Chapter 4: Regulation of Clusterin activity by calcium.
ABSTRACT In this chapter, the attention is put on Ca(2+) effect on Clusterin (CLU) activity. We showed that two CLU forms (secreted and nuclear) are differently regulated by Ca(2+) and that Ca(2+) fluxes affect CLU gene expression. A secretory form (sCLU) protects cell viability whereas nuclear form (nCLU) is proapoptotic. Based on available data we suggest, that different CLU forms play opposite roles, depending on intracellular Ca(2+) concentration, time-course of Ca(2+) current, intracellular Ca(2+) compartmentalization, and final Ca(2+) targets. Discussion will be motivated on how CLU acts on cell in response to Ca(2+) waves. The impact of Ca(2+) on CLU gene activity and transcription, posttranscriptional modifications, translation of CLU mRNA, and posttranslational changes as well as biological effects of CLU will be discussed. We will also examine how Ca(2+) signal and Ca(2+)-dependent proteins are attributable to changes in CLU characteristics. Some elucidation of CLU gene activity, CLU protein formation, maturation, secretion, and intracellular translocations in response to Ca(2+) is presented. In response to cell stress (i.e., DNA damage) CLU gene is activated. We assume that commonly upregulated mRNA for nCLU versus sCLU and vice versa are dependent on Ca(2+) accessibility and its intracellular distribution. It looks as if at low intracellular Ca(2+) the delay in cell cycle allows more time for DNA repair; otherwise, cells undergo nCLU-dependent apoptosis. If cells are about to survive, intrinsic apoptosis is abrogated by sCLU interacting with activated Bax. In conclusion, a narrow range of intracellular Ca(2+) concentrations is responsible for the decision whether nCLU is mobilized (apoptosis) or sCLU is appointed to improve survival. Since the discovery of CLU, a huge research progress has been done. Nonetheless we feel that much work is left ahead before remaining uncertainties related to Ca(2+) signal and the respective roles of CLU proteins are unraveled.
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ABSTRACT: Expression of clusterin (Clu) in the murine first molar tooth germ was markedly increased at postnatal developmental stages. The time-course of expression of this gene paralleled those of other genes encoding proteins involved during the secretory phase of odontogenesis, as described previously. Immunohistochemical studies of clusterin in murine molar tooth germs suggested this protein to be located in outer enamel epithelium, regressing enamel organ, secretory ameloblasts, and the dental epithelium connecting the tooth to the oral epithelium at an early eruptive stage. Immunolabelling of transforming growth factor beta-1 (TGF-β1) revealed it to be located close to clusterin. The levels of expression of Clu and Tgfb1 were markedly decreased following in-vivo transfection with anti-miR-214. In contrast, the expression of several genes associated with regulation of growth and development were increased by this treatment. We suggest that clusterin has functions during secretory odontogenesis and the early eruptive phase. Bioinformatic analysis after treatment with anti-miR-214 suggested that, whilst cellular activities associated with tooth mineralization and eruption were inhibited, activities associated with an alternative developmental activity (i.e. biosynthesis of contractile proteins) appeared to be stimulated. These changes probably occur through regulation mediated by a common cluster of transcription factors and support suggestions that microRNAs (miRNAs) are highly significant as regulators of differentiation during odontogenesis.European Journal Of Oral Sciences 08/2013; 121(4):303-312. · 1.42 Impact Factor
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ABSTRACT: We demonstrated that glyphosate possesses tumor promoting potential in mouse skin carcinogenesis and SOD 1, calcyclin (S100A6), and calgranulin B (S100A9) have been associated with this potential, although the mechanism is unclear. We aimed to clarify whether imbalance in between [Ca(2+)] i levels and oxidative stress is associated with glyphosate-induced proliferation in human keratinocytes HaCaT cells. The [Ca(2+)] i levels, ROS generation, and expressions of G1/S cyclins, IP3R1, S100A6, S100A9, and SOD 1, and apoptosis-related proteins were investigated upon glyphosate exposure in HaCaT cells. Glyphosate (0.1 mM) significantly induced proliferation, decreases [Ca(2+)] i , and increases ROS generation in HaCaT cells, whereas antioxidant N-acetyl-L-cysteine (NAC) pretreatment reverts these effects which directly indicated that glyphosate induced cell proliferation by lowering [Ca(2+)] i levels via ROS generation. Glyphosate also enhanced the expression of G1/S cyclins associated with a sharp decrease in G0/G1 and a corresponding increase in S-phases. Additionally, glyphosate also triggers S100A6/S100A9 expression and decreases IP3R1 and SOD 1 expressions in HaCaT cells. Notably, Ca(2+) suppression also prevented apoptotic related events including Bax/Bcl-2 ratio and caspases activation. This study highlights that glyphosate promotes proliferation in HaCaT cells probably by disrupting the balance in between [Ca(2+)] i levels and oxidative stress which in turn facilitated the downregulation of mitochondrial apoptotic signaling pathways.ISRN dermatology. 01/2013; 2013:825180.
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ABSTRACT: Epigallocatechin-3-gallate (EGCG) is an important bioactive constituent of green tea extract (GTE) that was widely believed to reduce proliferation of many cancer cell lines. The purpose of this study was to verify the possible pro-apoptotic action of GTE/EGCG in human colon adenocarcinoma COLO 205 cells. The effect of EGCG/GTE treatments on cell viability was studied using methyl thiazolyl tetrazolium (MTT) assay. Cell proliferation was assessed with crystal violet staining, whereas protein expression levels were evaluated by western blotting followed by densitometric analysis. Obtained results were analyzed statistically. Surprisingly, EGCG/GTE dose-dependently up-regulated COLO 205 cells viability and proliferation. Observed effects were mediated by lipid rafts, as cholesterol depletion significantly prevented EGCG/GTE-dependent cell survival. Furthermore, treatment of COLO 205 cells with EGCG/GTE resulted in activation of MEK/ERK1/2, but not Akt1/2/GSK-3β signaling pathway. The presence of MEK inhibitor - PD98059 but not PI3-K inhibitor - LY294002, both reduced EGCG/GTE-induced ERK1/2 activation and the proliferative effect of catechins. Furthermore, EGCG/GTE stimulated secretory clusterin (sClu) expression level, which underwent complex control through lipid rafts/PKC/Wnt/β-catenin system. Our studies demonstrated that EGCG and GTE stimulate cell survival and proliferation of COLO 205 cells in a lipid rafts-dependent manner via at least MEK/ERK1/2 signaling pathway. Furthermore, EGCG/GTE mediated positive effects on viability and mitogenicity of COLO 205, while suppression of β-catenin activity was positively correlated with sClu clusterin expression.Journal of physiology and pharmacology: an official journal of the Polish Physiological Society 08/2011; 62(4):449-59. · 2.48 Impact Factor