J. Biochem, 2003, Vol. 134, No. 2 269-276
© 2003 Japanese Biochemical Society
BIOCHEMISTRY |
Defect of Delta-Sarcoglycan Gene Is Responsible for Development of Dilated Cardiomyopathy of a Novel Hamster Strain, J2N-k: Calcineurin/PP2B Activity in the Heart of J2N-k Hamster
1 Division of Biochemical Oncology and Immunology, Institute for Genetic Medicine, Hokkaido University, Kita-15, Nishi-7, Kita-ku, Sapporo 060-0815; 2 Tokyo Research Laboratories Pharmaceutical Division KOWA Co., Ltd., Tokyo; 3 Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Hokkaido University; 4 Division of Cardiology, National Hakodate Hospital, Hokkaido; 5 Division of Cardiology, Hokkaido Central Hospital for Social Insurance, Sapporo; and 6 First Department of Medicine, School of Medicine, Hokkaido University
It has been shown that calcineurin (CN), a serine/threonine protein phosphatase type 2B (PP2B), plays an important role in the development and diseases of cardiac muscles. However, reports on CN activity in dilated cardiomyopathy (DCM) are inconsistent, since there are few good disease models and the measurement of the amount of CN is difficult. Previously, we developed a novel line of DCM hamster, J2N-k, and its healthy control counterpart, J2N-n, by crossbreeding cardiomyopathy (CM) hamsters, Bio 14.6, and Golden hamsters followed by consecutive sib mating. In this study, we identified the DCM-causative gene in J2N-k by analysis of F2 of these two lines, and then we analyzed the change in CN gene expression in the course of the disease, and the change in CN activity using a newly developed method. We show that: (i) the DCM gene of J2N-k hamster is the 
- sarcoglycan (SG) gene, (ii) CN expression and potential CN activities (CN activity fully activated with Ca2+ and calmodulin) in the hearts of J2N-k and J2N-n hamsters are the same levels, (iii) transcription levels of natriuretic peptides, which are augmented by activation of Ca2+/calmodulin-dependent enzyme including CN, are significantly increased in the DCM stage in J2N-k hamster. J2N-k and J2N-n hamsters will be a useful tool for studying the pathogenesis, therapy, and prevention of human DCM. Although the total amount and potential activity of CN did not change in the cell extracts, targets of CN in vivo were activated in cardiomyocytes of DCM, suggesting that CN activity in the cells is activated by the raising of Ca2+ concentration in cardiomyocytes of DCM, which is caused by the defect in the -SG gene. Our results reveal the complexity of CN regulation in the heart and indicate the need for additional experimentation.
* To whom correspondence should be addressed. Tel/Fax: +81-11-706-7541, E-mail: kikuchi{at}imm.hokudai.ac.jp
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