Oral 3 - 3.1
1,2Shin-Haw Lee, 1,2Sina Hadipour-Lakmehsari, 1,3,4Natalie Gibb, 1,2Allen C.T. Teng, 2,11Tetsuaki Miyake, 1,2Jake Cosme, 1,7Jessica C. Yu, 5Peter Liu, 8Filio Billia, 1,3,7,10Rodrigo Fernandez-Gonzalez, 6Igor Stagljar, 2,12Parveen Sharma, 9Thomas Kislinger, 3,4Ian C. Scott, 1,2Anthony O. Gramolini
1 Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, Toronto, Ontario, Canada M5G 1M1; 2 Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada M5S 1M8; 3 Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8; 4 Department of Molecular Genetics, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada M5S 1M8; 5 Ottawa Heart Institute, Ottawa, Ontario, Canada K1Y 4W7; 6 Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada M5S 1M8; 7 Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G9; 8 Toronto General Research Institute, University Health Network, Toronto, Ontario, Canada M5G 2C4; 9 Princess Margaret Cancer Centre, Toronto, Ontario, Canada M5G 1L7; 10 Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada M5S 3G5
Congestive Heart Failure (CHF) remains the leading cause of hospitalization and mortality characterized by impaired ventricular function and reduced cardiac output. Although the etiology of CHF varies, investigations into cardiac diseases have shown that the sarcoplasmic reticulum SR plays an important role in the development and progression of many heart diseases, responsible for biochemical changes, structural remodeling, and deterioration of the muscle. The SR provides many critical functions in cells. However, many aspects of its structural organization remain largely unknown, particularly in cells with a highly differentiated SR. Here, we report cardiac enriched, SR membrane protein, REEP5 that is centrally involved in regulating SR morphology and stress responses in cardiac myocytes. Advanced three-dimensional confocal imaging showed REEP5 localization to the SR and the junctional sarcoplasmic reticulum (j-SR) in differentiated myocytes. Targeted lentiviral-mediated depletion of REEP5 in primary cardiac myocytes led to SR membrane vacuolization and a marked decrease in myocyte contractility along with disrupted Ca2+ cycling shown by transmission electron microscopy and optical mapping functional imaging. Furthermore, REEP5 depletion contributed to the SR stress response observed during cardiac disease progression. Consequently, In vivo morpholino-mediated REEP5 reduction in zebrafish embryos was associated with reduced heart rates, defective cardiac looping and cardiac dysfunction. These findings provide significant insight into SR biology and physiology and reveal the previously unknown, and indispensable role of REEP5 in SR organization and function in the heart.