Cardiomyopathy-associated and basic residue mutations in myopalladin alter actin binding, bundling, and structural...

Area of Science:

• Muscle biology and protein structure
• Cardiovascular research
• Molecular genetics

Background:

• Myopalladin (MYPN) is crucial for sarcomere integrity in striated muscle.
• Mutations in MYPN's Ig3 domain are linked to cardiomyopathy (CM).
• Understanding MYPN-actin interactions is key to CM pathogenesis.

Purpose of the Study:

• To investigate the molecular mechanisms of MYPN-actin binding and bundling.
• To elucidate how CM-associated mutations in the MYPN Ig3 domain affect its function.
• To provide mechanistic insight into MYPN-associated cardiomyopathies.

Main Methods:

• Alanine-scanning mutagenesis of MYPN Ig3 domain.
• Co-sedimentation assays to assess actin binding and bundling.
• Circular dichroism and sedimentation equilibrium analysis.
• In vivo studies using Drosophila melanogaster models.

Main Results:

• Mutations in the MYPN Ig3 domain impair actin binding and bundling.
• The P961L variant exhibits altered conformation, leading to aggregation and mislocalization.
• MYPN Ig3 promotes actin polymerization and bundling independently of calcium.
• MYPN Ig3 functions as a monomer, bundling actin via dual binding sites.

Conclusions:

• Disruption of MYPN-actin interactions is a pathogenic mechanism in CM.
• Ig3 domain mutations impair actin dynamics and sarcomere organization.
• This study provides direct evidence linking MYPN Ig3 domain defects to cardiomyopathies.