Phosphoregulation of the Titin-cap Protein Telethonin in Cardiac Myocytes

Alexandra J. Candasamy, Robert S. Haworth, Friederike Cuello, Michael Ibrahim, Sriram Aravamudhan, Marcus Krueger, Mark R. Holt, Cesare M. N. Terracciano, Manuel Mayr, Mathias Gautel, Metin Avkiran*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)
146 Downloads (Pure)

Abstract

Telethonin (also known as titin-cap or t-cap) is a muscle-specific protein whose mutation is associated with cardiac and skeletal myopathies through unknown mechanisms. Our previous work identified cardiac telethonin as an interaction partner for the protein kinase D catalytic domain. In this study, kinase assays used in conjunction with MS and site-directed mutagenesis confirmed telethonin as a substrate for protein kinase D and Ca2+/calmodulin-dependent kinase II in vitro and identified Ser-157 and Ser-161 as the phosphorylation sites. Phosphate affinity electrophoresis and MS revealed endogenous telethonin to exist in a constitutively bis-phosphorylated form in isolated adult rat ventricular myocytes and in mouse and rat ventricular myocardium. Following heterologous expression in myocytes by adenoviral gene transfer, wild-type telethonin became bis-phosphorylated, whereas S157A/S161A telethonin remained non-phosphorylated. Nevertheless, both proteins localized predominantly to the sarcomeric Z-disc, where they partially replaced endogenous telethonin. Such partial replacement with S157A/S161A telethonin disrupted transverse tubule organization and prolonged the time to peak of the intracellular Ca2+ transient and increased its variance. These data reveal, for the first time, that cardiac telethonin is constitutively bis-phosphorylated and suggest that such phosphorylation is critical for normal telethonin function, which may include maintenance of transverse tubule organization and intracellular Ca2+ transients.

Original languageEnglish
Pages (from-to)1282-1293
Number of pages12
JournalJournal of Biological Chemistry
Volume289
Issue number3
Early online date1 Jan 2014
DOIs
Publication statusPublished - 17 Jan 2014

Keywords

  • CaMKII
  • Cardiac Muscle
  • Cardiomyopathy
  • Excitation-Contraction Coupling
  • Protein Kinase D (PKD)
  • Protein Phosphorylation
  • SARCOMERIC PROTEIN
  • KINASE-D
  • Z-DISC
  • DILATED CARDIOMYOPATHY
  • MUSCULAR-DYSTROPHY
  • TUBULE STRUCTURE
  • MAMMALIAN HEART
  • TROPONIN-I
  • T-CAP
  • PHOSPHORYLATION

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