Ryanodine-Inositol 1,4,5-triphosphate receptor calcium channels

The ryanodine-inositol 1,4,5-triphosphate receptor Ca²⁺ channel (RIR-CaC) family includes Ryanodine receptors and Inositol trisphosphate receptors. Members of this family are large proteins, some exceeding 5000 amino acyl residues in length. This family belongs to the Voltage-gated ion channel (VIC) superfamily. Ry receptors occur primarily in muscle cell sarcoplasmic reticular (SR) membranes, and IP₃ receptors occur primarily in brain cell endoplasmic reticular (ER) membranes where they effect release of Ca²⁺ into the cytoplasm upon activation (opening) of the channel. They are redox sensors, possibly providing a partial explanation for how they control cytoplasmic Ca²⁺. Ry receptors have been identified in heart mitochondria where they provide the main pathway for Ca²⁺ entry. Sun et al. (2011) have demonstrated oxygen-coupled redox regulation of the skeletal muscle ryanodine receptor-Ca²⁺ release channel (RyR1;TC# 1.A.3.1.2) by NADPH oxidase 4.