Physiologically, hormone induced release of Ca 2+ from intracellular stores occurs in response to inositol 1,4,5-trisphosphate (IP 3 ) binding to its receptors expressed on the membranes of intracellular organelles, mainly endoplasmic reticulum. These IP 3 receptors act as channels, releasing Ca 2+ into the cytoplasmic space where it is responsible for regulating a host of distinct cellular processes. The depletion of intracellular Ca 2+ stores leads to activation of store-operated Ca 2+ channels on the plasma membrane which replenishes lost Ca 2+ and sustain Ca 2+ signalling. There are three isoforms of IP 3 receptor, each exhibiting distinctive properties, however, little is known about the role of each isoform in the activation of store-operated Ca 2+ entry. Recent evidence suggest that at least in some cell types the endoplasmic reticulum is not a homogeneous Ca 2+ store, and there might be a sub-compartment specifically linked to the activation of store-operated Ca 2+ channels, and Ca 2+ release activated Ca 2+ (CRAC) channel in particular. Furthermore, this sub-compartment might express only certain types of IP 3 receptor but not the others. Here we show that H4IIE liver cells express all three types of IP 3 receptor, but only type 1 and to a lesser extent type 3, but not type 2, participate in the activation of CRAC current (I CRAC ), while type 1 and type 2, but not type 3, participate in observed Ca 2+ release in response to receptor stimulation. Presented results suggest that in H4IIE rat liver cells the sub-compartment of intracellular Ca 2+ store linked to the activation of I CRAC predominantly expresses type 1 IP 3 receptors.
|Number of pages||7|
|Journal||Biochimica Et Biophysica Acta (BBA) - Biomembranes|
|Publication status||Published - Mar 2011|