Heart failure (HF) continues to be a leading cause of morbidity and mortality. A universal characteristic of human and experimental heart failure is impaired sarcoplasmic reticulum (SR) Ca-cycling, reflecting partially the depressed Ca-sequestration through SERCA2a/phospholamban (PLN). Despite recent advances, the mechanisms responsible for the deteriorated function caused by SERCA2a/PLN activity remain elusive. Importantly, our original simple understanding of PLN serving as the sole physiological brake to inhibit SERCA2a and contractility has recently evolved, as we have identified additional interacting proteins in this complex. These include the cytosolic anti-apoptotic HS-1 associated protein X-1 (HAX-1), the heat shock protein 90 and the intraluminal histidine-rich Ca-binding (HRC) protein. HAX-1 directly interacts with PLN and promotes PLN inhibition of SERCA2a, while Hsp90 binds to HAX-1 and provides an additional layer of PLN regulation, decreasing SERCA's Ca-affinity and contractility. In addition, HRC interacts with SERCA2a in the lumen of the SR and modulates the maximal rates of SR Ca-transport. HRC also interacts with triadin and regulates ryanodine receptor (RyR) activity. Thus, HRC may mediate an important "link" between SR Ca- uptake and Ca-release, impacting overall cardiomyocyte Ca-handling. Indeed, a human genetic variant in HRC (S96A) is associated with impaired SR Ca-cycling and arrhythmias in dilated cardiomyopathy patients. The central hypothesis of the proposed studies is that there is a fine cross-talk between Ca-handling and apoptotic proteins at the SR level which regulates contractility, survival and remodeling in the heart. The innovation of this proposal is the first identification of an Hsp90/HAX-1/PLN/SERCA2a/HRC/Triadin/RyR interactome, suggesting that perturbations in the levels or activity of a single protein in this network will influence the rest of the partners, eliciting amplification of its effects. Our goal i to define the triggers and mechanisms, which disrupt the function of this SR regulatory complex in response to clinically relevant stress and potentially reveal new therapeutic targets. Accordingly, our Aims will provide a first comprehensive characterization of the: a) functional significance of Hsp90/HAX-1 in regulation of PLN/SERCA2a activity and SR Ca-load, impacting cardiomyocyte contractility and apoptosis through the ER and mitochondria pathways, which may lead to remodeling under stress conditions;and b) the mechanisms underlying aberrant SR Ca- cycling by alterations in HRC levels or activity and their role in cardiomyocyte function and survival. We will employ an integrative approach with studies at the molecular, biochemical and physiological levels. Our pilot studies are exciting and suggest that the proposed experiments are feasible and highly relevant since the levels of HAX-1 and HRC decrease in failing hearts. The findings will provide new mechanistic insights underlying the role of impaired SR Ca-cycling in heart failure and arrhythmia development and may reveal new molecular pathways and targets associated with cardiomyocyte stress conditions.
Heart disease remains the leading cause of death and disability in the western world. Current therapy aims at treating the symptoms rather than the etiology of heart failure development. A universal characteristic of failing hearts is impaired calcium cycling through the sarcoplasmic reticulum, reflecting depressed pumping action of the heart. We have identified novel regulators of sarcoplasmic reticulum calcium cycling activity and cell death, the anti-apoptotic protein HAX-1, the heat shock protein 90 (Hsp90) and the histidine-rich Ca-binding protein. Here we will focus on understanding the function of these regulators in depth with emphasis on cardiac contractility and cell death. These studies will provide the basis to develop new therapeutic targets to improve the depressed function and survival of the failing cardiac cells.
|Haghighi, Kobra; Bidwell, Philip; Kranias, Evangelia G (2014) Phospholamban interactome in cardiac contractility and survival: A new vision of an old friend. J Mol Cell Cardiol 77:160-7|
|Rubinstein, Jack; Lasko, Valerie M; Koch, Sheryl E et al. (2014) Novel role of transient receptor potential vanilloid 2 in the regulation of cardiac performance. Am J Physiol Heart Circ Physiol 306:H574-84|
|Sivakumaran, Vidhya; Stanley, Brian A; Tocchetti, Carlo G et al. (2013) HNO enhances SERCA2a activity and cardiomyocyte function by promoting redox-dependent phospholamban oligomerization. Antioxid Redox Signal 19:1185-97|
|Lam, Chi Keung; Zhao, Wen; Cai, Wenfeng et al. (2013) Novel role of HAX-1 in ischemic injury protection involvement of heat shock protein 90. Circ Res 112:79-89|
|Singh, Vivek P; Rubinstein, Jack; Arvanitis, Demetrios A et al. (2013) Abnormal calcium cycling and cardiac arrhythmias associated with the human Ser96Ala genetic variant of histidine-rich calcium-binding protein. J Am Heart Assoc 2:e000460|
|Sassi, Yassine; Abi-Gerges, Aniella; Fauconnier, Jeremy et al. (2012) Regulation of cAMP homeostasis by the efflux protein MRP4 in cardiac myocytes. FASEB J 26:1009-17|
|Wang, Hong-Sheng; Arvanitis, Demetrios A; Dong, Min et al. (2011) SERCA2a superinhibition by human phospholamban triggers electrical and structural remodeling in mouse hearts. Physiol Genomics 43:357-64|
|Han, Peidong; Cai, Wenfeng; Wang, Yanru et al. (2011) Catecholaminergic-induced arrhythmias in failing cardiomyocytes associated with human HRCS96A variant overexpression. Am J Physiol Heart Circ Physiol 301:H1588-95|
|Arvanitis, Demetrios A; Vafiadaki, Elizabeth; Sanoudou, Despina et al. (2011) Histidine-rich calcium binding protein: the new regulator of sarcoplasmic reticulum calcium cycling. J Mol Cell Cardiol 50:43-9|
|Altschafl, Beth A; Arvanitis, Demetrios A; Fuentes, Oscar et al. (2011) Dual role of junctin in the regulation of ryanodine receptors and calcium release in cardiac ventricular myocytes. J Physiol 589:6063-80|
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