Figure 6. ROS and Calcium crosstalk between endoplasmic reticulum and mitochondria.

The ER is a major site of calcium ions (Ca²⁺) storage within muscle cells. Calcium from ER cisternae is flowing mainly through calcium release channels as inositol 1,4,5-trisphosphate receptors (IP3R) and ryanodine receptors (RyR). High levels of calcium stimulate respiratory chain activity leading to higher amounts of reactive oxygen species (ROS) through RISP. ROS can further target ER-based calcium channels leading to increased release of calcium and further increased ROS levels.