Imaging interorganelle contacts and local calcium dynamics at the ER-mitochondrial interface.
The ER-mitochondrial junction provides a local calcium signaling domain that is critical for both matching energy production with demand and the control of apoptosis. Here, we visualize ER-mitochondrial contact sites and monitor the localized [Ca(2+)] changes ([Ca(2+)](ER-mt)) using drug-inducible fluorescent interorganelle linkers. We show that all mitochondria have contacts with the ER, but plasma membrane (PM)-mitochondrial contacts are less frequent because of interleaving ER stacks in both RBL-2H3 and H9c2 cells. Single mitochondria display discrete patches of ER contacts and show heterogeneity in the ER-mitochondrial Ca(2+) transfer. Pericam-tagged linkers revealed IP(3)-induced [Ca(2+)](ER-mt) signals that exceeded 9 microM and endured buffering bulk cytoplasmic [Ca(2+)] increases. Altering linker length to modify the space available for the Ca(2+) transfer machinery had a biphasic effect on [Ca(2+)](ER-mt) signals. These studies provide direct evidence for the existence of high-Ca(2+) microdomains between the ER and mitochondria and suggest an optimal gap width for efficient Ca(2+) transfer.
Csordás
György
G
Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Várnai
Péter
P
Golenár
Tünde
T
Roy
Swati
S
Purkins
George
G
Schneider
Timothy G
TG
Balla
Tamás
T
Hajnóczky
György
G
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002463:Cell Membrane Permeability; D002470:Cell Survival; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure; D021621:Imaging, Three-Dimensional / Q000379:methods*; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D051336:Mitochondrial Membranes / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D013997:Time Factors
D053496:Inositol 1,4,5-Trisphosphate Receptors; D002118:Calcium