Adenophostin A Induces Spatially Restricted Calcium Signaling in Xenopus laevis Oocytes

• Published in: The Journal of biological chemistry 1999-07, Vol.274 (29), p.20643-20649
• Main Authors: Bird, G S, Takahashi, M, Tanzawa, K, Putney, Jr, J W
• Format: Article
• Language: English
• Subjects: adenophostin A; Adenosine - analogs & derivatives; Adenosine - pharmacology; Animals; Calcium Signaling - drug effects; Female; inostiol 2,4,5-trisphosphate; Kinetics; Microscopy, Confocal; Microscopy, Fluorescence; Oocytes - drug effects; Oocytes - metabolism; Xenopus laevis
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.29.20643

The activation of intracellular calcium release and calcium entry across the plasmalemma in response to intracellular application of inositol 2,4,5-trisphosphate and adenophostin A, two metabolically stable agonists for inositol 1,4,5-trisphosphate receptors, was investigated using Xenopus laevis oocytes and confocal imaging. Intracellular injection of inositol 2,4,5-trisphosphate induced a rapidly spreading calcium signal associated with regenerative calcium waves; the calcium signal filled the peripheral regions of the cell in 1–5 min. Injection of high concentrations of adenophostin A (250 n m ) similarly induced rapidly spreading calcium signals. Injection of low concentrations of adenophostin A resulted in calcium signals that spread slowly (>1 h). With extremely low concentrations of adenophostin A (∼10 p m ), stable regions of Ca 2+ release were observed that did not expand to peripheral regions. When the adenophostin A-induced calcium signal was restricted to central regions, compartmentalized calcium oscillations were sometimes observed. Restoration of extracellular calcium caused a rise in cytoplasmic calcium restricted to the region of adenophostin A-induced calcium mobilization. The limited diffusion of adenophostin A provides an opportunity to examine calcium signaling processes under spatially restricted conditions and provides insights into mechanisms of intracellular calcium oscillations and capacitative calcium entry.