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Use of the yeast three-hybrid system as a tool to study caspases
W Van Criekinge1, M van Gurp, E Decoster
1Department of Molecular Biology, Flanders Interuniversity Institute for Biotechnology and University of Gent, Gent, B-9000, Belgium.
Abstract:
Caspases are a family of heteromeric (p20/p10) cysteine proteases with important functions in the regulation of apoptosis and inflammation. Up to now, tools to identify new substrates for caspases have mostly been limited to the random screening of in vitro translated proteins that are known, or assumed, to play a role in apoptosis. We describe the use of a yeast three-hybrid approach as a tool that adapts the classical two-hybrid system to the needs of heteromeric caspases for functional dissection of known interactions or screening for physiological substrates and inhibitors. Functional heteromeric caspase-1 was obtained by coexpression of p20(Cys285Ser) and p10 caspase-1 subunits that were each fused to the Gal4 DNA-binding domain. Upon coexpression of a third hybrid of the Gal4 activation domain and the viral caspase-1 pseudosubstrate inhibitors CrmA or p35, or the prototype physiological caspase-1 substrate prointerleukin-1beta, a functional Gal4 transcription factor could be reconstituted. In contrast, no interaction was found between CrmA or p35 and the immature p45 or p30 precursor forms of caspase-1. Therefore, the three-hybrid system might allow screening for new physiological substrates and inhibitors of heteromeric caspases.
Insights
A novel yeast three-hybrid system enables the identification of new caspase substrates and inhibitors. This method successfully identified interactions with functional caspase-1, but not its precursor forms.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Caspases are critical cysteine proteases regulating apoptosis and inflammation.
- Existing methods for identifying caspase substrates are limited, often relying on random screening of apoptosis-related proteins.
Purpose of the Study:
- To develop and validate a yeast three-hybrid system for studying heteromeric caspases.
- To adapt the classical two-hybrid system for dissecting caspase interactions and screening for substrates and inhibitors.
Main Methods:
- Utilized a yeast three-hybrid system by coexpressing caspase-1 subunits (p20 and p10) fused to the Gal4 DNA-binding domain.
- Introduced a third hybrid containing the Gal4 activation domain fused to known caspase-1 inhibitors (CrmA, p35) or a substrate (prointerleukin-1beta).
Main Results:
- Reconstitution of a functional Gal4 transcription factor was observed upon coexpression with inhibitors or the substrate.
- No interaction was detected between inhibitors and the immature precursor forms (p45, p30) of caspase-1.
Conclusions:
- The yeast three-hybrid system is a viable tool for functional dissection of heteromeric caspases.
- This system holds potential for screening novel physiological substrates and inhibitors of caspases.