PI3-kinase inhibition: a target for drug development?

The μ-opioid receptor induces miR-21 expression and is ERK/PKCμ-dependent

Micro RNA-21 (miR-21) is believed to perform an important role in the transition from inflammation to resolution in the innate immune response. The biochemical basis for the induction of miR-21 remains uncertain. However, the activation of the μ-opioid receptor (MOR) induces the expression of miR-21. Our results show that human monocytes treated with μ-opioid agonists exhibit a significant increase in miR-21 expression. We found that MOR-induction of miR-21 requires the activation of the Ras-Raf-MEK-ERK signaling cascade, and to our surprise, the activation of PKCμ (PKD1). These results are significant given the role of miR-21 in the sensitivity to pain.

Recent progress in the synthesis of the furanosteroid family of natural products

This review focuses on an overview of recent advances in the synthesis of furanosteroids and illustrates their applications in medicinal chemistry over the period of 2005–present.

A novel phosphoinositide kinase Fab1 regulates biosynthesis of pathogenic aflatoxin in Aspergillus flavus

Aspergillus flavus (A. flavus) is one of the most important model environmental fungi which can produce a potent toxin and carcinogen known as aflatoxin. Aflatoxin contamination causes massive agricultural economic loss and a critical human health issue each year. Although a functional vacuole has been highlighted for its fundamental importance in fungal virulence, the molecular mechanisms of the vacuole in regulating the virulence of A. flavus remain largely unknown. Here, we identified a novel vacuole-related protein in A. flavus, the ortholog of phosphatidylinositol-3-phosphate-5-kinase (Fab1) in Saccharomyces cerevisiae. This kinase was located at the vacuolar membrane, and loss of fab1 function was found to affect the growth, conidia and sclerotial development, cellular acidification and metal ion homeostasis, aflatoxin production and pathogenicity of A. flavus. Further functional analysis revealed that Fab1 was required to maintain the vacuole size and cell morphology. Additional quantitative proteomic analysis suggested that Fab1 was likely to play an important role in maintaining vacuolar/cellular homeostasis, with vacuolar dysregulation upon fab1 deletion leading to impaired aflatoxin synthesis in this fungus. Together, these results provide insight into the molecular mechanisms by which this pathogen produces aflatoxin and mediates its pathogenicity, and may facilitate dissection of the vacuole-mediated regulatory network in A. flavus.

Class II phosphatidylinositol 3-kinase α and β isoforms are required for vascular smooth muscle Rho activation, contraction and blood pressure regulation in mice

Class II phosphatidylinositol 3-kinases (PI3K), PI3K-C2α and PI3K-C2β, are involved in cellular processes including endocytosis, cilia formation and autophagy. However, the role of PI3K-C2α and PI3K-C2β at the organismal level is not well understood. We found that double knockout (KO) mice with both smooth muscle-specific KO of PI3K-C2α and global PI3K-C2β KO, but not single KO mice of either PI3K-C2α or PI3K-C2β, exhibited reductions in arterial blood pressure and substantial attenuation of contractile responses of isolated aortic rings. In wild-type vascular smooth muscle cells, double knockdown of PI3K-C2α and PI3K-C2β but not single knockdown of either PI3K markedly inhibited contraction with reduced phosphorylation of 20-kDa myosin light chain and MYPT1 and Rho activation, but without inhibition of the intracellular Ca²⁺ mobilization. These data indicate that PI3K-C2α and PI3K-C2β play the redundant but essential role for vascular smooth muscle contraction and blood pressure regulation mainly through their involvement in Rho activation.

Interferon gamma induces inflammatory responses through the interaction of CEACAM1 and PI3K in airway epithelial cells

BACKGROUND

Interferon gamma (IFNγ) plays an important role in the development of chronic lung diseases via the production of inflammatory mediators, although the exact mechanism remains unclear. The present study aimed at investigating the potential mechanisms by which IFNγ induced over-production of interleukins through the interaction between carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) pathway.

METHODS

IFN-γ induced over-production of interleukin (IL) 6 and IL8, and RNA expression of CEACAM1 and its subtypes or PI3K and its subtypes in human bronchial epithelial cells (HBE). The production of IL6 and IL8 or cell proliferation and movement were also evaluated in cell^CEACAM1- or cell^CEACAM1+ after the induction of IFN-γ. Roles of PI3K subtype proteins, e.g. PI3Kp110α/δ, Akt, p110α/γ/δ/β/mTOR, PI3Kp110α/δ/β, PI3Kp110δ, or pan-PI3K in IFN-γ-induced CEACAM1 subtype alterations were furthermore validated using those proteins of PI3K subtypes.

RESULTS

CEACAM1, especially CEACAM1-S isoforms, was significantly up-regulated in HBE cells after treatment with IFN-γ. CEACAM1 played roles in expression of IL-6 and IL-8, and facilitated cellular proliferation and migration. IFN-γ up-regulated the expression of CEACAM1 in airway epithelial cells, especially CEACAM1-S isoforms, promoting cellular proliferation, migration, and the production of inflammatory factors. PI3K (p110δ)/Akt/mTOR pathway was involved in the process of IFN-γ-upregulated CEACAM1, especially CEACAM1-S. On the other hand, CEACAM1 could promote the activation of PI3K/Akt/mTOR pathway.

CONCLUSION

IFN-γ could induce inflammatory responses, cellular growth and proliferation through the interaction of CEACAM1 (especially CEACAM1-S isoforms) and PI3K(p110δ)/Akt/mTOR in airway epithelial cells, which might be new alternative of future therapies against epithelial transition from inflammation to cancer.

The relation between PI3K/AKT signalling pathway and cancer

Phosphatidylinositol 3-kinases (PI3Ks) are crucial coordinators of intracellular signalling in response to the extracellular stimulators. Hyperactivation of PI3K signalling cascades is one among the most ordinary events in human cancers. Focusing on the PI3K pathway remains both a chance and a challenge for cancer therapy. The high recurrence of phosphoinositide 3-kinase (PI3K) pathway adjustments in cancer has led to a surge in the progression of PI3K inhibitors. Recent developments incorporate a re-assessment of the oncogenic mechanisms behind PI3K pathway modifications. Receptor tyrosine kinases upstream of PI3K, the p110a catalytic fractional unit of PI3K, the downstream kinase, AKT, and therefore the negative regulator, PTEN, are all often altered in cancer. In this review, we consider about the phosphoinositide 3-kinases family and mechanisms of PI3K-Akt stimulation in cancer.

The class II phosphoinositide 3-kinases PI3K-C2α and PI3K-C2β differentially regulate clathrin-dependent pinocytosis in human vascular endothelial cells

Pinocytosis is an important fundamental cellular process that is used by the cell to transport fluid and solutes. Phosphoinositide 3-kinases (PI3Ks) regulate a diverse array of dynamic membrane events. However, it is not well-understood which PI3K isoforms are involved in specific mechanisms of pinocytosis. We performed knockdown studies of endogenous PI3K isoforms and clathrin heavy chain (CHC) mediated by small interfering RNA (siRNA). The results demonstrated that the class II PI3K PI3K-C2α and PI3K-C2β, but not the class I or III PI3K, were required for pinocytosis, based on an evaluation of fluorescein-5-isothiocyanate (FITC)-dextran uptake in endothelial cells. Pinocytosis was partially dependent on both clathrin and dynamin, and both PI3K-C2α and PI3K-C2β were required for clathrin-mediated-but not clathrin-non-mediated-FITC-dextran uptake at the step leading up to its delivery to early endosomes. Both PI3K-C2α and PI3K-C2β were co-localized with clathrin-coated pits and vesicles. However, PI3K-C2β, but not PI3K-C2α, was highly co-localized with actin filament-associated clathrin-coated structures and required for actin filament formation at the clathrin-coated structures. These results indicate that PI3K-C2α and PI3K-C2β play differential, indispensable roles in clathrin-mediated pinocytosis.

Effect of luteinizing hormone on goat theca cell apoptosis and steroidogenesis through activation of the PI3K/AKT pathway

Luteinizing hormone (LH) is a glycoprotein that regulates the function of ovarian follicular cells. Theca cells (TCs) also have a key role in follicular growth and atresia. The effects and intracellular signaling mechanisms were investigated of LH on apoptosis and steroidogenesis in goat gonadotropin-independent follicular (1.0-4.0 mm) TCs. The results indicated that LH increased androstenedione secretion and relative abundance of CYP17A1 and BCL2 mRNA in the TCs, whereas LH in combination with LY294002, a PI3K/AKT inhibitor, decreased LH-induced function. The apoptosis ratio and expression of the BAX gene in TCs were less with LH treatment, and the extent of this inhibition was decreased by suppressing the PI3K/AKT pathway. In conclusion, results of the present study indicate LH regulates apoptosis and steroidogenesis in goat TCs by activating the PI3K/AKT pathway.

Sevoflurane and isoflurane inhibit KCl-induced Class II phosphoinositide 3-kinase α subunit mediated vasoconstriction in rat aorta

BACKGROUND

Class II phosphoinositide 3-kinase α-isoform (PI3K-C2α) is involved in regulating KCl-induced vascular smooth muscle contraction. The current study was to investigate the effects of sevoflurane (SEVO) and isoflurane (ISO) on KCl-elicited PI3KC2α mediated vasoconstriction in rat aortic smooth muscle.

METHODS

Isometric force, in the absence or presence of SEVO or ISO (1 ~ 3 minimum alveolar concentration, MAC), PI3K inhibitor LY294002, Rho kinase inhibitor Y27632, and membrane translocation of PI3K-p85, PI3K-C2α, Rho kinase (Rock II), or phosphorylation of MYPT1/Thr853, MYPT1/Thr696, CPI-17/Thr38 and MLC in response to KCl (60 mM) was measured by using isometric force transducer and western blotting analysis, respectively.

RESULTS

KCl elicited a rapid and sustained contraction of rat aortic smooth muscle that was inhibited by both SEVO and ISO in a concentration-dependent manner, and also suppressed by LY294002 (1 mM) and Y27632 (1 uM). LY294002 (1 mM) and Y27632 (1 uM) also inhibited KCl-induced MLC phosphorylation. LY294002 (1 mM) inhibited KCl-induced PI3K-p85, PI3K-C2α membrane translocation in response to KCl (p <0.05, p < 0.01, respectively). Not only Y27632 (1 uM), but also LY294002 (1 mM), inhibited KCl-induced Rock-II membrane translocation (p < 0.01). SEVO and ISO inhibited KCl-stimulated MLC phosphorylation, PI3K-C2α and Rock-II,not PI3K p85 membrane translocation in a concentration-dependent manner in rat aorta. Both SEVO and ISO suppressed the MYPT1/Thr853, not MYPT1/Thr696 and CPI-17/Thr38, MLC phosphorylation in response to KCl.

CONCLUSION

PI3K-C2α mediates part of SEVO and ISO-mediated vasodilation in rat aorta. The cellular mechanisms underlying the inhibitory effect of volatile anesthetics might be mediated by KCl/PI3K-C2α/Rho kinase/MYPT1/MLC pathway.

External Qi of Yan Xin Life Science Technology Can Revive or Suppress Enzyme Activity of Phosphatidylinositol 3-Kinase

Phosphatidylinositol 3 kinase (PI 3-kinase) is an important enzyme that is involved in the regulation of a variety of biological processes such as apoptosis, cell division, and ion channel activity and can play a role in the pathological development of a number of diseases, including AIDS and cancer. The authors’ data indicate that external qi of Yan Xin Life Science Technology (YXLST) can modulate enzyme activity in two directions. Within a time window of 3 days of the initial emission of external qi of YXLST, PI 3-kinase activity was restored in an outdated enzyme sample that had lost activity, and PI 3-kinase activity was suppressed in a freshly purified sample relative to an untreated control sample so that its activity was nearly undetectable. The data presented are consistent with the hypothesis that external qi of YXLST can alter molecular events. The uniqueness of this and other observations mandates further study.

Exploring the role of two interacting phosphoinositide 3-kinases of Haemonchus contortus

Background

Phosphoinositide 3-kinases (PI3Ks) are relatively conserved and important intracellular lipid kinases involved in signalling and other biological pathways. In the free-living nematode Caenorhabditis elegans, the heterodimeric form of PI3K consists of catalytic (AGE-1) and regulatory (AAP-1) subunits. These subunits are key components of the insulin-like signalling pathway and play roles in the regulation of the entry into and exit from dauer. Although, in parasitic nematodes, similar components are proposed to regulate the transition from free-living or arrested stages to parasitic larvae, nothing is known about PI3Ks in relation to the transition of third-stage larvae (L3s) to parasitism in Haemonchus contortus.

Methods

An integrated molecular approach was used to investigate age-1 and aap-1 of H. contortus (Hc-age-1 and Hc-aap-1) in C. elegans.

Results

The two genes Hc-age-1 and Hc-aap-1 were transcribed in all life stages, with the highest levels in the egg, infective L3 and adult female of H. contortus. The expression of these genes was localized to the intestine, contrasting the pattern of their orthologues in C. elegans (where they are expressed in both head neurons and the intestine). The yeast two-hybrid analysis demonstrated that the adaptor-binding domain of Hc-AGE-1 interacted strongly with the Hc-AAP-1; however, this complex did not rescue the function of its orthologue in age-1-deficient C. elegans.

Conclusions

This is the first time that the PI3K-encoding genes have been characterized from a strongylid parasitic nematode. The findings provide insights into the role of the PI3K heterodimer represented by Hc-age-1 and Hc-aap-1 in the developmental biology of H. contortus.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-014-0498-2) contains supplementary material, which is available to authorized users.

Cytohesin 2/ARF6 regulates preadipocyte migration through the activation of ERK1/2

Preadipocyte migration is vital for the development of adipose tissue, which plays a crucial role in lipid metabolism. ADP-ribosylation factor 6 (ARF6) small GTPase, which regulates membrane trafficking, is activated by GTP-exchange factors (GEFs) such as cytohesin 2. Cytohesin 2 and ARF6 have previously been implicated in the regulation of 3T3-L1 preadipocyte migration. We investigated here the molecular mechanism underlying the cytohesin 2 and ARF6 mediated regulation of preadipocyte migration. Preadipocyte migration and the activation of ARF6 and ERK1/2 were studied by using a number of approaches, including pharmacological inhibitors, siRNA and the inhibitory peptides. The siRNA mediated down regulation of ARF6 and cytohesin 2 expression confirmed the requirement of both for migration of preadipocytes. Phosphatidylinositol 3-kinase (PI3K) and PI 4,5-bisphosphate (PIP2) have also found to be essential for the cytohesin 2/ARF6 induced preadipocyte migration. Pharmacological inhibition of the activation of ARF6, ERK1/2 or dynamin led to significant reduction in migration of 3T3-L1 preadipocytes. Furthermore, our study revealed the activation of ARF6 and ERK1/2 during migration of preadipocytes. In the migrating preadipocytes, ARF6 activation was inhibited with SecinH3 (cytohesin inhibitor) and LY294002 (PI3K inhibitor) whereas the ERK1/2 phosphorylation was inhibited with SecinH3, LY294002, PBP10 (a PIP2 sequester peptide) and PD98059 (MAPKK inhibitor). However, dynosore (dynamin inhibitor) had inhibited neither ARF6 activation nor ERK1/2 phosphorylation during preadipocyte migration. These results together suggest that cytohesin 2 activates ARF6 in a PI3K dependent manner and then the active ARF6 causes phosphorylation of ERK1/2 during preadipocyte migration.

Signaling in chemotactic amoebae remains spatially confined to stimulated membrane regions

Recent work has demonstrated that the receptor-mediated signaling system in chemotactic amoeboid cells shows typical properties of an excitable system. Here, we delivered spatially confined stimuli of the chemoattractant cAMP to the membrane of differentiated Dictyostelium discoideum cells to investigate whether localized receptor stimuli can induce the spreading of excitable waves in the G-protein-dependent signal transduction system. By imaging the spatiotemporal dynamics of fluorescent markers for phosphatidylinositol (3,4,5)-trisphosphate (PIP₃), PTEN and filamentous actin, we observed that the activity of the signaling pathway remained spatially confined to the stimulated membrane region. Neighboring parts of the membrane were not excited and no receptor-initiated spatial spreading of excitation waves was observed. To generate localized cAMP stimuli, either particles that carried covalently bound cAMP molecules on their surface were brought into contact with the cell or a patch of the cell membrane was aspirated into a glass micropipette to shield this patch against freely diffusing cAMP molecules in the surrounding medium. Additionally, the binding site of the cAMP receptor was probed with different surface-immobilized cAMP molecules, confirming results from earlier ligand-binding studies.

Diagnostic application of PIK3CA mutation analysis in Chinese esophageal cancer patients

Background

The PIK3CA gene mutation was found to associate with prognosis and might affect molecular targeted therapy in esophageal carcinoma (EC). The aim of this study is to compare different methods for analyzing the PIK3CA gene mutation in EC.

Methods

Genomic DNA was extracted from 106 surgically resected EC patient tissues. The PIK3CA mutation status (exons 9 and 20) were screened by mutant-enrich liquid chip (ME-Liquidchip), Sanger sequencing, and pyrosequencing. And all samples with mutations were independently reassessed using amplification refractory mutation system (ARMS) methods again.

Results

PIK3CA mutation rates were identified as 11.3% (12/106) by ME-Liquidchip. 10 mutations occurred in exon 9 and 2 in exon 20, including G1624A:E542K (n = 4), G1633A:E545K (n = 6) and A3140G:H1047R (n = 2). The results were further verified by ARMS methods. Among these 12 cases characterized for PIK3CA mutation, however, only 7 and 6 cases were identified by Sanger sequencing (6.6%,7/106) and pyrosequencing (5.7%,6/106), respectively.

Conclusion

Sanger sequencing and pyrosequencing are less sensitive and are not efficiently applicable to the detection of PIK3CA mutation in EC samples. Choosing between ME-Liquidchip and ARMS will depend on laboratory facilities and expertise.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_153

Selective and potent small-molecule inhibitors of PI3Ks

Class I PI3Ks are composed of four catalytic subunit variants (p110α, p110β, p110δ and p110γ). The PI3K pathway is among the most frequently activated pathways in many diseases, and has emerged as an attractive target for drug development, in particular for the treatment of many human cancers including breast, prostate, ovarian, gastric, colon and hepatocellular cancers. One of the challenges in the discovery of drugs that target kinases is designing small-molecule inhibitors that are sufficiently selective to minimize off-target activity and reduce the risk of potential toxicity. This review explores the current landscape of PI3K-selective inhibitor development and highlights recent advances in achieving selectivity for PI3Ks over other protein kinases, with an emphasis on available structural information.

Frequency, characterization, and prognostic analysis of PIK3CA gene mutations in Chinese esophageal squamous cell carcinoma

PIK3CA gene mutations are found in numerous cancers but correlate differently with prognosis. Although the frequency of PIK3CA gene mutation in esophageal squamous cell carcinoma (ESCC) has been previously studied, a prognostic analysis has not been reported. Ninety-six surgically resected ESCC tissues were collected from Chinese patients and DNA was extracted. Gene mutations in PIK3CA (exons 9 and 20), EGFR (exons 18, 19, 20 and 21), KRAS (exons 2 and 3), and BRAF (exons 11 and 15) were screened using mutant-enriched liquid chip technology. PIK3CA gene mutations were identified in 12 of 96 ESCC cases (12.5%). No mutations were identified in EGFR, KRAS or BRAF genes in this study. Correlations between clinicopathological features and PIK3CA mutation status were analyzed and finally, patient survival information was used to determine the prognostic significance of PIK3CA mutation. Interestingly, the frequency of PIK3CA mutation was higher in female ESCC patients (31.3%, 5/16) than in males (8.8%, 7/80), and higher in patients with non-lymph node metastasis (19.6%, 10/51, P = .013) than in patients with lymph node metastasis (4.4%, 2/45, P = .025). Furthermore, patients with PIK3CA-mutated tumors showed a trend towards favorable overall survival (P = .085) but not disease-free survival (P = .238), suggesting that PIK3CA gene status may be a favorable predictive marker in ESCC patients.

Involvement of PI 3 kinase/Akt-dependent Bad phosphorylation in Toxoplasma gondii-mediated inhibition of host cell apoptosis

Toxoplasma gondii-infected cells are resistant to various apoptotic stimuli, however, the role of the pro-apoptotic BH3-only Bad protein in T. gondii-imposed inhibition of host cell apoptosis in connection with the phosphoinositide 3-kinase (PI3K)-PKB/Akt pathway was not well delineated. Here, we investigated the signaling patterns of Bad, Bax and PKB/Akt in T. gondii-infected and uninfected THP-1 cells treated with staurosporine (STS) or PI3K inhibitors. STS treatment, without T. gondii infection, reduced the viability of THP-1 cells in proportion to STS concentration and triggered many cellular death events such as caspase-3 and -9 activation, Bax translocation, cytochrome c release from host cell mitochondria into cytosol, and PARP cleavage in the host cell. However, T. gondii infection eliminated the STS-triggered mitochondrial apoptotic events described above. Additionally, T. gondii infection in vitro and in vivo induced the phosphorylation of PKB/Akt and Bad in a parasite-load-dependent manner which subsequently inhibited Bax translocation. The PI3K inhibitors, LY294002 and Wortmannin, both blocked parasite-induced phosphorylation of PKB/Akt and Bad. Furthermore, THP-1 cells pretreated with these PI3K inhibitors showed reduced phosphorylation of Bad in a dose-dependent manner and subsequently failed to inhibit the Bax translocation, also these cells also failed to overcome the T. gondii-imposed inhibition of host cell apoptosis. These data demonstrate that the PI3K-PKB/Akt pathway may be one of the major route for T. gondii in the prevention of host cell apoptosis and T. gondii phosphorylates the pro-apoptotic Bad protein to prevent apoptosis.

Development of isoform selective PI3-kinase inhibitors as pharmacological tools for elucidating the PI3K pathway

Using a parallel synthesis approach to target a non-conserved region of the PI3K catalytic domain a pan-PI3K inhibitor 1 was elaborated to provide alpha, delta and gamma isoform selective Class I PI3K inhibitors 21, 24, 26 and 27. The compounds had good cellular activity and were selective against protein kinases and other members of the PI3K superfamily including mTOR and DNA-PK.

Prevention of the wortmannin-induced inhibition of phosphoinositide 3-kinase by sulfhydryl reducing agents

The effects of the sulfhydryl reducing agents 2-mercaptoethanol and dithiothreitol on wortmannin-induced inhibition of phosphoinositide 3-kinase (PI3K) were studied in order to examine whether the sulfhydryl reducing agents directly affect the wortmannin inhibition of PI3K. These reducing agents are commonly used to stabilize enzyme structures by maintaining protein sulfhydryl groups in the reduced state. Preincubation of wortmannin with millimolar levels of 2-mercaptoethanol, a sulfhydryl derivative of ethanol, markedly prevented subsequent wortmannin-induced inhibition of PI3K. In contrast, ethanol, 2-mercaptoethanol lacking sulfhydryl group, and 2-(methylthio)ethanol, a methyl derivative of the sulfhydryl group of 2-mercaptoethanol, had little effect on the wortmannin-induced inhibition of PI3K, which suggests that the prevention of wortmannin-induced inhibition by 2-mercaptoethanol occurs through the sulfhydryl group of this agent. Moreover, dithiothreitol, a second sulfhydryl reducing agent, also markedly prevented wortmannin-induced inhibition of PI3K. These results indicate that the wortmannin-induced inhibition of PI3K is markedly prevented by millimolar concentrations of sulfhydryl reducing agents such as 2-mercaptoethanol and dithiothreitol in the medium, presumably by the binding of wortmannin to the agents.

Sublytic C5b-9 complexes induce proliferative changes of glomerular mesangial cells in rat Thy-1 nephritis through TRAF6-mediated PI3K-dependent Akt1 activation

The proliferation of glomerular mesangial cells (GMCs) and secretion of extracellular matrix (ECM) in rat Thy-1 nephritis (Thy-1N), resembling human mesangioproliferative glomerulonephritis (MsPGN), have been studied for many years, but the mechanisms, especially the role of signalling pathway activation and its regulation in GMCs triggered by sublytic C5b-9 complexes in Thy-1N rats remain largely unclear. In the study, the proliferation of GMCs and production of ECM as well as the role of PI3K/Akt and its regulation, both in GMCs induced by sublytic C5b-9 (in vitro) and in the renal tissues of rats with Thy-1N (in vivo), were determined and the results revealed that GMCs proliferation and ECM secretion, both in vitro and in vivo, were notably increased, and that PI3K/Akt1 activation and its regulation, such as TNF receptor-associated factor 6 (TRAF6)-mediated Akt1 ubiquitination and PI3K-dependent Akt1 phosphorylation, were involved in the process of Thy-1N induction. On the other hand, silence of the TRAF6, PI3K or Akt1 genes could obviously diminish the proliferative damages and urinary protein secretion of Thy-1N rats. Together, these data implicated that sublytic C5b-9 complexes in Thy-1N rats could promote GMCs proliferation and ECM production through TRAF6-mediated PI3K-dependent Akt1 activation, in which the ubiquitination and phosphorylation of the Akt1 signal molecule played an important role in the initiation and development of the proliferative changes in the rats with Thy-1N.

Molecular simulation of a series of benzothiazole PI3Kα inhibitors: probing the relationship between structural features, anti-tumor potency and selectivity

The phosphatidylinositol 3-kinase α (PI3Kα) was genetically validated as a promising therapeutic target for developing novel anticancer drugs. In order to explore the structure-activity correlation of benzothiazole series as inhibitors of PI3Kα, comparative molecular field analysis (CoMFA), comparative molecular similarity indices analysis (CoMSIA) were performed on 61 promising molecules to build 3D-QSAR models based on both the ligand- and receptor-based methods. The best CoMFA and CoMSIA models had a cross-validated coefficient r(cv)(2) of 0.618 and 0.621, predicted correlation coefficient r(pred) (2) of 0.812 and 0.83, respectively, proving their high correlative and predictive abilities on both the training and test sets. In addition, docking analysis and molecular dynamics simulation (MD) were also applied to elucidate the probable binding modes of these inhibitors at the ATP binding pocket. Based on the contour maps and MD results, some key structural factors responsible for the activity of this series of compounds were revealed as follows: (1) Ring-A has a strong preference for bulky hydrophobic or aromatic groups; (2) Electron-withdrawing groups at the para position of ring-B and hydrophilic substituents in ring-B region may benefit the potency; (3) A polar substituent like -NHSO(2)- between ring-A and ring-B can enhance the activity of the drug by providing hydrogen bonding interaction with the protein target. The satisfactory results obtained from this work strongly suggest that the developed 3D-QSAR models and the obtained PI3Kα inhibitor binding structures are reasonable for the prediction of the activity of new inhibitors and be helpful in future PI3Kα inhibitor design.

Progress in the preclinical discovery and clinical development of class I and dual class I/IV phosphoinositide 3-kinase (PI3K) inhibitors

The phosphoinositide 3-kinases (PI3Ks) constitute an important family of lipid kinase enzymes that control a range of cellular processes through their regulation of a network of signal transduction pathways, and have emerged as important therapeutic targets in the context of cancer, inflammation and cardiovascular diseases. Since the mid-late 1990s, considerable progress has been made in the discovery and development of small molecule ATP-competitive PI3K inhibitors, a number of which have entered early phase human trials over recent years from which key clinical results are now being disclosed. This review summarizes progress made to date, primarily on the discovery and characterization of class I and dual class I/IV subtype inhibitors, together with advances that have been made in translational and clinical research, notably in cancer.

Neuroprotective effects of an herbal medicine, Yi-Gan San on MPP+/MPTP-induced cytotoxicity in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

A traditional herb, Yi-Gan San, has been widely used for the management of neurodegenerative disorders in traditional East Asian Medicine.

AIM OF THE STUDY

The present study investigated the neuroprotective effects of Yi-Gan San in 1-methyl-4-phenylpyridine/1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced cytotoxicity in vitro and in vivo and sought to clarify its underlying mechanisms.

MATERIALS AND METHODS

The effect of Yi-Gan San on 1-methyl-4-phenylpyridine was measured in terms of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assays, caspase-3 activity, and western blot analysis of phosphorylated Akt, one of the survival-related signaling proteins in SH-SY5Y cells. The effects of Yi-Gan San were also confirmed in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinsonian mouse model using a rotarod test and tyrosine hydroxylase-immunohistochemistry.

RESULTS

Pretreatment of Yi-Gan San with 1-methyl-4-phenylpyridine showed a significant protective effect on SH-SY5Y cells and significantly decreased the level of caspase-3 activity compared to the values for the 1-methyl-4-phenylpyridine-treated cells. This process increased the protein expressions of phosphorylated Akt, and an inhibitor of phosphatidylinositol 3-kinase (PI3K)/Akt, LY294002, significantly decreased this protective effect of Yi-Gan San. In the mouse Parkinson's disease model, treatment with Yi-Gan San also significantly improved motor functioning and prevented dopaminergic loss related to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine challenge.

CONCLUSION

Using both in vitro and in vivo methods, this study revealed that Yi-Gan San has neuroprotective effects and rescues dopaminergic neurons from 1-methyl-4-phenylpyridine/1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity, possibly via the PI3K/Akt pathway.

Multiple phosphatidylinositol 3-kinases regulate vaccinia virus morphogenesis

Poxvirus morphogenesis is a complex process that involves the successive wrapping of the virus in host cell membranes. We screened by plaque assay a focused library of kinase inhibitors for those that caused a reduction in viral growth and identified several compounds that selectively inhibit phosphatidylinositol 3-kinase (PI3K). Previous studies demonstrated that PI3Ks mediate poxviral entry. Using growth curves and electron microscopy in conjunction with inhibitors, we show that that PI3Ks additionally regulate morphogenesis at two distinct steps: immature to mature virion (IMV) transition, and IMV envelopment to form intracellular enveloped virions (IEV). Cells derived from animals lacking the p85 regulatory subunit of Type I PI3Ks (p85α^−/−β^−/−) presented phenotypes similar to those observed with PI3K inhibitors. In addition, VV appear to redundantly use PI3Ks, as PI3K inhibitors further reduce plaque size and number in p85α^−/−β^−/− cells. Together, these data provide evidence for a novel regulatory mechanism for virion morphogenesis involving phosphatidylinositol dynamics and may represent a new therapeutic target to contain poxviruses.

Increased cardiac microvascular permeability and activation of cardiac endothelial nitric oxide synthase in high tidal volume ventilation-induced lung injury

Background: Positive pressure ventilation with large tidal volumes has been shown to cause lung injury via the serine/threonine kinase-protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS)-pathways. However, the effects of high tidal volume (VT) ventilation on the heart are unclear. Objectives: Evaluate the effect of VT ventilation on the cardiac vascular permeability and intracellular Akt and eNOS signaling pathway. Methods: C57BL/6 and Akt knock-out (heterozygotes, +/−) mice were exposed to high VT (30 mL/kg) mechanical ventilation with room air for one and/or five hours. Results: High VT ventilation increased cardiac microvascular permeability and eNOS phosphorylation in a timedependent manner. Serum cardiac troponin I was increased after one hour of high VT ventilation. Cardiac Akt phosphorylation was accentuated after one hour and attenuated after five hours of high VT ventilation. Pharmacological inhibition of Akt with LY294002 and high VT ventilation of Akt+/− mice attenuated cardiac Akt phosphorylation, but not eNOS phosphorylation. Conclusion: High VT ventilation increased cardiac myocardial injury, microvascular permeability, and eNOS phosphorylation. Involvement of cardiac Akt in high VT ventilation was transient.

Luteinizing hormone-induced Akt phosphorylation and androgen production are modulated by MAP Kinase in bovine theca cells

BACKGROUND

Theca cells play an important role in controlling ovarian steroidogenesis by providing aromatizable androgens for granulosa cell estrogen biosynthesis. Although it is well established that the steroidogenic activity of theca cells is mainly regulated by LH, the intracellular signal transduction mechanisms that regulate thecal proliferation and/or steroidogenesis remain obscure. In this study, we examined whether and how LH controls the PI3K/Akt signaling pathway and androgen production in bovine theca cells. We also explored whether this LH-induced PI3K/Akt activation is modulated with other signaling pathways (i.e. PKA and MAPK).

METHODS

Ovarian theca cells were isolated from bovine small antral follicles and were incubated with LH for various durations. Phospho-Akt and total-Akt content in the cultured theca cells were examined using Western blotting. Androstenedione levels in the spent media were determined using EIA. Semi-quantitative RT-PCR analyses were conducted to analyze the mRNA levels of CYP17A1 and StAR in the theca cells. To examine whether Akt activity is involved in theca cell androgen production, the PI3K inhibitors wortmannin and LY294002 were also added to the cells.

RESULTS

Akt is constitutively expressed, but is gradually phosphorylated in cultured bovine theca cells through exposure to LH. LH significantly increased androstenedione production in bovine theca cells, whereas addition of the wortmannin and LY294002 significantly decreased LH-induced androstenedione production. LH significantly increased CYP17A1 mRNA level in theca cells, whereas addition of LY294002 significantly decreased LH-induced CYP17A1 expression. Neither LH nor PI3K inhibitors alter the mRNA levels of StAR in theca cells. Although H89 (a selective inhibitor of PKA) does not affect LH-mediated changes in Akt, U0126 (a potent MEK inhibitor) suppressed LH-induced Akt phosphorylation, CYP17A1 expression, and androgen production in theca cells.

CONCLUSION

These results indicate that LH stimulates CYP17 mRNA expression and androgen production in theca cells via activation of the PI3K/Akt pathway. The LH-induced Akt phosphorylation and androgen production are modulated by the MAPK signaling in bovine theca cells.

Targeting specific cell signaling transduction pathways by dietary and medicinal phytochemicals in cancer chemoprevention

Natural phytochemicals derived from dietary sources or medicinal plants have gained significant recognition in the potential management of several human clinical conditions. Much research has also been geared towards the evaluation of plant extracts as effective prophylactic agents since they can act on specific and/or multiple molecular and cellular targets. Plants have been an abundant source of highly effective phytochemicals which offer great potential in the fight against cancer by inhibiting the process of carcinogenesis through the upregulation of cytoprotective genes that encode for carcinogen detoxifying enzymes and antioxidant enzymes. The mechanistic insight into chemoprevention further includes induction of cell cycle arrest and apoptosis or inhibition of signal transduction pathways mainly the mitogen-activated protein kinases (MAPK), protein kinases C (PKC), phosphoinositide 3-kinase (PI3K), glycogen synthase kinase (GSK) which lead to abnormal cyclooxygenase-2 (COX-2), activator protein-1 (AP-1), nuclear factor-kappaB (NF-κB) and c-myc expression. Effectiveness of chemopreventive agents reflects their ability to counteract certain upstream signals that leads to genotoxic damage, redox imbalances and other forms of cellular stress. Targeting malfunctioning molecules along the disrupted signal transduction pathway in cancer represent a rational strategy in chemoprevention. NF-κB and AP-1 provide mechanistic links between inflammation and cancer, and moreover regulate tumor angiogenesis and invasiveness, indicating that signaling pathways that mediate their activation provide attractive targets for new chemotherapeutic approaches. Thus cell signaling cascades and their interacting factors have become important targets of chemoprevention and phenolic phytochemicals and plant extracts seem to be promising in this endeavor.

Vanillin suppresses metastatic potential of human cancer cells through PI3K inhibition and decreases angiogenesis in vivo

Vanillin, a food flavoring agent, has been shown to suppress cancer cell migration and metastasis in a mouse model, but its mechanism of action is unknown. In this report, we have examined the antimetastatic potential of vanillin and its structurally related compounds, vanillic acid, vanillyl alcohol, and apocynin on hepatocyte growth factor (HGF)-induced migration of human lung cancer cells by the Transwell assay. Vanillin and apocynin could inhibit cell migration, and both compounds selectively inhibited Akt phosphorylation of HGF signaling, without affecting phosphorylation of Met and Erk. Vanillin and apocynin could inhibit the enzymatic activity of phosphoinositide 3-kinase (PI3K), as revealed by an in vitro lipid kinase assay, suggesting that inhibition of PI3K activity was a mechanism underlying the inhibitory effect on cancer cell migration, and the presence of an aldehyde or ketone group in the vanillin structure was important for this inhibition. Vanillin and apocynin also inhibited angiogenesis, determined by the chick chorioallantoic membrane assay.

Take your PIK: phosphatidylinositol 3-kinase inhibitors race through the clinic and toward cancer therapy

The phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway is currently one of the most exciting drug targets in oncology. However, only a short time ago, the paradigm existed that drugs targeted to the four PI3K class I isoforms would be too toxic for use in cancer therapy due to effects on physiologic signaling. Since that time, studies have delineated the roles of these four isoforms in nonpathologic signaling as well as their roles in cancer. An extensive effort has gone into developing agents that inhibit one or more PI3K isoforms, as well as closely related proteins implicated in cancer. These agents have proved to be tolerable and therapeutically beneficial in animal studies, and a number are in clinical testing. The agents, their properties, and their molecular targets are discussed in this review.

Effects of PI3-k/Akt short hairpin RNA on proliferation, fibronectin production and synthesis of thrombospondin-1 and transforming growth factor-beta1 in glomerular mesangial cells induced by sublytic C5b-9 complexes

OBJECTIVES

To explore proliferation of glomerular mesangial cells (GMC) and secretion of extracellular matrix (fibronectin induced by sublytic C5b-9 complexes), and then ascertain the role of phosphatidylinositol 3-kinase (PI3-k)/Akt signal pathway in these processes, by using small hairpin RNAs.

MATERIAL AND METHODS

The expression of cyclin D(2), (3)H-thymidine into DNA and production of fibronectin including thrombospondin-1 and transforming growth factor-beta(1) in the GMCs stimulated by sublytic C5b-9 or transfected with expression vectors of PI3-k and Akt short hairpin RNA or LY294002 (PI3-k inhibitor) were measured by Real-time quantitative polymerase chain reaction (PCR), Western blot, enzyme-linked immunosorbent assay (ELISA) and (3)H-thymidine incorporation ((3)H-TdR), respectively.

RESULTS

The expression of cyclin D(2), (3)H-thymidine into DNA and fibronectin in the GMCs stimulated by sublytic C5b-9 could all be increased, and the elevations of these parameters mentioned above were also markedly reduced in the GMCs transfected with vectors of PI3-k and Akt short hairpin RNA or LY294002, respectively.

CONCLUSIONS

These data indicate that sublytic C5b-9 can promote proliferation of GMCs and secretion of fibronectin as well as synthesis of thrombospondin-1 and transforming growth factor-beta(1). The PI3-k/Akt signal pathway in these reactions, mediated by sublytic C5b-9 complexes, may play at least a partial role.

Phosphatidylinositol-and related-kinases: a genome-wide survey of classes and subtypes in the Schistosoma mansoni genome for designing subtype-specific inhibitors

Phosphatidylinositol kinases (PIK) are at the heart of one of the major pathways of intracellular signal transduction. The signals made by PIK influence a wide variety of cellular functions, including cell growth, differentiation and survival, glucose metabolism and cytoskeletal organization. Wortmannin strongly binds in vitro to all PIK subtypes and it is therefore an effective antiproliferative agent. This study is the first report on a survey made by similarity searches against Schistosoma mansoni genome available to date for phosphatidylinositol- and related-kinases (SmPIKs). We classified the SmPIKs according to five models (1-5). SmPIK sequences were retrieved from GeneDB (http://www.genedb.org) by means of a combinatorial approach which uses terms defined in genome annotation associated with PFAM (Protein Families) domains, BLAST analysis and COGs (Clusters of Orthologous Groups of proteins). This approach detects the kinase (catalytic) domain structure and also the recently described FAT and FATC motifs.

Inhibitors of phosphoinositide-3-kinase: a structure-based approach to understanding potency and selectivity

Phosphoinositide-3-kinase is a pivotal protein involved in a wide variety of signaling cascades and there has been a great deal of interest in the development of potent and selective inhibitors of this enzyme. In this review, the potency and selectivity of the known inhibitors is presented along with key structural information that helps rationalize the observed trends.

Phosphatidylinositol 3-kinase inhibitors: promising drug candidates for cancer therapy

Phosphatidylinositol 3-kinases (PI3K) are a group of lipid kinases that phosphorylate phosphoinositides at the 3-hydroxyl group of the inositol ring to generate phosphatidylinositol 3,4,5-trisphosphate, a second messenger with key roles in fundamental cellular responses such as cell proliferation and metabolism. Frequent mutations found in or amplification of the PIK3CA gene and loss of phosphatase and tensin homolog deleted on chromosome 10 function in human tumors suggest that PI3K is a potential target for cancer therapy. During the last 5 years, several specific PI3K inhibitors were developed that were directed against various diseases. Some of them revealed potent anticancer efficacy and are now undergoing clinical trials. Some PI3K inhibitors showed antiangiogenic effects. Combined use of PI3K inhibitors with other chemotherapeutic agents or with radiotherapy produced synergistic therapeutic efficacies in treating cancer and showed reduced side effects. The rapid progress made in developing novel PI3K inhibitors in recent years promises bright prospects for finding a PI3K-targeted anticancer drug in the near future.

The efficacy and selectivity of tumor cell killing by Akt inhibitors are substantially increased by chloroquine

This study was to evaluate the enhancement value of chloroquine (CQ) in cancer cell killing when used in combination with Akt inhibitors. The results showed that the combination of CQ and Akt inhibitors is much more effective than either one alone. Importantly, the CQ-mediated chemosensitization of cell killing effects by Akt inhibitors is cancer specific. In particular, when combined with 10 microM CQ, 1,3-dihydro-1-(1-((4-(6-phenyl-1H-imidazo[4,5-g]quinoxalin-7-yl)phenyl)methyl)-4-piperidinyl)-2H-benzimidazol-2-one (an Akt1 and 2 inhibitor; compound 8) killed cancer cells 10-120 times more effectively than normal cells. Thus, CQ is a very effective and cancer-specific chemosensitizer when used in combination with Akt inhibitors.

Structural analysis of PI3-kinase isoforms: identification of residues enabling selective inhibition by small molecule ATP-competitive inhibitors

A series of small molecule, ATP-competitive phosphoinositide 3-kinase inhibitors have been examined in homology models of the four class I isoforms, p110alpha, p110beta, p110delta and p110gamma. This analysis provided an insight into the mode of binding of these inhibitors to the hinge and to other key regions of the ATP binding site in each of the four subtypes. Significantly, residues were identified that differ between these proteins, and which help explain the isoform-selective inhibition profiles of the compounds.