Abstract
BackgroundChanges in ionic concentration have a fundamental effect on numerous physiological processes. For example, IP3-gated thapsigargin sensitive intracellular calcium (Ca2+) storage provides a source of the ion for many cellular signaling events. Less is known about the dynamics of other intracellular ions. The present study investigated the intracellular source of zinc (Zn2+) that has been reported to play a role in cell signaling.ResultsIn primary cultured cortical cells (neurons) labeled with intracellular fluorescent Zn2+ indicators, we showed that intracellular regions of Zn2+ staining co-localized with the endoplasmic reticulum (ER). The latter was identified with ER-tracker Red, a marker for ER. The colocalization was abolished upon exposure to the Zn2+ chelator TPEN, indicating that the local Zn2+ fluorescence represented free Zn2+ localized to the ER in the basal condition. Blockade of the ER Ca2+ pump by thapsigargin produced a steady increase of intracellular Zn2+. Furthermore, we determined that the thapsigargin-induced Zn2+ increase was not dependent on extracellular Ca2+ or extracellular Zn2+, suggesting that it was of intracellular origin. The applications of caged IP3 or IP3-3Kinase inhibitor (to increase available IP3) produced a significant increase in intracellular Zn2+.ConclusionsTaken together, these results suggest that Zn2+ is sequestered into thapsigargin/IP3-sensitive stores and is released upon agonist stimulation.
Highlights
Changes in ionic concentration have a fundamental effect on numerous physiological processes
The present study investigates the intracellular source of free Zn2+, if thapsigargin can trigger the release of Zn2+
Intracellular Regions of Elevated Zn2+ Co-localize with the Endoplasmic Reticulum Cells labeled with intracellular fluorescent Zn2+ indicators and examined under basal conditions showed consistent regions of elevated fluorescent intensity in the soma and processes, and in a region that was identified as the endoplasmic reticulum by a fluorescent marker for the organelle
Summary
Changes in ionic concentration have a fundamental effect on numerous physiological processes. IP3-gated thapsigargin sensitive intracellular calcium (Ca2+) storage provides a source of the ion for many cellular signaling events. The present study investigated the intracellular source of zinc (Zn2+) that has been reported to play a role in cell signaling. Zn2+ may act as a cellular messenger in physiological and cytotoxic signaling, and the changes in Zn2+ homeostasis have a fundamental effect in cell function [4,5]. Many studies have shown the accumulation of excessive Zn2+ to precede cell death or neurodegeneration in response to cytotoxic stress [6,7]. To characterize Zn2+-mediated signaling pathways or Zn2+-induced cytotoxicity, it is important to determine the source(s) of intracellular free Zn2+ in response to specific stimuli or injury
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