Redox-sensitive mTOR-eIF4A signaling promotes selective P-glycoprotein translation

Area of Science:

• Cellular Biology
• Biochemistry
• Toxicology

Background:

• Cells require rapid protein synthesis for adaptation to acute oxidative stress before transcriptional responses are fully active.
• P-glycoprotein (P-gp), encoded by ABCB1, is crucial for cellular detoxification.
• Understanding mechanisms that rapidly modulate P-gp levels is vital for addressing cellular defense against toxins.

Purpose of the Study:

• To investigate how low-dose glucosamine (GlcN) affects P-gp expression and cellular adaptation to oxidative stress.
• To elucidate the signaling pathways and translational machinery involved in GlcN-mediated P-gp upregulation.
• To evaluate the protective role of GlcN-induced P-gp in vivo models of paraquat poisoning.

Main Methods:

• Utilized cell culture models and polysome profiling to analyze mRNA translation.
• Investigated the PI3K-AKT-mTORC1 signaling pathway and its components, including eIF4A.
• Employed pharmacological inhibitors and genetic depletion of EIF4A1.
• Analyzed the 5'-untranslated region of ABCB1 mRNA for structural elements.
• Used mouse models of paraquat poisoning, including Abcb1a/Abcb1b knockout mice.

Main Results:

• Low-dose glucosamine induced a transient, oxidation-sensitive response activating PI3K-AKT-mTORC1 signaling, increasing P-gp abundance without altering total ABCB1 mRNA levels.
• GlcN enhanced 4E-BP1 phosphorylation and promoted preferential translation of ABCB1 mRNA via the eIF4A translation factor.
• A structured G-rich element in the ABCB1 5'-untranslated region was identified as a potential mediator of eIF4A sensitivity.
• In vivo, GlcN increased pulmonary P-gp, reduced paraquat accumulation, and improved survival, effects diminished in Abcb1a/Abcb1b knockout mice.

Conclusions:

• A redox-sensitive mTOR-eIF4A signaling pathway preferentially enhances ABCB1/P-gp translation.
• This translational control mechanism provides rapid cellular adaptation to oxidative insults.
• GlcN-mediated P-gp upregulation plays a significant role in pulmonary detoxification and protection against paraquat toxicity.