Differential stereoselectivity of D- and L-myo-inositol 1,2,4,5-tetrakisphosphate binding to the inositol 1,4,5-trisphosphate receptor and 3-kinase

D- and L-myo-inositol 1,2,4,5-tetrakisphosphate (Ins(1,2,4,5)P₄) were investigated for their ability to bind to the D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P₃) receptor in a bovine adrenal cortical membrane fraction, to mobilize intracellular Ca²⁺ stores in Xenopus oocytes, and to bind to the rat brain Ins(1,4,5)P₃ 3-kinase overexpressed and purified in E. coli. In competitive binding experiments with the Ins(1,4,5)P₃ receptor, D-Ins(1,2,4,5)P₄ effectively displaced [³H]Ins(1,4,5)P₃ in a concentration-dependent manner with a potency comparable to that of D-Ins(1,4,5)P₃, while L-Ins(1,2,4,5)P₄ was ~50-fold less effective than D-Ins(1,4,5)P₃ and D-Ins(1,2,4,5)P₄. The DL-Ins(1,2,4,5)P₄ racemate bound to the Ins(1,4,5)P₃ receptor with an apparent intermediate efficiency. Injection of D-Ins(1,2,4,5)P₄ into oocytes evoked a chloride current dependent on intracellular Ca²⁺ mobilization in which the agonists ranked in a similar order of potency as in the Ins(1,4,5)P₃ receptor binding. On the other hand, D-Ins(1,2,4,5)P₄ only inhibited the binding of [³H]Ins(1,4,5)P₃ to 3-kinase very weakly with a markedly reduced potency compared to D-Ins(1,4,5)P₃, indicating that D-Ins(1,2,4,5)P₄ is not an effective competitor in the phosphorylation of [³H]-Ins(1,4,5)P₃ by 3-kinase. The results, therefore, clearly indicate that D-Ins(1,2,4,5)P₄ is as effective as D-Ins(1,4,5)P₃ in the binding to the receptor but not 3-kinase, and access of Ins(1,2,4,5)P₄ over the Ins(1,4,5)P₃ receptor calls for stringent stereospecificity with D-Ins(1,2,4,5)P₄ being the active form in DL-Ins(1,2,4,5)P₄-mediated Ca²⁺ mobilization. Copyright (C) 2000 Elsevier Science Ltd.