Insulin Signaling Augments eIF4E-Dependent Nonsense-Mediated mRNA Decay in Mammalian Cells

Area of Science:

• Molecular Biology
• Cellular Signaling
• Gene Regulation

Background:

• Nonsense-mediated mRNA decay (NMD) is a surveillance pathway that degrades mRNAs with premature termination codons (PTCs).
• NMD is translation-dependent, but the effects of enhanced translation on NMD are less understood.
• Insulin signaling is a key pathway regulating cellular metabolism and growth.

Purpose of the Study:

• To investigate the correlation between enhanced translation, driven by insulin signaling, and its impact on NMD.
• To elucidate the molecular mechanisms by which insulin signaling influences NMD of eIF4E-bound transcripts.

Main Methods:

• Investigated the effect of insulin stimulation on translation and NMD.
• Utilized rapamycin to assess its impact on insulin-mediated NMD enhancement.
• Examined the role of AKT phosphorylation and PTEN inhibition in NMD.
• Assessed the binding and colocalization of UPF1 and eIF4E in response to insulin.

Main Results:

• Insulin-mediated enhancement of translation augments NMD, an effect abrogated by rapamycin.
• Increased AKT phosphorylation, induced by PTEN inhibition, facilitates NMD.
• Insulin stimulation increases UPF1 binding to eIF4E-bound PTC-containing transcripts.
• Insulin induces the colocalization of UPF1 and eIF4E within processing bodies.

Conclusions:

• Extracellular insulin signaling promotes the degradation of eIF4E-bound NMD targets by enhancing translation.
• The study reveals a novel link between insulin signaling, translation, and mRNA surveillance.
• These findings provide insights into how cellular signaling pathways regulate gene expression quality control.