2006 Fiscal Year Final Research Report Summary
Molecular mechanisms of Ca^<2+> uptake by sarcolipin in cardiac sarcoplasmic reticulum.
| Project/Area Number |
16500269
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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 |
Neurophysiology and muscle physiology
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| Research Institution | Jikei University School of Medicine |
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Principal Investigator |
KURIHARA Satoshi Jikei University, School of Medicine, Professor, 医学部, 教授 (90057026)
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| Co-Investigator(Kenkyū-buntansha) |
HONGO Kenichi Jikei University, School of Medicine, Associate Professor, 医学部, 助教授 (00256447)
KAWAI Makoto Jikei University, School of Medicine, Lecturer, 医学部, 講師 (40277025)
OTSU Kinya Osaka University, Graduate School of Medicine, Associate Professor, 大学院医学系研究科, 助教授 (20294051)
KUSAKARI Yoichiro Jikei University, School of Medicine, Lecturer, 医学部, 講師 (80338889)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Ca^<2+> / sarcoplasmic reticulum / sarcolipin / skinned preparation / saponin / mouse / cardiac muscle / Ca^<2+> transients |
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| Research Abstract |
The aim of the study was to explore the role of Ca^<2+> handling-related protein, sarcolipin (SLN) for the regulation of intracellular Ca^<2+> concentration. Sarcoplasmic reticulum (SR)(SERCA2a) is regulated by phospholamban (PLB) and SLN which couple with SERCA2a. Both non-phosphorylated-PLB and -SLN decrease the Ca^<2+> uptake rate of SR. We overexpressed SLN in ventricular muscles of mouse (SLN-TG) and investigated how SERCA2a is influenced by SLN. We measured the Ca^<2+> transients and contraction in intact left ventricular papillary muscles of mouse using the aequorin method. Also, we used saponin-treated thin trabeculae to investigate Ca^<2+> uptake, Ca^<2+> release and Ca^<2+> leakage. In twitch contraction, Hz, the peaks of the Ca^<2+> transient and contraction in SLN-TG were lower than those of the control. The rate of decline of the Ca^<2+> transient and tension was slower than that of the control. In the skinned fiber, Ca^<2+> was loaded in the SR in the presence of ATP and Ca^<2+> (pCa 6.2) for various periods, and Ca^<2+> in the SR was released by caffeine. We measured the released Ca^<2+> with fluo-3. The rate of Ca^<2+> uptake in SLN-TG was slower when the Ca^<2+> loading time was short but no difference was observed when the loading time was longer. The maximal Ca^<2+> content of SR at a steady state in both TG and non-TG cardiac muscles did not differ. Ca^<2+>-induced Ca^<2+> release (CICR) in SLN-TG did not differ from that in non-TG. Ca^<2+> leakage was estimated by measuring the leaked Ca in the solution without ATP and Ca^<2+> after Ca^<2+> loading. Ca^<2+> leakage in SLN-TG was not different from that in non-TG. Thus, SLN decreases the Ca^<2+> uptake in SR and influences intracellular Ca^<2+> concentration. The role of SLN is significant in beat-to-beat contraction, but SLN does not play a significant role at a steady state.
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