Rapid Microwave Fixation of the Brain Reveals Seasonal Changes in the Phosphoproteome of Hibernating Thirteen-Lined Ground Squirrels

Hibernating mammals such as the thirteen-lined ground squirrel (Ictidomys tridecemlineatus) experience significant reductions in oxidative metabolism and body temperature when entering a state known as torpor. Animals entering or exiting torpor do not experience permanent loss of brain function or other injuries, and the processes that enable such neuroprotection are not well understood. To gain insight into changes in protein function that occur in the dramatically different physiological states of hibernation, we performed quantitative phosphoproteomics experiments on thirteen-lined ground squirrels that are summer-active, winter-torpid, and spring-active. An important aspect of our approach was the use of focused microwave irradiation of the brain to sacrifice the animals and rapidly inactivate phosphatases and kinases to preserve the native phosphoproteome. Overall, our results showed pronounced changes in phosphorylated proteins for the transitions into and out of torpor, including proteins involved in gene expression, DNA maintenance and repair, cellular plasticity, and human disease. In contrast, the transition between the active states showed minimal changes. This study offers valuable insight into the global changes in brain phosphorylation in hibernating mammals, the results of which may be relevant to future therapeutic strategies for brain injury.

Evo312: An Evodiamine Analog and Novel PKCβI Inhibitor with Potent Antitumor Activity in Gemcitabine-Resistant Pancreatic Cancer

As an obstinate cancer pancreatic cancer (PC) poses a major challenge due to limited treatment options which include resection surgery, radiation therapy, and gemcitabine-based chemotherapy. In cancer cells, protein kinase C βI (PKCβI) participates in diverse cellular processes, including cell proliferation, invasion, and apoptotic pathways. In the present study, we created a scaffold to develop PKCβI inhibitors using evodiamine-based synthetic molecules. Among the candidate inhibitors, Evo312 exhibited the highest antiproliferative efficacy against PC cells, PANC-1, and acquired gemcitabine-resistant PC cells, PANC-GR. Additionally, Evo312 robustly inhibited PKCβI activity. Mechanistically, Evo312 effectively suppressed the upregulation of PKCβI protein expression, leading to the induction of cell cycle arrest and apoptosis in PANC-GR cells. Furthermore, Evo312 exerted an antitumor activity in a PANC-GR cell-implanted xenograft mouse model. These findings position Evo312 as a promising lead compound for overcoming gemcitabine resistance in PC through novel mechanisms.

Proteomic landscape of epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is a deadly disease with limited diagnostic biomarkers and therapeutic targets. Here we conduct a comprehensive proteomic profiling of ovarian tissue and plasma samples from 813 patients with different histotypes and therapeutic regimens, covering the expression of 10,715 proteins. We identify eight proteins associated with tumor malignancy in the tissue specimens, which are further validated as potential circulating biomarkers in plasma. Targeted proteomics assays are developed for 12 tissue proteins and 7 blood proteins, and machine learning models are constructed to predict one-year recurrence, which are validated in an independent cohort. These findings contribute to the understanding of EOC pathogenesis and provide potential biomarkers for early detection and monitoring of the disease. Additionally, by integrating mutation analysis with proteomic data, we identify multiple proteins related to DNA damage in recurrent resistant tumors, shedding light on the molecular mechanisms underlying treatment resistance. This study provides a multi-histotype proteomic landscape of EOC, advancing our knowledge for improved diagnosis and treatment strategies.

Screening and Structural Characterization of Heat Shock Response Elements (HSEs) in Entamoeba histolytica Promoters

Entamoeba histolytica (E. histolytica) exhibits a remarkable capacity to respond to thermal shock stress through a sophisticated genetic regulation mechanism. This process is carried out via Heat Shock Response Elements (HSEs), which are recognized by Heat Shock Transcription Factors (EhHSTFs), enabling fine and precise control of gene expression. Our study focused on screening for HSEs in the promoters of the E. histolytica genome, specifically analyzing six HSEs, including Ehpgp5, EhrabB1, EhrabB4, EhrabB5, Ehmlbp, and Ehhsp100. We discovered 2578 HSEs, with 1412 in promoters of hypothetical genes and 1166 in coding genes. We observed that a single promoter could contain anywhere from one to five HSEs. Gene ontology analysis revealed the presence of HSEs in essential genes for the amoeba, including cysteine proteinases, ribosomal genes, Myb family DNA-binding proteins, and Rab GTPases, among others. Complementarily, our molecular docking analyses indicate that these HSEs are potentially recognized by EhHSTF5, EhHSTF6, and EhHSTF7 factors in their trimeric conformation. These findings suggest that E. histolytica has the capability to regulate a wide range of critical genes via HSE-EhHSTFs, not only for thermal stress response but also for vital functions of the parasite. This is the first comprehensive study of HSEs in the genome of E. histolytica, significantly contributing to the understanding of its genetic regulation and highlighting the complexity and precision of this mechanism in the parasite's survival.

Design, synthesis, and biological evaluation of novel ciprofloxacin derivatives as potential anticancer agents targeting topoisomerase II enzyme

A series of novel ciprofloxacin (CP) derivatives substituted at the N-4 position with biologically active moieties were designed and synthesised. 14 compounds were 1.02- to 8.66-fold more potent than doxorubicin against T-24 cancer cells. Ten compounds were 1.2- to 7.1-fold more potent than doxorubicin against PC-3 cancer cells. The most potent compounds 6, 7a, 7b, 8a, 9a, and 10c showed significant Topo II inhibitory activity (83-90% at 100 μM concentration). Compounds 6, 8a, and 10c were 1.01- to 2.32-fold more potent than doxorubicin. Compounds 6 and 8a induced apoptosis in T-24 (16.8- and 20.1-fold, respectively compared to control). This evidence was supported by an increase in the level of apoptotic caspase-3 (5.23- and 7.6-fold, sequentially). Both compounds arrested the cell cycle in the S phase in T-24 cancer cells while in PC-3 cancer cells the two compounds arrested the cell cycle in the G1 phase. Molecular docking simulations of compounds 6 and 8a into the Topo II active site rationalised their remarkable Topo II inhibitory activity.

Chemopreventive Effects of Oral Pterostilbene in Multistage Carcinogenesis of Skin Squamous Cell Carcinoma Mouse Model Induced by DMBA/TPA

Skin squamous cell carcinoma (SCC) is a type of non-melanoma skin cancer. Pterostilbene is a natural compound proven to exhibit various pharmacological properties, including chemo-preventive effects. This study aimed to explore the chemo-preventive effect of oral pterostilbene during initiation, promotion or continuous on multistage skin SCC mouse models induced by 7,12-Dimethylbenz(a)anthracene (DMBA)/12-O-Tetradecanoylphorbol-13-acetate (TPA). The experimental design consists of five groups of female Institute of Cancer Research (ICR) mice, with two control groups of vehicle and cancer. Three oral pterostilbene groups consisted of orally administered pterostilbene during initiation, promotion, or continuously. Oral pterostilbene significantly reduced the number and volume of tumours. Oral pterostilbene demonstrated less severe skin histology changes compared to the cancer control group, with less pleomorphic in the cells and nuclei, and the basement membrane remained intact. Our results showed fewer invasive tumours in oral PT-treated groups than in cancer groups that displayed mitotic bodies, highly pleomorphic cells and nuclei, and basement membrane invasion. The cell proliferation marker (Ki-67) was reduced in oral pterostilbene-treated groups. Overall, oral pterostilbene is a promising chemo-preventive intervention due to its anti-initiation and anti-promotion on skin carcinogenesis. Thus, the potential molecular mechanisms of oral pterostilbene chemo-prevention agent should be explored.

Effect of 4-Allyl-1-hydroxy-2-methoxybenzene (eugenol) in the expression of genes involved in cellular cycle and apoptotic process in dental pulp fibroblasts

OBJECTIVE

This study sought to evaluate the effect of eugenol on the cell morphology and expression of genes involved in the apoptotic process in human dental pulp fibroblasts (hDPFs) from deciduous teeth.

MATERIALS AND METHODS

hDPFs were cultured with 4 concentrations of eugenol (0.06 nM, 0.6 nM, 6 nM, 12 nM) and compared with a control group. After a 72 h incubation period, the cytotoxic effect on cell morphology by optical microscopy and gene expression by RT-PCR were evaluated.

RESULTS

At 0.06 nM and 0.6 nM eugenol concentrations, vacuolisation of the cytoplasm was observed with atypical granulation of the hDPFs, and, at 6 nM and 12 nM cytoplasmic extensions disappeared almost completely. Casp-3, Casp-9, and telomerase genes were not expressed at the concentrations evaluated nor in the control group. The relative expression responses of Bcl-2 and TGF-β genes were overexpressed at the 4 concentrations. MAKP's 0.06 nM (p < .001), 0.6 nM (p < .05) and 12 nM (p < .05) and Cyclin 1 at 12 nM showed significant difference versus the control group (p < .05).

CONCLUSION

Eugenol is capable of causing morphological changes in hDPFs in a dose-dependent manner, higher concentrations may promote overexpression of apoptotic genes.

Protein kinase C targeting of luminal (T-47D), luminal/HER2-positive (BT474), and triple negative (HCC1806) breast cancer cells in-vitro with AEB071 (Sotrastaurin) is efficient but mediated by subtype specific molecular effects

Purpose

Protein kinase C (PKC) plays a pivotal role in malignant cell proliferation, apoptosis, invasiveness and migration. However, its exploitation as therapeutic target in breast cancer has been merely explored. Here were evaluated the AEB071 (Sotrastaurin™) treatment efficiency of breast cancer cell lines derived from estrogen receptor positive (T-47D), estrogen/HER2 receptor positive (BT474), and triple negative (HCC1806) breast cancer cells under 2D (monolayer) and 3D (multicellular tumor spheroids) culture conditions. Additionally, spheroid cocultures of BC and N1 fibroblasts were analyzed.

Methods

We quantitatively assessed the proliferation capacity of breast cancer cells and fibroblasts as a function of AEB071 treatment using flow cytometry. The activities of PKC isoforms, substrates, and key molecules of the PKC signaling known to be involved in the regulation of tumor cell proliferation and cellular survival were additionally evaluated. Moreover, a multigene expression analysis (PanCancer Pathways assay) using the nanoString™ technology was applied.

Results

All breast cancer cell lines subjected to this study were sensitive to AEB071 treatment, whereby cell proliferation in 2D culture was considerably (BT474) or moderately (HCC1806) retarded in G0/G1 or in G2/M phase (T-47D) of the cell cycle. Regardless of the breast cancer subtype the efficiency of AEB071 treatment was significantly lower in the presence of N1 fibroblast cells. Subtype specific driver molecules, namely IL19, c-myb, and NGFR were mostly affected by the AEB071 treatment.

Conclusion

A combined targeting of PKC and a subtype specific driver molecule might complement specified breast cancer treatment.

Evidence that PKCα inhibition in Dalton's Lymphoma cells augments cell cycle arrest and mitochondrial-dependent apoptosis

Protein kinase Cα (PKCα), belonging to ser/thr protein kinase, perform various biological functions. Overexpression of PKCα has been observed in multiple human malignancies including lymphoma. However, the molecular pathogenesis and involvement of PKCα in Non-Hodgkin lymphoma (NHL) are not clearly understood. Hence, deciphering the role of PKCα in NHL management may provide a better therapeutic option. In the present study, we used selective pharmacological inhibitors Gö6976 and Ro320432 that potentially inhibit PKCα-mediated signaling in DL cells, resulting in the inhibition of cell growth and mitochondrial-dependent apoptosis. PKCα inhibition by these inhibitors also displays cell cycle arrest at the G1 phase and causes growth retardation of DL cells. Our results extended the mechanism of PKCα in NHL, and provided potential implications for its therapy.

Coronin-1 is phosphorylated at Thr-412 by protein kinase Cα in human phagocytic cells

Coronin-1, a hematopoietic cell-specific actin-binding protein, is thought to be involved in the phagocytic process through its interaction with actin filaments. The dissociation of coronin-1 from phagosomes after its transient accumulation on the phagosome surface is associated with lysosomal fusion. We previously reported that 1) coronin-1 is phosphorylated by protein kinase C (PKC), 2) coronin-1 has two phosphorylation sites, Ser-2 and Thr-412, and 3) Thr-412 of coronin-1 is phosphorylated during phagocytosis. In this study, we examined which PKC isoform is responsible for the phosphorylation of coronin-1 at Thr-412 by using isotype-specific PKC inhibitors and small interfering RNAs (siRNAs). Thr-412 phosphorylation of coronin-1 was suppressed by Gö6976, an inhibitor of PKCα and PKCβI. This phosphorylation was attenuated by siRNA for PKCα, but not by siRNA for PKCβ. Furthermore, Thr-412 of coronin-1 was phosphorylated by recombinant PKCα in vitro, but not by recombinant PKCβ. We next examined the effects of Gö6976 on the intracellular distribution of coronin-1 in HL60 cells during phagocytosis. The confocal fluorescence microscopic observation showed that coronin-1 was not dissociated from phagosomes in Gö6976-treated cells. These results indicate that phosphorylation of coronin-1 at Thr-412 by PKCα regulates intracellular distribution during phagocytosis.

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Phosphorylation of coronin-1 at Thr-412 is suppressed by PKCα/β inhibitor.

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PKCα not PKCβ phosphorylates coronin-1 at Thr-412 in vitro.

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Dissociation of coronin-1 from phagosome is regulated by PKCα.

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Phosphorylation of coronin-1 at Thr-412 may trigger phagosome maturation.

Cellular Energetics of Mast Cell Development and Activation

Mast cells are essential first responder granulocytes in the innate immune system that are well known for their role in type 1 immune hypersensitivity reactions. Although mostly recognized for their role in allergies, mast cells have a range of influences on other systems throughout the body and can respond to a wide range of agonists to properly prime an appropriate immune response. Mast cells have a dynamic energy metabolism to allow rapid responsiveness to their energetic demands. However, our understanding of mast cell metabolism and its impact on mast cell activation and development is still in its infancy. Mast cell metabolism during stimulation and development shifts between both arms of metabolism: catabolic metabolism-such as glycolysis and oxidative phosphorylation-and anabolic metabolism-such as the pentose phosphate pathway. The potential for metabolic pathway shifts to precede and perhaps even control activation and differentiation provides an exciting opportunity to explore energy metabolism for clues in deciphering mast cell function. In this review, we discuss literature pertaining to metabolic environments and fluctuations during different sources of activation, especially IgE mediated vs. non-IgE mediated, and mast cell development, including progenitor cell types leading to the well-known resident mast cell.

Equivocal, explicit and emergent actions of PKC isoforms in cancer

The maturing mutational landscape of cancer genomes, the development and application of clinical interventions and evolving insights into tumour-associated functions reveal unexpected features of the protein kinase C (PKC) family of serine/threonine protein kinases. These advances include recent work showing gain or loss-of-function mutations relating to driver or bystander roles, how conformational constraints and plasticity impact this class of proteins and how emergent cancer-associated properties may offer opportunities for intervention. The profound impact of the tumour microenvironment, reflected in the efficacy of immune checkpoint interventions, further prompts to incorporate PKC family actions and interventions in this ecosystem, informed by insights into the control of stromal and immune cell functions. Drugging PKC isoforms has offered much promise, but when and how is not obvious.

A cancer-associated, genome protective programme engaging PKCε

Associated with their roles as targets for tumour promoters, there has been a long-standing interest in how members of the protein kinase C (PKC) family act to modulate cell growth and division. This has generated a great deal of observational data, but has for the most part not afforded clear mechanistic insights into the control mechanisms at play. Here, we review the roles of PKCε in protecting transformed cells from non-disjunction. In this particular cell cycle context, there is a growing understanding of the pathways involved, affording biomarker and interventional insights and opportunities.

Recurrent copy number gains drive PKCι expression and PKCι-dependent oncogenic signaling in human cancers

PRKCI is frequently overexpressed in multiple human cancers, and PKCι expression is often prognostic for poor patient survival, indicating that elevated PKCι broadly plays an oncogenic role in the cancer phenotype. PKCι drives multiple oncogenic signaling pathways involved in transformed growth, and transgenic mouse models have revealed that PKCι is a critical oncogenic driver in both lung and ovarian cancers. We now report that recurrent 3q26 copy number gain (CNG) is the predominant genetic driver of PRKCI mRNA expression in all major human cancer types exhibiting such CNGs. In addition to PRKCI, CNG at 3q26 leads to coordinate CNGs of ECT2 and SOX2, two additional 3q26 genes that collaborate with PRKCI to drive oncogenic signaling and tumor initiation in lung squamous cell carcinoma. Interestingly however, whereas 3q26 CNG is a strong driver of PRKCI mRNA expression across all tumor types examined, it has differential effects on ECT2 and SOX2 mRNA expression. In some tumors types, particularly those with squamous histology, all three 3q26 oncogenes are coordinately overexpressed as a consequence of 3q26 CNG, whereas in other cancers only PRKCI and ECT2 mRNA are coordinately overexpressed. This distinct pattern of expression of 3q26 genes corresponds to differences in genomic signatures reflective of activation of specific PKCι oncogenic signaling pathways. In addition to highly prevalent CNG, some tumor types exhibit monoallelic loss of PRKCI. Interestingly, many tumors harboring monoallelic loss of PRKCI express significantly lower PRKCI mRNA and exhibit evidence of WNT/β-catenin signaling pathway activation, which we previously characterized as a major oncogenic pathway in a newly described, PKCι-independent molecular subtype of lung adenocarcinoma. Finally, we show that CNG-driven activation of PKCι oncogenic signaling predicts poor patient survival in many major cancer types. We conclude that CNG and monoallelic loss are the major determinants of tumor PRKCI mRNA expression across virtually all tumor types, but that tumor-type specific mechanisms determine whether these copy number alterations also drive expression of the collaborating 3q26 oncogenes ECT2 and SOX2, and the oncogenic PKCι signaling pathways activated through the collaborative action of these genes. Our analysis may be useful in identifying tumor-specific predictive biomarkers and effective PKCι-targeted therapeutic strategies in the multitude of human cancers harboring genetic activation of PRKCI.

Phospholipase C beta1 (PI-PLCbeta1)/Cyclin D3/protein kinase C (PKC) alpha signaling modulation during iron-induced oxidative stress in myelodysplastic syndromes (MDS)

MDS are characterized by anemia and transfusion requirements. Transfused patients frequently show iron overload that negatively affects hematopoiesis. Iron chelation therapy can be effective in these MDS cases, but the molecular consequences of this treatment need to be further investigated. That is why we studied the molecular features of iron effect and Deferasirox therapy on PI-PLCbeta1 inositide signaling, using hematopoietic cells and MDS samples. At baseline, MDS patients showing a positive response after iron chelation therapy displayed higher levels of PI-PLCbeta1/Cyclin D3/PKCalpha expression. During treatment, these responder patients, as well as hematopoietic cells treated with FeCl₃ and Deferasirox, showed a specific reduction of PI-PLCbeta1/Cyclin D3/PKCalpha expression, indicating that this signaling pathway is targeted by Deferasirox. The treatment was also able to specifically decrease the production of ROS. This effect correlated with a reduction of IL-1A and IL-2, as well as Akt/mTOR phosphorylation. In contrast, cells exposed only to FeCl₃ and cells from MDS patients refractory to Deferasirox showed a specific increase of ROS and PI-PLCbeta1/Cyclin D3/PKCalpha expression. All in all, our data show that PI-PLCbeta1 signaling is a target for iron-induced oxidative stress and suggest that baseline PI-PLCbeta1 quantification could predict iron chelation therapy response in MDS.

Anti-Diabetic Atherosclerosis by Inhibiting High Glucose-Induced Vascular Smooth Muscle Cell Proliferation via Pin1/BRD4 Pathway

Methods

Diabetic Apoe-/- mice induced by streptozotocin were treated with vehicle, the Pin1 inhibitor juglone, or the BRD4 inhibitor JQ1 for 3 weeks. VSMCs were pretreated with juglone, JQ1, or vehicle for 45 min, and then exposed to high glucose for 48 h. Hematoxylin–eosin staining was performed to assess atherosclerotic plaques of the thoracic aorta. Western blotting was used to detect expression levels of Pin1, BRD4, cyclin D1, and matrix metalloproteinase-9 (MMP-9) in the thoracic aorta and VSMCs. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and transwell assay were used to measure proliferation and migration of VSMCs.

Results

Juglone and JQ1 significantly improved atherosclerosis of diabetic Apoe-/- mice and reduced high glucose-induced VSMC proliferation and migration. Cyclin D1 and MMP-9 levels in the thoracic aorta were lower in diabetic Apoe-/- mice treated with juglone and JQ1 compared with vehicle-treated diabetic Apoe-/- mice. Additionally, BRD4 protein expression in high glucose-induced VSMCs was inhibited by juglone and JQ1. Upregulation of Pin1 expression by transduction of the Pin1 plasmid vector promoted BRD4 expression induced by high glucose, and stimulated proliferation and migration of VSMCs.

Conclusions

Inhibition of Pin1/BRD4 pathway may improve diabetic atherosclerosis by inhibiting proliferation and migration of VSMCs.

Exploring the controversial role of PI3K signalling in CD4+ regulatory T (T-Reg) cells

The immune system is a complex network that acts to protect vertebrates from foreign microorganisms and carries out immunosurveillance to combat cancer. In order to avoid hyper-activation of the immune system leading to collateral damage tissues and organs and to prevent self-attack, the network has the intrinsic control mechanisms that negatively regulate immune responses. Central to this negative regulation are regulatory T (T-Reg) cells, which through cytokine secretion and cell interaction limit uncontrolled clonal expansion and functions of activated immune cells. Given that positive or negative manipulation of T-Regs activity could be utilised to therapeutically treat host versus graft rejection or cancer respectively, understanding how signaling pathways impact on T-Regs function should reveal potential targets with which to intervene. The phosphatidylinositol-3-kinase (PI3K) pathway controls a vast array of cellular processes and is critical in T cell activation. Here we focus on phosphoinositide 3-kinases (PI3Ks) and their ability to regulate T-Regs cell differentiation and function.

Recent advances in MDS mutation landscape: Splicing and signalling

Recurrent cytogenetic aberrations, genetic mutations and variable gene expression have been consistently recognized in solid cancers and in leukaemia, including in Myelodysplastic Syndromes (MDS). Besides conventional cytogenetics, the growing accessibility of new techniques has led to a deeper analysis of the molecular significance of genetic variations. Indeed, gene mutations affecting splicing genes, as well as genes implicated in essential signalling pathways, play a pivotal role in MDS physiology and pathophysiology, representing potential new molecular targets for innovative therapeutic strategies.

PKCδ promotes fertilization of mouse embryos in early development via the Cdc25B signaling pathway

Protein kinase C type δ (PKCδ) is involved in B-cell signaling and the regulation of growth, apoptosis and differentiation of a variety of cell types. Cell division cycle 25 (Cdc25) is a key mediator of cell cycle progression that activates cyclin-dependent kinase complexes that drive the cell cycle and participates in the regulation of DNA damage checkpoints. Cdc25B is a member of the Cdc25 family of phosphatases. The present study investigated the role and mechanism of PKCδ in regulating the fertilization of mouse embryos in early development. The expression and subcellular localization of PKCδ and Cdc25B were detected using reverse transcription-quantitative polymerase chain reaction, western blotting and immunofluorescence in one-cell stage mouse embryos. Specific small interfering RNAs targeting PKCδ were used to knockdown the expression of PKCδ. Subsequently, Scansite software was used to predict the target of phosphorylated Cdc25B. Western blotting was used to measure the effects of phosphorylation and dephosphorylation in one-cell stage mouse embryos at different cell cycle phases. PKCδ was expressed during M phase and served a positive role in one-cell stage mouse embryos. Immunofluorescence data revealed that PKCδ and Cdc25B were expressed during G₁, S, G₂ and M phases of the cell cycle. Furthermore, phosphorylated levels of Cdc25B-Ser96 were observed during G₂ and M phases. Microinjection with mimics of phosphorylated Cdc25B-Ser96 mRNA promoted the development of one-cell stage mouse embryos. When PKCδ was suppressed, microinjection with mimics of phosphorylated Cdc25B-Ser96 mRNA reversed the inhibition of PKCδ. To conclude, PKCδ serves a positive role in the first cell cycle of mouse embryos by phosphorylating Cdc25B-Ser96, and provides novel insights for the regulation of early embryonic development.

Role of lysophosphatidic acid in vascular smooth muscle cell proliferation

Lysophosphatidic acid (LPA) is an important lipid molecule for signal transduction in cell proliferation. Although the effects of LPA on vascular smooth muscle (VSM) cell growth have been reported previously, the underlying mechanisms of its action are not fully understood. The present study was undertaken to investigate the effects of some inhibitors of different protein kinases and other molecular targets on LPA-induced DNA synthesis as well as gene expression in the aortic VSM cells. The DNA synthesis was studied by the [³H]thymidine incorporation method and the gene expression was investigated by the real-time PCR technique. It was observed that the LPA-induced DNA synthesis was attenuated by inhibitors of protein kinase C (PKC) (staurosporine, calphostin C, and bisindolylmaleimide), phosphoinositide 3-kinase (PI3K) (wortmannin and LY294002), and ribosomal p70S6 kinase (p70S6K) (rapamycin). The inhibitors of guanine protein coupled receptors (GPCR) (pertussis toxin), phospholipase C (PLC) (U73122 and D609), and sodium-hydrogen exchanger (NHE) (amiloride and dimethyl amiloride) were also shown to depress the LPA-induced DNA synthesis. Furthermore, gene expressions for PLC β1 isoform, PKC δ and ε isoforms, casein kinase II β isoform, and endothelin-1A receptors were elevated by LPA. These results suggest that the LPA-induced proliferation of VSM cells is mediated through the activation of GPCR and multiple protein kinases as well as gene expressions of some of their specific isoforms.

Nuclear Phosphoinositides: Their Regulation and Roles in Nuclear Functions

Polyphosphoinositides (PPIns) are a family of seven lipid messengers that regulate a vast array of signalling pathways to control cell proliferation, migration, survival and differentiation. PPIns are differentially present in various sub-cellular compartments and, through the recruitment and regulation of specific proteins, are key regulators of compartment identity and function. Phosphoinositides and the enzymes that synthesise and degrade them are also present in the nuclear membrane and in nuclear membraneless compartments such as nuclear speckles. Here we discuss how PPIns in the nucleus are modulated in response to external cues and how they function to control downstream signalling. Finally we suggest a role for nuclear PPIns in liquid phase separations that are involved in the formation of membraneless compartments within the nucleus.

Phosphatidylinositol Kinases and Phosphatases in Entamoeba histolytica

Phosphatidylinositol (PtdIns) metabolism is indispensable in eukaryotes. Phosphoinositides (PIs) are phosphorylated derivatives of PtdIns and consist of seven species generated by reversible phosphorylation of the inositol moieties at the positions 3, 4, and 5. Each of the seven PIs has a unique subcellular and membrane domain distribution. In the enteric protozoan parasite Entamoeba histolytica, it has been previously shown that the PIs phosphatidylinositol 3-phosphate (PtdIns3P), PtdIns(4,5)P₂, and PtdIns(3,4,5)P₃ are localized to phagosomes/phagocytic cups, plasma membrane, and phagocytic cups, respectively. The localization of these PIs in E. histolytica is similar to that in mammalian cells, suggesting that PIs have orthologous functions in E. histolytica. In contrast, the conservation of the enzymes that metabolize PIs in this organism has not been well-documented. In this review, we summarized the full repertoire of the PI kinases and PI phosphatases found in E. histolytica via a genome-wide survey of the current genomic information. E. histolytica appears to have 10 PI kinases and 23 PI phosphatases. It has a panel of evolutionarily conserved enzymes that generate all the seven PI species. However, class II PI 3-kinases, type II PI 4-kinases, type III PI 5-phosphatases, and PI 4P-specific phosphatases are not present. Additionally, regulatory subunits of class I PI 3-kinases and type III PI 4-kinases have not been identified. Instead, homologs of class I PI 3-kinases and PTEN, a PI 3-phosphatase, exist as multiple isoforms, which likely reflects that elaborate signaling cascades mediated by PtdIns(3,4,5)P₃ are present in this organism. There are several enzymes that have the nuclear localization signal: one phosphatidylinositol phosphate (PIP) kinase, two PI 3-phosphatases, and one PI 5-phosphatase; this suggests that PI metabolism also has conserved roles related to nuclear functions in E. histolytica, as it does in model organisms.

Structural Basis of Protein Kinase Cα Regulation by the C-Terminal Tail

Protein kinase C (PKC) isoenzymes are multi-modular proteins activated at the membrane surface to regulate signal transduction processes. When activated by second messengers, PKC undergoes a drastic conformational and spatial transition from the inactive cytosolic state to the activated membrane-bound state. The complete structure of either state of PKC remains elusive. We demonstrate, using NMR spectroscopy, that the isolated Ca²⁺-sensing membrane-binding C2 domain of the conventional PKCα interacts with a conserved hydrophobic motif of the kinase C-terminal region, and we report a structural model of the complex. Our data suggest that the C-terminal region plays a dual role in regulating the PKC activity: activating, through sensitization of PKC to intracellular Ca²⁺ oscillations; and auto-inhibitory, through its interaction with a conserved positively charged region of the C2 domain.

Response of high-risk MDS to azacitidine and lenalidomide is impacted by baseline and acquired mutations in a cluster of three inositide-specific genes

Specific myeloid-related and inositide-specific gene mutations can be linked to myelodysplastic syndromes (MDS) pathogenesis and therapy. Here, 44 higher-risk MDS patients were treated with azacitidine and lenalidomide and mutations analyses were performed at baseline and during the therapy. Results were then correlated to clinical outcome, overall survival (OS), leukemia-free-survival (LFS) and response to therapy. Collectively, 34/44 patients were considered evaluable for response, with an overall response rate of 76.25% (26/34 cases): 17 patients showed a durable response, 9 patients early lost response and 8 patients never responded. The most frequently mutated genes were ASXL1, TET2, RUNX1, and SRSF2. All patients early losing response, as well as cases never responding, acquired the same 3 point mutations during therapy, affecting respectively PIK3CD (D133E), AKT3 (D280G), and PLCG2 (Q548R) genes, that regulate cell proliferation and differentiation. Moreover, Kaplan–Meier analyses revealed that this mutated cluster was significantly associated with a shorter OS, LFS, and duration of response. All in all, a common mutated cluster affecting 3 inositide-specific genes is significantly associated with loss of response to azacitidine and lenalidomide therapy in higher risk MDS. Further studies are warranted to confirm these data and to further analyze the functional role of this 3-gene cluster.

PKCβ1 regulates meiotic cell cycle in mouse oocyte

PKCβI, a member of the classical protein kinase C family, plays key roles in regulating cell cycle transition. Here, we report the expression, localization and functions of PKCβI in mouse oocyte meiotic maturation. PKCβI and p-PKCβI (phosphor-PKCβI) were expressed from germinal vesicle (GV) stage to metaphase II (MII) stage. Confocal microscopy revealed that PKCβI was localized in the GV and evenly distributed in the cytoplasm after GV breakdown (GVBD), and it was concentrated at the midbody at telophase in meiotic oocytes. While, p-PKCβI was concentrated at the spindle poles at the metaphase stages and associated with midbody at telophase. Depletion of PKCβI by specific siRNA injection resulted in defective spindles, accompanied with spindle assembly checkpoint activation, metaphase I arrest and failure of first polar body (PB1) extrusion. Live cell imaging analysis also revealed that knockdown of PKCβI resulted in abnormal spindles, misaligned chromosomes, and meiotic arrest of oocytes arrest at the Pro-MI/MI stage. PKCβI depletion did not affect the G2/M transition, but its overexpression delayed the G2/M transition through regulating Cyclin B1 level and Cdc2 activity. Our findings reveal that PKCβI is a critical regulator of meiotic cell cycle progression in oocytes. Abbreviations: PKC, protein kinase C; COC, cumulus-oocyte complexes; GV, germinal vesicle; GVBD, germinal vesicle breakdown; Pro-MI, first pro-metaphase; MI, first metaphase; Tel I, telophase I; MII, second metaphase; PB1, first polar body; SAC, spindle assembly checkpoint.

Hepatocyte growth factor acts as a mitogen for equine satellite cells via protein kinase C δ-directed signaling

Hepatocyte growth factor (HGF) signals mediate mouse skeletal muscle stem cell, or satellite cell (SC), reentry into the cell cycle and myoblast proliferation. Because the athletic horse experiences exercise-induced muscle damage, the objective of the experiment was to determine the effect of HGF on equine SC (eqSC) bioactivity. Fresh isolates of adult eqSC were incubated with increasing concentrations of HGF and the initial time to DNA synthesis was measured. Media supplementation with HGF did not shorten (P > 0.05) the duration of G0/G1 transition suggesting the growth factor does not affect activation. Treatment with 25 ng/mL HGF increased (P < 0.05) eqSC proliferation that was coincident with phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and AKT serine/threonine kinase 1 (AKT1). Chemical inhibition of the upstream effectors of ERK1/2 or AKT1 elicited no effect (P > 0.05) on HGF-mediated 5-ethynyl-2'-deoxyuridine (EdU) incorporation. By contrast, treatment of eqSC with 2 µm Gö6983, a pan-protein kinase C (PKC) inhibitor, blocked (P < 0.05) HGF-initiated mitotic activity. Gene-expression analysis revealed that eqSC express PKCα, PKCδ, and PKCε isoforms. Knockdown of PKCδ with a small interfering RNA (siRNA) prevented (P > 0.05) HGF-mediated EdU incorporation. The siPKCδ was specific to the kinase and did not affect (P > 0.05) expression of either PKCα or PKCε. Treatment of confluent eqSC with 25 ng/mL HGF suppressed (P < 0.05) nuclear myogenin expression during the early stages of differentiation. These results demonstrate that HGF may not affect activation but can act as a mitogen and modest suppressor of differentiation.

Evolving mechanisms of vascular smooth muscle contraction highlight key targets in vascular disease

Vascular smooth muscle (VSM) plays an important role in the regulation of vascular function. Identifying the mechanisms of VSM contraction has been a major research goal in order to determine the causes of vascular dysfunction and exaggerated vasoconstriction in vascular disease. Major discoveries over several decades have helped to better understand the mechanisms of VSM contraction. Ca2+ has been established as a major regulator of VSM contraction, and its sources, cytosolic levels, homeostatic mechanisms and subcellular distribution have been defined. Biochemical studies have also suggested that stimulation of Gq protein-coupled membrane receptors activates phospholipase C and promotes the hydrolysis of membrane phospholipids into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 stimulates initial Ca2+ release from the sarcoplasmic reticulum, and is buttressed by Ca2+ influx through voltage-dependent, receptor-operated, transient receptor potential and store-operated channels. In order to prevent large increases in cytosolic Ca2+ concentration ([Ca2+]c), Ca2+ removal mechanisms promote Ca2+ extrusion via the plasmalemmal Ca2+ pump and Na+/Ca2+ exchanger, and Ca2+ uptake by the sarcoplasmic reticulum and mitochondria, and the coordinated activities of these Ca2+ handling mechanisms help to create subplasmalemmal Ca2+ domains. Threshold increases in [Ca2+]c form a Ca2+-calmodulin complex, which activates myosin light chain (MLC) kinase, and causes MLC phosphorylation, actin-myosin interaction, and VSM contraction. Dissociations in the relationships between [Ca2+]c, MLC phosphorylation, and force have suggested additional Ca2+ sensitization mechanisms. DAG activates protein kinase C (PKC) isoforms, which directly or indirectly via mitogen-activated protein kinase phosphorylate the actin-binding proteins calponin and caldesmon and thereby enhance the myofilaments force sensitivity to Ca2+. PKC-mediated phosphorylation of PKC-potentiated phosphatase inhibitor protein-17 (CPI-17), and RhoA-mediated activation of Rho-kinase (ROCK) inhibit MLC phosphatase and in turn increase MLC phosphorylation and VSM contraction. Abnormalities in the Ca2+ handling mechanisms and PKC and ROCK activity have been associated with vascular dysfunction in multiple vascular disorders. Modulators of [Ca2+]c, PKC and ROCK activity could be useful in mitigating the increased vasoconstriction associated with vascular disease.

Ketamine-induced neurotoxicity blocked by N-Methyl-d-aspartate is mediated through activation of PKC/ERK pathway in developing hippocampal neurons

Ketamine, a non-competitive N-methyl d-aspartate (NMDA) receptor antagonist, is widely used in pediatric clinical practice. However, prolonged exposure to ketamine results in widespread anesthetic neurotoxicity and long-term neurocognitive deficits. The molecular mechanisms that underlie this important event are poorly understood. We investigated effects of anesthetic ketamine on neuroapoptosis and further explored role of NMDA receptors in ketamine-induced neurotoxicity. Here we demonstrate that ketamine induces activation of cell cycle entry, resulting in cycle-related neuronal apoptosis. On the other hand, ketamine administration alters early and late apoptosis of cultured hippocampus neurons by inhibiting PKC/ERK pathway, whereas excitatory NMDA receptor activation reverses these effects. Ketamine-induced neurotoxicity blocked by NMDA is mediated through activation of PKC/ERK pathway in developing hippocampal neurons.

Diacylglycerol kinase synthesized by commensal Lactobacillus reuteri diminishes protein kinase C phosphorylation and histamine-mediated signaling in the mammalian intestinal epithelium

Lactobacillus reuteri 6475 (Lr) of the human microbiome synthesizes histamine and can suppress inflammation via type 2 histamine receptor (H2R) activation in the mammalian intestine. Gut microbes such as Lr promote H2R signaling and may suppress H1R proinflammatory signaling pathways in parallel by unknown mechanisms. In this study, we identified a soluble bacterial enzyme known as diacylglycerol kinase (Dgk) from Lr that is secreted into the extracellular milieu and presumably into the intestinal lumen. DgK diminishes diacylglycerol (DAG) quantities in mammalian cells by promoting its metabolic conversion and causing reduced protein kinase C phosphorylation (pPKC) as a net effect in mammalian cells. We demonstrated that histamine synthesized by gut microbes (Lr) activates both mammalian H1R and H2R, but Lr-derived Dgk suppresses the H1R signaling pathway. Phospho-PKC and IκBα were diminished within the intestinal epithelium of mice and humans treated by wild-type (WT) Lr, but pPKC and IκBα were not decreased in treatment with ΔdgkA Lr. Mucosal IL-6 and systemic interleukin (IL)-1α, eotaxin, and granulocyte colony-stimulating factor (G-CSF) were suppressed in WT Lr, but not in ΔdgkA Lr colonized mice. Collectively, the commensal microbe Lr may act as a "microbial antihistamine" by suppressing intestinal H1R-mediated proinflammatory responses via diminished pPKC-mediated mammalian cell signaling.

Nuclear translocation of PKC-α is associated with cell cycle arrest and erythroid differentiation in myelodysplastic syndromes (MDSs)

PI-PLCβ1 is involved in cell proliferation, differentiation, and myelodysplastic syndrome (MDS) pathogenesis. Moreover, the increased activity of PI-PLCβ1 reduces the expression of PKC-α, which, in turn, delays the cell proliferation and is linked to erythropoiesis. Lenalidomide is currently used in low-risk patients with MDS and del(5q), where it can suppress the del(5q) clone and restore normal erythropoiesis. In this study, we analyzed the effect of lenalidomide on 16 patients with low-risk del(5q) MDS, as well as del(5q) and non-del(5q) hematopoietic cell lines, mainly focusing on erythropoiesis, cell cycle, and PI-PLCβ1/PKC-α signaling. Overall, 11 patients were evaluated clinically, and 10 (90%) had favorable responses; the remaining case had a stable disease. At a molecular level, both responder patients and del(5q) cells showed a specific induction of erythropoiesis, with a reduced γ/β-globin ratio, an increase in glycophorin A, and a nuclear translocation of PKC-α. Moreover, lenalidomide could induce a selective G₀/G₁ arrest of the cell cycle in del(5q) cells, slowing down the rate proliferation in those cells. Altogether, our results could not only better explain the role of PI-PLCβ1/PKC-α signaling in erythropoiesis but also lead to a better comprehension of the lenalidomide effect on del(5q) MDS and pave the way to innovative, targeted therapies.-Poli, A., Ratti, S., Finelli, C., Mongiorgi, S., Clissa, C., Lonetti, A., Cappellini, A., Catozzi, A., Barraco, M., Suh, P.-G., Manzoli, L., McCubrey, J. A., Cocco, L., Follo, M. Y. Nuclear translocation of PKC-α is associated with cell cycle arrest and erythroid differentiation in myelodysplastic syndromes (MDSs).

Research advances in kinase enzymes and inhibitors for cardiovascular disease treatment

The targeting of protein kinases has great future potential for the design of new drugs against cardiovascular diseases (CVDs). Enormous efforts have been made toward achieving this aim. Unfortunately, kinase inhibitors designed to treat CVDs have suffered from numerous limitations such as poor selectivity, bad permeability and toxicity. So, where are we now in terms of discovering effective kinase targeting drugs to treat CVDs? Various drug design techniques have been approached for this purpose since the discovery of the inhibitory activity of Staurosporine against protein kinase C in 1986. This review aims to provide context for the status of several emerging classes of direct kinase modulators to treat CVDs and discuss challenges that are preventing scientists from finding new kinase drugs to treat heart disease.

Nuclear Localization of Diacylglycerol Kinase Alpha in K562 Cells Is Involved in Cell Cycle Progression

Phosphatidylinositol (PI) signaling is an essential regulator of cell motility and proliferation. A portion of PI metabolism and signaling takes place in the nuclear compartment of eukaryotic cells, where an array of kinases and phosphatases localize and modulate PI. Among these, Diacylglycerol Kinases (DGKs) are a class of phosphotransferases that phosphorylate diacylglycerol and induce the synthesis of phosphatidic acid. Nuclear DGKalpha modulates cell cycle progression, and its activity or expression can lead to changes in the phosphorylated status of the Retinoblastoma protein, thus, impairing G1/S transition and, subsequently, inducing cell cycle arrest, which is often uncoupled with apoptosis or autophagy induction. Here we report for the first time not only that the DGKalpha isoform is highly expressed in the nuclei of human erythroleukemia cell line K562, but also that its nuclear activity drives K562 cells through the G1/S transition during cell cycle progression. J. Cell. Physiol. 232: 2550-2557, 2017. © 2016 Wiley Periodicals, Inc.

Prenatal morphine exposure during late embryonic stage enhances the rewarding effects of morphine and induces the loss of membrane-bound protein kinase C-α in intermediate medial mesopallium in the chick

The susceptibility to drug abuse may be associated with the structural and/or functional changes in the reward-related brain regions induced by drug exposure during sensitive periods of embryonic development. Previously, we have found that prenatal morphine exposure during embryonic days 17-20 may be crucial for developing the susceptibility to morphine reward after hatching. However, the underlying structure and cellular mechanisms need further investigation. In the present study, the chicks of a few days old, which were prenatally exposed to morphine during E17-20, obviously showed higher preference for the morphine-paired chamber and hyperactivity during the expression of morphine conditioned place preference (CPP), and the reduction in membrane-bound of PKCα of the bilateral intermediate medial mesopallium (IMM) assayed immunologically. These results indicate that the decreased expression of PKCα in IMM may participate in the development of the susceptibility to the rewarding effects of morphine in chicks prenatally exposed to morphine, and provide further support for the cross-species evolutionary concordance among amniotes.

Effect of PMA-induced protein kinase C activation on development and apoptosis in early zebrafish embryos

Protein kinase C (PKC) isoforms have been implicated in several key steps during early development, but the consequences of xenobiotic-induced PKC activation during early embryogenesis are still unknown. In this study, zebrafish embryos were exposed to a range of phorbol 12-myristate 13-acetate (PMA) concentrations (0-200μg/L) at different time points after fertilization. Results showed that 200μgPMA/L caused development of yolk bags, cardiac edema, slow blood flow, pulsating blood flow, slow pulse, elongated heart, lack of tail fins, curved tail, and coagulation. PMA exposure decreased survival rate of the embryos starting within the first 24h and becoming more pronounced after prolonged exposure (96h). PMA increased the number of apoptotic cells in the brain region as demonstrated by acridine orange staining and caused up-regulation of caspase 9 (casp9) and p53 up-regulated modulator of apoptosis (puma) mRNA in whole embryos. PMA caused oxidative stress in the embryos as demonstrated by decreased mRNA expression of catalase and superoxide dismutase 2. Inhibition of Pkc with GF109203X improved overall survival rate, reduced apoptosis in the brain and decreased expression of casp9 and puma in the PMA-exposed embryos. However, Pkc inhibition neither prevented development of deformities nor reversed oxidative stress in the PMA-exposed embryos. These data suggest that direct over-activation of Pkc during early embryogenesis of zebrafish is associated with apoptosis and decreased survival rate of the embryos.

Label-free quantitative phosphoproteomic profiling of cellular response induced by an insect cytokine paralytic peptide

Paralytic peptide (PP) participates in diverse physiological processes as an insect cytokine, such as immunity control, paralysis induction, regulation of cell morphology and proliferation. To investigate the molecular mechanism underlying those physiological activities, we systematically investigated the global phosphorylation events in fat body of silkworm larvae induced by PP through label-free quantitative phosphoproteomics. 2534 phosphosites were finally identified, of which the phosphorylation level of 620 phosphosites on 244 proteins was significantly up-regulated and 67 phosphosites on 43 proteins was down-regulated. Among those proteins, 13 were protein kinases (PKs), 13 were transcription factors (TFs) across 10 families and 17 were metabolism related enzymes. Meanwhile, Motif-X analysis of the phosphorylation sites showed that 16 motifs are significantly enriched, including 8 novel phosphorylation motifs. In addition, KEGG and functional interacting network analysis revealed that phosphorylation cascades play the crucial regulation roles in PP-dependent signaling pathways, and highlighted the potential central position of the mitogen-activated protein kinases (MAPKs) in them. These analyses provide direct insights into the molecule mechanisms of cellular response induced by PP.

SIGNIFICANCE

PP as an insect cytokine participated in diverse functions including immunity control paralysis induction, regulation of cell morphology and proliferation. In this study, we performed firstly a label-free quantitative phosphoproteomics analysis. We found some new phosphorylation targets of PP-stimulation. Meanwhile, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and functional networks revealed that phosphorylation cascades play the crucial regulation roles in PP-dependent signaling pathways. In addition, the potential central position of the mitogen-activated protein kinases (MAPKs) was highlighted in PP-dependent signaling pathways. We think our findings may help us gain a systematic understanding of the cytokine-dependent response regulation in insects.

The role of epsilon PKC in acute and chronic diseases: Possible pharmacological implications of its modulators

Epsilon Protein kinase C (εPCK) is a particular kinase that, when activated, is able to protect against different stress injuries and therefore has been proposed to be a potential molecular target against acute and chronic diseases. Particular attention has been focused on εPCK for its involvement in the protective mechanism of Ischemic Preconditioning (IPC), a powerful endogenous mechanism characterized by subthreshold ischemic insults able to protect organs against ischemic injury. Therefore, in the past decades several εPCK modulators have been tested with the object to emulate εPCK mediate protection. Among these the most promising, so far, has been the ΨεRACK peptide, a homologous of RACK receptor for εPKC, that when administrated can mimic its effect in the cells. However, results from studies on εPCK indicate controversial role of this kinase in different organs and diseases, such as myocardial infarct, stroke, diabetes and cancer. Therefore, in this review we provide a discussion on the function of εPCK in acute and chronic diseases and how the different activators and inhibitors have been used to modulate its activity. A better understanding of its function is still needed to definitively target εPCK as novel therapeutic strategy.

Protein Kinase C as Regulator of Vascular Smooth Muscle Function and Potential Target in Vascular Disorders

Vascular smooth muscle (VSM) plays an important role in maintaining vascular tone. In addition to Ca2+-dependent myosin light chain (MLC) phosphorylation, protein kinase C (PKC) is a major regulator of VSM function. PKC is a family of conventional Ca2+-dependent α, β, and γ, novel Ca2+-independent δ, ɛ, θ, and η, and atypical ξ, and ι/λ isoforms. Inactive PKC is mainly cytosolic, and upon activation it undergoes phosphorylation, maturation, and translocation to the surface membrane, the nucleus, endoplasmic reticulum, and other cell organelles; a process facilitated by scaffold proteins such as RACKs. Activated PKC phosphorylates different substrates including ion channels, pumps, and nuclear proteins. PKC also phosphorylates CPI-17 leading to inhibition of MLC phosphatase, increased MLC phosphorylation, and enhanced VSM contraction. PKC could also initiate a cascade of protein kinases leading to phosphorylation of the actin-binding proteins calponin and caldesmon, increased actin-myosin interaction, and VSM contraction. Increased PKC activity has been associated with vascular disorders including ischemia-reperfusion injury, coronary artery disease, hypertension, and diabetic vasculopathy. PKC inhibitors could test the role of PKC in different systems and could reduce PKC hyperactivity in vascular disorders. First-generation PKC inhibitors such as staurosporine and chelerythrine are not very specific. Isoform-specific PKC inhibitors such as ruboxistaurin have been tested in clinical trials. Target delivery of PKC pseudosubstrate inhibitory peptides and PKC siRNA may be useful in localized vascular disease. Further studies of PKC and its role in VSM should help design isoform-specific PKC modulators that are experimentally potent and clinically safe to target PKC in vascular disease.

SLA-PGN-primed dendritic cell-based vaccination induces Th17-mediated protective immunity against experimental visceral leishmaniasis: a crucial role of PKCβ

Emergence of drug resistance during visceral leishmaniasis (VL) is a major obstacle imposed during successful therapy. An effective vaccine strategy against this disease is therefore necessary. Our present study exploited the SLA (soluble leishmanial antigen) and PGN (peptidoglycan) stimulated bone marrow-derived dendritic cells (DCs) as a suitable vaccine candidate during experimental VL. SLA-PGN-stimulated DCs showed a significant decrease in hepatic and splenic parasite burden, which were associated with increased production of nitric oxide and pro-inflammatory cytokines such as IL-12, IFN-γ and IL-17. Elevated level of IL-17 was accompanied with the generation of more Th17 cells. Further studies on DC provided the evidence that these SLA-PGN-stimulated DCs played an important role in providing necessary cytokines such as IL-6, IL-23 and TGF-β for the generation of Th17 cells. Interestingly, inhibition of protein kinase C-β (PKCβ) in DCs led to decreased production of Th17 polarizing cytokines, causing reduction of the Th17 population size. Altogether, our finding highlighted the important role of DC-based PKCβ in regulation of the function and generation of Th17 cells.

Pseudomonas aeruginosa Activates PKC-Alpha to Invade Middle Ear Epithelial Cells

Otitis media (OM) is a group of complex inflammatory disorders affecting the middle ear which can be acute or chronic. Chronic suppurative otitis media (CSOM) is a form of chronic OM characterized by tympanic membrane perforation and discharge. Despite the significant impact of CSOM on human population, it is still an understudied and unexplored research area. CSOM is a leading cause of hearing loss and life-threatening central nervous system complications. Bacterial exposure especially Pseudomonas aeruginosa is the most common cause of CSOM. Our previous studies have demonstrated that P. aeruginosa invades human middle ear epithelial cells (HMEECs). However, molecular mechanisms leading to bacterial invasion of HMEECs are not known. The aim of this study is to characterize the role of PKC pathway in the ability of P. aeruginosa to colonize HMEECs. We observed that otopathogenic P. aeruginosa activates the PKC pathway, specifically phosphorylation of PKC-alpha (PKC-α) in HMEECs. The ability of otopathogenic P. aeruginosa to phosphorylate PKC-α depends on bacterial OprF expression. The activation of PKC-α was associated with actin condensation. Blocking the PKC pathway attenuated the ability of bacteria to invade HMEECs and subsequent actin condensation. This study, for the first time, demonstrates that the host PKC-α pathway is involved in invasion of HMEECs by P. aeruginosa and subsequently to cause OM. Characterizing the role of the host signaling pathway in the pathogenesis of CSOM will provide novel avenues to design effective treatment modalities against the disease.

Inositide-dependent signaling pathways as new therapeutic targets in myelodysplastic syndromes

INTRODUCTION

Nuclear inositide signaling pathways specifically regulate cell proliferation and differentiation. Interestingly, the modulation of nuclear inositides in hematological malignancies can differentially affect erythropoiesis or myelopoiesis. This is particularly important in patients with myelodysplastic syndromes (MDS), who show both defective erythroid and myeloid differentiation, as well as an increased risk of evolution into acute myeloid leukemia (AML).

AREAS COVERED

This review focuses on the structure and function of specific nuclear inositide enzymes, whose impairment could be linked with disease pathogenesis and cancer. The authors, stemming from literature and published data, discuss and describe the role of nuclear inositides, focusing on specific enzymes and demonstrating that targeting these molecules could be important to develop innovative therapeutic approaches, with particular reference to MDS treatment.

EXPERT OPINION

Demethylating therapy, alone or in combination with other drugs, is the most common and current therapy for MDS patients. Nuclear inositide signaling molecules have been demonstrated to be important in hematopoietic differentiation and are promising new targets for developing a personalized MDS therapy. Indeed, these enzymes can be ideal targets for drug design and their modulation can have several important downstream effects to regulate MDS pathogenesis and prevent MDS progression to AML.

A novel DAG-dependent mechanism links PKCɑ and Cyclin B1 regulating cell cycle progression

Through the years, different studies showed the involvement of Protein Kinase C (PKC) in cell cycle control, in particular during G1/S transition. Little is known about their role at G2/M checkpoint. In this study, using K562 human erythroleukemia cell line, we found a novel and specific mechanism through which the conventional isoform PKC⍺ positively affects Cyclin B1 modulating G2/M progression of cell cycle. Since the kinase activity of this PKC isoform was not necessary in this process, we demonstrated that PKC⍺, physically interacting with Cyclin B1, avoided its degradation and stimulated its nuclear import at mitosis. Moreover, the process resulted to be strictly connected with the increase in nuclear diacylglycerol levels (DAG) at G2/M checkpoint, due to the activity of nuclear Phospholipase C β1 (PLCβ1), the only PLC isoform mainly localized in the nucleus of K562 cells. Taken together, our findings indicated a novel DAG dependent mechanism able to regulate the G2/M progression of the cell cycle.

Ultra‑performance liquid chromatography coupled with quadrupole time‑of‑flight mass spectrometry‑based metabolic profiling of human serum prior to and following radical resection of colorectal carcinoma

Nearly one quarter of patients with colorectal carcinoma (CRC) were diagnosed at an advanced stage. Under these circumstances, radical resection of the tumor is the best strategy to enhance the five-year survival rate. However, up to 50% of post-operative patients experience cancer recurrence within the first few years. Therefore, post‑operative surveillance is important. However, currently performed post‑operative monitoring relies on relatively dated methods with insufficient sensitivity and specificity. The present study applied an advanced technology of ultra‑performance liquid chromatography coupled with quadrupole time‑of‑flight mass spectrometry in order to examine changes in metabolite patterns in serum with the aim of identifying reliable biomarkers in patients with CRC at various time-points. Serum samples were collected from and 20 CRC patients prior to radical resection (group 1) and one month following radical resection (group 2) as well as from 20 healthy volunteers (group 3). Multivariate pattern recognition was used to identify potential biomarkers of CRC. Compared with healthy volunteers, three groups of biomarkers were identified in patients with CRC (P<0.05), namely phosphatidylcholines (PCs), lysophosphatidylcholines (LPCs) and diacylglycerols (DAGs). However, no statistical difference in the levels of these biomarkers between pre‑operative and post‑operative CRC patients was identified (P>0.05). PCs and LPCs, which contain polyunsaturated fatty acids, were decreased, whereas LPCs and DAGs, which contain saturated fatty acids, were increased in CRC patients. The present study demonstrated that obvious metabolic disturbances occur during the development of CRC and provided a novel analytic method, which is likely to be used as a diagnostic tool for CRC and may help to improve the patients' prognosis.

Targeting Protein Kinase C Downstream of Growth Factor and Adhesion Signalling

The signaling outputs of Receptor Tyrosine Kinases, G-protein coupled receptors and integrins converge to mediate key cell process such as cell adhesion, cell migration, cell invasion and cell proliferation. Once activated by their ligands, these cell surface proteins recruit and direct a diverse range of proteins to disseminate the appropriate response downstream of the specific environmental cues. One of the key groups of proteins required to regulate these activities is the family of serine/threonine intracellular kinases called Protein Kinase Cs. The activity and subcellular location of PKCs are mediated by a series of tightly regulated events and is dependent on several posttranslational modifications and the availability of second messengers. Protein Kinase Cs exhibit both pro- and anti-tumorigenic effects making them an interesting target for anti-cancer treatment.

Shifts in temperature within the physiologic range modify strand-specific expression of select human microRNAs

Previous studies have revealed that clinically relevant changes in temperature modify clinically relevant gene expression profiles through transcriptional regulation. Temperature dependence of post-transcriptional regulation, specifically, through expression of miRNAs has been less studied. We comprehensively analyzed the effect of 24 h exposure to 32°C or 39.5°C on miRNA expression profile in primary cultured human small airway epithelial cells (hSAECs) and its impact on expression of a targeted protein, protein kinase C α (PKCα). Using microarray, and solution hybridization-based nCounter assays, with confirmation by quantitative RT-PCR, we found significant temperature-dependent changes in expression level of only five mature human miRNAs, representing only 1% of detected miRNAs. Four of these five miRNAs are the less abundant passenger (star) strands. They exhibited a similar pattern of increased expression at 32°C and reduced expression at 39.5°C relative to 37°C. As PKCα mRNA has multiple potential binding sites for three of these miRNAs, we analyzed PKCα protein expression in HEK 293T cells and hSAECs. PKCα protein levels were lowest at 32°C and highest at 39.5°C and specific miRNA inhibitors reduced these effects. Finally, we analyzed cell-cycle progression in hSAECs and found 32°C cells exhibited the greatest G1 to S transition, a process known to be inhibited by PKCα, and the effect was mitigated by specific miRNA inhibitors. These results demonstrate that exposure to clinically relevant hypothermia or hyperthermia modifies expression of a narrow subset of miRNAs and impacts expression of at least one signaling protein involved in multiple important cellular processes.

Synthesis, antitumor activity, and mechanism of action of 6-acrylic phenethyl ester-2-pyranone derivatives

Based on the scaffolds of caffeic acid phenethyl ester (CAPE) as well as bioactive lactone-containing compounds, 6-acrylic phenethyl ester-2-pyranone derivatives were synthesized and evaluated against five tumor cell lines (HeLa, C6, MCF-7, A549, and HSC-2). Most of the new derivatives exhibited moderate to potent cytotoxic activity. Moreover, HeLa cell lines showed higher sensitivity to these compounds. In particular, compound showed potent cytotoxic activity (IC50 = 0.50-3.45 μM) against the five cell lines. Further investigation on the mechanism of action showed that induced apoptosis, arrested the cell cycle at G2/M phases in HeLa cells, and inhibited migration through disruption of the actin cytoskeleton. In addition, ADMET properties were also calculated in silico, and compound showed good ADMET properties with good absorption, low hepatotoxicity, and good solubility, and thus, could easily be bound to carrier proteins, without inhibition of CYP2D6. A structure-activity relationship (SAR) analysis indicated that compounds with ortho-substitution on the benzene ring exhibited obviously increased cytotoxic potency. This study indicated that compound is a promising compound as an antitumor agent.

Phosphoinositide-specific phospholipase C in health and disease

Phospholipases are widely occurring and can be found in several different organisms, including bacteria, yeast, plants, animals, and viruses. Phospholipase C (PLC) is a class of phospholipases that cleaves phospholipids on the diacylglycerol (DAG) side of the phosphodiester bond producing DAGs and phosphomonoesters. Among PLCs, phosphoinositide-specific PLC (PI-PLC) constitutes an important step in the inositide signaling pathways. The structures of PI-PLC isozymes show conserved domains as well as regulatory specific domains. This is important, as most PI-PLCs share a common mechanism, but each of them has a peculiar role and can have a specific cell distribution that is linked to a specific function. More importantly, the regulation of PLC isozymes is fundamental in health and disease, as there are several PLC-dependent molecular mechanisms that are associated with the activation or inhibition of important physiopathological processes. Moreover, PI-PLC alternative splicing variants can play important roles in complex signaling networks, not only in cancer but also in other diseases. That is why PI-PLC isozymes are now considered as important molecules that are essential for better understanding the molecular mechanisms underlying both physiology and pathogenesis, and are also potential molecular targets useful for the development of innovative therapeutic strategies.

PLC and PI3K/Akt/mTOR signalling in disease and cancer

Cancer cell metabolism is deregulated, and signalling pathways can be involved. For instance, PI3K/Akt/mTOR is associated with normal proliferation and differentiation, and its alteration is detectable in cancer cells, that exploit the normal mechanisms to overcome apoptosis. On the other hand, also the family of Phospholipase C (PLC) enzymes play a critical role in cell growth, and any change concerning these enzymes or their downstream targets can be associated with neoplastic transformation. Here, we review the role of PLC and PI3K/Akt/mTOR signal transduction pathways in pathophysiology.