Ablation of the calpain-targeted site in cardiac myosin binding protein-C is cardioprotective during ischemia-reperfusion injury

J Mol Cell Cardiol. 2019 Apr:129:236-246. doi: 10.1016/j.yjmcc.2019.03.006. Epub 2019 Mar 9.

Abstract

Cardiac myosin binding protein-C (cMyBP-C) phosphorylation is essential for normal heart function and protects the heart from ischemia-reperfusion (I/R) injury. It is known that protein kinase-A (PKA)-mediated phosphorylation of cMyBP-C prevents I/R-dependent proteolysis, whereas dephosphorylation of cMyBP-C at PKA sites correlates with its degradation. While sites on cMyBP-C associated with phosphorylation and proteolysis co-localize, the mechanisms that link cMyBP-C phosphorylation and proteolysis during cardioprotection are not well understood. Therefore, we aimed to determine if abrogation of cMyBP-C proteolysis in association with calpain, a calcium-activated protease, confers cardioprotection during I/R injury. Calpain is activated in both human ischemic heart samples and ischemic mouse myocardium where cMyBP-C is dephosphorylated and undergoes proteolysis. Moreover, cMyBP-C is a substrate for calpain proteolysis and cleaved by calpain at residues 272-TSLAGAGRR-280, a domain termed as the calpain-target site (CTS). Cardiac-specific transgenic (Tg) mice in which the CTS motif was ablated were bred into a cMyBP-C null background. These Tg mice were conclusively shown to possess a normal basal structure and function by analysis of histology, electron microscopy, immunofluorescence microscopy, Q-space MRI of tissue architecture, echocardiography, and hemodynamics. However, the genetic ablation of the CTS motif conferred resistance to calpain-mediated proteolysis of cMyBP-C. Following I/R injury, the loss of the CTS reduced infarct size compared to non-transgenic controls. Collectively, these findings demonstrate the physiological significance of calpain-targeted cMyBP-C proteolysis and provide a rationale for studying inhibition of calpain-mediated proteolysis of cMyBP-C as a therapeutic target for cardioprotection.

Keywords: Calpain; Cardioprotection; Ischemia-reperfusion injury; MYBPC3; cMyBP-C.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calpain / metabolism*
  • Cardiotonic Agents / metabolism*
  • Carrier Proteins / metabolism*
  • Female
  • Heart Function Tests
  • Humans
  • Male
  • Mice, Transgenic
  • Middle Aged
  • Myocardial Infarction / metabolism
  • Myocardial Reperfusion Injury / metabolism*
  • Myocardial Reperfusion Injury / physiopathology
  • Myocardium / metabolism*
  • Phosphorylation
  • Proteolysis

Substances

  • Cardiotonic Agents
  • Carrier Proteins
  • myosin-binding protein C
  • Calpain