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The anti-apoptotic protein HAX-1 is a regulator of cardiac function

Wen Zhao1, Jason R Waggoner, Zhi-Guo Zhang

  • 1Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0575, USA.

Proceedings of the National Academy of Sciences of the United States of America
|November 19, 2009
PubMed

Insights

HS-1 associated protein X-1 (HAX-1) regulates heart contractility by affecting calcium cycling. HAX-1 reduces sarcoplasmic reticulum Ca-ATPase activity, impacting myocyte mechanics and calcium kinetics.

Area of Science:

  • Cardiology
  • Molecular Biology
  • Biochemistry

Background:

  • HS-1 associated protein X-1 (HAX-1) is known to protect cardiomyocytes from cell death.
  • Cardiac contractility and calcium handling are critical for heart function.

Purpose of the Study:

  • To investigate the role of HAX-1 in regulating cardiac contractility and calcium cycling.
  • To elucidate the molecular mechanisms by which HAX-1 influences cardiac function.

Main Methods:

  • Studied HAX-1 effects on isolated cardiomyocytes and in vivo models.
  • Assessed sarcoplasmic reticulum Ca-ATPase (SERCA2) pump activity and myocyte calcium kinetics.
  • Investigated the interaction of HAX-1 with phospholamban (PLN) and its phosphorylation status.

Main Results:

  • Overexpression of HAX-1 reduced SERCA2 activity, leading to depressed myocyte calcium kinetics and mechanics.
  • Downregulation of HAX-1 enhanced calcium cycling and contractility.
  • HAX-1's inhibitory effects were dependent on phospholamban's phosphorylation state.
  • HAX-1 promotes phospholamban monomer formation, which are the active units of the calcium pump.
  • Ablation of PLN rescued HAX-1-mediated inhibition of contractility.

Conclusions:

  • HAX-1 is a novel regulator of cardiac calcium cycling and contractility.
  • HAX-1 influences cardiac function by modulating phospholamban activity.
  • HAX-1 plays a role in cardiac calcium homeostasis and response to sympathetic stimulation.

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