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Microcystin-LR stabilizes c-myc protein by inhibiting protein phosphatase 2A in HEK293 cells

Huihui Fan1, Yan Cai2, Ping Xie3

  • 1College of Fisheries, Huazhong Agricultural University, Wuhan, China; Donghu Experimental Station of Lake Ecosystems, State Key Laboratory of Freshwater Ecology and Biotechnology of China, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China.

Toxicology
|March 11, 2014
PubMed

Insights

Microcystin-LR, a potent cyanotoxin, increases c-myc protein and transcription. This occurs by inhibiting protein phosphatase 2A, potentially driving liver cancer development.

Area of Science:

  • Environmental Toxicology
  • Molecular Carcinogenesis

Background:

  • Microcystin-LR (MC-LR) is a prevalent cyanotoxin linked to potential carcinogenicity.
  • The molecular mechanisms of MC-LR-induced cancer, particularly its effect on the proto-oncogene c-myc, are not fully understood.

Purpose of the Study:

  • To elucidate the molecular mechanisms by which Microcystin-LR affects c-myc expression and protein levels.
  • To investigate the role of protein phosphatase 2A (PP2A) in MC-LR's impact on c-myc.

Main Methods:

  • Exposure of HEK293 cells to Microcystin-LR.
  • Coexpression of PP2A and c-myc mutants (c-myc(T58A), c-myc(S62A)).
  • Luciferase reporter assay to assess c-myc promoter activity.

Main Results:

  • Microcystin-LR exposure led to increased c-myc protein levels in cells.
  • MC-LR inhibited PP2A activity, affecting c-myc phosphorylation at serine 62.
  • MC-LR enhanced c-myc promoter activity, suggesting transcriptional activation.

Conclusions:

  • Microcystin-LR stimulates both c-myc transcription and protein stabilization.
  • Inhibition of PP2A activity by MC-LR is a key mechanism for c-myc protein accumulation.
  • These findings suggest a pathway contributing to Microcystin-LR-induced hepatic tumorigenesis.
Keywords:
CarcinogenicityMicrocystin-LRProtein phosphatase 2Ac-myc

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