Endoplasmic reticulum calcium tunnels integrate signalling in polarised cells

One of the most crucial aspects of Ca2+ signalling is the ability to generate highly localised transient elevations of the cytosolic Ca2+ concentration at specific strategically important target sites. Inevitably this necessitates a relatively high Ca2+ buffering power of the cytoplasm, which in turn makes movement of Ca2+ from one part of a cell to another difficult. Nature has evolved an elegant solution to this problem by creating operational Ca2+ tunnels through the endoplasmic reticulum. Very recently direct evidence that such tunnelling also occurs in neurons has been provided. (c) 2007 Elsevier Ltd. All rights reserved.