<scp>HEK</scp>293 cells exposed to microcystin‐<scp>LR</scp> show reduced protein phosphatase 2A activity and more stable cytoskeletal structure when overexpressing α4 protein

Huang, Pu; Wang, Beilei; Xing, Mingluan; Guo, Zonglou; Xu, Lihong

doi:10.1002/tox.22230

Cited by 12 publications

(8 citation statements)

References 46 publications

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“…In summary, our results from the current study indicate that although elevated α4 expression did not rescue the decreased PP2A activity, it did counteract the toxicity of MC‐LR on cytoskeletal structures, which is similar to that of our previous finding in α4‐overexpressing HEK 293 cells . However, the protective mechanism may not be entirely through stabilizing PP2A function for the reason that serious inhibition of PP2A activity was also observed, which is similar to that in normal HL7702 cells exposed to MC‐LR.…”

Section: Discussionsupporting

confidence: 82%

“…The relationship of α4 with the cytoskeletal structures and oxidative damage when cells are insulted with MC‐LR will be our next step in future research. In addition, the results obtained in the current study indicate some differences from α4‐overexpressing HEK 293 cells treated with MC‐LR . Although, in both α4‐overexpressing cell lines, the PP2A activity was inhibited significantly and the cytoskeletal structure remained unchanged, the response of PP2A and the phosphorylation profiles of cytoskeleton‐related proteins were quite different, indicating the distinctive response pattern varies in different cell lines even under the same chemical toxicant stress.…”

Section: Discussionmentioning

confidence: 53%

“…In our previous study, α4 was found to be involved in the cellular toxicity of MC‐LR on the cytoskeleton via the change of PP2A activity in human embryonic kidney 293 (HEK 293) cells and human hepatoma SMMC 7721 cells . In addition, the α4‐overexpressing HEK 293 cells showed a more stable cytoskeletal structure than the behavior of “normal” HEK 293 cells under the MC‐LR insult . These results suggest that elevated α4 can relieve the toxic effect of MC‐LR on the cytoskeleton.…”

Section: Introductionmentioning

confidence: 87%

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Alpha4‐overexpressing HL7702 cells can counteract microcystin‐LR effects on cytoskeletal structure

Huang

Wang

Weng

et al. 2018

Environmental Toxicology

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Our previous studies indicated that α4 was involved in the toxicity of MC-LR on the cytoskeleton via the change of PP2A activity in HEK 293. To explore the role of α4 in MC-LR toxicity via PP2A regulation in different cell lines, the HL7702 cell overexpressing α4 protein was exposed to MC-LR, and the change of PP2A, cytoskeletal structure, and cytoskeleton-related proteins were investigated. The results showed that PP2A activity was decreased, PP2A/C subunit expression and phosphorylation (Tyr307) increased significantly, but methylation (Leu 309)clearly decreased. The structure of the actin filaments and microtubules (MTs) remained unchanged, and the expression and phosphorylation of the cytoskeleton-related proteins showed different changes. In addition, the main components of the MAPK pathway, JNK, P38, and ERK1/2, were activated together. Our results indicated that elevated α4 expression did confer some resistance to MC-LR-induced cytoskeletal changes, but the responses of different cell lines to MC-LR, under the α4-overexpression condition, are not exactly the same.

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Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 53%

Section: Introductionmentioning

confidence: 87%

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Alpha4‐overexpressing HL7702 cells can counteract microcystin‐LR effects on cytoskeletal structure

Huang

Wang

Weng

et al. 2018

Environmental Toxicology

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“…However, under cellular stress or when the existing PP2A complexes become unstable, release of PP2A/C from α4 is essential for the adaptive increase of PP2A activity (Kong et al, ). Accordingly, α4 plays a key role in PP2A core enzyme assembly and stability (Huang et al, ). Our PP2A activity assay and immunoprecipitation results supported this model.…”

Section: Discussionmentioning

confidence: 99%

Microcystin-LR induces a wide variety of biochemical changes in the A549 human non-small cell lung cancer cell line: Roles for protein phosphatase 2A and its substrates

Wang

Liu

et al. 2016

Environ. Toxicol.

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Our previous studies have described the toxic effects of microcystin-LR (MC-LR) in various normal cell lines and human hepatoma SMMC-7721 cells, but the specific effects of MC-LR in other types of cancer cells with respect to protein phosphatase 2A (PP2A) have not been fully elaborated. A549 human lung adenocarcinoma cells have been identified to express organic anion-transporting polypeptides (OATP) involved in cellular uptake of MC-LR, and thus probably make an appropriate in vitro model to assess MC-LR's cytotoxicity. Hence, in our present study, A549 cells were treated with various concentrations of MC-LR for 24 h. The presence of MC-LR in A549 cells was confirmed, and PP2A activity, PP2A substrates, cytoskeleton, apoptosis, and proliferation were subsequently explored. The results showed that 5-10 μM MC-LR inhibited PP2A activity significantly but 0.5-1 μM MC-LR did not change PP2A activity dramatically. The inhibition could result from the hyperphosphorylation of PP2A/C at Tyr307, an elevation in the total PP2A/C expression and the dissociation of α4/PP2A/C complexes. Moreover, MC-LR led to rearrangements of filamentous actin and microtubules, which might be correlated with the hyperphosphorylation of Ezrin, VASP and HSP27 due to PP2A inhibition and mitogen-activated protein kinase (MAPK) activation. However, exposure to MC-LR for 24 h failed to trigger either apoptosis or proliferation, which might be related to PP2A-inhibition-induced hyperphosphorylation of Bcl-2 and Bad and the activation status of Akt. In conclusion, our data indicated that MC-LR induced extensive molecular and cellular alterations in A549 cells through a PP2A-centered pathway, which differed in some respects from our previous study in SMMC-7721 cells. To our knowledge, this is the first report comprehensively demonstrating the effects of MC-LR in A549 cells, and our findings provide insights into the mechanism of MC-LR toxicity in cancer cells. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1065-1078, 2017.

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“…In addition, LR Y47A treatment significantly reduced the level of pT125-LR, which further proved that Y47-LR is the upstream node of T125-LR. The application of PP1c inhibitor Microcystin-LR (Mic-LR) [31] or siPP1c treatment could significantly block the down-regulation of pT125-LR after LR Y47A treatment (Fig. S4d and S4e).…”

Section: The Role Of Pp1c In the Regulation Pt125-lrmentioning

confidence: 99%

The role of LR-TIMAP/PP1c complex in the occurrence and development of no-reflow

et al. 2021

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Background:The presence of no-reflow can increase the risk of major adverse cardiac events and is widely regarded as an important sign of serious prognosis. Previous studies show that laminin receptor (LR) is closely related to the morphology and function of microvessels. However, whether LR is involved in the occurrence and development of no-reflow is still unknown. Methods: In vivo, positron emission tomography (PET) perfusion imaging was performed to detect the effects of intramyocardial gene (LR-AAV and LR-siRNA-AAV) delivery treatment on the degree of no-reflow. In vitro, LC-MS/MS analysis was conducted to identify the LR phosphorylation sites of human cardiac microvascular endothelial cells (HCMECs) treated with oxygen-glucose deprivation (OGD) for 4 h. Western blot analyses were used to evaluate the phosphorylation levels of LR at residues Tyr47 (phospho-Tyr47-LR/pY47-LR) and Thr125 (phospho-Thr125-LR/pT125-LR) and their effects on the phosphorylation of VE-cadherin residue Ser665 (phospho-Ser665-VE-cad). Findings: LR over-expression, LR T125A (phosphonull) and LR Y47A (phosphonull) treatments were found to reduce the level of phospho-Ser665-VE-cad, and subsequently maintain adherent junctions and endothelial barrier integrity in hypoxic environments. Mechanistically, TIMAP/PP1c can combine with LR on the cell membrane to form a novel LR-TIMAP/PP1c complex. The level of pY47-LR determined the stability of LR-TIMAP/PP1c complex. The binding of TIMAP/PP1c on LR activated the protein phosphatase activity of PP1c and regulated the level of pT125-LR. Interpretation: This study demonstrates that low level of phospho-LR reduces no-reflow area through stabilizing the LR-TIMAP/PP1c complex and promoting the stability of adherens junctions, and may help identify new therapeutic targets for the treatment of no-reflow.

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HEK293 cells exposed to microcystin‐LR show reduced protein phosphatase 2A activity and more stable cytoskeletal structure when overexpressing α4 protein

Cited by 12 publications

References 46 publications

Alpha4‐overexpressing HL7702 cells can counteract microcystin‐LR effects on cytoskeletal structure

Alpha4‐overexpressing HL7702 cells can counteract microcystin‐LR effects on cytoskeletal structure

Microcystin-LR induces a wide variety of biochemical changes in the A549 human non-small cell lung cancer cell line: Roles for protein phosphatase 2A and its substrates

The role of LR-TIMAP/PP1c complex in the occurrence and development of no-reflow

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