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XIAP Interacts with and Regulates the Activity of FAF1
Marcos J Caballero-López1, Manuel Nieto-Díaz1, Mónica Yunta2
1Molecular Neuroprotection Laboratory, Hospital Nacional de Parapléjicos, SESCAM, Toledo, Spain.
Abstract:
Cell death depends on the balance between the activities of pro- and anti-apoptotic factors. X-linked inhibitor of apoptosis protein (XIAP) plays an important role in the cytoprotective process by inhibiting the caspase cascade and regulating pro-survival signaling pathways. While searching for novel interacting partners of XIAP, we identified Fas-associated factor 1 (FAF1). Contrary to XIAP, FAF1 is a pro-apoptotic factor that also regulates several signaling pathways in which XIAP is involved. However, the functional relationship between FAF1 and XIAP is unknown. Here, we describe a new interaction between XIAP and FAF1 and describe the functional implications of their opposing roles in cell death and NF-κB signaling. Our results clearly demonstrate the interaction of XIAP with FAF1 and define the specific region of the interaction. We observed that XIAP is able to block FAF1-mediated cell death by interfering with the caspase cascade and directly interferes in NF-κB pathway inhibition by FAF1. Furthermore, we show that XIAP promotes ubiquitination of FAF1. Conversely, FAF1 does not interfere with the anti-apoptotic activity of XIAP, despite binding to the BIR domains of XIAP; however, FAF1 does attenuate XIAP-mediated NF-κB activation. Altered expression of both factors has been implicated in degenerative and cancerous processes; therefore, studying the balance between XIAP and FAF1 in these pathologies will aid in the development of novel therapies.
Insights
The X-linked inhibitor of apoptosis protein (XIAP) interacts with Fas-associated factor 1 (FAF1), a pro-apoptotic factor. XIAP blocks FAF1-induced cell death and regulates NF-κB signaling, offering therapeutic insights.
Area of Science:
- Cellular biology
- Molecular mechanisms of cell death
- Apoptosis and cell survival signaling
Background:
- Cell death is regulated by the balance of pro- and anti-apoptotic factors.
- X-linked inhibitor of apoptosis protein (XIAP) is a key anti-apoptotic factor inhibiting caspases and regulating survival pathways.
- Fas-associated factor 1 (FAF1) is a pro-apoptotic factor involved in similar signaling pathways to XIAP.
Purpose of the Study:
- To investigate the functional relationship between XIAP and FAF1.
- To identify the interaction between XIAP and FAF1.
- To elucidate their opposing roles in cell death and NF-κB signaling.
Main Methods:
- Protein-protein interaction studies to identify and map the XIAP-FAF1 interaction.
- Caspase cascade activity assays.
- NF-κB pathway activation and inhibition assays.
- Ubiquitination assays.
Main Results:
- Demonstrated a direct interaction between XIAP and FAF1, defining the specific interaction regions.
- XIAP inhibits FAF1-mediated cell death by interfering with the caspase cascade.
- XIAP blocks FAF1's inhibition of the NF-κB pathway.
- XIAP promotes FAF1 ubiquitination.
- FAF1 binding to XIAP's BIR domains does not impede XIAP's anti-apoptotic function but attenuates XIAP-mediated NF-κB activation.
Conclusions:
- XIAP and FAF1 interact, with XIAP acting as a negative regulator of FAF1's pro-apoptotic functions.
- The balance between XIAP and FAF1 influences cell death and NF-κB signaling.
- Understanding this interplay is crucial for developing therapies for degenerative diseases and cancer.