Inositol 1,4,5-triphosphate receptor, also known as IP3R or InsP3R, is a member of the intracellular calcium release
channel family, and is located in the endoplasmic reticulum.
It functions as a Ca2+ release channel for intracellular stores
of calcium ions. There are three types of IP3 receptors (IP3
receptor 1, 2 and 3) that require the second messenger
inositol 1,4,5-triphosphate (IP3) for activation (3). Four
individual receptor subunits, resulting in homo- or hetero-oligomerization
of the receptor isoform, form a functional
channel (4). Phosphorylation of IP3R1 at Ser1756 by cyclic-
AMP-dependent protein kinase A (PKA) regulates the
sensitivity of IP3R1 to IP3 and may thus be a mode of
regulation for Ca2+ release (5, 6). IP3R1 mediated calcium
release appears to have an effect on the induction of long
term depression (LTD) in Purkinje cells (7).