2005 Fiscal Year Final Research Report Summary
Acquisition of resistance against heart failure by incorporation of ryanodine receptor stabilizing peptide to cardiomyocyte
| Project/Area Number |
16590689
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Circulatory organs internal medicine
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| Research Institution | Yamaguchi University |
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Principal Investigator |
YANO Masafumi Yamaguchi University, Hospital, Assistant Professor, 医学部附属病院, 講師 (90294628)
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| Co-Investigator(Kenkyū-buntansha) |
IKEDA Yasuhiro Yamaguchi University, Faculty of Medicine, Research Associate, 医学部, 助手 (00260349)
YAMAMOTO Takeshi Yamaguchi University, Faculty of Medicine, Research Associate, 医学部, 助手 (50363122)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Heart failure / Sarcoplasmic reticulum / Ryanodine receptor / Calcium |
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| Research Abstract |
An abnormal regulation of intracellular Ca2+ by sarcoplasmic reticulum (SR) has been shown to be involved in the mechanism underlying contractile and relaxation dysfunction in heart failure. Recently, PKA-mediated hyperphosphorylation of ryanodine receptors (RyR) in SR has been shown to cause dissociation of FKBP12.6 from RyR in heart failure. This results in an abnormal Ca2+ leak through RyR, leading to increased cytosolic diastolic Ca2+ concentration, prolongation in the Ca2+ transient, and delayed/slowed diastolic decline in cytosolic Ca2+ concentration. According to our hypothesis, two domains within the ryanodine receptor (RyR) of sarcoplasmic reticulum (SR) {N-terminal (0-600) and central (2000-2500) domains}, where many mutations have been found in the patients with polymorphic VT (pVT), interact with each other as a regulatory switch for channel gating. Here, we investigated whether the defective FKBP12.6-mediated stabilization of RyR in heart failure is produced by an abnormal
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inter-domain interaction.
SR vesicles were isolated from dog LV muscles, then the RyR moiety of the SR was fluorescently labeled with methylcoumarin acetate (MCA) using DPc10,a synthetic peptide corresponding to Gly2460-Pro2495 of RyR (one of mutable domains in pVT), as a site-directing carrier ; the carrier was removed from the RyR after MCA labeling. Addition of DPc10 induced an unzipped state of the interacting N-terminal and central domains, as evidenced by an increase in the accessibility of the RyR-bound MCA fluorescence to a large-size fluorescence quencher. Domain unzipping resulted in Ca2+ leak through RyR, and facilitated cAMP-dependent hyper-phosphorylation of RyR and FKBP12.6 dissociation from RyR. When DPc10 was introduced into the isolated myocytes, the magnitude of intracellular Ca2+ transient decreased and its decay time was prolonged. In the SR isolated from pacing-induced dog failing hearts, the domain unzipping has already occurred together with FKBP12.6 dissociation and Ca2+ leak. A specific peptide within central domain inhibited SR Ca2+ leak and improved failing cardiomyocyte function.
Conclusions. The specific domain interaction within the RyR regulates the channel gating property and the defectiveness in the mode of the inter-domain interaction seems to be the initial critical step of the pathogenesis of heart failure. Stabilization of ryanodine receptor may be a new therapeutic strategy against heart failure. Less
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Research Products
(5 results)
