PLC-gamma1 regulates fibronectin assembly and cell aggregation

Phospholipase Cγ1 (PLCG1) overexpression is associated with tumor growth and poor survival in IDH wild-type lower-grade gliomas in adult patients

Gliomas are the most common and recalcitrant intracranial tumors, approximately a quarter of which are classified as lower-grade gliomas (WHO II-III). Although the prognosis of lower-grade gliomas (LGGs) is significantly better than that of higher-grade gliomas, as a highly heterogeneous tumor type, the prognosis of LGGs varies greatly based on the molecular diagnosis. IDH wild-type used to be regarded as a dismal prognostic biomarker in LGGs; however, several studies revealed that IDH wild-type LGGs might not always be equivalent to glioblastoma (WHO IV). Hence, we hypothesize that underlying biological events in LGGs can result in different prognosis. In our study, transcriptome profiling was performed in 24 samples of LGG, and the results showed that the expression of phospholipase Cγ1 (PLCG1) was significantly correlated with IDH1/2 status and patients' clinical outcome. Furthermore, the cancer genome atlas (TCGA) and the Chinese glioma genome atlas (CGGA) databases verified that elevated PLCG1 expression was associated with tumor progression and poor survival in LGG patients. Moreover, PLCG1-targeted siRNA dramatically affected the growth, migration and invasiveness of IDH wild-type LGG cell lines. In in vitro and in vivo experiments, the PLC-targeted drug significantly suppressed the tumor growth of IDH wild-type LGG cell lines in vitro and tumors in mouse models. Taken together, our results demonstrated that higher PLCG1 expression was associated with tumor growth and worse prognosis in IDH wild-type LGGs and PLCG1 could serve as a potential therapeutic target for IDH wild-type LGG patients.

Examining the feasibility of a "top-down" approach to enhancing the keratinocyte-implant adhesion

The adhesion of human epidermal keratinocytes to the implant surface is one of the most critical steps during the patient's recovery from implantation of transcutaneous prosthesis. To improve the success rate of transcutaneous prosthetic implants, we explored a new "top-down" approach to promoting this dynamic adhering process through modulation of upstream cell signaling pathways. To examine the feasibility of this novel approach, we first established an in vitro platform that is capable of providing a non-invasive, real-time, quantitative characterization of the keratinocyte-implant interaction. This platform is based on the dissipation monitoring function of the quartz crystal microbalance with dissipation monitoring (QCM-D) in conjunction with the open-module setup of the QCM-D. We then employed this platform to assess the effects of various pathways-specific modulators on the adhering process of keratinocytes. We demonstrated that this "top-down" approach is as effective in enhancing the adhesion of keratinocytes as the conventional "bottom-up" approach that relies on modifying the substrate surface with the adhesion protein such as fibronectin. We envision that this new "top-down" approach combined with the QCM-D-based in vitro platform will help facilitate the future development of new therapies for enhancing osseointegration and promoting wound healing.

Annexin A5 regulates hepatocarcinoma malignancy via CRKI/II-DOCK180-RAC1 integrin and MEK-ERK pathways

As a calcium-dependent phospholipid binding annexin protein, annexin A5 (Anxa5) links to the progression, metastasis, survival, and prognosis of a variety of cancers. Current work showed ANXA5 overexpression was positively correlated with the upregulations of CRKI/II and RAC1 in hepatocarcinoma (HCC) patients’ tissues, which potentially enhanced the clinical progression and lymphatic metastasis of HCC. The role and action mechanism of ANXA5 in hepatocarcinoma was then investigated using a hepatocarcinoma Hca-P cell line, an ideal and well-established murine cell model with 100% inducible tumorigenicity of implanted mice with low (~25%) lymph node metastatic (LNM) rate. In vitro evidences indicated ANXA5 stable knockdown resulted in decreased proliferation, migration, invasion and adhesion to lymph node (LN), and increased intercellular cohesion behaviors of hepatocarcinoma Hca-P cells. Consistently, stable ANXA5 knockdown led to reduced in vivo tumorigenicity and malignancy, LNM rate and level potentials of Hca-P- transplanted mice via inhibiting CD34 and VEGF3. The levels of CRKI/II and RAC1 were reduced in tumor tissues from mice transplanted with Hca-P cells with stable ANXA5 knockdown. Molecular action investigation further showed ANXA5 downregulation apparently suppressed the expressions of molecules CRKI/II, DOCK180, RAC1 in integrin pathway, p-MEK, p-ERK, c-Myc, and MMP-9 in MEK- ERK pathway together with VIMINTIN in Hca-P cells in appropriate to knockdown extent. Collectively, Anxa5 was able to mediate HCC carcinogenesis via integrin and MEK-ERK pathways. It is of potential use in the research and treatment of HCC.

Regulation of retinal angiogenesis by phospholipase C-β3 signaling pathway

Angiogenesis has an essential role in many pathophysiologies. Here, we show that phospholipase C-β3 (PLC-β3) isoform regulates endothelial cell function and retinal angiogenesis. Silencing of PLC-β3 in human umbilical vein endothelial cells (HUVECs) significantly delayed proliferation, migration and capillary-like tube formation. In addition, mice lacking PLC-β3 showed impaired retinal angiogenesis with delayed endothelial proliferation, reduced endothelial cell activation, abnormal vessel formation and hemorrhage. Finally, tumor formation was significantly reduced in mice lacking PLC-β3 and showed irregular size and shape of blood vessels. These results suggest that regulation of endothelial function by PLC-β3 may contribute to angiogenesis.

Anti-inflammatory activities of phospholipase C inhibitor U73122: Inhibition of monocyte-to-macrophage transformation and LPS-induced pro-inflammatory cytokine expression

A wide range of biological processes are controlled by phospholipase C (PLC)/Ca(2+) signaling, which could be blocked by PLC-specific inhibitor U73122. Whether inhibition of PLC with chemical inhibitor U73122 affects the inflammatory response in monocytes/macrophages is currently unknown. In this study, we demonstrated that U73122 inhibited PMA-induced in vitro differentiation of human promonocytic U937 cells into macrophages as reflected by the reduction of cell adherence and the decreased expression of macrophage specific marker CD163. It is possible that U73122 blocked PMA-induced adhesion of U937 cells partially by down regulation and inactivation of both Pyk2 and paxillin signaling. Furthermore, the expression of LPS-induced pro-inflammatory cytokines TNF-α and IL-1β was significantly blocked by U73122 in both dU937 cells and mouse primary peritoneal macrophages. These results suggest that PLC is involved in the sophisticated inflammatory response by monocytes/macrophages, and thereby chemical antagonists of PLC may be potential agents for the suppression of inflammatory response.

PDGF regulates chondrocyte proliferation through activation of the GIT1- and PLCγ1-mediated ERK1/2 signaling pathway

Studies investigating the effects of cytokines on chondrocytes have significant application potential, since the culture of cartilage cells in vitro is a vital step for cartilage tissue engineering. Platelet-derived growth factor (PDGF), one of the growth factors occurring at the early stage of the healing process of damaged tissue, is critical in bone healing. The present study investigated the effects of the activation of PDGF on cell proliferation, apoptosis and the underlying mechanisms of chondrocytes in vitro. The results indicated that the stimulation of PDGF led to overexpression of the G-protein-coupled receptor kinase interacting protein-1 (GIT1) and promotion of the phosphorylation of phospholipase Cγ1 (PLCγ1). Furthermore, PDGF induced chondrocyte proliferation and inhibited apoptosis via activation of the extracellular signal-regulated kinase (ERK) 1/2 pathway. Following knocking down GIT1 expression by small interfering RNA, phosphorylation of PLCγ1 and activation of the ERK1/2 pathway was no longer promoted by PDGF. In addition, the effects of PDGF on proliferation and apoptosis were suppressed. The expression levels of GIT1 were not affected; however, the phosphorylation of ERK1/2 was suppressed through inhibition of the phosphorylation of PLCγ1 by U73122. The results demonstrated that GIT1 is upstream of PLCγ1. Although the ability of PDGF to induce cell proliferation was inhibited by the inhibition of the ERK1/2 pathway by PD98059, apoptosis was not suppressed. In conclusion, the present study demonstrated that PDGF was able to activate the GIT1‑PLCγ1‑mediated ERK1/2 pathway to control chondrocyte proliferation.

Lypopolysaccharide downregulates the expression of selected phospholipase C genes in cultured endothelial cells

The signaling system of phosphoinositides (PI) is involved in a variety of cell and tissue functions, including membrane trafficking, ion channel activity, cell cycle, apoptosis, differentiation, and cell and tissue polarity. Recently, PI and related molecules, such as the phosphoinositide-specific phospholipases C (PI-PLCs), main players in PI signaling were supposed to be involved in inflammation. Besides the control of calcium levels, PI-PLCs contribute to the regulation of phosphatydil-inositol bisphosphate metabolism, crucial in cytoskeletal organization. The expression of PI-PLCs is strictly tissue specific and evidences suggest that it varies under different conditions, such as tumor progression or cell activation. In a previous study, we obtained a complete panel of expression of PI-PLC isoforms in human umbilical vein endothelial cells (HUVEC), a widely used experimental model for endothelial cells. In the present study, we analyzed the mRNA concentration of PI-PLCs in lipopolysaccharide (LPS)-treated HUVEC by using the multiliquid bioanalyzer methodology after 3, 6, 24, 48, and 72 h from LPS administration. Marked differences in the expression of most PI-PLC codifying genes were evident.

Phosphoinositide pathway and the signal transduction network in neural development

The development of the nervous system is under the strict control of a number of signal transduction pathways, often interconnected. Among them, the phosphoinositide (PI) pathway and the related phospholipase C (PI-PLC) family of enzymes have been attracting much attention. Besides their well-known role in the regulation of intracellular calcium levels, PI-PLC enzymes interact with a number of molecules belonging to further signal transduction pathways, contributing to a specific and complex network in the developing nervous system. In this review, the connections of PI signalling with further transduction pathways acting during neural development are discussed, with special regard to the role of the PI-PLC family of enzymes.

Quantitative and robust assay to measure cell-cell contact assembly and maintenance

Epithelial junction formation and maintenance are multistep processes that rely on the clustering of macromolecular complexes. These events are highly regulated by signalling pathways that involve Rho small GTPases. Usually, when analysing the contribution of different components of Rho-dependent pathways to cell-cell adhesion, the localisation of adhesion receptors at junctions is evaluated by immunofluorescence. However, we find that this method has limitations on the quantification (dynamic range), ability to detect partial phenotypes and to differentiate between the participation of a given regulatory protein in assembly and/or maintenance of cell-cell contacts.In this chapter, we describe a suitable method, the aggregation assay, in which we adapted a quantitative strategy to allow objective and reproducible detection of partial phenotypes. Importantly, this methodology estimates the ability of cells to form junctions and their resistance to mechanical shearing forces (stabilisation).

Expression of phosphoinositide-specific phospholipase C isoforms in human umbilical vein endothelial cells

Aims

The signalling system of phosphoinositides (PIs) is involved in a number of cell and tissue functions including membrane trafficking, ion channel activity, cell cycle, apoptosis, differentiation and cell and tissue polarity. Recently, a role in cell migration was hypothesised for PI and related molecules including the phosphoinositide-specific phospholipases C (PI-PLCs), main players in PI signalling. The expression of PI-PLCs is tissue-specific and evidence suggests that it varies under different conditions such as tumour progression or cell activation. In order to obtain a complete picture, the expression of all PI-PLC isoforms was analysed in human endothelial cells (EC).

Methods

Using molecular biology methods (RT-PCR), the expression of PI-PLC isoforms was analysed in human umbilical vein endothelial cells (HUVEC), a widely used experimental model for human EC.

Results

All the PI-PLC isoforms except PI-PLC β1, PI-PLC ɛ and PI-PLC ζ were expressed in HUVEC.

Conclusions

The growing interest in the complex cascade of events occurring in angiogenesis will provide useful insights for therapeutic strategies. The expression of PI-PLC isoforms in HUVEC is a useful tool for further studies directed to understanding their role in angiogenesis. However, although HUVEC represent a widely used experimental model for human macrovascular EC, limitations remain in that they cannot fully represent the metabolic properties and interactions of the EC distributed in the entire organism.