Comprehensive analysis of the RSK gene family in acute myeloid leukemia determines a prognostic signature for the prediction of clinical prognosis and treatment responses.

OBJECTIVE: The prognosis of acute myeloid leukemia (AML) remains poor although the basic and translational research has been highly productive in understanding the genetics and pathopoiesis of AML and a plethora of targeted therapies have been developed. Consequently, it is crucial to deepen the knowledge of molecular pathogenesis underlying AML for the advancement of new treatment options. METHOD: A RSK gene family-related signature was constructed to investigate whether RSK gene family members were useful in predicting the prognosis of AML patients. The relationship between the RSK gene family-related signature and the infiltration of immune cells was further assessed using the CIBERSORT algorithm. The 'oncoPredict' package was used to analyze relationships between the RSK gene family-related signature and the sensitivity to drugs or small molecules. RESULTS: Patients were classified into two groups using the RSK gene family-related signature following the median risk score. Overall survival (OS) was significantly longer in patients with low-risk scores than that in patients with high-risk scores as showed by both training and validation datasets. Moreover, the signature was helpful in predicting 1-year, 3-year, and 5-year OS in training and validation datasets. In addition, it was identified that low-risk patients exhibited greater sensitivity to 20 drugs or small molecules and that high-risk patients had higher sensitivity to 38 drugs or small molecules. CONCLUSION: RSK gene family members, particularly RPS6KA1 and RPS6KA4, may help to predict prognosis for AML patients. Furthermore, RPS6KA1 may serve as a novel drug target for AML.

A motif in the 5'untranslated region of messenger RNAs regulates protein synthesis in a S6 kinase-dependent manner.

The 5' untranslated regions (UTRs) in messenger RNAs (mRNAs) play an important role in the regulation of protein synthesis. We had previously identified a group of mRNAs that includes human semaphorin 7A (SEMA7A) whose translation is upregulated by the Erk/p90S6K pathway in human eosinophils, with a potential negative impact in asthma and airway inflammation. In the current study, we aimed to find a common 5'UTR regulatory cis-element, and determine its impact on protein synthesis. We identified a common and conserved 5'UTR motif GGCTG-[(C/G)T(C/G)]n-GCC that was present in this group of mRNAs. Mutations of the first two GG bases in this motif in SEMA7A 5'UTR led to a complete loss of S6K activity dependence for maximal translation. In conclusion, the newly identified 5'UTR motif present in SEMA7A has a critical role in regulating S6K-dependent protein synthesis.

Beyond controlling cell size: functional analyses of S6K in tumorigenesis.

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

Associations of the Methylation Levels of NFAT5, PVT1, RPS6KA1, and MIB1 with Steroid-Resistant Asthma.

BACKGROUND: This study detected the methylation levels of nuclear factor-5 (NFAT5), PVT1, ribosomal protein S6 kinase A-1 (RPS6KA1), and MIB1 in patients with steroid-resistant asthma (SRA) and explored their associations with SRA. METHODS: In our pilot study, we found abnormal methylation of NFAT5, PVT1, RPS6KA1, and MIB1 in SRA patients according to genome-wide methylation screening. This study expanded the sample size to further validate the results of the pilot study. Twenty patients with SRA, 20 patients with bronchial asthma, and 20 healthy volunteers constituted the SRA group, asthma control group, and healthy control group, respectively. The clinical data of all the participants were collected. Peripheral blood was taken for DNA extraction. The methylation loci and levels of NFAT5, PVT1, RPS6KA1, and MIB1 were detected using the Sequenom MassARRAY Nanodispenser RS1000. Data were processed and analyzed with SPSS 22.0 software. RESULTS: There were 24 CpG loci detected in the NFAT5 segment 7 in the PVT1 segment, 4 in the RPS6KA1 segment, and 3 in the MIB1 segment. Among these genes, RPS6KA exhibited hypomethylation in the SRA group, which showed significant differences at the CpG_1, CpG_2, and CpG_3 loci compared with the other groups (p < 0.05). No significant differences in the methylation levels of NFAT5, PVT1, and MIB1 were observed among the groups (p > 0.05). CONCLUSIONS: RPS6KA1 is hypomethylated in SRA patients, which may play a role in the development of SRA via the MAPK signaling pathway. However, the influence of the methylation of NFAT5, PVT1, and MIB1 on SRA development remains to be explored.

Overexpression of Ribosomal Protein S6 Kinase A4 (RPS6KA4) Predicts a Poor Prognosis in Hepatocellular Carcinoma Patients: A Study Based on TCGA Samples.

AIM: This study aims to comprehensively analyse the Ribosomal Protein S6 Kinase A4 (RPS6KA4) and determine the prognostic value for hepatocellular carcinoma (HCC). BACKGROUND: Liver cancer is a common type of tumor worldwide, and HCC accounts for about 75 to 85% of all primary liver cancer cases. The Ribosomal S6 protein kinases (RSK) family plays an important regulatory role in cell growth, movement, survival, and proliferation. METHODS: We collected the expression and clinicopathological features of RPS6KA4 in The Cancer Genome Atlas (TCGA) cohort and evaluated the prognostic value of RPS6KA4 in HCC. Gene Ontology (GO)/ Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Set Enrichment Analysis (GSEA) were performed to determine the enrichment pathways of RPS6KA4. Correlation between RPS6KA4 expression and immune infiltration was analyzed. Protein-protein interaction (PPI) network analysis was performed to screen hub genes. RESULTS: RPS6KA4 overexpression is statistically significant in HCC relative to normal tissues (P < 0.001). Increased expression of RPS6KA4 is associated with higher T stage (p=0.021), pathological stage (p=0.006), α-fetoprotein (AFP) value (p=0.026), and vascular invasion (p=0.023) of HCC. Overexpression of RPS6KA4 predicted worse overall survival (OS, P=0.002), disease-specific survival (DSS, P=0.012), and progress-free interval (PFI, P=0.031) for HCC. Univariate/multivariate Cox regression analysis confirmed that RPS6KA4 was an independent risk factor for HCC (P=0.002 in univariate analysis; P=0.014 in multivariate analysis). GO/KEGG analysis and GSEA analysis suggest that RPS6KA4 plays a precancer role in HCC through epigenetics, cell adhesion, tumor-driven GTPase pathways, infection-related carcinogenesis, and adaptive immunity. Immune infiltration analysis confirmed the strong negative relationship between RPS6KA4 and B cells, CD4+ T cells, macrophages, neutrophils, as well as dendritic cells. Protein-protein interactions (PPI) analysis and hub gene identification revealed the cancer-promoting effects of RPS6KA4 related to RSKs, AP-2, clathrin, and MAPK/ ERK pathways. CONCLUSION: RPS6KA4 is a potentially valuable molecule for understanding HCC tumorigenesis. Increased RPS6KA4 might be a promising prognostic factor for low HCC survival.

Ribosomal protein S6 kinase beta-1 gene variants cause hypertrophic cardiomyopathy.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is a genetic heart muscle disease with preserved or increased ejection fraction in the absence of secondary causes. Mutations in the sarcomeric protein-encoding genes predominantly cause HCM. However, relatively little is known about the genetic impact of signalling proteins on HCM. METHODS AND RESULTS: Here, using exome and targeted sequencing methods, we analysed two independent cohorts comprising 401 Indian patients with HCM and 3521 Indian controls. We identified novel variants in ribosomal protein S6 kinase beta-1 (RPS6KB1 or S6K1) gene in two unrelated Indian families as a potential candidate gene for HCM. The two unrelated HCM families had the same heterozygous missense S6K1 variant (p.G47W). In a replication association study, we identified two S6K1 heterozygotes variants (p.Q49K and p.Y62H) in the UK Biobank cardiomyopathy cohort (n=190) compared with matched controls (n=16 479). These variants are neither detected in region-specific controls nor in the human population genome data. Additionally, we observed an S6K1 variant (p.P445S) in an Arab patient with HCM. Functional consequences were evaluated using representative S6K1 mutated proteins compared with wild type in cellular models. The mutated proteins activated the S6K1 and hyperphosphorylated the rpS6 and ERK1/2 signalling cascades, suggesting a gain-of-function effect. CONCLUSIONS: Our study demonstrates for the first time that the variants in the S6K1 gene are associated with HCM, and early detection of the S6K1 variant carriers can help to identify family members at risk and subsequent preventive measures. Further screening in patients with HCM with different ethnic populations will establish the specificity and frequency of S6K1 gene variants.

Investigation of the hepatic mTOR/S6K1/SREBP1 signalling pathway in rats at different ages: from neonates to adults.

BACKGROUND: Dysfunctions in the lipogenic process controlled by the hepatic mTOR/S6K1/SREBP-1c signaling pathway may contribute to the pathogenesis of various chronic diseases. In the present study, we aimed to determine age-related changes in the mTOR/S6K1/SREBP1 pathway in rat liver tissues. METHODS AND RESULTS: We performed Western Blot analysis to determine age-related changes in the mTOR/S6K1/SREBP1 pathway in Sprague Dawley male rats liver tissues of six different age groups representing neonatal, infant, weaning, puberty, young adult, adult life periods, and Oil Red O staining to evaluate age-related lipid accumulation. We observed an increase in Akt and p-Akt levels with age in compared to the 0-day-old group. Total mTOR and SREBP1 expression increased from the 0-day-old to the 28-day-old group but decreased in the following age groups. p-mTOR and p-S6K1 levels in the 0-day-old group were higher than the other groups. S6K1 expression was lowest in the 0-day-old group and showed changes among the age groups. Lipid accumulation was seen in liver sections taken from the 12-month-old group. mTOR/S6K1/SREBP1 pathway expression showed changes with age during the neonatal-adult life cycle stages in rat liver tissues. CONCLUSION: We suggest that understanding the molecular mechanisms age-related changes of lipogenesis function is necessary to contribute to the development of therapeutic approaches.

IL-23 amplifies the epithelial-mesenchymal transition of mechanically conditioned alveolar epithelial cells in rheumatoid arthritis-associated interstitial lung disease through mTOR/S6 signaling.

Epithelial-mesenchymal transition (EMT) creates an environment facilitating fibrosis following alveolar epithelial cell injury. IL-23 has important roles in chronic autoimmune conditions like rheumatoid arthritis (RA), but its role in the interstitial lung disease that affects patients with RA is unclear. This study aimed to determine the profibrogenic role of IL-23 on somatic alveolar type I (ATI) epithelial cells. Primary ATI cells were isolated from rats and cultured on plastic dishes for 1-3 wk. After prolonged culture (≥14 days) on rigid culture dishes, primary ATI cells gradually acquired a mesenchymal phenotype, identified by decreased expression of caveolin-1, and reorganization of F-actin cytoskeleton, indicating the initiation of EMT by matrix stiffness. To determine how IL-23 promotes EMT in vitro, transitioning ATI cells, cultured on a stiff substrate for ≥14 days were stimulated with IL-23. The EMT phenotype was significantly enhanced by IL-23, which upregulated α-smooth muscle actin (α-SMA), collagen I/III protein, and decreased caveolin-1. Furthermore, IL-23 significantly promoted cell invasion, as well as apoptotic resistance on transitioning ATI cells. Mechanistically, IL-23-induced EMT was mammalian target of rapamycin/ribosomal protein S6 (mTOR/S6) signaling dependent and reversible by rapamycin. Transcriptional sequencing analysis of human lung fibrosis biopsy tissue revealed key roles for IL-23 in rheumatoid arthritis-associated interstitial lung disease (RA-ILD). This result was further validated by significantly upregulated IL-23 expression at the mRNA level in RA-ILD lung sections. Notably, transitioning ATI epithelial cells were abundantly detected in RA-ILD tissue. Taken together, these data support a role for IL-23 in the pathogenesis of RA lung fibrosis by promoting EMT in alveolar epithelial cells through mTOR/S6 signaling.

Hypertrophy of Rat Skeletal Muscle Is Associated with Increased SIRT1/Akt/mTOR/S6 and Suppressed Sestrin2/SIRT3/FOXO1 Levels.

Despite the intensive investigation of the molecular mechanism of skeletal muscle hypertrophy, the underlying signaling processes are not completely understood. Therefore, we used an overload model, in which the main synergist muscles (gastrocnemius, soleus) of the plantaris muscle were surgically removed, to cause a significant overload in the remaining plantaris muscle of 8-month-old Wistar male rats. SIRT1-associated pro-anabolic, pro-catabolic molecular signaling pathways, NAD and H2S levels of this overload-induced hypertrophy were studied. Fourteen days of overload resulted in a significant 43% (p < 0.01) increase in the mass of plantaris muscle compared to sham operated animals. Cystathionine-ß-synthase (CBS) activities and bioavailable H2S levels were not modified by overload. On the other hand, overload-induced hypertrophy of skeletal muscle was associated with increased SIRT1 (p < 0.01), Akt (p < 0.01), mTOR, S6 (p < 0.01) and suppressed sestrin 2 levels (p < 0.01), which are mostly responsible for anabolic signaling. Decreased FOXO1 and SIRT3 signaling (p < 0.01) suggest downregulation of protein breakdown and mitophagy. Decreased levels of NAD+, sestrin2, OGG1 (p < 0.01) indicate that the redox milieu of skeletal muscle after 14 days of overloading is reduced. The present investigation revealed novel cellular interactions that regulate anabolic and catabolic processes in the hypertrophy of skeletal muscle.

Growth promotion in Arabidopsis thaliana by bacterial cyclodipeptides involves the TOR/S6K pathway activation.

Cyclodipeptides (CDPs) are the smallest peptidic molecules that can be produced by diverse organisms such as bacteria, fungi, and animals. They have multiple biological effects. In this paper, we examined the CDPs produced by the bacteria Pseudomonas aeruginosa PAO1, which are known as opportunistic pathogens of humans and plants on TARGET OF RAPAMYCIN (TOR) signaling pathways, and regulation of root system architecture. This bacterium produces the bioactive CDPs: cyclo(L-Pro-L-Leu), cyclo(L-Pro-L-Phe), cyclo(L-Pro-L-Tyr), and cyclo(L-Pro-L-Val). In a previous report, these molecules were found to modulate basic cellular programs not only via auxin mechanisms but also by promoting the phosphorylation of the S6 ribosomal protein kinase (S6K), a downstream substrate of the TOR kinase. In the present work, we found that the inoculation of Arabidopsis plants with P. aeruginosa PAO1, the non-pathogenic P. aeruginosa ΔlasI/Δrhll strain (JM2), or by direct exposure of plants to CDPs influenced growth and promoted root branching depending upon the treatment imposed, while genetic evidence using Arabidopsis lines with enhanced or decreased TOR levels indicated a critical role of this pathway in the bacterial phytostimulation.

Elevated serum miR-3129-5p contributes to the progression of coronary heart disease via targeting mTOR.

The current study aims to explore the miRNA changes that occur in the serum of patients with coronary heart disease (CHD) and healthy controls using a microarray technique, thereby exploring the potential biomarkers in the diagnosis of CHD and the underlying mechanism. Clinical data were reviewed, and venous blood samples were collected from 66 cases of CHD and 58 cases of healthy controls. MicroRNA-wide expression profiling identified 16 miRNAs that were aberrantly decreased by ~2-fold in the serum of patients with CHD compared to that of healthy controls. RT-PCR analysis indicated that the expression of miR-3129-5p was increased the most in patients with CHD compared with that of controls. Moreover, serum miR-3129-5p was found to be highest in the severe stenosis group, followed by the moderate stenosis group and mild stenosis group. ROC analysis showed that serum miR-3129-5p could differentiate patients with CHD from controls. Further study showed that mTOR was a target gene of miR-3129-5p. Western blot assays demonstrated that miR-3129-5p significantly suppressed the phosphorylation of S6 but increased LC3II/LC3I and Beclin1 levels. Consistently, GFP-LC3 and TEM assays indicated that miR-3129 increased autophagy puncta in H9C2 cells. More importantly, silencing mTOR significantly decreased the expression of p-S6 but increased LC3II/LC3I and Beclin expression even in H9C2 cells transfected with miR-3129-5p inhibitor, indicating that miR-3129-5p-induced cell autophagy was mediated via mTOR in H9C2 cells. In summary, elevated serum miR-3129-5p contributes to CHD by targeting mTOR signaling and may be a therapeutic target in the treatment of CHD.

FoxO directly regulates the expression of TOR/S6K and vitellogenin to modulate the fecundity of the brown planthopper.

As a conserved transcription factor, FoxO plays a crucial role in multiple physiological processes in vivo, including stress resistance, longevity, growth and reproduction. Previous studies on FoxO have focused on human, mouse, Drosophila melanogaster and Caenorhabditis elegans, while there are few reports on agricultural pests and little is known about how FoxO modulates insect fecundity. In Asia, the brown planthopper (BPH) Nilaparvata lugens (Stål) is one of the most serious pests in rice production and high fecundity is the basis of the outbreak of BPH. Here, using the genome-wide ChIP-seq of NlFoxO in BPH, we found that NlFoxO binds to the promoters of ribosomal proteinS6 kinase (NlS6K) and serine/threonine-protein kinase mTOR (NlTOR) and increases their expression levels. We also found that NlFoxO directly binds to the exon of vitellogenin (NlVg) and has a specific inhibitory effect on its expression. In addition, the number of eggs laid and their hatching rate decreased significantly after injection of NlFoxO double-stranded RNA into BPH adults. Our findings provide direct evidence that FoxO modulates insect fecundity through binding to the promoters of NlS6K, NlTOR and the exon of NlVg and affecting their gene expression in the Vg network.

Evaluation of B-cell intracellular signaling by monitoring the PI3K-Akt axis in patients with common variable immunodeficiency and activated phosphoinositide 3-kinase delta syndrome.

BACKGROUND: Primary antibody deficiencies (PADs) are characterized by hypogammaglobulinemia and impaired B-cell differentiation. Patients with common variable immunodeficiency (CVID) present severe reductions in at least 2 serum immunoglobulins and impaired terminal differentiation of B cells. Most patients with CVID do not appear to present monogenic defects. Activated phosphoinositide 3-kinase delta syndrome (APDS), caused by gain-of-function mutations in the PIK3CD gene (p110δ), can present in patients with a CVID-like phenotype. Memory B-cell differentiation requires the orchestrated activation of numerous intracellular signaling pathways, which promote transcriptional programs required for long-term B-cell survival. The aim of this study was to develop a flow cytometry assay to trace the PI3K-Akt-mTOR pathway, a critical component of B-cell homeostasis, and analyze its status in PADs. METHODS: We analyzed the intracellular expression of Akt and S6 by flow cytometry and their phosphorylation status in both baseline conditions and upon B-cell receptor activation with anti-IgM in various primary B-cell subsets of patients with CVID and APDS. RESULTS: B cells from CVID patients showed reduced phosphorylation in Akt and S6 proteins after anti-IgM stimulation. Constitutive high baseline B-cell levels of Akt and S6 phosphorylation in a patient with APDS were reduced once m-TOR inhibition therapy was initiated. CONCLUSIONS: Intracellular flow cytometry can be routinely employed to explore alterations in the PI3K-Akt-mTOR pathway in B cells from patients with PADs. AKT and S6 phosphorylation levels are informative biomarkers that could be employed as mTOR inhibitors for monitoring therapies targeting this pathway.

Abnormal expression of Rab27B in prostatic epithelial cells of benign prostatic hyperplasia alters intercellular communication.

Abnormal intraglandular stromal-epithelial interactions have been known as a main key contributing factor for development of Benign Prostatic Hyperplasia (BPH). However, the underlying mechanism for the dysregulated intercellular communication remains unclear. In this study we compared the proteomic profiles of hyperplastic tissue with adjacent normal tissue of BPH and identified Rab27B small GTPase, a key regulator of exocytosis, as a protein that was overexpressed in the epithelium of BPH tissue. Overexpression of Rab27B in prostatic epithelial cells strongly increased the signaling activities of the PI3K/AKT and ERK1/2 pathways, whereas, downregulation of Rab27B expression in the epithelial cells of BPH reduced the signaling activities and decreased cell proliferation. The elevated Rab27B expression caused an overall increase in cell surface presentation of growth factor receptors without affecting their expression. However, the small GTPase also possesses an inhibitory activity against mTORC1 independent of its role in cell surface presentation of growth factor receptors. Our findings demonstrate a pivotal role of the small GTPase in autocrine and paracrine signaling and suggest that its abnormal expression underlies the dysregulated stromal-epithelial interactions in BPH.

P-S6K is associated with insect diapause via the ROS/AKT/ S6K/CREB/HIF-1 pathway in the cotton bollworm, Helicoverpa armigera.

Diapause is a complex physiological response that allows insects to survive unfavorable environmental conditions, and many signaling pathways participate in regulating this process. However, little is known about TOR signaling in the regulation of diapause. In this study, we found that the TOR pathway-related proteins TOR and Raptor are expressed at low levels in the brains of diapause-destined pupae of Helicoverpa armigera, consistent with a previous report that TOR signaling is associated with development. Interestingly, another TOR signaling-related protein, p-S6K, was increased in the brains of diapause-destined pupae. Our results showed that p-S6K in the brains of diapause-destined pupae can respond to the upstream signals reactive oxygen species (ROS) and AKT and that S6K activates the level of CREB, which binds to the HIF-1α promoter and increases its expression. Previous study has shown that HIF-1α levels elevated by ROS in the brains of diapause-destined pupae cause low mitochondrial activity for insect diapause. Thus, p-S6K in response to ROS/AKT regulates HIF-1α via activating transcription factor CREB for diapause initiation.

Circular RNA hsa_circ_0006168 contributes to cell proliferation, migration and invasion in esophageal cancer by regulating miR-384/RBBP7 axis via activation of S6K/S6 pathway.

OBJECTIVE: Esophageal cancer (EC) ranks as the sixth leading cause of cancer-related mortality worldwide. Circular RNAs (circRNAs) are involved in the pathogenesis of different cancers. However, the regulatory mechanism of circ_0006168 in EC progression is still unclear. MATERIALS AND METHODS: The expression of circ_0006168, microRNA (miR)-384, and retinoblastoma binding protein 7 (RBBP7) in tumors and cells was measured by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The stability of circ_0006168 was analyzed after RNase R treatment. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay was conducted to evaluate cell viability. Transwell assay was applied to determine cell migration and invasion. Glucose consumption and lactate production were detected using glucose detection and lactic acid detection kits. The interaction between miR-384 and circ_0006168 or RBBP7 was certified by Dual-Luciferase reporter system. Protein expression of pyruvate kinase (PK), RBBP7, S6 ribosomal protein kinase (S6K), phosphorylated S6K (p-S6K), S6, phosphorylated S6 (p-S6) was analyzed by Western blot. RESULTS: Circ_0006168 and RBBP7 were over-expressed while miR-384 was low-expressed in EC tumors and cells. The repression of circ_0006168 attenuated cell proliferation, migration, invasion, and glycolysis in EC. Of note, circ_0006168 functioned as a sponge while RBBP7 acted as a target of miR-384 in EC. Rescue experiment revealed that miR-384 inhibitor abrogated circ_0006168 silencing-induced repression on cell proliferation, migration, and invasion in EC. Meanwhile, upregulation of RBBP7 restored the inhibition of miR-384 on EC cell progression. Moreover, circ_0006168 was able to improve RBBP7 level by interacting with miR-384. Also, circ_0006168 could activate S6K/S6 pathway by regulating RBBP7 expression. CONCLUSIONS: Abundance of circ_0006168 contributes to cell proliferation, migration, invasion, and glycolysis in EC by competitively sponging miR-384 to facilitate RBBP7 expression, representing prospective targets for EC therapy.

Exercise intervention attenuates neuropathic pain in diabetes via mechanisms of mammalian target of rapamycin (mTOR).

This study was to examine the role of exercise intervention in modulating neuropathic pain induced by diabetes. Diabetes was induced by streptozotocin (STZ, i.p.) in rats and mechanical hyperalgesia was observed three weeks after STZ. Mechanical withdrawal thresholds were increased after four to five weeks of exercise in STZ rats. We also examined the role of signal of mammalian target of rapamycin (mTOR) in regulating neuropathic pain. Inhibition of neuropathic pain by exercise in STZ rats was accompanied with decreases of p-mTOR, p-S6K1, and p-4E-BP1 in sensory nerves. Blocking mTOR also elevated mechanical withdrawal thresholds in STZ rats. Furthermore, pro-inflammatory IL-6 was greater in sensory nerves of STZ rats. Inhibition of IL-6 decreased mTOR and increased mechanical withdrawal thresholds in STZ rats. Overall, our data suggest the role played by exercise in improving neuropathic pain after STZ and that IL-6-mTOR signal is a part of mechanisms engaged in the effects of exercise.

Identification of PP2A and S6 Kinase as Modifiers of Leucine-Rich Repeat Kinase-Induced Neurotoxicity.

Mutations in LRRK2 are currently recognized as the most common monogenetic cause of Parkinsonism. The elevation of kinase activity of LRRK2 that frequently accompanies its mutations is widely thought to contribute to its toxicity. Accordingly, many groups have developed LRRK2-specific kinase inhibitors as a potential therapeutic strategy. Given that protein phosphorylation is a reversible event, we sought to elucidate the phosphatase(s) that can reverse LRRK2-mediated phosphorylation, with the view that targeting this phosphatase(s) may similarly be beneficial. Using an unbiased RNAi phosphatase screen conducted in a Drosophila LRRK2 model, we identified PP2A as a genetic modulator of LRRK2-induced neurotoxicity. Further, we also identified ribosomal S6 kinase (S6K), a target of PP2A, as a novel regulator of LRRK2 function. Finally, we showed that modulation of PP2A or S6K activities ameliorates LRRK2-associated disease phenotype in Drosophila.

PKD deletion promotes autophagy and inhibits hypertrophy in cardiomyocyte.

Protein kinase D (PKD) plays an important role in the development of cardiac hypertrophy induced by pressure overload. However, the mechanism involved is unclear. This study, using primary cardiomyocyte culture, PKD knockdown and overexpression, and other molecular techniques, tested our hypothesis that PKD pathway mediates cardiac hypertrophy by negatively regulating autophagy in cardiomyocyte. Neonatal cardiomyocytes were isolated from Wistar rats and cell hypertrophy was induced by norepinephrine treatment (PE, 10-4 mol/L), and divided into the following groups: (1) Vehicle; (2) PE; (3) PE + control siRNA; (4) PE + Rapamycin (100 nM); (5) PE + PKD-siRNA (2 × 108 U/0.1 ml); (6) PE + PKD siRNA + 3 MA (10 mM). The results showed that PE treatment induced cardiomyocyte hypertrophy, which were confirmed by cell size and biomarkers of cardiomyocyte hypertrophy including increased ANP and BNP mRNA. PKD knockdown or Rapamycin significantly inhibited PE-induced cardiomyocyte hypertrophy. In addition, PKD siRNA increased autophagy activity determined by electron microscopy, increased biomarkers of autophagy by Western blot, accompanied by down-regulated AKT/mTOR/S6K pathway. All the effects of PKD knockout were inhibited by co-treatment with 3-MA, an autophagy inhibitor. Oppositely, the autophagy in cardiomyocytes was inhibited by PKD overexpression. These results suggest that PKD participates in the development of cardiac hypertrophy by regulating autophagy via AKT/mTOR/S6K pathway.

Effects of Early Exposure of Isoflurane on Chronic Pain via the Mammalian Target of Rapamycin Signal Pathway.

Persistent post-surgical pain (PPSP) is a chronic pain condition, often with neuropathic features, that occurs in approximately 20% of children who undergo surgery. The biological basis of PPSP has not been elucidated. Anesthetic drugs can have lasting effects on the developing nervous system, although the clinical impact of this phenomenon is unknown. Here, we used a mouse model to test the hypothesis that early developmental exposure to isoflurane causes cellular and molecular alteration in the pain perception circuitry that causes a predisposition to chronic, neuropathic pain via a pathologic upregulation of the mammalian target of the rapamycin (mTOR) signaling pathway. Mice were exposed to isoflurane at postnatal day 7 and select cohorts were treated with rapamycin, an mTOR pathway inhibitor. Behavioral tests conducted 2 months later showed increased evidence of neuropathic pain, which did not occur in rapamycin-treated animals. Immunohistochemistry showed neuronal activity was chronically increased in the insular cortex, anterior cingulate cortex, and spinal dorsal horn, and activity was attenuated by rapamycin. Immunohistochemistry and western blotting (WB) showed a co-incident chronic, abnormal upregulation in mTOR activity. We conclude that early isoflurane exposure alters the development of pain circuits and has the potential to contribute to PPSP and/or other pain syndromes.