Inositol-(1,4,5)-triphosphate receptors (InsP(3)Rs) are ligand-gated Ca(2+) channels that control Ca(2+) release from intracellular stores and play a central role in a wide range of cellular responses. In most epithelial cells, InsP(3)Rs are not uniformly distributed within the endoplasmic reticulum (ER) membrane, with the consequence that agonist stimulation results in compartmentalized Ca(2+)...

Methods used to quantify inositol phosphates in seeds lack the sensitivity and specificity necessary to accurately detect the lower concentrations of these compounds contained in the leaves of many plants. In order to measure inositol hexakisphosphate (InsP₆) and inositol pentakisphosphate (InsP₅) levels in leaves of different plants, a method was developed to concentrate and pre-purify these c...

Many cellular functions are regulated by agonist-induced InsP(3)-evoked Ca2+ release from the internal store. In non-excitable cells, predominantly, the initial Ca2+ release from the store by InsP(3) is followed by a more sustained elevation in [Ca2+](i) via store-operated Ca2+ channels as a consequence of depletion of the store. Here, in smooth muscle, we report that the initial transient incr...

This review assesses the authenticity of inositol hexakisphosphate (InsP(6)) being a wide-ranging regulator of many important cellular functions. Against a background in which the possible importance of localized InsP(6) metabolism is discussed, there is the facile explanation that InsP(6) is merely an "inactive" precursor for the diphosphorylated inositol phosphates. Indeed, many of the propos...

Plants sense positional changes relative to the gravity vector. To date, the signaling processes by which the perception of a gravistimulus is linked to the initiation of differential growth are poorly defined. We have investigated the role of inositol 1,4,5-trisphosphate (InsP(3)) in the gravitropic response of oat (Avena sativa) shoot pulvini. Within 15 s of gravistimulation, InsP(3) levels i...

Modulation of the type 1 inositol (1,4,5)-trisphosphate receptors (InsP(3)R1) by cytosolic calcium (Ca(2+)) plays an essential role in their signaling function, but structural determinants and mechanisms responsible for the InsP(3)R1 regulation by Ca(2+) are poorly understood. Using DT40 cell expression system and Ca(2+) imaging assay, in our previous study we identified a critical role of E210...

In Swiss 3T3 fibroblasts bradykinin stimulated inositol phosphate (InsP) formation and prostaglandin E2 (PGE2) synthesis. The EC50 values for stimulation of PGE2 synthesis and InsP formation by bradykinin were similar, 200 pM and 275 pM, respectively. Guanosine-5'-[gamma-thio]triphosphate stimulated PGE2 synthesis and InsP formation, and guanosine-5'-[beta-thio]diphosphate inhibited both PGE2 s...

Store-operated channels (SOCs) provide an important means for mediating longer-term Ca(2+) signals and replenishment of Ca(2+) stores in a multitude of cell types. However, the coupling mechanism between endoplasmic reticulum stores to activate plasma membrane SOCs remains unknown. In DT40 chicken B lymphocytes, the permeant inositol trisphosphate receptor (InsP(3)R) modifier, 2-aminoethoxydiph...

The ubiquitous inositol 1,4,5-trisphosphate (InsP(3)) receptor (InsP(3)R) channel, localized primarily in the endoplasmic reticulum (ER) membrane, releases Ca(2+) into the cytoplasm upon binding InsP(3), generating and modulating intracellular Ca(2+) signals that regulate numerous physiological processes. Together with the number of channels activated and the open probability of the active chan...

The inositol 1,4,5-trisphosphate (InsP(3)) receptor (InsP(3)R) plays a critical role in generation of complex Ca(2+) signals in many cell types. In patch clamp recordings of isolated nuclei from insect Sf9 cells, InsP(3)R channels were consistently detected with regulation by cytoplasmic InsP(3) and free Ca(2+) concentrations ([Ca(2+)](i)) very similar to that observed for vertebrate InsP(3)R. ...