Thin filament protein isoform composition remains stable in adults despite turnover rates of 3 to 10 days, and is unaffected by aging, ischemia, or dilated cardiomyopathy.
This review highlights that while thin filament protein isoforms switch during development, they remain stable in adulthood and disease, with troponin I cleavage serving as a marker of irreversible myocardial injury rather than reversible stunning.
In the heart, the contractile apparatus is adapted to the specific demands of the organ for continuous rhythmic contraction. The specialized contractile properties of heart muscle are attributable to the expression of cardiac-specific isoforms of contractile proteins. This review describes the isoforms of the thin filament proteins actin and tropomyosin and the three troponin subunits found in human heart muscle, how the isoform profiles of these proteins change during development and disease, and the possible functional consequences of these changes. During development of the heart, there is a distinctive switch of isoform expression at or shortly after birth; however, during adult life, thin filament protein isoform composition seems to be stable despite protein turnover rates of 3 to 10 days. The pattern of isoforms of actin, tropomyosin, troponin I, troponin C, and troponin T is not affected by aging or heart disease (ischemia and dilated cardiomyopathy). The evidence for proteolysis of thin filament proteins in situ during ischemia and stunning is evaluated, and it is concluded that C-terminal cleavage of troponin I is a feature of irreversibly injured myocardium but may not play a role in reversible stunning.
Marston et al. (Thu,) conducted a review in Heart disease (ischemia and dilated cardiomyopathy). Thin filament protein isoform composition remains stable in adults despite turnover rates of 3 to 10 days, and is unaffected by aging, ischemia, or dilated cardiomyopathy.