Carbonylated cardiac myosin binding protein C as an indicator of doxorubicin-induced cardiotoxicity

Monday, September 22, 2014 — Poster Session II
4:00 p.m. – 6:00 p.m.	FAES Academic Center	FDA/CBER	MOLBIO-1

Authors

• B. P. Aryal
• J. Jeong
• V. A. Rao

Abstract

Dose-dependent oxidative stress by the anthracycline doxorubicin (Dox) and other chemotherapeutic agents causes irreversible cardiac damage, restricting their clinical effectiveness. We hypothesized that irreversible protein oxidation caused by oxidative stress could be correlated with physiological functional impairment. We focused our study on protein carbonylation as an indicator of severe oxidative damage. We identified a specific cardiac protein that showed selective carbonylation under Dox-induced cardiotoxic conditions in a spontaneously hypertensive rat (SHR) model and this protein was confirmed to be a 140 kDa cardiac myosin binding protein C (MyBPC). We further analyzed and confirmed the carbonylation and degradation of this protein using HL-1 cardiomyocytes under Dox-induced oxidative stress, and a purified recombinant rat cardiac MyBPC under metal-catalyzed oxidative stress conditions. Using HL-1 cells we demonstrated that carbonylated MyBPC undergoes proteasome-mediated degradation under Dox-induced oxidative stress. Using immunoprecipitation, co-sedimentation, and actin-binding assays we confirmed the functional impairment of MyBPC as a consequence of carbonylation. Carbonylation of recombinant MyBPC showed significant impairment in its actin binding properties with a dissociation constant of 7.35±1.9 µM compared to 2.7±0.6 µM for native MyBPC. Overall, our findings indicate that MyBPC carbonylation serves as a critical determinant of cardiotoxicity.

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