Impact of disease-causing mutations on inter-domain interactions in cMyBP-C: a steered molecular dynamics study

Area of Science:

• Cardiovascular biology
• Molecular cardiology
• Biophysics

Background:

• Sarcomeric protein interactions regulate cardiac function.
• Mutations in MYBPC3, encoding cardiac myosin-binding protein-C (cMyBP-C), are a leading cause of hypertrophic cardiomyopathy (HCM).
• The N-terminal C1-C2 complex of cMyBP-C is crucial for cardiac muscle contraction regulation, but its unbinding mechanisms in health and disease remain unclear.

Purpose of the Study:

• To investigate the molecular mechanisms of C1-C2 complex unbinding in wild-type and hypertrophic cardiomyopathy (HCM)-associated mutant forms of cMyBP-C.
• To elucidate how specific mutations (E258K in C1, E441K in C2, and a double mutation) affect the stability and unbinding dynamics of the cMyBP-C N-terminal complex.

Main Methods:

• Utilized steered molecular dynamics (SMD) simulations to model the unbinding pathways of the cMyBP-C C1-C2 complex.
• Simulated wild-type, single (E258K in C1, E441K in C2), and double (E258K in C1 + E441K in C2) mutant complexes.
• Calculated the force required for domain unbinding to quantify changes in complex stability.

Main Results:

• The double mutation results in a more rigid complex, requiring significantly higher force and longer simulation times for unbinding.
• Unbinding initiates with the C1 domain preceding the C2 domain, irrespective of the mutation.
• The C2 domain consistently requires greater force to unbind compared to the C1 domain across all simulated conditions.

Conclusions:

• HCM-associated mutations in cMyBP-C can alter the native binding affinity of its N-terminal domains.
• These alterations in domain assembly and stability are critical for normal cardiac function and may underlie HCM pathogenesis.
• Understanding these molecular unbinding mechanisms provides insight into HCM development and potential therapeutic targets.