Module 2: Figure Ca2+-induced Ca2+ release

The role of Ca2+-induced Ca2+ release (CICR) in mobilizing Ca2+ from internal stores.

The Ca2+-sensitive channels are the ryanodine receptors (R) and the InsP3 receptors (I) located on the endoplasmic reticulum (ER). CICR has two important functions. Firstly, it provides a mechanism for transferring information from the plasma membrane to these internal release channels. The primary mechanism is based on the voltage-operated channels (VOCs) that open in response to membrane depolarization to allow a small amount of Ca2+ to enter, which then diffuses into the cell to activate either R or I. The other important function of CICR is to link together these intracellular channels so that the Ca2+ being released from one channel diffuses across to neighbouring channels that are excited to release further Ca2+, thereby setting up regenerative waves (yellow arrows).