title: Distribution and Function of Cardiac Ryanodine Receptor Clusters in Live Ventricular Myocytes.
abstract: The cardiac Ca(2+) release channel (ryanodine receptor, RyR2) plays an essential role in excitation-contraction coupling in cardiac muscle cells. Effective and stable excitation-contraction coupling critically depends not only on the expression of RyR2, but also on its distribution. Despite its importance, little is known about the distribution and organization of RyR2 in living cells. To study the distribution of RyR2 in living cardiomyocytes, we generated a knock-in mouse model expressing a GFP-tagged RyR2 (GFP-RyR2). Confocal imaging of live ventricular myocytes isolated from the GFP-RyR2 mouse heart revealed clusters of GFP-RyR2 organized in rows with a striated pattern. Similar organization of GFP-RyR2 clusters was observed in fixed ventricular myocytes. Immunofluorescence staining with the anti-α-actinin antibody (a z-line marker) showed that nearly all GFP-RyR2 clusters were localized in the z-line zone. There were small regions with dislocated GFP-RyR2 clusters. Interestingly, these same regions also displayed dislocated z-lines. Staining with di-8-ANEPPS revealed that nearly all GFP-RyR2 clusters were co-localized with transverse but not longitudinal tubules, whereas staining with MitoTracker Red showed that GFP-RyR2 clusters were not co-localized with mitochondria in live ventricular myocytes. We also found GFP-RyR2 clusters interspersed between z-lines only at the periphery of live ventricular myocytes. Simultaneous detection of GFP-RyR2 clusters and Ca(2+) sparks showed that Ca(2+) sparks originated exclusively from RyR2 clusters. Ca(2+) sparks from RyR2 clusters induced no detectable changes in mitochondrial Ca(2+) level. These results reveal, for the first time, the distribution of RyR2 clusters and its functional correlation in living ventricular myocytes.
authors.affiliation: From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology and.
authors.forename: Florian
authors.initials: F
authors.lastname: Hiess
authors.affiliation: the Department of Automatic Control, Universitat Politècnica de Catalunya, 08034 Barcelona, Spain.
authors.forename: Alexander
authors.initials: A
authors.lastname: Vallmitjana
authors.affiliation: From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology and.
authors.forename: Ruiwu
authors.initials: R
authors.lastname: Wang
authors.affiliation: the Department of Medicine, University of California at San Diego, La Jolla, California 92161, and.
authors.forename: Hongqiang
authors.initials: H
authors.lastname: Cheng
authors.affiliation: the Libin Cardiovascular Institute of Alberta, Department of Cardiac Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
authors.forename: Henk E D J
authors.initials: HE
authors.lastname: ter Keurs
authors.affiliation: the Department of Medicine, University of California at San Diego, La Jolla, California 92161, and.
authors.forename: Ju
authors.initials: J
authors.lastname: Chen
authors.affiliation: the Cardiovascular Research Centre CSIC-ICCC, Hospital de Sant Pau, 08025 Barcelona, Spain.
authors.forename: Leif
authors.initials: L
authors.lastname: Hove-Madsen
authors.affiliation: the Department of Automatic Control, Universitat Politècnica de Catalunya, 08034 Barcelona, Spain.
authors.forename: Raul
authors.initials: R
authors.lastname: Benitez
authors.affiliation: From the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology and swchen@ucalgary.ca.
authors.forename: S R Wayne
authors.initials: SR
authors.lastname: Chen
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D032383:Myocytes, Cardiac / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel; D049452:Green Fluorescent Proteins; D002118:Calcium
keywords: calcium imaging; calcium intracellular release; excitation-contraction coupling (E-C coupling); ryanodine receptor; sarcoplasmic reticulum (SR)