Genotoxicity-Stimulated and CYLD-Driven Malignant Transformation.

Area of Science:

• Cellular Biology
• Molecular Oncology
• Signal Transduction

Background:

• Oxidative stress and DNA damage can activate TNF-R1 and c-Abl, promoting cytoplasmic translocation.
• Persistent cytoplasmic c-Abl is linked to cellular transformation.
• c-Abl's phosphorylation of OTULIN disrupts its interaction with LUBAC, initiating a signaling cascade.

Purpose of the Study:

• To elucidate the role of c-Abl, OTULIN, LUBAC, SPATA2, CYLD, and IKKβ in NF-κB activation following genotoxic stress.
• To investigate the dual role of CYLD as both an oncoprotein and tumor suppressor in cellular signaling.
• To understand the mechanism by which CYLD regulates NF-κB activity and cellular homeostasis.

Main Methods:

• Investigated molecular interactions including c-Abl-OTULIN, OTULIN-LUBAC, LUBAC-SPATA2, and SPATA2-CYLD.
• Analyzed the phosphorylation events on OTULIN (tyrosine 56) and CYLD (serine 568).
• Examined the activation of IKKβ and subsequent NF-κB transcriptional activity.

Main Results:

• c-Abl phosphorylates OTULIN, leading to LUBAC release and recruitment to the TNF-R1 complex.
• This facilitates SPATA2-CYLD interaction, crucial for IKKβ activation and NF-κB signaling.
• IKKβ-mediated phosphorylation of CYLD at serine 568 is essential for its deubiquitinating activity and termination of signaling.

Conclusions:

• CYLD exhibits dual activity, initiating NF-κB signaling as an oncoprotein and terminating it as a tumor suppressor.
• Failure in CYLD phosphorylation by IKKβ leads to sustained oncogenic activity and dysregulated NF-κB.
• This dysregulation disrupts cellular homeostasis, favoring transformation and potentially contributing to cancer development.