Progesterone modulates SERCA2a expression and function in rabbit cardiomyocytes

• Published in: American Journal of Physiology: Cell Physiology Vol. 307; no. 11; p. C1050
• Main Authors: Moshal, Karni S, Zhang, Zhe, Roder, Karim, Kim, Tae Yun, Cooper, Leroy, Patedakis Litvinov, Bogdan, Lu, Yichun, Reddy, Vishal, Terentyev, Dmitry, Choi, Bum-Rak, Koren, Gideon
• Format: Journal Article
• Language: English
• Published: United States 01-12-2014
• Subjects: Animals; Animals, Newborn; Female; Gene Expression Regulation, Enzymologic - drug effects; Male; Myocytes, Cardiac - drug effects; Myocytes, Cardiac - enzymology; Progesterone - pharmacology; Proteolysis - drug effects; Rabbits; RNA, Messenger - genetics; RNA, Messenger - metabolism; Sarcoplasmic Reticulum Calcium-Transporting ATPases - genetics; Sarcoplasmic Reticulum Calcium-Transporting ATPases - metabolism; Ubiquitination - drug effects; cardiomyocytes; neonate; SERCA2a; long QT syndrome; hormones
• ISSN: 1522-1563
• DOI: 10.1152/ajpcell.00127.2014

We recently showed that progesterone treatment abolished arrhythmias and sudden cardiac death in a transgenic rabbit model of long QT syndrome type 2 (LQT2). Moreover, levels of cardiac sarco(endo)plasmic reticulum Ca(2+)-ATPase type 2a (SERCA2a) were upregulated in LQT2 heart extracts. We hypothesized that progesterone treatment upregulated SERCA2a expression, thereby reducing Ca(2+)-dependent arrhythmias in LQT2 rabbits. We therefore investigated the effect of progesterone on SERCA2a regulation in isolated cardiomyocytes. Cardiomyocytes from neonatal (3- to 5-day-old) rabbits were isolated, cultured, and treated with progesterone and other pharmacological agents. Immunoblotting was performed on total cell lysates and sarcoplasmic reticulum-enriched membrane fractions for protein abundance, and mRNA transcripts were quantified using real-time PCR. The effect of progesterone on baseline Ca(2+) transients and Ca(2+) clearance was determined using digital imaging. Progesterone treatment increased the total pool of SERCA2a protein by slowing its degradation. Using various pharmacological inhibitors of degradation pathways, we showed that progesterone-associated degradation of SERCA2a involves ubiquitination, and progesterone significantly decreases the levels of ubiquitin-tagged SERCA2a polypeptides. Our digital imaging data revealed that progesterone significantly shortened the decay and duration of Ca(2+) transients. Progesterone treatment increases protein levels and activity of SERCA2a. Progesterone stabilizes SERCA2a, in part, by decreasing the ubiquitination level of SERCA2a polypeptides.