title: Irreversible inhibition of Ca2+ release in saponin-treated macrophages by the photoaffinity derivative of inositol-1, 4, 5-trisphosphate.
abstract: D-myo-inositol-1,4,5-trisphosphate (InsP3) is a putative intracellular second messenger for the mobilization of Ca2+ from intracellular stores, in particular, the endoplasmic reticulum. Specific binding sites on the endoplasmic reticulum may participate in the InsP3-induced release of Ca2+ from the Ca2+ pool. To examine the specific binding sites on the endoplasmic reticulum, we synthesized an arylazide derivative of InsP3 for photoaffinity labelling; InsP3 coupled to p-azidobenzoic acid (InsP3-pAB) using N,N'-carbonyldiimidazole (CDI) was obtained at a 9-11% yield. Here, we report that InsP3-pAB, but not an arylazide derivative of inositol-1,4-bisphophate (Ins(1,4)P2), causes the irreversible inhibition of InsP3-induced release of Ca2+ in saponin-permeabilized photo-irradiated macrophages. The irreversible inhibition by InsP3-pAB after photo-irradiation was prevented by a 10-fold excess of unmodified InsP3.
mesh_terms: D000345:Affinity Labels; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D010777:Photochemistry; D012503:Saponins; D013329:Structure-Activity Relationship; D013403:Sugar Phosphates / Q000494:pharmacology*
chemical_list: D000345:Affinity Labels; D007295:Inositol Phosphates; D012503:Saponins; D013403:Sugar Phosphates; D002118:Calcium