Key Points
- To determine how dilated cardiomyopathy mutations (R141W and ΔK210) engineered into the fetal troponin T isoform (TnT1) impair cardiac contractile function.
- Engineered dilated cardiomyopathy mutations R141W and ΔK210 into recombinant human fetal cardiac troponin T (TnT1).
- Reconstituted detergent-skinned porcine cardiac muscle fibers with troponin complexes containing cardiac troponin I or slow skeletal troponin I alongside troponin C.
- Measured calcium sensitivity of isometric force development and actomyosin ATPase activity across neutral (pH 7.0) and acidic (pH 6.5) conditions.
- TnT1 mutations R141W and ΔK210 significantly decreased calcium sensitivity of force development relative to wild-type TnT1 when reconstituted with either cardiac or slow skeletal troponin I complexes at both pH 7.0 and pH 6.5.
- The ΔK210 mutation caused a larger reduction in calcium sensitivity and maximal isometric force development than R141W across both fetal and adult troponin T isoforms.
- Both mutations markedly suppressed maximal actomyosin ATPase activity compared with wild-type TnT1 when complexed with either troponin I isoform.
Structured PICO
Do TnT1 DCM mutations (R141W and ΔK210) alter Ca2+ sensitivity and actomyosin ATPase activity in fetal troponin isoforms?
PPopulationPorcine cardiac skinned fibers
IInterventionReconstitution with fetal TnT1 isoform containing dilated cardiomyopathy (DCM) mutations (R141W and ΔK210) and cardiac TnI·TnC or ssTnI·TnC
CComparatorReconstitution with TnT1-wild-type (WT) or TnT3-WT
OOutcomeCa2+ sensitivity of force development and maximal actomyosin ATPase activitysurrogate
Decreased maximal actomyosin ATPase activity and Ca2+ sensitivity of force development caused by DCM mutations in the fetal TnT1 isoform may explain the severe infantile DCM phenotype.