COOH-terminal truncated human cardiac MyBP-C alters myosin filament organization

Area of Science:

• Muscle biology
• Cardiovascular research
• Molecular genetics

Background:

• Myosin-binding protein C (MyBP-C) is crucial for striated muscle structure and regulation.
• Mutations in cardiac MyBP-C are linked to familial hypertrophic cardiomyopathy, often resulting in truncated proteins.
• Understanding the impact of these truncated proteins on muscle structure is vital for disease mechanism elucidation.

Purpose of the Study:

• To investigate the structural consequences of truncated cardiac MyBP-C on alpha-myosin heavy chain (alpha-MyHC) filament organization.
• To compare the effects of full-length and truncated human cardiac MyBP-C on MyHC organization.
• To determine if truncated MyBP-C contributes to sarcomeric disorganization in familial hypertrophic cardiomyopathy.

Main Methods:

• Transient expression of cDNA constructs for rat alpha-MyHC and human cardiac MyBP-C (full-length and truncated) in COS cells.
• Characterization of alpha-MyHC filament organization in the presence of MyBP-C variants.
• Analysis of MyBP-C's N-terminal peptide interactions with MyHC.

Main Results:

• Full-length cardiac MyBP-C organized MyHC into dense, uniformly wide structures.
• A truncated cardiac MyBP-C peptide, while stable and capable of MyHC interaction, did not produce the same organized structure as the full-length protein.
• The truncated MyBP-C variant led to disorganization of sarcomeric MyHC.

Conclusions:

• Truncated cardiac MyBP-C, a common outcome of familial hypertrophic cardiomyopathy mutations, impairs the proper organization of myosin filaments.
• The structural disorganization caused by truncated MyBP-C likely contributes to the pathogenesis of familial hypertrophic cardiomyopathy.
• These findings highlight the importance of the full-length MyBP-C structure for maintaining sarcomeric integrity.