title: 3-position modification of myo-inositol 1,4,5-trisphosphate: consequences for intracellular Ca2+ mobilisation and enzyme recognition.
abstract: The ability of the novel D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) analogues, L-chiro-inositol 2,3,5-trisphosphate (L-ch-Ins(2,3,5)P3) and D-3-deoxy-3-fluoro-myo-inositol 1,4,5-trisphosphate (3F-Ins(1,4,5)P3), to bind to the Ins(1,4,5)P3 receptor, mobilise intracellular Ca2+ stores and interact with metabolic enzymes has been investigated. L-ch-Ins(2,3,5)P3 and 3F-Ins(1,4,5)P3 were bound by the Ins(1,4,5)P3 receptor from bovine adrenal cortex with relatively high affinity (Ki values 60.4 and 8.0 nM respectively) but with lower affinity than Ins(1,4,5)P3 (KD = 5.9 nM). Both analogues were apparent full agonists at the Ca2+ mobilising receptor in SH-SY5Y cells, but were less potent than Ins(1,4,5)P3 (EC50 L-ch-Ins(2,3,5)P3 = 1.4 microM, 3F-Ins(1,4,5)P3 = 0.37 microM and Ins(1,4,5)P3 = 0.12 microM). L-ch-Ins(2,3,5)P3 and 3F-Ins(1,4,5)P3 were resistant to Ins(1,4,5)P3 3-kinase, and were potent inhibitors of the enzyme (Ki values 7.1 and 8.6 microM respectively). 3F-Ins(1,4,5)P3 was hydrolysed by Ins(1,4,5)P3 5-phosphatase at a similar rate to Ins(1,4,5)P3, but inhibited dephosphorylation of [3H]Ins(1,4,5)P3 with high potency (apparent Ki = 3.9 microM) L-ch-Ins(2,3,5)P3 was also recognised by the enzyme with high affinity (Ki = 7.7 microM) but was resistant to hydrolysis. These results suggest that the environment around C-3 is of major importance for recognition not only by Ins(1,4,5)P3 3-kinase but also by Ins(1,4,5)P3 5-phosphatase.
authors.affiliation: Department of Pharmacology and Therapeutics, University of Leicester, UK.
authors.forename: S T
authors.initials: ST
authors.lastname: Safrany
authors.forename: R A
authors.initials: RA
authors.lastname: Wilcox
authors.forename: C
authors.initials: C
authors.lastname: Liu
authors.forename: B V
authors.initials: BV
authors.lastname: Potter
authors.forename: S R
authors.initials: SR
authors.lastname: Nahorski
mesh_terms: D000311:Adrenal Glands / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D004910:Erythrocyte Membrane / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000737:chemistry / Q000378:metabolism*; D009447:Neuroblastoma / Q000201:enzymology / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010770:Phosphotransferases / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor); D013379:Substrate Specificity
chemical_list: D015544:Inositol 1,4,5-Trisphosphate; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C051038:Inositol 1,4,5-trisphosphate 3-kinase; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase; D002118:Calcium