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Assessment of Sarcoplasmic Reticulum Calcium Reserve and Intracellular Diastolic Calcium Removal in Isolated Ventricular Cardiomyocytes
11:00

Assessment of Sarcoplasmic Reticulum Calcium Reserve and Intracellular Diastolic Calcium Removal in Isolated Ventricular Cardiomyocytes

Published on: September 18, 2017

Reduced sarcoplasmic reticulum Ca2+ -ATPase activity and dephosphorylated phospholamban contribute to contractile

Holger M Nef1, Helge Möllmann, Woitek Skwara

  • 1Department of Cardiology, Kerckhoff Heart Centre, Benekestr. 2-8, Bad Nauheim 61231, Germany.

Molecular and Cellular Biochemistry
|December 1, 2005
PubMed

Insights

Human hibernating myocardium involves impaired calcium handling, specifically reduced SERCA2a activity due to phospholamban (PLN) dysfunction. This leads to decreased cardiac contractility, which is reversible after revascularization.

Area of Science:

  • Cardiology
  • Molecular Biology
  • Biochemistry

Background:

  • Human hibernating myocardium (HHM) exhibits reversible contractile dysfunction due to chronic ischemia.
  • Disturbed calcium homeostasis is a key factor in reduced cardiac function in heart diseases.

Purpose of the Study:

  • Investigate calcium-handling proteins in HHM.
  • Determine the role of SERCA2a and PLN in HHM contractile dysfunction.

Main Methods:

  • Analyzed myocardial biopsies from 12 HHM patients using immunohistochemistry and electron microscopy.
  • Quantified SERCA2a, PLN, phosphorylated PLN, NCX, and RyR2 levels via RT-PCR and Western-blotting.
  • Measured SERCA2a activity using an enzyme-coupled assay.

Main Results:

  • Maximal SERCA2a activity was significantly reduced in HHM (424.5 U) compared to controls (609.0 U).
  • Increased PLN mRNA and protein levels resulted in a higher PLN:SERCA2a ratio.
  • Phosphorylation of PLN at Ser16 and Thr17 was significantly decreased in HHM.

Conclusions:

  • Decreased SERCA2a activity, caused by impaired PLN phosphorylation, contributes to HHM contractile dysfunction.
  • An elevated PLN/SERCA2a ratio reduces SERCA2a's calcium affinity, impacting cardiac function.
  • Functional recovery after revascularization suggests these molecular changes are reversible.

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