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Activation of inositol 1,4,5-trisphosphate receptors induces transient changes in cell shape of fertilizedXenopus eggs

✍ Scribed by Muto, Akira ;Mikoshiba, Katsuhiko

Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
493 KB
Volume
39
Category
Article
ISSN
0886-1544

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✦ Synopsis

Injection of inositol 1,4,5-trisphosphate (InsP 3 ) into fertilized Xenopus eggs induced transient changes in cell shape. The region around the injected site contracted during the first 2 min, followed by swelling. These changes which initiated at the injected site extended toward the opposite side. Injection of adenophostin B, a potent InsP 3 receptor agonist, also induced similar morphological changes, which suggested that InsP 3 receptor activation, and not the action of InsP 3 metabolites, is responsible for these changes. To determine whether these changes correlate to InsP 3 receptor-mediated calcium release, we examined the morphological changes and those in intracellular free calcium concentrations ([Ca 2ϩ ] i ). A calcium wave was observed to precede the propagation of changes in cell shape by about 2 min. The extent of propagation of cell shape changes varied with the eggs but consistently depended on the extent of the calcium wave propagation. Changes in cell shape were inhibited in eggs injected with the calcium chelator, BAPTA, indicating that calcium released from the InsP 3 -sensitive calcium store is required for cell shape changes. During the cell shape changes, the contracted region was strongly stained with rhodamine-phalloidin, which suggests that structural changes of actin filaments are involved in the cortical changes. We propose that spatiotemporally controlled elevation of intracellular calcium induces successive cortical cytoskeletal changes that are responsible for changes in cell shape. These observations provide insight into the potency of InsP 3 /calcium signaling in the regulation of cortical cytoskeleton. Cell Motil.

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