A troponin T mutation that causes infantile restrictive cardiomyopathy increases Ca2+ sensitivity of force development and impairs the inhibitory properties of troponin

作者：Pinto Jose R; Parvatiyar Michelle S; Jones Michelle A; Liang Jingsheng; Potter James D^*

来源：JOURNAL OF BIOLOGICAL CHEMISTRY, 2008, 283(4): 2156-2166.

DOI：10.1074/jbc.M707066200

Restrictive cardiomyopathy (RCM) is a rare disorder characterized by impaired ventricular filling with decreased diastolic volume. We are reporting the functional effects of the first cardiac troponin T (CTnT) mutation linked to infantile RCM resulting from a de novo deletion mutation of glutamic acid 96. The mutation was introduced into adult and fetal isoforms of human cardiac TnT (HCTnT3-Delta E96 and HCTnT1-Delta E106, respectively) and studied with either cardiac troponin I (CTnI) or slow skeletal troponin I (SSTnI). Skinned cardiac fiber measurements showed a large leftward shift in the Ca2+ sensitivity of force development with no differences in the maximal force. HCTnT1-Delta E106 showed a significant increase in the activation of actomyosin ATPase with either CTnI or SSTnI, whereas HCTnT3-Delta E96 was only able to increase the ATPase activity with CTnI. Both mutants showed an impaired ability to inhibit the ATPase activity. The capacity of the CTnI center dot CTnC and SSTnI center dot CTnC complexes to fully relax the fibers after TnT displacement was also compromised. Experiments performed using fetal troponin isoforms showed a less severe impact compared with the adult isoforms, which is consistent with the cardioprotective role of SSTnI and the rapid onset of RCM after birth following the isoform switch. These data indicate that troponin mutations related to RCM may have specific functional phenotypes, including large leftward shifts in the Ca2+ sensitivity and impaired abilities to inhibit ATPase and to relax skinned fibers. All of this would account for and contribute to the severe diastolic dysfunction seen in RCM.

• 出版日期2008-1-25