Thesis Format

Monograph

Roles of STIM1 Cys56 and Cys49 in Store-Operated Ca2+ Entry and Cardiac Rhythm during Myocardial Ischemia and Reperfusion

Author

Kaiyuan Wang, The University of Western OntarioFollow

Degree

Master of Science

Program

Physiology and Pharmacology

Supervisor

Feng Qingping

Abstract

Calcium (Ca²⁺) overload and oxidative stress are major pathological mechanisms underlying cardiac injury and arrhythmogenesis during myocardial ischemia and reperfusion. Stromal interaction molecule 1 (STIM1) regulates store-operated Ca²⁺ entry (SOCE) in cardiomyocytes. Upon Ca²⁺ depletion in sarcoplasmic reticulum, STIM1 activates Ca²⁺-release-activated channel (CRAC) to mediate SOCE. Excessive or insufficient SOCE activities increase the risk of cardiac arrhythmias. STIM1 Cys56/49Ala double mutation decreases SOCE activation while oxidant-induced S-glutathionylation of Cys56 upregulates SOCE. This thesis tested the hypothesis that STIM1 Cys56Ser or Cys49Ser mutation leads to SOCE dysregulation and enhances cardiac arrhythmia in myocardial I/R injury. The results show that STIM1 Cys56Ser or Cys49Ser mutant mice exhibited a significantly higher incidence of cardiac arrhythmias than WT mice during myocardial I/R. In STIM1 mutant cardiomyocytes, basal SOCE activities were reduced while H₂O₂ stimulated SOCE activities were enhanced. Collectively, these data show important physiological roles of STIM1 Cys49 and Cys56 in regulating SOCE activity and protecting the heart from cardiac arrhythmia during myocardial I/R.

Summary for Lay Audience

As a leading cause of death worldwide, myocardial infarction (MI) is characterized by the blockage of the coronary artery resulting in myocardial death and progression to heart failure. Timely reperfusion to the heart is the most effective therapy to reduce ischemic injury and limit infarct size. However, reperfusion itself can also cause reperfusion injuries including reperfusion-related cardiac arrhythmia. Calcium (Ca²⁺) overload and oxidative stress play important roles in the generation of cardiac arrhythmia and myocardial cell death during myocardial ischemia and reperfusion. Stromal interaction molecule 1 (STIM1) is a Ca²⁺ sensory protein that regulates store-operated Ca²⁺ entry (SOCE) in various cell types, including cardiomyocytes. The endoplasmic reticulum or sarcoplasmic reticulum (ER/SR) is the major Ca²⁺ storage site in the cells. Upon Ca²⁺ depletion in the sarcoplasmic reticulum, STIM1 activates SOCE through the Ca²⁺-release-activated channel (CRAC) to mediate Ca²⁺ influx into the cells. Excessive or insufficient SOCE activities can increase the risk of cardiac arrhythmias. Mutations on STIM1 were found to cause abnormal SOCE activities in the cells and cardiac arrhythmia in human patients. Specifically, cellular studies have shown that STIM1 Cys56/49Ala double mutation decreases SOCE activation while oxidant-induced S-glutathionylation of Cys56 upregulates SOCE. This thesis tested the hypothesis that STIM1 Cys56Ser or Cys49Ser mutation leads to SOCE dysregulation and enhances cardiac arrhythmia in myocardial ischemia/reperfusion (I/R) injury. The results show that STIM1 Cys56Ser or Cys49Ser mutant mice exhibited a significantly higher incidence of cardiac arrhythmias than WT mice during myocardial I/R. The SOCE activity in STIM1 mutant cardiomyocytes was lower in basal conditions compared to the wild-type (WT) cells. However, introducing oxidative stress by H₂O₂ treatment enhanced SOCE activities in the mutant cardiomyocytes but not in the WT cells. Collectively, these data show important physiological roles of STIM1 Cys49 and Cys56 in regulating SOCE activity and protecting the heart from cardiac arrhythmia during myocardial I/R.

Recommended Citation

Wang, Kaiyuan, "Roles of STIM1 Cys56 and Cys49 in Store-Operated Ca2+ Entry and Cardiac Rhythm during Myocardial Ischemia and Reperfusion" (2022). Electronic Thesis and Dissertation Repository. 8993.
https://ir.lib.uwo.ca/etd/8993