Nuclear phospholipase C-β1 and diacylglycerol LIPASE-α in brain cortical neurons

Altered PLCβ/IP3/Ca2+ Signaling Pathway Activated by GPRCs in Olfactory Neuronal Precursor Cells Derived from Patients Diagnosed with Schizophrenia

Background: Schizophrenia (SZ) is a multifactorial chronic psychiatric disorder with a worldwide prevalence of 1%. Altered expression of PLCβ occurs in SZ patients, suggesting alterations in the PLCβ/IP3/Ca2+ signaling pathway. This cascade regulates critical cellular processes in all cell types, including the neuronal lineage; however, there is scarce evidence regarding the functionality of this transduction signaling in neuronal cells derived from SZ patients. Objective: We evaluated the functionality of the PLCβ/IP3/Ca2+ pathway in olfactory neuronal precursor cells (hONPCs) obtained from SZ patients. Methods: Cryopreserved hONPCs isolated from SZ patients and healthy subjects (HS) were thawed. The cellular types in subcultures were corroborated by immunodetection of the multipotency and lineage markers SOX-2, Musashi-1, nestin, and β-III tubulin. The PLCβ/IP3/Ca2+ pathway was activated by GPCR (Gq) ligands (ATP, UTP, serotonin, and epinephrine). In addition, PLCβ and IP3R were directly stimulated by perfusing cells with the activators m-3M3FBS and ADA, respectively. Cytosolic Ca2+ was measured by microfluorometry and by Ca2+ imaging. The amount and subcellular distribution of the PLCβ1 and PLCβ3 isoforms were evaluated by confocal immunofluorescence. IP3 concentration was measured by ELISA. Results: The results show that the increase of cytosolic Ca2+ triggered by GPCR ligands or directly through either PLCβ or IP3R activation was significantly lower in SZ-derived hONPCs, regarding HS-derived cells. Moreover, the relative amount of the PLCβ1 and PLCβ3 isoforms and IP3 production stimulated with m-3M3FBS were reduced in SZ-derived cells. Conclusions: Our results suggest an overall functional impairment in the PLCβ/IP3/Ca2+ signaling pathway in SZ-derived hONPCs.

PLCβ1 by-passes early growth response -1 to induce the differentiation of neuronal cells

The Gαq/phospholipase C-β (PLCβ) signaling system mediates calcium responses to a variety of hormones and neurotransmitters. Recent studies suggest that PLCβ1 expression plays a role in the differentiation of two types of cultured neuronal cells (PC12 and SK-N-SH) through a mechanism independent of Gαq. Here, we show that, similar to that observed in PC12 and SK-N-SH cells, PLCβ1 expression increases when human NT2 cells are induced to differentiate either through cytosine-β-D-arabinofuranoside or retinoic acid. Preventing this increase, abolishes differentiation, and down-regulating PLCβ1 in rat primary astrocytes causes cells to adapt an undifferentiated morphology. Surprisingly, transfecting PLCβ1 into undifferentiated PC12 or NT2 cells induces differentiation without the need for differentiating agents. Studies to uncover the underlying mechanism focused on the transcription factor early growth response 1 (Egr-1) which mediates PLCβ1 expression early in differentiation. Over-expressing PLCβ1 in HEK293 cells enhances Egr-1 expression and induces morphological changes. We show that increased levels of cytosolic PLCβ1 in undifferentiated PC12 cells disrupts the association between Egr-1 and its cytosolic binding partner (Tar RNA binding protein), promoting relocalization of Egr-1 to the nucleus, which promotes transcription of proteins needed for differentiation. These studies show a novel mechanism through which differentiation can be modulated.

Simulation of biochemical dynamics of C a 2 + and P L C in fibroblast cell

Calcium dynamics is not only responsible for maintaining the framework and functions of the cell but also plays a role in the dynamics of other biochemical systems in the cell. Phospholipase C-γ l (P L C ) has a crucial role in the function of fibroblast cells. Experiments have shown thatP L C andC a 2 + have interdependent dynamics in fibroblast cells. However, no reaction-diffusion model exists for the two-way feedback system dynamics ofC a 2 + andP L C in fibroblasts till date. The computational model is designed to investigate the impact of variations in several processes, such as theS E R C A pump, buffer process, source inflow, etc., on the system dynamics ofC a 2 + andP L C in fibroblast cells. The computational findings are obtained using finite element techniques, and the consequences of dysregulation in various processes on the spatiotemporal calcium andP L C dynamics in fibroblasts are investigated. The results lead to the conclusion that the effects of buffer, source influx, diffusion, andS E R C A pump can cause fluctuations in the dynamics ofC a 2 + andP L C in fibroblasts. Disruptions in these constitutive processes can result in changes in the dynamics of calcium andP L C . Thus, the current model provides new/novel information regarding the precise dysregulatory constitutive systems that regulate calcium andP L C kinetics, such as source inflow, diffusion,S E R C A , and buffer, can be responsible for excessive calcium andP L C concentrations leading to fibrotic illnesses such as cancer and fibrosis.

Phospholipases in Gliomas: Current Knowledge and Future Perspectives from Bench to Bedside

Phospholipases are essential intermediaries that work as hydrolyzing enzymes of phospholipids (PLs), which represent the most abundant species contributing to the biological membranes of nervous cells of the healthy human brain. They generate different lipid mediators, such as diacylglycerol, phosphatidic acid, lysophosphatidic acid, and arachidonic acid, representing key elements of intra- and inter-cellular signaling and being involved in the regulation of several cellular mechanisms that can promote tumor progression and aggressiveness. In this review, it is summarized the current knowledge about the role of phospholipases in brain tumor progression, focusing on low- and high-grade gliomas, representing promising prognostic or therapeutic targets in cancer therapies due to their influential roles in cell proliferation, migration, growth, and survival. A deeper understanding of the phospholipases-related signaling pathways could be necessary to pave the way for new targeted therapeutic strategies.

Molecular regulation of PLCβ signaling

Phospholipase C (PLC) enzymes convert the membrane phospholipid phosphatidylinositol-4,5-bisphosphate (PIP2) into inositol-1,4,5-triphosphate (IP3) and diacylglycerol (DAG). IP3 and DAG regulate numerous downstream pathways, eliciting diverse and profound cellular changes and physiological responses. In the six PLC subfamilies in higher eukaryotes, PLCβ is intensively studied due to its prominent role in regulating crucial cellular events underlying many processes including cardiovascular and neuronal signaling, and associated pathological conditions. In addition to GαqGTP, Gβγ generated upon G protein heterotrimer dissociation also regulates PLCβ activity. Here, we not only review how Gβγ directly activates PLCβ, and also extensively modulates Gαq-mediated PLCβ activity, but also provide a structure-function overview of PLC family members. Given that Gαq and PLCβ are oncogenes, and Gβγ shows unique cell-tissue-organ specific expression profiles, Gγ subtype-dependent signaling efficacies, and distinct subcellular activities, this review proposes that Gβγ is a major regulator of Gαq-dependent and independent PLCβ signaling.

Endocannabinoid 2-Arachidonoylglycerol Synthesis and Metabolism at Neuronal Nuclear Matrix Fractions Derived from Adult Rat Brain Cortex

In this report, we describe the kinetics characteristics of the diacylglycerol lipase-α (DGLα) located at the nuclear matrix of nuclei derived from adult cortical neurons. Thus, using high-resolution fluorescence microscopy, classical biochemical subcellular fractionation, and Western blot techniques, we demonstrate that the DGLα enzyme is located in the matrix of neuronal nuclei. Furthermore, by quantifying the 2-arachidonoylglycerol (2-AG) level by liquid chromatography and mass spectrometry when 1-stearoyl-2-arachidonoyl-sn-glycerol (SAG) was exogenously added as substrate, we describe the presence of a mechanism for 2-AG production through DGLα dependent biosynthesis with an apparent K_m (K_m^app) of 180 µM and a V_max of 1.3 pmol min^-1 µg^-1 protein. We also examined the presence of enzymes with hydrolytic and oxygenase activities that are able to use 2-AG as substrate, and described the localization and compartmentalization of the major 2-AG degradation enzymes, namely monoacylglycerol lipase (MGL), fatty acid amide hydrolase (FAAH), α/β-hydrolase domain 12 protein (ABHD12) and cyclooxygenase-2 (COX2). Of these, only ABHD12 exhibited the same distribution with respect to chromatin, lamin B1, SC-35 and NeuN as that described for DGLα. When 2-AG was exogenously added, we observed the production of arachidonic acid (AA), which was prevented by inhibitors (but not specific MGL or ABHD6 inhibitors) of the ABHD family. Overall, our results expand knowledge about the subcellular distribution of neuronal DGLα, and provide biochemical and morphological evidence to ensure that 2-AG is produced in the neuronal nuclear matrix. Thus, this work paves the way for proposing a working hypothesis about the role of 2-AG produced in neuronal nuclei.

CircMAP3K4 protects human lens epithelial cells from H2O2-induced dysfunction by targeting miR-193a-3p/PLCD3 axis in age-related cataract

Circular RNAs (circRNAs) have shown pivotal regulatory roles in multiple human ocular diseases, including age-related cataract (ARC). Here, we explored the role of circRNA mitogen-activated protein kinase kinase kinase 4 (circMAP3K4, hsa_circ_0078619) in ARC pathology and its associated mechanism. The expression of RNAs and proteins was examined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot assay. Cell viability, senescence, proliferation, and apoptosis were analyzed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, senescence-associated-β-galactosidase (SA-β-Gal) staining, 5-ethynyl-20-deoxyuridine (EdU) assay, and flow cytometry. The oxidative stress status of SRA01/04 cells was analyzed using the commercial kits. The interaction between microRNA-193a-3p (miR-193a-3p) and circMAP3K4 or phospholipase C delta 3 (PLCD3) was verified by dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay, and RNA-pull down assay. CircMAP3K4 was significantly down-regulated in ARC patients and H2O2-induced SRA01/04 cells. H2O2 treatment restrained the viability and proliferation and promoted the senescence, apoptosis, and oxidative stress of SRA01/04 cells, and circMAP3K4 overexpression protected SRA01/04 cells from H2O2-induced dysfunction. MiR-193a-3p was a direct target of circMAP3K4, and circMAP3K4 overexpression-mediated protective effects in H2O2-induced SRA01/04 cells were largely reversed by the accumulation of miR-193a-3p. MiR-193a-3p interacted with the 3' untranslated region (3'UTR) of PLCD3, and PLCD3 knockdown largely overturned miR-193a-3p silencing-induced protective effects in H2O2-induced SRA01/04 cells. CircMAP3K4 up-regulated the expression of PLCD3 via sponging miR-193a-3p in SRA01/04 cells. In conclusion, circMAP3K4 protected SRA01/04 cells from H2O2-induced dysfunction in ARC through mediating miR-193a-3p/PLCD3 axis.

Endocannabinoid dysfunction in neurological disease: neuro-ocular DAGLA-related syndrome

The endocannabinoid system is a highly conserved and ubiquitous signalling pathway with broad-ranging effects. Despite critical pathway functions, gene variants have not previously been conclusively linked to human disease. We identified nine children from eight families with heterozygous, de novo truncating variants in the last exon of DAGLA with a neuro-ocular phenotype characterized by developmental delay, ataxia and complex oculomotor abnormality. All children displayed paroxysms of nystagmus or eye deviation accompanied by compensatory head posture and worsened incoordination most frequently after waking. RNA sequencing showed clear expression of the truncated transcript and no differences were found between mutant and wild-type DAGLA activity. Immunofluorescence staining of patient-derived fibroblasts and HEK cells expressing the mutant protein showed distinct perinuclear aggregation not detected in control samples. This report establishes truncating variants in the last DAGLA exon as the cause of a unique paediatric syndrome. Because enzymatic activity was preserved, the observed mislocalization of the truncated protein may account for the observed phenotype. Potential mechanisms include DAGLA haploinsufficiency at the plasma membrane or dominant negative effect. To our knowledge, this is the first report directly linking an endocannabinoid system component with human genetic disease and sets the stage for potential future therapeutic avenues.

Impact of phospholipase C β1 in glioblastoma: a study on the main mechanisms of tumor aggressiveness

Glioblastoma represents the most lethal brain tumor in adults. Several studies have shown the key role of phospholipase C β1 (PLCβ1) in the regulation of many mechanisms within the central nervous system suggesting PLCβ1 as a novel signature gene in the molecular classification of high-grade gliomas. This study aims to determine the pathological impact of PLCβ1 in glioblastoma, confirming that PLCβ1 gene expression correlates with glioma's grade, and it is lower in 50 glioblastoma samples compared to 20 healthy individuals. PLCβ1 silencing in cell lines and primary astrocytes, leads to increased cell migration and invasion, with the increment of mesenchymal transcription factors and markers, as Slug and N-Cadherin and metalloproteinases. Cell proliferation, through increased Ki-67 expression, and the main survival pathways, as β-catenin, ERK1/2 and Stat3 pathways, are also affected by PLCβ1 silencing. These data suggest a potential role of PLCβ1 in maintaining a normal or less aggressive glioma phenotype.

Sex differences in the expression of the endocannabinoid system within V1M cortex and PAG of Sprague Dawley rats

BACKGROUND

Several chronic pain disorders, such as migraine and fibromyalgia, have an increased prevalence in the female population. The underlying mechanisms of this sex-biased prevalence have yet to be thoroughly documented, but could be related to endogenous differences in neuromodulators in pain networks, including the endocannabinoid system. The cellular endocannabinoid system comprises the endogenous lipid signals 2-AG (2-arachidonoylglycerol) and AEA (anandamide); the enzymes that synthesize and degrade them; and the cannabinoid receptors. The relative prevalence of different components of the endocannabinoid system in specific brain regions may alter responses to endogenous and exogenous ligands.

METHODS

Brain tissue from naïve male and estrous staged female Sprague Dawley rats was harvested from V1M cortex, periaqueductal gray, trigeminal nerve, and trigeminal nucleus caudalis. Tissue was analyzed for relative levels of endocannabinoid enzymes, ligands, and receptors via mass spectrometry, unlabeled quantitative proteomic analysis, and immunohistochemistry.

RESULTS

Mass spectrometry revealed significant differences in 2-AG and AEA concentrations between males and females, as well as between female estrous cycle stages. Specifically, 2-AG concentration was lower within female PAG as compared to male PAG (*p = 0.0077); female 2-AG concentration within the PAG did not demonstrate estrous stage dependence. Immunohistochemistry followed by proteomics confirmed the prevalence of 2-AG-endocannabinoid system enzymes in the female PAG.

CONCLUSIONS

Our results suggest that sex differences exist in the endocannabinoid system in two CNS regions relevant to cortical spreading depression (V1M cortex) and descending modulatory networks in pain/anxiety (PAG). These basal differences in endogenous endocannabinoid mechanisms may facilitate the development of chronic pain conditions and may also underlie sex differences in response to therapeutic intervention.

Fit-for-purpose based testing and validation of antibodies to amino- and carboxy-terminal domains of cannabinoid receptor 1

Specific and selective anti-CB₁ antibodies are among the most powerful research tools to unravel the complex biological processes mediated by the CB₁ receptor in both physiological and pathological conditions. However, low performance of antibodies remains a major source of inconsistency between results from different laboratories. Using a variety of techniques, including some of the most commonly accepted ones for antibody specificity testing, we identified three of five commercial antibodies against different regions of CB₁ receptor as the best choice for specific end-use purposes. Specifically, an antibody against a long fragment of the extracellular amino tail of CB₁ receptor (but not one against a short sequence of the extreme amino-terminus) detected strong surface staining when applied to live cells, whereas two different antibodies against an identical fragment of the extreme carboxy-terminus of CB₁ receptor (but not one against an upstream peptide) showed acceptable performance on all platforms, although they behaved differently in immunohistochemical assays depending on the tissue fixation procedure used and showed different specificity in Western blot assays, which made each of them particularly suitable for one of those techniques. Our results provide a framework to interpret past and future results derived from the use of different anti-CB₁ antibodies in the context of current knowledge about the CB₁ receptor at the molecular level, and highlight the need for an adequate validation for specific purposes, not only before antibodies are placed on the market, but also before the decision to discontinue them is made.

Location-dependent role of phospholipase C signaling in the brain: Physiology and pathology

Phosphoinositide-specific phospholipases C (PI-PLCs) are a class of enzymes involved in the phosphatidylinositol metabolism, which is implicated in the activation of several signaling pathways and which controls several cellular processes. The scientific community has long accepted the existence of a nuclear phosphoinositide (PI) metabolism, independent from the cytoplasmic one, critical in nuclear function control. Indeed, nuclear PIs are involved in many activities, such as cell cycle regulation, cell proliferation, cell differentiation, membrane transport, gene expression and cytoskeletal dynamics. There are several types of PIs and enzymes implicated in brain activities and among these enzymes, PI-PLCs contribute to a specific and complex network in the developing nervous system. Moreover, considering the abundant presence of PI-PLCβ1, PI-PLCγ1 and PI-PLCβ4 in the brain, a specific role for each PLC subtype has been suggested in the control of neuronal activity, which is important for synapse function, development and other mechanisms. The focus of this review is to describe the latest research about the involvement of PI-PLC signaling in the nervous system, both physiologically and in pathological conditions. Indeed, PI-PLC signaling imbalance seems to be also linked to several brain disorders including epilepsy, movement and behavior disorders, neurodegenerative diseases and, in addition, some PI-PLC subtypes could become potential novel signature genes for high-grade gliomas.

The Gαq/phospholipase Cβ signaling system represses tau aggregation

Alzheimer's disease is typified by calcium dysfunction and neurofibrillary tangles of tau aggregates along with mitotic proteins. Using PC12 cells as a model system, we determined whether the Gαq/PLCβ/ calcium signaling pathway impacts the manifestation of Alzheimer's disease. Down-regulating PLCβ significantly increases tau protein expression and causes a large increase in tau aggregation. Stimulating Gαq to activate PLCβ results in a modest reduction in tau aggregation while inhibiting PLCβ activity results in a modest enhancement of tau aggregation. These results suggest that PLCβ may effect tau aggregation by an additional mechanism that is independent of its ability to transduce calcium signals. To this end, we found that a cytosolic population of PLCβ binds to a mitotic protein found in neurofibrillary tangles, CDK18, which promotes tau phosphorylation and aggregation. Taken together, our studies show that the loss of PLCβ1 can promote Alzheimer's disease by a combination of its catalytic activity and its interaction with mitotic proteins thus offering an orthogonal method to control tau aggregation.

Cerebrospinal fluid lipidomics: effects of an intravenous triglyceride infusion and apoE status

INTRODUCTION

High-fat diets increase risk for Alzheimer's disease, but individuals with the risk gene APOE ε4 (E4) paradoxically have improved memory soon after high fat feeding. Little is known about how dietary lipids affect CNS lipids, especially in older adults.

OBJECTIVES

We analyzed the lipidomic signature of cerebrospinal fluid (CSF) in older adults who underwent both a saline and TG infusion. We further analyzed these data by E4 carrier status.

METHODS

Older adults (n = 21, age 67.7 ± 8.6) underwent a 5-h TG and saline infusion on different days in random crossover design; lumbar CSF was collected at the end of the infusion. Lipids were extracted using dichloromethane/methanol and 13 classes of lipids analyzed using the Lipidyzer platform consisting of an AB Sciex 5500 MS/MS QTraps system equipped with a SelexION for differential mobility spectrometry (DMS). Multiple reaction monitoring was used to target and quantify 1070 lipids in positive and negative ionization modes with and without DMS.

RESULTS

The TG infusion increased total lipids in the CSF, including the appearance of more lipids at the detection limit in the TG samples compared to saline (Chi square p < 0.0001). The infusion increased the total level of diacylglycerols and lysophosphatidylcholines and reduced dihydroceramides. Of the possible 1070 lipids detectable, we found 348 after saline and 365 after TG infusion. Analysis using MetaboAnalyst revealed 11 specific lipids that changed; five of these lipids decreased after TG infusion, and four of them differed by E4 status, but none differed by cognitive diagnosis or sex.

CONCLUSION

These results in older adults show that blood lipids affect lipid profiles in CSF and such profiles are modified by APOE status. This suggests that how the CNS handles lipids may be important in the AD phenotype.

Inhibition of Methamphetamine Self-Administration and Reinstatement by Central Blockade of Angiotensin II Receptor in Rats

The molecular mechanism and treatment of methamphetamine (METH) use disorder remain unclear. The current study aimed to investigate the role of central angiotensin II receptor (ATR) in drug taking and seeking behavior associated with METH use disorder. The effect of an ATR type 1 (AT1R) antagonist, candesartan cilexetil, on the reinforcing and motivational effects of METH was first assessed using the animal model of METH self-administration (SA) and reinstatement. The levels of dopamine D2 receptor (D2R) and AT1R were subsequently examined. Furthermore, the present study determined the expression of microRNAs (miRNAs) by comparing METH SA, METH-yoked, and Saline-yoked groups. The target miRNAs were further overexpressed in the nucleus accumbens (NAc) via a lentivirus vector to investigate the effects of target miRNAs on METH SA maintained under a fixed ratio 1, progressive ratio, and cue/drug reinstatement of METH SA. The potential role of the AT1R-PLCβ-CREB signaling pathway was finally investigated. The results suggest that AT1R blockade effectively reduced METH SA and reinstatement, in conjunction with the counter-regulation of D2R and AT1R. A total of 17 miRNAs targeting Ang II in NAc were found to be associated with the voluntary intake of METH. Furthermore, overexpression of specific miR-219a-5p targeting AT1R-regulated METH SA and reinstatement. The AT1R-PLCβ-CREB signaling pathway was found to be associated with the effect of AT1R on the drug-taking and drug-seeking behavior involving METH use disorder.

Inositide-Dependent Nuclear Signalling in Health and Disease

Nuclear inositides have a specific subcellular distribution that is linked to specific functions; thus their regulation is fundamental both in health and disease. Emerging evidence shows that alterations in multiple inositide signalling pathways are involved in pathophysiology, not only in cancer but also in other diseases. Here, we give an overview of the main features of inositides in the cell, and we discuss their potential as new molecular therapeutic targets.

Nuclear phospholipase C isoenzyme imbalance leads to pathologies in brain, hematologic, neuromuscular, and fertility disorders

Phosphoinositide-specific phospholipases C (PI-PLCs) are involved in signaling pathways related to critical cellular functions, such as cell cycle regulation, cell differentiation, and gene expression. Nuclear PI-PLCs have been studied as key enzymes, molecular targets, and clinical prognostic/diagnostic factors in many physiopathologic processes. Here, we summarize the main studies about nuclear PI-PLCs, specifically, the imbalance of isozymes such as PI-PLCβ1 and PI-PLCζ, in cerebral, hematologic, neuromuscular, and fertility disorders. PI-PLCβ1 and PI-PLCɣ1 affect epilepsy, depression, and bipolar disorder. In the brain, PI-PLCβ1 is involved in endocannabinoid neuronal excitability and is a potentially novel signature gene for subtypes of high-grade glioma. An altered quality or quantity of PI-PLCζ contributes to sperm defects that result in infertility, and PI-PLCβ1 aberrant inositide signaling contributes to both hematologic and degenerative muscle diseases. Understanding the mechanisms behind PI-PLC involvement in human pathologies may help identify new strategies for personalized therapies of these conditions.

Nuclear inositide signaling and cell cycle

Phosphatidylinositols (PIs) are responsible for several signaling pathways related to many cellular functions, such as cell cycle regulation at different check-points, cell proliferation, cell differentiation, membrane trafficking and gene expression. PI metabolism is not only present at the cytoplasmic level, but also at the nuclear one, where different signaling pathways affect essential nuclear mechanisms in eukaryotic cells. In this review we focus on nuclear inositide signaling in relation to cell cycle regulation. Many evidences underline the pivotal role of nuclear inositide signaling in cell cycle regulation and cell proliferation associated to different strategic physiopathological mechanisms in several cell systems and diseases.

PLCD3, a flotillin2-interacting protein, is involved in proliferation, migration and invasion of nasopharyngeal carcinoma cells

Phospholipase C (PLC) is a pivotal enzyme in the phosphoinositide pathway that promotes the second messengers, diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3), to participate in eukaryotic signal transduction. Several PLC isozymes are associated with cancer, such as PLC-β1, PLC-δ1, PLC-ε and PLC-γ1. However, the role of PLC-δ3 (PLCD3) in nasopharyngeal carcinoma (NPC) has not been investigated to date. In our previous study, we demonstrated that flotillin2 (Flot2) plays a pro-neoplastic role in NPC and is involved in tumour progression and metastasis. In the present study, we screened the interacting proteins of Flot2 using the yeast two-hybrid (Y2H) method and verified the interaction between PLCD3 and Flot2 by co-immunoprecipitation. We also investigated the biological functions of PLCD3 in NPC. Inhibition of PLCD3 expression impaired the malignant potential of 5–8F, a highly metastatic NPC cell line, by restraining its growth, proliferation, mobility and migration. The present study demonstrated that PLCD3 may be an oncogenic protein in NPC and that it plays an important role in the progression of NPC partially by interacting with Flot2.

Nuclear Inositide Signaling Via Phospholipase C

The existence of an independent nuclear inositide pathway distinct from the cytoplasmic one has been demonstrated in different physiological systems and in diseases. In this prospect we analyze the role of PI-PLCβ1 nuclear isoform in relation to the cell cycle regulation, the cell differentiation, and different physiopathological pathways focusing on the importance of the nuclear localization from both molecular and clinical point of view. PI-PLCβ1 is essential for G1/S transition through DAG and Cyclin D3 and plays also a central role in G2/M progression through Cyclin B1 and PKCα. In the differentiation process of C2C12 cells PI-PLCβ1 increases in both myogenic differentiation and osteogenic differentiation. PI-PLCβ1 and Cyclin D3 reduction has been observed in Myotonic Dystrophy (DM) suggesting a pivotal role of these enzymes in DM physiopathology. PI-PLCβ1 is also involved in adipogenesis through a double phase mechanism. Moreover, PI-PLCβ1 plays a key role in the normal hematopoietic differentiation where it seems to decrease in erythroid differentiation and increase in myeloid differentiation. In Myelodysplastic Syndromes (MDS) PI-PLCβ1 has a genetic and epigenetic relevance and it is related to MDS patients' risk of Acute Myeloid Leukemia (AML) evolution. In MDS patients PI-PLCβ1 seems to be also a therapeutic predictive outcome marker. In the central nervous system, PI-PLCβ1 seems to be involved in different pathways in both brain cortex development and synaptic plasticity related to different diseases. Another PI-PLC isozyme that could be related to nuclear activities is PI-PLCζ that is involved in infertility processes. J. Cell. Biochem. 118: 1969-1978, 2017. © 2017 Wiley Periodicals, Inc.

Nuclear Lipids in the Nervous System: What they do in Health and Disease

In the last 20 years it has been widely demonstrated that cell nucleus contains neutral and polar lipids localized in nuclear membranes, nucleoli, nuclear matrix and chromatin. Nuclear lipids may show specific organization forming nuclear lipid microdomains and have both structural and functional roles. Depending on their localization, nuclear lipids play different roles such as the regulation of nuclear membrane and nuclear matrix fluidity but they also can act as platforms for vitamin and hormone function, for active chromatin anchoring, and for the regulation of gene expression, DNA duplication and transcription. Crosstalk among different kinds of lipid signalling pathways influence the physiopathology of numerous cell types. In neural cells the nuclear lipids are involved in cell proliferation, differentiation, inflammation, migration and apoptosis. Abnormal metabolism of nuclear lipids might be closely associated with tumorigenesis and neurodegenerative diseases such as Alzheimer disease and Parkinson disease among others.

Targeted Lipidomics of Fontal Cortex and Plasma Diacylglycerols (DAG) in Mild Cognitive Impairment and Alzheimer's Disease: Validation of DAG Accumulation Early in the Pathophysiology of Alzheimer's Disease

Previous studies have demonstrated augmented levels of diacylglycerols (DAG) in the frontal cortex and plasma of Alzheimer's disease (AD) patients. We extended these findings from non-targeted lipidomics studies to design a lipidomics platform to interrogate DAGs and monoacylglycerols (MAG) in the frontal cortex and plasma of MCI subjects. Control subjects included both aged normal controls and controls with normal cognition, but AD pathology at autopsy, individuals termed non-demented AD neuropathology. DAGs with saturated, unsaturated, and polyunsaturated fatty acid substituents were found to be elevated in MCI frontal cortex and plasma. Tandem mass spectrometry of the DAGs did not reveal any differences in the distributions of the fatty acid substitutions between MCI and control subjects. While triacylglycerols were not altered in MCI subjects there were increases in MAG levels both in the frontal cortex and plasma. In toto, increased levels of DAGs and MAGs appear to occur early in AD pathophysiology and require both further validation in a larger patient cohort and elucidation of the lipidomics alteration(s) that lead to the accumulation of DAGs in MCI subjects.

Phosphoinositide signaling in somatosensory neurons

Somatosensory neurons of the dorsal root ganglia (DRG) and trigeminal ganglia (TG) are responsible for detecting thermal and tactile stimuli. They are also the primary neurons mediating pain and itch. A large number of cell surface receptors in these neurons couple to phospholipase C (PLC) enzymes leading to the hydrolysis of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and the generation of downstream signaling molecules. These neurons also express many different ion channels, several of which are regulated by phosphoinositides. This review will summarize the knowledge on phosphoinositide signaling in DRG neurons, with special focus on effects on sensory and other ion channels.

BMP-2 Induced Expression of PLCβ1 That is a Positive Regulator of Osteoblast Differentiation

Bone morphogenetic protein 2 (BMP-2) is a critical growth factor that directs osteoblast differentiation and bone formation. Phosphoinositide-phospholipase Cβ 1 (PLCβ1) plays a crucial role in the initiation of the genetic program responsible for muscle differentiation. Differentiation of C2C12 mouse myoblasts in response to insulin stimulation is characterized by a marked increase in nuclear PLCβ1. Here, the function of PLCβ1 in the osteogenic differentiation was investigated. Briefly, in C2C12 cells treated with BMP-2 we assist to a remarkable increase in PLCβ1 protein and mRNA expression. The data regarding the influence on differentiation demonstrated that PLCβ1 promotes osteogenic differentiation by up-regulating alkaline phosphatase (ALP). Moreover, PLCβ1 is present in the nuclear compartment of these cells and overexpression of a cytosolic-PLCβ1mutant (cyt-PLCβ1), which lacks a nuclear localization sequence, prevented the differentiation of C2C12 cells into osteocytes. Recent evidence indicates that miRNAs act as important post transcriptional regulators in a large number of processes, including osteoblast differentiation. Since miR-214 is a regulator of Osterix (Osx) which is an osteoblast-specific transcription factor that is needful for osteoblast differentiation and bone formation, we further investigated whether PLCβ1 could be a potential target of miR-214 in the control of osteogenic differentiation by gain- and loss- of function experiment. The results indicated that inhibition of miR-214 in C2C12 cells significantly enhances the protein level of PLCβ1 and promotes C2C12 BMP-2-induced osteogenesis by targeting PLCβ1.

Modulation of nuclear PI-PLCbeta1 during cell differentiation

PI-PLCbeta1 plays an important role in cell differentiation, and particularly in myogenesis, osteogenesis and hematopoiesis. Indeed, the increase of PI-PLCbeta1, along with Cyclin D3, has been detected in C2C12 mouse myoblasts induced to differentiate, as well as in human cells obtained from myotonic dystrophy. Also in the case of osteogenic differentiation there is a specific induction of PI-PLCbeta1, but in this case the role of PI-PLCbeta1 seems to be independent from Cyclin D3, so that a different mechanism could be involved. As for the hematopoietic system, PI-PLCbeta1 has a peculiar behavior: it increases during myeloid differentiation and decreases during erythroid differentiation, thus confirming the role of PI-PLCbeta1 as a modulator of hematopoiesis.

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.

Phospholipase Cβ connects G protein signaling with RNA interference

Phosphoinositide-specific-phospholipase Cβ (PLCβ) is the main effector of Gαq stimulation which is coupled to receptors that bind acetylcholine, bradykinin, dopamine, angiotensin II as well as other hormones and neurotransmitters. Using a yeast two-hybrid and other approaches, we have recently found that the same region of PLCβ that binds Gαq also interacts with Component 3 Promoter of RNA induced silencing complex (C3PO), which is required for efficient activity of the RNA-induced silencing complex. In purified form, C3PO competes with Gαq for PLCβ binding and at high concentrations can quench PLCβ activation. Additionally, we have found that the binding of PLCβ to C3PO inhibits its nuclease activity leading to reversal of RNA-induced silencing of specific genes. In cells, we found that PLCβ distributes between the plasma membrane where it localizes with Gαq, and in the cytosol where it localizes with C3PO. When cells are actively processing small interfering RNAs the interaction between PLCβ and C3PO gets stronger and leads to changes in the cellular distribution of PLCβ. The magnitude of attenuation is specific for different silencing RNAs. Our studies imply a direct link between calcium responses mediated through Gαq and post-transcriptional gene regulation through PLCβ.

Primary phospholipase C and brain disorders

In the brain, the primary phospholipase C (PLC) proteins, PLCβ, and PLCγ, are activated primarily by neurotransmitters, neurotrophic factors, and hormones through G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs). Among the primary PLC isozymes, PLCβ1, PLCβ4, and PLCγ1 are highly expressed and differentially distributed, suggesting a specific role for each PLC subtype in different regions of the brain. Primary PLCs control neuronal activity, which is important for synapse function and development. In addition, dysregulation of primary PLC signaling is linked to several brain disorders including epilepsy, schizophrenia, bipolar disorder, Huntington's disease, depression and Alzheimer's disease. In this review, we included current knowledge regarding the roles of primary PLC isozymes in brain disorders.

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.

Nuclear diacylglycerol lipase-α in rat brain cortical neurons: evidence of 2-arachidonoylglycerol production in concert with phospholipase C-β activity

In this report, we describe the localization of diacylglycerol lipase-α (DAGLα) in nuclei from adult cortical neurons, as assessed by double-immunofluorescence staining of rat brain cortical sections and purified intact nuclei and by western blot analysis of subnuclear fractions. Double-labeling assays using the anti-DAGLα antibody and NeuN combined with Hoechst staining showed that only nuclei of neuronal origin were DAGLα positive. At high resolution, DAGLα-signal displayed a punctate pattern in nuclear subdomains poor in Hoechst's chromatin and lamin B1 staining. In contrast, SC-35- and NeuN-signals (markers of the nuclear speckles) showed a high overlap with DAGLα within specific subdomains of the nuclear matrix. Among the members of the phospholipase C-β (PLCβ) family, PLCβ1, PLCβ2, and PLCβ4 exhibited the same distribution with respect to chromatin, lamin B1, SC-35, and NeuN as that described for DAGLα. Furthermore, by quantifying the basal levels of 2-arachidonoylglycerol (2-AG) by liquid chromatography and mass spectrometry (LC-MS), and by characterizing the pharmacology of its accumulation, we describe the presence of a mechanism for 2-AG production, and its PLCβ/DAGLα-dependent biosynthesis in isolated nuclei. These results extend our knowledge about subcellular distribution of neuronal DAGLα, providing biochemical grounds to hypothesize a role for 2-AG locally produced within the neuronal nucleus.

Diacylglycerol, phosphatidic acid, and their metabolic enzymes in synaptic vesicle recycling

The synaptic vesicle (SV) cycle includes exocytosis of vesicles loaded with a neurotransmitter such as glutamate, coordinated recovery of SVs by endocytosis, refilling of vesicles, and subsequent release of the refilled vesicles from the presynaptic bouton. SV exocytosis is tightly linked with endocytosis, and variations in the number of vesicles, and/or defects in the refilling of SVs, will affect the amount of neurotransmitter available for release (Sudhof, 2004). There is increasing interest in the roles synaptic vesicle lipids and lipid metabolizing enzymes play in this recycling. Initial emphasis was placed on the role of polyphosphoinositides in SV cycling as outlined in a number of reviews (Lim and Wenk, 2009; Martin, 2012; Puchkov and Haucke, 2013; Rohrbough and Broadie, 2005). Other lipids are now recognized to also play critical roles. For example, PLD1 (Humeau et al., 2001; Rohrbough and Broadie, 2005) and some DGKs (Miller et al., 1999; Nurrish et al., 1999) play roles in neurotransmission which is consistent with the critical roles for phosphatidic acid (PtdOH) and diacylglycerol (DAG) in the regulation of SV exo/endocytosis (Cremona et al., 1999; Exton, 1994; Huttner and Schmidt, 2000; Lim and Wenk, 2009; Puchkov and Haucke, 2013; Rohrbough and Broadie, 2005). PLD generates phosphatidic acid by catalyzing the hydrolysis of phosphatidylcholine (PtdCho) and in some systems this PtdOH is de-phosphorylated to generate DAG. In contrast, DGK catalyzes the phosphorylation of DAG thereby converting it into PtdOH. While both enzymes are poised to regulate the levels of DAG and PtdOH, therefore, they both lead to the generation of PtdOH and could have opposite effects on DAG levels. This is particularly important for SV cycling as PtdOH and DAG are both needed for evoked exocytosis (Lim and Wenk, 2009; Puchkov and Haucke, 2013; Rohrbough and Broadie, 2005). Two lipids and their involved metabolic enzymes, two sphingolipids have also been implicated in exocytosis: sphingosine (Camoletto et al., 2009; Chan et al., 2012; Chan and Sieburth, 2012; Darios et al., 2009; Kanno et al., 2010; Rohrbough et al., 2004) and sphingosine-1-phosphate (Chan, Hu, 2012; Chan and Sieburth, 2012; Kanno et al., 2010). Finally a number of reports have focused on the somewhat less well studies roles of sphingolipids and cholesterol in SV cycling. In this report, we review the recent understanding of the roles PLDs, DGKs, and DAG lipases, as well as sphingolipids and cholesterol play in synaptic vesicle cycling.