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Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice
Published on: September 17, 2015
PICOT increases cardiac contractility by inhibiting PKCζ activity
Jae Gyun Oh1, Dongtak Jeong, Hyeseon Cha
1Global Research Laboratory and College of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
Journal of Molecular and Cellular Cardiology
|March 28, 2012
Summary
Protein kinase C (PKC)-interacting cousin of thioredoxin (PICOT) enhances cardiac contractility by inhibiting PKCζ, which subsequently down-regulates PKCα and protein phosphatase 2A activities, improving heart function.
Area of Science:
- Cardiovascular Biology
- Molecular Cardiology
- Signal Transduction
Background:
- Protein kinase C (PKC)-interacting cousin of thioredoxin (PICOT) has known anti-hypertrophic effects.
- The mechanism behind PICOT's inotropic (contractility-enhancing) function was previously unknown.
- PICOT's C-terminal domain inhibits calcineurin-NFAT signaling.
Purpose of the Study:
- To elucidate the molecular mechanism by which PICOT regulates cardiac contractility.
- To investigate the interaction of PICOT with protein kinase C zeta (PKCζ).
- To determine the downstream signaling pathways affected by PICOT in cardiac muscle.
Main Methods:
- Protein pull-down assays to identify PICOT-binding partners.
- In vitro kinase assays to assess PICOT's inhibitory effect on PKCζ.
- In vitro and ex vivo studies using cardiac tissue to evaluate contractility changes.
- Overexpression and knockdown studies of PICOT, PKCζ, PKCα, and protein phosphatase 2A (PP2A).
- Western blotting to analyze protein phosphorylation levels (PLB, TnI, TnT).
- In vivo studies using transgenic and AAV-mediated gene delivery in heart failure models.
Main Results:
- PICOT directly binds to and inhibits the kinase activity of PKCζ via its N-terminal domain.
- Inhibition of PKCζ activity increases cardiac contractility by up-regulating sarcoplasmic reticulum Ca(2+)-ATPase 2a (SERCA2a) and phospholamban (PLB) phosphorylation.
- PICOT/PKCζ inhibition down-regulates PKCα and PP2A activities, leading to increased troponin I (TnI) and troponin T (TnT) phosphorylation, enhancing contractility.
- Reduced PICOT expression leads to increased PKCα and PP2A activities and decreased contractility.
- PICOT overexpression in failing hearts restores contractility and prevents further deterioration.
Conclusions:
- PICOT exerts its inotropic effect by inhibiting PKCζ activity.
- This inhibition leads to a coordinated down-regulation of PKCα and PP2A signaling pathways.
- PICOT represents a novel therapeutic target for enhancing cardiac contractility in heart failure.
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