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Interaction of Fas(Apo-1/CD95) with proteins implicated in the ubiquitination pathway
K Becker1, P Schneider, K Hofmann
1Institute of Biochemistry, University of Lausanne, Epalinges, Switzerland.
Abstract:
Fas(Apo-1/CD95), a receptor belonging to the tumor necrosis factor receptor family, induces apoptosis when triggered by Fas ligand. Upon its activation, the cytoplasmic domain of Fas binds several proteins which transmit the death signal. We used the yeast two-hybrid screen to isolate Fas-associated proteins. Here we report that the ubiquitin-conjugating enzyme UBC9 binds to Fas at the interface between the death domain and the membrane-proximal region of Fas. This interaction is also seen in vivo. UBC9 transiently expressed in HeLa cells bound to the co-expressed cytoplasmic segment of Fas. FAF1, a Fas-associated protein that potentiates apoptosis (Chu et al. (1996) Proc. Natl. Acad. Sci. USA 92, 11894-11898), was found to contain sequences similar to ubiquitin. These results suggest that proteins related to the ubiquitination pathway may modulate the Fas signaling pathway.
Insights
The ubiquitin-conjugating enzyme UBC9 binds to Fas, a receptor that triggers apoptosis. This discovery suggests ubiquitination pathway proteins may regulate Fas signaling, impacting programmed cell death.
Area of Science:
- Cell biology
- Molecular biology
- Biochemistry
Background:
- Fas (Apo-1/CD95) is a tumor necrosis factor receptor family member that initiates apoptosis upon Fas ligand binding.
- Activated Fas recruits intracellular proteins to relay the apoptotic death signal.
- Understanding Fas-associated proteins is crucial for elucidating apoptosis regulation.
Purpose of the Study:
- To identify proteins that associate with Fas using a yeast two-hybrid screen.
- To investigate the role of ubiquitination pathway components in Fas-mediated apoptosis.
- To characterize the interaction between UBC9 and Fas.
Main Methods:
- Yeast two-hybrid screening to identify Fas-binding proteins.
- In vivo co-expression and binding assays in HeLa cells.
- Sequence analysis of Fas-associated Factor 1 (FAF1).
Main Results:
- The ubiquitin-conjugating enzyme UBC9 was identified as a Fas-associated protein.
- UBC9 binds to Fas at the junction of its death domain and membrane-proximal region.
- This UBC9-Fas interaction was confirmed in vivo in HeLa cells.
- Fas-associated Factor 1 (FAF1) exhibits sequence similarity to ubiquitin.
Conclusions:
- The ubiquitin-conjugating enzyme UBC9 directly interacts with Fas.
- Proteins involved in the ubiquitination pathway, such as UBC9, may play a regulatory role in Fas-mediated apoptosis.
- These findings highlight a potential link between ubiquitination and the modulation of programmed cell death pathways.