Somatic mutations in IRE1α regulate keratinocyte migration and survival by differentially activating Rho GTPases

Area of Science:

• Molecular Biology
• Cancer Research
• Cell Biology

Background:

• IRE1α (inositol-requiring enzyme 1 alpha) is an endoplasmic reticulum protein with kinase and endoribonuclease (RNase) domains.
• IRE1α regulates cellular responses to stress, including Xbp1 mRNA splicing and regulated IRE1α-dependent decay (RIDD) of other mRNAs.
• Somatic mutations in IRE1α are found in various human cancers, including non-melanoma skin cancer (NMSC).

Purpose of the Study:

• To investigate the role of IRE1α mutations, particularly those found in NMSC, in skin cancer pathogenesis.
• To understand the functional consequences of these mutations on cellular processes like migration, DNA repair, and stress response.

Main Methods:

• Generated immortalized mouse keratinocytes with inducible expression of engineered and cancer-associated IRE1α mutations.
• Utilized RNA-sequencing (RNA-Seq) for pathway analysis.
• Performed in vitro studies to assess cell migration, RhoA and Rac1 activation, and response to UVB irradiation.

Main Results:

• NMSC-associated IRE1α mutations were activating, showing increased autophosphorylation and enhanced RIDD activity compared to Xbp1 splicing.
• RNase-impaired mutations increased cell migration via elevated RhoA and Angptl4.
• Activating mutations led to increased Rac1 activation, DNA repair gene enrichment, elevated phospho-ATR, and improved UVB resistance.

Conclusions:

• IRE1α mutations in keratinocytes exhibit divergent functions, contributing to tumor promotion.
• Specific IRE1α mutations enhance cell migration and survival, crucial events in skin cancer development.
• These findings highlight the multifaceted role of IRE1α dysregulation in NMSC pathogenesis.