Related Experiment Videos
Calpain silencing by a reversible intrinsic mechanism
Tudor Moldoveanu1, Christopher M Hosfield, Daniel Lim
1Department of Biochemistry and the Protein Engineering Network of Centres of Excellence, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Abstract:
Uncontrolled activation of calpain can lead to necrotic cell death and irreversible tissue damage. We have discovered an intrinsic mechanism whereby the autolysis-generated protease core fragment of calpain is inactivated through the inherent instability of a key alpha-helix. This auto-inactivation state was captured by the 1.9 A Ca(2+)-bound structure of the protease core from m-calpain, and sequence alignments suggest that it applies to about half of the calpain isoforms. Intact calpain large subunits are also subject to this inhibition, which can be prevented through assembly of the heterodimers. Other isoforms or their released cores are not silenced by this mechanism and might contribute to calpain patho-physiologies.
Insights
Calpain
Area of Science:
- Biochemistry
- Molecular Biology
- Cellular Biology
Background:
- Uncontrolled calpain activation causes cell death and tissue damage.
- Calpains are calcium-dependent proteases implicated in various pathologies.
Purpose of the Study:
- To elucidate the auto-inactivation mechanism of calpain protease core fragments.
- To investigate the structural basis of calpain auto-inhibition.
Main Methods:
- X-ray crystallography to determine the Ca(2+)-bound structure of m-calpain protease core.
- Sequence alignments to assess the prevalence of the auto-inactivation mechanism across calpain isoforms.
Main Results:
- A key alpha-helix instability in the calpain protease core mediates auto-inactivation.
- The 1.9 A Ca(2+)-bound structure revealed this auto-inactivated state.
- This mechanism applies to approximately 50% of calpain isoforms.
- Heterodimerization of intact calpain large subunits prevents this inhibition.
Conclusions:
- Calpain auto-inactivation via alpha-helix instability is an intrinsic regulatory mechanism.
- This mechanism provides a potential target for therapeutic intervention in calpain-related diseases.
- Certain calpain isoforms may escape this inactivation, contributing to pathological conditions.