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miRNA-Dependent Regulation of AKT1 Phosphorylation

Mallory I Frederick1, Tarana Siddika1, Pengcheng Zhang1

  • 1Department of Biochemistry, The University of Western Ontario, 1151 Richmond Street, London, ON N6A 5C1, Canada.

Cells
|March 10, 2022
PubMed

Insights

MicroRNAs, specifically let-7, regulate the PI3K/AKT pathway in ovarian cancer. These miRNAs impact AKT1 phosphorylation, influencing cell survival and transition to metastatic states.

Area of Science:

  • Molecular Biology
  • Cancer Biology
  • Cell Signaling

Background:

  • The phosphoinositide-3-kinase (PI3K)/AKT pathway is crucial for cell survival and frequently over-activated in cancers, including ovarian cancer.
  • AKT1 activation involves phosphorylation at T308 and S473, and its pathway disruption inhibits epithelial-mesenchymal transition in epithelial ovarian cancer (EOC) cells.
  • Metastatic EOC cells form dormant spheroids, previously associated with low AKT1 S473 phosphorylation.

Purpose of the Study:

  • To investigate the role of let-7 microRNAs (miRNAs) in regulating AKT1 phosphorylation and activity in epithelial ovarian cancer cells.
  • To elucidate the impact of let-7 miRNAs on the transition of EOC cells from adherent to spheroid growth states.
  • To identify specific PI3K pathway components regulated by let-7 miRNAs.

Main Methods:

  • Analysis of AKT1 phosphorylation (T308 and S473) in adherent versus spheroid EOC cells.
  • Assessment of let-7 miRNA levels during the transition to spheroid growth.
  • Mechanistic studies in HEK 293T cells to determine the effect of let-7a, let-7b, and let-7g on AKT1 phosphorylation and downstream signaling.
  • Investigation of let-7a-dependent regulation of PI3K pathway components (PI3KC2A, PDK1, RICTOR).

Main Results:

  • EOC spheroids exhibit reduced T308 and S473 phosphorylation of AKT1 compared to adherent cells.
  • The transition to spheroid growth is associated with significantly increased let-7 miRNA levels.
  • Exogenous let-7a enhances AKT1 T308 phosphorylation, decreases S473 phosphorylation, and increases GSK-3β phosphorylation in HEK 293T cells.
  • Let-7b and let-7g also deregulated AKT signaling, rendering AKT1 insensitive to growth factor stimulation.
  • let-7a was found to regulate PI3K pathway components PI3KC2A, PDK1, and RICTOR, impacting AKT1 activity.

Conclusions:

  • Let-7 miRNAs play a novel role in regulating AKT signaling pathways.
  • Increased let-7 miRNA levels contribute to altered AKT1 phosphorylation during the transition to a spheroid, potentially dormant state in EOC.
  • These findings reveal a new mechanism by which miRNAs modulate cancer cell behavior and survival through the PI3K/AKT pathway.
Keywords:
miRNAoncogenic kinaseposttranslational modificationprotein phosphorylationsignaling

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