Title: Inositol 1,4,5-trisphosphate and ryanodine receptors mobilize calcium from a common functional pool in human U373 MG cells
Abstract: This investigation concentrates on the change in Ca2+ concentration ([Ca2+]) caused by ryanodine in U373 MG cells. This cell type from a human astrocytoma is a unique cellular model because it only expresses the type 3 ryanodine receptor (RyR3), which is generally the least abundant isoform. In the presence of physiological [Ca2+] in the extracellular medium, U373 MG cells are caffeine-insensitive, even after forskolin treatment, and ryanodine-sensitive only when an unusually high concentration (30 μM) is applied. Xestospongin C behaves like thapsigargin and therefore cannot be used as a selective antagonist of inositol 1,4,5-trisphosphate receptors (InsP3Rs). After ryanodine challenge, addition of an analog of Substance P (SP), which should deplete InsP3-sensitive stores, has no effect on [Ca2+]i. After thapsigargin treatment, which unmasks the calcium leak from intracellular stores, neither ryanodine nor SP change [Ca2+]i, suggesting that thapsigargin completely depletes the ryanodine-sensitive and the InsP3-sensitive stores of U373 MG cells. Finally, in experiments monitoring the [Ca2+] in intracellular stores, InsP3 stimulation of permeabilized cells causes a decrease in [Ca2+] that is not affected by subsequent ryanodine treatment. Our results support the conclusion that U373 MG cells express both InsP3Rs and RyRs that can individually or in combination mobilize only one functional Ca2+ pool.
Publication Year: 2004
Publication Date: 2004-11-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 5
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