Phosphorylation of RyR2 and shortening of RyR2 cluster spacing in spontaneously hypertensive rat with heart failure

1 Departments of Internal Medicine and Physiology, University of Kentucky College of Medicine, Lexington, Kentucky; 2 School of Nursing and 3 School of Medicine, University of Maryland, Baltimore, Maryland; 4 Department of Physiology, University Medical School of Debrecen, Debrecen, Hungary; and 5 Departments of Molecular Physiology and Biophysics, and Medicine (Cardiology), Baylor College of Medicine, Houston, Texas Submitted 14 May 2007 ; accepted in final form 11 July 2007 As a critical step toward understanding the role of abnormal intracellular Ca 2+ release via the ryanodine receptor (RyR 2 ) during the development of hypertension-induced cardiac hypertrophy and heart failure, this study examines two questions: 1 ) At what stage, if ever, in the development of hypertrophy and heart failure is RyR 2 hyperphosphorylated at Ser 2808 ? 2 ) Does the spatial distribution of RyR 2 clusters change in failing hearts? Using a newly developed semiquantitative immunohistochemistry method and Western blotting, we measured phosphorylation of RyR 2 at Ser 2808 in the spontaneously hypertensive rat (SHR) at four distinct disease stages. A major finding is that hyperphosphorylation of RyR 2 at Ser 2808 occurred only at late-stage heart failure in SHR, but not in age-matched controls. Furthermore, the spacing between RyR 2 clusters was shortened in failing hearts, as predicted by quantitative model simulation to increase spontaneous Ca 2+ wave generation and arrhythmias. ryanodine receptor; hypertension; cardiac hypertrophy; protein kinase A; spontaneously hypertensive rat Address for reprint requests and other correspondence: Y. Chen-Izu, Dept. of Internal Medicine, Univ. of Kentucky College of Medicine, 741 S. Limestone St., BBSRB, Rm. B255, Lexington, KY 40536-0509 (e-mail: YeChen-Izu{at}uky.edu )