Akap1 Deficiency Promotes Mitochondrial Aberrations and Exacerbates Cardiac Injury Following Permanent Coronary Ligation via Enhanced Mitophagy and Apoptosis

RESEARCH ARTICLE Akap1 Deficiency Promotes Mitochondrial Aberrations and Exacerbates Cardiac Injury Following Permanent Coronary Ligation via Enhanced Mitophagy and Apoptosis a11111 Gabriele Giacomo Schiattarella1,2, Fabio Cattaneo1, Gianluigi Pironti1,3, Fabio Magliulo1, Giuseppe Carotenuto1, Marinella Pirozzi4, Roman Polishchuk5, Domenica Borzacchiello1, Roberta Paolillo1, Marco Oliveti1, Nicola Boccella1, Marisa Avvedimento1, Maria Sepe6, Assunta Lombardi7, Rosa Anna Busiello7, Bruno Trimarco1, Giovanni Esposito1*, Antonio Feliciello6, Cinzia Perrino1* 1 Department of Advanced Biomedical Sciences, Federico II University, Naples, Italy, 2 Department of Internal Medicine (Cardiology), University of Texas Southwestern Medical Center, Dallas, Texas, United States of America, 3 Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden, 4 Institute of Protein Biochemistry, Italian National Research Council (CNR-IBP), Naples, Italy, 5 Telethon Institute of Genetic and Medicine (TIGEM), Naples, Italy, 6 Department of Molecular Medicine and Medical Biotechnologies, Federico II University, Naples, Italy, 7 Department of Biology, Federico II University, Naples, Italy OPEN ACCESS Citation: Schiattarella GG, Cattaneo F, Pironti G, Magliulo F, Carotenuto G, Pirozzi M, et al. (2016) Akap1 Deficiency Promotes Mitochondrial Aberrations and Exacerbates Cardiac Injury Following Permanent Coronary Ligation via Enhanced Mitophagy and Apoptosis. PLoS ONE 11 (5): e0154076. doi:10.1371/journal.pone.0154076 Editor: Sathyamangla Venakata Naga Prasad, Cleveland Clinic, UNITED STATES Received: December 17, 2015 Accepted: April 8, 2016 Published: May 2, 2016 Copyright: © 2016 Schiattarella et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was supported, in part, by grants from the Ministry of Health, Italy - Young Researcher Grant (www.ministerosalute.it - GR-2009-1596220) and from the Ministry of University and Research, Italy (www.miur.it - RBFR124FEN) to CP and by Associazione Italiana per la Ricerca sul Cancro Grant to AF (www.airc.it - IG15264). * (CP); (GE) Abstract A-kinase anchoring proteins (AKAPs) transmit signals cues from seven-transmembrane receptors to specific sub-cellular locations. Mitochondrial AKAPs encoded by the Akap1 gene have been shown to modulate mitochondrial function and reactive oxygen species (ROS) production in the heart. Under conditions of hypoxia, mitochondrial AKAP121 undergoes proteolytic degradation mediated, at least in part, by the E3 ubiquitin ligase Seven InAbsentia Homolog 2 (Siah2). In the present study we hypothesized that Akap1 might be crucial to preserve mitochondrial function and structure, and cardiac responses to myocardial ischemia. To test this, eight-week-old Akap1 knockout mice (Akap1-/-), Siah2 knockout mice (Siah2-/-) or their wild-type (wt) littermates underwent myocardial infarction (MI) by permanent left coronary artery ligation. Age and gender matched mice of either genotype underwent a left thoracotomy without coronary ligation and were used as controls (sham). Twentyfour hours after coronary ligation, Akap1-/- mice displayed larger infarct size compared to Siah2-/- or wt mice. One week after MI, cardiac function and survival were also significantly reduced in Akap1-/- mice, while cardiac fibrosis was significantly increased. Akap1 deletion was associated with remarkable mitochondrial structural abnormalities at electron microscopy, increased ROS production and reduced mitochondrial function after MI. These alterations were associated with enhanced cardiac mitophagy and apoptosis. Autophagy inhibition by 3-methyladenine significantly reduced apoptosis and ameliorated cardiac dysfunction following MI in Akap1-/- mice. These results demonstrate that Akap1 deficiency promotes cardiac mitochondrial aberrations and mitophagy, enhancing infarct size, pathological PLOS ONE | DOI:10.1371/journal.pone.0154076 May 2, 2016 1 / 16 Akap1, Mitochondria and Myocardial Ischemia Competing Interests: The authors have declared that no competing interests exist. cardiac remodeling and mortality under ischemic conditions. Thus, mitochondrial AKAPs might represent important players in the development of post-ischemic cardiac remodeling and novel therapeutic targets. Introduction Mitochondria are central to several cellular processes, as they are both the main source of energy and reactive oxygen species (ROS), and critical regulators of cell death or survival pathways [1]. Mitochondrial dysfunction has been observed in a variety of cardiac diseases, including coronary artery disease, left ventricular hypertrophy and heart failure [1–4]. During cardiac ischemia, mitochondrial ROS production represents one of the major determinants of infarct size and heart remodeling [4]. Recent studies have demonstrated the important role of a family of A Kinase Anchor Proteins (AKAPs) in the transmission of intracellular cyclic adenosine monophosphate (cAMP) signals to the outer membrane of mitochondria [3, 5]. Mitochondrial AKAPs (mitoAKAPs) are products of a single gene (Akap1), and are generated by alternative RNA splicing. All splice variants share the first 30 NH2-terminal residues mediating the targeting to the outer mitochondrial membrane and other functions, but diverge significantly at the C-terminus. Mitochondrial AKAP121 is transcriptionally regulated by cyclic adenosine monophosphate (cAMP) in vitro and in vivo [3]. Down-regulation of AKAP121 induced by cardiac pressure overload is associated with marked abnormalities in mitochondrial structure and function, and increased ROS generation [3]. In addition, AKAP121 undergoes a rapid post-translational degradation under hypoxic conditions mediated by the E3 ubiquitin ligase Seven In-Absentia Homolog 2 (Siah2) [6]. Siah2 also regulates the availability of hypoxia inducible factor-1α (HIF1-α) and other proteins [6–8], and its deletion prevents ischemia-induced cardiomyocyte cell death and reduces infarct size after coronary artery ligation [8]. These effects might be related, at least in part, to the regulation of AKAP121 availability and, in turn, of mitochondrial dynamics [8]. Stress-induced mitochondrial damage increases ROS production and can cause further damage to nearby mitochondria, the release of pro-apoptotic proteins and the amplification of cellular damage [9]. To prevent further injury, cells can induce the activation of quality control systems to remove damaged mitochondria by macro-autophagy or mitophagy [10, 11]. Selective degradation of damaged mitochondria may play an essential role in a number of cardiac pathologies associated with mitochondrial (...truncated)