Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Windhager, I.
Expression and phosphorylation of Ca2+ handling proteins in murine hearts with a ryanodine receptor mutation after pressure-induced hypertrophy
[ Diplomarbeit ] Medical University of Graz; 2012. pp. 63
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- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Kockskämper Jens
- Sedej Simon
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- Abstract:
- BACKGROUND: Cardiac ryanodine receptor (RyR2) dysfunction causes spontaneous sarcoplasmic reticulum (SR) calcium (Ca2+) release, leading to arrhythmias and reduced contractile function. RyR2 dysfunction can be acquired, as in heart failure (HF), or inherited by RyR2 mutations, as in catecholaminergic polymorphic ventricular tachycardia (CPVT). AIM: The aim of the present study was to elucidate whether an increased SR Ca2+ leak due to a RyR2 mutation alters the expression of cardiac Ca2+ handling proteins and their phosphorylation status in murine cardiomyocytes during pressure overload-induced hypertrophy. METHODS: We investigated mice harboring a CPVT-associated RyR2R4496C+/- (R4496C) mutation and their WT littermates one week after pressure-induced overload induced by minimally invasive transverse aortic constriction (TAC). Mice undergoing the surgery without aortic ligation served as controls (Sham). Quantification of Ca2+ handling proteins, including phospholamban (PLB), SR-Ca2+-ATPase 2a (SERCA2a) and calsequestrin (CASQ2), was performed by Western blotting. Phospho-site-specific antibodies were used for evaluation of the phosphorylation status of RyR2 and PLB by protein kinase A (PKA) (RyR2 at Ser2808 and PLB at Ser16, respectively) as well as Ca2+/calmodulin-dependent kinase II (CaMKII) (RyR2 at Ser2814 and PLB at Thr17, respectively). RESULTS: We observed unchanged expression of CASQ2 and PLB, however, SERCA2a expression was significantly reduced in both WT-TAC and R4496C-TAC mice in respect with WT-Sham. RyR2 phosphorylation status at PKA- and CaMKII-dependent sites, Ser2808 and Ser2814, respectively, was unchanged. While PKA had also no effect on the phosphorylation of PLB, the phosphorylation level at the CaMKII-dependent site (PLB-Thr17) was significantly reduced in both R4496C-Sham and R4496C-TAC hearts, compared to WT-Sham. CONCLUSION: Reduced SERCA2a expression and phosphorylation of PLB imply reduced SERCA2a activity in R4496C-TAC mice. Our data suggest an impaired SR Ca2+ reuptake and, thus, reduced SR Ca2+ content underlying contractile dysfunction in R4496C mice imposed to pressure overload.