Cardiomyocyte calcium-handling machinery

The cardiomyocyte calcium-handling machinery is a complex network of proteins and organelles that regulates the cyclical rise and fall of intracellular calcium levels, a process fundamental to cardiac contraction and relaxation (Taylor & Francis, 2022). This machinery facilitates excitation-contraction (E-C) coupling, where an action potential triggers calcium entry through L-type calcium channels (LTCC), which in turn stimulates a massive release of calcium from the sarcoplasmic reticulum (SR) via ryanodine receptor 2 (RyR2) (NIH, 2011; NIH, 2017). The subsequent binding of calcium to the myofilament protein troponin C initiates muscle contraction (MDPI, 2023). Relaxation occurs as calcium is removed from the cytosol, primarily through reuptake into the SR by the sarcoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) and extrusion via the sodium-calcium exchanger (NCX) (NIH, 2011; NIH, 2017). Dysregulation of these components, such as RyR2 leakage or impaired SERCA2a function, is a primary driver of heart failure and life-threatening arrhythmias (Frontiers, 2022; NIH, 2017). Consequently, this machinery is a major focus for therapeutic intervention, with drugs like calcium channel blockers, calcium sensitizers, and SERCA2a activators being used or developed to restore calcium homeostasis and improve cardiac performance (MDPI, 2023; NIH, 2011).

Other names

Cardiac calcium handling systemExcitation-contraction coupling machineryMyocardial Ca2+ handling machinery

The mechanism of action involves the modulation of calcium ion flux and sensitivity within the cardiomyocyte. Drugs may block L-type calcium channels to reduce influx, activate SERCA2a to enhance sarcoplasmic reticulum calcium reuptake, or stabilize ryanodine receptors to prevent diastolic calcium leak. These actions aim to optimize the calcium transient, thereby improving the force of contraction (inotropy) and the rate of relaxation (lusitropy) while minimizing the risk of triggered arrhythmias.