Atomic resolution probe for allostery in the regulatory thin filament

Area of Science:

• Cardiovascular Biology
• Molecular Biophysics
• Computational Biology

Background:

• Calcium binding and dissociation in the cardiac thin filament (CTF) regulates heart contraction and relaxation.
• Disruptions in this process are linked to human diseases, but atomic-level mechanisms are poorly understood, hindering targeted therapy development.

Purpose of the Study:

• To investigate the atomic-level mechanisms by which mutations in cardiac troponin complexes affect calcium binding and dissociation.
• To elucidate the role of cardiac troponin T mutations in genetic cardiomyopathies and their impact on cardiac function.

Main Methods:

• Utilized a fully atomistic CTF model to simulate Ca(2+) binding and dissociation in wild-type (WT) and mutant troponin complexes.
• Performed in vitro measurements of Ca(2+) dissociation rates in reconstituted WT and mutant cardiac troponin T filaments (R92L and R92W).
• Analyzed structural and dynamic changes induced by mutations distant from the primary calcium-binding site.

Main Results:

• Mutations in cardiac troponin T (R92L, R92W) did not affect Ca(2+) binding affinity or EF-hand structure but altered Ca(2+) interaction with cardiac troponin I.
• Demonstrated an indirect mechanism where mutations in one protein subunit alter interactions with a third protein via dynamic changes in a second.
• Observed mutation-specific alterations in thin filament function, leading to distinct pathogenic states in genetic cardiomyopathies.

Conclusions:

• Cardiac troponin T mutations can indirectly impact cardiac function by altering Ca(2+) interactions with cardiac troponin I through a novel allosteric mechanism.
• Provides atom-level insights into mutation-specific disease mechanisms, offering potential targets for novel therapeutic interventions in genetic cardiomyopathies.
• Highlights the importance of considering indirect allosteric effects in understanding and treating cardiovascular diseases.