Journal
CARDIOVASCULAR RESEARCH
Volume 68, Issue 1, Pages 98-108Publisher
OXFORD UNIV PRESS
DOI: 10.1016/j.cardiores.2005.05.019
Keywords
protein phoshatase 1; inhibitor-2; heart; transgenic mouse; contractility
Categories
Funding
- NIDDK NIH HHS [DK36569] Funding Source: Medline
Ask authors/readers for more resources
Objective: Protein phosphatase 1 (PP1) has been implicated in the control of cardiac function. Cardiac specific overexpression of the catalytic subunit, PP1c, results in hypertrophy and depressed contractility. Methods: To further address the role of PP1, transgenic mice (TG) were generated that overexpress in heart a functional COOH-terminally truncated form (amino acids 1-140) of the PP1 inhibitor-2 (I-2(140)). Results: The TG hearts show increased levels of I-2(140) mRNA as well as protein and activity. No increase in absolute or relative heart weight was observed, nor any changes in gross pathology or increase in morbidity or mortality in the TG mice. Immunohistochemical and biochemical analyses revealed that expression of the I-2(140) protein is confined to cardiomyocytes where it is mainly localized in the cytosol. The total protein phosphatase (PP) activity was reduced by 80% in TG hearts as compared to wild-type littermates (WT). The PP1c mRNA level was the same in TG and WT, while the protein level was increased by similar to 7-fold in TG animals. The maximal rates of contraction (+dP/ dt) and of relaxation (-dP/dt) were increased by 32% and 40%, respectively, in the intact catheterized TG mice compared to WT. However, the maximal contractile response to beta-adrenergic agonists was comparable in hearts from TG and WT mice. In isolated cardiomyocytes of TG mice, Ca2+ transient amplitude was increased by 50% under basal conditions and by 60% upon rapid caffeine application. The phospholamban (PLB) protein level was unchanged whereas the basal phosphorylation of PLB at Ser(16) was significantly increased in TG hearts. Conclusion: These results indicate that I-2(140) overexpression results in decreased PP1 activity and enhanced contractility in the heart, underscoring the fundamental role of PP1 in cardiac function. (c) 2005 European Society of Cardiology. Published by Elsevier B.V. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available