Sorting of calcium signals at the junctions of endoplasmic reticulum and mitochondria.
Calcium signal transmission between endoplasmic reticulum (ER) and mitochondria is supported by a local [Ca(2+)] control that operates between IP(3)receptor Ca(2+)release channels (IP(3)R) and mitochondrial Ca(2+)uptake sites, and displays functional similarities to synaptic transmission. Activation of IP(3)R by IP(3)is known to evoke quantal Ca(2+)mobilization that is associated with incremental elevations of mitochondrial matrix [Ca(2+)] ([Ca(2+)](m)). Here we report that activation of IP(3)R by adenophostin-A (AP) yields non-quantal Ca(2+)mobilization in mast cells. We also show that the AP-induced continuous Ca(2+)release causes relatively small [Ca(2+)](m)responses, in particular, the sustained phase of Ca(2+)release is not sensed by the mitochondria. Inhibition of ER Ca(2+)pumps by thapsigargin slightly increases IP(3)-induced [Ca(2+)](m)responses, but augments AP-induced [Ca(2+)](m)responses in a large extent. In adherent permeabilized cells exposed to elevated [Ca(2+)], ER Ca(2+)uptake fails to affect global cytosolic [Ca(2+)], but attenuates [Ca(2+)](m)responses. Moreover, almost every mitochondrion exhibits a region very close to ER Ca(2+)pumps visualized by BODIPY-FL-thapsigargin or SERCA antibody. Thus, at the ER-mitochondrial junctions, localized ER Ca(2+)uptake provides a mechanism to attenuate the mitochondrial response during continuous Ca(2+)release through the IP(3)R or during gradual Ca(2+)influx to the junction between ER and mitochondria.
Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia 19107, USA.
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D000241:Adenosine / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism*; D005470:Fluorometry; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000737:chemistry / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; C085029:adenophostin A; D015544:Inositol 1,4,5-Trisphosphate; D000252:Calcium-Transporting ATPases; D000241:Adenosine; D002118:Calcium