Ca2+tunnelling through the ER lumen as a mechanism for delivering Ca2+entering via store-operated Ca2+channels to specific target sites.
Ca2+signalling is perhaps the most universal and versatile mechanism regulating a wide range of cellular processes. Because of the many different calcium-binding proteins distributed throughout cells, signalling precision requires localized rises in the cytosolic Ca2+concentration. In electrically non-excitable cells, for example epithelial cells, this is achieved by primary release of Ca2+from the endoplasmic reticulum via Ca2+release channels placed close to the physiological target. Because any rise in the cytosolic Ca2+concentration activates Ca2+extrusion, and in order for cells not to run out of Ca2+, there is a need for compensatory Ca2+uptake from the extracellular fluid. This Ca2+uptake occurs through a process known as store-operated Ca2+entry. Ideally Ca2+entering the cell should not diffuse to the target site through the cytosol, as this would potentially activate undesirable processes. Ca2+tunnelling through the lumen of the endoplasmic reticulum is a mechanism for delivering Ca2+entering via store-operated Ca2+channels to specific target sites, and this process has been described in considerable detail in pancreatic acinar cells and oocytes. Here we review the most important evidence and present a generalized concept.
MRC Group, School of Biosciences and Systems Immunity Research Institute, Cardiff University, Cardiff, CF10 3AX, UK.
Ole H
0000-0002-6998-0380
OH
Petersen
Department of Physiology and Biophysics, Weill Cornell Medicine Qatar, Education City, Qatar Foundation, PO Box 24144, Doha, Qatar.
Raphael
R
Courjaret
Department of Physiology and Biophysics, Weill Cornell Medicine Qatar, Education City, Qatar Foundation, PO Box 24144, Doha, Qatar.
Khaled
0000-0001-6215-2411
K
Machaca
D061354:Acinar Cells / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006801:Humans; D009865:Oocytes / Q000378:metabolism
D015220:Calcium Channels; D002118:Calcium
calcium activated chloride current; calcium entry; calcium signalling