Assays to Study IRE1 Activation and Signaling

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• The endoplasmic reticulum (ER) stress sensor, inositol-requiring enzyme 1 (IRE1), is central to the unfolded protein response (UPR), a pathway vital for restoring proteostasis.
• Dysregulated IRE1 signaling is implicated in pathologies such as diabetes, neurodegenerative diseases, and cancer.
• IRE1 activation involves auto-phosphorylation and oligomerization, leading to endoribonuclease activity that splices XBP1 mRNA and degrades other RNAs via RIDD.

Purpose of the Study:

• To provide detailed protocols for studying IRE1 activation and signaling.
• To establish gold-standard experimental strategies for investigating IRE1 function in physiological and pathological contexts.

Main Methods:

• Phos-tag gels to assess IRE1 phosphorylation.
• Microscopy in TREX-IRE1-GFP cells to quantify IRE1 oligomerization.
• Conventional RT-PCR to analyze XBP1 mRNA splicing.
• Quantitative PCR to measure UPR target gene expression and RIDD activity.

Main Results:

• Detailed protocols for four distinct assays measuring IRE1 activation are presented.
• These methods allow for comprehensive evaluation of IRE1 phosphorylation, oligomerization, XBP1 splicing, and RIDD activity.
• The study establishes a framework for standardized IRE1 signaling analysis.

Conclusions:

• The presented experimental strategies serve as gold standards for studying IRE1 signaling.
• Accurate assessment of IRE1 activation is critical for understanding its role in UPR and associated diseases.
• These protocols will facilitate reproducible research into IRE1's physiological and pathological functions.