IP3R

IP3R stands for inositol trisphosphate receptor. It is a type of intracellular calcium channel found in the membrane of the endoplasmic reticulum and sarcoplasmic reticulum. IP3Rs play a crucial role in calcium signaling within cells.

When a cell receives certain external signals, such as hormones or neurotransmitters, a cascade of events can lead to the production of a second messenger molecule called inositol (1,4,5)-trisphosphate, or IP3. This IP3 then diffuses through the cytoplasm and binds to IP3 receptors on the endoplasmic reticulum.

Upon binding of IP3, the IP3 receptor undergoes a conformational change, opening its channel and allowing calcium ions (Ca2+) to flow out of the endoplasmic reticulum lumen into the cytosol. This rapid release of stored calcium dramatically increases the intracellular calcium concentration.

The resulting surge in cytosolic calcium acts as a signal, triggering a wide range of cellular processes. These include muscle contraction, neurotransmitter release, gene expression, cell proliferation, and cell death. Different types of IP3 receptors exist, encoded by different genes, which can lead to variations in their localization, function, and regulation within the cell. Dysfunction of IP3Rs has been implicated in various diseases.