Affiliation:
1. Department of Integrative Physiology and Neuroscience Washington State University, Pullman, WA
Abstract
Background
We hypothesized that the functional effects of R206L—a rat analog of the dilated cardiomyopathy (
DCM
) mutation R205L in human cardiac troponin T (TnT)—were differently modulated by myosin heavy chain (
MHC
) isoforms and T204E, a protein kinase C (
PKC
) phosphomimic of TnT. Our hypothesis was based on two observations: (1) α‐ and β‐
MHC
differentially influence the functional effects of TnT; and (2)
PKC
isoforms capable of phosphorylating TnT are upregulated in failing human hearts.
Methods and Results
We generated 4 recombinant TnT variants: wild type; R206L; T204E; and R206L+T204E. Functional effects of the TnT variants were tested in cardiac muscle fibers (minimum 14 per group) from normal (α‐
MHC
) and propylthiouracil‐treated rats (β‐
MHC
) using steady‐state and dynamic contractile measurements. Notably, in α‐
MHC
fibers, Ca
2+
‐activated maximal tension was attenuated by R206L (≈32%), T204E (≈63%), and R206L+T204E (≈64%). In β‐
MHC
fibers, maximal tension was unaffected by R206L, but was attenuated by T204E (≈33%) and R206L+T204E (≈40%). Thus, β‐
MHC
differentially counteracted the attenuating effects of the TnT variants on tension. However, in β‐
MHC
fibers, R206L+T204E attenuated tension to a greater extent when compared to T204E alone. In β‐
MHC
fibers, R206L+T204E attenuated the magnitude of the length‐mediated recruitment of new cross‐bridges (≈28%), suggesting that the Frank‐Starling mechanism was impaired.
Conclusions
Our findings are the first (to our knowledge) to demonstrate that the functional effects of a
DCM
‐linked TnT mutation are not only modulated by
MHC
isoforms, but also by the pathology‐associated post‐translational modifications of TnT.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine
Cited by
4 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献