cIAP1 regulates TNF-mediated cdc42 activation and filopodia formation

Area of Science:

• Cell Biology
• Molecular Biology
• Cancer Research

Background:

• Tumour necrosis factor-α (TNF) is a pleiotropic cytokine involved in various cellular processes.
• TNF receptor signaling typically activates NF-κB through a complex including TRAF2, RIP1, and cIAP1.
• The role of cIAP1 in non-NF-κB pathways, particularly cytoskeleton dynamics, remains less understood.

Purpose of the Study:

• To investigate the role of cIAP1 in TNF-induced actin cytoskeleton reorganization.
• To elucidate the molecular mechanism linking cIAP1, cdc42, and actin remodeling.
• To determine the impact of cIAP1 on cell transformation and tumor progression.

Main Methods:

• Utilized cIAP1-deficient (cIAP1(-/-)) mouse embryonic fibroblasts (MEFs).
• Employed genetic manipulation including gene deletion, expression of cIAP1 mutants, and gene silencing (TRAF2, RIP1).
• Investigated protein-protein interactions (cIAP1-cdc42) and downstream effects on actin cytoskeleton, cell polarization, adhesion, and tumor growth models.

Main Results:

• cIAP1 deletion abrogated TNF-induced filopodia formation and cdc42 activation, independent of NF-κB.
• cIAP1's E3 ligase activity and TRAF2 binding were crucial for filopodia formation.
• cIAP1 directly binds and stabilizes cdc42, with TNF signaling reducing this interaction to promote actin remodeling.
• cIAP1 deficiency impaired cell polarization, adhesion, and intercalation, and suppressed HRas-V12-mediated transformation, including tumor growth and metastasis.

Conclusions:

• cIAP1 plays a critical role in regulating actin cytoskeleton dynamics through a novel NF-κB-independent pathway involving cdc42 stabilization.
• This cIAP1-cdc42 axis is essential for TNF-induced cellular responses and influences oncogenic transformation and tumor progression.