微囊藻毒素LR刺激HEK293細(xì)胞產(chǎn)生的PP2A調(diào)節(jié)機(jī)制及其對(duì)細(xì)胞凋亡命運(yùn)的影響
[Abstract]:The eutrophication of water bodies and the resulting cyanobacteria are serious problems faced by humans today. The effects of microcystin (MCs, microcystins) on human health are particularly concerned. For example, the microcystin LR (MCLR, microcystin-LR) has hepatotoxicity, nephrotoxicity, and nerve. Toxicity and so on, and one of the most toxic microcystins. Studies have shown that MCLR can cause both apoptosis and tumor promoting effect. However, the determinants of their fate have yet to be revealed after the cells are exposed to MCLR.
Protein phosphatase 2A (PP2A, protein phosphatase2A) is the major target of MCLR in cells,.PP2A, which plays an important role in cells. It participates in almost all cell physiological activities, including cell proliferation, cell metabolism, cell differentiation and transformation, DNA repair, apoptosis and other.PP2A total enzymes from structural subunits (PP2A/A), active subunits (PP2A/C) and modulation. The subunit (PP2A/B) consists of a subunit that regulates the downstream substrates, subcellular localization and specific physiological functions of the PP2A whole enzyme. 75 PP2A total enzymes have been found and all enzymes have numerous substrates. In addition, a small portion of the PP2A/C subunit is associated with the A4 protein but only has a lower activity. There is an important correlation between the regulation of PP2A activity under stress.
It has been shown that the loss of PP2A activity caused by the binding of MCLR directly with the active subunit of PP2A (PP2A/C) is an important mechanism for cell damage caused by MCLR. However, it is not clear whether MCLR affects other subunits of PP2A, and how MCLR affects the activity of PP2A total enzyme in cells. In addition, because PP2A has important physiological functions, cells regulate the activity of PP2A closely in stress state, such as PP2A/C phosphorylation, methylation and post-translational modification; after producing ceramide, it activates a part of PP2A (CAPP, ceramide activated protein phosphatase), and the dissociation of alpha 4 protein and low activity PP2A is compensatory activity loss. In this case, we ask: what regulatory mechanisms are produced by the cell response to the MCLR; are these regulatory mechanisms sufficient to compensate for the inhibitory effect of MCLR on intracellular PP2A activity, and what cytological effects will be produced accordingly?
According to the proteomics study of the earlier experiment, it was found that after the cells were exposed to MC, many of the signal proteins in the cells changed, and most of these proteins were associated with PP2A. This study assumed that after the cells were exposed to MCLR, the activity of intracellular PP2A, especially the activity of its whole enzyme, and the regulation mechanism of cell to PP2A, were used for cells. The determination of fate plays an important role. In this study, the cells of HEK293 (Human Embryonic Kidney293), a kidney source, were selected as the research object. Immunoblotting, immunofluorescence, immunofluorescence and other methods were used to study the PP2A subunit in HEK293 cells under the condition that MCLR had no serious lethal effect on the cell viability. The changes in basal level and activity, the phosphorylation level of PP2A substrate, the regulatory mechanism of PP2A activity, the morphology of cytoskeleton and cell mucin, and the selection of cell fate. In addition, this study also selected mice as a living object to verify the renal toxicity of MCLR.
Main results:
1. MCLR binds directly to PP2A/C subunit in HEK293 cells. At this concentration, MCLR has a downward trend in cell viability, but has no serious inhibitory effect.
2. MCLR did not affect the level of intracellular PP2A/A, PP2A/C and PP2A/B56 delta protein, but up regulation of PP2A/B55 alpha and PP2A/B56 alpha protein; MCLR downregulated intracellular PP2A/C methylation, but did not affect its phosphorylation; MCLR caused PP2A and its ubiquitin ligase dissociation; high concentration MCLR resulted in partial dissociation and partial dissociation. In Golgi body, there is no obvious effect on the localization of PP2A/C and PP2A/B56 alpha subunits. MCLR causes the dissociation of intracellular PP2A/C and alpha 4 protein, and the alpha 4 protein is located in the nucleus.
3. the effect of MCLR on the overall activity of PP2A in cells showed low concentration activity and high inhibitory activity.
4. MCLR caused HEK293 cells to produce ceramide. After the cells were co treated with ceramide synthase inhibitor DESI, the up-regulation effect of MCLR induced PP2A/B55 alpha and PP2A/B56 alpha protein was eliminated; the low concentration MCLR caused the up regulation effect of PP2A activity to be eliminated; high concentration MCLR enhanced the activity of PP2A, so that PP2A activity was almost completely completely activated. Inhibition.
5. MCLR decreased the phosphorylation of the downstream substrate c-Myc of the PP2A/B56a whole enzyme, but did not affect its protein level; the level of Bad protein in the downstream substrate of PP2A/B56a was elevated, the ratio of phosphorylation to.MCLR also caused the decrease of the apoptosis related protein Bcl-2 protein level, but did not affect the level of Bax protein. After CO processing with DESI, MCLR was to Bcl-2 and Bad protein levels. The altered.MCLR weakened the phosphorylation of p38MAPK and JNK protein.
6. MCLR caused the morphologic change of HEK293 cells to cause the cell microprotein depolymerization, the vimentin and microtubulin condensation in one of the intermediate fibers, this phenomenon was similar to the change of the cytoskeleton after the ceramide treated the HEK293 cells. After CO processing with DESI, the modification of the cytoskeleton of MCLR weakened.MCLR and caused the skeleton related protein Rac1 and Mi. D1 is located in the nucleus.
7. MCLR caused the morphologic changes of the adhesion protein of HEK293 cells, and caused the weakening of cell adhesion ability by.MCLR, which caused cell nuclear polycondensation and fragmentation and caused cell apoptosis. After CO processing with DESI, the effect of MCLR on cell adhesion and the effect of stimulating cell apoptosis was weakened.
8. after the intraperitoneal injection of MCLR toxin, the kidney could detect ceramide production and detect increased apoptosis.
The main conclusions are as follows:
MCLR can not only directly bind to PP2A in HEK293 cells, but also induce the regulation of cell to PP2A, including the production of ceramide, PP2A/C and alpha 4 protein dissociation. In addition, the effect of MCLR on the cytoskeleton, cell adhesion and apoptosis is related to ceramide, and the inference of the loss of the original function after the dissociation of alpha 4 protein and PP2A/C .MCLR can also stimulate the production of ceramide and induce apoptosis in the kidney of mice. The results of this experiment show that the PP2A total enzyme activity and the regulation of cell to PP2A play an important role in determining the apoptosis fate of MCLR.
【學(xué)位授予單位】:浙江大學(xué)
【學(xué)位級(jí)別】:博士
【學(xué)位授予年份】:2013
【分類號(hào)】:R114
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