title: Roles of the NH2-terminal domains of cardiac ryanodine receptor in Ca2+ release activation and termination.
abstract: The NH2-terminal region (residues 1-543) of the cardiac ryanodine receptor (RyR2) harbors a large number of mutations associated with cardiac arrhythmias and cardiomyopathies. Functional studies have revealed that the NH2-terminal region is involved in the activation and termination of Ca(2+) release. The three-dimensional structure of the NH2-terminal region has recently been solved. It is composed of three domains (A, B, and C). However, the roles of these individual domains in Ca(2+) release activation and termination are largely unknown. To understand the functional significance of each of these NH2-terminal domains, we systematically deleted these domains and assessed their impact on caffeine- or Ca(2+)-induced Ca(2+) release and store overload-induced Ca(2+) release (SOICR) in HEK293 cells. We found that all deletion mutants were capable of forming caffeine- and ryanodine-sensitive functional channels, indicating that the NH2-terminal region is not essential for channel gating. Ca(2+) release measurements revealed that deleting domain A markedly reduced the threshold for SOICR termination but had no effect on caffeine or Ca(2+) activation or the threshold for SOICR activation, whereas deleting domain B substantially enhanced caffeine and Ca(2+) activation and lowered the threshold for SOICR activation and termination. Conversely, deleting domain C suppressed caffeine activation, abolished Ca(2+) activation and SOICR, and diminished protein expression. These results suggest that domain A is involved in channel termination, domain B is involved in channel suppression, and domain C is critical for channel activation and expression. Our data shed new insights into the structure-function relationship of the NH2-terminal domains of RyR2 and the action of NH2-terminal disease mutations.
authors: From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors: Yingjie
authors: Y
authors: Liu
authors: From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors: Bo
authors: B
authors: Sun
authors: From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors: Zhichao
authors: Z
authors: Xiao
authors: From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors: Ruiwu
authors: R
authors: Wang
authors: From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors: Wenting
authors: W
authors: Guo
authors: Department of Physiology and HeartOtago, University of Otago, Dunedin 9054, New Zealand, and.
authors: Joe Z
authors: JZ
authors: Zhang
authors: From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors: Tao
authors: T
authors: Mi
authors: From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors: Yundi
authors: Y
authors: Wang
authors: Department of Physiology and HeartOtago, University of Otago, Dunedin 9054, New Zealand, and.
authors: Peter P
authors: PP
authors: Jones
authors: Cardiovascular Research Group, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
authors: Filip
authors: F
authors: Van Petegem
authors: From the Libin Cardiovascular Institute of Alberta, Departments of Physiology and Pharmacology and Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada, swchen@ucalgary.ca.
authors: S R Wayne
authors: SR
authors: Chen
mesh_terms: D015153:Blotting, Western; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D009206:Myocardium / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry / Q000378:metabolism*
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D002118:Calcium
keywords: Calcium Imaging; Calcium Intracellular Release; Cardiac Muscle; Ryanodine Receptor; Sarcoplasmic Reticulum (SR)
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