TNNI3K is a novel mediator of myofilament function and phosphorylates cardiac troponin I

Abstract

The phosphorylation of cardiac troponin I (cTnI) plays an important role in the contractile dysfunction associated with heart failure. Human cardiac troponin I-interacting kinase (TNNI3K) is a novel cardiac-specific functional kinase that can bind to cTnI in a yeast two-hybrid screen. The purpose of this study was to investigate whether TNNI3K can phosphorylate cTnI at specific sites and to examine whether the phosphorylation of cTnI caused by TNNI3K can regulate cardiac myofilament contractile function. Co-immunoprecipitation was performed to confirm that TNNI3K could interact with cTnI. Kinase assays further indicated that TNNI3K did not phosphorylate cTnI at Ser23/24 and Ser44, but directly phosphorylated Ser43 and Thr143 in vitro. The results obtained for adult rat cardiomyocytes also indicated that enhanced phosphorylation of cTnI at Ser43 and Thr143 correlated with rTNNI3K (rat TNNI3K) overexpression, and phosphorylation was reduced when rTNNI3K was knocked down. To determine the contractile function modulated by TNNI3K-mediated phosphorylation of cTnI, cardiomyocyte contraction was studied in adult rat ventricular myocytes. The contraction of cardiomyocytes increased with rTNNI3K overexpression and decreased with rTNNI3K knockdown. We conclude that TNNI3K may be a novel mediator of cTnI phosphorylation and contribute to the regulation of cardiac myofilament contraction function.

Inhibition of the Cardiomyocyte-Specific Troponin I–Interacting Kinase Limits Oxidative Stress, Injury, and Adverse Remodeling due to Ischemic Heart Disease

“…These data are in contrast with prior work showing that TNNI3K localizes to the sarcomere Z disc 5 and also conflicts with a recent study suggesting that troponin I may indeed be a substrate of TNNI3K. 6 These data do, however, add to a growing literature investigating the relevance of TNNI3K in cardiac function. This cardiac-specific kinase was first identified nearly a decade ago in a yeast2-hybrid screen for proteins that interact with cardiac troponin I.…”

“…Phosphorylation of cardiac troponin I is known to affect myofilament sensitivity and cardiac inotropy. 6 Overexpression of TNNI3K has been shown to enhance phosphorylation at serine 43 and threonine 143 and was associated with increased isolated myocyte contractility. 6 In addition, overexpression of TNNI3K is associated with increased sarcomere length and titin isoform switching, which were independent of p38 phosphorylation.…”

“…6 Overexpression of TNNI3K has been shown to enhance phosphorylation at serine 43 and threonine 143 and was associated with increased isolated myocyte contractility. 6 In addition, overexpression of TNNI3K is associated with increased sarcomere length and titin isoform switching, which were independent of p38 phosphorylation. 5 Both of these alterations would potentially have significant effects on cardiac systolic and diastolic function.…”

MicroRNA-223 Displays a Protective Role Against Cardiomyocyte Hypertrophy by Targeting Cardiac Troponin I-Interacting Kinase

“…It was shown that TNNI3K could promote concentric hypertrophy with enhancement of cardiac function via regulating the phosphorylation of cTnI [26] and thus contributed to the regulation of cardiac myofilament contraction [27]. Troponin I (TnI) is a known inhibitory unit of the troponin complex associated with the thin filament.…”

Overexpression of Cardiac-Specific Kinase TNNI3K Promotes Mouse Embryonic Stem Cells Differentiation into Cardiomyocytes

“…Kinases in this family share characteristic amino acid sequences of both tyrosine and serine/threonine kinases in the catalytic domain [9]. Integrin-linked kinase (ILK), is another member of the mixed-lineage family, which, to a large extent, is similar to the TNNI3K in structure, function, and gene sequences on the chromosome [10].…”