Cardiomyopathy-causing deletion K210 in cardiac troponin T alters phosphorylation propensity of sarcomeric proteins

Area of Science:

• Cardiology
• Molecular Biology
• Biochemistry

Background:

• Familial dilated cardiomyopathy (DCM) is often linked to mutations in cardiac troponin T (cTnT).
• The deletion of lysine 210 (DeltaK210) in cTnT is a known cause of DCM, primarily through myofilament calcium desensitization.
• Phosphorylation of sarcomeric proteins is a critical regulator of cardiac function and may influence DCM progression.

Purpose of the Study:

• To investigate the impact of the DeltaK210 mutation in cTnT on the phosphorylation patterns of sarcomeric proteins.
• To explore how DeltaK210 affects protein-protein interactions within the sarcomere.
• To elucidate the molecular mechanisms underlying DeltaK210-associated DCM.

Main Methods:

• Analysis of cardiac myofibrils from DeltaK210 knock-in mice and wild-type controls.
• Immunoblotting with phospho-specific antibodies.
• In vitro kinase assays.
• Molecular modeling of cTnT structure.
• Yeast two-hybrid assays to assess protein binding.

Main Results:

• Decreased phosphorylation of cardiac troponin I (cTnI), cTnT, and myosin-binding protein C (MyBP-C) in DeltaK210 hearts.
• Increased phosphorylation of cTnT at Thr(203) and decreased phosphorylation of cTnI at Ser(23/24) in mutant myocardium.
• In vitro assays showed DeltaK210 enhances cTnT-Thr(203) phosphorylation.
• Molecular modeling indicated altered electrostatic environment around cTnT Thr(203) in DeltaK210.
• Yeast two-hybrid assays revealed stronger binding between cTnT-DeltaK210 and cTnI.

Conclusions:

• The DeltaK210 mutation significantly alters the phosphorylation status of key sarcomeric proteins, including cTnI and cTnT.
• These alterations in post-translational modifications, alongside changes in cTnI-cTnT binding, contribute to the pathogenesis of DCM.
• The findings provide insights into the complex molecular mechanisms driving DeltaK210-associated cardiomyopathy.