Oxidation-Induced C-Terminal Amidation Marks Proteins for Degradation

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Proteostasis relies on the ubiquitin-proteasome system (UPS) for eliminating damaged proteins.
• Degrons, protein degradation signals, were traditionally considered genetically encoded or enzymatically generated.
• Emerging evidence points to nonenzymatic chemical damage creating functional degradation signals.

Purpose of the Study:

• To investigate the role of oxidative stress-induced protein modifications in creating degradation signals.
• To identify the molecular mechanisms linking chemical damage to protein clearance via the UPS.
• To explore the implications of this pathway in disease-associated mutations.

Main Methods:

• Genome-wide CRISPR screening to identify factors involved in CTAP recognition.
• Biochemical assays to assess ubiquitination and proteasomal degradation of amidated substrates.
• Analysis of FBXO31 mutants and their effect on protein stability and cellular function.

Main Results:

• Oxidative stress generates C-terminal amide groups (CTAPs) on proteins, acting as a novel class of degrons.
• The SCF-FBXO31 E3 ligase complex selectively recognizes and binds to CTAPs.
• FBXO31 is essential for the ubiquitination and proteasomal degradation of CTAP-bearing proteins.
• FBXO31 mutations lead to impaired proteostasis and aberrant degradation of non-amidated proteins, causing cytotoxicity.

Conclusions:

• Chemically induced modified amino acid degrons (MAADs) represent a new class of degradation signals.
• This study establishes a mechanistic link between oxidative damage and selective protein degradation.
• Dysregulation of this pathway contributes to cellular dysfunction and disease phenotypes.