title: A saturable receptor for 32P-inositol-1,4,5-triphosphate in hepatocytes and neutrophils.
abstract: Several receptors for neurotransmitters, hormones and growth factors cause accelerated phosphodiesteratic breakdown of polyphosphoinositides when activated. One of the soluble products of this reaction, inositol-1,4,5-trisphosphate (Ins(1,4,5)P3) is thought to act as a second messenger signalling the release of Ca2+ from intracellular stores. In support of this hypothesis, several studies have shown that Ins(1,4,5)P3 releases sequestered Ca2+ from permeable cells and microsomes. On the basis of certain structural requirements for Ca2+-releasing activity by inositol phosphates, it has been postulated that Ins(1,4,5)P3 acts by binding to a specific intracellular receptor, probably on a component of the endoplasmic reticulum. Here we report that 32P-Ins(1,4,5)P3 binds to a specific saturable site in permeabilized guinea pig hepatocytes and rabbit neutrophils, and that the properties of this binding site suggest that it is the physiological receptor for Ins(1,4,5)P3.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D015220:Calcium Channels; D006168:Guinea Pigs; D015544:Inositol 1,4,5-Trisphosphate; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007295:Inositol Phosphates / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D009504:Neutrophils / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear; D013403:Sugar Phosphates / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007295:Inositol Phosphates; D010761:Phosphorus Radioisotopes; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D013403:Sugar Phosphates; D015544:Inositol 1,4,5-Trisphosphate