Amino Acid Biosynthesis Regulation during Endoplasmic Reticulum Stress Is Coupled to Protein Expression Demands

Area of Science:

• Cellular Biology
• Molecular Biology
• Biochemistry

Background:

• The endoplasmic reticulum (ER) stress response, or unfolded protein response (UPR), is a critical cellular mechanism to manage protein misfolding within the ER.
• The UPR involves complex transcriptional and translational regulatory pathways, including the PERK-mediated branch, to restore ER homeostasis.

Purpose of the Study:

• To investigate the link between amino acid biosynthesis regulation and protein synthesis demands during ER stress.
• To elucidate the role of the UPR in coordinating amino acid supply with the requirements of UPR-induced proteins.

Main Methods:

• Analysis of PERK-dependent gene expression changes during ER stress.
• Quantification of amino acid biosynthesis and tRNA synthetase activity.
• Bioinformatic analysis of amino acid composition in UPR-regulated proteins.

Main Results:

• The UPR induces the biosynthesis of specific amino acids and upregulates their corresponding tRNA synthetases in a PERK-dependent manner.
• Proteins upregulated by the UPR are significantly enriched with these induced amino acids.
• Secreted proteins, which escape ER-targeted protein repression, show a marked enrichment of UPR-induced amino acids.

Conclusions:

• ER stress and the UPR coordinate amino acid supply (biosynthesis and tRNA loading) with the demand from newly synthesized proteins.
• This coordination represents an additional regulatory layer controlling protein synthesis under ER stress conditions.
• The findings highlight a mechanism ensuring adequate resources for the production of essential proteins, especially secreted ones, during cellular stress.