Inositol-1,3,4,5-tetrakisphosphate induces calcium mobilization via the inositol-1,4,5-trisphosphate receptor in SH-SY5Y neuroblastoma cells.

Abstract

myo-Inositol-1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4]-induced Ca2+ mobilization was examined in saponin-permeabilized SH-SY5Y cells using myo-inositol hexakisphosphate-supplemented buffer to prevent Ins(1,3,4,5)P4-3-phosphatase-catalyzed back-conversion of exogenous Ins(1,3,4,5)P4 to myo-inositol-1,4,5-trisphosphate [Ins(1,4,5)P3]. The Ins(1,3,4,5)P4 concentration-response curve for Ca2+ release in SH-SY5Y cells exhibited an EC50 of 2.5 microM, compared with 52 nM for Ins(1,4,5)P3, with the maximally effective concentration of Ins(1,3,4,5)P4 (100 microM) mobilizing the entire Ins(1,4,5)P3-sensitive pool. Both Ins(1,3,4,5)P4- and Ins(1,4,5)P3-induced Ca2+ mobilizations were heparin sensitive. Further, L-chiro-inositol-2,3,5-trisphosphorothioate, a recently identified low intrinsic activity Ins(1,4,5)P3 receptor partial agonist, shifted both the Ins(1,4,5)P3 and Ins(1,3,4,5)P4 concentration-response curves significantly rightward, with similar potencies. However, binding studies demonstrate that L-chiro-inositol-2,3,5-trisphosphorothioate interacts very poorly (IC50 > 30 microM) with specific Ins(1,3,4,5)P4 binding sites that have been previously characterized in pig cerebellum. Carbachol-pretreated SH-SY5Y cells (1 mM, > or 6 hr) exhibit a decrease in Ins(1,4,5)P3 receptor number, accompanied by both a rightward shift and a reduced maximal Ca2+ release in their Ins(1,4,5)P3 concentration-response curve. Here both Ins(1,4,5)P3 and Ins(1,3,4,5)P4 concentration-response curves were found to exhibit identically reduced maximal Ca2+ release responses and about 4-fold rightward shifts in EC50 values. Together, these observations provide compelling evidence for our hypothesis that Ins(1,3,4,5)P4 exhibits weak but full agonist status at Ins(1,4,5)P3 receptor-operated Ca2+ channels in SH-SY5Y cells.

• Authors: R A Wilcox, R A Challiss, C Liu, B V Potter, S R Nahorski
• Journal: Molecular pharmacology (Mol Pharmacol) Vol. 44 Issue 4 Pg. 810-7 (Oct 1993) ISSN: 0026-895X [Print] United States
• PMID: 8232232 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Calcium Channels
• ITPR1 protein, human
• Inositol 1,4,5-Trisphosphate Receptors
• Inositol Phosphates
• Receptors, Cytoplasmic and Nuclear
• Saponins
• inositol-1,3,4,5-tetrakisphosphate
• Inositol 1,4,5-Trisphosphate
• Carbachol
• Phosphoric Monoester Hydrolases
• Calcium

Topics

• Calcium (metabolism, physiology)
• Calcium Channels (metabolism)
• Carbachol (pharmacology)
• Cell Membrane Permeability (drug effects)
• Chromatography, High Pressure Liquid
• Humans
• Inositol 1,4,5-Trisphosphate (metabolism, pharmacology)
• Inositol 1,4,5-Trisphosphate Receptors
• Inositol Phosphates (metabolism, pharmacology)
• Kinetics
• Neuroblastoma (metabolism, ultrastructure)
• Phosphoric Monoester Hydrolases (antagonists & inhibitors, metabolism)
• Receptors, Cytoplasmic and Nuclear (metabolism)
• Saponins (pharmacology)
• Time Factors
• Tumor Cells, Cultured