Adenophostin A induces spatially restricted calcium signaling in Xenopus laevis oocytes.
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 nM) 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 (approximately 10 pM), stable regions of Ca2+ 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.
Calcium Regulation Section, Laboratory of Signal Transduction, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
G S
GS
Bird
M
M
Takahashi
K
K
Tanzawa
J W
JW
Putney
D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects*; D005260:Female; D007700:Kinetics; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D014982:Xenopus laevis
C085029:adenophostin A; D000241:Adenosine