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Biophysical characterization of the interaction between the full-length XIAP and Smac/DIABLO
Panagis Polykretis1, Enrico Luchinat2
1CERM - Magnetic Resonance Center, University of Florence, via Luigi Sacconi 6, 50019, Sesto Fiorentino, Florence, Italy.
Abstract:
XIAP is multi-functional protein which regulates apoptosis acting as a direct caspase inhibitor. It is overexpressed in cancer cells, where it antagonizes the pro-apoptotic action of chemotherapeutics, and therefore it has become an important target for the treatment of cancer. In cells undergoing programmed cell death, the pro-apoptotic protein Smac is released by the mitochondria and binds to XIAP, thereby blocking caspase inhibition. Thus, Smac is considered a master regulator of apoptosis in mammals. In this regard, several Smac mimetic compounds have been developed to inhibit XIAP activity in cancer tissues. These compounds have shown low efficacy, partly due to the lack of structural knowledge of the XIAP-Smac interaction. In this work, through SEC-MALS and circular dichroism, we provide the first biophysical characterization of the interaction between the full-length form of XIAP and Smac, determining the stoichiometry of the complex and providing important information to develop more effective XIAP inhibitors.
Insights
Understanding the interaction between X-linked inhibitor of apoptosis protein (XIAP) and Smac is crucial for developing effective cancer therapies. This study provides the first biophysical characterization of this interaction, aiding in the design of improved XIAP inhibitors.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- X-linked inhibitor of apoptosis protein (XIAP) is a key regulator of apoptosis and is overexpressed in cancer cells, where it promotes tumor survival.
- XIAP antagonizes chemotherapy by inhibiting caspases, making it a significant therapeutic target for cancer treatment.
- The pro-apoptotic protein Smac (Second mitochondria-derived activator of caspases) binds to XIAP, blocking its inhibitory activity and promoting programmed cell death.
Purpose of the Study:
- To provide the first biophysical characterization of the interaction between full-length XIAP and Smac.
- To determine the stoichiometry of the XIAP-Smac complex.
- To generate structural insights for the development of more effective XIAP inhibitors.
Main Methods:
- Size exclusion chromatography coupled with multi-angle light scattering (SEC-MALS).
- Circular dichroism (CD) spectroscopy.
Main Results:
- The study presents the first biophysical characterization of the full-length XIAP-Smac interaction.
- Stoichiometry of the XIAP-Smac complex was determined.
- Key biophysical information was obtained to guide the development of novel XIAP inhibitors.
Conclusions:
- Understanding the biophysical properties of the XIAP-Smac interaction is essential for designing potent XIAP-targeting cancer therapeutics.
- The generated data provides a foundation for structure-based drug design of improved XIAP inhibitors.
- This work contributes to the field of apoptosis regulation and cancer therapy development.
