A novel dimeric dipeptide mimetic of the BDNF selectively activates the MAPK-Erk signaling pathway

On the basis of the structure of beta-turn of loop 2 of brain-derived neurotrophic factor (BDNF), its new dimeric dipeptide mimetic bis-(N-hexanoyl-L-seryl-L-lysine) hexamethylenediamide (GTS-201) was created. It activated TrkB and Erk, did not activate Akt, and exhibited neuroprotective activity in vitro at concentrations of 10^–5–10^–8 M. Unlike the mimetics that activate Erk and Akt, GTS-201 did not exhibit antidepressant properties. For the manifestation of the antidepressant activity of BDNF mimetics, the activation of its both major signaling pathways is required.     

Antibacterial,Anticancer and Neuroprotective Activities of Rare Actinobacteria from Mangrove Forest Soils

Mangrove is a complex ecosystem that contains diverse microbial communities, including rare actinobacteria with great potential to produce bioactive compounds. To date, bioactive compounds extracted from mangrove rare actinobacteria have demonstrated diverse biological activities. The discovery of three novel rare actinobacteria by polyphasic approach, namely Microbacterium mangrovi MUSC 115^T, Sinomonas humi MUSC 117^T and Monashia flava MUSC 78^T from mangrove soils at Tanjung Lumpur, Peninsular Malaysia have led to the screening on antibacterial, anticancer and neuroprotective activities. A total of ten different panels of bacteria such as Methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300, ATCC 70069, Pseudomonas aeruginosa NRBC 112582 and others were selected for antibacterial screening. Three different neuroprotective models (hypoxia, oxidative stress, dementia) were done using SHSY5Y neuronal cells while two human cancer cells lines, namely human colon cancer cell lines (HT-29) and human cervical carcinoma cell lines (Ca Ski) were utilized for anticancer activity. The result revealed that all extracts exhibited bacteriostatic effects on the bacteria tested. On the other hand, the neuroprotective studies demonstrated M. mangrovi MUSC 115^T extract exhibited significant neuroprotective properties in oxidative stress and dementia model while the extract of strain M. flava MUSC 78^T was able to protect the SHSY5Y neuronal cells in hypoxia model. Furthermore, the extracts of M. mangrovi MUSC 115^T and M. flava MUSC 78^T exhibited anticancer effect against Ca Ski cell line. The chemical analysis of the extracts through GC–MS revealed that the majority of the compounds present in all extracts are heterocyclic organic compound that could explain for the observed bioactivities. Therefore, the results obtained in this study suggested that rare actinobacteria discovered from mangrove environment could be potential sources of antibacterial, anticancer and neuroprotective agents.     

Dipeptide Mimetic of the BDNF GSB-106 with Antidepressant-Like Activity Stimulates Synaptogenesis

Dipeptide mimetic of the brain-derived neurotrophic factor bis(N-monosuccinyl-L-seryl-L-lysine) hexamethylenediamide (working name GSB-106), which reproduces the homodimeric structure of BDNF and the beta-turn of its fourth loop, activates TrkB, AKT, and ERK, exhibits neuroprotective and antidepressant activity, and is able to stimulate neurogenesis in the hippocamp of stressed mice. Using Western blot hybridization and synaptophysin (synaptogenesis marker), we showed the ability of chronically administered GSB-106 to stimulate synaptogenesis, increasing the synaptic density in the hippocamp by 50%. Under the same conditions, GSB-106 exhibited antidepressant activity (decreased (by 18%) immobility of animals in Porsolt test), which may be associated with the stimulation of neurogenesis and synaptogenesis in the hippocamp.     

Effect and mechanisms of sacral nerve stimulation on visceral hypersensitivity mediated by nerve growth factor

To investigate the efficacy of sacral nerve stimulation (SNS) on nerve growth factor (NGF) mediated visceral sensitivity in normal rat and visceral hypersensitivity model rats. 120 male newborn rats were randomly divided into 6 groups: group A was normal model group; group B ~ F were all sensitized with acetic acid enema and grouped again. Group c2 was given NGF antagonist, d2 group was given NGF agonist, e2 group was given PI3K inhibitor, and f2 group was given PLC‐γ inhibitor. After treatment, the expression of NGF, TrKA, PI3K, AKT, PLC‐γ, NF‐κB, TRPV1, pTRPV1 and intracellular Ca²⁺ content were detected. The expression of protein TRPV1 and pTRPV1 was increased, and Ca²⁺ was increased in the visceral hypersensitive group. NGF, TrKA in NGF antagonist group, PI3K, AKT, NF‐κB in PI3K inhibitor group, PLC‐γ in PLC‐γ inhibitor group were all almost not expressed. The relative expression of NGF, TrKA, PI3K, AKT, PLC‐γ and NF‐κB in NGF antagonist group was lower than that in visceral hypersensitivity group and NGF activator group (P < .01). The relative expression of NGF, TrKA, PI3K and AKT mRNA in NGF antagonist group was lower than that in the normal model group (P < .01). There was no significant difference in the relative expression of PLC‐γ and NF‐κB mRNA (P > .05). The expression level of MAPK, ERK1 and ERK2 in visceral hypersensitivity group was higher than that in PI3K inhibitor group and PLC‐γ inhibitor group. The normal group Ca²⁺ curve was flat, and the NGF agonist group had the highest Ca²⁺ curve peak. Calcium concentration in visceral hypersensitivity group was higher than that in PI3K inhibitor group and that in PLC‐γ inhibitor group was higher than that in NGF antagonist group. The binding of TrkA receptor to NGF activates the MAPK/ERK pathway, the PI3K/Akt pathway and the PLC‐γ pathway, causing changes in the fluidity of intracellular and extracellular Ca²⁺, resulting in increased sensitivity of visceral tissues and organs.     

Bis(acetylacetonato)-oxidovanadium(IV) and sodium metavanadate inhibit cell proliferation via ROS-induced sustained MAPK/ERK activation but with elevated AKT activity in human pancreatic cancer AsPC-1 cells

In this study, the antiproliferative effect of bis(acetylacetonato)-oxidovanadium(IV) and sodium metavanadate and the underlying mechanisms were investigated in human pancreatic cancer cell line AsPC-1. The results showed that both exhibited an antiproliferative effect through inducing G2/M cell cycle arrest and can also cause elevation of reactive oxygen species (ROS) levels in cells. Moreover, the two vanadium compounds induced the activation of both PI3K/AKT and MAPK/ERK signaling pathways dose- and time-dependently, which could be counteracted with the antioxidant N-acetylcysteine. In the presence of MEK-1 inhibitor, the degradation of Cdc25C, inactivation of Cdc2 and accumulation of p21 were relieved. However, the treatment of AKT inhibitor did not cause any significant effect. Therefore, it demonstrated that the ROS-induced sustained MAPK/ERK activation rather than AKT contributed to vanadium compounds-induced G2/M cell cycle arrest. The current results also exhibited that the two vanadium compounds did not induce a sustained increase of ROS generation, but the level of ROS reached a plateau instead. The results revealed that an intracellular feedback loop may be against the elevated ROS level induced by vanadate or VO(acac)₂, evidenced by the increased GSH content, the unchanged level at the expression of antioxidant enzymes. Therefore, vanadium compounds can be regarded as a novel type of anticancer drugs through the prolonged activation of MAPK/ERK pathway but retained AKT activity. The present results provided a proof-of-concept evidence that vanadium-based compounds may have the potential as both antidiabetic and antipancreatic cancer agents to prevent or treat patients suffering from both diseases.     

Neuroprotection of Interleukin-6 Against NMDA-induced Neurotoxicity is Mediated by JAK/STAT3, MAPK/ERK, and PI3K/AKT Signaling Pathways

We have previously shown that interleukin-6 (IL-6) has neuroprotective effect against N-methyl-d-aspartate (NMDA)-induced excitotoxicity. The current study aimed to reveal signal transduction pathways involved in the IL-6 neuroprotection. Cerebellar granule neurons (CGNs) from postnatal 8-day infant rats were exposed to IL-6 (120 ng/ml) for 8 days and stimulated with NMDA (100 μM) for 15 or 30 min. Dynamic intracellular Ca²⁺ fluorescence intensity, cytosolic Ca²⁺-dependent phospholipase A2 (cPLA2) expression, and apoptosis and necrosis in cultured CGNs were measured by laser scanning confocal microscope, real-time PCR and Western blot, and annexin V-FITC/propidium iodide staining, respectively. NMDA stimulation of neurons evoked an intracellular Ca²⁺ overload, an upregulated expression of cPLA2, and an increase in cell death. Chronic IL-6 exposure prevented the NMDA-evoked neuronal Ca²⁺ overload, cPLA2 expression upregulation, and apoptosis and necrosis. Anti-gp130 monoclonal antibody (mAb), a blocker of gp130 that is a 130-kDa signal-transducing β-subunit of IL-6 receptor complex, blocked these effects of IL-6 preventing NMDA neurotoxicity. AG490, PD98059, or LY294002, inhibitors specific for the intracellular signals, JAK, MAPK, and PI3K, respectively, partially blocked these IL-6 neuroprotective effects. Phosphorylation levels of STAT3, ERK1/2, and AKT, the downstream proteins for these enzymes of JAK, MAPK, and PI3K, respectively, were elevated by IL-6 pretreatment. The enhanced activation of STAT3, ERK1/2, and AKT by IL-6 was abolished by AG490, PD98059, and LY294002, respectively. Anti-gp130 mAb attenuated the activation of all the three detected signaling molecules. The present findings suggest that IL-6 neuroprotection is jointly mediated by the cellular signal transduction pathways, gp130-JAK-STAT3, gp130-MAPK-ERK, and gp130-PI3K-AKT.     

Taxonomic description and draft genome of <Emphasis Type="Italic">Pseudomonas sediminis</Emphasis> sp. nov., isolated from the rhizospheric sediment of <Emphasis Type="Italic">Phragmites karka</Emphasis>

The taxonomic position of a Gram-stain-negative, rod-shaped bacterial strain, designated PI11^T, isolated from the rhizospheric sediment of Phragmites karka was characterized using a polyphasic approach. Strain PI11^T could grow optimally at 1.0% NaCl concentration with pH 7.0 at 30°C and was positive for oxidase and catalase but negative for hydrolysis of starch, casein, and esculin ferric citrate. Phylogenetic analysis of 16S rRNA gene sequences indicated that the strain PI11^T belonged to the genus Pseudomonas sharing the highest sequence similarities with Pseudomonas indoloxydans JCM 14246^T (99.72%), followed by, Pseudomonas oleovorans subsp. oleovorans DSM 1045^T (99.29%), Pseudomonas toyotomiensis JCM 15604^T (99.15%), Pseudomonas chengduensis DSM 26382^T (99.08%), Pseudomonas oleovorans subsp. lubricantis DSM 21016^T (99.08%), and Pseudomonas alcaliphila JCM 10630^T (99.01%). Experimental DNA-DNA relatedness between strain PI11^T and P. indoloxydans JCM 14246^T was 49.4%. The draft genome of strain PI11^T consisted of 4,884,839 bp. Average nucleotide identity between the genome of strain PI11^T and other closely related type strains ranged between 77.25–90.74%. The polar lipid pattern comprised of phosphatidylglycerol, diphosphatidylglycerol, and phosphatidylcholine. The major (> 10%) cellular fatty acids were C_18:1ω6c/ω7c, C_16:1ω6c/ω7c, and C_16:0. The DNA G + C content of strain PI11^T was 62.4 mol%. Based on the results of polyphasic analysis, strain PI11^T was delineated from other closely related type strains. It is proposed that strain PI11^T represents represents a novel species of the genus Pseudomonas, for which the name Pseudomonas sediminis sp. nov. is proposed. The type strain is PI11^T (= KCTC 42576^T = DSMZ 100245^T).     

Metagenomic analysis reveals the contribution of anaerobic methanotroph-1b in the oxidation of methane at the Ulleung Basin,East Sea of Korea

We have previously identified a sulfate methane transition zone (SMTZ) within the methane hydrate-bearing sediment in the Ulleung Basin, East Sea of Korea, and the presence of ANME-1b group in the sediment has been shown by phylogenetic analysis of a 16S rRNA gene. Herein, we describe taxonomic and functional profiling in the SMTZ sample by metagenomic analysis, comparing with that of surface sediment. Metagenomic sequences of 115 Mbp and 252 Mbp were obtained from SMTZ and surface sediments, respectively. The taxonomic profiling using BLASTX against the SEED within MG-RAST showed the prevalence of methanogens (19.1%), such as Methanosarcinales (12.0%) and Methanomicrobiales (4.1%) predominated within the SMTZ metagenome. A number of 185,200 SMTZ reads (38.9%) and 438,484 surface reads (62.5%) were assigned to functional categories, and methanogenesis-related reads were statistically significantly overrepresented in the SMTZ metagenome. However, the mapping analysis of metagenome reads to the reference genomes, most of the sequences of the SMTZ metagenome were mapped to ANME-1 draft genomes, rather than those of methanogens. Furthermore, the two copies of the methyl-coenzyme M reductase gene (mcrA) segments of the SMTZ metagenome were clustered with ANME-1b in the phylogenetic cluster. These results indicate that ANME-1b reads were miss-annotated to methanogens due to limitation of database. Many of key genes necessary for reverse methanogenesis were present in the SMTZ metagenome, except for N⁵,N¹⁰-methenyl-H₄MPT reductase (mer) and CoB-CoM heterodisulfide reductase subunits D and E (hdrDE). These data suggest that the ANME-1b represents the primary player the anaerobic methane oxidation in the SMTZ, of the methane hydrate-bearing sediment at the Ulleung Basin, East Sea of Korea.     

Intestinal enterobacteria of the hibernating <Emphasis Type="Italic">Apis mellifera mellifera</Emphasis> L. bees

Dynamics of enterobacteria of normal intestinal microflora was studied in Apis mellifera mellifera L. bees hibernating under snow in the Western Urals. The cell numbers (N) of the predominant species Klebsiella oxytoca increased from 10-10⁶ CFU/bee in November 2004 to 10⁴-10⁷ CFU/bee in March 2005; its frequency of occurrence (P) increased from 92 to 100%. Increase of Providencia rettgeri (11.2004: N up to 10⁶, P 25%; 03.2005: N 10²-10⁶, P 80%) was accompanied by the substitution of Morganella morganii (11.2004: N up to 10⁶, P 25%) with Proteus vulgaris (03.2005: N up to 10⁵, P 8%). By spring, Hafnia alvei and Citrobacter sp., which are pathogenic to bees, disappeared (11.2004: N up to 10⁵, P 13 and 10%, respectively). Endophytic species Pantoea agglomerans, Leclecria sp., and other representatives of the “Enterobacter agglomerans” group were present in November and after the first emergence in spring (N up to 10⁵; November: P 15%; April: P 23%). In April, the number of enterobacteria decreased to 10⁵, and P. rettgeri became the predominant species (P 54%) instead of K. oxytoca (P 43%).     

Protective Effect of Aliskiren in Experimental Ischemic Stroke: Up-Regulated p-PI3K,p-AKT,Bcl-2 Expression,Attenuated Bax Expression

Aliskiren (ALK), a pharmacological renin inhibitor, is an effective antihypertensive drug and has potent anti-apoptotic activity, but it is currently unknown whether ALK is able to attenuate brain damage caused by acute cerebral ischemia independent of its blood pressure-lowering effects. This study aimed to investigate the role of ALK and its potential mechanism in cerebral ischemia. C57/BL6 mice were subjected to transient middle cerebral artery occlusion (tMCAO) and treated for 5 days with Vehicle or ALK (10 or 25 mg/kg per day via intragastric administration), whereas Sham-operated animals served as controls. Treatment with ALK significantly improved neurological deficits, infarct volume, brain water content and Nissl bodies after stroke (P < 0.05), which did not affect systemic blood pressure. Furthermore, the protection of ALK was also related to decreased levels of apoptosis in mice by enhanced activation of phosphatidylinositol 3-kinase (PI3K)/AKT pathway, increased level of Bcl-2 and reduced Bax expression (P < 0.05). In addition, ALK’s effects were reversed by PI3K inhibitors LY294002 (P < 0.05). Our data indicated that ALK protected the brain from reperfusion injuries without affecting blood pressure, and this effect may be through PI3K/AKT signaling pathway.     

Quorum sensing systems of regulation,synthesis of phenazine antibiotics,and antifungal activity in rhizospheric bacterium <Emphasis Type="Italic">pseudomonas chlororaphis</Emphasis> 449

Strain Pseudomonas chlororaphis 449, an antagonist of a broad spectrum of phytopathogenic microorganisms isolated from the maize rhizosphere, was shown to produce three phenazine antibiotics: phenazine-1-carboxylic acid (PCA), 2-hydroxylphenazine-1-carboxylic acid (2-OH-PCA), and 2-hydroxylphenazine (2-OH-PHZ). Two Quorum Sensing (QS) systems of regulation were identified: Phz/R and CsaI/R. Genes phzI and csaI were cloned and sequenced. Cells of strain 449 synthesize at least three types of AHL: N-butanoyl-L-homoserine lactone (C₄-AHL), N-hexanoyl-L-homoserine lactone (C₆-AHL), and N-(3-oxo-hexanoyl)-L-homoserine lactone (30C₆-AHL). Transposon mutagenesis was used to generate mutants of strain 449 deficient in synthesis of phenazines, which carried inactivated phzA and phzB genes of the phenazine operon and gene phzO. Mutations phzA ^? and phzB ^? caused a drastic reduction in the antagonistic activity of bacteria toward phytopathogenic fungi. Both mutants lost the ability to protect cucumber and leguminous plants against phytopathogenic fungi Rhizoctonia solani and Sclerotinia sclerotiorum. These results suggest a significant role of phenazines in the antagonistic activity of P. chlororaphis 449.     

Protective Effects of Paeoniflorin Against MPP<Superscript>+</Superscript>-induced Neurotoxicity in PC12 Cells

In the present study, we investigated the protective mechanism of paeoniflorin (PF), a monoterpene glycoside extracted from Radix Paeoniae alba roots, on MPP⁺-induced neurotoxicity in cultured rat pheochromocytoma cells (PC12). Our work included examination of cell viability assessment, amounts of released lactic dehydrogenase (LDH), intracellular Ca²⁺ concentration, cell apoptosis, mitochondrial membrane potential, caspase-3 activity, and expression profiling of two apoptosis-related genes (Bcl-2 and Bax). It was shown that, PF functioned as an MPP⁺ antagonist, being able to suppress apoptosis, decrease LDH release and Ca²⁺ concentration, attenuate membrane potential collapse and, inhibit caspase-3 activation, decrease in Bax/Bcl-2 ratio. These observations suggest that PF could protect PC12 cells against MPP⁺-induced injury and the mechanism PF’s neuroprotective effect was closely associated with Bcl-2 up-regulation and Bax down-regulation. PF has neuroprotective effects on MPP⁺-induced apoptosis in PC12 cells via regulating mitochondrial membrane potential and Bcl-2/Bax/caspase-3 signaling pathways, and this new insight will help develop a PF-based therapeutic strategy for treatmenting neurodegenerative diseases and injury.     

Crosstalk between Raf/MEK/ERK and PI3K/AKT in suppression of Bax conformational change by Grp75 under glucose deprivation conditions

During glucose deprivation (GD)-induced cellular stress, the molecular chaperone glucose-regulated protein 75 (Grp75)/Mortalin/PBP74/mtHSP70 (hereafter termed “Grp75”) plays an important role in the suppression of apoptosis by inhibiting the Bax conformational change that delays the release of cytochrome c. The molecular pathways by which it carries out these functions are still unclear. We hypothesize that the anti-apoptotic effect by the overexpression of Grp75 was through the signal of AKT activated by classic phosphoinositide 3-kinase (PI3K) and also involved PI3K-independent pathways. Using the PC12 cell GD model, we demonstrated a novel mechanism of Grp75 activating AKT, which may be PI3K independent and associated with Raf/MEK (mitogen-activated protein kinase/ERK kinase)/ERK signaling. The PI3K inhibitor LY294002 did not influence the activation of AKT by the Grp75 overexpression under GD; however, the MEK inhibitor U0126 dramatically inhibited AKT phosphorylation in the same assay. In addition to the PI3K/AKT signal pathway, Grp75 overexpression also inhibited the Bax conformational change through the Raf/MEK/ERK signal pathway. In conclusion, Grp75 overexpression in activating AKT can be PI3K independent and associated with Raf/MEK/ERK signaling under GD. At the same time, PI3K may also crosstalk with Raf-1, in which the prosurvival signal of PI3K maintains the expression of Raf-1. The activated AKT and extracellular signal-regulated protein kinases 1 and 2 by Grp75 inhibited the Bax conformational change and subsequent apoptosis.     

The same cellular signaling pathways mediate survival in sensory neurons that switch their trophic requirements during development

A distinct subpopulation of rat dorsal root sensory (DRG) neurons, termed P-neurons, switch their trophic requirements for survival during development from nerve growth factor (NGF) at embryonic stages to basic fibroblast growth factor (bFGF) just after birth. We investigated in cultured P-neurons the intracellular signaling pathways mediating survival before and after this switch. The NGF-induced survival was completely blocked by either wortmannin (100 nM) or PD98059 (25-50 nM), which selectively inhibit the phosphatidylinositol 3-kinase-AKT (PI3 kinase-AKT) and mitogen-activated kinase kinase extracellular regulated kinase (MEK-ERKs) pathways, respectively. NGF activated AKT and ERKs in single embryonic P-neurons, as assayed by immunofluorescence of phosphorylated proteins. In concordance with the survival assays, wortmannin and PD98059 blocked AKT and ERKs activation, respectively. Following the trophic switch, bFGF used the same signaling pathways to promote survival of post-natal P-neurons, as either wortmannin or PD98059 blocked its effect. Also, bFGF activated AKT and ERKs in single P-neurons, and this activation was blocked by the same inhibitors. These results strongly suggest that both pathways concurrently mediate the action of NGF and bFGF during embryonic and post-natal periods, respectively. Thus, we report the novel result that the switch in trophic requirements occurs with conservation of the signaling pathways mediating survival.     

Bacteria-induced static batch fungal fermentation of the diterpenoid cyathin A<Subscript>3</Subscript>, a small-molecule inducer of nerve growth factor

Cyathin A₃, produced by the fungus Cyathus helenae, is a member of the cyathane family of diterpene natural products. While many of the cyathanes display antibacterial/antimicrobial activity or have cytotoxic activity against human cancer cell lines, their most exciting therapeutic potential is derived from their ability to induce nerve growth factor (NGF) release from glial cells, making the cyathanes attractive lead molecules for the development of neuroprotective therapeutics to prevent/treat Alzheimer’s disease. To investigate if cyathin A₃ has NGF-inducing activity, we set out to obtain it using published C. helenae bench-scale fungal fermentations. However, to overcome nonproducing fermentations, we developed an alternative, bacteria-induced static batch fermentation approach to the production of cyathin A₃, as described in this report. HPLC, UV absorption spectra, and mass spectrometry identify cyathin A₃ in fungal fermentations induced by the timely addition of Escherichia coli K12 or Bacillus megabacterium. Pre-filtration of the bacterial culture abolishes cyathin A₃ induction, suggesting that bacteria-associated media changes or physical interaction between the fungus and bacteria underlie the induction mechanism. Through alteration of incubation conditions, including agitation, the timing of induction, and media composition, we optimized the fermentation to yield nearly 1 mg cyathin A₃/ml media, a sixfold increase over previously described yields. Additionally, by comparison of fermentation profiles, we reveal that cyathin A₃ biosynthesis is regulated by carbon catabolite repression. We have used an enzyme-linked immunosorbent assay to illustrate that cyathin A₃ induces NGF release from cultured glial cells, and therefore cyathin A₃ warrants further examination in the development of neuroprotective therapeutics.     

Lamotrigine Attenuates Proteasome Inhibition-Induced Apoptosis by Suppressing the Activation of the Mitochondrial Pathway and the Caspase-8- and Bid-Dependent Pathways

Proteasome impairment has been shown to be involved in neuronal degeneration. Antiepileptic lamotrigine has been demonstrated to have a neuroprotective effect. However, the effect of lamotrigine on the proteasome inhibition-induced neuronal cell death has not been studied. Therefore, we assessed the effect of lamotrigine on the proteasome inhibition-induced neuronal cell apoptosis in relation to cell death process using differentiated PC12 cells and SH-SY5Y cells. The proteasome inhibitors MG132 and MG115 induced a decrease in the levels of Bid and Bcl-2 proteins, an increase in the levels of Bax and p53, loss of the mitochondrial transmembrane potential, cytochrome c release and activation of caspases (-8, -9 and -3). The addition of lamotrigine reduced the proteasome inhibitor-induced changes in the apoptosis-related protein levels, production of reactive oxygen species, depletion and oxidation of glutathione (GSH), and cell death in both cell lines. Lamotrigine and N-acetylcysteine alone did not affect the levels of 26S proteasome and activity of 20S proteasome. MG132 did not alter the levels of 26S proteasome but decreased activity of 20S proteasome. Lamotrigine and N-acetylcysteine attenuated MG132-induced decrease in the activity of 20S proteasome. The results show that lamotrigine appears to suppress the proteasome inhibitor-induced apoptosis in PC12 cells by suppressing the activation of the mitochondrial pathway and the caspase-8- and Bid-dependent pathways. The suppressive effect of lamotrigine appears to be associated with its inhibitory effect on the production of reactive oxygen species, the depletion and oxidation of GSH and the activity reduction of 20S proteasome.     

MYO18B promotes hepatocellular carcinoma progression by activating PI3K/AKT/mTOR signaling pathway

Background

MYO18B has been identified as a novel tumor suppressor gene in several cancers. However, its specific roles in the progression of hepatocellular carcinoma (HCC) has not been well defined.

Methods

We firstly identified the expression and prognostic values of MYO18B in HCC using TCGA cohort and our clinical data. Then, MYO18B knockdown by RNA inference was implemented to investigate the effects of MYO18B on HCC cells. Quantitative RT-PCR and Western blot were used to determine gene and protein expression levels. CCK-8 and colony formation assays were performed to examine cell proliferation capacity. Wound healing and transwell assays were used to evaluate the migration and invasion of HepG2 cells.

Results

MYO18B was overexpressed and correlated with poor prognosis in HCC. MYO18B expression was an independent risk factor for overall survival. Knockdown of MYO18B significantly inhibited the proliferation, migration and invasion of HepG2 cells. Meanwhile, MYO18B knockdown could effectively suppress the phosphorylation of PI3K, AKT, mTOR and P70S6K, suggesting that MYO18B might promote HCC progression by targeting PI3K/AKT/mTOR signaling pathway.

Conclusions

MYO18B promoted tumor growth and migration via the activation of PI3K/AKT/mTOR signaling pathway. MYO18B might be a promising target for clinical intervention of HCC.