Origin sites of calcium release and calcium oscillations in frog sympathetic neurons.

McDonough SI, Cseresnyés Z, Schneider MF (2000) Origin sites of calcium release and calcium oscillations in frog sympathetic neurons. J Neurosci 20(24), 9059-9070.

Abstract

In many neurons, Ca(2+) signaling depends on efflux of Ca(2+) from intracellular stores into the cytoplasm via caffeine-sensitive ryanodine receptors (RyRs) of the endoplasmic reticulum. We have used high-speed confocal microscopy to image depolarization- and caffeine-evoked increases in cytoplasmic Ca(2+) levels in individual cultured frog sympathetic neurons. Although caffeine-evoked Ca(2+) wave fronts propagated throughout the cell, in most cells the initial Ca(2+) release was from one or more discrete sites that were several micrometers wide and located at the cell edge, even in Ca(2+)-free external solution. During cell-wide cytoplasmic [Ca(2+)] oscillations triggered by continual caffeine application, the initial Ca(2+) release that began each Ca(2+) peak was from the same subcellular site or sites. The Ca(2+) wave fronts propagated with constant amplitude; the spread was mostly via calcium-induced calcium release. Propagation was faster around the cell periphery than radially inward. Local Ca(2+) levels within the cell body could increase or decrease independently of neighboring regions, suggesting independent action of spatially separate Ca(2+) stores. Confocal imaging of fluorescent analogs of ryanodine and thapsigargin, and of MitoTracker, showed potential structural correlates to the patterns of Ca(2+) release and propagation. High densities of RyRs were found in a ring around the cell periphery, mitochondria in a broader ring just inside the RyRs, and sarco-endoplasmic reticulum Ca(2+) ATPase pumps in hot spots at the cell edge. Discrete sites at the cell edge primed to release Ca(2+) from intracellular stores might preferentially convert Ca(2+) influx through a local area of plasma membrane into a cell-wide Ca(2+) increase.

Leibniz-HKI-Autor*innen

Zoltán Cseresnyés

Identifier

PMID: 11124983