Enhanced cardiac function in mice overexpressing protein phosphatase Inhibitor-2

Uwe Kirchhefer, Hideo A. Baba, Peter Bokník, Kristine M. Breeden, Nirmala Mavila, Nicole Brüchert, Isabel Justus, Marek Matus, Wilhelm Schmitz, Anna De Paoli-Roach, Joachim Neumann

Research output: Contribution to journalArticle

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Abstract

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-2140). Results: The TG hearts show increased levels of I-2140 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-2140 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∼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 β-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 Ser16 was significantly increased in TG hearts. Conclusion: These results indicate that I-2140 overexpression results in decreased PP1 activity and enhanced contractility in the heart, underscoring the fundamental role of PP1 in cardiac function.

Original languageEnglish
Pages (from-to)98-108
Number of pages11
JournalCardiovascular Research
Volume68
Issue number1
DOIs
StatePublished - Oct 1 2005

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Transgenic Mice
Protein Phosphatase 1
Cardiac Myocytes
Proteins
protein phosphatase inhibitor-2
Myocardial Contraction
Adrenergic Agonists
Messenger RNA
Genetically Modified Animals
Phosphoprotein Phosphatases
Caffeine
Cytosol
Hypertrophy
Catalytic Domain
Phosphorylation
Pathology
Morbidity
Amino Acids
Weights and Measures
Mortality

Keywords

  • Contractility
  • Heart
  • Inhibitor-2
  • Protein phoshatase 1
  • Transgenic mouse

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

Cite this

Kirchhefer, U., Baba, H. A., Bokník, P., Breeden, K. M., Mavila, N., Brüchert, N., ... Neumann, J. (2005). Enhanced cardiac function in mice overexpressing protein phosphatase Inhibitor-2. Cardiovascular Research, 68(1), 98-108. https://doi.org/10.1016/j.cardiores.2005.05.019

Enhanced cardiac function in mice overexpressing protein phosphatase Inhibitor-2. / Kirchhefer, Uwe; Baba, Hideo A.; Bokník, Peter; Breeden, Kristine M.; Mavila, Nirmala; Brüchert, Nicole; Justus, Isabel; Matus, Marek; Schmitz, Wilhelm; De Paoli-Roach, Anna; Neumann, Joachim.

In: Cardiovascular Research, Vol. 68, No. 1, 01.10.2005, p. 98-108.

Research output: Contribution to journalArticle

Kirchhefer, U, Baba, HA, Bokník, P, Breeden, KM, Mavila, N, Brüchert, N, Justus, I, Matus, M, Schmitz, W, De Paoli-Roach, A & Neumann, J 2005, 'Enhanced cardiac function in mice overexpressing protein phosphatase Inhibitor-2', Cardiovascular Research, vol. 68, no. 1, pp. 98-108. https://doi.org/10.1016/j.cardiores.2005.05.019
Kirchhefer U, Baba HA, Bokník P, Breeden KM, Mavila N, Brüchert N et al. Enhanced cardiac function in mice overexpressing protein phosphatase Inhibitor-2. Cardiovascular Research. 2005 Oct 1;68(1):98-108. https://doi.org/10.1016/j.cardiores.2005.05.019
Kirchhefer, Uwe ; Baba, Hideo A. ; Bokník, Peter ; Breeden, Kristine M. ; Mavila, Nirmala ; Brüchert, Nicole ; Justus, Isabel ; Matus, Marek ; Schmitz, Wilhelm ; De Paoli-Roach, Anna ; Neumann, Joachim. / Enhanced cardiac function in mice overexpressing protein phosphatase Inhibitor-2. In: Cardiovascular Research. 2005 ; Vol. 68, No. 1. pp. 98-108.
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abstract = "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-2140). Results: The TG hearts show increased levels of I-2140 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-2140 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∼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 β-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 Ser16 was significantly increased in TG hearts. Conclusion: These results indicate that I-2140 overexpression results in decreased PP1 activity and enhanced contractility in the heart, underscoring the fundamental role of PP1 in cardiac function.",
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AU - Mavila, Nirmala

AU - Brüchert, Nicole

AU - Justus, Isabel

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