| Project/Area Number |
15590712
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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 | Hirosaki University |
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Principal Investigator |
OKAMURA Ken Hirosaki University, School of Medicine, Professor, 医学部, 教授 (20185549)
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| Co-Investigator(Kenkyū-buntansha) |
OSANAI Tomohiro Hirosaki University, School of Medicine, Associate Professor, 医学部, 助教授 (00169278)
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2004: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2003: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | coronary spastic angina / Phospholipase C-δ1 / small G protein / P122 protein / Vasospastic angina / Hypertension / Phospholipase C / Transgenic mouse / Intracellular calcium / Acethylcholine |
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| Research Abstract |
Phospholipase C (PLC)-d1, an isozyme of phospholipase C that constitutes a key enzyme for the mechanism for cellular contraction, is activated by Ca^<++> and induces a further increment in the [Ca^<2+>]_i and enhanced response to the constrictor stimuli. We previously reported that PLC activity in the membrane fraction of the cultured skin fibroblasts obtained from the patients with coronary spastic angina is enhanced compared with that of control subjects and PLC activity shows a positive correlation with the basal tone of the coronary artery and its response to the constrictor stimulus (J Am Coll Cardiol,2000). By the sequence analysis of the cDNA coding for PLC-d1 obtained from fibroblasts, we recently found a conversion of guanine to adenine (A) at nucleotide position 864, resulting in the amino acid replacement of arginine 257 by histidine (R257H)(Circulation,2002). The incidence of 864A/A in genomic DNA was greater in patients with CSA than in male control subjects. The activity
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of the variant PLC-d1 protein was 2-fold higher than that of the wild-type protein. The peak increase in [Ca^<2+>]_i in response to acetylcholine was greater in the cells with the variant PLC-d1 than in those with the wild type. Thus, R257H variant in the PLC-d1 gene is associated with enhancement of enzyme activity, and can be a novel mechanism for the enhanced coronary vasomotility. However, R257H variant was detected only in 10% of the patients and we have sought other mechanisms for enhanced activity of PLC-d1.
It is known that small G protein Rho A suppresses PLC-d1 activity whereas P122 protein enhances the activity. We compared the protein expressions of Rho A and P122 between the patient groups with (n=11) and without coronary spastic angina (n=9) by Western blot analysis. Although there was no difference in the expression of Rho A protein between the 2 groups, the expression of P122 was markedly enhanced in the groups of coronary spastic angina compared with the group without spastic angina. The protein level of PLC-d1 was not different between the 2 groups. Thus, enhanced expression of P122 protein may explain the enhanced PLC-d1 activity in the patients with coronary spastic angina. We are now investigating the molecular mechanism for the enhanced expression of P122 protein. Less
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