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Proliferation and Differentiation of Murine Myeloid Precursor 32D/G-CSF-R Cells
Published on: February 21, 2018
GSK3β suppression inhibits MCL1 protein synthesis in human acute myeloid leukemia cells
Yuan-Chin Lee1, Yi-Jun Shi1, Liang-Jun Wang1
1Institute of Biomedical Sciences, National Sun Yat-Sen University, Kaohsiung, Taiwan.
Abstract:
Previous studies have shown that glycogen synthase kinase 3β (GSK3β) suppression is a potential strategy for human acute myeloid leukemia (AML) therapy. However, the cytotoxic mechanism associated with GSK3β suppression remains unresolved. Thus, the underlying mechanism of N-(4-methoxybenzyl)-N'-(5-nitro-1,3-thiazol-2-yl)urea (AR-A014418)-elicited GSK3β suppression in the induction of AML U937 and HL-60 cell death was investigated in this study. Our study revealed that AR-A014418-induced MCL1 downregulation remarkably elicited apoptosis of U937 cells. Furthermore, the AR-A014418 treatment increased p38 MAPK phosphorylation and decreased the phosphorylated Akt and ERK levels. Activation of p38 MAPK subsequently evoked autophagic degradation of 4EBP1, while Akt inactivation suppressed mTOR-mediated 4EBP1 phosphorylation. Furthermore, AR-A014418-elicited ERK inactivation inhibited Mnk1-mediated eIF4E phosphorylation, which inhibited MCL1 mRNA translation in U937 cells. In contrast to GSK3α, GSK3β downregulation recapitulated the effect of AR-A014418 in U937 cells. Transfection of constitutively active GSK3β or cotransfection of constitutively activated MEK1 and Akt suppressed AR-A014418-induced MCL1 downregulation. Moreover, AR-A014418 sensitized U937 cells to ABT-263 (BCL2/BCL2L1 inhibitor) cytotoxicity owing to MCL1 suppression. Collectively, these results indicate that AR-A014418-induced GSK3β suppression inhibits ERK-Mnk1-eIF4E axis-modulated de novo MCL1 protein synthesis and thereby results in U937 cell apoptosis. Our findings also indicate a similar pathway underlying AR-A014418-induced death in human AML HL-60 cells.
Insights
Glycogen synthase kinase 3β (GSK3β) suppression by AR-A014418 induces acute myeloid leukemia (AML) cell death. This occurs through inhibiting MCL1 synthesis via the ERK-Mnk1-eIF4E pathway, promoting apoptosis.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Biology
Background:
- Glycogen synthase kinase 3β (GSK3β) suppression is a promising strategy for acute myeloid leukemia (AML) therapy.
- The precise cytotoxic mechanism of GSK3β suppression in AML remains unclear.
Purpose of the Study:
- To investigate the mechanism of AR-A014418-induced GSK3β suppression in AML U937 and HL-60 cell death.
- To elucidate the role of the ERK-Mnk1-eIF4E axis in mediating MCL1 protein synthesis inhibition and subsequent apoptosis.
Main Methods:
- Utilized AR-A014418 to suppress GSK3β in AML cell lines (U937, HL-60).
- Assessed apoptosis, cell death, and protein/mRNA levels of key signaling molecules (MCL1, p38 MAPK, Akt, ERK, 4EBP1, eIF4E).
- Employed gene transfection techniques to manipulate GSK3β, MEK1, and Akt activity.
Main Results:
- AR-A014418 induced U937 cell apoptosis via MCL1 downregulation.
- Treatment increased p38 MAPK phosphorylation while decreasing phosphorylated Akt and ERK.
- Inactivation of Akt and ERK suppressed mTOR- and Mnk1-mediated phosphorylation of 4EBP1 and eIF4E, respectively, inhibiting MCL1 translation.
- GSK3β downregulation mimicked AR-A014418 effects; active GSK3β or MEK1/Akt suppressed AR-A014418-induced MCL1 downregulation.
- AR-A014418 sensitized cells to ABT-263 by suppressing MCL1.
Conclusions:
- AR-A014418-induced GSK3β suppression triggers AML cell apoptosis by inhibiting de novo MCL1 synthesis through the ERK-Mnk1-eIF4E pathway.
- This mechanism is relevant in both U937 and HL-60 AML cell lines.
- Targeting GSK3β offers a potential therapeutic strategy for AML by modulating MCL1 expression and sensitizing cells to other treatments.
