Signalling in the genomic era

Phosphoinositide-specific phospholipase C isoforms are conveyed by osteosarcoma-derived extracellular vesicles

Cancer cells are able to release high amounts of extracellular vesicles, thereby conditioning the normal cells in the surrounding tissue and/or in distant target organs. In the context of bone cancers, previous studies suggested that osteosarcoma cancer cells produce transforming extracellular vesicles able to induce a tumour-like phenotype in normal recipient cells. Indeed, phosphoinositide-specific phospholipase C (PI-PLC) enzymes are differentially expressed in osteosarcoma cell lines with increasing aggressiveness, thus providing helpful insights to better define their role and functions in this bone tumour. By confocal microscopy analysis, we demonstrated that osteosarcoma-derived extracellular vesicles convey all the assessed PI-PLC isoforms, and that they localize into cell membrane bubble-like structures, resembling extracellular vesicles about to be released, as conveyed and/or membrane protein. Cytofluorimetric analysis confirmed the presence of PI-PLC isoforms in the extracellular vesicles collected from conditioned media of osteosarcoma cells. These findings suggest the feasibility to use circulating extracellular vesicles as biomarkers of osteosarcoma progression and/or the monitoring of this distressing disease.

Phosphoinositide-specific phospholipase C in normal human liver and in alcohol abuse

The phosphoinositide (PI) signal transduction pathway participates in liver metabolism. Abnormal activity or expression of PI-specific phospholipase C (PLC) enzymes has been described in different liver diseases. We resume the role of the PI metabolism in liver and PLC abnormalities in different liver diseases. Moreover, we present the results of PLC analyses in a normal human liver and an alcohol-damaged liver. PLC enzymes and the expression of the corresponding genes in liver biopsies from individuals deceased for complications of the alcoholic liver disease (ALD) at different stages compared with normal controls (deceased individuals with histologically normal livers without alcohol addiction anamnesis) were analyzed by using immunohistochemistry and molecular biology techniques. The expression panel of PLCs was described in normal and alcohol abuse liver. Our observations suggest that the regulation of PLC expression might be due to posttranscriptional events and that alcohol affects the epigenetic control of PLC expression belonging to PI signaling. We also describe the alternate expression of PLCB1 and PLCH1 genes in liver. Our results corroborate literature data suggesting that PLC enzymes are differently expressed in normal versus pathological liver, playing a role in the histopathogenesis of liver tissue damage. The expression and/or localization of selected PLC isoforms is especially affected in alcohol-related liver tissue histopathology. Our present observations confirm that the modulation of protein synthesis plays a role in the regulation of PLC enzymes. We also suggest that this modulation might act at the transcription level. Further studies are required to investigate related epigenetic mechanisms.

Impairment and reorganization of the phosphoinositide-specific phospholipase C enzymes in suicide brains

A number of studies suggested that suicide may be associated with specific neurobiological abnormalities. Neurobiology studies focused upon abnormalities of signalling mechanisms with special regard to the serotonin system and the related Phosphoinositide (PI) signalling system. Previous data suggested the involvement of the PI-specific phospholipase C (PLC) family in neuropsychiatric disorders. By using PCR and morphological microscopy observation we examined the whole panel of expression of PLC isoforms in the brains of 28 individuals who committed suicide and in normal controls in order to evaluate the involvement of specific PLC isoforms. The overall PLC expression was reduced and a complex reorganization of the isoforms was observed. The knowledge of the complex network of neurobiological molecules and interconnected signal transduction pathways in the brain of suicide victims might be helpful to understand the natural history and the pathogenesis of the suicidal behavior. That might lead to obtain prognostic suggestions in order to prevent suicide and to new therapeutic agents targeting specific sites in this signalling cascade.

Ezrin-related Phosphoinositide pathway modifies RhoA and Rac1 in human osteosarcoma cell lines

Selected Phosphoinositide-specific Phospholipase C (PI-PLC) enzymes occupy the convergence point of the broad range of pathways that promote Rho and Ras GTPase mediated signalling, which also regulate the activation of ezrin, a member of the ezrin-radixin-moesin (ERM) proteins family involved in the metastatic osteosarcoma spread. Previous studies described that in distinct human osteosarcoma cell lines ezrin networks the PI-PLC with complex interplay controlling the expression of the PLC genes, which codify for PI-PLC enzymes. In the present study, we analyzed the expression and the sub-cellular distribution of RhoA and Rac1 respectively after ezrin silencing and after PI-PLC ε silencing, in order to investigate whether ezrin-RhoGTPAses signalling might involve one or more specific PI-PLC isoforms in cultured 143B and Hs888 human osteosarcoma cell lines. In the present experiments, both ezrin and PLCE gene silencing had different effects upon RhoA and Rac1 expression and sub-cellular localization. Displacements of Ezrin and of RhoA localization were observed, probably playing functional roles.

Ezrin silencing remodulates the expression of Phosphoinositide-specific Phospholipase C enzymes in human osteosarcoma cell lines

Ezrin, a protein belonging to the Ezrin, radixin and moesin (ERM) family, was engaged in the metastatic spread of osteosarcoma. The Protein 4.1, Ezrin, radixin, moesin (FERM) domain of Ezrin binds the membrane Phosphatydil inositol (4,5) bisphosphate (PIP2), a crucial molecule belonging to the Phosphoinositide (PI) signal transduction pathway. The cytoskeleton cross-linker function of Ezrin largely depends on membrane PIP2 levels, and thus upon the activity of related enzymes belonging to the PI-specific phospholipase C (PI-PLC) family. Based on the role of Ezrin in tumour progression and metastasis, we silenced the expression of Vil2 (OMIM *123900), the gene which codifies for Ezrin, in cultured human osteosarcoma 143B and Hs888 cell lines. After Ezrin silencing, the growth rate of both cell lines was significantly reduced and morphogical changes were observed. We also observed moderate variations both of selected PI-PLC enzymes within the cell and of expression of the corresponding PLC genes. In 143B cell line the transcription of PLCB1 decreased, of PLCG2 increased and of PLCE differed in a time-dependent manner. In Hs888, the expression of PLCB1 and of PLCD4 significantly increased, of PLCE moderately increased in a time dependent manner; the expression of PLCG2 was up-regulated. These observations indicate that Ezrin silencing affects the transcription of selected PLC genes, suggesting that Ezrin might influence the expression regulation of PI-PLC enzymes.

Neuropeptide Y reduces the expression of PLCB2, PLCD1 and selected PLC genes in cultured human endothelial cells

Endothelial cells (EC) are the first elements exposed to mediators circulating in the bloodstream, and react to stimulation with finely tuned responses mediated by different signal transduction pathways, leading the endothelium to adapt. Neuropeptide Y (NPY), the most abundant peptide in heart and brain, is mainly involved in the neuroendocrine regulation of the stress response. The regulatory roles of NPY depend on many factors, including its enzymatic processing, receptor subtypes and related signal transduction systems, including the phosphoinositide (PI) pathway and related phospholipase C (PI-PLC) family of enzymes. The panel of expression of PI-PLC enzymes differs comparing quiescent versus differently stimulated human EC. Growing evidences indicate that the regulation of the expression of PLC genes, which codify for PI-PLC enzymes, might act as an additional mechanism of control of the PI signal transduction pathway. NPY was described to potentiate the activation of PI-PLC enzymes in different cell types, including EC. In the present experiments, we stimulated human umbilical vein EC using different doses of NPY in order to investigate a possible role upon the expression PLC genes. NPY reduced the overall transcription of PLC genes, excepting for PLCE. The most significant effects were observed for PLCB2 and PLCD1, both isoforms recruited by means of G-proteins and G-protein-coupled receptors. NPY behavior was comparable with other PI-PLC interacting molecules that, beside the stimulation of phospholipase activity, also affect the upcoming enzymes' production acting upon gene expression. That might represent a mode to regulate the activity of PI-PLC enzymes after activation.