Xestospongins: Potent Membrane Permeable Blockers of the Inositol 1,4,5-Trisphosphate Receptor

Xestospongins (Xe's) A, C, D, araguspongine B, and demethylxestospongin B, a group of macrocyclic bis-1-oxaquinolizidines isolated from the Australian sponge, Xestospongia species, are shown to be potent blockers of IP3-mediated Ca2+ release from endoplasmic reticulum vesicles of rabbit cerebellum. XeC blocks IP3-induced Ca2+ release (IC50 = 358 nM) without interacting with the IP3-binding site...

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The Inositol 1,4,5-Trisphosphate Receptor of Cerebellum

A B S T RA C X The inositol 1,4,5-trisphosphate receptor (InsPaR), an intracellular calcium release channel, is found in virtually all cells and is abundant in the cerebellum. We used Mn 2+ as a tool to study two aspects of the cerebellar InsP3R. First, to investigate the structure of the ion pore, Mn 2+ permeation through the channel was determined. We found that Mn 2+ can pass through the Ins...

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The Inositol 1,4,5-Trisphosphate Receptor of Cerebellum

A B S T RA C X The inositol 1,4,5-trisphosphate receptor (InsPaR), an intracellular calcium release channel, is found in virtually all cells and is abundant in the cerebellum. We used Mn 2+ as a tool to study two aspects of the cerebellar InsP3R. First, to investigate the structure of the ion pore, Mn 2+ permeation through the channel was determined. We found that Mn 2+ can pass through the Ins...

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The Inositol 1,4,5-Trisphosphate Receptor of Cerebellum

A B S T RA C X The inositol 1,4,5-trisphosphate receptor (InsPaR), an intracellular calcium release channel, is found in virtually all cells and is abundant in the cerebellum. We used Mn 2+ as a tool to study two aspects of the cerebellar InsP3R. First, to investigate the structure of the ion pore, Mn 2+ permeation through the channel was determined. We found that Mn 2+ can pass through the Ins...

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The inositol trisphosphate phosphomonoesterase of the human erythrocyte membrane.

Human erythrocyte ghosts exhibit an inositol trisphosphate phosphomonoesterase activity that rapidly converts inositol 1,4,5-trisphosphate into inositol 1,4-bisphosphate and Pi. Degradation of the released inositol 1,4-bisphosphate is not observed. This activity is dependent on Mg2+ (or Mn2+) and it is not activated by Ca2+. Optimum activity is around pH 7 and activity is abolished by heat dena...

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Xestospongins: Potent Membrane Permeable Blockers of the Inositol 1,4,5-Trisphosphate Receptor

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