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Histidine-rich Ca-binding protein interacts with sarcoplasmic reticulum Ca-ATPase

Demetrios A Arvanitis1, Elizabeth Vafiadaki, Guo-Chang Fan

  • 1Molecular Biology Division, Center for Basic Research, Foundation for Biomedical Research of the Academy of Athens, Athens, Greece.

American Journal of Physiology. Heart and Circulatory Physiology
|May 29, 2007
PubMed

Insights

The histidine-rich Ca-binding protein (HRC) directly binds to SERCA2, regulating calcium cycling in the heart. This interaction fine-tunes calcium uptake and release, impacting cardiac function and potentially heart failure progression.

Area of Science:

  • Cardiovascular Physiology
  • Molecular Cardiology
  • Calcium Signaling

Background:

  • Depressed sarcoplasmic reticulum (SR) calcium cycling is linked to reduced cardiac contractility and heart failure.
  • The histidine-rich Ca-binding protein (HRC) interacts with triadin and influences calcium release via the ryanodine receptor.
  • HRC overexpression in mice impairs SR calcium uptake and relaxation, leading to cardiac hypertrophy.

Purpose of the Study:

  • To investigate the direct interaction between HRC and sarco(endo)plasmic reticulum Ca-ATPase type 2 (SERCA2) in cardiac muscle.
  • To elucidate the functional consequences of HRC-SERCA2 binding on cardiac calcium handling.

Main Methods:

  • Coimmunostaining and confocal microscopy to visualize HRC and SERCA2 localization.
  • Coimmunoprecipitation, pull-down assays, and blot overlays to confirm direct binding.
  • Analysis of HRC-SERCA2 and HRC-triadin interactions under varying calcium concentrations.

Main Results:

  • HRC directly binds to SERCA2 in cardiac muscle, involving specific domains of both proteins.
  • The interaction between HRC and SERCA2 is inversely regulated by calcium concentration.
  • HRC binding to SERCA2 decreases as calcium levels rise, while HRC-triadin interaction increases.

Conclusions:

  • HRC plays a critical role in regulating SR calcium cycling through direct interaction with SERCA2.
  • HRC mediates cross-talk between SR calcium uptake (SERCA2) and release (triadin-ryanodine receptor).
  • This regulatory mechanism is crucial for maintaining cardiac function and preventing heart failure progression.

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