed previously depends on Fgfr1 but not Fgfr2-4. Using pharmacological inhibitors and misexpression of constitutively active (CA) and dominant negative (DN) signaling intermediates, we find that while distinct Fgfrs regulate these two guidance genes, intracellular signaling downstream of Fgfrs appears to converge along the phosphoinositol 3-kinase (PI3K)-Akt signaling pathway. A common PI3K-Akt signaling pathway may allow for the coordinated expression of guidance cues that cooperate to direct axons at a guidance choice point.

Inclusion complex of saikosaponin-d with hydroxypropyl-β-cyclodextrin: Improved physicochemical properties and anti-skin cancer activity

BACKGROUND

Saikosaponin-d (SSD) is a triterpene saponin isolated from Bupleurum plants. It has been shown to exhibit antioxidant, anti-inflammatory, and anticancer activities. However, its biomedical applications are limited by its poor water solubility. Cyclodextrins are highly water soluble oligosaccharide compounds which can form inclusion complexes with lipophilic drugs.

PURPOSE

We complexed SSD with hydroxypropyl-β-cyclodextrin (HPBCD) in various ratios to form SSD-HPBCD inclusion complexes. The inclusion complexes were evaluated for their solubility, physicochemical properties and cytotoxic effects in cutaneous squamous cell carcinoma cells.

METHODS

Surface morphology of pure SSD and SSD-HPBCD inclusion complexes was evaluated by scanning electron microscopy. Crystalline structure was determined by X-ray diffractometry. Intermolecular hydrogen bond formation between SSD and HPBCD was investigated by Fourier transform infrared spectroscopy. Human cutaneous squamous cell carcinoma HSC-1 cell viability was determined by the MTS assay, and cell apoptosis by the caspase 3/7 assay. Signal transduction pathways were investigated by Western blotting.

RESULTS

SSD-HPBCD inclusion complexes showed greatly increased water solubility. This was associated with an improvement in physicochemical properties, including transformation of crystalline structure to amorphous form, and formation of hydrogen bonds between SSD and HPBCD. In addition, SSD-HPBCD inclusion complexes induced apoptosis in HSC-1 cells, and this was mediated through activation of MAPK and suppression of Akt-mTOR signaling pathways.

CONCLUSION

SSD-HPBCD inclusion complex shows improvement in water solubility and physicochemical properties, and exhibits anticancer effects against cutaneous squamous cell carcinoma cells. Therefore, it may be a potential drug formulation for the treatment of skin cancer.

Somatic ERK activation during transit amplification is essential for maintaining the synchrony of germline divisions in Drosophila testis

Transit amplification (TA) of progenitor cells maintains tissue homeostasis by balancing proliferation and differentiation. In Drosophila testis, the germline proliferation is tightly regulated by factors present in both the germline and the neighbouring somatic cyst cells (SCCs). Although the exact mechanism is unclear, the epidermal growth factor receptor (EGFR) activation in SCCs has been reported to control spermatogonial divisions within a cyst, through downstream activations of Rac1-dependent pathways. Here, we report that somatic activation of the mitogen-activated protein kinase (Rolled/ERK) downstream of EGFR is required to synchronize the mitotic divisions and regulate the transition to meiosis. The process operates independently of the Bag-of-marble activity in the germline. Also, the integrity of the somatic cyst enclosure is inessential for this purpose. Together, these results suggest that synchronization of germ-cell divisions through somatic activation of distinct ERK-downstream targets independently regulates TA and subsequent differentiation of neighbouring germline cells.

The Role of PI3K/Akt and ERK in Neurodegenerative Disorders

Disruption of Akt and Erk-mediated signal transduction significantly contributes in the pathogenesis of various neurodegenerative diseases (NDs), such as Parkinson's disease, Alzheimer's diseases, Huntington's disease, and many others. These regulatory proteins serve as the regulator of cell survival, motility, transcription, metabolism, and progression of the cell cycle. Therefore, targeting Akt and Erk pathway has been proposed as a reasonable approach to suppress ND progression. This review has emphasized on involvement of Akt/Erk cascade in the neurodegeneration. Akt has been reported to regulate neuronal toxicity through its various substrates like FOXos, GSK3β, and caspase-9 etc. Akt is also involved with PI3K in signaling pathway to mediate neuronal survival. ERK is another kinase which also regulates proliferation, differentiation, and survival of the neural cell. There has also been much progress in developing a therapeutic molecule targeting Akt and Erk signaling. Therefore, improved understanding of the molecular mechanism behind the regulatory aspect of Akt and Erk networks can make strong impact on exploration of the neurodegenerative disease pathogenesis.

Ras-Mediated Activation of the Raf Family Kinases

The extracellular signal-regulated kinase (ERK) cascade comprised of the Raf, MEK, and ERK protein kinases constitutes a key effector cascade used by the Ras GTPases to relay signals regulating cell growth, survival, proliferation, and differentiation. Of the ERK cascade components, the regulation of the Raf kinases is by far the most complex, involving changes in subcellular localization, protein and lipid interactions, as well as alterations in the Raf phosphorylation state. The Raf kinases interact directly with active, membrane-localized Ras, and this interaction is often the first step in the Raf activation process, which ultimately results in ERK activation and the downstream phosphorylation of cellular targets that will specify a particular biological response. Here, we will examine our current understanding of how Ras promotes Raf activation, focusing on the molecular mechanisms that contribute to the Raf activation/inactivation cycle.

Triciribine increases LDLR expression and LDL uptake through stabilization of LDLR mRNA

Low-density lipoprotein receptor (LDLR) is a key regulator of the metabolism of plasma low-density lipoprotein cholesterol (LDL-C), the elevated levels of which are associated with an increased risk of cardiovascular disease. Therefore, enhancing LDLR expression represents a potent treatment strategy for hypercholesterolemia. Here, we report that in cultured human hepatoma cells, triciribine, a highly selective AKT inhibitor, increases the stability of LDLR mRNA, an event that translates into upregulation of cell-surface LDLR levels and induction of cellular LDL uptake. This effect of triciribine requires ERK activity and is partially dependent on the intervening sequence between the AU-rich elements ARE3 and ARE4 in LDLR 3′UTR. We also show that triciribine downregulates the expression of PCSK9 mRNA and blunts the secretion of its protein. Notably, triciribine was found to potentiate the effect of mevastatin on LDLR protein levels and activity. We also show that primary human hepatocytes respond to triciribine by increasing the expression of LDLR. Furthermore, a pilot experiment with mice revealed that a two-weeks treatment with triciribine significantly induced the hepatic expression of LDLR protein. These results identify triciribine as a novel LDLR-elevating agent and warrant further examination of its potential as a hypocholesterolemic drug either as monotherapy or in combination with statins.

Structural snapshots of RAF kinase interactions

RAF (rapidly accelerated fibrosarcoma) Ser/Thr kinases (ARAF, BRAF, and CRAF) link the RAS (rat sarcoma) protein family with the MAPK (mitogen-activated protein kinase) pathway and control cell growth, differentiation, development, aging, and tumorigenesis. Their activity is specifically modulated by protein-protein interactions, post-translational modifications, and conformational changes in specific spatiotemporal patterns via various upstream regulators, including the kinases, phosphatase, GTPases, and scaffold and modulator proteins. Dephosphorylation of Ser-259 (CRAF numbering) and dissociation of 14-3-3 release the RAF regulatory domains RAS-binding domain and cysteine-rich domain for interaction with RAS-GTP and membrane lipids. This, in turn, results in RAF phosphorylation at Ser-621 and 14-3-3 reassociation, followed by its dimerization and ultimately substrate binding and phosphorylation. This review focuses on structural understanding of how distinct binding partners trigger a cascade of molecular events that induces RAF kinase activation.

Pharmacological Induction of RAS-GTP Confers RAF Inhibitor Sensitivity in KRAS Mutant Tumors

Targeting KRAS mutant tumors through inhibition of individual downstream pathways has had limited clinical success. Here we report that RAF inhibitors exhibit little efficacy in KRAS mutant tumors. In combination drug screens, MEK and PI3K inhibitors synergized with pan-RAF inhibitors through an RAS-GTP-dependent mechanism. Broad cell line profiling with RAF/MEK inhibitor combinations revealed synergistic efficacy in KRAS mutant and wild-type tumors, with KRAS^G13D mutants exhibiting greater synergy versus KRAS^G12 mutant tumors. Mechanistic studies demonstrate that MEK inhibition induced RAS-GTP levels, RAF dimerization and RAF kinase activity resulting in MEK phosphorylation in synergistic tumor lines regardless of KRAS status. Taken together, our studies uncover a strategy to rewire KRAS mutant tumors to confer sensitivity to RAF kinase inhibition.

Autoinhibition in Ras effectors Raf, PI3Kα, and RASSF5: a comprehensive review underscoring the challenges in pharmacological intervention

Autoinhibition is an effective mechanism that guards proteins against spurious activation. Despite its ubiquity, the distinct organizations of the autoinhibited states and their release mechanisms differ. Signaling is most responsive to the cell environment only if a small shift in the equilibrium is required to switch the system from an inactive (occluded) to an active (exposed) state. Ras signaling follows this paradigm. This underscores the challenge in pharmacological intervention to exploit and enhance autoinhibited states. Here, we review autoinhibition and release mechanisms at the membrane focusing on three representative Ras effectors, Raf protein kinase, PI3Kα lipid kinase, and NORE1A (RASSF5) tumor suppressor, and point to the ramifications to drug discovery. We further touch on Ras upstream and downstream signaling, Ras activation, and the Ras superfamily in this light, altogether providing a broad outlook of the principles and complexities of autoinhibition.

Electrochemically Reduced Water Delays Mammary Tumors Growth in Mice and Inhibits Breast Cancer Cells Survival In Vitro

Electrochemical reduced water (ERW) has been proposed to have beneficial effects on human health due to its rich content of H₂ and the presence of platinum nanoparticles with antioxidant effects. Many studies have demonstrated that ERW scavenging properties are able to reduce the damage caused by oxidative stress in different experimental models. Although few in vivo studies have been reported, it has been demonstrated that ERW may display anticancer effects by induction of tumor cells apoptosis and reduction of both angiogenesis and inflammation. In this study, we show that ERW treatment of MCF-7, MDA-MB-453, and mouse (TUBO) breast cancer cells inhibited cell survival in a time-dependent fashion. ERW decreased ErbB2/neu expression and impaired pERK1/ERK2 and AKT phosphorylation in breast cancer cells. In addition, ERW treatment induced apoptosis of breast cancer cell lines independently of the status of p53 and ER and PR receptors. Our in vivo results showed that ERW treatment of transgenic BALB-neuT mice delayed the development of mammary tumors compared to the control. In addition, ERW induced a significant prolongation of tumor-free survival and a reduction in tumor multiplicity. Overall, these results suggest a potential beneficial role of ERW in inhibiting cancer cells growth.

ROCK inhibitor enhances the growth and migration of BRAF-mutant skin melanoma cells

Rho-associated protein kinase (ROCK) plays crucial roles in the proliferation and migration of different types of cells. ROCK inhibitor Y-27632 was previously reported to inhibit melanoma cell growth, and ROCK signaling was suggested to be a therapeutic target for treating melanoma. However, the negative effect of Y-27632 on melanoma cells was mainly seen in studies on murine B16 melanoma cells. Here, we reported that ROCK inhibitor actually promoted human melanoma cell growth and migration in vitro. Y-27632 increased the growth and migration of BRAF-mutated melanoma cells but had a negative effect on wild-type melanoma cells or primary melanocytes. We discovered that Y-27632 enhanced the growth of BRAF-mutated melanoma cells through increased ATK and ERK activity. The in vivo study further confirmed the in vitro finding. These data suggested that the effect of ROCK inhibitor on melanoma cells is cell-context dependent, and the application of ROCK inhibitor in the treatment of melanoma requires further study.

Mesenchymal stem cell (MSC)-mediated survival of insulin producing pancreatic β-cells during cellular stress involves signalling via Akt and ERK1/2

Mesenchymal stem cells (MSC) are of interest for cell therapy since their secreted factors mediate immunomodulation and support tissue regeneration. This study investigated the direct humoral interactions between MSC and pancreatic β-cells using human telomerase-immortalized MSC (hMSC-TERT) and rat insulinoma-derived INS-1E β-cells. hMSC-TERT supported survival of cocultured INS-1E β-cells during cellular stress by alloxan (ALX) and streptozotocin (STZ), but not in response to IL-1β. Accordingly, hMSC-TERT had no effect on inflammatory cytokine-related signalling via NF-kB and p-JNK but maintained p-Akt and upregulated p-ERK1/2. Inhibition of either p-Akt or p-ERK1/2 did not abolish protection by hMSC-TERT but activated the respective non-inhibited pathway. This suggests that one pathway compensates for the other. Main results were confirmed in mouse islets except hMSC-TERT-mediated upregulation of p-ERK1/2. Therefore, MSC promote β-cell survival by preservation of p-Akt signalling and further involve p-ERK1/2 activation in certain conditions such as loss of p-Akt or insulinoma background.

Vasoactive intestinal peptide induces proliferation of human hepatocytes

OBJECTIVES

Proliferation of hepatocytes in vitro can be stimulated by growth factors such as epidermal growth factor (EGF), but the role of vasoactive intestinal peptide (VIP) remains unclear. We have investigated the effect of VIP on maintenance and proliferation of human hepatocytes.

MATERIALS AND METHODS

Human hepatocytes were isolated from liver specimens obtained from patients undergoing liver surgery. Treatment with VIP or EGF was started 24 h after plating and continued for 3 or 5 d. DNA replication was investigated by Bromodeoxyuridine (BrdU) incorporation and cell viability detected by MTT assay. Cell lysate was analysed by western blotting and RT-PCR. Urea and albumin secretion into the culture supernatants were measured.

RESULTS

VIP increased DNA replication in hepatocytes in a dose-dependant manner, with a peak response at day 3 of treatment. VIP treatment was associated with an increase in mRNA expression of antigen identified by monoclonal antibody Ki-67 (MKI-67) and Histone Cluster 3 (H3) genes. Western blotting analysis showed that VIP can induce a PKA/B-Raf dependant phosphorylation of extracellular signal-regulated kinases (ERK). Although EGF can maintain hepatocyte functions up to day 5, no marked efffect was found with VIP.

CONCLUSIONS

VIP induces proliferation of human hepatocytes with little or no effect on hepatocyte differentiation. Further investigation of the role of VIP is required to determine if it may ultimately support therapeutic approaches of liver disease.

EZH2 Methyltransferase Activity Controls Pten Expression and mTOR Signaling during Fear Memory Reconsolidation

Memory retrieval induces a transient period of increased transcriptional and translational regulation in neurons called reconsolidation, which is regulated by the protein kinase B (AKT)-mammalian target of rapamycin (mTOR) pathway. However, it is currently unknown how activation of the AKT-mTOR pathway is regulated during the reconsolidation process. Here, we found that in male rats retrieval of a contextual fear memory transiently increased Enhancer of Zeste Homolog 2 (EZH2) levels along with increased histone H3 lysine 27 trimethylation (H3K27me3) levels, which correlated with decreased levels of phosphatase and tensin homolog (PTEN), a potent inhibitor of AKT-mTOR-dependent signaling in the hippocampus. Further experiments found increased H3K27me3 levels and DNA methylation across the Pten promoter and coding regions, indicating transcriptional silencing of the Pten gene. Pten H3K27me3 levels did not change following training or after the retrieval of a remote (old) fear memory, suggesting that this mechanism of Pten repression was specific to the reconsolidation of a new memory. In vivo siRNA-mediated knockdown of Ezh2 in the hippocampus abolished retrieval-induced increases in H3K27me3 and prevented decreases in PTEN levels. Ezh2 knockdown attenuated increases in the phosphorylation of AKT and mTOR following retrieval, which could be restored by simultaneously reducing Pten, suggesting that H3K27me3 regulates AKT-mTOR phosphorylation via repression of Pten Consistent with these results, knockdown of Ezh2 in area CA1 before retrieval impaired memory on later tests. Collectively, these results suggest that EZH2-mediated H3K27me3 plays a critical role in the repression of Pten transcription necessary for AKT-mTOR activation and memory reconsolidation following retrieval.SIGNIFICANCE STATEMENT Understanding how critical translation pathways, like mTOR-mediated protein synthesis, are regulated during the memory storage process is necessary for improving memory impairments. This study tests whether mTOR activation is coupled to epigenetic mechanisms in the hippocampus following the retrieval of a contextual fear memory. Specifically, this study evaluates the role of epigenetic modifications in the form of histone methylation in downstream mTOR translational control during learning-dependent synaptic plasticity in neurons. Considering the broad implications of transcriptional and translational mechanisms in synaptic plasticity, psychiatric, and neurological and neurodegenerative disorders, these data are of interest to the neuroscience community due to the robust and specific regulation of mTOR signaling we found to be dependent on repressive histone methylation.

131 -Oxophorbine protopheophorbide A from Ziziphus lotus as a novel mesenchymal-epithelial transition factor receptor inhibitory lead for the control of breast tumor growth in vitro and in vivo

The failure of chemotherapy especially in triple negative breast cancer (TNBC) patients has been correlated with the overexpression of the mesenchymal-epithelial transition factor (c-Met) receptor. Thus, the hepatocyte growth factor (HGF)/c-Met signaling axis has gained considerable attention as a valid molecular target for breast cancer therapy. This study reports for the first time the discovery of the 13¹ -oxophorbines pheophorbide A and protopheophorbide A along with chlorophyllide A from Ziziphus lotus, an edible typical Tunisian plant, as the potent antiproliferative compounds against the human breast cancer cells MDA-MB-231 and MCF-7. Compared to other compounds, protopheophorbide A exerted the highest light-independent antiproliferative effect against the metastatic TNBC MDA-MB-231 cells (IC₅₀  = 6.5 μM). In silico, this compound targeted the kinase domain of multiple c-Met crystal structures. It potently inhibited the kinase domain phosphorylation of wild and mutant c-Met in Z-LYTE kinase assay. Protopheophorbide A inhibited HGF-induced downstream c-Met-dependent cell proliferation, survival, adhesion and migration through RAF/MEK/ERK and PI3K/PTEN/AKT signaling pathways modulation, ROS generation and activation of JNK and p38 pathways. Interestingly, this compound impaired the ability of the MDA-MB-231 cells to adhere at different extracellular matrix proteins by reducing the HGF-induced expression of integrins αv, β3, α2, and β1. Moreover, protopheophorbide A exhibited anti-migratory properties (IC₅₀  = 2.2 μM) through impacting the expression levels of E-cadherin, vimentin, β-catenin, FAK, Brk, Rac, and Src proteins. Importantly, treatment with protopheophorbide A significantly inhibited the MDA-MB-231 tumor growth in vivo. Our results suggest that protopheophorbide A could be a novel c-Met inhibitory lead with promise to control c-Met/HGF-dependent breast malignancies.

The effects of flutamide on cell-cell junctions in the testis, epididymis, and prostate

In this review, we summarize recent findings on the effect of the anti-androgen flutamide on cell-cell junctions in the male reproductive system. We outline developmental aspects of flutamide action on the testis, epididymis, and prostate, and describe changes in junction protein expression and organization of junctional complexes in the adult boar following prenatal and postnatal exposure. We also discuss findings on the mechanisms by which flutamide induces alterations in cell-cell junctions in reproductive tissues of adult males, with special emphasis on cytoplasmic effects. Based on the results from in vivo and in vitro studies in the rat, we propose that flutamide affects the expression of junction proteins and junction complex structure not only by inhibiting androgen receptor activity, but equally important by modulating protein kinase-dependent signaling in testicular cells. Additionally, results from studies on prostate cancer cell lines point to a role for the cellular molecular outfit in response to flutamide.

Administration of Oxygen Ultra-Fine Bubbles Improves Nerve Dysfunction in a Rat Sciatic Nerve Crush Injury Model

Ultra-fine bubbles (<200 nm in diameter) have several unique properties and have been tested in various medical fields. The purpose of this study was to investigate the effects of oxygen ultra-fine bubbles (OUBs) on a sciatic nerve crush injury (SNC) model rats. Rats were intraperitoneally injected with 1.5 mL saline, OUBs diluted in saline, or nitrogen ultra-fine bubbles (NUBs) diluted in saline three times per week for 4 weeks in four groups: (1) control, (sham operation + saline); (2) SNC, (crush + saline); (3) SNC+OUB, (crush + OUB-saline); (4) SNC+NUB, (crush + NUB-saline). The effects of the OUBs on dorsal root ganglion (DRG) neurons and Schwann cells (SCs) were examined by serial dilution of OUB medium in vitro. Sciatic functional index, paw withdrawal thresholds, nerve conduction velocity, and myelinated axons were significantly decreased in the SNC group compared to the control group; these parameters were significantly improved in the SNC+OUB group, although NUB treatment did not affect these parameters. In vitro, OUBs significantly promoted neurite outgrowth in DRG neurons by activating AKT signaling and SC proliferation by activating ERK1/2 and JNK/c-JUN signaling. OUBs may improve nerve dysfunction in SNC rats by promoting neurite outgrowth in DRG neurons and SC proliferation.